Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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39129 Publications

Robustness of the remanent magnetic domain pattern formation and associated stripe-bubble transitions in Co/Pt multilayers against field sequencing

Gentillon, A.; Richards, C.; Ortiz-Flores, L. A.; Metzner, J.; Montealegre, D.; Healey, M.; Cardon, K.; Westover, A.; Hellwig, O.; Chesnel, K.

Thin ferromagnetic [Co/Pt] multilayers with perpendicular magnetic anisotropy exhibit a variety of nanoscopic magnetic domain patternsat remanence, from long interlaced stripes to lattices of bubbles, depending on the multilayer structure but also on the magnetic historyof the sample. For optimized structural parameters, stripe-bubble transitions accompanied by drastic increases in domain density havebeen observed when the magnitude of the previously applied perpendicular fieldHmis finely tuned throughout the hysteresis loop. Here, we investigate the robustness of these morphological transitions against field sequencing and field cycling. We conducted this study on[Co(x)/Pt(7Å)]N=50where x varies from 4 to 60 Å. We mapped the morphological transition withHmvarying from 0 to 9 T, following bothan ascending sequence (0→9 T) and a descending sequence (9 T→0). We found that the optimal fieldHm=H∗at which the domain densityis maximized and its associated maximal density n∗ are not significantly affected by the field sequencing direction. We have also investigatedpossible pumping effects when cycling the applied field at the value H∗. We found that n∗ remains relatively stable through field cycling, andmuch more stable in the bubble state, compared to longer stripe states. The observed robustness of these morphological transitions againstfield sequencing and field cycling is of crucial importance for potential magnetic recording applications.

Permalink: https://www.hzdr.de/publications/Publ-32342
Publ.-Id: 32342


Magnetic and structural dimer networks in layered K2Ni(MoO4)2

Murugan, G. S.; Ramesh Babu, K.; Sankar, R.; Chen, W. T.; Panneer Muthuselvam, I.; Chattopadhyay, S.; Choi, K.-Y.

The magnetic and thermodynamic properties of layered single-crystal K2Ni(MoO4)2 having both structural and magnetic dimers have been investigated. The crystal structure of K2Ni(MoO4)2 is composed of edge-sharing NiO6-octahedral pairs bridged by the MoO4 2− polyatomic ion groups in a plane, and the K+ ions sit in the van der Waals gap between the layers. The temperature dependence of magnetic susceptibility shows a spin-singlet ground state with an activation gap of Δ/kB ≈ 38 K. A high-field magnetization study at T = 1.5 K exhibits a half-magnetization plateau at μ0H ∼ 25 T, corresponding to a level crossing of the singlet ground state with the lowest triplet state. Further, we have performed density functional theory calculations to determine magnetic exchange interactions. The nearest-neighbor coupling constant J1 ∼ 10 K between the Ni spins turns out to be an order of magnitude larger than all interdimer couplings. Our experimental and theoretical results suggest that K2Ni(MoO4)2 constitutes a nearly isolated two-dimensional S = 1 dimer model.

Permalink: https://www.hzdr.de/publications/Publ-32341
Publ.-Id: 32341


Experimental evidence for Zeeman spin–orbit coupling in layered antiferromagnetic conductors

Ramazashvili, R.; Grigoriev, P. D.; Helm, T.; Kollmannsberger, F.; Kunz, M.; Biberacher, W.; Kampert, W. A. G.; Fujiwara, H.; Erb, A.; Wosnitza, J.; Gross, R.; Kartsovnik, M. V.

Most of solid-state spin physics arising from spin–orbit coupling, from fundamental phenomena to industrial applications, relies on symmetry-protected degeneracies. So does the Zeeman spin–orbit coupling, expected to manifest itself in a wide range of antiferromagnetic conductors. Yet, experimental proof of this phenomenon has been lacking. Here we demonstrate that the Néel state of the layered organic superconductor κ-(BETS)2FeBr4 shows no spin modulation of the Shubnikov–de Haas oscillations, contrary to its paramagnetic state. This is unambiguous evidence for the spin degeneracy of Landau levels, a direct manifestation of the Zeeman spin–orbit coupling. Likewise, we show that spin modulation is absent in electron-doped Nd1.85Ce0.15CuO4, which evidences the presence of Néel order in this cuprate superconductor even at optimal doping. Obtained on two very different materials, our results demonstrate the generic character of the Zeeman spin–orbit coupling.

Permalink: https://www.hzdr.de/publications/Publ-32340
Publ.-Id: 32340


Intense Positron Sources driven by a Superconducting Electron LINAC

Wagner, A.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Liedke, M. O.; Krause-Rehberg, R.

The Helmholtz-Center Dresden-Rossendorf operates several user beamlines for materials research using positron annihilation energy and lifetime spectroscopy. The superconducting electron LINAC ELBE [1] drives a hard X-ray source which is used to generate positrons through pair production. The unique setup Gamma-induced Positron Source GiPS generates electron-positron pairs inside the sample under investigation directly [2] making it well suited for annihilation lifetime studies of materials which are not qualified for vacuum conditions or because they impose hazards or intrinsic radioactivity.
The high-intensity Mono-energetic Positron Source MePS utilizes moderated positrons with adjustable kinetic energies ranging from 500 eV to 18 keV [3] for depth profiling in thin films. A magnetic beam transport system consisting of a beam chopper, a beam buncher, and a post-accelerator guides the positron beam towards the sample under investigation. Full-digital data processing of positron annihilation lifetime events generates spectra nearly free from background and free from distortions with timing resolutions down to about 210 ps and count rates in excess of 120 kcps.
The MePS facility is currently complemented by an additional beamline named Apparatus for In-situ Defect Analysis, AIDA-II, where in-situ defect studies are to be performed in a wide temperature range during thin film growth and under ion irradiation. A complimentary but functionally similar setup, AIDA-I [4], is operated at a 22Na-based mono-energetic continuous positron beam [5] used for in-situ (coincidence) Doppler-broadening positron annihilation spectroscopy experiments.
All facilities serve as user facilities to the international scientific community. Recent developments at all beam lines and some exemplary experiments will be presented [6-8].

The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). The initial AIDA system was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox). The AIDA facility was funded through the Helmholtz Energy Materials Characterization Platform.

References
[1] F. Gabriel, et al., Nucl. Instr. Meth. B 161 (2000) 1143.
[2] M. Butterling, et al., Nucl. Instr. Meth. B 269 (2011) 2623.
[3] A. Wagner, et al., AIP Conference Proceedings 1970 (2018) 040003.
[4] M. O. Liedke, et al., Journal of Applied Physics 117 (2015) 163908.
[5] W. Anwand, et al., Defect and Diffusion Forum Vl. 331 (2012) 25.
[6] M. Reiner, et al., Scientific Reports 6 (2016) 29109.
[7] A. Quintana, et al., ACS Nano 12 (2018) 10291.
[8] J. Ji, et al., Scientific Reports 6 (2016) 31238.

Keywords: positron annihilation lifetime spectroscopy ELBE MePS EPOS GiPS defects porosity

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Positron Studies of Defects, 01.-05.03.2021, Mumbai, India

Permalink: https://www.hzdr.de/publications/Publ-32339
Publ.-Id: 32339


Challenges on cyclic nucleotide phosphodiesterases imaging with positron emission tomography: Novel radioligands and (pre-)clinical insights since 2016

Schröder, S.; Scheunemann, M.; Wenzel, B.; Brust, P.

Cyclic nucleotide phosphodiesterases (PDEs) represent one of the key targets in the research field of intracellular signaling related to the second messenger molecules cyclic adenosine monophosphate (cAMP) and/or cyclic guanosine monophosphate (cGMP). Hence, non-invasive imaging of this enzyme class by positron emission tomography (PET) using appropriate isoform-selective PDE radioligands is gaining importance. This methodology enables the in vivo diagnosis and staging of numerous diseases associated with altered PDE density or activity in the periphery and the central nervous system as well as the translational evaluation of novel PDE inhibitors as therapeutics. In this follow-up review, we summarize the efforts in the development of novel PDE radioligands and highlight (pre-)clinical insights from PET studies using already known PDE radioligands since 2016.

Keywords: positron emission tomography; cyclic nucleotide phosphodiesterases; PDE inhibitors; PDE radioligands; radiochemistry; imaging; recent (pre-)clinical insights

Permalink: https://www.hzdr.de/publications/Publ-32338
Publ.-Id: 32338


CTF and FLOCAL Thermal Hydraulics Validations and Verifications within a Multiscale and Multiphysics Software Development

Davies, S.; Rohde, U.; Litskevich, D.; Merk, B.; Bryce, P.; Levers, A.; Detkina, A.; Atkinson, S.; Ravindra, V.

Simulation codes allow to reduce the high conservativism in nuclear reactor design improving the reliability and sustainability associated to nuclear power. Full core coupled reactor physics at the rod level are not provided by most simulation codes. This has led in the UK to the development of a multiscale and multiphysics software development focused on LWRS. In terms of the thermal hydraulics, simulation codes suitable for this multiscale and multiphysics software development include the subchannel code CTF and the thermal hydraulics module FLOCAL of the nodal code DYN3D. In this journal article, CTF and FLOCAL thermal hydraulics validations and verifications within the multiscale and multiphysics software development have been performed to evaluate the accuracy and methodology available to obtain thermal hydraulics at the rod level in both simulation codes. These validations and verifications have proved that CTF is a highly accurate sub-channel code for thermal hydraulics. Also, these verifications have proved that CTF provides a wide range of crossflow and turbulent mixing methods while FLOCAL provides in general the simplified no crossflow method as the rest of the methods were only tested during its implementation into DYN3D.

Keywords: Nuclear Reactor; Thermal Hydraulics; Simulation; Subchannel Code; CTF; FLOCAL; PSBT

Permalink: https://www.hzdr.de/publications/Publ-32337
Publ.-Id: 32337


Effect of deposition current density on the Co–Ni/SiO2 alloy composite coatings Using Scanning Jet Electrodeposition

Jiang, W.; Qiu, M.; Shen, L.; Lou, G.; Yang, X.; Eckert, K.; Tian, Z.

Co–Ni/SiO2 alloy composite coatings were electrodeposited on copper substrate by scanning jet electrodeposition at various current densities to study its effect on the deposite morphologies, texture orientation, microhardness, adhesion force, wear resistance and corrosion resistance of Co–Ni/SiO2 alloy composite coatings. The structure and performance of the material were characterized using scanning electron microscope, XRD diffractometer, nanoindentation, scratch tester, friction and wear tester and electrochemical methods. The morphologies of the Co–Ni/SiO2 alloy composite coatings changed from sparse and slender structures to dense starfish structures with an increase in current density. A part of Co precipitated in the form of a face-centered cubic structure and formed a solid solution with Ni, while another part of Co precipitated in the structure of the composite coating in the form of a hexagonal close-packed structure. The Co–Ni/SiO2 alloy composite coating exhibited excellent adhesion force, wear resistance and corrosion resistance when the deposition current density was 130 A/dm2. Once the current density was exceeded, some microcracks appeared on the surface of the composite coating, after which the adhesion force and corrosion resistance decreased. The present study suggests that current density at 130 A/dm2 is more suitable than low current density for jet electrodeposition to prepare high-density and high-quality composite coating.

Keywords: Co–Ni/SiO2; Scanning jet electrodeposition; Deposition current density

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Permalink: https://www.hzdr.de/publications/Publ-32336
Publ.-Id: 32336


Treatment verification with prompt-gamma-imaging: Detection of anatomical changes in prostate-cancer proton therapy

Berthold, J.; Piplack, N.; Traneus, E.; Pietsch, J.; Khamfongkhruea, C.; Thiele, J.; Hölscher, T.; Janssens, G.; Smeets, J.; Stützer, K.; Richter, C.

Introduction
We present results of the worldwide first systematic study on the sensitivity of prompt-gamma-imaging (PGI) to detect anatomical changes in proton therapy for the ongoing evaluation in prostate-cancer treatments.

Materials&Methods
Spot-wise range shifts were monitored with a PGI-slit-camera during 40 fractions of hypo-fractionated prostate-cancer treatments (5 patients, 2 fields, each 1.5GyE). In-room CTs were acquired for these fractions and range shifts of spot-wise integrated depth-dose (IDD) profiles serve as ground-truth. For both PGI and IDD data, spots were clustered based on Bragg-peak position and proton number to mitigate statistical uncertainty in the PGI measurement using a low-dose spot cut-off at 5e7 protons, a minimum number of 3e9 protons per cluster, and a minimum/maximum cluster volume of 1cm3/8cm3. Clusters with absolute range shift ≥5mm were classified as relevant anatomical changes.

Results
A strong correlation (rPearson=0.72) was found between ground-truth IDD and PGI range shifts per cluster with an average absolute deviation of 1.3mm over all fractions. In total, 245/7143 (3.4%) clusters (found within 24/72 fields) contained relevant IDD-based range shifts. PGI detected these changes with a sensitivity of 68%, specificity of 96%, and accuracy of 95%. The results might be affected by potential intra-fractional changes between in-room CT acquisition and treatment delivery. A higher sensitivity is also expected for a gantry-mounted camera system with decreased positioning uncertainty.

Conclusion
Our systematic investigation on the sensitivity of a PGI-slit-camera with a first quantitative comparison of range shifts from PGI and IDD profiles demonstrates the capability to locally detect relevant anatomical changes in patients.

  • Lecture (Conference) (Online presentation)
    59th annual conference of the particle therapy co-operative group (PTCOG), 04.-07.06.2021, online, online
  • Open Access Logo Abstract in refereed journal
    International Journal of Particle Therapy (2022)
    DOI: 10.14338/IJPT-22-PTCOG59-9.3

Permalink: https://www.hzdr.de/publications/Publ-32335
Publ.-Id: 32335


First-In-Human Validation of CT-Based Proton Range Prediction Using Prompt Gamma Imaging in Prostate Cancer Treatments

Berthold, J.; Khamfongkhruea, C.; Petzoldt, J.; Thiele, J.; Hölscher, T.; Wohlfahrt, P.; Peters, N.; Jost, A.; Hofmann, C.; Janssens, G.; Smeets, J.; Richter, C.

Purpose
Uncertainty in computed tomography (CT)-based range prediction substantially impairs the accuracy of proton therapy. Direct determination of the stopping-power ratio (SPR) from dual-energy CT (DECT) has been proposed (DirectSPR), and initial validation studies in phantoms and biological tissues have proven a high accuracy. However, a thorough validation of range prediction in patients has not yet been achieved by any means. Here, we present the first systematic validation of CT-based proton range prediction in patients using prompt gamma imaging (PGI).

Methods and Materials
A PGI slit camera system with improved positioning accuracy, using a floor-based docking station, was used. Its overall uncertainty for range prediction validation was determined experimentally with both x-ray and beam measurements. The accuracy of range prediction in patients was determined from clinical PGI measurements during hypofractionated treatment of 5 patients with prostate cancer - in total 30 fractions with in-room control-CTs. For each pencil-beam-scanning spot, the range shift was obtained by comparing the PGI measurement to a control-CT-based PGI simulation. Three different SPR prediction approaches were applied in simulations: a standard CT-number-to-SPR conversion (Hounsfield look-up table [HLUT]), an adapted HLUT (DECT optimized), and DirectSPR. The spot-wise weighted mean range shift from all spots served as a measure for the accuracy of the respective range prediction approach.

Results
A mean range prediction accuracy of 0.0% ± 0.5%, 0.3% ± 0.4%, and 1.8% ± 0.4% was obtained for DirectSPR, adapted HLUT, and standard HLUT, respectively. The overall validation uncertainty of the second-generation PGI slit camera is about 1 mm (2σ) for all approaches, which is smaller than the range prediction uncertainty for deep-seated tumors.

Conclusions
For the first time, range prediction accuracy was assessed in clinical routine using PGI range verification in prostate cancer treatments. Both DECT–derived range prediction approaches agree well with the measured proton range from PGI verification, whereas the standard HLUT approach differs relevantly. These results endorse the recent reduction of clinical safety margins in DirectSPR-based treatment planning in our institution.

Keywords: proton therapy; range verification; prompt gamma imaging; SPR prediction; DECT

Permalink: https://www.hzdr.de/publications/Publ-32334
Publ.-Id: 32334


Which is the best ⁹Be carrier for ¹⁰Be/⁹Be accelerator mass spectrometry?

Merchel, S.; Braucher, R.; Lachner, J.; Rugel, G.

Commercial ⁹Be solutionss used for chemical preparation of samples for accelerator mass spectrometry contain the cosmogenic long-lived radionuclide ¹⁰Be at elevated but different ¹⁰Be/⁹Be levels. Within a systematic study of recently produced solutions, comparison to published data and new data on customised solutions from minerals, we recommend - if no customised solution is available - the ⁹Be solutions from Australian Chemical Reagents (ACR) or from LGC. They contain ¹⁰Be/⁹Be at the 3.4 x 10-15 level, which is still suitable for the majority of Earth science applications, compared to customised solutions at the 10-16 level for lowest-level studies. Commercial solutions from Scharlab having different lot numbers, i.e. an identification number assigned to a particular lot of material from a single manufacturer, vary in ¹⁰Be/⁹Be by up to a factor of nine. Hence, it seems an advisable strategy to buy a bigger quantity of a single production batch (such as 10 x 100 ml bottles of ⁹BeBe at 1 g l-1) and have them tested once at any AMS facility before first use.

  • The best ⁹Be carrier for low-level ¹⁰Be/⁹Be applications is a customised one from minerals like phenakite.
  • The best ⁹Be carriers for medium- and high-level ¹⁰Be/⁹Be applications are currently from Australian Chemical Reagents (ACR) or from LGC.
  • As ⁹Be carriers from Scharlab of different batches (LOT) contain ¹⁰Be/⁹Be at different levels, it is advisable to buy a bigger number of bottles of the same LOT of commercial carriers after being identified to have reasonably low isotope ratios.

Keywords: AMS; phenakite; carrier; blank; beryl

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Permalink: https://www.hzdr.de/publications/Publ-32333
Publ.-Id: 32333


Proton range verification with prompt gamma-ray timing and on-line proton bunch monitoring

Permatasari, F.; Lutz, B.; Pausch, G.; Römer, K.; Schellhammer, S.; Wagner, A.; Werner, R.-D.; Weinberger, D.; Werner, T.; Kögler, T.

Range verification is an important prerequisite to unfold the full potential of the finite range of proton beams and to improve treatment precision. The prompt gamma-ray timing (PGT) technique offers a non-invasive approach for range verification using the measured time distribution of the prompt gamma rays produced in the patient. PGT dispenses with a heavy collimator and can be integrated into existing treatment gantries. However, the high sensitivity of this technique to any instabilities in the proton bunch periodicity is a major challenge and demands online monitoring of the proton bunch arrival time. Therefore, we have developed a proton bunch monitor (PBM) comprising fast-scintillating fibers with a double-sided silicon photomultiplier readout. Placing the PBM in the beam halo allows the direct measurement of the proton arrival time at clinical beam intensities while maintaining a processable trigger rate. In a proof-of-principle experiment with a thick acrylic glass target and defined cylindrical air cavities as well as tissue equivalent inserts, a direct monitoring of proton bunches was carried out together with a PGT measurement. With the use of the PBM, another important step towards the clinical translation of the PGT method was taken.

Keywords: proton therapy; treatment verification; radiation detector development

Related publications

  • Poster (Online presentation)
    59th Annual Conference of the Particle Therapy Co-operative Group, 04.-07.06.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-32332
Publ.-Id: 32332


Complexation of Cm(III) and Eu(III) with aqueous phosphates at elevated temperatures

Jordan, N.; Huittinen, N. M.; Jessat, I.; Réal, F.; Vallet, V.; Starke, S.; Eibl, M.

Thermodynamic databases are essential for the safety assessments of radioactive waste repositories. They have to be reliable, comprehensive, and describe the key mechanisms controlling the mobility of contaminants in the environment. However, in many cases these prerequisites are not fulfilled. An important example is the complexation of actinides and lanthanides with aqueous phosphates, for which this work provides complexation constants for spectroscopically identified species at 298K and at elevated temperature.
The complexation of Cm(III) and Eu(III) was studied at submicromolar concentrations by laser-induced luminescence spectroscopy as a function of total phosphate concentration (0-0.06 M ΣPO₄) in the temperature range of 298-363K, using NaClO₄ as a background electrolyte at –log[H⁺] ranging from 2.5 to 3.6. The formation of both CmH₂PO₄²⁺/EuH₂PO₄²⁺ and Cm(H₂PO₄)₂⁺/Eu(H₂PO₄)₂⁺ complexes was revealed, the latter being spectroscopically evidenced for the first time. Complexation constants were found to increase when raising the ionic strength from 0.5 to 3.0 M.
Temperature-dependent complexation constants for the identified species were derived and recalculated to standard conditions using the van´t Hoff equation and the Specific Ion Interaction Theory. Endothermic and entropy driven reactions were established for both Cm(III) and Eu(III) phosphate complexes.
In addition, relativistic quantum chemical investigations were performed to study the complexation strength of Cm(III) with aqueous phosphates, to provide insight into potential changes of the coordination number with increasing temperature and to probe the character of the Cm water and Cm phosphate bonds.

Keywords: curium; phosphate; complexation; temperature; luminescence spectroscopy; thermodynamics; ab initio

  • Lecture (Conference) (Online presentation)
    Goldschmidt2021, 04.-09.07.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-32331
Publ.-Id: 32331


Comparison of Elemental Analysis Techniques for the Characterization of Commercial Alloys

Seidel, P.; Ebert, D.; Schinke, R.; Möckel, R.; Raatz, S.; Chao, M.; Niederschlag, E.; Kreschel, T.; Gloaguen, R.; Renno, A.

Better quality control for alloy manufacturing and sorting of post-consumer scraps relies heavily on the accurate determination of their chemical composition. In recent decades, analytical tech-niques, such as X-ray fluorescence spectroscopy (XRF), laser-induced breakdown spectroscopy (LIBS), and spark optical emission spectroscopy (spark-OES), found widespread use in the metal industry, though only a few studies were published about the comparison of these techniques for commercially available alloys. Hence, we conducted a study on the evaluation of four analytical techniques (energy-dispersive XRF, wavelength-dispersive XRF, LIBS, and spark-OES) for the de-termination of metal sample composition. It focuses on the quantitative analysis of nine commer-cial alloys, representing the three most important alloy classes: copper, aluminum, and steel. First, spark-OES is proven to serve as a validation technique in the use of certified alloy reference sam-ples. Following an examination of the lateral homogeneity by XRF, the results of the techniques are compared, and reasons for deviations are discussed. Finally, a more general evaluation of each technique with its capabilities and limitations is given, taking operation-relevant parameters, such as measurement speed and calibration effort, into account. This study shall serve as a guide for the routine use of these methods in metal producing and recycling industries.

Permalink: https://www.hzdr.de/publications/Publ-32330
Publ.-Id: 32330


B20-MnSi films grown on Si(100) substrates with magnetic skyrmion signature

Li, Z.; Yuan, Y.; Hübner, R.; Begeza, V.; Rebohle, L.; Helm, M.; Nielsch, K.; Prucnal, S.; Zhou, S.

Magnetic skyrmions have been suggested as information carriers for future spintronic devices. As the first material with experimentally confirmed skyrmions, B20-type MnSi has the research focus for decades. Although B20-MnSi films have been successfully grown on Si(111) substrates, there is no report about B20-MnSi films on Si(100) substrates, which would be more preferred for practical applications. In this letter, we present the first preparation of B20-MnSi on Si(100) substrates. It is realized by sub-second solid-state reaction between Mn and Si via flash-lamp annealing at ambient pressure. The regrown layer shows an enhanced Curie temperature of 43 K compared with bulk B20-MnSi. The magnetic skyrmion signature is proved in our films by magnetic and transport measurements. The millisecond-range flash annealing provides a promising avenue for the fabrication of Si-based skyrmionic devices.

Keywords: Skyrmions; B20-MnSi; Flash-lamp annealing

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Permalink: https://www.hzdr.de/publications/Publ-32329
Publ.-Id: 32329


Defective Nanographenes Containing Seven-Five-Seven (7–5–7)-Membered Rings

Fei, Y.; Fu, Y.; Bai, X.; Du, L.; Li, Z.; Komber, H.; Low, K.-H.; Zhou, S.; Lee Phillips, D.; Feng, X.; Liu, J.

Defects have been observed in graphene and are expected to playa key role in its optical, electronic, and magnetic properties. However, becausemost of the studies focused on the structural characterization, the implications oftopological defects on the physicochemical properties of graphene remain poorlyunderstood. Here, we demonstrate a bottom-up synthesis of three novelnanographenes (1−3) with well-defined defects in which seven-five-seven (7−5−7)-membered rings were introduced to their sp2carbon frameworks. From theX-ray crystallographic analysis, compound1adopts a nearly planar structure.Compound2, with an additionalfive-membered ring compared to1, possesses aslightly saddle-shaped geometry. Compound3, which can be regarded as the“head-to-head”fusion of1with two bonds, features two saddles connectedtogether. The resultant defective nanographenes1−3were well-investigated byUV−vis absorption, cyclic voltammetry, and time-resolved absorption spectra and further corroborated by density functional theory(DFT) calculations. Detailed experimental and theoretical investigations elucidate that these three nanographenes1−3exhibit ananti-aromatic character in their ground states and display a high stability under ambient conditions, which contrast with the reportedunstable biradicaloid nanographenes that contain heptagons. Our work reported herein offers insights into the understanding ofstructure-related properties and enables the control of the electronic structures of expanded nanographenes with atomically precise defects.

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Permalink: https://www.hzdr.de/publications/Publ-32328
Publ.-Id: 32328


Effect of PAA-induced surface etching on the adhesion properties of ZnO nanostructured films

Meinderink, D.; Kielar, C.; Sobol, O.; Ruhm, L.; Rieker, F.; Nolkemper, K.; Orive, A. G.; Ozcan, O.; Grundmeier, G.

Zinc oxide - polymer interfaces are known to exhibit interesting properties regarding molecular adhesion. This work is aimed at the investigation of the effect of the morphology and surface chemistry on the macroscopic adhesion of a model epoxy-based adhesive to nanorod (ZnO NR) and nanocrystalline (ZnO NC) ZnO-modified surfaces. Both ZnO films have been prepared using hydrothermal synthesis on hot-dip galvanized steel (HDG) surfaces by varying the precursor chemistry in order to control the film morphology. Poly (acrylic acid) (PAA) was used to improve the interfacial adhesion by modifying the morphology and surface chemistry of ZnO nanostructured films. The strong interaction of PAA from a dilute and neutral aqueous solution with the ZnO nanocrystallites was shown to significantly improve the interfacial adhesion by means of a nanoetching process. It was shown that the wet peel-forces correlate well with the considered morphology and surface chemistry.

Keywords: ZnO nanorods; Nanocrystalline ZnO films; Adhesion by mechanical interlocking; Poly(acrylic acid); Morphology control; Interfacial stability

Permalink: https://www.hzdr.de/publications/Publ-32327
Publ.-Id: 32327


Convergent Synthesis of Diversified Reversible Network Leads to Liquid Metal-Containing Conductive Hydrogel Adhesives

Xu, Y.; Rothe, R.; Voigt, D.; Hauser, S.; Cui, M.; Miyagawa, T.; Patino Gaillez, M.; Kurth, T.; Bornhäuser, M.; Pietzsch, J.; Zhang, X.

Many features of extracellular matrices, e.g., self-healing, adhesiveness, viscoelasticity, and conductivity, are associated with the intricate networks composed of many different covalent and non-covalent chemical bonds. Whereas a reductionism approach would have the limitation to fully recapitulate various biological properties with simple chemical structures, mimicking such sophisticated networks by incorporating many different functional groups in a macromolecular system is synthetically challenging. Herein, we propose a strategy of convergent synthesis of complex polymer networks to produce biomimetic electroconductive liquid metal hydrogels. Four precursors could be individually synthesized in one to two reaction steps and characterized, then assembled to form hydrogel adhesives. The convergent synthesis allows us to combine materials of different natures to generate matrices with high adhesive strength, enhanced electroconductivity, good cytocompatibility in vitro and high biocompatibility in vivo. The reversible networks exhibit self-healing and shear-thinning properties, thus allowing for 3D printing and minimally invasive injection for in vivo experiments.

Permalink: https://www.hzdr.de/publications/Publ-32326
Publ.-Id: 32326


Comprehensive Bonding Analysis of Tetravalent f-Element Complexes of the Type [M(salen)2]

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

Zip-File with the xyz-files of the optimized structures of the studied complexes. Further information can be found in the respective paper and supplementary information.

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Permalink: https://www.hzdr.de/publications/Publ-32325
Publ.-Id: 32325


Comprehensive Bonding Analysis of Tetravalent f-Element Complexes of the Type [M(salen)₂]

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

Key questions for the study of chemical bonding in actinide compounds are the degree of covalency that can be realized in the bonds to different donor atoms and the relative participation of 5f and 6d orbitals. A manifold of theoretical approaches is available to address these questions, but hitherto no comprehensive assessments are available. Here, we present an in-depth analysis of the metal–ligand bond in a series of actinide metal–organic compounds of the [M(salen)₂] type (M = Ce, Th, Pa, U, Np, Pu) with the Schiff base N,N′-bis(salicylidene)ethylenediamine (salen). All compounds except the Pa complex (only included in the calculations) have been synthesized and characterized experimentally. The experimental data are then used as a basis to quantify the covalency of bonds to both N- and O-donor atoms using simple electron-density differences and the quantum theory of atoms in molecules (QTAIM) with interacting quantum atoms. In addition, the orbital origin of any covalent contributions was studied via natural population analysis (NPA). The results clearly show that the bond to the hard, charged O-donor atoms of salen is consistently not only stronger but also more covalent than bonds to the softer N-donor atoms. On the other hand, in a comparison of the metals, Th shows the most ionic bond character even compared to its 4f analogue Ce. A maximum of the covalency is found for Pa or Np by their absolute and relative covalent bond energies, respectively. This trend also correlates with a significant f- and d-orbital occupation for Pa and Np. These results underline that only a comprehensive computational approach is capable of fully characterizing the covalency in actinide complexes.

Keywords: Actinides; Covalency; QTAIM; Coordination Chemistry; Metal-organic Chemistry; DFT; Electron Density

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-32324
Publ.-Id: 32324


A workflow for the sustainable development of closure models for bubbly flows

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

Many years of research in developing closure models for polydisperse bubbly flows have produced a plethora of empirical and semi-empirical models.
The continuous development and analysis of such models requires their constant validation with the steadily increasing number of validation cases in
the literature.
In this paper we present a pipeline for the fully-automated analysis of OpenFOAM simulations using the Snakemake workflow management system. The pipeline is applied to an extensive collection of well-established validation cases for bubbly flows and allows the fast and efficient production of large amounts of results that are summarized in well-structured reports. An optional post-processing step introduces a fuzzy-logic controller developed for the detailed analysis of these results by quantifying the agreement of the simulation with the available experimental data. It is demonstrated how such quantification enables the systematic evaluation of new closure models and contributes to a more sustainable model development.

Keywords: Baseline; bubbly flow; OpenFOAM; workflow; Artificial Intelligence

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Permalink: https://www.hzdr.de/publications/Publ-32323
Publ.-Id: 32323


Multilayer interfacial wave dynamics in upright circular cylinders with application to liquid metal batteries

Horstmann, G. M.

Liquid metal batteries (LMBs) are discussed today as an economic grid-scale energy storage, as required for the deployment of fluctuating renewable energies. These batteries consist of three stably stratified liquid layers: two liquid metal electrodes are separated by a thin molten salt electrolyte, this way forming an electrochemical concentration cell. Their completely liquid interior, which is on the one hand very beneficial for the energy efficiency, also poses some major challenges on the other hand. Strong cell currents in combination with electromagnetic fields make liquid metal batteries highly susceptible to various kinds of magnetohydrodynamic instabilities. In particular, the so-called metal pad roll instability (MPRI), which can drive uncontrollable wave motions in both interfaces, was identified as a key limiting factor for the batteries' operational safety.
In this seminar talk, I will present the key results of my PhD thesis, where I was concerned with multilayer interfacial wave dynamics in cylindrical LMB models. In the fist part, I will show the results of a potential flow theory describing gravity–capillary waves in three-layer stratifications. The theory is used to classify different wave coupling states, which comprise different manifestations of the MPRI. Accompanying numerical simulations substantiate that coupling effects will be present in most future LMBs. In the second part, a multilayer sloshing experiment will be introduced, which allows to mechanically excite the same interfacial wave motions as induced by the MPRI. Different sets of experiments emphasize the crucial role of the contact line as well as of viscous damping, both having a strong impact on instability onsets of cylindrical LMBs. In the final part, I will present a new hybrid interfacial sloshing model, which accounts for viscous damping and can explain the experimentally observed resonance dynamics. As a further unexpected result, the sloshing theory predicts the formation of novel spiral wave patterns under the effect of strong damping in higher wave modes.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Online seminars of the Morelia Unit of the Materials Research Institute at the National University of Mexico, 12.02.2021, Mexico City, Mexico

Permalink: https://www.hzdr.de/publications/Publ-32322
Publ.-Id: 32322


Coarse-graining master equation for periodically driven systems

Hotz, R.; Schaller, G.

We analyze Lindblad-Gorini-Kossakowski-Sudarshan-type generators for selected periodically driven open quantum systems. All these generators can be obtained by temporal coarse-graining procedures, and we compare different coarse-graining schemes. Similar to for undriven systems, we find that a dynamically adapted coarse-graining time, effectively yielding non-Markovian dynamics by interpolating through a series of different but invididually Markovian solutions, yields the best results among the different coarse-graining schemes, albeit at highest computational cost.

Keywords: open quantum systems; Floquet theory; periodic driving; Lindblad master equation

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Permalink: https://www.hzdr.de/publications/Publ-32321
Publ.-Id: 32321


Production of no-carrier-added 89Zr at an 18 MeV cyclotron, its purification and use in investigations in solvent extraction

Mansel, A.; Franke, K.

The chemical separation of zirconium from lanthanides by liquid-liquid extraction is challenging but critical for medical and technological applications. Using the example of 89Zr, we optimize the liquid-liquid-extraction process by means of the radiotracer technique. We produced 89Zr by proton irradiation of a metallic yttrium target at a cyclotron. The purification of the radionuclide was performed by a UTEVA resin. 89Zr was separated in no-carrier-added form in a sulfuric acid solution. 89Zr was successfully used in solvent extraction tests with calixarenes for the separation of zirconium from lanthanides. This reaction is suitable for the efficient extraction and purification of lanthanides.

Keywords: Zirconium-89; Solvent extraction with calixarenes; Natural yttrium-89 target; Proton induced nuclear reaction; Chemical separation

Permalink: https://www.hzdr.de/publications/Publ-32320
Publ.-Id: 32320


Nematic shells: new insights in topology- and curvature-induced effects

Napoli, G.; Pylypovskyi, O.; Sheka, D.; Vergoli, L.

Orientable materials, such as magnetic materials or liquid crystals, are known to give rise to several special textures, whose complexity is as beautiful as it is interesting to explore and understand their nature. Their confinement in curved layers gives rise to new geometry-induced effects that are not usually observed in flat layers. In this paper we draw a parallel between ferromagnetic and nematic shells, both of which are characterized by local interaction and anchoring potentials. We show that, the different nature of the order parameter, a vector in ferromagnets and a tensor in nematics, although leading to similar curvature-induced effects (such as anisotropy and chirality), yields different textures on genus zero surfaces. Thus, on a sphere, the textures of ferromagnets are characterised by integer charge vortices, while the textures of nematics also admit half-integer charge vortices.

Keywords: nematics; liquid crystals; spherical geometry; curvilinear geometry

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Permalink: https://www.hzdr.de/publications/Publ-32319
Publ.-Id: 32319


2020 Roadmap on Plasma Accelerators

Albert, F.; Couprie, M.-E.; Debus, A.; Downer, M.; Faure, J.; Flacco, A.; Gizzi, L.; Grismayer, T.; Huebl, A.; Joshi, C.; Labat, M.; Leemans, W.; Maier, A.; Mangles, S.; Mason, P.; Mathieu, F.; Muggli, P.; Nishiuchi, M.; Osterhoff, J.; Rajeev, P.; Schramm, U.; Schreiber, J.; Thomas, A.; Vay, J.-L.; Vranic, M.; Zeil, K.

Plasma-based accelerators use the strong electromagnetic fields that can be supported by plasmas to accelerate charged particles to high energies. Accelerating field structures in plasma can be generated by powerful laser pulses or charged particle beams. This research field has recently transitioned from involving a few small-scale efforts to the development of national and international networks of scientists supported by substantial investment in large-scale research infrastructure. In this New Journal of Physics 2020 Plasma Accelerator Roadmap, perspectives from experts in this field provide a summary overview of the field and insights into the research needs and developments for an international audience of scientists, including graduate students and researchers entering the field.

Permalink: https://www.hzdr.de/publications/Publ-32318
Publ.-Id: 32318


Photons or protons for reirradiation in (non-)small cell lung cancer: Results of the multicentric ROCOCO in silico study

Troost, E. G. C.; Wink, K. C. J.; Roelofs, E.; Simone Ii, C. B.; Makocki, S.; Löck, S.; van Kollenburg, P.; Dechambre, D.; Minken, A. W. H.; van der Stoep, J.; Avery, S.; Jansen, N.; Solberg, T.; Bussink, J.; de Ruysscher, D.

Objective: Locally recurrent disease is of increasing concern in (non-) small cell lung cancer [(N)SCLC] patients. Local reirradiation with photons or particles may be of benefit to these patients. In this multicentre in silico trial performed within the Radiation Oncology Collaborative Comparison (ROCOCO) consortium, the doses to the target volumes and organs at risk (OARs) were compared when using several photon and proton techniques in patients with recurrent localised lung cancer scheduled to undergo reirradiation. Methods: 24 consecutive patients with a second primary (N)SCLC or recurrent disease after curative-intent, standard fractionated radio(chemo)therapy were included in this study. The target volumes and OARs were centrally contoured and distributed to the participating ROCOCO sites. Remaining doses to the OARs were calculated on an individual patient’s basis. Treatment planning was performed by the participating site using the clinical treatment planning system and associated beam characteristics. Results: Treatment plans for all modalities (five photon and two proton plans per patient) were available for 22 patients (N = 154 plans). 3D-conformal photon therapy and double-scattered proton therapy delivered significantly lower doses to the target volumes. The highly conformal techniques, i.e., intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), CyberKnife, TomoTherapy and intensity-modulated proton therapy (IMPT), reached the highest doses in the target volumes. Of these, IMPT was able to statistically significantly decrease the radiation doses to the OARs. Conclusion: Highly conformal photon and proton beam techniques enable high-dose reirradiation of the target volume. They, however, significantly differ in the dose deposited in the OARs. The therapeutic options, i.e., reirradiation or systemic therapy, need to be carefully weighed and discussed with the patients. Advances in knowledge: Highly conformal photon and proton beam techniques enable high-dose reirradiation of the target volume. In light of the abilities of the various highly conformal techniques to spare specific OARs, the therapeutic options need to be carefully weighed and patients included in the decision-making process.

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Permalink: https://www.hzdr.de/publications/Publ-32317
Publ.-Id: 32317


Specific requirements for translation of biological research into clinical radiation oncology

Krause, M.; Alsner, J.; Linge, A.; Bütof, R.; Löck, S.; Bristow, R.

Radiotherapy has been optimized over the last decades not only through technological advances, but also through the translation of biological knowledge into clinical treatment schedules. Optimization of fractionation schedules and/or the introduction of simultaneous combined systemic treatment have significantly improved tumour cure rates in several cancer types.
With modern techniques, we are currently able to measure factors of radiation resistance or radiation sensitivity in patient tumours; the definition of new biomarkers is expected to further enable personalized treatments. In this Review article, we overview important translation paths and summarize the quality requirements for preclinical and translational studies that will help to avoid bias in trial results.

Keywords: biomarkers; clinical trials; personalized treatment; quality; radiotherapy; translational research

Permalink: https://www.hzdr.de/publications/Publ-32316
Publ.-Id: 32316


Exploring point defects and trap states in undoped SrTiO3 single crystals

Siebenhofer, M.; Baiutti, F.; de Dios Sirvent, J.; Huber, T. M.; Viernstein, A.; Smetaczek, S.; Herzig, C.; Liedke, M. O.; Butterling, M.; Wagner, A.; Hirschmann, E.; Limbeck, A.; Tarancon, A.; Fleig, J.; Kubicek, M.

The defect chemistry and electronic trapping energies in undoped single crystalline SrTiO3 were examined by electrochemical impedance spectroscopy (EIS) at low (25-160°C) and intermediate (500-700°C) temperatures. At intermediate temperatures, the electronic and ionic conductivity as well as the chemical capacitance of SrTiO3 were determined as a function of T and p(O2) by employing a modified transmission line equivalent circuit to accurately describe the measured system. Defect modelling based on chemical capacitance measurements is established as a new method to determine the concentrations and the thermodynamic properties of ionic and electronic defects in SrTiO3. This method has potential for a wide application for mixed ionic and electronic conducting materials. Impedance spectroscopy at low temperatures was used to further quantify the electronic trapping energies of the main ionic defects of SrTiO3. Utilization of the chemical capacitance allows the establishment of a defect model based solely on electrochemical measurements, which correctly predicts the conductivity and the chemical capacitance, unveiling the concentrations of internal defects. This analysis yields a concentration of 6 ppm for acceptor-type titanium vacancies in the investigated SrTiO3 single crystals, which was experimentally confirmed by complementary Positron Annihilation Lifetime Spectroscopy measurements. The employed method is sensitive for electronically relevant defects in concentrations even below 1 ppm.

Keywords: electrochemical impedance spectroscopy; positron annihilation lifetime spectroscopy; SrTiO3; defects

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Permalink: https://www.hzdr.de/publications/Publ-32315
Publ.-Id: 32315


Quantum-mechanical calculations of novel heterocycles as building blocks of 2D-COFs with extended π-conjugation

Asteriadis, A.

For more than a decade, Covalent Organic Frameworks (COFs) have been investigated for various applications. Recently, focus is especially on 2D COFs, a field which is constantly under development. They exhibit very interesting properties, for example, for gas storage, drug delivery, or more recently for electronic transport.

COFs are generally built of organic molecules, such as benzene or naphthalene, which act as linkers, and inorganic heterocycles, such as borazine or boroxine, which are the so-called connectors. Since the first synthesis of COFs back in 2005 by Yaghi, many molecules were used to build these materials with various properties. These properties can be tuned by stoichiometry, size, and functionalization of the building blocks.

The main idea of this project is to investigate the geometries and electronic properties of novel building blocks, especially the connectors, which can be used to build 2D COFs. For this purpose, four novel inorganic heterocyclic molecules, namely B₃N₃H₆, N₃S₃H₃, B₃S₃H₃ and Al₃N₃H₆, as proposed by our experimental collaborator from TU Dresden (Dr. A. Schneemann) were used as connectors. These were expected to provide good π-conjugations within the heterocycles. These molecules, joint together with the organic linkers, are expected to offer extended conjugation over the periodic COFs, providing interesting electronic transport properties.

In this study, we used these four new heterocycle molecules together with nine well-known organic linkers and calculated their geometric and electronic properties, including the single building blocks, finite models, and 2D COFs. All calculations were carried out using TZP basis set and PBE exchange-correlation functional as implemented in the AMS-code, settings selected after extended benchmarking of methods. All of the investigated finite fragments and periodic COFs showed extended π-conjugation, indicating that the electronic properties of finite building blocks are retained in the extended systems upon formation of the 2D COF. The latter were also investigated for their band structures, which showed interesting properties: i) light electrons and heavy holes or vice versa, depending on the heterocycle molecule, which are interesting for transport applications; ii) the expected signatures of kagome (kgm) and honeycomb (hcb) lattices are presented in the band structures of COFs and the interesting points could be reached by doping or functionalization.

  • Master thesis
    Leipzig University, 2021
    Mentor: PD Dr. A. B. Kuc
    68 Seiten

Permalink: https://www.hzdr.de/publications/Publ-32314
Publ.-Id: 32314


Control Over Self-Assembled Janus Clusters by the Strength of Magnetic Field in H₂O₂

Alsaadawi, Y.; Eichler-Volf, A.; Heigl, M.; Zahn, P.; Albrecht, M.; Erbe, A.

Colloidal Janus microparticles can be propelled by controlled chemical reactions on their surfaces. Such microswimmers have been used as model systems for the behavior on the microscale and ascarriers for cargo to well-defined positions in hard-to-access areas. Here we demonstrate the propagation motion of clusters of magnetic Janus particles driven by the catalytic decomposition of H₂O₂ on their metallic caps. The magnetic moments of their caps lead to certain spatial arrangements of Janus particles, which can be influenced by external magnetic fields. We investigate how the arrangement of the particles and caps determines the driven motion of the particle clusters. In addition, we show the influence ofconfining walls on the cluster motion, which will be encountered in any real-life biological system.

Keywords: Janus particles; Magnetic caps; Hydrogen peroxide propulsion; Catalytic propulsion; Magnetic manipulation

Permalink: https://www.hzdr.de/publications/Publ-32313
Publ.-Id: 32313


X-ray Spectroscopic Studies of a Solid-Density Germanium Plasma Created by a Free Electron Laser

Perez-Callejo, G.; Vinko, S. M.; Ren, S.; Royle, R.; Humphries, O. S.; Preston, T. R.; Hammel, B. A.; Chung, H.-K.; Burian, T.; Vozda, V.; Lin, M.-F.; Brandt Van Driel, T.; Wark, J. S.

The generation of solid-density plasmas in a controlled manner using an X-ray free electron laser (XFEL) has opened up the possibility of diagnosing the atomic properties of hot, strongly coupled systems in novel ways. Previous work has concentrated on K-shell emission spectroscopy of low Z (<= 14) elements. Here, we extend these studies to the mid-Z(=32) element Germanium, where the XFEL creates copious L-shell holes, and the plasma conditions are interrogated by recording of the associated L-shell X-ray emission spectra. Given the desirability of generating as uniform a plasma as possible, we present here a study of the effects of the FEL photon energy on the temperatures and electron densities created, and their uniformity in the FEL beam propagation direction. We show that good uniformity can be achieved by tuning the photon energy of the XFEL such that it does not overlap significantly with L-shell to M-shell bound-bound transitions, and lies below the L-edges of the ions formed during the heating process. Reasonable agreement between experiment and simulations is found for the emitted X-ray spectra, demonstrating that for these higher Z elements, the selection of appropriate XFEL parameters is important for achieving uniformity in the plasma conditions.

Keywords: High energy density; Plasma opacity; XFEL; spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-32312
Publ.-Id: 32312


Electrical tunability of terahertz nonlinearity in graphene

Kovalev, S.; Hafez, H. A.; Tielrooij, K.-J.; Deinert, J.-C.; Ilyakov, I.; Awari, N.; Alcaraz, D.; Soundarapandian, K.; Saleta, D.; Germanskiy, S.; Chen, M.; Bawatna, M.; Green, B. W.; Koppens, F. H. L.; Mittendorff, M.; Bonn, M.; Gensch, M.; Turchinovich, D.

Graphene is conceivably the most nonlinear optoelectronic material. Its nonlinear optical coefficients in the terahertz (THz) frequency range surpass those of other materials by many orders of magnitude. This, in particular, allows one to use graphene for extremely efficient up-conversion of sub-THz electronic input signals into the THz frequency range at room temperature and under ambient conditions, thus paving the way for practical graphene-based ultrahigh-frequency electronic technology. Here, we show that the THz nonlinearity of graphene can be efficiently controlled using electrical gating, with gating voltages as low as a few volts. For example, optimal electrical gating enhances the power conversion efficiency in THz third-harmonic generation in graphene by about two orders of magnitude. We demonstrate gating control of THz nonlinearity of graphene for both ultrashort single-cycle and quasi-monochromatic multi-cycle input signals. Our experimental results are in quantitative agreement with a physical model of graphene nonlinearity, describing the time-dependent thermodynamic balance maintained within the electronic population of graphene during interaction with ultrafast electric fields. Our results can serve as a basis for straightforward and accurate design of devices and applications for efficient electronic signal processing in graphene at ultra-high frequencies.

Keywords: Graphene; THz-driven dynamics; Terahertz; Dirac material; Electrical gating; High harmonic generation; Optoelectronics; Ultrafast

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Permalink: https://www.hzdr.de/publications/Publ-32311
Publ.-Id: 32311


Printable Giant Magnetoresistive Sensors for Highly Compliant On-Skin Electronics

Ha, M.; Canon Bermudez, G. S.; Kosub, T.; Zabila, Y.; Oliveros Mata, E. S.; Illing, R.; Faßbender, J.; Makarov, D.

Magnetic field sensors, which can perceive environmental changes with respect to altered magnetic fields, enable proximity sensing ranging from touchless human-machine interaction to noninvasive medical diagnostics. In this regard, magnetic field sensors should be aimed toward perfect mounting on the curved human body and uneven organs without any mechanical constraints, at the same time, pursuing high sensitivity in low magnetic fields at 1 mT for the practical use of wearable electronics to the general public. Here, we demonstrate that high performance giant magnetoresistive (GMR) sensors can be printed on ultrathin 3-µm-thick polymeric foils enabling the mechanically imperceptible magnetoelectronics. Thanks to their excellent compliancy, the printed GMR sensors well adapt to the periodic buckling surface. They constitute the first example of printed GMR sensors, revealing 2 orders of magnitude improvements in mechanical stability and sensitivity at small magnetic fields, compared to the state-of-the-art printed magnetoelectronics [1]. Even when bent to a radius of 16 µm, the sensors screen printed on ultrathin foils remain fully intact and possess high sensitivity of 3 /T in a low magnetic field of 0.88 mT. With this performance, the compliant GMR sensors can be used as components of on-skin interactive electronics as we demonstrate with a touchless control of virtual objects including zooming in and out of interactive maps and scrolling through electronic documents.
[1] Meyer, J., Rempel, T., Schäfers, M., Wittbracht, F., Müller, C., Patel, A., Hütten, A., Smart Mater. Struct. 22 (2013) 025032-025037.

  • Lecture (Conference)
    6th International Conference on Advances in Functional Materials, 15.-17.02.2021, Jeju Island, South Korea

Permalink: https://www.hzdr.de/publications/Publ-32310
Publ.-Id: 32310


Mineral Dissolution Rates: Importance of Surface Reactivity

Schabernack, J.; Fischer, C.

Mineral dissolution plays a key role in many environmental and technical fields, e.g., weathering, building materials, as well as host rock characterization for potential nuclear waste repositories. The rate of mineral dissolution in water is controlled by two parameters: (1) transport of dissolved species over and from the interface determined by advective fluid flow and diffusion (transport control) and (2) crystal surface reactivity (surface reactivity control). Current reactive transport models (RTM) simulating species transport commonly calculate mineral dissolution by using rate laws [1]. These rate laws solely depend on species concentration in the fluid and therefore do not include intrinsic variability of surface reactivity. Experimental studies under surface-controlled conditions have shown a heterogeneous distribution of reaction rates [2]. This rate heterogeneity is caused by nanotopographical structures on the crystal surface, such as steps and etch pits that are generated at lattice defects. At these structures, the high density of reactive kink sites is leading to a local increase in dissolution rates.
In this study, we test whether experimentally observed rate heterogeneities can be reproduced by using current RTMs. We apply a standard RTM approach combined with the measured surface topography of a calcite single crystal [2]. Calcite is one of the larger mineral components in the sandy facies of the Opalinus clay formation, that is under consideration for nuclear waste storage. The calculated surface dissolution rate maps are compared to experimentally derived rate maps. The results show that the measured rate heterogeneities cannot be reproduced with the existing RTM approach. To improve the predictive capabilities of RTMs, the surface reactivity that is intrinsic to the mineral needs to be implemented into rate calculations. Investigating calcite surface reactivity in the context of dissolution can also yield information about other kinetic surface processes such as the adsorption of radionuclides. We discuss parameterization of surface reactivity via proxy parameters, such as surface roughness or surface slope. The implementation of these proxy parameters will allow for a more precise prediction of host rock-fluid interaction over large time scales in RTMs, relevant for safety assessment.
[1] P. Agrawal, A. Raoof, O. Iliev and M. Wolthers, Evolution of pore-shape and its impact on pore conductivity during CO2 injection in calcite: Single pore simulations and microfluidic experiments, Advances in Water Resources, 136, 103480 (2020).
[2] I. Bibi, R.S. Arvidson, C. Fischer and A. Luttge: Temporal Evolution of Calcite Surface Dissolution Kinetics, Minerals, 8, 256 (2018).

