Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

36659 Publications

The magnetized spherical couette system: From numerics to experiments

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

The study of magnetohydrodynamic (MHD) instabilities occurring in liquid metals, with
imposed differential rotation and magnetic field, is of fundamental importance in the astrophysical
context. MHD instabilities are especially relevant in planets or stars, where electrically conducting
flows are confined within their interiors. Such environments could be modeled by solving the
Navier-Stokes and induction equations with appropriate conditions in a spherical shell composed of
two concentric spheres. In particular, we consider the case where the liquid metal (GaInSn in our
case), bounded by a stationary outer sphere and a uniformly rotating inner sphere, is subjected to an
axial magnetic field. When the aspect ratio of the radii of the two spheres is fixed, only two
parameters, namely, the Reynolds number (associated with the differential rotation) and the
Hartmann number (associated with the applied magnetic field strength), govern the dynamics of the
system (see [1,2] for full details).
For the magnetized spherical Couette system, three different types of instabilities have so far
been identified and characterized by means of numerical simulations (e.g. [1,3]), and also in
experiments (e.g. [2,4]). These instabilities can each be described as a hydrodynamic radial jet
instability, a return flow instability, and a Kelvin-Helmholtz-like Shercliff layer instability. We
provide an overview of these instabilities with a focus on the description and analysis of the
different spatio-temporal symmetries of the MHD flow. In particular, numerical and experimental
bifurcation diagrams of nonlinear waves in the quasi-laminar regime (with moderate differential
rotation) are presented and some numerical tools, related to nonlinear dynamics and chaos theory
[5], are outlined. These tools include the numerical continuation of periodic solutions and their
stability assessment, time series analysis such as the computation of the fundamental frequencies in
one or several spatial dimensions, time dependent frequency spectra, and Poincaré sections.
Our results show how periodic and quasiperiodic MHD flows with two, three and even four
incommensurable frequencies, as well as MHD chaotic flows, are developed following a sequence
of bifurcations from the base state. The knowledge of the different routes to chaos is of fundamental
importance in turbulence theory. In addition, by taking into account the symmetries of the solutions
several regions of multistability (and also hysteretic behavior) are identified in the parameter space
with a good agreement between simulations and experiments, both in their temporal and spatial
structures. Although unstable MHD flows are not experimentally realized, their numerical
computation as in [1,6] provides a more complete picture of the dynamics and aids the
understanding of transient and hysteretic behaviors in experiments.
This work is funded by the European Research Council (ERC), Horizon 2020 research and
innovation programme (grant agreement No. 787544). The authors wish to thank Kevin Bauch for
technical support.

1. Garcia, F. and Stefani, F., Continuation and stability of rotating waves in the magnetized spherical Couette
system: Secondary transitions and multistability. – Proc. R. Soc. A (474), 2018. – p. 20180281.
2. Ogbonna, J., Garcia, F., Gundrum, T., Seilmayer, M. and Stefani, F., Experimental investigation of the return
flow instability in magnetized spherical Couette flows. – Phys. Fluids (32), 2020. – p. 124119.
3. Travnikov, V., Eckert, K. and Odenbach, S., Influence of an axial magnetic field on the stability of spherical
Couette flows with different gap widths. – Acta Mech. (219), 2011. – p. 255.
4. Kasprzyk, C., Kaplan, E., Seilmayer, M. and Stefani, F., Transitions in a magnetized quasi-laminar spherical
Couette flow. – Magnetohydrodynamics (53), 2017. – p. 393.
5. Kuznetsov, Y. A., Elements of Applied Bifurcation Theory, 2nd Edition – Springer, New York, 1998.
6. Garcia, F., Seilmayer, M., Giesecke, A. and Stefani, F., Four-frequency solution in a magnetohydrodynamic
Couette flow as a consequence of azimuthal symmetry breaking. – Phys. Rev. Lett. (125), 2020. – p. 264501.

  • Open Access Logo Lecture (Conference) (Online presentation)
    The Fourth Russian Conference on Magnetohydrodynamics, RMHD-2021, 20.-22.09.2021, Perm, Russia

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34046
Publ.-Id: 34046


Contactless inductive flow tomography for Rayleigh-Bénard convection

Sieger, M.; Mitra, R.; Stefani, F.; Schindler, F.; Vogt, T.; Eckert, S.

In this talk we give an overview of the current state of the developments of the contactless inductive flow tomography (CIFT) for two different cylindrical cells with aspect ratio 1 and 0.5 for Rayleigh-Bénard convection. Both cylindrical vessels are filled with the eutectic alloy GaInSn. We address the challenges in the flow induced magnetic field measurement and show first reconstructions of the complex three-dimensional flow structure in the cell with aspect ratio 0.5.

Keywords: contactless inductive flow tomography; flow measurement; liquid metal; Rayleigh-Bénard convection

  • Invited lecture (Conferences)
    Institutskolloquium des Fachgebiets technische Thermodynamik, 11.11.2021, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34040
Publ.-Id: 34040


11C-Methionine Uptake in the Lactating Human Breast

Michler, E.; Hilliger, S.; Kopka, K.; Kotzerke, J.

A 33-year-old nursing mother who underwent resection of a glioblastoma of the right hemisphere was referred for a 11C-methionine PET/MR scan to exclude cancer recurrence. In whole-body PETimaging, a slight radiotracer uptake could be observed in themammary glands, reflecting lactation status. In this case report, we initially describe 11C-methionine uptake in the human breast and discuss any consequences arising from this special situation.

Keywords: 11C-methionine; lactating breast; PET

Downloads:

  • Secondary publication expected from 01.01.2023

Permalink: https://www.hzdr.de/publications/Publ-34032
Publ.-Id: 34032


Extraordinary anisotropic magnetoresistance in CaMnO3/CaIrO3 heterostructures

Vagadia, M.; Sardar, S.; Tank, T.; Das, S.; Gunn, B.; Pandey, P.; Hübner, R.; Rodolakis, F.; Fabbris, G.; Choi, Y.; Haskel, D.; Frano, A.; Rana, D. S.

The realization of fourfold anisotropic magnetoresistance (AMR) in 3d-5d heterostructures has boosted major efforts in antiferromagnetic (AFM) spintronics. However, despite the potential of incorporating strong spinorbit coupling, only small AMR signals have been detected thus far, prompting a search for mechanisms to enhance the signal. In this paper, we demonstrate an extraordinarily elevated fourfold AMR of 70% realized in CaMnO3/CaIrO3 thin film superlattices.We find that the biaxial magnetic anisotropy and the spin-flop transition in a nearly Mott insulating phase form a potent combination, each contributing one order of magnitude to the total signal. Dynamics between these phenomena capture a subtle interaction of pseudospin coupling with the lattice and external magnetic field, an emergent phenomenon creating opportunities to harness its potential in AFM spintronics.

Permalink: https://www.hzdr.de/publications/Publ-34027
Publ.-Id: 34027


Initial observations of the femtosecond timing jitter at the European XFEL

Kirkwood, H. J.; Letrun, R.; Tanikawa, T.; Liu, J.; Nakatsutsumi, M.; Emons, M.; Jezynski, T.; Palmer, G.; Lederer, M.; Bean, R.; Buck, J.; Di Dio Cafiso, S. D.; Graceffa, R.; Grünert, J.; Göde, S.; Höppner, H.; Kim, Y.; Konopkova, Z.; Mills, G.; Makita, M.; Pelka, A.; Preston, T. R.; Sikorski, M.; Takem, C. M. S.; Giewekemeyer, K.; Chollet, M.; Vagovic, P.; Chapman, H. N.; Mancuso, A. P.; Sato, T.

Intense, ultrashort, and high-repetition-rate X-ray pulses, combined with a femtosecond optical laser, allow pump-probe experiments with fast data acquisition and femtosecond time resolution. However, the relative timing of the X-ray pulses and the optical laser pulses can be controlled only to a level of the intrinsic error of the instrument which, without characterization, limits the time resolution of experiments. This limitation inevitably calls for a precise determination of the relative arrival time, which can be used after measurement for sorting and tagging the experimental data to a much finer resolution than it can be controlled to. The observed root-mean-square timing jitter between the X-ray and the optical laser at the SPB/SFX instrument at European XFEL was 308\&\#x00A0;fs. This first measurement of timing jitter at the European XFEL provides an important step in realizing ultrafast experiments at this novel X-ray source. A method for determining the change in the complex refractive index of samples is also presented.

Keywords: Electric fields; Femtosecond lasers; Free electron lasers; Refractive index; X ray lasers

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34026
Publ.-Id: 34026


Incommensurate two-dimensional checkerboard charge density wave in the low-dimensional superconductor Ta4Pd3Te16

Zhenzhong, S.; Kuhn, S. J.; Flicker, F.; Helm, T.; Lee, J.; Steinhardt, W.; Dissanayake, S.; Graf, D.; Ruff, J.; Fabbris, G.; Haskel, D.; Haravifard, S.

We report the observation of a two-dimensional (2D) checkerboard charge density wave (CDW) in the low-dimensional superconductor Ta4Pd3Te16. By determining its CDW properties across the temperature-pressure (T−P) phase diagram and comparing with prototypical CDW materials, we conclude that Ta4Pd3Te16 features (a) an incommensurate CDW with a mixed character of dimensions [quasi-1D (Q1D) considering its needlelike shape along the b axis, Q2D as the CDW has checkerboard wave vectors, and 3D because of CDW projections along all three axes], and (b) one of the weakest CDWs compared to its superconductivity (SC), i.e., enhanced SC with respect to CDW, suggesting an interesting interplay of the two orders.

Permalink: https://www.hzdr.de/publications/Publ-34021
Publ.-Id: 34021


Relativistically transparent magnetic filaments: scaling laws, initial results and prospects for strong-field QED studies

Rinderknecht, H. G.; Wang, T.; Laso García, A.; Bruhaug, G.; Wei, M. S.; Quevedo, H. J.; Ditmire, T.; Williams, J.; Haid, A.; Doria, D.; Spohr, K. M.; Toncian, T.; Arefiev, A.

Relativistic transparency enables volumetric laser interaction with overdense plasmas and direct laser acceleration of electrons to relativistic velocities. The dense electron current generates a magnetic filament with field strength of the order of the laser amplitude (>10⁵ T). The magnetic filament traps the electrons radially, enabling efficient acceleration and conversion of laser energy into MeV photons by electron oscillations in the filament. The use of microstructured targets stabilizes the hosing instabilities associated with relativistically transparent interactions, resulting in robust and repeatable production of this phenomenon. Analytical scaling laws are derived to describe the radiated photon spectrum and energy from the magnetic filament phenomenon in terms of the laser intensity, focal radius, pulse duration, and the plasma density. These scaling laws are compared to 3D particle-in-cell (PIC) simulations, demonstrating agreement over two regimes of focal radius. Preliminary experiments to study this phenomenon at moderate intensity (a₀ ∼ 30) were performed on the Texas Petawatt Laser. Experimental signatures of the magnetic filament phenomenon are observed in the electron and photon spectra recorded in a subset of these experiments that is consistent with the experimental design, analytical scaling and 3D PIC simulations. Implications for future experimental campaigns are discussed.

Keywords: relativistic transparency; laser-plasma interactions; strong-field physics

Permalink: https://www.hzdr.de/publications/Publ-34020
Publ.-Id: 34020


Trajectory-dependent electronic excitations at keV ion energies

Lohmann, S.; Holeňák, R.; Primetzhofer, D.

We present experiments directly demonstrating the significance of charge-state dynamics in close collisions at ion velocities below the Bohr velocity resulting in a drastic trajectory dependence of the specific energy loss.
Experiments were performed with the time-of-flight medium energy ion scattering set-up at Uppsala University [1]. In our 3D-transmission approach [2], pulsed beams of singly charged ions are transmitted through self-supporting Si(100) nanomembranes and detected behind the sample. We record ion energy together with the angular distributions of deflected particles and can additionally insert a deflector to measure exit charge states [3].
We specifically studied the difference in energy loss between channelled (ΔEch) and random trajectories (ΔEr) for ions with masses ranging from 1 (protons) to 40 u (Ar+) as shown in Fig. 1 [4,5]. For protons, the observed effect can be explained with increasing contributions of core-electron excitations in close collisions only attainable in random geometry. For He and heavier ions we observe a reverse trend – a decrease of the ratio ΔEch/ ΔEr with decreasing ion velocity. Due to the inefficiency of core-electron excitations at these velocities, we explain this behaviour by contributions of collision-induced charge-exchange events along random trajectories. The resulting higher mean charge state leads to higher electronic stopping along random trajectories. For heavier ions, local losses due to electron promotion, also including several electrons, are expected to contribute strongly to the energy deposition in random geometry. By studying the trajectory dependence of the statistical distribution of electronic excitations (electronic energy straggling), we present evidence that for heavier ions, individual events with large energy transfer indeed significantly contribute to the energy loss. Finally, we show that our experimental approach leads to results that can serve to benchmark dynamic theories such as time-dependent density functional theory [5].

References
[1] M. A. Sortica et al., Nucl. Instrum. Methods Phys. Res. B 463 (2020) 16-20.
[2] R. Holeňák, S. Lohmann and D. Primetzhofer, Ultramicroscopy 217 (2020) 113051.
[3] R. Holeňák et al., Vacuum 185 (2021) 109988.
[4] S. Lohmann and D. Primetzhofer, Phys. Rev. Lett. 124 (2020) 096601.
[5] S. Lohmann, R. Holeňák and D. Primetzhofer, Phys. Rev. A 102 (2020) 062803.

  • Invited lecture (Conferences) (Online presentation)
    25th International Conference on Ion Beam Analysis & 17th International Conference on Particle Induce X-ray Emission & International Conference on Secondary Ion Mass Spectrometry, 11.-15.10.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-34019
Publ.-Id: 34019


Bioleaching of metals from mine waste by acidophilic consortium

Opara, C.

An acidophilic consortium leached over 70% of the total Zn, As, Co and Cd contents of a tailing and waste rock samples obtained from Neves Corvo mine, Portugal. Also, about 20 and 50 % of the total Cu and Mn contents of the sulfidic mine wastes were also leached by the consortium.

Keywords: bioleaching; tailing; waste rock; acidophilic consortium

  • Lecture (others) (Online presentation)
    SULTAN Network Wide Event 5, 17.-19.02.2021, Clausthal, Germany

Permalink: https://www.hzdr.de/publications/Publ-34018
Publ.-Id: 34018


Microwave-assisted bioleaching of metals from mine waste

Opara, C. B.

The bioleaching of metals (Pb, Ag and In) by marine sulfur-oxidising bacteria was improved after microwave roasting of a waste rock sample at 400 and/or 500°C. The bioleaching of Pb, Ag and In was increased from 20, 6 and 0 % (before microwave roasting) to 63, 37 and 27 % after microwave roasting.

Keywords: bioleaching; microwave roasting; marine sulfur-oxidising bacteria

  • Lecture (others)
    SULTAN Network Wide Event 6, 30.08.-03.09.2021, University of OULU, Finland

Permalink: https://www.hzdr.de/publications/Publ-34017
Publ.-Id: 34017


An Innovative Bioleaching Approach for the Extraction of Valuable and Hazardous Metals from Mining Waste

Opara, C. B.

The global demand for various metals has greatly increased over the past few years and this demand is envisaged to double over the next coming decades. The extractive waste residue (tailings) by the EU mining industries is a large waste stream and could constitute various environmental hazards such as acid mine drainage, especially when poorly managed. Reprocessing of these tailings could be a significant source of valuable metals and could alleviate environmental risks. This calls for a cost-effective metal mining technology with minimal damaging effect to the environment. We hereby propose the use of (halo)alkaliphilic and/or marine sulfur-oxidizing bacteria that live at neutral to alkaline conditions for the bioleaching of elements from these tailings. This will prevent the acidification of the environment, which is the case when bioleaching with acidophilic bacteria. In addition, this bioleaching approach which could be applicable in seawater is beneficial as fresh water could be saved.

Keywords: biomining; extractive waste residue; sulfur-oxidizing bacteria

  • Lecture (Conference) (Online presentation)
    10th International Symposium on Biomining (Biomining '21), 07.-10.06.2021, Falmouth, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-34015
Publ.-Id: 34015


An Innovative bioleaching Approach for the Extraction of Valuable and Hazardous Elements from Mining Waste

Opara, C.

The use of microorganisms and their products for the extraction of metals from low grade ores has proven overtime to be more economically viable than other extractive metallurgical processes such as pyrometallurgy. However, the most extensively studied microorganisms for bioleaching are the acidophilic Sulfur and/or Iron-oxidizing chemolithotrophs that are able to catalyze mineral dissolution at low pH. The use of acidophilic bacteria for bioleaching leads to the acidification of the environment as these activities are usually performed at pH ≤ 2. This could have a negative impact on the environment. We hereby propose the use of (halo)alkaliphilic and/or marine sulphur-oxidising microorganisms that live at less acidic, neutral or alkaline conditions for the bioleaching of metals from mining waste. This will prevent the acidification of the environment and save fresh water, as this bioleaching approach could be applicable in seawater. Bioleaching results with Thioclava electrotropha and Thioclava pacifica autotrophs seem promising, as up to 30% Co and 10% Cu, Pb, Zn, Cd, As, K and Mn were solubilised from a fresh waste rock sample. To optimize the bioleaching process, the interaction of these microorganisms with minerals will be studied. The tailing residues cleaned via this approach will be analyzed for subsequent valorization into various circular-economy applications such as inorganic polymers, green cements and ceramics.

Keywords: bioleaching; mine waste; sulfur-oxidizing bacteria

  • Open Access Logo Lecture (Conference) (Online presentation)
    8th International Conference on Microbial Communication for Young Scientists, 29.-31.03.2021, Jena, Germany

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34014
Publ.-Id: 34014


Exploiting Isospin Symmetry to Study the Role of Isomers in Stellar Environments

Hallam, S.; Lotay, G.; Gade, A.; Doherty, D. T.; Belarge, J.; Bender, P. C.; Brown, B. A.; Browne, J.; Catford, W. N.; Elman, B.; Estradé, A.; Hall, M. R.; Longfellow, B.; Lunderberg, E.; Montes, F.; Moukaddam, M.; O’Malley, P.; Ong, W.-J.; Schatz, H.; Seweryniak, D.; Schmidt, K.; Timofeyuk, N. K.; Weisshaar, D.; Zegers, R. G. T.

Proton capture on the excited isomeric state of 26Al strongly influences the abundance of 26Mg ejected in explosive astronomical events and, as such, plays a critical role in determining the initial content of radiogenic 26Al in presolar grains. This reaction also affects the temperature range for thermal equilibrium between the ground and isomeric levels. We present a novel technique, which exploits the isospin symmetry of the nuclear force, to address the long-standing challenge of determining proton-capture rates on excited nuclear levels. Such a technique has in-built tests that strongly support its veracity and, for the first time, we have experimentally constrained the strengths of resonances that dominate the astrophysical 26mAl(p,γ)27Si reaction. These constraints demonstrate that the rate is at least a factor ∼8 lower than previously expected, indicating an increase in the stellar production of 26Mg and a possible need to reinvestigate sensitivity studies involving the thermal equilibration of 26Al.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34013
Publ.-Id: 34013


SiPM readout for NeuLAND - status report 2021

Hensel, T.; Weinberger, D.; Bemmerer, D.; R3B, Collaboration

Statusreport SiPM readout for NeuLAND (saturation effects, dark rate and time resolution measurements)

Keywords: SiPM; NeuLAND; saturation

  • Lecture (Conference) (Online presentation)
    R3B Collaboration Meeting, 13.12.2021, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34012
Publ.-Id: 34012


Patentschrift DE 10 2020 120 788 B3 2021.12.09: MULTIPIXEL-PHOTODETEKTOR MIT AVALANCHE-PHOTODIODEN, STRAHLUNGSDETEKTOR UND POSITRONEN-EMISSIONS-TOMOGRAPH

Weinberger, D.

