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38996 Publications

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30813
Publ.-Id: 30813


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30812
Publ.-Id: 30812


Radiopharmaceutical Sciences

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30811
Publ.-Id: 30811


Transmission helium ion imaging and time-of-flight spectroscopy

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

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

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

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

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

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

Related publications

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

Permalink: https://www.hzdr.de/publications/Publ-30810
Publ.-Id: 30810


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

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

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

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

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

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

Related publications

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

Permalink: https://www.hzdr.de/publications/Publ-30809
Publ.-Id: 30809


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

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

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

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

Related publications

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

Permalink: https://www.hzdr.de/publications/Publ-30808
Publ.-Id: 30808


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30807
Publ.-Id: 30807


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

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

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

Keywords: scheelite flotation; colloidal silica; depressant

Permalink: https://www.hzdr.de/publications/Publ-30806
Publ.-Id: 30806


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

Kupka, N.; Möckel, R.; Rudolph, M.

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

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

  • Open Access Logo Physicochemical Problems of Mineral Processing 56(2020)2, 238-251
    Online First (2020) DOI: 10.5277/ppmp19101
    ISSN: 1643-1049

Permalink: https://www.hzdr.de/publications/Publ-30805
Publ.-Id: 30805


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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30804
Publ.-Id: 30804


Special issue of the American Journal of Science

Fischer, C.; Arvidson, R. S.

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30803
Publ.-Id: 30803


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

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30802
Publ.-Id: 30802


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30801
Publ.-Id: 30801


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30800
Publ.-Id: 30800


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30799
Publ.-Id: 30799


Random singlet state in Ba5CuIr3O12 single crystals

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30798
Publ.-Id: 30798


On the positioning accuracy of a novel immobilization device

Karsch, L.; Anders, P.; Troost, E. G. C.; Hoffmann, A. L.

Purpose: The technical feasibility of simultaneous proton beam irradiation and magnetic resonance (MR) imaging has recently been demonstrated by phantom experiments performed on a 0.22 T open MR scanner that was integrated with a static proton beam line in a clinical environment [1]. Since the scanner and Faraday cage were mounted together on a mobile transport platform, the whole setup is movable to a pencil beam scanning beam line that allows for volumetric irradiation. In perspective, this setup may be used for first in-beam MR-guided proton therapy of patients with soft-tissue sarcoma of the forearm. However, the geometry of the Faraday cage and the MR scanner limits the patient’s freedom of positioning. Patients can only be treated in a seated position with the affected arm extended sideways into the imaging and irradiation field. However, the CT scan used for treatment planning is acquired in supine position with the arm extended over the head. An in-house developed prototype CT-MR compatible positioning aid was used for reproducible positioning of the forearm in the seated position at the in-beam MR scanner as well as in supine position at the CT scanner. The aim of the present study was to assess the accuracy of arm positioning using this novel immobilization device.
Materials and Method: Six healthy volunteers (4 male, 2 female) were included in this study, that was approved by the local ethics committee. To mimic the setup at the CT scanner, they first underwent a T1-weighted gradient echo MRI scan at a clinical 3T system in supine position while being positioned on a flat tabletop overlay with their forearm fixed in the device. Secondly, the 3T MR image was digitally merged with a 0.22 T MR image of fiducial markers which have a fixed position relative to the beam in the irradiation room and are always within the field of view at the 0.22 T system. The merged image is considered the reference image prescribing the position of the forearm in the irradiation position planned for the future and is the aim of the positioning process. Thirdly, the volunteers underwent a T1-weighted gradient echo MRI scan at the 0.22 T system in seated position with their arm extended sideways in the device. In-house developed image processing software was used to rigidly co-register the locations of the markers in the latter MR image to those in the reference image. The forearm was repositioned in the device not more than twice to match the position in the reference image. The residual positioning difference of the radial bone was a measure of the positioning accuracy. Additionally, the distance of the bones to the skin surface was assessed as a measure for deformation of the arm.
Results: In 5 out of 6 the volunteers the largest positioning error in one dimension was less than 3 mm, which is comparable to that currently achieved in the clinic. The average time needed for repositioning was approximately 20 min, which is substantially longer than in routine clinical practice. Furthermore, the arm underwent a deformation that changed the skin-surface-to-bone distance mostly by approximately 3 mm.
Lastly, the device was not tolerated well by 5 volunteers due to uncomfortable arm positioning.
Conclusions: The positioning accuracy of a prototype CT-MR compatible arm holder device for in-beam MR-guided proton therapy of patients with a soft-tissue sarcoma of the forearm was evaluated. The device enables the immobilization of the forearm both in supine and seated position, with a clinically acceptable repositioning accuracy. Adjustments of the prototype holder are required to improve the patient’s comfort and to avoid the deformation of the arm.

Keywords: IGRT; soft tissue sarcoma IGRT; soft tissue sarcoma; immobilization device

  • Poster
    3rd European Congress of Medical Physics, 16.-19.06.2021, Torino, Italien

Permalink: https://www.hzdr.de/publications/Publ-30797
Publ.-Id: 30797


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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30796
Publ.-Id: 30796


High-field phase transitions in the orbitally ordered multiferroic GeV4S8

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

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

Permalink: https://www.hzdr.de/publications/Publ-30795
Publ.-Id: 30795


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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30794
Publ.-Id: 30794


Noncollinear magnetic structure in U2Pd2In at high magnetic fields

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

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

Permalink: https://www.hzdr.de/publications/Publ-30793
Publ.-Id: 30793


Slurm in Docker

Pape, D.

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30792
Publ.-Id: 30792


GitLab HPC Driver Protoype

Pape, D.

GitLab HPC Driver prototype implementation.

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

  • Software in external data repository
    Publication year 2020
    Programming language: Bash
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/gitlab-hpc-driver-prototype:

Permalink: https://www.hzdr.de/publications/Publ-30791
Publ.-Id: 30791


GitLab HPC Driver

Pape, D.

