Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

35172 Publications

Process Simulation: Zinc and Cadmium production, Lead refining

Bartie, N. J.; Heibeck, M.
Researcher: Bartie, Neill Jacques; Researcher: Heibeck, Magdalena

A process simulation model for the production and purification of Zinc via the Roast-Leach-Electrowinning (RLE) process and the subsequent production of its byproduct, Cadmium. It also includes a process for the precipitation of jarosite, and produces residues that can be further processed for the production of Copper and Cobalt. The refining of crude Lead (Pb) bullion is included as a separate stand-alone section.

The simulation was created using flowsheet configurations and operating parameters available in the public domain. Feed and product stream compositions are therefore metallurgically sound and representative of industrial operations that use the processes modelled. The simulation remains an abstraction of reality, however, and should be verified and adopted to the specific operation under consideration. 

The model was developed using the HSC Sim Flowsheet Module in HSC Chemistry 10 (version


Note: The authors do not accept responsibility for any errors. The onus is on the user to verify and validate results against the system being investigated, as system configurations and operating parameters differ from site to site.

Keywords: Process Simulation; Metal production; Zinc; Cadmium; Lead; Copper; Cobalt; Jarosite

  • Software in the HZDR data repository RODARE
    Publication date: 2020-11-27
    DOI: 10.14278/rodare.614
    License: CC-BY-4.0


Publ.-Id: 31779

Justification of best-estimate transient calculations in comparison to the steady-state bounding-case approach

Sangiorgi, M.; Carenini, L.; Brumm, S.; Le Tellier, R.; Viot, L.; Wu, Z.; Xia, S.; Bakouta, N.; Ederli, S.; Mascari, F.; Harti, M.; Lecomte, M.; Sagan, M.; Pandazis, P.; Jobst, Matthias; Gencheva, R.; Groudev, P.; Barnak, M.; Matejovic, P.; Villanueva, W.; Chen, Y.; Ma, W.; Bechta, S.; Kaliatka, A.; Valinius, M.; Kostka, P.; Techy, Z.; Vorobyov, Y.; Thomas, R.; Vokac, P.; Kotouc, M.; Korpinen, A.; Fichot, F.

In the scope of the European IVMR (In-Vessel Melt Retention) project, calculations of In-Vessel retention (IVR) strategy with state of the art Severe Accident (SA) computer codes were performed, including the integral codes ASTEC, ATHLET-CD, MAAP, MELCOR and RELAP5/SCDAPSIM. Further codes dedicated to the study of lower plenum behaviour were also included. Simulations were performed for several types of reactors (PWR, VVER-440, VVER-1000, BWR) and several severe accident scenarios (Station Blackout (SBO) accidents and Loss-Of-Coolant accidents of several leak sizes combined with SBO). The code improvements for IVR simulation, implemented during the project, are summarized and the results obtained with the improved codes are presented in the paper.

Keywords: In-vessel melt retention; Severe Accidents; PWR; VVER-1000; VVER-440; BWR; Accident Management Measures; SBO; LOCA

  • Contribution to proceedings
    International Seminar “In-vessel retention: outcomes of IVMR project”, 20.-21.01.2020, Juan-les-Pins, France

Publ.-Id: 31778

Structural and magnetic properties of swift heavy-ion irradiated SiC

Zhang, X.; Zhang, Z.; Akhmadaliev, S.; Zhou, S.; Wu, Y.; Guo, B.

Ferromagnetism has been observed in ion and neutron irradiated SiC single crystals. In this paper, we present a structural and magnetic investigation on 6H–SiC irradiated by swift heavy ions. The co-exist of paramagnetism, superparamagnetism and ferromagnetism is revealed by using different magnetometry methods. The ferromagnetic component persists well above room temperature. This study confirms the general existence of defect-induced magnetism in SiC.

Keywords: Ferromagnetism Magnetometry; Heavy ions; Silicon carbide; Superparamagnetism; Ferromagnetic component; Induced magnetism; Neutron irradiated SiC single crystals; Structural and magnetic properties; Swift heavy ions; Silicon compounds

Publ.-Id: 31777

Research Data for: ctmmweb: A graphical user interface for autocorrelation-informed home range estimation

Calabrese, J. M.; Fleming, C.; Noonan, M. J.; Dong, X.

Estimating animal home ranges is a primary purpose of collecting tracking data. All conventional home range estimators in widespread usage, including minimum convex polygons and kernel density estimators, assume independently sampled data. In stark contrast, modern GPS animal tracking datasets are almost always strongly autocorrelated. This incongruence between estimator assumptions and empirical reality leads to systematically underestimated home ranges. Autocorrelated kernel density estimation (AKDE) resolves this conflict by modeling the observed autocorrelation structure of tracking data during home range estimation, and has been shown to perform accurately across a broad range of tracking datasets. However, compared to conventional estimators, AKDE requires additional modeling steps and has heretofore only been accessible via the command-line ctmm R package. Here, we introduce ctmmweb, which provides a point-and-click graphical interface to ctmm, and streamlines AKDE, its prerequisite autocorrelation modeling steps, and a number of additional movement analyses. We demonstrate ctmmweb’s capabilities, including AKDE home range estimation and subsequent home range overlap analysis, on a dataset of four jaguars from the Brazilian Pantanal. We intend ctmmweb to open AKDE and related autocorrelation-explicit analyses to a wider audience of wildlife and conservation professionals.

Keywords: AKDE; animal movement; autocorrelation; ctmm; telemetry; tracking data

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-27
    DOI: 10.14278/rodare.612


Publ.-Id: 31776

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

Bok, F.; Moog, H. C.; Altmaier, M.; Freyer, D.; Thoenen, T.

1 Introduction
The disposal of nuclear waste including the assessment of long-term safety is still an open question in Germany. In addition to the pending decision about the repository host rock (salt, granite, or clay) and the associated site selection, the basic necessity of a consistent and obligatory thermodynamic reference database persists. Such a database is essential to assess potential radionuclide migration scenarios accu-rately and to make well-founded predictions about the long-term safety up to one million years. Specific challenges are comprehensive datasets covering also elevated temperatures and high salinities. Concern-ing the required elements (actinides, fission products as well as matrix and building materials), no other thermodynamic database is available that is compatible with the expected conditions. Due to these defi-ciencies THEREDA [1,2], a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany and Switzerland, was started in the year 2006.

2 Database features
THEREDA offers evaluated thermodynamic data for many compounds (solid phases, aqueous species, or constituents of the gaseous phase) of elements relevant according to the present state of research. In particular, all oxidation states expected for disposal site conditions are considered. In the present release, THEREDA includes data for actinides and their chemical analogues (Th, U, Np, Pu, Am, Cm & Nd), fission products (Se, Sr, Tc & Cs) and matrix elements (Na, K, Mg, Ca, Al, Si | Cl, SO₄, CO₃). For the calculation of cementitious phases the current version of CEMDATA (18.1) was integrated [3].
THEREDA is based on a relational databank whose structure intrinsically ensures the internal consisten-cy of thermodynamic data. Data considered respond to the needs of both Gibbs Energy Minimizers (ChemApp, GEMS) and Law-of-Mass-Action codes (Geochemist’s Workbench, PHREEQC, ToughReact). The database is designed generically so that it can store interaction parameters for various models. Namely, the PITZER ion interaction approach to describe activity coefficients of hydrated ions and molecules in saline solutions [4] as well as ideal and non-ideal solid solution approaches are consid-ered in the actual dataset.
After free registration, THEREDA is accessible via internet through This is not only a portal to view the data itself, their uncertainties and the primary references of the data; it provides also additional information on issues concerning the database. Ready-to-use parameter files are available for download in a variety of formats (geochemical code specific formats and generic ASCII type). They are also used for internal test calculations – one essential element of the quality assurance scheme. The capa-bilities of THEREDA are demonstrated using approx. 400 application case calculations, whose results were compared with experimental values published in literature.

[1] Altmaier, M. et al., “THEREDA - Ein Beitrag zur Langzeitsicherheit von Endlagern nuklearer und nichtnuklearer Abfälle”, atw, 53, 249–253 (2008).
[2] Moog, H.C. et al., “Disposal of nuclear waste in host rock formations featuring high-saline solutions – Implementation of a thermodynamic reference database (THEREDA)”, Appl. Geochem., 55, 72–84 (2015).
[3] Lothenbach, B. et al., “Cemdata18: A chemical thermodynamic database for hydrated Portland cements and alkali-activated materials”, Cem. Concr. Res., 115, 472–506 (2019).
[4] Pitzer, K.S., Activity Coefficients in Electrolyte Solutions, 2nd Ed., pp. 542, CRC Press, Boca Raton (1991).
[5] Ryan, J. L., et al. “The solubility of uranium(IV) hydrous oxide in sodium hydroxide solutions under reducing conditions”, Polyhedron, 2, 947 (1983).
[6] Rai, D. et al. “The Solubility of Th(IV) and U(IV) Hydrous Oxides in Concentrated NaCl and MgCl₂ Solutions” Radiochim. Acta, 79, 239–247 (1997).
[7] Neck, V. et al. “Solubility and hydrolysis of tetravalent actinides”, Radiochim. Acta, 89, 1–16 (2001),

Keywords: THEREDA; Thermodynamic database; Nuclear waste disposal; Geochemical modelling; Pitzer ion interaction approach

  • Poster (Online presentation)
    Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Deutschland
  • Lecture (Conference) (Online presentation)
    Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Deutschland

Publ.-Id: 31775

Deformation behavior of nanocrystalline body-centered cubic iron with segregated, foreign Interstitial: A molecular dynamics study

Almotasem, A. T.; Posselt, M.; Polcar, T.

In the present work, modified embedded atom potential and large-scale molecular dynamics’ simulations were used to explore the effect of grain boundary (GB) segregated foreign interstitials on the deformation behavior of nanocrystalline (nc) iron. As a case study, carbon and nitrogen (about 2.5 at.%) were added to (nc) iron. The tensile test results showed that, at the onset of plasticity, grain boundary sliding mediated was dominated, whereas both dislocations and twinning were prevailing deformation mechanisms at high strain. Adding C/N into GBs reduces the free excess volume and consequently increases resistance to GB sliding. In agreement with experiments, the flow stress increased due to the presence of carbon or nitrogen and carbon had the stronger impact. Additionally, the simulation results revealed that GB reduction and suppressing GBs’ dislocation were the primary cause for GB strengthening. Moreover, we also found that the stress required for both intragranular dislocation and twinning nucleation were strongly dependent on the solute type.

Keywords: iron; molecular dynamics; segregation; dislocation; twinning

Publ.-Id: 31773

Investigations of internal stresses in high-voltage devices with deep trenches

Hieckmann, E.; Mühle, U.; Chekhonin, P.; Zschech, E.; Gambino, J.

Deep trenches, as essential elements of silicon chips used in electronic high-power and high-frequency devices, are known as starting points for dislocation generation under the influence of internal mechanical stresses resulting mainly from the difference in the thermal expansion coefficients between silicon and silicon dioxide. Since the electrical insulation of the devices requires a sequence of mechanical, chemical, and high-temperature processes during the preparation of the deep trenches, including the formation of an amorphous SiO2 edge layer, the emergence of the internal stresses is hardly avoidable. The method of cross correlation backscattered electron diffraction in the scanning electron microscope is used here to quantitatively determine the magnitude and local distribution of internal stresses in silicon around the deep trenches after four different process steps. For this purpose, Kikuchi diffraction images are recorded of the wafer cross section areas along lines perpendicular and parallel to the deep trenches. After Fourier transformation, these images are cross correlated with the Fourier transform of the diffraction image from a stressfree reference sample site. The well-established numerical evaluation of cross correlation functions provides the complete distortion tensor for each measuring point of the line scan, from which the stress tensor can be calculated using Hooke’s law. It is found that the in-plane normal stress component σ11 perpendicular to the long edges of the deep trench is larger than the other stress components. That means it essentially determines the magnitude of the von-Mises stress, which was determined as a general stress indicator for all measuring points, too. A characteristic feature is the local distribution of the stress component σ11 with maximum tensile stresses of some hundred megapascals at transition between Si and amorphous SiO2 on the long edges of the deep trench, and with even higher maximum compressive stresses immediately below the bottom of the deep trench. At a distance of about 2 μm from the edges of a single deep trench, all stress components decrease to negligibly small values so that steep stress gradients occur. The range and distribution of tensile and compressive stresses are in accordance with finite element simulations; however, the measured stresses are higher than expected for all investigated states so that dislocation formation seems to be possible. The influence of the electron acceleration voltage on the determination of the internal stresses is discussed as well.