Ein Multipixel-Photodetektor weist elektrisch parallel geschaltete erste Avalanche-Photodioden mit jeweils einer Lichteintrittsfläche und elektrisch parallel geschaltete zweite Avalanche-Photodioden mit jeweils einer Lichteintrittsfläche auf. Die Lichteintrittsfläche jeder ersten Avalanche-Photodiode ist gleich oder größer einer Referenzfläche. Die Lichteintrittsfläche jeder zweiten Avalanche-Photodiode ist kleiner als die Referenzfläche. Die Lichteintrittsflächen der ersten und zweiten Avalanche-Photodioden bilden Teilflächen eines Belichtungsfeldes des Multipixel-Photodetektors.

Keywords: Multipixel-Photodetektor; Avalanche-Photodioden

  • Test
    (2021)09.12.2021

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34011
Publ.-Id: 34011


Magnetochiral effect of phonons

Zherlitsyn, S.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    II International Advanced Study Conference Condensed Matter & Low Temperature Physics 2021, 06.-12.06.2021, Kharkiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34010
Publ.-Id: 34010


Quantum Magnets from the perspective of Electron Spin Resonance Spectroscopy

Bhaskaran, L.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    Grete-Herrmann Network (GHN), 07.12.2021, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34009
Publ.-Id: 34009


Status of the Pulsed-Magnet Program at the Dresden High Field Magnetic Laboratory

Zherlitsyn, S.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    MT27, 27th International Conference on Magnet Technology, 15.-19.11.2021, Fukuoka, Japan

Permalink: https://www.hzdr.de/publications/Publ-34005
Publ.-Id: 34005


Dominance of gamma-gamma electron-positron pair creation in a plasma driven by high-intensity lasers

He, Y.; Blackburn, T.; Toncian, Toma; Arefiev, A.

Creation of electrons and positrons from light alone is a basic prediction of quantum electrodynamics, but yet to be observed. Our simulations show that the required conditions are achievable using a high-intensity two-beam laser facility and an advanced target design. Dual laser irradiation of a structured target produces high-density gamma rays that then create > 10(8) positrons at intensities of 2 x 10(22) Wcm(-2). The unique feature of this setup is that the pair creation is primarily driven by the linear Breit-Wheeler process (gamma gamma -> e(+)e(-)), which dominates over the nonlinear Breit-Wheeler and Bethe-Heitler processes. The favorable scaling with laser intensity of the linear process prompts reconsideration of its neglect in simulation studies and also permits positron jet formation at experimentally feasible intensities. Simulations show that the positrons, confined by a quasistatic plasma magnetic field, may be accelerated by the lasers to energies >200 MeV.

Keywords: PHOTON-EMISSION;PHYSICS;LIGHT;PARTICLE;SCOLLISION;CASCADES;FIELD

Permalink: https://www.hzdr.de/publications/Publ-34004
Publ.-Id: 34004


Magnetostriction measurements in Dresden high magnetic field lab

Miyata, A.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    FBG meeting, 22.02.2021, Tokyo, Japan

Permalink: https://www.hzdr.de/publications/Publ-34003
Publ.-Id: 34003


Pressure-tuned magnetic interactions in a triangular-lattice quantum antiferromagnet

Zvyagin, S.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    II International Advanced Study Conference "Condensed Matter and Low Temperature Physics 2021" (CM and LTP 2021), 06.-12.06.2021, Kharkov, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34001
Publ.-Id: 34001


Software engineering in scientific computing: spin-lattice simulations as an example

Pylypovskyi, O.; Tomilo, A.

Nanomagnets of complex geometrical shape and nanosized characteristic scales are hardly accessible via conventional solutions for numerical modelling. In the meantime, they are of high fundamental and applied interest, showing a novel interplay between geometry and magnetic sublattice. Recent advances in fabrication and characterization of curvilinear magnets hold an additional interest to them and force the further development of analytical and numerical tools to address such systems at the large scale. The latter include a flexible user interface to describe the concrete problem, and parallel computing to handle billions of degrees of freedom. Here, we will overview the present approaches to design spin-lattice and micromagnetic solvers based on the Landau-Lifshitz equation and discuss our experience in the software engineering of these tools.

Keywords: spin-lattice simulations; antiferromagnetism

  • Lecture (others) (Online presentation)
    Hardware & Numerics, 07.12.2021, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-33995
Publ.-Id: 33995


Noncollinear antiferromagnetic textures in confined geometries

Pylypovskyi, O.; Hedrich, N.; Wagner, K.; Tomilo, A.; Shields, B.; Kosub, T.; Sheka, D.; Faßbender, J.; Makarov, D.

In comparison with ferromagnetic domain walls and skyrmions, their coun-
terparts in antiferromagnets (AFMs) demonstrate appealing properties in
their control and dynamics, e.g., absence of Walker limit and Magnus force
[1]. The complex intrinsic magnetic structure of AFMs leads to special prop-
erties such as negligibly small stray fields, exchange-enhanced resonance
frequencies up to THz range, and the presence of staggered spin-orbit torques.
Together they render AFMs as prospective materials for spintronic and
spin-orbitronic applications [2]. Here, we consider bipartite, easy-axis AFM
samples of finite size. We derive the boundary conditions for the Neel order
parameter in the presence of Dzyaloshinskii-Moriya interactions (DMI) of
Bloch type in addition to exchange (see Fig. 1), and apply them to describe
domain walls and skyrmions. DMI leads to the deformation of the uniform
ground state at the side faces, with the twist angle proportional to the DMI
coefficient. Both domain walls and skyrmions become wider and change
their type to the mixed Bloch-Neel one when approaching the top (bottom)
surface of the sample. The characteristic depth where the influence of the
boundary on magnetic texture is significant is about 5 magnetic lengths [3].
In the absence of the intrinsic DMI, the exchange-driven boundary conditions
determine the behavior of domain walls in AFMs with a patterned surface.
Imaging the domain wall in a single crystal Cr 2O3 using nitrogen vacancy
(NV) magnetometry, we show that it mimics the behavior of an elastic
ribbon deformed by the effective pinning sites created by mesas. Crossing
the mesa at an angle, the domain wall shape experiences an additional bend, determined by the aspect ratio of the mesa A=t/w with t and w being
its thickness and width, see Fig. 2. This deformation can be described by the
effective Snell’s law as sin θi/sin θr ≈ 1 + 3.1 A with θi and θr being incidence
and refraction angles at the top surface [4].
[1] O. Gomonay, V. Baltz, A. Brataas et al. Nat. Phys. Vol. 14, P. 213
(2018). [2] V. Baltz, A. Manchon, M. Tsoi etal. Rev. Mod. Phys. Vol. 90, P.
015005 (2018), H. Yan, Z. Feng, P. Qin etal. Avd. Mat. Vol. 32, P. 1905603
(2020). [3] O. V. Pylypovskyi, A. V. Tomilo, D. D. Sheka et al. Phys. Rev.
B, Vol. 103, P. 134413 (2021) [4] N. Hedrich, K. Wagner, O. V. Pyly-
povskyi et al. Nat. Phys. Vol. 17, P. 574 (2021)

Keywords: antiferromagnetism

  • Lecture (Conference) (Online presentation)
    MMM Intermag 2022, 10.01.2022, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-33994
Publ.-Id: 33994


Influence of Boundaries and Geometrical Curvatures on Antiferromagnetic Textures

Pylypovskyi, O.; Tomilo, A.; Borysenko, Y.; Faßbender, J.; Sheka, D.; Makarov, D.

A complex structure of magnetic subsystem in antiferromagnets (AFMs) determines challenges and technological perspectives for both, fundamental
research and their applications for spintronic and spin-orbitronic devices [1]. In this respect, properties of the confined samples are of key interest because
of the possibility to tune magnetic responses via effects of boundary and geometrical curvature [2]. Here, we consider textures in (i) AFM slabs with the
Dzyaloshniskii-Morya interaction (DMI) of bulk symmetry [3] and (ii) the intrinsically achiral curvilinear spin chains arranged along space curves [4].
We derive a transition from spin lattice of G-type AFM to the sigma-model with the respective boundary conditions for the AFM order parameter [3]. The
DMI influences a texture via boundary conditions modifying the ground state, domain wall shape and skyrmion profiles. Approaching the boundary in the
slab with easy-axis anisotropy, the domain wall becomes broader and of mixed Bloch-Neel type near the top surface. Near the edges of the sample, the
domain wall plane possesses and additional twist. Note, that the edge twists appear in achiral AFMs as well if the domain wall plane lies at an angle to the
side faces [5]. Similarly, skyrmions of any radius become of the Bloch-Neel type approaching the top/bottom surfaces of the sample. The radius of narrow
skyrmions changes up to 10% due to the boundary effects.
AFM spin chains arranged along space curves can model the simplest curvilinear nanoarchitectures. Their geometry is described by the curvature and
torsion, determining local bends and twists of the curve. The geometry-driven anisotropy and inhomogeneous DMI render them as chiral helimagnets [6].
In addition, the exchange interaction generates the weakly ferromagnetic response, scaling linearly with curvature and torsion. The inter- and single-ion
anisotropies in curvilinear AFM chains lead to the additional anisotropic contributions, scaling with curvature. The single-ion anisotropy leads to the
homogeneous DMI mixing normal and tangential components of ferro- and antiferromagnetic vector order parameters. Both anisotropy models contribute
to the additional easy axes, which determine the direction of the order parameters in spin-flop phase [4].
[1] V. Baltz et al, Rev. Mod. Phys. 90, 015005 (2018); A. Manchon et al, Rev. Mod. Phys. 91, 035004 (2019)
[2] P. Fischer et al, APL Mat. 8, 010701 (2020); R. Streubel et al, J. Appl. Phys. 129, 210902 (2021); D. D. Sheka, Appl. Phys. Lett. 118, 230502 (2021)
[3] O. V. Pylypovskyi et al, Phys. Rev. B 103, 134413 (2021)
[4] O. V. Pylypovskyi et al, Appl. Phys. Lett. 118, 182405 (2021)
[5] N. Hedrich et al, Nat. Phys. 17, 574 (2021)
[6] O. V. Pylypovskyi, D. Y. Kononenko et al, Nano Lett. 20, 8157 (2020)

Keywords: antiferromagnetism

  • Lecture (Conference) (Online presentation)
    2021 MRS Fall Meeting November 29--December 8, 2021, 07.12.2021, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-33993
Publ.-Id: 33993


Nematic versus ferromagnetic shells: new insights in curvature-induced effects

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

We draw a parallel between ferromagnetic materials and nematic liquid crystals
confined on curved surfaces, which are both characterized by local interaction and
anchoring potentials. We show that the extrinsic curvature of the shell combined with
the out-of-plane component of the director field gives rise to chirality effects. This
interplay produces an effective energy term reminiscent of the chiral term in
cholesteric liquid crystals, with the curvature tensor acting as a sort of anisotropic
helicity. We discuss also how the different nature of the order parameter, a vector in
ferromagnets and a tensor in nematics, yields different textures on surfaces with
the same topology as the sphere.

Keywords: nematics; curvilinear shells

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications. 717. WE-Heraeus-Seminar, 24.06.2021, On-line, Germany

Permalink: https://www.hzdr.de/publications/Publ-33992
Publ.-Id: 33992


Micromagnetic Description of Symmetry-Breaking Effects in Curvilinear Ferromagnetic Shells

Sheka, D.; Pylypovskyi, O.; Landeros, P.; Kakay, A.; Makarov, D.

The behaviour of any physical system is governed by the order parameter,
determined by the geometry of the physical space of the object, namely their
dimensionality and curvature. Usually, the effects of curvature are described
using local interactions only, e.g. local spin-orbit- or curvature-induced
Rashba and Dzyaloshinskii-Moriya interactions (DMI). In the specific case
of ferromagnetism, until recently, there was no analytical framework, which
was treating curvature effects stemming from local [1] and non-local [2]
interactions on the same footing. The lack of a proper theoretical foundation
impedes the description of essential micromagnetic textures like magnetic
domains, skyrmion-bubbles and vortices. Here, we present a micromag-
netic theory of curvilinear ferromagnetic shells, which allows to describe the
geometry-driven effects stemming from exchange and magnetostatics within
the same framework [3]. A general description of magnetic curvilinear shells
can be done using tangential derivatives of the unit magnetization vector.
Tangential derivatives are represented by the covariant derivatives of in-
surface components and the regular derivative of the normal magnetiza-
tion component, normalized by the square root of the corresponding metric
tensor coefficient. This allows to separate the explicit effects of curvature
and spurious effects of the reference frame. The shape of a given thin shell
can be determined by two principal curvatures k1 and k2, which are functions
of coordinate. The respective classification of curvilinear surfaces operates
with (i) developable surfaces, where one of the principal curvatures equals
to zero; (ii) minimal ones, where the mean curvature k1 + k2 = 0; and (iii)
the general case. The local geometry-driven energy contributions are repre-
sented by the DMI and anisotropy, whose coefficients are determined by
powers of the principal curvatures. This allows to cancel the influence of one
of the DMI terms for the developable surfaces for any magnetic texture. The
magnetostatic interaction is a source of new chiral effects, which are essen-
tially non-local in contrast to the conventional DMI. The physical origin is
the non-zero mean curvature of a shell and the non-equivalence between the
top and bottom surfaces of the shell. We demonstrate that the analysis of
non-local effects in curvilinear thin shells can become more straightforward
when introducing three magnetostatic charges. In this respect, in contrast
to the classical approach by Brown [4], we split a conventional volume
magnetostatic charge into two terms: (i) magnetostatic charge, governed by
the tangent to the sample’s surface, and (ii) geometrical charge, given by the
normal component of magnetization and the mean curvature. In addition to
the shape anisotropy (local effect), there appear four additional non-local
terms, determined by the surface curvature. Three of them are zero for any
magnetic texture in shells with the geometry of minimal surfaces. The fourth
term is determined by the non-equivalence of the top and bottom surfaces
of the shell and becomes zero only for the special symmetries of magnetic
textures. The discovered non-local magnetochiral effects introduce hand-
edness in an intrinsically achiral material and enables the design of magne-
to-electric and ferro-toroidic responses. This will stimulate to rethink the
origin of chiral effects in different systems, e.g. in fundamentally appealing
and technologically relevant skyrmionic systems, and further theoretical
investigations in the field of curvilinear magnetism as well as experimental
validation of these theoretical predictions. These developments will pave the
way towards new device ideas relying on curvature effects in magnetic nano-
structures. The impact of effects predicted in this work goes well beyond
the magnetism community. Our description of the vector field behaviour
can be applied to different emergent field of studies of curvature effects.
The prospective applications include curved superconductors [5], twisted
graphene bilayers [6], flexible ferroelectrics [7], curved liquid crystals [8].

[1] Yu. Gaididei, V. P. Kravchuk, D. D. Sheka, Phys. Rev. Lett., 112,
257203 (2014); D. D. Sheka, V. P. Kravchuk, Yu. Gaididei, J. Phys. A:
Math. Theor., 48, 125202 (2015); O. V. Pylypovskyi, V. P. Kravchuk,
D. D. Sheka et al, Phys. Rev. Lett., 114, 197204 (2015); V. P. Kravchuk,
D. D. Sheka, A. Kakay et al, Phys. Rev. Lett., 120, 067201 (2018) [2] P.
Landeros, A. S. Nunez, J. Appl. Phys. Vol. 108, p. 033917 (2010); J. A.
Otalora, M. Yan, H. Schultheiss et al, Phys. Rev. Lett., 117, 227203 (2016);
J. A. Otalora, M. Yan, H. Schultheiss et al, Phys. Rev. B, 95, 184415 (2017)
[3] D. D. Sheka, O. V. Pylypovskyi, P. Landeros et al., Comm. Phys. 3, 128
(2020) [4] W. F. Brown Jr. Micromagnetics (Wiley, New York, 1963) [5]
V. Vitelly, A. M. Turner, Phys. Rev. Lett., 93, 215301 (2004) [6] W. Yan,
W.-Y. He, Z.-D. Chu et al, Nat. Comm., 4, 2159 (2013) [7] M. Owczarek, K.
A. Hujsak, D. P. Ferris et al, Nat. Comm., 7, 13108 (2016) [8] G. Napoli, L.
Vergori, Phys. Rev. Lett., 108, 207803 (2012)

Keywords: curvilinear magnetism; micromagnetism

  • Lecture (Conference) (Online presentation)
    IEEE International Magnetics Virtual Conference INTERMAG21, 30.04.2021, On-line, On-line

Permalink: https://www.hzdr.de/publications/Publ-33991
Publ.-Id: 33991


Genesis of sulphide vein mineralization at the Sakkatti Ni-Cu-PGE deposit, Finland

Fröhlich, F.; Siikaluoma, J.; Osbahr, I.; Gutzmer, J.

The Sakatti Ni-Cu-platinum-group element deposit is situated in northern Finland and comprises massive, disseminated, and
vein sulfide mineralization. A stockwork is formed by chalcopyrite-rich sulfide veins, which contain exceptionally high
platinum-group elements and Au grades. The mineralogy and geochemistry of this stockwork zone ore is documented in this
investigation. The results are used to develop the first robust genetic concept and its relationship to massive and
disseminated mineralization of the Sakatti deposit. This model is similar to that proposed for many Cu-rich magmatic sulfide
ores, most importantly the Cu-rich footwall veins described from the Sudbury Complex in Canada and the Cu-rich ore at
Noril’sk-Talnakh in Russia. Detailed petrographic studies using a sample suite from exploration drill core intersecting veinstyle
mineralization revealed a classic magmatic sulfide assemblage of chalcopyrite 6 pyrrhotite, pentlandite, and pyrite.
More than 1000 platinum-group mineral grains belonging almost exclusively to the moncheite (PtTe2) – merenskyite (PdTe2)
– melonite (NiTe2) solid solution series were identified in the studied samples. Notably, almost two thirds of the platinumgroup
element-bearing minerals consist of melonite. Some of the platinum-group minerals contain inclusions of Ag-rich gold
(AgAu2) and muthmannite (AuAgTe2). Most of the platinum-group minerals occur as inclusions in chalcopyrite, although a
few grains are located at base-metal sulfide grain boundaries and in fractures in base-metal sulfides. The whole-rock
compositions of the stockwork veins are Cu-rich and are interpreted to represent a fractionated Cu-rich sulfide liquid
enriched in Pt, Pd, Au, Ag, As, Bi, Pb, Se, Te, Zn, which separated from a monosulfide solid solution (mss). An intermediate
solid solution (iss) solidified from the Cu-rich sulfide liquid, recrystallizing chalcopyrite at,550 8C. Simultaneously, small
volumes of intercumulus residual melt contained mainly the precious metals, Bi, and Te due to their incompatibility in iss.
Solitary and composite platinum-group minerals as well as Au-minerals crystallized first from the residual melt (,600 8C),
followed by a succession of various Bi-, Ag-, and Pb-tellurides (~540 8C), and finally sphalerite and galena. Melonite
crystallized as mostly large, solitary grains exsolved directly from Ni-bearing intermediate solid solution (~600 C), shortly
after the formation of moncheite and merenskyite from the residual melt. Finally, remobilization of the platinum-group
minerals occurred at temperatures of,300 C, as suggested by the presence of minor amounts of Cl-bearing minerals and
ragged grain shapes. © 2021 Mineralogical Association of Canada. All rights reserved.

