Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34118 Publications

Helium Ion Microscope Imaging and Time-of-Flight Secondary Ion Mass Spectrometry depth profiling of sample cross sections

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

The Helium ion microscope is well known for its high-resolution imaging and nanofabrication performance. We have recently developed and presented a time-of-flight based secondary ion mass spectrometer that can be retrofitted to existing microscopes [1, 2].

Depth profiling in SIMS in general is usually done by sputtering into deeper layers and plotting the signal intensity over time. The actual milling depth can only be estimated and the common approach is to measure the crater depth with atomic force microscopy every time a compositional change is observed.

Direct imaging and chemical analysis of a cross-section with high spatial resolution can avoid this challenge. The cross sections will be prepared ex-situ by milling, grinding and low energy argon ion polishing.

[1] Klingner, N.; Heller, R.; Hlawacek, G.; von Borany, J.; Notte, J. A.; Huang, J. and
Facsko, S.; Ultramicroscopy 162(2016), 91-97
[2] Klingner, N.; Heller, R.; Hlawacek, G.; Facsko, S. and von Borany, J.; Ultramicroscopy 198(2019), 10-17

  • Lecture (Conference)
    PicoFIB - Advances in Gas-Ion Microscopy, 20.01.2020, Sheffield, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-30149
Publ.-Id: 30149


Numerical simulation of adiabatic two phase flow in horizontal elbow bends

Abdlgwad, A.

In industry there is need for predicting the morphology of two-phase liquid-gas flows that are part of e.g. distillation processes, pipeline transport units, chemical reactors or heat transfer units. Knowledge of the behavior of the flow and its regime facilitate for the engineers to have proper design of downstream processes and the pipeline in order to achieve the best reliable and economic outcome. One topic that is not studied sufficiently is the characterization of not fully developed flow due originated from insufficient developing or calming length as it can be found downstream of elbow bends and in short straight pipes, which are frequently encountered in industrial applications. In order to study this topic and characterize the flows, an experimental instrumentation was set up using Wire-mesh Sensors. This work is a numerical work using ANSYS CFX 19.1 in order to set up simulations of the experimentally investigated pipe geometries and flow regimes, followed by validation with the WMS data. Therefore, this work is concerned with gas-liquid flow in a horizontal straight pipe of DN50 and DN200 and horizontal elbow bends with the same diameters and curvature ratio of R/D=1. Each of the geometries is studied for annular and stratified wavy flow.

  • Master thesis
    Grenoble INP, 2019
    Mentor: Alexander Döß
    36 Seiten

Permalink: https://www.hzdr.de/publications/Publ-30148
Publ.-Id: 30148


Charakterisierung von Zweiphasenströmungen in komplexen Rohrgeometrien

Junge, P.

Die vorliegende Arbeit beschäftigt sich mit der Charakterisierung einer Zweiphasenströmung durch eine komplexe Rohrgeometrie in Form eines horizontalen 90°-Rohrbogens mit einem Innendurchmesser D = 50mm und einem relativen Radius R=1 . Basierend auf experi-mentellen Gittersensordaten wird der Bereich stromauf- und stromabwärts der Bogengeometrie untersucht. Die experimentellen Untersuchungen erfolgten an einer horizontalen, nicht vollständig eingelaufenen Zweiphasenströmung. Schwerpunkt der Untersuchungen war da-bei die Beurteilung des Einflusses der Rohrleitungslänge. Ein bleibender Einfluss des Rohrbogens auf die Strömungsmorphologie konnte nicht festgestellt werden. Für die Bestimmung des Gasanteils und des Zweiphasendruckverlustes wurden existierende Modellansätze systematisiert und bezüglich der Anwendung auf nicht eingelaufende Zweiphasenströmungen, bzw. den Bereich des Rohrbogens überprüft. Basierend auf der Abweichung der Korrelationen wurden kombinierte Berechnungsansätze für den Gasanteil und den Zweiphasendruck-verlust ausgewählt, welche die experimentellen Daten mit bester Näherung korrelierten.

  • Diploma thesis
    TU Dresden, 2019
    Mentor: Alexander Döß
    107 Seiten

Permalink: https://www.hzdr.de/publications/Publ-30147
Publ.-Id: 30147


Process Metallurgy in Circular Economy System Design: The Copper and Base Metal Value Chain

Abadias Llamas, A.; Valero, A.; Bartie, N. J.; Stelter, M.; Reuter, M.

Evaluating the economic viability as well as the sustainability of the Circular Economy (CE) system requires a deep understanding of the distribution of all elements, compounds, alloys, materials etc. in flows. In this paper, the circularity of the copper value chain, including primary and secondary processing, is rigorously evaluated. The studied system comprises the metallic copper production from primary sources (from mineral to metal), copper-containing commodity production (copper is mixed with other metals) and copper recycling through secondary smelting to close the loop. This is linked to photovoltaic (PV) panels and battery storage. A simulation model of this system is created using HSC Sim, considering more than 30 elements (and its various compounds), 180 unit operations and 800 flows. From the mass and energy balances obtained through the simulation, an exergy analysis is conducted to evaluate the resource consumption from a second law (entropy) perspective. Additionally, these results are complemented through a Life Cycle Assessment (LCA), the recovery of technology elements and by-products is discussed, while quantifying the losses through the value chain. Through the digitalization of the complete system, a better CAPEX and OPEX understanding of the metal recovery and losses can be obtained, as well as the associated resource consumption and environmental impacts. New flowsheets and technologies can be evaluated. Several scenarios show how the resource consumption and the environmental impacts are affected by the recovery of different materials to produce different products.

Keywords: Copper Value Chain; Exergy; Life Cycle Assessment; Process Simulation; Sustainability Evaluation

  • Lecture (Conference)
    10th Copper International Conference, COPPER 2019 / Conference of Metallurgists, COM 2019, 18.-21.08.2019, Vancouver, Canada

Permalink: https://www.hzdr.de/publications/Publ-30145
Publ.-Id: 30145


Maxwell solver in PIC simulations

Bussmann, M.; Steiniger, K.

Keywords: pseudo-spectral time domain; particle-in-cell; finite difference

  • Invited lecture (Conferences)
    CASUS Miniworkshop on Numerics, 13.-14.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30144
Publ.-Id: 30144


Modeling and understanding the dynamics of relativistic plasmas with particle-in-cell simulations

Bastrakov, S.; Bussmann, M.; Debus, A.; Garten, M.; Hübl, A.; Matthes, A.; Pausch, R.; Widera, R.; Starke, S.; Steiniger, K.

Keywords: particle-in-cell; plasma; laser particle acceleration

  • Poster
    CASUS Opening Symposium, 26.-28.08.2019, Görlitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30143
Publ.-Id: 30143


Industrial By-Products as Non-Conventional Supplementary Cementitious Material

Astoveza, J.; Abadias Llamas, A.; Soth, R.; Trauchessec, R.; Reuter, M.; Pontikes, Y.

The extensive efforts on reducing the carbon footprint of cement production have motivated the investigations on the use of supplementary cementitious materials (SCM) as additive and/or substitute in cement blends. However, previous studies were focused on limited types of SCM including natural pozzolans, ground granulated blast furnace slag (GGBFS) and fly ash – which could readily exhibit reactivity in cementitious systems. In this article, a review on the advances in the valorisation of novel industrial by-products (non-ferrous slag, municipal incinerator bottom ash, and jarosite waste) are presented to provide solution in reducing the volume of industrial landfills while creating greener materials for building applications. The second part of this paper demonstrates a case study applying exergy to compare the footprint of the flowsheets derived from the valorisation of industrial by-products as SCM.

Keywords: green cements; slag; supplementary cementitious materials; bottom ash; jarosite; exergy; life cycle assessment

  • Open Access Logo Lecture (Conference)
    iiSBE Forum of Young Researchers in Sustainable Building, 01.07.2019, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-30142
Publ.-Id: 30142


Accelerator mass spectrometry: Detection of "One in a Quadrillion"

Merchel, S.; Lachner, J.; Rugel, G.; Wallner, A.

Für die Veranstaltung ist kein Abstract erforderlich.

Keywords: AMS

  • Lecture (others)
    Mass Spectrometry Christmas updates seminar, 17.12.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30141
Publ.-Id: 30141


HIFIS Software website: software.hifis.net

Erxleben, F.; Hüser, C.; Huste, T.

HIFIS Software Services' mission is to empower scientists of any domain to implement and to perpetuate modern scientific software development principles in order to make research software engineering more sustainable. The website of the platform is built using the static site generator Jekyll and available via https://software.hifis.net.

Keywords: Open Source; Software Engineering; Software; Development

  • Software in external data repository
    Publication year 2019
    Programming language: HTML, CSS, Javascript, Jekyll
    System requirements: Firefox, Chrome, Safari, Edge
    License: Code: GPLv3 Content: CC-BY-4.0 (Link to license text)
    Hosted on HZDR GitLab: Link to location

Permalink: https://www.hzdr.de/publications/Publ-30140
Publ.-Id: 30140


Observation of sub-femtosecond structures in laser wakefield accelerated electron bunches

Zarini, O.; Köhler, A.; Couperus Cabadağ, J. P.; Pausch, R.; Laberge, M.; Kurz, T.; Schöbel, S.; Bussmann, M.; Schramm, U.; Downer, M.; Debus, A.; Irman, A.

Laser wakefield accelerators (LWFA) feature unique electron bunch characteristics, namely micrometer beam size with duration ranging from a few fs to tens of fs. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future table-top x-ray light-sources.
Spectral measurements of broadband transition radiation from LWFA electron bunches passing through a metal foil are especially promising for non-destructively analyzing ultrashort longitudinal bunch characteristics with single-shot capability.

Our broadband, single-shot spectrometer combines the TR spectrum in UV/VIS (200-1000nm), NIR (0.9-1.7μm) and mid-IR (1.6-12μm). A complete characterization and calibration of the spectrometer have been done with regard to wavelengths, relative spectral sensitivities, and absolute photometric sensitivity. Our spectrometer is able to characterize electron bunches with charges as low as 1 pC and resolve time-scales from 0.4 to 40 fs. In addition, complementary data on the transverse bunch profile is provided by simultaneously imaging the CTR in the far- and near-field.

We present recent experimental results of different LWFA injection mechanisms, such as self-truncated ionization-injection and self-injection. By analyzing the transition radiation spectra and reconstructing electron bunch profiles including error analysis, we determine electron bunch profiles and peak currents of the respective injection regimes. In addition to bunch durations and peak currents, we discuss sub-fs beam micro-structures and systematic experimental scans of the nitrogen doping concentration for ionization-induced injection.

  • Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop, 15.-21.09.2019, Elba, Italien

Permalink: https://www.hzdr.de/publications/Publ-30139
Publ.-Id: 30139


Optimierungsaspekte bei der Herstellung von L-[11C]Methionin mit dem Tracerlab FXC-pro System

Mäding, P.; Zessin, J.; Knieß, T.

L-[11C]Methionin ([11C]Met) ist ein oft verwendetes PET-Radiopharmakon zur Diagnose Hirn-, Kopf-, Hals- sowie vom multiplen Myelom indizierten Tumoren. Die Radiosynthese von [11C]Met ausgehend von [11C]CO2 mit dem TRACERlab FXC-pro System liefert mitunter schwankende Ausbeuten, deren Ursache unklar ist.

Permalink: https://www.hzdr.de/publications/Publ-30137
Publ.-Id: 30137


Copper-mediated automated radiofluorination and biological evaluation of a highly affine cannabinoid receptors type 2 ligand with PET

Teodoro, R.; Toussaint, M.; Gündel, D.; Deuther-Conrad, W.; Wenzel, B.; Brust, P.; Moldovan, R.-P.

Objectives: The development of CB2R PET radioligands has been intensively explored due to the pronounced CB2R upregulation in various pathological conditions. Herein we report on the development of a series of highly affine fluorinated indole-carbamate ligands targeting the CB2R. Starting from a pinacol-ester precursor, cooper-mediated automated radiofluorination and preliminary biological evaluation were also performed for the most promising ligand.
Methods: A series of fifteen indole-carbamate derivatives was synthesized and their binding affinities (Ki) towards CB2R were determined. Compound RM365 was further selected for PET development due to its high CB2R affinity (KiCB2 = 2.1 nM) and pronounced selectivity over CB1R (factor >300). A fully automated copper-mediated radiofluorination of [18F]RM365 was established starting with the corresponding arylboronic ester precursor. The metabolic stability of [18F]RM365 was investigated in plasma and brain samples (30 min p.i) by radio HPLC. PET studies with [18F]RM365 were performed under baseline and blocking conditions (60 min scan).

Results: [18F]RM365 was obtained with moderate radiochemical yield (5%), high radiochemical purity (>98%) and molar activities of about 35 GBq/µmol. PET studies revealed that [18F]RM365 readily crossed the blood-brain barrier and accumulated in the spleen, a CB2R-rich organ. Metabolite studies at 30 min p.i. showed that 55% and 90% of the total extracted activity accounted for the percentage of parent tracer, in plasma and brain samples, respectively.

Conclusion: A fully automated cooper-mediated radiosynthesis was established for [18F]RM365. Further blocking experiments will demonstrate the CB2R specificity of [18F]RM365 in vivo and will be use as pass-fail criterion for further application of the radiotracer in CB2R-related animal models.

  • Poster
    Society of Nuclear Medicine and Molecular Imaging, 12.-16.06.2020, New Orlans, USA

Permalink: https://www.hzdr.de/publications/Publ-30134
Publ.-Id: 30134


Directionality of metal-induced crystallization and layer exchange in amorphous carbon/nickel thin film stacks

Janke, D.; Munnik, F.; Julin, J. A.; Hübner, R.; Grenzer, J.; Wüstefeld, C.; Gemming, S.; Rafaja, D.; Krause, M.

In thin amorphous carbon (a-C) films being in contact with a thin nickel layer, metal-induced crystallization and layer exchange (LE) occur at temperatures lower than 700 °C. Analysis of thin film stacks with different architectures (a-C/Ni, Ni/a-C and Ni/a-C/Ni) by means of ion beam analysis, Raman spectroscopy, X-ray diffraction and transmission electron microscopy revealed that the degree of LE and the structural quality of the crystallized carbon layers depend on the initial layer sequence. A LE degree of approx. 93 % was found for Ni/a-C bilayers, where graphenic layers formed on the Ni surface, whereas in a-C/Ni bilayers only 83 % of carbon was transferred from the surface towards the fused silica substrate. The diffusion of carbon in the outward direction produces turbostratic carbon with basal planes oriented parallel to the Ni surface, while for the inward direction planar and curved turbostratic structures coexist. The crystallization and the LE are driven by the crystallization energy of a-C. The LE is mediated by the wetting of the Ni grain boundaries by carbon. The directionality of the LE was explained primarily by the difference in the surface and interface energies in the a-C/Ni and Ni/a-C stacks that were obtained from thermodynamic considerations.

Keywords: metal-induced crystallization; layer exchange; carbon/nickel; thin films; turbostratic carbon; Raman spectroscopy; ion beam analysis

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  • Secondary publication expected from 05.12.2021

Permalink: https://www.hzdr.de/publications/Publ-30133
Publ.-Id: 30133


The Evolving Landscape of Biomarkers for Anti-PD-1 or Anti-PD-L1 Therapy

Tunger, A.; Sommer, U.; Wehner, R.; Kubasch, A. S.; Grimm, M.-O.; Bachmann, M.; Platzbecker, U.; Bornhaeuser, M.; Baretton, G.; Schmitz, M.

The administration of antibodies blocking the immune checkpoint molecules programmed cell death protein 1 (PD-1) or programmed cell death 1 ligand 1 (PD-L1) has evolved as a very promising treatment option for cancer patients. PD-1/PD-L1 inhibition has significantly enhanced expansion, cytokine secretion, and cytotoxic activity of CD4(+) and CD8(+) T lymphocytes, resulting in enhanced antitumor responses. Anti-PD-1 or anti-PD-L1 therapy has induced tumor regression and improved clinical outcome in patients with different tumor entities, including melanoma, non-small-cell lung cancer, and renal cell carcinoma. These findings led to the approval of various anti-PD-1 or anti-PD-L1 antibodies for the treatment of tumor patients. However, the majority of patients have failed to respond to this treatment modality. Comprehensive immune monitoring of clinical trials led to the identification of potential biomarkers distinguishing between responders and non-responders, the discovery of modes of treatment resistance, and the design of improved immunotherapeutic strategies. In this review article, we summarize the evolving landscape of biomarkers for anti-PD-1 or anti-PD-L1 therapy.

Keywords: cancer immunotherapy; immune monitoring; immune checkpoints; programmed cell death protein 1; programmed cell death 1 ligand 1

Permalink: https://www.hzdr.de/publications/Publ-30131
Publ.-Id: 30131


Test Eintrag

Huste, T.; Fiedler, M.

Test abstract Test abstract Test abstract Test abstract

Keywords: Test; Test2; Test3

  • Open Access Logo Lecture (others)
    Testkonferenz, 11.-12.12.2019, Dresden, Deutschland
    Published in the HZDR-Repository RODARE (Test)
    DOI 10.14278/rodare.390

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30130
Publ.-Id: 30130


Test: Testtitle

Hüser, C.

test abstract test abstract test abstract test abstract

Keywords: keyword1; keyword2

  • Open Access Logo Lecture (others)
    Testkonferenz, 16.-19.12.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30129
Publ.-Id: 30129


Radiopharmacological Evaluation of Cyclohexanediamine-Triazole-Peptide Conjugates Labeled via the Al18F-Approach

Sihver, W.; Böhme, J.; Walther, M.; Wodtke, R.; Reissig, F.; Mamat, C.; Neuber, C.; Ullrich, M.; Pietzsch, J.; Pietzsch, H.-J.

