Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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Approved and published publications
Only approved publications
Effect of uniaxial stress on the electronic band structure of NbP
Schindler, C.; Noky, J.; Schmidt, M.; Felser, C.; Wosnitza, J.; Gooth, J.
The Weyl semimetal NbP exhibits a very small Fermi surface consisting of two electron and two hole pockets, whose fourfold degeneracy in k space is tied to the rotational symmetry of the underlying tetragonal crystal lattice. By applying uniaxial stress, the crystal symmetry can be reduced, which successively leads to a degeneracy lifting of the Fermi-surface pockets. This is reflected by a splitting of the Shubnikov–de Haas frequencies when the magnetic field is aligned along the c axis of the tetragonal lattice. In this study, we present the measurement of Shubnikov–de Haas oscillations of single-crystalline NbP samples under uniaxial tension, combined with state-of-the-art calculations of the electronic band structure. Our results show qualitative agreement between calculated and experimentally determined Shubnikov–de Haas frequencies, demonstrating the robustness of the band-structure calculations upon introducing strain. Furthermore, we predict a significant shift of the Weyl points with increasing uniaxial tension, allowing for an effective tuning to the Fermi level at only 0.8% of strain along the a axis.
Impact of the microbial origin and active microenvironment on the shape of biogenic elemental selenium nanomaterials
The role of the microbial origin and environment of the discharged nanomaterials in their shape change was investigated. Here, we show that the biogenic elemental selenium nanospheres (BioSe-Nanospheres) produced under mesophilic conditions (30 °C) by Escherichia coli K-12 remain spherically when exposed to heating (55 °C for 7 days), whereas those obtained by anaerobic granular sludge transform to biogenic elemental selenium nanorods (BioSe-Nanorods). The larger quantity of proteins present in the corona of the BioSe-Nanospheres produced by E. coli K-12 are responsible for their shape stability. However, the protein corona of BioSe-Nanospheres produced by E. coli K-12 was degraded by extracellular peptidases secreted upon co-incubation with Bacillus safensis JG-B5T bacteria, which led to their transformation to BioSe-Nanorods. This study consequently demonstrates that the shape of biogenic nanomaterials depends both on their microbial origin and microbial surrounding, which increases the complexity in determining their risk assessment.
Environmental Science & Technology 55(2021), 9161-9171
Online First (2021) DOI: 10.1021/acs.est.0c07217
Evolution of a hydrothermal ore-forming system recorded by sulphide mineral chemistry: A case study from the Plaka Pb-Zn-Ag Deposit, Lavrion, Greece
Laser ablation inductively-coupled plasma mass spectrometry and electron probe microanalysis were used to investigate the trace-element contents of sphalerite, chalcopyrite and pyrite from the Plaka Pb-Zn-Ag deposit, Lavrion, Greece. Using petrographic observations, the analytical results could be linked to the temporal evolution of the Plaka ore-forming system.
Sphalerite chemistry (Ga, Ge, In, Mn and Fe content) reliably records the temperature evolution of the system, with formation temperatures estimated by sphalerite geothermometry reproducing microthermometric results from previous fluid inclusion studies. Chalcopyrite chemistry also shows systematic variations with formation temperature, particularly for Cd, Co, Ge, In, Sn and Zn concentrations. Pyrite was only found in association with early high-temperature mineralisation, and no clear temperature trends could therefore be identified. We note, however, that its Se content is consistent with formation at the temperatures estimated from sphalerite chemistry.
In addition to these observations, comparing the results for the three investigated minerals allowed us to identify different classes of trace elements according to their temporal and spatial distribution in the ore-forming system. For instance, In concentrations appear to be highest in early high-temperature sulphide assemblages from the southern part of the deposit, while Ge concentrations are highest in late low-temperature assemblages from any part of the deposit.
These results demonstrate that the detailed study of multiple minerals in a single ore-forming system, well documented in terms of geology, paragenesis and conditions of formation, still has considerable untapped potential to provide important new insights into ore-forming processes.
Keywords: Sphalerite; Chalcopyrite; Pyrite; Trace elements; LA-ICP-MS; Lavrion
Mineralium Deposita 57(2022), 417-438
Online First (2021) DOI: 10.1007/s00126-021-01067-y
Cited 9 times in Scopus
Adding CUDA® Support to Cling: JIT Compile to GPUs
Jupyter Notebooks are omnipresent in the modern scientist's and engineer's toolbox just as CUDA C++ is in accelerated computing. We present the first implementation of a CUDA C++ enabled read-eval-print-loop (REPL) that allows to interactively "script" the popular CUDA C++ runtime syntax in Notebooks. With our novel implementation, based on LLVM, Clang and CERN's C++ interpreter Cling, the modern CUDA C++ developer can work as interactively and productively as (I)Python developers while keeping all the benefits of the vast C++ computing and library ecosystem coupled with first-class performance.
Keywords: Cling; CUDA; Jupyter Notebook; interactive C++; LLVM; interactive simulation; rapid prototyping
2020 Virtual LLVM Developers' Meeting, 06.-08.10.2020, Virtuell, USA
Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation
Origin-files, data for figure 3 and figure 4 of publication in J. Nucl. Mater.
Keywords: Neutron irradiation; FeCr alloys and steels
- DOI: 10.1016/j.jnucmat.2020.152341 references this (Id 31356) publication
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-21 Open access
Evaluation of Recyclability of a WEEE Slag by Means of Integrative X-Ray Computer Tomography and SEM-Based Image Analysis
Waste of electrical and electronic equipment (WEEE) is one of the fastest growing waste streams globally. Therefore, recycling of the valuable metals of this stream plays a vital role in establishing a circular economy. The smelting process of WEEE leads to significant amounts of valuable metals and rare earth elements (REEs) trapped in the slag phase. The effective manipulation of this phase transfer process necessitates detailed understanding and effective treatment to minimize these contents. Furthermore, an adequate process control to bring these metal contents into structures that make recycling economically applicable is required. Within the present study, a typical slag from a WEEE melting process is analyzed in detail. Therefore, the material is investigated with the help of X-ray computed tomography (XCT) and scanning electron microscopy (SEM)-based mineralogical analysis (MLA) to understand the typical structures and its implications for recycling. The influencing factors are discussed, and further processing opportunities are illustrated.
Keywords: waste of electrical and electronic equipment; X-ray computed tomography; mineral liberation analysis
Spectral X-ray Computed Micro Tomography: 3-dimensional chemical imaging
We present a new approach to 3-dimensional chemical imaging based on computed tomography (CT), which allows a reconstruction of the internal elemental chemistry. The method uses a conventional laboratory based CT scanner combined with a semiconductor detector (CdTe). Based on the X-ray absorption spectrum, elements in a sample can be distinguished by their K-edge energy, which is specific. Different experiments have been preformed to test the performance of the system i.e. single pure element particle measurements, element differentiation in mixtures, and mineral differentiation in a gold ore sample. The results show that the method is able to distinguish elements in the samples with K-edges in the range of 20 to 160 keV, which corresponds to an elemental range from Ag to U. Furthermore, the spectral information allows a distinction between materials, which show no variation in contrast in the reconstructed CT image.
Keywords: X-ray computed tomography; Spectral X-ray tomography; Photon counting detector; 3D imaging
X-Ray Spectrometry 50(2021), 92-105
Online First (2020) DOI: 10.1002/xrs.3200
Cited 10 times in Scopus
CFD Modeling and Experimental Validation of Top-Submerged-Lance Gas Injection in Liquid Metal
Reuter, M. A.; Akashi, M.; Kriebitzsch, S.; Meyer, B.; Obiso, D.; Eckert, S.; Richter, A.
In the present work, the dynamics of a downward gas injection into a liquid metal bath is studied using a numerical modeling approach, and validated with experimental data. As in a top-submerged-lance (TSL) smelter, gas is injected through the lance into the melt. By this means, the properties of the liquid are closer to the actual industrial process than the typically used water/glycerol–air/helium systems. The experimental activity was carried out in a quasi-2D vessel (144 x 144 x 12 mm3) filled with GaInSn, a metal alloy with eutectic at room temperature. Ar was used as the inert gas. The structure and behavior of the gas phase were visualized and quantitatively analyzed by X-ray radiography and high-speed imaging. Computational Fluid Dynamics (CFD) was applied to simulate the multiphase flow in the vessel and the Volume Of Fluid (VOF) model chosen to track the interface using a geometric reconstruction of the interface. Three different vertical lance positions were investigated, applying a gas flow rate of Qgas = 6850 cm³/min: The CFD model is able to predict the bubble detachment frequency, the average void fraction distributions, and the bubble size and hydrodynamic behavior, demonstrating its applicability to simulate such complex multiphase systems. The use of numerical models also provides a deep insight into fluid dynamics to study particular phenomena such as bubble break-up and free surface oscillations.
Keywords: top-submerged-lance (TSL),; X-ray,; Computational Fluid Dynamics (CFD),; Volume Of Fluid (VOF),
Metallurgical and Materials Transactions B 51(2020), 1509-1525
Online First (2020) DOI: 10.1007/s11663-020-01864-2
Cited 14 times in Scopus
Engineering telecom single-photon emitters in silicon for scalable quantum photonics
We create and isolate single-photon emitters with a high brightness approaching 10⁵ counts per second in commercial silicon-on-insulator (SOI) wafers. The emission occurs in the infrared spectral range with a spectrally narrow zero phonon line in the telecom O-band and shows a high photostability even after days of continuous operation. The origin of the emitters is attributed to one of the carbon-related color centers in silicon, the so-called G center, allowing purification with the ¹²C and ²⁸Si isotopes. Furthermore, we envision a concept of a highly-coherent scalable quantum photonic platform, where single-photon sources, waveguides and detectors are integrated on the same SOI chip. Our results provide a route towards the implementation of quantum processors, repeaters and sensors compatible with the present-day silicon technology.
Keywords: Signe photon source; telecommunication window; silicon photonics; quantum communication; color centers
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31352) publication
Investigation of inter-fraction target motion variations in the context of pencil beam scanned proton therapy in non-small cell lung cancer patients
Den Otter, L. A.; Anakotta, R. M.; Weessies, M.; Roos, C. T. G.; Sijtsema, N. M.; Muijs, C. T.; Dieters, M.; Wijsman, R.; Troost, E. G. C.; Richter, C.; Meijers, A.; Langendijk, J. A.; Both, S.; Knopf, A.-C.
Purpose: For locally advanced-stage non-small cell lung cancer (NSCLC), inter-fraction target motion variations during the whole time span of a fractionated treatment course are assessed in a large and representative patient cohort. The primary objective is to develop a suitable motion monitoring strategy for pencil beam scanning proton therapy (PBS-PT) treatments of NSCLC patients during free breathing. Methods: Weekly 4D computed tomography (4DCT; 41 patients) and daily 4D cone beam computed tomography (4DCBCT; 10 of 41 patients) scans were analyzed for a fully fractionated treatment course. Gross tumor volumes (GTVs) were contoured and the 3D displacement vectors of the centroid positions were compared for all scans. Furthermore, motion amplitude variations in different lung segments were statistically analyzed. The dosimetric impact of target motion variations and target motion assessment was investigated in exemplary patient cases. Results: The median observed centroid motion was 3.4 mm (range: 0.2–12.4 mm) with an average variation of 2.2 mm (range: 0.1–8.8 mm). Ten of 32 patients (31.3%) with an initial motion <5 mm increased beyond a 5-mm motion amplitude during the treatment course. Motion observed in the 4DCBCT scans deviated on average 1.5 mm (range: 0.0–6.0 mm) from the motion observed in the 4DCTs. Larger motion variations for one example patient compromised treatment plan robustness while no dosimetric influence was seen due to motion assessment biases in another example case. Conclusions: Target motion variations were investigated during the course of radiotherapy for NSCLC patients. Patients with initial GTV motion amplitudes of < 2 mm can be assumed to be stable in motion during the treatment course. For treatments of NSCLC patients who exhibit motion amplitudes of > 2 mm, 4DCBCT should be considered for motion monitoring due to substantial motion variations observed. ©2020 The Authors. Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.
Keywords: free breathing; lung cancer; moving target; spencil beam scanning proton therapy; inter-fractional motion monitoring
Adenosine/A2B Receptor Signaling Ameliorates the Effects of Aging and Counteracts Obesity
Gnad, T.; Navarro, G.; Lahesmaa, M.; Reverte-Salisa, L.; Copperi, F.; Cordomi, A.; Naumann, J.; Hochh€Auser, A.; Haufs-Brusberg, S.; Wenzel, D.; Suhr, F.; Zenius Jespersen, N.; Scheele, C.; Tsvilovskyy, V.; Brinkmann, C.; Rittweger, J.; Dani, C.; Kranz, M.; Deuther-Conrad, W.; Eltzschig, H. K.; Niemi, T.; Taittonen, M.; Brust, P.; Nuutila, P.; Pardo, L.; Fleischmann, B. K.; Bleuher, M.; Franco, R.; Bloch, W.; Virtanen, K. A.; Pfeifer, A.
The combination of aging populations with the obesity pandemic results in an alarming rise in non-communicable diseases. Here, we show that the enigmatic adenosine A2B receptor (A2B) is abundantly expressed in skeletal muscle (SKM) as well as brown adipose tissue (BAT) and might be targeted to counteract age-related muscle atrophy (sarcopenia) as well as obesity. Mice with SKM-specific deletion of A2B exhibited sarcopenia, diminished muscle strength, and reduced energy expenditure (EE), whereas pharmacological A2B activation counteracted these processes. Adipose tissue-specific ablation of A2B exacerbated age-related processes and reduced BAT EE, whereas A2B stimulation ameliorated obesity. In humans, A2B expression correlated with EE in SKM, BAT activity, and abundance of thermogenic adipocytes in white fat. Moreover, A2B agonist treatment increased EE from human adipocytes, myocytes, and muscle explants. Mechanistically, A2B forms heterodimers required for adenosine signaling. Overall, adenosine/A2B signaling links muscle and BAT and has both anti-aging and anti–obesity potential.
Advanced flow profiler for two-phase flow imaging on distillation trays
A profound knowledge of the two-phase cross-flow on large-scale distillation trays is pivotal to their efficient design and operation. For such trays, a novel flow profiler comprising of multiple dual-tip probes for simultaneous local conductivity measurements is proposed in this work. The profiler is applied for a DN800 air/water column simulator equipped with sieve trays. 3D distribution of liquid holdup and tracer-based liquid flow in the two-phase dispersion are assessed in high resolution. Non-uniform holdup is found along the dispersion height. Contrarily, the liquid flow is largely uniform and symmetric with respect to the tray centerline. Prior to measurements, the profiler design, electronic scheme, measurement principle and data processing schemes are described.
Keywords: column tray; two-phase cross-flow; 3D flow imaging; conductivity measurement; liquid holdup; tracer dispersion
Chemical Engineering Science 231(2021), 116280
Online First (2020) DOI: 10.1016/j.ces.2020.116280
Cited 4 times in Scopus
- Final Draft PDF 1,4 MB Secondary publication
Numerical study of the appearance of short-circuits in liquid metal batteries
The report gives an overview on small-scale interface instabilities in liquid metal batteries.
École normale supérieure Paris-Saclay, 2020
Magnetoelectric coupling in a frustrated spinel studied using high-field scanning probe microscopy
Rossi, L.; Brüning, D.; Ueda, H.; Scurschii, I.; Lorenz, T.; Bryant, B.
Below its Neél temperature, the frustrated magnet CdCr2O4 exhibits an antiferromagnetic spin-spiral ground state. Such states can give rise to a sizable magnetoelectric coupling. In this report, we measure the electric polarization induced in single-crystalline CdCr2O4 by large applied magnetic field. Because the detection of a macroscopic polarization is hindered by the structural domains in the tetragonal spin-spiral phase, we have pioneered an alternative method of measuring polarization induced by high magnetic fields, using electrostatic force microscopy. This method enables us to measure polarization from nanoscale areas of the sample surface, as well as imaging how charge inhomogeneities change with magnetic field.