Publ.-Id: 31772

Data for: Electron-phonon coupling in n-type Ge two-dimensional systems

Ciano, C.; Persichetti, L.; Montanari, M.; Di Gaspare, L.; Capellini, G.; Baldassarre, L.; Ortolani, M.; Pashkin, O.; Helm, M.; Winnerl, S.; Virgilio, M.; de Seta, M.

Summary of degenerate pump-probe experiment on SiGe QWs for nonradiative lifetime estimation
 FELBE beamtime 04-07 April 2019

  • : alignment and measure of a rectangular structure (2261) featuring intersubband transition above the longitudinal - optical phonon. FEL wavelength 26.5 mm.
  • : measure of a rectangular structure (2263) featuring intersubband transition below the longitudinal - optical phonon and of an asymmetric-coupled QWs structure (2217). FEL wavelength 45.8 mm.
  • : measure of the same rectangular structure (2263) and of a step well (2264). FEL wavelength 52.6 mm.
  • : measure of the same rectangular structure (2263), of the step well (2264) and of another ACQW (2216) at much lower pump intensities. FEL wavelength 45.8 mm and 52.6 mm.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-24
    DOI: 10.14278/rodare.598


Publ.-Id: 31771

CdTe refining + photovoltaic manufacturing + recycling HSC model

Heibeck, M.; Bartie, N. J.; Abadias Llamas, A.; Reuter, M.
Project Leader: Heibeck, Magdalena; Supervisor: Bartie, Neill Jacques; Supervisor: Abadias Llamas, Alejandro; Supervisor: Reuter, Markus Andreas

This file contains an HSC model for cadmium and tellurium refining starting from by-products coming from a copper precious metals refinery, lead and zinc flowsheets, manufacturing of a CdTe photovoltaic module and its recycling process based on data found in literature. The model was used to perform a resource efficiency, including exergy, and environmental impact (LCA) evaluation of the life cycle of a CdTe photovoltaic module. This model was used in the Master’s thesis “Simulation-based assessment of resource efficiency and environmental impacts of a CdTe photovoltaic life cycle” by Magdalena Heibeck and for the publications “The simulation-based analysis of the circular economy – the enabling role of metallurgical infrastructure” published in the “Mineral Processing and Extractive Metallurgy” journal on 08/11/2019 ( and “Simulation-based Exergy Analysis of Large Circular Economy Systems: Zinc Production Coupled to CdTe Photovoltaic Module Life Cycle” published in the “Journal of Sustainable Metallurgy” on 17/12/2019 (

Detailed information about the literature sources used for developing the model can be found in the references above.

The model can only be opened with HSC software and was made with HSC version (

Keywords: Process Simulation Model; Resource Efficiency; Photovoltaics; Recycling; LCA; Exergy; Digital Twin; Metallurgy

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-26
    DOI: 10.14278/rodare.608
    License: CC-BY-4.0


Publ.-Id: 31770

Development of the First Potential Nonpeptidic Positron Emission Tomography Tracer for the Imaging of CCR2 Receptors

Wagner, S.; De, M. G. F.; Silva, D.; Ortiz, Z. N.; Zweemer, A.; Hermann, S.; De, M. M.; Koch, M.; Weiss, C.; Schepmann, D.; Heitman, L.; Tschammer, N.; Kopka, K.; Junker, A.

Herein we report the design and synthesis of a series of highly selective CCR2 antagonists as 18F-labeled PET tracers. The derivatives were evaluated extensively for their off-target profile at 48 different targets. The most potent and selective candidate was applied in vivo in a biodistribution study, demonstrating a promising profile for further preclinical development. This compound represents the first potential nonpeptidic PET tracer for the imaging of CCR2 receptors.

Keywords: CCR2; CCR5 antagonists; chemokine receptors; molecular imaging; PET; radiolabeling; TAK-779

Publ.-Id: 31767

Unconventional Hall response in the quantum Limit of HfTe5

Galeski, S.; Zhao, X.; Wawrzynczak, R.; Meng, T.; Förster, T.; Lozano, P. M.; Honnali, S.; Lamba, N.; Ehmcke, T.; Markou, A.; Li, Q.; Gu, G.; Zhu, W.; Wosnitza, J.; Felser, C.; Chen, G. F.; Gooth, J.

Interacting electrons confined to their lowest Landau level in a high magnetic field can form a variety of correlated states, some of which manifest themselves in a Hall effect. Although such states have been predicted to occur in three-dimensional semimetals, a corresponding Hall response has not yet been experimentally observed. Here, we report the observation of an unconventional Hall response in the quantum limit of the bulk semimetal HfTe5, adjacent to the three-dimensional quantum Hall effect of a single electron band at low magnetic fields. The additional plateau-like feature in the Hall conductivity of the lowest Landau level is accompanied by a Shubnikov-de Haas minimum in the longitudinal electrical resistivity and its magnitude relates as 3/5 to the height of the last plateau of the three-dimensional quantum Hall effect. Our findings are consistent with strong electron-electron interactions, stabilizing an unconventional variant of the Hall effect in a three-dimensional material in the quantum limit.

Publ.-Id: 31765

Screening Arrays of Laminin Peptides on Modified Cellulose for Promotion of Adhesion of Primary Endothelial and Neural Precursor Cells

Wetzel, R.; Hauser, S.; Lin, W.; Berg, P.; Werner, C.; Pietzsch, J.; Kempermann, G.; Zhang, Y.

Neural precursor cells (NPC) are primary cells intensively used in the context of research on adult neurogenesis and modelling of neuronal development in health and diseased states. Substrates that can facilitate NPC adhesion will be very useful for culturing these cells. Due to the presence of laminin in basal lamina as well as their involvement in differentiation, migration, and adhesion of many types of cells, we focused on surfaces modified with laminin-derived peptides and compared them with the widely used fibronectin-derived RGD peptides. We synthesized an array of 46 peptides on cellulose paper (SPOT) to identify laminin-derived peptides that promote short-term adhesion of murine NPC and human primary endothelial cells. Various previously reported peptide sequences have been re-evaluated in this work. Initial adhesion experiments showed NPC preferred several laminin-derived peptides by up to 5-time higher cell numbers, compared to the well-known promiscuous integrin binding RGD peptide. Importantly, screening of cell adhesion has revealed a synergetic effect of filamentous matrix, peptide sequence, surface property, ligand density, and the dynamic process of NPC adhesion.

Keywords: peptide array; SPOT synthesis; laminin peptides; neural precursor cells; endothelial cells

Publ.-Id: 31762

Coordination of Trivalent Lanthanum and Cerium, and Tetravalent Cerium and Actinides (An = Th(IV), U(IV), Np(IV)) by a 4-Phosphoryl 1H-Pyrazol-5-olate Ligand in Solution and the Solid State

Zhang, J.; Wenzel, M.; Schnaars, K.; Hennersdorf, F.; Schwedtmann, K.; März, J.; Roßberg, A.; Kaden, P.; Kraus, F.; Stumpf, T.; Weigand, J. J.

Structural investigations of three actinide(IV) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(IV), U(IV), Np(IV)) and their cerium(IV) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(IV) complex shows that in dependence of the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(IV) metal centre to bi-capped trigonal prismatic. Further, single crystal analyses of the La(III) and Ce(III) complexes show that the ligand can also act as a neutral ligand by protonation of the pyrazoyl moiety. All complexes were comprehensively characterized by NMR, IR and Raman spectroscopy. A single resonance in each of the 31P NMR spectra for the La(III), Ce(III), Ce(IV), Th(IV) and Np(IV) complex indicates the formation of highly symmetric complex species in solution. Extended X-ray absorption fine structure (EXAFS) investigations provide evidence for the same local structure of the U(IV) and Np(IV) complex in toluene solution, confirming the observations made in the solid state.

Related publications


  • Secondary publication expected from 12.02.2022

Publ.-Id: 31761

Comparative Studies of Light-Responsive Swimmers: Janus Nanorods versus Spherical Particles

Eichler-Volf, A.; Huang, T.; Vazquez Luna, F.; Alsaadawi, Y.; Stierle, S.; Cuniberti, G.; Steinhart, M.; Baraban, Larysa; Erbe, A.

The shape of objects has a strong influence on their dynamics. Here, we present comparative studies of two different motile objects, spherical Ag/AgCl Janus particles and polystyrene Janus nanorods, that move due to an ionic self-diffusiophoretic propulsion mechanism when exposed to blue light. In this paper, we propose a method to fabricate Janus rodlike particles with high aspect ratios and hemispherical tip shapes. The inherent asymmetry due to the ratio between capped and uncapped parts of the particles as well as the shape anistropy of Janus nanorods enables imaging and quantification of rotational dynamics. The dynamics of microswimmers are compared in terms of velocities and diffusion coefficients. We observe that despite a small amount of the Ag/AgCl reagent on the surface of rodlike objects, these new Janus micromotors reveal high motility in pure water. While the velocities of spherical particles reach 4.2 μm/s, the single rodlike swimmers reach 1.1 μm/s, and clusters reach 1.6 μm/s. The effect of suppressed rotational diffusion is discussed as one of the reasons for the increased velocities. These Janus micro- and nanomotors hold the promise for application in light-controlled propulsion transport.


  • Secondary publication expected from 14.10.2021

Publ.-Id: 31760

TOPFLOW Pressure Chamber – versatile techniques to simplify design and instrumentation of thermal fluid dynamic experiments at high pressure

Prasser, H.-M.; Hampel, U.; Schütz, P.

The present paper describes the design and function of the TOPFLOW Pressure Chamber of the Helmholtz Zentrum Dresden-Rossendorf. The facility opened new opportunities for experiments at pressures of up to 50 bar. The actual test equipment can be constructed as a not pressure carrying installation. The TOPFLOW steam generator, located in an adjacent hall, was used to supply steam at saturation conditions. In the paper, three experimental programs that were carried out in the pressure chamber are introduced briefly, mainly with the purpose to highlight the advantages of the pressure chamber technique.

Keywords: TOPFLOW; Pressure chamber; Experimental program; Infrared observation; Video recording of the flow structure

Publ.-Id: 31758

On the consensus nomenclature rules for radiopharmaceutical chemistry – reconsideration of radiochemical conversion

Herth, M.; Ametamey, S.; Antuganov, D.; Bauman, A.; Berndt, M.; Brooks, A.; Bormans, G.; Choe, Y.; Gillings, N.; Häfeli, U.; James, M.; Kopka, K.; Kramer, V.; Krasikova, R.; Madsen, J.; Mu, L.; Neumaier, B.; Piel, M.; Rösch, F.; Ross, T.; Schibli, R.; Scott, P.; Shalgunov, V.; Vasdev, N.; Wadsak, W.; Zeglis, B.

Radiochemical conversion is an important term to be included in the “Consensus nomenclature rules for radiopharmaceutical chemistry”. Radiochemical conversion should be used to define reaction efficiency by measuring the transformation of components in a crude reactionmixture at a given time,whereas radiochemical yield is better suited to define the efficiency of an entire reaction process including, for example, separation, isolation, filtration, and formulation.

Keywords: Nomenclature; Terminology; Consensus guidelines; Radiopharmaceutical sciences; Nuclear chemistry; Radiochemistry; Radiochemical conversion; Radiochemical yield


  • Secondary publication expected from 18.11.2021

Publ.-Id: 31755

Simulation of bubble dynamics under pool scrubbing conditions

Liao, Y.; Lucas, D.

Pool scrubbing is an effective method for removing radioactive aerosols during severe nuclear accidents and protecting the health of nearby residents and the environment. After the pool scrubbing research is revived by the Fukushima Daiichi accident, experimental studies tend to provide CFD-level data on phase distribution and bubble dynamics owing to improved measuring techniques. In contrast, CFD investigations on bubble dynamics under pool scrubbing conditions are still scarce due to the challenges of reliable models and high computational cost. To achieve best practice guidelines for the use of CFD for such complex multiphase flow situations in nuclear safety analyses, there is still a long way to go and a large amount of simulation practice is desirable. This work aims to investigate the bubble dynamics under pool scrubbing conditions using the interface-tracking method available in the open-source CFD code OpenFOAM. At first, the impact of numerical setups such as domain dimension, mesh resolution, and time step on the simulation results is studied in detail for a basic case, which provides good guidelines for the setup of next benchmark cases. Bubble shape, bubble detachment size, and frequency as well plume structure are compared with the results of other institutions that participate in the benchmark simulations as well as experimental observations. Good qualitative and quantitative agreement was obtained. The work provides a basis for investigation on bubble dynamics in pool scrubbing with aerosol particles using the CFD methodology in the next step.

Keywords: Bubble dynamics; Pool scrubbing; CFD; Nuclear reactor safety; OpenFOAM

  • Contribution to proceedings
    V-CFD4NRS8, 25.-27.11.2020, virtual, France
  • Lecture (Conference) (Online presentation)
    V-CFD4NRS8, 25.-27.11.2020, Virtual, France

Publ.-Id: 31753

Barium-131 as starting point for the development of radiotheranostic approaches

Reissig, F.; Bauer, D.; Ullrich, M.; Kreller, M.; Kopka, K.; Pietzsch, J.; Pietzsch, H.-J.; Walther, M.; Mamat, C.

We understand 131Ba as a radionuclide, which enables imaging by SPECT in nuclear medicine and provides a diagnostic match for the therapeutic alpha-emitting radionuclides 223Ra and 224Ra. Recently, we reported on a sufficient production route for 131Ba by irradiating a 133Cs target with 27.5 MeV proton beams, and the straight-forward resin-based radiochemical separation, yielding 131Ba with high radionuclide purity. An average amount of 190 MBq of 131Ba was produced per irradiation. Apart from 0.1% isotopic impurity of 133Ba, no more side-products were detectable. For the first time, radiolabeling of the complexing agent macropa (known to be an appropriate 225Ac chelator) with 131Ba was reported and mild labeling conditions as well as reaction control using TLC systems were applicable. The radiopharmacological characterization of 131Ba-labeled macropa was carried out in healthy mice using uncomplexed [131Ba]Ba2+ as a reference, including biodistribution studies and small animal SPECT/CT. The results revealed the rapid bone uptake of free [131Ba]Ba2+ ions, whereas 131Ba-labeled macropa showed a fast renal clearance and significantly lower (P < 0.001) accumulation in the bones. We therefore conclude, that 131Ba is a promising “new” radionuclide for SPECT imaging purposes and delivers appropriate quality for preclinical investigations. Moreover, the successful labeling of macropa and the in vivo stability of the 131Ba-complex are viewed as a promising starting point for the development of new heavy earth alkaline metal chelators, especially for the therapeutically relevant radium isotopes. This enables 131Ba to achieve its goal as diagnostic match and monitoring tool for 223/224Ra.

Keywords: Barium-131; SPECT; Radium-223; Theranostics; Radium-224

  • Open Access Logo Lecture (Conference) (Online presentation)
    6th International Electronic Conference on Medicinal Chemistry (ECMC2020), 01.-30.11.2020, Basel, Schweiz
    DOI: 10.3390/ECMC2020-07459

Publ.-Id: 31752

Electron-phonon coupling in n-type Ge two-dimensional systems

Ciano, C.; Persichetti, L.; Montanari, M.; Di Gaspare, L.; Capellini, G.; Baldassarre, L.; Ortolani, M.; Pashkin, O.; Helm, M.; Winnerl, S.; Virgilio, M.; de Seta, M.

Electron-optical phonon interaction is the dominant energy-loss mechanism in low-dimensional Ge/SiGe heterostructures and represents a key parameter for the design and realization of electronic and optoelectronic devices based on this material system compatible with the mainstream Si complementary metal-oxide semiconductor technology. Here we investigate the intersubband relaxation dynamics of n-type Ge/SiGe multiquantum wells with different symmetry and design by means of single-color pump-probe spectroscopy. By comparing the experimental differential transmittance data as a function of the pump-probe delay with numerical calculations based on an energy-balance rate-equation model, we could quantify an effective value for the optical phonon deformation potential describing the electron-phonon coupling in two-dimensional Ge-based systems. We found nonradiative relaxation times longer than 20 ps even in samples having intersubband energy separations larger than the optical phonon energy, evidencing the presence of a less effective electron-phonon coupling with respect to that estimated in bulk Ge.

Related publications


Publ.-Id: 31751

KRAS mutation effects on the 2-[18F]FDG PET uptake of colorectal adenocarcinoma metastases in the liver

Popovic, M.; Talarico, O.; van den Hoff, J.; Kunin, H.; Zhang, Z.; Lafontaine, D.; Dogan, S.; Leung, J.; Kaye, E.; Czmielewski, C.; Et Al, S.

Deriving individual tumor genomic characteristics from patient imaging analysis is desirable. We explore the predictive value of 2-[18F]FDG uptake with regards to the KRAS mutational status of colorectal adenocarcinoma liver metastases (CLM).
2-[18F]FDG PET/CT images, surgical pathology and molecular diagnostic reports of
37 patients who underwent PET/CT-guided biopsy of CLM were reviewed under an IRB-approved retrospective research protocol. Sixty CLM in 39 interventional PET scans of the 37 patients were segmented using two different auto-segmentation tools implemented in 37 different commercially available software packages. PET standard uptake values (SUV) were corrected for: 1) partial volume effect (PVE) using cold wall-corrected contrast recovery coefficients derived from phantom spheres with variable diameter; and 2) variability of arterial tracer supply and variability of uptake time after injection until start of PET scan derived from the tumor-to-blood standard uptake ratio (SUR) approach. The correlations between the KRAS mutational status and the mean, peak, and maximum SUV were investigated using Student’s t-test, Wilcoxon rank sum test with continuity correction, logistic regression and receiver operation characteristic (ROC) analysis. These correlation analyses were also performed for the ratios of the mean, peak and maximum tumor uptake to the mean blood activity concentration at the time of scan: SURMEAN, SURPEAK, and SURMAX, respectively.
Results: Fifteen patients harbored KRAS missense mutations (KRAS+) while another 3 harbored KRAS gene amplification. For 31 lesions the mutational status was derived from the PET/CT-guided biopsy. The Student’s-t p-values for separating KRAS mutant cases decreased after applying PVE correction to all uptake metrics of each lesion and when applying correction for uptake time variability to the SUR metrics. The observed correlations were strongest when both corrections were applied to SURMAX and when the patients harboring gene amplification were grouped with the wild type: p ≤ 0.001; ROC area under the curve (AUC) = 0.77 and 0.75 for the two different segmentations respectively with a mean specificity of 0.69 and sensitivity of 0.85.
The correlations observed after applying the described corrections show potential for assigning probabilities for the KRAS missense mutation status in CLM using 2-[18F]FDG PET images.

Keywords: PET; colorectal adenocarcinoma; liver metastases; KRAS mutations


Publ.-Id: 31750

Solid-liquid flow in Stirred Tanks: Euler-Euler / RANS Modeling

Rzehak, R.; Shi, P.

Stirred tanks are widely used equipment to process solid-liquid dispersions in the chemical and minerals engineering industries. CFD simulations of such equipment on industrial scales are principally feasible within the Euler-Euler / RANS approach. Practical application, however, requires suitable closure models to account for phenomena on the scale of individual particles, which are not resolved in this approach. The present work applies a set of closure relations that originates from a comprehensive review of existing results from analytical, numerical, and experimental studies. Focus is on the modeling of interfacial forces which includes drag, lift, and turbulent dispersion. To validate the model a comprehensive set of experimental data including particle concentration as well as liquid velocity and turbulence has been assembled from different literature sources. The necessity for model extensions is confirmed via the comparison of simulation results obtained by different sets of closure correlations, i.e. the presently proposed one and others that have been frequently used in previous studies, with the experimental data.

Keywords: multiphase CFD simulation; particulate flow; closure modeling; stirred tanks

  • Lecture (Conference)
    14th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries (CFD2020), 12.-14.10.2020, Trondheim, Norway

Publ.-Id: 31749

Direct tray and point efficiency measurements including weeping effects through a convenient addon for air/water simulators

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

A direct approach for determining the tray and point efficiencies of an industrial-scale distillation tray is proposed. The stripping of isobutyl acetate from an aqueous solution with air was used, which is a manageable and non-hazardous method applicable for performance tests in large hydraulic column mockups. This work represents the first application of this system in the case of tray columns exemplified for a sieve tray. A column of 800 mm internal diameter was used for conducting the stripping experiments. The distribution of isobutyl acetate in the liquid phase on the tray was obtained via liquid sampling at several deck positions and UV-spectroscopy analysis. A definition for the liquid-side tray efficiency at weeping conditions is proposed together with an experimental approach for determining tray and point efficiencies in such conditions. The derived efficiency data show a good agreement with the model predictions and correlations.

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

Related publications


  • Secondary publication expected from 17.02.2022

Publ.-Id: 31747

Benchmarking of computational fluid dynamic models for bubbly flows

Colombo, M.; Rzehak, R.; Fairweather, M.; Liao, Y.; Lucas, D.

Eulerian-Eulerian computational fluid dynamic (CFD) models allow the prediction of complex and large-scale industrial multiphase gas-liquid bubbly flows with a relatively limited computational load. However, the interfacial transfer processes are entirely modelled, with closure relations that often dictate the accuracy of the entire model. Numerous sets of closures have been developed, often optimized over few experimental data sets and achieving remarkable accuracy that, however, becomes difficult to replicate outside of the range of the selected data. This makes a reliable comparison of available model capabilities difficult and obstructs their further development. In this paper, the CFD models developed at the University of Leeds and the Helmholtz-Zentrum Dresden-Rossendorf are benchmarked against a large database of bubbly flows in vertical pipes. The research groups adopt a similar modelling strategy, aimed at identifying a single universal set of widely applicable closures. The main focus of the paper is interfacial momentum transfer, which essentially governs the void fraction distribution in the flow, and turbulence modelling closures. To focus on these aspects, the validation database is limited to experiments with a monodispersed bubble diameter distribution. Overall, the models prove to be reliable and robust and can be applied with confidence over the range of parameters tested. Areas are identified where further development is needed, such as the modelling of bubble-induced turbulence and the near-wall region. A benchmark is also established and is available for the testing of other models. Similar exercises are encouraged to support the confident application of multiphase CFD models, together with the definition of a set of experiments accepted community-wide for model benchmarking.

Keywords: computational fluid dynamics; multiphase flows; bubbly flows; interfacial closures; multiphase turbulence


  • Secondary publication expected from 15.04.2022

Publ.-Id: 31746

Multiconfigurational calculations of ground state and excited states of tetravalent uranium complexes

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

The peculiarities of computational actinide chemistry concerning the ground and excited state require state-of-the-art electronic structure methods. Currently, the most popular one is the CASSCF- method for the inclusion of static correlation in combination with CASPT2 for dynamic correlation and CASSI for spin-orbit coupling. This combination is used for the evaluation of excited state energies and transitions for simulating electronic spectra and comparing with experimental findings. Furthermore, for the evaluation of a proper active space the DMRG method is used for a choice based on objective reasonings. It is found, that the CASSCF+CASPT2+CASSI combination is able to recover experimental values quite well even for a small basis set. However, the DMRG method reveals that the active space could potentially be improved by not only considering the two electrons in the seven 5f-orbitals but also including C-N-pi and corresponding C-N-pi* orbitals.

Keywords: CASSCF; DMRG; electron correlation; actinides; uranium; tetravalent; coordination chemistry

  • Lecture (Conference)
    Theory Frontiers in Actinide Sciences, 02.-05.02.2020, Santa Fe, USA
  • Invited lecture (Conferences)
    XIIIth Workshop on Modern Methods in Quantum Chemistry, 02.-05.03.2020, Mariapfarr, Österreich

Publ.-Id: 31745

2D THz Optoelectronics

Mittendorff, M.; Winnerl, S.; Murphy, T. E.

The terahertz (THz) region of the electromagnetic spectrum spans the gap between optics and electronics and has historically suffered from paucity of optoelectronic devices, in large part because of inadequate optical materials that function in this spectral range. 2D materials, including graphene and a growing family of related van der Waals materials, have been shown to exhibit unusual optical and electrical properties that can enable diverse new applications in the THz regime. In this review, some of the unusual properties of 2D materials that make them promising for THz applications are explained, the recent work in the field of 2D THz optoelectronics is summarized, and the challenges and opportunities that await this promising new field are outlined.