Aim/Introduction: The Al18F-labeling method is as modern technique an alternative to conventional 18F-labeling procedures that allows radiofluorination of biomolecules such as peptides and proteins in a one-step procedure in aqueous solution [1]. In search for versatile applicable chelators, which allow stable binding of both 18F and radiometals such as 68Ga or 111In, a cyclohexanediamine-triazole-chelator was designed. This chelator was conjugated via copper-catalyzed azide-alkyne cycloaddition (CuAAC) to the well-known binding motif (glutamate-urea-lysine) of the prostate-specific membrane antigen (PSMA) [2-5] complemented by 2-azidoacetyl moiety as linker unit (ligand L1). Furthermore, ligand L2 was synthesized bearing a 6-azidohexanoyl moiety as linker to investigate the influence of the linker on the stability of final 18F or radiometal complex.
The aim of this study was to investigate the radiopharmacological potential of L1 and L2 after radiolabeling regarding binding properties, cell internalization, and in vivo behavior in a murine prostate cancer model.
Methods: For the in vitro assays PSMA-positive LNCaP cells were used. The incubation with the respective radiolabeled ligand (RCY>95%) was terminated via a cell harvester. Internalization experiments were carried out by the “acid wash” method. In vivo studies (biodistribution and small animal PET) were performed with mice bearing a prostate tumor.
Results: In competition assays versus [177Lu]Lu-PSMA-617 (“gold standard”), the affinity of non-labeled L1 and L2 was slightly lower than that of PSMA-617. Saturation analysis of [68Ga]Ga-L1, [111In]In-L1, and [18F]F-L1 binding on LNCaP homogenate was comparable to [18F]F-L2 binding. The obtained Kd values were in a range of 20 to 30 nM. Internalization experiments with LNCaP cells revealed a lower uptake of the differently labeled L1 and L2 conjugates compared to [64Cu]Cu-PSMA-617.
Furthermore, in vivo behavior of both [18F]F-L1 and [18F]F-L2 was investigated in prostate carcinoma bearing mice by biodistribution experiments and small animal PET imaging. Thereby, PSMA dependent tumor uptake could be observed.
Conclusion: After successful radiolabeling, the conjugates L1 and L2 showed promising binding properties towards PSMA. The chelator presented here offers a flexible platform for radiolabeling of peptides or proteins for various PET and SPECT applications.
References: [1] F. Cleeren, Bioconjugate Chem. 2016, 27, 790. [2] K. Kopka, J. Nucl. Med. 2017, 58,17S. [3] H.R. Kulkarni, Br. J. Radiol. 2018, 91, 20180308. [4] Y. Tolkach, Breast Cancer Res.Treat. 2018, 169, 447. [5] M.C. Haffner, Hum.Pathol. 2009, 40, 1754.

Keywords: chelator; Al18F-labeling; 111In- and 68Ga-labeling; PSMA

  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 46(2019)Suppl 1, OP-337
    DOI: 10.1007/s00259-019-04486-2

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30128
Publ.-Id: 30128


Effect of the dopant location and the number of Bragg mirrors on the performance of superlattice infrared photodetectors

Pereira, P. H.; Penello, G. M.; Pires, M. P.; Helm, M.; Schneider, H.; Souza, P. L.

We have investigated the influence of the position of the dopants and the number of Bragg mirrors in the confinement of localized states in the continuum of a InGaAs/InAlAs superlattice with a structural defect. The potential profile of the conduction band of the superlattice was determined by self-consistently solving the Schrödinger-Poisson equations. The influence of these parameters was analyzed by the oscillator strength of the optical transition between the ground state and the first localized state in the continuum. The best location for the dopants is in the structural defect quantum well, for which an oscillator strength of 0.25 was obtained. It is found that two Bragg mirrors are enough to confine the first localized state in the continuum without decreasing the oscillator strength of the optical transition from the ground state.

Keywords: superlattice infrared photodetector; InGaAs/AlGaAs; quantum well; continuum state

  • Contribution to proceedings
    IEEE Symposium on Microelectronics Technology and Devices (SBMicro), 26.-30.08.2019, São Paulo, Brazil
    2019 34th Symposium on Microelectronics Technology and Devices (SBMicro)
    DOI: 10.1109/SBMicro.2019.8919485

Permalink: https://www.hzdr.de/publications/Publ-30127
Publ.-Id: 30127


Exploring the multiparameter nature of EUV-visible wave mixing at the FERMI FEL

Foglia, L.; Capotondi, F.; Höppner, H.; Gessini, A.; Giannessi, L.; Kurdi, G.; Lopez Quintas, I.; Masciovecchio, C.; Kiskinova, M.; Mincigrucci, R.; Naumenko, D.; Nikolov, I. P.; Pedersoli, E.; Rossi, G. M.; Simoncig, A.; Bencivenga, F.

The rapid development of extreme ultraviolet (EUV) and x-ray ultrafast coherent light sources such as free electron lasers (FELs) has triggered the extension of wave-mixing techniques to short wavelengths. This class of experiments, based on the interaction of matter with multiple light pulses through the Nth order susceptibility, holds the promise of combining intrinsic ultrafast time resolution and background-free signal detection with nanometer spatial resolution and chemical specificity. A successful approach in this direction has been the combination of the unique characteristics of the seeded FEL FERMI with dedicated four-wave-mixing (FWM) setups, which leads to the demonstration of EUV-based transient grating (TG) spectroscopy. In this perspective paper, we discuss how the TG approach can be extended toward more general FWM spectroscopies by exploring the intrinsic multiparameter nature of nonlinear processes, which derives from the ability of controlling the properties of each field independently.

Keywords: free-electron laser pulses; x-ray; four-wave-mixing experiments; coherence; spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-30124
Publ.-Id: 30124


A hybrid inclined rotating fixed bed reactor model for the identification of process intensification potential

Timaeus, R.; Schubert, M.; Hampel, U.

The superimposed rotation and inclination of a catalytic fixed bed reactor is a promising process intensification strategy for gas-limited multiphase reactions. The reactor inclination forces flow stratification and the rotation leads to a binary and intermittent catalyst wetting. This way, the accessibility of the gas-phase to the catalyst is enhanced and a twofold increase of the conversion for the α-methylstyrene hydrogenation was shown experimentally. In this contribution, a hybrid model approach is introduced to predict the space-time-yield for the hydrogenation of α-methylstyrene and to identify beneficial operating conditions to enhance the process performance.

Keywords: Multiphase reactor; transport phenomena; process intensification; reactor modeling

  • Invited lecture (Conferences)
    Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-14), 30.05.-03.06.2019, Guilin, China

Permalink: https://www.hzdr.de/publications/Publ-30122
Publ.-Id: 30122


Identification of the process windows of inclined rotating fixed-bed reactors with concentric tube – a hydrodynamic analysis

Timaeus, R.; Schleicher, E.; Bieberle, A.; Hampel, U.; Schubert, M.

The inclined rotating fixed-bed reactor with inner tube is a promising process intensification concept for gas-limited reactions. In order to take full advantage of the reactor concept the installation of an inner concentric displacement tube is proposed to support the wetting intermittency of the whole fixed-bed at different liquid filling levels. The effects of operating conditions and design parameters on flow stratification, liquid filling level and specific pressure drop are analysed to identify the process window. In particular, the influence of superficial phase velocities, inclination angle, rotational velocity, particle diameter and inner tube diameter are studied. The liquid phase distribution is characterized with a capacitance-based wire-mesh sensor, which is adapted to cope with organic liquid, porous alumina catalyst packings and reactor rotation. Furthermore, the radial porosity distribution in the annular fixed-beds is determined using gamma-ray computed tomography.

Keywords: Inclined rotating fixed-bed; Process intensification; Capacitance wire-mesh sensor; Multiphase reactor

Related publications

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  • Secondary publication expected from 20.07.2021

Permalink: https://www.hzdr.de/publications/Publ-30121
Publ.-Id: 30121


Test: Upload Presentation

Huste, T.

Test abstract with extremely important content.

Keywords: Test; PDF; RODARE; tag with space

  • Open Access Logo Lecture (others)
    Testkonferenz, 11.12.2019, Dresden, Deutschland
    Published in the HZDR-Repository RODARE (Test)
    DOI 10.14278/rodare.384

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30120
Publ.-Id: 30120


Kit-like 18F-labeling using triazole-linked conjugates for [18F]aluminum monofluoride complexation

Walther, M.; Neuber, C.; Bergmann, R.; Pietzsch, J.; Pietzsch, H.-J.

Objectives: For about 10 years, numerous ligands have been developed and tested for their suitability for 18F-labeling in the form of [18F]aluminum monofluoride. Initially, the well-known macrocyclic ligands NOTA and NODA [1,2] with high temperature reactions were used. Under current approaches, open chain ligands, derived from ethylene diamine, provide a much faster complex formation at lower temperatures (<40°C) [3]. The use of a terminal alkyne linker, as one of these new approaches, also enables the conjugation to target molecules via copper catalyzed azide-alkyne cycloaddition (CuAAC) as the final step in ligand synthesis. Furthermore, these triazole-containing ligands offer interesting additional applications, besides kit-like 18F-labeling, they also can be used for the stable fixation of other radiometal ions preferring a six-fold coordination. Radionuclides like 68Ga, 111In or 64Cu show promising results with these ligands and are under current investigation.
Methods: Ligand L1-L3 synthesis was carried out via CuAAC with subsequent product characterization. Radiolabeling reactions with the ligands L1-L3 were carried out under comparable conditions for different radionuclides: 0.1 M sodium acetate buffer pH 4-5, 10 µg ligand, 20 min mixing at room temperature with [68Ga]GaCl3, [111In]InCl3, [64Cu]CuCl2 or freshly prepared [18F]AlFCl2-solution. Examples for the ligand synthesis, radiolabeling experiments with different radionuclides, stability studies and initial in vitro and in vivo studies will be presented in this work.
Results: The [68Ga]Ga-L1, [64Cu]Cu-L1, and [18F]AlF-L1 complexes show comparable in vivo behavior 5 min after single intravenous injection in NMRI nu/nu mice. The gallium and fluorine labeled species show faster renal elimination than the copper compound. The [68Ga]Ga-L1 complex also shows higher stability in serum than the corresponding copper complex [64Cu]Cu-L1. The 18F-labeled species show very low defluorination in vivo and therefore high stability.
Conclusion: The incorporation of the ligand via CuAAC opens up many new possibilities for the radiolabeling of peptides and small antibody-derived proteins by 18F as coordinated [18F]aluminum monofluoride. Additional options are given due to the flexibility of the triazole-containing conjugates for further radionuclides like 68Ga, 64Cu and 111In.

Keywords: 18F-radiolabeling; aluminum monofluoride

  • Lecture (Conference)
    23rd International Symposium on Radiopharmaceutical Sciences, 26.-31.05.2019, Beijing, China
    DOI: 10.1002/jlcr.3724

Permalink: https://www.hzdr.de/publications/Publ-30119
Publ.-Id: 30119


Finite-size effects in ultrafast remagnetization dynamics of FePt

Willig, L.; von Reppert, A.; Deb, M.; Ganss, F.; Hellwig, O.; Bargheer, M.

We investigate the ultrafast magnetization dynamics of FePt in the L10phase after an optical heating pulse, asused in heat-assisted magnetic recording. We compare continuous and nano-granular thin films and emphasizethe impact of the finite size on the remagnetization dynamics. The remagnetization speeds up significantlywith increasing external magnetic field only for the continuous film, where domain-wall motion governs thedynamics. The ultrafast remagnetization dynamics in the continuous film are only dominated by heat transportin the regime of high magnetic fields, whereas the timescale required for cooling is prevalent in the granular filmfor all magnetic field strengths. These findings highlight the necessary conditions for studying the intrinsic heattransport properties in magnetic materials.

Permalink: https://www.hzdr.de/publications/Publ-30118
Publ.-Id: 30118


In vivo stable bisarylmercury bispidine as a tool for Hg‐197(m) applications

Gilpin, M.; Walther, M.; Pietzsch, J.; Pietzsch, H.-J.

Intro
Reactor‐produced Hg‐197 saw previous medical use in radiolabelled chlormerodrin for SPECT imaging[1] in the 1960s and 70s but was discontinued because of the up-and‐coming Tc‐99m generator system's widespread use, the uncertain in vivo stability of Hg‐197 labelled compounds and the low molar activity of the Hg‐197 itself (<2 GBq/μmol).[2] Cyclotron produced Hg‐197(m) is able to overcome the chemical toxicity issue, due to the much higher molar activity achieved (>500 GBq/μmol),[3] allowing access, at innocuous mercury concentrations, to the theranostically useful decay modes and half‐life of the radiometal's metastable nuclear isomer (γ for SPECT imaging and conversion and auger electrons for tumour therapy. Hg‐197g T1/2 = 64.1 h, Hg‐197m T1/2 = 23.8 h).
Objective
The development of an in vivo stable mercury compound able to conjugate to a cancer‐targeting carrier. Radiopharmaceutical applications obviously require high in vivo stability but the fast metabolism of most mercury compounds in solution is a prevalent issue.[4] However, Hg‐C organometallics show good water‐stability and bypass the issue of Hg‐S bonds suffering from competition by common thiol‐containing biomolecules, e.g., cysteine. Therefore, this project is specifically focussed on the strongest of this kind: the mercury‐phenyl bond.[5] Previous study has shown that the syntheses of monodentate ligands for κ1‐L2Hg species suffer from significant cleavage. [6] For this reason, our research is centred on the synthesis of a bidentate chelator design, due to the entropic advantage, the improved formation kinetics and the stability imparted by steric shielding.
Current Results
Separation from the gold target leaves the produced Hg‐197(m) in an acidic aqueous solution as the chloride salt. Consequently, transmetallation, via boronic acid or stannyl derivatives, was chosen as a feasible route for forming the mercury‐carbon bonds. Following several chelator attempts, all showing low selectivity for the 1:1‐compound, a better fitting structure was found using the bispidine backbone (being known in co‐ordination chemistry for a variety of metals, good bio‐stability and its bridge linking‐functionalisation).[7] After improvement of the reaction conditions, radiolabelling experiments showed good evidence of specific binding with the bispidine derivative 9‐butyl‐1,5‐diphenyl‐3,7‐bis(2‐(trimethylstannyl)benzyl)‐3,7‐diazabicyclo[3.3.1]nonan‐9‐ol “L1(SnMe3)2,” as analysed by thiol‐impregnated radio‐TLC and supported by radio‐HPLC, whilst ESI‐MS of the stable mercury compound provided evidence that the desired 1:1 product had been formed. The in vitro stability tests conducted on the radiolabelled compound showed exciting results, with negligible degradation after 5 days (thereafter the activity was below analytical levels) in solutions with excess glutathione and 2,2′,2″‐nitrilotris (ethane‐1‐thiol). The only noticeable (ca. 5% degradation after 48 h), but expected reaction, was with sodium sulphide. Biodistribution experiments in healthy male Wistar rats showed no build‐up in the kidneys, with excretion occurring through the liver, indicating no de‐metallation.
Summary
The bisarylmercury bispidine (L1Hg) shows good stability in vitro as well as in vivo and is a promising candidate as a biocompatible mercury binding compound. Further
research is continuing into full characterisation, conjugation to peptides and proteins, subsequent in vivo studies and for derivatives based on the structural design.

ACKNOWLEDGEMENTS
Regina Herrlich, Ulrike Gesche, Thomas Wünsche. Hg‐197(m) measurements were carried out at the CANAM infrastructure of the NPI CAS Rez supported through MEYS project no. LM2011019.

REFERENCES
1. Sodee DB. Comparison of 99mTc‐pertechnetate and 197Hgchlormerodrin for brain scanning. J Nucl Med 1968;9(12):645.
2. Ribeiro Guevara S, Zizek S, Repinc U, Perez CS, Jacimovic R, Horvat M. Anal Bioanal Chem 2007;387:2185–2197.
3. Walther M, Preusche S, Bartel S, Wunderlich G, Freudenberg R, Steinbach J, Pietzsch H‐J. Appl Radiat Isot 2015;97:177‐181.
4. Henke KR, Robertson D, Krepps MK, Atwood DA. Wat Res 2000;34:3005‐3013.
5. Dean JA. Lange's Handbook of Chemistry, 15th ed. McGraw‐Hill, Inc: 1998.606 p.
6. Wilhelm M, Saak W, Strasdeit H. Z Naturforsch 2000;55b:35‐38.
7. Comba P, Haaf C, Wadepohl H. Inorg Chem 2009;48:6604‐6614.

Keywords: Mercury-197; Chelator; Ligand; Radiometal; Bispidine; Cancer; Theragnostics

  • Lecture (Conference)
    23rd International Symposium on Radiopharmaceutical Sciences, 26.-31.05.2019, BeiJing, China

Permalink: https://www.hzdr.de/publications/Publ-30116
Publ.-Id: 30116


Carbon monoxide-releasing molecules for biomedicinal applications

Kubeil, M.; Geri, S.; Mamat, C.; Stephan, H.

Carbon monoxide has been demonstrated to exhibit several beneficial effects on biological targets (anti-inflammatory, anti-proliferative, anti-apoptotic effects, causes vasodilation, etc.).1 Consequently, the development of CO releasing molecules (CORMs), that allows for controlled release of CO under physiological conditions, has therefore become a major field of scientific and medical interest.2,3 Considerable research interest has been drawn on light-activated CORMs (photoCORMs) which only release CO upon radiation with a certain energy. However, despite a large number of photoCORMs reported, relatively little information is available on the precise mechanism of CO release from most photoCORMs and even less compounds have been tested as anti-cancer agents in cells so far.
Herein, we report about the synthesis of ruthenium(II) dicarbonyl complexes functionalized with bidentate or tridentate (pyridyl, phenanthroline or diquinolyl) ligands and appending dyes for tuning the release properties as well as tracking the compound in cells. The mechanism of CO release in aqueous media (before and after light-activation) has been investigated. The photo-induced CO release kinetics of the Ru(II) photoCORMs, as well as in vitro studies in cancerous and healthy cell lines will be presented.4,5

References

[1] R. Motterlini, L. E. Otterbein, Nat. Rev. Drug Discov. 9 (2010) 728-743.
[2] U. Schatzschneider, Br. J. Pharmacol. 172 (2015) 1638-1650.
[3] F. Zobi, Future Med. Chem. (2013) 5, 175-188.
[4] M. Kubeil, R. R. Vernooij, C. Kubeil, B. R. Wood, B. Graham, H. Stephan, L. Spiccia, Inorg. Chem. 56 (2017) 5941-5952.
[5] M. Kubeil, T. Joshi, B. R. Wood, H. Stephan, ChemistryOpen (2019) 8, 637-642.

Acknowledgements

MK was supported by a Marie Curie International Outgoing Fellowship from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 627113.

Keywords: CORM; photoactivatable; ruthenium; in vitro studies

  • Lecture (Conference)
    3rd International Caparica Christmas Conference on Translational Chemistry, 01.-05.12.2019, Caparica, Lisboa, Portugal

Permalink: https://www.hzdr.de/publications/Publ-30115
Publ.-Id: 30115


Simulation and economic assessment of a small ammonia production plant using electricity purchased in the day-ahead market

Rodriguez Garcia, G.; Bergander, S.; Hampel, U.

