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39002 Publications

Radiolabelled Cyclic Bisarylmercury: High Chemical and in vivo Stability for Theranostics

Gilpin, I. M.; Ullrich, M.; Wünsche, T.; Zarschler, K.; Lebeda, O.; Pietzsch, J.; Pietzsch, H.-J.; Walther, M.

We show the synthesis of an in vivo stable mercury compound with functionality suitable for radiopharmaceuticals. The designed cyclic bisarylmercury was based on the water tolerance of organomercurials, higher bond dissociation energy of Hg-Ph to Hg-S, and the experimental evidence that acyclic structures suffer significant cleavage of one of the Hg-R bonds. The bispidine motif was chosen for its in vivo stability, chemical accessibility, and functionalization properties. Radionuclide production results in 197(m)HgCl2(aq), so the desired mercury compound was formed via a water-tolerant organotin transmetallation. The Hg-bispidine compound showed high chemical stability in tests with an excess of sulphur-containing competitors and high in vivo stability, without any observable protein interaction by human serum assay, and good organ clearance demonstrated by biodistribution and SPECT studies in rats. In particular no retention in the kidneys typical of unstable mercury compounds. The natHg analogue allowed full characterization by NMR and HRMS.

Keywords: bispidine; mercury; organomercury; radiopharmaceuticals; radiotheranostics

Publ.-Id: 31687

ISAAC - In Situ Animation of Accelerated Computations

Meyer, F.; Widera, R.; Pausch, R.; Matthes, A.; Hübl, A.; Gerber, V.; Zenker, E.; Kosukhin, S.

Many computations like physics or biologists simulations these days run on accelerated hardware like CUDA GPUs or Intel Xeon Phi, which are itself distributed in a big compute cluster communicating over MPI. The goal of ISAAC is to visualize this data without the need to download it to the host while using the high computation speed of the accelerator.

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Publ.-Id: 31686

A New Highly Anisotropic Rh-Based Heusler Compound for Magnetic Recording

He, Y.; Fecher, G. H.; Fu, C.; Pan, Y.; Manna, K.; Kroder, J.; Jha, A.; Wang, X.; Hu, Z.; Agrestini, S.; Herrero-Martin, J.; Valvidares, M.; Scurschii, I.; Schnelle, W.; Stamenov, P.; Borrmann, H.; Tjeng, L. H.; Schaefer, R.; Parkin, S. S. P.; Coey, J. M. D.; Felser, C.

The development of high-density magnetic recording media is limited by superparamagnetism in very small ferromagnetic crystals. Hard magnetic materials with strong perpendicular anisotropy offer stability and high recording density. To overcome the difficulty of writing media with a large coercivity, heat-assisted magnetic recording was developed, rapidly heating the media to the Curie temperature Tc before writing, followed by rapid cooling. Requirements are a suitable Tc, coupled with anisotropic thermal conductivity and hard magnetic properties. Here, Rh2CoSb is introduced as a new hard magnet with potential for thin-film magnetic recording. A magnetocrystalline anisotropy of 3.6 MJ m−3 is combined with a saturation magnetization of μ0Ms = 0.52 T at 2 K (2.2 MJ m−3 and 0.44 T at room temperature). The magnetic hardness parameter of 3.7 at room temperature is the highest observed for any rare-earth-free hard magnet. The anisotropy is related to an unquenched orbital moment of 0.42 μB on Co, which is hybridized with neighboring Rh atoms with a large spin–orbit interaction. Moreover, the pronounced temperature dependence of the anisotropy that follows from its Tc of 450 K, together with a thermal conductivity of 20 W m−1 K−1, make Rh2CoSb a candidate for the development of heat-assisted writing with a recording density in excess of 10 Tb in.−2.

Publ.-Id: 31685

Superconducting Accelerators as Sources for Intense Secondary Radiations

Wagner, A.

The Helmholtz-Center Dresden-Rossendorf operates a superconducting electron linear accelerator (named ELBE radiation source) as a driver for secondary beams of electromagnetic radiation, neutrons, and positrons. The combination of high-intensity secondary beams, superior timing resolution, and adjustable beam repetition rates allows performing experiments, which are hardly possible using alternative technologies. The facility runs as a dedicated user facility thus serving an international community. Applications range from tunable coherent infra-red radiation from an Free-Electron Laser, coherent super-radiant THz radiation with sub-ps timing, high-energy gamma-rays and neutrons for nuclear physics to secondary positron beams for materials research.
Several recent scientific results will be presented and plans for a successor, the Dresden Advanced Light Infrastructure (DALI), will be shown.

Keywords: ELBE; DALI; positrons; THz; FELBE; TELBE; neutrons; gammas; Felsenkeller; nuclear astrophysics

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  • Lecture (others) (Online presentation)
    Physikalisches Kolloquium der Martin-Luther Universität Halle-Wittenberg, 05.11.2020, Halle/Saale, Deutschland

Publ.-Id: 31684

Rare earth minerals and rare-earth mining

Lorenz, T.; Bertau, M.; Möckel, R.

The book chapter is about the geology of rare earth elements, their mineral carrier as well as secondary raw materials.

  • Book chapter
    Prof. Dr. Rainer Pöttgen, Prof. Dr. Christian Strassert, Prof. Dr. Thomas Jüstel: Rare Earth Chemistry, Berlin/Boston: Walter de Gruyter, 2020, 978-3110653601, 15-36
    DOI: 10.1515/9783110654929-002

Publ.-Id: 31683

Nanoparticle emission by electronic sputtering of CaF2 single crystals

Alencar, I.; Hatori, M.; Marmitt, G. G.; Trombini, H.; Grande, P. L.; Dias, J. F.; Papaléo, R. M.; Mücklich, A.; Assmann, W.; Toulemonde, M.; Trautmann, C.

Material sputtered from CaF2 single crystals by 180 MeV Au ions impinging at different incidence angles were collected on high-purity amorphous C-coated Cu grids and Si100 wafer catcher surfaces over a broad angular range. These catcher surfaces were characterized complementary by transmission electron microscopy, atomic force microscopy and medium energy ion scattering, revealing the presence of a distribution of partially buried CaF2 nanoparticles in conjunction to a thin layer of deposited CaF2 material. Particle size distributions do not follow simple power laws and depend on the angles of ion incidence and particle detection. It is shown that the particle ejection is directly related to the jet-like component of sputtering, previously observed in ionic crystals, contributing significantly to the total yield. This contribution enhances as the impinging ions approach grazing incidence. Possible scenarios for the emission of particles are discussed in light of these observations.

Keywords: Atomic force microscopyCatcher technique; Nanoparticle; Medium energy ion scattering; Electronic sputtering; Swift heavy ions; Transmission electron microscopy

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Publ.-Id: 31682

Cerebral blood flow of the frontal lobe in untreated children with trigonocephaly vs healthy controls: an arterial spin labeling study

de Planque, C. A.; Petr, J.; Gaillard, L.; Mutsaerts, H. J.; van Veelen, M. L. C.; Versnel, S. L.; Dremmen, M.; Mathijssen, I. M. J.

Background: Craniofacial surgery is the standard of treatment for children with moderate to severe trigonocephaly. However, assessing the risk of suboptimal neurodevelopment and added value of surgery is difficult in individual cases. In this study we aim to address the hypothesis that brain development is restricted in trigonocephaly patients by investigating cerebral blood flow in the frontal lobe.
Methods: Between 2018 and 2020, we prospectively included trigonocephaly patients for whom a surgical correction was considered in an MRI study measuring cerebral perfusion with arterial spin labeling (ASL). The mean value of cerebral blood flow (CBF) in the frontal lobe was calculated for each subject and compared between the trigonocephaly patients and healthy controls.
Results: MRI scans of 36 trigonocephaly patients (median age 0.5y, IQR 0.3, 11 females) were included and compared with 16 controls without cerebral pathology (median age 0.83y, IQR 0.56, 10 females). The mean CBF values in the frontal lobe of the trigonocephaly patients (73.0 ml/100g/min) did not appear to be significantly different in comparison with controls (70.5 ml/100g/min, p = 0.6479). The superior, middle, and inferior part of the frontal lobe showed no significant differences either.
Conclusions: Before surgery, the frontal lobe of trigonocephaly patients aged under 18 months old has a normal CBF. In addition to the previously reported very low prevalence of papilledema or impaired skull growth, this finding further supports our hypothesis that craniofacial surgery for trigonocephaly is rarely indicated for signs of raised intracranial pressure.


  • Secondary publication expected from 31.01.2023

Publ.-Id: 31681

Pictures worth more than a thousand words: prediction of survival in medulloblastoma patients

Rabasco Meneghetti, A.; Zwanenburg, A.; Löck, S.

In this invited comment we discuss the results of the manuscript of Yan et al. EbioMedicine, with title "Incremental prognostic value and underlying biological pathways of radiomics patterns in medulloblastoma"

Publ.-Id: 31680

Definition and validation of a radiomics signature for loco-regional tumour control in patients with locally advanced head and neck squamous cell carcinoma

Rabasco Meneghetti, A.; Zwanenburg, A.; Leger, S.; Leger, K.; Troost, E. G. C.; Linge, A.; Lohaus, F.; 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.; Krause, M.; Baumann, M.; Löck, S.

Purpose: To develop and validate a CT-based radiomics signature for the prognosis of loco-regional tumour control (LRC) in patients with locally advanced head and neck squamous cell carcinoma (HNSCC) treated by primary radiochemotherapy (RCTx) based on retrospective data from 6 partner sites of the German Cancer Consortium – Radiation Oncology Group (DKTK-ROG).
Material and methods: Pre-treatment CT images of 318 patients with locally advanced HNSCC were collected. Four-hundred forty-six features were extracted from each primary tumour volume and then filtered through stability analysis and clustering. First, a baseline signature was developed from demographic and tumour-associated clinical parameters. This signature was then supplemented by CT imaging features. A final signature was derived using repeated 3-fold cross-validation on the discovery cohort. Performance in external validation was assessed by the concordance index (C-Index). Furthermore, calibration and patient stratification in groups with low and high risk for loco-regional recurrence were analysed.
Results: For the clinical baseline signature, only the primary tumour volume was selected. The final signature combined the tumour volume with two independent radiomics features. It achieved moderately good discriminatory performance (C-Index [95% confidence interval]: 0.66 [0.55-0.75]) on the validation cohort along with significant patient stratification (p=0.005) and good calibration.
Conclusion: We identified and validated a clinical-radiomics signature for LRC of locally advanced HNSCC using a multi-centric retrospective dataset. Prospective validation will be performed on the primary cohort of the HNprädBio trial of the DKTK-ROG once follow-up is completed.

Keywords: HNSCC; Radiomics; Validation; Biomarker; Machine Learning; Loco-regional control

Publ.-Id: 31679

Voltage‐driven motion of nitrogen ions: a new paradigm for magneto‐ionics

de Rojas, J.; Quintana, A.; Lopeandia, A.; Salguero, J.; Muñiz, B.; Ibrahim, F.; Chshiev, M.; Nicolenco, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Sireus, V.; Abad, L.; Jensen, C.; Liu, K.; Nogues, J.; Costa-Krämer, J.; Sort, J.; Menéndez, E.

Magneto‐ionics, understood as voltage‐driven ion transport in magnetic materials, has largely relied on controlled migration of oxygen ions. Here, we demonstrate room‐temperature voltagedriven nitrogen transport (i.e., nitrogen magneto‐ionics) by electrolyte‐gating of a CoN film.
Nitrogen magneto‐ionics in CoN is compared to oxygen magneto‐ionics in Co3O4. Both materials are nanocrystalline (face‐centered‐cubic structure) and show reversible voltage‐driven ON‐OFF ferromagnetism. In contrast to oxygen, nitrogen transport occurs uniformly creating a plane‐wavelike migration front, without assistance of diffusion channels. Remarkably, nitrogen magnetoionics requires lower threshold voltages and exhibits enhanced rates and cyclability. This is due to the lower activation energy for ion diffusion and the lower electronegativity of nitrogen compared to oxygen. These results may open new avenues in applications such as brain‐inspired computing or iontronics in general.

Keywords: positron annihilation spectroscopy; magneto-ionics; positron annihilation lifetime spectroscopy; defetcs; nitrogen; Co

Publ.-Id: 31678

Lithium-assisted Exfoliation and Photoelectrocatalytic Water Splitting of 2D Palladium Thiophosphate

Wu, B.; Kempt, R.; Kovalska, E.; Luxa, J.; Kuc, A. B.; Heine, T.; Sofer, Z.

Efficient photoelectrocatalytic (PEC) water splitting could be the solution for environmental and energy problems on planet Earth. Here, we explore 2D palladium thiophosphate Pd3(PS4)2, which is a promising photocatalyst absorbing light in the visible range. We obtain a few-layer Pd3(PS4)2 through lithium-assisted exfoliation from the bulk phase and characterize it employing Raman spectroscopy, XPS, AFM, and STM combined with DFT calculations. The measured band gap for as-obtained few-layer Pd3(PS4)2 is 2.57 eV (indirect) and its band edges span the electrochemical potentials of the hydrogen and oxygen evolution reactions. The performance in the water-splitting reaction is studied under acidic, neutral, and alkaline conditions under violet irradiation at 420 nm. 2D palladium phosphochalcogenides semiconductor with bifunctional electrocatalytic and photoelectrocatalytic properties. Our results show competitive performance compared with industrial Pt/C catalysts for solar-driven water splitting under acidic and alkaline conditions.


Publ.-Id: 31677

TiOx/Pt3Ti(111) Surface-Directed Formation of Electronically Responsive, Supramolecular Assemblies of Tungsten Oxide Clusters

Moors, M.; An, Y.; Kuc, A. B.; Monakhov, K.

Highly ordered titanium oxide films grown on the Pt3Ti(111) alloy surface have been utilized for the controlled immobilization and the tip-induced electric field triggered electronic manipulation of nanoscopic W3O9 clusters. Depending on the operating conditions two different stable oxide phases z’-TiOx and w’-TiOx were produced. These phases show a strong effect on the adsorption characteristics and reactivity of W3O9 clusters that are formed as a result of thermal evaporation of WO3 powder on the complex TiOx/Pt3Ti(111) surfaces under ultra-high vacuum conditions. The physisorbed tritungsten nonaoxides were found as isolated single units located on metallic attraction points or as supramolecular self-assemblies with a W3O9-capped hexagonal scaffold of W3O9 units. By applying the scanning tunneling microscopy to the W3O9(W3O9)6 structures individual units undergo a tip induced reduction to W3O8. At elevated temperatures agglomeration and the growth of large WO3 islands, which thickness is strongly limited to a maximum of two unit cells, is observed. The findings boost progress toward the template-directed nucleation, growth, networking and charge state-manipulation of functional molecular nanostructures at surfaces using operando techniques.

Publ.-Id: 31676

Tuning valleys and wave functions of van der Waals heterostructures by varying the number of layers: A first-principles study

Ramzan, M. S.; Kunstmann, J.; Kuc, A. B.

In van der Waals heterostructures of two-dimensional transition-metal dichalcogenides (2D TMDCs) electron and hole states are spatially localized in different layers forming long-lived interlayer excitons. Here, we have investigated, from first principles, the influence of additional electron or hole layers on the electronic properties of a MoS2/WSe2 heterobilayer (HBL), which is a direct band gap material. Additional layers modify the interlayer hybridization, mostly affecting the quasiparticle energy and real-space extend of hole states at the G and electron states at the Q valleys. For a sufficient number of additional layers, the band edges move from K to Q or G, respectively. Adding electron layers to the HBL leads to more delocalized Q states, while G states do not extend much beyond the HBL, even when more hole layers are added. These results suggest a simple and yet powerful way to tune band edges and the real-space extend of the electron and hole wave function in TMDC heterostructures, strongly affecting the lifetime and dynamics of interlayer excitons.

Publ.-Id: 31675

The dithiol-dithione tautomerism of 2,3-pyrazinedithiol in the synthesis of copper and silver coordination compounds

Henfling, S.; Kempt, R.; Klose, J.; Kuc, A. B.; Kersting, B.; Krautscheid, H.

A promising strategy for new electrically conductive coordination polymers is the combination of d10 metal ions, which tolerate short metal···metal distances, with dithiolene linkers, known for their “non-innocent” redox behavior. This study explores the coordination chemistry of 2,3-pyrazinedithiol (H2pdt) towards Cu+ and Ag+ ions, highlighting similarities and differences. The synthetic approach, starting with the fully protonated ligand, allowed the isolation of a homoleptic bis(dithiolene) complex with formal CuI atoms, [Cu(H2pdt)2]Cl (1). This complex was further transformed to a one-dimensional coordination polymer with short metal···metal distances, 1D[Cu(Hpdt)] (2Cu). The larger Ag+ ion directly built up a very similar coordination polymer 1D[Ag(Hpdt)] (2Ag), without any appearance of an intermediate metal complex. The coordination polymer 1D[Cu(H2pdt)I] (4), like complex 1, bears fully protonated H2pdt ligands in their dithione form. Upon heating, both compounds underwent auto-oxidation coupled with a dehydrogenation of the ligand to form the open shell neutral copper(II) complex [Cu(Hpdt)2] (3) and the coordination polymer 1D[Cu2I2(Hpdt)(H2pdt)] (5), respectively. For all presented compounds, crystal structures are discussed in-depth. Furthermore, properties of 1, 3, as well as of the three one-dimensional coordination polymers 2Ag, 2Cu and 4, were investigated by UV-Vis-NIR spectroscopy, cyclic voltammetry, and variable temperature magnetic susceptibility, and DC-conductivity measurements. The experimental results are compared and discussed with the aid of DFT simulations.