Keywords: Geochemistry; Mineral Liberation Analysis; Ni-Cu-PGE deposits; PGM; Sakatti

Permalink: https://www.hzdr.de/publications/Publ-33986
Publ.-Id: 33986


Second harmonic generation exploiting ultra-stable resistive switching devices for secure hardware systems

Chen, Z.; Du, N.; Kiani, M.; Zhao, X.; Skorupa, I.; Schulz, S.; Bürger, D.; Di Ventra, M.; Polian, I.; Schmidt, H.

In the era of big data and internet of things (IoT), information security has emerged as an essential system and application metric. The information exchange among the ubiquitously connected smart electronic devices requires functioning reliably in harsh environments, which highlights the need for securing the hardware root of trust. In this work, by leveraging the uniform nonlinear resistive switching of emerging electroforming-free analog memristive device based on BiFeO3 (BFO) thin film, the security-oriented hardware primitive (SoHP) system is developed and optimized with high-security level. The SoHP system utilizes the distinguishable power conversion efficiency generated at second and higher harmonics in low resistance state (memristor with diodelike behavior) and high resistance state (memristor with high resistive behavior) of memristive devices. By exploring the significant influence of writing bias and operational frequency in sourcing input voltage on the dynamic switching behavior of memristive device, the novel 2-memristor encoding scheme and 1-memristor decoding scheme are developed for SoHP system, which realizes a frequency enhancement of 4000 times in comparison to 1-memristor encoding scheme and 2-memristor decoding scheme. The encoded data bits that generated from physically implemented SoHP system pass diverse statistical test suites (i.e. ENT, BSI, and NIST SP-800.22 statistical test suites), which indicates the high randomness distribution of the encoded data and the high-security level of the proposed memristive encoding system.

Keywords: Electrodes; Hardware; hardware security; Harmonic analysis; Memristors; power conversion efficiency; second harmonic generation; Switches; ultra-stable resistive switching; Voltage; Writing

Permalink: https://www.hzdr.de/publications/Publ-33983
Publ.-Id: 33983


20 kW Pilot scale steam‑oxygen gasification of solid recovered fuel with a focus on newly developed off-line and on-line tar measurement methods

Chen, Y.-H.; Parvez, A. M.; Schmid, M.; Scheffknecht, G.; Chen, T.-L.

The steam‑oxygen gasification process of solid recovered fuel (SRF) was proved as a promising approach for energy and resource sustainability through a comprehensive product analysis. A high content of syngas was produced and suitable for the downstream chemical synthesis and hydrogen energy source. However, tar is a significant hazardous mixture from waste gasification, resulting in low gasification performance and releasing toxic containments. Tar monitoring is thus important. To improve existing tar measurement methods, a flexible tar sampling system (FTSS) and a novel gas chromatography (GC) were developed for off-line and on-line tar monitoring in the pilot-scale gasification process. FTSS is an improvement compared to the standard tar sampling system (STSS) regarding robustness, operation time, and handling. It showed a consistent tar capture performance with STSS. On the other hand, the on-line GC realized real-time tar qualification and quantification. For the gasification at 850 °C, loads of benzene, toluene, and xylene examined by the on-line GC (18.7 g/m3) were highly correspondent to the result from the off-line GC (17.8 g/m3). The carbon fractions of total hydrocarbon tar were also evaluated by the on-line GC with 68 and 25 gC/m3 at the gasification temperatures of 650 and 850 °C, respectively.

Keywords: New tar measurement methods; Solid recovered fuels; Steam‑oxygen gasification; Hydrogen-rich syngas

Permalink: https://www.hzdr.de/publications/Publ-33982
Publ.-Id: 33982


Targeting PARP for Chemoradiosensitization: Opportunities, Challenges, and the Road Ahead

Willers, H. A.; Krause, M.; Faivre-Finn, C. C.; Chalmers, A. J.

In many patients with cancer, the dose of radiation therapy (RT) that can be safely administered is insufficient to achieve high rates of local tumor control and cure. In others, damage to normal tissues is a concern even at moderate doses. In these settings, RT, or chemoradiation therapy (CRT), ideally would be combined with novel targeted drugs that can enhance the tumoricidal effects of standard therapy but without significantly increased normal tissue toxicity.
Over the past decade, major advances in precision medicine have supplied the field of radiation oncology with countless opportunities to enhance the antitumor effects of CRT. However, a large body of preclinical research and clinical investigations on molecular targeted drugs has not yet translated into any meaningful number of combinations of RT or CRT with targeted radiosensitizers that are approved by the US Food and Drug Administration.3 In fact, to date the epidermal growth factors receptor-directed monoclonal antibody cetuximab remains the only targeted agent approved by the Food and Drug Administration for concurrent administration with RT in head and neck (H&N) cancers. There are considerable challenges to clinical translation of combining targeted drugs with CRT or RT that the field has only recently begun to fully appreciate.

Permalink: https://www.hzdr.de/publications/Publ-33981
Publ.-Id: 33981


Screening and Validation of Molecular Targeted Radiosensitizers

Willers, H.; Pan, X.; Borgeaud, N.; Korovina, I.; Koi, L.; Egan, R.; Greninger, P.; Rosenkranz, A.; Kung, J.; Liss, A. S.; Parsels, L. A.; Morgan, M. A.; Lawrence, T. S.; Lin, S. H.; Hong, T. S.; Yeap, B. Y.; Wirth, L. J.; Hata, A. N.; Ott, C. J.; Benes, C. H.; Baumann, M.; Krause, M.

The development of molecular targeted drugs with radiation and chemotherapy is critically important for improving the outcomes of patients with hard-to-treat, potentially curable cancers. However, too many preclinical studies have not translated into successful radiation oncology trials. Major contributing factors to this insufficiency include poor reproducibility of preclinical data, inadequate preclinical modeling of intertumoral genomic heterogeneity that influences treatment sensitivity in the clinic, and a reliance on tumor growth delay instead of local control (TCD50) endpoints. There exists an urgent need to overcome these barriers to facilitate successful clinical translation of targeted radiosensitizers. To this end, we have used 3-dimensional (3D) cell culture assays to better model tumor behavior in vivo. Examples of successful prediction of in vivo effects with these 3D assays include radiosensitization of head and neck cancers by inhibiting epidermal growth factor receptor or focal adhesion kinase signaling, and radioresistance associated with oncogenic mutation of KRAS. To address the issue of tumor heterogeneity, we leveraged institutional resources that allow high-throughput 3D screening of radiation combinations with small-molecule inhibitors across genomically characterized cell lines from lung, head and neck, and pancreatic cancers. This high-throughput screen is expected to uncover genomic biomarkers that will inform the successful clinical translation of targeted agents from the National Cancer Institute Cancer Therapy Evaluation Program portfolio and other sources. Screening "hits" need to be subjected to refinement studies that include clonogenic assays, addition of disease-specific chemotherapeutics, target/biomarker validation, and integration of patient-derived tumor models. The chemoradiosensitizing activities of the most promising drugs should be confirmed in TCD50 assays in xenograft models with or without relevant biomarker and using clinically relevant radiation fractionation. We predict that appropriately validated and biomarker-directed targeted therapies will have a higher likelihood than past efforts of being successfully incorporated into the standard management of hard-to-treat tumors.

Permalink: https://www.hzdr.de/publications/Publ-33980
Publ.-Id: 33980


Recurrent HNSCC Harbor an Immunosuppressive Tumor Immune Microenvironment Suggesting Successful Tumor Immune Evasion

Watermann, C.; Pasternack, H.; Idel, C.; Ribbat-Idel, J.; Brägelmann, J.; Kuppler, P.; Offermann, A.; Jonigk, D.; Philipp Kühnel, M.; Schröck, A.; Dreyer, E.; Rosero, C.; Nathansen, J.; Dubrovska, A.; Tharun, L.; Kirfel, J.; Wollenberg, B.; Perner, S.; Krupar, R.

Purpose: Recurrent tumors (RT) of head and neck squamous cell carcinoma (HNSCC) occur in up to 60%, with poor therapeutic response and detrimental prognosis. We hypothesized that HNSCC RTs successfully evade antitumor immune response and aimed to reveal tumor immune microenvironment (TIME) changes of primary tumors (PT) and corresponding RTs.

Experimental Design: Tumor-infiltrating leukocytes (TIL) of 300 PTs and 108 RTs from two large independent and clinically well-characterized HNSCC cohorts [discovery cohort (DC), validation cohort (VD)] were compared by IHC. mRNA expression analysis of 730 immune-related genes was performed for 18 PTs and RTs after adjuvant chemoradiotherapy (CRT). The effect of chemotherapy and radiation resistance was assessed with an in vitro spheroid/immunocyte coculture model.

Results: TIME analysis revealed overall decrease of TILs with significant loss of CD8+ T cells (DC P = 0.045/VC P < 0.0001) and B lymphocytes (DC P = 0.036/VC P < 0.0001) in RTs compared with PTs in both cohorts. Decrease predominantly occurred in RTs after CRT. Gene expression analysis confirmed loss of TILs (P = 0.0004) and B lymphocytes (P < 0.0001) and showed relative increase of neutrophils (P = 0.018), macrophages (P < 0.0001), dendritic cells (P = 0.0002), and mast cells (P = 0.0057) as well as lower overall expression of immune-related genes (P = 0.018) in RTs after CRT. Genes involved in B-lymphocyte functions and number of tertiary lymphoid structures showed the strongest decrease. SPP1 and MAPK1 were upregulated in vivo and in vitro, indicating their potential suitability as therapeutic targets in CRT resistance.

Conclusions: HNSCC RTs have an immunosuppressive TIME, which is particularly apparent after adjuvant CRT and might substantially contribute to poor therapeutic response and prognosis.

Permalink: https://www.hzdr.de/publications/Publ-33979
Publ.-Id: 33979


Tumor DNA-methylome derived epigenetic fingerprint identifies HPV-negative head and neck patients at risk for locoregional recurrence after postoperative radiochemotherapy

Tawk, B.; Wirkner, U.; Schwager, C.; Rein, K.; Zaoui, K.; Federspil, P. A.; Adeberg, S.; Linge, A.; Ganswindt, U.; Hess, J.; Unger, K.; Tinhofer, I.; Budach, V.; Lohaus, F.; Krause, M.; Guberina, M.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A. L.; Schäfer, H.; Zips, D.; Combs, S. E.; Pigorsch, S.; Zitzelsberger, H.; Baumeister, P.; Kirchner, T.; Bewerunge-Hudler, M.; Weichert, W.; Hess, J.; Herpel, E.; Belka, C.; Baumann, M.; Debus, J.; Abdollahi, A.; DKTK-ROG

Biomarkers with relevance for loco-regional therapy are needed in human papillomavirus negative aka HPV(-) head and neck squamous cell carcinoma (HNSCC). Based on the premise that DNA methylation pattern is highly conserved, we sought to develop a reliable and robust methylome-based classifier identifying HPV(-) HNSCC patients at risk for loco-regional recurrence (LR) and all-event progression after postoperative radiochemotherapy (PORT-C). The training cohort consisted of HPV-DNA negative HNSCC patients (n = 128) homogeneously treated with PORT-C in frame of the German Cancer Consortium-Radiation Oncology Group (DKTK-ROG) multicenter biomarker trial. DNA Methylation analysis was performed using Illumina 450 K and 850 K-EPIC microarray technology. The performance of the classifier was integrated with a series of biomarkers studied in the training set namely hypoxia-, 5-microRNA (5-miR), stem-cell gene-expression signatures and immunohistochemistry (IHC)-based immunological characterization of tumors (CD3/CD8/PD-L1/PD1). Validation occurred in an independent cohort of HPV(-) HNSCC patients, pooled from two German centers (n = 125). We identified a 38-methylation probe-based HPV(-) Independent Classifier of disease Recurrence (HICR) with high prognostic value for LR, distant metastasis and overall survival (P < 10-9 ). HICR remained significant after multivariate analysis adjusting for anatomical site, lymph node extracapsular extension (ECE) and size (T-stage). HICR high-risk tumors were enriched for younger patients with hypoxic tumors (15-gene signature) and elevated 5-miR score. After adjustment for hypoxia and 5-miR covariates, HICR maintained predicting all endpoints. HICR provides a novel mean for assessing the risk of LR in HPV(-) HNSCC patients treated with PORT-C and opens a new opportunity for biomarker-assisted stratification and therapy adaptation in these patients.

Keywords: DNA methylation; disease recurrence; head and neck cancers; radiotherapy; stratification

  • Open Access Logo International Journal of Cancer 150(2022), 603-616
    Online First (2021) DOI: 10.1002/ijc.33842

Permalink: https://www.hzdr.de/publications/Publ-33978
Publ.-Id: 33978


Comparison of the composition of lymphocyte subpopulations in non-relapse and relapse patients with squamous cell carcinoma of the head and neck before, during radiochemotherapy and in the follow-up period: a multicenter prospective study of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG)

Niu, M.; E. Combs, S.; Linge, A.; Krause, M.; Baumann, M.; Lohaus, F.; Ebert, N.; Tinhofer, I.; Budach, V.; von der Grün, J.; Rödel, F.; Grosu, A.-L.; Multhoff, G.

Background
Radiochemotherapy (RCT) has been shown to induce changes in immune cell homeostasis which might affect antitumor immune responses. In the present study, we aimed to compare the composition and kinetics of major lymphocyte subsets in the periphery of patients with non-locoregional recurrent (n = 23) and locoregional recurrent (n = 9) squamous cell carcinoma of the head and neck (SCCHN) upon primary RCT.
Methods
EDTA-blood of non-locoregional recurrent SCCHN patients was collected before (t0), after application of 20–30 Gy (t1), in the follow-up period 3 (t2) and 6 months (t3) after RCT. In patients with locoregional recurrence blood samples were taken at t0, t1, t2 and at the time of recurrence (t5). EDTA-blood of age-related, healthy volunteers (n = 22) served as a control (Ctrl). Major lymphocyte subpopulations were phenotyped by multiparameter flow cytometry.
Results
Patients with non-recurrent SCCHN had significantly lower proportions of CD19+ B cells compared to healthy individuals before start of any therapy (t0) that dropped further until 3 months after RCT (t2), but reached initial levels 6 months after RCT (t3). The proportion of CD3+ T and CD3+/CD4+ T helper cells continuously decreased between t0 and t3, whereas that of CD8+ cytotoxic T cells and CD3+/CD56+ NK-like T cells (NKT) gradually increased in the same period of time in non-recurrent patients. The percentage of CD4+/CD25+/FoxP3+ regulatory T cells (Tregs) decreased directly after RCT, but increased above initial levels in the follow-up period 3 (t2) and 6 (t3) months after RCT. Patients with locoregional recurrence showed similar trends with respect to B, T cells and Tregs between t0 and t5. CD4+ T helper cells remained stably low between t0 and t5 in patients with locoregional recurrence compared to Ctrl. NKT/NK cell subsets (CD56+/CD69+, CD3−/CD56+, CD3−/CD94+, CD3−/NKG2D+, CD3−/NKp30+, CD3−/NKp46+) increased continuously up to 6 months after RCT (t0-t3) in patients without locoregional recurrence, whereas in patients with locoregional recurrence, these subsets remained stably low until time of recurrence (t5).
Conclusion
Monitoring the kinetics of lymphocyte subpopulations especially activatory NK cells before and after RCT might provide a clue with respect to the development of an early locoregional recurrence in patients with SCCHN. However, studies with larger patient cohorts are needed.

Keywords: SCCHN; Prediction of locoregional recurrence; Immunophenotyping; Radiochemotherapy; Lymphocyte subpopulations; NK cell subsets

Permalink: https://www.hzdr.de/publications/Publ-33977
Publ.-Id: 33977


Correction to: Value of PET imaging for radiation therapy

Lapa, C.; Nestle, U.; Albert, N. L.; Baues, C.; Beer, A.; Buck, A.; Budach, V.; Bütof, R.; Combs, S. E.; Derlin, T.; Eiber, M.; Fendler, W. P.; Furth, C.; Gani, C.; Gkika, E.; Grosu, A.-L.; Henkenberens, C.; Ilhan, H.; Löck, S.; Marnitz-Schulze, S.; Miederer, M.; Mix, M.; Nicolay, N. H.; Niyazi, M.; Pöttgen, C.; Todica, A. S.; Weber, W.; Wegen, S.; Wiegel, T.; Zamboglou, C.; Zips, D.; Zöphel, K.; Zschaeck, S.; Thorwarth, D.; Troost, E. G. C.

Correction to:
Strahlenther Onkol 2021
https://doi.org/10.1007/s00066-021-01812-2

Permalink: https://www.hzdr.de/publications/Publ-33975
Publ.-Id: 33975


Value of PET imaging for radiation therapy

Lapa, C.; Nestle, U.; Albert, N. L.; Baues, C.; Beer, A.; Buck, A.; Budach, V.; Bütof, R.; Combs, S. E.; Derlin, T.; Eiber, M.; Fendler, W. P.; Furth, C.; Gani, C.; Gkika, E.; Grosu, A.-L.; Henkenberens, C.; Ilhan, H.; Löck, S.; Marnitz-Schulze, S.; Miederer, M.; Mix, M.; Nicolay, N. H.; Niyazi, M.; Pöttgen, C.; Rödel, C. M.; Schatka, I.; Schwarzenboeck, S. M.; Todica, A. S.; Weber, W.; Wegen, S.; Wiegel, T.; Zamboglou, C.; Zips, D.; Zöphel, K.; Zschaeck, S.; Thorwarth, D.; Troost, E. G. C.

his comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Keywords: PET; Radiation oncology; Functional imaging; Radiomics

Permalink: https://www.hzdr.de/publications/Publ-33973
Publ.-Id: 33973


Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

Klionsky, D. J.; Cordes, N.; Dubrovska, A.; Tong, C.-K.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct auto-phagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Keywords: Autophagosome; cancer; flux; LC3; lysosome; macroautophagy; neurodegeneration; phagophore; stress; vacuole

Permalink: https://www.hzdr.de/publications/Publ-33971
Publ.-Id: 33971


ERCC2 gene single-nucleotide polymorphism as a prognostic factor for locally advanced head and neck carcinomas after definitive cisplatin-based radiochemotherapy

Guberina, M.; Sak, A.; Pöttgen, C.; Tinhofer-Keilholz, I.; Budach, V.; Balermpas, P.; von der Grün, J.; Michael Rödel, C.; Gkika, E.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Belka, C.; Pigorsch, S.; E. Combs, S.; Mönnich, D.; Zips, D.; De-Colle, C.; Welz, S.; Linge, A.; Lohaus, F.; Baretton, G.; Gauler, T.; Baumann, M.; Krause, M.; Schuler, M.; Bankfalvi, A.; Höing, B.; Lang, S.; Stuschke, M.