Ammonia is one of the most highly produced chemicals in the world, being the source of all nitrogen-based fertilizers. Its conventional production relies on fossil fuels reforming as its source of hydrogen, cryogenic air separation for nitrogen, and the Haber-Bosch process for the ammonia synthesis itself. This route has made ammonia production responsible for the consumption of 1% of all energy worldwide, and for the emissions of 298 Mt CO2 eq./year. In a future where most energy comes from fluctuating sources, such as the one envisioned in the Energiewende, energy intensive industries like ammonia production would need to adapt its operation to mimic that of energy generation. A potential alternative for ammonia production is to obtain hydrogen and nitrogen from water electrolysis, and pressure swing adsorption (PSA) respectively. In our effort for the flexibilization of the chemical industry, we have designed a small ammonia production plant using these technologies. With it we intend to cover the fertilizing needs of a large German farm (1,000 ha), requiring a minimum production of 100 t NH3/year. As a first step, we purchased the electricity used for the water electrolyzer in the day-ahead market. The rest of the plant relied on a steady industrial supply. Our first results indicated the plant was not profitable. The main reason behind this are the capital investment in the intermediate hydrogen storage unit

  • Contribution to proceedings
    Oberlausitzer Energiesymposyum & Zittauer Energieseminar, 07.-08.11.2019, Zittau, Deutschland
    Sektorkopplung - eine Herausforderung, Zittau: Hochschule Zittau/Görlitz, 978-3-00-064125-1, 49-53

Permalink: https://www.hzdr.de/publications/Publ-30114
Publ.-Id: 30114


Correlative microscopy of lung epithelial in vitro model exposed to nanoparticles by using super-resolution optical and advanced ion/electron based techniques

Podlipec, R.; Klingner, N.; Heller, R.; Majaron, H.; Pelicon, P.; Strancar, J.; Borany, J.

Clear understanding of molecular events followed by lung epithelial cells/tissue response to inhaled nanoparticles is still lacking. As these interaction events in lungs eventually lead to diseases and potentially persistent inflammation [1,2], one urgently needs new and relevant investigation methods which could provide new insights into the key mechanisms of interaction. In our latest research we have thus focused on this toxicology problem first by developing an appropriate in vitro lung epithelial model and second by developing and implementing relevant advanced correlative imaging techniques capable of gathering more insight of interaction properties on scales well below optical resolution limit. In order to understand the mechanisms of molecular initiative events we have first performed live cell imaging using STED super-resolution microscopy by which few tens to hundred nm resolution was achieved locally. As the technique is incapable of providing resolution further down to nm and lacks the visualization of non-labeled surrounding structures and morphology, we thus introduced suitable complementary correlative microscopy techniques with high surface contrast, SEM and Helium Ion Microscopy (HIM). Main focus, besides sample and sample holder preparation for these high vacuum techniques, was dedicated to HIM measurements which in general are capable of providing better resolution and sensitivity compared to SEM [3]. From this ongoing study we briefly present the first interesting results of correlative microscopy combining optical, electron and ion based techniques on the epithelial cells exposed to TiO2 nanoparticles from micro to nano scale.
References:
1. Li, X., Jin, L. & Kan, H. Air pollution: a global problem needs local fixes. Nature 570, 437–439 (2019).
2. Underwood, E. The polluted brain. Science 355, 342–345 (2017).
3. Hlawacek, G. et Al. Helium Ion Microscopy. J. Vac. Sci. Technol. 32, (2014)

Keywords: Correlative microscopy; optical microscopy; helium ion microscopy; lung epithelium; in-vitro model; TiO2 nanoparticles

  • Lecture (Conference)
    COMULIS & BioImaging Austria - CMI Conference 2019, Correlated Multimodal Imaging, 21.-22.11.2019, Vienna, Austria
  • Poster
    COMULIS & BioImaging Austria - CMI Conference 2019, 21.-22.11.2019, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-30111
Publ.-Id: 30111


Towards correlative live-cell imaging using super-resolution optical and ion/electron based techniques and development of special holders

Podlipec, R.; Sebastijanovic, A.; Vogel Mikus, K.; Pelicon, P.; Strancar, J.

Clear understanding of molecular phenomena of cells/tissue response after interacting with dangerous metal nanoparticles is still lacking. In our research we thus focus on highly relevant scientific/toxicology problem, which is understanding of the mechanisms of molecular initiative events between nanoparticles (typically smaller than 100 nm) and lung tissue cells during inhalation [1]. It is strongly believed that nanoparticles can trigger toxic effects with increasing risk for further cardiovascular diseases [2]. However, limited spatial resolution of optical microscopy, even in super-resolution mode, prevents visualization of interaction phenomena at smaller, nanometer scales which could reveal some of still unclear molecular events. In order to get better insight on the phenomena at such small scales one needs to introduce proper correlative microscopy techniques which in our case are electron (eSEM) and ion based (PIXE, HIM). Since these techniques are commonly employed in high vacuum and detection principles differ reasonably in comparison to optical imaging techniques, special sample holders have to be developed in order to perform efficient correlative microscopy on different submicron scales.
In this pilot study we first tested the performance of correlative microscopy on epithelial cells nebulized with TiO2 nanoparticles using optical, eSEM and RISE techniques, while in the second pilot study we developed the concept for robust special holder preparation in order to enable super-resolution optical imaging (STED) as well as ion based imaging on the same sample site. Despite integrating few to few tens micron sized layers consisting of Mylar foil, water and glass which introduce refractive index mismatches, we were able to improve confocal resolution by at least factor 2-3 using STED imaging. This was a proof-of-concept that we can perform high resolution optical imaging on these holders which can successfully be implemented as well in correlative electron/ion based imaging, thus giving the opportunity to gain better insight of the measured complex samples from nano to micro scale.

[1] Iztok Urbančič et al., “Nanoparticles Can Wrap Epithelial Cell Membranes and Relocate Them Across the Epithelial Cell Layer,” Nano Letters 18, 5294–5305.
[2] Robert D. Brook et al., “Air Pollution and Cardiovascular Disease: A Statement for Healthcare Professionals From the Expert Panel on Population and Prevention Science of the American Heart Association,” Circulation 109, 2655–2671

Keywords: Correlative microscopy; sammple holder; STED imaging; SEM; Helium Ion Microscopy; TiO2 nanoparticles; epithelial cells

  • Lecture (Conference)
    89th IUVSTA Workshop, Biological and soft matter sample preparation for high resolution imaging by high vacuum techniques, 19.-24.05.2019, Zakopane, Poland
  • Poster
    89th IUVSTA Workshop, Biological and soft matter sample preparation for high resolution imaging by high vacuum techniques, 19.-24.05.2019, Zakopane, Poland

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Permalink: https://www.hzdr.de/publications/Publ-30110
Publ.-Id: 30110


Deep Learning Ensemble for Hyperspectral Image Classification

Chen, Y.; Wang, Y.; Gu, Y.; He, X.; Ghamisi, P.; Jia, X.

Deep learning models, especially deep convolutional neural networks (CNNs), have been intensively investigated for hyperspectral image (HSI) classification due to their powerful feature extraction ability. In the same manner, ensemble-based learning systems have demonstrated high potential to effectively perform supervised classification. In order to boost the performance of deep learning-based HSI classification, the idea of deep learning ensemble framework is proposed here, which is loosely based on the integration of deep learning model and random subspace-based ensemble learning. Specifically, two deep learning ensemble-based classification methods (i.e., CNN ensemble and deep residual network ensemble) are proposed. CNNs or deep residual networks are used as individual classifiers and random subspaces contribute to diversify the ensemble system in a simple yet effective manner. Moreover, to further improve the classification accuracy, transfer learning is investigated in this study to transfer the learnt weights from one individual classifier to another (i.e., CNNs). This mechanism speeds up the learning stage. Experimental results with widely used hyperspectral datasets indicate that the proposed deep learning ensemble system provides competitive results compared with state-of-the-art methods in terms of classification accuracy. The combination of deep learning and ensemble learning provides a significant potential for reliable HSI classification.

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Permalink: https://www.hzdr.de/publications/Publ-30109
Publ.-Id: 30109


Automatic Design of Convolutional Neural Network for Hyperspectral Image Classification

Chen, Y.; Zhu, K.; Zhu, L.; He, X.; Ghamisi, P.; Benediktsson, J. A.

Hyperspectral image (HSI) classification is a core task in the remote sensing community, and recently, deep learning-based methods have shown their capability of accurate classification of HSIs. Among the deep learning-based methods, deep convolutional neural networks (CNNs) have been widely used for the HSI classification. In order to obtain a good classification performance, substantial efforts are required to design a proper deep learning architecture. Furthermore, the manually designed architecture may not fit a specific data set very well. In this paper, the idea of automatic CNN for the HSI classification is proposed for the first time. First, a number of operations, including convolution, pooling, identity, and batch normalization, are selected. Then, a gradient descent-based search algorithm is used to effectively find the optimal deep architecture that is evaluated on the validation data set. After that, the best CNN architecture is selected as the model for the HSI classification. Specifically, the automatic 1-D Auto-CNN and 3-D Auto-CNN are used as spectral and spectral-spatial HSI classifiers, respectively. Furthermore, the cutout is introduced as a regularization technique for the HSI spectral-spatial classification to further improve the classification accuracy. The experiments on four widely used hyperspectral data sets (i.e., Salinas, Pavia University, Kennedy Space Center, and Indiana Pines) show that the automatically designed data-dependent CNNs obtain competitive classification accuracy compared with the state-of-the-art methods. In addition, the automatic design of the deep learning architecture opens a new window for future research, showing the huge potential of using neural architectures' optimization capabilities for the accurate HSI classification.

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Permalink: https://www.hzdr.de/publications/Publ-30108
Publ.-Id: 30108


UAVs as a Tool for Socially Acceptable Exploration of Waste Rock Dumps

Ajjabou, L.; Kirsch, M.; Lorenz, S.; Zimmermann, R.; Farci, A.; Viezzoli, A.; Gloaguen, R.

There is a growing demand for mineral resources worldwide, and yet industry is facing increasing obstacles in obtaining public acceptance for new exploration and mining projects. Numerous recent citizen protests highlight the public perception of ‘dirty’ mining projects and increase the reluctance of investors to finance explorations. Non-invasive exploration techniques can be defined as energy efficient, low-impact technologies. They assist in the detection and mapping of mineral deposits and improve exploration targeting with minimal environmental impact, while demonstrating that industry cares about reducing disturbance to the communities and environment in which they operate. However, it is increasingly understood that non-invasive technologies can help to maintain the social licence to operate and consequently lower the investment risk of exploration. To demonstrate this premise, we established an EU-funded research initiative called INFACT (Innovative, Non-Invasive and Fully Acceptable Exploration Technologies), which supports the development of innovative exploration and stakeholder engagement approaches. Our project will establish a set of permanent, accessible reference sites to trial and assess the technological and social performance of existing and emerging innovative, non-invasive exploration techniques like UAVs infrared hyperspectral imaging, magnetics, EM and radiometry.

  • Invited lecture (Conferences)
    First EAGE Workshop on Unmanned Aerial Vehicles, 02.-04.12.2019, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-30107
Publ.-Id: 30107


Multi-Source Hyperspectral Data Integration using Image Feature Extraction for Mineral Mapping

Lorenz, S.; Seidel, P.; Ghamisi, P.; Zimmermann, R.; Tusa, L.; Khodadadzadeh, M.; Contreras Acosta, I. C.; Gloaguen, R.

The fusion of remote sensing datasets for combined classifications has recently received great attention. Separate data acquisition and subsequent fusion allow for sensor-specific adjustments of experimental parameters and flexible sensor combinations. In mineral exploration, multi-sensor approaches are particularly promising to extend the range and accuracy of mineral phase detection. However, the time-efficient and accurate integration of data with differing resolution, field of view or acquisition modi remains challenging. This motivates us to promote a multi-source data integration based on efficient feature extraction strategies. An important pre-requisite for a successful integration is data co-registration. A workflow combining automated keypoint detection and matching provides an accurate and fast method to align multi-sensor datasets of different spatial sampling distances for a joint processing. For feature extraction, we employ innovative methods that consider both spatial and spectral aspects such as Orthogonal Total Variation Component Analysis (OTVCA). Besides the reduction of dimensionality and consequently processing time, the method allows the integration of textural and spectral information, such as short wave and long wave hyperspectral imagery or reflectance and luminescence data that are not directly interpretable with a single method. Application-relevant mineral assemblage classes such as alteration zones, ore zones or mineralized veins, become then discriminable as the spatio-spectral patterns are evident by extracting relevant features from all datasets. We use a Support Vector Machine with Radial Basis Function Kernel (SVM-RBF) to demonstrate the classification of mineralogical domains from such multi-source feature fused sets. We choose SVM as it is particularly robust when handling high-dimensional data with low number of training samples and against the heterogeneity of classes that is typical for mineralogical datasets. The optimal classification parameters are determined by five-fold cross- validation to ensure the best possible classification result with the given data. Training data required for the classification can be defined according to user knowledge, high resolution mineralogical analyses or spectral point measurements. The proposed multi-source data integration workflow shows to exceed the classification accuracy of single-source data and could be beneficial for many potential application fields in mineral exploration, mineral processing, recycling or food industry.

  • Lecture (Conference)
    10th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 24.-26.09.2019, Amsterdam, Nederland

Permalink: https://www.hzdr.de/publications/Publ-30105
Publ.-Id: 30105


Impact of Hydrogen-Rich Silicon Nitride Material Properties on Light-Induced Lifetime Degradation in Multicrystalline Silicon

Bredemeier, D.; Walter, D. C.; Heller, R.; Schmidt, J.

The root cause of “Light and Elevated Temperature Induced Degradation” (LeTID) of the carrier lifetime in multicrystalline silicon (mc-Si) wafers is investigated by depositing hydrogen-rich silicon nitride (SiN x :H) films of different compositions on boron-doped mc-Si wafers. The extent of LeTID observed in mc-Si after rapid thermal annealing (RTA) shows a positive correlation with the amount of hydrogen introduced from the SiN x :H layers into the bulk. The concentration of in-diffused hydrogen is quantified via measuring the resistivity change due to the formation of boron–hydrogen pairs in boron-doped float-zone silicon wafers processed in parallel to the mc-Si wafers. The measurements clearly show that the in-diffusion of hydrogen into the silicon bulk during RTA depends on both the atomic density of the SiN x :H film as well as the film thickness. Importantly, the impact of SiN x :H film properties on LeTID shows the same qualitative dependence as the hydrogen content in the silicon bulk, providing evidence that hydrogen is involved in the LeTID defect activation process.

Keywords: carrier lifetime; hydrogen; LeTID defects; light-induced lifetime degradation; silicon nitride; ulticrystalline silicon

Permalink: https://www.hzdr.de/publications/Publ-30103
Publ.-Id: 30103


Numerical simulation of mass transfer enhancement in liquid metal batteries by means of electro-vortex flow

Weber, N.; Nimtz, M.; Personnettaz, P.; Weier, T.; Sadoway, D.

Mass transfer is of paramount importance for an efficient operation of liquid metal batteries. We show for the first time that electrodynamically driven flow can indeed improve mixing of liquid electrodes, and reduces concen tration polarisation substantially. Simulating the discharge of a realistic Li||Bi cell at 1 A/cm², the corresponding overpotential reduces by up to 62%. Moreover, the formation of intermetallic phases is delayed, which improves
capacity usage. Finally, we demonstrate that vertical magnetic fields – which are originating from external sources – change the flow structure entirely, and will homogenise the positive electrode even better.

Permalink: https://www.hzdr.de/publications/Publ-30100
Publ.-Id: 30100


Advanced modelling of complex boron dilution transients in PWRs – Validation of ATHLET 3D-Module against the experiment ROCOM E2.3

Diaz Pescador, E.; Grahn, A.; Kliem, S.; Schäfer, F.; Höhne, T.

Inherent boron dilution in PWRs constitutes one of the key issues in nuclear safety research. This issue has been therefore widely investigated analytically and experimentally through several test facilities in Germany. Besides the knowledge gained on the matter, the experimental research has contributed to the creation of large databases for the validation of computational tools used in accident analyses such as system and computational fluid dynamic (CFD) codes. In Part I of a series of two papers, the multidimensional features of the thermal-hydraulic system code ATHLET are assessed based on the experimental results from the boron dilution experiment E2.3 carried out at the ROCOM test facility. In Part II, a code to code evaluation is performed against the CFD code ANSYS CFX. The aim of the present paper is twofold: first to validate the 3D-Module of ATHLET as well as the “Profile Model I” boron transport model concerning the transport and thermal mixing in the developed multidimensional vessel during the progression of a complex boron dilution event. The obtained results with ATHLET 3.1A are satisfactory and meet the validation exercise goals, especially concerning the calculation of the average boron concentration. However, the limitations of the code to simulate thermal mixing in the cold legs lead to few deviations concerning the calculation of the minimum boron concentration.

Keywords: ATHLET; ROCOM E2.3; thermal mixing; boron dilution; validation exercise

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  • Secondary publication expected from 31.07.2021

Permalink: https://www.hzdr.de/publications/Publ-30098
Publ.-Id: 30098


Modelling of fluid mixing in reactor circuits with the thermal-hydraulic system code ATHLET

Diaz Pescador, E.

Modelling of fluid mixing in reactor circuits with the thermal-hydraulic system code ATHLET

  • Lecture (Conference)
    51. Kraftwerkstechnisches Kolloquium, 22.-23.10.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-30097
Publ.-Id: 30097


Thermal-hydraulic insights during a main steam line break in a generic PWR KONVOI reactor with ATHLET 3.1A

Diaz Pescador, E.; Schäfer, F.; Kliem, S.

The present paper gathers the main insights obtained during the numerical simulation of a 10 % main steam line break (MSLB) in a generic German PWR KONVOI reactor with the thermal-hydraulic system code ATHLET 3.1 A. The contents of this paper are focused first on the transient thermal-hydraulic calculation during affected steam generator (SG) 1 boil-off and subsequently on the multidimensional fluid mixing study of the overcooled water stream and the coolant in the reactor pressure vessel. With this aim, the boundary conditions from the test PKL G3.1, carried out at the PKL test facility in the framework of the OECD/PKL-II project, are implemented in the simulation over the plant nominal parameters from the KONVOI reactor. The thermal-hydraulic and fluid mixing results obtained in the simulations are qualitatively assessed against suitable experimental data from the PKL and ROCOM test facilities, showing a good agreement between simulation and test behaviour.

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  • Secondary publication expected from 01.10.2020

Permalink: https://www.hzdr.de/publications/Publ-30096
Publ.-Id: 30096


Local liquid fraction measurement in annular two-phase flow using x-ray microtomography

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

Annular-dispersed two-phase flow in pipes consists of a thin wavy liquid film covering the pipe wall and a gas core with entrained liquid droplets. Knowledge of the film thickness and entrained liquid fraction is of importance in numerous industrial applications, such as the thermal design of heat exchangers.
The application of X-ray microtomography to obtain these parameters in case of small diameter pipes is presented here. The three-dimensional, time-averaged liquid fraction distribution has been measured in air-water annular flow in a horizontal pipe. In combination with pressure drop measurements, the film and entrained liquid mass flow rates are derived using a simple annular flow model. The portrayed method may also serve as a basis for the validation of computational fluid dynamics simulations of annular flow.

Keywords: horizontal annular flow; X-ray microtomography; droplet entrainment

  • Lecture (Conference)
    10th International Conference on Multiphase Flow, 19.-24.05.2019, Rio de Janeiro, Brazil

Permalink: https://www.hzdr.de/publications/Publ-30095
Publ.-Id: 30095


PREDICT – Predictive Geometallurgy

Bachmann, K.; Tolosana Delgado, R.; Wopat, K.; Smith, A.; Gutzmer, J.

The long‐term availability of minerals and metals from primary (i.e. geogenic) and secondary (i.e. recycling) resources is not only the key to most economic activity, but also to the realization of important societal developments, such as the transition to a renewables‐based energy system and the rollout of e‐mobility. Due to several factors, the utilization of raw materials from geogenic sources will continue to form an essential part of the raw materials supply for a growing global population. In order to develop a highly skilled work force, to develop novel approaches for raw materials utilization, approaches that deploy resource‐ and energy‐efficient technologies for the delineation, extraction and beneficiation of mineral resources, while at the same time minimizing environmental risks, the Helmholtz International Research School for Predictive Geometallurgy (PREDICT) provides the first‐ever training programme dedicated to predictive geometallurgy and adaptive processing. PREDICT has pooled the interdisciplinary and intersectoral expertise of leading German and South African research institutes, world‐leading mining and metallurgical companies, covering all the links in the raw materials chain from exploration to mineral beneficiation and mine planning. PREDICT not only develops cuttingedge methodologies to take geometallurgical resource potential models to an entire new level but also implements and tests an optimal adaptive processing approach for a beneficiation plant model. In addition, we will combine both models by establishing feedback loops for model reconciliation.
Furthermore, PREDICT will close the loop by implementation of the model results in a simulation‐based mine‐planning block model.

  • Invited lecture (Conferences)
    Helmholtz International Research School Selection Meeting, 29.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30094
Publ.-Id: 30094


Predictive geometallurgical modelling

Bachmann, K.

The modern mining industry faces a number of important technical challenges, such as declining ore grades, complex mineral associations, fine-grain size and increasing geological variability. To meet these challenges geometallurgical models are constructed to quantita-tively predict how ores will behave during extraction and beneficiation. Current geometal-lurgical programs carried out by industry, focus on the definition of larger spatial domains that have similar characteristics. However, a consequent application and further develop-ment of geometallurgical programs should lead to an implementation of spatially more highly resolved geometallurgical resource models that are truly predictive for each mined block (including uncertainty), in order to improve raw material quality control and the process efficiency of mining operations. Such an approach would also enable the targeted recovery of by-products, which may generate significant additional revenue and improve overall efficiency. In order to construct relevant resource models, detailed quantitative information on the spatial distribution and geometallurgical behaviour of the by-products within the deposit is crucial.
The aim of this thesis is the development and creation of a predictive geometallurgical model by means of a case study and the presentation of the resulting advantages for the extraction of ores. Based on this, a general structure for the development of predictive geo-metallurgical models is developed, which can be applied to different types of commodities, as well as by-products, is cost-efficient, able to adapt to future data, and predicts metallurgi-cal parameters. As the case study serves the Thaba Chromium Mine in the western Bushveld Complex (South Africa), which is operated by Cronimet Chrome Mining SA (Pty) Ltd. In par-ticular, this thesis focusses on four distinct chromitite seams of the Lower and Middle Groups (LG and MG) at Thaba Mine, namely the LG-6, LG-6A, MG-1 and MG-2, which are considered as target seams for an open-cast and future underground mining scenario.
In order to understand the geological and geochemical architecture of the Thaba Mine deposit and as a foundation of the predictive geometallurgical model, an extensive geo-chemical dataset as well as logging and drill core data provided by Cronimet was evaluated and a 3D geological model was developed. A statistical assessment was performed to evalu-ate the variability within and between the chromitite seams and to separate the mine lease area into distinct geochemical clusters. The distribution of the samples belonging to the dif-ferent geochemical clusters was then transposed onto the geology of the mine lease area. This allowed the definition of spatial domains. These spatial domains, recognized by the as-sessment of assay data only, are then validated by mineralogical attributes; implications for mineral beneficiation are tested and verified.
According to this assessment, the chromitites of the Thaba Mine area can be subdivided into three distinct geochemical domains, domains that constitute the suitable foundation for a geometallurgical model. An extensive supergene altered domain or weathered domain is distinguished from a domain affected by hydrothermal alteration. The latter domain occurs below the depth of modern weathering, but in obvious proximity to faults and around a prominent dunite pipe. The third domain is represented by ores least affected by post-magmatic alteration processes. This domain occupies the centre of fault blocks below the extent of modern weathering.
Furthermore, the geochemical data is used to develop a tailored and easy-to-use multi-variate classification scheme for the chromitite layers in the Thaba Mine, based on a com-prehensive classification routine for the LG and MG chromitites. This routine allows a clear attribution with known uncertainty of all relevant chromitite layers. It comprises of a hierar-chical discrimination approach relying on linear discriminant analysis and involves five dis-tinct steps. Overall classification results for unknown samples belonging to one of the layers are 81 %. The approach may, however, be extended across the entire Bushveld, provided that an appropriate geochemical data set is available.
For detailed characterization of the mineral assemblages in the chromitite ores, selected core samples of the target layers were analysed in detail by various analytical methods, such as Mineral Liberation Analysis and Electron Probe Microanalysis. Therefore, we extended the common measurement protocols for electron probe microanalysis to ensure applicability to a wider range of PGM compositions and its overall accuracy as well as consistency. Based on the results two distinct major mineral assemblages are defined: The first assemblage is rich in platinum group element-sulphides, along with variable proportions of malanite/ cu-prorhodsite and alloys of Fe and Sn. The associated base metal sulphides are dominated by chalcopyrite and pentlandite, along with pyrite and subordinate millerite/ violarite. Associ-ated silicates are mainly primary magmatic orthopyroxene and plagioclase. The second as-semblage is rich in platinum group element-sulpharsenides and -arsenides as well as -antimonides and -bismuthides, which are associated with a base metal sulphide assemblage dominated by pentlandite and Co-rich pentlandite. The assemblage is also marked by an abundance of alteration minerals, such as talc, serpentine and/or carbonates, which are closely associated with the platinum group minerals. Statistical evaluation reveals that these two mineral assemblages cannot be attributed to their derivation from different chromitite layers, but document the effects of pervasive hydrothermal alteration.
The knowledge of the detailed mineralogical investigation was transferred to a large da-taset comprising similar mineralogical data for unweathered ore of the deposit. Hence, it was possible to identify seven distinct ore types via statistical assessment, subsequently val-idated through beneficiation tests of drill core material. In addition, metallurgical test work for large batch samples of the weathered domain was carried out. Furthermore, beneficia-tion tests were aligned with process chemistry and mineralogy to monitor the results.
The predictive geometallurgical model aims to express the recoverability of PGE as by-product from the chromite processing stream. Within this context, the weathered ores were regarded as a single domain, as chromite ores from this oxidized zone were consistently found to have very low PGE recoveries. Any attempt to recover PGE by flotation from this zone appears to be challenging. For unweathered ores, the approach towards a predictive geometallurgical model needs to be somewhat more complex. The following steps were performed:
(i) Building a predictive model of the recoverability of PGE as a function of chemical composition, i.e. establish a chemical proxy for PGE recoverability;
(ii) Performing a geostatistical modelling of the geochemical dataset, i.e. interpolation through cokriging, and
(iii) Combining step (i) and (ii) to generate a spatially-resolved geometallurgical model able to predict the potential to recover PGE by flotation in terms of probabilities.
The resultant predictive, spatially-resolved geometallurgical model displays the PGE pro-cessing potential in terms of probabilities and therefore incorporates uncertainty.
Based on the work flow applied in this study, a more generic framework towards a predictive geometallurgical model can be proposed that can be applied to different commodities, is able to adapt to future data, and predicts metallurgical parameters, e.g. the recoverability of an ore as probabilities (and therefore including uncertainty). Furthermore, the model can be applied to main as well as by-product and therefore represents a holistic modelling approach. Most of the modelled parameters are derived from primary ore properties (e.g. rock or particle stream), e.g. modal mineralogy, mineral association, densities, etc., combined with a minimum of empirical test work.

  • Doctoral thesis
    TU Bergakademie Freiberg, 2020
    Mentor: Dr. Jens Gutzmer, Dr. Raimon Tolosana-Delgado

Permalink: https://www.hzdr.de/publications/Publ-30092
Publ.-Id: 30092


A First Order Geometallurgical Model for PGEs in a Chromite Ore

Bachmann, K.

In the effort to become more sustainable the mining industry currently faces a number of important challenges. One important direction of change would be to achieve a more holistic use of mineral resources, i.e., by considering the efficient extraction and beneficiation of all possible valuable constituents – rather than only focusing on the major commodity. Thus, geometallurgical models need to be adapted accordingly. Instead of only centring on the efficient extraction and beneficiation of a single (economically most relevant) commodity, future geometallurgical models should be expanded to consider all potential products.
In the present contribution, a generic framework is proposed that can be applied to a large variety of different commodities; it is able to adapt to future data, predicts metallurgical parameters, e.g. the recoverability of an ore as probabilities, and can be extended to include environmental footprint calculations. Most of the parameters are derived from primary ore properties (e.g. rock or particle streams), e.g. modal mineralogy, mineral association, densities, etc., combined with a minimum of conventional test work. The work flow is demonstrated with a case study, in which the beneficiation potential of PGE as a by-product in an existing chromite mine in the Bushveld Complex of South Africa is considered. All available data were incorporated in a geological block model and interpreted to form geometallurgical domains of sufficient size to be considered during mine planning. The resultant predictive, spatially-resolved geometallurgical model displays the PGE processing potential in terms of probabilities and therefore incorporates uncertainty. The viability of the geometallurgical model relates well to the original geological architecture, is cost- and time-effective and highly versatile to form a foundation for further use and development during exploitation.

  • Invited lecture (Conferences)
    Workshop on Geometallurgy - SGA 2019, 26.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30091
Publ.-Id: 30091


Imaging and writing magnetic domains in the non-collinear antiferromagnet Mn₃Sn

Reichlova, H.; Janda, T.; Godinho, J.; Markou, A.; Kriegner, D.; Schlitz, R.; Zelezny, J.; Soban, Z.; Bejarano, M.; Schultheiß, H.; Nemec, P.; Jungwirth, T.; Felser, C.; Wunderlich, J.; Goennenwein, S.

Non-collinear antiferromagnets are revealing many unexpected phenomena and they became crucial for the field of antiferromagnetic spintronics. To visualize and prepare a well-defined domain structure is of key importance. The spatial magnetic contrast, however, remains extraordinary difficult to be observed experimentally. Here, we demonstrate a magnetic imaging technique based on a laser induced local thermal gradient combined with detection of the anomalous Nernst effect. We employ this method in one the most actively studied representative of this class of materials - Mn₃Sn. We undoubtedly proof that the observed contrast is of magnetic origin. We further show an algorithm to prepare a well defined domain pattern at room temperature based on heat assisted recording principle. Our study opens a prospect to study spintronics phenomena in non-collinear antiferromagnets with spatial resolution.

Keywords: Information Storage; Magnetic properties and materials; Spintronics; Surfaces, interfaces and thin films

Permalink: https://www.hzdr.de/publications/Publ-30090
Publ.-Id: 30090


Magnetization dynamics in synthetic antiferromagnets: the role of dynamical energy and mutual spin-pumping

Sorokin, S.; Gallardo, R.; Fowley, C.; Lenz, K.; Titova, A.; Dennehy, G.; Atcheson, G.; Rode, K.; Faßbender, J.; Lindner, J.; Deac, A. M.

We investigate magnetization dynamics in asymmetric interlayer exchange coupled Py/Ru/Py trilayers using both vector network analyzer-based and electrically-detected ferromagnetic resonance techniques. Two different ferromagnetic resonance modes, in-phase and out-of-phase, are observed across all three regimes of the static magnetization configurations, through antiparallel alignment at low fields, the spin-flop transition at intermediate fields and the parallel alignment at high fields. The non-monotonic behavior of the modes as a function of the external field is explained in detail by analyzing the interlayer exchange and Zeeman energies, and is found to be solely governed by the interplay of their dynamical components. In addition, the linewidths of both modes were determined across the three regimes and the different behaviors of the linewidths versus external magnetic field are attributed to mutual spin pumping induced in the samples. Interestingly, the difference between the linewidths of the out-of-phase and in-phase modes decreases at the spin-flop transition and is reversed between the antiparallel and parallel aligned magnetization states.

Keywords: spin-pumping; magnetoresistance; interlayer exchange coupling; synthetic antiferromagnets; magnetization dynamics; ferromagnetic resosnance; electrically-detected ferromagnetic resonance

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Permalink: https://www.hzdr.de/publications/Publ-30089
Publ.-Id: 30089


Inertiale Lage- und Bewegungsverfolgung für instrumentierte Strömungsfolger zur Strömungscharakterisierung in Bioreaktoren

Buntkiel, L.; Reinecke, S.; Hampel, U.

Zur Untersuchung der ablaufenden Prozesse in großen Behältern, wie z. B. Biogasfermentern, Bioreaktoren und Belebtschlammbecken, wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt [1],[2]. Bisher wurden damit die Strömungsverhältnisse mit probabilistischen Auswertemethoden ausschließlich basierend auf der Messung der vertikalen Position als Funktion des hydrostatischen Drucks charakterisiert und Parameter einfacher Prozessmodelle für Anlagen im Labor- und Pilotmaßstab bestimmt.
Derzeit wird das Konzept des Sensorsystems mit dem Ziel weiterentwickelt, eine räumliche Lage- und Bewegungsverfolgung für Bioreaktoren basierend auf Inertialsensoren zu realisieren. Dies umfasst sowohl die dafür zu qualifizierenden Sensoren für Beschleunigung, Drehrate, Magnetfeld sowie Umgebungsdruck als auch die Softsensor-Algorithmen zur Bestimmung der Lage und der Bewegung. Damit sollen zukünftig Auftriebsmanöver der Sensorpartikel autonom ablaufen und die räumliche Strömungscharakterisierung erfolgen.
Im Beitrag werden drei Softsensor-Algorithmen zur Bewegungsverfolgung vorgestellt und verglichen. Diese sind ein linearisiertes Kalman-Filter (Error State Kalman Filter ESKF) und zwei nichtlineare Komplementärfilter (Direct und Passive Complementary Filter DCF, PCF) nach [3]. Diese Algorithmen wurden mit praxisrelevanten simulierten Strömungsbewegungen (siehe Abb. 1) unter Berücksichtigung von Unsicherheiten der Sensoren und realen Sensordaten analysiert. Die Simulationsergebnisse zeigen, dass durch die genaue Lagebestimmung, die Beschleunigung permanent im Koordinatensystem des Behälters nahezu driftfrei bestimmt wird (Abb. 1 und 2). Der Beitrag führt einen umfassenden Vergleich anhand simulierter und gemessener Referenztrajektorien von drei qualifizierten, kommerziellen Inertialsensoreinheiten und diskutiert die relevanten Implikationen für die Auslegung des Sensorsystems.

Keywords: Strömungsfolger; Bioreaktor; Inertialnavigation

  • Open Access Logo Contribution to proceedings
    14. Dresdner Sensor-Symposium, 02.-04.12.2019, Dresden, Deutschland
    Inertiale Lage- und Bewegungsverfolgung für instrumentierte Strömungsfolger zur Strömungscharakterisierung in Bioreaktoren, 978-3-9819376-1-9, 52-58
    DOI: 10.5162/14dss2019/3.5
  • Lecture (Conference)
    14.Dresdner Sensor-Symposium, 02.-04.12.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30088
Publ.-Id: 30088


Demonstration of X-ray Thomson scattering as diagnostics for miscibility in warm dense matter

Frydrych, S.; Vorberger, J.; Hartley, N.; Schuster, A.; Ramakrishna, K.; Saunders, A. M.; van Driel, T.; Falcone, R. W.; Fletcher, L. B.; Galtier, E.; Gamboa, E. J.; Glenzer, S. H.; Granados, E.; Macdonald, M. J.; Mackinnon, A. J.; Mcbride, E. E.; Nam, I.; Neumayer, P.; Pak, A.; Voigt, K.; Roth, M.; Sun, P.; Gericke, D. O.; Döppner, T.; Kraus, D.

The gas and ice giants in our solar system can be seen as a natural laboratory for the physics of highly compressed matter at temperatures of a few thousand kelvins. In turn, our understanding of their structure and evolution depends critically on our ability to model such matter. One key aspect is the miscibility of the elements in their interiors. Here, we demonstrate the feasibility of X-ray Thomson scattering to quantify the degree of species separation in a 1:1 carbon-hydrogen mixture at a pressure of ~150GPa and a temperature of ~5,000 K. Our measurements provide absolute values of the structure factor that encodes the microscopic arrangement of the particles. From these data, we find a lower limit of 24+6-7 % of the carbon atoms forming isolated carbon clusters. In principle, this procedure can be employed for investigating the miscibility behaviour of any binary mixture at the high-pressure environment of planetary interiors, in particular, for non-crystalline samples where it is difficult to obtain conclusive results from X-ray diffraction. Moreover, this method will enable unprecedented measurements of mixing/demixing kinetics in dense plasma environments, e.g., induced by chemistry or hydrodynamic instabilities.

Permalink: https://www.hzdr.de/publications/Publ-30087
Publ.-Id: 30087


Ionization in high-density plasmas: an ab initio study for carbon at Gbar pressures

Bethkenhagen, M.; Witte, B. B. L.; Röpke, G.; Döppner, T.; Kraus, D.; Glenzer, S. H.; Redmer, R.

We apply density functional theory molecular dynamics (DFT-MD) simulations to calculate the ionization degree of plasmas in the warm dense matter regime. Standard descriptions of the ionization potential depression (IPD) have been challenged recently by experiments approaching unprecedentedly high densities indicating that improved IPD models are required to describe warm dense matter. We propose a novel ab initio method to calculate the ionization degree directly from the dynamic electrical conductivity using the Thomas-Reiche-Kuhn (TRK) sum rule. This approach is demonstrated for carbon at a temperature of 100 eV and pressures in the Gbar range. We find substantial deviations from widely applied IPD models like Stewart-Pyatt and Ecker-Kröll implying that condensed matter and quantum effects like band structure and Pauli blocking need to be included explicitly in ionization models. Our results will help to precisely model matter under conditions occurring, e.g., during inertial confined fusion implosions or inside astrophysical objects such as brown dwarfs and low-mass stars.

Permalink: https://www.hzdr.de/publications/Publ-30086
Publ.-Id: 30086


Exploring THz-driven dynamics on sub-cycle timescales at the TELBE facility

Deinert, J.-C.; Green, B. W.; Ilyakov, I.; Awari, N.; Wang, Z.; Germanskiy, S.; Chen, M.; Bawatna, M.; Gensch, M.; Kovalev, S.

The TELBE Terahertz (THz) facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) offers narrowband high-field high-repetition rate THz radiation for driving low-energy excitations in matter in the spectral region between 0.1 THz and 1.5 THz [1]. In combination with our pulse-resolved data acquisition and the numerous available probing techniques based on table-top laser systems, we can resolve THz-driven dynamics with few 10 fs time resolution and high dynamic range of up to 120 dB [2]. This makes TELBE a unique facility for exploring low-energy THz excitations offering (resonant) access to a multitude of fundamental modes, e.g., lattice vibrations, molecular rotations, spin precession and the motion of free electrons [3]. Recently, we demonstrated THz high harmonic generation (HHG) in the model 2D material graphene [4]. Here, the ultrafast collective thermal response of free background electrons near the Dirac point [5] enables very efficient generation of harmonics in the technologically relevant THz frequency range. We further show that the underlying principle of the collective response can be generalized to other 2D and 3D Dirac materials, such as CdAs. The crucial role of doping in graphene can be exploited by, e.g. electrochemical gating, which allows tuning of the HHG efficiency by almost two orders of magnitude. The corresponding setup for phase-resolved nonlinear THz spectroscopy further enables a novel technique: Higgs spectroscopy, which offers new ways for understanding unconventional superconductivity. Using this technique, we recently discovered a new collective mode distinct from the heavily damped Higgs mode in different families of cuprates [6]. Our results establish Higgs spectroscopy as a new approach to uncover interactions directly relevant to superconductivity.
In this contribution, I will also discuss experiments on the selective THz control of magnetic properties in a number of different materials [7], which is enabled by probing techniques, such as Faraday Rotation or MOKE, using the NIR and UV output from our table-top sources.
[1] B. Green et al., Sci. Rep. 6, 22256 (2016)
[2] S. Kovalev et al., Struct. Dyn. 4, 024301 (2017)
[3] T. Kampfrath et al. Nat. Photonics 7, 680–690 (2013)
[4] H. Hafez et al., Nature 561, 507 (2018)
[5] Z. Mics et al., Nature Communications 6, 7655 (2015)
[6] H. Chu et al., arXiv preprint, arXiv:1901.06675 (2019)
[7] S. Kovalev et al., J. Phys. D: Appl. Phys. 51, 114007 (2018)

Keywords: Terahertz; pump-probe; nonlinear dynamics; high harmonic generation; graphene; Dirac materials; superradiance

  • Invited lecture (Conferences)
    10th International Workshop on Infrared Microscopy and Spectroscopy with Accelerator Based Sources WIRMS 2019, 24.09.2019, Ubatuba, Brasil

Permalink: https://www.hzdr.de/publications/Publ-30085
Publ.-Id: 30085


Ultrafast Photoelectron Spectroscopy - How to Make Movies of Elementary Electronic Processes

Deinert, J.-C.

How does functionality in quantum devices emerge? The answer lies in the numerous elementary processes, the interactions and correlations of (quasi-)particles that happen on timescales of femtoseconds. Thorough understanding of these processes can eventually lead to more efficient OLEDs, faster microprocessors, and other functional materials. A complex, but highly insightful method to access the required spectral and dynamic information in solid state systems is time- and angle-resolved photoemission spectroscopy. This lecture attempts to give an overview on this powerful technique for exploring non-equilibrium properties of matter. This includes discussions of elementary scattering processes, experimental techniques, and latest results on optoelectronic systems and correlated materials.

Keywords: Photoelectron spectroscopy; ultrafast; electronic structure; band structure; phase transitions; pump-probe

  • Invited lecture (Conferences)
    Ultrafast Science: Lasers, Fundamentals and Spectroscopy (SoSe 2019) Guest Lecture, 16.05.2019, Bielefeld, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30084
Publ.-Id: 30084


Terahertz high harmonic generation in Dirac materials

Deinert, J.-C.; Kovalev, S.; Hafez, H.; Chen, M.; Green, B. W.; Bawatna, M.; Germanskiy, S.; Awari, N.; Wang, Z.; Ilyakov, I.; Turchinovich, D.; Gensch, M.

The exploration of nonlinear optical phenomena has not only deepened the understanding of light-matter interaction, but it also enabled novel technologies that make use of the resulting synthesis of electromagnetic radiation at new frequencies. Whereas the nonlinear responses of matter in the microwave and optical regimes are well explored, research addressing the intermediate Terahertz (THz) regime is still largely in its infancy, despite its high technological relevance, e.g. for novel high-speed (opto-)electronics.
For these future applications in the THz range, graphene is a highly promising material, because of the unique optical properties originating from its prototypical Dirac-type electronic structure. Soon after its discovery, there have multiple predictions of efficient harmonic generation in the THz range [1, 2], but experimental evidence has remained incomplete. Recently, we experimentally demonstrated the highly efficient THz harmonics generation (HG) in a single layer graphene sample (up to 7th order) at ambient conditions upon excitation with a moderate THz field of only 85 kV/cm (see Fig. 1) [3]. Our observations have been successfully described by a thermodynamic model, which clearly explains the experimentally observed crucial role of the graphene doping level for THz HG [3, 4]. By using gated graphene samples and multilayer structures, we are able to predictably modify the HG efficiency and thereby corroborate the thermodynamic model.

In addition, we employed the same experimental scheme to other Dirac materials, such as topological insulators and Dirac/Weyl semimetals, showing that THz HG is a rather universal phenomenon based on the linear band dispersion in the vicinity of the Dirac point.

[1] S. Mikhailov et al., Microelectron. J. 40 (2009) 712.
[2] I. Al-Naib, Phys. Rev. B, 90 (2014) 245423
[3] H. Hafez, S. Kovalev et al., Nature, 561 (2018) 507
[4] Z. Mics et al., Nat. Commun., 6 (2015) 7655

Keywords: Graphene; Dirac materials; high harmonic generation; terahertz

  • Lecture (Conference)
    Graphene 2019, 26.06.2019, Roma, Italia

Permalink: https://www.hzdr.de/publications/Publ-30083
Publ.-Id: 30083


Investigation of ⁵⁴Fe(n,gamma)⁵⁵Fe and ³⁵Cl(n,gamma)³⁶Cl reaction cross sections at keV energies by Accelerator Mass Spectrometry

Slavkovská, Z.; Wallner, A.; Reifarth, R.; Pavetich, S.; Brückner, B.; Al-Khasawneh, K.; Merchel, S.; Volknandt, M.; Weigand, M.

Activations with neutrons in the keV energy range were routinely performed at the Karlsruhe Institute of Technology (KIT) in Germany in order to simulate stellar conditions for neutron-capture cross sections. A quasi-Maxwell-Boltzmann neutron spectrum of kT = 25 keV, being of interest for the astrophysical s-process, was produced by the ⁷Li(p,n) reaction utilizing a 1912 keV proton beam at the Karlsruhe Van de Graaff accelerator. Activated samples resulting in long-lived nuclear reaction products with half-lives in the order of yr - 100 Myr were analyzed by Accelerator Mass Spectrometry (AMS). Comparison of this data to cross sections from Time-of-Flight (ToF) measurements showed that the selected AMS data is systematically lower than the ToF data. To investigate this discrepancy, ⁵⁴Fe(n,gamma)⁵⁵Fe and ³⁵Cl(n,gamma)³⁶Cl reaction cross sections were newly measured at the Frankfurt Neutron Source (FRANZ) in Germany. To complement the existing data, an additional neutron activation of ⁵⁴Fe and ³⁵Cl at a proton energy of 2 MeV was performed. The results will give implications for the stellar environment at kT = 90 keV, reaching the yet not experimentally explored high-energy s-process range. AMS measurements of the activated samples are scheduled.

Keywords: AMS; nuclear reactions; s-process

Permalink: https://www.hzdr.de/publications/Publ-30082
Publ.-Id: 30082


Definition of geochemical domains in a chromite mine, Bushveld Complex, South Africa

Bachmann, K.; Menzel, P.; Tolosana Delgado, R.; Gutzmer, J.

The Lower and Middle Group chromitites of the Bushveld Complex are the source of a very large portion of the global chrome supply. Yet, the effectiveness of chromite beneficiation circuits is highly sensitive to mineralogical and textural variations in feed composition. The use of geochemical proxies, based on data acquired routinely during the exploration and mining process may provide a cost- and time-efficient alternative to more time-consuming and expensive mineralogical analyses. Such an approach is presented in this study, which focuses on the LG-6, LG-6A, MG-1 and MG-2 chromitite seams at the Thaba mine located on the western limb of the Bushveld Complex. According to a sound statistical assessment, the chromitites of the Thaba mine area can be subdivided into three distinct domains, domains that constitute the suitable fundament for a geometallurgical model. Accordingly, a least altered (orthomagmatic) domain is distinguished from a supergene altered domain and a domain affected by widespread hydrothermal alteration. The latter domain occurs below the depth of modern weathering, but in obvious proximity to faults and around a prominent dunite pipe. The orthomagmatic domain is represented by ores least affected by post-magmatic alteration processes. This domain occupies the centre of fault blocks below the extent of modern weathering.

  • Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30081
Publ.-Id: 30081


Lower Group and Middle Group chromitites of the Bushveld Complex – the effect of weathering on the distribution of platinum-group elements

Junge, M.; Bachmann, K.; Oberthür, T.; Groshev, N. Y.

The Bushveld Complex in South African contains vast resources of Cr, PGE and V. Currently, the Merensky Reef, the Platreef and the UG-2 chromitite seam are the major mining targets for PGE, although chromitites of the Lower Group (LG) and Middle Group (MG) may also contain concentrations up to several ppm PGE.
In a suite of chromitite samples from the Thaba Mine in the western Bushveld Complex it was shown that Pt concentrations in weathered chromitite seams (LG-6 to MG-4) generally exceed those of Pd. However, differences are observed by comparing individual chromitite seams as total PGE concentrations of weathered chromitites from the LG-6 to MG-4 range between 760 and 1300 ppb. Elevated concentrations of Pt and Pd are also present in hanging and footwalls of chromitite seams (median 333 ppb Pt). The PPGE (Rh, Pt, Pd) contents of weathered ores are generally lower than those of the pristine ores. The IPGE (Os, Ir, Ru) are very similar in both pristine and weathered ores. Particularly, Ru concentration are in the same range as the pristine ores.
Platinum concentrations increase from LG-6 to MG-4, whereas Pd remains at near-constant levels, resulting in a strong increase of the Pt/Pd ratio from 2.2 to 15.3. Platinum, largely remains within the chromitite seams and is only locally mobilized within the chromitites and their surrounding hanging and footwalls, whereas a large proportion of the Pd is leached out. Weathering causes mobilization of Pt and Pd out of the chromitites, locally into the hanging and footwall. The general decrease (in particular of Pd) can also be observed by comparing the average Pt/Pd ratio of pristine chromitites from the Thaba Mine. The IPGE are generally less affected by weathering processes which may be explained by the fact that laurite [(Ru,Os,Ir)S2] commonly occurs as inclusions in chromite, and PGM incorporated in chromite are largely unaffected by weathering processes.

  • Contribution to proceedings
    GeoMünster 2019, 22.-25.09.2019, Münster, Germany

Permalink: https://www.hzdr.de/publications/Publ-30080
Publ.-Id: 30080


Platinum-group elements in weathered Lower Group and Middle Group chromitites of the Bushveld Complex

Junge, M.; Bachmann, K.; Oberthür, T.

All major sources of economically important platinum-group elements (PGE) are associated with sulfides and chromite in mafic-ultramafic rocks. The Bushveld Complex in South Africa is the largest PGE deposit worldwide. Chromitites of the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex hold PGE contents of a few ppm. However, these chromitites are mainly mined for chromium only and extraction of PGE as a by-product is limited. Surface weathering in the area of the Bushveld Complex is up to 50 m down from surface. Attempts to recover Pt and Pd from these weathered ores lead to recoveries of <30 %, despite that Pt and Pd concentrations are similar in pristine and weathered ores. The recovery of PGE from near-surface chromitites of the LG and MG would increase the resource efficiency of current mining operations.. Therefore, an efficient utilization of these ores requires geochemical and mineralogical characterization of the PGE within these ores and the development of novel approaches of mineral beneficiation.

  • Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30079
Publ.-Id: 30079


Spectral tomography - 3D mineral classification

Da Assuncao Godinho, J. R.; Renno, A.; de Schryver, T.; Masschaele, B.

A new analytical tool for mineral analysis will be introduced: Laboratory-based Spectral 3D X-ray Computed Tomography (Sp-CT). Results from a spectral imaging detector, prototype installed inside a TESCAN CoreTOM micro-CT system, will be presented and discussed in the context of mineralogical and chemical analysis of geological materials. The technique will be demonstrated to allow:
a) 3D mineral classification from the transmitted energy spectrum characteristic of a mineral phase.
b) Quick bulk chemical quantification of heavy elements with K-edge > 20 keV at high concentrations that are difficult to analyse by other methods.
c) Reducing common CT artefacts such as scattering and beam hardening, as well as improved contrast by selectively choose the most convenient energy range.
The advantages of Sp-CT will open new possibilities in geometallurgy and minerals processing research to move from the predominant 2D based image characterization towards more representative 3D characterization. These are fundamental steps to enable automated and routine 3D characterization that ultimately has the potential to provide faster and lower cost analysis to, for example, the mining industry, as well as more comprehensive rock characterization technique for Earth sciences research.

  • Open Access Logo Poster
    Goldschmidt 2019, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-30077
Publ.-Id: 30077


High energy ion beams as a powerful tool for the analysis of the elemental composition of thin layers

Munnik, F.

Keywords: Ion Beam Analysis

  • Lecture (others)
    Kolloquium am Ferdinand-Braun-Institut, Berlin, 29.11.2019, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-30076
Publ.-Id: 30076


Volume quantification in interphase voxels of ore minerals using 3D imaging

Da Assuncao Godinho, J. R.; Kern, M.; Renno, A.; Gutzmer, J.

This contribution presents and validates a new method to correct for the main limitations of volume quantification using X-ray computed tomography: limited spatial resolution and lack of mineralogical classification. The volume of a phase of interest (cassiterite, SnO2) is calculated using the intensity of voxels at interphases, which are typically the regions of main uncertainty in 3D imaging. Instead of traditional segmentation methods that define boundaries between phases, our method considers interphases as regions that can be several voxels across. The method is validated using a feedback loop between 2D scanning electron microscopy-based image analysis and bulk chemical analysis where the advantages of each technique are used to correct for the limitations of another. The percent of cassiterite derived from our method are within 10% deviation from those measured by scanning electron microscopy-based image analysis and bulk chemical analysis, when the P50 of the particle size distribution is at least 5 times the voxel size of the scan, which is a better agreement than results derived from other segmentation methods. Therefore, our method reduces the uncertainty of volume quantification and lowers the limit of grain sizes for which volumes can be reliably measured using computed tomography. The reduced uncertainty and bias can contribute to broadening the application of 3D imaging to mineral engineering as complementary to well established techniques.

Keywords: Partial volume effect; Computed tomography; Mineral processing; Raw materials; X-ray imaging; Geometallurgy

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  • Secondary publication expected from 01.12.2020

Permalink: https://www.hzdr.de/publications/Publ-30075
Publ.-Id: 30075


Improvement of luminescence properties of n-GaN using TEGa precursor

Hubáčeka, T.; Hospodková, A.; Kuldová, K.; Slavická Zíková, M.; Pangrác, J.; Čížek, J.; Liedke, M. O.; Butterling, M.; Wagner, A.; Hubík, P.; Hulicius, E.

The aim of this work is to compare and improve optical and structural properties of GaN layers prepared using TMGa or TEGa precursors. MOVPE grown GaN buffer layers on sapphire substrates are usually grown from TMGa precursor at the temperatures above 1000 °C. These layers contain deep and shallow acceptor levels which are responsible for blue and yellow defect bands in luminescent spectra. Both defect bands are detrimental for all major nitride device applications. Especially n-doped GaN layers suffer from strong yellow defect bands. In this work, it is shown that yellow band photoluminescence intensity can be suppressed by using TEGa precursor during the growth of n–doped GaN layers. Different kinds of growth parameters, such as growth temperature or growth rate, have been studied. It is also shown that the change of carrier gas (H2 or N2) has very strong influence on the layer quality. H2 carrier gas increased intensity of yellow band in sample grown from TEGa precursor while N2 carrier gas had the same effect for sample grown from TMGa precursor. Variable energy positron annihilation spectroscopy showed creation of single VGa in H2 atmosphere and clustering of VGa to big complexes ((VGa)3(VN)n) in N2 atmosphere.

Keywords: MOVPE; TEGa precursor; n-GaN; yellow band; VGa defect

Permalink: https://www.hzdr.de/publications/Publ-30073
Publ.-Id: 30073


Enhanced flux pinning isotropy by tuned nanosized defect network in superconducting YBa2Cu3O6+x films

Khan, M. Z.; Rivasto, E.; Tikkanen, J.; Rijckaert, H.; Malmivirta, M.; Liedke, M. O.; Butterling, M.; Wagner, A.; Huhtinen, H.; van Driessche, I.; Paturi, P.