Publ.-Id: 31674

Image Performance Characterization of an In-Beam Low-Field Magnetic Resonance Imaging Systemm During Static Proton Beam Irradiation

Gantz, S.; Schellhammer, S.; Hoffmann, A. L.

Image guidance using in-beam real-time magnetic resonance (MR) imaging is expected to improve the targeting accuracy of proton therapy for moving tumors, by reducing treatment margins, detecting inter- and intrafractional anatomical changes and enabling beam gating. The aim of this study was to quantitatively characterize the static magnetic field and image quality of a 0.22 T open MR scanner that has been integrated with a static proton research beamline. The magnetic field and image quality studies were performed using high-precision magnetometry and standardized diagnostic image quality assessment protocols, respectively. The magnetic field homogeneity was found to be typical of the scanner used (98 ppm). Operation of the beamline magnets changed the central resonance frequency and magnetic field homogeneity by a maximum of 16 Hz and 3 ppm, respectively. It was shown that the in-beam MR scanner features sufficient image quality and influences of simultaneous irradiation on the images are restricted to a small sequencedependent image translation and a minor reduction in signalto-noise ratio. Nevertheless, specific measures have to be taken to minimize these effects in order to achieve accurate and reproducible imaging which is required for a future clinical application of MR integrated proton therapy.

Keywords: MRI; proton therapy; image quality; magnetometry; MR guided radiotherapy


Publ.-Id: 31673

Asphericity of tumor FDG uptake in non-small cell lung cancer: Reproducibility and implications for harmonization in multicenter studies

Rogasch, J.; Furth, C.; Bluemel, S.; Radojewski, P.; Amthauer, H.; Hofheinz, F.


Asphericity (ASP) of the primary tumor’s metabolic tumor volume (MTV) in FDG-PET/CT is independently predictive for survival in patients with non-small cell lung cancer (NSCLC). However, comparability between PET systems may be limited. Therefore, reproducibility of ASP was evaluated at varying image reconstruction and acquisition times to assess feasibility of ASP assessment in multicenter studies.


This is a retrospective study of 50 patients with NSCLC (female 20; median age 69 years) undergoing pretherapeutic FDG-PET/CT (median 3.7 MBq/kg; 180 s/bed position). Reconstruction used OSEM with TOF4/16 (iterations 4; subsets 16; in-plane filter 2.0, 6.4 or 9.5 mm), TOF4/8 (4 it; 8 ss; filter 2.0/6.0/9.5 mm), PSF + TOF2/17 (2 it; 17 ss; filter 2.0/7.0/10.0 mm) or Bayesian-penalized likelihood (Q.Clear; beta, 600/1750/4000). Resulting reconstructed spatial resolution (FWHM) was determined from hot sphere inserts of a NEMA IEC phantom. Data with approx. 5-mm FWHM were retrospectively smoothed to achieve 7-mm FWHM. List mode data were rebinned for acquisition times of 120/90/60 s. Threshold-based delineation of primary tumor MTV was followed by evaluation of relative ASP/SUVmax/MTV differences between datasets and resulting proportions of discordantly classified cases.


Reconstructed resolution for narrow/medium/wide in-plane filter (or low/medium/high beta) was approx. 5/7/9 mm FWHM. Comparing different pairs of reconstructed resolution between TOF4/8, PSF + TOF2/17, Q.Clear and the reference algorithm TOF4/16, ASP differences was lowest at FWHM of 7 versus 7 mm. Proportions of discordant cases (ASP > 19.5% vs. ≤ 19.5%) were also lowest at 7 mm (TOF4/8, 2%; PSF + TOF2/17, 4%; Q.Clear, 10%). Smoothing of 5-mm data to 7-mm FWHM significantly reduced discordant cases (TOF4/8, 38% reduced to 2%; PSF + TOF2/17, 12% to 4%; Q.Clear, 10% to 6%), resulting in proportions comparable to original 7-mm data. Shorter acquisition time only increased proportions of discordant cases at < 90 s.


ASP differences were mainly determined by reconstructed spatial resolution, and multicenter studies should aim at comparable FWHM (e.g., 7 mm; determined by in-plane filter width). This reduces discordant cases (high vs. low ASP) to an acceptable proportion for TOF and PSF + TOF of < 5% (Q.Clear: 10%). Data with better resolution (i.e., lower FWHM) could be retrospectively smoothed to the desired FWHM, resulting in a comparable number of discordant cases.

Publ.-Id: 31672

"Full-Core" VVER-1000 calculation benchmark

Sprinzl, D.; Krysl, V.; Mikolas, P.; Zavorka, J.; Timr, J.; Bilodid, Y.; Temesvari, E.; Pos, I.; Kalinin, Y.; Shcherenko, A.; Aleshin, S.; Bahadir, T.

This work deals with the \Full-Core" VVER-1000 calculation benchmark which was proposed on the 26th Symposium of AER [1]. Recently, the calculation benchmarks \Full-Core" VVER-440 [2] and its extension [3] have been introduced in the AER community with positive response [4, 5]. Therefore we have decided to prepare a similar benchmark for VVER-1000. This benchmark is also a 2D calculation benchmark based on the VVER-1000 reactor core cold state geometry, explicitly taking into account the geometry of the radial reflector. The loading pattern for this core is very similar to the fresh fuel loading of cycle 9 at Unit 1 of the Temelin NPP (Czech Republic). This core is filled with six types of fuel assemblies with enrichment from 1.3%w 235U to 4.0%w 235U with up to 9 fuel pins with Gd burnable absorber per FA. The main task of this benchmark is to test the pin-by-pin power distribution in fuel assemblies predicted by macro-codes that are used for neutron-physics calculations especially for VVER reactors. In this contribution we present the overview of available macro-codes results.

Publ.-Id: 31671

Tailoring magnetocaloric effect in all- d -metal Ni-Co-Mn-Ti Heusler alloys: a combined experimental and theoretical study

Taubel, A.; Beckmann, B.; Pfeuffer, L.; Fortunato, N.; Scheibel, F.; Ener, S.; Gottschall, T.; Skokov, K. P.; Zhang, H.; Gutfleisch, O.

Novel Ni-Co-Mn-Ti all- d -metal Heusler alloys are exciting due to large multicaloric effects combined with enhanced mechanical properties. An optimized heat treatment for a series of these compounds leads to very sharp phase transitions in bulk alloys with isothermal entropy changes of up to 38 J kg−1 K−1 for a magnetic field change of 2 T. The differences of as-cast and annealed samples are analyzed by investigating microstructure and phase transitions in detail by optical microscopy. We identify different grain structures as well as stoichiometric (in)homogenieties as reasons for differently sharp martensitic transitions after ideal and non-ideal annealing. We develop alloy design rules for tuning the magnetostructural phase transition and evaluate specifically the sensitivity of the transition temperature towards the externally applied magnetic fields (dTt0dH) by analyzing the different stoichiometries. We then set up a phase diagram including martensitic transition temperatures and austenite Curie temperatures depending on the e/a ratio for varying Co and Ti content. The evolution of the Curie temperature with changing stoi- chiometry is compared to other Heusler systems. Density Functional Theory calculations reveal a correlation of TC with the stoichiometry as well as with the order state of the austenite. This combined approach of experiment and theory allows for an efficient development of new systems towards promising magnetocaloric properties. Direct adiabatic temperature change measurements show here the largest value of -4 K in a magnetic field change of 1.93 T for Ni35Co15Mn37Ti13.


Publ.-Id: 31670

Photo-neutron cross-section of natDy in the bremsstrahlung end-point energies of 12, 14, 16, 65, and 75 MeV

Naik, H.; Kim, G. N.; Schwengner, R.; Wooyoung, J.; Hien, N. T.; Kim, K.; Shin, S. G.; Kye, Y.; Junghans, A.; Wagner, A.; Cho, M.-H.

The flux-weighted average cross-sections of natDy(γ, xn)159,157,155Dy reactions were measured at the bremsstrahlung end-point energies of 12, 14, 16, 65 and 75 MeV with the activation and off-line γ-ray spectrometric technique using the 20 MeV Electron Linac for beams with high Brilliance and low Emittance (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany and the 100 MeV electron linac at the Pohang Accelerator Laboratory, Korea. The natDy(γ, xn)157,155Dy reaction cross sections as a function of photon energy were also calculated theoretically using TALYS 1.9 code. Then the flux-weighted average values at different end-point energies were obtained based on the theoretical values of mono-energetic photons. These values were compared with the flux-weighted values of present work and are found to be in general agreement. It was also found that the experimental and theoretical formation cross sections of 159Dy, 157Dy and 155Dy from the natDy(γ, xn) reactions increased from their respective threshold values to a certain energy where other reaction channels opened. After reaching a maximum value, the individual reaction cross-sections slowly decreased with the increase of the bremsstrahlung energy due to the initiation of other competing reactions at higher energy, which indicates the impact of the excitation energy. However, the production cross sections of 157Dy and 155Dy from the natDy(γ, xn) reactions slightly increase in between and then decreased slowly with bremsstrahlung energy, which is due to the contributing reactions of higher mass isotopes.

Keywords: Photonuclear reactions; photoabsorption cross section; photodissociation

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Publ.-Id: 31669

Screening of a test charge in a free-electron gas at warm dense matter and dense non-ideal plasma conditions

Moldabekov, Z.; Dornheim, T.; Bonitz, M.

The screening of a test charge by partially degenerate non-ideal free electrons at conditions related to warm dense matter and dense plasmas is investigated using linear response theory and the local field correction based on ab inito Quantum Monte-Carlo simulations data. The analysis of the obtained results is performed by comparing to the random phase approximation and the Singwi-Tosi-Land-Sjölander approximation. The applicability of the long-wavelength approximation for the description of screening is investigated. The impact of electronic exchange-correlations effects on structural properties and the applicability of the screened potential from linear response theory for the simulation of the dynamics of ions are discussed.

Publ.-Id: 31668

Dynamic properties of the warm dense electron gas based on ab initio path integral Monte Carlo simulations

Hamann, P.; Dornheim, T.; Vorberger, J.; Moldabekov, Z.; Bonitz, M.

There is growing interest in warm dense matter (WDM), an exotic state on the border between condensed matter and plasmas. Due to the simultaneous importance of quantum and correlation effects, WDM is complicated to treat theoretically. A key role has been played by ab initio path integral Monte Carlo (PIMC) simulations, and recently extensive results for thermodynamic quantities have been obtained. The first extension of PIMC simulations to the dynamic structure factor of the uniform electron gas was reported by Dornheim et al. [Phys. Rev. Lett. 121, 255001 (2018)]. This was based on an accurate reconstruction of the dynamic local field correction. Here we extend this concept to other dynamical quantities of the warm dense electron gas including the dynamic susceptibility, the dielectric function, and the conductivity.


Publ.-Id: 31667

Wire-Mesh Sensor Super-Resolution Based on Statistical Reconstruction

de Assis Dias, F.; Pipa, D. R.; Morales, R. E. M.; Da Silva, M. J.

Wire-mesh sensor (WMS) is an instrument used to visualize and estimate derived parameters of multiphase flows, i.e. gas void fraction and liquid hold-up. Due to its high temporal and spatial resolution, the sensor has been widely applied in the investigation of fluid dynamics. However, the structure of WMS is composed of intrusive electrodes and its image resolution is associated to the number of crossing points formed by the transmitter and receiver wires. In many processes, however, the intrusiveness caused by the electrodes may be a limitation on its use, since they increase the pressure drop and might fragment bubbles depending on the flow condition. Therefore, the reduction of the number of electrodes could probably extend the application field of wire-mesh sensors. Thus, we propose an image reconstruction method to increase resolution of WMS data with fewer wires than most WMS reported in the literature. Hence a reduction of intrusive effects on the process may be achieved. The proposed reconstruction method is based on the Minimum Mean Squared Error (MMSE) estimator. Experimental flow data from a 16x16 WMS are used to produce a Multivariate Gaussian flow model, which in turn is used as regularization in the reconstruction. A sensitive matrix is estimated by finite element method (FEM). Experimental data from two-phase water-gas at slug flow condition are used to validate the proposed method and compared with cubic interpolation. The results show that the MMSE estimator performs better than cubic interpolation and the standard direct problem formulation, reducing the void fraction deviation from 18.20% to 7.92% in the worst case (2x2 WMS).

Keywords: Inverse problem; multiphase flow; statistical image reconstruction; Wire-Mesh sensor


Publ.-Id: 31666

Ion energy-loss characteristics and friction in a free-electron gas at warm dense matter and nonideal dense plasma conditions

Moldabekov, Z.; Dornheim, T.; Bonitz, M.; Ramazanov, T.

We investigate the energy-loss characteristics of an ion in warm dense matter (WDM) and dense plasmas concentrating on the influence of electronic correlations. The basis for our analysis is a recently developed ab initio quantum Monte Carlo– (QMC) based machine learning representation of the static local field correction (LFC) [Dornheim et al., J. Chem. Phys. 151, 194104 (2019)], which provides an accurate description of the dynamical density response function of the electron gas at the considered parameters. We focus on the polarization-induced stopping power due to free electrons, the friction function, and the straggling rate. In addition, we compute the friction coefficient which constitutes a key quantity for the adequate Langevin dynamics simulation of ions. Considering typical experimental WDM parameters with partially degenerate electrons, we find that the friction coefficient is of the order of γ/ωpi=0.01, where ωpi is the ionic plasma frequency. This analysis is performed by comparing QMC-based data to results from the random-phase approximation (RPA), the Mermin dielectric function, and the Singwi-Tosi-Land-Sjölander (STLS) approximation. It is revealed that the widely used relaxation time approximation (Mermin dielectric function) has severe limitations regarding the description of the energy loss of ions in a correlated partially degenerate electrons gas. Moreover, by comparing QMC-based data with the results obtained using STLS, we find that the ion energy-loss properties are not sensitive to the inaccuracy of the static local field correction (LFC) at large wave numbers, k/kF>2 (with kF being the Fermi wave number), but that a correct description of the static LFC at k/kF≲1.5 is important.


Publ.-Id: 31665

Path-integral Monte Carlo simulations of quantum dipole systems in traps: Superfluidity, quantum statistics, and structural properties

Dornheim, T.

We present extensive ab initio path-integral Monte Carlo (PIMC) simulations of two-dimensional quantum dipole few-body systems (2≤N≤7) in a harmonic confinement, taking into account both Bose- and Fermi-statistics. This allows us to study the nonclassical rotational inertia, which can lead to a negative superfluid fraction in the case of fermions [Phys. Rev. Lett. 112, 235301 (2014)]. Moreover, we study in detail the structural characteristics of such systems and are able to clearly resolve the impact of quantum statistics on density profiles and the respective shell structure. Further, we present results for a more advanced center-two-particle correlation function [Phys. Rev. E 91, 043104 (2015)], which allows detection of differences between Fermi and Bose systems even when they are almost absent in other observables like the density. Overall, we find that bosonic systems sensitively react to even small values of the dipole-dipole coupling strength, whereas such a weak interaction is effectively masked for fermions by the Pauli exclusion principle. In addition, the abnormal superfluid fraction for fermions is not reflected by the structural properties of the system, which are equal to the bosonic case even though the moments of inertia diverge from each other. Lastly, we have explored the possibility of fermionic PIMC simulations of quantum dipole systems despite the notorious fermion sign problem, which can be further extended in future investigations in this field.


Publ.-Id: 31664

Restricted configuration path integral Monte Carlo

Yilmaz, A.; Hunger, K.; Dornheim, T.; Groth, S.; Bonitz, M.

Quantum Monte Carlo (QMC) belongs to the most accurate simulation techniques for quantum many-particle systems. However, for fermions, these simulations are hampered by the sign problem that prohibits simulations in the regime of strong degeneracy. The situation changed with the development of configuration path integral Monte Carlo (CPIMC) by Schoof et al. [Contrib. Plasma Phys. 51, 687 (2011)] that allowed for the first ab initio simulations for dense quantum plasmas [Schoof et al., Phys. Rev. Lett. 115, 130402 (2015)]. CPIMC also has a sign problem that occurs when the density is lowered, i.e., in a parameter range that is complementary to traditional QMC formulated in coordinate space. Thus, CPIMC simulations for the warm dense electron gas are limited to small values of the Brueckner parameter—the ratio of the interparticle distance to the Bohr radius—rs=r⎯⎯⎯/aB≲1
. In order to reach the regime of stronger coupling (lower density) with CPIMC, here we investigate additional restrictions on the Monte Carlo procedure. In particular, we introduce two different versions of “restricted CPIMC”—called RCPIMC and RCPIMC+—where certain sign changing Monte Carlo updates are being omitted. Interestingly, one of the methods (RCPIMC) has no sign problem at all, but it introduces a systematic error and is less accurate than RCPIMC+, which neglects only a smaller class of the Monte Carlo steps. Here, we report extensive simulations for the ferromagnetic uniform electron gas with which we investigate the properties and accuracy of RCPIMC and RCPIMC+. Furthermore, we establish the parameter range in the density–temperature plane where these simulations are both feasible and accurate. The conclusion is that RCPIMC and RCPIMC+ work best at temperatures in the range of Θ = kBT/EF ∼ 0.1…0.5, where EF is the Fermi energy, allowing to reach density parameters up to rs ∼ 3…5, thereby partially filling a gap left open by existing ab initio QMC methods.


Publ.-Id: 31663

Reconstruction of austenite grain boundaries in bainitic reactor pressure vessel steels by EBSD

Chekhonin, P.; Bergner, F.

The reconstruction of austenite grain boundaries in bainitic reactor pressure vessel (RPV) steels by means of electron backscatter diffraction (EBSD) was done on two examples. In the case of VVER-440 RPV steel the reconstruction works very well, while in JFL RPV steel the reconstruction is faulty due to the accented presence of low angle boundaries.

  • Lecture (Conference) (Online presentation)
    AK-Treffen Mikrostrukturcharakterisierung im REM, 22.10.2020, Freiberg, Germany

Publ.-Id: 31662

Enhanced spin correlations in the Bose-Einstein condensate compound Sr3Cr2O8

Nomura, T.; Scurschii, I.; Quintero-Castro, D. L.; Zvyagin, A. A.; Suslov, A. V.; Gorbunov, D.; Yasin, S.; Wosnitza, J.; Kindo, K.; Islam, A. T. M. N.; Lake, B.; Kohama, Y.

Combined experimental and modeling studies of the magnetocaloric effect, ultrasound, and magnetostriction were performed on single-crystal samples of the spin-dimer system Sr3Cr2O8 in large magnetic fields to probe the spin-correlated regime in the proximity of the field-induced XY-type antiferromagnetic order also referred to as a Bose-Einstein condensate of magnons. The magnetocaloric effect, measured under adiabatic conditions, reveals details of the field-temperature (H, T ) phase diagram, a dome characterized by critical magnetic-fields Hc1 = 30.4, Hc2 = 62 T, and a single maximum ordering temperature Tmax(45 T) = 8 K. The sample temperature was observed to drop significantly as the magnetic field is increased, even for initial temperatures above Tmax, indicating a significantmagnetic entropy associated with the field-induced closure of the spin gap. The ultrasound and magnetostriction experiments probe the coupling between the lattice degrees of freedom and the magnetism in Sr3Cr2O. Our experimental results are qualitatively reproduced by a minimalistic phenomenological model of the exchange striction by which sound waves renormalize the effective exchange couplings.


Publ.-Id: 31661

Strong anisotropy of the electron-phonon interaction in NbP probed by magnetoacoustic quantum oscillations

Schindler, C.; Gorbunov, D.; Zherlitsyn, S.; Galeski, S.; Schmidt, M.; Wosnitza, J.; Gooth, J.

In this study, we report on the observation of de Haas–van Alphen–type quantum oscillations (QOs) in the ultrasound velocity of NbP as well as “giant QOs” in the ultrasound attenuation in pulsed magnetic fields. The difference in the QO amplitude for different acoustic modes reveals a strong anisotropy of the effective deformation potential, which we estimate to be as high as 9 eV for certain parts of the Fermi surface. Furthermore, the natural filtering of QO frequencies and the tracing of the individual Landau levels to the quantum limit allows for a more detailed investigation of the Fermi surface of NbP, as was previously achieved by means of analyzing QOs observed in magnetization or electrical resistivity.

Publ.-Id: 31660

Detection of manufactured nanomaterials in complex environmental compartments – An expert review

Schymura, S.; Hildebrand, H.; Völker, D.; Schwirn, K.; Franke, K.; Fischer, C.

Manufactured nanomaterials (NMs) are materials in which 50% or more of the particles have one or more dimensions between 1 nm and 100 nm. These NMs show interesting properties. However, the same properties that motivate their use in applications are also reason for concern, as NMs can cause toxic reactions and have mobilities in the environment different from bulk materials of the same elements. Despite considerable scientific efforts, the selective detection of manufactured NMs in environmental compartments is still a very complex and challenging task. An expert review of the literature has been conducted to identify relevant methods for nanomaterial detection in complex media in the context of environmental monitoring and a need for action was concluded from the existing body of work.
A literature review was performed using predominantly “Web of Science”. More than 150 scientific publications which themselves refer to more than 10000 sources were evaluated concerning nanoparticle detection methods. The techniques identified through the literature review were evaluated for their capability to detect the relevant NM-related properties such as size, concentration, com- position, shape, etc. of arbitrary NMs in environmental samples.
Evaluating the relevant literature quickly led to the conclusion that while some detection methods will lend themselves more easily towards detection of NMs in a specific environmental compartment, there is no strictly compartment specific method. NMs can be detected with any of the different methods after application of suitable sample preparation techniques. Consequently, a generalized method for NM detection in environmental samples would consist of standardized sampling procedures followed by an extraction step that serves to largely remove the complex matrix followed by a size fractionation step which would then lead into a multi-method analysis depending on the desired information depth.
The need for action for the establishment of routine environmental monitoring of manufactured NMs is thus the development, validation and coupling of suitable extraction, pre-sorting and if necessary pre- concentration procedures, as well, as analysis techniques. One promising combined approach would consist of: CPE, AF4, MALS and sp-ICP-TOF-MS.

Keywords: nanoparticles; detection; environmental compartments

  • Poster (Online presentation)
    Nanosafe 2020, 16.-20.11.2020, Grenoble, France

Publ.-Id: 31659

Assessing nanoparticle release from waste water treatment using radiolabeled nanoparticles

Schymura, S.; Hildebrand, H.; Neugebauer, M.; Lange, T.; Schneider, P.; Franke, K.

Waste water treatment plants (WWTPs) represent an important step in the life cycle of manufactured nanomaterials. A considerable amount of nanoparticles (NPs) that are released from consumer products will end up in WWTPs, so that WWTPs can both serve as a potential end of life point for these nanoparticles, as well as a point of reentry into the environment via the WWTP effluents. It is thus of utmost importance to accurately quantify the fate of manufactured nanomaterials in waste water treatment in order to assess the risk
We used the radiolabeling of nanoparticles to accurately quantify the distribution of nanoparticles between the effluents of a model waste water treatment plant. In order to achieve this TiO2 NP were radiolabeled with V-48 using proton irradiation at our cyclotron. Multi-wall carbon nanotubes (MWCNT) were radiolabeled with Be-7 via recoil at our cyclotron. CdSe/ZnS Quantum dots were radiolabeled with Zn-65 and Se-75 via radiosynthesis. The radiolabeled NPs were used in batch experiments and model waste water treatment plant experiments.
The radiolabeling allowed us to quantify NP distribution between sludge and water phase in the WWTP and in the WWTP effluents. A distribution of about 10000 : 1 between sludge-associated NPs and free NPs in water is reached in the WWTP already shortly after injection of the NPs. Thus the elimination of the NPs from the WWTP is mainly controlled by the removal of surplus sludge taking place every day of operation. The NPs are eliminated from the WWTP with a half-life of about 6 days reflecting the pre-set sludge age. After about 22 days of operation 10 % of the initial NPs remain in the WWTP. Approximately 1 % of the NPs leave the WWTP via the cleared waste water, mainly associated with non-sedimented sludge particles, such that only about 1 ‰ of the NPs leave the WWTP as free particles via the cleared water. An impact of the NPs on the clearing process, as monitored by chemical oxygen demand of the inflow vs. the outflow, was not observed.

Keywords: nanoparticles; waste water treatment; radiolabeling

  • Lecture (Conference) (Online presentation)
    Nanosafe 2020, 16.-20.11.2020, Grenoble, France

Publ.-Id: 31658

Radiolabeling as a versatile tool in nanosafety research – accurate quantification in complex media

Schymura, S.; Hildebrand, H.; Rybkin, I.; Fricke, T.; Neugebauer, M.; Freyer, A.; Rijavec, T.; Lapanje, A.; Strok, M.; Lange, T.; Holzwarth, U.; Gibson, N.; Franke, K.

Accurate quantification of nanoparticles (NPs) in complex media remains a considerable challenge when assessing the risk that manufactured nanoparticles pose for humans and environment. The radiolabeling of nanoparticles is a valuable tool for conducting lab-studies with realistic systems and realistically low NP concentrations.
We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles. The labeling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [13/1419Ce]CeO2, [7Be]MWCNT, [64Cu]SiO2, [44/45Ti]TiO2, etc. for accurate quantification in complex media at environmentally relevant low concentrations.
The nanoparticles labeled by our methods can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary. The methods are adaptable for a wide range of other nanoparticles. The labeled particles have been successfully used in release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.

Keywords: Radiolabeling; Nanoparticles

  • Poster
    Nanosafe 2020, 16.-20.11.2020, Grenoble, France

Publ.-Id: 31657

When Beneficial Biofilm on Materials Is Needed: Electrostatic Attachment of Living Bacterial Cells Induces Biofilm Formation

Deev, D.; Rybkin, I.; Rijavec, T.; Lapanje, A.

Bacterial attachment is crucial in many biotechnological applications, but many important bacterial strains cannot form biofilms. Biofilms can damage materials, and current strategies to manage biofilms are focused on inhibition and removal of biofilm. Biofilm formation is inevitable when materials are exposed to microbes and instead of biofilm prevention, we propose management of microbial composition by formation of biofilms with beneficial microbes. Since bacteria need to overcome a high repulsive force to attach to the surface and later to grow and multiply on it, electrostatic modification of the surfaces of cells or the material by polyelectrolytes (PE) was used in our approach, enabling efficient attachment of viable bacterial cells. Since highly positively charged PEs are known to be bactericidal, they were acetylated to reduce their toxicity, while preserving their net positive charge and ensuring cell viability. In our study bacterial strains were selected according to their intrinsic capability of biofilm formation, their shape variety and cell wall structure. These strains were tested to compare how the artificially prepared vs. natural biofilms can be used to populate the surface with beneficial bacteria. Using an artificial biofilm constructed of the potentially probiotic isolate Bacillus sp. strain 25.2. M, reduced the attachment and induced complete inhibition of E. coli growth over the biofilm. This study also revealed that the modification of the surfaces of cells or material by polyelectrolytes allows the deposition of bacterial cells, biofilm formation and attachment of biofilm non-forming cells onto surfaces. In this way, artificial biofilms with extended stability can be constructed, leading to selective pressure on further colonization of environmental bacteria.

Keywords: artificial biofilms; polyelectrolytes; cell encapsulation; biofilm management; surface modification

Publ.-Id: 31656

Scalable Workflows for OpenFOAM Evaluation

Evdokimov, I.; Hänsch, S.; Schlegel, F.

The proposed research paper has a strong application bias and aims to address the practical problem of managing dozens, potentially hundreds of OpenFOAM cases. The workflow management includes routine tasks such as migrations on new solver versions, testing sub-models and solvers, as well as developing entirely new OpenFOAM applications validated against established setups. The proposed methodology was successfully tested on a set of 55 OpenFOAM cases specifically designed for the validation of new sub-models for Euler-Euler simulations of multiphase flows.

Keywords: workflow; OpenFOAM; validation

  • Contribution to proceedings
    The Open Conference of the ISPRAS, 10.-11.12.2020, Moscow, Russia
  • Lecture (Conference) (Online presentation)
    The Open Conference of the ISPRAS, 11.12.2020, Moscow, Russia

Publ.-Id: 31655

Series of Tetravalent Actinide Amidinates: Structure Determination and Bonding Analysis.

Kloditz, R.; Fichter, S.; Kaufmann, S.; Brunner, T. S.; Kaden, P.; Patzschke, M.; Stumpf, T.; Roesky, P. W.; Schmidt, M.; März, J.

NMR spectra for the complex series in the publication together with the xyz coordinates of the optimized complexes. An example input-file for ORCA v4.1.2 for the calculation of the wavefunction used for QTAIM is presented as well.

Keywords: actinides; NMR; DFT; QTAIM; NPA; coordination chemistry; transuranium

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Publ.-Id: 31654

Data for: Spectral X-ray Computed Micro Tomography: 3-dimensional chemical imaging

Sittner, J.; Da Assuncao Godinho, J. R.; Renno, A.; Cnudde, V.; Boone, M.; de Schryver, T.; van Loo, D.; Merkulova, M.; Roine, A.; Liipo, J.

The files show the data we used for the publication.

Keywords: X-ray computed tomography; Spectral X-ray tomography; Photon counting detector; 3D imaging

Related publications


Publ.-Id: 31653

Don't Publish - Previewer test for splitted zip file 23

Gruber, T.
Other: Pape, David

Test if large zip files can be splittet and read by the previewer. Looks like it works.

Keywords: update Keyword


Publ.-Id: 31651

Are two-dimensional materials radiation tolerant?

Krasheninnikov, A.

Two-dimensional (2D) materials have many unique properties, which can be exploited in various applications. In particular, electronic devices based on 2D materials should ideally be suited for the operation in outer cosmic space due to their low weight, small size and low power consump- tion. This brings about the issue of their radiation hardness, or tolerance, which has recently been addressed in a number of studies. The results of these investigations are somewhat counterintu- itive: although one can naively expect that atomically thin structures should easily be destroyed by the beams of energetic particles, the devices made from 2D materials were reported to exhibit extraordinary radiation hardness. In this Focus article, an overview of the recent studies on the subject is given, followed by the discussion of the origin of the reported high tolerance, which is inherently related to the response of 2D materials, the systems with the reduced dimensionality, to irradiation. The analysis of the experimental and theoretical data on the behavior of 2D systems under irradiation indicates that although free-standing 2D materials can indeed be referred to as radiation resilient systems under irradiation conditions corresponding to the outer space, this is generally not the case, as the environment, e.g., the substrate, can strongly influence the radiation tolerance of 2D materials and devices based on these systems.

Keywords: 2D materials; irradiation; radiation tolerance

Related publications


Publ.-Id: 31650

Influence of chemical zoning on sandstone calcite cement dissolution: The case of manganese and iron

Trindade Pedrosa, E.; Fischer, C.; Morales, L. F.; Rohlfs, R. D.; Luttge, A.

Chemical zoning of crystals is often found in nature. Crystal zoning can play a role in a mineral's thermodynamic stability and in its kinetic response in the presence of fluids. Dissolution experiments at far-from-equilibrium conditions were performed using a sandstone sample containing calcite cement crystal patches. The surface normal retreat of the calcite crystals was obtained by vertical scanning interferometry (VSI) in their natural position in the rock. Dissolution rate maps showed contrasting surface dissolution areas within the crystals, in the same locations where electron microprobe (EMP) maps showed the presence of manganese (Mn) and iron (Fe) substitutions for calcium in the calcite structure. Iron zoning was only identified in combination with manganese. Maximum registered manganese contents were 1.9(9) wt% and iron were 2(1) wt%. Manganese zoning of only 0.9(5) wt% resulted in around 40% lower dissolution rates than the adjacent pure calcite zones. The combination of both Mn and Fe cation substitutions resulted in one order of magnitude lower dissolution rates compared to pure calcite in the same sample. These results show that mineral zoning can significantly affect reaction rates, a parameter that needs better understanding for the improvement of kinetic geochemical models at the pore scale.

Keywords: Sandstone; Calcite; Dissolution; Zoning; Manganese; Iron

Publ.-Id: 31649

Dyke apertures record stress accumulation during sustained volcanism

Thiele, S. T.; Cruden, A. R.; Micklethwaite, S.; Köpping, J.; Bunger, A. P.

The feedback between dyke and sill intrusions and the evolution of stresses within volcanic systems is poorly understood, despite its importance for magma transport and volcano instability. Long-lived ocean island volcanoes are crosscut by thousands of dykes, which must be accommodated through a combination of flank slip and visco-elastic deformation. Flank slip is dominant in some volcanoes (e.g., Kilauea), but how intrusions are accommodated in other volcanic systems remains unknown. Here we apply digital mapping techniques to collect > 400,000 orientation and aperture measurements from 519 sheet intrusions within Volcán Taburiente (La Palma, Canary Islands, Spain) and investigate their emplacement and accommodation. We show that vertically ascending dykes were deflected to propagate laterally as they approached the surface of the volcano, forming a radial dyke swarm, and propose a visco-elastic model for their accommodation. Our model reproduces the measured dyke-aperture distribution and predicts that stress accumulates within densely intruded regions of the volcano, blocking subsequent dykes and causing eruptive activity to migrate. These results have significant implications for the organisation of magma transport within volcanic edifices, and the evolution and stability of long-lived volcanic systems.

Publ.-Id: 31648

High Performance Computing: ISC High Performance 2020 International Workshops

Jagode, H.; Anzt, H.; Juckeland, G.; Ltaief, H.

This book constitutes the refereed post-conference proceedings of 10 workshops held at the 35th International ISC High Performance 2020 Conference, in Frankfurt, Germany, in June 2020:

First Workshop on Compiler-assisted Correctness Checking and Performance Optimization for HPC (C3PO); First International Workshop on the Application of Machine Learning Techniques to Computational Fluid Dynamics Simulations and Analysis (CFDML); HPC I/O in the Data Center Workshop (HPC-IODC); First Workshop \Machine Learning on HPC Systems" (MLHPCS); First International Workshop on Monitoring and Data Analytics (MODA); 15th Workshop on Virtualization in High-Performance Cloud Computing (VHPC).

The 25 full papers included in this volume were carefully reviewed and selected. They cover all aspects of research, development, and application of large-scale, high performance experimental and commercial systems. Topics include high-performance computing (HPC), computer architecture and hardware, programming models, system software, performance analysis and modeling, compiler analysis and optimization techniques, software sustainability, scientific applications, deep learning.

Keywords: artificial intelligence; computer hardware; computer networks; computer science; computer systems; distributed computer systems; distributed systems; education; HPC; parallel architectures

Publ.-Id: 31647

The resource potential of mine waste – More than metal concentrations

Büttner, P.; Nühlen, J.; Engelhardt, J.

In the last decade, several national and European funding programs addressed the resource potential of mine wastes (including tailings and metallurgical slag dumps), with a clear focus on the development of new sources for critical raw materials (CRM). The European Commission defined CRMs as highly important for the European high tech industry. European and national resource strategies refer to this definition and include the development of new CRM sources as one of their main objectives. The German Federal Ministry for Research and Education (BMBF) funded the program “r3 –strategic metals and minerals – innovative technologies for resource efficiency” that started in 2012. The aim of the program was to ensure the domestic supply of strategically significant metals and minerals. Suitable projects had to act in the fields of recycling and substitution of raw materials as well as in the field of reduced material consumption. Urban mining and the evaluation of resource efficiency were further topics that suited the program. The Helmholtz Institute Freiberg for Resource Technology (HIF) and the Fraunhofer Institute for Environmental, Safety, and Energy Technology (UMSICHT) worked already together in different projects about mine waste characterization and resource extraction in r3.
The Helmholtz Institute Freiberg for Resource Technology pursues the objective of developing innovative technologies for the economy so that mineral and metalliferous raw materials become more available, undergo highly efficient processes and recycle in an environmentally
friendly manner. As a part of the national strategy for raw materials in 2011, the German government initiated the HIF. It is a constituent part of the Helmholtz-Zentrum Dresden-Rossendorf and works in close collaboration with TU Bergakademie Freiberg. The HIF is a core member of the European EIT RawMaterials network, having played a decisive role in its establishment. Fraunhofer UMSICHT is a pioneer for sustainable energy and raw materials management by supplying and transferring scientific results into companies, society and politics. The dedicated UMSICHT team researches and develops, together with partners, sustainable products, processes and services. Together with industry and public partners, such as the Geological Survey of Germany (BGR), UMSICHT and HIF founded the r³-mine-waste-cluster in order to determine a realistic mine waste
potential for Germany and give a reliable resource estimation for secondary raw materials. Nowadays, however, there is a political and public interest beyond the potential of valuable metals from mine wastes. After the catastrophic tailings accident in Vales Corrego do Feijão mine, Brazil, the social pressure to lower these risks raised on the mining industry, on the mine waste owners (e.g. states) and on the politics. With the new Global Industry Standard on Tailings Management a new set of guidelines was developed in order to avoid these accidents in the future. “The International Council
on Mining and Metals (ICMM), the United Nations Environment Programme (UNEP) and the Principles for Responsible Investment (PRI) share a commitment to the adoption of global best practices on tailings storage facilities. They have co-convened this global tailings review to establish an international standard.” Their environmental risks and at the same time their high potential as a source for (critical) raw materials make mine waste projects a complex exercise. There is a need for solutions that respect environmental, technical, civil and economic issues and provide holistic and sustainable approaches. In order to validating and adjusting different approaches, the HIF coordinates the recomine-alliance. Local stakeholders representing environmental, technical, scientific, governmental and civil institutions assemble in recomine for a development of holistic mine waste solutions for a worldwide application.

Keywords: re-mining; resources; HIF; tailings; mine waste; mining; CRM; slag dump; mine water; WIR!; r3; recomine; Freiberg; Network; Alliance; BMBF; holistic; remediation; sustainable

  • World of Mining - Surface & Underground 72(2020)5, 264-269
    ISSN: 1613-2408

Publ.-Id: 31646

Anode-metal drop formation and detachment mechanisms in liquid metal batteries

Benard, S.; Weber, N.; Horstmann, G. M.; Landgraf, S.; Weier, T.

We study numerically localised short-circuits in Li||Bi liquid metal batteries. In the prototype of a classical, three liquid-layer system, we assume a perceptible local deformation of the Li-salt interface. We find that there exists always a critical current at which a Li-droplet is cut off from this hump, and transferred to the Bi-phase. In a second case, we assume that the molten Li is contained in a metal foam, and that a small Li-droplet emerges below this foam due to insufficient wetting. This droplet is deformed by Lorentz forces, until eventually being pinched off. Here, the critical current is slightly lower than in the three layer system, and both, a droplet transfer and complete short-circuits are observed. Finally, we discuss the relevance of our simulations for experimentally observed short-circuits and non-faradaic Li-transfer.


Publ.-Id: 31645

Spin-wave dynamics and symmetry breaking in an artificial spin ice

Saha, S.; Zhou, J.; Hofhuis, K.; Kakay, A.; Scagnoli, V.; Heyderman, L. J.; Gliga, S.

Artificial spin ices are periodic arrangements of interacting nanomagnets that have been successfully used to investigate emergent phenomena in the presence of geometric frustration. Recently, it has become clear that artificial spin ices equally have the potential to be used as building blocks for creating functional materials, such as magnonic crystals and ratchets, in addition to supporting a large number of programmable magnetic states. In this context, we investigate the magnetization dynamics in a system exhibiting asymmetric magnetostatic interactions owing to locally broken structural symmetry. We find that this gives rise to a rich spectrum that can be tuned through an external field. We also determine the evolution of the observed excitation modes, starting with building blocks and evolving into larger arrays, highlighting the role of symmetry breaking in defining the mode spectrum of the system. Concurrently, the increasing complexity of the spectrum leads to the existence of a large number of modes over a narrow range of frequencies. These results contribute to the understanding of magnetization dynamics in spin ice systems beyond the kagome and square ice geometries with a view towards the realization of reconfigurable magnonic crystals based on spin ices.

Keywords: artificial spin ice; symmetry breaking; spin-wave dynamics; reconfigurable; magnonic crystal


Publ.-Id: 31644

A FDG-PET radiomics signature detects esophageal squamous cell carcinoma patients who do not benefit from chemoradiation

Li, Y.; Beck, M.; Päßler, T.; Lili, C.; Wu, H.; Ha, D.; Amthauer, H.; Biebl, M.; Thuss-Patience, P.; Berger, J.; Stromberger, C.; Tinhofer, I.; Kruppa, J.; Budach, V.; Hofheinz, F.; Lin, Q.; Zschaeck, S.

Detection of patients with esophageal squamous cell carcinoma (ESCC) who do not benefit from standard chemoradiation (CRT) is an important medical need. Radiomics using 18-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising approach. In this retrospective study of 184 patients with locally advanced ESCC. 152 patients from one center were grouped into a training cohort (n = 100) and an internal validation cohort (n = 52). External validation was performed with 32 patients treated at a second center. Primary endpoint was disease-free survival (DFS), secondary endpoints were overall survival (OS) and local control (LC). FDG-PET radiomics features were selected by Lasso-Cox regression analyses and a separate radiomics signature was calculated for each endpoint. In the training cohort radiomics signatures containing up to four PET derived features were able to identify non-responders in regard of all endpoints (DFS p < 0.001, LC p = 0.003, OS p = 0.001). After successful internal validation of the cutoff values generated by the training cohort for DFS (p = 0.025) and OS (p = 0.002), external validation using these cutoffs was successful for DFS (p = 0.002) but not for the other investigated endpoints. These results suggest that pre-treatment FDG-PET features may be useful to detect patients who do not respond to CRT and could benefit from alternative treatment.

Publ.-Id: 31643

An Experimental and Numerical Study of Precision Cooling to Determine Minimum Coolant Velocity of Downsized Internal Combustion Engines Using Boiling

Qasemian, A.; Keshavarz, A.; Setoodeh, H.; Mohammadi, A.; Chitsaz, I.

Nowadays, due to the internal combustion engine industry's orientation towards downsizing, modern efficient cooling systems with lower power consumption, small size and high compactness are essential. To improve these items, applying precision cooling and boiling phenomenon are inevitable. Having an appropriate coolant flow velocity which leads to utilize only the advantages of boiling heat transfer has always been a challenge. Two experimental test rigs, one for modeling and accurate prediction of subcooled flow boiling and the other for measurement and validation of coolant velocity in a water jacket by particle image velocimetry method are set up. An accurate and robust empirical correlation for modeling of subcooled flow boiling which occurs in the water jacket is developed. Then, through a three dimensional thermal analysis, the heat transfer parameters such as heat flux and temperature distribution of the internal combustion engine cylinder block and head are obtained numerically. Finally, as the main achievement of this study, a diagram is presented which combines the concept of precision cooling and subcooled flow boiling and gives the minimum coolant velocity in terms of heat flux. Without going into detail thermo-fluids analysis, this provides a convenient tool to determine the minimum velocity of the coolant flow over the different regions of the internal combustion engine water jacket wall to keep it at its allowable temperature range.

Keywords: Internal combustion engine; Downsizing; Heat transfer; Precision cooling; Subcooled flow boiling

Publ.-Id: 31642

Dissolution of donor-vacancy clusters in heavily doped n-type germanium

Prucnal, S.; Liedke, M. O.; Wang, X.; Butterling, M.; Posselt, M.; Knoch, J.; Windgassen, H.; Hirschmann, E.; Berencen, Y.; Rebohle, L.; Wang, M.; Napoltani, E.; Frigerio, J.; Ballabio, A.; Isella, G.; Hübner, R.; Wagner, A.; Bracht, H.; Helm, M.; Zhou, S.

The n-type doping of Ge is a self-limiting process due to the formation of vacancy-donor complexes (DnV with n ≤ 4) that deactivate the donors. This work unambiguously demonstrates that the dissolution of the dominating P4V clusters in heavily phosphorus-doped Ge epilayers can be achieved by millisecond-flash lamp annealing at about 1050 K. The P4V cluster dissolution increases the carrier concentration by more than three-fold together with a suppression of phosphorus diffusion. Electrochemical capacitance-voltage measurements in conjunction with secondary ion mass spectrometry, positron annihilation lifetime spectroscopy and theoretical calculations enabled us to address and understand a fundamental problem that has hindered so far the full integration of Ge with complementary-metal-oxide-semiconductor technology.

Keywords: Ge; vacancies; doping; positron annihilation lifetime spectroscopy; flash lamp annealing

Related publications

Publ.-Id: 31641

A new research infrastructure for investigating flow hydraulics and process equipment at critical fluid properties

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

An optimized equipment design for natural gas processing and liquefaction plants becomes increasingly difficult with changing process conditions: Particularly low values of surface tension create rising challenges on the design of phase separators and column internals. The TERESA test rig at HZDR was designed to allow the investigation of multi-phase thermohydraulics and phase separator performance under critical fluid properties in industrial dimensions. A versatile pipe test section is available in DN200 and equipment internals may be tested in a sectional DN300/DN500 test separator. The applied test fluid shows a high vapor-liquid density difference between 1470 and 940 kg/m³, viscosity as low as 0.12 mm²/s, and surface tension down to 1.3 mN/m. Volumetric liquid and vapor flow rates may be varied up to 9 and 530 m³/h in the test rig, respectively.

Keywords: critical fluid properties; hydraulics; phase separation; two-phase flow

Publ.-Id: 31640

The GeDI project-a German DIBH database

Duma, M. N.; Krause, M.; Hoinkis, C.; Gurtner, K.; Richter, C.; Corradini, S.; Pazos, M. E.; Schoencker, S.; Walke, M.; Gabriel, C.; Brunner, T.; Krug, D.; Hoerner-Rieber, J.; Grosu, A. L.; Nicolay, N. H.; Wittig, A.

Background: Studies indicate that all left-sided breast cancer patients benefit from the deep inspiration breath hold technique (DIBH), however, not all patients experience the same benefit. A meta-analysis performed by Latty et al. reviewed 18 studies evaluating DIBH, which demonstrated a relative reduction of mean dose (Dmean) to the heart ranging from 26.2% to 75% as compared to irradiation in free breathing. However, as most papers report averages rather than patient-by-patient analyses, outliers remain unidentified. Thus, a lack of data and knowledge exists in determining selection criteria to predict individual patient benefit from DIBH.

Methods: We are planning to establish a large retrospective database of breast cancer patients treated with deep inspiration breath hold (DIBH) radiotherapy techniques. Data will be collected anonymized from all participating centres. A detailed analysis of:

1. Differences in OAR sparing by anatomical conditions
2. Differences in OAR sparing by used DIBH techniques (free breathing, RPM, surface scanning with camera or laser systems etc)
3. Differences in OAR sparing by fractionation schedules (normalized to EQD2)
4. Differences in OAR sparing by PTV volumes and CTV definitions

but not limited to, will be performed.

Discussion: Patient data will be stratified according to different anatomical conditions (such as large breasts vs. small breasts), radiation techniques, fractionation schedules and PTV volumes (for e.g. chest wall after mastectomy vs. breast only vs. breast and lymphatics etc). This multicentre database will allow for the first time an in depth analysis of the impact of DIBH. It will enhance our knowledge on outliers and will provide selection criteria to predict individual patient benefit from DIBH.

  • Lecture (Conference) (Online presentation)
    DEGRO, 24.-28.06.2020, Wiesbaden, Deutschland

Publ.-Id: 31639

Magnetic-field-assisted electrodeposition of metal to obtain conically structured ferromagnetic layers

Huang, M.; Eckert, K.; Mutschke, G.

Micro- or nano-structured ferromagnetic layers often possess superior electrocatalytic properties but are difficult to manufacture in general. The present work investigates how a magnetic field can possibly support local cone growth on a planar electrode during electrodeposition, thus simplifying fabrication. Analytical and numerical studies were performed on conical structures of mm size to elaborate the influence of the magnetic forces caused by an electrode-normal external field. It is shown that, beside the Lorentz force studied earlier in the case of single cones [1], the magnetic gradient force enabled by the field alteration near the ferromagnetic cathode significantly supports cone growth. Detailed studies performed for sharp and flat single cones allow conclusions to be drawn on the support at different stages in the evolution of conical deformations. Furthermore, the influence from neighboring cones is studied with arrays of cones at varying distances apart. Nearby neighbors generally tend to mitigate the flow driven by the magnetic forces. Here, the support for cone growth originating from the magnetic gradient force is less heavily affected than that from the Lorentz force. Our results clearly show that the magnetic field has a beneficial effect on the growth of ferromagnetic conical structures, which could also be useful on the micro- and nanometer scales.

Keywords: metal electrodeposition; magnetic field; surface-structured electrode; Lorentz force; magnetic gradient force; numerical simulation


Publ.-Id: 31638

Capacity and sizing of wire mesh mist eliminators at critical fluid properties

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

Wire mesh flooding point measurements at low surface tension < 10 mN m-1 were conducted using a refrigerant as model fluid. A new method for the calculation of wire mesh capacity was developed based on experimental data from literature and data from this study. In comparison to the well-known and widely adapted K-value method given in the Gas Processors Suppliers Association (GPSA) Engineering Databook and various other sources, the new method yields 3-38 % reduced wire mesh cross-sections for fluid systems at pressures above 20 bar(g) while retaining an inherent safety margin.

Keywords: flooding point; K-value; wire-mesh; mist eliminator capacity

Publ.-Id: 31637

Morphology of flashing feeds at critical fluid properties in larger pipes

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

Tailored conditioning and control of flashing feeds in industrial applications requires knowledge of the evolving flow morphology and phase fractions along the feed pipe. Design methods obtained from reference systems (e.g. water/air) are hardly applicable for commercial scales and critical fluid properties (e.g. high vapor densities, low surface tension). In this study, the flow morphology of flashing feeds in a novel refrigerant test rig at critical fluid properties was analyzed using wire-mesh sensors at two locations along the feed pipe and experimental data from the water/air system.

Keywords: Flashing feed; Refrigerant cycle process; Two-phase flow morpholog; Wire-mesh sensor

Publ.-Id: 31636

Vortrag der Gleichstellungsbeauftragten des HZDR vor dem AGBR

Fiedler, F.

Vortrag der GSB vor dem AGBR

  • Lecture (others) (Online presentation)
    Treffen des AGBR, 27.10.2020, Dresden, Deutschland

Publ.-Id: 31635

Two-phase flow morphology and phase fractions in larger feed line sections

Döß, A.; Schubert, M.; Hampel, U.; Mehringer, C.; Geipel, C.; Schleicher, E.

The design of industrial feed line sections and the selection of appropriate inlet devices requires knowledge about the two-phase flow morphology and phase fractions in order to reduce costly overdesign. Since experimental data for two-phase pipe flows at industrial scale are hardly available, current prediction methods are subject to high unertainities. In this study, horizontal two-phase flow morphologies for different industrial feed line sections were studied using wire-mesh sensors at multiple locations along the pipe. The obtained phase fraction data are compared with correlations.

Keywords: Feed section; Flow morphology; Horizontal bend; Two-phase flow; Wire-mesh sensor

Publ.-Id: 31634

Electron dose rate and oxygen depletion protect zebrafish embryos from radiation damage

Pawelke, J.; Brand, M.; Hans, S.; Hideghéty, K.; Karsch, L.; Leßmann, E.; Löck, S.; Schürer, M.; Szabo, E. R.; Beyreuther, E.