Keywords: terahertz; 2D materials; optoelectronics; THz detectors; THz emitters; THz modulators


  • Secondary publication expected from 04.02.2022

Publ.-Id: 31744

Observation of strong magneto plasmonic nonlinearity in bilayer graphene discs

Chin, M. L.; Matschy, S.; Stawitzki, F.; Poojali, J.; Hafez, H. A.; Turchinovich, D.; Winnerl, S.; Kumar, G.; Myers-Ward, R. L.; Dejarld, M. T.; Daniels, K. M.; Drew, H. D.; Murphy, T. E.; Mittendorff, M.

Graphene patterned into plasmonic structures like ribbons or discs strongly increases the linear and nonlinear optical interaction at resonance. The nonlinear optical response is governed by hot carriers, leading to a red-shift of the plasmon frequency. In magnetic fields, the plasmon hybridizes with the cyclotron resonance, resulting in a splitting of the plasmonic absorption into two branches. Here we present how this splitting can be exploited to tune the nonlinear optical response of graphene discs. In the absence of a magnetic field, a strong pump-induced increase in on-resonant transmission can be observed, but fields in the range of 3 T can change the characteristics completely, leading to an inverted nonlinearity. A two temperature model is provided that describes the observed behavior well.

Keywords: magnetoplasmonics; graphene; nonlinear optics

Related publications

Publ.-Id: 31743

Microbial interaction with and tolerance of radionuclides: underlying mechanisms and biotechnological applications

Lopez Fernandez, M.; Jroundi, F.; Ruiz. Fresneda, M. A.; Merroun, M. L.

Radionuclides (RN) generated by nuclear and civil industries are released in natural ecosystems and may have a hazardous impact on human health and the environment. RN polluted environments harbor different microbial species that become highly tolerant of these elements through mechanisms including biosorption, biotransformation, biomineralization and intracellular accumulation. Such microbial-RN interaction processes hold biotechnological potential for the design of bioremediation strategies to deal with several contamination problems. This paper, with its multidisciplinary approach, provides a state-of-the-art review of most research endeavors aimed to elucidate how microbes deal with radionuclides and how they tolerate ionizing radiations. In addition, the most recent findings related to new biotechnological applications of microbes in the bioremediation of radionuclides and in the long-term disposal of nuclear wastes are described and discussed.

Publ.-Id: 31741

Multisystem combined uranium resistance mechanisms and bioremediation potential of Stenotrophomonas bentonitica BII-R7: Transcriptomics and microscopic study

Pinel-Cabello, M.; Jroundi, F.; Lopez Fernandez, M.; Geffers, R.; Jarek, M.; Jauregui, R.; Link, A.; Vílchez-Vargas, R.; Merroun, M. L.

The potential use of microorganisms in the bioremediation of U pollution has been extensively described.
However, a lack of knowledge on molecular resistance mechanisms has become a challenge for the use of these technologies. We reported on the transcriptomic and microscopic response of Stenotrophomonas bentonitica BII-R7 exposed to 100 and 250 μM of U. Results showed that exposure to 100 μM displayed up-regulation of 185 and 148 genes during the lag and exponential phases, respectively, whereas 143 and 194 were down-regulated, out of 3786 genes (>1.5-fold change). Exposure to 250 μM of U showed up-regulation of 68 genes and down-regulation of 290 during the lag phase. Genes involved in cell wall and membrane protein synthesis, efflux systems and phosphatases were up-regulated under all conditions tested. Microscopic observations evidenced the formation of U-phosphate minerals at membrane and extracellular levels. Thus, a biphasic process is likely to occur: the increased cell wall would promote the biosorption of U to the cell surface and its precipitation as U-phosphate minerals enhanced by phosphatases. Transport systems would prevent U accumulation in the cytoplasm. These findings contribute to an understanding of how microbes cope with U toxicity, thus allowing for the development of efficient bioremediation strategies.

Publ.-Id: 31740

Oxide microstructure, surface chemistry and point defects derived from oxidation of metallic zinc. Thin film transistor and sensoric behaviour of ZnO films

Hoffmann, R. C.; Sanctis, S.; Liedke, M. O.; Butterling, M.; Wagner, A.; Schneider, J. J.

Zinc oxide thin films are fabricated by controlled oxidation of sputtered zinc metal films on a hotplate in air at temperatures between 250 and 450°C. The nanocrystalline films possess high relative densities and show preferential growth in (100) orientation. Integration in thin film transistors reveal moderate charge carrier mobilities as high as 0.2 cm2/(Vs). The semiconducting properties depend on the calcination temperature, whereby the best performance is achieved at 450 °C. The defect structure of the thin ZnO film can be tracked by Doppler-broadening positron-annihilation-spectroscopy as well as positron-lifetime studies. Comparably long positron lifetimes suggest interaction of zinc vacancies (VZn) with one or more oxygen vacancies (Vo) in larger structural entities. Such VO-VZn defect clusters act as shallow acceptors and thus reduce the overall electron conductivity of the film. The concentration of these defect clusters decreases at higher calcination temperatures as indicated by changes of the S and W parameters. Such zinc oxide films obtained by conversion of metallic zinc can be also used as seed-layers for solution-deposition of zinc oxide nanowires employing a mild microwave-assisted process. The functionality of the obtained nanowire arrays was tested in a UV sensor device. Best results with respect to sensor sensitivity are achieved with thinner seed layers for device construction.

Keywords: positron annihilation spectroscopy; ZnO; defects; Positronium

Publ.-Id: 31739

Oxidation of amorphous HfNbTaTiZr high entropy alloy thin films prepared by DC magnetron sputtering

Hruška, P.; Lukáč, F.; Cichoň, S.; Vondráček, M.; Čížek, J.; Fekete, L.; Lančok, J.; Veselý, J.; Minárik, P.; Cieslar, M.; Melikhova, O.; Kmječ, T.; Liedke, M. O.; Butterling, M.; Wagner, A.

High entropy alloys represent a new type of materials with a unique combination of physical properties originating from the occurrence of single-phase solid solutions of numerous elements. The preparation of nanostructured or amorphous structure in a form of thin films promises increased effective surface and high intergranular diffusion of elements as well as a high affinity to oxidation. In this work, we studied HfNbTaTiZr thin films were deposited at room temperature by DC magnetron sputtering from a single bcc phase target. Films exhibit cellular structure (~100 nm) with fine substructure (~10 nm) made of round-shape amorphous clusters. Films composition is close to equimolar with slight Ti enrichment and without any mutual segregation of elements. Oxidation at the ambient atmosphere leads to the formation of Ti, Zr, Nb, Hf, and Ta oxide clusters in the film up to the depth of 200 – 350 nm out of the total film thickness of 1650 nm. Oxygen absorption takes place preferentially in the large vacancy clusters located in between the amorphous cluster aggregates. The dominant type of defect is small open volumes with a size comparable with vacancy. The distribution of these defects is uniform with depth and is not influenced by the presence of oxygen in the film.

Keywords: positron annihilation spectroscopy; high entropy alloys; defects; monovacancy; HfNbTaTiZr; sputtering


  • Secondary publication expected from 21.11.2021

Publ.-Id: 31738

Methodology for DNS Data-driven Machine Learning Bubble Drag Model and Its Integration to OpenFOAM

Tai, C.-K.; Evdokimov, I.; Schlegel, F.; Lucas, D.; Bolotnov, I.

This work aims to develop a two-phase DNS data-driven bubble drag model and to implement it into a multiphase flow CFD simulation. To accomplish the goal, a Tensorflow (TF)-OpenFOAM(OF) integration interface has been established. Such an interface is capable of calling and making machine learning model to predict a quantity of interest on the fly. A benchmark case for the bubble drag coefficient is proposed to validate the interface. A Feed forward neural network (FNN) approach was utilized to approximate the drag correlation (Tomiyama et al., 1998) using artificially generated data. Results of the integration showed good consistency in radial void fraction and velocity profiles. As the next step actual DNS bubble tracking datasets are used as a data source (Fang et al., 2017, Cambareri et al., 2019). The data segments where bubble have quasi-stable main-stream velocity were filtered out for drag coefficient calculation. The DNS-informed model predicts bubble drag coefficient by taking bubble Reynolds number (Re) and Eötvös number (Eo) as input to consider the effects from local fluid and bubble shape. The model is applied in a Euler-Euler two-phase flow simulation of a bubbly pipe flow in OF. The required closure terms, except the drag model, utilize the baseline model of Liao et al. (2020) The results of radial void fraction and velocity profiles are discussed and compared to a reference solution with the baseline model.

Keywords: DNS; bubbly flow; drag; machine learning

  • Lecture (Conference) (Online presentation)
    APS DFD Annual Meeting, 22.-24.11.2020, Chicago - online, USA
  • Contribution to proceedings
    APS DFD Annual Meeting, 22.-24.11.2020, Chicago - online, USA

Publ.-Id: 31737

Short-duration dynamic FDG PET imaging: Optimization and clinical application

Samimi, R.; Kamali-Asl, A.; Geramifar, P.; van den Hoff, J.; Rahmim, A.

We aimed to investigate whether short dynamic PET imaging started at injection, complemented with routine clinical acquisition at 60-min post-injection (static), can achieve reliable kinetic analysis.
Dynamic and static 18F-2-fluoro-2-deoxy-D-glucose (FDG) PET data were generated using realistic simulations to assess uncertainties due to statistical noise as well as bias. Following image reconstructions, kinetic parameters obtained from a 2-tissue-compartmental model (2TCM) were estimated, making use of the static image, and the time duration of dynamic PET data were incrementally shortened. We also investigated, in the first 2-min, different frame sampling rates, towards optimized dynamic PET imaging. Kinetic parameters from shortened dynamic datasets were additionally estimated for 9 patients (15 scans) with liver metastases of colorectal cancer, and were compared with those derived from full dynamic imaging using correlation and Passing–Bablok regression analyses.
The results showed that by reduction of dynamic scan times from 60-min to as short as 5-min, while using static data at 60-min post-injection, bias and variability stayed comparable in estimated kinetic parameters. Early frame samplings of 5, 24 and 30 s yielded highest biases compared to other schemes. An early frame sampling of 10 s generally kept both bias and variability to a minimum. In clinical studies, strong correlation (r ≥ 0.97, P < 0.0001) existed between all kinetic parameters in full vs. shortened scan protocols.
Shortened 5-min dynamic scan, sampled as 12 × 10 + 6 × 30 s, followed by 3-min static image at 60-min post-injection, enables accurate and robust estimation of 2TCM parameters, while enabling generation of SUV estimates.

Keywords: Dynamic PET; Kinetic modelling; GATE; STIR; FDG PET


Publ.-Id: 31736

Message from the Guest Editor of the 17th Multiphase Flow Conference Special Issue

Lucas, D.

Selected contributions of the 17th Multiphase Flow Conference at HZDR were published in a special issue of the Open Access Journal Experimental and Computational Multiphase Flow. In this contribution an overview on the conference and a short introduction to the single papers is given.

Keywords: multiphase flow; conference

  • Open Access Logo Abstract in refereed journal
    Experimental and Computational Multiphase Flow 3(2021)3, 137-138
    DOI: 10.1007/s42757-020-0087-x

Publ.-Id: 31735

Data for: Bonding Trends in Tetravalent Th–Pu Monosalen Complexes

Radoske, T.; März, J.; Patzschke, M.; Kaden, P.; Walter, O.; Schmidt, M.; Stumpf, T.

[AnCl2(salen)(Pyx)2] (H2salen=N,N′‐bis(salicylidene)ethylenediamine; Pyx=pyridine, 4‐methylpyridine, 3,5‐dimethylpyridine) + An(IV) with An=Th, U, Np, and Pu.

EA data, QC calculation results, NMR spectra and data analysis.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-15
    DOI: 10.14278/rodare.585


Publ.-Id: 31730

Measurement of Ehrlich-Schwoebel barrier contribution to the self-organized formation of ordered surface patterns on Ge(001)

Myint, P.; Erb, D.; Zhang, X.; Wiegart, L.; Zhang, Y.; Fluerasu, A.; Headrick, R.; Facsko, S.; Ludwig, K.

Normal-incidence 1-keV Ar+ ion bombardment leads to amorphization and ultrasmoothing of Ge at room temperature, but at elevated temperatures the Ge surface remains crystalline and is unstable to the formation of self-organized nanoscale patterns of ordered pyramid-shaped pits. The physical phenomenon distinguishing the high-temperature patterning from room-temperature ultrasmoothing is believed to be a surface instability due to the Ehrlich-Schwoebel barrier for diffusing vacancies and adatoms, which is not present on the amorphous material. This real-time grazing-incidence small-angle x-ray scattering study compares smoothing of a prepatterned Ge sample at room temperature with patterning of an initially flat Ge sample at an elevated temperature. In both experiments, when the nanoscale structures are relatively small in height, the average kinetics can be explained by a linear theory. The linear theory coefficients, indicating surface stability or instability, were extracted for both experiments. A comparison between the two measurements allows estimation of the contribution of the Ehrlich-Schwoebel barrier to the self-organized formation of ordered nanoscale patterns on crystalline Ge surfaces.


Publ.-Id: 31729

The role of computational methods for automating and improving clinical target volume definition

Unkelbach, J.; Bortfeld, T.; Cardenas, C. E.; Gregoire, V.; Hager, W.; Heijmen, B.; Jeraj, R.; Korreman, S. S.; Ludwig, R.; Pouymayou, B.; Shusharina, N.; Söderberg, J.; Toma-Dasu, I.; Troost, E. G. C.; Osorio, E. V.

Treatment planning in radiotherapy distinguishes three target volume concepts: the gross tumor volume (GTV), the clinical target volume (CTV), and the planning target volume (PTV). Over time, GTV definition and PTV margins have improved through the development of novel imaging techniques and better image guidance, respectively. CTV definition is sometimes considered the weakest element in the planning process. CTV definition is particularly complex since the extension of microscopic disease cannot be seen using currently available in-vivo imaging techniques. Instead, CTV definition has to incorporate knowledge of the patterns of tumor progression. While CTV delineation has largely been considered the domain of radiation oncologists, this paper, arising from a 2019 ESTRO Physics research workshop, discusses the contributions that medical physics and computer science can make by developing computational methods to support CTV definition. First, we overview the role of image segmentation algorithms, which may in part automate CTV delineation through segmentation of lymph node stations or normal tissues representing anatomical boundaries of microscopic tumor progression. The recent success of deep convolutional neural networks has also enabled learning entire CTV delineations from examples. Second, we discuss the use of mathematical models of tumor progression for CTV definition, using as example the application of glioma growth models to facilitate GTV-to-CTV expansion for glioblastoma that is consistent with neuroanatomy. We further consider statistical machine learning models to quantify lymphatic metastatic progression of tumors, which may eventually improve elective CTV definition. Lastly, we discuss approaches to incorporate uncertainty in CTV definition into treatment plan optimization as well as general limitations of the CTV concept in the case of infiltrating tumors without natural boundaries.

Keywords: Automatic image segmentation; Clinical target volume; Computational tumor growth models

Publ.-Id: 31728

Numerical modeling and simulation of reactive flow and transport processes in subsurface formations

Yuan, T.

Subsurface water-rock interactions involve the coupled phenomena of chemical reactions and fluid transport, in which the chemical reactions between minerals and water can cause mineral dissolution/precipitation and aqueous species adsorption/desorption. The subsurface reactive transport processes play an important role in the enhanced prediction of oil and gas migration in the petroleum reservoirs as well as radionuclides migration in the host rocks. Consequently, an efficient numerical model that can rigorously capture such coupled phenomena is thus essential to the optimized design of implementations for those addressed problems.
In this talk, we first present a 3D mathematical model that couples the Stokes-Brinkman equation and reactive transport model for modeling the coupled processes of reactive flow and transport in fractured porous media. The numerical experiments show that the proposed model can efficiently simulate the coupled processes of fluid flow, reactive transport, and alterations of rock properties in fractured porous media under both linear and radial flow. Secondly, we focus on radionuclides transport and retention in claystone formations using GeoPET analysis and reactive transport modeling. We propose an integrated upscaling workflow to predict effective diffusivity of radionuclides diffusion in the shaly facies of Opalinus clay based on the reconstructed multi-scale digital rocks. The GeoPET measurements provide analytical insights into spatial and temporal tracer distribution, which can be utilized to validate the numerical model. The combination of pore-scale reactivity and core scale transport modeling provides critical insight into the radionuclide migration heterogeneity. We discuss these results with a focus on upscaling strategies to the field scale of host rocks.

  • Invited lecture (Conferences) (Online presentation)
    Numerical simulation of subsurface flow, 25.09.2020, Beijing, China

Publ.-Id: 31727

Quantification of the Inconvenient Truths about the Circular Economy (CE) Digital Twinning of Very Large Systems

Bartie, N. J.; Reuter, M.

We discuss the limitations to material flows from recycling in the circular economy, using as a case the simulation-based analysis of the CdTe Photovoltaic cells. It is important to use a simulation basis for the analysis, since this permits the quantification of all material losses both in terms of exergy and energy simultaneously i.e. 1st and 2nd law of thermodynamics. Harmonizing this with the power supply flowing into the system and minimizing energy usage as well as exergy losses will maximize the resource efficiency.

  • Open Access Logo Contribution to external collection
    Dagmar Boedicker, Sebastian Jekutsch, Dietrich Meyer-Ebrecht: FIfF-Kommunikation 3/2020 Technologie und Ökologie, Bremen: FIfF e.V., 2020, 0938-3476, 43-48


Publ.-Id: 31726

Radionuclide transport and retention at the core scale identified by GeoPET analysis and reactive transport modeling

Yuan, T.; Kulenkampff, J.; Bollermann, T.; Fischer, C.

Low-permeability Opalinus clay formations are considered as a potential host rock for the storage of high-level nuclear waste (Nagra 2002). The diffusion of dissolved species is the dominating transport process in this rock type (Van Loon et al. 2003). Stratification and spatial variability of composition cause anisotropic and heterogeneous diffusion patterns, which could significantly speed up diffusive transport compared to commonly assumed homogeneous conditions. Anisotropy of diffusive transport has been studied on oriented samples in diffusion cells and with positron emission tomography (Kulenkampff et al. 2016). The heterogeneity of the diffusive spreading is increased still further due to sandy layers and diagenetic carbonates, affecting the radionuclide migration behavior at the core scale.
Here, we parameterize a reactive transport model by using experimental and analytical data on Eu(III) sorption efficiency at the pore scale. The effective retention coefficients calculated at the pore scale serve as input values for the reactive transport simulation at the core scale. Diffusive transport model parametrization utilizes GeoPET/μCT results on the migration behavior of 22Na+ at the core scale. Numerical simulation is performed using an existing code (Yuan et al. 2019), which contains the reactive transport model for simulating reactive diffusion process at the core scale. The combination of pore-scale reactivity and core scale transport modeling provides critical insight into the radionuclide migration heterogeneity. We discuss these results with a focus on upscaling strategies to the field scale of host rocks.

  • Lecture (Conference) (Online presentation)
    InterPore 2020, 31.08.-04.09.2020, Qing Dao, China

Publ.-Id: 31725

Convection in Liquid Metal Batteries

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

The quest for renewable energy sources entails an increasingly intermittent electricity supply.
Transmission grid updates can only partially account for balancing the resulting variations and large-scale stationary storage will gain importance in future energy landscapes dominated by volatile sources.
Today’s battery technologies were, with the notable exception of redox-flow batteries, mainly designed for and driven by mobile applications. Those prioritize properties (energy density, power rating) that are less important for stationary storage. Thus, battery technologies developed from the ground up to meet the needs of stationary storage have the potential to much better address the specifics of huge capacity installations.
Liquid metal batteries (LMBs) are a new technology for grid-scale energy storage. They consist of all liquid cells that operate with liquid metals as electrodes and molten salts as electrolytes. The liquids separate into three stably stratified layers by virtue of density and mutual immiscibility. This conceptually very simple and self-assembling structure has the unique advantage to allow for an easy scale-up at the cell level: single-cell cross sections can potentially reach several square-meters. Such cell sizes enable highly favourable and otherwise unattainable ratios of active to construction material because of the cubic scaling (volume) of the former and the quadratic scaling (surface) of the latter. The total costs should therefore largely be determined by those of the active materials.
The talk will start with a general introduction to LMBs and then focus on the fluid mechanics in these devices. Electric currents, magnetic fields, and heat and mass transfer are tightly coupled with the cells’ electrochemistry. First a number of fluid dynamic instabilities will be discussed in relation to operational safety. The remainder of the talk will deal with transport phenomena in the positive electrode. While transport in most modern battery systems is typically dominated by diffusion and migration in micrometer-scale liquid layers and solids, convection - with exception of the aforementioned redox-flow batteries - rarely plays a role. This is in stark contrast to LMBs were mediated by the fully liquid interior fluid flow can be driven by various mechanisms. The influence of solutal convection on the cycling behavior of a cell will be demonstrated. Electromagnetically induced convection can be used to improve mixing thereby mitigating diffusion overpotentials.

  • Invited lecture (Conferences) (Online presentation)
    Liquid Metal Technologies, 20.11.2020, Morelia, Mexiko

Publ.-Id: 31723

Accurate determination of quasi-particle electronic and optical spectra of anatase titanium dioxide

Sruthil Lal, S. B.; Devaraj, M.; Posselt, M.; Sharan, A.

The electronic structure and quasi-particle absorption spectra of anatase titanium dioxide has been calculated by employing state of the art density functional theory(DFT) and Many-Body Perturbation Theory methods(MBPT) within the framework of Hybrid Density Functional(HSE). GW methods are used in combination with Bethe-Salpeter Equation (BSE) to determine the Quasi Particle energy levels and the role of excitons in optical absorption spectra. Accurate optical and electronic band gap are determined from these methods. In addition to it an analysis of charge redistribution within the anatase unit cell is also presented within the PBE - DFT to analyze the orbital hybridization patterns and the character of chemical bonds.

Keywords: Anatase Titanium Oxide; Density Functional Theory; Electronic structure; Optical Spectra


Publ.-Id: 31722

Tailoring Particle-enzyme Nanoconjugates for Biocatalysis at the Organic-organic Interface

Sun, Z.; Cai, M.; Hübner, R.; Ansorge-Schumacher, M. B.; Wu, C.

Nonaqueous Pickering emulsions (PEs) are a powerful platform for catalysis design, offering both a large interface contact and a preferable environment for water-sensitive synthesis. However, up to now, little progress has been made to incorporate insoluble enzymes into the nonaqueous system for biotransformation. Herein, we present biocatalytically active nonaqueous PEs, stabilized by particle-enzyme nanoconjugates, for the fast transesterification and esterification, and eventually for biodiesel synthesis. Our nanoconjugates are the hybrid biocatalysts tailor-made by loading hydrophilic Candida antarctica lipase B onto hydrophobic silica nanoparticles, resulting in not only catalytically active but highly amphiphilic particles for stabilization of a methanol-decane emulsion. The enzyme activity in these PEs is significantly enhanced, ca. 375-time higher than in the nonaqueous biphasic control. Moreover, the PEs can be multiply reused without significant loss of enzyme performance. With this proof‐of‐concept, we reasonably expect that our system can be expanded for many advanced syntheses using different enzymes in the future.

Keywords: biphasic biocatalysis; nonaqueous Pickering emulsions; solvent-free reactions; enzyme catalysis; nanoconjugates

Publ.-Id: 31721

Mechanosynthesis of polymer-stabilized lead bromide perovskites: insight into the formation and phase conversion of nanoparticles

Jiang, G.; Erdem, O.; Hübner, R.; Georgi, M.; Wei, W.; Fan, X.; Wang, J.; Demir, H. V.; Gaponik, N.

The application of polymers to replace oleylamine (OLA) and oleic acid (OA) as ligands for perovskite nanocrystals is an effective strategy to improve their stability and durability especially for the solution-based processing. Herein, we report a mechanosynthesis of lead bromide perovskite nanoparticles (NPs) stabilized by partially hydrolyzed poly(methyl methacrylate) (h-PMMA) and high-molecular-weight highly-branched poly(ethylenimine) (PEI-25K). The as-synthesized NP solutions exhibited green emission centered at 516 nm, possessing a narrow full-width at half-maximum of 17 nm and as high photoluminescence quantum yield (PL QY) as 85%, while showing excellent durability and resistance to polar solvents, e.g., methanol. The colloids of polymer-stabilized NPs were directly processable to form stable and strongly-emitting thin films and solids, making them attractive as gain media. Furthermore, the roles of h-PMMA and PEI-25K in the grinding process were studied in depth. The h-PMMA can form micelles in the grinding solvent of dichloromethane to act as size-regulating templates for the growth of NPs. The PEI-25K with large amounts of amino groups induced significant enrichment of PbBr2 in the reaction mixture, which in turn caused the formation of CsPb2Br5-mPbBr23-Cs4PbBr6-nCsBr NPs. The presence of CsPbBr3-Cs4PbBr6-nCsBr NPs was responsible for the high PL QY, as the Cs4PbBr6 phase with a wide energy bandgap can passivate the surface defects of the CsPbBr3 phase. This work describes a direct and facile mechanosynthesis of polymer-coordinated perovskite NPs and promotes in-depth understanding of the formation and phase conversion for perovskite NPs in the grinding process.

Keywords: lead bromide perovskites; mechanosynthesis; polymer ligands; polymer micelles; poly(ethyleneimine)-i

Publ.-Id: 31720

Nonlinear IR and THz Spectroscopy of Semiconductor Nanowires

Helm, M.; Fotev, I.; Balaghi, L.; Lang, D.; Rana, R.; Winnerl, S.; Schneider, H.; Dimakis, E.; Pashkin, A.

We report nonlinear charge-carrier response in GaAs/InGaAs core/shell nanowires that are driven by intense THz pulses. In the first experiment, half-cycle THz pulses emitted from an organic DSTMS crystal lead to a red-shift of the plasmon Peak indicating intervalley transfer of the electrons. In the second experiment, a single, highly electron doped nanowire is investigated by scattering near-field infrared microscopy using intense free-electron laser (FEL) pulses. Here the observed red shift of the mid-infrared plasma resonance depends on the pulse energy and can be explained by heating the electron system in the nonparabolic conduction band.

Keywords: nanowire; THz; infrared; free-electron laser; near-field microscopy; nonlinear

  • Invited lecture (Conferences) (Online presentation)
    45th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2020), 08.-13.11.2020, Buffalo, USA

Publ.-Id: 31719

Data for: Nonlinear losses in magnon transport due to four-magnon scattering

Hula, T.; Schultheiß, K.; Buzdakov, A.; Körber, L.; Bejarano, M.; Flacke, L.; Liensberger, L.; Weiler, M.; Shaw, J. M.; Nembach, H. T.; Faßbender, J.; Schultheiß, H.

We utilized the following methods in order to obtain the presented data: micro focused Brilluoin light scattering (BLS), micromagnetic simulations in MuMax3 and micro focused magneto-optical Kerr effect (MOKE). The experimental data were obtained on the sample which is labeled with: 'CoFe_WMI_6'. On that sample, we investigated the structures 'E1' and 'F1' which are essentially rectangular stripes (5 micrometer x 65 micrometer, thickness: 30 nm) out of Co25Fe75 alloy. The metadata for all measurements (including ALL parameters) are included in the uploaded primary data subdirectories. The references to the directory of the measured data within our local IT infrastructure are given along with the files themselves. All scripts that were used for data analysis (in Python) are included as well with a short description.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-26
    DOI: 10.14278/rodare.604


Publ.-Id: 31718

Response of endothelial cells to gelatin-based hydrogels

Krüger-Genge, A.; Hauser, S.; Neffe, A. T.; Liu, Y.; Lendlein, A.; Pietzsch, J.; Jung, F.

Dysfunctional or incomplete endothelium on cardiovascular devices has been identified as key factor of thrombus formation. Therefore, the establishment of confluent endothelial cell (EC) monolayers is a challenge in cardiovascular device engineering. Previous studies revealed that arterial EC were able to endothelialize gelatin-based hydrogels. However, as EC differ markedly in their function dependent from their origin, this study investigated whether venous EC (HUVEC) also form a monolayer on gelatin-based hydrogels obtained by reacting gelatin with different molar ratios of lysine diisocyanate ethyl ester (using a 3-, 5- or 8-fold excess) exhibiting variations in their elastic properties. The density of adherent HUVEC on the soft hydrogel at 37 °C (G’ = 1.02 kPa, E = 1.1±0.3 kPa) was significantly lower than on the stiffer hydrogels (G’ = 2.515 and 5.02 kPa, E = 4.8±0.8 and 10.3±1.2 kPa). This was accompanied by increased matrix metalloproteases and stress fiber formation, while cell-to-cell contacts were comparable. The pattern of eicosanoids and cytokines corresponded to those results. The expression of pro-inflammatory markers COX-2, COX-1, and RAGE were slightly elevated, indicating a weak inflammation. The study revealed that hydrogels with higher moduli approached the status of a functionally-confluent HUVEC monolayer. The results indicate the promising potential especially of the hydrogels with higher G’ as biomaterials for implants foreseen for the venous system.

Keywords: endothelialization; gelatin-based hydrogel; substrate elasticity; HUVEC function; cell-material-interaction

Publ.-Id: 31717

Bonding Trends in Tetravalent Th–Pu Monosalen Complexes

Radoske, T.; März, J.; Patzschke, M.; Kaden, P.; Walter, O.; Schmidt, M.; Stumpf, T.

We report the synthesis of three complex series of the form [AnCl₂(salen)(pyx)₂] (H₂salen = N,N’-bis(salicyl¬idene)ethylene-diamine; Pyx = pyridine, 4-methylpyridine, 3,5-dimethylpyridine) with tetravalent early actinides (An = Th, U, Np, Pu) with the goal to elucidate the affinity of these heavy elements for small neutral N-donor molecules. Structure determination via single-crystal XRD and characterization of bulk powders with infrared spectroscopy reveal isostructurality within each respective series and the same complex conformation in all reported structures. While the trend of interatomic distances for An–Cl and An–N (imine nitrogen of salen or pyridyl nitrogen of Pyx) were found to reflect an ionic behaviour, the trend of the An–O distances can only be described with additional covalent interactions for all elements heavier than thorium. All experimental results are supported by quantum chemical calculations, which confirm the mostly ionic character in the An–N and An–Cl bonds, as well as the highest degree of covalency of the An–O bonds. Structurally, the calculations indicate just minor electronic or steric effects of the additional Pyx substituents on the complex properties.

Keywords: tetravalent actinide; salen; covalency; pyridine; bonding analysis; thorium; uranium; neptunium; plutonium

Related publications

Publ.-Id: 31714

"CFD-grade" Experimental data for Solid-liquid Flow in a Stirred Tank

Sommer, A.-E.; Rox, H.; Eckert, K.; Shi, P.; Rzehak, R.

A solid-liquid flow in stirred tanks occurs frequently in different branches of process engineering where particles need to be suspended in a liquid. Computational Fluid Dynamics (CFD) simulations of such flow on industrial scales are feasible if the closure models implemented therein are appropriate. A large number of closure models exist, but due to a lack of data sources for validation, no systematic assessment of these different models has appeared so far. The present dataset aims to accumulate a comprehensive ''CFD-grade'' database based on experiments of the single-phase and two-phase flows in a standardized stirred tank with a diameter of 90 mm. The velocity fields of the liquid (deionized water) and, in the two-phase case, the solid phase were measured with Particle Image Velocimetry (PIV) and Particle Shadow Velocimetry (PSV), respectively. The experiments cover a range of parameters to achieve an extensive database. A narrow particle distribution of nearly neutrally buoyant particles (polyethylene spheres), as well as heavy particles (glass spheres) in the suspension, are considered over a wide range of particle diameter (63µm-500µm), solid volume fraction (0.025 vol% - 0.1vol%), as well as impeller rotation speed (650rpm - 1500rpm). The transient flow field on the plane midway between two baffles was recorded over 50 impeller rotations to achieve statistical significance. The time-averaged (resp. angle-resolved) mean and fluctuation velocities were then obtained by averaging the transient data in the laboratory frame of reference (resp. the frame of reference rotating with the impeller). The data is organized and analyzed as described in the corresponding journal publication "Solid-liquid Flow in Stirred Tanks: ”CFD-grade” Experimental Investigation".

Keywords: stirred tanks; solid-liquid flow; Particle Image Velocimetry (PIV); Particle Shadow Velocimetry (PSV); "Computational Fluid Dynamics (CFD)-grade" database

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-15
    DOI: 10.14278/rodare.263


Publ.-Id: 31713

Terahertz magneto-optical investigation of quadrupolar spin-lattice effects in magnetically frustrated Tb2Ti2O7

Amelin, K.; Alexanian, Y.; Nagel, U.; Rõõm, T.; Robert, J.; Debray, J.; Simonet, V.; Decorse, C.; Wang, Z.; Ballou, R.; Constable, E.; de Brion, S.

Condensed matter magneto-optical investigations can be a powerful probe of a material's microscopic magnetoelectric properties. This is because subtle interactions between electric and magnetic multipoles on a crystal lattice show up in predictable and testable ways in a material's optical response tensor, which dictates the polarization state and absorption spectrum of propagating electromagnetic waves. Magneto-optical techniques are therefore strong complements to probes such as neutron scattering, particularly when spin-lattice coupling effects are present. Here we perform a magneto-optical investigation of vibronic spin-lattice coupling in the magnetically frustrated pyrochlore Tb2Ti2O7. Coupling of this nature involving quadrupolar mixing between the Tb3+ electronic levels and phonons in Tb2Ti2O7 has been a topic of debate for some time. This is particularly due to its implication for describing the exotic spin-liquid phase diagram of this highly debated system. A manifestation of this vibronic effect is observed as splitting of the ground and first excited crystal field doublets of the Tb3+ electronic levels, providing a fine structure to the absorption spectra in the terahertz (THz) frequency range. In this investigation, we apply a static magnetic field along the cubic [111] direction while probing with linearly polarized THz radiation. Through the Zeeman effect, the magnetic field enhances the splitting within the low-energy crystal field transitions revealing new details in our THz spectra. Complementary magneto-optical quantum calculations including quadrupolar terms show that indeed vibronic effects are required to describe our observations at 3 K. A further prediction of our theoretical model is the presence of a novel magneto-optical birefringence as a result of this vibronic process. Essentially, spin-lattice coupling within Tb2Ti2O7 may break the optical isotropy of the cubic system, supporting two different electromagnetic wave propagations within the crystal. Together our results reveal the significance of considering quadrupolar spin-lattice effects when describing the spin-liquid ground state of Tb2Ti2O7. They also highlight the potential for future magneto-optical investigations to probe complex materials where spin-lattice coupling is present and reveal new magneto-optical activity in the THz range.

Publ.-Id: 31712

Broad Beam-Induced Fragmentation and Joining of Tungsten Oxide Nanorods: Implications for Nanodevice Fabrication and the Development of Fusion Reactors

Rajbhar, M. K.; Möller, W.; Satpati, B.; Manju, U.; Chaudhary, Y. S.; Chatterjee, S.

In this work, for the first time, fragmentation and joining of tungsten oxide (WO3) nanorods induced by a broad ion beam are reported. Although at low energy (5 keV) and moderate ion fluence, nanorods fragment into smaller pieces along the length, at higher ion energies (50-100 keV), a contrary process occurs, which leads to the joining of the nanorods. A state-of-the-art ion-solid interaction simulation, namely, TRI3DYN, has been invoked to explore the possible mechanisms that reveal subtle contributions of surface defects, ion-beam mixing, and sputtering. High-resolution electron microscopy, photoluminescence study, and X-ray photoelectron spectroscopy support the observed results and proposed mechanisms. Such modifications have interesting effects on the electrical conductivity of the nanorod assembly. The change in sample color upon ion irradiation from initial white to yellow, light blue, deep blue, light green, and cyan shows an excellent and reversible chromatic response of tungsten oxide nanorods to irradiation. Such a property can be exploited to fabricate radiation sensors. The fragmentation and joining at different energy scales have essential implications in nanodevice fabrication through the bottom-up approach as well as for the development of fusion reactors.

Keywords: electrical conductivity; fusion reactor material; ion irradiation; nanofragmentation; nanojoining; radiation sensor; tungsten oxide nanorods; wettability

Publ.-Id: 31710

Hypofractionated Versus Standard Fractionated Radiotherapy in Patients With Early Breast Cancer or Ductal Carcinoma In Situ in a Randomized Phase III Trial: The DBCG HYPO Trial

Offersen, B. V.; Alsner, J.; Nielsen, H. M.; Jakobsen, E. H.; Nielsen, M. H.; Krause, M.; Stenbygaard, L.; Mjaaland, I.; Schreiber, A.; Kasti, U.-M.; Overgaard, J.