Striving to improve the critical current density Jc of superconducting YBa 2 Cu 3 o 6+x (YBCO) thin films via enhanced vortex pinning, the interplay between film growth mechanisms and the formation of nanosized defects, both natural and artificial, is systematically studied in undoped and BaZrO 3 (BZO)-doped YBCO thin films. The films were grown via pulsed laser deposition (PLD), varying the crystal grain size of the targets in addition to the dopant content. The microstructure of the PLD target has been observed to have a great impact on that of the deposited thin films, including the formation of vortex pinning centers, which has direct implications on the superconducting performance, especially on the isotropy of flux pinning properties. Based on experimentally measured angular dependencies of Jc, coupled with a molecular dynamics (MD) simulation of flux pinning in the YBCO films, we present a quantitative model of how the splay and fragmentation of BZO nanorods artifically introduced into the YBCO film matrix explain the majority of the observed critical current anisotropy. To obtain the freedom to engineer future high-temperature superconductor (HTS) applications for desired operating magnetic field and temperature ranges, it is necessary to optimize the vortex pinning landscape for an enhanced, isotropic flux pinning performance 1-6. In addition to naturally formed crystalline defects, which typically have spatial dimensions distinctly below the superconducting coherence length, defect-engineering with artificially produced pinning centers (APCs) with dimensionalities of 1D-3D have been observed to be extremely effective 7-10. However, the complex nucleation process of YBCO during PLD process, that leads to growth island size variation, and the manner in which this could affect the size and distribution of the nanoscale structural defects is chiefly neglected. Especially, a clear gap exists in the current literature regarding how ordered arrays of nanoscale defects can also influence and regulate the distribution and growth of more effective APCs and thus decrease the anisotropy by allowing vortices to be trapped in a wider angular range 11. Partly, the clear lack of information on the subject is arguably be due to the rather general assumption that during PLD process, the film growth method of our choice, the target material is largely decomposed on the atomic level, and thus its properties should not have an effect on the formation and nucleation of particles on the substrate surface. This assumption, which our studies have led us to challenge, would precariously force one to downplay the potential importance of target microstructure on the functional properties of derived films. The angular dependence of the J c has an excellent physical importance providing an approach to the problem of flux pinning and vortex dynamics anisotropy in HTSs, both from the experimental and theoretical point of view. For instance, in the angular dependent critical current plots, one can easily observe how the various types of pinning centers such as correlated linear, columnar or planar defects and, on the other hand, defects based on growth mechanisms together with YBCO's intrinsic pinning can dramatically alter the angular dependence of J c (B) 4. For understanding the origin of angular dependent flux pinning J c (θ), experimental tools like transmission electron microscopy (TEM) are often exploited to probe the structural properties and features, such as the defects naturally formed during the film growth, as well as the size, shape, orientation and distribution of the artificially produced and self-assembled pinning centers 5,12,13. However, methods like positron annihilation spectroscopy,

Keywords: superconductivity; YBa2Cu3O6; YBCO; positron annihilation spectroscopy; PAS

Permalink: https://www.hzdr.de/publications/Publ-30072
Publ.-Id: 30072


An Integrated Multi-Sensor System for the In-Line Monitoring of Material Streams

Seidel, P.; König, S.; Lorenz, S.; Sudharshan, V.; Shaik Fareedh, J.; Zimmermann, R.; Ghamisi, P.; Kaever, P.; Gloaguen, R.; Reuter, M.

We present an innovative multi-sensor system, based on non-invasive optical spectroscopy for the characterization of material streams. The novel hardware and software set-ups are explained in detail and first results from RGB stereoscopy and object detection are shown.

  • Contribution to proceedings
    IEEE Sensors 2019, 27.-30.10.2019, Montreal, Canada
    Proceedings of IEEE Sensors 2019

Permalink: https://www.hzdr.de/publications/Publ-30069
Publ.-Id: 30069


Structural, magnetic and magnetocaloric properties of NdPrFe14B and its hydrides

Tereshina, I.; Kaminskaya, T.; Ivanov, L.; Politova, G.; Drulis, H.; Gorbunov, D.; Paukov, M.; Tereshina-Chitrova, E.; Andreev, A.

A systematic study of the influence of interstitial hydrogen on the structure, morphology of surface, magnetic and magnetothermal properties in multicomponent (Nd0.5Pr0.5)2Fe14BHx (x = 0; 2.7; 4.3) are reported. Partial substitution of Pr for Nd allows a decrease of the spin-reorientation transition temperature from 135 K for Nd2Fe14B to 73 K for (Nd0.5Pr0.5)2Fe14B. Hydrides (Nd0.5Pr0.5)2Fe14BHx crystallize in a tetragonal crystal structure (space group P42/mnm) of the Nd2Fe14B-type. Both lattice constants and unit cell volume increase upon hydrogen absorption. It was also found that the surface of the hydrogenated sample was very severely damaged by the introduction of hydrogen. Magnetic studies of both initial compound and the hydrides were performed on bulk and powder samples in static and pulsed magnetic fields up to 14 and 58 T, respectively. Hydrogenation has a significant effect on magnetic properties of a multicomponent alloy (Nd0.5Pr0.5)2Fe14B: Curie temperature and saturation magnetization increase, while temperature of SRT decreases (TSRT = 63 K for (Nd0.5Pr0.5)2Fe14BHx with x = 2.7 and 4.3). The magnetocaloric effect (MCE) in the range of spin-reorientation transition also decreases significantly. We analyzed magnetic properties of (Nd0.5Pr0.5)2Fe14BHx and compare them with that of Nd2Fe14BHx. Magnetic phase diagrams are constructed.

Permalink: https://www.hzdr.de/publications/Publ-30068
Publ.-Id: 30068


Evidence of one-dimensional magnetic heat transport in the triangular-lattice antiferromagnet Cs2CuCl4

Schulze, E.; Arsenijevic, S.; Opherden, L.; Ponomaryov, O.; Wosnitza, J.; Ono, T.; Tanaka, H.; Zvyagin, S.

We report on low-temperature heat-transport properties of the spin-1/2 triangular-lattice antiferromagnet Cs2CuCl4. Broad maxima in the thermal conductivity along the three principal axes, observed at about 5 K, are interpreted in terms of the Debye model, including the phonon umklapp scattering. For thermal transport along the b axis, we found a pronounced field-dependent anomaly, close to the transition into the three-dimensional long-range-ordered state. No such anomalies were found for the transport along the a and c directions.We argue that this anisotropic behavior is related to an additional heat-transport channel through magnetic excitations, that can best propagate along the direction of the largest exchange interaction. In addition, peculiarities of the heat transport of Cs2CuCl4 in magnetic fields up to the saturation field and above are discussed.

Permalink: https://www.hzdr.de/publications/Publ-30067
Publ.-Id: 30067


Diffusion and Interaction of In and As Implanted into SiO2 Films

Tyschenko, I. E.; Voelskow, M.; Mikhaylov, A. N.; Tetelbaum, D. I.

By means of Rutherford backscattering spectrometry, electron microscopy, and energy-dispersive X-ray spectroscopy, the distribution and interaction of In and As atoms implanted into thermally grown SiO2 films to concentrations of about 1.5 at % are studied in relation to the temperature of subsequent annealing in nitrogen vapors in the range of T = 800–1100°C. It is found that annealing at T = 800–900°C results in the segregation of As atoms at a depth corresponding to the As+-ion range and in the formation of As nanoclusters that serve as sinks for In atoms. An increase in the annealing temperature to 1100°C yields the segregation of In atoms at the surface of SiO2 with the simultaneous enhanced diffusion of As atoms. The corresponding diffusion coefficient is DAs = 3.2 × 10–14 cm2 s–1.

Keywords: As; diffusion; In; ion implantation; silicon oxide

Permalink: https://www.hzdr.de/publications/Publ-30063
Publ.-Id: 30063


Deep Learning for Hyperspectral Image Classification: An Overview

Li, S.; Song, W.; Fang, L.; Chen, Y.; Ghamisi, P.; Benediktsson, J. A.

Hyperspectral image (HSI) classification has become a hot topic in the field of remote sensing. In general, the complex characteristics of hyperspectral data make the accurate classification of such data challenging for traditional machine learning methods. In addition, hyperspectral imaging often deals with an inherently nonlinear relation between the captured spectral information and the corresponding materials. In recent years, deep learning has been recognized as a powerful feature-extraction tool to effectively address nonlinear problems and widely used in a number of image processing tasks. Motivated by those successful applications, deep learning has also been introduced to classify HSIs and demonstrated good performance. This survey paper presents a systematic review of deep learning-based HSI classification literature and compares several strategies for this topic. Specifically, we first summarize the main challenges of HSI classification which cannot be effectively overcome by traditional machine learning methods, and also introduce the advantages of deep learning to handle these problems. Then, we build a framework that divides the corresponding works into spectral-feature networks, spatial-feature networks, and spectral-spatial-feature networks to systematically review the recent achievements in deep learning-based HSI classification. In addition, considering the fact that available training samples in the remote sensing field are usually very limited and training deep networks require a large number of samples, we include some strategies to improve classification performance, which can provide some guidelines for future studies on this topic. Finally, several representative deep learning-based classification methods are conducted on real HSIs in our experiments.

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Permalink: https://www.hzdr.de/publications/Publ-30062
Publ.-Id: 30062


Cascaded Recurrent Neural Networks for Hyperspectral Image Classification

Hang, R.; Liu, Q.; Hong, D.; Ghamisi, P.

By considering the spectral signature as a sequence, recurrent neural networks (RNNs) have been successfully used to learn discriminative features from hyperspectral images (HSIs) recently. However, most of these models only input the whole spectral bands into RNNs directly, which may not fully explore the specific properties of HSIs. In this paper, we propose a cascaded RNN model using gated recurrent units to explore the redundant and complementary information of HSIs. It mainly consists of two RNN layers. The first RNN layer is used to eliminate redundant information between adjacent spectral bands, while the second RNN layer aims to learn the complementary information from nonadjacent spectral bands. To improve the discriminative ability of the learned features, we design two strategies for the proposed model. Besides, considering the rich spatial information contained in HSIs, we further extend the proposed model to its spectral-spatial counterpart by incorporating some convolutional layers. To test the effectiveness of our proposed models, we conduct experiments on two widely used HSIs. The experimental results show that our proposed models can achieve better results than the compared models.

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Permalink: https://www.hzdr.de/publications/Publ-30061
Publ.-Id: 30061


Hyperspectral Image Classification with Multi-Scale Feature Extraction

Bing, T.; Nanying, L.; Leyuan, F.; Danbing, H.; Ghamisi, P.

Spectral features cannot effectively reflect the differences among the ground objects and distinguish their boundaries in hyperspectral image (HSI) classification. Multi-scale feature extraction can solve this problem and improve the accuracy of HSI classification. The Gaussian pyramid can effectively decompose HSI into multi-scale structures, and efficiently extract features of different scales by stepwise filtering and downsampling. Therefore, this paper proposed a Gaussian pyramid based multi-scale feature extraction (MSFE) classification method for HSI. First, the HSI is decomposed into several Gaussian pyramids to extract multi-scale features. Second, we construct probability maps in each layer of the Gaussian pyramid and employ edge-preserving filtering (EPF) algorithms to further optimize the details. Finally, the final classification map is acquired by a majority voting method. Compared with other spectral-spatial classification methods, the proposed method can not only extract the characteristics of different scales, but also can better preserve detailed structures and the edge regions of the image. Experiments performed on three real hyperspectral datasets show that the proposed method can achieve competitive classification accuracy.

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Permalink: https://www.hzdr.de/publications/Publ-30060
Publ.-Id: 30060


Crystallization of colourless hexanitratoneptunate(IV) with anhydrous H+ countercations trapped into hydrogen bond polymer with diamide linkers

Takao, K.; März, J.; Matsuoka, M.; Mashita, T.; Kazama, H.; Tsushima, S.

Colourless crystalline compounds of centrosymmetric [Np(NO3)6]2− were yielded from 3 M HNO3 aq under presence of double-headed 2-pyrrolidone derivatives (L). In the obtained crystal structures, H+ was also involved as a countercation to compensate the negative charge of [Np(NO3)6]2−, where initial hydration around H+ was fully removed during crystallization despite its strongest hydration enthalpy. Instead, such an anhydrous H+ was captured by L to form a [H+···L]n hydrogen bond polymer. In [Np(NO3)6]2−, Np4+ centre is twelve-coordinated with 6 bidentate NO3−, and therefore, present in an icosahedral geometry bearing inversion centre. In such a centrosymmetric system, any f-f transitions stemming from 5f3 electronic configuration of Np4+ are electric-dipole forbidden. This is the reason why the compounds currently obtained were colourless unlike ordinary Np(IV) species with olive-green.

Permalink: https://www.hzdr.de/publications/Publ-30059
Publ.-Id: 30059


Spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy study of thermally treated Co60Fe20B20 thin films

Hoffmann, M.; Sharma, A.; Matthes, P.; Okano, S.; Hellwig, O.; Ecke, R.; Zahn, D.; Salvan, G.; Schulz, S.

We report the optical and magneto-optical properties of amorphous and crystalline Co60Fe20B20 films with thicknesses in the range of 10 nm to 20 nm characterized using spectroscopy ellipsometry (SE) and magneto-optical Kerr effect (MOKE) spectroscopy. We derived the spectral dependence of the dielectric tensor from experimental data for samples prior and after annealing in vacuum. The features of the dielectric function can be directly related to the transitions between electronic states and the observed changes upon annealing can be ascribed to an increase of the crystalline ordering of CoFeB.

Keywords: CoFeB; spectroscopic ellipsometry; magneto-optical Kerr effect spectroscopy; x-ray diffraction

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Permalink: https://www.hzdr.de/publications/Publ-30057
Publ.-Id: 30057


Studies on the interaction of plant cells with U(VI) and Eu(III) and on stress-induced metabolite release

Jessat, J.

Uranium(VI) and Europium(III) can interact with Brassica napus suspension cell cultures. This can lead to bioassociation (immobilisation of metals due to the cell metabolism), which is discussed in more detail here. Heavy metal stress can also lead to the formation of protective metabolites by the plant cells, whose complex formation behaviour with U(VI) has been investigated.

Keywords: canola; plants; uranium; europium; metabolites; WiN; Women in Nuclear; bioassociation; heavy metal; plant cells; suspension cell cultures

  • Invited lecture (Conferences)
    Finale der WiN Preisverleihung, 11.10.2019, Karlstein/Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30056
Publ.-Id: 30056


Femtosecond X-ray induced changes of the electronic and magnetic response of solids from electron redistribution

Higley, D.; Reid, A.; Chen, Z.; Le Guyader, L.; Hellwig, O.; Lutman, A.; Liu, T.; Shafer, P.; Chase, T.; Dakovski, G.; Mitra, A.; Yuan, E.; Schlappa, J.; Dürr, H.; Schlotter, W.; Stöhr, J.

Resonant X-ray absorption, where an X-ray photon excites a core electron into an unoccupiedvalence state, is an essential process in many standard X-ray spectroscopies. With increasingX-ray intensity, the X-ray absorption strength is expected to become nonlinear. Here, wereport the onset of such a nonlinearity in the resonant X-ray absorption of magnetic Co/Pdmultilayers near the Co L3edge. The nonlinearity is directly observed through the change ofthe absorption spectrum, which is modified in less than 40 fs within 2 eV of its threshold.This is interpreted as a redistribution of valence electrons near the Fermi level. For ourmagnetic sample this also involves mixing of majority and minority spins, due to sampledemagnetization. Ourfindings reveal that nonlinear X-ray responses of materials may alreadyoccur at relatively low intensities, where the macroscopic sample is not destroyed, providinginsight into ultrafast charge and spin dynamics.

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Permalink: https://www.hzdr.de/publications/Publ-30055
Publ.-Id: 30055


Critical behavior of intercalated quasi-van der Waals ferromagnet Fe0.26TaS2

Zhang, C.; Yuan, Y.; Wang, M.; Li, P.; Zhang, J.; Wen, Y.; Zhou, S.; Zhang, X. X.

In the present work, single-crystalline quasi-van der Waals ferromagnet Fe0.26TaS2 was successfully synthesized with Fe atoms intercalated at ordered positions between TaS2 layers. Its critical behavior was systematically studied by measuring the magnetization around ferromagnetic to paramagnetic phase transition temperature, TC∼100.7K, under different magnetic fields. The critical exponent β for the spontaneous magnetization below TC, γ for the inverse initial susceptibility above TC, and δ for the magnetic isotherm at TC were determined with modified Arrott plots, the Kouvel-Fisher method, the Widom scaling law, and critical isotherm analysis, and found to be the following values: β=0.459(6),γ=1.205(11), and δ=3.69(1). The obtained critical exponents are self-consistent and follow the scaling equation, indicating the reliability and intrinsicality of these parameters. A close analysis within the framework of renormalization group theory reveals that the spin coupling inside Fe0.26TaS2 crystal is of the three-dimensional Heisenberg ({d:n}={3:3}) type with long-range magnetic interaction and that the exchange interaction decays with distance as J(r)∼r-4.71

Keywords: quasi-van der Waals ferromagnet; critical behavior; three-dimensional Heisenberg

Permalink: https://www.hzdr.de/publications/Publ-30054
Publ.-Id: 30054


New tools for calibrating diffraction setups

Kieffer, J.; Vals, V.; Blanc, N.; Hennig, C.

This work presents new calibration tools in the pyFAI suite for processing scattering experiments acquired with area detectors: a new graphical user interface for calibrating the detector position in a scattering experiment performed with a fixed, large area detector as well as a library to be used in Jupyter notebooks for calibrating the motion of a detector on a goniometer arm (or any other moving table) to perform diffraction experiments.

Keywords: powder diffraction; detector calibration; pyFAI

Permalink: https://www.hzdr.de/publications/Publ-30053
Publ.-Id: 30053


Bio-Fishing for Rare Earth Recycling

Lederer, F.

Rare earth elements (REE) are a group of seventeen elements consisting of scandium, yttrium as well as what are known as lanthanides. These elements are found only in a few regions worldwide in quantities worth mining. REEs are considered key components in the high-tech industry and are utilized, for example, in wind turbines, smartphones and energy-saving lamps.

  • G.I.T. Laboratory Journal 23(2019)5, 30-31

Permalink: https://www.hzdr.de/publications/Publ-30051
Publ.-Id: 30051


Two-Dimensional Noble-Metal Dichalcogenides and Phosphochalcogenides

Kempt, R.; Kuc, A. B.; Heine, T.

Noble-metal chalcogenides, dichalcogenides and phosphochalcogenides are an emerging class of two- dimensional materials. Their properties can be broadly tuned via quantum confinement (number of layers) and defect engineering, including metal-to-semiconductor transitions, magnetic ordering, and topological surface states. They possess various polytypes, often of similar formation energy, which can be assessed by selective synthesis approaches. They excel in mechanical, optical and chemical sensing applications, and feature long-term air- and moisture stability. In this review, we summarize the recent progress in the field of noble metal chalcogenides and phosphochalcogenides and highlight the structural complexity and its impact on applications.

Permalink: https://www.hzdr.de/publications/Publ-30050
Publ.-Id: 30050


Bio-compatible flotation of Chlorella vulgaris: Study of zeta potential and flotation efficiency

Matho, C.; Schwarzenberger, K.; Eckert, K.; Keshavarzi, B.; Walther, T.; Steingroewer, J.; Krujatz, F.

