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37535 Publications

Data publication: Electrokinetic Janus micromotors moving on topographically flat chemical patterns

Huang, T.; Misko, V.; Caspari, A.; Synytska, A.; Ibarlucea, B.; Nori, F.; Faßbender, J.; Cuniberti, G.; Makarov, D.; Baraban, L.

Uploaded data show the research discussions of the electroosmotic flows at the boundary between positive and negative surfaces .

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-08-18
    DOI: 10.14278/rodare.1835
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-35042
Publ.-Id: 35042


Comparison of manual and automated ventricle segmentation in the maternal immune stimulation rat model of schizophrenia

Winter, R.; Akinola, B.; Barroeta-Hlusicka, E.; Meister, S.; Pietzsch, J.; Winter, C.; Bernhardt, N.

Maternal immune stimulation (MIS) is strongly implicated in the etiology of neuropsychiatric disorders. Magnetic resonance imaging (MRI) studies provide evidence for brain structural abnormalities in rodents following prenatal exposure to MIS. Reported volumetric changes in adult MIS offspring comprise among others larger ventricular volumes, consistent with alterations found in patients with schizophrenia. Linking rodent models of MIS with non-invasive small animal neuroimaging modalities thus represents a powerful tool for the investigation of structural endophenotypes. Traditionally manual segmentation of regions-of-interest, which is laborious and prone to low intra- and inter-rater reliability, was employed for data analysis. Recently automated analysis platforms in rodent disease models are emerging. However, none of these has been found to reliably detect ventricular volume changes in MIS nor directly compared manual and automated data analysis strategies. The present study was thus conducted to establish an automated, structural analysis method focused on lateral ventricle segmentation. It was applied to ex-vivo rat brain MRI scans. Performance was validated for phenotype induction following MIS and preventive treatment data and compared to manual segmentation. In conclusion, we present an automated analysis platform to investigate ventricular volume alterations in rodent models thereby encouraging their preclinical use in the search for new urgently needed treatments.

Permalink: https://www.hzdr.de/publications/Publ-35041
Publ.-Id: 35041


Resummation for quantum propagators in bounded spaces

Edwards, J. P.; González-Domínguez, V. A.; Huet, I.; Trejo Espinosa, M. A.

We outline an approach to calculating the quantum mechanical propagator in the presence of geometrically nontrivial Dirichlet boundary conditions. The method is based on a generalization of an integral transform of the propagator studied in previous work (the so-called “hit function”) and a convergent sequence of Padé approximants that exposes the limit of perfectly reflecting boundaries. In this paper the generalized hit function is defined as a many-point propagator, and we describe its relation to the sum over trajectories in the Feynman path integral. We then show how it can be used to calculate the Feynman propagator. We calculate analytically all such hit functions in D = 1 and D = 3 dimensions, giving recursion relations between them in the same or different dimensions and apply the results to the simple cases of propagation in the presence of perfectly conducting planar and spherical plates. We use these results to conjecture a general analytical formula for the propagator when Dirichlet boundary conditions are present in a given geometry, also explaining how it can be extended for application for more general, nonlocalized potentials. Our work has resonance with previous results obtained by Grosche in the study of path integrals in the presence of delta potentials. We indicate the eventual application in a relativistic context to determining Casimir energies using this technique.

Keywords: Integral equations; Quantum theory; Bounded spaces; Convergent sequences; Dirichlet boundary conditions; Feynman path integrals; Generalisation; Integral transform; Pade approximants; Quantum mechanical; Reflecting boundary; Resummation

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Permalink: https://www.hzdr.de/publications/Publ-35038
Publ.-Id: 35038


Enhanced Longitudinal Relaxation of Magnetic Solitons in Ultrathin Films

Yastremsky, I. A.; Faßbender, J.; Ivanov, B. A.; Makarov, D.

Relaxation fundamentally determines the operation speed and energy efficiency of spintronic and
spinorbitronic devices. We develop a theory of the longitudinal contribution to the relaxation of domain
walls in ferromagnetic films of any thickness with the Dzyaloshinskii-Moriya interaction, which allows
quantitative comparison with experiments. We show that the longitudinal contribution increases with a
decrease of the transversal relaxation (e.g., the Gilbert constant). We predict a substantial enhancement
of the contribution of the longitudinal relaxation to the damping of magnetic solitons with a decrease of
the film thickness. We demonstrate that for ultrathin ferromagnetic films, the contribution of the longitudinal
relaxation to the damping of domain walls is comparable to or stronger than any other traditional
transversal mechanisms, including spin pumping. Although in this work we focus on the analysis of longitudinal
relaxation for domain walls, in ultrathin samples it should be taken into account also for other
magnetic solitons including skyrmions. This work adds to the fundamental understanding of the design
and optimization of spintronic and spinorbitronic devices based on moving solitons in ultrathin films.

Keywords: Longitudinal Relaxation; magnetic thin films; magnetic solitons

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Permalink: https://www.hzdr.de/publications/Publ-35037
Publ.-Id: 35037


Laser-generated supersonic plasma jets and shocks in a transverse magnetic field

Bohlin, H.; Brack, F.-E.; Cervenak, M.; Chodukowski, T.; Cikhardt, J.; Dostál, J.; Dudžák, R.; Hubner, J.; Huo, W.; Jelinek, S.; Klír, D.; Kroll, F.; Krupka, M.; Krůs, M.; Pisarczyk, T.; Rusiniak, Z.; Schramm, U.; T.-H, N.-B.; Weber, S.; Zaraś-Szydłowska, A.; Zeil, K.; Kumar, D.; Schlegel, T.; Tikhonchuk, V.

The influence of a transverse magnetic field on the formation and evolution of supersonic plasma jets and shocks was studied experimentally, and compared with 3D numerical simulations. An improved jet collimation was seen due to the change in the magnetic field topology restricting the radial expansion of the ablated plasma. The magnetic field was also shown to strongly affect the shock structures, both indirectly through the modified jet geometry, as well as due to a compression of the field lines in the shock region. The interaction characteristics were found to depend on the relative contribution of the magnetic and plasma pressure in balancing the ram pressure of the jet.

Keywords: Laser; Plasma; Astrophysics; Pulsed Magnet

Permalink: https://www.hzdr.de/publications/Publ-35035
Publ.-Id: 35035


Numerical modeling of horizontal stratified two-phase flows using the AIAD model

Yan, H.; Zhang, H.; Höhne, T.; Liao, Y.; Lucas, D.; Liu, L.

In nuclear reactor safety research, the countercurrent gas-liquid two-phase flow in the hot leg of a pressurized water reactor (PWR) has attracted considerable attention. Previous work has proven that the algebraic interfacial area density (AIAD) model implemented in ANSYS CFX can effectively capture the gas-liquid interface and avoid the loss of information regarding the interfacial structure, which occurs after phase averaging in the Euler–Euler two-fluid approach. To verify the accuracy of the AIAD module implementation in ANSYS Fluent, the model based on the experimental data from the WENKA facility is validated in this work. The effects of the subgrid wave turbulence model, turbulence damping model, and droplet entrainment model are simultaneously investigated, which have been shown to be important in the previous work with CFX. The results show that the simulations are considerably and significantly deviate from the experiments when the turbulence damping is not considered. The free surface modeling of two-phase flow can be optimized by using the droplet entrainment model. The consistency between the simulation and experimental results is not enhanced after the subgrid wave turbulence model is adopted. Further investigations regarding the implementation of the subgrid wave turbulence model are necessary.

Keywords: AIAD; CFD; droplet entrainment; subgrid wave turbulence; thermal hydraulics; turbulence damping

Permalink: https://www.hzdr.de/publications/Publ-35031
Publ.-Id: 35031


Understanding structure–properties relationships of porphyrin linked to graphene oxide through π–π-stacking or covalent amide bonds

Lewandowska-Andralojc, A.; Gacka, E.; Pedzinski, T.; Burdzinski, G.; Lindner, A. A.; O’Brien, J. M.; Senge, M. O.; Siklitskaya, A.; Kubas, A. G.; Marciniak, B.; Walkowiak-Kulikowska, J.

Two graphene oxide nanoassemblies using 5-(4-(aminophenyl)-10,15,20-triphenylporphyrin
(TPPNH2) were fabricated by two synthetic methods: covalent (GO-CONHTPP) and noncovalent
bonding. GO-CONHTPP was achieved through amide formation at the periphery of GO sheets and the
hybrid material was fully characterized by FTIR, XPS, Raman spectroscopy, and SEM. Spectroscopic
measurements together with theoretical calculations demonstrated that assembling TPPNH2
on the GO surface in DMF-H2O (1:2, v/v) via non-covalent interactions causes changes in the absorption
spectra of porphyrin, as well as efficient quenching of its emission. Interestingly, covalent binding
to GO does not affect notably neither the porphyrin absorption nor its fluorescence. Theoretical
calculations indicates that close proximity and π–π-stacking of the porphyrin molecule with the GO
sheet is possible only for the non-covalent functionalization. Femtosecond pump–probe experiments
revealed that only the non-covalent assembly of TPPNH2 and GO enhances the efficiency of the
photoinduced electron transfer from porphyrin to GO. In contrast to the non-covalent hybrid,
the covalent GO-CONHTPP material can generate singlet oxygen with quantum yields efficiency
(ΦΔ = 0.20) comparable to that of free TPPNH2 (ΦΔ = 0.26), indicating the possible use of covalent
hybrid materials in photodynamic/photothermal therapy. The spectroscopic studies combined with
detailed quantum-chemical analysis provide invaluable information that can guide the fabrication of
hybrid materials with desired properties for specific applications.

Keywords: porphyrin; graphene oxide; photochemistry

Permalink: https://www.hzdr.de/publications/Publ-35030
Publ.-Id: 35030


Ressourceneffizienzsteigerung in der Metallindustrie - Substitution von Primärrohstoffen durch optimiertes legierungsspezifisches Recycling

Raatz, S.; Seidel, P.; Tuma, A.; Thorenz, A.; Helbig, C.; Reller, A.; Faulstich, M.; Joachimsthaler, C.; Steger, S.; Hagedorn, W.; Bickel, M.; Liedtke, C.

Das durch das Umweltbundesamt geförderte Projekt befasst sich mit der Ressourceneffizienz-
steigerung in der Metallindustrie in Hinblick auf die Substitution von Primärrohstoffen, die im
Recyclingprozess zur Verdünnung unerwünschter Begleitelemente beim Recycling eine wesent-
liche Rolle spielen. Das damit einhergehend Downcycling soll mittels innovativer Sortiertechni-
ken (Kamera-/Sensorsysteme) vermindert und der Recyclingprozess von metallischen Legie-
rungen durch eine höhere Trennschärfe deutlich verbessert werden.
Der Fokus der Untersuchungen liegt in diesem Projekt auf der Untersuchung eines legierungs-
spezifischen Recyclings von Stahl-, Aluminium-, Kupfer- und Zinkschrotten. Hier soll der Ver-
gleich verschiedener Schrottfraktionen vor bzw. nach innovativen Analyse- bzw. Sortier- und Se-
parier-Prozessen neue Erkenntnisse liefern. Darüber hinaus werden definitorische Grundlagen
sowie Steuerungsgrößen für Up- und Downcycling und Regeln für sortenarmes Design erarbei-
tet.
Auf Grundlage der Analyseergebnisse werden politische Empfehlungen zur besseren Erschlie-
ßung bisher nicht genutzter, hochwertiger Metallpotenziale erarbeitet. Zu den Bewertungsmaß-
stäben gehören die Einsparpotenziale von primären Rohstoffen und damit Treibhausgasemissio-
nen sowie die Kostenstruktur für die Herstellung von möglichst hochwertigen Legierungen aus
Rezyklaten.
Eine erfolgreiche, das heißt mit minimalen Downcycling-Prozessen „belastete“ Bereitstellung
von sekundären Rohstoffen erfordert eine umfassende Wissensbasis über die wissenschaftli-
chen Hintergründe von Downcycling, bestehende Recyclingstrukturen und verwendete Sortier-
techniken, technologische Potenziale, metallurgische Prozesssimulationen und Bewertungsan-
sätzen von Recyclingprozessen, die im Rahmen dieses Projektes entwickelt und genutzt werden.

Keywords: Metallwirtschaft; OptiMet; Ressourceneffizienz; Downcycling; Sortierung; Recycling; Legierung; Sortiertechnologien; LIBS; XRT; XRF; NAA

  • Open Access Logo Other report
    06844 Dessau-Roßlau: Umweltbundesamt, 2022
    354 Seiten

Permalink: https://www.hzdr.de/publications/Publ-35029
Publ.-Id: 35029


A terminology for downcycling

Raatz, S.; Huether, J.; Joachimsthaler, C.; Lehmann, C.; Helbig, C.; Thorenz, A.; Faulstich, M.; Tuma, A.

The term downcycling is often used anecdotally to describe imperfections in recycling. However, it is rarely defined. Here, we identify six meanings of the term downcycling as used in scientific articles and reports. These encompass the material quality of reprocessed materials, target applications, product value, alloying element losses, material systems, and additional primary production. In a proposal for harmonized and more specific terminology, we define downcycling as the phenomenon of quality reduction of materials reprocessed from waste relative to their original quality. We further identify that the reduced quality can express itself thermodynamically, functionally, and economically, covering all perspectives on downcycling. Dilution, contamination, reduced demand for recycled materials, and design-related issues can cause those downcycling effects. We anticipate that this more precise terminology can help quantify downcycling, keep materials in the loop longer, use materials more often and at higher quality, and therefore assist in reducing material-related environmental impacts.

Keywords: circular economy; downcycling; downgrading; industrial ecology; recycling; waste

Permalink: https://www.hzdr.de/publications/Publ-35028
Publ.-Id: 35028


Non-van der Waals quasi-2D materials; recent advances in synthesis, emergent properties and applications

Balan, A. P.; Puthirath, A. B.; Roy, S.; Costin, G.; Oliveira, E. F.; Saadi, M. A. S. R.; Sreepal, V.; Friedrich, R.; Serles, P.; Biswas, A.; Iyengar, S. A.; Chakingal, N.; Bhattacharyya, S.; Saju, S. K.; Pardo, S. C.; Sassi, L. M.; Filleter, T.; Krasheninnikov, A.; Galvao, D. S.; Vajtai, R.; Nair, R. R.; Ajayan, P. M.