Applied Physics Letters 116(2020), 262901
Cited 2 times in Scopus
Contribution to WWW
arXiv:1912.12853 [cond-mat.mtrl-sci]: https://arxiv.org/abs/1912.12853
A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar
The mobility of heavy metal contaminants and radionuclides in the environment is directly controlled by their interactions with charged mineral surfaces, hence an assessment of their potential toxicity, e.g. in the context of nuclear waste disposal sites, requires understanding of sorption processes on the molecular level. Here, we investigate the sorption of a variety of rare earth elements (REE) and trivalent actinides (Am, Cm) on K-feldspar using batch sorption and column transport experiments, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and a surface complexation model. Initially, a reliable pKa for K-feldspar’s surface deprotonation reaction was determined as 2.5 ± 0.02, in excellent agreement with a measured pHIEP of 2.8. Batch sorption experiments over a broad range of experimental conditions in terms of mineral grain size, pH, [M3+], ionic radius, solid/liquid ratio, ionic strength, and equilibration procedures were carried out to quantify macroscopic immobilization. Similar pH-dependent uptake behavior was found for all investigated trivalent REE and actinides. In parallel, spectroscopic investigations provided insight into surface speciation. Cm TRLFS spectra indicate the formation of three inner-sphere sorption complexes with increasing hydrolysis. Additionally, a ternary K-feldspar/Cm/silicate complex was found for pH > 10, and batch and spectroscopic data at low pH (< 4) point to small amounts of outer sphere sorption complexes. Based on TRLFS data, batch sorption, and titration data, a generic geochemical sorption model was developed, that describes sorption edges for all investigated M3+/K-feldspar systems satisfactorily. The derived stability constants for the binary sorption complexes (logK1-4 = −3.6, −7.7, −11.5, and −17.4, respectively) are in good agreement with previous studies on similar systems, and could successfully be used to reproduce literature data. The stability constants obtained for the surface complexes were included into the database for the Smart Kd-concept, which will further improve the safety assessment of potential repositories for radioactive waste.
Keywords: sorption; trivalent metal ions; actinides; K-feldspar; surface complexation model; TRLFS
Journal of Colloid and Interface Science 591(2021), 490-499
Online First (2020) DOI: 10.1016/j.jcis.2020.11.041
Cited 12 times in Scopus
Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation
Konstantinovic, M. J.; Ulbricht, A.; Brodziansky, T.; Castina, N.; Malerba, L.
Vacancy-solute clustering in neutron irradiated Fe-Cr alloys with various concentrations of Cr and minor solutes (Ni, Si and P) were studied by using
coincidence Doppler broadening spectroscopy and small angle neutron scattering techniques. The results from both experiments, supported by an object kinetic Monte Carlo model, show in a very consistent way the existence and formation of vacancy-CrNiSiP clusters that play detrimental role in irradiation hardening. Similar solute cluster number density of about 30 to 50 x10^16cm-3 and an average diameter of about 1 nm were estimated for all alloys containing minor solutes, irrespectively of the chromium content. In Fe9Cr ferritic and Fe9Cr ferritic/martensitic alloys, with significantly reduced concentration of minor solute elements, the main defects are vacancy clusters, with an average cluster size size of about 10 and 2 vacancies, respectively. Large concentration of alpha'-precipitates was observed in Fe14Cr(NiSiP). However, both vacancy clusters and alpha'-precipitates provide significantly less impact to hardening in comparison to vacancy-CrNiSiP clusters. The fact that vacancy clustering in Fe9Cr ferritic alloy resembles that of pure iron suggests that Cr solutes may play lesser role in irradiation hardening of ferritic alloys and steels than previously believed.
Keywords: Neutron irradiation; FeCr alloys; Steels
Journal of Nuclear Materials 540(2020), 152341
Online First (2020) DOI: 10.1016/j.jnucmat.2020.152341
Cited 9 times in Scopus
- Final Draft PDF 849 kB Secondary publication
Uranium(VI) toxicity in tobacco BY-2 cell suspension culture - a physiological study
For the first time, the physiological and cellular responses of Nicotiana tabacum (BY-2) cells to uranium (U) as an abiotic stressor was studied in a multi analytic approach combining biochemical analysis, thermodynamic modeling and spectroscopic studies. It was focused on the determination of the U threshold toxicity in tobacco BY-2 cells, the influence of U on the homeostasis of micro-macro essential nutrients as well as the effect of Fe starvation on U bioassociation in cultured BY-2 cells. Our findings showed that U interferes with the homeostasis of essential elements. The interaction of U with BY-2 cells showed a time and concentration dependent kinetic. Under Fe deficiency, less U was detected in the cells compared to Fe sufficient conditions. Interestingly, blocking of Ca channels by gadolinium chloride caused a decrease in U concentration in BY-2 cells. Spectroscopic studies evidenced changes in the U speciation in the culture media with increasing exposure time under Fe sufficient and deficient conditions. Thusly, different stress response reactions related to the Fe metabolism are assumed. It is suggested that U toxicity in BY-2 cells is highly dependent on the existence of other micro-macro elements as showed by negative synergistic effects of U and Fe on the viability of cells.
Keywords: Nicotiana tabacum cells; uranium; toxicity; physiology; bioavailability; Fe starvation; speciation; plants; plant cells
Ecotoxicology and Environmental Safety 211(2021), 111883
Online First (2021) DOI: 10.1016/j.ecoenv.2020.111883
Cited 11 times in Scopus
Band Bending and Valence Band Quantization at Line Defects in MoS2
The variation of the electronic structure normal to 1D defects in quasi-freestanding MoS2, grown by molecular beam epitaxy, is investigated through high resolution scanning tunneling spectroscopy at 5K. Strong upward bending of valence and conduction bands toward the line defects is found for the 4|4E mirror twin boundary and island edges but not for the 4|4P mirror twin boundary. Quantized energy levels in the valence band are observed wherever upward band bending takes place. Focusing on the common 4|4E mirror twin boundary, density functional theory calculations give an estimate of its charging, which agrees well with electrostatic modeling. We show that the line charge can also be assessed from the filling of the boundary-localized electronic band, whereby we provide a measurement of the theoretically predicted quantized polarization charge at MoS2 mirror twin boundaries. These calculations elucidate the origin of band bending and charging at these 1D defects in MoS2. The 4|4E mirror twin boundary not only impairs charge transport of electrons and holes due to band bending, but holes are additionally subject to a potential barrier, which is inferred from the independence of the quantized energy landscape on either side of the boundary.
Keywords: 2D materials; Line defects; first-principles calculations
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31342) publication
ACS Nano 14(2020), 9176-9187
Online First (2020) DOI: 10.1021/acsnano.0c04945
Cited 17 times in Scopus
- Final Draft PDF 7,5 MB Secondary publication
Strain robust spin gapless semiconductors/half-metals in transition metal embedded MoSe2 monolayer
The realization of spin gapless semiconductor (SGS) and half-metal (HM) behavior in two-dimensional (2D) transition metal (TM) dichalcogenides is highly desirable for their applications in spintronic devices. Here, using density functional theory calculations, we demonstrate that Fe, Co, Ni substitutional impurities can not only induce magnetism in MoSe2 monolayer, but also convert the semiconducting MoSe2 to SGS/HM system. We also study the effects of mechanical strain on the electronic and magnetic properties of the doped monolayer. We show that for all TM impurities we considered, the system exhibits the robust SGS/HM behavior regardless of biaxial strain values. Moreover, it is found that the magnetic properties of TM–MoSe2 can effectively be tuned under biaxial strain by controlling the spin polarization of the 3d orbitals of Fe, Co, Ni atoms. Our findings offer a new route to designing the SGS/HM properties and modulating magnetic characteristics of the TM–MoSe2 system and may also facilitate the implementation of SGS/HM behavior and realization of spintronic devices based on other 2D materials.
Keywords: 2D materials; first-principles simulations; magnetism
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31341) publication
Journal of Physics: Condensed Matter 32(2020), 365305
Cited 9 times in Scopus
- Final Draft PDF 6,5 MB Secondary publication
Reversible crystalline-to-amorphous phase transformation in monolayer MoS2 under grazing ion irradiation
By combining scanning tunneling microscopy, low-energy electron diffraction, photoluminescence and Raman spectroscopy experiments with molecular dynamics simulations, a comprehensive picture of the structural and electronic response of a monolayer of MoS2 to 500 eV Xe+ irradiation is obtained. The MoS2 layer is epitaxially grown on graphene/Ir(1 1 1) and analyzed before and after irradiation in situ under ultra-high vacuum conditions. Through optimized irradiation conditions using low-energy ions with grazing trajectories, amorphization of the monolayer is induced already at low ion fluences of 1.5 × 1014 ions cm−2 and without inducing damage underneath the MoS2 layer. The crystalline-to-amorphous transformation is accompanied by changes in the electronic properties from semiconductor-to-metal and an extinction of photoluminescence. Upon thermal annealing, the re-crystallization occurs with restoration of the semiconducting properties, but residual defects prevent the recovery of photoluminescence.
Keywords: 2D materilas; irradiation; atomistic simulations; defects
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31340) publication
- Final Draft PDF 12,4 MB Secondary publication
Increasing the Diversity and Understanding of Semiconductor Nanoplatelets by Colloidal Atomic Layer Deposition
Nanoplatelets (NPLs) are a remarkable class of quantum confined materials with size-dependent optical properties, which are determined by the defined thickness of the crystalline platelets. To increase the variety of species, the colloidal atomic layer deposition method is used for the preparation of increasingly thicker CdSe NPLs. By growing further crystalline layers onto the surfaces of 4 and 5 monolayers (MLs) thick NPLs, species from 6 to 13 MLs are achieved. While increasing the thickness, the heavy-hole absorption peak shifts from 513 to 652 nm, leading to a variety of NPLs for applications and further investigations. The thickness and number of MLs of the platelet species are determined by high-resolution transmission electron microscopy (HRTEM) measurements, allowing the interpretation of several contradictions present in the NPL literature. In recent years, different assumptions are published, leading to a lack of clarity in the fundamentals of this field. Regarding the ongoing scientific interest in NPLs, there is a certain need for clarification, which is provided in this study.
Keywords: CdSe; colloidal atomic layer deposition; nanoplatelets
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31339) publication
Physica Status Solidi (RRL) (2020), 2000282
Online First (2020) DOI: 10.1002/pssr.202000282
Cited 3 times in Scopus
Unraveling Structure and Device Operation of Organic Permeable Base Transistors
Organic permeable base transistors (OPBTs) are of great interest for flexible electronic circuits, as they offer very large on-current density and a record-high transition frequency. They rely on a vertical device architecture with current transport through native pinholes in a central base electrode. This study investigates the impact of pinhole density and pinhole diameter on the DC device performance in OPBTs based on experimental data and TCAD simulation results. A pinhole density of NPin = 54 μm−2 and pinhole diameters around LPin = 15 nm are found in the devices. Simulations show that a variation of pinhole diameter and density around these numbers has only a minor impact on the DC device characteristics. A variation of the pinhole diameter and density by up to 100% lead to a deviation of less than 4% in threshold voltage, on/off current ratio, and sub-threshold slope. Hence, the fabrication of OPBTs with reliable device characteristics is possible regardless of statistical deviations in thin film formation.
Keywords: organic permeable base transistors; organic electronics; technology computer-aided design simulation
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31338) publication
Elucidation of the electron transfer mechanism in Eu2+ and Sm3+ codoped CaF2: A step towards better understanding of trapping and detrapping in luminescent materials
Many-electron multiconfigurational ab initio calculations are combined with x-ray spectroscopy to scrutinize a popular model for electron transfer in lanthanide-doped crystals which hypothesizes that the electrons are conveyed by the conduction band of the host. Contrary to this accepted picture, our combined theoretical-experimental effort shows that the reversible electron phototransfer from Eu2+ to Sm3+ in CaF2 is direct, from metal to metal. It is theoretically predicted and experimentally verified that visible light induces the reverse electron transfer.
- Open Access Version from biblio.ugent.be
- Secondary publication expected
Phase coherence and phase jumps in the Schwabe cycle
Guided by the working hypothesis that the Schwabe cycle of solar activity is synchronized by the 11.07 years alignment cycle of the tidally dominant planets Venus, Earth and Jupiter, we reconsider the phase diagrams of sediment accumulation rates in lake Holzmaar, and of methanesulfonate (MSA) data in the Greenland ice core GISP2, which are available for the period 10000-9000 cal. BP. Since some half-cycle phase jumps appearing in the output signals are, very likely, artifacts of applying a biologically substantiated transfer function, the underlying solar input signal with a dominant 11.04 years periodicity can be considered as mainly phase-coherent over the 1000 years period in the early Holocene. For more recent times, we show that the re-introduction of a hypothesized “lost cycle” at the beginning of the Dalton minimum would lead to a real phase jump. Similarly, by analyzing various series of 14C and 10Be data and comparing them with Schove’s historical cycle maxima, we support the existence of another “lost cycle” around 1565, also connected with a real phase jump. Viewed synoptically, our results lend greater plausibility to the starting hypothesis of a tidally synchronized solar cycle, which at times can undergo phase jumps, although the competing explanation in terms of a non-linear solar dynamo with increased coherence cannot be completely ruled out.
Keywords: Solar cycle; Synhcronization
Astronomische Nachrichten 341(2020)6-7, 600-615
Online First (2020) DOI: 10.1002/asna.202013809
Cited 12 times in Scopus
Bioassociation of U(VI) and Eu(III) by plant (Brassica napus) suspension cell cultures – A spectroscopic investigation
In this study, we investigated the interaction of U(VI) and Eu(III) with Brassica napus suspension plant cells as a model system. Concentration-dependent (0-200 µM) bioassociation experiments showed that more than 75% of U(VI) and Eu(III) were immobilized by the cells. In addition to this phenomenon, time-dependent studies for 1 to 72 h of exposure showed a multi-stage bioassociation process for cells that were exposed to 200 µM U(VI), where, after initial immobilization of U(VI) within 1 h of exposure, it was released back into culture medium starting within 24 h. A re-mobilization to this extent has not been previously observed. The MTT assay was used to correlate the bioassociation behavior of Eu and U with the cell vitality. Speciation studies by spectroscopy and in silico methods highlighted various U and Eu species over the course of exposure. We were able to observe a new U species, which emerged simultaneously with the re-mobilization of U back into solution, which we assume to be a U(VI) phosphate species. Thus, the interaction of U(VI) and Eu(III) with released plant metabolites could be concluded.
Keywords: plant cells; bioassociation; Brassica napus; time-resolved laser-induced fluorescence spectroscopy; radionuclides; uranium; europium; speciation
Environmental Science and Technology 55(2021)10, 6718-6728
Online First (2021) DOI: 10.1021/acs.est.0c05881
Cited 4 times in Scopus
- Final Draft PDF 472 kB Secondary publication
Data set on DBTTs from SPT and CVN
The data set is related to a manuscript entitled "Use of the small punch test for the estimation of ductile-to-brittle transition temperature shift of irradiated steels". Contents raw data of small punch tests, evaluation data of small punch tests and Charpy impact tests, correlation and regression analysis.
Keywords: small punch test; Charpy impact test; ductile-to-brittle-transition temperature; reactor pressure vessel steel; neutron irradiation
- DOI: 10.1016/j.nme.2021.100918 references this (Id 31334) publication
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-16 Restricted access
Use of the small punch test for the estimation of ductile-to-brittle transition temperature shift of irradiated steels
The small punch test is evaluated as a screening procedure for irradiation embrittlement of reactor pressure vessel steels. In particular, the correlation between ductile-to-brittle transition temperatures obtained from this small specimen test technique and from the standard Charpy impact test is investigated. Small punch tests and Charpy impact tests at different temperatures were performed on various steels including materials from original reactor pressure vessels in the unirradiated, neutron irradiated and annealed condition. It is demonstrated that the small punch test is a reliable and effective supportive means for the estimation of the irradiation-induced shift of the ductile-to-brittle transition temperature. It was found that a tanh-fit of the normalized small punch energy in dependence of temperature is preferable in comparison to the two-curve fit of the total small punch energy.
Keywords: small punch test; ductile-to-brittle-transition temperature; reactor pressure vessel steel; neutron irradiation; annealing
Nuclear Materials and Energy 26(2021), 100918
Cited 8 times in Scopus
Magnetic separation of rare-earth ions: Transport processes and pattern formation
Despite the relevance of the Kelvin force in many physical and electrochemical systems involving magnetic species, the underlying convective flows are scarcely understood. For that purpose, we simulate a simplified rare-earth system in the presence of competing Kelvin and gravity forces. The results are experimentally validated using interferometry and microscopic particle image velocimetry. Based on the excellent agreement of numerical and experimental results, the underlying mechanism of ions' magnetic separation can be explained, which paves the way for a prospective application in rare-earth beneficiation.
Keywords: magnetic separation; rare-earth ions; solutomagnetic convection; magnetophoresis; interferometer; Pattern formation; Rayleigh-Taylor instability; Rayleigh-Bénard convection; Paramagnetism
Physical Review Fluids 6(2021)2, L021901
Online First (2021) DOI: 10.1103/PhysRevFluids.6.L021901
Cited 4 times in Scopus
- Final Draft PDF 9,5 MB Secondary publication
DGN-Handlungsempfehlung (S1-Leitlinie): PSMA-Liganden-PET/CT in der Diagnostik des Prostatakarzinoms
Afshar-Oromieh, A.; Eiber, M.; Fendler, W.; Schmidt, M.; Rahbar, K.; Ahmadzadehfar, H.; Umutlu, L.; Hadaschik, B.; Hakenberg, O. W.; Formara, P.; Kurth, J.; Neels, O.; Wester, H. J.; Schwaiger, M.; Kopka, K.; Haberkorn, U.; Hermann, K.; Krause, B. J.
Das Ziel der vorliegenden Leitlinie ist es, den Arzt bei der Indikationsstellung, der standardisierten Durchführung, der Interpretation und der Dokumentation der Befunde einer Positronen-Emissions-Tomographie/Computertomographie (PET/CT) mit PSMA-Liganden bei Patienten mit Prostatakarzinom zu unterstützen. Es werden Empfehlungen zu Patientenselektion, Bilderfassung, Interpretation und Befundung ausgesprochen sowie Limitationen der PSMA-Liganden-PET/CT präsentiert. Die Leitlinie basiert auf einer Zusammenführung wissenschaftlicher Veröffentlichungen, Empfehlungen der Autoren und evidenzbasierter Daten.
- PSMA-Liganden-PET/CT in der Diagnostik des Prostatakarzinoms 10(2019) 031-055
Safety Cases for Design-Basis Accidents in LWRs Featuring Passive Systems Part 2 - Numerical Investigations
Buchholz, S.; Bonfigli, G.; Schäfer, F.; Kaczmarkiewicz, N.; Schuster, C.; Sporn, M.
This paper deals with the improvement and validation of numerical tools for the simula-tion of design basis accidents in nuclear power plants equipped with passive safety sys-tems. Numerical models are implemented in the framework of the 1-D thermal-hydraulic system code ATHLET developed by GRS. Experimental reference data for the validation were obtained at the INKA test facility, a model of the KERENA reactor, reproducing the passive safety systems nearly at full scale.
The validation effort focuses firstly on the accuracy of the models for the single passive components, and secondly on the ability of the numerical simulation to reproduce the in-teraction of all components of the KERENA design under realistic conditions as repro-duced in the INKA test facility. Thermal-hydraulic models are presented and validated for two passive components of the KERENA reactor: the passive pressure pulse trans-mitter and the pressure-controlled flooding valve. Finally, the full model of the INKA fa-cility, including these and other passive components, is discussed and numerical results for simulations reproducing three different design basis accidents are validated by com-parison with the corresponding experimental data.
Keywords: Passive Safety Systems; passive pressure pulse transmitter; passive core flooding sys-tem; ATHLET; AC2; INKA; KERENA
Nuclear Engineering and Design 372(2021), 110996
Cited 1 times in Scopus
Safety Cases for Design-Basis Accidents in LWRs Featuring Passive Systems Part 1 - Experimental Investigations
Mull, T.; Wagner, T.; Bonfigli, G.; Buchholz, S.; Schäfer, F.; Schleicher, E.; Schuster, C.; Sporn, M.
This paper presents results from a series of integral tests performed at Framatome’s INKA test facility in Karlstein (Germany) which simulates a KERENA boiling water reac-tor (BWR). The scope of the test series was on the behaviour of and interaction be-tween the different passive systems and components under the conditions of extended loss of alternating power (ELAP). These SBO-like conditions were aggravated in three out of four tests by parallel LOCA (Loss of Coolant Accident). The scenarios of all four tests fully correspond to Design Basic Conditions (DBC). They were: main steam line break, feed water line break, reactor pressure vessel (RPV) bottom leak and station blackout (SBO, non-LOCA).
In the tests, the passive systems integrated in KERENA and INKA, respectively, have fulfilled their design functions fully satisfactorily and as follows:
The Passive Pressure Pulse Transmitter (PPPT) triggered the RPV depressurization without delay. The Emergency Condenser (EC) system removed decay heat along with stored energy from the RPV to the containment. The Containment Cooling Condenser (CCC) system forwarded said power to a heat sink outside of the containment. The passive containment pressure suppression system kept the containment pressure within the design range, partially displacing surplus thermal energy from the drywell to the wetwell, in particular in the early phases after occurrence of LOCA. The passive core flooding system replenished the coolant inventory of the RPV thereby ensuring water levels in the RPV which are fully sufficient for core cooling.
Moreover, the systems have cooperated as anticipated by the designers, quietly and without perturbing each other.
Hence the test results, which are reported and discussed more in detail within this pa-per, soundly confirm the underlying design and its passive features.
Said tests were carried out as a part of the joint research project EASY (Evidence of Design Basis Accidents Mitigation solely with passive safety Systems), the overarching objective of which was the development and validation of the code system AC2 of GRS (Gesellschaft für Anlagen- und Reaktorsicherheit gGmbH).
Keywords: INKA, KERENA, BWR, DBC, Passive Safety Systems
Nuclear Engineering and Design 387(2022), 111095
Online First (2021) DOI: 10.1016/j.nucengdes.2021.111095
Cited 1 times in Scopus
Nature of Magnetic Excitations in the High-Field Phase of α-RuCl3
We present comprehensive electron spin resonance (ESR) studies of in-plane oriented single crystals of α-RuCl3, a quasi-two-dimensional material with honeycomb structure, focusing on its high-field spin dynamics. The measurements were performed in magnetic fields up to 16 T, applied along the  and  directions. Several ESR modes were detected. Combining our findings with recent inelastic neutronand Raman-scattering data, we identified most of the observed excitations. Most importantly, we show that the low-temperature ESR response beyond the boundary of the magnetically ordered region is dominated by single- and two-particle processes with magnons as elementary excitations. The peculiarities of the excitation spectrum in the vicinity of the critical field are discussed.
Physical Review Letters 125(2020), 037202
Cited 26 times in Scopus
- Final Draft PDF 1 MB Secondary publication
Earthquake-induced deformation structures in glacial sediments—evidence on fault reactivation and instability at the Vaalajärvi fault in northern Fennoscandia
Late and postglacial reverse faults and seismically-induced landslides are characteristic features of deglaciated terrain in the northern Fennoscandia. The main focus of this study was to investigate the rupturing history of the reverse Vaalajärvi fault complex in Sodankylä, Finland, based on remote sensing, on-site geophysics and sedimentology in excavations trenched across the faulted terrain. In addition to the previously known NNW–SSE-trending Vaalajärvi segment, we discovered six new SW–NE-trending fault segments that probably belong to the same Vaalajärvi ‘postglacial’ fault complex. Our analysis indicate that the Vaalajärvi fault segment was triggered by stress change caused by ruptures on the surrounding SW–NE-trending reverse faults. In total, at least two to three slip events have taken place in different segments of the Vaalajärvi complex since the Early Weichselian with the most recent event(s) being postglacial in timing. By using the scaling laws of fault surface rupture length and offset and under different scenarios of which segments or systems ruptured in a single or separate event, we estimate that the Vaalajärvi complex potentially hosted an earthquake that ranged between Mw ≈ 6.7–7.0. This magnitude is comparable to the landslide-inferred magnitudes in the Vaalajärvi area.
Keywords: Postglacial fault; Paleoseismology; Moment magnitude; LiDAR; Vaalajärvi; Finland
Journal of Seismology 24(2020)3, 549-571
Online First (2020) DOI: 10.1007/s10950-020-09915-6
Cited 3 times in Scopus
Halogen Bonded Assemblies of Arylene-imides and -diimides: Insight from Electronic, Structural and Computational studies
Mandal, K.; Bansal, D.; Kumar, Y.; Khan, R.; Shukla, J.; Mukhopadhyay, P.
Halogen bonding interactions in electron deficient π-scaffolds has largely been underexplored. Herein, we have studied the halogen bonding properties of arylene-imide/-diimide-based electron deficient scaffolds. We probed the influence of: scaffold size, e.g. from small phthalimide (PTMI), moderately-sized pyromelliticdiimide (PMDI) or naphthalenediimides (NDIs) to large perylenediimide (PDI); axial-group modifications; varied number of halogens, etc. on the halogen bonding and its self-assembly in a set of nine molecules. The structural modification leads to tunable optical as well as redox property. Gratifyingly, we realized single crystals of all the nine systems, which revealed Br∙∙∙O, Br∙∙∙Br or Br∙∙∙π halogen bonding interactions, with few systems capable of forming all the three-types. These interactions lead to halogen bonded rings (up to 12-membered), which propagate to form stacked 1D-, 2D- or corrugated sheets. We also identified few outliers, e.g. molecule which prefer C-H∙∙∙O hydrogen bonding over halogen bonding; or a non-centrosymmetric organization over the centrosymmetric ones. Computational studies based on Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analysis provided
further insight into the halogen bonding interactions. This study can lead to a predictive design tool-box to further explore related systems on surfaces reinforced by these weak directional forces.
Chemistry - A European Journal 26(2020)46, 10607-10619
Online First (2020) DOI: 10.1002/chem.202001706
Cited 3 times in Scopus
International Standardization of Basic Industrial Radiotracer and Radiation Applications – Current State
Jentsch, T.; Thereska, J.; Brisset, P.
The International Atomic Energy Agency (IAEA) in cooperation with the International Society for Tracer and Radiation Applications (ISTRA) promotes the international standardization of basic industrial radiotracer and radiation applications. Besides the revision and – if necessary – the update or amendment of existing ISO-standards the need for new standards in this field is analyzed and demonstrated.
A new international standard on non-destructive testing - gamma ray scanning method on process columns as a possibility to check the interior and to locate the cause of malfunction in tray and packed bed columns that are widely used in petrochemical and chemical process plants was prepared during the last three years. The final draft of this new standard was published as FDIS/ISO 23159 in June 2020.
In the field of flow rate measurements of fluids in conduits using radioactive tracers several international standards are known.
- Measurement of water flow in closed conduits (ISO 2975)
- Measurement of gas flow in conduits (ISO 4053)
- Measurement of liquid flow in open channels (ISO 9555).
A preparation of further international standards using radioactive tracer methods is already planned for the near future. One of them will deal with leak testing in pressured vessels and underground pipelines and another one will be on the measurement of sediment transport. For the leak testing standard a working draft was already prepared and submitted.
ISO standards are part of accreditation of radiotracer and radiation applications groups, facilitating the promotion and implementation of these competitive technologies in national, regional and international scale.
Keywords: ISO standard; radioactive tracer; radiotracer; radiation application; measurement; fluid flow rate; gamma ray scanning; leak detection
Second International Conference on Applications of Radiation Science and Technology (ICARST-2021), 22.-26.08.2022, Wien, Österreich
Benchmarking of Computational Fluid Dynamics Codes for Reactor Vessel Design
Computational Fluid Dynamics (CFD) codes have reached a level of maturity, at least for single-phase applications, to be utilized in the design process of Nuclear Power Plant (NPP) components, such that advanced NPPs over the past years have increasingly utilized CFD codes in their design. A recently completed Cooperative Research Project (CRP) addressed the application of CFD codes to the process of optimizing the design of components in Pressurized Water-cooled Reactors (PWRs). Following several initiatives within the IAEA where CFD codes have been applied to situations of interest in nuclear reactor technology, this CRP aimed to contribute to a consistent application of CFD codes by establishing a common platform to assess their capabilities and level of qualification.
Eleven participant organizations from nine Member States performed simulations against four “CFD-grade” experiments performed to investigate key phenomena for CFD simulations. Two are based on test data from the ROCOM (ROssendorf COolant Mixing) facility at HZDR in Germany, and another two are based on rod-bundle experiments in the OFEL (Omni Flow Experimental Loop) facility at KAERI in Korea.
This paper outlines the objectives of the CRP, provides a description of the test facilities and experiments, and discusses selected results obtained for the four above benchmark exercises.
Keywords: Computational Fluid Dynamics; Reactor Design; CFD benchmark
Wien: IAEA, 2020
Protecting-Group-Directed Diastereo- and Enantioselective Approach to Substituted Chiral Tetrahydropyrroloquinolines.
Chaudhari, T.; Mallampudi, N.; Bansal, D.; Mohapatra, D.; Tandon, V.
A novel synthetic method for chiral tricyclic tetrahydropyrroloquinolines following a protecting‐group‐directed domino reaction consisting of Michael addition and Mannich cyclization under mild reaction conditions was developed.
European Jounal of Organic Chemistry 18(2020), 2771-2780
Online First (2020) DOI: 10.1002/ejoc.202000348
Cited 2 times in Scopus
Evaluation of tube size variations to improve resolution in tube-of-response based image reconstruction for ⁶⁸Ga PET
Ga68-labeled tracers like Ga68-PSMA or Ga68-DOTATOC play a relevant role in clinical PET, but the substantial positron range of Ga68 (mean/max range in water: 2.7/8 mm) deteriorates spatial resolution. Integration of isotope-specific resolution recovery into iterative reconstruction should therefore be considered. In our in-house PET image reconstruction – THOR – this is possible by adjusting the tube diameter in the used tube-of-response projector. We have, therefore, investigated the potential of tube diameter optimization on achievable image resolution for Ga68.
We performed measurements with a resolution phantom at three different target-to-background ratios (20:1, 10:1, 5:1) for F18 and Ga68, respectively (Philips Ingenuity-TF PET/MR). All measurements were reconstructed with the vendor reconstruction as well as with THOR using different tube diameters and voxel sizes (2mm, 4mm). Image resolution, noise level, and magnitude of Gibbs artifacts (GA) were derived. The optimal tube diameters for F18 and Ga68 were determined respectively and applied to exemplary clinical Ga68 PSMA data.
The vendor reconstruction yields a resolution (FWHM) of [6.7+/-0.2] mm for Ga68 which is ~10% worse than for F18 while THOR yielded [5.0+/-0.4] mm using the default – F18-optimized – tube size which is ~14% worse than for F18. Increasing the tube diameter in THOR by up to 30% is possible for Ga68 (but not for F18) without causing notable GAs. This improves the achieved resolution by ~8% to ~4.6 mm. This is only slightly worse than the THOR result for F18 and much better than the resolution achievable for Ga68 with the vendor reconstruction. First clinical examples also demonstrate the beneficial effects of an isotope-specific tube size, exhibiting visually superior image quality.
Our preliminary results indicate that an isotope-dependent tube diameter does improve image resolution for challenging isotopes like Ga-68 without introducing notable GAs that often plaque resolution recovery attempts.
Keywords: positron emission tomography; PET; Ga68; positron range; image reconstruction; tube-of-response; nuclear medicine
58. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 07.07.2020, Leipzig, Deutschland
Multi Geometry Critical Heat Flux Observation facility (MORENA): Investigation of Critical Heat Flux (CHF) at 3 K and 5 K subcooled flow boiling - Infrared thermography (IR) data set
Experiments have been conducted to investigate the boiling heat transfer and local development of Critical Heat Flux (CHF) at subcooled flow boiling in a heated vertical tube. This data set contains the raw and processed Infrared thermography (IR) data along with measured operational data of the experimental facility for 3 K and 5 K subcooled flow boiling.
Keywords: Critical Heat Flux (CHF); Subcooled flow boiling; Infrared thermography
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-14 Restricted access
Berührungslose induktive Strömungstomographie für Modelle des kontinuierlichen Stranggießens von Stahl
Das Stranggießen von Stahl ist mit 96% Marktanteil das weltweit wichtigste Verfahren zur Stahlherstellung. Im Gießprozess beeinflusst das Strömungsprofil in der Kokille entscheidend die Qualität des resultierenden Stahls. Um eine möglichst optimale Strömung zu erhalten, werden Aktuatoren eingesetzt, die die Strömung kontaktlos mithilfe der Lorentzkraft beeinflussen. Diese Aktuatoren würden auch eine Regelung der Strömung ermöglichen, wenn eine geeignete Messtechnik vorhanden wäre. Allerdings messen bisher verfügbare Messtechniken für heiße Schmelzen vor allem lokal in der Nähe der Randgebiete der Strömung und sind oft in ihrer zeitlichen Auflösung limitiert. Eine neue infrage kommende Messtechnik ist die berührungslose induktive Strömungstomographie (contactless inductive flow tomography, CIFT), die aus der gemessenen strömungsinduzierten Verzerrung eines angelegten Magnetfeldes die dreidimensionale Strömung rekonstruieren kann.
In dieser Arbeit wird anhand eines 1:8-Labormodells einer Stranggusskokille und numerischen Simulationen untersucht, ob CIFT bei Anlagen mit elektromagnetischen Bremsen eingesetzt werden kann. Besondere Herausforderungen entstehen aufgrund der Verzerrung des CIFT-Anregungsmagnetfeldes durch die ferromagnetische Bremse, der großen Dynamik von 6 Größenordnungen zwischen dem Magnetfeld der Bremse und dem strömungsinduzierten Magnetfeld sowie intrinsischen Strömungsoszillationen mit einer charakteristischen Frequenz im Bereich der üblicherweise verwendeten CIFT-Anregungsfrequenzen. Es wird dargelegt, dass sich CIFT in derartigen Aufbauten einsetzen lässt, wenn (a) eine geeignete Anregungsmagnetfeldstruktur erzeugt werden kann, (b) gradiometrische Induktionsspulen als Magnetfeldsensoren eingesetzt werden und (c) die Anregungsfrequenz in einem optimalen, schmalen Bereich gewählt wird. Diese Messungen werden erst durch in dieser Arbeit angefertigte theoretische und experimentell validierte Analysen der Induktionsspulen möglich, wofür Schwerpunkte auf deren Modellierung, Design und Messunsicherheit gelegt wurden. Außerdem werden für dieses Stranggussmodell erstmals experimentelle Ergebnisse mit horizontal anstatt vertikal orientierten Anregungsmagnetfeldern präsentiert.
Um die Skalierbarkeit von CIFT in Richtung industrieller Anlagen zu demonstrieren, werden zum einen neue Rekonstruktionen in einem heißen 1:2-Labormodell einer Kokille vorgestellt. Andererseits wird die in industriellen Kokillen typischerweise aufgebrachte ferromagnetische Nickelbeschichtung und ihre Auswirkung auf CIFT mit numerischen Simulationen quantifiziert. Diese Beschichtung stellt aufgrund ihrer zeitlich und räumlich schwankenden Permeabilität eines der größten Hindernisse für die Anwendung von CIFT im industriellen Stahlguss dar. Für dieses Szenario werden neue Anregungsgeometrien untersucht und erste Rekonstruktionen gezeigt.
Keywords: CIFT; contactless inductive flow tomography; kontinuierliches Stranggießen; magnetische Bremse
TU Dresden, 2020
Mentor: Prof. Dr.-Ing. Dr. h.c. habil. Uwe Hampel
Superconductivity with broken time-reversal symmetry inside a superconducting s-wave state
Grinenko, V.; Sarkar, R.; Kihou, K.; Lee, C. H.; Morozov, I.; Aswartham, S.; Büchner, B.; Chekhonin, P.; Skrotzki, W.; Nenkov, K.; Hühne, R.; Nielsch, K.; Drechsler, S.-L.; Vadimov, V. L.; Silaev, M. A.; Volkov, P. A.; Eremin, I.; Luetkens, H.; Klauss, H.-H.
In general, magnetism and superconductivity are antagonistic to each other. However, there are several families of superconductors in which superconductivity coexists with magnetism, and a few examples are known where the superconductivity itself induces spontaneous magnetism. The best known of these compounds are Sr2RuO4 and some non-centrosymmetric superconductors. Here, we report the finding of a narrow dome of an s + is' superconducting phase with apparent broken time-reversal symmetry (BTRS) inside the broad s-wave superconducting region of the centrosymmetric multiband superconductor Ba1−xKxFe2As2 (0.7 ≲ x ≲ 0.85). We observe spontaneous magnetic fields inside this dome using the muon spin relaxation (μSR) technique. Furthermore, our detailed specific heat study reveals that the BTRS dome appears very close to a change in the topology of the Fermi surface. With this, we experimentally demonstrate the likely emergence of a novel quantum state due to topological changes of the electronic system
Femtosecond laser produced periodic plasma in a colloidal crystal probed by XFEL radiation
Mukharamova, N.; Lazarev, S.; Meijer, J.-M.; Gorobtsov, O. Y.; Singer, A.; Chollet, M.; Bussmann, M.; Dzhigaev, D.; Feng, Y.; Garten, M.; Huebl, A.; Kluge, T.; Kurta, R. P.; Lipp, V.; Santra, R. J.; Sikorski, M.; Song, S.; Williams, G.; Zhu, D.; Ziaja-Motyka, B.; Cowan, T. E.; Petukhov, A. V.; Vartanyants, I. A.
With the rapid development of short-pulse intense laser sources, studies of matter under extreme irradiation conditions enter further unexplored regimes. In addition, an application of X-ray Free-Electron Lasers (XFELs) delivering intense femtosecond X-ray pulses, allows to investigate sample evolution in IR pump - X-ray probe experiments with an unprecedented time resolution. Here we present a detailed study of the periodic plasma created from the colloidal crystal. Both experimental data and theory modeling show that the periodicity in the sample survives to a large extent the extreme excitation and shock wave propagation inside the colloidal crystal. This feature enables probing the excited crystal, using the powerful Bragg peak analysis, in contrast to the conventional studies of dense plasma created from bulk samples for which probing with Bragg diffraction technique is not possible. X-ray diffraction measurements of excited colloidal crystals may then lead towards a better understanding of matter phase transitions under extreme irradiation conditions.
The fate of anthropogenic nanoparticles, nTiO2 and nCeO2, in waste water treatment
Lange, T.; Schneider, P.; Schymura, S.; Franke, K.
Wastewater treatment is one of the main end-of-life scenarios, as well as a possible reentry point into the environment, for anthropogenic nanoparticles (NP). These can be released from consumer products such as sunscreen or antibacterial clothing, from health-related applications or from manufacturing processes such as the use of polishing materials (nCeO2) or paints (nTiO2). The use of NP has dramatically increased over recent years and initial studies have examined the possibility of toxic or environmentally hazardous effects of these particles, as well as their behavior when released. This study focuses on the fate of nTiO2 and nCeO2 during the wastewater treatment process using lab scale wastewater treatment systems to simulate the NP mass flow in the wastewater treatment process. The feasibility of single particle mass spectroscopy (sp-ICP-MS) was tested to determine the NP load. The results show that nTiO2 and nCeO2 are adsorbed to at least 90 percent of the sludge. Furthermore, the results indicate that there are processes during the passage of the treatment system that lead to a modification of the NP shape in the effluent, as NP are observed to be partially smaller in effluent than in the added solution. This observation was made particularly for nCeO2 and might be due to dissolution processes or sedimentation of larger particles during the passage of the treatment system.
Keywords: synthetic nanoparticles; nTiO₂ and nCeO₂; waste water treatment; sp-ICP-MS nanoparticles tracking
Polarization tunability in multiferroic DyMn2O5: Influence of Y and Eu co-doping and 3d-4f exchange
Yang, L.; Wang, C.; Zeng, M.; Hou, Z.; Fan, Z.; Chen, D.; Qin, M.; Lu, X.; Li, Q.; Gao, X.
Coupling effects among spin, charge, and lattice in a strongly correlated system are critical for next generation spintronic and data storage devices. However, the complex effects are elusive and difficult to distinguish their contributions to polarization modulation. Here we tailored the polarization by co-doping of non-magnetic Y and Eu at A-sites in DyMn2O5. The structure, specific heat, magnetism, and ferroelectricity of the polycrystalline Dy1-x(Eu0.24Y0.76)xMn2O5 ceramics were comprehensively explored. Interestingly, the co-doping does not cause lattice distortion of DyMn2O5, and all the ceramics are orthorhombic structures, while the independent Dy3+ spin order and the Dy3+-Mn3+ coupling can be suppressed. With increasing the co-doping content x, the spins related properties associated with the Dy3+-Mn4+-Dy3+ sub-lattice are progressively inhibited, while they keep less disturbance in the Mn3+-Mn4+-Mn3+ block. Moreover, the spin coupling of Dy3+-Mn3+ ions is stronger again the magnetic field than that of Dy3+-Mn3+. Our results enhance the understanding of ferrielectricity in DyMn2O5, and provide a method for controlling the polarization in the multiferroic manganite coexisting 3d and 4f elements.
Keywords: DyMn2O5; Multiferroicity; Ferrielectricity; Manganite
Solid State Communications 307(2020), 113809
Online First (2020) DOI: 10.1016/j.ssc.2019.113809
Probing the local atomic structure of In and Cu in sphalerite by XAS spectroscopy enhanced by reverse Monte-Carlo algorithm
Trigub, A. L.; Trofimov, N. D.; Tagirov, B. R.; Nickolsky, M. S.; Kvashnina, K. O.
The distortion of the atomic structure around In and Cu atoms in sphalerite ZnS was explored by reverse Monte Carlo (RMC) method applied to the Extended x-ray absorption fine structure (EXAFS) interpretation. Parameters of the local atomic structure (interatomic distances) around dopants in synthetic In- and In-Cu-bearing sphalerites were determined by fitting In and Cu K-edge EXAFS spectra using evolutionary algorithm (EA) of the RMC method. These data were complemented with quantum chemical Density Functional Theory (DFT) calculations and theoretical modeling of XANES spectra. The RMC-EXAFS method showed that the three coordination shells of In-bearing sphalerite are characterized by almost symmetrical Gaussian type peaks, which shapes are close to the one of pure sphalerite. This shape of the peaks is characteristic of symmetrical undisturbed structural environment of In in the sphalerite solid solution which is formed via the charge compensation schemes 3Zn2+↔2In3++□, where □ is a Zn vacancy. However, in case of (In,Cu)-bearing sphalerites formation of solid solution state follows the charge compensation scheme 2Zn2+↔Cu++In3+. In this case some splitting of the RDF peaks are observed, the splitting rate correlates with impurities concentrations. In contrast to In, the local atomic structure around Cu is not symmetric. The 2nd coordination shell around Cu (which consists of 12 metal atoms) can be described by three distinct Gaussian contributions. This splitting of interatomic distances in the 2nd coordination shell points out on the significant distortion of the ZnS crystal structure around Cu. The theoretical calculation of Cu K-edge XANES based on the distorted structural environment near Cu provides better agreement with the experiment than the symmetrical atomic model. According to our DFT calculations, considerable splitting of the 2nd coordination shell (up to 0.1 Å for Cu) occurs in the case of close positions of the impurity atoms or the Zn vacancy. The DFT calculations showed that the geometries with the close arrangement (clustering) of the impurities – In and Cu atoms, or the In atom and a vacancy, are energetically more favorable than the random distribution of the defects. However, as no heavy In atoms were detected in the 2nd shell of Cu, and the 2nd shell of In is almost undisturbed, we conclude that the defects are distributed randomly (or at least not close to each other). The disagreement of RMC-EXAFS fittings with results of DFT calculations, according to which the closest arrangement of dopants is the most stable configuration, can be explained by the presence of other defects of the sphalerite crystal lattice which were not considered in the DFT calculations.
- DOI: 10.1107/S1600577520014265 is cited by this (Id 31311) publication
Minerals 10(2020)10, 841
Modelling thermal-hydraulic effects of zinc borate deposits in the PWR core after LOCA - Experimental strategies and test facilities
The German software tool ATHLET (Analysis of THermohydraulics of Leaks and Transients) is continuously being developed for the simulation of the nuclear power plant behaviour in the event of transients and accidents. The focus of a current joint research project named „ATHLET Modul Zinkborat“ (AZora) is the development and validation of an ATHLET module on the basis of the current state of research on chemical long-term effects according to PWR LOCA. The module is intended to simulate thermohydraulic effects of zinc borate precipitations in the reactor core originating from long-term corrosion processes in the reactor sump during sump recirculation operation after postulated loss-of-coolant accidents in PWR. To develop and validate the sub-models, generic experiments at lab-scale as well as at semi-technical scale are planned to be carried out in unique test facilities. The structure of the module as well as the experimental strategies and the related facilities are described in the article.
Keywords: loss-of-coolant accident; LOCA; pressurized water reactor; nuclear safety research; zinc borate; corrosion; simulation; chemical effects
atw - International Journal for Nuclear Power 65(2020)6/7, 341-345
- Secondary publication expected
Study of the Influence of the Crystallographic Orientation of Cassiterite Observed with Colloidal Probe Atomic Force Microscopy and its Implications for Hydrophobization by an Anionic Flotation Collector
Wu, H.; Renno, A. D.; Weber, C.; Rudolph, M.
In this study, SnO2(110), SnO2(100) as well as SnO2(001) were investigated by using direct force measurements. The high-resolution force spectroscopy measurements were conducted between a silica sphere and sample surfaces in 1 mM KCl between pH 3.1 and 6.2 using colloidal probe atomic force microscopy (cp-AFM- hydrophilic). Dissimilar interactions were detected on different oriented surface. The pH values where the force switched from positive to negative can be clearly distinguished and be ordered as SnO2 (100) < SnO2 (001) ≈SnO2 (110). This observation implies that there is a difference in surface properties between the three orientations. However, no clear interpretation can be made by fitting of the interaction forces in the framework of the Derjaguin-Landau-Verwey-Overbeck (DLVO) theory.1,2
To study the implication of crystallographic orientation to surfactant adsorption, we used Aerosol® 22 (sulfosuccinamate) as anionic collector for cassiterite flotation to functionalize the different samples at pH 3. The contact angle measurements, the topography visualizations by AFM as well as the force measurement using cp-AFM with hydrophobized spheres (cp-AFM-hydrophobized) have shown that the adsorption of Aerosol® 22 followed the range of SnO2(110) > SnO2(100) > SnO2(001) in the concentration from 1x10-6 M to 1x10-4 M.
Keywords: crystallographic orientations; cassiterite; adsorption; colloidal probe atomic force microscopy
Numerical simulations of short-circuits appearance in liquid metal batteries
The mid-term report gives an overview on S. Bénards work at HZDR concerning local short-circuits in liquid metal batteries.
Paris: École normale supérieure Paris-Saclay, 2020
Microfocus X-ray tomography data set of boiling flow in vertical rod bundle with spacer grid at constant heat flux condition
The test section of the rod bundle experimental facility at HZDR consists of a vertically aligned PMMA channel with an upward flow of the working fluid. The cross-section of the channel is quadratic (inner edge length: 37 mm) and contains nine directly electrically heated rods (material: titanium-alloy, diameter: 10 mm, wall thickness: 0.3 mm) which are arranged in an orthogonal 3 by 3 matrix (rod axis distance: 12.8 mm). Circa 190 mm downstream of the start of the heating zone a 30 mm long spacer for the rods with tilted flow guiding vanes is mounted. These vanes are aimed to increase lateral flow velocities within the subchannels. Working fluid was octafluorocyclobutane (CAS 115-25-3, RC318). The experimental facility is comprehensively instrumented for measurement of flow, temperature and pressure/pressure difference. For non-invasive three-dimensional high-resolution measurement of a temporally averaged volumetric void fraction within the working fluid flowing around the heating rods in the subchannels an X-ray computer tomography measurement system was set up.
The presented dataset contains measurement data of the experimental facility's instrumentation and tomographic void fraction data of experiments with four different configurations of the flow guiding vanes (without vanes, 20°, 29°, 40°) for four different flow velocities between 0.4 m/s and 1.3 m/s at a heat flow density of 85.7 kW/m².
Keywords: X-Ray Computed Tomography; Phase fraction; Rod bundle; Boiling flow
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-08 Restricted access
Validierung eines Open-source-Modells für die Simulation von PEM-Brennstoffzellen und Anwendung auf eine luftatmende Brennstoffzelle
Die vorliegende Arbeit beschäftigt sich mit der dreidimensionalen und mehrphasigen CFD-Simulation von PEM-Brennstoffzellen. Dabei wird die Validierung eines in OpenFOAM implementierten Modells zur Gesamtzellensimulation anhand von drei, von verschiedenen Forschungsgruppen vorgestellten, Experimenten durchgeführt.
Aufbauend auf der Modellvalidierung wird die Anwendbarkeit des Modells auf eine luft-atmende Brennstoffzelle überprüft. In diesem Zusammenhang wird der Einfluss der Orientierung auf die Transportprozesse in einer luftatmenden Brennstoffzelle mit zylindrischer Form untersucht. Dafür wird sowohl die Brennstoffzelle, als auch deren Umgebung beachtet. Die bei variierender Orientierung auftretenden Unterschiede von Naturkonvektion, Temperatur und Massenverteilung von Wasser und Sauerstoff werden dargestellt und diskutiert. Zusätzlich wird auf die Grenzen des verwendeten Modells und mögliche Verbesserungen hingewiesen.
TU Dresden, 2020
Heavy ion irradiation damage in Zr3(Al0.9Si0.1)C2 MAX phase
Qarra, H. H.; Knowles, K. M.; Vickers, M. E.; Zapata-Solvas, E.; Akhmadaliev, S.