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

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

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

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/gitlab-hpc-driver:

Permalink: https://www.hzdr.de/publications/Publ-30790
Publ.-Id: 30790


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

Greifenhagen, R.; (for the HADES collaboration)

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

Permalink: https://www.hzdr.de/publications/Publ-30789
Publ.-Id: 30789


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

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

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

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

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30788
Publ.-Id: 30788


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30787
Publ.-Id: 30787


Revealing the defect-dominated oxygen evolution activity of hematene

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

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

Keywords: hemetene; defect; electrocatalysis; oxygen evolution reaction

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Permalink: https://www.hzdr.de/publications/Publ-30786
Publ.-Id: 30786


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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30785
Publ.-Id: 30785


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30784
Publ.-Id: 30784


Spin-polarized positrons. Who cares?

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

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

Keywords: spin-polarized positrons

Related publications

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

Permalink: https://www.hzdr.de/publications/Publ-30783
Publ.-Id: 30783


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

Wagner, A.

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

Keywords: Materials Research Positrons atomic defects nano-scale porosimetry

Related publications

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

Permalink: https://www.hzdr.de/publications/Publ-30782
Publ.-Id: 30782


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

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

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

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

Related publications

Permalink: https://www.hzdr.de/publications/Publ-30781
Publ.-Id: 30781


THEREDA – Thermodynamic Reference Database for the nuclear waste disposal in Germany

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

INTRODUCTION
The disposal of nuclear waste including the assessment of long-term safety is still an open question in Germany. In addition to the pending decision about the repository host rock (salt, granite, or clay) and the associated site selection, the basic necessity of a consistent and obligatory thermodynamic reference database persists. Such a database is essential to assess potential radionuclide migration scenarios accurately and to make well-founded predictions about the long-term safety up to one million years. Specific challenges are comprehensive datasets covering also elevated temperatures and high salinities. Concerning the required elements (actinides, fission products as well as matrix and building materials), no other thermodynamic database is available that is compatible with the expected conditions. Due to these deficiencies THEREDA, a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany and Switzerland, was started in the year 2006.

DATABASE FEATURES

THEREDA offers evaluated thermodynamic data for many compounds (solid phases, aqueous species, or constituents of the gaseous phase) of elements relevant according to the present state of research. In particular, all oxidation states expected for disposal site conditions are considered. In the present release, THEREDA includes data for actinides and their chemical analogues (Th, U, Np, Pu, Am, Cm & Nd), fission products (Se, Sr, Tc & Cs) and matrix elements (Na, K, Mg, Ca, Al, Si | Cl, SO4, CO3). For the calculation of cementitious phases the current version of CEMDATA (18.1) was integrated.
THEREDA is based on a relational databank whose structure intrinsically ensures the internal consistency of thermodynamic data. Data considered respond to the needs of both Gibbs Energy Minimizers (ChemApp, GEMS) and Law-of-Mass-Action codes (Geochemist’s Workbench, PHREEQC, ToughReact). The database is designed generically so that it can store interaction parameters for various models. Namely, the PITZER ion interaction approach to describe activity coefficients of hydrated ions and molecules in saline solutions as well as ideal and non-ideal solid solution approaches are considered in the actual dataset.
After free registration, THEREDA is accessible via internet through www.thereda.de. This is not only a portal to view the data itself, their uncertainties and the primary references of the data; it provides also additional information on issues concerning the database. Ready-to-use parameter files are available for download in a variety of formats (geochemical code specific formats and generic ASCII type). They are also used for internal test calculations – an essential element of the quality assurance scheme. The capabilities of THEREDA are demonstrated using approx. 400 application case calculations, whose results were compared with experimental values published in literature.

Keywords: THEREDA; Solubility; Thermodynamic database; Pitzer ion-interaction approach

  • Poster (Online presentation)
    International Symposium on Solubility Phenomena (ISSP-19), 11.-16.07.2021, Albuquerque, USA

Permalink: https://www.hzdr.de/publications/Publ-30780
Publ.-Id: 30780


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

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

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30779
Publ.-Id: 30779


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

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

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

  • Patent
    DE102018124501 - Erteilung 13.02.2020

Permalink: https://www.hzdr.de/publications/Publ-30778
Publ.-Id: 30778


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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30776
Publ.-Id: 30776


Annual Report 2019 - Institute of Resource Ecology

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30774
Publ.-Id: 30774


Magnetic response of FeRh to static and dynamic disorder

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30773
Publ.-Id: 30773


Accurate MR image registration to anatomical reference space for diffuse glioma

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

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

Permalink: https://www.hzdr.de/publications/Publ-30772
Publ.-Id: 30772


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

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

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

Keywords: transmutation; nuclear fuel; XANES; EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-30771
Publ.-Id: 30771


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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30769
Publ.-Id: 30769


Strömungsmorphologie flashender Feeds bei kritischen Stoffwerten

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30768
Publ.-Id: 30768


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30767
Publ.-Id: 30767


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30766
Publ.-Id: 30766


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

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30765
Publ.-Id: 30765


In-depth 3D characterization of sieve tray hydrodynamics

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

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

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30764
Publ.-Id: 30764


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30763
Publ.-Id: 30763


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

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

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

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30761
Publ.-Id: 30761


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

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

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

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

Code for reproduction of our analyses can be obtained from https://github.com/oncoray/cnn-hnscc. There, you also find instructions on how to load our models.

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

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Permalink: https://www.hzdr.de/publications/Publ-30759
Publ.-Id: 30759


Preface of a special issue of the American Journal of Science

Fischer, C.; Arvidson, R. S.

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

Permalink: https://www.hzdr.de/publications/Publ-30758
Publ.-Id: 30758


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30757
Publ.-Id: 30757


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30756
Publ.-Id: 30756


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30753
Publ.-Id: 30753


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

Jobst, M.

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30752
Publ.-Id: 30752


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

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

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30751
Publ.-Id: 30751


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30750
Publ.-Id: 30750


Development of tailored packings for Rotating Packed Beds

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30749
Publ.-Id: 30749


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

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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30748
Publ.-Id: 30748


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

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30747
Publ.-Id: 30747


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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30746
Publ.-Id: 30746


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30744
Publ.-Id: 30744


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30743
Publ.-Id: 30743


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

Zöllner, R.; Kämpfer, B.

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

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Permalink: https://www.hzdr.de/publications/Publ-30742
Publ.-Id: 30742


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

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

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

Keywords: uranyl; luminescence; complexation; halides; quenching

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Permalink: https://www.hzdr.de/publications/Publ-30741
Publ.-Id: 30741


Steel related activities and capabilities at HZDR

Gerbeth, G.

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

Permalink: https://www.hzdr.de/publications/Publ-30740
Publ.-Id: 30740


Fast Reconstruction Algorithm for Contactless Inductive Flow Tomography

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

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

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

  • Lecture (Conference)
    10th International Conference on Advanced Computer Information Technologies (ACIT 2020), 13.-15.05.2020, Deggendorf, Deutschland
  • Contribution to proceedings
    10th International Conference on Advanced Computer Information Technologies (ACIT 2020), 13.-15.05.2020, Deggendorf, Deutschland
    Proceedings of the 10th International Conference on Advanced Computer Information Technologies (ACIT 2020), 217-220
    DOI: 10.1109/ACIT49673.2020.9208853
    Cited 3 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-30739
Publ.-Id: 30739


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30738
Publ.-Id: 30738


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30737
Publ.-Id: 30737


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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30736
Publ.-Id: 30736


Highly sensitive silicon nanowire biosensor devices for the investigation of UniCAR platform in immunotherapy

Nguyen Le, T. A.; Sandoval Bojorquez, D. I.; Arnau, P. R.; Bergoi, I.; Feldmann, A.; Gianaurelio, C.; Bachmann, M.; Baraban, L.

Although showing impressive therapeutic potential, treatments of leukemias with T-cells expressing chimeric antigen receptors (CARs) is limited by their risk of several severe side effects [1,2]. To overcome these problem, a switchable CAR platform has been developed termed UniCAR [2-4]. Unlike conventional CAR which directed against tumor-associated antigens, UniCAR treatment involve an intermediate target module (TM) which can cross-link UniCAR T cells with tumor cells and lead to destruction [4]. The development of these novel TMs against different tumor targets require numerous repetitive tests on different synthesizing trials which is usually limited in quantity and time-consuming. Meanwhile, nano-biosensors are lately known as analytical tools which are highly sensitive, label-free, rapid and reagent-saving [5]. Among them, silicon nanowire (SiNW) sensor is extensively investigated by researchers over the past decades thanks to its compability with CMOS technology enabling mass production [6,7]. In this work, we demonstrated the application of previously published SiNW biosensor [8] on detection of the binding of UniCAR and a part of different TMs. The results underline advantage of SiNW sensor over ELISA method in term of ease of preparation, speed and sensitivity. The method is able to evaluate binding affinity of UniCAR to different TMs and open a potential to quantify the number of active UniCAR T-cells in in-vivo-sample in later stage. In the end, the application of nanosensor may speed up the R&D process of UniCAR concept and later play an important role in clinical monitoring of immunotherapy, especially, in the era of precision medicine.

Keywords: biosensor; immunotherapy

Permalink: https://www.hzdr.de/publications/Publ-30735
Publ.-Id: 30735


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

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

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

Keywords: ITO thin films; conducting; transmission; optoelectronics

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Permalink: https://www.hzdr.de/publications/Publ-30734
Publ.-Id: 30734


Sputtering of nanostructured tungsten and comparison to modelling with TRI3DYN

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30733
Publ.-Id: 30733


Hollow Au@TiO2 porous electrospun nanofibers for catalytic applications

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30732
Publ.-Id: 30732


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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30731
Publ.-Id: 30731


Electric and magnetic dipole strength in 54Fe

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30730
Publ.-Id: 30730


Thermodynamic Reference Database (THEREDA) – Present activities

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

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

[1] H. C. Moog et al. (2015): Appl. Geochem. (55) 72-84. http://dx.doi.org/10.1016/j.apgeochem.2014.12.016.
[2] K. S. Pitzer (1991): Activity Coefficients in Electrolyte Solutions (2nd ed.). CRC Press, ISBN 0-8493-5415-3.

Keywords: THEREDA; Pitzer; Thermodynamic Reference Database

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

Permalink: https://www.hzdr.de/publications/Publ-30728
Publ.-Id: 30728


A self-adaptive particle-tracking methodology for minerals processing

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30727
Publ.-Id: 30727


Status update of the PEnELOPE laser system

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

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

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

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

Permalink: https://www.hzdr.de/publications/Publ-30726
Publ.-Id: 30726


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

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

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

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

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30724
Publ.-Id: 30724


Slice2Volume: A registered dataset of multimodal medical imaging and light microscopy data in irradiation-injured brain tissue

Müller, J.; Suckert, T.; Beyreuther, E.; Schneider, M.; Boucsein, M.; Bodenstein, E.; Stolz-Kieslich, L.; Krause, M.; von Neubeck, C.; Haase, R.; Lühr, A.; Dietrich, A.

Recent years have shown that particle therapy offers highly conformal brain irradiation and optimized healthy tissue sparing. Nevertheless, elevated dose levels in healthy tissue, particularly in the distal beam region, can lead to undesirable long-term side effects. The biological mechanisms of such effects, however, remain unclear. A major obstacle towards correlating effects on clinical and cellular imaging levels is the mapping of radiation dose to specific brain regions or individual cell populations.
We present a publicly available dataset of registered, multimodal imaging data of nine mice that received proton brain irradiation of different doses in a clinically relevant setting. It is available open access (https://rodare.hzdr.de/record/801) and comprises a baseline computed tomography (CT) scan, simulated distributions of dose and linear energy transfer, a co-aligned mouse brain atlas as well as magnetic resonance imaging (MRI) follow-up of up to six months. Additionally, we provide registered histological brain sections with eight histological stainings, reflecting all major cell types in adult mice brains. We used the self-developed tool Slice2Volume together with existing methods (Elastix & Big Warp) to fuse image data. The software is available open source: https://github.com/jo-mueller/Slice2Volume
The provided image data spans several orders of magnitude of scale. Images of all modalities can be freely overlaid for every mouse as is demonstrated on Figure 1. This, for instance, allows tracing MRI image changes to specific cell populations. Hence, the dataset enables direct correlations and mechanistic observations regarding effects of proton radiation on the anatomical (atlas), clinical (MRI) and microscopic level (histology).

Keywords: proton therapy; preclincal; open source; image fusion

  • Lecture (Conference) (Online presentation)
    Particle therapy co-operative group (PTCOG) annual meeting, 04.-07.06.2021, Taipeh, Taiwan

Permalink: https://www.hzdr.de/publications/Publ-30723
Publ.-Id: 30723


Regulation of bone regeneration

Jung, F.; Pietzsch, J.

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30722
Publ.-Id: 30722


Computer assisted beam modeling for particle therapy

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

Purpose:

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

Methods:

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

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

Conclusion:

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

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

Permalink: https://www.hzdr.de/publications/Publ-30721
Publ.-Id: 30721


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

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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-30720
Publ.-Id: 30720


Flüssigmetallbatterien zur erfolgreichen Sektorkoppelung

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

Flüssigmetallbatterien bieten die Möglichkeit, große Mengen elektrischer Energie zu Speichern und bieten durch ihre Masse und ihr Temperaturniveau ebenfalls ein gewisses Potential zur Speicerung thermischer Energie. Der Vortrag stellt die Technologie und die Forschung am HZDR sowie einzelne Ergebnisse zur Simulation von Flüssigmetallbatterien vor.

Keywords: Flüssigmetallbatterien; Energiespeicher; Simulation; Sektorkoppelung

  • Invited lecture (Conferences)
    CIO-Arbeitskreis Energiespeicher, 04.02.2020, Zittau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30719
Publ.-Id: 30719


HIM and AFM Data set from first AFM in the HIM test

Hlawacek, G.; Andany, S.
Project Member: Stefan Hummel; Project Leader: Georg Fantner

In this work, the integration of an atomic force microscope (AFM) into a helium ion microscope
(HIM) is reported for the first time. The helium ion microscope is a powerful instrument, capable of sub-
nanometer resolution imaging and machining nanoscale structures, while the AFM is a well-established
versatile tool for multiparametric nanoscale metrology. Combining the two techniques opens the way for
unprecedented, in-situ, correlative analysis at the nanoscale. Nanomachining and analysis can be
performed without contamination of the sample as well as avoiding environmental changes between
processing steps. The practicality of the resulting tool lies in the complementarity of the two techniques as
the AFM offers not only true 3D topography maps---something the HIM can only provide in an indirect
way---but also allows for nanomechanical property mapping, as well as electrical and magnetic
characterisation of the sample after focused ion beam materials modification with the HIM. The
experimental setup is described and evaluated through a series of correlative experiments, demonstrating
the feasibility of the integration.

Keywords: Helium Ion Microscopy; Atomic Force Microscopy

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Permalink: https://www.hzdr.de/publications/Publ-30718
Publ.-Id: 30718


Dynamics of Bubble Formation at Micro-orifices under Constant Gas Flow Conditions

Mohseni, E.; Jose Kalayathine, J.; Reinecke, S.; Hampel, U.

Fine gas dispersion into a liquid is requested in a number of industrial applications. One way to achieve finer gas dispersion is to downsize the openings at which the gas bubbles are generated. Accordingly, we have investigated the dynamics of bubble formation from submerged orifices ranging from 0.04 to 0.8 mm at a comprehensive range of gas flow rates for a system of air and deionized water. In this range of orifice size, we observe a different mechanism of bubble formation compared with millimeter-range orifices. We discuss the observations on the basis of temporal change of the bubble shape, bubble base expansion, and detachment criteria. At submillimeter orifices, the mechanism of bubble formation is highly influenced by the capillary pressure and the gas kinetic energy. The latter results in congregation of small bubbles in the vicinity of the orifice, even at very small gas flow rates. Moreover, we studied the evolution of individual forces applied to the surface of bubbles during their formation. We found that the formation of bubbles at submillimeter orifices cannot be described with a quasi-static force balance. Finally, we present a bubbling regime map using proper dimensionless numbers.

Keywords: Bubble Formation; Stainless Steel Orifice; Bubbling Dynamics; Bubbling Regime; Submillimeter Orifices

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Permalink: https://www.hzdr.de/publications/Publ-30717
Publ.-Id: 30717


The Link Between Photovoltaics, Sustainability, and the Metals Industry

Bartie, N. J.; Reuter, M.

Metals make modern societies function, and increasingly, various high purity precious and special metals endow sustainability-driving technologies with specific functionalities. These metals become heavily intertwined within products, complicating end-of-life treatment. To counteract the resulting downcycling and potential depletion of scarce resources, maximising both the quantities and qualities of materials recovered during primary extraction and recycling processes should be a priority in the pursuit of sustainable circular economy.
Adopting a process simulation approach, a digital twin for the life cycle of cadmium-telluride solar photovoltaic (CdTe PV) modules was created. The system comprises an integrated metallurgical production system that produces, among others, cadmium, tellurium, selenium, zinc, copper, and lead, all of which are required to manufacture PV modules. System-wide resource efficiency and environmental impacts are assessed using exergy analysis and life cycle assessment, respectively.
Simulation of this large and complex product life cycle at a high level of detail allows for the evaluation of potential system-wide effects of various production, recycling and residue exchange scenarios aimed at maximising the sustainability of the entire system. It diminishes the need to make arbitrary choices about allocation methods for the distribution of environmental impacts in multiple-output production systems. Furthermore, it demonstrates the key importance of metallurgy in achieving Circular Economy.

Keywords: Metals; Circular Economy; Sustainability; Process Simulation; Systems; Cadmium Telluride; Photovoltaics

  • Contribution to proceedings
    IMPC2020 - XXX International Mineral Processing Congress, 18.-22.10.2020, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-30715
Publ.-Id: 30715


The Late Paleozoic tectonometamorphic evolution of Patagonia revisited: Insights from the pressure-temperature-deformation-time (P-T-D-t) path of the Gondwanide basement of the North Patagonian Cordillera (Argentina)

Oriolo, S.; Schulz, B.; Gonzalez, P. D.; Bechis, F.; Olaizola, E.; Krause, J.; Renda, E. M.; Vizàn, H.

Combined field structural analysis with in situ EPMA (electron probe microanalysis) Th-U-Pb monazite dating, petrologic and microstructural data provide a reconstruction of the pressure-temperature-deformation-time (P-T-D-t) path of the Gondwanide basement of the North Patagonian Cordillera. For samples from the Challhuaco hill, the timing of development of the metamorphic S2 foliation and associated L2 lineation and tight to isoclinal F2 folds is constrained by monazite ages of 299 ± 8 and 302 ± 16 Ma during peak metamorphic conditions of ca. 650 °C and 11 kbar, achieved during prograde metamorphism and progressive deformation. Metamorphism and deformation of metamorphic complexes of the North Patagonian Andes seem to record Late Paleozoic crustal thickening and are coeval with metamorphism of accretionary complexes exposed further west in Chile, suggesting a coupled Late Devonian-Carboniferous evolution. Instead of the result of continental collision, the Gondwanide orogeny might thus be essentially linked to transpression due to advancing subduction along the proto-Pacific margin of Gondwana. On the other hand, a second generation of monazite ages of 171 ± 9 and 170 ± 7 Ma constrain the timing of low-grade metamorphism related to kink band and F3 open fold development during Jurassic transtension and emplacement of granitoids. Finally, a Cretaceous overprint, likely resulting from hydrothermal processes, is recorded by monazite ages of 110 ± 10 and 80 ± 20 Ma, which might be coeval with deformation along low-grade shear zones during the onset of Andean transpression.

Keywords: EPMA Th-U-Pb monazite dating; in situ petrochronology; garnet metapelite thermobarometry; Upper Paleozoic; Terra Australis; southwestern Gondwan

Permalink: https://www.hzdr.de/publications/Publ-30714
Publ.-Id: 30714


Epithermal Ag-(Au)-Zn-Pb mineralisation in the northern part of the Freiberg District, Germany

Swinkels, L.; Rossberg, C.; Schulz-Isenbeck, J.; Frenzel, M.; Gutzmer, J.; Burisch, M.

The polymetallic veins in the Freiberg district form one of the largest epithermal systems in Europe. It produced over 5600 t of Ag during active mining between 1168 and 1969. Historically, exploration focused on the centre of the district, with peripheral sub-districts exploited only to shallow depth. Recent exploration activity focuses on these peripheral regions, yet only a limited amount of modern geochemical data is available and the underlying ore-forming processes are insufficiently understood. Here, we present preliminary geochemical, fluid inclusion, and petrographic data for 55 samples from the historical mine camps of Reinsberg and Kleinvoigtsberg (northern peripheral sub-district). Samples were selected from the scientific collections of the TU Bergakademie Freiberg and collected from outcrops in the field. They include vertical profiles of two major veins extending from 18 to 532 meters below ground level. The data is combined with previous literature descriptions to develop a genetic model for the northern sector of the Freiberg district. Mineralisation in the Reinsberg and Kleinvoigtsberg mine camps is hosted by polystadial Ag-(Au)-Zn-Pb veins. The paragenetically oldest mineralisation, Stage I, is dominated by base metal sulphides and quartz; it has been encountered most prominently in the deepest levels of the historic mines. The occurrence of carbonates and the introduction of Ag-Sb sulphides and sulfosalts mark the transition to Stage IIa. At shallower mining levels, carbonate recedes and quartz returns as the major gangue mineral, indicating the transition to Stage IIb. Stage IIb vein infill is often breccia-textured and carry the highest silver grades. At the present day surface, veins consist of quartz and host rock fragments, forming a cockade breccia texture (stage III). Although no visible sulphides are present, such quartz breccias contain up to 2.5 g/t Au. Recent studies show that the main ore-forming process in the northern district seems to be cooling - causing distinct district and vein-scale zoning. Effervescence of CO2 is most likely the underlying process behind the transition from quartz to carbonate gangue. An understanding of mineral zonation and its underlying ore-forming processes can be translated into mappable exploration criteria. In this case, the highest ore grades (Ag and Au) are associated with Stage IIb (Ag-Sb-sulfosalts-quartz assemblage). This assemblage occurs always wedged between the carbonate-rich assemblage of Stage IIa (below) and the sulphide-poor quartz Stage III (above). This systematic relation may well constitute an important exploration vector for the Freiberg district.

  • Lecture (Conference)
    Geomünster 2019, 22.-25.09.2019, Münster, BRD

Permalink: https://www.hzdr.de/publications/Publ-30713
Publ.-Id: 30713


Mineralogical zoning within the Freiberg epithermal Ag- (Au)-Pb-Zn-Cu system, Germany

Swinkels, L.; Rossberg, C.; Schulz-Isenbeck, J.; Burisch, M.; Frenzel, M.; Gutzmer, J.

The Freiberg epithermal system comprises numerous hydrothermal veins with rich Ag-(Au)-Pb-Zn-Cu mineralisation. Even after more than 800 years of extensive mining, substantial resources remain in the northern sub-districts. This area is subject to recent exploration activity. Preliminary petrographic data of two vertical profiles from the northern part of the district are presented and a new model for the district-scale zoning is proposed. The highest Ag grades occur in Ag-Sb-S-quartz veins and seem to systematically occur above an Ag-Sb-S-Carbonate stage and below Sb-S-quartz mineralisation. This high-grade Ag mineralisation is relatively distal, shallow, and abundant in the northwest sector of the Freiberg district. This, and similar insights may be used to develop new exploration vectors for the Freiberg district.

  • Poster
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 26.-30.08.2019, Glasgow, UK

Permalink: https://www.hzdr.de/publications/Publ-30712
Publ.-Id: 30712


Explaining metal zonation at the Lisheen Zn-Pb deposit, Ireland

Frenzel, M.; Röhner, M.; Gutzmer, J.; Burisch, M.; Cook, N. J.; Gilbert, S.; Ciobanu, C. L.; Güven, J.

Metal zonation is an important feature of low-temperature carbonate-hosted Zn-Pb deposits. Its origin, however, remains poorly understood. In this article, we use the Lisheen deposit in Ireland as a case study to show how thermodynamic modelling can explain these zonation patterns. Based on input data derived from fluid inclusion studies, bulk ore geochemistry and accepted models of ore formation in the Irish Orefield we construct a reaction path model that successfully accounts for the major features of the mineralisation, most importantly the presence of Cu-Ni-As-rich core zones around hydrothermal feeder structures, surrounded by more distal Fe-Zn-Pb-rich mineralisation. The outcomes of this study strongly support current metallogenetic models for Irish-type deposits and have implications for near-deposit exploration.

  • Lecture (Conference)
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 26.-30.08.2019, Glasgow, UK
  • Lecture (Conference)
    Geomünster 2019, 22.-25.09.2019, Münster, BRD

Permalink: https://www.hzdr.de/publications/Publ-30711
Publ.-Id: 30711


2.05 Ga A1-type felsic to intermediate igneous suite and related Nb-Zr-REE mineralization at Otanmäki, central Finland

Kärenlampi, K.; Hanski, E.; Kontinen, A.; Huhma, H.; Krause, J.; Heinig, T.; Lahaye, Y.

A-type granites record ancient rifting events and host deposits of high-tech metals, such as the rare earth elements (REE). We have studied the geology, geochemistry, geochronology and Sm-Nd isotope compositions of a globally uncommon suite of ca. 2.04–2.06 Ga ferroan A1-type igneous rocks in central Finland, Fennoscandian Shield[1]. The suite consists of gneissic peralkaline to peraluminous granites and related syenite, monzonite and monzodiorite[1].
The Otanmäki A-type rocks have εNd(2050 Ma) values ranging from +2.5 to -3.4 and trace element characteristics similar to ocean island basalts (OIB), suggesting their derivation from mafic mantle-derived parental magmas similarly as has been proposed for many other A1-type suites globally[1]. However, the peraluminous granites exceptionally show Nb/U, Nb/Yb and Th/Yb ratios more similar to those of Archean granitoids than OIBs, indicating role of crustal contamination in their genesis[1].
The Otanmäki suite A-type rocks host two Nb-Zr- REE deposits: Kontioaho, consisting of an up to 50-m-thick tabular granitic body, and Katajakangas, comprising several closely-spaced 0.1- to 1.4-m-thick quartz-rich veins. A peraluminous monzogranite forms the wall rock for both deposits, but the mineralized rocks have a geochemical signature similar that of peralkaline-metaluminous alkali feldspar granite adjacent to the monzogranite. The main ore minerals are allanite, zircon and titanite with minor Nb-REETh-U oxides. Geochemical and geochronological data and Nd isotope compositions of the mineralized rocks indicate that they formed from highly fractionated, volatile-bearing (e.g., F, CO2) late-stage residual melts of the A-type magmatism.

[1] Kärenlampi, K., Kontinen, A., Huhma H. & Hanski, E. Geology, geochemistry and geochronology of the 2.05 Ga gneissic A1-type granites and related intermediate rocks in central Finland: implication for the tectonic evolution of the Karelia craton margin. Bulletin of the Geological Society of Finland (2019) (in press)

  • Contribution to proceedings
    Goldschmidt Barcelona 2019, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-30710
Publ.-Id: 30710


Radionuclides from Space

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

The determination of long-lived radionuclides by means of accelerator mass spectrometry (AMS) is usually outstandingly successful when an interdisciplinary team comes together. The “heart” of AMS research is of course an accelerator equipped with sophisticated ion sources, analytical tools and detectors run by experienced and ambitious physicists. Setting-up and further developing AMS systems is one of the most interesting and challenging topics.
Another essential part in AMS research is the radiochemical sample preparation preceding the measurement where the goals are: 1.) Enrichment of nuclides of interest by reduction of the matrix. 2.) Depletion of isobars. 3.) Production of a thermally stable chemical compound such as AgCl, AgI, Al₂O₃, BeO, CaF₂, Fe₂O₃, MnO₂ etc. of relatively high purity.
One of the most interesting applications of AMS is the analysis of extraterrestrial material such as meteorites. While being at the surface of their so-called parent body (asteroids, Moon, Mars,…) and again while travelling through space as a so-called meteoroid, these unique pieces are bombarded by high-energy particles from the cosmic radiation. Long-lived radionuclides are produced in the material by nuclear reactions in both stages potentially until saturation. However, they start decaying in a third stage, when meteorites have landed on Earth because the cosmic radiation is shielded by the Earth’s atmosphere and magnetic field. Hence, the concentrations of radionuclides are records of all three stages allowing the reconstruction of the exposure history (duration, shielding, size,…) of the individual meteorite and the cosmic radiation itself.
Meteorite projects and projects with artificially-irradiated targets are also well-suited to develop measurements of “new” AMS radionuclides as the isotopic ratios are at much higher levels (up to 10-10 radioactive/stable) than e.g. in terrestrial natural samples (10-14-10-16). The AMS community is very open to any input and questions from “outside”. The DREsden AMS (DREAMS) and other European AMS facilities offer researchers from academia free measurements via a Trans-National-Access proposal program (www.ionbeamcenters.eu) and also national access (www.dresden-ams.de; DREAMS only).

Keywords: AMS; meteorite; cosmogenic; cosmic radiation; radionuclide

Related publications

  • Poster
    53rd Annual Conference of the German Society for Mass Spectrometry DGMS including 27th ICP-MS User´s Meeting, 01.-04.03.2020, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30709
Publ.-Id: 30709


Modelling indium deportment in a polymetallic sulfide ore

Frenzel, M.; Bachmann, K.; Carvalho, J.; Relvas, J.; Pacheco, N.; Gutzmer, J.

Based on a combination of bulk-ore geochemistry and mineralogical and microanalytical data, this study is the first to develop a quantitative model of indium deportment in massive sulfide ores, demonstrating how regularities in indium partitioning between different minerals can be used to predict its mineralogical deportment in individual drill-core samples. Bulk-ore assays of As, Cu, Fe, Pb, S, Sb, Sn, Zn, and In are found to be sufficient for reasonably accurate predictions. The movement of indium through the ore processing plants is fully explained by its mineralogical deportment, allowing for specific mine and process planning. The novel methodologies implemented in this contribution for (1) the assessment of analytical uncertainties, (2) the prediction of complex mineralogical deportments from bulk geochemical data, and (3) the modeling of byproduct recoveries from individual mining blocks, are of general applicability to the geometallurgical assessment of many other byproduct metals in polymetallic sulfide ores, including Ga, Ge, Mo, Re, Se, Te, as well as the noble metals.