The discovery of novel materials that are stable at ambient conditions with emergent functionalities is a pressing need of the
21st century to keep the pace of social and technological advancement in a sustainable manner. Nanotechnology and
nanomaterials are one of this kind and the current era has already witnessed several groundbreaking discoveries of
materials and disruptive technological advancements. Starting from 0D fullerene, the invention of 1D carbon nanotubes, and
most recently 2D graphene, all are allotropes of carbon, have brought a lot of research opportunities to understand different
physical and chemical phenomena at atomic and molecular scales and to convert such properties into useful applications.
Among them, 2D materials find special attention due to unique properties such as ballistic carrier transport, immunity from
substrate effects and commendable in plane mechanical robustness. However, the library of such materials is limited, and
one can see that most of the technically viable materials that are already industrialized in a large scale belong to the class of
non-van der Waals materials. The effect of confinement in one dimension on non-van der Waals materials remains
unexplored owing to the difficulty in fabricating these materials to the ultra-thin limit with large lateral size or area. Recent
advancement of cleaving non-van der Waals bulk materials to their ultra-thin counter parts through the state-of-the-art liquid
phase exfoliation approach leads to renewed research interest among scientific community. The existence of
cleaving/parting planes in certain directions of non-van der Waals materials, where the bonding strength is relatively weak
compared to other crystallographic directions of the bulk crystal, facilitate smooth exfoliation when subjected to shear force
through suitable methods. Herein, we attempt to discuss the rationale of such methods in the synthesis of non-van der
Waals 2D materials that possess cleavage/parting planes with a special attention to natural ores, and to review the recent
progress made in non-van der Waals two-dimensional materials with a special emphasis on emergent magnetism, catalysis,
energy storage, and optoelectronics and related applications.

Keywords: 2D magnetism; 2D materials; Catalysis; Non-van der Waals materials; Photodetectors; Tribology

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Permalink: https://www.hzdr.de/publications/Publ-35023
Publ.-Id: 35023


Experimental Study on Inter-Bubble Distances in Dense Bubbly Flows

Kipping, R.; Hampel, U.

The design of bubble column reactors require a comprehensive understanding of the fluid dynamics. The type of gas distributor has a main impact on bubble size distribution and flow regime. With increasing gas flow rate, the interaction of the bubble increases and the dispersion of the bubbles changes. Although these effects play an important role also on the mass transfer in bubble columns, the distance parameters of bubbles in dense swarms has been poorly investigated so far.

This contribution presents an experimental study carried out with ultrafast X-ray CT (UFXCT) on a dense bubbly flow. Experiments were conducted in a bubble column of 10 cm inner diameter and for gas superficial velocities up to 3.5 cms-1. UFXCT allows for non-invasive plane measurement of the phase distribution at different scanning heights of the column. Based on the extracted coordinates of the bubble centers the distances of nearest neighbors of all bubbles were computed. In addition, pair correlation function has been applied to reveal information on the near order of bubbles. The Sauter Mean Diameter was found to have a remarkable influence on the clustering characteristics and the near order of the bubbles.

  • Lecture (Conference) (Online presentation)
    15th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-15), 07.-10.08.2022, Ottawa, Canada

Permalink: https://www.hzdr.de/publications/Publ-35022
Publ.-Id: 35022


Tailored engineering of crystalline surface enabled by ion-irradiation-assisted femtosecond laser ablation

Ren, Y.; Wang, C.; Cui, Z.; Liu, H.; Han, X.; Liu, P.; Akhmadaliev, S.; Zhou, S.; Cai, Y.

Ion irradiation and femtosecond laser ablation (FLA) are powerful technologies for micro-/nano-machining of transparent materials. In this work, we demonstrate selective surface engineering of optical crystal surface via ion irradiation and subsequent FLA, namely ion-irradiation-assisted FLA. Based on the material modification effects in the ion-irradiated layers, different types of surface structuring characterized by grooves, nanogratings or sub-micron tracks are selectively induced by FLA. It is revealed that the ion-electron interaction induced localized lattice defects and related property modulation in target crystal play important roles in the formation and evolution of laser ablation regimes. Furthermore, the formation process of high-spatial-frequency nanograting is illustrated with the periodical enhancement of local field through the excitation of surface plasmon polaritons, which is experimentally supported through the measurements of transmission electron microscope and energy-dispersive spectroscopy. Our findings further clarify the ion- and laser-matter interactions and the correlation between these processes and surface modifications. The approach proposed in this work shows potential applications in the rapid fabrication of hybrid and versatile surface structures on crystalline materials.

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  • Secondary publication expected from 15.07.2023

Permalink: https://www.hzdr.de/publications/Publ-35021
Publ.-Id: 35021


Plasmonic Nanoparticles Embedded in Nanomembrane Microcavity for Flexible Optical Tuning

Pang, C.; Li, R.; Dong, H.; Saggau, C. N.; Kern, F. L.; Potapov, P.; Schultz, J.; Lubk, A.; Hübner, R.; Kentsch, U.; Zhou, S.; Helm, M.; Chen, F.; Ma, L.; Schmidt, O. G.

The combination of plasmonic nanoparticles and optical microcavities has attracted broad interest for both fundamental and applied studies. However, the conventional scheme of plasmonic nanoparticles being located at microcavity outer surfaces suffers from serious problems such as significant radiative/scattering losses and chemical/mechanical instabilities. Here, silver nanoparticles (NPs) and dispersed ions embedded in nanomembrane-formed whispering-gallery-mode (WGM) microtube cavities are prepared by ion implantations as compact and stable optoplasmonic microcavities. Upon low ion fluence implantation, dispersed silver ions are generated in the tube cavity wall, leading to a redshift of the WGM resonant cavity modes due to the increased refractive index. The silver ions start to aggregate into plasmonic NPs in the cavity wall when increasing implantation ion fluences. The competition and transition between redshift induced by the refractive index increase and blueshift induced by the formation of plasmonic NPs are investigated. Moreover, quality factor enhancement of the WGM modes is observed owing to the improved light confinement caused by the presence of NPs. This work demonstrates a convenient approach for the fabrication of stable optoplasmonic microcavities and fine tuning of resonant modes, indicating wide applications such as wavelength selective tuning and enhanced light–matter interactions.

Keywords: ion implantation; microtube cavity; nanomembrane; plasmonic nanoparticles; resonant mode tuning

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Permalink: https://www.hzdr.de/publications/Publ-35020
Publ.-Id: 35020


Application of a Microfabricated Microwave Resonator in a Co-Pd–Based Magnetic Hydrogen-Gas Sensor

Schefer, T. A.; Narkovic, R.; Lenz, K.; Ganss, F.; Roberts, M. P.; Hellwig, O.; Martyniuk, M.; Lindner, J.; Kostylev, M.

We investigate the ferromagnetic resonance (FMR) response of microfabricated microwave resonators loaded with small Co16Pd84 alloy rectangles. A major increase in the FMR signal-to-noise ratio is achieved by employing the microwave-resonator structure. A FMR peak shift similar to that of Co16Pd84 continuous films is measured in the presence of hydrogen gas in the sample environment. We show that the very high sensitivity of the FMR signal of the Co16Pd84 alloy rectangle to hydrogen exposure can be used to measure relatively small hydrogen-concentration steps near 100% H2. Additionally, we also demonstrate that this structure can measure hydrogen over a concentration range from 3% to 100% H2 in N2. In time-dependent FMR measurements, we discover a temperature dependence of the FMR signal, which we relate to intrinsic temperature-dependent changes in saturation magnetization and the magnetic anisotropy of the Co-Pd alloy.

Keywords: hydrogen sensors; ferromagnetic resonance; CoPd alloys; Nanostructures; gas sensors

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-35018
Publ.-Id: 35018


Control and tunability of magnetic bubble states in multilayers with strong perpendicular magnetic anisotropy at ambient conditions

Salikhov, R.; Samad, F.; Sai Phani Kanth Arekapudi, S.; Ehrler, R.; Lindner, J.; Kiselev, N. S.; Hellwig, O.

The reversal of magnetic bubble helicity through topologically trivial transient states provides an additional
degree of freedom that promises the development of multidimensional magnetic memories. A key requirement
for this concept is the stabilization of bubble states at ambient conditions on application-compatible substrates.
In the present work, we demonstrate a stabilization routine for remanent bubble states in high perpendicular
magnetic anisotropy [Co(0.44 nm)/Pt(0.7 nm)]X , X = 48, 100, and 150 multilayers on Si/SiO2 substrates by
exploring the effect of external magnetic fields (Hm) of different strength and angles (θ) with respect to the
film surface normal. By systematic variation of these two parameters, we demonstrate that remanent bubble
density and mean bubble diameter can be carefully tuned and optimized for each sample. Our protocol based on
magnetometry only reveals the densest remanent bubble states at Hm = 0.87Hs (Hs is the magnetic saturation
field) and θ = 60◦–75◦ for all X with a maximum of 3700 domains/100 μm2 for the X = 48 sample. The
experimental observations are supported by micromagnetic simulations, taking into account the nanoscale lateral
grain structure of multilayers synthesized by magnetron sputter deposition, and thus helping to understand the
different densities of the bubble states found in these systems.

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Permalink: https://www.hzdr.de/publications/Publ-35017
Publ.-Id: 35017


LDOS/SNAP data for MALA: Beryllium at 298K

Fiedler, L.; Cangi, A.

Beryllium data set for Machine Learning applications

This dataset contains DFT inputs, outputs, LDOS data and fingerprint vectors for a beryllium cell at ambient conditions and varying sizes. Different levels of k-grid convergence were employed:
-  Gamma point (gamma_point)
-  total energy convergence (k-grid converged to 1meV/atom to total energy difference, total_energy_convergence)
-  LDOS convergence (k-grid converged to LDOS without unphyiscal oscillations, ldos_convergence)

The data set contains a .zip file for each system size (see below), as well as one .zip file containing sample scripts for recalculation and preprocessing of data.
The cutoff energy was converged with respect to the energy convergence and held fixed 40Ry for all three levels of k-grids. Note that not for all sizes of unit cells data for all types of k-grid were generated.

Authors:

- Fiedler, Lenz (HZDR / CASUS)
- Cangi, Attila (HZDR / CASUS)

Affiliations:

HZDR - Helmholtz-Zentrum Dresden-Rossendorf

CASUS - Center for Advanced Systems Understanding

Dataset description

- Total size: 143G GB 
- System: Be128, Be256, Be512, Be1024, Be2048
- Temperature(s): 298K
- Mass density(ies): 1.896 gcc
- Crystal Structure: hpc (material mp-87 in the materials project)
- Number of atomic snapshots: 145
    - 40 (Be128)
    - 35 (Be256)
   - 30 (Be512)
   - 20 (Be1024)
   - 10 (Be2048)
- Contents:
   - ideal crystal structure: yes
    - MD trajectory: yes
    - Atomic positions: yes
   - DFT inputs: yes
    - DFT outputs (energies): yes
    - SNAP vectors: yes (partially, see below)
        - dimensions: XxYxZx94 (last dimension: first three entries are x,y,z coordinates, data size is 91), where X, Y, Z are:
         - Be128: 72x72x120 (size per file: 447MB)
         - Be256: 144x72x120  (size per file: 893MB)
         - Be512: 144x144x120 (size per file: 1.8GB)
        - units: a.u./Bohr
    - LDOS vectors: yes (partially, see below)
        - dimensions: XxYxZx250, where X, Y, Z are:
         - Be128: 72x72x120 (size per file: 1.2GB)
         - Be256: 144x72x120  (size per file: 2.4GB)
         - Be512: 144x144x120 (size per file: 4.7GB)
        - units: 1/eV
      - note: LDOS parameters are the same for all sizes of the unit cell
    - trained networks: no

Data generation

Ideal crystal structures were obtained using the Materials Project. (https://materialsproject.org/materials/mp-87/)
DFT-MD calculations were performed using either QuantumESPRESSO (https://www.quantum-espresso.org/, QE, for Be128, Be256 and Be512) or the Vienna Ab initio Simulation Package (https://www.vasp.at/, VASP, for Be1024, Be2048). DFT calculations were performed using QuantumESPRESSO. 
For the VASP calculations, the standard VASP pseudopotentials were used. For Quantum Espresso, pslibrary was used (https://dalcorso.github.io/pslibrary/).
SNAP vectors were calculated using MALA (https://github.com/mala-project/mala) and its LAMMPS (https://github.com/mala-project/mala) interface. The LDOS was preprocessed using MALA as well.

Dataset structure

The folder called "sample_inputs" is provided to show how MALA preprocessing and LDOS calculation have been performed. 
For each temperature/mass density/number of atoms, the following subfolders exist:

- md_inputs: Input files for the MD simulations, either as QE or VASP file(s)
- md_outputs: The MD trajectory plus a numpy array containing the temperatures at the individual time steps
- gamma_point
- total_energy_convergence
- ldos_convergence

Each gamma_point/total_energy_convergence/ldos_convergence contains the following folders:

- ldos: holds the LDOS vectors
- fingerprints: holds the SNAP fingerprint vectors
- snapshots: holds the atomic positions of the atomic snapshots for which DFT and LDOS calculations were performed (as .xyz files)
- dft_outputs: holds the outputs from the DFT calculations, i.e. energies in the form of a QE output file
- dft_inputs: holds the inputs for the DFT calculations, in the form of a QE input file

Please note that the numbering of the snapshots is contiguous per temperature/mass density/number of atoms, NOT within the k-grids themselves. 
Also, LDOS and fingerprint files have only been calculated for snapshots in the ldos_convergence 
folders. Therefore, no LDOS and fingerprint files have been calculated for the 1024 anf 2048 atom systems.
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-02-18
    DOI: 10.14278/rodare.1833
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-35016
Publ.-Id: 35016


Ultrahigh Photogain Short-Wave Infrared Detectors Enabled by Integrating Graphene and Hyperdoped Silicon

Jiang, H.; Wang, M.; Fu, J.; Li, Z.; Shaikh, M. S.; Li, Y.; Nie, C.; Sun, F.; Tang, L.; Yang, J.; Qin, T.; Zhou, D.; Shen, J.; Sun, J.; Feng, S.; Zhu, M.; Kentsch, U.; Zhou, S.; Shi, H.; Wei, X.