Background and purpose
In consequence of a previous study, where no protecting proton Flash effect was found for zebrafish embryos, potential reasons and requirements for inducing a Flash effect should be investigated with the beam pulse structure and the partial oxygen pressure (pO2) as relevant parameters.
Materials and methods
The experiments were performed at the research electron accelerator ELBE, whose variable pulse structure enables dose delivery as electron Flash and quasi-continuously (reference). Zebrafish embryos were irradiated with ~26 Gy either continuously with a dose rate of ~6.7 Gy/min or in one 111 µs long pulse with a pulse dose rate of 109 Gy/s and a mean dose rate of 105 Gy/s, respectively. Using the OxyLite system to measure the pO2 a low- (pO2 ≤ 5 mmHg) and a high-pO2 group were defined on basis of the oxygen depletion kinetics in sealed embryo samples.
A protective Flash effect was seen for most endpoints ranging from 4 % less reduction in embryo length to about 20 – 25 % less embryos with spinal curvature and pericardial edema, relative to reference irradiation. The reduction of pO2 below atmospheric levels (148 mmHg) resulted in higher protection, which was however more pronounced in the low-pO2 group.
The Flash experiment at ELBE showed that the zebrafish embryo model is appropriate for studying the radiobiological response of high dose rate irradiation. Pulse dose and pulse dose rate as important beam parameters were confirmed as well as the pivotal role of pO2 during irradiation.

Keywords: Electron Flash effect; Oxygen depletion; Normal tissue toxicity; Zebrafish embryo

Related publications


Publ.-Id: 31633

Experience with the Sperradiant THz user Facility Driven by a Quasi-CW SRF Accelerator at ELBE

Bawatna, M.; Green, B. W.

Instabilities in beam and bunch parameters, such as bunch charge, beam energy, or changes in the phase or amplitude of the accelerating field in the RF cavities can be the source of noise in the various secondary sources driven by the electron beam. Bunch charge fluctuations lead to in-tensity instabilities in the superradiant THz sources. The primary electron beam driving the light sources has a maximum energy of 40 MeV and a maximum current of 1.6 mA. Depending on the mode of operation required, there are two available injectors in use at ELBE. The first is the thermionic injector, which is used for regular operating modes and supports repetition rates up to 13 MHz and bunch charges up to 100 pC. The second is the SRF photo-cathode injector, which is used for experiments that may require lower emittance or higher bunch charges of up to 1 nC. It has a maximum repetition rate of 13 MHz, which can be adjusted to lower rates if desired, also including different macro pulse modes of operation. In this contribution, we will present our work in the pulse-resolved intensity measurement that allows for the correction of intensity instabilities.

Related publications

  • Open Access Logo Contribution to proceedings
    FEL2019 - 39th International Free-Electron Laser Conference, 26.-30.08.2019, Hamburg, Germany
    Proceedings of the 39th International Free-Electron Laser Conference: JACoW, 978-3-95450-210-3
    DOI: 10.18429/JACoW-FEL2019-TUP007


Publ.-Id: 31632

Data for: Scanning transmission imaging in the helium ion microscope using a microchannel plate with a delay line detector

Serralta Hurtado De Menezes, E.; Klingner, N.; de Castro, O.; Mousley, M.; Eswara, S.; Duarte Pinto, S.; Wirtz, T.; Hlawacek, G.

  A detection system based on a microchannel plate with a delay line readout structure has been developed to perform scanning transmission ion microscopy (STIM) in the helium ion microscope (HIM). This system is an improvement over other existing approaches since it combines the information of the scanning beam position on the sample with the position (scattering angle) and time of the transmission events. Various imaging modes such as bright and dark field or the direct image of the transmitted signal can be created by post-processing the collected STIM data. Furthermore, the detector has high spatial and time resolution, is sensitive to both ions and neutral particles over a wide energy range, and shows robustness against ion beam-induced damage. A special in-vacuum movable support gives the possibility of moving the detector vertically, placing the detector closer to the sample for the detection of high-angle scattering events, or moving it down to increase the angular resolution and distance for time-of-flight measurements. With this new system, we show composition-dependent contrast for amorphous materials and the contrast difference between small and high angle scattering signals. We also detect channeling related contrast on polycrystalline silicon, thallium chloride nanocrystals, and single crystalline silicon by comparing the signal transmitted at different directions for the same data set.

Keywords: helium ion microscopy; scanning transmission ion microscopy; delay line detector; channeling; bright field; dark field

Related publications


Publ.-Id: 31631

A new approach for determining tray and point efficiencies via revamping of hydraulic air/water column mockups

Marchini, S.; Vishwakarma, V.; Schubert, M.; Brunazzi, E.; Hampel, U.

Tray and point efficiencies are the key parameters for characterizing the performance of a distillation tray.
The tray efficiencies are experimentally determined mostly by sampling the incoming and exiting streams of liquid and gas over the tray. Contrarily, the point efficiency determination is technically challenging and thus, it is derived mainly from correlations or small-scale experiments. Only few studies on the experimental determination of point efficiencies on large-scale distillation trays exist. However, the traditional physical systems pose several technical restrictions and safety concerns that often prevent their integration with the available air/water column mockups.
In this study, the stripping of isobutyl acetate from an aqueous solution using air is proposed as a physical system. It offers several advantages over the traditional ones (in terms of adaptability to different gas and liquid flow rates, safety and minimum revamping requirements), and is proved suitable for being readily integrated into existing cold fluid air/water mockups without any major modification.
The liquid concentration distribution on an 800 mm dia. distillation sieve tray was investigated by sampling the liquid at different deck locations for subsequent UV-spectroscopy. The concentration distribution was used to obtain the point efficiency values accounting for both axial and transverse liquid mixing on the tray. The concentration distributions, tray and point efficiency values obtained for different weir loads showed good agreement with the predictions given by the correlations and models used in the literature. The proposed approach can also account for the effect of weeping on the tray efficiency.
Potential future application of the proposed approach can address the investigation and design of novel tray concepts (e.g. with liquid flow conditioners), the development and validation of point and tray efficiency models as well as the validation of CFD simulations.

Keywords: tray efficiency; point efficiency; isobutyl acetate stripping; tray column; sieve tray; mockup revamp; weeping

  • Contribution to proceedings
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Wärme- und Stoffübertragung, 24.-26.02.2021, Leipzig, Germany

Publ.-Id: 31630

Negative resistance for colloids driven over two barriers in a microchannel

Zimmermann, U.; Löwen, H.; Kreuter, C.; Erbe, A.; Leiderer, P.; Smallenburg, F.

When considering the flow of currents through obstacles, one core expectation is that the total resis- tance of sequential single resistors is additive. While this rule is most commonly applied to electronic circuits, it also applies to other transport phenomena such as the flow of colloids or nanoparti- cles through channels containing multiple obstacles, as long as these obstacles are sufficiently far apart. Here we explore the breakdown of this additivity for fluids of repulsive colloids driven over two energetic barriers in a microchannel, using real-space microscopy experiments, particle-resolved simulations, and dynamical density functional theory. If the barrier separation is comparable to the particle correlation length, the resistance is highly non-additive, such that the resistance added by the second barrier can be significantly higher or lower than that of the first. Surprisingly, in some cases the second barrier can even add a negative resistance, such that two identical barriers are easier to cross than a single one. We explain this counterintuitive observation in terms of the structuring of particles trapped between the barriers.

Keywords: colloidal model systems; soft matter; transport phenomena

Related publications

Publ.-Id: 31629

Metal Pad Roll Instability at Room Temperature Using Pairs of Liquid Metals

Herreman, W.; Nore, C.; Cappanera, L.; Guermond, J.-L.; Weier, T.

Metal pad roll instability is a well known phenomenon that occurs in aluminium reduction cells [1] Since long, scientists and engineers have been searching for an experimental model that recreates the metal pad roll instability in a well controlled laboratory environment. [2] partly succeeded in this task by using GaInSn eutectic alloy in replacement of aluminium and a steel wire array, in replacement of the badly conducting cryolite layer. A rolling wave motion was observed but comparison to fluid based theoretical models remains difficult.
In this talk, we demonstrate that it is possible to observe metal pad roll instability in a centimeter scale cylindrical set-up at room temperature and using different liquid metal pairs as working fluids: gallium liquid metal over mercury (immiscible case) or gallium over GaInSn eutectic alloy (miscible case). Despite the small difference in electrical conductivity, the stability theory of [3] suggests that metal pad roll instability occurs for reasonable values of the imposed magnetic field and electrical current. We confirm this theoretical prediction with some very challenging direct numerical simulations of the multiphase magnetohydrodynamical flow in this set-up, done with our massively parallel solver SFEMaNS [4].

Keywords: liquid metal battery; aluminum reduction cell; metal pad roll instability

  • Lecture (Conference) (Online presentation)
    14th World Congress on Computational Mechanics, 11.-15.01.2021, Paris, Frankreich

Publ.-Id: 31628

Propagation of spin waves through a Néel domain wall

Wojewoda, O.; Hula, T.; Flajšman, L.; Vaňatka, M.; Gloss, J.; Holobrádek, J.; Staňo, M.; Stienen, S.; Körber, L.; Schultheiß, K.; Schmid, M.; Schultheiß, H.; Urbánek, M.

Spin waves have the potential to be used as a next-generation platform for data transfer and processing as they can reach wavelengths in the nanometer range and frequencies in the terahertz range. To realize a spin-wave device, it is essential to be able to manipulate the amplitude as well as the phase of spin waves. Several theoretical and recent experimental works have also shown that the spin-wave phase can be manipulated by the transmission through a domain wall (DW). Here, we study propagation of spin waves through a DW by means of micro-focused Brillouin light scattering microscopy (μBLS). The 2D spin-wave intensity maps reveal that spin-wave transmission through a Néel DW is influenced by a topologically enforced circular Bloch line in the DW center and that the propagation regime depends on the spin-wave frequency. In the first regime, two spin-wave beams propagating around the circular Bloch line are formed, whereas in the second regime, spin waves propagate in a single central beam through the circular Bloch line. Phase-resolved μBLS measurements reveal a phase shift upon transmission through the domain wall for both regimes. Micromagnetic modeling of the transmitted spin waves unveils a distortion of their phase fronts, which needs to be taken into account when interpreting the measurements and designing potential devices. Moreover, we show that, by means of micromagnetic simulations, an external magnetic field can be used to move the circular Bloch line within the DW and to manipulate spin-wave propagation.
The authors thank R. Schäfer and O. Fruchart for the discussions on the DW classification.
This research was supported by the CEITEC Nano+ project (No. CZ.02.1.01/0.0/0.0/16013/0001728) and Austrian Science Fund (FWF) project I1937. M. Staňo acknowledges support by the ESF under the project CZ.02.2.69/0.0/0.0/19_074/0016239. CzechNanoLab project LM2018110 funded by MEYS CR is gratefully acknowledged for the financial support of the measurement and sample fabrication at the CEITEC Nano Research Infrastructure.

Keywords: Magnetic ordering; Spectrum analyzer; Light scattering; Magnetic force microscopy

Publ.-Id: 31627

Zero-field propagation of spin waves in waveguides prepared by focused ion beam direct writing

Flajšman, L.; Wagner, K.; Vaňatka, M.; Gloss, J.; Křižáková, V.; Schmid, M.; Schultheiß, H.; Urbánek, M.

Metastable face-centered-cubic Fe78Ni22 thin films are excellent candidates for focused ion beam direct writing of magnonic structures due to their favorable magnetic properties after ion-beam-induced transformation. The focused ion beam transforms the originally nonmagnetic fcc phase into the ferromagnetic bcc phase with additional control over the direction of uniaxial magnetic in-plane anisotropy and saturation magnetization. Local magnetic anisotropy direction control eliminates the need for external magnetic fields, paving the way towards complex magnonic circuits with waveguides pointing in different directions. In the present study, we show that the magnetocrystalline anisotropy in transformed areas is strong enough to stabilize the magnetization in the direction perpendicular to the long axis of narrow waveguides. Therefore, it is possible to propagate spin waves in these waveguides in the favorable Damon-Eshbach geometry without the presence of any external magnetic field. Phase-resolved microfocused Brillouin light scattering yields the dispersion relation of these waveguides in zero as well as in nonzero external magnetic fields.

Keywords: Ferromagnetism; Magnetic Anisotropy; Magnetic phase transition; Magnetization Dynamics; Spin Dynamics; Spin Waves; Structural Phase transition; Focused ion beam


Publ.-Id: 31626

Performance investigation of bulk photoconductive semiconductor switch based on reversely biased p+in+ structure

Hu, L.; Xu, M.; Li, X.; Wang, Y.; Wang, Y.; Dong, H.; Schneider, H.

We present an investigation of a low-energy-triggered bulk gallium arsenide (GaAs) photoconductive semiconductor switch (PCSS) that is characterized by powerful avalanche domains. The performance of the switch is investigated using a reversely biased p⁺-i-n⁺ structure with 0.625-mm thickness, and the 8.0-kV, 170-ps bulk PCSS that is triggered by a 905-nm laser at the energy of 5.7 nJ is achieved. In the low-energy-triggered mode, it is found experimentally that the reduction of required energy for switching operation is not always kept by the continuous increase of the bias field in the bulk PCSS due to Franz–Keldysh effect. We also analyze the triggering efficiency depending on the laser wavelength numerically, and results indicate that the earlier formation of the powerful avalanche domains is realized by the increased wavelength, which causes lower laser energy for switching operation. Moreover, the prestudy of high-power microwave (HPM) applications is also introduced utilizing bulk PCSS, and we constructed the basic units for ultrawide-band (UWB) pulse and HPM-driven pulse.

Keywords: photoconductive semiconductor switch; avalanche domain; GaAs


Publ.-Id: 31625

Mode-locked short pulses from an 8 μm wavelength semiconductor laser

Hillbrand, J.; Opačcak, N.; Piccardo, M.; Schneider, H.; Strasser, G.; Capasso, F.; Schwarz, B.

Quantum cascade lasers (QCL) have revolutionized the generation of mid-infrared light. Yet, the ultrafast carrier transport in mid-infrared QCLs have so far constituted a seemingly insurmountable obstacle for the formation of ultrashort light pulses. Here, we demonstrate that careful quantum design of the gain medium and control over the intermode beat synchronization enable transform-limited picosecond pulses from QCL frequency combs. Both an interferometric radio-frequency technique and second-order autocorrelation shed light on the pulse dynamics and confirm that mode-locked operation is achieved from threshold to rollover current. Furthermore, we show that both antiphase and in-phase synchronized states exist in QCLs. Being electrically pumped and compact, mode-locked QCLs pave the way towards monolithically integrated non-linear photonics in the molecular fingerprint region beyond 6 μm wavelength.

Keywords: quantum cascade laser; two-photon QWIP; mid-infrared, frequency comb

Publ.-Id: 31624

Wire-mesh sensor measurements of single-phase liquid flows at different temperatures

Wiedemann, P.; de Assis Dias, F.; Schleicher, E.; Hampel, U.

The dataset contains raw data belonging to Wiedemann et al.: Temperature Compensation for Conductivity-Based Phase Fraction Measurements with Wire-Mesh Sensors in Gas-Liquid Flows of Dilute Aqueous Solutions, Sensors 2020, 20(24), 7114;

A 16x16 conductivity-based wire-mesh sensor was placed in a single-phase liquid loop with adjustable fluid temperature. The dataset includes the wire-mesh sensor measurements with water at several temperature levels from 12.5°C to 80°C and the corresponding electrical conductivites. Two water samples, namely deionized water and a mixed water sample, were investigated. The latter one is composed of 95% deionized water and 5% local tap water.

Keywords: wire-mesh sensor; temperature compensation; electrical conductivity

Related publications


Publ.-Id: 31623

High-Intensity Laser-Driven Oxygen Source from CW Laser-Heated Titanium Tape Targets

Kondo, K.; Nishiuchi, M.; Sakaki, H.; Dover, N. P.; Lowe, H. F.; Miyahara, T.; Watanabe, Y.; Ziegler, T.; Zeil, K.; Schramm, U.; Ditter, E. J.; Hicks, G. S.; Ettlinger, O. C.; Najmudin, Z.; Kiriyama, H.; Kando, M.; Kondo, K.

The interaction of high-intensity laser pulses with solid targets can be used as a highly charged, energetic heavy ion source. Normally, intrinsic contaminants on the target surface suppress the performance of heavy ion acceleration from a high-intensity laser–target interaction, resulting in preferential proton acceleration. Here, we demonstrate that CW laser heating of 5 µm titanium tape targets can remove contaminant hydrocarbons in order to expose a thin oxide layer on the metal surface, ideal for the generation of energetic oxygen beams. This is demonstrated by irradiating the heated targets with a PW class high-power laser at an intensity of 5 x 10^21 W/cm^2, showing enhanced acceleration of oxygen ions with a non-thermal-like distribution. Our new scheme using a CW laser-heated Ti tape target is promising for use as a moderate repetition energetic oxygen ion source for future applications.

Keywords: Ti Sapphire laser; high-power laser; laser-driven heavy ion acceleration; surface treatment; CW laser heating; oxygen ion source

Publ.-Id: 31622

Chemical reactions in bubbly flows

Hampel, U.; Kipping, R.; Zähringer, K.; Kováts, P.; Sommerfeld, M.; Taborda, M. A.; Rzehak, R.; Hlawitschka, M.; Klüfers, P.; Oßberger, M.