Identifying patients with locally advanced head and neck carcinoma on high risk of recurrence after definitive concurrent radiochemotherapy is of key importance for the selection for consolidation therapy and for individualized treatment intensification. In this multicenter study we analyzed recurrence-associated single-nucleotide polymorphisms (SNPs) in DNA repair genes in tumor DNA from 132 patients with locally advanced head and neck carcinoma (LadHnSCC). Patients were treated with definitive radiotherapy and simultaneous cisplatin-based chemotherapy at six partner sites of the German Cancer Consortium (DKTK) Radiation Oncology Group from 2005 to 2011. For validation, a group of 20 patients was available. Score selection method using proportional hazard analysis and leave-one-out cross-validation were performed to identify markers associated with outcome. The SNPs rs1799793 and rs13181 were associated with survival and the same SNPs and in addition rs17655 with freedom from loco-regional relapse (ffLRR) in the trainings datasets from all patients. The homozygote major rs1799793 genotype at the ERCC2 gene was associated with better (Hazard ratio (HR): 0.418 (0.234-0.744), p = 0.003) and the homozygote minor rs13181 genotype at ERCC2 with worse survival (HR: 2.074, 95% CI (1.177-3.658), p = 0.017) in comparison to the other genotypes. At the ffLRR endpoint, rs1799793 and rs13181 had comparable prognostic value. The rs1799793 and rs13181 genotypes passed the leave-one-out cross-validation procedure and associated with survival and ffLRR in patients with LadHnSCC treated with definitive radiochemotherapy. While findings were confirmed in a small validation dataset, further validation is underway within a prospective biomarker study of the DKTK.

Keywords: Cancer genetics; Prognostic markers

Permalink: https://www.hzdr.de/publications/Publ-33969
Publ.-Id: 33969


Correction: ERCC2 gene single-nucleotide polymorphism as a prognostic factor for locally advanced head and neck carcinomas after definitive cisplatin-based radiochemotherapy

Guberina, M.; Sak, A.; Pöttgen, C.; Tinhofer-Keilholz, I.; Budach, V.; Balermpas, P.; von der Grün, J.; Michael Rödel, C.; Gkika, E.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Belka, C.; Pigorsch, S.; E. Combs, S.; Mönnich, D.; Zips, D.; De-Colle, C.; Welz, S.; Linge, A.; Lohaus, F.; Baretton, G.; Gauler, T.; Baumann, M.; Krause, M.; Schuler, M.; Bankfalvi, A.; Höing, B.; Lang, S.; Stuschke, M.

The original version of this Article contained an error in the spelling of the author Eleni Gkika, which was incorrectly given as Eleni Gikka. As well as the author Stephanie E. Combs, this was incorrectly given as Stephanie Combs. Both have now been corrected in the PDF and HTML versions of the Article.

Permalink: https://www.hzdr.de/publications/Publ-33968
Publ.-Id: 33968


Joint EANM/SNMMI/ESTRO practice recommendations for the use of 2‑[18F]FDG PET/CT external beam radiation treatment planning in lung cancer V1.0

Vaz, S.; Adam, J.; Delgado Bolton, R.; Vera, P.; van Elmpt, W.; Herrmann, K.; Hicks, R.; Lievens, Y.; Santos, A.; Schöder, H.; Dubray, B.; Visvikis, D.; Troost, E. G. C.; de Geus-Oei, L.

Purpose 2-[18F]FDGPET/CT is of utmost importance for radiation treatment (RT) planning and response monitoring in lung cancer patients, in both non-small and small cell lung cancer (NSCLC and SCLC). This topic has been addressed in guidelines composed by experts within the feld of radiation oncology. However, up to present, there is no procedural guideline on this subject, with involvement of the nuclear medicine societies.
Methods A literature review was performed, followed by a discussion between a multidisciplinary team of experts in the different fields involved in the RT planning of lung cancer, in order to guide clinical management. The project was led by experts of the two nuclear medicine societies (EANM and SNMMI) and radiation oncology (ESTRO).
Results and conclusion This guideline results from a joint and dynamic collaboration between the relevant disciplines for this topic. It provides a worldwide, state of the art, and multidisciplinary guide to 2-[18F]FDG PET/CT RT planning in NSCLC and SCLC. These practical recommendations describe applicable updates for existing clinical practices, highlight potential faws, and provide solutions to overcome these as well. Finally, the recent developments considered for future application are also reviewed.

Keywords: Radiotherapy; EANM; SNMMI; ESTRO; 2-[18F]FDG PET; CT; Radiation therapy; Planning; Lung cancer

Permalink: https://www.hzdr.de/publications/Publ-33967
Publ.-Id: 33967


Correction: Görte et al. Comparative Proton and Photon Irradiation Combined with Pharmacological Inhibitors in 3D Pancreatic Cancer Cultures. Cancers 2020, 12, 3216

Görte, J.; Beyreuther, E.; Danen, E. H. J.; Cordes, N.

The authors wish to make the following corrections to this paper [...].

Permalink: https://www.hzdr.de/publications/Publ-33966
Publ.-Id: 33966


Toxicity and Efficacy of Local Ablative, Image-guided Radiotherapy in Gallium-68 Prostate-specific Membrane Antigen Targeted Positron Emission Tomography-staged, Castration-sensitive Oligometastatic Prostate Cancer: The OLI-P Phase 2 Clinical Trial

Hölscher, T.; Baumann, M.; Kotzerke, J.; Zöphel, K.; Paulsen, F.; Müller, A.-C.; Zips, D.; Koi, L.; Thomas, C.; Löck, S.; Krause, M.; Wirth, M.; Lohaus, F.

Background: Local ablative radiotherapy (aRT) of oligometastatic prostate cancer (PCa) is very promising and has become a focus of current clinical research.

Objective: We hypothesize that aRT is safe and effective in gallium-68 prostate-specific membrane antigen targeted positron emission tomography (PSMA-PET)-staged oligometastatic PCa patients.

Design, setting, and participants: A nonrandomized, prospective, investigator-initiated phase 2 trial recruited patients with oligometastatic PCa (five or fewer lymph node or osseous metastases) after local curative therapy, without significant comorbidity and androgen deprivation therapy (ADT), at two German centers from 2014 to 2018.

Intervention: All PSMA-PET-positive metastases were treated with aRT. No systemic therapy was initiated.

Outcome measurements and statistical analysis: The primary endpoint was treatment-related toxicity (grade ≥2) 24 mo after aRT. A one-sided single-sample test of proportions was planned to test whether the endpoint occurs in <15% of the patients. Key secondary endpoints were time to progression of prostate-specific antigen (PSA) and time to ADT, which were associated with potential prognostic factors by Cox regression.

Results and limitations: Of 72 patients, 63 received aRT (13% dropout rate). The median follow-up was 37.2 mo. No treatment-related grade ≥2 toxicity was observed 2 yr after treatment. The median time to PSA progression and time to ADT were 13.2 and 20.6 mo, respectively. Of the patients, 21.4% were free of PSA progression after 3 yr.

Conclusions: It was observed that aRT is safe, and midterm PSA progression and ADT-free time were achieved in one of five patients. Randomized clinical trials are indicated to further evaluate the option of delaying ADT in selected patients.

Patient summary: In this clinical trial, 63 patients with up to five metastases of prostate cancer without androgen deprivation therapy were included. We showed that local ablative radiotherapy is safe and that one in five patients had no recurrent prostate-specific antigen value after 3 yr. Local ablative radiotherapy might be an option to avoid systemic therapy in selected patients.

Keywords: Adult; Image guided Radiosurgery; Male; Neoplasm metastasis; Positron emission tomography; Prospective studies; Prostate-specific antigen; Prostatic neoplasms; Radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-33965
Publ.-Id: 33965


High Sulfur in Primitive Arc Magmas, Its Origin and Implications

Zelenski, M.; S. Kamenetsky, V.; Nekrylov, N.; Kontonikas-Charos, A.

Sulfur contents in 98.5% of melt inclusions (MI) from calc-alkaline subduction basalts do not exceed 4000 ppm, whereas experimentally established limits of sulfur solubility in basaltic melts with high fO2 (characteristic of subduction zones, e.g., QFM + 2) surpass 14,000 ppm. Here we show that primitive (Mg# 62-64) subduction melts may contain high sulfur, approaching the experimental limit of sulfur solubility. Up to 11,700 ppm S was measured in olivine-hosted MI from primitive arc basalt from the 1941 eruption of the Tolbachik volcano, Kamchatka. These MI often contain magmatic sulfide globules (occasionally enriched in Cu, Ni, and platinum-group elements) and anhydrite enclosed within a brown, oxidized glass. We conclude that the ubiquitous low sulfur contents in MI may originate either from insufficient availability of sulfur in the magma generation zone or early magma degassing prior to inclusion entrapment. Our findings extend the measured range of sulfur concentrations in primitive calc-alkaline basaltic melts and demonstrate that no fundamental limit of 4000 ppm S exists for relatively oxidized subduction basalts, where the maximum sulfur content may approach the solubility limit determined by crystallization of magmatic anhydrite.

Keywords: primitive basalts; olivine; melt inclusions; sulfur; igneous petrology

Permalink: https://www.hzdr.de/publications/Publ-33964
Publ.-Id: 33964


Noble metals in arc basaltic magmas worldwide: A case study of modern and pre-historic lavas of the Tolbachik volcano, Kamchatka

Kutyrev, A.; Zelenski, M.; Nekrylov, N.; Savelyev, D.; Kontonikas-Charos, A.; S. Kamenetsky, V.

Platinum-group elements (PGE) and gold are a promising tool to assess the processes of
mantle melting beneath the subduction zones. However, fractionation processes in
magmas inevitably overwrite the initial metal budgets of magmas, making constraints
on the melting processes inconclusive. Moreover, little is still known about the geochemical
behavior of a particular metal in a single arc magmatic system, from mantle melting
towards magma solidification. Here we compare noble metals in lavas from several
eruptions of the Tolbachik volcano (Kamchatka arc) to better understand the effects of
magma differentiation, estimate primary melt compositions and make constraints on the
mantle melting. We show that Ir, Ru, Rh and, to a lesser extent, Pt are compatible during
magmatic differentiation. The pronounced incompatible behavior of Cu and Pd, observed
in Tolbachik magmas, rules out the significant influence of sulfide melts on the early
magmatic evolution in this particular case. Gold is also incompatible during magmatic
differentiation; however, its systematics can be affected by the inferred gold recycling in the
plumbing system of Tolbachik. Although the Tolbachik lavas show only slightly higher PGE
fractionation than in MORB, a notable negative Ru anomaly (higher Pt/Ru and Ir/Ru) is
observed. We attribute this to be a result of greater oxidation in the subarc mantle (by 1–4
log units), which promotes crystallization of Ru-bearing phases such as Fe3+-rich Cr-spinel
and laurite. The estimated Pd contents for the parental melt of the Tolbachik lavas
approaches 6.5 ppb. This is several times higher than reported MORB values (1.5 ±
0.5 ppb), suggesting the enrichment of Pd in the mantle wedge. Our results highlight
the influence of the subduction-related processes and mantle wedge refertilization on the
noble metal budgets of arc magmas.

Keywords: basalt; island arc and continental margin arc environment; platinum; PGE; gold; sulfide; primitive basalts; igneous petrology

Permalink: https://www.hzdr.de/publications/Publ-33963
Publ.-Id: 33963


Origin of alkali-rich volcanic and alkali-poor intrusive carbonatites from a common parental magma

F. Chayka, I.; S. Kamenetsky, V.; V. Vladykin, N.; Kontonikas-Charos, A.; R. Prokopyev, I.; Yu Stepanov, S.; P. Krasheninnikov, S.

The discrepancy between Na-rich compositions of modern carbonatitic lavas (Oldoinyo Lengai volcano) and alkali-poor ancient carbonatites remains a topical problem in petrology. Although both are supposedly thought to originate via fractional crystallization of a “common parent” alkali-bearing Ca-carbonatitic magma, there is a significant compositional gap between the Oldoinyo Lengai carbonatites and all other natural compositions reported (including melt inclusions in carbonatitic minerals). In an attempt to resolve this, we investigate the petrogenesis of Ca-carbonatites from two occurrences (Guli, Northern Siberia and Tagna, Southern Siberia), focusing on mineral textures and alkali-rich multiphase primary inclusions hosted within apatite and magnetite. Apatite-hosted inclusions are interpreted as trapped melts at an early magmatic stage, whereas inclusions in magnetite represent proxies for the post-cumulus interstitial environment. Melts obtained by heating and quenching the inclusions, show a progressive increase in alkali concentrations transitioning from moderately-alkaline Ca-carbonatites through to the calcite-nyerereite/fairchildite peritectic, and finally towards Oldoinyo Lengai lava compositions. These results give novel empirical evidence supporting the view that Na-carbonatitic melts, similar to those of the Oldoinyo Lengai, may form via fractionation of a moderately alkaline Ca-carbonatitic melt, and therefore provide the “missing piece” in the puzzle of the Na-carbonatite’s origin. In addition, we conclude that the compositions of the Guli and Tagna carbonatites were in fact alkali-rich at the solidus, but were subsequently altered by replacement of alkaline assemblages by calcite and dolomite.

Keywords: Carbonatites; Melt inclusions; Igneous petrology

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33962
Publ.-Id: 33962


Trajectory-dependent electronic excitations of keV ions

Lohmann, S.; Holeňák, R.; Primetzhofer, D.

We present experiments directly demonstrating the significance of charge-exchange events for the energy deposition of ions with velocities below the Bohr velocity. The observed effects lead to a drastic trajectory-dependence of the specific energy loss.
Experiments were performed with the time-of-flight medium energy ion scattering set-up at Uppsala University [1]. We employed pulsed beams of singly charged ions with masses ranging from 1 (H+) to 40 u (Ar+) and energies between 20 and 350 keV. Ions were transmitted through self-supporting Si(100) nanomembranes and detected behind the sample. We assessed the energy and angular distributions of deflected particles for different alignments of the initial beam direction with the crystal axes and planes. A set-up for measuring the exit charge state was constructed to support the analysis [2].
For all ions we observe lower electronic stopping for channelled trajectories as compared to random ones as shown in Fig. 1 [3]. For protons, this difference is explained by increasing contributions of core-electron excitations more likely to happen at small impact parameters accessible only in random geometry. For heavier ions, core-electron excitations at employed ion velocities are inefficient and we, therefore, explain these results by reionisation events occurring in close collisions of ions with target atoms [4]. These events in turn result in trajectory-dependent mean charge states, which heavily affects the energy loss, and could be confirmed by first qualitative measurements of the trajectory dependence of exit charge states. The simplicity of our experimental geometry leads to results that can serve as excellent benchmark systems for calculations using time-dependent density functional theory.

References
[1] M. A. Sortica et al., Nucl. Instrum. Methods Phys. Res. B, 463 (2020) 16-20.
[2] R. Holeňák et al., Vacuum, 185 (2021) 109988.
[3] S. Lohmann et al., Phys. Rev. A, 102 (2020) 062803.
[4] S. Lohmann and D. Primetzhofer, Phys. Rev. Lett., 124 (2020) 096601.

  • Lecture (Conference)
    Applied Nuclear Physics Conference, 12.-16.09.2021, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-33961
Publ.-Id: 33961


Ion-electron dynamics studied in a 3D-transmission approach

Lohmann, S.; Holeňák, R.; Grande, P. L.; Primetzhofer, D.

We present experiments demonstrating trajectory-dependent electronic excitations at low ion velocities attributed to charge-exchange events. Experiments were performed with the time-of-flight medium energy ion scattering set-up at Uppsala University [1]. We employed pulsed beams of singly charged ions with masses from 1 (H+) to 40 u (Ar+) and energies between 20 and 300 keV. Ions are transmitted through self-supporting Si(100) nanomembranes and detected behind the sample. Fig. 1 demonstrates our experimental approach, in which ion energy loss is measured together with angular distributions for different beam-crystal alignments. We have analysed both trajectory-dependent electronic stopping and electronic energy-loss straggling. Our results show higher electronic stopping for random than for channelled trajectories for all studied ions [2]. For ions heavier than protons, direct core-electron excitations at employed ion velocities are inefficient. We, therefore, explain our observation by reionisation events occurring in close collisions of ions with target atoms mainly accessible in random geometry [3]. These events result in trajectory-dependent mean charge states, which heavily affects the energy loss. The electronic energy-loss straggling likewise exhibits a strong dependence on ion type, velocity and trajectory. For all ions, straggling in random geometry is higher than in channelling orientation. While for He straggling increases with ion velocity, for B travelling along random trajectories a minimum is observed in the studied velocity range. We compare experimental results for these two ions with predictions by the Chu model and transport cross section calculations (Penn-TCS model). We provide strong evidence that electron-hole pair creation alone cannot explain electronic excitations by slow ions other than protons. Especially for heavy ions, additional energy-loss processes such as charge exchange and autoionisation including possible alterations of the scattering potential [4] have to be taken into account.
References
[1] M. A. Sortica et al., Nucl. Instrum. Methods Phys. Res. B, 463 (2020) 16-20.
[2] S. Lohmann et al., Phys. Rev. A, 102 (2020) 062803.
[3] S. Lohmann and D. Primetzhofer, Phys. Rev. Lett., 124, (2020) 096601.
[4] R. A. Wilhelm and P. L. Grande, Communications Physics, 2 (2019) 89.

  • Invited lecture (Conferences) (Online presentation)
    27th International Symposium on Ion-Atom Collisions (ISIAC), 14.-16.07.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33960
Publ.-Id: 33960


[Treatment Planning and Dose Verification for Combined Internal and External Radiotherapy (CIERT)]

Freudenberg, R.; Hartmann, H.; Andreeff, M.; Oehme, L.; Leichtner, T.; Fischer, A.; Paulus, T.; Krause, M.; Kotzerke, J.

Aim: The combined internal and external radiotherapy (CIERT) take advantage of the benefits from radionuclide therapy and external beam irradiation. These include steep dose gradients and a low toxicity to normal tissue due to the use of unsealed radioisotopes as well as homogeneous dose distribution within the tumor due to external beam irradiation. For a combined irradiation planning, an infrastructure has to be developed that takes into account the dose contributions from both modalities. A physical verification of the absorbed dose distribution should follow by measurements using OSL detectors.

Method: Internal irradiation was performed using Re-188 in a cylindrical phantom with three inserts. SPECT images were acquired to calculate the internal dose using the software STRATOS. The dose distribution was exported as DICOM-RT data and imported in the software Pinnacle. Based on the internal dose distribution the external irradiation using 6 MV photons was planned. The dose contributions of both modalities separately as well as for combined irradiation was measured using OSL detectors made out of Beryllium oxide.

Results: The planed doses of combined irradiation (1 Gy, 2 Gy, 4 Gy) could be verified within the uncertainty of the detectors. The mean energy response to Re-188 was (88.6 ± 2.4) % with respect to the calibration with 200 kV X-ray irradiation. The energy response to 6 MV photons was (146.0 ± 4.9) %.

Conclusion: A workflow for the treatment planning of combined internal and external radiotherapy has been developed and tested. Measurements verified the calculated doses. Therefore, the physical and technical basis for the dosimetry of combined irradiation were worked out.

Keywords: CIERT; kombinierte Bestrahlung; OSL; Dosimetrie

Permalink: https://www.hzdr.de/publications/Publ-33959
Publ.-Id: 33959


In reply to the Letter to the Editor by Chen and Lui regarding "Radiotherapy enhances uptake and efficacy of 90 Y-cetuximab: A preclinical trial" by A Dietrich et al

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.

It is the reply to the Letter to the Editor by Chen and Lui regarding "Radiotherapy enhances uptake and efficacy of 90 Y-cetuximab: A preclinical trial" by A Dietrich et al.
Abstract: 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.