  • Lecture (others)
    Geometallurgy Workshop, 15th SGA Biennial Meeting, Glasgow, 26.08.2019, Glasgow, UK

Permalink: https://www.hzdr.de/publications/Publ-30708
Publ.-Id: 30708


Laser ablation ICP-MS trace element systematics of hydrothermal pyrite in gold deposits of the Kalgoorlie district, Western Australia

Godefroy-Rodríguez, M.; Hagemann, S.; Frenzel, M.; Evans, N. J.

The Kalgoorlie district in the Archean Yilgarn Craton of Western Australia containstwoworld-classgolddeposits:thegiant Golden Mile shear-zone system and the Mt Charlotte quartz-vein stockworks. Mineralization occurs in three styles:(a) Fimiston style is characterized by ankerite-pyrite ± hematite-magnetite-gold replacement, (b) Oroya style overprintsFimiston ore in the shear zones and is characterized by silica-ankerite-V-muscovite-pyrite ± pyrrhotite-gold-telluridereplacement and (c) Mt. Charlotte style is characterized by veins with ankerite-sericite ± albite-pyrite-pyrrhotite-goldselvages. Hydrothermal pyrite is ubiquitous in all styles and occurs in several stages. Laser ablation inductively coupledplasma mass spectrometry (LA-ICP-MS) spot analyses (n= 652) were collected on 54 representative samples of pyritefrom three deposits. Smooth sections in the ablation spectra were selected for quantitative analysis excluding peakscaused by micron-sized inclusions. Linear mixed effects (LME) modeling of the analytical results indicates no system-atic differences between the Fimiston, Oroya and Mt Charlotte styles. The variance introduced to the dataset bygeological variability reflected in random differences between samples and deposits is large. This may be a major reasonfor difficulties in distinguishing the differences due to mineralization style. However, there are clear differences betweenpyrites co-existing with different mineral assemblages. These indicate a strong control on pyrite chemistry by thecomposition of the hydrothermal fluids. Finally, Au-Te-As systematics show that a substantial proportion of the analyzedpyrites in all deposits fall into the field of gold saturation consistent with the known metallurgical character of the ores.Mineralogical studies, ultra-fine grinding and recovery by cyanide leach show that > 82% of all gold is present in nativegrains or in Au-Ag-tellurides. The refractory nature of theFimiston pyrite concentrates is due to clusters of micron- tonano-sized inclusions rather thandue to abundant lattice-bound gold.

Keywords: Kalgoorlie; trace elements; LA-ICP-MS; gold; pyrite

Permalink: https://www.hzdr.de/publications/Publ-30707
Publ.-Id: 30707


High resolution mineral-chemical analysis of scheelite from the Felbertal tungsten deposit, Austria

Haupt, C.; Krause, J.; Schulz, B.; Aupers, K.; Schmidt, S.

The Felbertal tungsten deposit is situated in the Hohe Tauern range, near Mittersill, Austria. The ore is hosted in the volcano-sedimentary, polymetamorphic units of the Pre-Permian Habach Complex as disseminated and stockwork mineralization, mostly associated to quarz. An Eastern and a Western ore zone (EOZ and WOZ), which are spacially devided by the NS oriented valley, have been distinguished. The genetical relation of different postulated mineralization events of scheelite in the EOZ and WOZ has not yet been fully resolved. Previous studies reported four different generations, characterized mainly by different fluorescence colour and molybdenum (Mo) content. The first and second generation are characterised by yellow fluorecence and relatively high Mo contents, whereas the later third and fourth generation where observed to have whitish to blue fluorescence colour with low Mo concentration. Processes of remobilisation and recrystallization have been accepted to be responsible for different generations.(Höll, R., & Eichhorn, R., 2000)

Formly less well explored ore bodies have been targeted in the WOZ in the last years. Scheelite in this study was collected in recently worked districts of the mine, namely K8 ore body, K2 Brekzie and scheelite-dotted (SD)-gneiss. Associated scheelites display complex and diverse zonation under UV light.

To target this, new quantitative and qualitative analysis of scheelites have been made using electron probe micro analysis (EPMA). Qualitative molybdenum distribution maps, quantitative element profiles and cathodoluminescence (CL) images have been combined with microtextural analysis to reveal a new view into the mineralisation history.
Molybdenum distribution maps of scheelite grains between 0,5 and 300 mm are of multiphase character with often sharp, irregular edges between plateaus of even concentration, fractures and peripheral areas contain microscale Mo-sulfides. Profiles show a mostly fluctuating pattern between concentrations of 0,00 to 4,14 wt% ox. Mo. The element maps reveal a more complex microscale distribution of Mo, than can be visualized by UV-light.
Under the microscope scheelite shows ondulating extinction, complex fracturing and occasional recrystallization.

The formation of the scheelite apparently involved multiple dissolution and reprecipitation during a fluid-mineral interaction where relatively Mo-poor scheelite replaced Mo-rich scheelite. This was followed by predominantly brittle deformation but with occasional dynamic recrystallization of scheelite. These new observations will ultimately influence the genetical interpretation of the Felbertal tungsten deposit.

References:

Höll, R., & Eichhorn, R. (2000). Tungsten mineralization and metamorphic remobilization in the Felbertal scheelite deposit, Central Alps, Austria. Chapter, 11, 233-264.

  • Contribution to proceedings
    GEOMünster 2019 Present, Past, Future, 22.-25.09.2019, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30706
Publ.-Id: 30706


Halogens in hydrothermal sphalerite record origin of ore-forming fluids

Frenzel, M.; Cook, N. J.; Ciobanu, C. L.; Slattery, A.; Wade, B.; Gilbert, S.; Ehrig, K.; Burisch, M.; Verdugo-Ihl, M. R.; Voudouris, P.