A Zr3(Al0.9Si0.1)C2 MAX phase-based ceramic with 22 wt.% ZrC and 10 wt.% Zr5Si3 has been irradiated with 52 MeV I9+ ions at room temperature, achieving a maximum dose of 8 displacements per atom (dpa). The response of this MAX phase-rich material to irradiation has been studied using scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. Post-irradiation examination of the material revealed a number of crystalline changes to the MAX phase. At low doses, Zr3(Al0.9Si0.1)C2 maintained a high degree of crystallinity, while at the highest doses, its degree of crystallinity was reduced significantly. A number of radiation-induced phase transformations were observed, including the decomposition of Zr3(Al0.9Si0.1)C2 into ZrC and other phases, and the formation of β-Zr3(Al,Si)C2, a MAX phase with a rearranged stacking sequence. Microstructural examination revealed that the majority of the extended defects in Zr3(Al0.9Si0.1)C2 lie in the (0001) basal planes. Analysis of X-ray diffraction profiles after heat treating the 8 dpa-irradiated material for 1 h at 300 °C and at 600 °C showed that there were only subtle changes to the profiles relative to that of the 8 dpa-irradiated material which had not been heat treated. Overall, the experimental results of this study show that the Zr3(Al0.9Si0.1)C2 MAX phase responds less well to irradiation relative to other MAX phases irradiated with high energy heavy ions at room temperature.
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31304) publication
Journal of Nuclear Materials 540(2020), 152360
Cited 4 times in Scopus
Two types of alternating spin-1/2 chains and their field-induced transitions in ε-LiVOPO4
Mukharjee, P. K.; Ranjith, K. M.; Baenitz, M.; Scurschii, I.; Tsirlin, A. A.; Nath, R.
Thermodynamic properties, 31P nuclear magnetic resonance (NMR) measurements, and density-functional band-structure calculations for ε-LiVOPO4 are reported. This quantum magnet features a singlet ground state and comprises two types of alternating spin-1/2 chains that manifest themselves by the double maxima in the susceptibility and magnetic specific heat, and by the two-step magnetization process with an intermediate 1/2-plateau. From thermodynamic data and band-structure calculations, we estimate the leading couplings of J1 ≃ 20 K and J2 ≃ 60 K and the alternation ratios of α1 = J’1/J1 ≃ 0.6 and α2 = J’2/J2 ≃ 0.3 within the two chains, respectively. The zero-field spin gap Δ0/kB ≃ 7.3 K probed by thermodynamic and NMR measurements is caused by the J1-J’1 spin chains and can be closed in the applied field of μ0Hc1 ≃ 5.6 T, giving rise to a field-induced long-range order. The NMR data reveal predominant three-dimensional spin-spin correlations at low temperatures. Field-induced magnetic ordering transition observed above Hc1 is attributed to the Bose-Einstein condensation of triplons in the sublattice formed by the J1-J’1 chains with weaker exchange couplings.
Physical Review B 101(2020), 224403
Cited 3 times in Scopus
Contribution to WWW
arXiv:2002.12907 [cond-mat.str-el]: https://arxiv.org/abs/2002.12907
Studies on the affinity of 6-[(: N -(cyclo)aminoalkyl)oxy]-4 H -chromen-4-ones for sigma 1/2 receptors
Sigma represent attractive targets for the development of potential agents for the treatment of neurodegenerative disorders. In search of multitarget small molecules (MSMs) against Morbus Alzheimer and related diseases, we have discovered that 6-(4-(piperidin-1-yl)butoxy)-4H-chromen-4-one (7), a previously identified MSM with potent dual-target activities against acetylcholinesterase and monoamine oxidase B, exhibited S1/S2 receptor modulatory activity. A further chromenone, 6-((5-morpholinopentyl)oxy)-4H-chromen-4-one (12), was identified to be almost equipotent to S1RA, an established 1 receptor antagonist.
Keywords: ADME; chromenones; docking; multitarget small molecules; radioligand assay; receptor binding; sigma 1/2 receptors
Polar structure formation in solid solution of strontium substituted fluorapatite-gelatin composites: from structural and morphogenetic aspects to pyroelectric properties
Knaus, J.; Sommer, M.; Duchstein, P.; Gumeniuk, R.; Akselrud, L. G.; Sturm, S.; Auffermann, G.-D.; Hennig, C.; Zahn, D.; Hulliger, J.; Sturm, E. V.
Strontium substituted apatite-(CaF)-gelatin composites have been synthesized within a gelatin gel using the dou-ble diffusion technique. All experimental parameters were kept constant while systematically varying the strontium/ calcium molar ratio in solution. The effect of the presence of strontium ions in the growth solution on composition, morphogenesis and morphology as well as pyroelectric properties of synthetic aggregates was systemically analyzed. It was shown that stron-tium ions significantly inhibit the growth process of composite aggregates and increase growth anisotropy along , which were also confirmed and explained by molecular dynamic simulations. Furthermore, it was observed the promotion of the crystal branching processes and spherulite formation. Pyroelectric microscopy (SPEM) measurements on mixed substi-tuted apatite-(CaSrF)-gelatin composite aggregates showed an increase in polar properties, suggesting a lowering of the crys-tal symmetry. This was verified by Rietveld refinement of synchrotron pXRD, which revealed the non-centrosymmetric P63apatite crystal structure. These data could shed new light on understanding piezoelectric and pyroelectric properties of apa-tite based biological hard tissues.
- DOI: 10.1107/S1600577520014265 is cited by this (Id 31301) publication
Chemistry of Materials 32(2020)19, 8619-8632
Cited 1 times in Scopus
ROBL-II at ESRF: A synchrotron toolbox for actinide research
Scheinost, A.; Claußner, J.; Exner, J.; Feig, M.; Findeisen, S.; Hennig, C.; Kvashnina, K.; Naudet, D.; Prieur, D.; Roßberg, A.; Schmidt, M.; Qiu, C.; Colomp, P.; Cohen, C.; Dettona, E.; Dyadkin, V.; Stumpf, T.
ROBL-II provides four different experimental stations to investigate actinide and other alpha- and beta-emitting radionuclides at the new EBS storage ring of ESRF within an energy range of 3 to 35 keV. The XAFS station consists of a highly automatized, high sample throughput installation in a glovebox, to measure EXAFS and conventional XANES of samples routinely at temperatures down to 10 K, and with a detection limit in the sub-ppm range. The XES station with its 5 bent-crystal analyzer, Johann-type setup with Rowland circles of 1.0 and 0.5 m radii provides high-energy resolution fluorescence detection (HERFD) for XANES, XES, and RIXS measurements, covering both actinide L and M edges together with other elements accessible in the 3 to 20 keV energy range. The 6-circle heavy duty goniometer of XRD-1 is equipped for both high-resolution powder diffraction as well as surface-sensitive CTR and RAXR techniques. Single crystal diffraction, powder diffraction with high temporal resolution, as well as X-ray tomography experiments can be performed at a Pilatus 2M detector stage. Elaborate radioprotection features enable a safe and easy exchange of samples between the four different stations to allow the combination of several methods for an unprecedented level of information on radioactive samples for both fundamental and applied actinide and environmental research.
Keywords: XAFS; XANES; XES; XRD; RIXS; RAXR; CTR; actinides
- DOI: 10.1107/S1600577520014265 is cited by this (Id 31300) publication
Journal of Synchrotron Radiation 28(2021), 333-349
Online First (2020) DOI: 10.1107/S1600577520014265
Cited 30 times in Scopus
Scanning transmission imaging in the helium ion microscope with a position-sensitive detector
The helium ion microscope (HIM) is an instrument for high-resolution imaging, nanofabrication, composition analysis, and material modification at the nanometer scale . The npSCOPE instrument is a unique HIM prototype with three special add-ons, namely: secondary ion mass spectroscopy (SIMS), cryo-microscopy, and scanning transmission helium ion microscopy (STHIM).
In this work, we focus on STHIM. Our STHIM detection system is based on a position- and time-sensitive detector comprising a microchannel plate and a delay line readout structure. A dedicated software interface for data acquisition and post-processing allows the reconstruction of images for selected scattering directions, and the visualization of different contrast regimes for a given sample. Using STHIM, we analyzed material contrast for layered films of various thicknesses and materials. Channeling contrast in transmission for poly- and single-crystalline materials is also detected. In the case of biological samples, STHIM provides a way of identifying sub-surfaces structures that can help to localize nanomaterials for toxicology studies, as shown in Figure 1.
Keywords: Helium Ion Microscopy; Scanning transmission ion microscopy
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31299) publication
CMD2020GEFES, 31.08.-04.09.2020, Madrid, España
Virtual Early Career European Microscopy Congress 2020, 24.-26.11.2020, København, Danmark
Developments in nuclear medicine – new radioisotopes in use and associated challenges: proceedings of a scientific seminar held in Luxembourg on 13 November 2019
The European Commission organises every year, in cooperation with the Group of Experts referred to in Article 31 of the Euratom Treaty, a scientific seminar on emerging issues in radiation protection – generally addressing new research findings with potential policy and/or regulatory implications. Leading scientists are invited to present the status of scientific knowledge in the selected topic.
Based on the outcome of the scientific seminar, the Group of Experts referred to in Article 31 of the Euratom Treaty may recommend research, regulatory or legislative initiatives. The European Commission takes into account the conclusions of the Experts when setting up its radiation protection programme. The Experts' conclusions are valuable input to the process of reviewing and potentially revising European radiation protection legislation.
Keywords: Conference proceedings; Energy research; Nuclear accident; Nuclear medicine; Public health; Radiation exposure; Radiation protection
Contribution to proceedings
EU Scientific Seminar November 2019, 13.11.2019, Luxembourg, Luxembourg
Proceedings of EU Scientific Seminar November 2019, 978-92-76-27010-2
Direct Characterisation of Solute Transport inUnsaturated Porous Media using 4D X-raySynchrotron Microtomography
Sharul, H.; Vahid, J.-N.; Nikolaos, K. K.; Da Assuncao Godinho, J. R.; Nghia, T. V.; Senyou, A.; Arash, A.; Holger, S.
Solute transport in unsaturated porous materials is a complex pro-cess, which exhibits some distinct features differentiating it fromtransport under saturated conditions. These features emerge mostlydue to the different transport time scales at different regions of theflow network, which can be classified into flowing and stagnantregions, predominantly controlled by advection and diffusion, re-spectively. Under unsaturated conditions, the solute breakthroughcurves show early arrivals and very long tails, and this type of trans-port is usually referred to as non-Fickian. This is the first studywhich directly characterise transport through an unsaturated porousmedium in three spatial dimensions at the resolution of 3.25μm andthe time resolution of 6s. Using advanced high-speed, high spa-tial resolution, synchrotron-based X-Ray Computed Microtomogra-phy (sCT) we obtained the first detailed information on solute trans-port through a glass-bead packing at different saturations. A largeexperimental dataset (>50TB) was produced, while imaging the evo-lution of the solute concentration with time at any given point withinthe field of view. We show that the fluids’ topology has a critical sig-nature on the non-Fickian transport, which has not been addressedin the theories of transport through unsaturated porous media. Wedemonstrate that the "fully-mixing" assumption at pore scale is notvalid, due to the significant impact of the no-slip boundary of thesolid walls. Results demonstrate that dispersivity, as a major trans-port parameter, is changing with saturation, being two-fold larger atsmaller saturations compared to that at high saturations.
Keywords: contaminant transport; X-ray microtomography; stagnant saturation; non-Fickian transport; unsaturated flow
Proceedings of the National Academy of Sciences of the United States of America 117(2020)38, 23443-2344
Cited 31 times in Scopus
Spectral tomography for 3D element detection and mineral analysis
This paper demonstrates the potential of a new 3D imaging technique, Spectral Computed To-mography (Sp-CT), to identify heavy elements inside materials, which can be used to classify mineral phases. The method combines the total X-ray transmission measured by a normal pol-ychromatic X-ray detector, and the transmitted X-ray energy spectrum measured by a detector that discriminates between X-rays with energies of about 1.1 keV resolution. Analysis of the en-ergy spectrum allows to identify sudden changes of transmission at k-edge energies that are specific of each element. The additional information about the elements in a phase improves the classification of mineral phases from grey-scale 3D images that would be otherwise difficult due to artefacts or to the lack of contrast between phases. The ability to identify the elements inside the minerals that compose ore particles and rocks is crucial to broaden the application of 3D imaging in Earth sciences research and mineral process engineering, which will represent an important complement to traditional 2D imaging mineral characterization methods. In this pa-per, the first applications of sp-CT to classify mineral phases are showcased and the limitations and further developments are discussed.
Keywords: computed tomography; minerals engineering; raw materials; X-ray imaging; geometallurgy; 3D mineral classification; spectral tomography; sp-CT; 3D imaging
Magnetization dynamics and mutual spin-pumping in SAFs
Some of the file are auxiliary or analisys files for faster display of the main results (like .opj, .ods files). Main raw data files are in the archives.
Keywords: Magnetization dynamics; Spin-pumping; SAFs, SAF; synthetic antiferromagnets; coupled magnetic trilayers; magnetic multilayers; ferromagnetic resonance; electrically-detected ferromagnetic resonance; FMR; ED-FMR; ST-FMR
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31295) publication
Reseach data in the HZDR data repository RODARE
Publication date: 2019-12-09 Open access
The influence of an applied magnetic field on the self-assembly of magnetic nanogels
Using Langevin dynamics simulations, we investigate the self-assembly of magnetic nanogels in the presence of applied magnetic fields of moderate strength. We find that even weak fields lead to drastic changes in the structure factors of both, the embedded magnetic nanoparticles and of whole nanogel particles. Nanogels assemble by uniting magnetic particle clusters forming inter-gel bridges. At zero field the average amount of such bridges for a pair of nanogels is close to one, whereas even for weak fields it fastly doubles. Rapid growth of cluster size at low values of the applied field is followed by a broad region of slow increase, caused by the mechanical constraints imposed the polymer matrix. The influence of the latter manifests itself in both, the slow growth of the magnetisation curve at intermediate fields and the slow decay of the total Zeeman energy.
Keywords: Magnetic nanogels; Self-assembly; Molecular dynamics
Journal of Molecular Liquids 307(2020), 112902
Online First (2020) DOI: 10.1016/j.molliq.2020.112902
Cited 14 times in Scopus
Contribution to WWW
arXiv:2004.00725 [cond-mat.soft]: https://arxiv.org/abs/2004.00725
Diffusion of single active-dipolar cubes in applied fields
“Active matter” refers to a class of out-of-equilibrium systems whose ability to transform environmental energy to kinetic energy is sought after in multiple fields of science and at very different length scales. At microscopic scales, an important challenge lies in overpowering the particles reorientation due to thermal fluctuations, especially in nano-sized systems, to create non-random, directed motion, needed for a wide range of possible applications. In this article, we employ molecular dynamics simulations to show that the diffusion of a self-propelling dipolar nanocube can be enhanced in a pre-defined direction with the help of a moderately strong applied magnetic field, overruling the effect of the thermal fluctuations. Furthermore, we show that the direction of diffusion is given by the orientation of the net internal magnetisation of the cube. This can be used to determine experimentally the latter in synthetically crafted active cobalt ferrite nanocubes.
Keywords: Active matter; Magnetic cubes; Molecular dynamics
Journal of Molecular Liquids 304(2020), 112688
Online First (2020) DOI: 10.1016/j.molliq.2020.112688
Cited 4 times in Scopus
Contribution to WWW
arXiv:2002.04299 [cond-mat.soft]: https://arxiv.org/abs/2002.04299
Measuring FORCs diagrams in computer simulations as a mean to gain microscopic insight
FORCs (first-order reversal curves) diagrams prove to be an efficient experimental technique to investigate magnetic interactions in complex systems. In experiments, as a rule, it is difficult to relate actual microstructural changes to the evolution of FORCs diagrams. Here, using Molecular Dynamics simulations, we calculate FORCs for two simple models of a magnetic elastomer. The simplicity of these models allows to relate directly both, the rigidity of the matrix and the magnetoelastic coupling to the shape and intensity of FORCs diagrams.
Keywords: FORC Molecular dynamics; Magnetic elastomers; Magneto-elastic coupling
Journal of Magnetism and Magnetic Materials 501(2020), 166393
Online First (2020) DOI: 10.1016/j.jmmm.2020.166393
Cited 4 times in Scopus
- Final Draft PDF 603 kB Secondary publication
Unknotting of quasi-two-dimensional ferrogranular networks by in-plane homogeneous magnetic fields
Our ongoing research addresses, by means of experiments and computer simulations, the aggregation process that takes place in a shaken granular mixture of glass and magnetized ferrous alloy beads when the shaking amplitude is suddenly decreased. After this quenching, the magnetized beads form a transient network that coarsens in time into compact clusters, following a viscoelastic phase separation. Here we focus on the quasi-two-dimensional case, analyzing in computer simulations the effects of a magnetic field parallel to the system plane. Our results evidence that the field drastically changes the structure of the forming network: chains and elongated clusters parallel to the field are favored whereas perpendicular connecting structures tend to be suppressed, leading to the unknotting of the networks which are observed at zero field. Importantly, we found that moderate field strengths lead to the formation of larger clusters at intermediate time intervals than in the case of weak and strong fields. Moreover, the latter tend to limit the overall growth of the clusters at longer time scales. These results may be relevant in different systems governed by similar magnetically driven aggregation processes as, for example, in the formation of iron-rich planetesimals in protoplanetary discs or for magnetic separation systems.
Keywords: Ferrogranulate mixture; Field induced network unknotting; Susceptible dipolar hard spheres; Langevin dynamics simulations; Viscoelastic phase separation; Transient network
Journal of Magnetism and Magnetic Materials 499(2020), 166182
Online First (2020) DOI: 10.1016/j.jmmm.2019.166182
Cited 1 times in Scopus
Contribution to WWW
arXiv:1910.00317 [cond-mat.soft]: https://arxiv.org/abs/1910.00317
The influence of crosslinkers and magnetic particle distribution along the filament backbone on the magnetic properties of supracolloidal linear polymer-like chains
Diverse polymer crosslinking techniques allow the synthesis of linear polymer-like structures whose monomers are colloidal particles. In the case where all or part of these colloidal particles are magnetic, one can control the behaviour of these supracolloidal polymers, known as magnetic filaments (MFs), by applied magnetic fields. However, the response of MFs strongly depends on the crosslinking procedure. In the present study, we employ Langevin dynamics simulations to investigate the influence of the type of crosslinking and the distribution of magnetic particles within MFs on their response to an external magnetic field. We found that if the rotation of the dipole moment of particles is not coupled to the backbone of the filament, the impact of the magnetic content is strongly decreased.
Keywords: Supracolloidal magnetic polymers; Magnetisation; Crosslinking methods; Langevin dynamics simulations
Journal of Magnetism and Magnetic Materials 497(2020), 166029
Online First (2019) DOI: 10.1016/j.jmmm.2019.166029
Contribution to WWW
arXiv:1910.11607 [cond-mat.soft]: https://arxiv.org/abs/1910.11607
Suspensions of magnetic nanogels at zero field: Equilibrium structural properties
Magnetic nanogels represent a cutting edge of magnetic soft matter research due to their numerous potential applications. Here, using Langevin dynamics simulations, we analyse the influence of magnetic nanogel concentration and embedded magnetic particle interactions on the self-assembly of magnetic nanogels at zero field. For this, we calculated radial distribution functions and structure factors for nanogels and magnetic particles within them. We found that, in comparison to suspensions of free magnetic nanoparticles, where the self-assembly is already observed if the interparticle interaction strength exceeds the thermal fluctuations by approximately a factor of three, self-assembly of magnetic nanogels only takes place by increasing such ratio above six. This magnetic nanogel self-assembly is realised by means of favourable close contacts between magnetic nanoparticles from different nanogels. It turns out that for high values of interparticle interactions, corresponding to the formation of internal rings in isolated nanogels, in their suspensions larger magnetic particle clusters with lower elastic penalty can be formed by involving different nanogels. Finally, we show that when the self-assembly of these nanogels takes place, it has a drastic effect on the structural properties even if the volume fraction of magnetic nanoparticles is low.
Keywords: Magnetic nanogels; Magnetic self-assembly; Langevin dynamics; Structure factor
Journal of Magnetism and Magnetic Materials 498(2020), 166152
Cited 5 times in Scopus
Contribution to WWW
arXiv:1911.06031 [cond-mat.soft]: https://arxiv.org/abs/1911.06031v1
The structure of clusters formed by Stockmayer supracolloidalmagnetic polymers
Unlike Stockmayer fluids, that prove to undergo gas-liquid transition on cooling, the system of dipolar hard or soft spheres without any additional central attraction so far has not been shown to have a critical point. Instead, in the latter, one observes diverse self-assembly scenarios. Crosslinking dipolar soft spheres into supracolloidal magnetic polymer-like structures (SMPs) changes the self-assembly behaviour. Moreover, aggregation in systems of SMPs strongly depends on the constituent topology. For Y- and X-shaped SMPs, under the same conditions in which dipolar hard spheres would form chains, the formation of very large loose gel-like clusters was observed (E. Novak et al., J. Mol. Liq. 271, 631 (2018)). In this work, using molecular dynamics simulations, we investigate the self-assembly in suspensions of four topologically different SMPs --chains, rings, X and Y-- whose monomers interact via Stockmayer potential. As expected, compact drop-like clusters are formed by SMPs in all cases if the central isotropic attraction is introduced, however, their shape and internal structure turn out to depend on the SMPs topology.
- Final Draft PDF 634 kB Secondary publication
Particle Surfaces to Study Macrophage Adherence, Migration, and Clearance
Septiadi, D.; Lee, A.; Spuch‐Calvar, M.; Lee, M. T.; Spiaggia, G.; Abdussalam, W.; Rodriguez‐Lorenzo, L.; Taladriz‐Blanco, P.; Rothen‐Rutishauser, B.; Petri‐Fink, A.
Nanoparticle adsorption to substrates pose a unique challenge to understand uptake mechanisms as it involves the organization of complex cytoskeletal components by cells to perform endocytosis/phagocytosis. In particular, it is not well‐understood from a cell mechanics perspective how the adhesion of particles on substrate will influence the ease of material clearance. By using a particle model, key contributing factors underlying cell adhesion on nonporous silica particle surfaces, migration and engulfment, are simulated and studied. Following a 24 h incubation period, monocyte‐derived macrophages and A549 epithelial cells are able to adhere and remove particles in their local vicinity through induction of adhesive pulling arise from cell traction forces and phagocytic/endocytic mechanisms, in a size‐dependent manner. It is observed that such particle‐decorated surfaces can be used to address the influence of surface topography on cell behavior. Substrates which presented 480 nm silica particles are able to induce greater development and maturation of focal adhesions, which play an important role in cellular mechanoregulation. Moreover, under a chemotactic influence, in the presence of 30% fetal bovine serum, macrophages are able to uptake the particles and be directed to translocate along a concentration gradient, indicating that local mechanical effects do not substantially impair normal physiological functions.
Advanced Functional Materials 30(2020)34, 2002630
Cited 4 times in Scopus
Atomistic simulation of PDADMAC/PSS oligoelectrolyte multilayers: overall comparison of tri- and tetra-layer systems
By employing large-scale molecular dynamics simulations of atomistically resolved oligoelectrolytes in aqueous solutions, we study in detail the first four layer-by-layer deposition cycles of an oligoelectrolyte multilayer made of poly(diallyl dimethyl ammonium chloride)/poly(styrene sulfonate sodium salt) (PDADMAC/PSS). The multilayers are grown on a silica substrate in 0.1 M NaCl electrolyte solutions and the swollen structures are then subsequently exposed to varying added salt concentration. We investigated the microscopic properties of the films, analyzing in detail the differences between three- and four-layer systems. Our simulations provide insights into the early stages of growth of a multilayer, which are particularly challenging for experimental observations. We found rather strong complexation of the oligoelectrolytes, with fuzzy layering of the film structure. The main charge compensation mechanism is for all cases intrinsic, whereas extrinsic compensation is relatively enhanced for the layer of the last deposition cycle. In addition, we quantified other fundamental observables of these systems, such as the film thickness, water uptake, and overcharge fractions for each deposition layer.
- Final Draft PDF 3,2 MB Secondary publication
Single-step, High Pressure, and Two-Step Spark Plasma Sintering of UO2 nanopowders
Three different Spark Plasma Sintering (SPS) treatments were applied to highly sinteractive, near-stoichiometric UO2.04 nanocrystalline (5 nm) powders produced by U(IV) oxalate hydrothermal decomposition at 170 °C. The sintering conditions for reaching 95 % Theoretical Density (TD) in regular SPS, high pressure SPS (HP-SPS), and, for the first time, two-step SPS (2S-SPS), were found. Densification to 95 % TD was achieved at 1000 °C in regular SPS (70 MPa applied pressure), 660 °C in HP-SPS (500 MPa), and 650-550 °C in 2S-SPS (70 MPa). With the goal of minimising the grain growth during densification, the sintering treatments were optimised to favour densification over coarsening, and the final microstructures thus obtained are compared. Otherwise identical, stochiometric UO2 samples of different grain sizes, ranging from 3.08 μm to 163 nm, were produced. Room-temperature oxidation of the powders could not be avoided due to their nanometric dimensions, and a final annealing treatment was designed to reduce hyper stoichiometric samples to UO2.00.
Keywords: Spark Plasma Sintering; Uranium Dioxide; Microstructure; Coarsening; Two Step Sintering
Journal of the European Ceramic Society 41(2021)6, 3655-3663
Cited 4 times in Scopus
Itinerant metamagnetic transition in the ferromagnet LuCo3 induced by high field: Instability of the 3d-electron subsystem
Neznakhin, D. S.; Radzivonchik, D. I.; Gorbunov, D.; Andreev, A. V.; Sebek, J.; Lukoyanov, A. V.; Bartashevich, M. I.
LuCo3 is an itinerant ferromagnet whose magnetic properties strongly depend on the position of the 3d electronic states relative to the Fermi level. Here, we report on the magnetization of a LuCo3 single crystal in pulsed magnetic fields up to 58 T. We find a field-induced phase transition just below 50 T from a low-spin to a high-spin state. The transition shows a pronounced anisotropy of the magnetization jump and hysteresis. A series of ab initio calculations based on the density functional theory show that the transition is due to a significant change in the occupancies of the Co 3d electronic states. At the same time, some features in the majority spin density of the Co 3d states are slightly modified and pass through the Fermi level when the spin state is changed, which leads to the instability of the 3d-electron subsystem. Thereby, the applied magnetic field causes a significant redistribution in the majority and minority spin states in the Co 3d subsystem, which results in the sharp change in the magnetization.
Enhanced magnetocaloric effect in distilled terbium and emergence of novel properties after severe plastic deformation
Tereshina-Chitrova, E. A.; Korneeva, Y. V.; Ozherelkov, D. Y.; Dolezal, P.; Tereshina, I. S.; Kaminskaya, T. P.; Gorbunov, D.; Dobatkin, S. V.; Minarik, P.
We report the magneto-structural and magnetocaloric properties study of Tb purified by distillation and further processed by severe plastic deformation (SPD). Both parent and the SPD-processed Tb contain nanosized structural elements and have a very pronounced (00 l ) texture. We observe an improved magnetocaloric effect (MCE) in the distilled nanocrystalline Tb while novel properties emerge in the sample after severe plastic deformation. The latter demonstrates zero thermal expansion over a wide temperature range while its MCE vanishes. We show that the absolutely new physical properties in Tb result from the structural transformation and modification of magnetic interactions.
The old, unique C1 chondrite Flensburg – Insight into the first processes of aqueous alteration, brecciation, and the diversity of water-bearing parent bodies and lithologies
Bischoff, A.; Alexander, C.; Barrat, J.-A.; Burkhardt, C.; Busemann, H.; Degering, D.; Di Rocco, T.; Fischer, M.; Fockenberg, T.; Foustoukos, D.; Gattacceca, J.; Da Assuncao Godinho, J. R.; Harries, D.; Heinlein, D.; Hellmann, J.; Hertkorn, N.; Holm, A.; Jull, A. J. T.; Kerraouch, I.; King, A. J.; Koll, D.; Lachner, J.; Ludwig, T.; Merchel, S.; Mertens, C.; Neumann, W.; Pack, A.; Patzek, M.; Pavetich, S.; Morino, P.; Reitze, M. P.; Rüfenacht, M.; Rugel, G.; Schmidt, C.; Schmitt-Kopplin, P.; Schönbächler, M.; Trieloff, M.; Wallner, A.; Wimmer, K.; Wölfer, E.; Kleine, T.
On September 12, 2019 at 12:49:48 (UT) a bolide was observed by hundreds of eye-witnesses from the Netherlands, Germany, Belgium, Denmark and the UK. One day later a small meteorite stone was found by accident in Flensburg. The presence of short-lived cosmogenic radionuclides with half-lives as short as 16 days proves the recent exposure of the found object to cosmic rays in space linking it clearly to the bolide event. An exceptionally short exposure time of ~5000 years was determined. The 24.5 g stone has a fresh black fusion crust, a low density of <2 g/cm³, and a magnetic susceptibility (MS) of logχ= 4.35 (χ in 10-9 m³/kg). The rock consists of relict chondrules and clusters of sulfide and magnetite grains set in a fine-grained matrix. The most abundant phases are phyllosilicates. Carbonates (~3.9 vol.%) occur as calcites, dolomites, and a Na-rich phase. The relict chondrules (often surrounded by sulfide laths) are free of anhydrous silicates and contain abundant serpentine. Lithic clasts are also surrounded by similar sulfide laths partly intergrown with carbonates. ⁵³Mn-⁵³Cr ages of carbonates in Flensburg indicate that brecciation and contemporaneous formation of the pyrrhotite-carbonate intergrowths by hydrothermal activities happened no later than 4564.6±1.0 Ma (using D'Orbigny as Mn-Cr anchor). This corresponds to 2.6±1.0 or 3.4±1.0 Ma after CAIs, depending on the exact age CAI age. This is the oldest dated evidence for brecciation and carbonate formation, which likely occurred during parent body growth and incipient heating due to ²⁶Al.
The O isotope composition of Flensburg reveals that it plots at the ¹⁶O-rich end of the CM chondrite field and in the transition field to the CV-CK-CR chondrites. This is unexpected since the O-isotope compositions of strongly aqueously-altered chondrites are generally found to be at the ¹⁶O-poor end of the CM range. The mass-dependent Te isotopic compositionof Flensburg is slightly different from mean CM chondrites and is most similar to those of the ungrouped C2 chondrite Tagish Lake. On the other hand, the 50Ti and 54Cr isotope nomalies indicate that Flensburg is similar to CM chondrites, as do the ~10 wt.% H₂O. Yet, the bulk Zn, Cu, and Pb concentrations are about 30% lower than those of mean CM chondrites. The He, Ne and, Ar isotopes of Flensburg show no solar wind contribution; its trapped noble gas signature is similar to that of CMs with a slightly lower concentration of ²⁰Netr.
Based on the bulk H, C and N elemental abundances and isotopic compositions, Flensburg is clearly unique among the analyzed chondrites as it has the lightest bulk H and N isotopic compositions of any type 1 or 2 chondrite. The number of soluble organic compounds in Flensburg is even lower than that of the brecciated CI chondrite Orgueil.
The extraordinary significance of Flensburg is given by the observation that it represents the oldest chondrite sample, in which the contemporaneous episodes of aqueous alteration and brecciation are 81 perfectly visible. The characterization of a large variety of carbonaceous chondrites with different alteration histories is important for interpreting returned samples from the OSIRIS-REx and Hayabusa 2 missions.
Keywords: AMS; meteorite; cosmic exposure
- DOI: 10.17815/jlsrf-3-159 is cited by this (Id 31282) publication
Geochimica et Cosmochimica Acta 293(2021), 142-186
Online First (2020) DOI: 10.1016/j.gca.2020.10.014
Cited 13 times in Scopus
Benchmark hyperspectral field and laboratory data against X-ray diffraction (XRD), Portable X-ray fluorescence (pXRF) and Scanning Electron Microscopy with Mineral Liberation Analysis (SEM-MLA) data.
A benchmarking databank based on different spectral, multiscale, multisensor exploration technologies was created. The benchmarking is composed of 63 rock samples from drill cores from a polymetallic (Cu-Zn-Pb) massive sulphide deposit in the Iberian Pyrite Belt. The samples had been analyzed by portable XRF, point hyperspectral spectrometer, portable FTIR, VNIR-SWIR imaging hyperspectral sensor and a LWIR imaging thermal hyperspectral sensor.
The mineralogical information from the boreholes will be complemented with mineral chemistry extracted from the spectral features of the alteration minerals that display chemical variations. The chemical variations in minerals generate shifts on the position of the metal-OH vibrational absorptions. This systematic variation can be recorded using the SWIR wavelength region of hyperspectral data. The shifts sometimes occur systematically with respect to ore deposits and hence mineral chemical information extracted from hyperspectral surveys can be used for mineral exploration. The mineral chemistry of the samples will be validated using scanning electron microscopy data integrated with the mineral liberation analysis (SEM-MLA).
In order to apply this type of research techniques aiming at a 3D model of the alteration areas of the entire deposit based on the hyperspectral data, it is essential to have the availability of drill cores along the whole extension of the mineral deposit. Consequently, the research was focused in a study area in the Southern Spain, the Elvira deposit of the MATSA–VALORIZA mining company, where 7 km of drill core were scanned with the hyperspectral sensors.
New exploration technologies (NEXT) is a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement nº 776804.
Keywords: Benchmarking; Hyperspectral; Drill core scanner; pFTIR; PXRF; VNIR - SWIR - LWIR
HIF, Freiberg: NEXT Project, 2020
Intrinsic plasticity of silicon nanowire neurotransistors: plots of the figures 1-2
Data and Figures supporting the publication
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-01 Open access
Rapidly Switchable Universal CAR-T Cells for Treatment of CD123-Positive Leukemia
Chimeric antigen receptor T cells (CAR-T) targeting CD19 or B cell maturation antigen (BCMA) are highly effective against B cell malignancies. However, application of CAR-T to less differentially expressed targets remains a challenge due to lack of tumor-specific antigens and CAR-T controllability. CD123, a highly promising leukemia target, is expressed not only by leukemic and leukemia-initiating cells, but also by myeloid, hematopoietic progenitor, and certain endothelial cells. Thus, CAR-T lacking fine-tuned control mechanisms pose a high toxicity risk. To extend the CAR-T target landscape and widen the therapeutic window, we adapted our rapidly switchable universal CAR-T platform (UniCAR) to target CD123. UniCAR-T efficiently eradicated CD123+ leukemia in vitro and in vivo. Activation, cytolytic response, and cytokine release were strictly dependent on the presence of the CD123-specific targeting module (TM123) with comparable efficacy to CD123-specific CAR-T in vitro. We further demonstrated a pre-clinical proof of concept for the safety-switch mechanism using a hematotoxicity mouse model wherein TM123-redirected UniCAR-T showed reversible toxicity toward hematopoietic cells compared to CD123 CAR-T. In conclusion, UniCAR-T maintain full anti-leukemic efficacy, while ensuring rapid controllability to improve safety and versatility of CD123-directed immunotherapy. The safety and efficacy of UniCAR-T in combination with TM123 will now be assessed in a phase I clinical trial (ClinicalTrials.gov: NCT04230265).
Molecular Therapy Oncolytics 17(2020), 408-420
Cited 32 times in Scopus
Development and In Vivo Application of a Water-Soluble Anticancer Copper Ionophore System Using a Temperature-Sensitive Liposome Formulation
Liposomes containing copper and the copper ionophore neocuproine were prepared and characterized for in vitro and in vivo anticancer activity. Thermosensitive PEGylated liposomes were prepared with di_erent molar ratios of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and hydrogenated soybean phosphatidylcholine (HSPC) in the presence of copper(II) ions. Optimal, temperature dependent drug release was obtained at 70:30 DPPC to HSPC weight ratio. Neocuproine (applied at 0.2 mol to 1 mol phospholipid) was encapsulated through a pH gradient while using unbuffered solution at pH 4.5 inside the liposomes, and 100 mM HEPES bu_er pH 7.8 outside the liposomes. Copper ions were present in excess, yielding 0.5 mM copper-(neocuproine)2 complex and 0.5 mM free copper. Pre-heating to 45 °C increased the toxicity of the heat-sensitive liposomes in short-term in vitro experiments, whereas at 72 h all investigated liposomes exhibited similar in vitro toxicity to the copper(II)-neocuproine complex (1:1 ratio). Thermosensitive liposomes were found to be more effective in reducing tumor growth in BALB/c mice engrafted with C26 cancer cells, regardless of the mild hyperthermic treatment. Copper uptake of the tumor was verified by PET/CT imaging following treatment with [64Cu]Cu-neocuproine liposomes. Taken together, our results demonstrate the feasibility of targeting a copper nanotoxin that was encapsulated in thermosensitive liposomes containing an excess of copper.
Keywords: eocuproine; themosensitive liposomal formulation; mild hyperthermia; copper nanotoxin; MRPS; in vivo antitumor effect
Heisenberg limit for detecting vacuum birefringence
Quantum electrodynamics predicts the vacuum to behave as a nonlinear medium, including effects such as birefringence. However, for experimentally available field strengths, this vacuum polarizability is extremely small and thus very hard to measure. In analogy to the Heisenberg limit in quantum metrology, we study the minimum requirements for such a detection in a given strong field (the pump field). Using a laser pulse as the probe field, we find that its energy must exceed a certain threshold depending on the interaction time. However, a detection at that threshold, i.e., the Heisenberg limit, requires highly nonlinear measurement schemes--while for ordinary linear-optics schemes, the required energy (Poisson or shot noise limit) is much larger. Finally, we discuss several currently considered experimental scenarios from this point of view.
Keywords: Quantum Electrodynamics; Vacuum birefringence; Heisenberg limit
Physical Review D 101(2020), 116019
Online First (2020) DOI: 10.1103/PhysRevD.101.116019
Cited 6 times in Scopus
An overview on electrochemical simulation with OpenFOAM
Modelling electrochemical devices, such as fuel cells, batteries or electrolysers asks typically for coupling electrochemistry with flow simulation and mass transfer. While solvers for mass transfer and fluid dynamics are well established in the open-source CFD library OpenFOAM, electrochemistry simulations are a rather young field of application. The presentation shall give therefore an overview on different approaches on how to simulate potential and current distributions as well as the cell voltage of electrochemical devices using OpenFOAM.
OpenFOAM Conference, 13.10.2020, Online, Deutschland
Status of the STM-FPGA-DAQ HLS-Cores for LaBr Peak Detection and Zero Suppression
Brief overview and status of the STM-FPGA-DAQ HLS-Cores for LaBr peak detection, moving window deconvolution and zero suppression
Keywords: Data Management; DAQ; FPGA; Mu2e
Invited lecture (Conferences)
Mu2e Collaboration Meeting, STM Workshop, 16.06.2020, Online, Online
Interprofessionelle Kooperation: Bedarf und Komplexizität bei prospektiv-nuklearmedizinischen Studien am Beispiel des DKTK-Multicenter-Trials mit [68Ga]Ga-PSMA-11
Ziel/Aim: Um neue PET-Tracer in die Patientenversorgung überführen zu können, werden in der nuklearmedizinischen Forschung zunehmend prospektiv-klinische Studien mit den vielversprechendsten Radioliganden initiiert. Damit diese Studien möglichst effizient und effektiv durchgeführt werden können, bedarf es der möglichst engen Kooperation und Kommunikation von Expert*innen aus verschiedenen Berufsgruppen.
Methodik/Methods: Wir beleuchten am Beispiel der Multicenter-Studie „Ga-68-PSMA-11 in Hochrisiko-Prostatakrebs“ der Phasen-I/-II, welche wesentlichen Professionen aus forschender Klinik, Wirkstoffherstellung und Verwaltung bei der Planung, Vorbereitung und Durchführung prospektiv-nuklearmedizinischer Studien involviert sein können und welche Aufgaben diese zur Studienverwirklichung wahrnehmen. Darauf aufbauend leiten wir organisatorische Maßnahmen ab, durch die die interprofessionelle Kooperation bei prospektiven Bildgebungsstudien (auch über mehrere Prüfzentren) gefördert werden kann.
Ergebnisse/Results: In die Beispielstudie sind im engeren fachlichen Kreis Mediziner aus Nuklearmedizin/Urologie/Pathologie, MTA-Rs, Studienassistenten, Radiochemiker/-pharmazeuten, BTA/CTA, MTA und Gesundheits-/Krankenpfleger involviert. Im weiteren fachlichen Kreis sind ferner Strahlenschutzbeauftragte, Qualitätsmanager, klinische Monitore, Juristen, Datenschutzbeauftragte, Projektmanager und Studienkoordinatoren eingebunden, und dies jeweils an bis zu elf Prüfzentren in Deutschland, Österreich und der Schweiz.
Schlussfolgerungen/Conclusions: Interprofessionelle Kooperation ist für die Durchführung prospektiv-nuklearmedizinischer Studien essentiell. Hierzu bedarf es u. a. der grundlegenden Bereitschaft, sich in andere (Tätigkeits-)Rollen hineinzuversetzen und über Professionsgrenzen hinaus kooperieren zu wollen, ausreichend Zeit zum gegenseitigen Austausch, Fähigkeit/Fertigkeiten zum berufsübergreifenden Projektmanagement und eine integrale Betrachtung benötigter Expertisen mit Stärkung professionsübergreifender Kommunikation insbesondere über die Leitungsebene.
58. DGN-Jahrestagung 2020, 06.-09.07.2020, Leipzig, Deutschland
GMP Requirements for a Clinical Trial with 68Ga-PSMA-11 - Experience from a Multi-Centre Trial
Invited lecture (Conferences)
Annual Congress of the European Association of Nuclear Medicine, 15.-19.10.2016, Barcelona, Spanien
Cited 3 times in Scopus
Molecular Imaging of Prostate Cancer: A direct comparison of the preclinical characteristics of [18F]DCFPyL and [18F]PSMA-1007 and the impact of glutamic acids on [18F]PSMA-1007
Aim: For the imaging of PSMA-positive prostate cancer, several fluorine-18 (18F)-labelled compounds have been developed and translated into the clinics. Next to a clinical study comparing the tracer-specific characteristics of [18F]DCFPyL and [18F]PSMA-1007 intra-individually(1), a direct comparison of their preclinical characteristics has only recently been published(2). In this work, the importance of glutamic acids in the structure of [18F]PSMA-1007 is further elucidated using derivatives with none to three glutamic acids (Glu), respectively. Furthermore, [18F]DCFPyL and [18F]PSMA-1007 are evaluated regarding their preclinical characteristics using the in vitro and in vivo methods established at DKFZ Heidelberg, Germany. Materials and Methods: The precursors for radiofluorination containing different amino acid linkers (0-3 Glu) were synthesized by means of solid phase chemistry. The radiolabeling of [18F]PSMA-1007, its derivatives, and [18F]DCFPyL were performed prior to each experiment as described(3,4). The binding affinities of non-radioactive reference compounds were determined by competitive binding assays against [68Ga]Ga-PSMA-10 in LNCaP cells. The internalization of the respective radioligands in LNCaP cells was compared. Biodistribution and pharmacokinetics were evaluated in vivo in LNCaP-tumor bearing BALB/c Nude mice using μPET. Results: The Glu variation in the linker structure resulted in similar binding affinities (Ki 3-14 nM) whereby the insertion of three Glu showed the highest Ki values. Internalization assays revealed that the insertion of Glu influences the internalization rate, whereby the insertion of two Glu ([18F]PSMA-1007) leads to the highest internalization rate (54.04±13.7%) in a total range between 27.3±3% to 54±13.7%. In comparison to [18F]PSMA-1007, a higher proportion of [18F]DCFPyL remains cell surface bound; only 27.83 ± 4.31% of the radiotracer is internalized. [18F]DCFPyL also has a slightly lower binding affinity (18.02±9.63 nM). μPET imaging showed outstanding imaging properties, especially of [18F]DCFPyL and [18F]PSMA-1007. In mice, the liver uptake is reduced by introduction of Glu linkers. The data will be analysed more detailed soon. Conclusion: Comparative cell experiments revealed a high binding affinity for all tracers and the highest internalization rate for [18F]PSMA-1007. The insertion of Glu in the linker structure plays an important role in pharmacokinetics due to the decreased lipophilicity of the respective radiotracer. Especially [18F]DCFPyL and [18F]PSMA-1007 are of excellent imaging quality. Their apparent non-inferiority is currently under further assessment in clinical trials. References: (1) Giesel F et al (2017): JNM, doi: 10.2967/jnumed.117.204669. (2) Robu S et al (2018): EJNMMI Res., 8(1):30. (3) Cardinale J et al. (2017): JNM, 58(3):425-431. (4) Chen Y et al. (2011): Clin Cancer Res., 17(24):7645-53.
Annual Congress of the European Association of Nuclear Medicine, 13.-17.10.2018, Düsseldorf, Deutschland
Cited 4 times in Scopus
Initiation Of A Prospective Clinical Multicentre Trial With Local Production Of A Short-Lived PSMA-PET Radiopharmaceutical In The D-A-CH-Region: Chances And Experiences
Aim/Introduction: The development of innovative radiotracers targeting PSMA for non-invasive imaging of prostate cancer and successive treatment results in an increasing number of multicentre clinical trials using the most promising PSMA ligand candidates. For prospective studies with short-lived radiopharmaceuticals like [68Ga]Ga-PSMA-11, a regulatory and country-specific structure has to be established before recruitment of patients is possible. This structure allows the decentralized manufacturing of the investigational medicinal product (IMP) according to Good Manufacturing (GMP) and subsequent implementation of the respective tracer compliant with Good Clinical Practice (GCP). Materials and Methods: For the multicenter clinical trial (phases-I/-II) ,,Ga-68-PSMA-11 in high-risk prostate cancer“ (NCT03362359) within DKTK a harmonized decentralized radiotracer production in multiple radiopharmacies has been set up for the very first time in the German speaking Radiopharmacy/Nuclear Medicine Community. In this prospective clinical study Nuclear Medicine physicians, radiopharmacists, urologists, pathologists and study related experts like lawyers and study nurses out of eleven study sites within the so-called D-A-CH region (Germany-Austria-Switzerland) have been involved. The basis for the accurately specified radioactive IMP manufacturing procedure was defined by EU-GMP requirements plus national standards (e.g. Medicinal Products Act and Radiation Protection Law). Results: For the recruiting study sites the required allowances, e.g. manufacturing authorization from local authorities as well as approval from ethics committees and national regulatory bodies such as BfS and BfArM in Germany, BASG in Austria as well as BAG and Swissmedic in Switzerland, have been obtained. The challenge of manufacturing a short-lived radiopharmaceutical at each of the participating geographically different sites with identical specification by adaption of production and quality control processes and parameters according to the IMP dossier (IMPD) during the starting phase of the clinical trial under a centralized quality assurance management has been achieved. Conclusion: The initiation and establishment of a multicentre clinical trial including the manufacturing of a short-lived radiopharmaceutical IMP across local study sites is very complex, but manageable. In view of the high European and national regulatory and legal burdens and the number of involved partners it is feasible in a defined time frame. Based on the achieved structures, the decentralized manufacture of novel short-lived radiopharmaceuticals can be established in the D-A-CH region and even on a European level for further investigator initiated multicentre clinical trials. We estimate our experiences important for the development of the field Nuclear Medicine at the national and international level taking into account the new EU regulation No 536/2014. References: None.
Annual Congress of the European Association of Nuclear Medicine, 12.-16.10.2019, Barcelona, Spanien
Supplementary Video sets for the publication
6 supplementary videos
- DOI: 10.1002/adfm.202003851 references this (Id 31268) publication
Reseach data in the HZDR data repository RODARE
Publication date: 2020-06-29 Open access
Inverse Solidification Induced by Active Janus Particles
Crystals melt when thermal excitations or the concentration of defects in the lattice is sufficiently high. Upon melting, the crystalline long-range order vanishes, turning the solid to a fluid. In contrast to this classical scenario of solid melting, here we demonstrate a counter-intuitive behavior of the occurrence of crystalline long-range order in an initially disordered matrix. This unusual solidification is demonstrated in a system of passive colloidal particles accommodating chemically active defects - photocatalytic Janus particles. The observed crystallization occurs when the amount of active-defect-induced fluctuations (which is the measure of the effective temperature) reaches critical value. The driving mechanism behind this unusual behavior is purely internal and resembles a blast-induced solidification. Here the role of "internal micro-blasts" is played by the photochemical activity of defects residing in the colloidal matrix. The defect-induced solidification occurs under non-equilibrium conditions: the resulting solid exists as long as a constant supply of energy in the form of ion flow is provided by the catalytic photochemical reaction at the surface of active Janus particle defects. Our findings could be useful for understanding of the phase transitions of matter under extreme conditions far from thermodynamic equilibrium.
Advanced Functional Materials 30(2020)29, 2003851
Cited 15 times in Scopus
Contribution to WWW
arXiv:2010.03794 [cond-mat.soft]: https://arxiv.org/abs/2010.03794
Intrinsic plasticity of silicon nanowire neurotransistors for dynamic memory and learning functions
Neuromorphic architectures merge learning and memory functions within a single unit cell and in a neuron-like fashion. Research in the field has been mainly focused on the plasticity of artificial synapses. However, the intrinsic plasticity of the neuronal membrane is also important in the implementation of neuromorphic information processing. Here we report a neurotransistor made from a silicon nanowire transistor coated by an ion-doped sol–gel silicate film that can emulate the intrinsic plasticity of the neuronal membrane. The neurotransistors are manufactured using a conventional complementary metal–oxide–semiconductor process on an 8-inch (200 mm) silicon-on-insulator wafer. Mobile ions allow the film to act as a pseudo-gate that generates memory and allows the neurotransistor to display plasticity. We show that multiple pulsed input signals of the neurotransistor are non-linearly processed by sigmoidal transformation into the output current, which resembles the functioning of a neuronal membrane. The output response is governed by the input signal history, which is stored as ionic states within the silicate film, and thereby provides the neurotransistor with learning capabilities.
Nature Electronics 3(2020), 398-408
Online First (2020) DOI: 10.1038/s41928-020-0412-1
Cited 19 times in Scopus
- Secondary publication expected
Nanosensors-Assisted Quantitative Analysis of Biochemical Processes in Droplets
Belyaev, D.; Schütt, J.; Ibarlucea, B.; Rim, T.; Baraban, L.; Cuniberti, G.
Here, we present a miniaturized lab-on-a-chip detecting system for an all-electric and label-free analysis of the emulsion droplets incorporating the nanoscopic silicon nanowires-based field-effect transistors (FETs). We specifically focus on the analysis of β-galactosidase activity, which is an important enzyme in the glycolysis metabolic pathway. Furthermore, the efficiency of the synthesis and action of β-galactosidase can be one of the markers for several diseases, eg., cancer, hyper/hypoglycemia, cell senescence, or other disruptions in cell functioning. We measure the reaction and reaction kinetics-associated shift of the source-to-drain current I sd in the system, which is caused by the change of the ionic strength of the microenvironment. With these results, we demonstrate that the ion-sensitive FETs are able to sense the interior of the aqueous reactors; thus, the conjunction of miniature nanosensors and droplet-based microfluidic systems conceptually opens a new route toward a sensitive, optics-less analysis of biochemical processes.
Experimental control of laser proton acceleration beyond 50 MeV
Ziegler, T.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Garten, M.; Gaus, L.; Gebhardt, R.; Helbig, U.; Irman, A.; Kiriyama, H.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Nishiuchi, M.; Obst-Hübl, L.; Püschel, T.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.
We report on the ongoing plasma accelerator development at the HZDR, moving from plasma-acceleration studies towards real plasma-accelerators that can be controlled and applied in the lab.
We show experimental investigations of proton acceleration from laser-irradiated solid foils with the DRACO PW laser, where highest proton cut-off energies were achieved for temporal pulse shape parameters well different from that of a Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal laser pulse shape and to study the effect on proton acceleration from thin foil targets. The results show that short and asymmetric pulses generated by positive third order dispersion values are favourable for proton acceleration and can lead to maximum energies of 60 MeV for thin plastic foils. Assuming appropriate control of the spectral phase of the laser and comparable temporal contrast conditions, we believe that the presented method can be universally applied to improve the proton acceleration performance using any other laser system operated in the PW regime.
6. Annual Matter and Technology Meeting, 17.-18.06.2020, Jülich, Deutschland
Synthesis, characterization and evaluation of 68Ga labelled monomeric and dimeric quinazoline derivatives of the HBED-CC chelator targeting the epidermal growth factor receptor
Liolios, C.; Shegani, A.; Roupa, I.; Kiritsis, C.; Makarem, A.; Paravatou-Petsotas, M.; Pelecanou, M.; Bouziotis, P.; Papadopoulos, M.; Kopka, K.; Pirmettis, I.
Tyrosine kinase (TK) receptors including epidermal growth factor receptors (EGFRs) are known to be overexpressed in a wide variety of solid tumors associated with poor prognosis. The HBED-CC chelator N,N′-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N′-diacetic acid 1 was coupled via one or both its propionic acid moieties with the quinazoline EGFR-TK inhibiting pharmacophore 4-amino-N-(4-((3-bromophenyl)amino)quinazolin-6-yl)butanamide 3 resulting in either a monomeric 4 or a dimeric 5 species. Ligands 4 and 5 reacted with Ga3+ generating the corresponding complexes Ga4 and Ga5. Both ligands and complexes were characterized with mass spectrometry and NMR spectroscopy and evaluated in vitro with MTT assays in A431 cells, where they showed IC50 values in the range 51.6 to 68.8 μM. Labeling of ligands 4 and 5 with the PET radionuclide 68Ga was quantitative and resulted in tracers [68Ga]Ga4 and [68Ga]Ga5 with radiochemical purities greater than 98%, which were also characterised by comparative RP-HPLC studies with Ga4 and Ga5 respectively. Radiotracers [68Ga]Ga4 and [68Ga]Ga5 were stable (in tact tracer over 98%) in the reaction mixture (120 min) and in human serum (30 min). Both tracers were evaluated in vivo with biodistribution experiments in SCID mice bearing A431 tumors presenting tumor uptake of 1.34 for [68Ga]Ga4 and 1.01 %ID/g for [68Ga]Ga5 at 5 min, which was slightly decreased at 60 min p.i. and then remained stable until 120 min p.i. To the best of our knowledge, this is the first report of monomeric and dimeric quinazoline conjugates with the chelator HBED-CC, which can serve as a basis for further development of EGFR-TKI targeting tracers.
Keywords: Epidermal growth factor tyrosine kinase (EGFR-TK); tyrosinekinase inhibitors (TKIs); Quinazoline Gallium complexes; 68Ga; HBED-CC
Bioorganic Chemistry 100(2020), 103855
Online First (2020) DOI: 10.1016/j.bioorg.2020.103855
Cited 11 times in Scopus
Enhanced Sorption of Radionuclides by Defect-Rich Graphene Oxide
Extremely defect graphene oxide (dGO) is proposed as an advanced sorbent for treatment of radioactive waste and con-taminated natural waters. dGO prepared using a modified Hummers oxidation procedure, starting from reduced graphene oxide (rGO) as a precursor, shows significantly higher sorption of U(VI), Am(III) and Eu(III) compared to standard gra-phene oxides (GO). Earlier studies revealed the mechanism of radionuclide sorption related to defects in GO sheets. There-fore, explosive thermal exfoliation of graphite oxide was used to prepare rGO with large number of defects and holes. De-fects and holes are additionally introduced by Hummers oxidation of rGO thus providing extremely defect-rich material. Analysis of characterization by XPS, TGA, FTIR shows that dGO oxygen functionalization is predominantly related to de-fects, such as flake edges and edge atoms of holes, whereas standard GO exhibits oxygen functional groups mostly on the planar surface. The high abundance of defects in dGO results in a 15-fold increase in sorption capacity of U(VI) compared to standard Hummers GO. The improved sorption capacity of dGO is related to abundant carboxylic groups attached hole edge atoms of GO flakes as revealed by synchrotron-based extended X-ray absorption fine structure (EXAFS) and high-energy resolution fluorescence detected X-Ray absorption near edge structure (HERFD-XANES) spectroscopy.
- DOI: 10.1107/S1600577520014265 is cited by this (Id 31261) publication
ACS Applied Materials and Interfaces 12(2020)40, 45122-45135
Online First (2020) DOI: 10.1021/acsami.0c11122
Cited 28 times in Scopus
- Final Draft PDF 1,4 MB Secondary publication
The state of trace elements (In, Cu, Ag) in sphalerite studied by X-ray absorption spectroscopy of synthetic minerals
The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In-and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%.
- DOI: 10.1107/S1600577520014265 is cited by this (Id 31260) publication
Fingerprinting mean composition of lithium polysulfide standard solutions by applying high energy resolution fluorescence detected X-ray Absorption Spectroscopy
Robba, A.; Barchasza, C.; Bučar, K.; Petric, M.; Žitnik, M.; Kvashnina, K.; Vaughan, G. B. M.; Bouchet, R.; Alloin, F.; Kavčič, M.
In a lithium/sulfur (Li/S) battery, the reduction of sulfur during discharge involves a particular mechanism, where the active material successively dissolves into the electrolyte to form lithium polysulfide intermediate species (Li2Sx), with x being a function of the state of charge. In this work, sulfur K-edge Resonant Inelastic X-ray Scattering measurements were performed for the characterization of different Li2Sx polysulfide standard solutions. High Energy Resolution Fluorescence Detected X-ray Absorption Spectroscopy allowed clear separation the pre-edge absorption peak corresponding to terminal sulfur atoms from the main absorption peak due to internal atoms, and to evaluate quantitatively the evolution of the peak area ratio as a function of the polysulfide chain length. Results of this experimental work demonstrate that the normalized area of the pre-edge is a reliable fingerprint of Li2Sx mean chain length in agreement with recent theoretical predictions. As a perspective, this work confirms that operando HERFD XAS can be used to differentiate mean polysulfide composition, which is key issue in the characterization of Li/S cells.
Journal of Physical Chemistry Letters 11(2020), 5446-5450
Cited 8 times in Scopus
- Final Draft PDF 1,1 MB Secondary publication
Study of nanoscopic porosity in black metals by positron annihilation spectroscopy
Black and smooth Al films were characterized by the variable energy positron annihilation spectroscopy (VEPAS). It was found that in smooth films positronium (Ps) is formed on the surface only while in black metal films, it is formed also in nanoscopic pores inside the film. The mean pore size increases from the substrate to the surface due to increasing film roughness.
Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; black metals; Positronium
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 31258) publication
A secret luminescence killer in deepest QWs of InGaN/GaN multiple quantum well structures
This work suggests new alternative explanation why a single InGaN quantum well (QW) or the deepest QWs in the multiple quantum well (MQW) structures suffer with a high non-radiative recombination rate. According to SIMS results, positron annihilation spectroscopy and photoluminescence measurements we suggest that vacancy of Ga in complex with hydrogen atoms can play a dominant role in non-radiative Shockley-Read-Hall recombination of the deepest QWs in InGaN/GaN MQW structures. Vacancy of gallium originate dominantly in GaN buffer layers grown at higher temperatures in H2 atmosphere and are transported to the InGaN/GaN MQW region by diffusion, where they are very effectively trapped in InGaN layers and form complex defects with hydrogen atoms during epitaxy of InGaN layers. Trapping of gallium vacancies is another suggested mechanism explaining why the widely used In containing prelayers help to increase the luminescence efficiency of the InGaN/GaN MQW active region grown above them. Understanding the mechanism why the luminescence efficiency is suppressed in deeper QWs may be very important for LED community and can help to develop new improved technologies for the growth of InGaN/GaN MQW active region.
Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; quantum wells; InGaN; hydrogen complexes; GaN; vacancy
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 31257) publication
Journal of Crystal Growth 536(2020), 125579
Cited 2 times in Scopus
P1819 - Verfahren zur Herstellung eines keramischen Materials mit lokal einstellbarem Permeabilitätsgradienten, dessen Anwendung in einem Beschichtungsverfahren sowie dessen Verwendung
Bürger, D.; Krüger, S.; Skorupa, I.; Schmidt, H.; Du, N.
Die Erfindung betrifft ein Verfahren zur Herstellung eines keramischen Materials mit lokal einstellbarem Permeabilitätsgradienten, dessen Anwendung in einem Beschichtungsverfahren- Materialbearbeitungsverfahren sowie dessen Verwendung. Die Aufgabe ein Material zur Verfügung zu stellen, welches zum Leiten und Isolieren von Magnetfeldern geeignet ist sowie in magnetischen Kopplungselementen verwendet werden kann, wird durch ein Verfahren zur Herstellung eines keramischen Materials mit lokal einstellbarem Permeabilitätsgradienten gelöst, wobei das Verfahren folgende Schritte umfasst: - Erzeugen eines keramischen Materials mittels Erhitzen einer Ausgangsmaterialkomposition bis zu einer Temperatur unterhalb der Schmelztemperatur der Ausgangsmaterialkomposition, - Abkühlen des erzeugten keramischen Materials auf Raumtemperatur nach einer definierten Abkühlrate zur Einstellung einer Vortex-Dichte in dem erzeugten keramischen Material, und - nachfolgende lokale Temperaturbehandlung zum Erhitzen des keramischen Materials über dessen ferroelektrische Ordnungstemperatur und zum Einstellen des lokalen Permeabilitätsgradienten.
DE102018125270 - Offenlegung 16.04.2020; Nachanmeldungen: WO
Boosting Room-Temperature Magneto-Ionics in a Non-Magnetic Oxide Semiconductor
de Rojas, J.; Quintana, A.; Lopeandía, A.; Salguero, J.; Costa-Krämer, J. L.; Abad, L.; Liedke, M. O.; Butterling, M.; Wagner, A.; Henderick, L.; Dendooven, J.; Detavernier, C.; Sort, J.; Menéndez, E.
Voltage control of magnetism through electric field-induced oxygen motion (magneto-ionics) could represent a significant breakthrough in the pursuit for new strategies to enhance energy efficiency in magnetically actuated devices. Boosting the induced changes in magnetization, magneto-ionic rates and cyclability continue to be key challenges to turn magneto-ionics into real applications. Here, it is demonstrated that room-temperature magneto-ionic effects in electrolyte-gated paramagnetic Co3O4 films can be largely increased both in terms of generated magnetization (6 times larger) and speed (35 times faster) if the electric field is applied using an electrochemical capacitor configuration (utilizing an underlying conducting buffer layer) instead of placing the electric contacts at the side of the semiconductor (electricdouble-layer transistor-like configuration). This is due to a greater uniformity and strength of the electric field in the capacitor design. These results are appealing to widen the use of ion migration in technological applications such as neuromorphic computing or iontronics in general.
Keywords: positron annihilation spectroscopy; Co3O4; Doppler broadening; ionic transport; magnetic switch; defects
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 31255) publication
Advanced Functional Materials 30(2020)36, 2003704
Cited 17 times in Scopus
A New Mechanism for Void-Cascade Interaction from Non-destructive Depth-resolved Atomic-scale Measurements of Ion Irradiation-induced Defects in Fe
Agarwal, S.; Liedke, M. O.; Jones, A. C. L.; Reed, E.; Kohnert, A. A.; Uberuaga, B. P.; Wang, Y. Q.; Cooper, J.; Kaoumi, D.; Li, N.; Auguste, R.; Hosemann, P.; Capolungo, L.; Edwards, D. J.; Butterling, M.; Hirschmann, E.; Wagner, A.; Selim, F. A.
The non-destructive investigation of single vacancies and vacancy clusters in ion irradiated samples requires a depth-resolved probe with atomic sensitivity to defects. The recent development of short-pulsed positron beams provides such a probe. Here, we combine depth-resolved Doppler broadening and positron annihilation lifetime spectroscopies to identify vacancy clusters in ion irradiated Fe and measure their density as a function of depth. Despite large concentrations of dislocations and voids in the pristine samples, positron annihilation measurements uncovered the structure of vacancy-clusters and the change in their size and density with irradiation dose. When combined with TEM measurements, the study demonstrates that the increase in the density of small vacancy clusters with irradiation is associated with a remarkable reduction in the size of large voids, revealing a novel mechanism for the interaction of cascade damage with voids in ion irradiated materials, a consequence of the high porosity of the initial microstructure.
Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; Doppler broadening; irradiation; Fe; defects; vacancy clusters; TEM
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 31254) publication
Characterisation of micropores in plasma deposited SiOx films by means of positron annihilation lifetime spectroscopy
The effect of average incorporated ion energy and impinging atomic oxygen flux on the structure and permeability of SiOx thin films by a microwave driven low-pressure discharge with additional RF bias is studied by means of positron annihilation lifetime spectroscopy (PALS) and complementary analytical approaches. The film growth and structure were controlled by the particle fluxes. Acorrelation between the pore sizes and pore size distribution as measured by positron annihilation lifetime spectroscopy (PALS) and the adjusted plasma parameters was established. The corresponding barrier performance was measured by oxygen transmission rate (OTR) and could be explained by the pore size distribution. The dominant pore size characteristic for dangling bonds within the SiOx-network was found to be in the range of 0.8 nm. The chemical composition and morphology were analysed by means of X-ray photoelectron spectroscopy (XPS), FTIR diffuse reflectance measurements (DRIFT) and atomic force microscopy (AFM). It was observed that a combination of both an increase in incorporated energy per deposited Si atom and low oxygen to silicon ratio resulted in an enhanced cross-linking of the SiOx network and thereby lead to a decrease in micropore density and to a shift of the pore size distribution function to lower values.
Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; positron; SiOx; Doppler broadening; PALS; FTIR
- DOI: 10.17815/jlsrf-2-58 is cited by this (Id 31253) publication
Journal of Physics D: Applied Physics 53(2020), 47
Online First (2020) DOI: 10.1088/1361-6463/aba8ba
Cited 5 times in Scopus
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