Highly sensitive short-wave infrared (SWIR) detectors, compatible with the silicon-based complementary metal oxide semiconductor (CMOS) process, are regarded as the key enabling components in the miniaturized system for weak signal detection. To date, the high photogain devices are greatly limited by a large bias voltage, low-temperature refrigeration, narrow response band, and complex fabrication processes. Here, we demonstrate high photogain detectors working in the SWIR region at room temperature, which use graphene for charge transport and Te-hyperdoped silicon (Te–Si) for infrared absorption. The prolonged lifetime of carriers, combined with the built-in potential generated at the interface between the graphene and the Te–Si, leads to an ultrahigh photogain of 109 at room temperature (300 K) for 1.55 μm light. The gain can be improved to 1012, accompanied by a noise equivalent power (NEP) of 0.08 pW Hz–1/2 at 80 K. Moreover, the proposed device exhibits a NEP of 4.36 pW Hz–1/2 at 300 K at the wavelength of 2.7 μm, which is exceeding the working region of InGaAs detectors. This research shows that graphene can be used as an efficient platform for silicon-based SWIR detection and provides a strategy for the low-power, uncooled, high-gain infrared detectors compatible with the CMOS process.

Keywords: short-wave infrared detector; lifetime; built-in potential; photogain; graphene; Te-hyperdoped Si

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Permalink: https://www.hzdr.de/publications/Publ-35014
Publ.-Id: 35014


Data publication: Time-of-Flight spectroscopy for laser-driven proton beam monitoring

Reimold, M.; Assenbaum, S.; Bernert, C.; Beyreuther, E.; Brack, F.-E.; Karsch, L.; Kraft, S.; Kroll, F.; Löser, M.; Nossula, A.; Pawelke, J.; Püschel, T.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

This dataset contains the raw and evaluated data of the paper plus the script for plotting the results.

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-08-10
    DOI: 10.14278/rodare.1831
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-35011
Publ.-Id: 35011


hmctFOAM - heat mass concentration transport FOAM

Personnettaz, P.; Weber, N.; Weier, T.

This software illustrates the applications of the programming
techniques detailed in the book chapter

Norbert Weber, Tom Weier (2022) Liquid Metal Batteries. In: Steven
Beale, Werner Lehnert (eds.) Electrochemical Cell Calculations with
OpenFOAM. Lecture Notes in Energy 42, pp. 193-212.

The included solver handles the heat and mass transport equations
under the assumption of pure diffusion and with solutal convection.
It is a single region solver that is based on laplacianFoam and
boussinesqPimpleFoam from OpenFOAM 6.

Keywords: liquid metal batteries; OpenFOAM

Related publications

  • Software in the HZDR data repository RODARE
    Publication date: 2022-08-05
    DOI: 10.14278/rodare.1827
    License: GPL-3.0-only

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Permalink: https://www.hzdr.de/publications/Publ-35001
Publ.-Id: 35001


Aliovalent Ta-Doping-Engineered Oxygen Vacancy Configurations for Ultralow-Voltage Resistive Memory Devices: A DFT-Supported Experimental Study

Barman, A.; Das, D.; Deshmukh, S.; Sarkar, P. K.; Banerjee, D.; Hübner, R.; Gupta, M.; Saini, C. P.; Kumar, S.; Johari, P.; Dhar, S.; Kanjilal, A.

Alteration of transport properties of any material, especially metal oxides, by doping suitable impurities is not straightforward as it may introduce multiple defects like oxygen vacancies (Vo) in the system. It plays a decisive role in controlling the resistive switching (RS) performance of metal oxide-based memory devices. Therefore, a judicious choice of dopants and their atomic concentrations is crucial for achieving an optimum Vo configuration. Here, we show that the rational designing of RS memory devices with cationic dopants (Ta), in particular, Au/Ti1−xTaxO2−δ/Pt devices, is promising for the upcoming non-volatile memory technology. Indeed, a current window of ∼104 is realized at an ultralow voltage as low as 0.25 V with significant retention (∼104 s) and endurance (∼105 cycles) of the device by considering 1.11 at % Ta doping. The obtained device parameters are compared with those in the available literature to establish its excellent performance. Furthermore, using detailed experimental analyses and density functional theory (DFT)-based first-principles calculations, we comprehend that the meticulous presence of Vo configurations and the columnar-like dendritic structures is crucial for achieving ultralow-voltage bipolar RS characteristics. In fact, the dopant-mediated Vo interactions are found to be responsible for the enhancement in local current conduction, as evidenced from the DFT-simulated electron localization function plots, and these, in turn, augment the device performance. Overall, the present study on cationic-dopant-controlled defect engineering could pave a neoteric direction for future energy-efficient oxide memristors.

Keywords: resistive memory; vacancy engineering; ultralow-voltage switching; conducting filaments; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-35000
Publ.-Id: 35000


Data publication: Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography

Kaever, C.; Windisch, D.

Benchmark data for the student work "Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography" by Christian Kaever.

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-08-04
    DOI: 10.14278/rodare.1825
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-34999
Publ.-Id: 34999


Three-Dimensional, Km-Scale Hyperspectral Data of Well-Exposed Zn–Pb Mineralization at Black Angel Mountain, Greenland

Lorenz, S.; Thiele, S. T.; Kirsch, M.; Unger, G.; Zimmermann, R.; Guarnieri, P.; Baker, N.; Vest Sørensen, E.; Rosa, D.; Gloaguen, R.

Hyperspectral imaging is an innovative technology for non-invasive mapping, with increas- ing applications in many sectors. As with any novel technology, robust processing workflows are required to ensure a wide use. We present an open-source hypercloud dataset capturing the complex but spectacularly well exposed geology from the Black Angel Mountain in Maarmorilik, West Green- land, alongside a detailed and interactive tutorial documenting relevant processing workflows. This contribution relies on very recent progress made on the correction, interpretation and integration of hyperspectral data in earth sciences. The possibility to fuse hyperspectral scans with 3D point cloud representations (hyperclouds) has opened up new possibilities for the mapping of complex natural targets. Spectroscopic and machine learning tools allow or the rapid and accurate characterization of geological structures in a 3D environment. Potential users can use this exemplary dataset and the associated tools to train themselves or test new algorithms. As the data and the tools have a wide range of application, we expect this contribution to benefit the scientific community at large.

Keywords: open-source dataset; hyperspectral data; spectral imaging; 3D hyperclouds; photogrammetry; Black Angel Maarmorilik; minimum wavelength mapping; interactive workflow

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Permalink: https://www.hzdr.de/publications/Publ-34996
Publ.-Id: 34996


Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts using ion implantation and flash lamp annealing

Echresh, A.; Prucnal, S.; Li, Z.; Hübner, R.; Ganss, F.; Steuer, O.; Bärwolf, F.; Jazavandi Ghamsari, S.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) with low resistance and linear characteristics remain a major challenge in germanium-based nanoelectronics. Here, we present a combined approach to fabricate Ohmic contacts on n-type-doped GeNWs. Phosphorus (P) implantation followed by millisecond rear-side flash lamp annealing was used to produce highly n-type-doped Ge with an electron concentration in the order of 10^19-10^20 cm^{-3}. Electron beam lithography, inductively coupled plasma reactive ion etching, and nickel (Ni) deposition were used to fabricate GeNW-based devices with symmetric Hall bar configuration, which allows detailed electrical characterization of the NWs. Afterward, rear-side flash lamp annealing was applied to form Ni germanide at the Ni-GeNWs contacts to reduce the Schottky barrier height. The two-probe current-voltage measurements on P-doped GeNWs exhibit linear Ohmic behavior. Also, the size-dependent electrical measurements showed that carrier scattering near the NW surfaces and reduction of the effective NW cross-section dominate the charge transport in the GeNWs.

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-08-03
    DOI: 10.14278/rodare.1823

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Permalink: https://www.hzdr.de/publications/Publ-34995
Publ.-Id: 34995


Cyclam with a phosphinate-bis(phosphonate) pendant arm is a bone-targeting carrier of copper radionuclides

Pazderová, L.; Benešová, M.; Havlíčková, J.; Vojtíčková, M.; Kotek, J.; Lubal, P.; Ullrich, M.; Walther, M.; Schulze, S.; Neuber, C.; Rammelt, S.; Pietzsch, H.-J.; Pietzsch, J.; Kubíček, V.; Hermann, P.

Ligands combining a bis(phosphonate) group with a macrocycle function as metal isotope carriers for radionuclide-based imaging and for treating bone metastases associated with several cancers. However, bis(phosphonate) pendant arms often slow down complex formation and decrease radiochemical yields. Nevertheless, their negative effect on complexation rates may be mitigated by using a suitable spacer between bis(phosphonate) and the macrocycle. To demonstrate the potential of bis(phosphonate) bearing macrocyclic ligands as a copper radioisotope carrier, we report the synthesis of a new cyclam derivative bearing a phosphinate-bis(phosphonate) pendant (H5te1PBP). The ligand showed a high selectivity to CuII over ZnII and NiII ions, and the bis(phosphonate) group was not coordinated in the CuII complex, strongly interacting with other metal ions in solution. The CuII complex formed quickly, in 1 s, at pH 5 and at a millimolar scale. The complexation rates significantly differed under a ligand or metal ion excess due to the formation of reaction intermediates differing in their metal-to-ligand ratio and protonation state, respectively. The CuII-te1PBP complex also showed a high resistance to acid-assisted hydrolysis (t1/2 2.7 h; 1 M HClO4, 25 °C) and was effectively adsorbed on the hydroxyapatite surface. H5te1PBP radiolabeling with [64Cu]CuCl2 was fast and efficient, with specific activities of approximately 30 GBq 64Cu per 1 μmol of ligand (pH 5.5, room temperature, 30 min). In a pilot experiment, we further demonstrated the excellent suitability of [64Cu]CuII-te1PBP for imaging active bone compartments by dedicated small animal PET/CT in healthy mice and subsequently in a rat femoral defect model, in direct comparison with [18F]fluoride. Moreover, [64Cu]CuII-te1PBP showed a higher uptake in critical bone defect regions. Therefore, our study highlights the potential of [64Cu]CuII-te1PBP as a PET radiotracer for evaluating bone healing in preclinical and clinical settings with a diagnostic value similar to that of [18F]fluoride, albeit with a longer half-life (12.7 h) than 18F (1.8 h), thereby enabling extended observation times.

Permalink: https://www.hzdr.de/publications/Publ-34988
Publ.-Id: 34988


Current- and Oersted-field- dynamics of a Bloch Point in cylindrical Ni nanowires

Fernandez Roldan, J. A.; Oksana, C.-F.

As three-dimensional nanomagnetism evolves, novel non-trivial magnetic textures emerge as appealing information carriers for spintronics based on curved nanosystems and particularly Cylindrical Nanowires (NWs) [1,2]. One of the most fascinating candidates that is likely to reach the high velocities required for fast recording technologies is the Bloch Point (BP) domain wall (DW). Recently, theoretical evidence indicated that BPs in NWs could reach high velocities close to 2 km/s in the magnonic regime [2]. While the observation of the BP DW in cylindrical NWs is no longer recent [2], scarce numerical studies that combine both spin-polarized current and Oersted field have been published in NWs [4,5], despite first attempts to measure DW velocities are in progress [6].
In this work we evaluate the dynamics of the BP DW under both current directions in a Ni NW with 100 nm in diameter. We investigate two cases: i) pre-nucleated BP DW, and ii) the BP DW formed from the transformation of a Vortex-Antivortex DW. Here the effects of both spin-polarized current and Oersted field are considered. We discuss in detail the role of the chirality of the BP in relation to the Oersted field, also reported previously in precursors of BPs [4].

Here we show that while the pre-nucleated DW with the same chirality as that of the Oersted field propagates always against the current direction, the BP originated either from the transformation of the BP with the opposite chirality or from the vortex-antivortex DW can either stop the propagation or propagate parallel to the current. Finally, we provide values of the velocities achieved by the BP in the NW as a function of applied current in Fig. 1.

We conclude that BPs with vanishing momentum propagate opposite to the current with velocities that may be suppressed by the Oersted field. Importantly for spintronic applications, momentum plays a major role in the dynamics of BPs that has not been envisaged up to know.

[1] A. Fernandez-Pacheco et al., Three-dimensional nanomagnetism. Nat Commun 8, 15756 (2017)
[2] S. Da Col et al., Observation of Bloch-point domain walls in cylindrical magnetic nanowires, Phys. Rev. B, 89, 180405 (2014).
[3] X.-P. Ma et al., Cherenkov-type three-dimensional breakdown behavior of the Bloch-point domain wall motion in the cylindrical nanowire, Appl. Phys. Lett. 117, 062402 (2020).
[4] J.A. Fernandez-Roldan et al., Electric current and field control of vortex structures in cylindrical magnetic nanowires, Phys. Rev. B 102, 024421 (2020).
[5] C. Bran et al, Magnetic Configurations in Modulated Cylindrical Nanowires, Nanomaterials 11, 600 (2021). DOI: 10.3390/nano11030600
[6] M. Schöbitz et al., Fast Domain Wall Motion Governed by Topology and Oersted Fields in Cylindrical Magnetic Nanowires. Phys. Rev. Lett. 123, 217201 (2019).

Keywords: Bloch Point; magnetic domain wall; cylindrical nanowire; current; Oersted field

  • Poster
    XXXVIII Biennial of Physics of the Spanish Royal Physics Society (R.S.E.F.), 11.-15.07.2022, Murcia, Spain
  • Lecture (Conference)
    2022 Joint European Magnetic Symposia (JEMS), 24.-29.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34983
Publ.-Id: 34983


Data: Study of a possible silicon photomultiplier based readout of the large plastic scintillator neutron detector NeuLAND

Hensel, T.; Weinberger, D.; Bemmerer, D.; Boretzky, K.; Gasparic, I.; Stach, D.; Wagner, A.; Zuber, K.

The NeuLAND (New Large-Area Neutron Detector) plastic scintillator based time of flight detector for 0.2-1.6 GeV
neutrons is currently under construction at the Facility for Antiproton and Ion Research (FAIR), Darmstadt, Germany.
In its final configuration, NeuLAND will consist of 3,000 2.7 m long plastic scintillator bars that are read out on each
end by fast timing photomultipliers.
Here, data from a comprehensive study of an alternative light readout scheme using silicon photomultipliers (SiPM)
are reported.  For this purpose, a typical NeuLAND bar was instrumented on each end with a prototype of the same
geometry as a 1” photomultiplier tube, including four 6×6 mm2 SiPMs, amplifiers, high voltage supply, and micro-
controller.
Tests were carried out using the 35 MeV electron beam from the ELBE superconducting linac with its ps-level time jitter in two different modes of operation, namely parasitic mode with one electron per bunch and single-usermode with 1-60 electrons per bunch, using Acqiris fast digitizers. In addition, offline tests using cosmic rays and the NeuLAND data acquisition scheme were carried out.
Typical time resolutions of σ≤120 ps were found for ≥ 95% efficiency, improving on previous work at ELBE and exceeding the NeuLAND timing goal of σ <150 ps. Over a range of 10-300 MeV deposited energy in the NeuLAND bar,  the  gain  was  found  to  deviate  by ≤ 10%  (≤20%)  from  linearity  for  35μm  (75μm)  SiPM  pitch,  respectively, satisfactory for calorimetric use of the full NeuLAND detector.  The dark rate of the prototype studied was found to
be 70-200 s-1, comparable with the unavoidable cosmic-ray induced background.