Keywords: Reactive Transport Model; Mineral Dissolution; Crystal Surface Reactivity

  • Poster (Online presentation)
    2. Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-32309
Publ.-Id: 32309


OpenFOAM hybrid - A Morphology Adaptive Multifield Two-fluid Model

Schlegel, F.; Meller, R.; Krull, B.; Lehnigk, R.; Tekavcic, M.

The simulation of industrial multiphase flows is challenging, because these flows are typically characterized by coexisting morphologies. Modern simulation methods are well established for dispersed (e.g., Euler-Euler) or resolved (e.g., Volume-of-Fluid) interfacial structures. We propose a morphology adaptive multifield two-fluid model, which is able to handle dispersed and resolved interfacial structures coexisting in the computational domain with the same set of equations. The interfacial drag formulation of Štrubelj and Tiselj (Int J Numer Methods Eng, 2011, Vol. 85, 575-590) is used to describe large interfacial structures in a volume-of-fluid-like manner. For the dispersed structures, the HZDR baseline model is applied. The functionality of the framework is demonstrated by investigating a gas bubble, rising in a liquid, which is laden with micro gas bubbles, a 2D stagnant stratification of water and oil, sharing a large-scale interface, which is penetrated by micro gas bubbles, and an isothermal counter-current stratified flow case. For the latter the framework symmetric and asymmetric turbulence damping is used to account for turbulent flow conditions near an interface. Recent developments focus on the transition region, where bubbles are either over- or under-resolved for Euler-Euler or Volume-of-Fluid (Fig. 1). A drag model to allow tangential slip at an interface and a filtering technique are proposed for stable and robust handling interfacial structures in the transition region. Furthermore, a concept is presented for the transition of oversized dispersed bubbles into the resolved phase.

Keywords: Multiphase Flow; Numerical Simulation; Euler-Euler; OpenFOAM; Hybrid Model

  • Lecture (Conference) (Online presentation)
    19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH 19), 06.-11.03.2022, Brüssel, Belgien
  • Contribution to proceedings
    19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-19), 06.-11.03.2022, Brüssel, Belgien
    Proceedings of the 19th International Topical Meeting on Nuclear Reactor Thermal Hydraulics
  • Nuclear Science and Engineering (2022)
    Online First (2022) DOI: 10.1080/00295639.2022.2120316

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  • Secondary publication expected from 21.11.2023

Permalink: https://www.hzdr.de/publications/Publ-32308
Publ.-Id: 32308


U(VI) and Eu(III) bioassociation behavior and uptake mechanisms of plant cells

Jessat, J.; Moll, H.; Bilke, M.-L.; John, W.; Hübner, R.; Steudtner, R.; Drobot, B.; Bok, F.; Stumpf, T.; Sachs, S.

For a safety assessment of nuclear waste repositories, it is necessary to consider accident scenarios through which radionuclides (RN) can enter the biosphere up to the food chain via groundwater and soil. It is necessary to generate detailed knowledge about the uptake pathways and the interaction of RN with plants to contribute to the molecular process understanding required for a reliable biogeochemical modeling. We investigated the uptake and immobilization (bioassociation) of U(VI) and Eu(III) as a non-radioactive analogue for trivalent actinides by two typical crop plant cell cultures as model systems: canola (Brassica napus) and carrot (Daucus carota). For both metals a time- and concentration-dependent bioassociation behavior was observed, which shows differences between the two plant cell types. U(VI) and Eu(III) were used as luminescence probes to explore their speciation in the two systems. Therefore, time-resolved laser-induced fluorescence spectroscopy (TRLFS) was performed under cryogenic conditions. For an investigation of possible uptake pathways of the metals, it must be considered that both U and Eu are non-essential heavy metals for plants. Therefore, it can be assumed that they have no specific uptake pathway into the plant cells. Possible uptake routes are the use of transport systems of essential micronutrients, whose homeostasis can be disturbed by U(VI) and Eu(III), but uptake via endocytosis and mechanosensitive ion channels is also possible. Experiments were performed to investigate whether the metals can be unspecifically taken up into the cells by blocking Ca(II) ion channels with GdCl3. The investigations are supplemented by transmission electron microscopy combined with energy-dispersive X-ray spectroscopy (TEM with EDX mapping), which contribute to an improved understanding of the processes taking place by localizing the metals in the plant cell.

Keywords: plant cells; radionuclides; uptake mechanisms

  • Lecture (Conference) (Online presentation)
    Goldschmidt 2021, 04.-09.07.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-32307
Publ.-Id: 32307


Euler-Euler modelling of bubbly flow using particle-center-averaging method

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

The standard Euler-Euler two-fluid modelling is based on the phase averaging method and the bubble forces are functions of the gas volume fraction. Therefore, it is not guaranteed that all the gas belonging to the same bubble experiences the same force and moves with the same velocity. However, closure models for interfacial forces are typically developed based on the assumption that the bubbles’ motion can be represented by their center-of-mass on which the forces act. This inconsistency can lead to a nonphysical gas concentration in the center of a pipe or near its wall if the mesh size is smaller than the bubble diameter. In addition, a mesh independent solution may not exist in such simulations. In the present contribution, a particle-center-averaged method is used to average quantities related to the disperse phase such that the bubble forces act on the bubble centers. A systematic approach for the simulation of bubbly flows using the particle-center-averaged method is developed by combining the HZDR baseline closure models, a diffusion-based method for the field coupling and the Euler-Euler framework using the particle-center-averaged method. A physically motivated model for the wall-contact force is introduced to ensure that the bubble centers cannot come arbitrarily close to the walls. To validate this approach, a comparison is made with experimental data for monodisperse and fixed polydisperse bubbly flows in two different pipes. The results show that the particle-center-averaged method can alleviate the over-prediction of the peaks in the gas volume fraction profiles in the near wall region.

Keywords: Particle-center-averaging method; bubble's number density; diffusion equation; bubble force

  • Contribution to proceedings
    19th International Meeting on Nuclear Reactor Thermal Hydraulics, 06.-11.03.2022, Square Brussels Meeting Centre, Belgium

Permalink: https://www.hzdr.de/publications/Publ-32306
Publ.-Id: 32306


Recovery of nanodiamonds produced by laser-induced shock compression of polystyrene

Schuster, A.; Hartley, N.; Lütgert, B. J.; Voigt, K.; Vorberger, J.; Zhang, M.; Benad, A.; Eychmüller, A.; Klemmed, B.; Gericke, D. O.; Rack, A.; Bagnoud, V.; Blazevic, A.; Brabetz, C.; Eisenbarth, U.; Götte, S.; Reemts, D.; Schumacher, D.; Toimil Molares, M. E.; Tomut, M.; Kraus, D.

Hydrocarbons are highly abundant in icy giant planets like Uranus and Neptune and their interior conditions can be created in the laboratory on a nanosecond timescale by applying the technique of laser-induced shock compression using high energy lasers. Based on this method, nanodiamond formation in a simplified hydrocarbon representative, polystyrene (C₈H₈), was observed via in situ X-ray diffraction (XRD). The goal is to physically recover the nanodiamonds that are ejected at hypervelocities upon shock-break out to un-derstand the underlying hydrocarbon separation mechanism by analysing their shape, size, surface mod-ifications and defects. This work is important for planetary interior modelling and may present an additional route for nanodiamond production.

  • Open Access Logo Contribution to external collection
    in: News and Reports from High Energy Density generated by Heavy Ion and Laser Beams 2019, Darmstadt: GSI, 2020
    DOI: 10.15120/GSI-2020-01321

Permalink: https://www.hzdr.de/publications/Publ-32305
Publ.-Id: 32305


How Hyperspectral Image Unmixing and Denoising Can Boost Each Other

Rasti, B.; Koirala, B.; Scheunders, P.; Ghamisi, P.

Hyperspectral linear unmixing and denoising are highly related hyperspectral image (HSI) analysis tasks. In particular, with the assumption of Gaussian noise, the linear model assumed for the HSI in the case of low-rank denoising is often the same as the one used in HSI unmixing. However, the optimization criterion and the assumptions on the constraints are different. Additionally, noise reduction as a preprocessing step in hyperspectral data analysis is often ignored. The main goal of this paper is to study experimentally the influence of noise on the process of hyperspectral unmixing by: (1) investigating the effect of noise reduction as a preprocessing step on the performance of hyperspectral unmixing; (2) studying the relation between noise and different endmember selection strategies; (3) investigating the performance of HSI unmixing as an HSI denoiser; (4) comparing the denoising performance of spectral unmixing, state-of-the-art HSI denoising techniques, and the combination of both. All experiments are performed on simulated and real datasets.

Keywords: hyperspectral image; unmixing; denoising; linear mixing model; low-rank model; noise reduction; abu

Permalink: https://www.hzdr.de/publications/Publ-32304
Publ.-Id: 32304


Feature Extraction for Hyperspectral Imagery: The Evolution From Shallow to Deep: Overview and Toolbox

Rasti, B.; Hong, D.; Hang, R.; Ghamisi, P.; Kang, X.; Chanussot, J.; Benediktsson, J. A.

Hyperspectral images (HSIs) provide detailed spectral information through hundreds of (narrow) spectral channels (also known as dimensionality or bands), which can be used to accurately classify diverse materials of interest. The increased dimensionality of such data makes it possible to significantly improve data information content but provides a challenge to conventional techniques (the so-called curse of dimensionality) for accurate analysis of HSIs.

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Permalink: https://www.hzdr.de/publications/Publ-32303
Publ.-Id: 32303


Direct observation of shock‐induced disordering of enstatite below the melting temperature

Hernandez, J.-A.; Morard, G.; Guarguaglini, M.; Alonso-Mori, R.; Benuzzi-Mounaix, A.; Bolis, R.; Fiquet, G.; Galtier, E.; Gleason, A. E.; Glenzer, S.; Guyot, F.; Ko, B.; Lee, H. J.; Mao, W. L.; Nagler, B.; Ozaki, N.; Schuster, A.; Shim, S. H.; Vinci, T.; Ravasio, A.

We report in situ structural measurements of shock‐compressed single crystal orthoenstatite up to 337 ± 55 GPa on the Hugoniot, obtained by coupling ultrafast X‐ray diffraction to laser‐driven shock compression. Shock compression induces a disordering of the crystalline structure evidenced by the appearance of a diffuse X‐ray diffraction signal at nanosecond timescales at 80 ± 13 GPa on the Hugoniot, well below the equilibrium melting pressure (>170 GPa). The formation of bridgmanite and post‐perovskite have been indirectly reported in microsecond‐scale plate‐impact experiments. Therefore, we interpret the high‐pressure disordered state we observed at nanosecond scale as an intermediate structure from which bridgmanite and post‐perovskite crystallize at longer timescales. This evidence of a disordered structure of MgSiO₃ on the Hugoniot indicates that the degree of polymerization of silicates is a key parameter to constrain the actual thermodynamics of shocks in natural environments.

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Permalink: https://www.hzdr.de/publications/Publ-32302
Publ.-Id: 32302


Comparing the optical properties and thermal stability of green (TbPO4), yellow (DyPO4), and red (PrPO4) emitting single crystal samples

Sharma, S.; Beyer, J.; Gloaguen, R.; Heitmann, J.

Blue, green and red-emitting phosphors for near-UV/blue based phosphor blend converted white-light emitting devices have been investigated extensively over the past years. Herein, we present our results on the optical spectroscopy of single crystal samples of TbPO4, DyPO4 and PrPO4 exhibiting prominent emission at green (545 nm), yellow (574 nm) and red (616 nm) region of the electromagnetic spectrum, respectively. We study the temperature dependence of their emission spectra for excitations at 365 and 455 nm, to mimic experimental conditions for phosphor converted light emitting diodes, to show that their thermal quenching temperature is 730 K for TbPO4 (excitation 365 nm), 490 and 520 K for DyPO4 (excitation at 365 and 455 nm), and 540 K for PrPO4 (excitation 455 nm). The TbPO4 emission does not show any considerable blue/red shift at elevated temperatures, while DyPO4 emission is observed close to the center of CIE coordinate diagram. The PrPO4 sample possesses high color purity which shows slight yellow-shift at elevated temperatures. The ground state of Pr3+ and Tb3+ are found to be within the band gap suggesting that both are able to trap holes from the valence band as evinced from the thermoluminescence glow curve data which shows peak maxima at 422 and 437 K due to hole release from the Pr4+ and Tb4+, respectively. The result suggests that the samples have large potential for solid state lighting devices upon choice of an appropriate excitation wavelength.

Permalink: https://www.hzdr.de/publications/Publ-32301
Publ.-Id: 32301


Library of UV-Visible Absorption Spectra of Rare Earth Orthophosphates, LnPO4 (Ln = La-Lu, except Pm)

Sharma, S. K.; Behm, T.; Köhler, T.; Beyer, J.; Gloaguen, R.; Heitmann, J.

In recent times, rare earth orthophosphates ( Ln PO 4 ) have shown great potential as efficient optical materials. They possess either monazite or xenotime –type structures. These light or heavy rare earth bearing orthophosphates also exhibit an extraordinary stability over geological time scale in nature, ∼10 9 years. In the present contribution, we measure, collect, and present a library of absorption spectra of all the Ln PO 4 hosts ( Ln = La–Lu, except Pm) using their single crystal samples, to conclude that the observed spectral features for wavelengths longer than 200 nm were attributable to either Ln- or defect related centers, which corroborate the fact that they have a bandgap higher than 8.0 eV. The absorption band around wavelength, 275 nm, corresponds to defect absorption related to PO 3 centers and/or oxygen vacancies. The hosts can potentially be used to study and interpret unperturbed rare earth emissions due to absence of host related absorption above 300 nm. The information presented herein is expected to serve as a library of absorption spectra for geologists, physicists, material scientists, and chemists working in the field of rare earths.

Keywords: orthophosphate; lanthanide; monazite/xenotime-structure; absorption spectra

Permalink: https://www.hzdr.de/publications/Publ-32300
Publ.-Id: 32300


Development of Sustainable Test Sites for Mineral Exploration and Knowledge Spillover for Industry

Kesselring, M.; Wagner, F.; Kirsch, M.; Ajjabou, L.; Gloaguen, R.

In mineral exploration, pressure is growing to develop innovative technologies and methods with a lower impact on the social and physical environment. To assess the performance and impact of these technologies and methods, test sites are required. Embedded in the literature on sustainable development, this paper explores how social and environmental measures can be implemented in the design of test sites and what industry stake can learn from sustainable test sites. Through qualitative research, two value networks were developed, one for a sustainable test site approach and another for the existing business practice in mineral exploration. Respondents include public sector officials as well as experts in the social, environmental, business, geoscience, and industry fields. The analysis identifies key drivers for the development of socially and environmentally accepted test sites, thus drawing up actionable points for the mineral exploration industry to increase sustainability. The findings of this paper suggest that the integration of experts and partners from social, as well as environmental, sciences drives sustainability at test sites. For industry application, this results in the need to adapt the activities performed, align resource use with sustainability indicators, and also reconfigure the network of partners towards more socially and environmentally oriented business practices.

Keywords: mineral exploration; sustainable development; test sites

Permalink: https://www.hzdr.de/publications/Publ-32299
Publ.-Id: 32299


Large-Scale Neural Solvers for Partial Differential Equations

Stiller, P.; Bethke, F.; Böhme, M.; Pausch, R.; Debus, A.; Torge, S.; Vorberger, J.; Bussmann, M.; Hoffmann, N.

Solving partial differential equations (PDE) is an indispensable part of many branches of science as many processes can be modelled in terms of PDEs. However, recent numerical solvers require manual discretization of the underlying equation as well as sophisticated, tailored code for distributed computing. Scanning the parameters of the underlying model significantly increases the runtime as the simulations have to be cold-started for each parameter configuration. Machine Learning based surrogate models denote promising ways for learning complex relationship among input, parameter and solution. However, recent generative neural networks require lots of training data, i.e. full simulation runs making them costly. In contrast, we examine the applicability of continuous, mesh-free neural solvers for partial differential equations, physics-informed neural networks (PINNs) solely requiring initial/boundary values and validation points for training but no simulation data. The induced curse of dimensionality is approached by learning a domain decomposition that steers the number of neurons per unit volume and significantly improves runtime. Distributed training on large-scale cluster systems also promises great utilization of large quantities of GPUs which we assess by a comprehensive evaluation study. Finally, we discuss the accuracy of GatedPINN with respect to analytical solutions- as well as state-of-the-art numerical solvers, such as spectral solvers.

Keywords: PDE solving; Physics-informed Neural Networks; Machine Learning; HPC

  • Contribution to proceedings
    SMC 2020: Driving Scientific and Engineering Discoveries Through the Convergence of HPC, Big Data and AI pp, 26.-28.08.2020, Virtual Conference, Virtual Conference
    Driving Scientific and Engineering Discoveries Through the Convergence of HPC, Big Data and AI: Springer Nature Switzerland AG 2020, 978-3-030-63393-6
    DOI: 10.1007/978-3-030-63393-6

Permalink: https://www.hzdr.de/publications/Publ-32298
Publ.-Id: 32298


Structural Similarity Based Anatomical and Functional Brain Imaging Fusion

Kumar, N.; Hoffmann, N.; Oelschlägel, M.; Koch, E.; Kirsch, M.; Gumhold, S.

Multimodal medical image fusion helps in combining contrasting features from two or more input imaging modalities to represent fused information in a single image. One of the pivotal clinical applications of medical image fusion is the merging of anatomical and functional modalities for fast diagnosis of malign tissues. In this paper, we present a novel end-to-end unsupervised learning based Convolutional neural network (CNN) for fusing the high and low frequency components of MRI-PET grayscale image pairs publicly available at ADNI by exploiting Structural Similarity Index (SSIM) as the loss function during training. We then apply color coding for the visualization of the fused image by quantifying the contribution of each input image in terms of the partial derivatives of the fused image. We find that our fusion and visualization approach results in better visual perception of the fused image, while also comparing favorably to previous methods when applying various quantitative assessment metrics.