The energy-intensive dewatering of algae biomass, the first step of most downstream processes, remains one of the big challenges for economically relevant photoautotrophic bioprocesses. Due to its scalability and easy construction, froth flotation using the interactions between cells and bubbles shows considerable potential for this type of cost-efficient initial dewatering step. Comprehensive knowledge on both the physico-chemical conditions and the cellular surface properties are an important precondition to harvest cells by flotation. This study investigates the impact of changing the medium composition, specifically varying the pH and adding (bio-) collectors, on the zeta potential of Chlorella vulgaris SAG 211-1b. Decreasing the pH value from physiological to acidic conditions (pH 1–1.5) resulted in a strongly reduced cellular zeta potential. As validated by dispersed-air flotation, this yields a significantly enhanced cell recovery R > 95 %. The impact of the synthetic collector cetyltrimethylammonium bromide and the biopolymer chitosan on the cellular zeta potential and flotation performance was studied, resulting in a 3.3-fold decrease in the surfactant dose when chitosan was used . The basic mechanisms of cell-chitosan interaction were analysed in terms of particle size distribution and surface tension measurements, revealing interactions between flocculation and adsorption during the dispersed-air flotation of C.vulgarisSAG 211-1b.

Keywords: Chlorella vulgaris; Flotation; Zeta potential; Dispersed-air flotation; Chitosan; CTAB

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Permalink: https://www.hzdr.de/publications/Publ-30048
Publ.-Id: 30048


Wie uns die Biologie beim Recycling von Elektroschrott hilft

Lederer, F.

Gold, Kupfer, Palladium und Seltene Erden sind wichtige Bestandteile von Smartphones und anderen Geräten unseres täglichen Lebens. Jedes dieser Metalle erfüllt ganz gezielt Aufgaben im Gerät und ist daraus nicht wegzudenken. Ihre Gewinnung aus den Bergbauminen dieser Erde ist häufig mit enormen Schäden für Mensch und Natur verbunden. Die Verwendung von recycelten Metallen bietet dazu eine deutlich umweltfreundlichere Alternative. Da die Metalle aber in sehr kleinen Mengen und fein verteilt im Gerät verbaut sind, ist ihr Recycling häufig nicht wirtschaftlich. Hier können neue biologische Recyclingwege Abhilfe leisten. Forscher des Helmholtz Instituts Freiberg für Ressourcentechnologie arbeiten an der Entwicklung von Metallspezifischen Antikörpern, welche gezielt ein Wertmetall nach dem anderen auch in kleinsten Konzentrationen in Form von Bioangeln aus einem Metallgemisch herausfischen können.

Keywords: Recycling; Elektroschrott; Bioangeln

  • Lecture (others)
    Campus Talks - Forschung auf den Punkt gebracht, 19.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30047
Publ.-Id: 30047


Metallgewinnung durch Mikrobiologie - Biologisch assistierte Prozesse in der Rohstofftechnologie

Lederer, F.

Präsentation der Arbeiten der Abteilung Biotechnologie des Helmholtz Institut Freiberg für Ressourcentechnologie sowie der Arbeiten der Nachwuchsforschergruppe BioKollekt

Keywords: Biokollektoren; Peptide; Recycling

  • Lecture (others)
    Institutskolloquium, 25.09.2019, Waldheim, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30046
Publ.-Id: 30046


BioKollekt - A biobased material recycling process promotes circular economy

Lederer, F.; Pollmann, K.

Recycling high-value products is a pivotal part of a circular economy. Current high-tech products contain a highly complex mixture of elements in low concentrations. Elements in these mixtures usually possess similar chemical and physical properties, which poses technical difficulties when considering a potential recycling process. Currently, only 22% terbium, 1% cerium and 1% lanthanum used in electronic devices like fluorescent light bulbs is recycled.1 A large proportion of these precious elements is lost. There is a need for novel techniques to be developed in order to recycle elements that are in low concentrations and in a complex matrix. Junior research group BioKollekt has begun the design and development of highly selective bio-based collector materials for a more sustainable recycling process of these elements. Biological peptide structures were identified in a highly competitive process for their selectivity and affinity for the fluorescent phosphor lanthanum phosphate doped with cerium and terbium (LAP). LAP-selective binding peptides coupled to a carrier material could be used in the future as separation tools for the selective recycling of LAP from lamp phosphors of fluorescent light bulbs. The BioKollekt approach uses LAP as a “proof of principle” to show the efficiency of biocollector materials. Figure 1 demonstrates the BioKollekt concept. The identification of highly selective biomolecules for preferred target materials (step 1) has been already achieved. In the second step, carrier materials (e.g. hydrophobic beads) will be functionalized with material binding-selective peptides. Biocollectors will interact selectively with their target material in a separation process (step 3-4). Finally, the target material and biocollector will be recycled and reused (step 5). The talk will present the BioKollekt concept and its achievements.

Keywords: Recycling; Peptides; Fluorescent Phosphor; Lanthanum

  • Invited lecture (Conferences)
    European Congress and Exhibition on Advanced Matertials and Processes (EUROMAT 2019), 01.-05.09.2019, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-30044
Publ.-Id: 30044


Distinct defect appearance in Gd implanted polar and nonpolar ZnO surfaces in connection to ion channeling effect

Jagerová, A.; Malinský, P.; Mikšová, R.; Nekvindová, P.; Cajzl, J.; Akhmadaliev, S.; Holý, V.; Macková, A.

(0001) c-plane, (11-20) a-plane, and m-plane (10-10) ZnO bulk crystals were implanted with 400-keV Gd+ ions using fluences of 5 × 1014, 1 × 1015, 2.5 × 1015, and 5 × 1015 cm-2. Structural changes during the implantation and subsequent annealing were characterized by Rutherford backscattering spectrometry in channeling mode (RBS-C); the angular dependence of the backscattered ions (angular scans) in c-, a-, and m-plane ZnO was realized to get insight into structural modification and dopant position in various crystallographic orientations. X-ray diffraction (XRD) with mapping in reciprocal space was also used for introduced defect identification. Defect-accumulation depth profiles exhibited differences for c-, a-, and m-plane ZnO, with the a-plane showing significantly lower accumulated disorder in the deeper layer in Zn-sublattice, accompanied by the preservation of ion channeling phenomena in a-plane ZnO. Enlargement of the main lattice parameter was evidenced, after the implantation, in all orientations. The highest was evidenced in a-plane ZnO. The local compressive deformation was seen with XRD analysis in polar (c-plane) ZnO, and the tensile deformation was observed in nonpolar ZnO (a-plane and m-plane orientations) being in agreement with RBS-C results. Raman spectroscopy showed distinct structural modification in various ZnO orientations simultaneously with identification of the disordered structure in O-sublattice. Nonpolar ZnO showed a significant increase in disorder in O-sublattice exhibited by E2(high) disappearance and enhancement of A1(LO) and E1(LO) phonons connected partially to oxygen vibrational modes. The lowering of the E2(low) phonon mode and shift to the lower wavenumbers was observed in c-plane ZnO connected to Zn-sublattice disordering. Such observations are in agreement with He ion channeling, showing channeling effect preservation with only slight Gd dopant position modification in a-plane ZnO and the more progressive diminishing of channels with subsequent Gd movement to random position with the growing ion fluence and after the annealing in c-plane and m-plane ZnO.

Keywords: doped c-, a- plane and m-plane ZnO; damage accumulation asymmetry; rare-earth ion implantation; RBS channelling; damage-depth profiling

Permalink: https://www.hzdr.de/publications/Publ-30043
Publ.-Id: 30043


Multiconfigurational calculations of ground and excited states of actinide complexes

Kloditz, R.; Patzschke, M.; Stumpf, T.

Multiconfigurational wavefunction based methods are the state of the art methods to quantitatively compute excited state energies and transition moments for heavy element systems where the inclusion of electron correlation and relativistic effects is crucial. Since the advent of these methods, e.g. the complete active-space self-consistent field (CASSCF) method and the density-matrix renormalization group (DMRG) method, it is possible to accurately interpret and predict the UV-Vis spectra of these heavy element systems.
In this talk the CASSCF and DMRG methods are introduced and used to simulate the UV-Vis spectrum of the Uranium-bissalen complex. The active space is set up and varied to accurately describe the wavefunction. CASPT2 and RASSI are used to obtain quantitative results for excited state energies and transition moments.

Keywords: CASSCF; DMRG; Actinides; Excited states; Correlation

  • Invited lecture (Conferences)
    Arbeitsgruppenseminar des AK Thomas Heine (TU Dresden), 26.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30035
Publ.-Id: 30035


Revealing the metal-ligand bonding character in tetravalent f-element complexes with Schiff-base ligands

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

The contribution of the f-orbitals to chemical bonding leads to the rich chemistry of the actinides. This is in contrast to the lanthanides, where it is known that this contribution is less important. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study compares the different bonding behavior of tetravalent actinides and lanthanides with the Schiff base salen by means of real-space bonding analysis. Our approach makes use of the quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) analysis and density differences complemented by natural population analysis (NPA). Especially the local properties at the bond critical points, for instance charge, density, ellipticity and others, can be used to characterize a bond’s order, strength, and covalent contribution.
First results reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker. The delocalization index, density and Laplacian reveal a significant increase of covalency for Pa to Pu compared to Th and Ce being an indicator of the contribution of the f-electrons. Tetravalent Ce as a lanthanide analogue of Th is expected to show a similar bonding behavior, but, surprisingly, this is not the case for all investigated bonding properties.
This detailed analysis of the electronic properties of actinide compounds will help to improve understanding of their behavior in the environment as well as in technical processes and leads to the possibility to predict properties of unknown complexes.

Keywords: DFT; QTAIM; DMRG; Actinides; Quantum chemistry; Bonding

  • Poster
    European Summerschool of Quantum Chemistry, 08.-21.09.2019, Palermo, Italien
  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30034
Publ.-Id: 30034


Insights into the excited states of 5f systems: Protactinium and Uranium

Kloditz, R.; Patzschke, M.; Stumpf, T.

The calculation of the excited states of actinide systems is a challenging task because of the delicate influence of electron correlation and relativistic effects. Density functional theory is not applicable for obtaining quantitative results, hence multiconfigurational wavefunction based methods have to be used. State of the art is a combination of spinfree CASSCF and CASPT2/NEVPT2 and a following inclusion of spin-orbit coupling.
This talk presents quantitative excited state energy calculations of simple Protactinium and Uranium systems in comparison with qualitative group-theoretical considerations.

Keywords: CASSCF; Actinides; Excited states; Group theory

  • Invited lecture (Conferences)
    Arbeitsgruppenseminar des AK Markus Reiher (ETH Zürich), 10.07.2019, Zürich, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-30033
Publ.-Id: 30033


Analysis of the metal-ligand bonding character in tetravalent f-element complexes with Schiff-base ligands

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

The contribution of the f-orbitals to chemical bonding leads to the rich chemistry of the actinides. This is in contrast to the lanthanides, where it is known that this contribution is less important. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study compares the different bonding behavior of tetravalent actinides and lanthanides with the Schiff base salen by means of real-space bonding analysis. Our approach makes use of the quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) analysis and density differences complemented by natural population analysis (NPA). Especially the local properties at the bond critical points, for instance charge, density, ellipticity and others, can be used to characterize a bond’s order, strength, and covalent contribution.
First results reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker. The delocalization index, density and Laplacian reveal a significant increase of covalency for Pa to Pu compared to Th and Ce being an indicator of the contribution of the f-electrons. Tetravalent Ce as a lanthanide analogue of Th is expected to show a similar bonding behavior, but, surprisingly, this is not the case for all investigated bonding properties.
This detailed analysis of the electronic properties of actinide compounds will help to improve understanding of their behavior in the environment as well as in technical processes and leads to the possibility to predict properties of unknown complexes.

Keywords: Actinides; DFT; QTAIM; bonding; covalency; quantum chemistry

  • Poster
    Molecular Quantum Mechanics, 30.06.-05.07.2019, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30032
Publ.-Id: 30032


Towards multiscale and multisource remote sensing mineral exploration using RPAS: A case study in the Lofdal Carbonatite-Hosted REE Deposit, Namibia

Booysen, R.; Zimmermann, R.; Lorenz, S.; Gloaguen, R.; Nex, P. A. M.; Andreani, L.; Möckel, R.

Traditional exploration techniques usually rely on extensive field work supported by geophysical ground surveying. However, this approach can be limited by several factors such as field accessibility, financial cost, area size, climate, and public disapproval. We recommend the use of multiscale hyperspectral remote sensing to mitigate the disadvantages of traditional exploration techniques. The proposed workflow analyzes a possible target at different levels of spatial detail. This method is particularly beneficial in inaccessible and remote areas with little infrastructure, because it allows for a systematic, dense and generally noninvasive surveying. After a satellite regional reconnaissance, a target is characterized in more detail by plane-based hyperspectral mapping. Subsequently, Remotely Piloted Aircraft System (RPAS)-mounted hyperspectral sensors are deployed on selected regions of interest to provide a higher level of spatial detail. All hyperspectral data are corrected for radiometric and geometric distortions. End-member modeling and classification techniques are used for rapid and accurate lithological mapping. Validation is performed via field spectroscopy and portable XRF as well as laboratory geochemical and spectral analyses. The resulting spectral data products quickly provide relevant information on outcropping lithologies for the field teams. We show that the multiscale approach allows defining the promising areas that are further refined using RPAS-based hyperspectral imaging. We further argue that the addition of RPAS-based hyperspectral data can improve the detail of field mapping in mineral exploration, by bridging the resolution gap between airplane- and ground-based data. RPAS-based measurements can supplement and direct geological observation rapidly in the field and therefore allow better integration with in situ ground investigations. We demonstrate the efficiency of the proposed approach at the Lofdal Carbonatite Complex in Namibia, which has been previously subjected to rare earth elements exploration. The deposit is located in a remote environment and characterized by difficult terrain which limits ground surveys.

Keywords: Carbonatite complex; Hyperspectral sensors; Mineral exploration; Multiscale; Namibia; Remotely Piloted Aircraft System

Permalink: https://www.hzdr.de/publications/Publ-30031
Publ.-Id: 30031


Active Targeting of Dendritic Polyglycerols for Diagnostic Cancer Imaging

Kritee, P.; Neuber, C.; Zarschler, K.; Wodtke, J.; Meister, S.; Rainer, H.; Pietzsch, J.; Stephan, H.

Active tumor targeting involves the decoration of nanomaterials (NM) with oncotropic vector biomolecules that selectively recognize certain antigens on malignant cells or in the tumor microenvironment. This strategy can facilitate intracellular uptake of NM through specific interactions such as receptor-mediated endocytosis and can lead to prolonged retention in the malignant tissues by preventing rapid efflux from the tumor. Here, the design of actively targeting, renally excretible bimodal dendritic polyglycerols (dPGs) for diagnostic cancer imaging is described. Single-domain antibodies (sdAb) specifically binding to the epidermal growth factor receptor (EGFR) are employed herein as targeting warheads owing to their small size and high affinity for their corresponding antigen. The dPGs equipped with EGFR-targeting feature are compared head-to-head with their non-targeting counterparts in terms of interaction with EGFR-overexpressing cells in vitro as well as accumulation at receptor-positive tumors in vivo. Experimental results reveal a higher specificity and preferential tumor accumulation for the α-EGFR dPGs, resulting from the introduction of active targeting capabilities on their backbone. These results highlight the potential for improving the tumor uptake properties of dPGs by strategic use of sdAb functionalization, which could ultimately prove useful to the development of ultrasmall NM with highly specific tumor accumulation.

Keywords: polymeric nanoparticles; targeting; single-domain antibodies; multimodality imaging; optical imaging; positron emission tomography

Permalink: https://www.hzdr.de/publications/Publ-30029
Publ.-Id: 30029


X-ray absorption near edge spectroscopy study of warm dense MgO

Bolis, R.; Hernandez, J.-A.; Recoules, V.; Guarguaglini, M.; Dorchies, F.; Jourdain, N.; Ravasio, A.; Vinci, T.; Brambrink, E.; Ozaki, N.; Bouchet, J.; Remus, F.; Musella, R.; Mazevet, S.; Hartley, N.; Guyot, F.; Benuzzi-Mounaix, A.

We report time-resolved X-ray Absorption Near Edge Spectroscopy (XANES) measurements of warm dense MgO. We used a high power nanosecond pulse to drive a strong uniform shock wave into an MgO sample, and a picosecond pulse to generate a broadband X-ray source near the Mg K-edge. We used this setup to obtain XANES spectra across a large area of the phase diagram, with densities up to 6.8 g/cc and temperatures up to 30 000 K, conditions at which no prior investigations of electronic and ionic structure exist. Our XANES results, together with quantum molecular dynamic simulations, demonstrate that the sample metallizes due to the bandgap closure as it melts, after which it shows typical behavior for a disordered ionic liquid.

Keywords: Lasers; Metallization process; Band gap; Laser plasma interactions; Shock waves; High-density liquid; X-ray absorption spectroscopy; Phase transitions

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30026
Publ.-Id: 30026


NORM research and strategy at the HZDR, Germany

Arnold, T.

The presentation gives an overview of the NORM research at the HZDR

Keywords: NORM; radioecology; uranium; research; strategy

  • Invited lecture (Conferences)
    Cores Symposium on Radon and NORM – regulatory aspects, scientific achievements and research needs, 03.-04.09.2019, Helsinki, Finland

Permalink: https://www.hzdr.de/publications/Publ-30025
Publ.-Id: 30025


CFD simulation of multiphase flow in evaporators

Schlottke, J.; Kühnel, W.; Porombka, P.; Lucas, D.

Inside evaporators of air-conditioning systems, uneven mass flow distribution of refrigerant leads to a loss of efficiency and finally a reduction of comfort in passenger compartments. The distribution is influenced by the flow field and two-phase distribution (flow pattern) in various elements, comprising developing and developed two-phase flow in straight and angled ducts, headers, flat tubes and the connection between these.
This talk presents on-going efforts to predict this type of flow with CFD.
In a first step, extensive experimental investigations on generic geometries are done using advanced measurement techniques. This data are then used to develop and validate numerical models capable of reproducing the relevant physics.
Important two-phase phenomena are: multiple regimes (continuous-disperse + separated flow), wall films, stripping/impingement, particle size distribution, two-phase heat transfer, boiling/condensation. In a final step, the developed modeling strategy is applied to real evaporators.
In comparing simulation results to experimental data, we find both good agreement as well as discrepancies which confirm that there is still more work on developing appropriate models to do.

Keywords: evaporator; CFD; flow distribution; air-conditioning systems; Euler-Euler method

  • Lecture (Conference)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30024
Publ.-Id: 30024


The Inverse Trans Influence in a novel Uranium(IV)bis(carbene) Complex

Köhler, L.; Patzschke, M.; März, J.; Stumpf, T.

The trans influence is an extensively investigated electronic concept in transition metal chemistry. It can be defined as the extent to which a bond in trans position to a ligand L is weakened.[1,2] In contrast, f-block elements exhibit an opposite effect, meaning a bond shortening and thus strengthening can be observed in the trans position to a strongly donating ligand. This is established as the inverse trans influence (ITI),[3–5] and is commonly assumed to be most prominent for actinides in high oxidation states.
A novel UIVbis(carbene) complex [UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) was synthesized by salt metathesis from UCl4 in the presence of iPrImHCl and TMSA. In the complex, the U centre is surrounded by two carbenes, three chloro- and one TMSA-ligand. The U–Cl bond in trans position to the TMSA is slightly shorter (0.01 Å) compared to the other U–Cl bonds, indicating an TMSA-induced ITI. However, this change is very small. For comparison, a structural optimization based on the SC-XRD data of 1 was carried out using tetravalent tungsten as a d-block analogue, because of its similar ionic radius to UIV. Tungsten’s transition metal behaviour should result in a trans influence. In the WIVbis(carbene) complex 2, the W–Cl bond trans to the TMSA ligand is indeed 0.05 Å longer than the other W–Cl bonds. This large change expresses the existence of a strong trans influence in 2 and hence ITI in 1.
References:
[1] A. Pidcock, R. E. Richards, L. M. Venanzi, J. Chem. Soc. Inorg. Phys. Theor. 1966, 0, 1707–1710.
[2] T. G. Appleton, H. C. Clark, L. E. Manzer, Coord. Chem. Rev. 1973, 10, 335–422.
[3] R. G. Denning, J. Phys. Chem. A 2007, 111, 4125–4143.
[4] H. S. La Pierre, K. Meyer, Inorg. Chem. 2013, 52, 529–539.
[5] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.

Keywords: uranium carbene complex; inverse trans influence; ITI; tungsten carbene complex

  • Lecture (Conference)
    Tagung Gesellschaft Deutscher Chemiker, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30023
Publ.-Id: 30023


Actinid-Komplexe mit N-heterocyclischen Carbenen

Köhler, L.; Patzschke, M.; März, J.; Stumpf, T.

The inverse trans influence (ITI) is an effect well-known to occur in high valent U(V/VI) complexes. It appears as a shortening of the M–L bond in trans position to a strongly donating ligand. The effect can be explained by electron density donation from the strong ligand to the metal center, which fills up the electron hole formed through electron density transfer from semi-core 6p to vacant 5f orbitals.[1,2] This results in the observed contraction and strengthening of the bond trans to the donating ligand.
To compare the ITI in UIV and UV complexes, the U compounds [UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) and [UV(TMSI)Cl₅](L¹H)₂ 2 (TMSI = NSiMe₃−) were synthesized from UIV starting material in the presence of iPrIm. In the case of 1 the metal center is surrounded by three chloro-, two carbene and one TMSA ligand, whereas 2 exhibits five chloro- and one TMSI ligand, thus generating an dianion, whose charge is compensated by the protonated carbene. In 1, the U–Cl bond, located trans to the TMSA ligand, is remarkably shorter (0.02 Å) than the other U–Cl bonds. This indicates the existence of an ITI, induced by TMSA. Based on the higher valent UV cation and stronger donating TMSI ligand, a similar or stronger effect should also be observed in 2. Surprisingly, this could not be confirmed by the experimental data. The U–Cl bond lying trans to the TMSI ligand is not the shortest U–Cl bond (2.68 Å compared to 2.66 Å for U–Cl1/2), but is in the same range as the other chloro ligands. The absence of a notable ITI can be attributed to intermolecular interactions in the crystal structure of 2. Structure optimization of the molecular UV complex dianion by DFT yield a U–Cl5 bond length of 2.55 Å, shorter than any other U–Cl bond by 0.02 Å. The difference between experiment and theory results from a great number of electrostatic interactions and hydrogen bonding between the complex dianion and the carbene counterions in 2. Similar intermolecular interactions are not present in the crystal structure of 1, which is why the ITI could be observed for this compound.
The results demonstrate that the ITI affects complex structures for both, UIV and UV compounds, but additional effects, such as the intermolecular network observed in the structure of 2 can surpass its relatively small structural contribution.

References
[1] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.
[2] B. Kosog, H. S. La Pierre, F. W. Heinemann, S. T. Liddle, K. Meyer, J. Am. Chem. Soc. 2012, 134, 5284–5289.

Keywords: carbenes; inverse trans influence; ITI; uranium(V) complex

  • Invited lecture (Conferences)
    Finale der WiN Preisverleihung, 11.10.2019, Karlstein/Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30022
Publ.-Id: 30022


The Inverse Trans Influence in U(IV/V) complexes

Köhler, L.; Patzschke, M.; März, J.; Stumpf, T.

The inverse trans influence (ITI) is an effect well-known to occur in high valent U(V/VI) complexes. It appears as a shortening of the M–L bond in trans position to a strongly donating ligand. The effect can be explained by electron density donation from the strong ligand to the metal center, which fills up the electron hole formed through electron density transfer from semi-core 6p to vacant 5f orbitals.[1,2] This results in the observed contraction and strengthening of the bond trans to the donating ligand.
To compare the ITI in UIV and UV complexes, the U compounds [UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) and [UV(TMSI)Cl₅](L¹H)₂ 2 (TMSI = NSiMe₃−) were synthesized from UIVstarting material in the presence of iPrIm. In the case of 1 the metal center is surrounded by three chloro-, two carbene and one TMSA ligand, whereas 2 exhibits five chloro- and one TMSI ligand, thus generating an dianion, whose charge is compensated by the protonated carbene. In 1, the U–Cl bond, located trans to the TMSA ligand, is remarkably shorter (0.02 Å) than the other U–Cl bonds. This indicates the existence of an ITI, induced by TMSA. Based on the higher valent UV cation and stronger donating TMSI ligand, a similar or stronger effect should also be observed in 2. Surprisingly, this could not be confirmed by the experimental data. The U–Cl bond lying trans to the TMSI ligand is not the shortest U–Cl bond (2.68 Å compared to 2.66 Å for U–Cl1/2), but is in the same range as the other chloro ligands. The absence of a notable ITI can be attributed to intermolecular interactions in the crystal structure of 2. Structure optimization of the molecular UV complex dianion by DFT yield a U–Cl5 bond length of 2.55 Å, shorter than any other U–Cl bond by 0.02 Å. The difference between experiment and theory results from a great number of electrostatic interactions and hydrogen bonding between the complex dianion and the carbene counterions in 2. Similar intermolecular interactions are not present in the crystal structure of 1, which is why the ITI could be observed for this compound.
The results demonstrate that the ITI affects complex structures for both, UIV and UV compounds, but additional effects, such as the intermolecular network observed in the structure of 2 can surpass its relatively small structural contribution.

References
[1] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.
[2] B. Kosog, H. S. La Pierre, F. W. Heinemann, S. T. Liddle, K. Meyer, J. Am. Chem. Soc. 2012, 134, 5284–5289.

Keywords: inverse trans influence; ITI; uranium(V); carbenes

  • Lecture (Conference)
    Journées des Actinides, 14.-18.04.2019, Erice, Italien

Permalink: https://www.hzdr.de/publications/Publ-30021
Publ.-Id: 30021


Trivalent Lanthanide and Actinide Incorporation into Zirconium(IV) Oxide – Spectroscopic Investigations of Defect Fluorite Structures

Eibl, M.; Shaw, S.; Hennig, C.; Morris, K.; Stumpf, T.; Huittinen, N. M.

The incorporation of trivalent lanthanides and actinides into zirconia (ZrO₂) was studied using PXRD and spectroscopic methods (EXAFS, TRLFS). In highly doped cubic zirconia three Eu(III) incorporation species could be found using TRLFS. A surface associated species with an excitation maximum of 578.1 nm and two bulk incorporation species with excitation maxima at 579.0 and 579.7 nm were found.

  • Lecture (Conference)
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30019
Publ.-Id: 30019


Trivalent Lanthanide and Actinide Incorporation into Zirconium(IV) Oxide – Spectroscopic Investigations of Defect Fluorite Structures

Eibl, M.; Shaw, S.; Hennig, C.; Morris, K.; Stumpf, T.; Huittinen, N. M.

The incorporation of trivalent lanthanides and actinides into zirconia (ZrO₂) was studied using PXRD and spectroscopic methods (EXAFS, TRLFS). In highly doped cubic zirconia three Eu(III) incorporation species could be found using TRLFS. A surface associated species with an excitation maximum of 578.1 nm and two bulk incorporation species with excitation maxima at 579.0 and 579.7 nm were found.

  • Lecture (Conference)
    17th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere., 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-30018
Publ.-Id: 30018


CFD simulation of flashing phenomena

Liao, Y.

Due to its relevance for technical applications, experimental and theoretical investigation on flashing flows through nozzles and tubes has gained great attention. Most of them have focused on area-averaged quantities such as mass flow rate and pressure drop, while little attention has been paid to the internal flow structure and interfacial exchanging processes. More recently, computational fluid dynamics is frequently utilized to explore the phase distribution in the flashing flows. Various gas-liquid mixture or two-fluid models have been proposed in the literature. However, knowledge on the non-equilibrium effects, interphase transfer as well as bubble dynamics under different flashing conditions is still insufficient, and a general and precise definition of the problem in numerical simulations remains a challenge. A broad consensus on the numerical methods for flashing flows is not available. Guidelines for selecting an appropriate model are desirable, which is, however, not an easy task due to the complex physics and lack of insights. The talk is focused on the elucidation of important interfacial processes such as interfacial area density, interfacial heat transfer, bubble nucleation, coalescence and breakup as well as available modelling approaches. Numerical simulations for various flashing scenarios, i.e. converging-diverging flow, pipe-blowdown, natural circulation loop and pressure release transient, are presented. The influence of chosen numerical methods is discussed, especially the mixture model versus two-fluid ones and mono-disperse versus poly-disperse approaches. Progresses towards developing a general framework for modelling of complex gas-liquid flows are demonstrated.

Keywords: Flashing flow; Numerical simulation; Phase change; Mono-disperse approach; Poly-disperse approach

  • Lecture (Conference)
    17th Multiphase Flow Conference & Short Course, 11.-15.11.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-30016
Publ.-Id: 30016


Accuracy and robustness of 4D logfile-based dose reconstruction and start of clinical application

Spautz, S.; Meijers, A.; Jakobi, A.; Peters, N.; Knopf, A.-C.; Troost, E. G. C.; Richter, C.; Stützer, K.

Introduction: We established a 4D logfile-based dose reconstruction for monitoring and potential intervention during intensity-modulated proton therapy (IMPT) of moving tumors. Before clinical application, we assessed the validity of reconstructed doses and the sensitivity against changes of selected input parameters by phantom experiments.
Material/Methods: A dynamic thorax phantom (CIRS, USA) with a soft-tissue target and radiochromic film insert was imaged by 4DCT and irradiated with either quasi-monoenergetic fields or 4D optimized proton plans. The surrogate signal (ANZAI, Japan) of the regular motion was recorded in synchronization with the machine logfiles. Reconstructions were performed with different dose grid resolutions (1mm/3mm), deformable image registrations (DIR; manually defined or automatically generated vector-fields) and artificial asynchronies between machine and motion logfiles.
Results: Characteristic dose patterns on radiochromic films were well reconstructed (Fig.1A). Gamma pass rates (2mm, 2%) for extracted characteristic profiles of the reconstructed and measured doses were >98% under static conditions, ranged between 99% and 86% for 5mm motion depending on applied reconstruction parameters, especially the DIR, and were about 80% for 30mm motion due to the predominant residual motion in the 4DCT (Fig.1B). Fig.1C demonstrates the robustness against potential minor asynchronies (≈5ms) between machine and motion logfiles. A workflow test during a pancreatic cancer IMPT treatment (Fig.2) revealed a data processing time of approximately 20min/fraction.
Conclusions: Due to satisfying accuracy and robustness for clinically aimed motion amplitudes (≤5mm), IMPT treatment of non-small cell lung cancer accompanied by daily 4D logfile-based dose monitoring will start in our institute within the first months of 2020.

  • Lecture (Conference) (Online presentation)
    PTCOG 2020 Online, 13.-14.09.2020, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-30015
Publ.-Id: 30015


Synthesis and Characterization of Tri- and Tetravalent Actinide Amidinates

Fichter, S.

Tri- and tetravalent actinide amidinates have been synthesized and characterized in solid state and in solution.

  • Lecture (others)
    FENABIUM Projekttreffen, 12.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30014
Publ.-Id: 30014


Some notes on eddy viscosity in wall-bounded turbulent bubbly flows

Ma, T.; Liao, Y.; Lucas, D.; Bragg, A.

Recently, based on data from Direct Numerical Simulations (DNS), Ma et al. (Phys. Rev. Fluids 2, 034301, 2017) proposed a model for closing the bubble-induced turbulence (BIT) in a typical Euler-Euler two-equation model, which appears to yield improved performance for predicting $k$ and $\varepsilon$ over the previous models. The present study departures from this BIT model and purpose to use the same DNS data to investigate the behavior of the $C_\mu$ constant and standard eddy viscosity definition. It can be shown that $C_\mu$ constant computed using the DNS database has a very different behavior than that in single-phase flow. Checking closely, the deficiency originates from the description of the standard eddy viscosity that is intrinsic to this general hierarchy of Euler-Euler $k-\varepsilon$ type model, hence, cannot be overcome by a more complex correction function for $C_\mu$. Departing from this point, a modification to the definition of the eddy viscosity in bubbly flows is derived for the Euler-Euler two-equation models. The new expression is based on the bubble length-scale and its corresponding velocity scale. We focus on the intermediate region -- a region extended from the core region, where bubble-induced production and dissipation are nearly in balance, and find that the modified model can lead to significantly improved predictions for the mean liquid, when compared with DNS data.

  • Lecture (Conference)
    72nd Annual Meeting of the APS/DFD, 23.-26.11.2019, Seattle, USA

Permalink: https://www.hzdr.de/publications/Publ-30013
Publ.-Id: 30013


A Flow Pattern Adaptive Multi-field Two-fluid Concept for Turbulent Two-phase Flows

Schlegel, F.; Meller, R.; Lehnigk, R.; Hänsch, S.; Tekavčič, M.

Industrial applications feature a huge variety of different flow patterns, such as bubbly flow, slug flow or annular flow. Thereby a broad range of flow morphologies and different physical scales is involved. With the objective of reproduction of occurring phenomena with one single multi-fluid solver, we present an Euler-Euler-approach, which combines a number of different methods for treatment of the partial aspects. The implementation into OpenFOAM is always with focus on sustainable research, including a state-of-the-art IT concept. A segregated approach is used for treatment of the phase momentum equations, phase fraction equations and the pressure equation, featuring a consistent momentum interpolation scheme (Cubero et al., 2014). To fulfil the kinematic condition at resolved interfaces between different continuous phases, the latter may be coupled either by an isotropic (Strubelj and Tiselj, 2011) or by an anisotropic drag. In both cases, the immensely strong phase coupling requires an adapted numerical method. State and evolution of bubble size distribution in disperse phase context is solved with either class or moment methods.
The overall objective is to take interactions between the all different aspects, such as disperse phases, resolved interfaces and turbulence with effects on momentum and mass transfer into account.

  • Poster
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30012
Publ.-Id: 30012


On non drag interfacial force and thermal phase change modelling of reactingEulerFoam

Peltola, J.; Pättikangas, T.; Bainbridge, W.; Lehnigk, R.; Schlegel, F.

The reactingEulerFoam framework included in OpenFOAM releases since 3.0.0 provides a highly flexible platform for the modelling of multiphase flows. Extensive selection of interfacial force models is provided along with alternate turbulence models. The thermal phase change capability [1,2] was first introduced in OpenFOAM 3.0.1 [3] and has since been extended and refined in subsequent releases.
The current OpenFOAM 7 release features include support for non-equilibrium wall boiling, n-phase thermal phase change and for bubble diameter modelling algebraic, IATE and inhomogeneous class method models are supported.The present simulations have been carried out with the OpenFOAM Foundation development release [4]. The goal is to aid those that intend to use the publicly available reactingEulerFoam by providing a summary of the models and demonstrations of a few modelling details by expanding upon tutorials recently added to the OpenFOAM Foundation development line.
DEDALE experiments [5] are used as a reference for the non-drag interfacial force modelling.
Subcooled nucleate boiling simulation results with different models combinations are compared to the DEBORA experiments [6,7]. Finally, a more complex direct contact condensation simulation of SEF-POOL test facility [8] is presented and results are compared to the experiment.

References

[1] Peltola, J., & Pättikangas, T.J.H. Development and validation of a boiling model for OpenFOAM multiphase solver. CFD4NRS-4 Conference Proceedings, Daejeon, Korea, paper 59, (2012).
[2] Peltola, J., Pättikangas, T., Bainbridge, W., Lehnigk, R., Schlegel, F., On development and validation of subcooled nucleate boiling models for OpenFOAM Foundation release. NURETH-18 Conference Proceedings, Portland, Oregon, United States (2019).
[3] OpenFOAM Foundation, “OpenFOAM 3.0.1,” http://openfoam.org/version/3.0.1/ (2015).
[4] OpenFOAM Foundation, “OpenFOAM-dev,” https://openfoam.org/version/dev/ (2014-2019).
[5] Grossetete, C., Experimental investigation and numerical simulations of void profile development in a vertical cylindrical pipe (No. EDF--96-NB-00120). Electricite de France (EDF), (1995).
[6] E. Manon, Contribution à l’anayse et à la modélisation locale des écoulements boillants sous-saturésdans les conditions des Réacteurs à Eau sous Pression, PhD thesis, Ecole Centrale Paris (2000).
[7] J. Garnier, E. Manon, G. Cubizolles, “Local measurements on flow boiling of refrigerant 12 in avertical tube”, Multiphase Science and Technology, pp. 1-111 (2001).
[8] M. Puustinen, J. Laine, A. Räsänen, E. Kotro, and K. Tielinen, “Characterizing tests in SEF-POOLfacility,” Technical Report, Lappeenranta University of Technology, Nuclear Engineering, INSTAB3/2017 (2017).

  • Lecture (Conference)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30011
Publ.-Id: 30011


Flexible development framework for the Euler Euler approach

Schlegel, F.; Greenshields, C.

The presentation gives a detailed insight into the OpenFOAM Developments for Euler-Euler simulations at HZDR, i.p. the multi-field two-fluid model approach, LES simulations, stratified flow simulations, entrainment modelling and more. Furthermore, the successfull development strategy and co-working with the OpenFOAM Foundation is explained.

Keywords: Euler-Euler; OpenFOAM; Numerical Simulation; Entrainment; Gentop; Stratified Flow

  • Invited lecture (Conferences)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30010
Publ.-Id: 30010


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