The halogens Cl and Br are sensitive indicators for the origin of ore-forming fluids. Here, we use a combination of microchemical and microscopic methods to show that measurable concentrations of these elements commonly occur as atomic-scale substitutions within hydrothermal sphalerite. Furthermore, the Cl/Br ratios of the halogen-rich sphalerites investigated in this study are indistinguishable from those of the corresponding ore fluids. Thus, they record fluid compositions, which are in turn closely related to fluid origin. Given the abundance of sphalerite in hydrothermal base-metal deposits, as well as the relative ease of conducting in-situ microchemical analyses, the halogen signature of sphalerite has the potential to become a sensitive proxy to distinguish between different ore-forming environments.

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Permalink: https://www.hzdr.de/publications/Publ-30705
Publ.-Id: 30705


Geology and Genesis of the Giant Gorevskoe Pb-Zn-Ag Deposit, Krasnoyarsk Territory, Russia

Belokonov, G.; Frenzel, M.; Priyatkina, N. S.; Renno, A.; Makarov, V.; Gutzmer, J.

The Gorevskoe Pb-Zn-Ag Mine is currently the largest producer of Pb and Zn in Russia, exploiting one of the largest sediment-hosted Pb-Zn deposits worldwide. Despite its size and economic importance, the Gorevskoe deposit remains poorly understood. It is located on the western margin of the Siberian Craton within the Yenisei Ridge, a Neoproterozoic orogenic belt. Mineralization consists of three tabular orebodies that are in turn composed of multiple stacked stratiform to stratabound lenses of galena-pyrrhotite-sphalerite-rich massive sulfide ores, hosted in organic-rich marine metalimestones and calcareous slates of Stenian to Tonian age (1,020 ± 70 Ma). Extensive Fe-Mg-Mn-carbonate alteration haloes surround the ore lenses in the hanging wall and the footwall. The Pb isotope signature of the deposit is consistent with derivation of the Pb, and probably all associated metals, from an evolved crustal source at the time of formation of the host rocks. The sulfur-isotopic composition of pyrrhotite, along with sphalerite, galena, arsenopyrite and pyrite (δ34S = 16.0 – 20.4 ‰) is within the range reported for contemporaneous seawater, indicating complete reduction of marine sulfate as the main source of sulfide.
The available geological and geochemical data indicate that the Gorevskoe deposit belongs to the sediment-hosted massive sulfide class of Zn-Pb deposits, with an affinity to Selwyn-type deposits. Hydrothermal mineralization appears to be related to rifting and distal mafic volcanism in a passive margin setting. Geological relationships suggest that sulfide orebodies formed in a diagenetic environment. Furthermore, the predominance of primary pyrrhotite over pyrite as the major iron sulfide, the presence of abundant siderite, and the virtual absence of barite from the deposit, all indicate highly reducing conditions during ore-formation. They also constrain the character of the metal-bearing fluid to be similarly reducing, and of moderate temperature (200 – 300°C). Gorevskoe may thus be regarded as one of the world’s largest Selwyn-type SHMS deposits.

Permalink: https://www.hzdr.de/publications/Publ-30703
Publ.-Id: 30703


Petrochronology by EPMA and automated SEM in the Saxothuringian high pressure nappes of the central and western Erzgebirge

Schulz, B.; Krause, J.; Lapp, M.

The Saxothuringian Zone of the Variscan orogen is composed of autochthonous and allochthonous domains. Dating of metamorphic events in the domains of the Saxonian Granulite Massiv, and the Münchberg, Frankenberg, and Erzgebirge nappe units is critical for resolving the complex geodynamic evolution during the Variscan orogeny. The in-situ chemical Th-U-Pb monazite (Th, U, Si, LREE, Y, Ca)PO4 dating by electron probe microanalysis (EPMA) has demonstrated its high potential to resolve polyphase metamorphism. The method is based on the premise that monazite inherits negligible amounts of common Pb and that the radiogenic Pb is retained due to very low diffusion rates even at high T [1]. A monazite dating routine, enclosing the analysis of HREE, was performed with a JEOL-8530F, producing 100 - 200 single analyses per sample. Also, energy dispersive x-ray mapping (GXMAP) by automated SEM was used for semiquantitative identification of garnet zonation pattern. Quantitative chemical compositions of garnet and related plagioclase, biotite and muscovite were then measured by EPMA for geothermobarometric estimates by cation exchange and net transfer reactions. Monazite is abundant in lenses of granulitic garnet gneisses ("saidenbachites") in the central Erzgebirge UHP unit. The monazite ThO2*-PbO data straightly define isochrons at around 335±3 Ma. High pyrope (27 mol%) garnet crystallised at 830 °C/19 kbar [2]. Despite such high T, the monazite Y contents are low. In the intercalated MP micaschists, the monazite ThO2*-PbO isochrones appear more diverse, between 334±4 and 344±5 Ma. Furthermore, monazite has been studied in the micaschists and related phyllites of the western Erzgebirge. The monazite ThO2*-PbO data define isochrones between 323±10 and 360±10 Ma, with most samples around 340 Ma, interpreted as the ages of Variscan regional metamorphism. Several samples bear an older minor monazite population at ages between 415 to 432 Ma. Special regard has been dedicated to metapelites within the Pöhla mineralisation. The Eibenstock granite Th-U-Pb monazite isochrone is at 321±2 Ma. In non-mineralised micaschists older monazites (329±8 Ma), and in mineralised parts younger (309±6 Ma) and hydrothermal low-Th monazites are observed.

[1] Montel, J.-M., Foret, S., Veschambre, M., Nicollet, C., Provost, A. (1996): Electron microprobe dating of monazite. - Chem. Geol., 131: 37-51.
[2] Tichomirowa, M., Whitehouse, M., Gerdes A., Schulz, B. (2018): Zircon (Hf, O isotopes) as melt indicator: Melt infiltration and abundant new zircon growth within melt rich layers of granulite-facies lenses versus solid-state recrystallization in hosting amphibolite-facies gneisses (central Erzgebirge, Bohemian Massif). - Lithos 302–303.

  • Contribution to proceedings
    GEOMünster 2019 Present, Past, Future, 22.-25.09.2019, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30702
Publ.-Id: 30702


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