Keywords: Medical image fusion; MRI-PET; Convolutional neural networks (CNN); Structural similarity index (SSIM)

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Permalink: https://www.hzdr.de/publications/Publ-32297
Publ.-Id: 32297


FuseVis: Interpreting Neural Networks for Image Fusion Using Per-Pixel Saliency Visualization

Kumar, Nishant; Gumhold, Stefan

Image fusion helps in merging two or more images to construct a more informative single fused image. Recently, unsupervised learning-based convolutional neural networks (CNN) have been used for different types of image-fusion tasks such as medical image fusion, infrared-visible image fusion for autonomous driving as well as multi-focus and multi-exposure image fusion for satellite imagery. However, it is challenging to analyze the reliability of these CNNs for the image-fusion tasks since no groundtruth is available. This led to the use of a wide variety of model architectures and optimization functions yielding quite different fusion results. Additionally, due to the highly opaque nature of such neural networks, it is difficult to explain the internal mechanics behind its fusion results. To overcome these challenges, we present a novel real-time visualization tool, named FuseVis, with which the end-user can compute per-pixel saliency maps that examine the influence of the input image pixels on each pixel of the fused image. We trained several image fusion-based CNNs on medical image pairs and then using our FuseVis tool we performed case studies on a specific clinical application by interpreting the saliency maps from each of the fusion methods. We specifically visualized the relative influence of each input image on the predictions of the fused image and showed that some of the evaluated image-fusion methods are better suited for the specific clinical application. To the best of our knowledge, currently, there is no approach for visual analysis of neural networks for image fusion. Therefore, this work opens a new research direction to improve the interpretability of deep fusion networks. The FuseVis tool can also be adapted in other deep neural network-based image processing applications to make them interpretable

Keywords: image fusion; convolutional neural networks (CNN); saliency visualization; jacobians; graphical use interface (GUI)

Permalink: https://www.hzdr.de/publications/Publ-32296
Publ.-Id: 32296


Deep white matter analysis (DeepWMA): Fast and consistent tractography segmentation

Zhang, F.; Karayumak, S. C.; Hoffmann, N.; Rathi, Y.; Golby, A. J.; O’Donnell, L. J.

White matter tract segmentation, i.e. identifying tractography fibers (streamline trajectories) belonging to anatomically meaningful fiber tracts, is an essential step to enable tract quantification and visualization. In this study, we present a deep learning tractography segmentation method (DeepWMA) that allows fast and consistent identification of 54 major deep white matter fiber tracts from the whole brain. We create a large-scale training tractography dataset of 1 million labeled fiber samples, and we propose a novel 2D multi-channel feature descriptor (FiberMap) that encodes spatial coordinates of points along each fiber. We learn a convolutional neural network (CNN) fiber classification model based on FiberMap and obtain a high fiber classification accuracy of 90.99% on the training tractography data with ground truth fiber labels. Then, the method is evaluated on a test dataset of 597 diffusion MRI scans from six independently acquired populations across genders, the lifespan (1 day - 82 years), and different health conditions (healthy control, neuropsychiatric disorders, and brain tumor patients). We perform comparisons with two state-of-the-art tract segmentation methods. Experimental results show that our method obtains a highly consistent tract segmentation result, where on average over 99% of the fiber tracts are successfully identified across all subjects under study, most importantly, including neonates and patients with space-occupying brain tumors. We also demonstrate good generalization of the method to tractography data from multiple different fiber tracking methods. The proposed method leverages deep learning techniques and provides a fast and efficient tool for brain white matter segmentation in large diffusion MRI tractography datasets.

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Permalink: https://www.hzdr.de/publications/Publ-32295
Publ.-Id: 32295


Visualisation of Medical Image Fusion and Translation for Accurate Diagnosis of High Grade Gliomas

Kumar, N.; Hoffmann, N.; Kirsch, M.; Gumhold, S.

The medical image fusion combines two or more modalities into a single view while medical image translation synthesizes new images and assists in data augmentation. Together, these methods help in faster diagnosis of high grade malignant gliomas. However, they might be untrustworthy due to which neurosurgeons demand a robust visualisation tool to verify the reliability of the fusion and translation results before they make pre-operative surgical decisions. In this paper, we propose a novel approach to compute a confidence heat map between the source-target image pair by estimating the information transfer from the source to the target image using the joint probability distribution of the two images. We evaluate several fusion and translation methods using our visualisation procedure and showcase its robustness in enabling neurosurgeons to make finer clinical decisions.

Keywords: Visualisation; Medical Image Fusion; Medical Image Translation; Mutual information

Permalink: https://www.hzdr.de/publications/Publ-32294
Publ.-Id: 32294


Review and new concepts for neutron-capture measurements of astrophysical interest

Domingo-Pardo, C.; Babiano-Suarez, V.; Balibrea-Correa, J.; Caballero, L.; Ladarescu, I.; Lerendegui-Marco, J.; Tain, J. L.; Calviño, F.; Casanovas, A.; Segarra, A.; Tarifeño-Saldivia, A. E.; Guerrero, C.; Millán-Callado, M. A.; Quesada, J. M.; Rodríguez-González, M. T.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Calviani, M.; Cano-Ott, D.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Gunsing, F.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krticka, M.; Kurtulgil, D.; Lederer-Woods, C.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Maugeri, E.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Ramos Doval, D.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.; The, N. T. C.

The idea of slow-neutron capture nucleosynthesis formulated in 1957 triggered a tremendous experimental effort in different laboratories worldwide to measure the relevant nuclear physics input quantities, namely (n, γ) cross sections over the stellar temperature range (from few eV up to several hundred keV) for most of the isotopes involved from Fe up to Bi. A brief historical review focused on total energy detectors will be presented to illustrate how advances in instrumentation have led to the assessment of new aspects of s-process nucleosynthesis and to the progressive refinement of stellar models. A summary will be presented on current efforts to develop new detection concepts, such as the Total-Energy Detector with γ-ray imaging capability (i-TED). The latter is based on the simultaneous combination of Compton imaging with neutron time-of-flight (TOF) techniques, in order to achieve a superior level of sensitivity and selectivity in the measurement of stellar neutron capture rates.

Permalink: https://www.hzdr.de/publications/Publ-32293
Publ.-Id: 32293


Neutron capture measurement at the n TOF facility of the 204Tl and 205Tl s-process branching points

Casanovas, A.; Tarifeño-Saldivia, A. E.; Domingo-Pardo, C.; Calviño, F.; Maugeri, E.; Guerrero, C.; Lerendegui-Marco, J.; Dressler, R.; Heinitz, S.; Schumann, D.; Tain, J. L.; Quesada, J. M.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Caballero, L.; Calviani, M.; Cano-Ott, D.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Gunsing, F.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krticka, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; J. Lonsdale, S.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Millán-Callado, M. A.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Doval, D. R.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.; Koester, U.

Neutron capture cross sections are one of the fundamental nuclear data in the study of the s (slow) process of nucleosynthesis. More interestingly, the competition between the capture and the decay rates in some unstable nuclei determines the local isotopic abundance pattern. Since decay rates are often sensible to temperature and electron density, the study of the nuclear properties of these nuclei can provide valuable constraints to the physical magnitudes of the nucleosynthesis stellar environment. Here we report on the capture cross section measurement of two thallium isotopes, 204Tl and 205Tl performed by the time-of-flight technique at the n TOF facility at CERN. At some particular stellar s-process environments, the decay of both nuclei is strongly enhanced, and determines decisively the abundance of two s-only isotopes of lead, 204Pb and 205Pb. The latter, as a long-lived radioactive nucleus, has potential use as a chronometer of the last s-process events that contributed to final solar isotopic abundances.

Permalink: https://www.hzdr.de/publications/Publ-32292
Publ.-Id: 32292


Neutron Capture Cross Section for 10Be

Volknandt, M.; Eberhardt, K.; Endres, A.; Erbacher, P.; Fix, M.; Göbel, K.; Heftrich, T.; Heinitz, S.; Hrivula, E.; Junghans, A.; Käppeler, F.; Kivel, N.; Langer, C.; Mengoni, A.; Reifarth, R.; Schmidt, S.; Schumann, D.; Thomas, B.; Veltum, D.; Weigand, M.; Wiehl, N.; Wolf, C.

The determination of the involved reaction cross sections is essential for the understanding of how the big bang nucleosynthesis and nuclear reactions in stars contribute to the observed abundances. One of those, which has not been measured so far, is the 10Be(n,γ) cross section.

A 10BeO sample, provided by PSI Villigen, was irradiated in a cyclic activation at the TRIGA reactor in Mainz. The characteristic γ-rays following the decay of 11Be were measured using LaBr3 scintillation detectors. The thermal neutron cross section and the resonance integral were experimentally determined for the first time.

Permalink: https://www.hzdr.de/publications/Publ-32291
Publ.-Id: 32291


80Se(n,γ) cross-section measurement at CERN n_TOF

Babiano-Suarez, V.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea-Correa, J.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Caballero, L.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Casanovas, A.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krticka, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; Lerendegui-Marco, J.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Maugeri, E.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Millán-Callado, M. A.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Quesada, J. M.; Ramos Doval, D.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A. E.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.

Radiative neutron capture cross section measurements are of fundamental importance for the study of the slow neutron capture (s-) process of nucleosynthesis. This mechanism is responsible for the formation of most elements heavier than iron in the Universe. Particularly relevant are branching nuclei along the s-process path, which are sensitive to the physical conditions of the stellar environment. One such example is the branching at 79Se (3.27 × 105 y), which shows a thermally dependent β-decay rate. However, an astrophysically consistent interpretation requires also the knowledge of the closest neighbour isotopes involved. In particular, the 80Se(n,γ) cross section directly affects the stellar yield of the "cold" branch leading to the formation of the s-only 82Kr. Experimentally, there exists only one previous measurement on 80Se using the time of flight (TOF) technique. However, the latter suffers from some limitations that are described in this presentation. These drawbacks have been significantly improved in a recent measurement at CERN n TOF. This contribution presents a summary of the latter measurement and the status of the data analysis.

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Permalink: https://www.hzdr.de/publications/Publ-32290
Publ.-Id: 32290


Radiotherapy enhances uptake and efficacy of 90Y-cetuximab: A preclinical trial

Dietrich, A.; Andreeff, M.; Koi, L.; Bergmann, R.; Schubert, M.; Schreiner, L.; Löck, S.; Sihver, W.; Freudenberg, R.; Hering, S.; Pietzsch, H.-J.; Steinbach, J.; Kotzerke, J.; Baumann, M.; Krause, M.

Background and purpose

Systemic molecular radiotherapy utilizes internal irradiation by radionuclide-labeled tumor-targeting agents with the potential to destroy (micro-)metastases. However, doses that are applicable in solid tumors do not reach the levels nessecary for tumor control. Thus, the combination of molecular and external radiotherapy is a promising treatment strategy, as enhanced tumor doses can be delivered with and without minor overlapping toxicities. Here, we combined a 90Y-labeled anti-EGFR antibody (Cetuximab) with clinically relevant fractionated radiotherapy in a preclinical trial using head and neck squamous cell carcinoma xenograft tumors.
Materials and methods

To model 90Y-Cetuximab uptake for treatment schedule optimization, FaDu-bearing mice were injected with near-infrared-labeled-Cetuximab at different time points during radiotherapy with differing doses. Cetuximab uptake was longitudinally followed by in vivo-optical imaging. Tumor control probability experiments with fractionated radiotherapy (30 fx, 6 weeks, 8 dose groups/ arm) in combination with 90Y-Cetuximab were performed to test the curative potential.

Results

Imaging of near-infrared-labeled-Cetuximab uptake revealed that low to moderate external beam doses can enhance antibody uptake. Using the optimized schedule, combination of molecular and external radiotherapy using 90Y-Cetuximab at a dose that did not result in permanent tumor inactivation in previous experiments, led to substantially increased tumor control compared to radiotherapy alone.
Conclusion

Our results indicate that combination of radiolabeled therapeutics with clinically relevant fractionated radiotherapy has a remarkable potential to improve curative treatment outcome. Application of some radiation dose prior to injection may improve drug uptake and enable patient stratification and treatment personalization via a corresponding PET-tracer during therapy.

Keywords: Molecular radiotherapy Combination therapy Cetuximab Preclinical imaging Radiation therapy Radioimmu

Permalink: https://www.hzdr.de/publications/Publ-32289
Publ.-Id: 32289


On-shot dosimetry setup for radiobiology studies on volumetric in-vivo samples with laser accelerated proton beams

Reimold, M.

Laser plasma-based accelerators promise to provide proton sources for radiobiological studies with extended possibilities compared to conventional accelerators due to short acceleration lengths, high pulse doses, high dose rates and the usage of compact magnets for beam guiding operated in pulsed mode. For the generation of radiobiological relevant proton energies, Petawatt (PW) class laser powers are required, which can be provided at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) by the DRACO laser system and the upcoming PENELOPE laser system. Both laser systems will be used to perform radiobiological in-vivo studies which require precise absolute dosimetry for three-dimensional depth-dose profiles on a millimeter scale. This presentation gives an overview of the dosimetry setup developed for radio-biological studies on volumetric samples consisting of a combination of several different detector types for on-shot dose measurement (ionization chambers, time-of-flight spectrometer), absolute calibration (radiochromic films) and spatial dose profile optimization (scintillators). Additionally, a recently developed detector system design based on scintillator emission tomography for the full reconstruction of an arbitrary proton depth profile generated by a single proton bunch will be presented. Details on the reconstruction of the 3D dose distribution inside the scintillator volume and the reverse calculation of the angularly resolved proton energy spectrum are discussed.

Related publications

  • Lecture (Conference) (Online presentation)
    LaPlaSS, 18.09.2020, Salamanca/ Dresden, Spanien/ Deutschland
  • Lecture (Conference) (Online presentation)
    BLIN4, 29.06.2020, München/ Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32288
Publ.-Id: 32288


Beam monitoring and dosimetry for in vivo studies with laser-driven protons at Draco PW

Reimold, M.

Petawatt laser-plasma based proton sources, capable of providing multi-10 MeV proton pulses at ultra-high dose rates of 10^9 Gy/s, are unique sources for radiobiological studies of ~mm size 3D in vivo samples in the recently strongly investigated FLASH regime.
At Draco PW (HZDR), a compact and tunable pulsed power beamline is utilized for efficient beam transport and spectral filtering for dose deposition in a sample. The setup was successfully used for in vivo radiobiological studies with up to 20 Gy single shot doses as well as for accumulative multi-shot low dose (~500 mGy) schemes for %-level accuracy of dose delivery.
Regarding beam monitoring and dosimetry, the inherent fluctuations of the laser-driven source, the ultra-high dose rate and the experimental environment (pulsed power, EMP) pose challenges for established dosimetry methods.
In this presentation, we present a non-invasive scintillator-based time-of-flight spectrometer as a unique tool for single-shot online beam optimization and monitoring of laser-driven proton pulses in application experiments. Calibration of the device against established dosimeters (here radiochromic film) in combination with Monto Carlo simulations additionally allows dosimetric use, overcoming saturation issues with dose rate or linear energy transfer present in other devices.
To illustrate the suitability of the time-of-flight spectrometer as a beam monitor and absolute dosimeter for laser-based protons, the time-of-flight data of two radiobiological in vivo irradiation campaigns performed at the implemented beamline at the DRACO PW facility are presented.

Keywords: time-of-flight spectrometer

Related publications

  • Lecture (Conference) (Online presentation)
    WHELMI-Meeting, 17.-18.12.2020, Dresden-Rossendorf/ Rechovot, Deutschland/ Israel
  • Lecture (Conference) (Online presentation)
    Gruppenseminar, 08.02.2021, Dresden, Deutschland
  • Lecture (Conference) (Online presentation)
    M&T Student Retreat, 01.02.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32287
Publ.-Id: 32287


Nanoparticle-Stabilized Perforated Lamellar Morphology in Block Copolymer/Quantum Dot Hybrids

Singh, S.; Horechyy, A.; Yadav, S.; Formanek, P.; Hübner, R.; Srivastava, R. K.; Sapra, S.; Fery, A.; Nandan, B.

We report on the surprising observation of a unique perforated lamellar (PL) morphology in a mixture of an asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer and CdSe−CdS quantum dots (QDs). The PL morphology formed by the PS-b-P4VP/CdSe−CdS composites consisted of alternating layers of PS and P4VP, where the layer formed by the minority PS block contained cylindrical perforations of the majority P4VP block. Most interestingly, the CdSe−CdS QDs were localized exclusively in the P4VP perforations. The swelling of the bulk samples in a P4VP selective solvent also allowed the isolation of the perforated PS nanosheets, with QDs localized in the perforations, which further provided strong evidence for the formation of the unique PL morphology. The observed PL morphology was, plausibly, energetically stabilized because of the localization of QDs within the P4VP perforations, which allowed for the conformational entropy minimization of the majority P4VP block. The present work reveals possibilities for the discovery of novel hierarchical structures in block copolymer/nanoparticle composite systems and also provides new opportunities for the application of such materials in nanotechnology.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-32286
Publ.-Id: 32286


Assessment of column tray flow patterns and separation efficiencies on large-scale distillation trays

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

Thorough characterization of mixing behavior and separation efficiencies of large-scale distillation trays is important especially in their design phase. A precise account of the tray operation would allow modifying their mixing and mass-transfer characteristics (via design modifications) for better separation efficiencies (see design strategy in Fig. 1, left).
Fig. 1. Design strategy for distillation trays (left), and relevant data on the distributions of liquid holdup, residence time, RTD variance, and species concentration (right).
The existing literature lacks a thorough hydrodynamic description of large-scale distillation trays. Thus, the CFD studies have relied either on trivial measurements (such as those of pressure drop, liquid weeping and entrainment, visual froth height, etc.) or the available low-resolution residence time data for model validation rather than on refined data on flow path and local mixing.
Meanwhile, an extensive description of the tray hydrodynamics can be made available using the recently proposed flow profiler.1 Based on recent developments in that regard, the distributions of liquid holdup, residence time and mixing are obtained over the entire deck (see Fig. 1, right) for several gas and liquid loadings at high resolution.
The acquired data permits to predict the tray efficiency by applying models that relate liquid flow patterns with the tray performance, such as the recently proposed ‘Refined RTD (RRTD) model’ that considers the mixing behavior at intermediary tray locations.2
Eventually, experimental data on air stripping of isobutyl acetate from the aqueous solution at tray loadings same as those during the hydrodynamic experiments can be applied to validate the proposed efficiency model. An example of species concentration distribution (i.e., examined using UV spectroscopy) over the tray deck is also shown in Fig. 1 (right).

[1] Vishwakarma, V., Schleicher, E., Schubert, M., Tschofen, M. and Löschau, M., 2020. Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten. Deutsches Patent und Markenamt, DE 10 2018 124 501.
[2] Vishwakarma, V., Schubert, M. and Hampel, U., 2019. Development of a refined RTD-based efficiency prediction model for cross-flow trays. Ind. Eng. Chem. Res., 58(8), pp.3258-3268.

  • Lecture (Conference) (Online presentation)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Wärme- und Stoffübertragung, 24.-26.02.2021, Online event, Germany

Permalink: https://www.hzdr.de/publications/Publ-32285
Publ.-Id: 32285


Experimental analysis of the hydrodynamic performance of an industrial-scale cross-flow sieve tray

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

This work reports the hydrodynamic description of a large-scale sieve tray equipped in an air/water column mockup. The test tray accommodates a multi-probe flow profiler for simultaneous conductivity measurements. 3D liquid holdup distribution, liquid residence time distribution and effective froth height distribution are obtained at high spatiotemporal resolution for several gas and liquid loadings. The liquid flow and mixing patterns are visualized via tracer-based experiments. The methodologies used for acquiring these distributions are discussed in this work. Thorough examination of the processed experimental data reveals the hydrodynamic characteristics of an operational sieve tray for the studied loadings.

Keywords: column tray; hydrodynamics; effective froth height; 3D liquid holdup; tracer-response analysis

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Permalink: https://www.hzdr.de/publications/Publ-32284
Publ.-Id: 32284


Transmission ion microscopy and time-of-flight spectroscopy

Mousley, M.; Möller, W.; Philipp, P.; Bouton, O.; Klingner, N.; Serralta Hurtado De Menezes, E.; Hlawacek, G.; Wirtz, T.

A Transmission Ion Microscope (TIM), the Galileo prototype, has been built at the Luxembourg Institute of Science and Technology ( LIST) [1]. This is part of a new interest in the imaging properties of transmitted helium ions [2] [3] [4]. This allows the combination of both helium ions and neutrals to be detected after passing through a sample , or, if post sample deflection is used, then only the signal from the neutrals ( Figure 1 A). The helium ions have an energy between 10 keV and 20 keV and are produced in a Duoplasmatron ion source.
The prototype instrument is very flexible and uses a microchannel plate (MCP) which can be configured in multiple ways to enable analysis modalities, producing datasets of varying dimensionality. 2D images can be obtained either with a phosphor screen and a defocussed beam in direct TIM mode (analogous to transmission electron microscopy) or with an anode plate to collect the total detector signal in scanning mode providing scanning-TIM (STIM) images. By using fast blanking electronics (similar to [5] ), pulses of ions can be used to add time-of-flight (TOF) information (Figure 3), allowing a TOF-STIM mode to collect 3D datasets (x, y, t). Alternatively, a delay line detector (DLD) can be used to provide detector plane images with corresponding TOF values at each detector pixel, to collect TOF-TIM (3D datasets (, x’, y’, t). Finally, detector imaged DLD TOF-STIM can be used, in this mode, for each beam position on the sample, the arrival time and position on the detector is recorded for each count (5D datasets, x, y, x’, y’, t). The prototype TIM is also equipped with a secondary electron (SE) detector providing additional SE intensity for each pixel position in STIM modes (Figure 1 B) .
Example TOF datasets from materials science related samples (e.g. Au on Si) will be presented. In addition to microscopy, the effects of 20 keV helium ion irradiation on Au-Silica core-shell nanoparticles have been evaluated. Using bright field Transmission Electron Microscopy (TEM) imaging of irradiated particles, the effects of irradiation were tracked for increasing fluences [6]. It was seen that satellite particles are formed around the main Au core (Figure 2 , A and B) and neighbouring silica shells fuse together (Figure 2, C and Figure 2D). These effects will determine the suitable doses when imaging nanoparticles with 20 keV helium ions.

[1] M. Mousley et al., “Stationary beam full-field transmission helium ion microscopy using sub-50 keV He+: Projected images and intensity patterns,” Beilstein J. Nanotechnol., vol. 10, pp. 1648–1657, Aug. 2019, doi: 10.3762/bjnano.10.160. [Online]. Available: https://www.beilstein-journals.org/bjnano/articles/10/160
[2] K. L. Kavanagh C. Herrmann and J. A. Notte, “Camera for transmission He + ion microscopy,” J. Vac. Sci. Technol. B, Nanotechnol. Microelectron. Mater. Process. Meas. Phenom., vol. 35, no. 6, p. 06G902, 2017, doi: 10.1116/1.4991898. [Online]. Available: http://avs.scitation.org/doi/10.1116/1.4991898
[3] T. Wirtz O. De Castro J.-N. Audinot and P. Philipp, “Imaging and Analytics on the Helium Ion Microscope,” Annu. Rev. Anal. Chem., vol. 12, no. 1, 2019, doi: 10.1146/annurev-anchem-061318-115457.
[4] E. Serralta et al., “Scanning transmission imaging in the helium ion microscope using a microchannel plate with a delay line detector,” Beilstein J. Nanotechnol., vol. 11, pp. 1854–1864, 2020, doi: 10.3762/BJNANO.11.167.
[5] N. Klingner R. Heller G. Hlawacek S. Facsko and J. von Borany, “Time-of-flight secondary ion mass spectrometry in the helium ion microscope,” Ultramicroscopy, vol. 198, no. March 2019, pp. 10–17, 2019, doi: 10.1016/j.ultramic.2018.12.014. [Online]. Available: https://doi.org/10.1016/j.ultramic.2018.12.014
[6] M. Mousley et al., “Structural and chemical evolution of Au-silica core–shell nanoparticles during 20 keV helium ion irradiation: a comparison between experiment and simulation,” Sci. Rep., vol. 10, no. 1, pp. 1–13, 2020, doi: 10.1038/s41598-020-68955-7. [Online]. Available: https://doi.org/10.1038/s41598-020-68955-7

Related publications

  • Poster
    Microscopy & Microanalysis 2021, 01.-05.08.2021, Pittsburgh, United States of America

Permalink: https://www.hzdr.de/publications/Publ-32283
Publ.-Id: 32283


Nonlinear response in warm dense matter

Vorberger, J.

Talk at Hirschegg workshop "41th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams"

Keywords: warm dense matter; nonlinear response; quantum Monte Carlo; Green's function

  • Lecture (Conference) (Online presentation)
    41th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams, 01.-05.02.2021, Hirschegg, Austria

Permalink: https://www.hzdr.de/publications/Publ-32282
Publ.-Id: 32282


Nonequilibrium in general and in warm dense matter

Vorberger, J.

Talk given at CASUS

Keywords: non-equilibrium; warm dense matter; Boltzmann; kadanoff-baym; two temperature model

  • Lecture (others) (Online presentation)
    MEC Seminar at CASUS, 26.01.2021, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-32281
Publ.-Id: 32281


The Impact of Barium Isotopes in Radiopharmacy and Nuclear Medicine – from Past to Presence

Reissig, F.; Kopka, K.; Mamat, C.

With the exception of beryllium, every alkaline earth metal is characterized by a calcimimetic behavior. Thus, in vivo biodistribution mostly occurs in form of a massive accumulation in bone tissues, consisting of hydroxyapatite to a major extent. Apart from the lightest elements beryllium and magnesium, animal studies and human studies regarding the overall in vivo behavior were carried out by using radioisotopes of the elements calcium, strontium, barium, and radium. To date, only strontium with its radioisotopes gained importance for applications in nuclear medicine, mainly for pain-reducing and palliative treatment of bone metastases. In contrast, barium isotopes can be useful imaging agents and possible diagnostic analogues for theranostic approaches. This review focuses on the characteristic and chemical behavior of barium compounds, possible radioactive barium isotopes for future applications in nuclear medicine and radiopharmacy as well as recent results regarding barium-131 as diagnostic match for radium isotopes used in targeted alpha therapy.

Keywords: Barium isotopes; bone seeker; alkaline earth metals; brachytherapy

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Permalink: https://www.hzdr.de/publications/Publ-32280
Publ.-Id: 32280


Dependence of the damage in optical metal/dielectric coatings on the energy of ions in irradiation experiments for space qualification

Pelizzo, M. G.; Corso, A. J.; Santi, G.; Hübner, R.; Garoli, D.; Doyle, D.; Lubin, P.; Cohen, A. N.; Erlikhman, J.; Favaro, G.; Bazzan, M.; Drobny, J.; Curreli, D.; Umansky, M.

Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. In this work, a TiO2/Al bi-layer coating has been irradiated with a He+ beam at three different energies. The same flux and dose have been used in order to investigate the damage dependence on the energy. The energies were selected to be in the range 4-100 keV, in order to consider those associated to the quiet solar wind and to the particles present in the near-Earth space environment. The optical, morphological and structural modifications have been investigated by using various techniques. Surprisingly, the most damaged sample is the one irradiated at the intermediate energy, which, on the other hand, corresponds to the case in which the interface between the two layers is more stressed. Results demonstrate that ion energies for irradiation tests must be carefully selected to properly qualify space components.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-32279
Publ.-Id: 32279


Annual Report 2020 - Institute of Resource Ecology

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

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

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-113 2021
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-32278
Publ.-Id: 32278


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

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

These data are related to the https://arxiv.org/abs/2011.04505 publication entitled: Spin-wave dynamics and symmetry breaking in an artificial spin ice

The archive-files.txt contains a detailed description of the files stored in the repository-files-paper.tar file.

The geometry .bmp files are also included, thus anyone can reproduce the results by using mumax3 from https://mumax.github.io

Keywords: nanomagnetism; artificial spin ice; spin wave; magnetization dynamics; magnonic crystal

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Permalink: https://www.hzdr.de/publications/Publ-32277
Publ.-Id: 32277


Sub-20 nm multilayer nanopillar patterning for hybrid SET/CMOS integration: Figs. 1a, 1b and 5

Engelmann, H.-J.
Project Leader: von Borany, Johannes

Energy-filtered transmission electron microscopy (EFTEM) images of stacked Si/SiO2/Si nanopillars

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-32276
Publ.-Id: 32276


Data file for manuscript on Interfacial Properties of Tridecyl Dimethyl Phosphine Oxide Adsorbed at the Surface of a Solution Drop in Hexane Saturated Air

Javadi, A.

Experimental data for paper: Interfacial Properties of Tridecyl Dimethyl Phosphine Oxide Adsorbed at the Surface of a Solution Drop in Hexane Saturated Air.

The presented data are measured dynamic surface tension of Tridecyl Dimethyl Phosphine Oxide in water against air and alkane vapors, by profile analysis tensiometry. It also includes data analysis standard deviation from Young-Laplace fitting, and theoretical analysis illustrating isotherm of adsorption.

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-32274
Publ.-Id: 32274


Data File for Drop Size Dependence of the Apparent Surface Tension of Aqueous Solutions in Hexane Vapor

Javadi, A.

Experimental data file for Paper on "Drop Size Dependence of the Apparent Surface Tension of Aqueous Solutions in Hexane Vapor as Studied by Drop Profile Analysis Tensiometry".

These data are measured dynamic surface tension and variations of deviations from Young Laplace fitting, of different drop size of surfactants solution Tridecyl dimethyl phosphine oxide C13DMPO and Oxyethylated alcohol С14ЕО8 in water against air and hexane vapor. 

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Permalink: https://www.hzdr.de/publications/Publ-32273
Publ.-Id: 32273


Increasing the recycling rate of spent lithium ion battery recycling by recovering spheroidized graphite

Vanderbruggen, A.; Rudolph, M.

Lithium ion battery is composed of a lot of raw materials such as Co, Ni, Li, Al, Cu and graphite. Graphite represents around 20 wt. % of a lithium-ion battery. Graphite from spent lithium-ion batteries is rarely recovered and usually remains in slags from the metallurgical treatments. During lithium-ion battery recycling, the graphite particles end up are liberated from the copper foils and end up in the fine fraction (below 100 µm). This fraction is also composed of lithium metal oxides. Lithium metal oxides and graphite can be separated by froth flotation. The aim of this research is to increase the recycling recovery of the LiBs by developing a new innovative process, which minimizes metal losses and is able to recover graphite. Two valuable products, one of graphite and one with the valuable metals are recovered using a batch mechanically agitated Outotec flotation cell. Batch flotation study shows that pre-treatment, such as attritioning, improves the process. This research aims to reach closed-loop system for spheroidized graphite from spent LiB.

Keywords: Recycling; Lithium ion battery; Froth flotation; critical raw material; Graphite

  • Invited lecture (Conferences)
    10th Advanced Automotive battery conferences AABC 2020 - Battery recycling Symposium, 12.-16.01.2021, Wiesbaden, Germany

Permalink: https://www.hzdr.de/publications/Publ-32272
Publ.-Id: 32272


Characterization of lithium ion battery recycling processes and estimation of liberation efficiency of electrodes using automated mineralogy

Vanderbruggen, A.; Hayagan, N. L.; Bachmann, K.; Rudolph, M.

Lithium-ion batteries (LIBs) are currently one of the most important electrochemical energy storage devices, powering electronic mobile devices and electric vehicles. Growing global demands for Co, Mn, Ni, Li, and graphite which are all used and present in LIBs as energy storage added difficulties to the already deficit and imbalance supply of sources of raw materials worldwide, which resulted to supply risks, price fluctuations and monopoly of market. In fact, Co and natural graphite are listed as critical raw materials (CRMs) in Europe since 2010 and Mn, and Li are on the boundary of criticality. While recycling is identified as a solution to potentially reduce the gap between the demand and supply. Recycling of lithium ion battery (LIB) has attracted a lot of attention in the recent years and focuses primarily on valuable metals such as cobalt, nickel and lithium. During the recycling processes, considerable amount of the components are lost like electrolyte, separator or graphite. For instance, graphite can either be slagged-off or consumed as a reductant agent during pyrometallurgical treatment. Some other loses are due to a lack of liberation of the targeted particles, elements such as Co are lost in the coarse fractions and a not recovered in the right product. Hence, there is a need to find innovative and comprehensive LIB recycling operations.
For understanding and be able to quantify the loses and recycling process efficiency a deeper characterization is required. This research proposes a new characterization method based on automated mineralogy. In this study, the particles morphologies (size, composition and phases associations) are analysed. The liberation of active materials from electrodes is quantified by comparing two recycling processes: mechanical and thermochemical-mechanical. The mechanical route operates with an impact shear crusher while for the thermomechanical operation the batteries were vacuum pyrolyzed at 500-650oC before to be crushed. The black mass, fraction below 1 mm from the recycling processes, were classified in 4 size fractions based on the particles size distribution. Each fraction was characterized by various analytical methods, including X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Atomic Absorption Spectrometry (AAS) and SEM-based automated mineralogy. The latter consists in the combination of a scanning electron microscopy (SEM) image analysis and energy dispersive X-ray spectroscopy (EDS). It is a powerful and well-known method for primary material characterization; however, it has not yet been applied to secondary material such as black mass, which is a challenging material to analyse due fine alloys particles and to the lack of an existing dedicated database.
In this research, a database for battery characterization is also aimed aside from the determination of the liberation efficiency of the processes employed. Furthermore, a unique procedure was used in preparing the grain mounts for SEM-EDS analysis. Here, iodoform is added to modify the grey level of resin, which improves the contrast with the carbon phases. This technic allows the quantification of the carbon phases which is also a limitation of XRF and XRD aside from the fact that these methods cannot provide images for qualitative evaluation. This study showed that the thermo-mechanical process liberates more active particles from the foils than only a mechanical process. For both processes, a liberation selectivity of the electrode foils was observed. Cu foil is better liberated than Al foils. By consequence, most of the graphite particles are concentrated in the <63μm fraction. However, it was
found that the process type has different effects on Al foil liberation. The thermomechanical process liberates more metal oxides from the Al foil than only mechanical process, but Al breakage is more affected by thermal treatment, which creates finer Al particles, which can be problematic for further hydrometallurgy routes.

Keywords: Recycling; Lithium ion battery; Automated mineralogy; critical raw material; Graphite

  • Poster (Online presentation)
    10. ProcessNet-Jahrestagung und 34. DECHEMA-Jahrestagung der Biotechnologen 2020, 21.-24.09.2021, Online, Germany
  • Abstract in refereed journal
    Chemie Ingenieur Technik 92(2020)9, 1233
    DOI: 10.1002/cite.202055471

Permalink: https://www.hzdr.de/publications/Publ-32271
Publ.-Id: 32271


Spheroidized graphite from lithium-ion battery

Vanderbruggen, A.; Rudolph, M.