Reactive bubbly flows are found in many chemical and biochemical process-es. They are characterized by complex hydrodynamics that govern global mass transfer and reaction rates. Effects, which have to be taken into account when modelling and simulating the reaction progress are enhanced bubble-bubble interaction and bubble-induced turbulence as well as swarm-induced macro-convection. This poses great challenges on both, experimental analysis and numerical simulation. Bubble swarms at higher gas fractions are opaque, which limits the use of optical flow measurement techniques. Moreover, simu-lations at industrial scale are only feasible with point-bubble-based Euler-Euler or Euler-Lagrange approaches. Such approaches require closure relations, which account for all relevant interfacial forces as well as bubble-induced tur-bulence and coalescence including swarm effects. This chapter describes the progress in the experimental analysis and CFD simulation of reactive bubbly flows achieved during the time of the DFG Priority Programme SPP 1740. Ex-perimental studies in bubble columns reported in this Chapter were carried out at TU Dresden and OVGU Magdeburg. CFD model development and simula-tion has been carried out at OVGU Magdeburg using the Euler-Euler and Euler-Lagrange method and at TU Kaiserslautern and Helmholtz-Zentrum Dresden-Rossendorf using the Euler-Euler approach. As reaction systems the chemi-sorption of CO2 in NaOH solution and the reaction of FeII(edta) with NO were studied.

  • Book chapter
    Michael Schlüter, Dieter Bothe, Sonja Herres-Pawlis, Ulrich Nieken: Reactive Bubbly Flows, Heidelberg: Springer, 2021, 978-3-030-72361-3, 583-619
    DOI: 10.1007/978-3-030-72361-3_23

Publ.-Id: 31621

Experimental studies on the hydrodynamics, mass transfer and reaction in bubble swarms with ultrafast X-ray tomography and local probes

Kipping, R.; Kryk, H.; Hampel, U.

The main focus of this project was the experimental investigation of hydrody-namics and mass transfer characteristics together with a chemical reaction in a bubble column at higher gas holdup. Experiments were performed for chemical absorption of CO2 in alkaline solution of different pH, at homogenous bubbly flow conditions and up to 17% gas holdup. Ultrafast electron beam X-ray to-mography (UFXCT) has been used to obtain local gas holdup data and bubble characteristics and a wire-mesh sensor was used to measure species concentra-tion fields in the liquid bulk. In addition, experiments with the reactive system FeII(edta)/NO were carried out and a new a fiber optical probe was employed for local measurement of product concentration in the bubble wake.

  • Book chapter
    Michael Schlüter, Dieter Bothe, Sonja Herres-Pawlis, Ulrich Nieken: Reactive Bubbly Flows, Heidelberg: Spinger, 2021, 978-3-030-72361-3, 115-136
    DOI: 10.1007/978-3-030-72361-3_7

Publ.-Id: 31620

Frequency control of auto-oscillations of the magnetization in spin Hall nano-oscillators

Hache, T.

This thesis experimentally demonstrates four approaches of frequency control of magnetic autooscillations in spin Hall nano-oscillators (SHNOs).
The frequency can be changed in the GHZ-range by external magnetic fields as shown in this work. This approach uses large electromagnets, which is inconvenient for future applications.The nonlinear coupling between oscillator power and frequency can be used to control the latter one by changing the applied direct current to the SHNO. The frequency can be controlled over a range of several 100 MHz as demonstrated in this thesis.
The first part of the experimental chapter demonstrates the synchronization (injection-locking) between magnetic auto-oscillations and an external microwave excitation. The additionally applied microwave current generates a modulation of the effective magnetic field, which causes the interaction with the auto-oscillation. Both synchronize over a range of several 100 MHz. In this range, the auto-oscillation frequency can be controlled by the external stimulus. An increase of power and a decrease of line width is achieved in the synchronization range. This is explained by the increased coherence of the auto-oscillations. A second approach is the synchronization of auto-oscillations to an alternating magnetic field. This field is generated by a freestanding antenna, which is positioned above the SHNO.
The second part of the experimental chapter introduces a bipolar concept of SHNOs and its experimental demonstration. In contrast to conventional SHNOs, bipolar SHNOs generate autooscillations for both direct current polarities and both directions of the external magnetic field. This is achieved by combining two ferromagnetic layers in an SHNO. The combination of two different ferromagnetic materials is used to switch between two frequency ranges in dependence of the direct current polarity since it defines the layer showing auto-oscillations. This approach can be used to change the frequency in the GHz-range by switching the direct current polarity.

Related publications


Publ.-Id: 31619

Frequency control of auto-oscillations of the magnetization in spin Hall nano-oscillators

Hache, T.

This thesis experimentally demonstrates four approaches of frequency control of magnetic autooscillations in spin Hall nano-oscillators (SHNOs).
The frequency can be changed in the GHZ-range by external magnetic fields as shown in this work. This approach uses large electromagnets, which is inconvenient for future applications.The nonlinear coupling between oscillator power and frequency can be used to control the latter one by changing the applied direct current to the SHNO. The frequency can be controlled over a range of several 100 MHz as demonstrated in this thesis.
The first part of the experimental chapter demonstrates the synchronization (injection-locking) between magnetic auto-oscillations and an external microwave excitation. The additionally applied microwave current generates a modulation of the effective magnetic field, which causes the interaction with the auto-oscillation. Both synchronize over a range of several 100 MHz. In this range, the auto-oscillation frequency can be controlled by the external stimulus. An increase of power and a decrease of line width is achieved in the synchronization range. This is explained by the increased coherence of the auto-oscillations. A second approach is the synchronization of auto-oscillations to an alternating magnetic field. This field is generated by a freestanding antenna, which is positioned above the SHNO.
The second part of the experimental chapter introduces a bipolar concept of SHNOs and its experimental demonstration. In contrast to conventional SHNOs, bipolar SHNOs generate autooscillations for both direct current polarities and both directions of the external magnetic field. This is achieved by combining two ferromagnetic layers in an SHNO. The combination of two different ferromagnetic materials is used to switch between two frequency ranges in dependence of the direct current polarity since it defines the layer showing auto-oscillations. This approach can be used to change the frequency in the GHz-range by switching the direct current polarity.

Keywords: spin Hall nano-oscillator; magnetic auto-oscillations; pure spin current; bipolar; injection-locking; microwave; spin-wave; spin orbit torque; spin-transfer torque; magnetization dynamic

Related publications

  • Doctoral thesis
    TU Chemnitz, 2021

Publ.-Id: 31617

Magnetic texture based magnonics

Yu, H.; Xiao, J.; Schultheiß, H.

The spontaneous magnetic orders arising in ferro-, ferri- and antiferromagnets stem from various magnetic interactions. Depending on the interplay and competition among the Heisenberg exchange interaction, Dzyaloshinskii-Moriya exchange interaction, magnetic dipolar interaction and crystal anisotropies, a great variety of magnetic textures may be stabilized, such as magnetic domain walls, vortices, Skyrmions and spiral helical structures. While each of these spin textures responds to external forces in a specific manner with characteristic resonance frequencies, they also interact with magnons, the fundamental collective excitation of the magnetic order, which can propagate in magnetic materials free of charge transport and therefore with low energy dissipation. Recent theories and experiments found that the interplay between spin waves and magnetic textures is particularly interesting and rich in physics. In this review, we introduce and discuss the theoretical framework of magnons living on a magnetic texture background, as well as recent experimental progress in the manipulation of magnons via magnetic textures. The flexibility and reconfigurability of magnetic textures are discussed regarding the potential for applications in information processing schemes based on magnons.

Keywords: magnetic textures; spin waves; magnetization dynamics; Skyrmions; antiferromagnets; Dzyaloshinskii Moria; chiral magnetism; domain walls; vortices


Publ.-Id: 31616

Potential microbial influence on the performance of subsurface, salt-based nuclear waste repositories

Swanson, J. S.; Bader, M.; Cherkouk, A.

Microrganisms can influence the performance of nuclear waste repositories through activities or processes that affect radionuclide migration. In the case of subterranean salt-based repositories, the influence of microorganisms may be limited by the unique constraints of such sutes (e.g. high ionic strength, low water activity, nutient supply) coupled with conditions of the repositories themselves (e.g. anoxia,radioactivity, high temperatures). Indigenous extremely halophilic archaea can survive long-term at high ionic strength and may remain viable throughout a repository´s lifetime. However, their ability to affect repository performance through waste and radionuclide transformation is uncertain, as they are mostly arobic and repositories are projected to be anoxic. Microorganisms introduced with waste may contribute to transformations within drums but may not survive high salt concentrations once drums have been breached and inundated with brine. However, both indigenous and introduced organisms may associate with radionuclides and enhance or mitigate radionuclide migration in this capacity.

  • Book chapter
    Jonathan Lloyd, Andrea Cherkouk: The Microbiology of Nuclear Waste Disposal 1st Edition, Amsterdam: Elsevier, 2020, 978-0-12-818695-4

Publ.-Id: 31615

Molecular techniques for understanding microbial abundance and activity in clay barriers used for geodisposal

Mijnendonckx, K.; Monsieurs, P.; Cerna, K.; Hlavackova, V.; Steinova, J.; Burzan, N.; Bernier-Latmani, R.; Boothman, C.; Miettinen, H.; Kluge, S.; Matschiavelli, N.; Cherkouk, A.; Jroundi, F.; Larbi Merroun, M.; Engel, K.; Neufeld, J. D.; Leys, N.

Clays are commonly used in design concepts for geological disposal of nuclear waste. It is thus essential to identify and quantify microbial communities in clay-rich samples to study microbial processes during geological disposal. Although advances in culture-independent techiques have enablesd detailed studies of microbial communities in diverse ecosystems, the efficiency and sensitivity of these molecular techniques depend on chartacteristics of the environment studied. Moreover, the outcome of nucleic acid-based approaches depends on the extraction method, prmer specificity, PCR amplification, sequencing artefacts and downstream bioinformatic analyses. Clays are recalcitrant to DNA extraction and are challenging for analysis by standard techniques using viability stains and measurement of metabolic activity. This chapter explores the impact of various sequencing and bioinformatic pipelines used for 16S rRNA gene profiling of microbial communities and compares the efficiency of different DNA extraction methods from clay. Moreover, non-DNA based techniques used to assess microbial activity and viability in clay samples will be also discussed.

  • Book chapter
    Jonathan Lloyd Andrea Cherkouk: The Microbiology of Nuclear Waste Disposal 1st Edition, Amsterdam: Elsevier, 2020, 978-0-12-818695-4

Publ.-Id: 31614

The Microbiology of Nuclear Waste Disposal

Lloyd, J.; Cherkouk, A.

The Microbiology of Nuclear Waste Disposal is a state-of-the-art reference featuring contributions focusing on the impact of microbes on the safe long-term disposal of nuclear waste. This book is the first to cover this important emerging topic, and is written for a wide audience encompassing regulators, implementers, academics, and other stakeholders. The book is also of interest to those working on the wider exploitation of the subsurface, such as bioremediation, carbon capture and storage, geothermal energy, and water quality.

Planning for suitable facilities in the U.S., Europe, and Asia has been based mainly on knowledge from the geological and physical sciences. However, recent studies have shown that microbial life can proliferate in the inhospitable environments associated with radioactive waste disposal, and can control the long-term fate of nuclear materials. This can have beneficial and damaging impacts, which need to be quantified.

  • Book (Editorship)
    Amsterdam: Elsevier, 2020
    ISBN: 9780128186954

Publ.-Id: 31613

Raw data: CoFeB beamtime overview

Awari, N.; Deinert, J.-C.

Collection of raw data and evaluated data for the CoFeB experiments carried out in collaboration with Stefano Bonetti et al.

Keywords: Spin dynamics; nutation; CoFeB; Terahertz

Related publications


Publ.-Id: 31612

Parametric optimization in rougher flotation performance of a sulfidized mixed copper ore

Hassanzadehmahaleh, A.; Azizi, A. A.; Masdarian, M. A.; Bahri, Z. C.; Niedoba, T. D.; Surowiak, A. D.

The dominant challenge of current copper beneficiation plants is the low recoverability of oxide copper-bearing minerals associated with sulfide type ones. Furthermore, applying commonly used conventional methodologies does not allow the interactional effects of critical parameters in the flotation processes to be investigated, which is mostly overlooked in the literature. To tackle this issue, the present paper aimed at characterizing the behavior of five key effective factors and their interactions in a sulfidized copper ore. In this context, dosage of collector (sodium di-ethydithiophosphate, 60–100 g/t), depressant (sodium silicate, 80–120 g/t) and frother (methyl isobutyl carbinol (MIBC), 6–10 g/t), pulp pH (7–11) and agitation rate (900–1300 rpm) were examined and statistically analyzed using response surface methodology. Flotation experiments were conducted in a Denver type agitated flotation cell at the rougher stage. The experimental results showed that increasing the pH (from 8 to 10) at low agitation rate (1000 rpm) enhanced the recovery from 80.36% to 85.22%, while at high agitation rate (1200 rpm), a slight declination occurred in the recovery. Meanwhile, increasing the collector dosage at a lower frother value (7 g/t), caused a reduction of about 4.44% in copper recovery owing to the interactions between factors, whereas at a higher frother level (9 g/t), the recovery was almost unchanged. The optimization process was also performed using the goal function approach, and maximum copper recovery of 92.75% was obtained using ~70 g/t collector, 110 g/t depressant, 7 g/t frother, pulp pH of 10 and 1000 rpm agitation rate.

Keywords: sulfidized copper ore; flotation; interaction effects; recovery; optimization

Publ.-Id: 31611

Sachbericht DELTA

Fogel, S.; Putra, R. A.

Das Ziel des Teilvorhabens des HZDR war die thermodynamische, strömungstechnische und regelungstechnische Beschreibung und Auslegung des Gesamtsystems des DELTA-Reaktors. Mit Hilfe von geeigneten Simulationsmethoden sollte das Betriebsverhalten des räumlich und thermisch eng gekoppelten Reaktorkonzepts von Hochtemperaturelektrolyse sowie Methanolsynthese untersucht und die durch den Projektpartner TUD-WKET durchgeführten Arbeiten zur konstruktiven Gestaltung des Prozesses begleitet und unterstützt werden. Im Projektverlauf sollte außerdem gemeinsam mit dem Projektpartner TUD-WKET ein Mess- und regelungstechnisches Konzept entwickelt sowie ein geeignetes Analysengerät zur Bestimmung des Produktgasgemisches des Reaktionssystems ausgewählt, beschafft und in die experimentelle Versuchsplattform integriert werden. Darüber hinaus sollte im Rahmen des Teilprojektes ein Simulationsmodell auf Systemebene erstellt und das Verhalten des DELTA-Reaktors unter fluktuierenden Lasten beschrieben werden.

Keywords: Power-to-X; Methanol; SOEC; Renewable Energies; Modelling; CFD; FEM

  • Other report
    Dresden: HZDR, 2020
    133 Seiten

Publ.-Id: 31610

Point and extended defects in heteroepitaxial β-Ga2O3 films

Saadatkia, P.; Agarwal, S.; Hernandez, A.; Reed, E.; Brackenbury, I. D.; Codding, C. L.; Liedke, M. O.; Butterling, M.; Wagner, A.; Selim, F. A.

Ga2O3 is emerging as an excellent potential semiconductor for high power and optoelectronic devices.
However, the successful development of Ga2O3 in a wide range of applications requires a full understanding of the role and nature of its point and extended defects. In this work, high quality epitaxial Ga2O3 films were grown on sapphire substrates by metal-organic chemical vapor deposition and fully characterized in terms of structural, optical, and electrical properties. Then defects in the films were investigated by a combination of depth-resolved Doppler broadening and lifetime of positron annihilation spectroscopies and thermally stimulated emission (TSE). Positron annihilation techniques can provide information about the nature and concentration of defects in the films, while TSE reveals the energy level of defects in the bandgap. Despite very good structural properties, the films exhibit short positron diffusion length, which is an indication of high defect density and long positron lifetime, a sign for the formation of Ga vacancy related defects and large vacancy clusters. These defects act as deep and shallow traps for charge carriers as revealed from TSE, which explains the reason behind the difficulty of developing conductive Ga2O3 films on non-native substrates. Positron lifetime measurements also show nonuniform distribution of vacancy clusters throughout the film depth. Further, the work investigates the modification of defect nature and properties through thermal treatment in various environments. It demonstrates the sensitivity of Ga2O3 microstructures to the growth and thermal treatment environments and the significant effect of modifying defect structure on the bandgap and optical and electrical properties of Ga2O3

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; Doppler broadening; defetcs; Ga2O3

Related publications


Publ.-Id: 31609

Contribution of bentonite and cementitious material to actinide retention under hyperalkaline conditions and increased ionic strength

Schmeide, K.