The dataset contains the with the Acqiris Digitzier recorded waveforms and analysis scripts for interpretation of the data. Also GEANT4 simulations of the light propagation in a NeuLAND bar and the electron beam propagation are included.

Keywords: SiPM; saturation; NeuLAND; dark rate; electron beam; timeresolution

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-07-29
    DOI: 10.14278/rodare.1821

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Permalink: https://www.hzdr.de/publications/Publ-34981
Publ.-Id: 34981


Preface: State of the art in mineral exploration

Alcalde, J.; Carbonell, R.; Pospiech, S.; Gil, A.; Bullock, L. A.; Tornos, F.

Minerals that comprise raw materials for energy, metal, construction and other industrial applications are considered strategic commodities, fundamental in stock markets worldwide, and key ingredients to sustain our ever more technology-based society (Wellmer et al., 2019). The utilization of such economically important minerals has shown a continued steady increase since the early twentieth century, with a greater focus in recent years on resources required for the development of renewable technologies, such as wind and solar operations, and for electrification of domestic and transportation systems (e.g. concrete, aluminium, chromium, copper, iron, manganese, molybdenum, nickel, zinc or rare earths) (Meinert et al., 2016). As our society ramps up the global transition to low-carbon energies and a reduced reliance on fossil fuels, the inevitable rise in consumption and demand for a more diverse range of resources can only be facilitated through increasingly novel methods of mineral exploration (Ali et al., 2017).

Keywords: mineral exploration; state of the art; geophysics; geochemistry; geology; remote sensing; critical raw materials

Permalink: https://www.hzdr.de/publications/Publ-34980
Publ.-Id: 34980


Spin-wave channeling in magnetization-graded nanostrips

Gallardo, R. A.; Alvarado-Seguel, P.; Brevis, F.; Roldán-Molina, A.; Lenz, K.; Lindner, J.; Landeros, P.

Magnetization-graded ferromagnetic nanostrips are proposed as potential prospects to channel spin waves. Here, a controlled reduction of the saturation magnetization enables the localization of the propagating magnetic excitations in the same way that light is controlled in an optical fiber with a varying refraction index. The approach is based on the dynamic matrix method, where the magnetic nanostrip is divided into small sub-strips. The dipolar and exchange interaction between sub-strips is accounted to reproduce the spin-wave dynamics of the magnonic fiber. The transition from one strip to an infinite thin film is presented for the Damon-Eshbach geometry, where the nature of the spin-wave modes is discussed. An in-depth analysis of the spin-wave transport as a function of the saturation magnetization profile is provided. It is predicted that it is feasible to induce a remarkable channeling of the spin waves along the zones with a reduced saturation magnetization, even when such a reduction is tiny. The results are compared with micromagnetic simulations, where a good agreement is observed between both methods. The findings have relevance for envisioned future spin-wave-based magnonic devices operating at the nanometer scale.

Keywords: spin waves; ferromagnetic resonance; magnetization dynamics; magnonics; magnetic gradients; theory

Permalink: https://www.hzdr.de/publications/Publ-34978
Publ.-Id: 34978


Data publication: Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344T

Hilpmann, S.; Roßberg, A.; Steudtner, R.; Drobot, B.; Hübner, R.; Bok, F.; Prieur, D.; Bauters, S.; Kvashnina, K.; Stumpf, T.; Cherkouk, A.

The stored data sets represent both the raw data and the evaluated data that were used for the publication about uranium(VI) reduction by a sulfate-reducing bacterium.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Opalinus Clay pore water; Pentavalent uranium; Membrane vesicles

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-07-28
    DOI: 10.14278/rodare.1819

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Permalink: https://www.hzdr.de/publications/Publ-34974
Publ.-Id: 34974


Sulfated glycosaminoglycans inhibit transglutaminase 2 by stabilizing its closed conformation

Müller, C. D.; Ruiz-Gómez, G.; Cazzonelli, S.; Möller, S.; Wodtke, R.; Löser, R.; Freyse, J.; Dürig, J.-N.; Rademann, J.; Hempel, U.; Pisabarro, M. T.; Vogel, S.

Transglutaminases (TGs) catalyze the covalent crosslinking of proteins via isopeptide bonds. The most prominent isoform, TG2, is associated with physiological processes such as extracellular matrix (ECM) stabilization and plays a crucial role in the pathogenesis of e.g. fibrotic diseases, cancer and celiac disease. Therefore, TG2 represents a pharmacological target of increasing relevance. The glycosaminoglycans (GAG) heparin (HE) and heparan sulfate (HS) constitute high-affinity interaction partners of TG2 in the ECM. Chemically modified GAG are promising molecules for pharmacological applications as their composition and chemical functionalization may be used to tackle the function of ECM molecular systems, which has been recently described for hyaluronan (HA) and chondroitin sulfate (CS). Herein, we investigate the recognition of GAG derivatives by TG2 using an enzyme-crosslinking activity assay in combination with in silico molecular modeling and docking techniques. The study reveals that GAG represent potent inhibitors of TG2 crosslinking activity and offers atom-detailed mechanistic insights.

Permalink: https://www.hzdr.de/publications/Publ-34973
Publ.-Id: 34973


Flexible and printed electronics: from interactive on-skin devices to bio/medical applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. We put forth the concept of shapeable magnetoelectronics [2] for various applications ranging from automotive through consumer electronics to virtual and augmented reality applications [3]. These skin-conformal flexible and printable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins for human-machine interfaces [4-9] and soft robotics [10].
Highly flexible functional elements are demanded for bio/medical applications. We will introduce an implantable, multifunctional device on ultrathin polymeric foils for targeted thermal treatment of cancer [11] as well as a flexible light weight diagnostic platform based on highly sensitive Si nanowire field effect transistors revealing remarkable limit of detection at 40 pM for Avian Influenza Virus (AIV) subtype H1N1 DNA sequences [12].
For the emerging field of biosensing technologies, we developed droplet-based magnetofluidic platforms encompassing integrated novel functionalities [13] including analytics in a flow cytometry format [14], magnetic detection, barcoding and sorting of magnetically encoded emulsion droplets using rigid [15,16] and flexible [17] microfluidic devices. These features are crucial to address the needs of modern medical research, e.g. drug discovery.

[1] D. Makarov et al., Adv. Mater. (Review) 34, 2101758 (2022).
[2] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[3] G. S. Cañón Bermúdez et al., Adv. Funct. Mater. (Review) 31, 2007788 (2021).
[4] G. S. Cañón Bermúdez et al., Science Advances 4, eaao2623 (2018).
[5] G. S. Cañón Bermúdez et al., Nature Electronics 1, 589 (2018).
[6] J. Ge et al., Nature Communications 10, 4405 (2019).
[7] M. Ha et al., Adv. Mater. 33, 2005521 (2021).
[8] P. Makushko et al., Adv. Funct. Mater. 31, 2101089 (2021).
[9] S. Li et al., Nano Energy 92, 106754 (2022).
[10] M. Ha et al., Adv. Mater. 33, 2008751 (2021).
[11] G. S. Cañón Bermúdez et al., Adv. Eng. Mater. 21, 1900407 (2019).
[12] D. Karnaushenko et al., Adv. Healthcare Mater. 4, 1517 (2015).
[13] G. Lin et al., Lab Chip (Review) 17, 1884 (2017).
[14] G. Lin et al., Small 12, 4553 (2016).
[15] J. Schütt et al., ACS Omega 5, 20609 (2020).
[16] W. Song et al., ACS Sensors 2, 1839 (2017).
[17] G. Lin et al., Lab Chip 14, 4050 (2014).

Keywords: curvature effects in magnetism; flexible magnetic field sensors; printed magnetic field sensors; lab-on-chip applications; skin-conformal electronics

Related publications

  • Invited lecture (Conferences)
    Joint European Magnetic Symposia (JEMS), 24.-29.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34972
Publ.-Id: 34972


Actinide physics and chemistry with synchrotron radiation

Kvashnina, K. O.; Butorin, S. M.; Wang, S.; Shi, W.

Actinide research is currently experiencing a renaissance in the fields of material science,
nanotechnology, medicine and environmental science. It is now possible to study the
chemistry and physics of the actinide elements (all radioactive) using state-of-the-art
non-destructive techniques at synchrotrons which have not been available before. The
beamlines and instruments dedicated to actinide research have made various spectro-
scopic and scattering methods accessible to scientists worldwide. The new synchrotron
sources at the large-scale facilities offer more advanced possibilities for the development
of new methodologies in actinide science in the future. Theoretical studies of actinides
are followed by unique experimental methods and novel experimental data.

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Permalink: https://www.hzdr.de/publications/Publ-34963
Publ.-Id: 34963


Uranium reduction by magnetite – mechanism of UO2 formation monitored by STEM, SAED and EELS

Lagrange, T.; Pan, Z.; Bártová, B.; Butorin, S. M.; Hyatt, N. C.; Stennett, M. C.; Kvashnina, K. O.; Bernier-Latmani, R.

Uranium (U) is a ubiquitous element in the Earth’s crust, having a concentration of about 2 ppm.
Soluble hexavalent uranium (U(VI)) is reduced and immobilized in anoxic environments. The
underlying reduction mechanism is unknown but is likely of critical importance to explain variability in
U biogeochemical behaviors. In this study, we focused on the mechanism of reduction of U(VI) by the
mixed-valence iron oxide magnetite

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Permalink: https://www.hzdr.de/publications/Publ-34961
Publ.-Id: 34961


Nanochips assisted peptide screening for clinical development of CAR-T cell immunotherapy

Anh Nguyen-Le, T.; Bartsch, T.; Wodtke, R.; Brandt, F.; Arndt, C.; Feldmann, A.; Isabel Sandoval Bojorquez, D.; Perez Roig, A.; Ibarlucea, B.; Lee, S.; Baek, C.-K.; Cuniberti, G.; Bergmann, R.; Puentes-Cala, E.; Andrés Soto, J.; T. Kurien, B.; Bachmann, Michael; Baraban, L.

Immunotherapy using CAR-T cells is a new paradigm technology for cancer treatment. To avoid severe side effects and tumor escape variants observed for conventional CAR-T cells approach, adaptor CAR technologies are under development, where intermediate target modules redirect immune cells against cancer cells. In this work, silicon nanowire field effect transistors are used to assist in the development of target modules for an optimized CAR-T cell operation. Focusing on a library of seven variants of E5B9 peptide that is used as CAR peptide epitope, we performed multiplexed binding tests in serum using nanosensor chips. Peptides have been immobilized onto the sensor to compare the signals of transistor upon titration with anti-E5B9 antibodies. Correlation analysis of binding affinities and sensitivities enabled a selection of best candidates for the interaction between CAR and target modules. Finally, cytotoxic functionality of CAR-T cells in combination with the selected target modules were successfully proven. Our results open the perspective for the nanobiosensorics to go beyond the early diagnostics in the field of clinical cancer research, and paves the way towards personalization and efficient monitoring of the immunotherapeutic treatment, where the quantitative analysis with the standard techniques is not an option.

Keywords: CAR-T cells; Nanobiosensors

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  • Secondary publication expected from 15.06.2023

Permalink: https://www.hzdr.de/publications/Publ-34960
Publ.-Id: 34960


CO2 Electroreduction on Unsupported PdPt Aerogels: Effects of Alloying and Surface Composition on Product Selectivity

Diercks, J. S.; Georgi, M.; Herranz, J.; Diklić, N.; Chauhan, P.; Clark, A. H.; Hübner, R.; Faisnel, A.; Chen, Q.; Nachtegaal, M.; Eychmüller, A.; Schmidt, T. J.

Due to its unique ability to reduce carbon dioxide (CO2) into CO or formate at high versus low overpotentials, respectively, palladium is a promising catalyst for the electrochemical CO2-reduction reaction (CO2RR). Further improvements aim at increasing its activity and selectivity toward either of these value-added species, while reducing the amount of hydrogen produced as a side product. With this motivation, in this work, we synthesized a range of unsupported, bimetallic PdPt aerogels and pure Pt or Pd aerogels and extensively characterized them using various microscopic and spectroscopic techniques. These revealed that the aerogels’ porous web consists of homogenous alloys of Pt and Pd, with palladium and platinum being present on their surface for all compositions. The subsequent determination of these aeorgels’ CO2RR performance unveiled that the high activity of these Pt surface atoms toward hydrogen evolution causes all PdPt alloys to favor this reaction over CO2 reduction. In the case of the pure Pd aerogel, although, its unsupported nature leads to a suppression of H2 evolution and a concomitant increase in the selectivity toward CO when compared to a commercial, carbon-supported Pd-nanoparticle catalyst.

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Permalink: https://www.hzdr.de/publications/Publ-34959
Publ.-Id: 34959


The influence of the bentonite type on the corrosion of cast iron

Sushko, V.; Dressler, M.; Kluge, S.; Matschiavelli, N.; Schierz, A.; Stumpf, T.; Cherkouk, A.

1 Introduction
Bentonite is considered as buffer and sealing material in a multi-barrier system for a deep geologic repositories (DGR) of nuclear waste and spent fuel [1]. Another part of the engineered barrier system is the containment of the radioactive waste. Cast iron is often taking into account for the construction of the containers as a candidate material [2]. But the cast iron components are fairly unstable, can corrode to insoluble corrosion products and react with the bentonite buffer matrix. Anaerobic corrosion together with microbially influenced corrosion are dominant forms of corrosion in the a DGR and the interactions at the metal/bentonite interface determines the performance of bentonite-based radioactive waste barriers [3]. The aim of the current study was to characterize the surface damage associated with corrosion of the cast iron and to compare the potential of the indigenous microorganisms present in different bentonites to influence the corrosion of cast iron.

2 Results
Three types of bentonite (B25, Calcigel, MX-80) were chosen for mesocosm-experiment setup as described in [4]. All three bentonites have different smectite content and an indigenous microbial community. The mesocosms with cast iron coupons, artificial Opalinus clay porewater and bentonite were incubated in N2/CO2 atmosphere for 271 days at 30 °C. Some of the mesocosms were supplemented with 5 mM sodium lactate and hydrogen (to a 0.5 bar of total pressure) to stimulate microbial activity. After the incubation period the content of the mesocosms was divided and subjected to different analysis, including geochemical analysis (as e.g. ICP-MS, ion and high-performance liquid chromatography), DNA isolation and amplification of the intergenic spacer to determine the microbial community structure, SEM-EDX and RAMAN spectroscopy to characterize the surface damage of the cast iron coupons.
The black precipitates were visible in the mesocosms containing Calcigel with lactate as substrate and for all the substrate-containing samples with MX-80. The obtained geochemical data confirmed the differences in the different microcosms by demonstrating unequal levels of sulphate and lactate consumption. Moreover, surface analysis of the cast iron coupons showed that corrosion rate and metabolite accumulation are also dependent on the bentonite type. In addition different microbial community structure was observered by intergenic spacer analysis (RISA) depending on the conditions applied and used bentonite. Therefore, the used bentonites varied in respect to reactivity and microbial activity.
Overall, the results show the importance of selection of suitable bentonite for DGR to adjust microbial implications and possibly faster corrosion rate of the metal containers.
We acknowledge funding by the BMBF (Grant 02NUK053B) and HGF (Grant SO-093).
References
[1] P. Sellin and etc., The Use of Clay as an Engineered Barrier in Radioactive-Waste Management – A Review, Clays and Clay Minerals 61(6), pp. 477-498 (2014).
[2] F. King. Container Materials for the Storage and Disposal of Nuclear Waste, Corrosion 69(10), pp. 986-1011 (2013).
[3] S. Kaufhold and etc. About the Corrosion Mechanism of Metal Iron in Contact with Bentonite, ACS Earth Space Chem. 4, 5, pp. 711–721 (2020).
[4] N. Matschiavelli and etc., The Year-Long Development of Microorganisms in Uncompacted Bavarian Bentonite Slurries at 30 and 60 °C, Environ. Sci. Technol., 53, 17, 10514–10524 (2019)

Keywords: Corrosion; Bentonite

  • Open Access Logo Poster (Online presentation)
    Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34957
Publ.-Id: 34957


Experimental simulation of phase evolution in conditions of underground storage: from million years to one day

Svitlyk, V.; Weiss, S.; Hennig, C.

Long-living radiotoxic isotopes present in spent nuclear fuel (SNF) requires procedures of complete immobilization of these species. Incorporation of the corresponding elements on atomic level into robust host crystalline matrices is one way to secure SNF during long-term underground storage. Derivatives of zirconia, ZrO2, are promising materials for these applications since these phases are known to remain structurally stable in geological cycles of up to 109 years [1]. The candidate host matrix must provide a sufficient solubility limit for radiotoxic elements, which is studied initially. Afterwards, structural stability of these phases against irradiation and leaching are established in order to asses possible discharge of the incorporated radioactive elements over a long-time scale. In this work we studied systematically structural behaviour of ZrO2-based materials incorporated with Th4+ and Ce4+ under extreme conditions of temperature (T) and pressure (P) in order to simulate experimentally possible phase evolution in conditions of underground storage.
In situ synchrotron radiation powder diffraction experiments under ambient and extreme conditions were performed at the HZDR ROBL BM20 beamline at ESRF, Grenoble, France [2]. It was found that cubic YSZ phases could dissolve 20% more of Th atoms compared to their tetragonal analogues. In situ T-dependent diffraction studies on radionuclide surrogate tetragonal and cubic Ce-YSZ series in a RT-1150 K range revealed excellent phase stabilities. No discharge of guest Ce4+ ions was observed. Nevertheless, application of external pressure on tetragonal Ce-YSZ phase induced transition towards a higher cubic symmetry around the P ~ 8.5 GPa. Remarkably, occupancy of Ce4+ remains stable throughout the transition. This together with T-dependent data indicates excellent affinity of guest Ce atoms with the YSZ structures. Thus, we suggest in situ studies under extreme conditions as a part of standard protocol to validate phases of interest as host matrixes for long-term underground storage of SNF.

References
[1] L. M. Heaman, A. N. LeCheminant, Chem. Geol. 110, 95 (1993). [2] A. C. Scheinost et al., J. Synchr. Rad. 28, 333 (2021).

Related publications

  • Lecture (Conference)
    Goldschmidt 2022, 10.-15.07.2022, Honolulu, HI, USA

Permalink: https://www.hzdr.de/publications/Publ-34954
Publ.-Id: 34954


Extreme conditions: towards secure and long-term storage of nuclear waste

Svitlyk, V.; Weiss, S.; Hennig, C.

Majority of man-made radiotoxic elements originate from spent nuclear fuel (SNF). It is composed essentially of uranium and plutonium and some minor actinides (An) like 237Np, 241Am/243Am, and 244Cm. Half-life of these elements can range from few decades up to millions of years (ca. 2.1 million years for 237Np [1]). Therefore, safe disposal of SNF requires matrix materials with strong resistance against corrosion and dissolution over a period of 106 years. Derivatives of zirconium-based ceramics, in particular zirconia, ZrO2, are promising materials for these applications since these phases are known to remain stable in geological cycles of up to 109 years [2]. Here scientific and technological goals are to obtain zirconium-based ceramic materials containing maximum possible tetravalent actinides (An) without Zr/An phase separation. In addition, structural stability of these phases under various external parameters, e.g. temperature (T), pressure (P), irradiation and leaching resistance is essential in order to exclude possible discharge of the incorporated radioactive elements over a long-time scale.
Two series of samples have been synthesized for current study: (I) Th-doped Y-stabilized ZrO2 (YSZ) and (II) Ce-doped YSZ phases, both of tetragonal and cubic symmetries. The series (I) was studied in order to determine maximum possible intake of Th4+ ions into the tetragonal and cubic YSZ matrices. The series II used Ce4+ species as surrogate ions for An4+ for studies under extreme conditions of T and P. Synchrotron radiation powder diffraction experiments under ambient and extreme conditions were performed at the ROBL BM20 beamline at ESRF [3]. Relevant technical details will be presented.
For the tetragonal YSZ phases maximum possible Th intake on the Zr/Y metal site reached ca. 10.3 at.%. Cubic phases could dissolve up to ca. 12.3 at.% Th under non-equilibrium conditions. Larger Th-Zr/Y solubility range for cubic phases was found to be symmetry related. Specifically, introduction of Th into tetragonal YSZ induces flattening of the Zr/YO8 polyhedra with concomitant decrease in tetragonality. This results in better accommodation of larger Th atoms via structural stabilization of longer bonding distances.
To simulate phase stability under conditions of underground nuclear repositories, Ce-based analogues were subjected to in situ studies under elevated temperatures and pressures. T-dependent diffraction studies on tetragonal and cubic Ce-YSZ series in a RT-1150 K range revealed excellent structural stability for all the studied compounds. In particular, occupancy of guest Ce4+ atoms as a function of temperature does not decrease in these systems. However, application of external pressure on tetragonal Ce-YSZ phase induced a structural transformation to a higher cubic symmetry around the P ~ 8.5 GPa. Remarkably, occupancy of Ce4+ remains stable throughout the transition. This together with T-dependent data indicates excellent affinity of guest Ce atoms with the YSZ structures. The parent YSZ phases are, therefore, promising candidates as host matrices for radiotoxic tetravalent elements like U, Th or Pu for a long-term underground storage.

References
[1] R. C. Ewing, W. J. Weber, J. Lian, J. Appl. Phys. 95, 5949 (2004).
[2] L. M. Heaman, A. N. LeCheminant, Chem. Geol. 110, 95 (1993).
[3] A. C. Scheinost et al., J. Synchr. Rad. 28, 333 (2021).

Related publications

  • Lecture (Conference) (Online presentation)
    New opportunities for High Pressure Science at the ESRF-EBS, 07.-09.02.2022, ESRF, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-34953
Publ.-Id: 34953


Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography

Kaever, C.

Ultrafast electron beam X-ray computed tomography [4] (UFXCT) is a non-invasive imaging technique based on scanning an electron beam on a tungsten target. This way, a moving X-ray source is generated without mechanically moving parts allowing for very high imaging rates up to 8000 fps.
This technique is used, e.g., for the investigation of multiphase flows, such as bubbly flow in industrial bubble column reactors. The goal of the ROOF experiment is to investigate the hydrodynamics of such a bubbly flow by apply UFXCT for scanning and tracking of objects alongside a vertical axis in real time based on the acquired cross-sectional images. To accomplish the tracking, software is needed to recognize objects in the reconstructed images, as a human would not fulfill realtime constraints. The current CPU-based implementation is the slowest step in the current workflow, thus, the goal of this work is to design a faster algorithm. In this work, the approach used by the RISA [5] (Realtime Image Stream Algorithms) software to realize the tracking of objects is presented and improved by using the GPU to recognize the objects.

Related publications

  • Study thesis
    TU Dresden, 2022
    Mentor: Dominic Windisch
    14 Seiten

Permalink: https://www.hzdr.de/publications/Publ-34952
Publ.-Id: 34952


Saccoite, Ca2Mn+32F(OH)8·0.5(SO4), a new, microporous mineral from the Kalahari Manganese Fields, South Africa

Giester, G.; Lengauer, C. L.; Chanmuang N., C.; Topa, D.; Gutzmer, J.; von Bezing, K.-L.

2
transparent, with white streak and vitreous luster. No luminescence is observed. Saccoite is uniaxial (–) with refractive indices at 589(1) nm  = 1.705(5) and  = 1.684(2). Pleochroism is distinct, i.e. bluish green (ω) and yellowish green (ε). The chemical composition was studied by means of an electron probe micro-analyser (EPMA) using wavelength-dispersive X-ray spectrometry (WDS). The empirical mineral formula is Ca2.06Mn3+1.78Cu0.10Mg0.07F0.97(OH)8.02(SO4)0.39. The unit-cell dimensions of saccoite (space group P4/ncc) are a = 12.834(3) Å, c = 5.622(2) Å, V = 926.0(4) Å3), and the calculated mass density is 2.73 g·cm-3. Saccoite exhibits a heteropolyhedral framework structure that is composed of edge- and cornersharing CaF2(OH)6 and M(OH)6 polyhedra (M = Mn3+, Cu2+) with large channels along [001], which host disordered and only partially occupied groups, especially SO42-. The hydrogen atoms of the OH groups point into the channel to form hydrogen bonds with the channel anions. Ca–F distances are about 2.3 Å, the Ca–OH distances in the range of 2.44 -2.58 Ǻ, and the M(OH)6 octahedron is strongly 4+2 Jahn-Teller distorted (4 × ~ 1.92 Å, 2 × 2.27 Å). The F atom is tetrahedrally coordinated to calcium atoms. The strongest lines in the X-ray powder pattern [d in Å (relative intensity) (hkl)] are: 9.0735 (35) (110), 4.5370 (95) (220), 4.0644 (20) (310), 3.0105 (100) (321), 2.8117 (20) (002), 2.7242 (75) (411), 1.9755 (35) (611), and 1.8142 (20) (550).

Keywords: saccoite; Ca2Mn+32F(OH)8·0.5(SO4); new mineral; microporous structure; Kalahari Manganese Field; South Africa

Permalink: https://www.hzdr.de/publications/Publ-34943
Publ.-Id: 34943


Unravelling the Origin of Ultra-Low Conductivity in SrTiO3 Thin Films: Sr Vacancies and Ti on A-Sites Cause Fermi Level Pinning

Morgenbesser, M.; Viernstein, A.; Schmid, A.; Herzig, C.; Kubicek, M.; Taibl, S.; Bimashofer, G.; Stahn, J.; Antonio Fernandes Vaz, C.; Döbeli, M.; Biautti, F.; de Dios Sirvent, J.; Liedke, M. O.; Butterling, M.; Kamiński, M.; Tolkiehn, M.; Vonk, V.; Stierle, A.; Wagner, A.; Tarancon, A.; Limbeck, A.; Fleig, J.

Different SrTiO3 thin films are investigated to unravel the nature of ultra-low conductivities recently found in SrTiO3 films prepared by pulsed laser deposition. Impedance spectroscopy reveals electronically pseudo-intrinsic conductivities for a broad range of different dopants (Fe, Al, Ni) and partly high dopant concentrations up to several percent. Using inductively-coupled plasma optical emission spectroscopy and reciprocal space mapping, a severe Sr deficiency is found and positron annihilation lifetime spectroscopy revealed Sr vacancies as predominant point defects. From synchrotron-based X-ray standing wave and X-ray absorption spectroscopy measurements, a change in site occupation is deduced for Fe-doped SrTiO3 films, accompanied by a change in the dopant type. Based on these experiments, a model is deduced, which explains the almost ubiquitous pseudo-intrinsic conductivity of these films. Sr deficiency is suggested as key driver by introducing Sr vacancies and causing site changes (FeSr and TiSr) to accommodate nonstoichiometry. Sr vacancies act as mid-gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably Ti_Sr) are present. Defect chemical modeling revealed that such a Fermi level pinning also causes a self-limitation of the Ti site change and leads to a very robust pseudo-intrinsic situation, irrespective of Sr/Ti ratios and doping.

Keywords: STO; Sr vacancies; conductivity; PALS

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Permalink: https://www.hzdr.de/publications/Publ-34942
Publ.-Id: 34942


Three-dimensional quasiquantized Hall insulator phase in SrSi2

Manna, K.; Kumar, N.; Chattopadhyay, S.; Noky, J.; Yao, M.; Park, J.; Förster, T.; Uhlarz, M.; Chakraborty, T.; Schwarze, B. V.; Hornung, J.; Strocov, V. N.; Borrmann, H.; Shekhar, C.; Sun, Y.; Wosnitza, J.; Felser, C.; Gooth, J.

In insulators, the longitudinal resistivity becomes infinitely large at zero temperature. For classical insulators, the Hall conductivity becomes zero at the same time. However, there are special systems, such as two-dimensional quantum Hall insulators, in which a more complex scenario is observed at high magnetic fields. Here, we report experimental evidence for a quasiquantized Hall insulator in the quantum limit of the three-dimensional compound SrSi2. Our measurements reveal a magnetic-field range, in which the longitudinal resistivity diverges with decreasing temperature, while the Hall conductivity approaches a quasiquantized value that is given only by the conductance quantum and the Fermi wave vector in the field direction. The quasiquantized Hall insulator appears in a magnetic field induced insulating ground state of three-dimensional materials and is deeply rooted in quantum Hall physics.

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Permalink: https://www.hzdr.de/publications/Publ-34941
Publ.-Id: 34941


Metal-assisted chemically etched silicon nanopillars hosting telecom photon emitters

Hollenbach, M.; Jagtap, N. S.; Fowley, C.; Baratech, J.; Guardia-Arce, V.; Kentsch, U.; Eichler-Volf, A.; Abrosimov, N. V.; Erbe, A.; Shin, C.; Kim, H.; Helm, M.; Lee, W.; Astakhov, G.; Berencen, Y.

Silicon, a ubiquitous material in modern computing, is an emerging platform for realizing a source of indistinguishable single photons on demand. The integration of recently discovered single-photon emitters in silicon into photonic structures is advantageous to exploit their full potential for integrated photonic quantum technologies. Here, we show the integration of an ensemble of telecom photon emitters in a two-dimensional array of silicon nanopillars. We developed a top-down nanofabrication method, enabling the production of thousands of nanopillars per square millimeter with state-of-the-art photonic-circuit pitch, all the while being free of fabrication-related radiation damage defects. We found a waveguiding effect of the 1278 nm-G center emission along individual pillars accompanied by improved brightness compared to that of bulk silicon. These results unlock clear pathways to monolithically integrating single-photon emitters into a photonic platform at a scale that matches the required pitch of quantum photonic circuits.

Keywords: G centers; Silicon nanopillars; Photonic integration; Metal-assisted chemical etching; Ion implantation

Related publications

  • Journal of Applied Physics 132(2022)3, 033101-1-033101-7
    Online First (2022) DOI: 10.1063/5.0094715

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  • Secondary publication expected from 15.07.2023

Permalink: https://www.hzdr.de/publications/Publ-34938
Publ.-Id: 34938


DNS and Highly-Resolved LES of Heat and Mass Transfer in Two-Phase Counter-Current Condensing Flow

Apanasevich, P.; Lucas, D.; Sato, Y.; Niceno, B.

A comprehensive study of direct-contact condensation heat transfer for turbulent, counter-current, liquid/vapour flow in a nearly horizontal channel at high pressure (i.e. 5MPa) has been carried out based on Direct Numerical Simulation (DNS) and highly-resolved Large Eddy Simulation (LES) approaches. To simulate the two-phase flow situation, driven in this case by a constant pressure gradient, a single set of Navier-Stokes equations, coupled with an enthalpy conservation equation, have been employed. The interfacial mass transfer, seen in this case to be dominated by condensation, has been calculated directly from the heat flux at the liquid/vapour interface. To investigate the effect of condensation on the turbulence phenomena, and vice versa, cases have been considered involving two friction Reynolds numbers: namely Re∗ = u∗h/ν = 178 and Re∗ = u∗h/ν = 590 (u∗ = (hΔP/ρ)^1/2). At the lower Reynolds number, three levels of water subcooling – 0K, 10K and 40K – have been investigated. The use of water subcooling of 0K has enabled the validation and verification procedures associated with the numerical approach to be compared against experimental and numerical data reported in the literature. The choice of the maximum degree of water subcooling is dictated by the need to justify the periodic boundary conditions applied in this numerical study. In the simulation for the higher Reynolds number, only the case of 10K subcooling has been included, as a consequence of the very high computation effort involved.

A detailed statistical analysis of the DNS and LES data obtained from the application of the well-known wall laws has also been assessed. In the vicinity of the liquid/vapour interface, the characteristics of the turbulent motions appear somewhat diverse, depending on whether the interface is basically flat or wavy in character. For a flat interface, some damping effect of the presence of the interface on the turbulence intensity has been observed, a feature which becomes enhanced as the level of liquid subcooling is increased. In the case of a wavy interface, the damping effect is predicted as considerably less pronounced.

Keywords: DNS; Highly-resolved LES; Multiphase flows; Phase change; Direct contact condensation; Interfacial heat transfer

Permalink: https://www.hzdr.de/publications/Publ-34937
Publ.-Id: 34937


Scalable fabrication of single quantum emitters in silicon

Astakhov, G.

Single-photon sources are one of the elementary building blocks for photonic quantum information and optical quantum computing. One of the upcoming challenges is the monolithic photonic integration and coupling of single-photon emission, reconfigurable photonic elements and single-photon detection on a silicon chip by a controllable manner. To this end, deterministic single-photon sources monolithically integrated with silicon quantum photonic integrated circuits (QPIC) represent a new tool in quantum photonics, complementing heralded probabilistic sources and offering very-large-scale integration (VLSI).
The isolation of single-photon emitters in the optical telecommunication O-band, such as the G centers and W centers, has recently been realized in silicon. In all previous cases, however, single-photon emitters were created randomly and uncontrollably, preventing their scalability. We realize the controllable fabrication of single G and W centers in silicon wafers using focused ion beams with high probability. We also implement a scalable, broad-beam implantation protocol compatible with the complementary-metal-oxide-semiconductor (CMOS) technology to fabricate single telecom emitters in desired positions on the nanoscale.
Our results enable the direct realization of QPIC with monolithically integrated single-photon sources with electrical control. Our findings also provide a route for the quasi-deterministic creation of single G and W centers at desired locations of photonic structures, including SOI waveguides and tunable cavities. This altogether unlocks clear pathways toward the implementation of industrial-scale photonic quantum processors.

Keywords: Single photons; Telecommunication band; Silicon; Quantum technologies

Related publications

  • Invited lecture (Conferences)
    Flagship Workshop: Defects in solids for quantum technologies, 12.-17.06.2022, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-34934
Publ.-Id: 34934


Combining Radiation- with Immunotherapy in Prostate Cancer: Influence of Radiation on T cells

Lindner, D.; Arndt, C.; Rodrigues Loureiro, L. R.; Feldmann, A.; Kegler, A.; Koristka, S.; Berndt, N.; Mitwasi, N.; Bergmann, R.; Frenz, M.; Bachmann, M.

Radiation of tumor cells can lead to the selection and outgrowth of tumor escape variants. As radioresistant tumor cells are still sensitive to retargeting of T cells, it appears promising to combine radio- with immunotherapy keeping in mind that the radiation of tumors favors the local conditions for immunotherapy. However, radiation of solid tumors will not only hit the tumor cells but also the infiltrated immune cells. Therefore, we wanted to learn how radiation influences the functionality of T cells with respect to retargeting to tumor cells via a conventional bispecific T cell engager (BiTE) and our previously described modular BiTE format UNImAb. T cells were irradiated between 2 and 50 Gy. Low dose radiation of T cells up to about 20 Gy caused an increased release of the cytokines IL2, TNF and interferon-g and an improved capability to kill target cells. Although radiation with 50 Gy strongly reduced the function of the T cells, it did not completely abrogate the functionality of the T cells.

Keywords: prostate stem cell antigen; prostate cancer; radiation; immunotherapy; bispecific T cell engager

Permalink: https://www.hzdr.de/publications/Publ-34932
Publ.-Id: 34932


Dataset for Diamond formation kinetics in shock-compressed C-H-O samples recorded by small-angle X-ray scattering and X-ray diffraction

Kraus, D.

Dataset for publication "Diamond formation kinetics in shock-compressed C-H-O samples recorded by small-angle X-ray scattering and X-ray diffraction"

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-13
    DOI: 10.14278/rodare.1695
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-34930
Publ.-Id: 34930


A FAIRly Integrated Scientific Project Lifecycle

Knodel, O.; Voigt, M.; Ufer, R.; Pape, D.; Lokamani, M.; Kelling, J.; Müller, S.; Gruber, T.; Juckeland, G.; Kessler, A.; Hein, J.; Schuller, B.

The talk introduces the general idea behind the HELIPORT project, which aims to make the entire life cycle of a scientific experiment or project discoverable, accessible, interoperable and reusable by providing an overview from a top-level perspective. Specifically, our data management solution addresses the areas from data generation to publication of primary research data, computing workflows performed and the actual research results.

Keywords: Data Management; Metadata; FAIR; Data provenance; Digital Objects; Digital Twins

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    HMC Dialogue, 15.07.2022, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-34929
Publ.-Id: 34929


Curvilinear magnetism: fundamentals and applications

Makarov, D.

In this talk I provide an overview of the activities of the FWID department with the focus on curvature effects in magnetic thin films and realization of flexible magnetic field sensors.

Keywords: curvature effects in magnetism; curvilinear magnetism; magnetic field sensing; human-machine interfaces; soft robotics

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  • Lecture (others)
    Invited talk at the Leibniz IFW (Institute for Metalic Materials), 12.07.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-34926
Publ.-Id: 34926


Simple Growth–Metabolism Relations Are Revealed by Conserved Patterns of Heat Flow from Cultured Microorganisms

Fahmy, K.

Quantitative analyses of cell replication address the connection between metabolism and growth. Various growth models approximate time-dependent cell numbers in culture media, but physio-logical implications of the parametrizations are vague. In contrast, isothermal microcalorimetry (IMC) measures with unprecedented sensitivity to heat (enthalpy) release via chemical turnover in metabolizing cells. Hence, the metabolic activity can be studied independently of modeling the time-dependence of cell numbers. Unexpectedly, IMC traces of various origins exhibit conserved patterns when expressed in the enthalpy domain rather than the time domain, as exemplified by cultures of Lactococcus lactis (prokaryote), Trypanosoma congolese (protozoan) and non-growing Brassica napus (plant) cells. The data comply extraordinarily well with a dynamic Langmuir ad-sorption reaction model of nutrient uptake and catalytic turnover generalized here to the non-constancy of catalytic capacity. Formal relations to Michaelis–Menten kinetics and common analytical growth models are briefly discussed. The proposed formalism reproduces the “life span” of cultured microorganisms from exponential growth to metabolic decline by a succession of distinct metabolic phases following remarkably simple nutrient–metabolism relations. The analysis enables the development of advanced enzyme network models of unbalanced growth and has fundamental consequences for the derivation of toxicity measures and the transferability of metabolic activity data between laboratories.

Keywords: bacteria; enzyme kinetics; heavy metals; isothermal microcalorimetry; Michaelis–Menten; toxicity

Permalink: https://www.hzdr.de/publications/Publ-34922
Publ.-Id: 34922


The Open-Access European Prevention of Alzheimer’s Dementia (EPAD) MRI dataset and processing workflow

Lorenzini, L.; Ingala, S.; Wink, A. M.; Kuijer, J. P. A.; Wottschel, V.; Dijsselhof, M.; Sudre, C. H.; Haller, S.; Molinuevo, J. L.; Gispert, J. D.; Cash, D. M.; Thomas, D. L.; Vos, S. B.; Prados, F.; Petr, J.; Wolz, R.; Palombit, A.; Schwarz, A. J.; Chételat, G.; Payoux, P.; Di Perri, C.; Wardlaw, J. M.; Frisoni, G. B.; Foley, C.; Fox, N. C.; Ritchie, C.; Pernet, C.; Waldman, A.; Barkhof, F.; Mutsaerts, H. J. M. M.

The European Prevention of Alzheimer Dementia (EPAD) is a multi-center study that aims to characterize the
preclinical and prodromal stages of Alzheimer’s Disease. The EPAD imaging dataset includes core (3D T1w, 3D
FLAIR) and advanced (ASL, diffusion MRI, and resting-state fMRI) MRI sequences.
Here, we give an overview of the semi-automatic multimodal and multisite pipeline that we developed to
curate, preprocess, quality control (QC), and compute image-derived phenotypes (IDPs) from the EPAD MRI
dataset. This pipeline harmonizes DICOM data structure across sites and performs standardized MRI pre-
processing steps. A semi-automated MRI QC procedure was implemented to visualize and flag MRI images next to
site-specific distributions of QC features — i.e. metrics that represent image quality. The value of each of these
QC features was evaluated through comparison with visual assessment and step-wise parameter selection based
on logistic regression. IDPs were computed from 5 different MRI modalities and their sanity and potential clinical
relevance were ascertained by assessing their relationship with biological markers of aging and dementia.
The EPAD v1500.0 data release encompassed core structural scans from 1356 participants 842 fMRI, 831
dMRI, and 858 ASL scans. From 1356 3D T1w images, we identified 17 images with poor quality and 61 with
moderate quality. Five QC features — Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), Coefficient of
Joint Variation (CJV), Foreground-Background energy Ratio (FBER), and Image Quality Rate (IQR) — were
selected as the most informative on image quality by comparison with visual assessment. The multimodal IDPs
showed greater impairment in associations with age and dementia biomarkers, demonstrating the potential of
the dataset for future clinical analyses.

Permalink: https://www.hzdr.de/publications/Publ-34920
Publ.-Id: 34920


Data publication: Electronic Density Response of Warm Dense Hydrogen: Ab initio Path Integral Monte Carlo Simulations

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

This repository contains the PIMC raw data for the static electronic density response of warm dense hydrogen. Units etc are the same as in the figures in the main text / supplemental material.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-07-13
    DOI: 10.14278/rodare.1806
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-34919
Publ.-Id: 34919


Equivariant neural networks for image segmentation

Venkatesh, D. K.; Lokamani, M.; Juckeland, G.; Weigert, M.; Steinbach, P.

Deep neural networks have by today been established as the goto candidate for semantic or instance segmentation at many scales and image modalities. The pressing challenge in supervised segmentation approaches remains to be the requirement of large annotated image datasets for good performance.
In recent years the expressive capabilities of neural networks have been demonstrated to improve through group convolutional operations which exploit existing symmetries present in the data.
The increased capacity for weight-sharing alongside gains in sample efficiency for training a neural network have led to the empirical success of equivariant neural networks. In our study, we propose and experiment on an equivariant U-net-based model for the task of image segmentation. In this talk, we will discuss our preliminary results on a synthetic datasets consisting of polygonal objects. The results indicate that the performance of our implementation of an equivariant network improves well beyond a vanilla Unet when exposed to symmetrical objects in data different scenarios.

References:

1. Taco S. Cohen, Max Welling, “Group Equivariant convolution networks”, arXiv preprint arXiv: 1602.07576, 2016.
2. Maurice Weiler and Gabriele Cesa, ”General E(2)-Equivariant Steerable CNNs”, NeurIPS 2019.

Keywords: equivariant neural networks; image segmentation; data augmentation; group theory; symmetry

  • Open Access Logo Lecture (Conference)
    Swiss Equivariant Learning Workshop, 11.-14.07.2022, Lausanne, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-34917
Publ.-Id: 34917


The effect of composition and microstructure on the creep behaviour of 14 Cr ODS steels consolidated by SPS

Meza, A.; Macía, E.; Chekhonin, P.; Altstadt, E.; Rabanal, M. E.; Torralba, J. M.; Campos, M.

There is a general need for alternative structural materials to improve power plants' efficiency and reduce CO2 emissions. Within this framework, two new compositions of temperature-resistant sintered ODS ferritic steels (14Cr-5Al-3W), strengthened by a fine dispersion of precipitates (5·1022 ox. /m3), have been developed. This work focuses on creep properties and microstructure evolution. The creep resistance (at 650°C) could be improved by prior microstructural optimisation, thanks to the consolidation by spark plasma sintering and the tailoring of precipitates' nature when a single compound introduces the oxide-forming elements (Y-Ti-Zr-O) synthesised for this purpose. To this end, the initial pre-alloyed ferritic powder was mechanically alloyed with the synthesised compound and sintered by spark plasma sintering (SPS). Afterwards, EBSD and TEM characterisation were employed to study the microstructures. Small punch creep tests (SPCT) were performed on the steels to analyse their creep performance. These showed an exceptional enhancement of the creep resistance in the steels containing the Y-Ti-Zr-O additions.

Keywords: 14Cr-ODS steel; fine grain; creep behaviour; SPCT

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  • Secondary publication expected from 27.06.2023

Permalink: https://www.hzdr.de/publications/Publ-34915
Publ.-Id: 34915


Modelling and Performance Analysis of Hydrocyclones: The Case of Buzwagi Gold Mine

Wikedzi, A.; Mütze, T.

The performance of hydrocyclones at Buzwagi Gold Mine (BGM) was investigated in three full scale survey campaigns. Thereafter, several empirical and theoretical hydrocyclone models were used for prediction of hydrocyclone performance. The survey data revealed poor performance of the grinding circuit caused by a circulating load higher than the design. Further, the poor performance of the grinding circuit had consequences on hydrocyclones overflow particle size (i.e. a much coarser product, xP,80 > 200 µm) than target (125 µm). In addition, the operation indicates overloading of the hydrocyclones due to feed rates being 10–18% above the design capacity. Apart from their deficiencies, BGM hydrocyclones can be categorized as very good or excellent separators in terms of separation efficiency based on partition curves, T(x). The modelling of BGM hydrocyclones revealed that Nageswararao’s model can well describe and predict the operation and is recommended for future simulation and optimization of the operation. Based on the survey data, there are opportunities to improve current operation through adjustment of operating conditions like dilution of hydrocyclone feed for improved classification efficiency.

Keywords: Grinding circuit; Hydrocyclone performance; Partition curve; Hydrocyclone Modelling

Permalink: https://www.hzdr.de/publications/Publ-34907
Publ.-Id: 34907


Data publication: ExponatONE: a high-precision small animal irradiation setup using proton radiography

Schneider, M.; Elisabeth, B.; Suckert, T.; Beyreuther, E.; Bock, J.; Dietrich, A.; Gantz, S.; Heuchel, L.; Krause, M.; von Neubeck, C.; Nexhipi, S.; Tillner, F.; Schürer, M.; Lühr, A.; Müller, J.

Daten, die für die Veröffentlichung "ExponatONE: eine hochpräzise Kleintierbestrahlungsanlage mit Protonenradiographie" verwendet wurden.
Das Repository enthält alle Daten, die zur Erstellung der quantitativen Ergebnisse und Abbildungen im eingereichten Manuskript verwendet wurden.
Satz von Skripten zur Aufnahme und Verarbeitung von Radiografiebildern/CTs, wie im zugehörigen Paper beschrieben.
Bei dem Datensatz handelt es sich um alle verwendeten Bilder und Grafen (CT, Röntgenbilder, Radiografiebilder, Simulationen, Mikroskopiebilder) für die Auswertung der Ergebnisse und die Darstellung in den Figures.

Keywords: Proton therapy; Proton radiography; Mouse brain irradiation; Preclinical high-precision setup; DNA damage; Relative biological effectiveness (RBE)

Permalink: https://www.hzdr.de/publications/Publ-34904
Publ.-Id: 34904


Data publication: Application of the Coordinate Transformation in Nodal Diffusion Calculations of Radially Expanding SFR Cores

Nikitin, E.; Fridman, E.

DYN3D calculations (inputs + outputs).

Keywords: DYN3D; Nodal methods; Serpent; SFR; Thermal expansion

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-29
    DOI: 10.14278/rodare.1769

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Permalink: https://www.hzdr.de/publications/Publ-34900
Publ.-Id: 34900


Application of the Coordinate Transformation in Nodal Diffusion Calculations of Radially Expanding SFR Cores

Nikitin, E.; Fridman, E.

In this study, the coordinate transformation technique was assessed for radial expansion of Sodium cooled Fast Reactor (SFR) cores with the focus on time-dependent calculations. This method was implemented into nodal diffusion code DYN3D and was tested against the already available direct mesh expansion model. The newly implemented method was tested for uniform radial core expansion cases. Within DYN3D, the coordinate transformation method was verified on steady-state cases and was validated on one of the transient scenarios from the Phenix reactor experiments. The obtained results demonstrate equivalence between the coordinate transformation and direct mesh expansion techniques and therefore presenting the viability of the former one in transient calculations of SFR cores.

Keywords: DYN3D; Nodal methods; Serpent; SFR; Thermal expansion

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  • Contribution to proceedings
    2019 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M&C 2019, 25.-29.08.2019, Portland, USA, 978-089448769-9, 1624-1631

Permalink: https://www.hzdr.de/publications/Publ-34898
Publ.-Id: 34898


Evolution of Single-Level-Model parameters in the Mechanically controllable Break Junctions

Kilibarda, F.; Günther, F.; Kelling, J.; Strobel, A.; Zahn, P.; Juckeland, G.; Kurt, G.; Elke, S.; Gemming, S.; Erbe, A.

The electrical properties of single molecules can be investigated using atomically sharp metallic electrodes in mechanically controllable break junctions (MCBJs). The current-voltage (IV) characteristics of single molecules in such junctions are affected by the binding positions of the end groups on the tip-facets and tip-tip separation. In this poster, we present MCBJ experiments on N,N’-Bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine (Salen). We discuss the evolution of the single level model (SLM) parameters namely, a) the energetic level (epsilon) of the dominant conducting channel and b) the coupling (Gamma) of the dominant conducting channel to the metallic electrodes. The SLM-parameters were evaluated for IV-curves recorded during opening measurements and fitted to the single level model. We explain the recurring peak-like features/protusions in the experimentally measured evolution of Gamma with increasing tip-tip separation, which we relate not only to the deformation of the molecule but also to the sliding of the anchor group above the electrode surface. We propose a novel, high-throughput approach to model the evolution of the SLM-parameters and perform transport calculations using the self-consistent charge scheme of the density-functional-based tight binding (SCC-DFTB) approach and the Green’s function formalism. Thereby, we consider many thermodynamically relevant configurations and assess the evolution of SLM-parameters using the SLM-curve fitting of the zero-bias transmission. The SLM-parameters are averaged using statistical weights obtained from a Metropolis simulation considering up to 200 000 configurations for selected tip-tip separations. The behavior of the averaged quantities with respect to the tip-tip separation reflects the experimentally observed evolution of the SLM-parameters astonishingly well.

Keywords: high-throughput approach; Mechanically controllable break junctions; single level model; Metropolis simulation; Evolution of Single-Level-Model parameters

  • Open Access Logo Poster (Online presentation)
    YOUNG RESEARCHER’S WORKSHOP ON MACHINE LEARNING FOR MATERIALS, 09.-13.05.2022, Trieste, Italy

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Permalink: https://www.hzdr.de/publications/Publ-34896
Publ.-Id: 34896


Free-electron lasers: past, present, and future challenges

Helm, M.

Free-electron lasers: past, present, and future challenges

Keywords: free electron laser

  • Invited lecture (Conferences) (Online presentation)
    International Conference on Free Electrons Laser Applications in Infrared and THz Studies of New States of Matter, 05.-08.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34887
Publ.-Id: 34887


Review of recent progress on advanced photocathodes for SC RF guns

Xiang, R.; Schaber, J.

As well known, the quality of the photocathodes is essential for the stability and the reliability of photo injector operation. Especially for the superconducting ratio frequency photo injectors (SRF guns), the photocathode represents one of the most critical parts. Benefit from the fast de-veloping photocathode technology in last years, several SRF guns were successfully operated or tested for the beam generation at kHz - MHz repetition rate. In this paper, we will review the achievements as well as the open questions in the applications of the photocathodes for SRF gun operation. Furthermore, we will discuss the possible improvement from cathodes side for the future CW electron sources.

Keywords: photocathode; SRF gun; superconducting RF photo injector; quantum efficiency

Permalink: https://www.hzdr.de/publications/Publ-34886
Publ.-Id: 34886


Exploring the Reduction Mechanism of ⁹⁹Tc(VII) in NaClO₄: A Spectro-Electrochimical Approach

Rodriguez Hernandez, D. M.; Mayordomo, N.; Parra-Puerto, A.; Schild, D.; Brendler, V.; Stumpf, T.; Müller, K.

Technetium (Tc) is an environmentally relevant radioactive contaminant whose migration is limited when Tc(VII) is reduced to Tc(IV). However, its reaction mechanisms are not well understood yet. We have combined electrochemistry, spectroscopy, and microscopy (cyclic voltammetry, rotating disk electrode, X-ray photoelectron spectroscopy, and Raman and scanning electron microscopy) to study Tc(VII) reduction in non-complexing media: 0.5 mM KTcO₄ in 2 M NaClO₄ in the pH from 2.0 to 10.0. At pH 2.0, Tc(VII) first gains 2.3 ± 0.3 electrons, following Tc(V) rapidly receives 1.3 ± 0.3 electrons yielding Tc(IV). At pH 4.0−10.0, Tc(IV) is directly obtained by transfer of 3.2 ± 0.3 electrons. The reduction of Tc(VII) produced always a black solid identified as Tc(IV) by Raman and XPS. Our results
narrow a significant gap in the fundamental knowledge of Tc aqueous chemistry and are important to understand Tc speciation.
They provide basic steps on the way from non-complexing to complex media.

Keywords: Technetium; Raman spectroscopy; X-ray photoelectron spectroscopy; Non-complexing media

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  • Secondary publication expected from 24.06.2023

Permalink: https://www.hzdr.de/publications/Publ-34883
Publ.-Id: 34883


Assessment of gene expressions from squamous cell carcinoma of the head and neck to predict radiochemotherapy-related xerostomia and dysphagia

Yahya, N.; Linge, A.; Leger, K.; Maile, T.; Kemper, M.; Haim, D.; Jöhrens, K.; Troost, E. G. C.; Krause, M.; Löck, S.

Purpose: We tested the hypothesis that gene expressions from biopsies of locally advanced head and neck squamous cell carcinoma (HNSCC) patients can supplement dose-volume parameters to predict dysphagia and xerostomia following primary radiochemotherapy (RCTx).
Material and methods: A panel of 178 genes previously related to radiochemosensitivity of HNSCC was considered for nanoString analysis based on tumour biopsies of 90 patients with locally advanced HNSCC treated by primary RCTx. Dose-volume parameters were extracted from the parotid, subman-
dibular glands, oral cavity, larynx, buccal mucosa, and lips. Normal tissue complication probability (NTCP) models were developed for acute, late, and for the improvement of xerostomia grade ≥2 and dysphagia grade ≥3 using a cross-validation-based least absolute shrinkage and selection operator (LASSO) approach combined with stepwise logistic regression for feature selection. The final signatures were included in a logistic regression model with optimism correction. Performance was assessed by the area under the receiver operating characteristic curve (AUC).
Results: NTCP models for acute and late xerostomia and the improvement of dysphagia resulted in optimism-corrected AUC values of 0.84, 0.76, and 0.70, respectively. The minimum dose to the contra-lateral parotid was selected for both acute and late xerostomia and the minimum dose to the larynx was selected for dysphagia improvement. For the xerostomia endpoints, the following gene expressions were selected: RPA2 (cellular response to DNA damage), TCF3 (salivary gland cells development), GBE1 (glycogen storage and regulation), and MAPK3 (regulation of cellular processes). No gene expression features were selected for the prediction of dysphagia.
Conclusion: This hypothesis-generating study showed the potential of improving NTCP models using gene expression data for HNSCC patients. The presented models require independent validation before potential application in clinical practice.

Keywords: gene expressions; head and neck cancer; xerostomia; dysphagia; radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-34881
Publ.-Id: 34881


Data publication: Tailoring pulsed laser deposition fabricated copper oxide film by controlling plasma parameters

Irimiciuc, S. A.; Chertopalov, S.; Volfová, L.; Hruska, P.; Cizek, J.; Vondracek, M.; Novotny, M.; Butterling, M.; Liedke, M. O.; Wagner, A.

Positron annihilation lifetime spectroscopy data from beamtime at ELBE

Keywords: pulsed laser deposition; copper oxide; defects; in situ plasma monitoring

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-07-04
    DOI: 10.14278/rodare.1765
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-34880
Publ.-Id: 34880


Controllable electrostatic manipulation of structure building blocks in noble metal aerogels

Wei, W.; Hübner, R.; Georgi, M.; Wang, C.; Wu, X.; Eychmüller, A.

The important role of structure homogeneity in three-dimensional network nanostructures serving as noble metal aerogels (NMAs) has attracted extensive attention in the field of electrochemistry in the last two decades, whereas a comprehensive study of tailoring skeleton units and element distributions in NMAs is still lacking. Herein, a new modulation strategy to easily prepare multiscale NMAs with tunable composition is developed by utilizing the electrostatic interaction between oppositely charged colloidal metal nanoparticles. The modulation rule of the chemical distribution in bimetallic aerogels leads to the construction of the as-tailored double skeleton aerogels for the first time. Considering their specific structures, the intrinsic and exceptional catalytic and electrocatalytic performances of NMAs were investigated. This study optimizes the structure homogeneity of noble metal aerogels by investigating nanoparticle–ligand interactions and provides further proof of their exceptional electrocatalytic
capabilities.

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Permalink: https://www.hzdr.de/publications/Publ-34871
Publ.-Id: 34871


Homogenization and short-range chemical ordering of Co-Pt alloys driven by the grain boundary migration mechanism

Pedan, R.; Makushko, P.; Dubikovskyi, O.; Bodnaruk, A.; Burmak, A.; Sidorenko, S.; Voloshko, S.; Kalita, V.; Hübner, R.; Makarov, D.; Vladymyrskyi, I.

Binary magnetic alloys like Co-Pt are relevant for applications as components of magnetic exchange coupled composites. Numerous approaches exist to tune the coercive field of Co-Pt alloys primarily relying on hightemperature processing aiming to realize chemically long-range ordered phases. The peculiarity of Co-Pt is that large coercive field and magnetic anisotropy can be achieved even in chemically disordered alloys relying on short-range order. Here, we study alloying of Co-Pt from bilayers of Pt(14 nm) Co(13 nm) at temperatures up to 550 degС, where bulk diffusion processes are suppressed and the dominant diffusion mechanism is grain boundary migration. We demonstrate that grain boundary diffusion mechanism can lead to the realization of a homogeneous yet chemically disordered Co56Pt44 alloy at temperatures of 500 degС and higher. A pronounced increase of the coercive field for samples processed at temperatures higher than 400 degС is attributed to short-range ordering. With this work, we pinpoint the grain boundary diffusion as the mechanism responsible not only for the homogenization of binary alloy films but also as a driving force for the realization of short-range order in Co-Pt. Our results motivate further research on grain boundary diffusion as a mechanism to realize chemically long-range ordered phases in Co-Pt alloys.

Keywords: grain boundary diffusion; magnetic thin films; short-range chemical order; Co-Pt alloy

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Permalink: https://www.hzdr.de/publications/Publ-34870
Publ.-Id: 34870


Pickering interfacial catalysts for asymmetric organocatalysis

Sun, Z.; Jurica, J.; Hübner, R.; Wu, C.

Proline-catalyzed aldol reactions have been developed as an important toolbox for the synthesis of valuable chiral intermediates, giving birth to asymmetric organocatalysis. Despite progress, their current applications are generally performed in highly polar solvents that are either difficult to remove or with low substrate/product solubility. In addition, prolines are often used as homogeneous organocatalysts in these solvents, thus, the recycling of catalyst for reuse is also challenging. To solve these problems, we develop a proline-based Pickering emulsion for asymmetric aldol reactions with high reactivity and selectivity. The emulsion was stabilized by proline-functionalized silica nanoparticles that are not only highly active in the presence of water but also easily recycled after the operation. Interestingly, their high stereoselectivity was not compromised after multiple reuse, i.e., >86 ee (enantiomeric excess) in the first and second use. With this demonstration, we prove the concept that efficient and selective aldol reactions are enabled by proline-based Pickering emulsions, which is a great and continuous contribution to the field of asymmetric organocatalysis.

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Permalink: https://www.hzdr.de/publications/Publ-34869
Publ.-Id: 34869


Artificially sporulated Escherichia coli cells as a robust cell factory for interfacial biocatalysis

Sun, Z.; Hübner, R.; Li, J.; Wu, C.

The natural bacterial spores have inspired the development of artificial spores, through coating cells with protective materials, for durable whole-cell catalysis. Despite attractiveness, artificial spores developed to date are generally limited to a few microorganisms with their natural endogenous enzymes, and they have never been explored as a generic platform for widespread synthesis. Here, we report a general approach to designing artificial spores based on Escherichia coli cells with recombinant enzymes. The artificial spores are simply prepared by coating cells with polydopamine, which can withstand UV radiation, heating and organic solvents. Additionally, the protective coating enables living cells to stabilize aqueous-organic emulsions for efficient interfacial biocatalysis ranging from single reactions to multienzyme cascades. Furthermore, the interfacial system can be easily expanded to chemoenzymatic synthesis by combining artificial spores with metal catalysts. Therefore, this artificial-spore-based platform technology is envisioned to lay the foundation for nextgeneration cell factory engineering.

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Permalink: https://www.hzdr.de/publications/Publ-34868
Publ.-Id: 34868


Plasticity within Aldehyde Dehydrogenase-Positive Cells Determines Prostate Cancer Radiosensitivity

Schwarz, F. M.; Schniewind, I.; Besso, M. J.; Lange, S.; Linge, A.; Patil, S. G.; Löck, S.; Klusa, D.; Dietrich, A.; Voss-Böhme, A.; Nowrouzi, A.; Krause, M.; Dubrovska, A.; Kurth, I.; Peitzsch, C.

Tumor heterogeneity and cellular plasticity are key determinants of tumor progression, metastatic spread, and therapy
response driven by the cancer stem cell (CSC) population. Within the current study, we analyzed irradiation-induced
plasticity within the aldehyde dehydrogenase (ALDH)-positive (ALDH+) population in prostate cancer. The radiosensitivity of
xenograft tumors derived from ALDH+ and ALDH-negative (ALDH-) cells was determined with local tumor control analyses
and demonstrated different dose-response profiles, time to relapse, and focal adhesion signaling. The transcriptional
heterogeneity was analyzed in pools of 10 DU145 and PC3 cells with multiplex gene expression analyses and illustrated a
higher degree of heterogeneity within the ALDH+ population that even increases upon irradiation in comparison with ALDH-
cells. Phenotypic conversion and clonal competition were analyzed with fluorescence protein-labeled cells to distinguish
cellular origins in competitive three-dimensional cultures and xenograft tumors. We found that the ALDH+ population
outcompetes ALDH- cells and drives tumor growth, in particular upon irradiation. The observed dynamics of the cellular state
compositions between ALDH+ and ALDH- cells in vivo before and after tumor irradiation was reproduced by a probabilistic
Markov compartment model that incorporates cellular plasticity, clonal competition, and phenotype-specific radiosensitivities.
Transcriptional analyses indicate that the cellular conversion from ALDH- into ALDH+ cells within xenograft tumors under
therapeutic pressure was partially mediated through induction of the transcriptional repressor SNAI2. In summary,
irradiation-induced cellular conversion events are present in xenograft tumors derived from prostate cancer cells and may be
responsible for radiotherapy failure. IMPLICATIONS: The increase of ALDH+ cells with stem-like features in prostate
xenograft tumors after local irradiation represents a putative cellular escape mechanism inducing tumor radioresistance.

Keywords: aldehyde dehydrogenase; genetics; human; male; prostate tumor; radiation tolerance; tumor recurrence; aldehyde dehydrogenase; neplasm recurrence; local

Permalink: https://www.hzdr.de/publications/Publ-34866
Publ.-Id: 34866


Unveiling the Zero-Phonon Line of the Boron Vacancy Center by Cavity-Enhanced Emission

Qian, C.; Villafañe, V.; Schalk, M.; Astakhov, G.; Kentsch, U.; Helm, M.; Soubelet, P.; Wilson, N. P.; Rizzato, R.; Mohr, S.; Holleitner, A. W.; Bucher, D. B.; Stier, A. V.; Finley, J. J.

Negatively charged boron vacancies (VB−) in hexagonal boron nitride (hBN) exhibit a broad emission spectrum
due to strong electron−phonon coupling and Jahn−Teller mixing of electronic states. As such, the direct measurement of the zero-
phonon line (ZPL) of VB− has remained elusive. Here, we measure the room-temperature ZPL wavelength to be 773 ± 2 nm by
coupling the hBN layer to the high-Q nanobeam cavity. As the wavelength of cavity mode is tuned, we observe a pronounced
intensity resonance, indicating the coupling to VB−. Our observations are consistent with the spatial redistribution of VB−
emission. Spatially resolved measurements show a clear Purcell effect maximum at the midpoint of the nanobeam, in accord with
the optical field distribution of the cavity mode. Our results are in good agreement with theoretical calculations, opening the way to using VB− as cavity spin−photon interfaces.

Keywords: 2D materials; Spins; hBN defect emitter; cavity-emitter coupling

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Permalink: https://www.hzdr.de/publications/Publ-34865
Publ.-Id: 34865


Patterns Of Practice for Adaptive and Real-Time Particle Therapy (POP-ART PT), part II: Plan adaptation for interfractional changes

Trnkova, P.; Zhang, Y.; Toshito, T.; Heijmen, B.; Richter, C.; Aznar, M.; Bolsi, A.; Daartz, J.; Knopf, A.; Bertholet, J.

Real-time respiratory motion management (RRMM, intra-fraction geometrical intervention) and Adaptive Particle Therapy (APT, inter-fraction adaptation of treatment plans) enable to account for anatomical variations and changes to optimize target coverage and organs-at-risk sparing. However, their current clinical implementation is unclear and expected to be highly heterogeneous. An institutional questionnaire, Patterns Of Practice for Adaptive and Real-Time Particle Therapy (POP-ART-PT), was distributed between 2021/01-06 to evaluate current clinical practice and wishes and barriers of the implementation. Here, we summarise the international survey results on APT for mitigation of interfractional anatomical changes from 70 particle therapy centers in 17 countries.

The response rate was 100% for Europe, 96% for Japan and 53% for USA. Of the 68 centers in operation, 84% (Figure1a) were APT users for at least one treatment site, with head and neck being the most common. APT was mostly performed offline (ad-hoc or per protocol) with only two users of online APT (plan library) and none using online daily replanning. Plan adaptation was in all cases motivated by both, target and OAR dose considerations (Figure1b). The most common imaging modality guiding APT was X-ray computed tomography. Sixty-eight percent of users plan to increase or change their APT technique. The greatest barriers to implementation were lack of integrated and efficient workflows and human resources (Figure2)

Offline APT has been widely implemented internationally, but online APT is still very rarely used. More research and development for integrated and efficient workflow is needed to facilitate the use of offline APT and enable online APT.

  • Lecture (Conference)
    PTCOG 60 - Jahreskonferenz der Particle Therapy Co-Operative Group, 28.06.-02.07.2022, Miami, USA

Permalink: https://www.hzdr.de/publications/Publ-34859
Publ.-Id: 34859


RawData - Liquid fraction investigations in a RPB (big printed zick-zack foam, multi point) using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.
DataCollector: Bieberle, André; Researcher: Schubert, Markus; RelatedPerson: Zippe, Cornelius

For liquid fraction investigations in a rotating printed zick-zack foam (big) packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected by a multi point injector. This repository contains:

  • the raw data of the gamma-ray CT scanner,
  • the extracted projection-averaged profile data matrix and
  • the restructured angular-resolved time-averaged sinogram data.

Keywords: Rotating Packed Bed; Process Intensivation; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-29
    DOI: 10.14278/rodare.1757

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Permalink: https://www.hzdr.de/publications/Publ-34858
Publ.-Id: 34858


RawData - Liquid fraction investigations in a RPB (small printed zick-zack foam 2, multi point) using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.
DataCollector: Bieberle, André; Researcher: Schubert, Markus; RelatedPerson: Zippe, Cornelius

For liquid fraction investigations in a rotating printed zick-zack foam (small) packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected by a multi point injector. This repository contains:

  • the raw data of the gamma-ray CT scanner,
  • the extracted projection-averaged profile data matrix and
  • the restructured angular-resolved time-averaged sinogram data.

Keywords: Rotating Packed Bed; Rotating Packed Bed; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-29
    DOI: 10.14278/rodare.1761

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Permalink: https://www.hzdr.de/publications/Publ-34857
Publ.-Id: 34857


RawData - Liquid fraction investigations in a RPB (small printed zick-zack foam, zero point) using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.
DataCollector: Bieberle, André; Researcher: Schubert, Markus; RelatedPerson: Zippe, Corneliusv

For liquid fraction investigations in a rotating printed zick-zack foam (small) packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected by a zero point injector. This repository contains:

  • the raw data of the gamma-ray CT scanner,
  • the extracted projection-averaged profile data matrix and
  • the restructured angular-resolved time-averaged sinogram data.

Keywords: Rotating Packed Bed; Process Intensivation; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-27
    DOI: 10.14278/rodare.1759

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Permalink: https://www.hzdr.de/publications/Publ-34856
Publ.-Id: 34856


RawData - Liquid fraction investigations in a RPB (small printed zick-zack foam, multi point) using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.
DataCollector: Bieberle, André; Researcher: Schubert, Markus; RelatedPerson: Zippe, Cornelius

For liquid fraction investigations in a rotating printed zick-zack foam (small) packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected by a multi point injector. This repository contains:

  • the raw data of the gamma-ray CT scanner,
  • the extracted projection-averaged profile data matrix and
  • the restructured angular-resolved time-averaged sinogram data.

Keywords: Rotating Packed Bed; Process Intensivation; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-29
    DOI: 10.14278/rodare.1755

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Permalink: https://www.hzdr.de/publications/Publ-34855
Publ.-Id: 34855


RawData - Liquid fraction investigations in a RPB (solid foam, single point) using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.
DataCollector: Bieberle, André; Researcher: Schubert, Markus; RelatedPerson: Zippe, Cornelius

For liquid fraction investigations in a rotating solid foam packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected by a single point injector. This repository contains

  • the raw data of the gamma-ray CT scanner,
  • the extracted projection-averaged profile data matrix and
  • the restructured angular-resolved time-averaged sinogram data.

Keywords: Rotating Packed Bed; Process Intensivation; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-29
    DOI: 10.14278/rodare.1751

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Permalink: https://www.hzdr.de/publications/Publ-34854
Publ.-Id: 34854


RawData - Liquid fraction investigations in a RPB (solid foam, 12 baffles) using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.
DataCollector: Bieberle, André; Researcher: Schubert, Markus; RelatedPerson: Zippe, Cornelius

For liquid fraction investigations in a rotating solid foam packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected by a 12 baffle disc injector. This repository contains:

  • the raw data of the gamma-ray CT scanner,
  • the extracted projection-averaged profile data matrix and
  • the restructured angular-resolved time-averaged sinogram data.

Keywords: Rotating Packed Bed; Process Intensivation; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-24
    DOI: 10.14278/rodare.1753

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Permalink: https://www.hzdr.de/publications/Publ-34853
Publ.-Id: 34853


RawData - Liquid fraction investigations in a RPB (solid foam, 32 baffles) using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.
DataCollector: Bieberle, André; Researcher: Schubert, Markus; RelatedPerson: Zippe, Cornelius

For liquid fraction investigations in a rotating solid foam packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected by a 32 baffle disc injector. This repository contains:

  • the raw data of the gamma-ray CT scanner,
  • the extracted projection-averaged profile data matrix and
  • the restructured angular-resolved time-averaged sinogram data. 

Keywords: Rotating Packed Bed; Process Intensivation; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-29
    DOI: 10.14278/rodare.1745

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Permalink: https://www.hzdr.de/publications/Publ-34852
Publ.-Id: 34852


Liquid fraction investigations in a RPB with different foam and liquid inlet geometries using GammaCT

Bieberle, A.; Loll, R.; