Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35175 Publications

UniCAR T cell immunotherapy enables efficient elimination of radioresistant cancer cells

Arndt, C.; Loureiro, L. R.; Feldmann, A.; Jureczek, J.; Bergmann, R.; Máthé, D.; Hegedüs, N.; Berndt, N.; Koristka, S.; Metwasi, N.; Fasslrinner, F.; Lamprecht, C.; Kegler, A.; Hoffmann, A.; Bartsch, T.; Köseer, A. S.; Egan, G.; Schmitz, M.; Hořejší, V.; Krause, M.; Dubrovska, A.; Bachmann, M.

Induction or selection of radioresistant cancer (stem) cells following standard radiotherapy is presumably one of the major causes for recurrence of metastatic disease. One possibility to prevent tumor relapse is application of targeted immunotherapies including e.g. chimeric antigen receptor (CAR) T cells. In light of long-term remissions it is highly relevant to clarify whether radioresistant cancer cells are susceptible to CAR T cell-mediated killing. To answer this question, we evaluated the anti-tumor activity of the switchable universal chimeric antigen receptor (UniCAR) system against highly radioresistant head and neck squamous cell carcinoma cells both in vitro and in vivo. Following specific UniCAR T cell engagement via EGFR or CD98 target modules, T cell effector mechanisms were induced including secretion of pro-inflammatory cytokines, up-regulation of granzyme B and perforin as well as T cell proliferation. CD98- or EGFR-redirected UniCAR T cells further possess the capability to efficiently lyse radioresistant tumor cells. Observed anti-tumor effects were comparable to those against the radiosensitive parental cell lines. Finally, redirected UniCAR T cells significantly inhibited growth of radioresistant cancer cells in immunodeficient mice. Taken together, our obtained data underline that the UniCAR system is able to overcome radio-resistance. Thus, it represents an attractive technology for the development of combined radioimmunotherapeutic approaches that might improve the outcome of patients with metastatic radioresistant tumor diseases.

Keywords: radio-resistance; CD98; EGFR; adaptor CAR; T cell immunotherapy

Publ.-Id: 30835

SiPM readout for NeuLAND

Hensel, T.; Weinberger, D.; Bemmerer, D.; R3B Collaboration

Statusreport SiPM readout for NeuLAND

Keywords: NeuLAND; SiPM; R3B

  • Lecture (Conference)
    R3B Collaboration Meeting, 29.10.2019, Darmstadt, Deutschalnd

Publ.-Id: 30834

General Colloidal Synthesis of Transition-Metal Disulfide Nanomaterials as Electrocatalysts for Hydrogen Evolution Reaction

Meerbach, C.; Klemmed, B.; Spittel, D.; Bauer, C.; Park, Y. J.; Hübner, R.; Jeong, H. Y.; Erb, D.; Shin, H. S.; Lesnyak, V.; Eychmüller, A.

The material-efficient monolayers of transition-metal dichalcogenides (TMDs) are a promising class of ultrathin nanomaterials with properties ranging from insulating through semiconducting to metallic, opening a wide variety of their potential applications from catalysis and energy storage to optoelectronics, spintronics, and valleytronics. In particular, TMDs have a great potential as emerging inexpensive alternatives to noble metal-based catalysts in electrochemical hydrogen evolution. Herein, we report a straightforward, low-cost, and general colloidal synthesis of various 2D transition-metal disulfide nanomaterials, such as MoS2, WS2, NiSx, FeSx, and VS2, in the absence of organic ligands. This new preparation route provides many benefits including relatively mild reaction conditions, high reproducibility, high yields, easy upscaling, no post-thermal annealing/treatment steps to enhance the catalytic activity, and, finally, especially for molybdenum disulfide nanosheets, high activity in the hydrogen evolution reaction. To underline the universal application of the synthesis, we prepared mixed CoxMo1-xS2 nanosheets in one step to optimize the catalytic activity of pure undoped MoS2, which resulted in an enhanced hydrogen evolution reaction performance characterized by onset potentials as low as 134 mV and small Tafel slopes of 55 mV/dec.

Publ.-Id: 30833

Promoting the Electrocatalytic Performance of Noble Metal Aerogels by Ligand-Directed Modulation

Fan, X.; Zerebecki, S.; Du, R.; Hübner, R.; Marzum, G.; Jiang, G.; Hu, Y.; Barcikowki, S.; Reichenberger, S.; Eychmüller, A.

Noble metal aerogels (NMAs) are an emerging class of porous materials. Embracing nano-sized highly-active noble metals and porous structures, they display unprecedented performance in diverse electrocatalytic processes. However, various impurities, particularly organic ligands, are often involved in the synthesis and remain in the corresponding products, hindering the investigation of the intrinsic electrocatalytic properties of NMAs. Here, starting from laser-generated inorganic-salt-stabilized metal nanoparticles, various impurity-free NMAs (Au, Pd, and Au-Pd aerogels) were fabricated. In this light, we demonstrate not only the intrinsic electrocatalytic properties of NMAs, but also the prominent roles played by ligands in tuning electrocatalysis through modulating the electron density of catalysts. These findings may offer a new dimension to engineer and optimize the electrocatalytic performance for various NMAs and beyond.

Keywords: aerogels; electrocatalysis; laser; ligand; noble metals

Publ.-Id: 30832

Engineering Multimetallic Aerogels for pH-Universal HER and ORR Electrocatalysis

Du, R.; Jin, W.; Hübner, R.; Zhou, L.; Hu, Y.; Eychmüller, A.

The advent of noble metal aerogels (NMAs), that feature the high catalytic activity of noble metals and unique structural attributes of aerogels, has stimulated research on a new class of outstanding electrocatalysts. However, limited by the available compositions, the explored electrocatalytic reactions on NMAs are highly restricted and certain important electrochemical processes have not been investigated. Here, an effective gelation approach is demonstrated by using a strong salting-out agent (i.e., NH4F), thereby expanding the composition of NMAs to various multimetallic systems and providing a platform to investigate composition-dependent electrocatalytic performance of NMAs. Combining structural features of aerogels and optimized chemical compositions, the Au-Pt and Au-Rh aerogel catalysts manifest remarkable pH-universal (pH = 0-14) performance surpassing commercial Pt/C and many other nanoparticle (NP)-based catalysts in the electrocatalytic oxygen reduction reaction, hydrogen evolution reaction, and water splitting, displaying enormous potential for the electrochemical hydrogen production, fuel cells, etc.

Keywords: electrocatalysis; hydrogen evolution reaction; metal aerogels; oxygen reduction reaction; pH

Publ.-Id: 30831

Tomographic imaging of two-phase flow

Hampel, U.; Barthel, F.; Bieberle, A.; Bieberle, M.; Boden, S.; Franz, R.; Neumann-Kipping, M.; Tas-Köhler, S.

Two-phase flow is to be found in many situations of nuclear reactor operation and accident sequences. Examples are loss of coolant accidents and boiling in fuel assemblies. Hence, mod-elling of two-phase flow is a primary concern in nuclear safety research. Model development and code validation frequently require experimental data, preferably taken under plant ther-mal-hydraulic conditions. Tomographic imaging techniques provide a way to analyze two-phase flow with high spatial resolution. In this paper we introduce recent developments in X-ray tomography and its application to three different problems related to nuclear safety.

Keywords: two-phase flow; core thermal hydraulics; tomography; steam condensation; boiling

Publ.-Id: 30830

Bipolar spin Hall nano-oscillators

Hache, T.; Li, Y.; Weinhold, T.; Scheumann, B.; Trindade Goncalves, F. J.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

We demonstrate a novel type of spin Hall nano-oscillators (SHNOs) that allow for efficient tuning of magnetic auto-oscillations over an extended range of gigahertz frequencies, using bipolar direct currents at constant magnetic elds. This is achieved by stacking two distinct magnetic materials with a platinum layer in between. In this device, the orientation of the spin polarised electrons accumulated at the top and bottom interfaces of platinum is switched upon changing the polarity of the direct current. As a result, the effective anti-damping required to drive large amplitude auto-oscillations can appear either at the top or bottom magnetic layer. Tuning of the auto-oscillation frequencies by several gigahertz can be obtained by combining two materials with sufficiently different saturation magnetization. Here we show that the combination of NiFe and CoFeB can result in 3 GHz shifts in the auto-oscillation frequencies. Bipolar SHNOs as such may bring enhanced synchronisation capabilities to neuromorphic applications.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-03-18
    DOI: 10.14278/rodare.269
    License: CC-BY-4.0


Publ.-Id: 30829

Round robin into best practices for the determination of indentation size effects

Ruiz-Moreno, A.; Hähner, P.; Kurpaska, L.; Jagielski, J.; Spätig, P.; Trebala, M.; Hannula, S.-P.; Merino, S.; de Diego, G. . .; Namburi, H.; Libera, O.; Terentyev, D.; Khvan, T.; Heintze, C.; Jennett, C.

The paper presents a statistical study of nanoindentation results obtained in seven European laboratories which have joined a round robin exercise to assess methods for the evaluation of indentation size effects. The study focuses on the characterization of ferritic/martensitic steels T91 and Eurofer97, envisaged as structural materials for nuclear fission and fusion applications, respectively. Depth-controlled single cycle measurements at various final indentation depths, force-controlled single cycle and force-controlled progressive multi-cycle measurements using Berkovich indenters at room temperature have been combined to calculate the indentation hardness and the elastic modulus as a function of depth applying the Oliver and Pharr method. Intra- and inter-laboratory variabilities have been evaluated. Elastic modulus corrections have been applied to the hardness data to compensate for materials related systematic errors, like pile-up behaviour, which is not accounted for by the Oliver and Pharr theory, and other sources of instrumental or methodological bias. The correction modifies the statistical hardness profiles and allows determining more reliable indentation size effects.

Publ.-Id: 30828

Rethinking ore sorting - The search for the optimal sensor

Kern, M.; Tusa, L.; Khodadadzadeh, M.; Leißner, T.; Gloaguen, R.; van den Boogaart, K. G.; Gutzmer, J.

Zusammenfassung: Sensorgestützte Sortierung ist eine Technologie, die in zunehmendem Maße zur Aufbereitung von Primärrohstoffen verwendet wird. Mit dem hier vorgestellten simulations-basierten Ansatz ist es möglich, den optimalen Sensor durch quantitative Analysen der Mineralogie und Datenverwertung in Kombination mit Maschinellem Lernen (ML) gezielt zu bestimmen. Dieses Vorgehen ist generisch und kann auf viele Rohstofftypen angepasst werden. Darüber hinaus birgt das Vorgehen das Potenzial, eine Schlüsseltechnologie zur Optimierung von Aufbereitungsprozessen zu werden.

Summary: Sensor-based sorting is a technology which is increasingly used for processing primary raw materials. With the simulation-based approach presented in this paper, it is possible to specifically determine the optimal sensor based on quantitative analyses of the mineralogy and data utilization in combination with machine learning (ML). This approach is generic and can be adapted to many types of raw material. Moreover, the approach has the potential to become a key technology for the optimization of processing operations.

  • AT Minerals Processing 61(2020)3, 54-64

Publ.-Id: 30826

Pilot-scale investigation of two Electric Pulse Fragmentation (EPF) approaches for the mineral processing of a low-grade cassiterite schist ore

Bru, K.; Sousa, R.; Machado Leite, M.; Broadbent, C.; Stuart, G.; Pashkevich, D.; Kern, M.; Parvaz, D. B.

Two approaches for the use of the Electric Pulse Fragmentation (EPF) in the beneficiation of a low-grade cassiterite schist ore were investigated through pilot-scale tests performed on samples of about 270 kg. The first approach used EPF treatment for pre-concentration while in the second approach the EPF technology was mostly used for crushing. Comparison with the use of conventional crushers was performed.
Results showed that the EPF pre-treatment led to a decrease of the Bond rod mill work index while the Bond ball mill work index remained unchanged. This means that the decrease in the energy consumption requested to grind the material down to 1.18 mm (closing screen of the Bond rod mill work index) is no longer noticeable with additional grinding stage to reach a size down to 106 μm (closing screen of the Bond ball mill work index).
This may be due to the fracture network generated during EPF being consumed immediately in the subsequent comminution step. Alternatively, it may be that the Bond ball mill work index is not appropriate for exhibiting the weakening effect of the EPF technology when the mineral liberation size is coarser than the closing screen size used for the test. Concentration tests performed on the sample treated with the first approach for EPF showed no marked change in separation performance. However, a higher concentrate grade was obtained when using this EPF pre-treatment, indicating a probable potential for improvement.

Keywords: Cassiterite; Electric Pulse Fragmentation; Selective comminution; Pre-concentration

Publ.-Id: 30825

The effect of noise on the synchronization dynamics of the Kuramoto model on a large human connectome graph

Ódor, G.; Kelling, J.; Deco, G.

We have extended the study of the Kuramoto model with additive Gaussian noise running on the KKI-18 large human connectome graph. We determined the dynamical behavior of this model by solving it numerically in an assumed homeostatic state, below the synchronization crossover point we determined previously. The desynchronization duration distributions exhibit power-law tails, characterized by the exponent in the range 1.1 < τt < 2, overlapping the in vivo human brain activity experiments by Palva et al. We show that these scaling results remain valid, by a transformation of the ultra-slow eigen-frequencies to Gaussian with unit variance.
We also compare the connectome results with those, obtained on a regular cube with N = 106 nodes, related to the embedding space, and show that the quenched internal frequencies themselves can cause frustrated synchronization scaling in an extended coupling space.

Keywords: Frustrated Synchronization; Human Connectome; Chimera states; Noisy Kuramoto; Criticality in resting state

Publ.-Id: 30824

Contemporary Synthesis of Ultrasmall (sub-10 nm) Upconverting Nanomaterials

Joshi, T.; Mamat, C.; Stephan, H.

Due to their unique photophysical properties, upconverting nanoparticles (UCNPs), i.e. particles capable of converting near-infrared (NIR) photons into tunable emissions in the range of ultraviolet (UV) to NIR, have great potential for use in various biomedical fields such as bioimaging, photodynamic therapy and bioanalytical applications. As far as biomedical applications concerned, these materials have a number of advantageous properties such as brilliant luminescence and exceptional photo-stability. Very small “stealth” particles (sub-10 nm), which can circulate in the body largely undetected by the immune system, are particularly important for in vivo use. The fabrication of such particles, which simultaneously have a defined (ultrasmall) size and the required optical properties, is a great challenge and an area that is in its infancy. This minireview provides a concise overview of recent developments on appropriate synthetic methodologies to produce such UCNPs. Particular attention was given to the influence of both surfactants and dopants used to precisely adjust size, crystalline phase and optical properties of UCNPs.

Keywords: Lanthanides; Nanomaterials; Synthesis; Ultrasmall; Upconversion

Publ.-Id: 30823

Bipolar spin Hall nano-oscillators

Hache, T.; Li, Y.; Weinhold, T.; Scheumann, B.; Trindade Goncalves, F. J.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

We demonstrate a novel type of spin Hall nano-oscillators (SHNOs) that allow for efficient tuning of magnetic auto-oscillations over an extended range of gigahertz frequencies, using bipolar direct currents at constant magnetic fields. This is achieved by stacking two distinct magnetic materials with a platinum layer in between. In this device, the orientation of the spin polarised electrons accumulated at the top and bottom interfaces of platinum is switched upon changing the polarity of the direct current. As a result, the effective anti-damping required to drive large amplitude auto-oscillations can appear either at the top or bottom magnetic layer. Tuning of the auto-oscillation frequencies by several gigahertz can be obtained by combining two materials with suffciently different saturation magnetization. Here we show that the combination of NiFe and CoFeB can result in 3 GHz shifts in the auto-oscillation frequencies. Bipolar SHNOs as such may bring enhanced synchronisation capabilities to neuromorphic applications.

Keywords: magnetism; spin Hall; nano-oscillator; auto-oscillations; bipolar; oscillator; nanofabrication; microwave; high-frequency

Related publications

  • Applied Physics Letters 116(2020), 192405
    DOI: 10.1063/5.0008988
  • Lecture (Conference) (Online presentation)
    65th Annual Conference on Magnetism and Magnetic Materials (MMM 2020), 02.-06.11.2020, virtual conference, virtual conference

Publ.-Id: 30822

Structure variations within RSi2 and R2TSi3 silicides. Part I. Structure overview

Nentwich, M.; Zschornak, M.; Sonntag, M.; Gumeniuk, R.; Gemming, S.; Leisegang, T.; Meyer, D. C.

Here, structural parameters of various structure reports on RSi2 and R2TSi3 compounds [where R is an alkaline earth metal, a rare earth metal (i.e. an element of the Sc group or a lathanide), or an actinide and T is a transition metal] are summarized. The parameters comprising composition, lattice parameters a and c, ratio c/a, formula unit per unit cell and structure type are tabulated. The relationships between the underlying structure types are presented within a group–subgroup scheme (Bärnighausen diagram). Additionally, unexpectedly missing compounds within the R2TSi3 compounds were examined with density functional theory and compounds that are promising candidates for synthesis are listed. Furthermore, a correlation was detected between the orthorhombic AlB2-like lattices of, for example, Ca2AgSi3 and the divalence of R and the monovalence of T. Finally, a potential tetragonal structure with ordered Si/T sites is proposed.

Keywords: silicide; lanthanide; ordering phenomena; structure prediction; DFT

Publ.-Id: 30821

Horizontal annular flow through orifice studied by X-ray microtomography

Porombka, P.; Boden, S.; Lucas, D.; Hampel, U.

A mobile X-ray microtomography (µCT) system was developed which enables 3D scanning of horizontal and vertical test sections. The µCT system has been applied to measure the local, time-averaged volume fraction distribution of developing annular air-water flow in a horizontal pipe with µm spatial resolution. Based on the volume fraction data the liquid film thickness profile is computed and the accumulation, stripping and renewal of the annular liquid film at a circular orifice is studied. The development length of the annular flow downstream of the orifice is evaluated based on the integral volume fraction and the change of the film thickness profile along the pipe axis. Both parameters give a consistent result, indicating that liquid film renewal can be judged based on integral measurement techniques in this case. The detailed 3D data is intended for validation of computational fluid dynamics codes based on phase-averaged variables such as the Euler-Euler approach.

Keywords: X-ray microtomography; film thickness; circular orifice; annular flow

Related publications

Publ.-Id: 30820

Novel cosmogenic datings in landslide deposits, San Juan, Argentina

Jeanneret, P.; Moreiras, S. M.; Merchel, S.; Gärtner, A.; Binnie, S.; Orgeira, M. J.; Aumaître, G.; Bourlès, D.; Keddadouche, K.

High-mountain environments in an active tectonic setting are prone to landsliding. The triggering mechanisms are still a challenge as these areas are influenced by several pre-conditioning factors coupled with active seismicity and climatic forcings. Understanding the intrinsic and external mechanisms in which these events are influenced would help to establish better constraints onto their timing and periodicity and, eventually, hazard assessment and prediction. Glacially eroded valleys are especially prone as they deeply incise mountain ranges leaving unstable slopes once they retreat. Establishing the timing of such events enables to link the causality and comprehend in a deeper level the triggering and pre-conditioning factors of landslides. To this aim, ¹⁰Be and ²⁶Al cosmogenic age determinations were performed in three landslide deposits in a poorly studied area of San Juan province, all of which are novel to the area. Coupled with remote sensing techniques, field observations and detailed stratigraphic and sedimentological studies, these new large landslides represent a first approach to understand this dynamic environment. The three landslides were categorized as rock avalanches found in the middle and lower reaches of the Blanco River, sourced from the Choiyoi Group with evidence of hydrothermal alteration and including/deforming moraine deposits during their fall. Ages range from 20.9±1.4, 10.8±0.7 and 12.8±0.9 ka from the lowermost deposit to the highest, respectively. Even though one sample per deposit is not enough to have statistically significant exposure ages, these values, along with the established chronostratigraphy, allow first order assumptions on the link between deglaciation processes and readjustment of the slopes via large landslide events.

Keywords: Landslide; chronostratigraphy; Arid Central Andes; Argentina

  • Book chapter
    in: Understanding and Reducing Landslide Disaster Risk. WLF 2020. ICL Contribution to Landslide Disaster Risk Reduction, Cham: Springer, 2020, 361-370
    DOI: 10.1007/978-3-030-60319-9_40

Publ.-Id: 30819

Grundlegende F&E-Arbeiten zu Methoden der Zustandsüberwachung von Transport- und Lagerbehältern für abgebrannte Brennelemente und wärmeentwickelnde hochradioaktive Abfälle bei verlängerter Zwischenlagerung

Wagner, M.; Rachamin, R.; Fiß, D.; Schmidt, S.; Reinicke, S.; Kratzsch, A.; Hampel, U.

Mit der verlängerten Zwischenlagerung von abgebrannten Brennelementen ergeben sich verschie-dene regulatorische und sicherheitstechnische Fragestellungen. Eine davon ist die nach der Lang-zeitintegrität der Brennelemente in den Trockenlagerbehältern. Ihre Beantwortung hat direkte Relevanz für den späteren Transport zum Endlager und die Umladung des abgebrannten Kernbrennstoffs in andere Behälter. In dem Verbundvorhaben untersuchten die TU Dresden und die Hochschule Zittau/Görlitz Potenziale und Grenzen von nichtinvasiven Verfahren zur Überwachung des Zustands des radioaktiven Inventars von Trockenlagerbehältern. Als solche wurden Thermographie, strahlungsbasierte Messverfahren sowie akustische Messverfahren betrachtet. Für diese erfolgte eine Bewertung der Empfindlichkeit und Nachweisgrenzen mittels numerischer Simulationen und Durchführung von Experimenten an skalierten Behältermodellen. Es stellte sich heraus, dass insbesondere die Myonenbildgebung und die Analyse der Gamma- und Neutronenstrahlungsfelder am Behälter für ein Überwachungskonzept geeignet sind. Mit diesen Verfahren können Brennstoffverlagerungen ortsaufgelöst detektiert werden.

Keywords: Zwischenlagerung; nicht-invasive Überwachung

  • Other report
    -: -, 2020

Publ.-Id: 30818

The influence of negatively charged silica nanoparticles on the surface properties of anionic surfactants: electrostatic repulsion or the effect of ionic strength?

Eftekhari, M.; Schwarzenberger, K.; Javadi, A.; Eckert, K.

The presence of negatively charged nanoparticles affects the surface activity of anionic surfactants in an aqueous phase. Recent studies suggest that electrostatic repulsive forces play an important role in increasing the surface activity of surfactants. However, the addition of nanoparticles also increases the ionic strength of the system, which has a significant impact on the surfactant's properties, e.g. its critical micelle concentration (CMC). To investigate how and to what extent electrostatic forces and ionic strength influence the behavior of ionic surfactants, the surface tension and elasticity of different solutions were measured using drop profile tensiometry as a function of the surfactant (SDBS), nanoparticle (silica) and salt (KNO3) concentration. It is observed that the surface activity of the surfactants is mainly influenced by the change in the system's ionic strength due to the presence of nanoparticles. Several characteristic parameters including the equivalent concentration of the surfactant, the CMC and the apparent partial molar area of the adsorbed surfactant are theoretically calculated and further employed to validate experimental observations. Both the nanoparticles and electrolyte decrease the CMC, while the equivalent concentration of the surfactant remains nearly constant. This paper presents a criterion to estimate the possible influence of such forces for nanoparticles of different sizes and mass fractions.

Related publications

Publ.-Id: 30817

Influence of finite temperature Exchange-Correlation effects in Hydrogen

Ramakrishna, K.; Dornheim, T.; Vorberger, J.

We use density functional molecular dynamics (DFT-MD) to study the effect of finite temperature exchange-correlation (xc) in Hydrogen. Using the Kohn-Sham approach, the xc energy of the system, $E_{xc}(r_{s})$ is replaced by the xc free energy $f_{xc}(r_{s},\theta)$ within the local density approximation (LDA) based on parametrized path integral Monte Carlo (PIMC) data for the uniform electron gas (UEG) at warm dense matter (WDM) conditions. We observe insignificant changes in the equation of state (EOS) at the region of metal-insulator transition compared to the regular LDA form, whereas significant changes are observed for T>10000 K, i.e., in the important WDM regime. Thus, our results further corroborate the need for temperature-dependent xc functionals for DFT simulations of WDM systems. Moreover, we present the first finite-temperature DFT results for the EOS of Hydrogen in the electron liquid regime up to $r_{s}=14$ and find a drastic impact (the EOS changes by more than 20%) of thermal xc effects, which manifests at lower temperatures compared to WDM. We expect our results to be important for many applications beyond DFT, like quantum hydrodynamics and astrophysical models.

Keywords: Computational Physics; Plasma Physics; Warm dense matter


Publ.-Id: 30815

Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov State with Segmented Vortices in the BCS-BEC-Crossover Superconductor FeSe

Kasahara, S.; Sato, Y.; Licciardello, S.; Culo, M.; Arsenijevic, S.; Ottenbros, T.; Tominaga, T.; Böker, J.; Eremin, I.; Shibauchi, T.; Wosnitza, J.; Hussey, N. E.; Matsuda, Y.

We present resistivity and thermal-conductivity measurements of superconducting FeSe in intense magnetic fields up to 35 Tapplied parallel to the ab plane. At low temperatures, the upper critical field μ0Hab c2 shows an anomalous upturn, while thermal conductivity exhibits a discontinuous jump at μ0H* ≈ 24 T well below μ0Hab c2, indicating a first-order phase transition in the superconducting state. This demonstrates the emergence of a distinct field-induced superconducting phase. Moreover, the broad resistive transition at high temperatures abruptly becomes sharp upon entering the high-field phase, indicating a dramatic change of the magnetic-flux properties.We attribute the high-field phase to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, where the formation of planar nodes gives rise to a segmentation of the flux-line lattice. We point out that strongly orbital-dependent pairing as well as spin-orbit interactions, the multiband nature, and the extremely small Fermi energy are important for the formation of the FFLO state in FeSe.

Publ.-Id: 30814

Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4O6

Knaflic, T.; Jeglic, P.; Komelj, M.; Zorko, A.; Biswas, P. K.; Ponomaryov, O.; Zvyagin, S.; Reehuis, M.; Hoser, A.; Geiß, M.; Janek, J.; Adler, P.; Felser, C.; Jansen, M.; Arcon, D.

Recently, a Verwey-type transition in the mixed-valence alkali sesquioxide Cs4O6 was deduced from the charge ordering of molecular peroxide O2− 2 and superoxide O 2 anions accompanied by the structural transformation and a dramatic change in electronic conductivity [Adler et al., Sci. Adv. 4, eaap7581 (2018)]. Here, we report that in the sister compound Rb4O6, a similar Verwey-type charge ordering transition is strongly linked to O 2 orbital and spin dynamics. On cooling, a powder neutron diffraction experiment reveals a charge ordering and a cubic-to-tetragonal transition at TCO = 290 K, which is followed by a further structural instability at Ts = 92 K that involves an additional reorientation of magnetic O 2 anions. Magnetic resonance techniques supported by density functional theory computations suggest the emergence of a peculiar type of π*-orbital ordering of the magnetically active O 2 units, which promotes the formation of a quantum spin state composed of weakly coupled spin dimers. These results reveal that as in 3d transition-metal compounds, also in the π* open-shell alkali sesquioxides the interplay between Jahn-Teller-like electron-lattice coupling and Kugel-Khomskii-type superexchange determines the nature of orbital ordering and the magnetic ground state.

Publ.-Id: 30813

Strongly coupled electron liquid: Ab initio path integral Monte Carlo simulations and dielectric theories

Dornheim, T.; Sjostrom, T.; Tanaka, S.; Vorberger, J.

The strongly coupled electron liquid provides a unique opportunity to study the complex interplay of strong coupling with quantum degeneracy effects and thermal excitations. To this end, we carry out extensive ab initio path integral Monte Carlo (PIMC) simulations to compute the static structure factor, interaction energy, density response function, and the corresponding static local field correction in the range of 20≤rs≤100 and 0.5≤θ≤4. We subsequently compare these data to several dielectric approximations and find that different schemes are capable to reproduce different features of the PIMC results at certain parameters. Moreover, we provide a comprehensive data table of interaction energies and compare those to two recent parametrizations of the exchange-correlation free energy, where they are available. Finally, we briefly touch upon the possibility of a charge-density wave. The present study is complementary to previous investigations of the uniform electron gas in the warm dense matter regime and, thus, further completes our current picture of this fundamental model system at finite temperature. All PIMC data are available online.

Keywords: warm dense matter; electron liquid; dielectric theory; quantum monte carlo; local field correction; ab initio

Related publications


Publ.-Id: 30812

Radiopharmaceutical Sciences

Ermert, J.; Benešová, M.; Hugenberg, V.; Gupta, V.; Spahn, I.; Pietzsch, H.-J.; Liolios, C.; Kopka, K.

Clinical Nuclear Medicine, 2nd ed., Chapter 2 Radiopharmaceutical Sciences
Abstract: Chapter 2 Radiopharmaceutical Sciences
Chapter 2 elucidates the field Radiopharmaceutical Sciences from the perspective of its clinical relevance. Radiopharmaceutical Sciences summarize all scientific aspects comprising chemistry, physics and biology/pharmacology that deal with incorporating a suitable radionuclide into a pharmaceutical or other biologically active molecule or molecular entity. The resulting radiopharmaceuticals are used in Nuclear Medicine applications both for diagnosis [meaning non-invasive scintigraphic imaging] and for internal radiotherapy. Internal radiotherapy is nowadays called radioligand therapy (RLT) or endoradiotherapy and altogether is summarized under the term radiothera(g)nostics.
To transfer Radiopharmaceutical Sciences into Clinical Nuclear Medicine first of all radionuclides with corresponding decay characteristics are demanded making these suitable for diagnostic or therapeutic applications. Depending on the short physical half-lives of the radionuclides fast and efficient radiolabeling strategies are required that can be also transferred into the GMP-compliant production of radiopharmaceuticals.
The major challenges in the development of a new radiopharmaceuticals include i.a. the identification of an adequate ligand that specifically binds to the biological target of interest, the chemical modification of the ligand to enable radiolabeling while preserving the binding affinity to the biological target, and the translation of the preclinical evaluations into first in-human studies.
In summary this chapter summarises in a concise manner the current status of clinically relevant radionuclides, SPECT and PET tracers as well as the introduced thera(g)nostic classes of radiopharmaceuticals through the eyes of eight representative radiopharmaceutical scientists.

  • Book chapter
    Ahmadzadehfar H, Biersack HJ, Freeman LM, Zuckier LS: Clinical Nuclear Medicine – 2nd edition, Springer Nature Switzerland AG: Springer International Publishing, 2020, 978-3-030-39455-4, 49-191
    DOI: 10.1007/978-3-030-39457-8

Publ.-Id: 30811

Transmission helium ion imaging and time-of-flight spectroscopy

Mousley, M.; Bouton, O.; Klingner, N.; Serralta Hurtado De Menezes, E.; Hlawacek, G.; Eswara, S.; Wirtz, T.

Helium ions are alternative imaging probes to electrons, offering lower de Broglie wavelengths at the same energies and the possibility for different contrast mechanisms [1] [2][3]. A prototype Transmission Helium Ion Microscope (THIM) has been constructed at the Luxembourg Institute of Science and Technology (LIST) [4]. The use of post sample deflection allows the detection of the transmitted ions and neutrals or neutrals only (Figure 1 A). The source is a duo plasmatron with a spot size on the sample of approximately 100 µm and a beam current between 0.1-2nA. There are 2 Einzel lenses and 3 XY deflectors along the column to guide the beam. A MCP detector behind the sample can be used in one of 4 different output mechanisms. Firstly a phosphor screen can be used to produce a transmission helium ion image (THIM) directly which can be captured by an external CCD. Secondly, an anode plate can be used to collect the current directly whilst the beam is scanned, the current recorded at each pixel can then form a scanning image (STHIM). Thirdly, fast electronics are used to blank the beam and provide the start signal for time of flight (TOF) measurements, whilst the anode signal can be used as the stop signal [5]. This allows the generation of TOF-STHIM data. Finally, a delay line detector (DLD) can be placed behind the MCP, from which location and time of flight, of individual particles, can be recorded simultaneously, producing energy spectra and images at the same time. The prototype can image in different modes, THIM , STHIM (scanning THIM), THIM TOF and STHIM TOF. When scanning the beam a secondary electron image can be recorded at the same time (Figure 1 B). In THIM mode the formation of spot patterns due to sample charging was seen when imaging insulating inorganic crystal samples with a stationary broad beam. This was found to be due to unexpectedly large sample charging. We will present preliminary TOF spectra for the transmitted helium ion signal recorded with an anode plate detector and a position sensitive delay line detector. Images formed from different time windows from the TOF spectra show different contrast (Figure 2B) and the spectra for a single layer graphene sample showed increased counts after the main peak (Figure 3), indicative of processes causing energy loss.

[1] Scipioni,L.;, Sanford,C. A.;, Notte,J.;, Thompson,B.;, McVey,S.;, J. Vac. Sci. Technol. B Microelectron. Nanom. Struct., 2009, vol. 27, no. 6, p. 3250, 10.1116/1.3258634.
[2] Kavanagh,K. L.;, Herrmann,C.;, Notte,J. A.;, J. Vac. Sci. Technol. B, Nanotechnol. Microelectron. Mater. Process. Meas. Phenom., 2017, vol. 35, no. 6, p. 06G902, 10.1116/1.4991898.
[3] Wirtz,T.;, De Castro,O.;, Audinot,J.-N.;, Philipp,P.;, Annu. Rev. Anal. Chem., 2019, vol. 12, no. 1, 10.1146/annurev-anchem-061318-115457.
[4] Mousley,M.;, Eswara,S.;, De Castro,O.;, Bouton,O.;, Klinger,N.;, Koch,C. T.;, Hlawacek,G.;, Wirtz,T.;, Submitt. to MRS Commun., vol. 1, pp. 1–10.
[5] Klingner,N.;, Heller,R.;, Hlawacek,G.;, Borany,J. von;, Notte,J.;, Huang,J.;, Facsko,S.;, Ultramicroscopy, 2016, vol. 162, pp. 91–97, 10.1016/j.ultramic.2015.12.005.

Figure 1: A) transmission images formed with ions and neutrals of a copper grid with a single layer graphene membrane pitch 85µm (31µm bar 54µm hole). B) Secondary electron and transmission ion images recorded concurrently in scanning mode.

Figure 2: A) The effect of offsetting the beam aperture on zero loss peak width B) STHIM images, of a 200 mesh copper grid, formed from two different peaks in the TOF spectrum.

Figure 3: The TOF spectrum for a single layer graphene sample on a 300 mesh copper grid, shows extra peaks compared to a background spectrum without a sample.

  • Lecture (Conference) (Online presentation)
    European Microscopy Congress 2020, 23.-28.08.2020, Copenhagen, Denmark

Publ.-Id: 30810

Correlative high resolution microscopy and mass spectrometry for morphological and chemical analysis of nanoparticles in biological systems

Biesemeier, A.; de Castro, O.; Serralta Hurtado De Menezes, E.; Klingner, N.; Hlawacek, G.; Gnauck, P.; Duarte Pinto, S.; Lucas, F.; Bebeacua, C.; Cambier, S.; Wirtz, T.

Combined morphological and chemical analysis of ultrastructures is gaining more and more attention in both material and life sciences. Especially the detection of nanoparticles within biological tissue has become a hot topic in environmental research, ecology, nanotoxicology, but also medicine and life science using nanoparticles as carriers for therapeutic drugs. Usually, several highly specialised instruments have to be used to investigate the respective key features of the sample.
Here, a new prototype instrument is presented that combines sub20nm SIMS on a helium ion microscope [HIM; 1] with dark and bright field imaging in one tool – the npSCOPE [2]: the multi-modal instrument couples a Gas Field Ion Source (GFIS) as primary ion beam source with a secondary ion mass spectrometer (SIMS) system featuring a continuous focal plane detector (FPD) and a STHIM detector for imaging the transmitted helium beam. The latter allows investigation of thin samples like biological tissue sections. For morphological/topographical analysis of charging and non-charging bulk samples with sub-nm resolution, the instrument is also equipped with a secondary electron detector and a flood gun. This setup allows (a) higher sensitivity than analytical electron microscopy combined with (b) better spatial resolution than available with other SIMS methodologies typically used for life science questions. The FPD yields a full mass spectrum per scanned pixel featuring the possibility of post hoc analysis of all elements/ion species detected.
Several examples will be presented to show how thin tissue sections can first be investigated with transmitted ions for proper contrast of biological membranes followed by chemical characterization of associated or ingested nanoparticles without the need to transfer samples between different instruments. Specific localisation of the nanoparticles outside the cell membrane or within the cytoplasm or subcellular compartments can be obtained.

In summary, a unique tool for all-in-one physico-chemical characterisation of nanoparticles both before contact to a living organism and after incorporation is presented. Pixel by pixel correlation of the different datasets are directly obtained by image fusion or co-registration methods. For future analysis of frozen-hydrated samples, a cryo-stage is currently being integrated into the npSCOPE. It will yield close to native chemical analysis of diagnostic, environmental and nanotoxicology samples with decreased experiment times and without artefacts due to sample transfer.
[1] T. Wirtz, O. De Castro, J.-N. Audinot, P. Philipp. Imaging and analytics on the Helium Ion Microscope. Annual Review of Analytical Chemistry 12 (2019) 523-543

[2] This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No. 720964.

Keywords: helium ion microscope; secondary ion mass spectrometer; scanning transmission ion microscopy

  • Lecture (Conference) (Online presentation)
    European Microscopy Congress 2020, 23.-28.08.2020, København, Danmark

Publ.-Id: 30809

npSCOPE: A new instrument combining SIMS imaging, SE imaging and transmission ion microscopy for high resolution in-situ correlative investigations

de Casto, O.; Biesemeier, A.; Serralta Hurtado De Menezes, E.; Klingner, N.; Hlawacek, G.; Gnauck, P.; Duarte Pinto, S.; Lucas, F.; Bebeacua, C.; Witrz, T.

In various research areas ranging from materials science to life sciences it becomes more and more important to be able to analyze the structure as well as the chemical composition at the nano-scale. For example, the size of electronic components becomes smaller and smaller increasing the need of having techniques to precisely follow dopant distributions with high spatial resolution. In the field of renewable energy devices, e.g. solar cells and batteries, the performance typically depends on the chosen material composition and distribution. Linking the underlying structure and composition at the nano-scale to the device’s performance is therefore of utmost importance [1,2]. Similar needs for having high spatial resolution and high-sensitivity chemical information can be found in life sciences [3]. In nano-toxicology for instance, it is important to be able to reveal sub-cellular structures and simultaneously determine their chemical, elemental or isotopic composition in order to better understand relevant processes [4]. In most of the afore mentioned studies a number of different instruments is nowadays used to perform these investigations using correlative approaches. Being able to do such correlative studies in one single instrument is definitely beneficial for reducing the analysis time, speeding up the throughput as well as for facilitating the precise localization of the region of interests on the investigated samples.
Therefore, we developed a multimodal nano-analytical platform allowing in-situ analysis of a same sample using different information channels. The instrument is equipped with the ultra-high resolution Gas Field Ion Source (GFIS) technology [5] allowing the sample to be irradiated with very finely focused He+ and Ne+ primary ion
beams. This allows sub-nanometer spatial resolution when working with the secondary electron (SE) detection mode as imaging mode. Furthermore, the instrument incorporates a compact secondary ion mass spectrometer (SIMS) for chemical analysis of samples with excellent sensitivity and high dynamic range. The mass spectrometer is based on a double focusing magnetic sector design and allows sub-20 nm chemical imaging resolution [6-8]. Moreover, the SIMS system incorporates a new kind of detector for parallel mass detection providing a full mass spectrum for each analyzed pixel. The third newly developed detection mode available within the instrument is a position sensitive transmission detector located at the backside of the sample in order to detect the transmitted He beam. This scanning transmission helium ion microscopy (STHIM) mode provides further in-situ structural/compositional data with tomographic capabilities.
In order to optimize the analysis of biological samples, one further key feature of the instrument is a 5-axis cryo-stage along with cryo-capabilities for sample transfers. This cryo-capability allows biological samples to be analyzed in a frozen-hydrated state, thus avoiding artefacts caused by classical sample preparation (e.g. chemical fixation) used for HV or UHV imaging of biological specimens at room temperature. Moreover, the cryo-mode can be beneficial for analyzing beam sensitive samples in materials science such as OLEDs and polymers.
In this work we will present the npSCOPE concept and the instrument’s overall setup, report on the performance of the different detection modes and discuss the correlative microscopy capabilities. We will present results from case studies in different fields, with a particular focus on nanoparticles (see Figure 1) [9].

Keywords: Helium Ion Microscopy; Scanning transmission ion microscopy; SIMS

  • Lecture (Conference)
    Microscopy & Microanalysis 2020, 02.-06.08.2020, Milwaukee, USA

Publ.-Id: 30808

Why should we care about microorganisms in the bentonite back fill material for the storage of high-level radioactive waste in deep geological repositories?

Matschiavelli, N.; Dressler, M.; Neubert, T.; Kluge, S.; Schierz, A.; Cherkouk, A.

Every year 12,000 metric tonnes of high-level radioactive waste (HLW) are produced worldwide. For the long-term storage of this highly radiotoxic waste, a deep geological disposal by using multiple barriers is favored. Bentonite is proposed as a potential material for sealing the space between the canister containing the HLW and the surrounding host rock. In order to investigate the microbial diversity and metabolic activity of naturally occurring microorganisms as well as their time-dependent evolution, we conducted anaerobic microcosm experiments containing bentonite and a synthetic Opalinus Clay pore water solution. During the one-year incubation at 30 and 60 °C, lactate- or H2-stimulated microcosms at 30 °C showed the dominance and activity of strictly anaerobic, sulfate-reducing and spore-forming microorganisms. The subsequent generation of hydrogen sulfide gas in the respective set ups, led to the formation of fractures and iron-sulfur precipitations. In microcosms that incubated at 60 °C, thermophilic bacteria dominated, independent from the availability of substrates. In the respective microcosms, no significant metabolic activity was detected and there was no change in the analyzed bio-geochemical parameters. Our results show that indigenous microorganisms evolve in a temperature- and substrate-dependent manner. Potentially formed metabolites could affect the dissolution behavior of minerals and ions within the bentonite as well as the corrosion process of the canister material and require further investigations.

  • Lecture (Conference)
    6th Joint Conference of DGHM & VAAM, 08.-11.03.2020, Leipzig, Deutschland

Publ.-Id: 30807

The Potential Role of Colloidal Silica as a Depressant in Scheelite Flotation

Kupka, N.; Babel, B. M.; Rudolph, M.

The main challenge in scheelite flotation lies in the contamination of the concentrate by other calcium-bearing minerals, mainly calcite. To remedy this problem, sodium silicate is frequently used as a depressant. According to the literature, one hypothesis for the mechanism of water glass consists in its absorption onto calcite through colloidal silica formation, preventing hydrophobization by the collector. This short communication presents research conducted on the direct use of colloidal silica as a depressant in scheelite flotation. Colloidal silica is shown to have an impact on scheelite flotation, especially by depressing silicates.

Keywords: scheelite flotation; colloidal silica; depressant

Publ.-Id: 30806

Acidified water glass in the selective flotation of scheelite from calcite, Part I: performance and impact of the acid type

Kupka, N.; Möckel, R.; Rudolph, M.

To improve the performance of sodium silicate in scheelite flotation and allow the selective separation of scheelite from other semi-soluble salt-type minerals such as calcite, three acids, sulfuric, oxalic and for the first time hydrochloric are used to acidify sodium silicate (also called water glass). A literature review of previous usage of acidified water glass shows that no comparison between acids was made before, that comparisons with alkaline water glass were limited and that the idea that acidified water glass is more efficient at lower dosages has not been proven in scheelite flotation. As a consequence, the impact of the acid type, the ratio between acid and sodium silicate and acid dosage is tested in single mineral flotation and batch flotation experiments. All three acids allow a higher performance of acidified water glass compared to alkaline water glass at lower dosages and with little addition of acid: the tungsten recovery and grade are improved while silicates and to a lesser extent calcium-bearing minerals float less. The dosage of acid is less determining than the mass ratio of the acid to sodium silicate, except in the case of hydrochloric acid. Overall, the acid type does not matter as all three acids perform well in flotation, whereby oxalic and hydrochloric acid are better.

Keywords: acidified water glass; scheelite calcite separation; froth flotation

  • Open Access Logo Physicochemical Problems of Mineral Processing 56(2020)2, 238-251
    DOI: 10.37190/ppmp19101

Publ.-Id: 30805

Rapid Thermodynamically Stable Complex Formation of [nat/111In]In3+, [nat/90Y]Y3+, and [nat/177Lu]Lu3+ with H6dappa

Kostelnik, T.; Xiaozhu, W.; Southcott, L. D.; Wagner, H.; Kubeil, M.; Stephan, H.; Jaraquemada-Pelaez, M. D. G.; Orvig, C.

A phosphinate-bearing picolinic acid-based chelating ligand (H6dappa) was synthesized and characterized to assess its potential in a bifunctional chelator (BFC) for inorganic radiopharmaceuticals. Nuclear magnetic resonance (NMR) spectroscopy was employed to investigate the chelator coordination chemistry with a variety of nonradioactive trivalent metal ions (In3+, Lu3+, Y3+, Sc3+, La3+, Bi3+). Density functional theory (DFT) calculations explored the coordination environments of aforementioned metal complexes. The thermodynamic stability of H6dappa with four metal ions (In3+, Lu3+, Y3+, Sc3+) was deeply investigated via potentiometric and spectrophotometric (UV-vis) titrations, employing a combination of acidic in-batch, joint potentiometric/spectrophotometric, and ligand-ligand competition titrations; high stability constants and pM values were calculated for all four metal complexes. Radiolabeling conditions for three clinically relevant radiometal ions were optimized ([111In]In3+, [177Lu]Lu3+, [90Y]Y3+), and the serum stability of [111In][In(dappa)]3- was studied. Through concentration-, time-, temperature-, and pH-dependent labeling experiments, it was determined that H6dappa radiolabels most effectively at near-physiological pH for all radiometal ions. Furthermore, very rapid radiolabeling at ambient temperature was observed, as maximal radiolabeling was achieved in less than one minute. Molar activities of 29.8 GBq/mol and 28.2 GBq/mol were achieved for [111In]In3+ and [177Lu]Lu3+, respectively.

Publ.-Id: 30804

Special issue of the American Journal of Science

Fischer, C.; Arvidson, R. S.

This is the second part of a special issue of the American Journal of Science examining a problem that defines, perhaps more than any other, the state-of-the-art in the geochemistry of fluid-solid interaction: how to integrate data from both observations and modeling of events of brief duration at essentially atomic scales (for example, attachment, diffusion, detachment, hydrolysis), to that of mesoscale, ensemble processes (crystal dissolution, growth, alteration). The ultimate goal is an understanding of the long-term, phenomenological consequences of these interactions, often termed “upscaling”. Success in predicting and constraining these latter outcomes determines the larger value of this field, both to neighbors in environmental sciences and engineering, as well as to the public in terms of policy, education, and support. Nanoscale observation of mineral surfaces via instruments such as AFM and VSI is now widespread; increases in resolution and analytical capability of these instruments have also evolved in tandem with advances in the power and resolution of simulation and modeling approaches. Closely tied to an emerging theoretical framework, this “soft” progress in simulation and modeling was the focus of the first part of this issue.

  • Book (Editorship)
    New Haven CT 06220-8109: American Journal of Science, Yale University, 2020
    101 Seiten


Publ.-Id: 30803

Resource Efficiency Evaluation of Pyrometallurgical Solutions to Minimize Iron-Rich Residues in the Roast-Leach-Electrowinning Process

Abadias Llamas, A.; Bartie, N.; Heibeck, M.; Stelter, M.; Reuter, M. A.

The Roast-Leach-Electrowinning process generates considerable quantities of iron-rich precipitates that must be landfilled, potentially causing a problem for the zinc smelters as well as negatively affecting the society and the environment. The integration of pyrometallurgical flowsheets into existing Roast-Leach-Electrowinning plants is evaluated in this paper. Ten different cases, including Direct Zinc Smelting, ferrite fuming or pyrometallurgical treatment of iron-rich residue, are assessed to find the most resource efficient and environmentally friendly solution to minimize the hydrometallurgical precipitates of the electrolytic process for the zinc production. The simulation-based methodology used provides indicators to evaluate the material recovery and losses, residue production, resource consumption, exergy destruction, and environmental impacts, which are used to find the best alternative that improves the resource efficiency and the environmental impact of the Roast-Leach-Electrowinning process. Furthermore, the social, environmental, and economic impacts associated to the different alternatives are discussed based on the indicators provided by the simulation.

Keywords: Exergy; Thermoeconomics; Process simulation; Sustainability evaluation; Jarosite treatment

  • Contribution to proceedings
    PbZn 2020: 9th International Symposium on Lead and Zinc Processing, 23.-27.02.2020, San Diego, United States
    PbZn 2020: 9th International Symposium on Lead and Zinc Processing: Springer, Cham, 978-3-030-37069-5, 351-364
    DOI: 10.1007/978-3-030-37070-1_31

Publ.-Id: 30802

Late complications following neo-/adjuvant radiotherapy and surgery for sarcomas of the extremities or pelvis/retroperitoneum Preventative measures

Jentsch, C.; Hofbauer, C.; Makocki, S.; Troost, E. G. C.

Radiotherapy is one of the pillars in the multimodal therapy of sarcomas of the extremities or pelvis/retroperitoneum. It can be delivered prior to or following surgery. Novel radiation techniques, such as intensity-modulated radiotherapy using high-energy photons or protons, contribute to the reduction of acute and late toxicities. This review article summarizes these concepts.

Keywords: Limb; Photon beam therapy; Proton beamtherapy; Radiotherapy, intensity-modulated; Soft tissue neoplasms


  • Secondary publication expected

Publ.-Id: 30801

L1 cell adhesion molecule confers radioresistance to ovarian cancer and defines a new cancer stem cell population

Terraneo, N.; Jacob, F.; Peitzsch, C.; Dubrovska, A.; Krudewig, C.; Huang, Y.-L.; Heinzelmann-Schwarz, V.; Schibli, R.; Béhé, M.; Grünberg, J.

Many solid tumors, including ovarian cancer, contain small populations of cancer stem cells (CSCs). These cells are usually resistant against conventional cancer therapies and play a role in disease recurrence. We demonstrated that the L1 cell adhesion molecule (L1CAM) is a new CSC target in ovarian cancer, triggering radioresistance. Using fluorescence-activated cell sorting, specific cell populations expressing L1CAM alone or in combination with the established CSC marker CD133 were isolated from three ovarian cancer cell lines. Double-positive L1CAM+/CD133+ cells displayed higher spherogenic and clonogenic properties in comparison to L1CAM−/CD133− cells. Furthermore, L1CAM+/CD133+ cells retained highest clonogenic capacity after irradiation and exhibited up-regulation of some CSC-specific genes, enhanced tumor-initiating capacity, selfrenewal and higher tumor take rate in nude mice when compared with other cell populations. Superior radioresistance by L1CAM expression was confirmed by deletion of L1CAM using CRISPR-Cas9 technology. Moreover, we found expression signatures associated with epithelial-tomesenchymal transition phenotype in L1CAM deleted cells. These results indicate that L1CAM in combination with CD133 defines a new cancer cell population of ovarian tumor-initiating cells with the implication of targeting L1CAM as a novel therapeutic approach for ovarian CSCs.

Keywords: L1 cell adhesion molecule; ovarian cancer; stem cells; radioresistance; CRISPR-Cas9; epithelial-to-mesenchymal transition

Publ.-Id: 30800

Identification of the regime boundaries in bubble columns based on the degree of randomness in the signals

Nedeltchev, S.; Top, Y.; Hlawitschka, M. W.; Schubert, M.; Bart, H.-J.

A new parameter (degree of randomness (DR)) was defined for the identification of the main transition velocities, Utrans. The new method reconstructs the time series into multiple state vectors, thus generating non-overlapping vector pairs and then compares the distance between them with a pre-selected cut-off length. The DR values were extracted from gauge and differential pressure fluctuations as well as x-ray tomographic scans. At every Utrans value, the DR index exhibited a well-pronounced local minimum. Three cylindrical bubble columns (BCs) with various diameters (0.1, 0.14, and 0.45 m in ID) and one rectangular BC (width = 0.2 m, depth = 0.04 m) were used. They were aerated by means of different perforated plate gas distributors. It was found that in the cylindrical BCs the disintegration of the bubbly flow regime took place always at Utrans = 0.04 m/s. In the case of the rectangular BC the first critical velocity appeared at Utrans = 0.012 m/s. The lower boundary of the churn-turbulent regime was identified at Utrans = 0.11 m/s in the smallest cylindrical BC and at about Utrans = 0.095 m/s in the other two cylindrical BCs. In the case of the rectangular BC, the second critical velocity was identified at Utrans = 0.039 m/s. The low Utrans in the rectangular BC imply that the hydrodynamic regimes are less stable in this particular column due to higher degree of liquid turbulence. The calculated DR values from the gauge pressure fluctuations successfully distinguished the upper boundary of the gas maldistribution and the first transition sub-regime.

Keywords: bubble columns; pressure fluctuations; regime transitions; signal randomness; tomographic scans


Publ.-Id: 30799

Random singlet state in Ba5CuIr3O12 single crystals

Volkov, P. A.; Won, C.-J.; Gorbunov, D.; Kim, J.; Ye, M.; Kim, H.-S.; Pixley, J. H.; Cheong, S.-W.; Blumberg, G.

We study the thermodynamic and high-magnetic-field properties of the magnetic insulator Ba5CuIr3O12, which shows no magnetic order down to 2 K, consistent with a spin-liquid ground state. While the temperature dependence of the magnetic susceptibility and the specific heat shows only weak antiferromagnetic correlations, we find that the magnetization does not saturate up to a field of 59 T, leading to an apparent contradiction. We demonstrate that the paradox can be resolved, and all of the experimental data can be consistently described within the framework of random singlet states. We demonstrate a generic procedure to derive the exchange coupling distribution P(J ) from the magnetization measurements and use it to show that the experimental data are consistent with the power-law form P(J ) ∼ J−α with α ≈ 0.6. Thus, we reveal that high-magnetic-field measurements can be essential to discern quantum spin-liquid candidates from disorder dominated states that do not exhibit long-range order.

Publ.-Id: 30798

Spin-lattice coupling in a ferrimagnetic spinel: Exotic H-T phase diagram of MnCr2S4 up to 110 T

Miyata, A.; Suwa, H.; Nomura, T.; Prodan, L.; Felea, V.; Scurschii, I.; Deisenhofer, J.; Krug Von Nidda, H.-A.; Portugall, O.; Zherlitsyn, S.; Tsurkan, V.; Wosnitza, J.; Loidl, A.

In antiferromagnets, the interplay of spin frustration and spin-lattice coupling has been extensively studied as the source of complex spin patterns and exotic magnetism. Here, we demonstrate that, although neglected in the past, the spin-lattice coupling is essential to ferrimagnetic spinels as well. We performed ultrahigh-field magnetization measurements up to 110 T on a Yafet-Kittel ferrimagnetic spinel, MnCr2S4, which was complemented by measurements of magnetostriction and sound velocities up to 60 T. Classical Monte Carlo calculations were performed to identify the complex high-field spin structures. Our minimal model incorporating spin-lattice coupling accounts for the experimental results and corroborates the complete phase diagram, including two new high-field phase transitions at 75 and 85 T.Magnetoelastic coupling induces striking effects: An extremely robust magnetization plateau is embedded between two unconventional spin-asymmetric phases. Ferrimagnetic spinels provide a new platform to study asymmetric and multiferroic phases stabilized by spin-lattice coupling.

Publ.-Id: 30796

High-field phase transitions in the orbitally ordered multiferroic GeV4S8

Felea, V.; Pham, T. C.; Prodan, L.; Gorbunov, D.; Nomura, T.; Scurschii, I.; Zherlitsyn, S.; Wosnitza, J.; Wang, Z.; Miyata, A.; Portugall, O.; Widmann, S.; Krug Von Niddy, H.-A.; Deisenhofer, J.; Tsurkan, V.; Loidl, A.

The high-field (H,T) phase diagram of the multiferroic lacunar spinel GeV4S8 has been studied by ultrasound, magnetization, and pyrocurrent experiments in magnetic fields up to 60 T. The title compound consists of molecular building blocks, with vanadium V4 clusters characterized by a unique electron density. These vanadium tetrahedra constitute a Jahn-Teller active entity, which drive an orbital-ordering transition at 30K with the concomitant appearance of ferroelectricity. Ultrasound and magnetization experiments reveal sharp anomalies in magnetic fields of 46 T, which are associated with a first-order phase transition into an orbitally disordered state characterized by significant field and temperature hystereses. We report a sequence of complex magnetic, polar, and orbitally ordered states, i.e., the appearance of two orbitally ordered phases OO1 and OO2 for μ0H < 45 T and T < 30K. Beyond the paraelectric phase we further evidenced three ferroelectric phases, FE1, FE2, and FE3. Finally, antiferromagnetic (AFM) order (T < 15 K) and fully polarized ferromagnetic order (μ0H > 60 T) have been observed in GeV4S8. At low temperatures and for fields below 40 T, AFM order coexists with the polar phase FE3 identifying a multiferroic state. Our results demonstrate a fascinating competition of the different orders, which the material manifests in high magnetic fields and at low temperatures.

Publ.-Id: 30795

Structure and magnetic properties of (Sm,Ho)2Fe17Nx (x = 0; 2.4)

Veselova, S. V.; Tereshina, I. S.; Verbetsky, V. N.; Neznakhin, D. S.; Tereshina-Chitrova, E. A.; Kaminskaya, T. P.; Karpenkov, A. Y.; Akimova, O. V.; Gorbunov, D.; Savchenko, A. G.

The structural and magnetic properties of the compound Sm1.2Ho0.8Fe17 and the nitride powders Sm1.2Ho0.8Fe17N2.4 prepared by high energy ball milling under various milling regimes are reported. Magnetic properties of the samples are investigated at 2–300 K in steady magnetic field up to 70 kOe and in pulsed magnetic field up to 600 kOe. The application of high magnetic field reveals the presence of the second-order transition in Sm1.2Ho0.8Fe17N2.4 at 500 kOe. Magnetic hysteresis properties study shows that ball milling enhances magnetic performance of Sm1.2Ho0.8Fe17N2.4 making it perspective for the magnets fabrication.

Publ.-Id: 30794

Noncollinear magnetic structure in U2Pd2In at high magnetic fields

Prokes, K.; Bartkowiak, M.; Gorbunov, D.; Prokhnenko, O.; Rivin, O.; Smeidbidl, P.

We report an unexpected magnetic-field-driven magnetic structure in the 5 f -electron Shastry-Sutherland system U2Pd2In. This phase develops at low temperatures from a noncollinear antiferromagnetic ground state above the critical field of 25.8 T applied along the a axis. All U moments have a net magnetic Moment in the direction of the applied field, described by a ferromagnetic propagation vector qF = (0 0 0) and an antiferromagnetic component described by a propagation vector qAF = (0 0.30 1/2 ) due to a modulation in the direction perpendicular to the applied field. We conclude that this surprising noncollinear magnetic structure is due to a competition between the single-ion anisotropy trying to keep moments, similar to the ground state, along the [110]-type directions, Dzyaloshinskii-Moryia interaction forcing them to be perpendicular to each other and application of the external magnetic field attempting to align them along the field direction.

Publ.-Id: 30793

Slurm in Docker

Pape, D.

A Docker image with a Slurm setup to enable testing of HPC software in a container.

Keywords: Docker; Slurm; batch system; high performance computing; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: Dockerfile, Shell
    System requirements: Docker Engine
    License: GPL v3 (Link to license text)
    Hosted on

Publ.-Id: 30792

GitLab HPC Driver Protoype

Pape, D.

GitLab HPC Driver prototype implementation.

Keywords: continuous integration; high performance computing; GitLab; Slurm; batch system; scientific software; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: Bash
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on

Publ.-Id: 30791

GitLab HPC Driver

Pape, D.

Um gute Performance und Skalierbarkeit von hochparalleler wissenschaftlicher Software sicherzustellen, ist es wichtig, diese in einer möglichst realitätsnahen Umgebung zu testen. Wünschenswert ist dabei ein möglichst einfacher Zugriff auf die HPC-Ressourcen über ein bereits etabliertes System wie GitLab CI. Dafür wurde ein Driver für den GitLab-Runner entwickelt, der es erlaubt Continuous-Integration-Jobs auf Hochleistungsrechnern auszuführen. Der Driver wird vom GitLab-Runner-Service aufgerufen und kann vom Nutzer auf die gleiche Art und Weise verwendet werden, wie andere im GitLab-Ökosystem bekannte CI-Systeme. Es werden HPC-Ressourcen unterstützt, die vom Batchsystem Slurm verwaltet werden.

To ensure high performance and scalability in scientific software, a realistic testing environment plays an important role. Preferably, easy access to HPC resources is enabled via an established tool like GitLab CI. For that, a driver for GitLab runner has been developed that allows the execution of CI jobs on a supercomputer. The driver is called by GitLab runner service and can be used in the same way as other tools in the GitLab ecosystem. It supports HPC resources managed by the Slurm batch system.

Keywords: continuous integration; high performance computing; GitLab; Slurm; batch system; scientific software; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on

Publ.-Id: 30790

Two-Pion Intensity Interferometry in Au + Au @ 1.23A GeV

Greifenhagen, R.; (for the HADES collaboration)

High-statistics π−π− HBT data for non-central Au + Au collisions at 1.23A GeV, measured with HADES at SIS18/GSI, are presented. The three-dimensional emission source is studied in dependence on pair transverse momentum and centrality. A tilt of the source relative to the beam axis is observed. The spatial extension and the tilt magnitude of the source decrease with transverse momentum. The spatial extension decreases and the tilt magnitude increases going from central to peripheral collisions. The derived eccentricity perpendicular to the beam axis fits well to the initial nucleonic overlap region at high transverse momentum.

Related publications

Publ.-Id: 30789

The tectono-sedimentary evolution of a major seismogenic zone with low slip rate activity: A geochronological and sedimentological investigation of the Dobrá Voda Depression (Western Carpathians)

Šujan, M.; Braucher, R.; Šujan, M.; Hók, J.; Povinec, P. P.; Šipka, F.; Rugel, G.; Scharf, A.

Seismically active fault zones receive a great deal of attention due to their potential for quantification of seismic hazards. Zones with low slip rates pose a challenge, however, since their poor topographic expression is related to difficulties in the quantification of fault movement. This study focuses on the Dobrá Voda Depression, an area with the highest level of seismic activity in the Western Carpathians. The Quaternary tectono-sedimentary evolution of the small intramontane basin was investigated with the use of facies analysis of cores, dated with the use of cosmogenic nuclide depth profiles (10Be, 26Al and 36Cl), together with 26Al/10Be burial dating and radiocarbon dating. A set of archived boreholes and geoelectric survey data was used for the correlation of results with those from new boreholes across the depression. Four facies associations were distinguished: (FA1) Colluvial deposits that comprise subaerial debris flows and mudflows; (FA2) Fluvial deposits with high sediment supply: accommodation ratio, composed mostly of sandy-gravelly channel fill facies; (FA3) Fluvial deposits with low sediment supply: accommodation ratio, consisting mostly of floodplain muds, overbank heterolithic facies and minor sandy-gravelly channel fills; and (FA4) Swamp deposits, which are mostly made up of peat. Geochronological results suggest that the studied part of FA3 was deposited before 1.0 Ma due to a rise in the base level following a major incision event. Overbank-dominated deposits of FA3 covered an incision surface, resulted in a difference of ca. 65 m of elevation of these strata, which represents the minimal thickness of FA3. The second phase of incision was related to reactivation of Miocene normal faults resulting in further topographic differentiation. The initiation of fault activity is recorded by the deposition of colluvial FA1 before ca. 250 ka. FA2 accumulated between ca. 160 and 100 ka, mostly at the toes of slopes bounding the fault scarps on the basin margins. The last documented phase of evolution represents an increase of accommodation, which was connected to the deposition of Holocene peat in swamps as well as floodplain muds of FA4 above FA2. The observed settings imply that variation between incision and accumulation in a scale of hundreds of thousands of years is characteristic for low relief tectonically active zones. The presented research demonstrates the significance of sedimentological analysis for reconstruction of tectonic evolution in areas with low slip rate activity.

Keywords: Depth profile exposure dating of 10Be; 26Al and 36Cl; AMS


  • Secondary publication expected

Publ.-Id: 30788

Positron annihilation analysis of nanopores and growth mechanism of oblique angle evaporated TiO₂ and SiO₂ thin films and multilayers

García-Valenzuela, A.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Trinh, T. T.; Elsherif, A. G. A.; Wagner, A.; Alvarez, R.; Gil-Rostra, J.; Rico, V.; Palmero, A.; González-Elipe, A. R.

The nano-porosity embedded into the tilted and separated nanocolumns characteristic of the microstructure of evaporated thin films at oblique angles has been critically assessed by various variants of the positron annihilation spectroscopy. This technique represents a powerful tool for the analysis of porosity, defects and internal interfaces of materials, and has been applied to different as-deposited SiO₂ and TiO₂ thin films as well as SiO₂/TiO₂ multilayers prepared by electron beam evaporation at 70° and 85° zenithal angles. It is shown that, under same deposition conditions, the concentration of internal nano-pores in SiO₂ is higher than in TiO₂ nanocolumns, while the situation is closer to this latter in TiO₂/SiO₂ multilayers. These features have been compared with the predictions of a Monte Carlo simulation of the film growth and explained by considering the influence of the chemical composition on the growth mechanism and, ultimately, on the structure of the films.

Keywords: Positron annihilation; Nanopores; OAD thin films; TiO₂; SiO₂; Growing mechanism

Publ.-Id: 30787

Revealing the defect-dominated oxygen evolution activity of hematene

Bishnupad, M.; Wei, Y.; Ghorbani Asl, M.; Krasheninnikov, A.; Parasmani, R.; Bikash, K. J.

Oxygen electrocatalysis is vital for advanced energy technologies, but inordinate challenges remain due to the lack of highly active earth-abundant catalysts. Herein, by nanostructuring and defect engineering, we enhance the catalytic properties of naturally occurring, but normally inactive ore hematite (Ht) by converting it to hematene (Hm) with oxygen vacancies (Ov-Hm), that becomes an efficient oxygen evolution reaction (OER) catalyst, being even superior to the state-of-the-art catalyst IrO2/C, with a current density of 10 mA/cm2 at a lower overpotential of 250 mV. The first-principles calculations reveal that the reduced dimensionality and defects on the Hm surface locally modify the charge around the adsorption sites, which results in a reduction of the potential barrier in the OER process. Our experimental and theoretical insights suggest a promising route to the development of a highly active electrocatalyst from the naturally occurring and abundant material for OER applications.

Keywords: hemetene; defect; electrocatalysis; oxygen evolution reaction


Publ.-Id: 30786

Chelation in One Fell Swoop: Optimizing Ligands for Smaller Radiometal Ions

Choudhary, N.; Jaraquemada-Pelaez, M.; Zarschler, K.; Wang, X.; Radchenko, V.; Kubeil, M.; Stephan, H.; Orvig, C.

44/47Sc3+, 68Ga3+ and 111In3+ are the three most attractive trivalent smaller radiometalnuclides, offering a wide range of distinct properties (emission energies and types) in the toolbox of nuclear medicine. In this study, all three of the metal ions are successfully chelated using a new oxine-based hexadentate ligand, H3glyox, which forms thermodynamically stable and kinetically inert neutral complexes with exceptionally high pM values [pIn (34) > pSc (26) > pGa (24.9)]. X-ray diffraction single crystal structures with stable isotopes revealed that the ligand is highly preorganized and has a perfect fit to size cavity to form [Sc(glyox)(H2O)] and [In(glyox)(H2O)] complexes. Quantitative radiolabeling of 68Ga (RCY > 95%, [L]= 10-5 M) and 111In (RCY > 99%, [L]= 10-8 M) was achieved at ambient conditions (RT, pH 7 and 15 min) with very high apparent molar activities of 750 MBq/mol and 650 MBq/nmol, respectively. Preliminary quantitative radiolabeling of 44ScCl3 (RCY > 99%, [L] = 10-6 M) was fast at room temperature (pH 7 and 10 min). In vitro experiments revealed exceptional stability of both 68Ga(glyox) and 111In(glyox) complexes against human serum (rate of transchelation < 2%) and its suitability for biological applications. Additionally, on chelation with metal ions, H3glyox exhibits enhanced fluorescence which was employed to determine the stability constants for Sc(glyox) complex in addition to the in-batch UV-vis spectrophotometric titrations; as a proof-of-concept these complexes were used to obtain fluorescence images of live HeLa cells using natSc(glyox) and natGa(glyox), confirming the viability of the cells. These initial investigations suggest H3glyox to be a valuable chelator for radiometalbased diagnosis (nuclear and optical imaging) and therapy.

Publ.-Id: 30785

Numerical simulation of formation and growth of fractal-like aggregates in a tubular aerosol reactor

Lehnigk, R.; Niemi, T.; Peltola, J.; Schlegel, F.

Ceramic powders produced by gas phase synthesis frequently consist of non-spherical, fractal-like particle aggregates. Their shape is a result of the simultaneous action of particle coagulation and sintering. Coagulation describes the process of particle agglomeration, e.g. due to ballistic or diffusion-limited collisions, whereas sintering stands for coalescence of primary particles and acts to create denser aggregates. A low density aggregate has a larger collisional cross-section and thus is more likely to collide with other particles or aggregates, which is reflected in the development of the aggregate size distribution and should be taken into account when modeling the process. To this end, a class method based population balance modeling approach available in OpenFOAM was extended to allow for a simplified bivariate treatment. Among the many shape-characterizing parameters, the average surface-area-to-volume ratio of each size class is tracked by a separate transport equation. Together with a fixed fractal dimension, it can be translated into a collisional diameter and further used when calculating coagulation rates. The functionality is showcased by a simulation of the vapor synthesis of Titania in a tubular aerosol reactor [Akhtar et al., AlChE J., 37(10): 1561-1570, 1991]. Data from a differential mobility sizer is used to validate the approach.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Computational Fluid Dynamics und Gasreinigung, 09.-11.03.2020, Bamberg, Deutschland

Publ.-Id: 30784

Spin-polarized positrons. Who cares?

Wagner, A.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Elsherif, A. G. A.

Proposal for a spin-polarized positron beam facility at the upcoming DALI facility

Keywords: spin-polarized positrons

  • Lecture (others)
    Treffen deutschsprachiger Positronengruppen, 13.-14.02.2020, Halle (Saale), Deutschland

Publ.-Id: 30783

Materials Research with Positrons – From atomic defects to nano-scale porosimetry

Wagner, A.

Materials Research with Positrons – From atomic defects to nano-scale porosimetry

Keywords: Materials Research Positrons atomic defects nano-scale porosimetry

  • Invited lecture (Conferences)
    Spectroscopic methods and synchrotron XRD for materials characterization, 05.03.2020, Kista, Sweden

Publ.-Id: 30782

Quaternary landscape evolution in a tectonically active rift basin (paleo-lake Mweru, south-central Africa)

Olivotos, S.; Niedermann, S.; Flügel, T.; Mouslopoulou, V.; Merchel, S.; Cotterill, F.; Bookhagen, B.; Gärtner, A.; Rugel, G.; Scharf, A.; Nadeau, M.-J.; Braucher, R.; Seiler, M.

Lake Mweru, located between the Northern Province of Zambia and the south-eastern Katanga Province of the Democratic Republic of Congo, is part of the southwest extension of the East African Rift System (EARS). Fault analyses have revealed that the Mweru-Mweru Wantipa fault system (MMFS) was formed due to the NW-SE rotation of the extension direction of the EARS and is responsible for the reorganization of the drainage system of the area since the Miocene, creating knickpoints as a result of intense seismic activity. Twenty-six quartzitic bedrock samples were collected predominantly from knickpoints across the Mporokoso Plateau (south of Lake Mweru, Zambia) and the eastern part of the Kundelungu Plateau (north of Lake Mweru, DRC). These samples were analyzed for in-situ cosmogenic ¹⁰Be and ²⁶Al using Accelerator Mass Spectrometry. Samples from the Mporokoso Plateau and close to the MMFS provide evidence of temporary cover. Samples located far from the MMFS have consistent ¹⁰Be and ²⁶Al exposure ages ranging up to ~830 ka, indicating that these surfaces were never covered since their initial exposure. The observed burial patterns, combined with morphotectonic analyses of the drainage system and evidence of lacustrine sediments, reveal the existence of an extensive paleo-lake during the Pleistocene.
Elevational analyses of the dated knickpoints constrain the level of the paleo-lake to around 1200 m asl and its area to around 40000 km².
Calculated high denudation rates (up to ~40 mm ka-1) along the eastern Kundelungu Plateau suggest that tectonic forcing caused the breaching of the paleo-lake. Ensuing outflow gouged a deep-sided canyon, today occupied by the underfitting Luvua River. The complex exposure histories recorded in our study area by ¹⁰Be and ²⁶Al can be a result of waterlevel fluctuations caused by intense climate variations across southeastern Africa, coupled with active rifting along the MMFS.

Keywords: Landscape evolution; Paleo-lake Mweru; Terrestrial cosmogenic nuclides; East African Rift System

Publ.-Id: 30781

Elucidating the mechanism of uranium uptake and processing in tobacco BY-2 cells

John, W.; Matschiavelli, N.; Thieme, D.; Hoehenwarter, W.; Sachs, S.

The release of uranium from waste repositories into the ground water and surrounding soil can have adverse effects on the biomes of affected sites. The bioavailability and chemical toxicity of U(VI) species, which are the most prevalent in oxic environments of soils and water bodies, can pose serious threats as they are transferred through the food chain. Despite remediation strategies employing the cultivation of crop plants to sequester uranium, little is known of the mechanisms used by plants in processing the uranium species that they encounter. The aim of this research therefore has been to shed light on the pathways involved in the uptake and processing of uranium by plant cells, using the undifferentiated tobacco BY-2 cells as model plant cells. Former experiments showing increases in the cytoplasmic glutathione pools upon exposure of Brassica napus cell cultures to uranium have led us to the hypothesis that tobacco cells are able to reduce U(VI) to U(IV). This research describes a novel method of exposing BY-2 cells to U(VI) in phosphate deficient medium, which maintains relatively high cell viability under phosphate deficient conditions, and reveals differentially expressed proteins in the presence of uranium. Uranium-spiked culture medium was seen to affect the uptake of trace elements and minerals as well as show changes in the profiles of polyacrylamide-resolved proteins. Proteomics is being used to identify candidate proteins involved in the processing of uranium by the cells and microscopic visualization techniques are utilized to confirm these pathways and mechanisms.

Acknowledgments: This work is funded by the German Federal Ministry of Education and Research under the contract number 02NUK051B.

Keywords: uranium; nuclear waste; metal uptake; tobacco cells

  • Lecture (Conference) (Online presentation)
    Biometals 2020, 05.-09.07.2020, Villard de Lans, Frankreich

Publ.-Id: 30779

P1817 - Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten

Vishwakarma, V.; Schleicher, E.; Schubert, M.; Tschofen, M.; Löschau, M.

Gegenstand der vorliegenden Erfindung ist eine Vorrichtung zur Bestimmung des Strömungsprofils von Mehrphasenströmungen mit mindestens einer Flüssigkeitskomponente mit vorgegebener Strömungsrichtung. Die Vorrichtung weist eine Mehrzahl von stabförmigen Sonden auf. Jede der Sonden weist zwei parallel verlaufende Elektroden aus, die in einer gemeinsamen elektrisch isolierenden Umhüllung angeordnet sind. Darüber hinaus weist jede Sonde mindestens eine Abschirmelektrode auf. Eine Elektrode jeder Sonde fungiert als Transmitter (Sender) und die zweite Elektrode jeder Sonde als Receiver (Empfänger). Eine Auswerteeinheit ist dazu eingerichtet, die Transmitterelektrode jeder Sonde mit elektrischer Spannung als Messspannung zu beaufschlagen und das Ergebnissignal an der Receiverelektrode derselben Sonde zu erfassen. Mindestens zwei Sonden sind zu einer Gruppe zusammengefasst, wobei die Auswerteeinheit zum gleichzeitigen Beaufschlagen der Sonden dieser Gruppe mit der Messspannung ausgebildet ist.

  • Patent
    DE102018124501 - Erteilung 13.02.2020

Publ.-Id: 30778

Essential Role of Heterocyclic Structure of N-Alkylated 2-Pyrrolidone Derivatives for Recycling Uranium from Spent Nuclear Fuels

Inoue, T.; Kazama, H.; Tsushima, S.; Takao, K.

In a simple and versatile reprocessing method for recycling U and Pu from spent nuclear fuels, cyclic amides like N-alkylated 2-pyrrolidone derivatives (NRPs) are exclusively employed. However, there have been no convincing rationales why such a heterocyclic structure is required. To answer this question, we employed N-cyclohexyl-2-pyrrolidone (NCP) and N-cyclohexylformamide (NCF) as cyclic and acyclic monodentate amides, and focused on the following 3 topics in this study; (1) structural chemistry of their uranyl dinitrato complexes, (2) precipitation behavior of UO22+ from HNO3(aq) by using these amides, and (3) their chemical stability in HNO3(aq) simulating the reprocessing process for spent nuclear fuels. Fundamental coordination chemistry of UO2(NO3)2(L)2 (L = NCP, NCF) were found to be common to both L, regardless of the presence or absence of the pyrrolidone ring. Furthermore, both L exhibit comparable capability in precipitation of UO22+ from HNO3(aq). The most critical difference between NCP and NCF was found in their chemical stability in HNO3(aq), where NCF was gradually decomposed through acid-catalyzed hydrolysis, while NCP remained intact for at least 4 h. In conclusion, the pyrrolidone ring of NRPs plays an important role to protect the carbonyl C from nucleophilic hydrolysis which initiates the amide C(=O)−N bond cleavage.

Publ.-Id: 30776

Annual Report 2019 - Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A.

The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden –Rossendorf (HZDR). Our research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Ra-diation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. The program NUSAFE, and therefore all work which is done at IRE, belong to the research field “Energy” of the HGF...

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-110 2020
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 30774

Magnetic response of FeRh to static and dynamic disorder

Eggert, B.; Schmeink, A.; Lill, J.; Liedke, M. O.; Kentsch, U.; Butterling, M.; Wagner, A.; Pascarelli, S.; Potzger, K.; Lindner, J.; Thomson, T.; Fassbender, J.; Ollefs, K.; Keune, W.; Bali, R.; Wende, H.

Atomic scale defects generated using focused ion as well as laser beams can activate ferromagnetism in initially non-ferromagnetic B2 ordered alloy thin film templates. Such defects can be induced locally, confining the ferromagnetic objects within well-defined nanoscale regions. The characterization of these atomic scale defects is challenging, and the mechanism for the emergence of ferromagnetism due to sensitive lattice disordering is unclear. Here we directly probe a variety of microscopic defects in systematically disordered B2 FeRh thin films that are initially antiferromagnetic and undergo a thermally-driven isostructural phase transition to a volatile ferromagnetic state. We show that the presence of static disorder i.e., the slight deviations of atoms from their equilibrium sites is sufficient to induce a non-volatile ferromagnetic state at room temperature. A static mean square relative displacement of 9.10-4 Å-2 is associated with the occurrence of non-volatile ferromagnetism and replicates a snapshot of the dynamic disorder observed in the thermally-driven ferromagnetic state. The equivalence of static and dynamic disorder with respect to the ferromagnetic behavior can provide insights into the emergence of ferromagnetic coupling as well as achieving tunable magnetic properties through defect manipulations in alloys.

Publ.-Id: 30773

Accurate MR image registration to anatomical reference space for diffuse glioma

Visser, M.; Petr, J.; Müller, D. M.; Eijgelaar, R. S.; Hendriks, E. J.; Witte, M.; Barkhof, F.; van Herk, M.; Mutsaerts, H. J.; de Munck, J. C.; Vrenken, H.; de Witt Hamer, P. C.

To summarize the distribution of glioma location within a patient population, registration of individual MR images to anatomical reference space is required. In this study, we quantified the accuracy of MR image registration to anatomical reference space with linear and non-linear transformations using estimated tumor targets of glioblastoma and
lower-grade glioma, and anatomical landmarks at pre- and post-operative time-points using six commonly-used registration packages (FSL, SPM5, DARTEL, ANTs, Elastix, and NiftyReg). Routine clinical pre- and post-operative, post-contrast T1-weighted images of 20 patients with glioblastoma and 20 with lower-grade glioma were collected. The 2009a
Montreal Neurological Institute brain template was used as anatomical reference space. Tumors were manually segmented in the patient space and corresponding healthy tissue was delineated as a target volume in the anatomical reference space. Accuracy of the tumor alignment was quantified using the Dice score and the Hausdorff distance. To measure the accuracy of general brain alignment, anatomical landmarks were placed in patient and in anatomical reference space, and the landmark distance after registration was quantified. Lower-grade gliomas were registered more accurately than glioblastoma. Registration accuracy for pre- and postoperative MR images did not differ. SPM5 and DARTEL registered tumors most accurate, and FSL least accurate. Non-linear transformations resulted in more accurate general brain alignment than linear transformations, but tumor alignment was similar between linear and non-linear transformation. We conclude that linear transformation suffices to summarize glioma locations in anatomical reference space.

Publ.-Id: 30772

On the O-rich domain of the U-Am-O phase diagram

Epifano, E.; Vauchy, R.; Lebreton, R.; Lauwerier, F.; Joly, A.; Scheinost, A.; Guéneau, C.; Valot, C.; Martin, P. M.

Uranium–Americium oxides U1−yAmyO2±x are promising candidates as possible transmutation targets for next generation nuclear reactors. In the context of a comprehensive investigation of their thermodynamic and thermal properties, the behaviour in oxidizing conditions is here studied. In a recent work, the behaviour in air of stoichiometric and sub-stoichiometric U1−yAmyO2−x compounds, with various Am content, was investigated by high-temperature X-ray Diffraction. Herein, the hyper-stoichiometric oxides obtained from that study are investigated by X-ray Absorption Spectroscopy. The new data, together with the previous XRD results, allow determining the exact compositions of the samples and hence obtaining phase diagram points in the O-rich domain of the U-Am-O system. Indeed, five phase diagram points at 1473 K are obtained: two tie-lines in the M4O9-M3O8 domain, for Am/(Am + U) = 0.10 and 0.15, one tie line in the MO2+x-M3O8 domain, for Am/(Am + U) = 0.28, and two points in the single phase MO2±x domain, for higher americium concentration. From these data, it is also concluded that trivalent americium has a small solubility in the M4O9 and M3O8 phases.

Keywords: transmutation; nuclear fuel; XANES; EXAFS


  • Secondary publication expected

Publ.-Id: 30771

Terahertz absorption-saturation and emission from electron-doped germanium quantum wells

Ciano, C.; Virgilio, M.; Bagolini, L.; Baldassarre, L.; Pashkin, O.; Helm, M.; Montanari, M.; Persichetti, L.; Di Gaspare, L.; Capellini, G.; Paul, D. J.; Scalari, G.; Faist, J.; de Seta, M.; Ortolani, M.

We study radiative relaxation at terahertz frequencies in n-type Ge/SiGe quantum wells, optically pumped with a terahertz free electron laser. Two wells coupled through a tunneling barrier are designed to operate as a three-level laser system with non-equilibrium population generated by optical pumping around the 1→3 intersubband transition at 10 THz. The non-equilibrium subband population dynamics are studied by absorption-saturation measurements and compared to a numerical model. In the emission spectroscopy experiment, we observed a photoluminescence peak at 4 THz, which can be attributed to the 3→2 intersubband transition with possible contribution from the 2→1 intersubband transition. These results represent a step towards silicon-based integrated terahertz emitters.

Publ.-Id: 30769

Strömungsmorphologie flashender Feeds bei kritischen Stoffwerten

Döß, A.; Schubert, M.; Wiezorek, M.; Hampel, U.; Flegiel, F.; Windmeier, C.; Schleicher, E.

Eine gängige Methode zur Konditionierung von Zulaufströmen in Rektifikations-kolonnen ist die Entspannungsverdampfung (flash) des Feedstroms mit nachgeschalteter oder integrierter Separation der kontinuierlichen und dispersen Phasenanteile. Die Gestaltung der Einspeisung in die Kolonne sowie die Auswahl von Einleitorganen erfordert eine möglichst exakte Vorhersage der sich einstellenden Strömungsmorphologie in der Feedleitung. Verfügbare Strömungsdaten beschränken sich fast ausschließlich auf Wasser-Luft-Systeme bei geringen Rohrdurchmessern (< DN100) und großen Einlauflängen (> 40 D). Deren Übertragbarkeit auf organische oder kryogene Systeme mit z. B. deutlich geringeren Grenzflächenspannungen für praxisnahe Rohrdimensionen unterliegt dabei großen Unsicherheiten. Zur Untersuchung flashender Feeds wurde daher ein Kältemittel-Versuchsstand im Technikums¬maßstab entwickelt. Das Arbeitsfluid wird durch eine Armatur in eine horizontale Feedleitung (DN200, Länge 20 D) entspannt und tritt als Zweiphasenströmung in die nachgeschaltete Kolonne ein. Die Dampfanteile nach der Entspannungsverdampfung werden über die jeweiligen Betriebsdrücke und -temperaturen mittels Elektroerhitzer und Kreislaufpumpe eingestellt, während der Betriebsdruck in der Teststrecke über einen Kondensator im Kopfstrom der Kolonne geregelt wird. Als Betriebsmedium wird das Kältemittel 3M™ Novec™649 eingesetzt, dessen Grenzflächenspannung in einem Bereich von 2 bis 8 mN m-1 bei einer Dichtedifferenz zwischen Dampf und Flüssigkeit von 800-1500 kg m-3 bei Betriebstemperaturen bis 140 °C eingestellt werden kann. Die Charakterisierung der sich entwickelnden Strömungsmorphologie in der horizontalen Feedleitung erfolgt mittels zeitlich und räumlich hochauflösender Gittersensormesstechnik. Schwerpunkte der Untersuchungen sind dabei die axiale Entwicklung der Strömungsform zwischen Entspannungsarmatur und Kolonneneintritt sowie die Bestimmung der Phasenanteile und Strömungs¬druck¬ver-luste
Diese Arbeit findet im Rahmen des Projektes TERESA statt und wird durch das Bundesministerium für Wirtschaft und Energie (BMWI) gefördert (FKZ 03ET1395D).

  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik, Adsorption und Extraktion 2020, 25.-28.02.2020, Berchtesgaden, Deutschland

Publ.-Id: 30768

Formation of Thin NiGe Films by Magnetron Sputtering and Flash Lamp Annealing

Begeza, V.; Mehner, E.; Stöcker, H.; Xie, Y.; García, A.; Hübner, R.; Erb, D.; Zhou, S.; Rebohle, L.

The nickel-monogermanide (NiGe) phase is known for its electrical properties such as low ohmic and low contact resistance in group-IV-based electronics. In this work, thin films of nickel germanides (Ni-Ge) were formed by magnetron sputtering followed by flash lamp annealing (FLA). The formation of NiGe was investigated on three types of substrates: on amorphous (a-Ge) as well as polycrystalline Ge (poly-Ge) and on monocrystalline (100)-Ge (c-Ge) wafers. Substrate and NiGe structure characterization was performed by Raman, TEM, and XRD analyses. Hall Effect and four-point-probe measurements were used to characterize the films electrically. NiGe layers were successfully formed on different Ge substrates using 3-ms FLA. Electrical as well as XRD and TEM measurements are revealing the formation of Ni-rich hexagonal and cubic phases at lower temperatures accompanied by the formation of the low-resistivity orthorhombic NiGe phase. At higher annealing temperatures, Ni-rich phases are transforms into NiGe, as long as the supply of Ge is ensured. NiGe layer formation on a-Ge is accompanied by metal-induced crystallization and a decline of its electrical conductivity compared with that of poly-Ge and c-Ge substrates. Specific resistivities for 30 nm Ni on Ge were determined to be 13.5 uOhm cm for poly-Ge, 14.6 uOhm cm for c-Ge and 20.1 uOhm cm for a-Ge.

Keywords: germanium; germanides; nickel; thin films; sputtering; flash lamp annealing

Publ.-Id: 30767

Thermo-mechanical modelling of reactor pressure vessel during core melt invessel retention

Villanueva, W.; Filippov, A.; Jules, S.; Lim, K.; Jobst, M.; Bouydo, A. M.; Qais, S.; Wang, H.; Fichot, F.; Bechta, S.

Thermo-mechanical behavior of ablated reactor pressure vessel (RPV) during in-vessel melt retention is assessed. Specifically, we provide a preliminary synthesis of a benchmark exercise on a generic Pressurized Water Reactor (PWR) RPV with external water cooling. A two-layer pool configuration with a molten metal layer atop, reaching a local heat flux of 2 MW/m² on the vessel wall is assumed reflecting a focusing effect which in turn results in a thin ablated wall with remaining thickness of 16 mm. The aim is to investigate the effect of internal pressure on the structural integrity of the RPV. A total of 7 contributions from different organizations using 5 different codes are analyzed. The results are divided into low internal pressure cases where no vessel failure is expected, and high internal pressure cases where vessel failure is found based on specific failure criteria applied by the users. At 3 bar internal pressure, all the results reflecting stresses and strains indicate no vessel failure. Four contributions found vessel failures at internal pressure of 40, 45, 50, and 52 bars. The mode of failure in all calculations is the same, which is plastic instability caused by high stresses, although the failures are indicated by different criteria. Further, the results are compared against a simplified approach and reasonable agreement is found. Finally, a preliminary failure map is generated to demonstrate the applicability of a previously proposed methodology that utilizes a safety criterion based on the relation between the minimum vessel thickness and the maximum internal load.

  • Contribution to proceedings
    International Seminar “In-vessel retention: outcomes of IVMR project”, 21.-22.01.2020, Juan-les-Pins, France
    Proceedings of the International Seminar “In-vessel retention: outcomes of IVMR project”

Publ.-Id: 30766

Collision probability of fine particles in the bubble wake - An experimental study with 4D particle tracking velocimetry

Sommer, A.-E.; Heitkam, S.; Eckert, K.

One highly relevant challenge in flotation is the recovery of fine particles. Due to their low inertia, these particles are mostly pushed aside by rising bubbles. Consequently, they typically exhibit low probability for bubble-particle collision and thus, a poor recovery rate. In this work, the trajectories of fine particles in the vicinity of rising bubbles were investigated. The measurements considered a chain of millimetric bubbles within a rectangular container filled with deionized water. The flow field near the bubbles was measured by tomographic particle image velocimetry (TPIV), employing fluorescent tracer particles of 33µm diameter. Subsequently, trajectories of larger particles and bubble-particle collision events are recorded with 4D particle tracking velocimetry using a high temporal and spatial resolution. The results reproduce the well-known collision of particles on the leading edge of a rising bubble. Additionally, collisions on the tailing edge were observed in cases with a low Stokes number. The TPIV results demonstrate, that the high turbulent kinetic energy in the bubble wake allows particles to divert from the fluid streamlines and collide with the tailing edge of the bubble. The tailing edge collision probability increases with the Reynolds number and with decreased particle inertia. Overall, the investigation shows that the collision of fine particles in the bubble wake should be considered for the development of further collision probability models. Furthermore, the importance of turbulence on the fine particle flotation was demonstrated.

Keywords: 4D Particle tracking velocimetry (PTV); tomographic particle image velocimetry (TPIV); fine particle flotation; collision probability; Bubble-particle interaction; wake induced collision

  • Contribution to proceedings
    XXX International Mineral Processing Congress in Cape Town, 18.-22.10.2020, Kapstadt, Südafrika
    Proceedings of the XXX. International Mineral Processing Congress

Publ.-Id: 30765

In-depth 3D characterization of sieve tray hydrodynamics

Vishwakarma, V.; Abdul Haq, S.; Schubert, M.; Schleicher, E.; Hampel, U.

Understanding the tray hydrodynamics is important for their effective design as well as for the assessment of their separation performance. Currently, the clear liquid height is considered as one of the most important hydrodynamic parameters [1]. For example, it is utilized to correlate dispersion density, liquid entrainment rate, weeping flux and flow regime transitions. This height is usually measured at a point on the tray floor by continuously flushing out the liquid into the manometer. It is debatable whether such point reading is representative for the true liquid content on large trays or three-dimensional analyses should be performed. For this purpose, a sieve tray column (800 mm dia.) mockup facility is used in this work with air and tap water at respective loadings of 1.4 – 2.0 Pa0.5 and 1.0 – 3.0 m3/h that correspond to the froth regime.

A novel conductivity-based sensor [2] is developed for the 3D two-phase flow quantification at high spatial and temporal resolution. Basically, the local phase holdups at multiple locations along the sensor measurement plane and at different dispersion heights are determined here. It is assessed if the integration of the holdup profiles can lead to better estimates of the clear liquid height. Pressure drops and weeping rates are also measured. Furthermore, stimulus-response experiments with de-ionized water as tracer are performed at selective dispersion heights for identifying the flow profiles via residence time distribution.

These new 3D tray hydrodynamic data may also serve as a reference for establishing CFD models in the future, which so far have largely relied either on clear liquid height data only or on the low resolution data of Solari and Bell [3].

[1] Lockett, M.J., 1986. Distillation tray fundamentals.
[2] Vishwakarma, V., Schleicher, E., Schubert, M., Tschofen, M. and Löschau, M., Deutsche Patentanmeldung DE 10 2018 124 501.7, Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten.
[3] Solari, R.B. and Bell, R.L., 1986. Fluid flow patterns and velocity distribution on commercial‐scale sieve trays. AIChE journal, 32(4), pp.640-649.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik, Adsorption und Extraktion, 26.-28.02.2020, Berchtesgaden, Germany

Publ.-Id: 30764

Application of Positron Emission Particle Tracking (PEPT) to measure the bubble-particle interaction in a turbulent and dense flow

Sommer, A.-E.; Ortmann, K.; van Heerden, M.; Richter, T.; Leadbeater, T.; Cole, K.; Heitkam, S.; Brito-Parada, P. R.; Eckert, K.

In a flotation cell, turbulence influences the motion of solid particles relative to the bubble surface, and, thus, affects the recovery rate. But, the impact of turbulence on the probability of a bubble-particle aggregation is still difficult to measure, especially in a dense flow. Therefore, the focus of this work was to apply PEPT as a method to investigate the effect of turbulence on the particle movement and bubble-particle interaction in an opaque flow. Single air bubbles (db=2.5 mm) were generated on a needle in a water flow channel. Upstream, a grid produced an isotropic turbulent flow with 5% to 15% turbulence intensity and a Kolmogorov microscale of 20µm. Depending on the distance to the grid, the flow near the captive bubble (Reb~450) was characterized by eddies of different length scales and magnitude with tomographic PIV. The solid suspension contained up to 0.3% PMMA particles (dp=200-400µm) and up to six radiolabelled particles (dp=300-400µm) coated with PMMA. The trajectories of the labelled particles were used to determine the average particle distribution in the turbulent field and describe the bubble-particle interactions. These results provide valuable information on the applicability of PEPT in turbulent and dense flow fields as well as on particle trajectories close to bubbles, enhancing our understanding of key flotation phenomena.

Keywords: Positron Emission Particle Tracking (PEPT); tomographic Particle Image Velocimetry (PIV); bubble-particle interaction; grid turbulence; dense flow; flotation


  • Secondary publication expected from 01.09.2021

Publ.-Id: 30763

INSPIRE: A multi-centric study to harmonize linear energy transfer (LET) calculations for biological assessments of proton therapy plans

Ödén, J.; Hahn, C.; Vestergaard, A.; Jensen, M. F.; Sokol, O.; Pardi, C.; Bourhaleb, F.; Leite, A.; de Marzi, L.; Rose, C.; Merchant, M.; Grzanka, L.; Dasu, A.; Lühr, A.

Purpose: Emerging clinical evidence supports the variability of relative biological effectiveness (RBE) in proton radiotherapy. This poses the need to account for RBE variability in proton planning. However, no harmonized concept exists on how to calculate the RBE-driving linear energy transfer (LET) in clinical practice. Therefore, a multi-centric study was set up with the objective to standardize clinical LET calculations in Europe.

Methods: Eight European institutions generated non-robust SOBP plans using common strict dose objectives. Multiple treatment field arrangements (single-field SOBP, perpendicular fields, opposing fields) were employed to cover a target cube in a water phantom. Each institution used its preferred treatment planning software and provided dose and corresponding LET distributions for a joint analysis.
Subsequently, RBE-weighted dose (DRBE) distributions were calculated for the single-field SOBP of one institution assuming the Wedenberg RBE model using Monte Carlo calculated unrestricted dose- and track-averaged LET (LETd/LETt) distributions considering (1) only primary protons, (2) all protons, (3) all particles with Z≤2.

Results: Institutional SOBP ranges and target average doses agreed within 2%. In contrast, near-minimum, average and near-maximum LETd differed up to 30%, 19% and 5% in the target, respectively. These discrepancies could partially be explained by different algorithms (Monte Carlo/analytical) and by different ions included in the LETd calculations.
LETd calculations were more sensitive to the considered secondary particle spectrum than LETt. Deriving DRBE using LETd yielded 0-11%, 4-12% and 12-45% higher DRBE in the entrance, target and distal edge regions, respectively, compared to LETt. The biological range extension using LETd (and LETt) was approximately 3 mm (and 1 mm).

Conclusions: Despite comparable dose distributions, substantial LET differences occurred among the participating institutions. These differences hamper the consistent analyses of clinical follow-up data as they translate to substantial discrepancies in predicted DRBE. Therefore, standardization of clinical LET calculations is of utmost importance.

  • Poster (Online presentation)
    2020 Joint AAPM/COMP Meeting, 12.-16.07.2020, Vancouver, Canada

Publ.-Id: 30761

2D and 3D convolutional neural networks for outcome modelling of locally advanced head and neck squamous cell carcinoma

Starke, S.; Leger, S.; Zwanenburg, A.; Leger, K.; Lohaus, F.; Linge, A.; Schreiber, A.; Kalinauskaite, G.; Tinhofer, I.; Guberina, N.; Guberina, M.; Balermpas, P.; von der Grün, J.; Ganswindt, U.; Belka, C.; Peeken, J. C.; Combs, S. E.; Böke, S.; Zips, D.; Richter, C.; Troost, E. G. C.; Krause, M.; Baumann, M.; Löck, S.

These are the results from the analyses presented in a paper submitted to Scientific Reports.

The zip file contains the trained model files and the plots that were used in the manuscript.

Code for reproduction of our analyses can be obtained from There, you also find instructions on how to load our models.

Keywords: convolutional neural networks; Keras; Deep learning; head and neck cancer; loco-regional-recurrence; Cox proportional hazards

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-27
    DOI: 10.14278/rodare.254
    License: CC-BY-NC-4.0


Publ.-Id: 30759

Preface of a special issue of the American Journal of Science

Fischer, C.; Arvidson, R. S.

This is the second part of a special issue of the American Journal of Science examining a problem that defines, perhaps more than any other, the state-of-the-art in the geochemistry of fluid-solid interaction: how to integrate data from both observations and modeling of events of brief duration at essentially atomic scales (for example, attachment, diffusion, detachment, hydrolysis), to that of mesoscale, ensemble processes (crystal dissolution, growth, alteration). The ultimate goal is an understanding of the long-term, phenomenological consequences of these interactions, often termed “upscaling”. Success in predicting and constraining these latter outcomes determines the larger value of this field, both to neighbors in environmental sciences and engineering, as well as to the public in terms of policy, education, and support. Nanoscale observation of mineral surfaces via instruments such as AFM and VSI is now widespread; increases in resolution and analytical capability of these instruments have also evolved in tandem with advances in the power and resolution of simulation and modeling approaches. Closely tied to an emerging theoretical framework, this “soft” progress in simulation and modeling was the focus of the first part of this issue.

Publ.-Id: 30758

Crystal surface reactivity analysis using a combined approach of X-ray micro-computed tomography and vertical scanning interferometry

Kahl, W.-A.; Yuan, T.; Bollermann, T.; Bach, W.; Fischer, C.

Dissolution rates of porous crystalline materials reflect the superposition of transport and surface control, mainly via the parameters saturation of the ambient fluid and distribution of surface energy. As a result, reacting surfaces evolve over time showing a heterogeneous distribution of surface rates. The spatiotemporal heterogeneity of surface reaction rates is analyzed using the rate map and rate spectra concept. Here, we quantify the dissolution rate variability covering the nm- to mm-scale of dissolving single-crystal and polycrystalline calcite samples, using a combined approach of X-ray micro-computed tomography (µ-CT) and vertical scanning interferometry (VSI). The dissolution experiments cover reaction periods from 15 minutes up to 54 days. The observed rate ranges are remarkably consistent over the entire reaction period but include a variability of about two orders of magnitude (10-9 - 3 * 10-7 mol m-2 s-1). The rate map data underscore the concurrent and superimposing impact of surface- vs. fluid flow controlled rate portions. The impact of fluid flow on reactivity at the mm-scale in the transport-controlled system is confirmed by 2-D reactive transport modeling. The sub-mm spatial heterogeneity of low vs. high reactivity surface portions of polycrystalline calcite is clearly below the mean crystal size. This suggests the dominant impact of highly reactive surface portions irrespective of the orientation of larger crystals on the overall surface reactivity. Correspondingly, the overall range of intrinsic reactivity heterogeneity as observed using singly crystal material is not further expanded for polycrystalline material. As a general conclusion, numerical reactive transport concepts would benefit from the implementation of a reactivity term resembling the experimentally observed existence of multiple rate components.

Keywords: crystal surface reactivity; rate map; dissolution rate variability; X-ray micro-computed tomography (µ-CT); vertical scanning interferometry (VSI); reactive transport; fluid-rock interaction

Publ.-Id: 30757

Recombinant expression of ecto-nucleotide pyrophosphatase/phosphodiesterase 4 (NPP4) and development of a luminescence-based assay to identify inhibitors

Lopez, V.; Lee, S.-Y.; Stephan, H.; Müller, C. E.

Nucleotide pyrophosphatase/phosphodiesterase 4 (NPP4) is a membrane-bound enzyme that hydrolyzes extracellular diadenosine polyphosphates such as Ap3A and Ap4A yielding mononucleotides. NPP4 on the surface of endothelial cells was reported to promote platelet aggregation by hydrolyzing Ap3A to ADP, which activates pro-thrombotic G protein-coupled P2Y1 and P2Y12 receptors. Thus, NPP4 inhibitors have potential as novel antithrombotic drugs. In the present study we expressed soluble human NPP4 in Sf9 insect cells and established an enzyme assay using diadenosine tetraphosphate (Ap4A) as a substrate. The reaction product ATP was quantified by luciferin-luciferase reaction in a 96-well plate format. The sensitive method displayed a limit of detection (LOD) of 14.6 nM, and a Z’-factor of 0.68 indicating its suitability for high-throughput screening. The new assay was applied for studying enzyme kinetics and led to the identification of the first NPP4 inhibitors.

Keywords: Antithrombotic drugs; assay development; ectonucleotidase; recombinant enzyme expression; high-throughput screening; luminescence detection; NPP4 inhibitors

Publ.-Id: 30756

Higher order ferromagnetic resonances in out-of-plane saturated magnetic multilayers

Fallarino, L.; Stienen, S.; Gallardo, R. A.; Arregi, J. A.; Uhlíř, V.; Lenz, K.; Hübner, R.; Hellwig, O.; Lindner, J.

Artificial ferromagnetic (FM)/nonmagnetic multilayers, with large enough FM thickness to prevent the dominance of interface anisotropies, offer a straightforward insight into the understanding and control of perpendicular standing spin wave (PSSW) modes. Here we present a study of the static and dynamic magnetic properties of [Co(3.0nm)/Au(0.6nm)]1≤N≤30 multilayer systems. Magnetometry reveals that the samples exhibit magnetization reversal properties typical of an effective single layer with weak perpendicular anisotropy, with the distinctive thickness-dependent magnetization reorientation transition from in-plane to out-of-plane. When such multilayer systems are out-of-plane saturated however, the dynamic response reveals the existence of several different ferromagnetic resonances in the form of PSSW modes that strongly depend on the material modulation characteristics along the total thickness. These modes are induced by the layer stacking itself as the effective single layer model fails to describe the complex dynamics observed in the system. In contrast to most systems considered in the past, described by a dynamic model of a single effectively homogeneous thick layer, the specific structures investigated here provide a unique platform for a large degree of tunability of the mode frequencies and amplitude profiles. We argue that the combination of periodic magnetic properties with vertical deformation gradients, arising from heteroepitaxial strain relaxation, generates a vertical regular array of two-dimensional pinning sites for the PSSW modes, which promotes the complex dynamics observed in the system.

Keywords: ferromagnetic resonance; multilayers; perpendicular anisotropy; spin waves


Publ.-Id: 30753

Analysis of In-Vessel Melt Retention for KONVOI PWR for selected severe accident scenarios

Jobst, M.

In the framework of the EU H2020 IVMR project, the applicability and technical feasibility of In-Vessel Melt Retention (IVMR) for high power reactors is assessed. HZDR contribution to the project was the investigation of the IVMR strategy for German Pressurized Water Reactor of type Konvoi (high power reactor with 1300 MWe). Four different severe accident scenarios with core material relocation to the lower head have been studied with the severe accident code ATHLET-CD, including Station Blackout (SBO), and Loss-of-Coolant accidents (LOCA) of various leak sizes in combination with SBO. The molten corium pool formed in the lower head and the ablation of vessel wall have been studied. The observed maximum heat flux on the outer surface of the wall is in the range between 1.47 MW/m² (SBO) and 1.67 MW/m² (LOCA). The corresponding minimum wall thickness is 25 mm and 21 mm, respectively. The simulations showed that with the assumptions made, IVMR seems to be possible for the investigated accident scenarios without vessel failure.

Keywords: PWR; Konvoi; severe accidents; In-vessel melt retention; ATHLET-CD

  • Poster
    IVMR 2020 - International Seminar “In-vessel retention: outcomes of IVMR project”, 21.-22.01.2020, Juan les Pins, France

Publ.-Id: 30752

Entwicklung eines Modells zur Grobstruktursimulation der Gas-Flüssigkeits-Strömung auf Querstromböden mit Hochleistungsventilen

Wiedemann, P.; Schubert, M.; Schleicher, E.; Hampel, U.

Motivation und Ziel
Trennkolonnen zur Separation von Mehrkomponentenströmen finden vielfältigen Einsatz in der chemischen Industrie. Für den Betrieb solcher Apparate ergeben sich im Zusammenhang mit der zunehmenden Energiebereitstellung aus erneuerbaren Quellen wachsende Anforderungen im Hinblick auf eine flexible Fahrweise. Vor allem vergrößerte Über- und Unterlastbereiche, in denen dennoch eine hohe Trenneffizienz gewährleistet werden soll, stellen für die Auslegung eine Herausforderung dar. Insbesondere für Querstromböden mit sogenannten Fixed- und Push-Valves mangelt es bislang an verlässlichen Methoden, um den Einfluss des Bodendesigns auf die komplexe Zweiphasenströmung von Flüssigkeit und Dampf abzuschätzen.
Im Rahmen eines AiF-Forschungsvorhabens verfolgt das hier vorgestellte Teilprojekt das Ziel, ein Simulationsmodell bereitzustellen, mit welchem die Einflüsse von Ventilart, -anzahl und -anordnung sowie verschiedener Betriebsbedingungen auf die makroskopische Strömungsausbildung auf dem Querstromboden untersucht werden können.

Strategie und Methoden
Ausgangspunkt für die Modellentwicklung bildet zunächst die Simulation der Strömung am Einzelventil unter Nutzung des am HZDR entwickelten Mehrfeld-Zweifluid-Konzeptes (GENTOP, vgl. [1]). Hiermit werden sowohl großräumig separierte als auch disperse Phasenverteilungen sowie Übergänge zwischen diesen Strömungsmorphologien erfasst. Nach einer Validierung mit experimentell ermittelten Vergleichsdaten dienen die für vielfältige Betriebsbedingungen vorliegenden Simulationsergebnisse als Basis für die Ableitung von Feinstrukturmodellen für einen grobskaligen Modellierungsansatz. Für letzteren wird ein Euler-Euler-Modell favorisiert, in welchem die Effekte der nicht aufgelösten Phaseninteraktion über pragmatische Schließungsgleichungen integriert werden und die Abbildung der Ventile mittels punktartiger Massen- und Impulsquellen realisiert werden kann. Zur Validierung dieses Modells werden zunächst Simulationen für einzelne Ventile und Ventilgruppen durchgeführt und diese mit experimentellen Daten verglichen. Dazu wird ein Versuchsstand aufgebaut, an dem die Zweiphasenströmung an Einzelventilen oder Ventilgruppen unter definierten Betriebsbedingungen untersucht werden kann. Hierbei ist u. a. der Einsatz bildgebender Messverfahren geplant, um detaillierte Informationen über die Strömungsfelder und -regime zu erhalten. Um die Eignung des Grobstukturmodells zu demonstrieren, sind abschließend Vergleiche mit Experimentaldaten einer Versuchsanlage im industriellen Maßstab geplant.

[1] Hänsch, S.; Lucas, D.; Krepper, E.; Höhne, T.: A multi-field two-fluid concept for transitions between different scales of interfacial structures. International Journal of Multiphase Flow 47 (2012) 171-182

  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Computational Fluid Dynamics und Gasreinigung, 10.-11.03.2020, Bamberg, Deutschland

Publ.-Id: 30751

2D and 3D convolutional neural networks for outcome modelling of locally advanced head and neck squamous cell carcinoma

Starke, S.; Leger, S.; Zwanenburg, A.; Leger, K.; Lohaus, F.; Linge, A.; Schreiber, A.; Kalinauskaite, G.; Tinhofer, I.; Guberina, N.; Guberina, M.; Balermpas, P.; von der Grün, J.; Ganswindt, U.; Belka, C.; Peeken, J. C.; Combs, S. E.; Böke, S.; Zips, D.; Richter, C.; Troost, E. G. C.; Krause, M.; Baumann, M.; Löck, S.

For treatment individualisation of patients with locally advanced head and neck squamous cell carcinoma (HNSCC) treated with primary radiochemotherapy, we explored the capabilities of different deep learning approaches for predicting loco-regional tumour control (LRC) from treatment-planning computed tomography images. Based on multicentre cohorts for exploration (206 patients) and testing (85 patients), multiple deep learning approaches including extraction of deep features, transfer learning and complete training from scratch with 2D and 3D convolutional layers were assessed and compared to a clinical model including the tumour volume. Analyses were based on Cox proportional hazards regression and performance was assessed by the concordance index (C-index). While all 2D approaches showed similar or worse performance than the clinical model on the test cohort (C-index 0.39), 3D convolutional neural networks achieved improved discrimination (C-index 0.31) and patient stratification into high and low risk groups of tumour recurrence (p=0.001), in particular when using model ensembles instead of single models. Prospective validation of this result is planned.

Keywords: head and neck cancer; loco-regional-recurrence; convolutional neural networks; Cox proportional hazards

Related publications

Publ.-Id: 30750

Development of tailored packings for Rotating Packed Beds

Gładyszewski, K.; Gross, K.; Qammar, H.; Kamiński, K.; Bieberle, A.; Schubert, M.; Skiborowski, M.; Górak, A.

Contribution to Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik, Adsorption und Extraktion

Keywords: Rotating packed beds; HIGEE; anisotropic; foam packings; mass transfer; hydrodynamic; computer tomography

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik, Adsorption und Extraktion, 26.-28.02.2020, Berchtesgaden, Deutschland

Publ.-Id: 30749

Iron recovery from dry tailing dumps of an iron processing plant using an efficient circuit

Gholami, H.; Habibollahzadeh, A.; Haghi, M.; Hassanzadeh, A.

This work aims at investigating the production feasibility of a high yield product from a landfill suitable for feeding to an iron concentration plant. For this purpose, the samples were taken from tailing dumps of 3 Chahoun mine contained less than 10% iron content. After primary sample preparations, the representative samples were divided into two parts i.e. coarser and finer than 4 mm. it was concentrated by a medium intensity magnetic separator (MIMS) with a velocity of 1.5 m/s at rougher stage. The tailing and product were crushed by a jaw crusher down to 10, 6, 2 mm and followed by a low intensity magnetic separator (LIMS) with speeds of 1.5, 3, 4 m/s in the cleaner and scavenger stages. The results show that iron recovery is most likely to occur in samples with coarse grain size in the tailings. The highest weight recovery, iron and iron oxide content were obtained in low intensity magnetic separator at a velocity of 1.5 m/s in the cleaner stage that was about 18 and 35%, respectively, with dimensions less than 2 mm, which it has the highest iron and iron oxide separation rates of 46 and 54%, respectively.

Keywords: Magnetic separator; iron grade; rougher and cleaner stages; tailing dumps

  • Contribution to proceedings
    IMPC 2020 - XXX International Mineral Processing Congress, 18.-22.10.2020, Cape Town, South Africa


Publ.-Id: 30748

The effect of ultrasonic pre-treatment on wettability and floatability of chalcopyrite, pyrite and quartz

Hassanzadehmahaleh, A.; van Hall, .; Öktem, A.; Özkan, G.; Rudolph, M.

Despite the four-decade study on ultrasound’s (US) impact on mineral’s floatabilities, there is still not a clear image regarding its role in mineral surface wettability. For this purpose, the current investigation endeavours the wettability and floatability characteristics of a chalcopyrite-pyrite-quartz (Cp-Py-Qtz) system in the presence and absence of an ultrasonic pre-treatment. The ultrasonic process was carried out by a Sonopuls at a constant frequency of 20 kHz with an adjustable power level from 30 to 200 W. Initially, impact of sonication time (15, 30, 45, 60 and 90 s as well as 10, 20 and 30 min) and power level (30, 60, 90, 120 and 180 W) were evaluated while the dissolved oxygen, temperature, conductivity and pH were monitored. Collector-less micro-flotation tests were carried out on the non-pre-treated and the US pre-treated samples at 60 W and 15 s. The samples’ hydrophobicities were determined by the drop shape analysis approach. The dissolved-oxygen level was varied using a mini bench pressurized water reactor to study the effect of O2(aq) concentration on the chalcopyrite and pyrite wettability characteristics. The results showed that the minerals’ hydrophilicities were relatively sensitive to the sonication’s time than its power that resulted in reducing all three minerals’ hydrophilicities. In addition, it was found that the dissolved oxygen content and creation of sub-micron sized bubbles led to an improvement on chalcopyrite and pyrite’ hydrophobicities. Finally, we proved that the Cp’s floatability increased and Qtz’s recovery reduced while being subjected to the ultrasonic irradiation (15 s at 60 W), however, Py’s recovery remained constant. This conclusion confirmed possibility of a selective separation in ultrasound-assisted copper ore flotation. We recommend further advanced investigations are highly required e.g. using an X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM) to profoundly understand the surface modification induced by the ultrasonication.

Keywords: Ultrasound; dissolved oxygen; floatability; chalcopyrite-pyrite-quartz system; contact angle

  • Contribution to proceedings
    IMPC 2020 - XXX International Mineral Processing Congress, 18.-22.10.2020, Cape Town, South Africa

Publ.-Id: 30747

Proton number fluctuations in sqrt(s_NN)= 2.4 GeV Au+Au collisions studied with HADES

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kohls, M.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.

We present an analysis of proton number fluctuations in sqrt(s_NN) = 2.4 GeV Au+Au collisions measured with the High-Acceptance DiElectron Spectrometer (HADES) at GSI. With the help of extensive detector simulations done with IQMD transport model events including nuclear clusters, various nuisance effects influencing the observed proton cumulants have been investigated. Acceptance and efficiency corrections have been applied as a function of fine grained rapidity and transverse momentum bins, as well as considering local track density dependencies. Next, the effects of volume changes within particular centrality selections have been considered and beyond-leading-order corrections have been applied to the data. The efficiency and volume corrected proton number moments and cumulants Kn of orders n = 1, . . . , 4 have been obtained as a function of centrality and phase-space bin, as well as the corresponding correlators C_n . We find that the observed correlators show a power-law scaling with the mean number of protons, i.e. Cn∝n, indicative of mostly long-range multi-particle correlations in momentum space. We also present a comparison of our results with Au+Au collision data obtained at RHIC at similar centralities, but higher sqrt(s_NN).


Publ.-Id: 30746

A modular, injectable, non-covalently assembled hydrogel system features widescale tunable degradability for controlled release and tissue integration

Rothe, R.; Xu, Y.; Kuriakose Thomas, A.; Meister, S.; Zhang, Y.; Pietzsch, J.; Hauser, S.

Biomaterials with attenuated adverse host tissue reactions, and meanwhile, combining biocompatibility with mimicry of mechanical and biochemical cues of native extracellular matrices (ECM) to promote integration and regeneration of tissues are important for many biomedical applications. Further, the materials should also be tailorable to feature desired application-related functions, like tunable degradability, injectability, or controlled release of bioactive molecules. Herein, a non-covalently assembled, injectable hydrogel system based on oligopeptides interacting with sulphated polysaccharides is reported, showing high tolerability and biocompatibility in immunocompetent hairless mice. Altering the peptide or polysaccharide component considerably varies the in vivo degradation rate of the hydrogels, ranging from a half-life of three weeks to no detectable degradation after three months. The hydrogel with sulphated low molecular weight hyaluronic acid exhibits sustained degradation-mediated release of heparin-binding molecules in vivo, as shown by small animal magnetic resonance imaging and fluorescence imaging, and enhances the expression of vascular endothelial growth factor in hydrogel surrounding. In vitro investigations indicate that M2-macrophages could be responsible for the moderate difference in pro-angiogenic effects. The ECM-mimetic and injectable hydrogels represent tunable bioactive scaffolds for tissue engineering, also enabling controlled release of heparin-binding signalling molecules including many growth factors.

Keywords: Biocompatibility; MMP-cleavable peptide; Modular building blocks; Small animal imaging; Sulphated hyaluronic acid

Publ.-Id: 30744

Survival of the basidiomycete Schizophyllum commune in soil under hostile environmental conditions in the Chernobyl Exclusion Zone

Traxler, L.; Wollenberg, A.; Steinhauser, G.; Chyzhevskyi, I.; Dubchak, S.; Großmann, S.; Günther, A.; Gupta, D. K.; Iwannek, K.-H.; Kirieiev, S.; Lehmann, F.; Schulz, W.; Walther, C.; Raff, J.; Kothe, E.

Radioactive contamination resulting from major 29 nuclear accidents presents harsh environmental conditions. Inside the Chernobyl exclusion zone, even more than 30 years after the accident, the resulting contamination levels still does not allow land-use or human dwellings. To study the potential of basidiomycete fungi to survive the conditions, a field trial was set up 5 km south-south-west of the destroyed reactor unit. A model basidiomycete, the lignicolous fungus Schizophyllum commune, was inoculated and survival in the soil could be verified. Indeed, one year after inoculation, the fungus was still observed using DNA dependent techniques. Growth led to spread at a high rate, with approximately 8 mm per day. This shows that also white-rot basidiomycetes can survive the harsh conditions in soil inside the Chernobyl exclusion zone. The resistance against radiation was higher than 20 μSv/day with this unadapted fungal strain.

Keywords: Chernobyl exclusion zone; fungi; soil; environment; Schizophyllum commune

Publ.-Id: 30743

Holographic vector meson melting in a thermal gravity-dilaton background related to QCD

Zöllner, R.; Kämpfer, B.

A holographic model of probe vector mesons (quarkonia) is presented, where the dynamical gravity-dilaton background is adjusted to the thermodynamics of 2 +1 flavor QCD with physical quark masses. The vector meson action is modified to account for various quark masses. We focus on the Φ, J/ψ and Υ meson melting in agreement with hadron phenomenology in heavy-ion collisions at LHC, that is the formation of hadrons at the observed freeze-out temperature of 155 MeV.


  • Secondary publication expected from 21.12.2021

Publ.-Id: 30742

Temperature-dependent luminescence spectroscopic investigations of U(VI) complexation with the halides F- and Cl-

Demnitz, M.; Hilpmann, S.; Lösch, H.; Bok, F.; Steudtner, R.; Patzschke, M.; Stumpf, T.; Huittinen, N. M.

In the present study we have investigated the complexation of uranyl(VI) with chloride and fluoride using luminescence spectroscopy (TRLFS, time-resolved laser-induced fluorescence spectroscopy). At 25 °C, in the presence of 0 − 0.175 M fluoride, the first single-component emission spectra for all four U(VI)-fluoride complexes, i.e. UO2F+, UO2F2, UO2F3−, and UO2F42− could be extracted. Based on the aqueous speciation derived from the TRLFS data, logK* values at I = 1 M were calculated for all these complexes and extrapolated to infinite dilution using the SIT approach. In the case of chloride, however, quenching of the U(VI)-luminescence hampered the experiments. Thus, U(VI)-complexation was studied with TRLFS at liquid nitrogen temperatures. Samples were prepared at 25 °C with chloride concentrations ranging from 0 to 1.0 M followed by instantaneous freezing and subsequent luminescence spectroscopic measurements at −120 °C. This allowed for the determination of the first luminescence spectra for the UO2Cl+ complex with the TRLFS method. The chloride quench reaction was further studied in the temperature range 1 – 45 °C using Stern-Volmer analysis. By applying the Arrhenius and the Eyring equations we obtained the first thermodynamic parameters for the dynamic quench process, i.e. the activation energy (Ea = 55.0 ± 12.9 kJ/mol), enthalpy (ΔHǂ = 52.5 ± 13.0 kJ/mol), and entropy (ΔSǂ = 103.9 ± 42.8 J/mol∙K).

Keywords: uranyl; luminescence; complexation; halides; quenching


  • Secondary publication expected from 01.05.2021

Publ.-Id: 30741

Steel related activities and capabilities at HZDR

Gerbeth, G.

  • Invited lecture (Conferences)
    Sino-German Symposium „Future Steel“, 18.07.2019, Shanhai, China

Publ.-Id: 30740

Fast Reconstruction Algorithm for Contactless Inductive Flow Tomography

Wondrak, T.; Jacobs, R. T.; Faber, P.

The contactless inductive flow tomography is a measurement technique for the determination of the flow structure of an electrically conducting liquid. The procedure is based on the measurement of the magnetic field and can potentially be applied for visualisation and online-monitoring of industrial processes as, for example, continuous steel casting or the production of mono-crystalline silicon using the Czochralski crystal growth method. With the aid of the measured field values, the velocity field is reconstructed by solving a linear inverse problem that is described by a system of coupled integral equations. The frame rate of the field measurement is typically in the order of one frame per second, whereas the inversion of the integral equations usually takes about twenty times as long, since a regularisation parameter needs to be determined for each reconstruction. In order to reduce this discrepancy, a new algorithm is introduced in this article. The algorithm relies on the pre-computation of inverted matrices, so that the inversion can be determined solely by performing matrix-vector products. This technique reduces the time required for the inversion process at each reconstruction to same length of time a measurement cycle takes, i.e. about one second. The efficiency of the method will be demonstrated using a modified Rayleigh-Bénard experiment with liquid metal at room temperature.

Keywords: Contactless inductive flow tomography; inverse problems; measurement technique

  • Lecture (Conference)
    10th International Conference on Advanced Computer Information Technologies (ACIT 2020), 13.-15.05.2020, Deggendorf, Deutschland
  • Contribution to proceedings
    10th International Conference on Advanced Computer Information Technologies (ACIT 2020), 13.-15.05.2020, Deggendorf, Deutschland
    Proceedings of the 10th International Conference on Advanced Computer Information Technologies (ACIT 2020), 217-220
    DOI: 10.1109/ACIT49673.2020.9208853

Publ.-Id: 30739

Synthesis, radiolabeling and first biological characterization of 18F-labeled xanthine derivatives for PET imaging of Eph receptors

Pretze, M.; Neuber, C.; Kinski, E.; Belter, B.; Köckerling, M.; Caflisch, A.; Steinbach, J.; Pietzsch, J.; Mamat, C.

Eph receptor tyrosine kinases, particulary EphA2 and EphB4, represent promising candidates for molecular imaging due to their essential role in cancer progression and therapy resistance. Xanthine derivatives were identified to be potent Eph receptor inhibitors with IC50 values in the low nanomolar range (1-40 nm).These compounds occupy the hydrophobic pocket of the ATP-binding site in the kinase domain. Based on lead compound 1, we designed two fluorine-18-labeled receptor tyrosine kinase inhibitors ([18F]2/3) as potential tracers for positron emission tomography (PET). Docking into the ATP-binding site allowed us to find the best position for radiolabeling. The replacement of the methyl group at the uracil residue ([18F]3) rather than the methyl group of the phenoxy moiety ([18F]2) by a fluoropropyl group was predicted to preserve the affinity of the lead compound 1. Herein, we point out a synthesis route to [18F]2 and [18F]3 and the respective tosylate precursors as well as a labeling procedure to insert fluorine-18. After radiolabeling, both radiotracers were obtained in approximately 5% radiochemical yield with high radiochemical purity (>98%) and a molar activity of >10 GBq/µmol. In line with the docking studies, first cell experiments revealed specific, time-dependent binding and uptake of [18F]3 to EphA2 and EphB4 overexpressing A375 melanoma cells, whereas [18F]2 did not accumulate at these cells. Since both tracers [18F]3 and [18F]2 are stable in rat blood, the novel radiotracers might be suitable for in vivo molecular imaging of Eph receptors by, e.g., PET.

Keywords: RTK imaging; cancer; malignant melanoma; radiolabeling; kinase inhibitors


  • Secondary publication expected from 28.04.2021

Publ.-Id: 30738

Numerical investigation on the effect of transversal fluid field deformation on heat transfer in a rod bundle with mixing vanes

Tas-Köhler, S.; Lecrivain, G.; Krepper, E.; Unger, S.; Hampel, U.

Spacer grids of fuel rod assemblies are equipped with vanes, which promote flow mixing and turbulence within and across the sub-channels, thereby enhancing the heat transfer. First, a literature study about the various effect of the spacer grid has on the sub-channel thermo-hydrodynamics is provided. It follows, that the multiple effects on the vane angle are insufficiently understood. The effect of the vane angle on design parameters, namely the evolution of the Nusselt number, the pressure drop, the cross and swirl flows, is here further discussed and supplemented by own simulations. The effect of the velocity gradient tensor ∇⊗u, decomposed into a strain and a vorticity contribution, is also looked at downstream of the spacer grid. The RNG k-ε turbulence model was found to provide results best matching the experimental data available in the literature. The use of vanes results in the formation of a downstream vortex. As the flow develops downstream of the spacer grid, the vortex migrates away from the sub-channel center and eventually weakens. In line with the presented literature survey, it is confirmed that a vane angle of about 30° provides optimal swirl and cross flows, resulting in an enhanced heat transfer.

Keywords: Literature analysis; Vortex generator; Vane angle; Rod bundle; Vorticity; Turbulent flow; Heat transfer

Publ.-Id: 30737

Understanding the local structure of Eu3+ and Y3+ stabilized zirconia – Insights from luminescence and X–ray absorption spectroscopic investigations

Eibl, M.; Shaw, S.; Prieur, D.; Roßberg, A.; Wilding, M. C.; Hennig, C.; Morris, K.; Rothe, J.; Stumpf, T.; Huittinen, N. M.

This study combines bulk structural and spectroscopic investigations of Eu3+ or Y3+/Eu3+ co–doped tetragonal and cubic zirconia polymorphs to an gain in–depth understanding of the solid solution formation process. Our bulk structural characterizations show that the dopant is homogenously distributed in the ZrO2 host structure resulting in an increase of the bulk symmetry with increasing dopant substitution (from 8 mol% to 26 mol%). The local site–symmetry around the Eu3+–dopant, however, determined with luminescence spectroscopy (TRLFS), remains low in all samples. Results obtained with X–ray pair distribution function (XPDF) and X–ray absorption spectroscopy (EXAFS) show that the average coordination environment in the stabilized zirconia structures remains practically unchanged. Despite of this very constant average dopant environment, site–selective TRLFS data show the presence of three non–equivalent Eu3+ environments in the ZrO2 solid structures. These Eu3+ environments are assumed to arise from Eu3+ incorporation at superficial sites which increase in abundance as the size of the crystallites decrease, and incorporation on two bulk sites differing in the location of the oxygen vacancies with respect to the dopant cation.