Spheroidized graphite is the major material used for anode production for lithium-ion batteries. Despite the growth in graphite consumption due to the electrical revolution and the fact that it is counted as a critical material in Europe, USA and Australia, there is little previous work focusing on graphite recycling. This talk will explain the importance of recycling graphite from spent lithium ion batteries and how graphite can be recovered.

Keywords: Recycling; Lithium ion battery; graphite; critical raw material

  • Invited lecture (Conferences) (Online presentation)
    Short course on Circular economy and sustainable material for li-battery, 18.-19.11.2021, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-32270
Publ.-Id: 32270


Recovery of spheroidized graphite from spent lithium-ion batteries

Vanderbruggen, A.; Rudolph, M.

Recycling of lithium ion battery has attracted a lot of attention and is particularly focusing on the valuable metals such as cobalt, nickel and lithium. Despite the growth in graphite consumption and the fact that it is counted as a critical material in Europe, USA and Australia, there is little previous work focusing on graphite recycling. Thus, graphite usually remains in slags from the metallurgical treatments. The aim of this research is to increase the recycling recovery of the LIBs by developing a new innovative process, which minimizes metal losses and is able to recover graphite. By integrating a flotation stage, this recycling process is able to separate battery electrode materials while preserving their functional integrity in order to reintegrate them in the value chain of LiB production. Two valuable products, one of graphite and one with the valuable metals are recovered using a batch mechanically agitated Outotec flotation cell. Batch flotation study shows that pre-treatment, such as attritioning, improves the process. The graphite recovery is +98 % with a grade of 80 wt. %. This research aims to reach closed-loop system for spheroidized graphite from spent LIBs.

Keywords: Recycling; Lithium ion battery; Froth flotation; Graphite; critical raw material

  • Invited lecture (Conferences)
    25th International Congress for Battery Recycling ICBR 2020, 16.-18.09.2021, Salzburg, Austria

Permalink: https://www.hzdr.de/publications/Publ-32269
Publ.-Id: 32269


Assessment of the liberation efficiency of lithium-ion battery components in recycling processes by using automated mineralogy

Vanderbruggen, A.; Bachmann, K.; Hayagan, N. L.; Rudolph, M.

Mechanical recycling processes aim at separating individual particles based on their properties, such as size, shape, density and composition. However, secondary material such as spent lithium ion battery are highly heterogeneous and complex in element and also material form. In order to improve recycling efficiency, characterization of the recycled products, on a particle level, is crucial. Nevertheless, conventional characterization techniques, such ICP-OES, XRF or XRD, provide bulked information for the products only. Tis research presents the development of a new analytical procedure based on individual particle characterization in order to monitor and diagnose lithium ion battery (LiB) recycling.
In this study, cylindrical lithium-ion batteries (INR18650-29E) are fed to a mechanical and thermo-mechanical recycling process route to release coated particles from the electrodes foils. In addition to the valuable metals, the focus is particularly on the recovery of graphite. The mechanical route works with a shear crusher, while for the thermo-mechanical tests the batteries were vacuum pyrolyzed at 500-650 °C before crushing. The fraction smaller than 1 mm, called black mass, was separated and classified into 4 size fractions based on the particle size distribution. The samples were analysed by automated mineralogy, this analytical tool enables the acquisition of particle-based information such as elemental and phase composition, morphology, association and degree of liberation. The Mineral Liberation Analyzer (MLA) system used for the measurements uses a combination of scanning electron microscopy (SEM) image analysis and energy-dispersive X-ray spectroscopy (EDS) and is established as a powerful method in the primary raw materials sector. However, there are no dedicated databases for use in the secondary raw materials sector in order to analyze black mass material in a fast and precise manner. An analytical challenge of this study is therefore to create a database for battery characterization and to be able to use it for a wide range of applications. The analysis shows a selective liberation of the anode components in comparison to the cathode components for the beneficiation processes, but with different liberation patterns of the Al foil. The lamination structure of the electrodes was conserved during mechanical process, which resultes in coarse aggregates. The thermo-mechanical process releases more individual and small aggregates of active particles from the foils than a mechanical process alone.

Keywords: Recycling; Lithium ion battery; Automated mineralogy; Black mass

  • Invited lecture (Conferences) (Online presentation)
    11th Advanced Automotive battery conferences AABC 2021 - Battery recycling Symposium, 19.-20.01.2021, Online, Germany

Permalink: https://www.hzdr.de/publications/Publ-32268
Publ.-Id: 32268


Brillouin Light Scattering Revisited

Schultheiß, K.; Schultheiß, H.

Since the 80’s, when Brillouin light scattering emerged as a powerful tool for investigating magnetization dynamics in thin films and multilayers, it developed into a versatile microscopic probe for studying collective spin excitations. Following a short introduction on studies of millimeter-sized films, we will give examples how to investigate individual magnetic structures down to tens of nanometers in dimension. We will introduce the concepts of time- and phase-resolved Brillouin light scattering which give full access to the spatio-temporal evolution of the optically accessible spin-wave spectrum. During our talk, we will provide hands-on demonstrations how to drive spin waves via spin currents and microwave excitations in magnetic nanostructures using the build in dc/ac probe station in our laboratory and show the capabilities of Brillouin light scattering for quantifying spin-wave phenomena. Furthermore, we will highlight similarities and differences to other optical scanning probe techniques such as time-resolved magneto-optical Kerr microscopy and optically detected magnetic resonance based on vacancy centers. We will outline how those techniques can potentially be combined with Brillouin light scattering to access complementary information.

Keywords: Brillouin light scattering; magnetization dynamics; spin waves; magneto optics

Related publications

  • Invited lecture (Conferences) (Online presentation)
    INTERMAG 2021, 26.-30.04.2021, online (planned: Lyon), online (planned: France)

Permalink: https://www.hzdr.de/publications/Publ-32267
Publ.-Id: 32267


Highlight selection of radiochemistry and radiopharmacy developments by editorial board (January-June 2020).

Al-Qahtani, M.; Behe, M.; Bormans, G.; Carlucci, G.; Dasilva, J.; Decristoforo, C.; Elsinga, P.; Kopka, K.; Li, X.; Mach, R.; Middel, O.; Passchier, J.; Patt, M.; Penuelas, I.; Rey, A.; Scott, P.; Todde, S.; Toyohara, J.; Vugts, D.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to describe trends in the field.
Results: This commentary of highlights has resulted in 19 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals.
Conclusion: Trends in radiochemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.

Permalink: https://www.hzdr.de/publications/Publ-32266
Publ.-Id: 32266


Curvilinear magnetism: fundamentals and applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring geometrical curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-4]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral responses and topologically induced magnetization patterning [5-7]. The possibility to tailor magnetic responses by geometry of the object is a new approach to material science, which allows to obtain a desired functionality of spintronic and spin-orbitronic devices yet without the need to rely on the optimization of the intrinsic material properties. The application potential of 3D-shaped magnetic thin films is currently being explored as mechanically shapeable magnetic field sensors [8] for automotive applications, magnetoelectrics for memory devices, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics [9-11]. The magnetosensitive smart skins allow digitizing the bodily motion and offer new means of touchless manipulation of virtual objects based on the interaction with magnetic stray fields of small permanent magnets [9,11] but also with geomagnetic field [10]. The fundamentals as well as application relevant aspects of curvilinear magnetism will be covered in this presentation.

[1] R. Streubel et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Sheka et al., Nonlocal chiral symmetry breaking in curvilinear magnetic shells. Communications Physics 3, 128 (2020)
[5] V. Kravchuk et al., Multiplet of Skyrmion states on a curvilinear defect: Reconfigurable Skyrmion lattices. Phys. Rev. Lett. 120, 067201 (2018)
[6] O. Pylypovskyi et al., Chiral Skyrmion and Skyrmionium States Engineered by the Gradient of Curvature. Phys. Rev. Appl. 10, 064057 (2018)
[7] O. Pylypovskyi et al., Coupling of chiralities in spin and physical spaces: The Möbius ring as a case study. Phys. Rev. Lett. 114, 197204 (2015)
[8] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[9] G. S. Cañón Bermúdez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[10] G. S. Cañón Bermúdez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[11] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).

Keywords: flexible electronics; curvilinear magnetism; magnetosensitive smart skins

Related publications

  • Lecture (others) (Online presentation)
    Seminar at the University of Kiel, 11.02.2021, Kiel, Germany

Permalink: https://www.hzdr.de/publications/Publ-32265
Publ.-Id: 32265


Mechanisms of pyrite biodepression with Acidithiobacillus ferrooxidans in seawater flotation

San Martin, F.; Kracht, W.; Vargas, T.; Rudolph, M.

It has been shown that bacterium Acidithiobacillus ferrooxidans can be used to depress pyrite in seawater flotation at natural pH, which opens the possibility for its use as an alternative to lime to depress pyrite in copper sulfide flotation. In order to have a better understanding of the mechanisms involved in pyrite depression with A. ferrooxidans, different kind of experiments were carried out, including, contact angle, attachment kinetics, and streaming potential measurements. All these experiments were carried out in seawater. Biodepression of pyrite was improved by increasing the pH from 4 to 8, with a decrease in recovery from 92% to 36%. This increase in depressing capability was accompanied by an increase in attachment density of bacteria on pyrite, from bacteria/g to bacteria/g at pH 4 and 8, respectively. These results suggest that the mechanism of depression is related to the attachment of bacteria to the pyrite surface. The streaming potential measurements showed that both bacteria and pyrite were negatively charged at pH 8. This indicates that electrostatic forces are mainly repulsive, therefore other forces cause the attachment of bacteria to the mineral. The contact angle of pyrite conditioned with seawater at pH 8 was 16, which increased to 54 when collector (sodium isopropyl xanthate) was added, indicating an increase in hydrophobicity. Nevertheless, when pyrite was previous conditioned with bacteria, the contact angle increased only to 44 when collector was added. Thus, the collector has a lower influence in the hydrophobicity of pyrite when the mineral has interacted with bacteria A. ferrooxidans.

Keywords: Flotation; Seawater; Pyrite; Biodepression; Acidithiobacillus ferrooxidans

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Permalink: https://www.hzdr.de/publications/Publ-32264
Publ.-Id: 32264


Advanced Analysis of Bubble Columns: Comparison of Euler/Lagrange Simulations and Experiments under CO2 chemisorption conditions

Taborda, M. A.; Kipping, R.; Hampel, U.; Sommerfeld, M.

The chemical absorption reaction of CO2 in a circular bubble column reactor was simulated with an Euler/Lagrange CFD method and results were compared with data from a laboratory scale bubble column. The experimental data comprises gas holdup and bubble size distributions obtained with ultrafast X-ray tomography and hydroxide ion conversion obtained with a wire-mesh sensor. Large Eddy Simulation (LES) is used for calculating the fluid flow and modelling the turbulence in the continuous phase, considering the effect of sub-grid-scale (SGS) turbulence on bubble motion, and also SGS turbulence modification by bubbles. Lagrangian bubble tracking is conducted considering all relevant forces, bubble oscillation via stochastic generation of eccentricity and motion angle and consequently non-steady mass transfer via a dynamic Sherwood number. The comparison of experimental and simulation results shows very good agreement for the given data.

Keywords: Euler/Lagrange approach; bubble dynamics model; reactive two-phase flow; dynamic Sherwood number; wire-mesh sensor; ultrafast X-ray computed tomography

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Permalink: https://www.hzdr.de/publications/Publ-32261
Publ.-Id: 32261


Study of the parameter dependence of laser-accelerated protons from a hydrogen cluster source

Aurand, B.; Schwind, K. M.; Toncian, T.; Aktan, E.; Cerchez, M.; Lessmann, L.; Mannweiler, C.; Prasad, R.; Khoukaz, A.; Willi, O.

We present a study on laser-driven proton acceleration from a hydrogen cluster target. Aiming for the optimisation of the proton source, we performed a detailed parametric scan of the interaction conditions by varying different laser and the target parameters. While the underlying process of a Coulomb-explosion delivers moderate energies, in the range of 100 s of keV, the use of hydrogen as target material comes with the benefit of a debris-free, single-species proton acceleration scheme, enabling high repetition-rate experiments, which are very robust against shot-to-shot fluctuations.

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Permalink: https://www.hzdr.de/publications/Publ-32260
Publ.-Id: 32260


Direct laser acceleration of electrons assisted by strong laser-driven azimuthal plasma magnetic fields

Gong, Z.; Mackenroth, F.; Wang, T.; Yan, X. Q.; Toncian, T.; Arefiev, A. V.

A high-intensity laser beam propagating through a dense plasma drives a strong current that robustly sustains a strong quasistatic azimuthal magnetic field. The laser field efficiently accelerates electrons in such a field that confines the transverse motion and deflects the electrons in the forward direction. Its advantage is a threshold rather than resonant behavior, accelerating electrons to high energies for sufficiently strong laser-driven currents. We study the electron dynamics via a test-electron model, specifically deriving the corresponding critical current density. We confirm the model's predictions by numerical simulations, indicating energy gains two orders of magnitude higher than achievable without the magnetic field.

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Permalink: https://www.hzdr.de/publications/Publ-32259
Publ.-Id: 32259


Application of Laser-Driven Capacitor-Coil to Target Normal Sheath Acceleration

Morita, H.; Arefiev, A.; Toncian, T.; Jorge Santos, J.; Golovin, D.; Shokita, S.; Mori, T.; Fai Farley Law, K.; Li, H.; Takizawa, R.; Matsuo, K.; Morace, A.; Yogo, A.; Fujioka, S.

A laser-driven accelerator generates protons with tens of MeV in energy by a compact, strong, and transient accelerating electric field produced as a result of laser–plasma interactions at relativistic intensities. In previous studies, two- and three-dimensional particle-in-cell simulations revealed that the application of a kT-level axial magnetic field results in an enhancement of proton acceleration via the target normal sheath acceleration mechanism due to reduced lateral electron divergence and improved electron heating efficiency. An experimental investigation of this scheme on the GEKKO-XII and the LFEX facilities found that the number and maximum energy of the accelerated protons decreased with increasing the temporal delay between the pulse driving the external magnetic-field and the pulse accelerating the protons, contrary to the theoretical and numerical expectations. We identify sources responsible for the degradation of the proton beam performance and we propose an alternative experimental setup to mitigate the degradation in future experiments.

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Permalink: https://www.hzdr.de/publications/Publ-32258
Publ.-Id: 32258


Generation of focusing ion beams by magnetized electron sheath acceleration

Weichman, K.; Santos, J. J.; Fujioka, S.; Toncian, T.; Arefiev, A. V.

We present the first 3D fully kinetic simulations of laser driven sheath-based ion acceleration with a kilotesla-level applied magnetic field. The application of a strong magnetic field significantly and beneficially alters sheath based ion acceleration and creates two distinct stages in the acceleration process associated with the time-evolving magnetization of the hot electron sheath. The first stage delivers dramatically enhanced acceleration, and the second reverses the typical outward-directed topology of the sheath electric field into a focusing configuration. The net result is a focusing, magnetic field-directed ion source of multiple species with strongly enhanced energy and number. The predicted improvements in ion source characteristics are desirable for applications and suggest a route to experimentally confirm magnetization-related effects in the high energy density regime. We additionally perform a comparison between 2D and 3D simulation geometry, on which basis we predict the feasibility of observing magnetic field effects under experimentally relevant conditions.

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Permalink: https://www.hzdr.de/publications/Publ-32257
Publ.-Id: 32257


A laser-driven droplet source for plasma physics applications

Aurand, B.; Aktan, E.; Schwind, K. M.; Prasad, R.; Cerchez, M.; Toncian, T.; Willi, O.

In this paper, we report on the acceleration of protons and oxygen ions from tens of micrometer large water droplets by a high-intensity laser in the range of 1020 W/cm2. Proton energies of up to 6 MeV were obtained from a hybrid acceleration regime between classical Coulomb explosion and shocks. Besides the known thermal energy spectrum, a collective acceleration of oxygen ions of different charge states is observed. 3D PIC simulations and analytical models are employed to support the experiential findings and reveal the potential for further applications and studies.

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Permalink: https://www.hzdr.de/publications/Publ-32256
Publ.-Id: 32256


A new approach to monitor 13C-targets degradation in situ for 13C(α,n)16O cross-section measurements at LUNA

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

Direct measurements of reaction cross-sections at astrophysical energies often require the use of solid targets able to withstand high ion beam currents for extended periods of time. Thus, monitoring target thickness, isotopic composition, and target stoichiometry during data taking is critical to account for possible target modifications and to reduce uncertainties in the final cross-section results. A common technique used for these purposes is the Nuclear Resonant Reaction Analysis (NRRA), which however requires that a narrow resonance be available inside the dynamic range of the accelerator used. In cases when this is not possible, as for example the 13C(𝛼,n)16O reaction recently studied at low energies at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy, alternative approaches must be found. Here, we present a new application of the shape analysis of primary γ rays emitted by the 13C(p,𝛾)14N radiative capture reaction. This approach was used to monitor 13C target degradation in situ during the 13C(𝛼,n)16O data taking campaign. The results obtained are in agreement with evaluations subsequently performed at Atomki (Hungary) using the NRRA method. A preliminary application for the extraction of the 13C(α,n)16O reaction cross-section at one beam energy is also reported.

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Permalink: https://www.hzdr.de/publications/Publ-32255
Publ.-Id: 32255


Sorption studies of Np(V) onto the zircaloy corrosion product ZrO₂

Jessat, I.; Foerstendorf, H.; Jordan, N.

The interactions of dissolved radionuclides, such as the actinide neptunium(V), with corroded phases in the near field of a repository are crucial processes to be considered in a safety assessment of a nuclear waste disposal for highly radioactive waste. Zirconia (ZrO₂), the corrosion product of the zircaloy cladding material of spent nuclear fuel rods, represents one of the first barriers encountered by mobilized radionuclide ions.
In this study, the interactions between Np(V) and monoclinic zirconia were studied at room temperature on a macroscopic and molecular scale. The influence of different parameters (time, pH, ionic strength, [Np(V)]) was investigated by means of batch sorption experiments to gain information on the macroscopic level. Starting at pH 3, an increased uptake of Np(V) with increasing pH was observed, reaching its maximum at pH ≥ 7. The Np(V) sorption was found to be independent of ionic strength, indicating Np(V) inner-sphere complexation on the ZrO₂ surface. This finding was supported by electrophoretic mobility measurements at different Np(V) concentrations. A shift of the isoelectric point of the neat ZrO₂ to higher pH values in the presence of Np(V) suggests the same Np(V) binding mode.
In situ ATR-FTIR spectroscopy was applied to gain a deeper understanding of the Np(V) sorption processes on a molecular level. These experiments allow a thorough characterization of the surface speciation including the number of occurring species, their denticity, and their reversibility of formation. Subsequently, this information will be used for the surface complexation modelling (SCM) to parametrize a comprehensive description of the Np(V)-ZrO₂ system, which in turn will contribute to a more reliable prediction of the fate of Np(V) in the environment.

Keywords: neptunium(V); zirconia; sorption; spectroscopy

  • Lecture (Conference)
    Goldschmidt 2021, 04.-09.07.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-32254
Publ.-Id: 32254


Data for: The surface expression of hydrocarbon seeps characterized by satellite image spectral analysis and rock magnetic data (Falcon basin, western Venezuela)

de La Rosa, R.; Aldana, M.; Costanzo-Alvarez, V.; Yepez, S.; Amon, C.

This work integrates satellite image spectral analyses with rock magnetic and geochemical data (i.e., mass-specific magnetic susceptibility χ, saturation isothermal remanent magnetization SIRM, analysis of SIRM acquisition curves, absorption spectro-radiometry, and X-ray diffraction analyses). The target area was an oil-prospective region in northwestern Venezuela (Falcon Basin) swarmed by hydrocarbon seeps. The study's main goal was to depict the spatial extension and vertical reach of the hydrocarbon-mediated alteration produced by these seeps and gain some knowledge about the processes involved in the subsequent mineral changes.

The dataset is composed of spreadsheets, compressing field samples data including their locations. Also, a database is presented with data from profiles extracted from the results of multispectral image processing and laboratory data of rock magnetism. 

Keywords: Satellite remote sensing; Spectral images; Spectral signature; Hydrocarbon seeps; Hydrocarbon- induced diagenesis; Rock magnetism; Weathered sequence; Two-Step Cluster Analysis

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Permalink: https://www.hzdr.de/publications/Publ-32253
Publ.-Id: 32253


The application of surface exposure dating method in case of Veliki vrh rockfall (Karavanke Mountains, Slovenia)

Mrak, I.; Merchel, S.; Braucher, R.; Benedetti, L.; Finkel, R. C.; Bourlès, D.

The use of terrestrial cosmogenic nuclides (TCN) has revolutionized Earth surface sciences over the last decade by their capacity to quantify geological surface processes. The uniqueness of these nuclides lies in their property of being produced in the top few meters of the lithosphere during exposure to cosmic radiation. There are various types of application of surface exposure dating such as chronological constraints on the timing and rates of environmental changes (glacial history, erosion) and hazard recurrence frequency (landslides and seismic activity). The method was used also in the case of Veliki vrh rockfall located in Karavanke Mountains (Slovenia). There are no reliable historical data about the rockfall event beside the oral heritage in form of a fairytale describing the catastrophic falling of rocks over the settlement in the valley, forcing the survivors to establish a new settlement (Tržic) further downstream. However, there are numerous written records about a historic rockfall (induced by an earthquake) taking place about 46 km away at Dobratsch, Carinthia on 25th January 1348 thus; it seems very likely that the same earthquake triggered both rockfalls. Surface exposure dating method has been applied on samples taken from the fresh bedrock and big blocks obviously originating from the Veliki vrh rockfall and the results are confirming our
hypothesis. They have also importantly improved geomorphologic interpretation of the area.

Keywords: AMS; cosmogenic radionuclide; rockfall; earthquake; dating

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  • Lecture (Conference)
    Association of American Geographers 2011 Annual Meeting, 10.-16.04.2011, Seattle, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-32252
Publ.-Id: 32252


Lipase At water air intereface data HZDR TUB 2018-2020

Javadi, A.

Dynamic surface tension and competitive adsorption of Lipase enzyme and surfactants at water air interface.

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Permalink: https://www.hzdr.de/publications/Publ-32251
Publ.-Id: 32251


alpaka, LLAMA & Vc: An ecosystem for performance portable parallelism

Stephan, J.

This talk covers the alpaka ecosystem for performance portable parallel programming in HPC and simulation environments. It focuses on alpaka, LLAMA and Vc, their interactions with each other and their impact on the C++ programming language.

Keywords: alpaka; LLAMA; Vc; C++; heterogeneous programming; portability; HPC; parallel programming

  • Open Access Logo Lecture (others) (Online presentation)
    7th MT Meeting, 01.-03.02.2021, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32250
Publ.-Id: 32250


Dataset for: Flow morphologies in straight and bent horizontal pipes (uncalibrated measurement files)

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

This data set is a supplementory to 'Dataset for: Flow morphologies in straight and bent horizontal pipes'. In addition to the void files (.v) given in the primary data sets we provide:

- Underlying uncalibrated measurements files (.dat, .dati)
- .log files for the corresponding .v-files
- Calibration measurements
- Geometry files for the used Wire-mesh sensors

Keywords: Flow morphologies; Horizontal Two-phase flow; Wire-mesh sensor; TERESA

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Permalink: https://www.hzdr.de/publications/Publ-32249
Publ.-Id: 32249


Data-driven magneto-elastic predictions with scalable classical spin-lattice dynamics

Nikolov, S.; Wood, M. A.; Cangi, A.; Maillet, J.-B.; Marinica, M.-C.; Thompson, A. P.; Desjarlais, M. P.; Tranchida, J.

A data-driven framework is presented for building magneto-elastic machine-learning interatomic potentials (ML-IAPs) for large-scale spin-lattice dynamics simulations. The magneto-elastic ML-IAPs are constructed by coupling a collective atomic spin model with an ML-IAP. Together they represent a potential energy surface from which the mechanical forces on the atoms and the precession dynamics of the atomic spins are computed. Both the atomic spin model and the ML-IAP are parametrized on data from first-principles calculations. We demonstrate the efficacy of our data-driven framework across magneto-structural phase transitions by generating a magneto-elastic ML-IAP for α-iron. The combined potential energy surface yields excellent agreement with first-principles magneto-elastic calculations and quantitative predictions of diverse materials properties including bulk modulus, magnetization, and specific heat across the ferromagnetic–paramagnetic phase transition.

Keywords: magnetism; molecular dynamics; spin dynamics; lattice dynamics; density functional theory; machine learning; interatomic potentials

Permalink: https://www.hzdr.de/publications/Publ-32248
Publ.-Id: 32248


Spin Dynamics in Quantum Sine-Gordon Spin Chains: High-Field ESR Studies

Zvyagin, S.

A spin-1/2 Heisenberg antiferromagnetic chain is one of the most important paradigmatic models in quantum magnetism. Its ground state is a spin singlet, while the excitation spectrum is formed by gapless fractional excitations, spinons. The presence of alternating g-tensors and/or the staggered Dzyaloshinskii-Moriya interaction results in opening the energy gap Δ∝H2/3, once the magnetic field H is applied. A fairly good understanding of this phenomenon was achieved in the framework of the sine-Gordon quantum-field theory, taking into account the effective transverse staggered field induced by the applied uniform field. The theory predicts solitons and antisolitons as elementary excitations, as well as their bound states, breathers. Here, I review recent high-field electron spin resonance spectroscopy studies of such systems, focusing on peculiarities of their spin dynamics in the sine-Gordon regime and beyond.

Permalink: https://www.hzdr.de/publications/Publ-32247
Publ.-Id: 32247


Die Bedeutung des Elementes Barium in der Nuklearmedizin

Reissig, F.; Kopka, K.; Mamat, C.

Von Erdalkalimetallionen außer Beryllium ist bekannt, dass sie ein calcimimetisches Verhalten zeigen. Damit ist ihr Schicksal in vivo vorgezeichnet, das in einem beträchtlichen Maße durch den Einbau in Knochengewebe, welches zum Hauptteil aus Hydroxylapatit besteht, charakterisiert ist. In diesem Sinne wurde auch die Verwendung von Radionukliden dieser Elemente als Knochensucher forciert. Mit Ausnahme von Beryllium und Magnesium wurden Tierexperimente und Humananwendungen mit Radionukliden von Calcium, Strontium, Barium und Radium durchgeführt, wobei bis heute lediglich Strontium und Radium, in der Hauptsache als Therapienuklide zur palliativen Behandlung von Knochenmetastasen, Eingang in nuklearmedizinische Routineanwendungen gefunden haben. In diesem Übersichtsartikel werden die Radionuklide des Bariums vorgestellt, sowie deren Herstellung und Verwendung. Aktuelle Forschungsergebnisse mit Radionukliden des Bariums in Radiopharmazie und Nuklearmedizin werden präsentiert.

Keywords: Bariumisotope; Knochensucher; Radium

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Permalink: https://www.hzdr.de/publications/Publ-32246
Publ.-Id: 32246


Open-source computational model for polymer electrolyte fuel cells

Weber, N.; Knüpfer, L.; Beale, S. B.; Lehnert, W.; Reimer, U.; Zhang, S.; Ferreira-Aparicio, P.; M. Chaparro, A.

Open-source fuel cell models outmatch commercial codes in many important aspects. By providing the source code, a simple reuse, modification and extension of the model as well as its comparison with other codes becomes at once easily possible. With this motivation, we present a three-dimensional, steady state, non-isothermal proton exchange membrane fuel cell (PEMFC) model, implemented in the open-source finite volume library OpenFOAM. At every stage of implementation, special care was taken to ensure a well documented, organised, and modular structure of the software. The resulting model suite can, and should be extended by new sub-modules by the user. Its main field of application, the modelling of fuel cells from an engineering perspective, is demonstrated by simulating two different conventional PEMFC, operated at CIEMAT and FZ Jülich, respectively.

  • Software in external data repository
    Publication year 2021
    Programming language: C++
    System requirements: OpenFOAM-v2012
    License: GNU GPLv3
    Hosted on GitLab: Link to location

Permalink: https://www.hzdr.de/publications/Publ-32245
Publ.-Id: 32245


Data for: Single-step, High Pressure, and Two-Step Spark Plasma Sintering of UO2 nanopowders

de Bona, E.

Three different Spark Plasma Sintering (SPS) treatments were applied to highly sinteractive, near-stoichiometric UO2.04 nanocrystalline (5 nm) powders produced by U(IV) oxalate hydrothermal decomposition at 170 °C. The sintering conditions for reaching 95 % Theoretical Density (TD) in regular SPS, high pressure SPS (HP-SPS), and, for the first time, two-step SPS (2S-SPS), were determined. Densification to 95 % TD was achieved at 1000 °C in regular SPS (70 MPa applied pressure), 660 °C in HP-SPS (500 MPa), and 650-550 °C in 2S-SPS (70 MPa). With the goal of minimising the grain growth during densification, the sintering treatments were optimised to favour densification over coarsening, and the final microstructures thus obtained are compared. Equally dense UO2 samples of different grain sizes, ranging from 3.08 µm to 163 nm, were produced. Room-temperature oxidation of the powders could not be avoided due to their nanometric dimensions, and a final annealing treatment was designed to reduce hyperstoichiometric samples to UO2.00.

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Permalink: https://www.hzdr.de/publications/Publ-32243
Publ.-Id: 32243


Validation of an LC-MS/MS method to quantify the new TRPC6 inhibitor SH045 (larixyl N-methylcarbamate) and its application in an exploratory pharmacokinetic study in mice

Chai, X.-N.; Ludwig, F.-A.; Müglitz, A.; Schaefer, M.; Yin, H.-Y.; Brust, P.; Regenthal, R.; Krügel, U.

TRPC6 (transient receptor potential cation channels; canonical subfamily C, member 6) are widespread localized in mammalian organs like kidney and lung and associated with progressive proteinuria and pathophysiological pulmonary alterations like reperfusion edema or lung fibroses. However, the understanding of TRPC6 channelopathies is still at the beginning. Recently, by chemical diversification of (+)-larixol originating from Larix decidua resin traditionally used for inhalation, its methyl carbamate congener, named SH045, was obtained and identified in functional assays as highly potent, subtype-selective inhibitor of TRPC6. To pave the way for use of SH045 in animal disease models we aimed to develop a capable bioanalytical method and to provide exploratory pharmacokinetic data for this promising derivative. According to international guidelines, a robust and selective LC-MS/MS method based on MRM detection in positive ion mode was established and validated for quantification of SH045 in mice plasma, whereby linearity and accuracy were demonstrated for the range of 2-1600 ng/mL.
Applying this method, the plasma concentration time course of SH045 following single intraperitoneal administration (20 mg/kg body weight) revealed a rather short half-life of 1.3 hours. However, the pharmacological profile of SH045 is promising as five hours after administration plasma levels still remained sufficiently higher than published low nanomolar IC50 values.
Summarizing, the LC-MS/MS quantification method and exploratory pharmacokinetic data provide important prerequisites for experimental pharmacological TRPC6 modulation and translational treatment of TRPC6 channelopathies.

Keywords: channelopathies; larixol; labdane; LC-MS/MS; mice; pharmacokinetics; SH045; TRP channels; TRPC6 inhibitor

Permalink: https://www.hzdr.de/publications/Publ-32242
Publ.-Id: 32242


Development of a ghrelin receptor inverse agonist for positron emission tomography

Bergmann, R.; Chollet, C.; Els-Heindl, S.; Ullrich, M.; Berndt, N.; Pietzsch, J.; MáThé, D.; Bachmann, M.; Beck-Sickinger, A. G.

Imaging of Ghrelin receptors in vivo provides unique potential to gain deeper understanding on Ghrelin and its receptors in health and disease, in particular, in cancer. Ghrelin, an octanoylated 28-mer peptide hormone activates the constitutively active growth hormone secretagogue receptor type 1a (GHS-R1a) with nanomolar activity. We developed novel compounds, derived from the potent inverse agonist K-(D-1-Nal)-FwLL-NH2 but structurally varied by lysine conjugation with 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA), palmitic acid and/or diethylene glycol (PEG2) to allow radiolabeling and improve pharmacokinetics, respectively. All compounds were tested for receptor binding, potency and efficacy in vitro, for biodistribution and -kinetics in rats and in preclinical prostate cancer models on mice. Radiolabeling with Cu-64 and Ga-68 was successfully achieved. The Cu-64- or Ga-68-NODAGA-NH-K-K-(D-1-NaI)-F-w-L-L-NH2 radiotracer were specifically accumulated by the GHS-R1a in xenotransplanted human prostate tumor models (PC-3, DU-145) in mice. The tumors were clearly delineated by PET. The radiotracer uptake was also partially blocked by K-(D-1-Nal)-FwLL-NH2 in stomach and thyroid. The presence of the GHS-R1a was also confirmed by immunohistology. In the arterial rat blood plasma, only the original compounds were found. The Cu-64- or Ga-68-NODAGA-NH-K-K-(D-1-NaI)-F-w-L-L-NH2 radiolabeled inverse agonists turned out to be potent and safe. Due to their easy synthesis, high affinity, medium potency, metabolic stability, and the suitable pharmacokinetic profiles, they are excellent tools for imaging and quantitation of GHS-R1a expression in normal and cancer tissues by PET. These compounds can be used as novel biomarkers of the Ghrelin system in precision medicine.

Keywords: Cancer; Prostate cancer; growth hormone secretagogue receptor (GHS-R); small animal imaging; Copper-64; Gallium-68

Permalink: https://www.hzdr.de/publications/Publ-32241
Publ.-Id: 32241


Non-radiative energy transfer and selective charge transfer in a WS2/(PEA)2PbI4 heterostructure

Karpińska, M.; Liang, M.; Kempt, R.; Finzel, K.; Kamminga, M.; Zhang, N.; Knodlseder, C.; Maude, D. K.; Baranowski, M.; Łopotowski, Ł.; Ye, J.; Kuc, A. B.; Plochocka, P.

Van der Waals heterostructures are currently the focus of intense investigation, this is essentially due to the unprecedented flexibility offered by the total relaxation of lattice matching requirements, and their new and exotic properties compared to the individual layers. Here, we investigate the hybrid transition metal dichalcogenide/2D perovskite heterostructure WS2 /(PEA)2 PbI4 . We present the first DFT calculations of a heterostructure ensemble, which reveal a novel band alignment, where direct electron transfer is blocked by the organic spacer of the 2D perovskite. In contrast, the valence band forms a cascade from WS2 through the PEA to the PbI4 layer allowing hole transfer. These predictions are supported by optical spectroscopy studies, which provide compelling evidence for both charge transfer, and non-radiative transfer of the excitation (energy transfer) between the layers. Our results show that TMD/2D perovskite heterostructures provide a flexible and convenient way to engineer the band alignment.

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Permalink: https://www.hzdr.de/publications/Publ-32240
Publ.-Id: 32240


Data for: Experimental investigation of the return flow instability in magnetic spherical Couette flow

Ogbonna, J. E.; Garcia Gonzalez, F.; Gundrum, T.; Seilmayer, M.; Stefani, F.

Experimental data, numerical data, and programming scripts

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Permalink: https://www.hzdr.de/publications/Publ-32239
Publ.-Id: 32239


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