Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35173 Publications

Demonstration of a Broadband Photodetector Based on a Two-Dimensional Metal- Organic Framework

Arora, H.; Dong, R.; Venanzi, T.; Zscharschuch, J.; Schneider, H.; Helm, M.; Feng, X.; Cánovas, E.; Erbe, A.

Metal-organic frameworks (MOFs) are emerging as an appealing class of highly tailorable electrically-conducting materials with potential applications in opto-electronics. Yet, the realization of their proof-of-concept devices remains a daunting challenge, attributed to their poor electrical properties. Following our recent report on a semiconducting Fe3(THT)2(NH4)3 (THT, 2,3,6,7,10,11-triphenylenehexathiol) two-dimensional MOF with record-high mobility and band-like charge transport, here, we demonstrate Fe3(THT)2(NH4)3 MOF-based photodetector operating in photoconductive mode capable of detecting a broad wavelength excitation of charge carriers. The narrow IR bandgap of the active layer (~0.45 eV) constrains the performance of the photodetector at room temperature by band-to-band thermal. At 77 K, the device performance is significantly improved; two orders of magnitude higher voltage responsivity, lower noise equivalent power, and higher specific detectivity of 7×108 cm Hz1/2 W–1 are achieved under 785 nm excitation. These figures of merit are retained over the analyzed spectral region (400–1575 nm) and are commensurate to those obtained with the first demonstrations of graphene and black phosphorus based photodetectors. This work demonstrates the feasibility of integrating conjugated MOFs as an active element into broadband photodetectors, thus bridging the gap between materials’ synthesis and technological applications.

Keywords: metal-organic frameworks; broadband photodetectors; low-temperature photodetection; two-dimensional semiconductors; photosensitivity

Permalink: https://www.hzdr.de/publications/Publ-30159
Publ.-Id: 30159


Effect of melt stirring during casting on the extrusion and mechanical properties of wrought aluminium alloys

Räbiger, D.; Willers, B.; Eckert, S.

The adjustment of fine grain morphologies has been approved to be a crucial issue for improving characteristics and properties of cast and wrought aluminium alloys. Several methods are known to achieve grain refinement in solidification processes: add-on of grain refiners, rapid cooling conditions, mechanical or electromagnetic stirring or ultrasonic treatment.
AC magnetic fields provide a contactless method to control the flow inside a liquid metal and the grain size of the solidified ingot. Many studies have shown that beneficial effects like a distinct grain refinement or the promotion of a transition from a columnar to an equiaxed dendritic growth (CET) can be obtained. However, electromagnetically-driven melt convection may also produce segregation freckles on the macroscale. The achievement of superior casting structures needs a well-aimed control of melt convection during solidification.
Previous investigations considered the use of time-modulated AC magnetic fields to control the heat and mass transfer at the solidification front. It has been shown recently under laboratory conditions that an accurate tuning of the magnetic field parameters can avoid segregation effects and homogenize the mechanical properties.
This present study examines the directional solidification of commercial wrought aluminium alloys EN AW 6082 from a water-cooled copper chill. Rotating time-modulated magnetic fields were used to agitate the melt. The impact of flow on the resulting macro and micro structure are investigated. The solidified structure was reviewed in comparison to an unaffected solidified ingot and ingot prepared with chemical grain refiner Ti3B. In addition results from extrusion process experiments and the achieved mechanical properties are introduced. Our results demonstrate the potential of time–modulated magnetic fields to control the grain size and to open the possibility to reduce the amount of grain refiner and to reduce the press capacity.

Keywords: wrought aluminium alloys; mechanical properties; electromagnetic stirring; forced convection

  • Lecture (Conference)
    LightMAT 2019 - 3rd International Conference on Light Materials – Science and Technology, 05.-07.11.2019, Manchester, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-30158
Publ.-Id: 30158


TEM observation of loops decorating dislocations and resulting source hardening of neutron-irradiated Fe-Cr alloys

Bergner, F.; Hernandez-Mayoral, M.; Heintze, C.; Konstantinovic, M. J.; Malerba, L.; Pareige, C.

Several open issues remain concerning the quantitative understanding of irradiation hardening in high-Cr steels. One of these issues is addressed here by correlating yield points that are observed in stress-strain curves with dislocation decoration observed by TEM for neutron-irradiated Fe-Cr alloys. It is found that both higher neutron exposure and higher Cr content promote irradiation-induced loops to arrange preferentially along dislocation lines. Consequently, the activation of dislocation sources requires unlocking from the decorating loops, thus resulting in a yield drop. This process is considered within the source hardening model as opposed to the dispersed barrier hardening model, the latter aimed to describe dislocation slip through a random array of obstacles. Microstructure-informed estimates of the unlocking stress are compared with measured values of the upper yield stress. As functions of neutron exposure, a cross-over from the dominance of dispersed-barrier hardening accompanied by smooth elastic-plastic transitions to the dominance of source hardening accompanied by yield drops is observed for Fe-9% Cr and Fe-12% Cr.

Keywords: iron-chromium alloy; neutron irradiation; hardening; tensile test; dislocation loop; TEM

Permalink: https://www.hzdr.de/publications/Publ-30157
Publ.-Id: 30157


Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiments and Models

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

n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The non-polar lattice of Ge and SiGe provides electron-phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic 2DEG distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is here compared to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross-sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1-3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, whose prediction of the saturation intensity is off by a factor 3.

Keywords: quantum wells; intersubband transitions; terahertz quantum cascade laser; electron-phonon interaction; optical pumping; free electron laser; silicon-germanium heterostructures; infrared spectroscopy; intersubband photoluminescence

Permalink: https://www.hzdr.de/publications/Publ-30156
Publ.-Id: 30156


Liquid Metal Batteries

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

Liquid metal batteries (LMBs) are fascinating electrochemical cells. Built as a stable density stratification of two liquid metals separated by a molten salt electrolyte, such cells offer cheap stationary energy storage and a long life time. Due to the totally liquid interior of the cells, fluid flow is of paramount importance for the safe operation of LMBs. As highly resistive electrolyte needs to be as thin as possible, a strong fluid flow might easily wipe it away and short circuit the cell. Aside from that, a slight flow might be highly beneficial. When discharing a Li-Bi LMB, Li will cross the electrolyte layer and alloy into Bi. As this process is diffusion-controlled, a Li-rich layer will build up on top of the positive electrode. A mild flow might equalize the alloy, thus reducing concentration polarization and improving the cell's efficiency.

The talk will first explain the set-up and operation of liquid metal batteries. Afterwards, different possible flow mechanisms in LMBs will be presented and discussed. These will include thermally driven Rayleigh-Benard convection, solutal convection, pinch effects, interface instabilities, the Tayler instability and electro-vortex flow. Besides of flow simulation, the modelling of the electric potential distribution, the current density and magnetic fields will be presented. Special attention will be paied to the implementation of the solvers in OpenFOAM, as well as the description of specialized discretisation schemes, which are necessary e.g. for computing the current density. Finally, it will be shown how different flows in the battery effect the cell voltage, and the integrity of the three layers.

  • Lecture (Conference)
    15th OpenFOAM Workshop, 23.06.2020, Arlington, USA

Permalink: https://www.hzdr.de/publications/Publ-30155
Publ.-Id: 30155


Ionisation chamber readings for proton beams in magnetic fields require dose correction factors

Gebauer, B.; Hoffmann, A. L.; Lühr, A.

Objectives: Proton therapy (PT) reduces the integral dose in healthy tissue compared to X-ray therapy (XT). At the same time PT is more sensitive to anatomical changes and organ motion than XT, making MRI guidance especially relevant for PT. Recently, we have integrated for the first time a 0.22 T in-beam MRI scanner with a proton therapy research beamline. As a next step, absolute and relative dosimetry in the presence of magnetic fields of the MRI scanner has to be established. This work investigates the influence of the static magnetic (B0) field of the MRI scanner on ionisation chamber (IC) readings for proton beams and the feasibility to correct the readings for the B0 field.

Materials & methods: Either a Semiflex 0.3 or a PinPoint3D IC was positioned in an MR-compatible water phantom to measure the absolute dose at five proton energies (70, 110, 150, 190, 226.7 MeV) in the entrance plateau area of the Bragg curve for a 10 x 10 cm2 pencil beam scanned irradiation field. The entrance window of the phantom was placed at the imaging isocentre of the MRI scanner. Dose measurements were repeated at the same position and under the same conditions without the B0 field. The IC signal was corrected to standard environmental conditions and for the beam quality.

Results & Conclusion: Systematic energy-dependent differences between dose readings with and without the B0 field were observed. For the Semiflex 0.3, the measured dose in the presence of the B0 field increased by 0.75%, 0.58%, 0.59% and 0.41% for 70 MeV, 110 MeV, 150 MeV and 190 MeV, respectively, and decreased by 0.36% for 226.7 MeV. For the same energies, the dose measured by the PinPoint3D increased by 0.81%, 0.69%, 0.63%, 0.47% and 0.31%. For all energies, the standard deviations were smaller than 0.10% and 0.19% for the Semiflex 0.3 and PinPoint3D IC, respectively.
Beam energy-dependent correction of IC readings is mandatory and appears feasible for accurate proton beam dosimetry in magnetic fields.

Keywords: dosimetry; MRgPT; correction factor; magnetic field

  • Lecture (Conference) (Online presentation)
    eDGMP 2020, 09.-11.09.2020, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30154
Publ.-Id: 30154


Inverse gas chromatography studies of the esterification of glass particles with different morphologies

Sygusch, J.; Rudolph, M.

The separation of fine particles is a challenging task where a proper understanding of the interfacial properties is crucial. In our research, we focus on flotation, which is a powerful and widely used separation technique, where valuable mineral particles are selectively separated from unwanted gangue, with particles in the size range of about 10 µm to 200 µm. For this process, particle properties such as wettability, size or morphology are fundamental separation features.
Although, it is a well-established processing technique that is used all over the world in industry, there are still some challenges with regard to the processing of ultrafine particles with sizes below 10 µm. The aim of this project, which is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart”, is to gain a deeper understanding of the microprocesses that occur during flotation and to have a closer look on the influence of particle properties, like wettability and morphology.
For this research glass particles are used as their surface chemistry can be modified in different ways. Here, the functionalisation was carried out by esterification with alcohols, where the wettability of the product can be controlled by the length of the alkyl chain. In order to investigate the effect of particle morphology on flotation three differently shaped glass particles were used and esterified, including fibres, spheres and fragments with differing shapes. Inverse gas chromatography is used to characterise the particles surface energy distributions, which provide information about the particles wettability as well as the heterogeneity of the surface.

Keywords: Ultrafine Particles; Surface Modification; Esterification of Glass Particles; Hydrophobisation; Surface Energy Distribution; Inverse Gas Chromatography; Flotation

  • Lecture (Conference)
    8th International IGC Symposium, 04.06.2019, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30153
Publ.-Id: 30153


The effect of morphology of microparticles hydrophobized via esterification with alcohols on the specific surface energies distributions

Sygusch, J.; Rudolph, M.

Froth flotation is a well-established and efficient particle processing technique especially for the selective separation of mineral particles from unwanted material within sizes ranging from 10 µm to 200 µm. However, there are still some challenges and unexplored opportunities when it comes to the separation of ultrafine particles (< 10 µm). Within the German research foundation priority programme DFG-SPP 2045 “MehrDimPart” we aim to develop a novel multidimensional separation device for such ultrafine particles based on the particle parameters of wettability, morphology (shape or roughness) and size.
One important aspect of our investigations in this new flotation device lies in the modification of the materials surface, which is achieved via esterification with alcohols. To study the effect of the particle morphology/shape on the hydrophobization of glass microparticles, three differently shaped but same sieve sized fractions are used for applying esterification, among them spherical particles, elongated particles and particle fragments with varying shapes. The characterisation of the particle wettability is realised using the inverse gas chromatography method with additional information on the surface energy components distributions. The wettability is varied using alcohols with different chain length and the resulting surface energy components distributions are put in context with flotabilities of the particles in two flotability characterisation set-ups, i.e. tube microflotation and particle adhesion to hydrocarbons.

Keywords: Ultrafine Particles; Surface Modification; Esterification of Silica; Hydrophobisation; Surface Energy Distribution; inverse Gas Chromatography; Flotation

  • Poster
    PARTEC 2019 - International Congress on Particle Technology, 09.-11.04.2019, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30152
Publ.-Id: 30152


Solution-Phase Synthesis of the Fluorogenic TGase 2 Acyl Donor Z-Glu(HMC)-Gly-OH and its Use for Inhibitor and Amine Substrate Characterisation

Wodtke, R.; Pietsch, M.; Löser, R.

A reliable solution-phase synthesis of the water-soluble dipeptidic fluorogenic transglutaminase substrate Z-Glu(HMC)-Gly-OH is presented. The route started from Z-Glu-OH, which was converted into the corresponding cyclic anhydride. This building block was transformed into the regioisomeric - and -dipeptides. Key step was the esterification of Z-Glu-Gly-OtBu with 4-methylumbelliferone. The final substrate compound was obtained in an acceptable yield and excellent purity without the need of purification by RP-HPLC. The advantage of this acyl donor substrate for the kinetic characterisation of inhibitors and amine-type acyl acceptor substrates is demonstrated by evaluating commercially available or literature-known irreversible inhibitors and the biogenic amines serotonin, histamine and dopamine, respectively.

Keywords: fluorogenic enzyme substrates; side-chain esterified peptides; aryl esters; peptide synthesis; enzyme kinetics; biogenic amines

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Permalink: https://www.hzdr.de/publications/Publ-30151
Publ.-Id: 30151


Simulation of coolant mixing in a BWR spent fuel storage pool and flood chamber

Höhne, T.

The waiting times in case of failure of the cooling system of the spent fuel storage pool were determined with the three-dimensional numerical calculation tool ANSYS CFX. With the calculated variant, it is assumed that the swivel gate is opened when required. For the decay heat of 1.5 MW, waiting times until the spent fuel storage pool has been heated to 60 °C or 80 °C were calculated and the temperature offset between the spent fuel storage pool and the storage chamber pool was determined.

The calculations showed that the coolant from the flood chamber and the storage chamber, which is located above the lower edge of the open swivel gate, mixes ideally with the water from the spent fuel pool. The results of the CFD analysis can be used for the cross-code verification of models in integral codes.

Keywords: Boiling; CFD; Mixing; spent fuel storage pool

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30150
Publ.-Id: 30150


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


Towards the clinical translation of the adenosine A2A receptor (A2AR) radioligand [18F]FLUDA: preclinical perspectives

Teodoro, R.; Lai, T. H.; Toussaint, M.; Gündel, D.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Kranz, M.; Schröder, S.; Moldovan, R.-P.; Brust, P.

Introduction
The A2AR has emerged as a potential therapeutic target due to its involvement in basic functions of the neuronal, cardiovascular and immune systems. Blockade of A2AR is regarded as potential tool related to CAR T-cell immunotherapy of cancer. Furthermore, A2AR are believed to regulate myocardial oxygen demand and to increase coronary circulation by vasodilation. With regard to Parkinson’s disease A2AR antagonists, such as the FDA approved Nourianz®, are used as an adjunctive treatment to levopoda®. Therefore noninvasive imaging to monitor changes of receptor density and/or occupancy during the A2aR-tailored therapy is of utmost importance. We recently developed the A2AR PET radiotracer [18F]FLUDA which demonstrated superior pharmacokinetic properties among the radiotracers available. Towards its clinical translation, an automated radiosynthesis was developed and the radiotracer was fully characterized in vitro and in vivo including toxicity and dosimetry1 studies.
Methods
The binding affinity (Ki) of FLUDA towards the human A2AR and A1R subtypes was estimated in vitro by competitive radioligand binding assays. In addition, selectivity studies were performed. An automated two-step one-pot radiosynthesis of [18F]FLUDA was developed. In vitro autoradiography was performed on cryosections of mice brain. Dynamic PET/MR studies under baseline and blocking conditions were assessed. The time-activity curves of the SUV ratio (SUVR) of striatum over cerebellum were used as measure for specific uptake. Metabolism was investigated in CD-1 mice via radio-HPLC analysis of extracted plasma and brain samples. Single-dose acute toxicity of FLUDA was assessed in male and female Wistar rats.
Results
A high A2aR binding affinity and high A1R selectivity were recorded for FLUDA (KiA2aR= 0.60 nM and KiA1R= XX nM). The two-step one-pot automated radiosynthesis of [18F]FLUDA was successfully established (radiochemical yield: 9±1%; radiochemical purity: ≥98%; molar activity= 69 333 GBq/µmol). In vitro autoradiography with [18F]FLUDA revealed a specific accumulation in the striatum, which is characterized by the binding parameters KD = 4.3 ± 0.7 nM and Bmax = 556 ± 143 fmol/mg wet weight (Fig.1A). In vivo evaluation in mice revealed that only the parent radiotracer was found in plasma and brain samples at 15 min p.i.. PET scans (n=3) showed a selective binding of [18F]FLUDA in striatum (SUVR15 30 min p.i.>8), which was significantly reduced by pre-treatment with 2.5 mg/kg i.p. tozadenant (30%, n=3, p<0.05, Fig.1B/C). The single dose toxicity study of FLUDA did not reveal any adverse effects for ~ 1000-fold of expected human dose.
Conclusion
The fully automated radiosynthesis of [18F]FLUDA allows its translation to clinical radiopharmacy. [18F]FLUDA exhibited a A2AR-specific accumulation in the striatum in vitro and in vivo. No safety concerns are expected upon administration of [18F]FLUDA according to toxicity and dosimetry studies. Altogether, these results encourage the performance of clinical trials to validate the potential of [18F]FLUDA for imaging of neuronal, cardiovascular and cancer-related diseases.
Acknowledgments
The authors thank the European Regional Development Fund and Sächsische Aufbaubank (SAB) for financial support (project no. 100226753).
[1] Kranz, M. et al. (2020) this volume.

Keywords: adenosine A2A receptor; [18F]FLUDA; PET; clinical translation

  • Open Access Logo Contribution to proceedings
    Society of Nuclear Medicine and Molecular Imaging Meeting (SNMMI 2020), 13.-16.06.2020, New Orleans, USA
    The Journal of Nuclear Medicine, USA: Society of Nuclear Medicine and Molecular Imaging, S267

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Permalink: https://www.hzdr.de/publications/Publ-30146
Publ.-Id: 30146


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


Characterization of the rotenone mouse model of Parkinson’s disease (PD) at early and late disease stage using radioligands for the α4β2 nicotinic acetylcholine receptor ((-)-[18F]Flubatine) and the adenosine A2A receptor ([18F]FESCH and [18F]FLUDA)

Toussaint, M.; Kranz, M.; Gündel, D.; Lai, T. H.; Schröder, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Teodoro, R.; Shang, Q.; Patt, M.; Reichmann, H.; Funk, R.; Sabri, O.; Pan-Montojo, F.; Brust, P.

Introduction
Systemic administration of rotenone is able to reproduce the main pathological and behavioral hallmarks of Parkinson’s Disease (PD) in mice. Therefore, those mice are potentially useful for the development of therapies targeting the nicotinic acetylcholine receptor (α4β2nAChR) or the adenosine A2A receptor (A2AR).
Thus, we evaluated the ability of the rotenone model to resemble the decreased availability of α4β2nAChR and the increased availability of A2AR found in the brain of PD patients [1,2,3]. PET/MR imaging was performed to quantify these changes at early and later stages of the disease.
Methods
Two groups of 12-14-months-old male C57BL/6JRj mice (27-36 g) treated for 2 months (n=6) or 4 months (n=7) with rotenone, 5 days/week, 5 mg/kg p.o., and their corresponding control groups (n=7 and n=5, respectively) were investigated. (-)-[18F]Flubatine (6.4±1.9 MBq; Am: 1185±713GBq/μmol) for α4β2nAChR investigation and [18F]FESCH (5.0±1.8 MBq; Am: 116±19 GBq/μmol, EOS) [4] or [18F]FLUDA (5.7±1.2 MBq; Am: 96±10 GBq/μmol, EOS) for A2AR investigation were injected intravenously followed by 60 min dynamic PET scans[4]. The cerebellum was used as a reference tissue. The time-activity curves (TACs) of the SUV ratio (SUVR) of thalamus or striatum over cerebellum were used as measure for specific uptake.
Results/discussion
Specific uptake of (-)-[18F]Flubatine was observed in the thalamus of control and rotenone mice (SUVR60min p.i. ~3.5, all groups included). However, for none of the two treatment groups changes in α4β2nAChR availability compared to the control group were detected (figure 1).
Specific uptake of [18F]FESCH and [18F]FLUDA was observed in the striatum of control and rotenone mice (SUVR10-20 min p.i. ~4.8, all groups included) (figure 2).
PET scans revealed no significant differences in A2AR availability between control group and 2 months rotenone treatment group. However, the SUVR of the 4 months rotenone treatment group were higher compared to the control group (SUVR20-40 min p.i. 3.4 vs. 2.9, respectively), although statistically not significant due to the rather small and highly variable data set.
Altogether, the trend of these results indicates no accordance with clinical findings although a slightly increased availability of A2AR during the course of the disease can be mentioned.
Conclusion
Taking into account the high variability of the dataset, the investigation by PET/MR of the rotenone mouse model after 2 mo. and 4 mo. treatment shows no concordance with the clinical findings regarding α4β2nAChR and A2AR availabilities.
We assume that the rotenone mouse model might not be suitable to assess PD-related changes in the availability of the two targets and thus perhaps not suitable for the investigation of the related targeting-drug.
Acknowledgments
The European Regional Development Fund and Sächsische Aufbaubank are acknowledged for financial support (Project No. 100226753).
References
[1] Vuorimaa et al. Contrast Media Mol Imaging 2017; 6975841. [2] Meyer et al., Arch Gen Psych 2009, 66 : 866-877. [3] Cannon et al., Neurobiol Dis 2009 ; 34 : 279-90. [4] Khanapur et al., J Nucl Med 2017; 58: 466–472.

Keywords: Adenosine 2A receptor; α4β2 nicotinic acetylcholine receptor; rotenone mouse model of Parkinson's disease; positon emission tomography

  • Poster (Online presentation)
    15th European Molecular Imaging Meeting, 24.-27.03.2020, Thessaloniki, Greece

Permalink: https://www.hzdr.de/publications/Publ-30138
Publ.-Id: 30138


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


Characterization of the sigma-1 receptors status with (S)-(-)-[18F]fluspidine PET of an orthotopic mouse model of glioblastoma to assess its potential in glioblastoma management

Toussaint, M.; Kranz, M.; Deuther-Conrad, W.; Patt, M.; Sabri, O.; Brust, P.

Introduction
The sigma-1 receptor (S1R) is a chaperone protein of the mitochondrion-associated endoplasmic reticulum membrane and regarded as potential therapeutic target for a variety of malignant tumors including glioblastoma. Noninvasive assessment of changes in the availability of S1R could help to better understand the pathophysiology of glioblastoma and to improve diagnosis or treatment follow-up. We aim to evaluate the potential of (S)-(−)-[18F]fluspidine, a highly specific S1R radioligand, to characterize the expression of S1R in an orthotopic glioblastoma model in mouse with small-animal PET/MRI.

Methods
U87 human glioblastoma cells were stereotactically implanted into the striatum of three female nude mice (8 weeks old). At a median tumor size of 27 mm3 (determined with MR) 60 min dynamic PET scans were performed after i.v. injection of (S)-(-)-[18F]fluspidine (9.1 ± 2.1 MBq; Am: 140 ± 50 GBq/µmol, EOS). Time-activity curves (TACs) from the tumor and the contralateral regions were analyzed (PMOD v3.9). Peak-to-end ratios (P/E; Peak: SUV mean from 2-9 min, end: SUV mean from 45-60 min) were used to compare regions. Statistics: unpaired two-tailed Student’s T-test (P < 0.05).
To determine the S1R affinity (KD) and density (Bmax) in the tumor and the contralateral region, in vitro autoradiography was performed with (S)-(-)-[18F]fluspidine using cryosections of tumor bearing mice.

Results & discussion
Autoradiography showed an equal affinity of [18F]fluspidine for S1R in the contralateral and tumor region (KD: 17.5 ± 1.3 vs. 18.0 ± 4.9 nM), but a higher Bmax in the tumor (490 ± 43 vs. 1756 ± 40 fmol/mg prot). PET TACs reflected significantly different kinetic profiles in the tumor and the contralateral side (P/E: 3.10 ± 0.48 vs. 1.81 ± 0.16, p < 0.05) (Figure 1). Interestingly, the tumor regions were characterized not only by a lower initial uptake compared to the contralateral side (SUV2-9 min p.i.: 0.89 vs. 1.17, p < 0.05) but also by a slower washout resulting in equivalent SUVs in both regions at 45 min p.i. (SUV45-60 min p.i.: 0.38 vs. 0.34 respectively). This slower radiotracer washout from the tumor compared to the contralateral side is assumed to be caused by the higher S1R site density found in the tumor, along with the specific pathophysiology of the tumor itself (neovascularization, oncotic pressure).

Conclusions
The PET investigation revealed a significant difference in the pharmacokinetics of (S)-(-)-[18F]fluspidine between the brain tumor and the contralateral region, probably related to different S1R availabilities. These results show the suitability of (S)-(-)-[18F]fluspidine for the non-invasive determination of the S1R status in an orthotopic glioblastoma model.

Keywords: Sigma-1 receptor; Positron emission tomography; orthotopic glioblastoma model

  • Poster (Online presentation)
    15th European Molecular Imaging Meeting, 24.-27.03.2020, Thessaloniki, Greece

Permalink: https://www.hzdr.de/publications/Publ-30135
Publ.-Id: 30135


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

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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


Systematic comparison of the structure of homoleptic tetradentate N₂O₂-type Schiff base complexes of tetravalent f-elements (M(IV) = Ce, Th, U, Np, and Pu) in solid state and in solution

Radoske, T.; Kloditz, R.; Fichter, S.; März, J.; Kaden, P.; Patzschke, M.; Schmidt, M.; Stumpf, T.; Walter, O.; Ikeda, A.

A series of tetradentate N₂O₂-type Schiff base complexes with tetravalent 4f-and 5f-block metals, [M(salpn)₂] (H₂salpn = N,N’-disalicylidene-1,3-diaminopropane; M = Ce, Th, U, Np, and Pu), were prepared to systematically investigate their solid state structure, and their complexation behaviour in solution with the goal to investigate the subtle differences between 4f and 5f-elements. X-ray diffraction revealed that all investigated metal cations form [M(salpn)₂] complexes. All the complexes show the same ligand arrangement with meridional conformation, amongst which only Ce(IV) exhibits unique behaviour upon crystallisation. [Ce(salpn)₂] crystallises in two less symmetric systems (P-1 or P2₁/n), whilst all the other [M(salpn)₂]
crystallise in a more symmetric orthorhombic system (Pban). Quantum chemical calculations suggest that the observed structural peculiarity of Ce(IV) stems from the geometrical flexibility due to the more "ionic" nature of bonds to the 4f element. ¹H NMR measurements revealed that [M(salpn)₂] forms two different species in solution with and without an additional solvent molecule, where the relative distribution of the two species depends mainly on the ionic radius of the metal centre. Again, Ce(IV) behaves differently from the tetravalent actinides with a higher ratio of the solvent-moleculecoordinated species than the ratio expected from its ionic radius. Hence, this study is successful in observing subtle differences between 4f- (i.e. Ce) and 5f-elements (actinides; Th, U, Np, and Pu) both in the solid state and in solution on an analytically distinguishable level, and in relating the observed subtle differences to their electronic structure.

Permalink: https://www.hzdr.de/publications/Publ-30126
Publ.-Id: 30126


High-current caesium sputter ion source with planar ionizer for accelerator mass spectrometry

Yordanov, D.; Hofsäss, H.; Rugel, G.; Akhmadaliev, S.; Borany, J.; Facsko, S.; Feige, J.

A new caesium sputter negative ion source with planar ionizer for Accelerator Mass Spectrometry (AMS) is being built, regarding quantifying the ratios of long-lived cosmogenic radionuclides in micrometeorites.
The focus of the ion source is on an optimal ion-optics design, together with a realization of new concepts for the construction and function of the ionizer, with the possibility of the precise in-situ adjustment of the ion-optical components, and optimization of the caesium ion beam and ion transport. In addition, the source is designed for operation with higher cathode voltage (up to 20 kV), which aims to increase the sputter rate of the sample, and in turn to increase the extracted negative current. Higher ion currents and better ion yields mean shorter measuring times, higher precision due to higher counting statistics and/or higher throughput of samples in an AMS runs.
The authors would like to thank the Federal Ministry of Education and Research of Germany for its financial support (project 05K2016), and the HZDR’s Ion Beam Center for its essential contribution to the realization of this project.

Keywords: New Mass Spectrometric Methods and Technical Developments

Permalink: https://www.hzdr.de/publications/Publ-30125
Publ.-Id: 30125


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

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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

Downloads:

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


Newly synthesized fluorinated cinnamylpiperazines possessing low in vitro MAO-B binding

Jevtić, I. I.; Lai, T. H.; Penjišević, J. Z.; Dukic-Stefanovic, S.; Andrić, D. B.; Brust, P.; Kostić-Rajačić, S. V.; Teodoro, R.

Herein, we report on the synthesis and pharmacological evaluation of ten novel fluorinated cinnamylpiperazines as potential monoamine oxidase B (MAO-B) ligands. The designed derivatives consist of either cinnamyl or 2-fluorocinnamyl moieties connected to 2-fluoropyridylpiperazines. The three-step synthesis starting from commercially available piperazine afforded the final products in overall yields between 9 and 29%. An in vitro competitive binding assay using L-[3H]Deprenyl as radioligand was developed and the MAO-B binding affinities of the synthesized derivatives were assessed. Docking studies revealed that the compounds 8–17 were stabilized in both MAO-B entrance and substrate cavities, thus resembling the binding pose of L-Deprenyl. Although our results revealed that the novel fluorinated cinnamylpiperazines 8–17 do not possess sufficient MAO-B binding affinity to be eligible as positron emission tomography (PET) agents, the herein developed binding assay and the insights gained within our docking studies will certainly pave the way for further development of MAO-B ligands.

Keywords: MAO-B; positron emission tomography; piperazine; cinnamic acid

Permalink: https://www.hzdr.de/publications/Publ-30106
Publ.-Id: 30106


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


Improvement of Euler-Euler simulation of two-phase flow by particle-center-averaged method

Lyu, H.; Schlegel, F.; Rzehak, R.; Lucas, D.

Current Euler-Euler modeling based on phase-averages shows inconsistencies since the finite size of the bubbles is not properly accounted for. As a result, nonphysical gas concentration can appear in the center or the near wall region of a pipe if the bubble diameter is larger than the mesh size (Tomiyama, Shimada et al. 2003). In addition, mesh independent solutions may not exist in these cases.
By employing particle-center-averages (Prosperetti 1998), these inconsistencies can be remedied and mesh independent solutions are obtained. In this approach, the number density of bubble centers is the primary variable. This requires an additional wall-contact force to ensure that bubble centers cannot come arbitrarily close to walls (Lucas, Krepper et al. 2007). The gas volume fraction can be calculated from the number density by a convolution (Kitagawa, Murai et al. 2001) with a kernel that has a support corresponding to the extent of a bubble. In addition, the derivation shows explicitly that bubbles respond to pressure and stress of the continuous liquid phase such that no additional closure models for the gas phase pressure or stress are required.
In the present contribution, the convolution method is replaced by a diffusion-based method (Sun and Xiao 2015), which is much easier to implement in CFD codes using unstructured meshes like OpenFOAM. A physically motivated model for the wall-contact force is introduced. The remedy of the issues with the conventional phase-averaged two-fluid model is demonstrated using a simplified two-dimensional test case. Furthermore, comparison is made for real pipe flow cases where experimental data are available.

References
Kitagawa, A., Y. Murai and F. Yamamoto (2001). "Two-way coupling of Eulerian–Lagrangian model for dispersed multiphase flows using filtering functions." International journal of multiphase flow 27(12): 2129-2153.
Lucas, D., E. Krepper and H.-M. Prasser (2007). "Use of models for lift, wall and turbulent dispersion forces acting on bubbles for poly-disperse flows." Chemical Engineering Science 62(15): 4146-4157.
Prosperetti, A. (1998). Ensemble averaging techniques for disperse flows. Particulate Flows, Springer: 99-136.
Sun, R. and H. Xiao (2015). "Diffusion-based coarse graining in hybrid continuum–discrete solvers: Theoretical formulation and a priori tests." International Journal of Multiphase Flow 77: 142-157.
Tomiyama, A., N. Shimada and H. Asano (2003). Application of Number Density Transport Equation for the Recovery of Consistency in Multi-Field Model. ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference, American Society of Mechanical Engineers.

Keywords: Particle-center-averaged method; Number density of bubble centers; Bubble dimension; Diffusion equation; Deformation force model; Equation of motion

  • Contribution to proceedings
    14th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 12.-14.10.2020, Trondheim, Norway
    Proceedings from the 14th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, Norway: SINTEF Academic Press, 978-82-536-1684-1

Permalink: https://www.hzdr.de/publications/Publ-30102
Publ.-Id: 30102


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


Electrochemical simulation of liquid metal batteries

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

Liquid metal batteries (LMBs) consist of a stable density stratification of two liquid metal electrodes, separated by a molten salt electrolyte. Discharing the cell, the anode metal dissolves in the cathode metal. Due to slow diffusion, concentration layers develop especially at high current densities, and lead to considerable concentration polarisation. As the density difference between the anode and cathode metal is usually large, the formed density stratification is often very stable. The talk will describe how to simulate the electric potential, current density and Lorentz force in a liquid metal battery. Finally, it will be shown that electrodynamically driven flow is able to mix the cathode alloy of an LMB, thus reducing concentration polarisation. A 10 cm Li||Bi cell, studied experimentally by Ning et al., will be used as reference case.

  • Lecture (Conference)
    14th WCCM & ECCOMAS Congress, 11.-15.01.2021, Paris, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-30099
Publ.-Id: 30099


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

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


Modelling of complex boron dilution transients in PWRs—Validation of CFD simulation with ANSYS CFX against the ROCOM E2.3 experiment

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

This part of a series of two papers compares CFD simulation results of a boron dilution scenario with experimental results. The simulation was carried out with ANSYS CFX using the SST turbulence scheme, experimental data were produced in the ROCOM test facility, experiment E2.3. The main features of the scenario are asymmetric, transient mass flow conditions in the affected loops 1 and 2 of a KONVOI-type reactor vessel and reduced density of the underborated coolant slugs fed into the reactor trough the cold legs of both loops. The CFD simulation was able to capture the density stratification in the loops affected by underboration and the mixing in the downcomer and in the lower plenum. Good agreement with the experiment was obtained for the temporal evolution of average boron concentration in several measuring sections of the reactor vessel and of the boron distribution in the core inlet. In general, minimal values of boron concentration were found to be lower in the simulation than in the experiment.

Keywords: Boron dilution; ROCOM; ANSYS CFX; Validation

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  • Secondary publication expected from 01.02.2022

Permalink: https://www.hzdr.de/publications/Publ-30093
Publ.-Id: 30093


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


Conductivity influence on interfacial waves in liquid metal batteries and related two-layer systems

Weier, T.; Grants, I.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Stefani, F.; Weber, N.

Fluid flows in liquid metal batteries can be generated by a number of effects. We start with a short overview of different driving mechanisms and then address questions specific to the metal pad role instabilities in three-layer systems. We focus on the role of the conductivity distribution in the cell, noting at the same time that interfacial tension should be considered as well for smaller cells. Following this discussion, numerical results on the excitation of interfacial waves in two-layer liquid metal systems with miscibility gaps bearing an interface normal electric current are presented. Confirming recent results from the literature, we find that magnetic damping plays a decisive role for strong vertical magnetic fields. In addition, boundary conditions for the electric field strongly influence critical currents and growth rates.

Keywords: liquid metal batteries; interfacial waves; sloshing

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  • Secondary publication expected from 30.09.2021

Permalink: https://www.hzdr.de/publications/Publ-30074
Publ.-Id: 30074


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


Effects of current distribution on mass transport in the positive electrode of a liquid metal battery

Personnettaz, P.; Landgraf, S.; Nimtz, M.; Weber, N.; Weier, T.

Liquid metal electrodes are one of the key components of different electrical energy storage technologies. The understanding of transport phenomena in liquid electrodes is mandatory in order to ensure efficient operation. In the present study we focus our attention on the positive electrode of the Li||Bi liquid metal battery. Starting from a real experimental setup, we numerically investigate the charge transfer in a molten salt electrolyte and the mass transport in the positive electrode. The two phenomena are tightly coupled, because the current distribution influences the concentration field in the positive electrode. The cell is studied during charging when compositional convection becomes apparent. First results of compositional convection from a non-uniform current distribution are presented, highlighting its capability to affect the flow in the positive electrode and the cell performance.

Keywords: Liquid metal electrode; mass transport; OpenFOAM; liquid metal battery

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  • Secondary publication expected from 27.09.2021

Permalink: https://www.hzdr.de/publications/Publ-30066
Publ.-Id: 30066


The effect of microwave’s location in a comminution circuit on improving grindability of a porphyry copper deposit

Gholami, H.; Bahram, B.; Hassanzadehmahaleh, A.; Mehdilo, A.; Jabbari, M. R.

The present work initially studies the impact of a laboratory microwave (MW)’s location (before and after a jaw crusher) on grindability of a copper ore. Additionally, the role of MW’s radiation time (15–150 sec) and grinding time (13, 15 and 17 min) on the produced particle size distribution (PSD), mineral liberation degree (LD) and energy consumption are investigated. relative work index (RWI), standard Bond work index (Wi), and grindability index (GI) together with the breakage and selection functions were utilized to assess the grinding efficiency and its kinetics of the untreated and MW-pretreated (at a constant power of 0.9 kW) samples. Bond work indices were obtained 13.70, 13.04 and 10.86 kWh/t for the untreated, MW-treated uncrushed and MW-treated crushed samples, respectively. Besides, the results confirmed that the microwave pretreatment was comparatively effective at the shortest grinding time (13 min). Furthermore, locating the microwave after the crushing stage indicated substantial improvements in the sample’s grindability and its kinetics rate. The product size (P80) of the MW-treated crushed sample (13 min, 0.9 kW, 150 sec) showed enhancements of 27% and 17% in comparison with the un-microwaved and MW-treated uncrushed samples. Finally, the comparative GIs acquired in the entire spectrum of the particle range were reasonably higher if the microwave was located after the jaw crusher, particularly for the coarse fraction sizes.

Keywords: Microwave irradiation; grinding kinetics; copper complex ore; liberation degree; untreated and microwave-treated

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Permalink: https://www.hzdr.de/publications/Publ-30065
Publ.-Id: 30065


Effect of microwave system location on floatability of chalcopyrite and pyrite in a copper ore processing circuit

Gholami, H.; Rezai, B.; Mehdilo, A.; Hassanzadehmahaleh, A.; Yarahmadi, M. R.

The present work aims at investigating the effect of microwave local positions (i.e. before crushing (BC), after crushing (AC) and after milling (AM)) on microwave-assisted flotation of chalcopyrite and pyrite in a porphyry copper complex deposit. Individual given samples for each state were pre-treated with a variable power microwave at a power level of 90 to 900W for 15, 30, and 60s. Furthermore, froth floatation experiments were carried out using a laboratory mechanical Denver flotation cell on both microwave-treated and untreated samples. Particle surface properties were characterized by a scanning electron microscopy (SEM) and an energy-dispersive X-ray spectroscopy (EDX) analysis. The results showed that the chalcopyrite and pyrite floatabilities increased monotonically by rising the exposure time and power level for the uncrushed preconditioned samples (BC) due to the enhancement of mineral liberation degrees together with the formation of sulphide species and polysulphides on the mineral surfaces. However, flotation results of treated samples for the crushed one (AC) revealed an optimum range. Formation of intensive oxide layers on the mineral surfaces of milled samples (AM) led to a substantial reduction in their recoveries by increasing the microwave’s power level and the sample’s exposure time. The results obtained from mineral’s floatabilities in recleaner stage showed that the microwave-assisted sample at 900W for 30s at BC state favourably provided 5% higher S.E.’s than that of the untreated sample. Finally, it was concluded that the microwave pretreatment of samples induced the best floatability responses if it located before the crusher.

Keywords: Microwave technology; Chalcopyrite; Pyrite; Comminution circuit; Separation efficiency

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Permalink: https://www.hzdr.de/publications/Publ-30064
Publ.-Id: 30064


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


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