Our research aligns to conditions reported by the 'AnSichT' project, which evaluated the feasibility of a repository in German clay formations [1]. According to the developed site model 'NORD', Ca-bentonite and concrete will be used in the geo-engineered barrier as buffer and borehole sealing material as well as for stabilization of disposal tunnels. Pore waters of the North German clay deposits are characterized by high ionic strengths up to 4 M [2, 3]. The contact of such saline formation waters with concrete can result in an enhanced corrosion of concrete which will lead to formation of secondary phases and to the evolution of highly alkaline cement pore waters (10 < pH < 13). The hyperalkaline solutions, in turn, can influence the retention potential of the bentonite buffer as well as of the surrounding clay host rock towards radionuclides.
The U(VI) retention on Ca-bentonite at hyperalkaline conditions in mixed electrolyte solutions (‘diluted Gipshut solution’, I = 2.6 M) was found to be very effective at pH>10, even in the presence of carbonate and despite the prevalence of anionic aqueous uranyl species [4]. Above a certain pH, depending on the concentration of carbonate in solution, carbonate does not play a role in the aqueous U(VI) speciation anymore due to the predominance of hydrolysis. Two U(VI) surface complexes were identified by site-selective TRLFS and XAS.
The stability of U(VI) and Cm(III) doped calcium (aluminate) silicate hydrate (C-(A-)S-H) phases, as main phases of hardened cement paste, at high ionic strengths conditions was studied applying leaching solutions which simulate the contact with North German claystone formation water [5, 6]. With regard to C-S-H stability and radionuclide release, differences were found in dependence on C/S ratio, composition of leaching solution and kind of radionuclide. The high retention capability of C-S-H gel towards U(VI) and Cm(III) remained constant in NaCl- and Na2SO4-containing solutions with increased ionic strength. In the presence of carbonate, however, U(VI) retention was coupled to the alteration stage of the C-S-H structure as well as to pH evolution of leaching solution. The Cm(III) mobilization from C-S-H gel was very low due to additional Cm(III) incorporation into secondary phases as shown by site-selective TRLFS and XRD.
The results show that both bentonite and cementitious material constitute an important retention barrier for radionuclides under hyperalkaline conditions and increased ionic strength.

Keywords: bentonite; cement; concrete; uranium; organics; ionic strength

Related publications

  • Lecture (Conference)
    DAEF 2022 – 3rd Conference on Key Topics in Deep Geological Disposal, 04.-06.07.2022, Köln, Germany

Publ.-Id: 31608

Non-plasmonic improvement in photoconductive THz emitters using nano- and micro-structured electrodes

Singh, A.; Welsch, M.; Winnerl, S.; Helm, M.; Schneider, H.

We investigate here terahertz enhancement effects arising from micrometer and nanometer structured electrode features of photoconductive terahertz emitters. Nanostructured electrode based emitters utilizing the palsmonic effect are currently one of the hottest topics in the research field. We demonstrate here that even in the absence of any plasmonic resonance with the pump pulse, such structures can improve the antenna effect by enhancing the local d.c. electric field near the structure edges. Utilizing this effect in Hilbert-fractal and grating-like designs, enhancement of the THz field of up to a factor of ~ 2 is observed. We conclude that the cause of this THz emission enhancement in our emitters is different from the earlier reported plasmonic-electrode effect in a similar grating-like structure. In our structure, the proximity of photoexcited carriers to the electrodes and local bias field enhancement close to the metallization cause the enhanced efficiency. Due to the nature of this effect, the THz emission efficiency is almost independent of the pump laser polarization. Compared to the plasmonic effect, these effects work under relaxed device fabrication and operating conditions.

Keywords: Terahertz sources; Teraherhertz emitter; Photoconductive THz emitter; Photoconductive antenna

Related publications

Publ.-Id: 31607

Successful user operation of a superconducting radio-frequency photo electron gun with Mg cathodes at ELBE

Teichert, J.; Arnold, A.; Ciovati, G.; Deinert, J.-C.; Evtushenko, P.; Justus, M.; Kneisel, P.; Kovalev, S.; Kuntzsch, M.; Lehnert, U.; Lu, P.; Ma, S.; Murcek, P.; Michel, P.; Ryzhov, A.; Schaber, J.; Schneider, C.; Schurig, R.; Steinbrück, R.; Vennekate, H.; Will, I.; Xiang, R.

At the ELBE high power radiation facility, the second version of a superconducting radio frequency (SRF) photoinjector has been put into operation and is now routinely applied for user operation at the ELBE electron accelerator. SRF guns are suitable for generating continuous wave (CW) electron beam with high average currents and high beam brightness. The SRF gun at ELBE has the goal to generate short electron pulses with bunch charges of 200-300 pC at typical repetition rates of 100 kHz for the production of super radiant, coherent terahertz radiation. The SRF gun includes a 3.5-cell, 1.3 GHz niobium cavity and a superconducting solenoid. A support system with liquid nitrogen (LN2) cooling allows the operation of normal-conducting, high quantum efficiency photo cathodes. In the paper we present the design and performance of the SRF gun as well as beam measurements for the operation with Mg photocathodes and an acceleration gradient of 8 MV/m (4 MeV kinetic energy). Finally, we discuss the SRF gun application for production of coherent terahertz radiation at the ELBE facility.

Keywords: electron source; THz radiation; electron accelerator; photo injector; superconducting radio-frequency; photo cathode

Related publications

Publ.-Id: 31606

Temperature Compensation for Conductivity-Based Phase Fraction Measurements with Wire-Mesh Sensors in Gas-Liquid Flows of Dilute Aqueous Solutions

Wiedemann, P.; de Assis Dias, F.; Schleicher, E.; Hampel, U.

Wire-mesh sensors are well-established scientific instruments for measuring the spatio-temporal phase distribution of two-phase flows based on different electrical conductivities of the phases. Presently, these instruments are also applied in industrial processes and need to cope with dynamic operating conditions increasingly. However, since the quantification of phase fractions is achieved by normalizing signals with respect to a separately recorded reference measurement, the results are sensitive to temperature differences in any application. Therefore, the present study aims at proposing a method to compensate temperature effects in the data processing procedure. Firstly, a general approach is theoretically derived from the underlying measurement principle and compensation procedures for the electrical conductivity from literature models. Additionally, a novel semi-empirical model is developed on the basis of electrochemical fundamentals. Experimental investigations are performed using a single-phase water loop with adjustable fluid temperature in order to verify the theoretical approach for wire-mesh sensor applications and to compare the different compensation models by means of real data. Finally, the preferred model is used to demonstrate the effect of temperature compensation with selected sets of experimental two-phase data from a previous study. The results are discussed in detail and show that temperature effects need to be handled carefully --- not merely in industrial applications, but particularly in laboratory experiments.

Keywords: wire-mesh sensor; temperature compensation; multicomponent electrolyte solution; ionic conductivity; two-phase thermohydraulics

Publ.-Id: 31605

Gallium-binding peptides as a tool for the sustainable treatment of industrial waste streams

Schönberger, N.; Taylor, C. J.; Schrader, M.; Drobot, B.; Matys, S.; Lederer, F.; Pollmann, K.

Metalliferous process wastewater not only represents a major ecotoxicological burden but can also serve as a secondary raw material source for the recovery of critical raw materials (CRM) like gallium. Smart, innovative strategies are needed for the economic recovery of industrial metals from such CRM sources. Biotechnological approaches are powerful tools to develop effective, selective and eco-friendly strategies in resource recovery. A particularly promising approach utilizes tailor-made biomolecules (such as peptides), that can be engineered to aid in the targeted extraction of individual metals. The application of phage Surface Display technology allows the directed molecular evolution of peptide ligands. This method has been used to identify the Ga-binding peptides TMHHAAIAHPPH, NYLPHQSSSPSR, SQALSTSRQDLR, HTQHIQSDDHLA and NDLQRHRLTAGP. In this study, the metal-binding properties of these peptides were further characterized. The peptides differed decisively in their interaction with gallium; in some cases, complex formation with gallium was strongly dependent on the surrounding buffer conditions. The peptide with the amino acid sequence NYLPHQSSSPSR showed the most promising gallium-binding properties. The site-selective and covalent immobilization of the gallium-binding peptide on polystyrene beads resulted in a robust and efficient material. It is suitable for the selective adsorption and desorption of gallium from industrial wastewater utilizing citric acid as environmentally friendly eluent. Biosorption studies performed with model and real water samples showed an up to ten-fold better adsorption of gallium as well as its effective separation from other contaminants like arsenic. Computer modeling suggests the probable structure of the peptide in aqueous solution and postulate a possible binding site for gallium.

Keywords: Industrial wastewater; Peptide-based material; Biosorption; Gallium; Arsenic; Computer modeling; Isothermale titration microcalorimetry


Publ.-Id: 31604

Accelerating Finite-temperature Kohn-Sham Density Functional Theory with Deep Neural Networks

Ellis, J. A.; Fiedler, L.; Popoola, G. A.; Modine, N. A.; Stephens, J. A.; Thompson, A. P.; Cangi, A.; Rajamanickam, S.

We present a numerical modeling workflow based on machine learning which reproduces the total energies produced by Kohn-Sham density functional theory (DFT) at finite electronic temperature to within chemical accuracy at negligible computational cost. Based on deep neural networks, our workflow yields the local density of states (LDOS) for a given atomic configuration. From the LDOS, spatially resolved, energy-resolved, and integrated quantities can be calculated, including the DFT total free energy, which serves as the Born-Oppenheimer potential energy surface for the atoms. We demonstrate the efficacy of this approach for both solid and liquid metals and compare results between independent and unified machine-learning models for solid and liquid aluminum. Our machine-learning density functional theory framework opens up the path towards multiscale materials modeling for matter under ambient and extreme conditions at a computational scale and cost that is unattainable with current algorithms.

Keywords: machine learning; density functional theory; materials science

  • Open Access Logo Physical Review B 104(2021), 035120
    DOI: 10.1103/PhysRevB.104.035120
    Cited 14 times in Scopus
  • Open Access Logo Poster (Online presentation)
    41st Workshop on High-Energy-Density Physics with laser and ion beams, 01.-05.02.2021, Online, Germany
  • Lecture (Conference) (Online presentation)
    APS March Meeting 2021, 15.-19.03.2021, Online, USA


Publ.-Id: 31603

Code, data and supplementary material for: An improved contact method for quantifying the mixing of a binary granular mixture

Papapetrou, T. N.; Lecrivain, G.; Bieberle, M.; Boudouvis, A.; Hampel, U.

This material is related to the publication "An improved contact method for quantifying the mixing of a binary granular mixture", submitted on 13.05.2020 to Granular Matter. The original camera video, an intermediate masked video and the final preprocessed video used in the calculations, made from frames 4-1004 of the masked one, are included. The code used for all calculations in the paper and supplementary material, including the implementation of the mixing index evaluation methods, as well as the static artificial images and the generated data, are also included. All images used in the calculations are stored in the required data form. The figures of the paper are also included, as well as two supplementary materials: a version of Figure 12 with the points of the original contact method, and a discussion on the calculation of the minimum modified contact length.

Keywords: binary particle mixing; rotating drum; image analysis; mixing index; contact method; variance method

Related publications


Publ.-Id: 31602

Insight into the structure-property relationship of UO2 nanoparticles

Gerber, E.; Romanchuk, A. Y.; Weiss, S.; Bauters, S.; Schacherl, B.; Vitova, T.; Hübner, R.; Shams Aldin Azzam, S.; Detollenaere, D.; Banerjee, D.; Butorin, S. M.; Kalmykov, S. N.; Kvashnina, K.

Fast chemical deposition of uranium(IV) under reducing conditions at pH 8-11 results in the formation of highly crystalline UO2 nanoparticles (NPs) with sizes of 2-3 nm, which is similar to the formation mechanism of PuO2 NPs. UO2 NPs are characterized by various microscopic and spectroscopic techniques including high energy transmission electron microscopy (HRTEM), high energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. Despite U(IV) being the dominant oxidation state of the freshly prepared UO2 NPs, they readily oxidize to U4O9 with time and under the X-ray beam. This oxidation of NPs is accompanied by their growth in size to 6 nm. The high tendency of UO2 NPs towards oxidation differs from PuO2 NPs’ behaviour due to the extremely high stability of Pu(IV) and much lower stability of oxidized Pu(V/VI) as compared to U(V/VI).

Related publications

  • Open Access Logo Inorganic Chemistry Frontiers 8(2021)4, 1102-1110
    Online First (2020) DOI: 10.1039/D0QI01140A

Publ.-Id: 31601

The effect of Pd(II) chloride complexes anchoring on the formation and properties of Pd/MgAlOx catalysts

Belskaya, O. B.; Zaikovskii, V. I.; Gulyaeva, T. I.; Talsi, V. P.; Trubina, S. V.; Kvashnina, K.; Nizovskii, A. I.; Kalinkin, A. V.; Bukhtiyarov, V. I.; A. Likholobov, V.

Pd(II) chloride complexes were anchored using magnesium-aluminum layered double
hydroxides (LDHs) with interlayer anions 3 2 and ), which possess different exchange properties, and MgAl mixed oxide during its rehydration. It was shown that the catalysts of the same chemical composition with different size, morphology and electronic state of supported palladium particles can be synthesized by varying the localization of Pd precursor. The properties of Pd/MgAlOx catalysts were studied in aqueous-phase hydrogenation of furfural.
Anchoring of the Pd precursor in the interlayer space of LDHs is accompanied by the formation of non-isometric agglomerated palladium particles which contain less oxidized metal and show a higher activity toward hydrogenation of furfural. Magnesium-aluminum oxides in Pd/MgAlOx catalysts are rehydrated in the aqueous-phase reaction to yield the activated MgAl-LDH species as a support, which promotes the furfural conversion via hydrogenation of the furan cycle.

Related publications


Publ.-Id: 31600

Multi- and Hyperspectral Imaging

Lorenz, S.; Jackisch, R.; Booysen, R.; Zimmermann, R.; Gloaguen, R.

Multi- and hyperspectral (MS and HS) imaging are currently deployed at a wide range of spatial dimensions (“scales”), ranging from satellites observing the Earth and other planets down to lab-scale sensing for small sample spectral analysis. New techniques such as UAS-borne imaging or terrestrial scanning of vertical targets are emerging and allow to observe any target at a wide and contiguous range of scales. Deploying spectral imaging on unmanned aerial platforms or drones creates one of the most promising application fields of spectral imaging in the last decade. Lightweight, low-cost, customizable and usable by anyone and nearly anywhere, UAS close the scale gap between airborne and ground-based spectroscopy and offer individual solutions for the respective application. The following chapter will give an insight on the principles of multi- and hyperspectral imaging that are required to understand the physical nature of spectroscopic processes as well as sensor-specific and external influence factors during the acquisition of spectral data. In later sections, the state of the art on drone-borne multi-and hyperspectral sensors, common and application-specific data correction and processing workflows are given to outline remaining challenges.

  • Open Access Logo Book chapter
    A. Eltner, D. Hoffmeister, A. Kaiser, P. Karrasch, L. Klingbeil, A. Rovere, C. Stöcker: UAV in Environmental Sciences, Darmstadt: Wissenschaftliche Buchgesellschaft (WBG), 2022, 978-3-534-40588-6

Publ.-Id: 31599

Development of New 14 Cr ODS Steels by Using New Oxides Formers and B as an Inhibitor of the Grain Growth

Meza, A.; Macía, E.; García-Junceda, A.; Antonio Díaz, L.; Chekhonin, P.; Altstadt, E.; Serrano, M.; Eugenia Rabanal, M.; Campos, M.

In this work, new oxide dispersion strengthened (ODS) ferritic steels have been produced by powder metallurgy using an alternative processing route and characterized afterwards by comparing them with a base ODS steel with Y2O3 and Ti additions. Different alloying elements like boron (B), which is known as an inhibitor of grain growth obtained by pinning grain boundaries, and complex oxide compounds (Y-Ti-Zr-O) have been introduced to the 14Cr prealloyed powder by using mechanical alloying (MA) and were further consolidated by spark employing plasma sintering (SPS). Techniques such as x-ray diffraction (XRD), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to study the obtained microstructures.
Micro-tensile tests and microhardness measurements were carried out at room temperature to analyze the mechanical properties of the differently developed microstructures, which was considered to result in a better strength in the ODS steels containing the complex oxide Y-Ti-Zr-O. In addition, small punch (SP) tests were performed to evaluate the response of the material under high temperatures conditions, under which promising mechanical properties were attained by the materials containing Y-Ti-Zr-O (14Al-X-ODS and 14Al-X-ODS-B) in comparison with the other commercial steel, GETMAT. The differences in mechanical strength can be attributed to the precipitate’s density, nature, size, and to the density of dislocations in each ODS steel.

Publ.-Id: 31597

Feature extraction for hyperspectral mineral domain mapping: A test of conventional and innovative methods

Lorenz, S.; Ghamisi, P.; Kirsch, M.; Jackisch, R.; Rasti, B.; Gloaguen, R.

Hyperspectral (HS) imaging holds great potential for the mapping of geological targets. Innovative acquisition modes such as drone-borne or terrestrial remote sensing open up new scales and angles of observation, which allow to analyze small-scale, vertical, or difficult-to-access outcrops. A variety of available sensors operating in different spectral ranges can provide information about the abundance and spatial location of various geologic materials. However geological outcrops are inherently uneven and spectrally heterogeneous, may be covered by dust, lichen or weathering crusts, or contain spectrally indistinct objects, which is why classifications or domain mapping approaches are often used in geoscientific and mineral exploration applications as a means to discriminate mineral associations (e.g. ore or alteration zones) based on overall variations in HS data. Feature extraction (FE) algorithms are prominently used as a preparatory step to identify the first order variations within the data and, simultaneously, reduce noise and data dimensionality. The most established FE algorithms in geosciences are, by far, Principal Component Analysis (PCA) and Minimum Noise Fraction (MNF). Major progress has been conducted in the image processing community within the last decades, yielding innovative FE methods that incorporate spatial information for smoother and more accurate classification results. In this paper, we test the applicability of conventional (PCA, MNF) and innovative FE techniques (OTVCA: Orthogonal total variation component analysis and WSRRR: Wavelet-based sparse reduced-rank regression) on three case studies from geological HS mapping campaigns, including drone-borne mineral exploration, terrestrial paleoseismic outcrop scanning and thermal HS lithological mapping. This allows us to explore the performance of different FE approaches on complex geological data with sparse or partly inaccurate validation data. For all case studies, we demonstrate advantages of innovative FE algorithms in terms of classification accuracy and geological interpretability. We promote the use of advanced image processing methods for applications in geoscience and mineral exploration as a tool to support geological mapping activities.

Keywords: feature extraction; domain mapping; mineral exploration; image processing; hyperspectral imaging; classification


Publ.-Id: 31596

Numerical dimensioning of a pre-cooler for sCO2 power cycles to utilize industrial waste heat

Unger, S.; Müller, J.; Bangalore Mohankumar, M.; Rath, S.; Hampel, U.

The annual waste heat available from industry in the European Union is more than 2,700 PJ. Consequently, the utilization of the unexploited thermal energy will decisively contribute to a reduced overall power consumption and lower greenhouse gas emissions. Supercritical carbon dioxide (sCO2) power cycles offer a variety of advantages for that purpose compared to established power cycles. Such are a high conversion efficiency and a turbomachinery with high power density. The pre-cooler is one of the essential components in a sCO2 power cycle and the prediction of the flow and heat transfer characteristics is a challenging task. In the present investigation, cycle layouts were developed for two waste heat sources: a cement plant and a gas compressor station. The pre-cooler design as well as the boundary conditions of the numerical simulation were assessed by an analytical model. The most promising design was the printed circuit heat exchanger with inlet temperatures of 209 °C and 352 °C for the cement kiln and the gas turbine respectively. Subsequently, these heat exchangers were examined in more detail by the numerical code ANSYS CFX for sCO2 mass fluxes between 100 kg/(m^2 s) and 900 kg/(m^2 s). The pressure drop along the sCO2 channel was found insensitive to the channel diameter, but increased with the channel length and mass flux. However, the pressure drop of the coolant stream significantly depends on the channel diameter and thus a larger coolant channel diameter is recommended to maintain a reasonably low pressure drop. The overall heat transfer coefficient is limited by the heat transfer on the coolant side. Ultimately, pre-cooler designs were proposed for both waste heat systems, consisting of compact modular stainless steel plates with an sCO2 channel diameter of 0.5 mm, a coolant channel diameter of 0.8 mm, an sCO2 mass flux of 700 kg/(m^2 s) and a coolant mass flux of 1029 kg/(m^2 s). Based on these results more complex channels having internal fins were studied. The connection angle and the fin height was optimized, in order to improve the heat transfer performance.

Keywords: pre-cooler; numerical simulation; heat transfer; flow characteristics; waste heat

  • Contribution to proceedings
    The 4th European sCO2 Conference for Energy Systems, 22.-26.03.2021, Prague, Tschechien
    Proceedings of the 4th European sCO2 Conference for Energy Systems
  • Open Access Logo Energies 14(24)(2021), 8278
    DOI: 10.3390/en14248278

Publ.-Id: 31595

Numerical Analysis Related to the ROCOM Pressurized Thermal Shock Benchmark

Höhne, T.; Kliem, S.

The development, verification and validation of Computational Fluid Dynamics (CFD) codes in reference to nuclear power plant (NPP) safety has been a focus of many research organizations over the last decades. Therefore, a collection of Rossendorf Coolant Mixing Test Facility (ROCOM) CFD-grade experiments were made obtainable to line up a global International Atomic Energy Agency (IAEA) benchmark regarding Pressurized Thermal Shock (PTS) situations. The benchmark experiment describes the complicated flow structures in mixed convection zones of the RPV during PTS events. The experiments were utilized to validate CFD codes. Additionally a test suit with no buoyancy forces was elite to point out the influence of density variations. Compared to the sooner studies, the turbulence models of the CFD code improved a lot. The turbulence modelling approaches show a respectable agreement with the experimental data.

Keywords: Computational Fluid Dynamics; Reactor Design; CFD benchmark; ROCOM; Mixing

Publ.-Id: 31594

Computing single-particle flotation kinetics using automated mineralogy data and machine learning

Pereira, L.; Frenzel, M.; Hoang, D. H.; Tolosana Delgado, R.; Rudolph, M.; Gutzmer, J.

Studies of flotation kinetics are essential for understanding, predicting, and optimizing the selective recovery of minerals and metals through flotation. Recently, much effort has been made to use intrinsic ore properties to model flotation behavior. Particle-based characterization methods, e.g. SEM-based image analysis, has enabled much of this development. However, currently available methods for studies of flotation kinetics can not accommodate single-particle data, resulting in incomplete use of data that is readily available today. In this contribution, a method is introduced to fit kinetic flotation models to individual particles. This method, based on lasso-regularized multinomial logistic regression, allows for an in-depth understanding of particle flotation behavior as a function of all measured particle characteristics. With the proposed method, the joint influences of particle size, shape, as well as modal and surface compositions on the recovery of individual particles can be taken into unprecedented consideration. The results of the simulated particle behavior showed a very good agreement to the outcome of experimental works and follow well-described froth-flotation recovery behavior.

Keywords: Geometallurgy; process mineralogy; machine learning; froth flotation; particle-tracking

Publ.-Id: 31593

Automated mineralogy particle dataset: apatite flotation

Hoang, D. H.; Pereira, L.; Kupka, N.; Tolosana Delgado, R.; Frenzel, M.; Rudolph, M.; Gutzmer, J.

This particle dataset was used for demonstrating the particle-tracking method presented in the paper "Computing single-particle flotation kinetics using automated mineralogy data and machine learning", submitted to Minerals Engineering in 08/10/2020, by Lucas Pereira, Max Frenzel, Duong Huu Hoang, Raimon Tolosana-Delgado, Martin Rudolph, Jens Gutzmer from the Helmholtz Institute Freiberg for Resource Technology.

This data belongs to the flotation tests performed by Duong Huu Hoang, and presented in:

Hoang, D.H., Kupka, N., Peuker, U.A., Rudolph, M., 2018. Flotation study of fine grained carbonaceous sedimentary apatite ore – Challenges in process mineralogy and impact of hydrodynamics. Miner. Eng. 121, 196–204.

For this study, phosphate rock samples from the Lao Cai province, Vietnam, were provided by the Vietnam Apatite Limited Company. The objective of the flotation experiments was to determine the best way to efficiently separate fluorapatite from dolomite, calcite and silicates. After grinding for 8 minutes in a laboratory ball mill to assure a d90 of 67 µm, batch flotation tests were performed in a flotation cell built at the TU Bergakademie Freiberg. Corn starch ((C6H10O5)n) gelatinized with sodium hydroxide (NaOH) was used in combination with sodium silicate (Na2SiO3) to depress gangue minerals. The latter also acts as a fine particle dispersant. Solution pH was kept at 10 using the modifier sodium carbonate (Na2CO3), which can also be regarded as a depressant. Berol 2015 was used as the collector. Four concentrate fractions were collected after 0.75 min (CA), 1.50 min (CB), 3.00 min (CC), and 6.00 min (CD). In addition, a final tailings sample was collected (TD). Five replicates of the test were done to ensure reproducibility and produce enough sample mass for detailed characterization. All samples, including the feed, were wet sieved into four size fractions (-20 µm, +20 to -32 µm, +32 to -50 µm, and +50 µm) before characterization by MLA at the Helmholtz Institute Freiberg for Resource Technology. Samples were analyzed on a FEI Quanta 650F scanning electron microscope equipped with two Bruker Quantax X-Flash 5030 EDX detectors. The SEM was operated at 25 kV overall electron beam accelerating voltage and Extended BSE Liberation Analysis measurement mode. MLA results were validated with ICP-OES chemical assays. Particles from the flotation product samples (concentrate and tailings) are in the Traindata.csv file, while particles from the feed sample are in the FeedData.csv file. The weight distribution of each sample is given below:

Sample | wt.%

CA -20µm | 6.7

CA 20-32µm | 5.8

CA 32-50µm | 4.6

CA +50µm | 2.2

CB -20µm | 6.4

CB 20-32µm | 5.4

CB 32-50µm | 3.9

CB +50µm | 2.8

CC -20µm | 5.8

CC 20-32µm | 4.3

CC 32-50µm | 3.5

CC +50µm | 2.0

CD -20µm | 4.7

CD 20-32µm | 2.8

CD 32-50µm | 2.3

CD +50µm | 1.1

TD -20µm | 11.3

TD 20-32µm | 7.0

TD 32-50µm | 6.7

TD +50µm | 10.7

Feed -20µm | 36.60

Feed 20-32µm | 23.88

Feed 32-50µm | 21.75

Feed +50µm | 17.78

Variable names:

  • Mineral composition: Actinolite, Albite, Almandine, Apatite, Barite, Biotite, Calcite, Chalcopyrite, Clinochlore, Diopside, Dolomite, Fluorite, Hematite, Muscovite, Orthoclase, Plagioclase, Phlogopite, Pyrite, Pyrrhotite, Quartz, Rutile, Sanidine, Sphalerite_Fe, Titanite, Zircon.
  • Surface composition:,,,,,,,,,,,,,,,,,,,,,,,,
  • Size and shape: AspectRatio, Solidity, ECD
  • Sample identifier: Class - In this case, particles identified with "CA20", for example, are the particles from the <20µm size fraction of the first concentrate sample, while "TD50" are the particles from the >50µm size fraction of the final tailings sample.

Keywords: Apatite; Froth flotation; Automated mineralogy; Geometallurgy; Particle-tracking

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Publ.-Id: 31592

Technetium immobilization by chukanovite and its oxidative transformation products: Neural network analysis of EXAFS spectra

Schmeide, K.; Roßberg, A.; Bok, F.; Shams Aldin Azzam, S.; Weiß, S.; Scheinost, A.

The uptake of the fission product technetium (Tc) by chukanovite, an Fe(II) hydroxy carbonate mineral formed as a carbon steel corrosion product in anoxic and carbonate-rich environments, was studied under anoxic, alkaline to hyperalkaline conditions representative for nuclear waste repositories in deep geological formations with cement-based inner linings. The retention potential of chukanovite towards Tc(VII) is high in the pH range 7.8 to 12.6, evidenced by high solid-water distribution coefficients, log Rd ~ 6, and independent of ionic strength (0.1 or 1 M NaCl). Using Tc K-edge X-ray absorption spectroscopy (XAS) two series of samples were investigated, Tc chukanovite sorption samples and coprecipitates, prepared with varying Tc loadings, pH values and contact times. From the resulting 37 XAS spectra, spectral endmembers and their dependence on chemical parameters were derived by self-organizing (Kohonen) maps (SOM), a neural network-based approach of machine learning. X-ray absorption near-edge structure (XANES) data confirmed the complete reduction of Tc(VII) to Tc(IV) by chukanovite under all experimental conditions. Consistent with mineralogical phases identified by X-ray diffraction (XRD), SOM analysis of the extended X-ray absorption fine-structure (EXAFS) spectra revealed the presence of three species in the sorption samples, the speciation predominately controlled by pH: Between pH 7.8 and 11.8, TcO₂-dimers form inner-sphere sorption complexes at the surface of the initial chukanovite as well as on the surface of secondary magnetite formed due to redox reaction. At pH ≥11.9, Tc(IV) is incorporated in a mixed, chukanovite-like, Fe/Tc hydroxy carbonate precipitate. The same species formed when using the coprecipitation approach. Reoxidation of sorption samples resulted in a small remobilization of Tc, demonstrating that both the original chukanovite mineral and its oxidative transformation products, magnetite and goethite, contribute to the immobilization of Tc in the long term, thus strongly attenuating its environmental transport.

Keywords: chukanovite; XRD; XAS; incorporation; adsorption; redox; goethite; magnetite; machine learning

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Publ.-Id: 31591

Transient CFD Modeling of Matte Settling Behavior and Coalescence in an Industrial Copper Flash Smelting Furnace Settler

Schmidt, A.; Montenegro, V.; Wehinger, G. D.

Copper losses into slag within the flash furnace settler is an economically important topic for the primary copper production. Since the settler is not easily accessible to experimental studies due to harsh reaction conditions, numerical simulations are a promising alternative to obtain more insights into the settling behavior of matte. This study aims to increase the process understanding by developing a CFD flash furnace settler model of an industrial flash furnace. Thereby, the CFD model accounts for bath level changes, polydispersity and coalescence of matte. Coalescence is modeled by an own empirical model focusing on gravitational coalescence. Matte settling shows size-dependent sedimentation within the slag layer, as supported by an own sampling study. Lowering the slag viscosity by a third decreases the copper loss by approximately 37%, while slightly increasing it leads to comparable results. Finally, average copper losses of 0:98wt.% are estimated, finding good agreement with industrial data.

Keywords: Flash Smelting Furnace Settler; Matte Coalescence; Copper Loss; CFD

Publ.-Id: 31590

Raw data: Magnetic field-induced even-order harmonic generation in the three-dimensional Dirac semimetal Cd3As2

Deinert, J.-C.

Raw files from the TELBE beamtime August 2020 for exchange.

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Publ.-Id: 31589

Interactive results viewer: Computing single-particle flotation kinetics using automated mineralogy data and machine learning

Pereira, L.; Frenzel, M.; Hoang, D. H.; Tolosana Delgado, R.; Rudolph, M.; Gutzmer, J.

This plotting application allows the reader to interact with all results obtained in the case study presented in the publication

"Computing single-particle flotation kinetics using automated mineralogy data and machine learning", submitted on 07/10/2020 to Minerals Engineering and currently under review.

The interactive plot displays the flotation kinetics modelling outcome (k, Rmax, km) for single-particles. The user is able to filter particles according to their intrinsic properties (modal composition, surface composition, size, and shape), thus allowing the user to understand the influence of every particle property in their process (i.e. flotation) behavior.

The platform contains a help function to guide the user.

It can be accessed here: Pereira et al. 2021 Flotation kinetics platform.

Keywords: Geometallurgy; Particle-tracking; Froth flotation; Automated mineralogy

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Publ.-Id: 31588

Results of a randomized controlled phase III trial: efficacy of polyphenol-containing cystus® tea mouthwash solution for the reduction of mucositis in head and neck cancer patients undergoing external beam radiotherapy

Ebert, N.; Kensche, A.; Löck, S.; Hadiwikarta, W. W.; Hänsch, A.; Dörr, W.; Krause, M.; Hannig, C.; Baumann, M.

Purpose: To determine the effect of Cystus® tea (Naturprodukte Dr. Pandalis GmbH & Co. KG) as mouthwash compared to sage tea on oral mucositis in patients undergoing radio(chemo)therapy for head and neck cancer. Methods: In this randomized, prospective phase III study, 60 head and neck cancer patients with primary or postoperative radio(chemo)therapy were included between 04/2012 and 06/2014. They received either sage or Cystus® tea for daily mouthwash under therapy. Mucositis was scored twice a week following the Radiation Therapy Oncology Group and the European Organization for Research and Treatment Cancer (RTOG/EORTC) scoring system. Dental parameters were also recorded. Statistical evaluation of the primary endpoint was performed using t test and log rank test. Results: Data from 57 patients could be evaluated. Patient characteristics showed no significant difference between the two groups (n = 27 sage; n = 30 Cystus®). A total of 55 patients received the prescribed dose (60–66 Gy postoperative; 70–76.8 Gy primary). Mucositis grade 3 was observed in 23 patients (n = 11 sage; n = 12 Cystus®) and occurred between day 16 and 50 after start of therapy. There was no significant difference between the two groups in latency (p = 0.75) and frequency (p = 0.85) of the occurrence of mucositis grade 3. The self-assessment of the oral mucosa and the tolerability of the tea also showed no significant differences. Occurrence of dental pathologies appeared to increase over time after radiotherapy. Conclusion: Cystus® and sage tea have a similar effect on the occurrence of radiation-induced mucositis regarding latency and incidence. Cystus® tea mouthwash solution is tolerated well and can be applied in addition to intensive oral care and hygiene along with the application of fluorides. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

Keywords: Herbal tea; HNSC; COral mucositis; Radiation side effect; Supportive treatment

Publ.-Id: 31587

BGM MLA data from grinding kinetics experiments

Belo Fernandes, I.

Datasource from two sets of grinding experiments:

- from top size fraction -1600µm+1250µm

- from top size fraction -425µm+315µm

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Publ.-Id: 31586

Long-range magnetic order in the S = 1/2 triangular lattice antiferromagnet KCeS2

Bastien, G.; Rubrecht, B.; Haeussler, E.; Schlender, P.; Zangeneh, Z.; Avdoshenko, S.; Sarkar, R.; Alfonso, A.; Luther, S.; Onykiienko, Y. A.; Walker, H. C.; Kühne, H.; Grinenko, V.; Guguchia, Z.; Kataev, V.; Klauss, H.-H.; Hozoi, L.; van den Brink, J.; Inosov, D. S.; Büchner, B.; Wolter, A. U. B.; Doert, T.

Recently, several putative quantum spin liquid (QSL) states were discovered in S󠆶 = 1/2 rare-earth based triangular-lattice antiferromagnets (TLAF) with the delafossite structure. In order to elucidate the conditions for a QSL to arise, we report here the discovery of a long-range magnetic order in the Ce-based TLAF KCeS2 below TN = 0.38 K, despite the same delafossite structure. Finally, combining various experimental and computational methods, we characterize the crystal electric field scheme, the magnetic anisotropy and the magnetic ground state of KCeS2.

Publ.-Id: 31585

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