PURPOSE Given the poor results using hypofractionated radiotherapy for early breast cancer, a dose of 50 Gy in 25 fractions (fr) has been the standard regimen used by the Danish Breast Cancer Group (DBCG) since 1982. Results from more recent trials have stimulated a renewed interest in hypofractionation, and the noninferiority DBCG HYPO trial ( identifier: NCT00909818) was designed to determine whether a dose of
40 Gy in 15 fr does not increase the occurrence of breast induration at 3 years compared with a dose of 50 Gy in 25 fr.

PATIENTS AND METHODS One thousand eight hundred eighty-two patients .40 years of age who underwent breast-conserving surgery for node-negative breast cancer or ductal carcinoma in situ (DCIS) were randomly assigned to radiotherapy at a dose of either 50 Gy in 25 fr or 40 Gy in 15 fr. The primary end point was 3-year grade 2-3 breast induration assuming noninferiority regarding locoregional recurrence.

RESULTS A total of 1,854 consenting patients (50 Gy, n 5937; 40 Gy, n 5917) were enrolled from 2009-2014 from eight centers. There were 1,608 patients with adenocarcinoma and 246 patients with DCIS. The 3-year rates of induration were 11.8% (95% CI, 9.7% to 14.1%) in the 50-Gy group and 9.0% (95% CI, 7.2% to 11.1%) in the 40-Gy group (risk difference, 22.7%; 95% CI, 25.6% to 0.2%; P 5 .07). Systemic therapies and radiotherapy boost did not increase the risk of induration. Telangiectasia, dyspigmentation, scar appearance, edema, and pain were detected at low rates, and cosmetic outcome and patient satisfaction with breast appearance were high with either no difference or better outcome in the 40-Gy cohort compared with the 50-Gy cohort. The 9-year risk of locoregional recurrence was 3.3% (95% CI, 2.0% to 5.0%) in the 50-Gy group and 3.0% (95% CI, 1.9% to 4.5%) in the 40-Gy group (risk difference, 20.3%; 95% CI, 22.3% to 1.7%). The 9-year overall survival was 93.4% (95% CI, 91.1% to 95.1%) in the 50-Gy group and 93.4% (95% CI, 91.0% to 95.2%)
in the 40-Gy group. The occurrence of radiation-associated cardiac and lung disease was rare and not influenced by the fractionation regimen.

CONCLUSION Moderately hypofractionated breast irradiation of node-negative breast cancer or DCIS did not result in more breast induration compared with standard fractionated therapy. Other normal tissue effects were minimal, with similar or less frequent rates in the 40-Gy group. The 9-year locoregional recurrence risk was low.

Publ.-Id: 31708

Underground experimental study finds no evidence of low-energy resonance in the 6Li(p,γ)7Be reaction

Piatti, D.; Chillery, T.; Depalo, R.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Ciani, G. F.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Gnech, A.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Kochanek, I.; Lugaro, M.; Marcucci, L. E.; Marigo, P.; Masha, E.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Takács, M. P.; Zavatarelli, S.

The astrophysical 6Li(p,γ)7Be reaction occurs during Big Bang nucleosynthesis and the pre-main sequence and main sequence phases of stellar evolution. The low-energy trend of its cross section remains uncertain, since different measurements have provided conflicting results. A recent experiment reported a resonancelike structure at center-of-mass energy 195 keV, associated to a positive-parity state of 7Be. The existence of such resonance is still a matter of debate. We report a new measurement of the 6Li(p,γ)7Be cross section performed at the Laboratory for Underground Nuclear Astrophysics, covering the center-of-mass energy range E=60–350 keV. Our results rule out the existence of low-energy resonances. The astrophysical S-factor varies smoothly with energy, in agreement with theoretical models.

Publ.-Id: 31707

Optimization of multi-group energy structures for diffusion analyses of sodium-cooled fast reactors assisted by simulated annealing – Part I: methodology demonstration

Di Nora, V. A.; Fridman, E.; Nikitin, E.; Bilodid, Y.; Mikityuk, K.

This study presents an approach to the selection of optimal energy group structures for multi-group nodal diffusion analyses of Sodium-cooled Fast Reactor cores. The goal is to speed up calculations, particularly in transient calculations, while maintaining an acceptable accuracy of the results.
In Part I of the paper, possible time-savings due to collapsing of energy groups are evaluated using 24-group energy structure as a reference. Afterwards, focusing on energy structures with a number of groups leading to significant calculation speedups, optimal grid configurations are identified. Depending on a number of possible energy grid configurations to explore, the optimization is conducted by either a direct search or applying the simulated annealing method. Speedup and optimization studies are performed on a selected case of the Superphénix static neutronic benchmark by using the nodal diffusion DYN3D code. The results demonstrate noticeable improvements in DYN3D performance with a marginal deterioration of the accuracy.

Keywords: Serpent; XS condensation; energy structure optimization; simulated annealing

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-26
    DOI: 10.14278/rodare.583


Publ.-Id: 31706

A Molecular Octafluoridoneptunate(IV) anion in (NH₄)₄[NpF₈] and Theoretical Investigations of the [MF₈]₄-System (M = Th - Bk)

Scheibe, B.; Patzschke, M.; März, J.; Conrad, M.; Kraus, F.

Olive-green single crystals of ammonium octafluoridoneptunate(IV), (NH₄)₄[NpF₈], were obtained by converting NpO₂ to a green neptunium tetrafluoride hydrate with hydrofluoric acid and subsequent treatment of the fluoride with an aqueous NH₄F solution. The crystal structure of the compound was determined by single-crystal X ray diffraction and observed to be isotypic to the uranium analogue. In (NH₄)₄[NpF₈], molecular [NpF₈]⁴‾ anions, which can either be described as a distorted square-antiprism or a bicapped trigonal prism, are present which are bound to the NH₄⁺ ions via N−H∙∙∙F hydrogen bonds. Quantum-chemical calculations of [MF₈]⁴‾ anions show that the M−F bonds are highly ionic and the energy differences between different ligand arrangements likely can be overcome by lattice energies of different crystal structures in the solid state.

Keywords: actinide; density functional calculations; neptunium; fluorine; single-crystal X-ray diffraction

Publ.-Id: 31705

HIM FIBID dataset for Superconducting properties of in-plane W-C nanowires grown by He+ Focused Ion Beam Induced Deposition

Hlawacek, G.
Project Member: Orus, Pablo

HIM images and NPVE dataset created during the preparation of the W(CO)6 nanowires.

Keywords: helium ion microscopy; focused ion beam induced deposition

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-11
    DOI: 10.14278/rodare.581
    License: CC-BY-4.0


Publ.-Id: 31704

Superconducting properties of in-plane W-C nanowires grown by He+ Focused Ion Beam Induced Deposition

Orús, P.; Córdoba, R.; Hlawacek, G.; de Teresa, J. M.

Focused Ion Beam Induced Deposition (FIBID) is a nanopatterning technique that makes use of a focused beam of charged ions to decompose a gaseous precursor. So far, the flexible patterning capabilities of FIBID have been widely exploited in the fabrication of superconducting nanostructures, using the W(CO) 6 precursor mostly in combination with a focused beam of Ga+ ions. Here, the fabrication and characterization of superconducting in-plane tungsten-carbon (W-C) nanostructures by He+ FIBID of the W(CO)6 precursor is reported. A virtually unattainable for Ga+ FIBID patterning resolution of 10 nm has been achieved. When the nanowires are patterned with widths of 20 nm and above, the deposited material is superconducting below 3.5 – 4 K. In addition, 60 and 90 nm-wide nanostructures have been found to sustain long-range controlled non-local superconducting vortex transfer along 3 μm. Overall, these findings strengthen the capabilities of He+ FIBID of W-C in the growth and patterning of in-plane superconducting nanodevices.

Keywords: superconductivity; Helium Ion Microscopy; FIBID; nanowires; vortexdynamics; electrical transport properties

Related publications


Publ.-Id: 31703

Evolution of cast iron- and copper- corrosion in "400 day-bentonite-microcosms"

Sushko, V.; Dressler, M.; Neubert, T.; Kühn, L.; Cherkouk, A.; Schierz, A.; Matschiavelli, N.

Copper and cast iron are potential materials for the storage canisters of high-level radioactive waste. We designed slurry-experiments for analyzing the microbial influence on the corrosion process of these metals. These slurry experiments contain the Bavarian B25 bentonite, synthetic Opalinus Clay pore water or diluted cap rock solution as well as copper- or cast iron plates in various combinations. During an incubation time of 400 days under anaerobic conditions at 37 °C cast iron plates corrode very fast. The respective metal surfaces show the formation of iron oxides and –carbonates which could form a passivating film that protects the cast iron from further corrosion.

  • Open Access Logo Lecture (Conference) (Online presentation)
    iCross annual meeting 2020, 25.-26.11.2020, Dresden-Webinar, Deutschland

Publ.-Id: 31702

Cd2+ incorporation in small pores LEV/ERI intergrown zeolites: a multi-methodological study

Cametti, G.; Scheinost, A.; Churakov, S. V.

Small pores zeolites are successfully employed as catalysts, sorbents and molecular sieves. Their physiochemical properties can be improved by modifying their extraframework (EF) cation content via ion exchange. In this study, we investigate the crystal structure of a Cd-exchanged levyne (LEV) intergrown with erionite (ERI) by combining Single Crystal X-ray Diffraction (SCXRD), Molecular Dynamic simulations (MD) and Extended X-ray Absorption Fine- Structure analysis spectroscopy (EXAFS). Data obtained from the different techniques, consistently indicated that Cd2+ distribute in an almost ordered fashion in LEV. In contrast, strong disorder of the EF species (Cd2+ and H2O) is observed in the ERI cavities. In the latter, Cd2+ form aqueous complexes that are more mobile in comparison towith respect Cd2+ in LEV, where it bonds to H2O and framework-oxygen atoms. The formation of Cd-clusters is excluded based on EXAFS analysis. Finally, to discriminate between thermal and static disorder, we proposed a new approach based on a combined MD and geometry optimization analysis.

Keywords: zeolite; levyne; MD simulations; DFT; XRD; EXAFS; ROBL


  • Secondary publication expected from 17.12.2021

Publ.-Id: 31700

Ideen zur Untersuchung der MIC Beständigkeit von vorgealterten Materialien

Raff, J.; Cherkouk, A.; Matschiavelli, N.; Sushko, V.; Dressler, M.

Neben abiotischen Faktoren können auch mikrobielle Prozesse einen Einfluss auf die Langzeitsicherheit eines nuklearen Endlagers haben. Darum wird aktuell im Rahmen des Projekts iCROSS die mikrobiellen Diversität in dem Verfüllmaterial Bentonit untersucht und die mikrobielle Aktivität mittels Mikrokosmosexperimenten bestimmt. Weitere Experimente befassen sich außerdem mit der mikrobiell beeinflussten Korrosion von Behältermaterialien. Letzteres ist auch von hoher Relevanz für andere technische Anlagen und Prozesse. Aus diesem Grund werden in dem Vortrag außerdem Möglichkeiten für weitere Projektideen aufgezeigt und diskutiert.

Keywords: Mikrobielle Diversität; nukleares Endlager; Bentonit; MIC

  • Lecture (Conference) (Online presentation)
    DECHEMA/GfKORR Fachgruppensitzung „Mikrobielle Materialzerstörung und Materialschutz“ 27.10.2020, 27.10.2020, Online, Deutschland

Publ.-Id: 31699

The effect of four lanthanides onto a rat kidney cell line (NRK-52E) is dependent on the composition of the cell culture medium

Heller, A.; Pisarevskaja, A.; Bölicke, N.; Barkleit, A.; Bok, F.; Wober, J.

Lanthanide (Ln) exposure poses a serious health risk to animals and humans. In this study, we investigated the effect of 10-9 - 10-3 M La, Ce, Eu, and Yb exposure onto the viability of rat renal NRK-52E cells in dependence on Ln concentration, exposure time, and composition of the cell culture medium. Especially, the influence of fetal bovine serum (FBS) and citrate onto Ln cytotoxicity, solubility, and speciation was investigated. For this, in vitro cell viability studies using the XTT assay and fluorescence microscopic investigations were combined with solubility and speciation studies using TRLFS and ICP-MS, respectively. The theoretical Ln speciation was predicted using thermodynamic modeling. All Ln exhibit a concentration- and time-dependent effect on NRK-52E cells. FBS is the key parameter influencing both Ln solubility and cytotoxicity. We demonstrate that FBS is able to bind Ln3+ ions, thus, promoting solubility and reducing cytotoxicity after Ln exposure for 24 and 48 h. In contrast, citrate addition to the cell culture medium has no significant effect on Ln solubility and speciation nor cytotoxicity after Ln exposure for 24 and 48 h. However, a striking increase of cell viability is observable after Ln exposure for 8 h. Out of the four Ln elements under investigation, Ce is the most effective. Results from TRLFS and solubility measurements correlate well to those from in vitro cell culture experiments. In contrast, results from thermodynamic modeling do not correlate to TRLFS results, hence, demonstrating that big gaps in the database render this method, currently, inapplicable for the prediction of Ln speciation in cell culture media. Finally, this study demonstrates the importance and the synergistic effects of combining chemical and spectroscopic methods with cell culture techniques and biological methods.

Keywords: f-elements; speciation; cytotoxicity; XTT; time-resolved laser-induced fluorescence spectroscopy; thermodynamic modeling

Publ.-Id: 31698

PIConGPU setup: PWFA simulations

Pausch, R.; Debus, A.; Steiniger, K.; Widera, R.

This is the PIConGPU source code and setup files for generating PWFA simulations. This setup was used to study wake elongation.

Keywords: PIConGPU, PWFA

  • Software in the HZDR data repository RODARE
    Publication date: 2020-11-10
    DOI: 10.14278/rodare.579
    License: GPL-3.0


Publ.-Id: 31697

Operating system (OS) independent job configuration for image reconstruction at HEMERA

Bieberle, A.; Wagner, M.; Windisch, D.; Hampel, U.

The Institute of Fluid Dynamics at the HZDR operates ultrafast electron beam X-ray CT scanners, a.k.a. ROFEX-CT scanners, that are used to visualize rapidly moving two-phase gas-liquid scenarios in technical devices with an imaging rate of up to 8,000 images per second. This means, radiographic projections are acquired from different angular positions of the two-phase flow and reconstruction algorithms, e.g. filtered back projection or algebraic reconstruction technique, are applied to obtain a stack of cross-sectional images as a sequence of time. The scanners can be operated in single or dual-plane mode. The presentation highlights the construct that is developed to start OS-independent data reconstruction jobs at HEMERA.

Keywords: X-ray CT scanner; HPC

  • Lecture (others) (Online presentation)
    Seminar Series - Hardware and Numerics, 08.12.2020, Dresden, Deutschland

Publ.-Id: 31696

Curium(III) and europium(III) as luminescence probes for plant cell (Brassica napus) interactions with potentially toxic metals

Moll, H.; Schmidt, M.; Sachs, S.

We have investigated the interaction of the actinide Cm(III) and its lanthanide homologue Eu(III) with cells of Brassica napus in suspension. This study combines biochemical techniques (plant cell response) with spectroscopic experiments to determine the chemical speciation of the metals in contact with the cells. Experiments conducted over a period of 7 d showed that B. napus cells were able to bioassociate both potentially toxic metals, with results confirming up to 0.58 µmol Eu/gfresh cells and 1.82 µmol Cm/gfresh cells at the lowest provided metal concentration. For Cm(III), a biosorption process could be identified as soon as 5 h post-exposure with 73±4% of the Cm(III) bioassociated. Additional luminescence spectroscopy results based on UV and site-selective excitation confirmed the existence of three Cm(III)/Eu(III), M(III), species in both the supernatants and cells. The findings detailed herein support that M(III) coordination to two kinds of carboxyl groups and phosphate groups.

Keywords: actinides; lanthanides; plant cells; laser spectroscopy; speciation


  • Secondary publication expected from 28.01.2022

Publ.-Id: 31695

mallocMC - Memory Allocator for Many Core Architectures

Widera, R.; Eckert, C.; Hübl, A.; Gruber, B. M.; Bastrakov, S.; Worpitz, B.; Grund, A.

This project provides a framework for fast memory managers on many core accelerators. It is based on alpaka to run on many different accelerators and implements the ScatterAlloc algorithm.

Keywords: CUDA; HIP; AMD; NVIDIA; memory allocation; many core; scatter alloc; C++

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: - OS: Linux/Windows/OSX - C++ 11 compiler - CUDA
    License: MIT
    Hosted on GitHub: Link to location
    DOI: 10.5281/zenodo.3862375


Publ.-Id: 31694

Influence of precursor thin-film quality on the structural properties of large-area MoS2 films grown by sulfurization of MoO3 on c-sapphire

Spanková, M.; Sojková, M.; Dobrocka, E.; Hutár, P.; Bodík, M.; Munnik, F.; Hulman, M.; Chromik, S.

In recent years, molybdenum disulfide (MoS2) has been investigated due to its unique electronic, optical, and mechanical properties with a variety of applications. Sulfurization of pre-deposited MoO3 layers is one of the methods of the preparation of large-area MoS2 thin films. The MoO3 layers have been grown on c-sapphire substrates, using two different techniques (rf sputtering, pulsed laser deposition). The films were subsequently annealed in vapors of sulfur at high temperatures what converted them to MoS2 films. The quality of MoS2 is strongly influenced by the properties of the precursor MoO3 layers. The pre-deposited MoO3, as well as the sulfurized MoS2, have been characterized by several techniques including Raman, Rutherford backscattering spectroscopy, atomic force microscopy, scanning electron microscopy, and X-ray diffraction. Here we compare two types of MoS2 films prepared from different MoO3 layers to determine the most suitable MoO3 layer properties providing good quality MoS2 films for future applications.

Keywords: Molybdenum disulfide; Sulfurization; Sputtering; Pulsed laser deposition; Structural properties

Publ.-Id: 31693

Diffraction techniques in nuclear materials

Bergner, F.

The presentation is aimed at introducing diffraction techniques and their applications in the field of structural nuclear materials. After a brief introduction, three selected experimental techniques are presented in more detail. These are X-ray line profile analysis (XLPA), electron backscatter diffraction (EBSD) and small-angle neutron scattering (SANS). XLPA is applied to derive microstructure parameters such as crystallite size, dislocation density and twin probability of a nanostructured high-entropy alloy processed by means of high pressure torsion. EBSD is shown to be useful for the characterization of the bainitic microstructure in terms of subunits of the prior austenite grains and their orientation relationship with the parent phase. As an example for the application of SANS, the effects of neutron flux and neutron fluence on the volume fraction and mean size of irradiation-induced solue atom clusters are characterized.

Keywords: Diffraction; Scattering; Nuclear materials; Irradiation effects

  • Invited lecture (Conferences) (Online presentation)
    European School on Nuclear Material Science, 09.-13.11.2020, Online, Online

Publ.-Id: 31692

Frequency- and magnetic-field-dependent properties of ordered magnetic nanoparticle arrangements

Neugebauer, N.; Hache, T.; Elm, M.; Hofmann, D. M.; Heiliger, C.; Schultheiß, H.; Klar, P. J.

We present a frequency and magnetic field dependent investigation of ordered arrangements of 20 nm magnetic
nanoparticles (MNPs) consisting of magnetite (Fe3O4) by employing micro Brillouin light scattering
microscopy. We utilized electron beam lithography to prepare hexagonally arranged, circularly shaped MNPassemblies
consisting of a single layer of MNPs using a variant of the Langmuir-Blodgett technique. By
comparing the results with non-structured, layered superlattices of MNPs, further insight into the influence
of size and geometry of the arrangement on the collective properties is obtained. We show that at low static
external field strengths, two signals occur in frequency dependent measurements for both non-structured and
structured assemblies. Enlarging the static external field strength leads to a sharpening of the main signal,
while the satellite signal decreases in its intensity and increases in its linewidth. The occurrence of multiple
signals at low external field strengths is also confirmed by sweeping the static external field and keeping the
excitation frequency constant. Micromagnetic simulations unravel the origin of the different signals and their
dependence on the static external field strength, enabling an interpretation of the observed characteristics in
terms of different local environments of an MNPs forming the MNP assembly.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-09
    DOI: 10.14278/rodare.577
    License: CC-BY-4.0


Publ.-Id: 31690

Optimization of multi-group energy structures for diffusion analyses of sodium-cooled fast reactors assisted by simulated annealing – Part I: methodology demonstration

Di Nora, V. A.; Fridman, E.; Nikitin, E.; Bilodid, Y.; Mikityuk, K.

This study presents an approach to the selection of optimal energy group structures for multi-group nodal diffusion analyses of Sodium-cooled Fast Reactor cores. The goal is to speed up calculations, particularly in transient calculations, while maintaining an acceptable accuracy of the results.
In Part I of the paper, possible time-savings due to collapsing of energy groups are evaluated using 24-group energy structure as a reference. Afterwards, focusing on energy structures with a number of groups leading to significant calculation speedups, optimal grid configurations are identified. Depending on a number of possible energy grid configurations to explore, the optimization is conducted by either a direct search or applying the simulated annealing method. Speedup and optimization studies are performed on a selected case of the Superphénix static neutronic benchmark by using the nodal diffusion DYN3D code. The results demonstrate noticeable improvements in DYN3D performance with a marginal deterioration of the accuracy.

Keywords: Serpent; XS condensation; energy structure optimization; simulated annealing

Related publications

Publ.-Id: 31688

ISAAC - In Situ Animation of Accelerated Computations

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

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

  • Software in the HZDR data repository RODARE
    Publication date: 2020-11-06
    DOI: 10.14278/rodare.573
    License: LGPL-3.0


Publ.-Id: 31686

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

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

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

Publ.-Id: 31685

Superconducting Accelerators as Sources for Intense Secondary Radiations

Wagner, A.

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

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

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

Publ.-Id: 31684

Rare earth minerals and rare-earth mining

Lorenz, T.; Bertau, M.; Möckel, R.

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

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

Publ.-Id: 31683

Nanoparticle emission by electronic sputtering of CaF2 single crystals

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

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

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

Publ.-Id: 31682

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

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

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

Publ.-Id: 31680

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

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

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

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

Publ.-Id: 31678

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

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

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


  • Secondary publication expected from 11.01.2022

Publ.-Id: 31677

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

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

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

Publ.-Id: 31676

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

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

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


  • Secondary publication expected from 22.10.2021

Publ.-Id: 31674

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

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


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


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


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


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

Publ.-Id: 31672

"Full-Core" VVER-1000 calculation benchmark

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

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

Publ.-Id: 31671

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

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

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

Publ.-Id: 31670

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

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

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

Keywords: Photonuclear reactions; photoabsorption cross section; photodissociation

Publ.-Id: 31669

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

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

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

Publ.-Id: 31668

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

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

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


Publ.-Id: 31667

Wire-Mesh Sensor Super-Resolution Based on Statistical Reconstruction

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

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

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

Related publications


  • Secondary publication expected from 10.02.2022

Publ.-Id: 31666

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

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

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


Publ.-Id: 31665

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

Dornheim, T.

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


Publ.-Id: 31664

Restricted configuration path integral Monte Carlo

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

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

Publ.-Id: 31663

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

Chekhonin, P.; Bergner, F.

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

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

Publ.-Id: 31662

Enhanced spin correlations in the Bose-Einstein condensate compound Sr3Cr2O8

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

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


Publ.-Id: 31661

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

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

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

Publ.-Id: 31660

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

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

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

Keywords: nanoparticles; detection; environmental compartments

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

Publ.-Id: 31659

Assessing nanoparticle release from waste water treatment using radiolabeled nanoparticles

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

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

Keywords: nanoparticles; waste water treatment; radiolabeling

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

Publ.-Id: 31658

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

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

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

Keywords: Radiolabeling; Nanoparticles

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

Publ.-Id: 31657

Scalable Workflows for OpenFOAM Evaluation

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

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

Keywords: workflow; OpenFOAM; validation

  • Lecture (Conference) (Online presentation)
    The Open Conference of the ISPRAS, 11.12.2020, Moscow, Russia

Publ.-Id: 31655

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

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

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

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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-17
    DOI: 10.14278/rodare.517


Publ.-Id: 31654

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

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

The files show the data we used for the publication.

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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-22
    DOI: 10.14278/rodare.525
    License: CC-BY-4.0


Publ.-Id: 31653

Are two-dimensional materials radiation tolerant?

Krasheninnikov, A.

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

Keywords: 2D materials; irradiation; radiation tolerance


  • Secondary publication expected from 18.09.2021

Publ.-Id: 31650

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

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

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

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

Publ.-Id: 31649

Dyke apertures record stress accumulation during sustained volcanism

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

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

Publ.-Id: 31648

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