Keywords: Eu3+; Y3+; incorporation; stabilized ZrO2; TRLFS; EXAFS; XPDF

Publ.-Id: 30736

Conductive ITO interfaces for optoelectronic applications based on highly ordered inverse opal thin films

Galle, L.; Ehrling, S.; Lochmann, S.; Kaskel, S.; Bischoff, L.; Grothe, J.

A three-step fabrication process for optically transparent, conducting ITO thin films with an intrinsic inverse opal structure is described. The preparation is based on colloidal crystal templating using polystyrene microspheres (100 nm - 600 nm). For the realization of varying periodicities in this structure, different sphere sizes were assembled to monolayers on a substrate by spin coating and infiltrated afterwards similarly. The influence of rotation parameters as well as dispersion concentration was studied. Using this approach different geometries of the surface are accessible by systematically varying the rotation parameters and infiltration volume. The thin films show excellent anti-reflection behavior, good transmission ( >80 % in the visible range) as well as a low resistance of 200 Ω/sq compared to other porous ITO interfaces. The properties are very promising for several optoelectronic applications such as in- or out-coupling structures in solar cells and organic light emitting diodes.

Keywords: ITO thin films; conducting; transmission; optoelectronics

Publ.-Id: 30734

Sputtering of nanostructured tungsten and comparison to modelling with TRI3DYN

Stadlmayr, R.; Szabo, P. S.; Mayer, D.; Cupak, C.; Dittmar, T.; Bischoff, L.; Möller, S.; Rasinski, M.; Wilhelm, R. A.; Möller, W.; Aumayr, F.

He-induced nanostructured tungsten (so called W-fuzz) was bombarded with Ar ions under 60 degree and the dynamic erosion behaviour experimentally investigated. By using a highly sensitive quartz-crystal-microbalance technique in a particle catcher configuration the sputtered particles distribution of Wfuzz could be evaluated. In contrast to a at sample, where sputtered particles are emitted primarily in forward direction, we find that W-fuzz samples emit sputtered particles preferably in backward direction (i.e. in the direction of the incident ion beam). After continuous Ar irradiation of a W-fuzz sample the distribution approaches that of a at sample. In addition to experimental data we also show modelling results obtained with a state-of-the-art Monte-Carlo (MC) binary collision approximation (BCA) code TRI3DYN in full 3D. Surface morphology changes as monitored by SEM as well as the dynamic sputtering behaviour can be well reproduced by the full 3D MC-BCA code.

Keywords: Erosion; Quartz crystal microbalance; TRI3DYN; Surface roughness; Sputtering; nanostructured tungsten; W-fuzz


Publ.-Id: 30733

Hollow Au@TiO2 porous electrospun nanofibers for catalytic applications

Kumar, L.; Singh, S.; Horechyy, A.; Formanek, P.; Hübner, R.; Albrecht, V.; Weißpflog, J.; Schwarz, S.; Puneet, P.; Nandan, B.

Catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles were fabricated using a combination of sol-gel chemistry and coaxial electrospinning technique. We report the fabrication of catalytically active porous and hollow titania nanofibers encapsulating gold nanoparticles (AuNPs) using a combination of sol-gel chemistry and coaxial electrospinning technique. The coaxial electrospinning involved the use of a mixture of poly(vinyl pyrrolidone) (PVP) and titania sol as the shell forming component, whereas a mixture of poly(4-vinyl pyridine) (P4VP) and pre-synthesized AuNPs constituted the core forming component. The core-shell nanofibers were calcined stepwise up to 600 °C which resulted in decomposition and removal of the organic constituents of the nanofibers. This led to the formation of porous and hollow titania nanofibers, where the catalytic AuNPs were embedded in the inner wall of the titania shell. The catalytic activity of the prepared Au@TiO2 porous nanofibers was investigated using a model reaction of catalytic reduction of 4-nitrophenol and Congo red dye in the presence of NaBH4. The Au@TiO2 porous and hollow nanofibers exhibited excellent catalytic activity and recyclability, and the morphology of the nanofibers remained intact after repeated usage. The presented approach could be a promising route for immobilizing various nanosized catalysts in hollow titania supports for the design of stable catalytic systems where the added photocatalytic activity of titania could further be of significance.

Publ.-Id: 30732

The role of boron on exchange coupling in NiFe/Ru1−xBx/FeCo trilayer structures

Mckinnon, T.; Hübner, R.; Heinrich, B.; Girt, E.

In this work, we study the interlayer exchange coupling, J, between two NiFe and FeCo layers in a series of NiFe/Ru1-xBx(d)/FeCo synthetic antiferromagnet (SAF) samples, where the thickness of the spacer layer, d, is varied from 0.4 nm to 0.9 nm, and the boron concentration, x, is varied from 0 to 15 at. %. The samples are studied as deposited and after being annealed at 250 °C. B is deposited into the Ru spacer layer to investigate what occurs after annealing a FeCoB/Ru/FeCoB SAF structure, which is commonly used in modern nanoscale magnetic devices, in which the FeCoB layer crystallizes to FeCo and B diffuses to adjacent layers. We find that J in as-deposited samples is relatively unaffected by adding up to 15% B into the Ru spacer layer. However, after annealing at 250 °C, J changes the sign from antiferromagnetic coupling to ferromagnetic coupling for spacer layers thinner than 0.45 nm for 5% and 10% B and thinner than 0.525 nm for 15% B. We used transmission electron microscopy energy-dispersive x-ray spectroscopy in order to investigate the diffusion of atoms within a similar Ta(2.5 nm)/NiFe(0.8 nm)/Ru1-xBx(23 nm) layer structure. We find that after annealing at 250 °C, the sample containing 15% B within the Ru85B15 layer had significantly more diffusion of Fe into the Ru85B15 layer, from the NiFe layer, as compared to the sample with 0% B. Thus, the presence of B within the spacer layer enhances diffusion of Fe into the spacer layer.

Publ.-Id: 30731

Electric and magnetic dipole strength in 54Fe

Schwengner, R.; Massarczyk, R.; Bemmerer, D.; Beyer, R.; Bhike, M.; Brown, B. A.; Butterling, M.; Derya, V.; Dietz, M.; Fiedler, F.; Frotscher, A.; Gayer, U.; Grieger, M.; Hartmann, A.; Junghans, A. R.; Kögler, T.; Krishichayan, F.; Ludwig, F.; Lutz, B.; Pai, H.; Römer, K.; Sieja, K.; Szücs, T.; Takacs, M.; Tornow, W.; Wagner, A.

The dipole strength of the N=28 nuclide 54Fe was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.5 and 13.9 MeV at the gELBE facility as well as using quasi-monoenergetic and linearly polarized photon beams of 26 energies within the range from 5.5 to 11.4 MeV at the HIgS facility. About 100 J=1 states were identified, out of them 19 with 1+ and 30 with 1- assignment. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical γ-ray cascades. As a result, the photoabsorpton cross section up to the neutron-separation energy was determined and compared with predictions of statistical reaction codes. The experimental M1 strengths from resolved 1+ states are compared with results of large-scale shell-model calculations.

Keywords: Photon scattering; nuclear resonance fluorescence; angular distributions; polarization; statistical gamma-ray cascades; photoabsorption cross section; dipole excitations; shell model

Publ.-Id: 30730

Thermodynamic Reference Database (THEREDA) – Present activities

Moog, H. C.; Bok, F.; Freyer, D.; Gaona, X.; Thoenen, T.

The THEREDA project [1] aims at providing an extensive thermodynamic database for the modeling of solubility equilibria in aqueous solutions within the context of nuclear waste disposal. Focus is laid on saline solutions, typically with an ionic strength > 1M, using the Pitzer approach [2].
THEREDA is operated by five research institutions. A web-based user interface is used for data capture and documentation. The primary products, however, are ready-to-use data files for PHREEQC, Geochemist’s Workbench, CHEMAPP, and (to a limited extent) EQ3/6. In addition, a code-independent, generic format (JSON) is available for download. Before release, data sets are subject to rigid, internal checks. More than 200 test calculations are used to continously ensure the correctness of calculated results, both in terms of earlier test runs and between different codes.
While extending the database, experimental data for various chemical systems are recorded. The agreement with model calculations using THEREDA are documented. This “positive list” is continously being extended.
In response to the limited lifetime of existing codes and to extend our user base, efforts are undertaken to support two additional codes, GEMS and TOUGHREACT.

[1] H. C. Moog et al. (2015): Appl. Geochem. (55) 72-84.
[2] K. S. Pitzer (1991): Activity Coefficients in Electrolyte Solutions (2nd ed.). CRC Press, ISBN 0-8493-5415-3.

Keywords: THEREDA; Pitzer; Thermodynamic Reference Database

  • Lecture (Conference) (Online presentation)
    Goldschmidt2020, 21.-26.06.2020, Honolulu, USA
  • Contribution to proceedings
    Goldschmidt2020, 21.-26.06.2020, Honolulu, USA
    Golschmidt2020: Geochemical Society

Publ.-Id: 30728

A self-adaptive particle-tracking methodology for minerals processing

Pereira, L.; Frenzel, M.; Khodadadzadeh, M.; Tolosana Delgado, R.; Gutzmer, J.

Resource and energy efficiency are essential for the raw-materials industry to secure a sufficient and economically feasible supply of minerals and metals for society in the coming decades. This task becomes more challenging as the complexity of primary resources increases. Mineral processing plant control systems, an important tool for guaranteeing efficient plant operations, are currently based on processing models that only consider bulk chemical and physical properties. They do not incorporate particle-level data – a significant limitation when dealing with complex bulk materials. This contribution presents a novel particle-based prediction model capable of dealing with complete particle datasets (i.e. no dimensionality reduction required), of operating without human-input and able to provide the probability of each particle in a system to deport to any one of the material streams within a given operation. The method is applicable to any processing unit that does not modify the physical dimensions of particles, such as comminution.
The particle-based prediction model consists of a regularized logistic regression model with a probability adjustment step to accommodate geological variability. Even though the method supports different types of particle-level characterization data, it is built around data obtained by scanning electron microscope-based image analysis. Constructed cases demonstrate the method’s efficiency in recreating characteristic recovery trends for magnetic separation, hydrocyclone and flotation units. In addition, the system is used to reconstruct a complete processing plant with three flotation and one magnetic separation circuits. Predicted results of masses and compositions for all of the intermediates and products correspond well to the results reported from the plant itself. The provided probabilities allow for the modelling of the interaction between particle properties and machine parameters, and can later be used for process simulation and optimization.

Keywords: geometallurgy; machine learning; mineral processing; particletracking; automated process prediction

Related publications


  • Secondary publication expected from 16.08.2021

Publ.-Id: 30727

Status update of the PEnELOPE laser system

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

We present a status update of the PEnELOPE laser system currently under construction at the Helmholtz-Zentrum Dresden-Rossendorf. We show the first energetic activation of the first major amplification stage on the 10 Joule-level in order to benchmark the performance of the whole last two amplifier sections and the progress at the last amplifier section in order to achieve a first activation.

Keywords: laser; diode; diode-pumping; ytterbium; petawatt; laser system; penelope

  • Invited lecture (Conferences) (Online presentation)
    The 9th Advanced Lasers and Photon Sources (ALPS2020), 20.-23.04.2020, Yokohama, Japan

Publ.-Id: 30726

Microstructure, texture and hardness of a metastable β-titanium alloy after bar-rolling and annealing

Gu, B.; Chekhonin, P.; Schaarschuch, R.; Oertel, C.-G.; Xin, S. W.; Ma, C. L.; Zhou, L.; Gan, W. M.; Skrotzki, W.

The microstructure and texture evolution of a metastable Ti-5Al-3V-3Mo-2Cr-2Zr-1Nb-1Fe alloy during bar-rolling and after various thermal treatments was investigated by high-energy synchrotron diffraction and electron backscatter diffraction. Bar-rolling is applied in the (α+β)-phase field in order to achieve a bi-modal (duplex) microstructure. The effect of dynamic recrystallized and recovered zones on texture of Ti5321was analyzed separately, as well as the texture of primary α-precipitates and secondary α-lamellae. The texture of the recovered zones is characterized by a cube component ({001}<100>) plus α- and γ-fibre with dominant {100}<110>, {112}<110>, {111}<110> components, while the texture of the recrystallized zones is a strong cube texture. After aging or recrystallization plus aging, this texture component remains, while it disappears after solution treatment. The primary α-precipitates have their c-axes perpendicular to the rolling direction and do not follow the Burgers orientation relationship. This texture characteristics remains after various thermal heat treatments. Secondary α-lamellae obey the Burgers orientation relationship. Moreover, a variant selection of secondary α-lamellae occurs. The mechanism of texture formation of the β-phase and the precipitation behavior of the α-phase is discussed.
The hardness increase can be attributed to size, shape and volume fraction of the α-precipitates.
Different combinations of primary α- and secondary α-precipitates make an increase in hardness of about 11%.

Keywords: Metastable β-titanium alloy; Bar-rolling; Microstructure; Texture; Microhardness


  • Secondary publication expected

Publ.-Id: 30724

Regulation of bone regeneration

Jung, F.; Pietzsch, J.

This editorial presents three comprehensive reviews of recent preclinical and clinical findings supporting the healing of critical bone defects through adjuvant therapy approaches, which have been published in a special issue. In summary, these articles highlight current concepts that attempt to improve osteogenesis and bone healing using small molecule drugs and intelligent drug delivery methods. The main conclusions lead to an evaluation of the modulation of angiogenesis and microcirculation as a very promising concept. The modulation of inflammation, on the other hand, was evaluated as critical with respect to the start and duration of therapy. Novel solutions are expected from a targeted modulation of bone metabolism, the use of bifunctional or hybrid compounds, appropriate drug combinations and delivery systems.

Keywords: Adjuvant drug-assisted bone healing; angiogenesis; anti-resorptive drugs; bone metabolism; critical bone defect; compound fracture; drug release; inflammation; local therapy; systemic therapy; osteoconductive drugs; osteoinductive drugs; pleiotropic effects; targeted therapy; tissue regeneration

  • Clinical Hemorheology and Microcirculation 73(2020)3, 379-380
    DOI: 10.3233/CH-199101


  • Secondary publication expected

Publ.-Id: 30722

Computer assisted beam modeling for particle therapy

Fuchs, H.; Elia, A.; Resch, A. F.; Kuess, P.; Lühr, A.; Vidal, M.; Grevillot, L.; Georg, D.

To develop a computer-driven and thus less user dependent method, allowing for a simple and straight forward generation of a Monte Carlo (MC) beam model of a scanned proton and carbon ion beam delivery system.

The method was applied on five different clinical as well as one research beam lines for proton and carbon ions of three different particle therapy centers using synchrotron or cyclotron accelerator systems: i) MedAustron ion therapy center, ii) University Proton Therapy Dresden, and iii) Center Antoine Lacassagne Nice. In a first step, experimental measurements were performed for proton and carbon ion energies in the available energy ranges. Data included depth dose profiles measured in water and spot sizes in air at various iso-center distances.
Using an automated regularization-based optimization process, GATE/Geant4 beam models of the respective beam lines were generated and compared to independent measurements. Sequentially, using least square weighting functions with and without regularization, the beam parameters energy, energy spread, beam sigma, divergence, and emittance were iteratively tuned until a user defined agreement was reached. Based on the parameter tuning for a set of energies a beam model was generated. The resulting beam models were validated for all centers comparing laterally integrated depth dose curves and spot sizes in air. For a representative center, 3D dose cubes were measured and compared to simulations.

Results: Beam ranges in the MC beam models agreed on average within 0.2 mm compared to measurements for all energies and beam lines. Spot sizes (full-width at half maximum) at all positions in air, differed by less than 0.4% from the measurements.
Dose calculation with the beam model for the MedAustron clinical beam line agreed better than 1.7% in absolute dose for a representative clinical case treated with protons.
For protons, beam model generation, including geometry creation, data conversion, and validation, was possible within three working days.The number of iterations required for the optimization process to converge, was found to be similar for all beam line geometries and particle types.

The presented method was demonstrated to work independently of the beam optics behavior of the different beam lines, particle types and geometries. Furthermore, it is suitable for non-expert users and requires only limited user interaction. Beam model validation for different beam lines based on different beam delivery systems, showed good agreement.

Keywords: Monte Carlo; beam modeling; optimization; proton therapy; carbon ions; particle therapy

Publ.-Id: 30721

Relationships between depth-resolved primary radiation damage, irradiation-induced nanostructure and nanoindentation response of ion-irradiated Fe-Cr and ODS Fe-Cr alloys

Vogel, K.; Heintze, C.; Chekhonin, P.; Akhmadaliev, S.; Altstadt, E.; Bergner, F.

Ion irradiations are indispensable for exploring radiation effects on materials, for example, radiation hardening. However, the extraction of radiation hardening as function of displacement damage from the nanoindentation (NI) response of self-ion-irradiated metallic alloys is a challenge. In particular, recent attempts suffer from interference with contributions arising from injected self-interstitial atoms. Moreover, instances of available microstructural evidence and NI results reported for the same material and same irradiation are rare. In order to tackle these issues, the depth-dependent irradiated microstructure and the NI response were analyzed for Fe-9Cr and oxide dispersion strengthened Fe-Cr alloys irradiated with 5 MeV iron ions. Cross-sectional transmission electron microscopy indicated the appearance of irradiation-induced dislocation loops but no other types of visible microstructural changes. NI indicated maxima of the radiation hardening as function of contact depth. Links between the depth-resolved primary radiation damage, the observed depth-dependent characteristics of loops and the measured hardening are considered. As a key point, the link between loops and hardening requires the integration of the local hardening contributions over the indentation plastic zone. Calculations and measurements are compared with respect to both the depth position of maximum hardening and the substrate effect. The role of the model assumptions is discussed with special emphasis on the plastic zone size and the superposition of hardening contributions. The latter is found to be material-specific. The model also allows hardening contributions arising from displacement damage and injected interstitials to be separated.

Keywords: Fe-alloys; ion irradiation; TEM; nanoindentation; irradiation hardening

Related publications


Publ.-Id: 30720

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