Downloads:

  • Secondary publication expected from 11.06.2022

Permalink: https://www.hzdr.de/publications/Publ-33958
Publ.-Id: 33958


Efficient Heat Shock Response Affects Hyperthermia-Induced Radiosensitization in a Tumor Spheroid Control Probability Assay

Chen, O.; Michlíková, S.; Eckhardt, L.; Wondrak, M.; M. De Mendoza, A.; Krause, M.; D. McLeod, D.; A. Kunz-Schughart, L.

Hyperthermia (HT) combined with irradiation is a well-known concept to improve the curative potential of radiotherapy. Technological progress has opened new avenues for thermoradiotherapy, even for recurrent head and neck squamous cell carcinomas (HNSCC). Preclinical evaluation of the curative radiosensitizing potential of various HT regimens remains ethically, economically, and technically challenging. One key objective of our study was to refine an advanced 3-D assay setup for HT + RT research and treatment testing. For the first time, HT-induced radiosensitization was systematically examined in two differently radioresponsive HNSCC spheroid models using the unique in vitro "curative" analytical endpoint of spheroid control probability. We further investigated the cellular stress response mechanisms underlying the HT-related radiosensitization process with the aim to unravel the impact of HT-induced proteotoxic stress on the overall radioresponse. HT disrupted the proteome's thermal stability, causing severe proteotoxic stress. It strongly enhanced radiation efficacy and affected paramount survival and stress response signaling networks. Transcriptomics, q-PCR, and western blotting data revealed that HT + RT co-treatment critically triggers the heat shock response (HSR). Pre-treatment with chemical chaperones intensified the radiosensitizing effect, thereby suppressing HT-induced Hsp27 expression. Our data suggest that HT-induced radiosensitization is adversely affected by the proteotoxic stress response. Hence, we propose the inhibition of particular heat shock proteins as a targeting strategy to improve the outcome of combinatorial HT + RT.

Keywords: head and heck squamous cell carcinomas (HNSCC); heat shock proteins (Hsps); hyperthermia; proteotoxic stress; radiation therapy; spheroids

Permalink: https://www.hzdr.de/publications/Publ-33957
Publ.-Id: 33957


Dual role of ER stress in response to metabolic co-targeting and radiosensitivity in head and neck cancer cells

Chen, O.; Manig, F.; Lehmann, L.; Sorour, N.; Löck, S.; Yu, Z.; Dubrovska, A.; Baumann, M.; M. Kessler, B.; Stasyk, O.; A. Kunz-Schughart, L.

Arginine deprivation therapy (ADT) is a new metabolic targeting approach with high therapeutic potential for various solid cancers. Combination of ADT with low doses of the natural arginine analog canavanine effectively sensitizes malignant cells to irradiation. However, the molecular mechanisms determining the sensitivity of intrinsically non-auxotrophic cancers to arginine deficiency are still poorly understood. We here show for the first time that arginine deficiency is accompanied by global metabolic changes and protein/membrane breakdown, and results in the induction of specific, more or less pronounced (severe vs. mild) ER stress responses in head and neck squamous cell carcinoma (HNSCC) cells that differ in their intrinsic ADT sensitivity. Combination of ADT with canavanine triggered catastrophic ER stress via the eIF2α-ATF4(GADD34)-CHOP pathway, thereby inducing apoptosis; the same signaling arm was irrelevant in ADT-related radiosensitization. The particular strong supra-additive effect of ADT, canavanine and irradiation in both intrinsically more and less sensitive cancer cells supports the rational of ER stress pathways as novel target for improving multi-modal metabolic anti-cancer therapy.

Keywords: 3-D culture; Arginine-deprivation therapy; Canavanine; ER stress; Head and neck squamous carcinoma; Metabolic targeting; Radiosensitization

Permalink: https://www.hzdr.de/publications/Publ-33956
Publ.-Id: 33956


Data publication: Describing chain-like assembly of ethoxygroup-functionalized organic molecules on Au(111) using high-throughput simulations

Lokamani, M.; Kelling, J.; Ohmann, R.; Meyer, J.; Kühne, T.; Cuniberti, G.; Wolf, J.; Juckeland, G.; Huhn, T.; Zahn, P.; Moresco, F.; Gemming, S.

Bei diesem Datensatz handelt es sich um die Grundzustandsstruktur von PEEB auf Au(111) und die Inputdatei für DFTB+.

Keywords: DFTB; 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene (PEEB); STM; High-Throughput; Meta-Structures

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-01-12
    DOI: 10.14278/rodare.1374
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33955
Publ.-Id: 33955


From conventional to unconventional superconductivity

Wosnitza, J.

  • Invited lecture (Conferences)
    Quantum Matter Bordeaux School 2021, 15.-19.11.2021, Bordeaux, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-33953
Publ.-Id: 33953


Verflüssigung von Wasserstoff durch magnetische Kühlung

Gottschall, T.

Magnetische Materialien ändern ihre Temperatur, wenn sie einem Magnetfeld ausgesetzt werden. Dieser sogenannte magnetokalorische Effekt lässt sich nutzen, um alternative Kühlkonzepte zu entwickeln. Während in den letzten Jahren der wissenschaftliche Fokus auf der Kühlung nahe Raumtemperatur lag, ist kürzlich die magnetische Verflüssigung von Wasserstoff als Anwendungsgebiet stärker ins Blickfeld gerückt. Die konventionelle Herstellung von Flüssigwasserstoff ist ein äußerst energieintensiver Prozess. Effizienzsteigerungen sind durch den Einsatz maßgeschneiderter magnetischer Materialien und hoher Magnetfelder möglich. In diesem Beitrag werden die physikalischen Grundlagen der magnetischen Kühlung diskutiert und ausgewählte magnetokalorische Materialklassen vorgestellt. Des Weiteren werden die technologischen Herausforderungen und Vorteile thematisiert.

  • Invited lecture (Conferences)
    Deutsche Kälte-und Klimatagung 2021 Dresden, 19.11.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33952
Publ.-Id: 33952


Magnetic cooling: from materials to application

Gottschall, T.

With the world's increasingly affluent population demanding more comfortable living and working conditions, it is vital that we address the development of much more efficient cooling technologies as an urgent priority. An alternative approach is based on solid-state refrigeration by one of the caloric effects – electrocaloric, magnetocaloric, barocaloric or elastocaloric - where the material's temperature is forced to change under the application of an electrical, magnetic, or mechanical field. However, there is also the possibility to combine these different effects in a beneficial way, in the so-called multicaloric cooling cycle. Magnetic Ni-Mn-based Heusler alloys are ideally suited for multicaloric applications due to their coupled magnetostructural transformation between martensite and austenite. In this work, we discuss the current progress in the characterization of these materials for novel cooling technologies.

  • Invited lecture (Conferences) (Online presentation)
    Phd-Retreat CRC 270, 02.12.2021, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33950
Publ.-Id: 33950


Magnetic properties and microstructure of Sm5Fe17-based composite magnets

Dirba, I.; Sepehri-Amin, H.; Skokov, K.; Scurschii, I.; Hono, K.; Gutfleisch, O.

We have investigated synthesis, magnetic properties and microstructure of Sm5Fe17-based hard magnetic phase with a Sm20Fe70Ti10 composition. Ultrahigh coercivities, μ0Hc = 7.18 T at room temperature and μ0Hc = 8.86 T at 10 K, have been achieved. The room-temperature coercivity, determined from high-field pulse measurements, reaches 35 % of the anisotropy field μ0Ha = 20.7±0.8 T. Further, it is demonstrated that a coercivity of 2.18 T is maintained even at 500 K. The Curie temperature Tc of Sm20Fe70Ti10 is 577 K and the calculated exchange stiffness parameter A is 7.72 pJ/m. Detailed transmission electron microscopy investigations show a two-phase microstructure consisting of the Sm6Fe17-based hard magnetic matrix phase with grain size below 200 nm and finer, below 100 nm, Fe2Ti grains. Majority of the Fe2Ti phase is located at the grain boundaries with some finer inclusions found also inside the 5:17 grains. Despite the high fraction of the Fe2Ti grains, nearly single-phase demagnetization loops are observed. In order to enhance Ms, the effect of Ti content on phase constitution, magnetic properties and microstructure was studied in detail. Ms increases and Hc decreases for the Ti-lean compositions.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33949
Publ.-Id: 33949


Anisotropic magnetization, critical temperature, and paramagnetic Curie temperature in the highly anisotropic magnetic Heusler compound Rh2CoSb

He, Y.; Sibille, R.; Chen, D.; Kroder, J.; Helm, T.; Schnelle, W.; Felser, C.; Fecher, G. H.

The paramagnetic Curie temperature θp is a concept that describes the magnetic ordering temperature in the well-established Curie-Weiss law. Despite the successful explanations of the magnetic behavior, the anisotropy is not usually considered. Although anisotropic θp has been reported for several layered antiferromagnetic or ferrimagnetic materials owing to the orientation-dependent exchange, in ferromagnetic systems, θp was thought to be almost isotropic for decades, and the occasionally reported small difference has remained unexplained. In this paper, we experimentally report the anisotropic magnetization, critical temperature, and paramagnetic Curie temperature in highly anisotropic magnetic Rh2CoSb caused by a large magnetocrystalline anisotropy. The saturation magnetization along the c axis is 25% larger than that along the a axis. The critical temperature and paramagnetic Curie temperature along the c axis are 6 and 15 K higher than those along the a axis, respectively, as deduced from the Arrott plots and inverse susceptibility. A simple modification of the Curie-Weiss law was made to calculate the anisotropic θp, which well explains not only Rh2CoSb, but also many other previously reported ferromagnetic materials.

Permalink: https://www.hzdr.de/publications/Publ-33948
Publ.-Id: 33948


New limits on double-beta decay of 190Pt and 198Pt

Danevich, F. A.; Hult, M.; Junghans, A.; Kasperovych, D. V.; Kropivyansky, B. N.; Lutter, G.; Marissens, G.; Polischuk, O. G.; Romaniuk, M. V.; Stroh, H.; Tessalina, S.; Tretyak, V. I.; Ware, B.

A search for double-beta decay of 190Pt and 198Pt
with emission of γ -ray quanta was realized at the HADES
underground laboratory with a 148 g platinum sample measured
by two ultralow-background HPGe detectors over 8946
h. The isotopic composition of the platinum sample has
been measured with high precision using inductively coupled
plasma mass spectrometry. New lower limits for the
half-lives of 190Pt relative to different channels and modes
of the decays were set on the level of lim T1/2 ∼ 10^14–10^16
year. A possible exact resonant 0νKN transition to the 1,2
1326.9 keV level of 190Os is limited for the first time as
T1/2 ≥ 2.5 × 10^16 year. A new lower limit on the double beta
decay of 198Pt to the first excited level of 198Hg was set
as T1/2 ≥ 3.2 × 10^19 year, one order of magnitude higher
than the limit obtained in the previous experiment.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33943
Publ.-Id: 33943


The effect of magnetic fields on freckle evolution during solidification

Shevchenko, N.; Kao, A.; Fan, X.; Tonry, C.; Clark, S.; Atwood, R.; Lee, P.; Pericleous, K.; Eckert, S.

The formation of freckle defects in the presence of a static magnetic field is studied by combining in-situ synchrotron imaging with numerical simulations. The formation, growth and motion of freckle channels during directional solidification are investigated in a Hele-Shaw cell for a low melting point Ga-In alloy. The solidification setup is developed at HZDR and is described in detail elsewhere. The solidification cell is placed in a permanent magnet system providing a flux density of about 120 mT within the cell. The turn of the magnet system about a vertical cell axis allow to get both the Bx (perpendicular to a X-ray beam) and the Bz (parallel to a X-ray beam) component of the magnetic field.
Numerical simulations, using a microscopic parallelized Cellular Automata lattice Boltzmann method, are validated by these in situ experiments. An excellent match between the numerical model and experiments conducted on thin rectangle sample alloy is achieved. Evaluation of the in situ X-ray data and numerical analysis shows the role of thermoelectric magnetohydrodynamics (TEMHD) and electromagnetic damping (EMD) in the formation of channels and ultimately freckle defects. For instance, Figures 1c and 1d show clear evidence of the effect of the magnetic field on the microstructure. Figure 1d displays the formation of a solute channel at the left side of the sample in the presence of a magnetic field. This channel development can be attributed to the thermoelectric Lorentz force acting on the inter-dendritic liquid flow by causing the solute to accumulate at one side of the cell.
In situ synchrotron experiments allow us to resolve the complex channel dynamics and simultaneously show how large-scale flow fields may alter them. Both temperature gradient and grain orientation can affect the dynamics of the segregation channels formation in the presence of the magnetic field. The effect of electromagnetic damping force to convective transport needs future investigations. The in situ synchrotron data and numerical modelling will provide further understanding of the underlying mechanisms and identifying further interesting phenomena.

Keywords: solidification; magnetic fields; freckle defects; in-situ synchrotron imaging; numerical modelling

  • Lecture (Conference) (Online presentation)
    Electromagnetic Processing of Materials, EPM 2021, 14.-16.06.2021, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-33932
Publ.-Id: 33932


Hysteretic effects and magnetotransport of electrically switched CuMnAs

Zubác, J.; Kaspar, Z.; Krizek, F.; Förster, T.; Campion, R. P.; Novak, V.; Jungwirth, T.; Olejnik, K.

Antiferromagnetic spintronics allows us to explore storing and processing information in magnetic crystals with vanishing magnetization. In this paper, we investigate magnetoresistance effects in antiferromagnetic CuMnAs upon switching into high-resistive states using electrical pulses. By employing magnetic field sweeps up to 14 T and magnetic field pulses up to ∼60 T, we reveal hysteretic phenomena and changes in the magnetoresistance, as well as the resilience of the switching signal in CuMnAs to the high magnetic field. These properties of the switched state are discussed in the context of recent studies of antiferromagnetic textures in CuMnAs.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33929
Publ.-Id: 33929


Quantum Oscillations in Ferromagnetic (Sb,V)2Te3 Topological Insulator Thin Films

Zhang, L.; Helm, T.; Lin, H.; Fan, F.; Le, C.; Sun, Y.; Markou, A.; Felser, C.

An effective way of manipulating 2D surface states in magnetic topological insulators may open a new route for quantum technologies based on the quantum anomalous Hall effect. The doping-dependent evolution of the electronic band structure in the topological insulator Sb2− V Te3 (0 ≤ x ≤ 0.102) thin films is studied by means of electrical transport. Sb2− V Te3 thin films were prepared by molecular beam epitaxy, and Shubnikov–de Hass (SdH) oscillations are observed in both the longitudinal and transverse transport channels. Doping with the 3d element, vanadium, induces long-range ferromagnetic order with enhanced SdH oscillation amplitudes. The doping effect is systematically studied in various films depending on thickness and bottom gate voltage. The angle-dependence of the SdH oscillations reveals their 2D nature, linking them to topological surface states as their origin. Furthermore, it is shown that vanadium doping can efficiently modify the band structure. The tunability by doping and the coexistence of the surface states with ferromagnetism render Sb2− V Te3 thin films a promising platform for energy band engineering. In this way, topological quantum states may be manipulated to crossover from quantum Hall effect to quantum anomalous Hall effect, which opens an alternative route for the design of quantum electronics and spintronics.

Permalink: https://www.hzdr.de/publications/Publ-33928
Publ.-Id: 33928


Experimentelle und numerische Untersuchung der Wärmeübertragungs- und Strömungscharakteristik von berippten Einzelrohren und Rohrbündeln mit neuartigem Rippendesign

Unger, S.

Die Übertragung thermischer Energie durch Wärmeübertrager ist ein essentieller Vorgang in unterschiedlichen, technischen Prozessen. Die am häufigsten vorkommende Wärmeübertragerbauform bei der Wärmeabgabe an ein Gas ist der Rippenrohrwärmeübertrager. Bis zu 85 % des thermischen Widerstandes treten nach Wang et al. (2002) dabei gasseitig auf, weshalb eine Verbesserung des Wärmeüberganges wesentlich zur Erhöhung der Gesamtleistung beiträgt. Eine typische Anwendung von geneigten Rippenrohren sind luftgekühlte Kondensatoren.
Der Einfluss der Rohrneigung auf die Wärmeübertragungs- und Strömungscharakteristik von Rippenrohren wurde in der Literatur bislang kaum untersucht. Luftgekühlte Kondensatoren werden allerdings in geneigter Orientierung installiert, um einen Kondensatablauf auf der Rohrinnenseite zu ermöglichen. Daher würde der Auslegungsprozess von luftgekühlten Kondensatoren wesentlich von einer experimentellen Charakterisierung des Einflusses der Rohrneigung auf die Wärmeübertragungs- und Strömungscharakteristik profitieren. Es existiert eine Vielzahl von Rippendesigns zur Erhöhung der luftseitigen Turbulenz entlang der Rippenoberfläche. In der Literatur konnten keine Rippendesigns gefunden werden, welche neben der Turbulenzerzeugung auch die Wärmeleitung von der Rippenbasis zur Rippenspitze verbessern und somit eine homogenere Temperaturverteilung erreichen. Wissenschaftliche Arbeiten zur Naturkonvektion beschränken sich auf numerische und experimentelle Analysen von berippten Einzelrohren. Rippenrohrbündel unter Naturkonvektion sowie der Einfluss der relevanten Rippen- und Rohrparameter auf die Wärmeübertragung der Rohrbündel wurde bislang kaum untersucht.
Für die experimentellen Untersuchungen wurde ein 6,5 𝑚 langer vertikaler Strömungskanal errichtet, in welchem unterschiedliche Gleichrichter zur Homogenisierung der Strömung installiert waren. Mittels einer Kombination aus analytischen Näherungsverfahren und Vermessung der lokal aufgelösten Rippenoberflächentemperatur wurde der Rippenwirkungsgrad bestimmt. Die Neigung der Rohrachse gegenüber der Horizontalen erhöht die Nusselt-Zahl bei erzwungener Konvektion und erniedrigt diese bei natürlicher Konvektion. Bei erzwungener Konvektion ist das Leistungsverhalten der Wärmeübertrager unter geneigter Orientierung aufgrund des höheren Druckverlustes reduziert. Für beide Konvektionsarten sinkt der Einfluss des Neigungswinkels auf die Nusselt-Zahl mit abnehmendem Rippenabstand. Basierend auf den experimentellen Untersuchungen wurden Korrelationen entwickelt, um den Wärmeübergang in Abhängigkeit von der Reynolds-Zahl oder Rayleigh-Zahl, dem Neigungswinkel und dem Rippenabstand zu beschreiben.
Die existierenden Rippendesigns zielen darauf ab, den gasseitigen konvektiven Wärmeübergang zu verbessern. Die Steigerung der Wärmeleitung durch das Rippendesign wird dabei weitestgehend vernachlässigt. Die Beeinflussung der Wärmeleitung, beispielsweise durch Veränderung des wärmeleitenden Querschnittes entlang des Rippenumfanges, ist durch konventionelle Fertigungstechnologien nur schwierig oder gar nicht realisierbar. Mit neuartigen Herstellungsverfahren, wie der additiven Fertigung, können diese komplexen Geometrien erzeugt und somit auch die Wärmeleitung lokal erhöht werden. Bei der additiven Fertigung wird ein Pulverbett selektiv mit einem Laser oder Elektronenstrahl aufgeschmolzen und das Bauteil schrittweise generiert. In der vorliegenden Arbeit wurde diese Technologie genutzt, um Rippen mit verstärkenden, in der Rippenoberfläche integrierten, Stiften zu fertigen. Dadurch werden die Wärmeleitung und die Konvektion entlang der Rippenoberfläche verbessert. Zwei neuartige Designs wurden additiv gefertigt, experimentell in einem vertikalen Strömungskanal charakterisiert und patentiert. Bei den Untersuchungen wurde festgestellt, dass das Leistungsbewertungskriterium der geschlitzten integrierten Stiftrippe (SIPF) um 78,5 % höher und die Kompaktheit der runden integrierten Stiftrippe (CIPF) um 24,3 % höher ist als bei der konventionellen glatten Rohrrippe. Die Rohre mit neuartigem Rippendesign wurden auch unter verschiedenen Neigungswinkeln untersucht. Die Zunahme des Druckverlustes mit dem Rohrneigungswinkel ist niedriger als bei der konventionellen Rippe. Die SIPF erreicht bei einer Neigung von 𝛼=20 ° das höchste Leistungsverhalten und die CIPF erreicht bei 𝛼=40 ° Neigung die höchste volumetrische Wärmestromdichte. Die entwickelten Korrelationen beschreiben die Abhängigkeit dieser Designs von der Reynolds-Zahl für verschiedene Rippenabstände sowie von der Reynolds-Zahl für verschiedenen Neigungswinkel.
Eine typische Anwendung von geneigten Rippenrohren sind luftgekühlte Kondensatoren, bei denen die Erfassung der thermischen Wärmeübertragungsleistung auf der Rohrinnenseite aufgrund des Phasenwechsels unter Umständen schwierig ist. Eine neue Messtechnik, der Temperatur-Anemometrie-Gittersensor (TAGS), wurde genutzt, um die luftseitige Temperatur und Strömungsgeschwindigkeit zeitgleich und ortsaufgelöst zur ermitteln. Die gemessene Temperaturverteilung ist für geneigte Rippenrohre stark ungleich verteilt. Fünf verschiedene Varianten zur Berechnung der thermischen Wärmeübertragungsleistung werden miteinander verglichen. Die Bestimmung mittels gewichteter Wärmestromdichten zeigt dabei die geringsten Abweichungen.
Der numerische Strömungsberechnungscode ANSYS CFX 19.0 wurde verwendet, um den Einfluss der Rippen- und Rohrparameter auf die Naturkonvektion von Rippenrohrbündeln qualitativ zu analysieren. Basierend auf der numerischen Studie wurden die zu optimierenden Rippen- und Rohrparameter ausgewählt. Zu diesen Parametern zählen die Rippendicke, der Rippenabstand, die Rippenhöhe, das Rohrachsenverhältnis, die Rohranordnung, die transversalen und longitudinalen Rohrabstände sowie die Rohrreihenanzahl. Diese Optimierung wurde mit Erkenntnissen bezüglich der erzwungenen Konvektion aus der Literatur kombiniert, wobei das ovale Rippenrohrbündel ein Achsenverhältnis von 1:2, eine Rippendicke von 1 𝑚𝑚, einen Rippenabstand von 5 𝑚𝑚 und eine Rippenhöhe von 17 𝑚𝑚 hat. Die versetzte Anordnung hat einen longitudinalen Rohrabstand von 63 𝑚𝑚 sowie einen transversalen Rohrabstand von 53 𝑚𝑚 und wurde in zwei- und dreireihiger Rohrreihenanzahl ausgeführt. Numerische Simulationen dieses optimierten Wärmeübertragers wurden für Naturkonvektion und für erzwungene Konvektion durchgeführt und qualitativ verglichen. Die Simulationsergebnisse zeigen für beide Konvektionsarten ähnliche Strömungsphänomene, wie beispielsweise Staupunkte am Rohr, Nachlaufgebiete stromabwärts des Rohres und Beschleunigungsbereich zwischen den Rohrrippen.
Die optimierten Rohrbündelwärmeübertrager wurden mit konventionellen Rippen und den neuartigen Rohrrippen in zweireihiger und dreireihiger Ausführung realisiert. In einer dafür angepassten Testsektion wurden die experimentellen Untersuchungen durchgeführt. Im Vergleich zur konventionellen Rippe zeigt die SIPF ein höheres Leistungsbewertungskriterium und eine um 52 % höhere Nusselt-Zahl für beide Ausführungen. Die CIPF erreicht eine um 22,4 % und 27,8 % höhere volumetrische Wärmestromdichte für die zweireihige und dreireihige Ausführung verglichen mit der konventionellen Rippe. Die Ergebnisse der experimentellen Untersuchungen der Rohrbündelwärmeübertrager unter Naturkonvektion in einem Kamin zeigen durchschnittlich 19,7 % und 10,9 % höhere Nusselt-Zahlen sowie 11,2 % und 4,0 % höhere volumetrische Wärmestromdichten der SIPF für die dreireihigen und zweireihigen Wärmeübertrager im Vergleich zum konventionellen Design. Ein verbessertes thermisches Leistungsverhalten für CIPF bei Naturkonvektion ist nicht zu erkennen.
Diese Arbeit zeigt, wie durch moderne Fertigungsverfahren und neue Designs auch Komponenten mit einem hohen technologischen Reifegrad weiter optimiert werden können. Durch verbesserte Wärmeübertragungsleistung bei gleichzeitig niedrigerem Materialverbrauch können Wärmeübertrager effizienter und ressourcenschonender hergestellt und betrieben werden.

  • Doctoral thesis
    Sächsische Landesbibliothek - Staats- und Universitätsbibliothek Dresden, 2021
    Mentor: Prof. Uwe Hampel
    188 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33927
Publ.-Id: 33927


High-Field Magnetization Study of Laves Phase (Gd,Y,Sm)Fe2-H

Tereshina, I. S.; Gorbunov, D.; Karpenkov, A. Y.; Doerr, M.; Drulis, H.; Granovski, S. A.; Tereshina-Chitrova, E. A.

The crystal structure and magnetic properties of the multicomponent Laves phase compounds (Gd1-xYx)0.8Sm0.2Fe2Hz (x = 0, 0.2, 0.4, 0.6, 0.8, 1; z = 0 and 3.4) are investigated. These compounds crystallize into an MgCu2 type of structure. Hydrogenation does not change the crystal structure type but boosts the unit cell volume of (Gd,Y,Sm)Fe2 by ∼25%. Both parent and the hydrogen-charged ferrimagnetic compounds demonstrate magnetic compensation (mutual cancellation of magnetic moments of the individual magnetic sublattices). The exact compositions with zero magnetization state (compensated compositions) predicted using a three-sublattice model are in good agreement with the experiment. In the hydrides, the magnetic compensation takes place at a lower Y content as compared to the parent alloys. Pulsed magnetic fields reveal a distinctly different behavior of magnetization in the hydrides. With the increase of magnetic field, magnetization increases much faster in the hydrides as compared to the parent compounds.

Permalink: https://www.hzdr.de/publications/Publ-33926
Publ.-Id: 33926


CFD applications in nuclear engineeering

Tian, W.; Petrov, V.; Erkan, N.; Liao, Y.; Wang, M.

Computational fluid dynamics (CFD) and computational multiphase fluid dynamics (CMFD) methods have attracted great attentions in predicting single-phase and multiphase flows under steady-state or transient conditions in the field of nuclear reactor engineering. The CFD research circle is rapidly expanding, and the CFD topic has been covered in many international conferences on nuclear engineering, such as ICONE, NURETH, NUTHOS, and CFD4NRS, which greatly extends the forum to exchange information in the application of CFD codes to nuclear reactor safety issues.
Currently, more and more scholars are devoting their efforts to CFD study in the nuclear engineering community, and a series of valuable research results have emerged in recent years. Therefore, this research topic was proposed, and the issue was organized by Tian from Xi’an Jiaotong University, Petrov from University of Michigan, Erkan from the University of Tokyo, Liao from Helmholtz-Zentrum Dresden-Rossendorf, and Wang from Xi’an Jiaotong University, aiming to share the most advanced progress and innovations related to CFD study in nuclear engineering around the world.
In this topic, the CFD simulation in rod bundles is carried out, and the simulation results are validated based on the LDA measurement in a 5 × 5 rod bundle installed with two split-mixing-vane grids (Xiong et al.). The models of internal heating and natural convention buoyancy, as well as the models of WMLES turbulence and phase changing, were applied in the open-source CFD software OpenFOAM to perform numerical simulations of the COPRA single-layer molten pool experiment (Xi et al.). Three-dimensional computational fluid dynamic (CFD) simulations were performed to study the long-term heat removal mechanisms in the General Atomics’ Modular High Temperature Gas-cooled Reactor (MHTGR) design during a P-LOFC accident (Wang et al.). The transient hydraulic characteristics of multistage centrifugal pump during start-up process were also studied using the CFD method (Long et al.).
In terms of two-phase flow simulation using the CFD method, the capabilities and advantages provided by a model that includes an elliptic-blending Reynolds stress turbulence closure (EB-RSM), allowing fine resolution of the velocity field in the near-wall region, are tested over a large database
(Colombo and Fairweather). Ling et al. (2020) present a numerical simulation of subcooled flow boiling at a high-pressure condition. An interface tracking method, VOSET, was used to handle the moving interface, and conjugate heat transfer between the wall and the fluid was included in the
numerical model. A comparison of the CFD simulation results with the high-resolution experimental data from a helical coil experimental setup operated with a mixture of water and air is discussed, with special emphasis on two-phase pressure drops and void fraction distributions (Che et al.). Zeng et al.
studied the detailed helium bubble rising behavior in the crosstype channel using CFD software ANSYS Fluent.
With the rapid development of the GEN-IV reactors, the application of CFD in liquid metal flow and heat transfer is also widely accepted. Chai et al. performed the wall-resolved large-eddy simulation (LES) to study the flow and heat transfer properties in a turbulent channel at low Prandtl number. The numerical study on the 19-pin wire-wrapped assembly cooled by lead–bismuth eutectic in liquid metal cooled reactor was also carried out using the CFD method (Li et al.).
Park et al. summarizes the recent activities in the development of SOPHIA code using smoothed particle hydrodynamics (SPH), which is effective to solve the nuclear safety issues encountered in natural disasters and severe accidents accompanied by highly nonlinear deformations. Numerical simulation and validation of aerosol particle removal by water spray droplets with OpenFOAM during the Fukushima daiichi fuel debris retrieval was performed by considering the collection mechanisms of inertial impaction, interception, and Brownian diffusion (Liang et al.).
Finally, 12 articles in total from the United States, Europe, Japan, Korea, and China were collected, to show the recent progress of CFD study in nuclear engineering around the world. This research topic covers across both light water reactors and liquid metal cooled reactors and is definitely a
pioneer in this field. It provides valuable references, guidelines, and is leading a fast-forwarding progress for the application of CFD in the nuclear reactor thermal hydraulic analysis. Anyway, we have to confess that the CFD is still developing, and more efforts are required to make it play a more significant role in the nuclear reactor design and safety analysis. We are planning to initiate a new special issue on the “CFD in Numerical Nuclear
Reactor” in future. Please feel free to contact us if you have any questions or suggestions.

Permalink: https://www.hzdr.de/publications/Publ-33924
Publ.-Id: 33924


Simulation-based Inference of Beamline Characteristics at BESSY

Steinbach, P.; Hartmann, G.

Poster presented at Helmholtz AI Conference 2021

Keywords: machine learning; simulation based inference; accelerator control

  • Open Access Logo Poster (Online presentation)
    Helmholtz AI annual conference, 14.-16.04.2021, virtual, Germany

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33922
Publ.-Id: 33922


The fate of fluvially-deposited organic carbon during transient floodplain storage

S. Scheingross, J.; N. Repasch, M.; Hovius, N.; Sachse, D.; Lupker, M.; Fuchs, M.; Halevy, I.; R. Gröcke, D.; Y. Golombek, N.; Haghipour, N.; I. Eglinton, T.; Orfeo, O.; Maria Schleicher, A.

CO2 release from particulate organic carbon (POC) oxidation during fluvial transit can influence climate over a range of timescales. Identifying the mechanistic controls on such carbon fluxes requires determining where POC oxidation occurs in river systems. While field data show POC oxidation and replacement moving downstream in lowland rivers, flume studies show that oxidation during active fluvial transport is limited. This suggests that most fluvial POC oxidation occurs during transient floodplain storage, but this idea has yet to be tested. Here, we isolate the influence of floodplain storage time on POC oxidation by exploiting a chronosequence of floodplain deposits above the modern groundwater table in the Rio Bermejo, Argentina. Measurements from 15 floodplain cores with depositional ages from 1 y to 20 ky show a progressive POC concentration decrease and 13C-enrichment with increasing time spent in floodplain storage. These results from the Rio Bermejo indicate that over 80% of fluvially-deposited POC can be oxidized over millennial timescales in aerated floodplains. Furthermore, POC in the oldest floodplain cores is more 14C-enriched than expected based on the independently-dated floodplain ages, indicating that a portion of this oxidized POC is replaced by autochthonous POC produced primarily by floodplain vegetation. We suggest floodplain storage timescales control the extent of oxidation of fluvially-deposited POC, and may play a prominent role in determining if rivers are significant atmospheric CO2 sources.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33919
Publ.-Id: 33919


Laboratory evidence for an asymmetric accretion structure upon slanted matter impact in young stars

Burdonov, K.; Revet, G.; Bonito, R.; Argiroffi, C.; Béard, J.; Bolanõs, S.; Cerchez, M.; Chen, S. N.; Ciardi, A.; Espinosa, G.; Filippov, E.; Pikuz, S.; Rodriguez, R.; Smid, M.; Starodubtsev, M.; Willi, O.; Orlando, S.; Fuchs, J.

Aims. Investigating the process of matter accretion onto forming stars through scaled experiments in the laboratory is important in
order to better understand star and planetary system formation and evolution. Such experiments can indeed complement observations
by providing access to the processes with spatial and temporal resolution. A previous investigation revealed the existence of a two-
component stream: a hot shell surrounding a cooler inner stream. The shell was formed by matter laterally ejected upon impact and
refocused by the local magnetic field. That laboratory investigation was limited to normal incidence impacts. However, in young
stellar objects, the complex structure of magnetic fields causes variability of the incident angles of the accretion columns. This led us
to undertake an investigation, using laboratory plasmas, of the consequence of having a slanted accretion impacting a young star.
Methods. Here, we used high power laser interactions and strong magnetic field generation in the laboratory, complemented by
numerical simulations, to study the asymmetry induced upon accretion structures when columns of matter impact the surface of
young stars with an oblique angle.
Results. Compared to the scenario where matter accretes perpendicularly to the star surface, we observe a strongly asymmetric plasma
structure, strong lateral ejecta of matter, poor confinement of the accreted material, and reduced heating compared to the normal
incidence case. Thus, slanted accretion is a configuration that seems to be capable of inducing perturbations of the chromosphere and
hence possibly influencing the level of activity of the corona.

Permalink: https://www.hzdr.de/publications/Publ-33918
Publ.-Id: 33918


Parametric study of high-energy ring-shaped electron beams from a laser wakefield accelerator

Maitrallain, A.; Brunetti, E.; Streeter, M.; Kettle, B.; Spesyvtsev, R.; Vieux, G.; Shazhad, M.; Ersfeld, B.; Yoffe, S.; Kornaszewski, A.; Finlay, O.; Ma, Y.; Albert, F.; Bourgeois, N.; Jd Dann, S.; Lemos, N.; Cipiccia, S.; M. Cole, J.; Gallardo González, I.; Higginbotham, A.; Hussein, A.; Smid, M.; Falk, K.; Krushelnick, K.; C. Lopes, N.; Gerstmayr, E.; Lumsdon, C.; Lundh, O.; Mangles, S.; Najmudin, Z.; P. Rajeev, P.; Symes, D.; G. R. Thomas, A.; A. Jaroszynski, D.

Laser wakefield accelerators commonly produce on-axis, low-divergence, high-energy electron beams. However, a high charge, annular shaped beam can be trapped outside the bubble and accelerated to high energies. Here we present a parametric study on the production of low-energy-spread, ultra-relativistic electron ring beams in a two-stage gas cell. Ring-shaped beams with energies higher than 750 MeV are observed simultaneously with on axis, continuously injected electrons. Often multiple ring shaped beams with different energies are produced and parametric studies to control the generation and properties of these structures were conducted. Particle tracking and particle-in-cell simulations are used to determine properties of these beams and investigate how they are formed and trapped outside the bubble by the wake produced by on-axis injected electrons. These unusual femtosecond duration, high-charge, high-energy, ring electron beams may find use in beam driven plasma wakefield accelerators and radiation sources.

Permalink: https://www.hzdr.de/publications/Publ-33917
Publ.-Id: 33917


Li‑Co–Ni‑Mn‑(REE) veins of the Western Erzgebirge, Germany—a potential source of battery raw materials

Burisch-Hassel, M.; Frenzel, M.; Seibel, H.; Gruber, A.; Oelze, M.; Pfänder, J. A.; Sanchez-Garrido, C.; Gutzmer, J.

Situated in the western Erzgebirge metallogenetic province (Vogtland, Germany), the Eichigt prospect is associated with
several quartz-Mn-Fe-oxyhydroxide veins that are exposed at surface. Bulk-rock geochemical assays of vein material yield
high concentrations of Li (0.6–4.1 kg/t), Co (0.6–14.7 kg/t), and Ni (0.2–2.8 kg/t), as well as signifcant quantities of Mn,
Cu, and light rare earth elements, a very unusual metal tenor closely resembling the mixture of raw materials needed for
Li-ion battery production. This study reports on the results of a frst detailed investigation of this rather unique polymetallic
mineralization style, including detailed petrographic and mineralogical studies complemented by bulk rock geochemistry,
electron microprobe analyses, and laser ablation inductively coupled mass spectrometry. The mineralized material comprises an oxide assemblage of goethite hematite, hollandite, and lithiophorite that together cement angular fragments of
vein quartz. Lithiophorite is the predominant host of Li (3.6–11.1 kg/t), Co (2.5–54.5 kg/t), and Ni (0.2–8.9 kg/t); Cu is
contained in similar amounts in hollandite and lithiophorite whereas light rare earth elements (LREE) are mainly hosted in
microcrystalline rhabdophane and forencite, which are fnely intergrown with the Mn-Fe-oxyhydroxides. 40Ar/39Ar ages
(~40–34 Ma) of coronadite group minerals coincide with tectonic activity related to the Cenozoic Eger Graben rifting. A
low-temperature hydrothermal overprint of pre-existing base metal sulfde-quartz mineralization on fault structures that were
reactivated during continental rifting is proposed as the most likely origin of the polymetallic oxyhydroxide mineralization
at Eichigt. However, tectonically enhanced deep-reaching fracture-controlled supergene weathering cannot be completely
ruled out as the origin of the mineralization.

Keywords: Lithiophorite; Coronadite group; Hollandite; Cryptomelane; 40Ar/39Ar geochronology; Trace elements; Lithium; Manganese; Cobalt; Exploration; Raw materials

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33916
Publ.-Id: 33916


Microstructured layered targets for improved laser-induced x-ray backlighters

Sander, S.; Ebert, T.; Hartnagel, D.; Hesse, M.; Pan, X.; Schaumann, G.; Smid, M.; Falk, K.; Roth, M.

We present the usage of two-layer targets with laser-illuminated front-side microstructures for x-ray backlighter applications. The targets consisted of a silicon front layer and copper back side layer. The structured layer was irradiated by the 500-fs PHELIX laser with an intensity above 1020Wcm−2. The total emission and one-dimensional extent of the copper Kα x-ray emission as well as a wide spectral range between 7.9 and 9.0 keV were recorded with an array of crystal spectrometers. The measurements show that the front-side modifications of the silicon in the form of conical microstructures maintain the same peak brightness of the Kα emission as flat copper foils while suppressing the thermal emission background significantly. The observed Kα source sizes can be influenced by tilting the conical microstructures with respect to the laser axis. Overall, the recorded copper Kα photon yields were in the range of 1011sr−1, demonstrating the suitability of these targets for probing applications without subjecting the probed material to additional heating from thermal line emission.

Downloads:

  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-33915
Publ.-Id: 33915


Observation and modelling of stimulated Raman scattering driven by an optically smoothed laser beam in experimental conditions relevant for shock ignition

Cristoforetti, G.; Hüller, S.; Koester, P.; Antonelli, L.; Atzeni, S.; Baffigi, F.; Batani, D.; Baird, C.; Booth, N.; Galimberti, M.; Glize, K.; Héron, A.; Khan, M.; Loiseau, P.; Mancelli, D.; Notley, M.; Oliveira, P.; Renner, O.; Smid, M.; Schiavi, A.; Tran, G.; Woolsey, N. C.; Gizzi, L. A.

We report results and modelling of an experiment performed at the Target Area West Vulcan laser facility, aimed at investigating laser–plasma interaction in conditions that are of interest for the shock ignition scheme in inertial confinement fusion (ICF), that is, laser intensity higher than 1016 W/cm2 impinging on a hot (T > 1 keV), inhomogeneous and long scalelength pre-formed plasma. Measurements show a significant stimulated Raman scattering (SRS) backscattering (∼ 4%−20% of laser energy) driven at low plasma densities and no signatures of two-plasmon decay (TPD)/SRS driven at the quarter critical density region. Results are satisfactorily reproduced by an analytical model accounting for the convective SRS growth in independent laser speckles, in conditions where the reflectivity is dominated by the contribution from the most intense speckles, where SRS becomes saturated. Analytical and kinetic
simulations well reproduce the onset of SRS at low plasma densities in a regime strongly affected by non-linear Landau damping and by filamentation of the most intense laser speckles. The absence of TPD/SRS at higher densities is explained by pump depletion and plasma smoothing driven by filamentation. The prevalence of laser coupling in the low-density profile justifies the low temperature measured for hot electrons (7−12 keV), which is well reproduced by
numerical simulations.

  • Open Access Logo High Power Laser Science and Engineering 10(2021)e60, 1-19
    Online First (2021) DOI: 10.1017/hpl.2021.48

Permalink: https://www.hzdr.de/publications/Publ-33914
Publ.-Id: 33914


Bionic Tracking - Making tracking tasks faster and more ergonomic with Eye Tracking in VR

Günther, U.

We present Bionic Tracking, a novel method for solving biological cell tracking problems with eye tracking in virtual reality using commodity hardware. Using gaze data, and especially smooth pursuit eye movements, we are able to track cells in time series of 3D volumetric datasets. The problem of tracking cells is ubiquitous in developmental biology, where large volumetric microscopy datasets are acquired on a daily basis, often comprising hundreds or thousands of time points that span hours or days. The image data, however, is only a means to an end, and scientists are often interested in the reconstruction of cell trajectories and cell lineage trees. Reliably tracking cells in crowded three-dimensional space over many timepoints remains an open problem, and many current approaches rely on tedious manual annotation and curation. In our Bionic Tracking approach, we substitute the usual 2D point-and-click annotation to track cells with eye tracking in a virtual reality headset, where users simply have to follow a cell with their eyes in 3D space in order to track it. We detail the interaction design of our approach and explain the graph-based algorithm used to connect different time points, also taking occlusion and user distraction into account. We demonstrate our cell tracking method using the example of two different biological datasets. Finally, we report on a user study with seven cell tracking experts, demonstrating the benefits of our approach over manual point-and-click tracking.

Related publications

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Euro Bioimaging Virtual Pub, 09.07.2021, Turku, Finland

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33912
Publ.-Id: 33912


Data publication: Realtime 3D graphics and VR with Kotlin and Vulkan

Günther, U.; Harrington, K.

This is the video recording of the talk.

Keywords: visualisation; rendering; kotlin; java; jvm

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-07
    DOI: 10.14278/rodare.1372
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33911
Publ.-Id: 33911


Realtime 3D graphics and VR with Kotlin and Vulkan

Günther, U.; Harrington, K.

This talk is gonna be about the scenery framework, a framework we have developed for visualising geometry and large volumetric data (TB+) using Kotlin and Vulkan or OpenGL. Coroutines, Kotlin's conciseness and syntactic sugar enabled the efficient codebase of scenery to integrate with popular image processing tools, and support Virtual Reality rendering, both on headsets and on distributed multi-projector systems like CAVEs. We'll show code, demos, lessons learned, and demonstrate how we use the framework in a visualisation software for end users, sciview, that we have also developed.

Keywords: visualisation; rendering; kotlin; java; jvm

Related publications

  • Open Access Logo Lecture (Conference) (Online presentation)
    FOSDEM 2021, 06.-07.02.2021, Brussels/online, Belgium

Permalink: https://www.hzdr.de/publications/Publ-33910
Publ.-Id: 33910


“recomine” – Sustainable Recycling of Contaminated Mine Waste with a Combination of Environmental Technology, Resource Technology and Digitalization

Büttner, P.; Engelhardt, J.

Abandoned contaminated mining sites such as heaps or slag usually cause major environmental problems, which are or have been rehabilitated in Germany by the government with large amount of taxes. However, they usually also contain significant amounts of urgently needed strategic raw materials and consist mainly of mineral components that can be used in the ceramics or construction materials industry. These components are not won as part of traditional coverage rehabilitation. “recomine” is a WIR! association of over 70 partnering institutions, funded by the German Federal Ministry of Education and Research (BMBF), that deals with the global challenges of contaminated soils and works on innovative, comprehensive concepts regarding their handling. For this matter, the association merges a vast know-how in the Erzgebirge region. The partnering institutions in the fields of environmental, and resource technology, digitalization, construction materials, and community are working together with the aim of marketing the developed, holistic concepts worldwide. First international success was achieved at the BHP Tailings Challenge where the recomine team was chosen by the raw materials conglomerate BHP as one of ten teams out of 153 international contenders for the ongoing proof-of-concept phase.

Keywords: re-mining; remining; recomine; HIF; circular economy; tailings; mine waste; mining; sustainable mining; recycling

  • Mining Report Glückauf 153(2021)6, 584-592
  • Open Access Logo Acamonta 28(2021), 32-33
  • Open Access Logo Lecture (others) (Online presentation)
    Lunch & Learn Seminar (#1), 04.02.2021, Online, Schweiz, Online
  • Contribution to WWW
    Recording of the 1st Lunch & Learn Seminar for the Young Mining Professionals Switzerland about recomine: https://youtu.be/Df8sIxmXiCE

Permalink: https://www.hzdr.de/publications/Publ-33909
Publ.-Id: 33909


Biotechnological production of the amphiphilic siderophore marinobactin for the usage as reagent in froth flotation process

Schrader, S.; Kutschke, S.; Pollmann, K.

The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of amphiphilic siderophores for the application as a reagent in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores is very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
The adapted biotechnological production for these amphiphilic siderophores, challenges the improvement of production rate under high stress conditions. Furthermore, this work presents interaction studies and flotation experiments of different scales of iron, copper and PGM containing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.

Keywords: Siderophores; Marinobactin; Marinobacter spp.

  • Lecture (Conference) (Online presentation)
    13th European Congress of Chemical Engineering and 6th European Congress of Applied Biotechnology, 20.-23.09.2021, Virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33908
Publ.-Id: 33908


Immunotargeting of CD98hc for Elimination of Radioresistant Head and Nek Squamous Cell Carcinoma

Köseer, A. S.; Arndt, C.; Feldmann, A.; Linge, A.; Bachmann, M.; Krause, M.; Dubrovska, A.

Majority of patients with head and neck squamous cell carcinomas (HNSCC) are diagnosed during the locally advanced (LA) stage and are given standard treatments such as primary radiochemotherapy (RCTx) or postoperative radiochemotherapy (PORT-C). Due to heterogenous tumor response, patients show various treatment outcomes. Our previous retrospective biomarker analyses showed that SLC3A2 is a promising biomarker for locoregional control (LRC) in LA HNSCC patients with HPV-negative tumors treated with primary RCTx or PORT-C, with increased LRC rates in patients with low SLC3A2 mRNA and its protein product CD98hc levels (1,2). The siRNA- and CRISPR-Cas9 mediated inhibition of CD98hc expression increased radiosensitivity of HNSCC cells. Hence, CD98hc is a promising target for radiosensitization of the HNSCC. One of the strategies for radiosensitization is targeted immunotherapy. However, Chimeric Antigen Receptor (CAR)-equipped T-cell therapy cannot be fully controlled. Therefore, the switchable Universal CAR (UniCAR) system was developed (3, 4) that is currently in phase I clinical trial (NCT04230265) (5). UniCAR T cell activity and specificity is controlled by the presence of target modules (TM) with short half-lives (3). We aim to define the clinical value of new treatment approaches by combining radio(chemo)therapy with CD98hc-targeted immunotherapy. We have used previously described radioresistant Cal33 HNSCC cells (2, 6). These tumor cells were co-cultured with UniCAR T cells in the presence or absence of a novel CD98 TM. Our data shows that CD98-redirected UniCAR T cells have the capability to induce cell lysis of radioresistant HNSCC cells in in vitro 3D culture. The most promising combination of therapeutic approach will be further tested in xenograft tumor models to evaluate the best performing combination of immunotherapy and radio(chemo)therapy. This system can be potentially used to approach the combination of the UniCAR system with radio(chemo)therapy for synergistic improvement of treatment efficacy of patients with metastatic radioresistant tumors.

  • Open Access Logo Lecture (Conference) (Online presentation)
    2nd International Conference “Cancer Metastasis”, 13.-17.12.2021, VIRTUAL, VIRTUAL

Permalink: https://www.hzdr.de/publications/Publ-33906
Publ.-Id: 33906


TiAl-based semi-finished material produced by reaction annealing of Ti/Al layered composite sheets

Pukenas, A.; Chekhonin, P.; Scharnweber, J.; Chulist, R.; Oertel, C.-G.; Freudenberger, J.; Skrotzki, W.

In this study multi-layered Ti/Al sheets prepared by accumulative roll bonding (ARB) underwent a two-step heat
treatment (HT) to form intermetallic compounds. The microstructure and crystal structure of the samples were
examined by scanning and transmission electron microscopy as well as energy-dispersive X-ray spectroscopy and synchrotron diffraction. In the first solid-state reaction annealing step, Ti-rich ARB samples containing 60 at% Ti and 40 at% Al were held at 600°C for 12 h under a uniaxial pressure between 0 MPa and 50 MPa applied along
the normal direction of the sheets. At this stage, Al is completely consumed by forming mainly Al-rich intermetallic
phases and to a lower extent other titanium aluminides such as Ti3Al and TiAl. In the second step, hightemperature annealing produces TiAl and Ti3Al as major phases during both pressureless annealing at 1100°C, 1200°C and 1300°C and annealing under an uniaxial pressure of about 100 MPa at 1200°C. Pore formation during the reaction annealing can be significantly reduced by the applied pressure. As a result, a TiAl-based semifinished material was fabricated.

Downloads:

  • Secondary publication expected from 15.12.2022

Permalink: https://www.hzdr.de/publications/Publ-33901
Publ.-Id: 33901


Resource selection of a nomadic ungulate in a dynamic landscape

Stratmann, T.; Dejid, N.; Calabrese, J.; Fagan, W.; Fleming, C.; Olson, K.; Mueller, T.

Nomadic movements are often a consequence of unpredictable resource dynamics. However, how nomadic ungulates select dynamic resources is still understudied. Here we examined resource selection of nomadic Mongolian gazelles (Procapra gutturosa) in the Eastern Steppe of Mongolia. We used daily GPS locations of 33 gazelles tracked up to 3.5 years. We examined selection for forage during the growing season using the Normalized Difference Vegetation Index (NDVI). In winter we examined selection for snow cover which mediates access to forage and drinking water. We studied selection at the population level using resource selection functions (RSFs) as well as on the individual level using step-selection functions (SSFs) at varying spatio-temporal scales from 1 to 10 days. Results from the population and the individual level analyses differed. At the population level we found selection for higher than average NDVI during the growing season. This may indicate selection for areas with more forage cover within the arid steppe landscape. In winter, gazelles selected for intermediate snow cover, which may indicate preference for areas which offer some snow for hydration but not so much as to hinder movement. At the individual level, in both seasons and across scales, we were not able to detect selection in the majority of individuals, but selection was similar to that seen in the RSFs for those individuals showing selection. Difficulty in finding selection with SSFs may indicate that Mongolian gazelles are using a random search strategy to find forage in a landscape with large, homogeneous areas of vegetation. The combination of random searches and landscape characteristics could therefore obscure results at the fine scale of SSFs. The significant results on the broader scale used for the population level RSF highlight that, although individuals show uncoordinated movement trajectories, they ultimately select for similar vegetation and snow cover.

Permalink: https://www.hzdr.de/publications/Publ-33899
Publ.-Id: 33899


Data publication: Estimating encounter location distributions from animal tracking data

Noonan, M.; Martinez-Garcia, R.; Davis, G.; Crofoot, M.; Kays, R.; Hirsch, B.; Caillaud, D.; Payne, E.; Sih, A.; Sinn, D.; Spiegel, O.; Fagan, W.; Fleming, C.; Calabrese, J.

Data from: Estimating encounter location distributions from animal tracking data

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33893
Publ.-Id: 33893


Estimating encounter location distributions from animal tracking data

Noonan, M.; Martinez-Garcia, R.; Davis, G.; Crofoot, M.; Kays, R.; Hirsch, B.; Caillaud, D.; Payne, E.; Sih, A.; Sinn, D.; Spiegel, O.; Fagan, W.; Fleming, C.; Calabrese, J.

Ecologists have long been interested in linking individual behaviour with higher level processes. For motile species, this ‘upscaling’ is governed by how well any given movement strategy maximizes encounters with positive factors and minimizes encounters with negative factors. Despite the importance of encounter events for a broad range of ecological processes, encounter theory has not kept pace with developments in animal tracking or movement modelling. Furthermore, existing work has focused primarily on the relationship between animal movement and encounter rates while the relationship between individual movement and the spatial locations of encounter events in the environment has remained conspicuously understudied. Here, we bridge this gap by introducing a method for describing the long-term encounter location probabilities for movement within home ranges, termed the conditional distribution of encounters (CDE). We then derive this distribution, as well as confidence intervals, implement its statistical estimator into open-source software and demonstrate the broad ecological relevance of this distribution. We first use simulated data to show how our estimator provides asymptotically consistent estimates. We then demonstrate the general utility of this method for three simulation-based scenarios that occur routinely in biological systems: (a) a population of individuals with home ranges that overlap with neighbours; (b) a pair of individuals with a hard territorial border between their home ranges; and (c) a predator with a large home range that encompassed the home ranges of multiple prey individuals. Using GPS data from white-faced capuchins Cebus capucinus, tracked on Barro Colorado Island, Panama, and sleepy lizards Tiliqua rugosa, tracked in Bundey, South Australia, we then show how the CDE can be used to estimate the locations of territorial borders, identify key resources, quantify the potential for competitive or predatory interactions and/or identify any changes in behaviour that directly result from location-specific encounter probability. The CDE enables researchers to better understand the dynamics of populations of interacting individuals. Notably, the general estimation framework developed in this work builds straightforwardly off of home range estimation and requires no specialized data collection protocols. This method is now openly available via the ctmm R package.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33892
Publ.-Id: 33892


Cell voltage model for Li-Bi liquid metal batteries

Weber, N.; Duczek, C.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Weier, T.; Sadoway, D. R.

The dataset contains the raw data and python codes for the publication: https://doi.org/10.1016/j.apenergy.2021.118331

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-01-06
    DOI: 10.14278/rodare.1368
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33890
Publ.-Id: 33890


Introducing natural adversarial observations to a Deep Reinforcement Learning agent for Atari Games

Hanfeld, P.

Deep Learning methods are known to be vulnerable to adversarial attacks. Since Deep Reinforcement Learning agents are based on these methods, they are prone to tiny input data changes. Three methods for adversarial example generation will be introduced and applied to agents trained to play Atari games. The attacks target either single inputs or can be applied universally to all possible inputs of the agents. They were able to successfully shift the predictions towards a single action or to lower the agent’s confidence in certain actions, respectively. All proposed methods had a severe impact on the agent’s performance while producing invisible adversarial perturbations. Since natural-looking adversarial observations should be completely hidden from a human evaluator, the negative impact on the performance of the agents should additionally be undetectable. Several variants of the proposed methods were tested to fulfil all posed criteria. Overall, seven generated observations for two of three Atari games are classified as natural-looking adversarial observations.

Keywords: Reinforcement Learning; Adversarial Attacks; Deep Learning

  • Master thesis
    Hochschule Mittweida, 2021
    Mentor: Chorowski, Jan; Villmann, Thomas
    75 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33889
Publ.-Id: 33889


Emergence of pion parton distributions

Cui, Z.-F.; Ding, M.; Morgado, J. M.; Raya, K.; Binosi, D.; Chang, L.; de Soto, F.; Roberts, C. D.; Rodriguez-Quintero, J.; Schmidt, S. M.

Supposing only that there is an effective charge which defines an evolution scheme for parton distribution functions (DFs) that is all-orders exact, strict lower and upper bounds on all Mellin moments of the valence-quark DFs of pion-like systems are derived. Exploiting contemporary results from numerical simulations of lattice-regularised quantum chromodynamics (QCD) that are consistent with these bounds, parameter-free predictions for pion valence, glue, and sea DFs are obtained. The form of the valence-quark DF at large values of the light-front momentum fraction is consistent with predictions derived using the QCD-prescribed behaviour of the pion wave function.

Permalink: https://www.hzdr.de/publications/Publ-33888
Publ.-Id: 33888


Concerning pion parton distributions

Cui, Z.-F.; Ding, M.; Morgado, J. M.; Raya, K.; Binosi, D.; Chang, L.; Papavassiliou, J.; Roberts, C. D.; Rodriguez-Quintero, J.; Schmidt, S. M.

Analyses of the pion valence-quark distribution function (DF), ${\mathpzc u}^\pi(x;\zeta)$, which explicitly incorporate the behaviour of the pion wave function prescribed by quantum chromodynamics (QCD), predict ${\mathpzc u}^\pi(x\simeq 1;\zeta) \sim (1-x)^{\beta(\zeta)}$, $\beta(\zeta \gtrsim m_p)>2$, where $m_p$ is the proton mass. Nevertheless, more than forty years after the first experiment to collect data suitable for extracting the $x\simeq 1$ behaviour of ${\mathpzc u}^\pi$, the empirical status remains uncertain because some methods used to fit existing data return a result for ${\mathpzc u}^\pi$ that violates this constraint. Such disagreement entails one of the following conclusions: the analysis concerned is incomplete; not all data being considered are a true expression of qualities intrinsic to the pion; or QCD, as it is currently understood, is not the theory of strong interactions. New, precise data are necessary before a final conclusion is possible. In developing these positions, we exploit a single proposition, \emph{viz}.\ there is an effective charge which defines an evolution scheme for parton DFs that is all-orders exact. This proposition has numerous corollaries, which can be used to test the character of any DF, whether fitted or calculated.

Permalink: https://www.hzdr.de/publications/Publ-33887
Publ.-Id: 33887


Optical absorption and carrier multiplication at graphene edges in a magnetic field

Queisser, F.; Lang, S.; Schützhold, R.

We study optical absorption at graphene edges in a transversal magnetic field. The magnetic field bends the trajectories of particle- and hole excitations into antipodal direction which generates a directed current. We find a rather strong amplification of the edge current by impact ionization processes. More concretely, the primary absorption and the subsequent carrier multiplication is analyzed for a graphene fold and a zigzag edge. We identify exact and approximate selection rules and discuss the dependence of the decay rates on the initial state.

Keywords: Graphene; Auger processes; optical absorption

Permalink: https://www.hzdr.de/publications/Publ-33886
Publ.-Id: 33886


Optical absorption and carrier multiplication at graphene edges in a magnetic field

Queisser, F.; Lang, S.; Schützhold, R.

We study optical absorption at graphene edges in a transversal magnetic field. The magnetic field bends the trajectories of particle- and hole excitations into antipodal direction which generates a directed current. We find a rather strong amplification of the edge current by impact ionization processes. More concretely, the primary absorption and the subsequent carrier multiplication is analyzed for a graphene fold and a zigzag edge. We identify exact and approximate selection rules and discuss the dependence of the decay rates on the initial state.

Keywords: Graphene; Auger processes; optical absorption

Permalink: https://www.hzdr.de/publications/Publ-33885
Publ.-Id: 33885


On the measurement of local concentrations in bubbly flows for the reaction of FeII(edta) with NO using fiber optical probe

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

Topics of current research activities within the DFG priority program SPP 1740 “Reactive Bubbly Flows” are studies on local mass transfer and reaction processes in order to gain a deeper understanding about the coupling of hydrodynamics, mass transfer and reaction kinetics in reactive bubbly flows.
This contribution presents the results of an experimental study on reaction of FeII(EDTA) and NO. The reaction forms a very stable complex of [Fe(EDTA)NO)2-]. The aim of the experiments is the measurement of the local species concentration of the product complex in the bubble wake. For this purpose, a fiber optical probe, especially designed for this application was used. The sensor is equipped with two LED’s and optical filters of different wavelengths (λ_1 = 435 nm, λ_2 = 780 nm), respectively. The selection of the wavelengths is based on the absorption spectra of [Fe(EDTA)NO)2-], in order to provide a product specific wavelength (λ_1 = 435 nm) and reference wavelength (λ_2 = 780 nm). In that way, the concentration of the product species and information about the prevailing phase (liquid or gas) were recorded simultaneously. Experiments were carried out in a bubble column with 74mm inner diameter and single needle gas injection (see Figure 1a). Figure 1b shows an example of the time signal of the concentration of the product species, where disturbed signals due to bubble-probe interactions are removed based on the signals of the reference wavelength. In this contribution, characteristic parameters of the species concentration in the bubble wake obtained from measurements with the fiber optical probe are presented for different initial concentrations of the solution and different hydrodynamic conditions.

The authors gratefully acknowledge the financial support provided by the German Research Foundation (DFG) within Priority Program “Reactive Bubbly Flows” SPP 1740.

  • Lecture (Conference) (Online presentation)
    Jahrestreffen der ProcessNet Fachgruppen Mehrphasenströmung (MPH) und Computational Fluid Dynamics (CFD), 09.-10.03.2021, Paderborn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33883
Publ.-Id: 33883


Tetra‐substituted p‐tert‐butylcalix[4]arene with phosphoryl and salicylamide functional groups: synthesis, complexation and selective extraction of f‐element cations

Glasneck, F.; Roode-Gutzmer, Q.; Stumpf, T.; Kersting, B.

A new series of lanthanide (1-5) and uranyl (6) complexes with a tetra-substituted bifunctional calixarene ligand H₂L is described.The coordination environment for the Ln³+ and UO₂²+ ions is provided by phosphoryl and salicylamidefunctional groups appended to the lower rim of the p-tert-butylcalix[4]arenescaffold. Ligand interactions with lanthanide cations (light: La³+, Pr³+; intermediate: Eu³+and Gd³+; and heavy: Yb³+), as well as the uranyl cation (UO₂²+) is examined in the solution and solid state, respectively with spectrophotometric titration and single crystal X-ray diffractometry. The ligand is fully deprotonated in the complexation of trivalent lanthanide ions forming di-cationic complexes 2:2 M:L, [Ln2(L)2(H2O)]2+(1-5), in solution, whereas uranyl formed a 1:1 M:L complex [UO2(L)(MeOH)]∞(6) that demonstrated very limited solubility in 12 organic solvents. Solvent extraction behaviour is examined for cation selectivity and extraction efficiency. H₂L was found to be an effective extracting agent for UO₂²+ over La³+ and Yb³+ cations. The separation factors at pH 6.0 are: ß UO₂²+/La³+ = 121.0 and ß UO₂²+/Yb³+ = 70.0.

Keywords: tetra-substituted calixarene; f-elements; uranyl; lanthanides; solvent extraction

Permalink: https://www.hzdr.de/publications/Publ-33882
Publ.-Id: 33882


Magnetic field assisted electrodeposition of metal on conically structured electrodes

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

The electrodeposition of metal on conically shaped diamagnetic and ferromagnetic electrodes is studied under the influence of a vertical magnetic field. Analytical and numerical results show a beneficial influence of the magnetic field to enhance the cone growth, which can be attributed to the electrolyte flow forced by the Lorentz force and the magnetic gradient force. The influences of cone shape, cone size and distance between neighbouring cones are investigated in detail. The results deliver insights into the feasibility of magnetic field assisted electrodeposition towards nano-structured conical electrodes.

  • Lecture (Conference) (Online presentation)
    International Congress of Theoretical and Applied Mechanics (ICTAM 2020+1), 26.08.2021, Milano, Italien

Permalink: https://www.hzdr.de/publications/Publ-33878
Publ.-Id: 33878


Laser induced crystallization of Co–Fe–B films

Almeida, M.; Sharma, A.; Matthes, P.; Köhler, N.; Busse, S.; Müller, M.; Hellwig, O.; Horn, A.; Zahn, D. R. T.; Salvan, G.; Schulz, S. E.

Local crystallization of ferromagnetic layers is crucial in the successful realization of miniaturized
tunneling magnetoresistance (TMR) devices. In the case of Co–Fe–B TMR devices, used most
successfully so far in applications and devices, Co–Fe–B layers are initially deposited in an amorphous
state and annealed post-deposition to induce crystallization in Co–Fe, thereby increasing the device
performance. In this work, first direct proof of locally triggered crystallization of 10 nm thick Co–Fe–B
films by laser irradiation is provided by means of X-ray diffraction (XRD) using synchrotron radiation.
A comparison with furnace annealing is performed for benchmarking purposes, covering different
annealing parameters, including temperature and duration in the case of furnace annealing, as
well as laser intensity and scanning speed for the laser annealing. Films of Co–Fe–B with different
stoichiometry sandwiched between a Ru and a Ta or MgO layer were systematically assessed by XRD
and SQUID magnetometry in order to elucidate the crystallization mechanisms. The transformation
of Co–Fe–B films from amorphous to crystalline is revealed by the presence of pronounced CoFe(110)
and/or CoFe(200) reflexes in the XRD θ-2θ scans, depending on the capping layer. For a certain window
of parameters, comparable crystallization yields are obtained with furnace and laser annealing.
Samples with an MgO capping layer required a slightly lower laser intensity to achieve equivalent Co–
Fe crystallization yields, highlighting the potential of laser annealing to locally enhance the TMR ratio.

Permalink: https://www.hzdr.de/publications/Publ-33873
Publ.-Id: 33873


Noncollinear Remanent Textures Induced by Surface Spin Flop in Synthetic Antiferromagnets with Perpendicular Anisotropy

Böhm, B.; Fallarino, L.; Pohl, D.; Rellinghaus, B.; Hellwig, O.

The surface spin flop, observed in synthetic antiferromagnets (SAFs) with uniaxial anisotropy and
strong antiferromagnetic (AF) interlayer exchange coupling, can be considered as a laterally homoge-
neous, vertical AF domain wall pushed into the SAF from either the top or the bottom in the presence
of a strong external vertical magnetic field. As a result, the AF domain wall can be described as a one-
dimensional entity. In this work, we present a concept to stabilize laterally homogeneous vertical AF
domain walls by local variation of the perpendicular magnetic anisotropy in Co/Pt-based SAFs. Our
approach not only allows the stabilization of the vertical AF domain wall in the absence of any exter-
nal magnetic field, but furthermore enables a deterministic selection among four different remanent states,
each one stable within a broad external magnetic field range of almost one tesla. We also demonstrate an
extension to our concept by stabilizing two coexisting vertical AF domain walls, thus yielding a system
with a total of six different selectable (and reprogrammable) remanent states. The controlled stabiliza-
tion of noncollinear AF textures in the form of vertical AF domain walls at remanence could be used as
an infrastructure for propagating spin waves within the AF domain wall itself, as well as for tuning the
dynamic behavior of perpendicular standing spin wave modes existing vertically across the SAF.

Permalink: https://www.hzdr.de/publications/Publ-33872
Publ.-Id: 33872


CoCrFeNi High-Entropy Alloy Thin Films Synthesised by Magnetron Sputter Deposition from Spark Plasma Sintered Targets

Schwarz, H.; Uhlig, T.; Rösch, N.; Lindner, T.; Ganss, F.; Hellwig, O.; Lampke, T.; Wagner, G.; Seyller, T.

Two magnetron sputter targets of CoCrFeNi High-Entropy Alloy (HEA), both in equal atomic ratio, were prepared by spark plasma sintering. One of the targets was fabricated from a homogeneous HEA powder produced via gas atomisation; for the second target, a mixture of pure element powders was used. Economic benefits can be achieved by mixing pure powders in the intended ratio in comparison to the gas atomisation of the specific alloy composition. In this work, thin films deposited via magnetron sputtering from both targets are analysed. The surface elemental composition is investigated by X-ray photoelectron spectroscopy, whereas the bulk stoichiometry is measured by X-ray fluorescence spectroscopy. Phase information and surface microstructure are investigated using X-ray diffraction and scanning electron microscopy, respectively. It is demonstrated that the stoichiometry, phase composition and microscopic structure of the as-deposited HEA thin films are almost identical if the same deposition parameters are used.

Keywords: high-entropy alloy; magnetron sputtering; spark plasma sintering; X-ray photoelectron spectroscopy; X-ray diffraction; scanning electron microscopy

Permalink: https://www.hzdr.de/publications/Publ-33871
Publ.-Id: 33871


Worldline instantons for nonlinear Breit-Wheeler pair production and Compton scattering

Degli Esposti, G.; Torgrimsson, G.

Worldline instantons have previously been used to study the probability of Schwinger pair production (both the exponential and pre-exponential parts) and photon-stimulated pair production (the exponential part). Previous studies obtained the pair-production probability on the probability level by using unitarity, i.e. the imaginary part of the effective action for Schwinger pair production or the imaginary part of the polarization tensor for photon-stimulated pair production. The corresponding instantons are closed loops in the complex plane. Here we show how to use instantons on the amplitude level, which means open instanton lines with start and end points representing fermions at asymptotic times. The amplitude is amputated with LSZ using, in general, field-dependent asymptotic states. We show how to use this formalism for photon-stimulated/Breit-Wheeler pair production and nonlinear Compton scattering.

Permalink: https://www.hzdr.de/publications/Publ-33869
Publ.-Id: 33869


Edge and Point-Defect Induced Electronic and Magnetic Properties in Monolayer PtSe₂

Li, J.; Joseph, T.; Ghorbani Asl, M.; Kolekar, S.; Krasheninnikov, A.; Batzill, M.

Edges and point defects in layered dichalcogenides are important for tuning their electronic and magnetic properties. By combining scanning tunneling microscopy (STM) with density functional theory (DFT), the electronic structure of edges and point defects in 2D-PtSe2 are investigated where the 1.8 eV- band gap of monolayer PtSe2 facilitates the detailed characterization of defect-induced gap states by STM. The stoichiometric zigzag edge terminations are found to be energetically favored. STM and DFT show that these edges exhibit metallic one-dimensional states with spin-polarized bands. Various native point defects in PtSe2 are also characterized by STM. A comparison of the experiment with simulated images enables the identification of Se-vacancies, Pt-vacancies, and Se-antisites as the dominant defects in PtSe2. In contrast to Se- or Pt- vacancies, the Se-antisites are almost devoid of gap states. Pt-vacancies exhibit defect-induced states that are spin-polarized, emphasizing their importance for inducing magnetism in PtSe2. The atomic-scale insights into defect-induced electronic states in monolayer PtSe2 provide the fundamental underpinning for defect engineering of PtSe2-monolayers and the newly identified spin-polarized edge states offer prospects for engineering magnetic properties in PtSe2 nanoribbons.

Keywords: 2D materials; defect engineering; edge states; spin polarized defects; electronic defect states; scanning probe microscopy

Permalink: https://www.hzdr.de/publications/Publ-33868
Publ.-Id: 33868


Dressed Dirac Propagator from a Locally Supersymmetric N=1 Spinning Particle

Degli Esposti, G.; Corradini, O.

We study the Dirac propagator dressed by an arbitrary number N of photons by means of a worldline approach, which makes use of a supersymmetric N=1 spinning particle model on the line, coupled to an external Abelian vector field. We obtain a compact off-shell master formula for the tree level scattering amplitudes associated to the dressed Dirac propagator. In particular, unlike in other approaches, we express the particle fermionic degrees of freedom using a coherent state basis, and consider the gauging of the supersymmetry, which ultimately amounts to integrating over a worldline gravitino modulus, other than the usual worldline einbein modulus which corresponds to the Schwinger time integral. The path integral over the gravitino reproduces the numerator of the dressed Dirac propagator.

Permalink: https://www.hzdr.de/publications/Publ-33866
Publ.-Id: 33866


Data, code, and metadata for: Daily torpor reduces the energetic consequences of microhabitat selection for a widespread bat

Alston, J.; Dillon, M. E.; Keinath, D. A.; Abernethy, I. M.; Goheen, J. R.

This repository contains all data, code, and metadata required to reproduce the results detailed in "Daily torpor reduces the energetic consequences of microhabitat selection for a widespread bat" by Alston et al.

Keywords: Bayesian hierarchical models; climate change; daily torpor; fringed myotis (Myotis thysanodes); temporal heterothermy; thermal ecology; VHF telemetry

Permalink: https://www.hzdr.de/publications/Publ-33865
Publ.-Id: 33865


The Potential of Machine Learning for a More Responsible Sourcing of Critical Raw Materials

Ghamisi, P.; Rafiezadeh Shahi, K.; Duan, P.; Rasti, B.; Lorenz, S.; Booysen, R.; Thiele, S. T.; Contreras Acosta, I. C.; Kirsch, M.; Gloaguen, R.

The digitization and automation of the raw material sector is required to attain the targets set by the Paris Agreements and support the sustainable development goals defined by the United Nations. While many aspects of the industry will be affected, most of the technological innovations will require smart imaging sensors. In this review, we assess the relevant recent developments of machine learning for the processing of imaging sensor data. We first describe the main imagers and the acquired data types as well as the platforms on which they can be installed. We briefly describe radiometric and geometric corrections as these procedures have been already described extensively in previous works. We focus on the description of innovative processing workflows and illustrate the most prominent approaches with examples. We also provide a list of available resources, codes, and libraries for researchers at different levels, from students to senior researchers, willing to explore novel methodologies on the challenging topics of raw material extraction, classification, and process automatization.

Keywords: Deep learning (DL); Earth observation; machine learning; Mining; Raw materials.

Related publications

  • Open Access Logo IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 14(2021), 8971-8988
    Online First (2021) DOI: 10.1109/JSTARS.2021.3108049

Permalink: https://www.hzdr.de/publications/Publ-33864
Publ.-Id: 33864


Unsupervised Data Fusion with Deeper Perspective: A Novel Multi-Sensor Deep Clustering Algorithm

Rafiezadeh Shahi, K.; Ghamisi, P.; Rasti, B.; Scheunders, P.; Gloaguen, R.

The ever-growing developments in technology to capture different types of image data (e.g., hyperspectral imaging and Light Detection and Ranging (LiDAR)-derived digital surface model (DSM)), along with new processing techniques, have led to a rising interest in imaging applications for Earth observation. However, analyzing such datasets in parallel remains a challenging task. In this paper, we propose a multi-sensor deep clustering (MDC) algorithm for the joint processing of multi-source imaging data. The architecture of MDC is inspired by autoencoder (AE)-based networks. The MDC paradigm includes three parallel networks, a spectral network using an autoencoder structure, a spatial network using a convolutional autoencoder structure, and lastly, a fusion network that reconstructs the concatenated image information from the concatenated latent features from the spatial and spectral network. The proposed algorithm combines the reconstruction losses obtained by the aforementioned networks to optimize the parameters (i.e., weights and bias) of all three networks simultaneously. To validate the performance of the proposed algorithm, we use two multi-sensor datasets from different applications (i.e., geological and rural sites) as benchmarks. The experimental results confirm the superiority of our proposed deep clustering algorithm compared to a number of state-of-the-art clustering algorithms. The code will be available at: https://github.com/Kasra2020/MDC.

Keywords: Multi-sensor Data Fusion; Deep Learning; Autoencoder; Convolutional Autoencoder; Remote Sensing

Related publications

  • Open Access Logo IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 15(2021), 284-296
    Online First (2021) DOI: 10.1109/JSTARS.2021.3132856

Permalink: https://www.hzdr.de/publications/Publ-33863
Publ.-Id: 33863


Quantum magnetism of ferromagnetic spin dimers in α-KVOPO4

Mukharjee, P. K.; Somesh, K.; Ranjith, K. M.; Baenitz, M.; Scurschii, I.; Adroja, D. T.; Khalyavin, D.; Tsirlin, A. A.; Nath, R.

Magnetism of the spin- 1/2 α-KVOPO4 is studied by thermodynamic measurements, 31P nuclear magnetic resonance, neutron diffraction, and density-functional band-structure calculations. Ferromagnetic Curie-Weiss temperature of θCW ≃ 15.9 K and the saturation field of μ0Hs ≃ 11.3 T suggest the predominant ferromagnetic coupling augmented by a weaker antiferromagnetic exchange that leads to a short-range order below 5 K and the long-range antiferromagnetic order below TN ≃ 2.7 K in zero field. Magnetic structure with the propagation vector k = (0, 1/2, 0) and the ordered magnetic moment of 0.58 μB at 1.5 K exposes a nontrivial spin lattice where strong ferromagnetic dimers are coupled antiferromagnetically. The reduction in the ordered magnetic moment with respect to the classical value (1 μB) indicates sizable quantum fluctuations in this setting, despite the predominance of ferromagnetic exchange. We interpret this tendency toward ferromagnetism as arising from the effective orbital order in the folded chains of the VO6 octahedra.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33862
Publ.-Id: 33862


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263] [264] [265] [266] [267] [268] [269] [270] [271] [272] [273] [274] [275] [276] [277] [278] [279] [280] [281] [282] [283] [284] [285] [286] [287] [288] [289] [290] [291] [292] [293] [294] [295] [296] [297] [298] [299] [300] [301] [302] [303] [304] [305] [306]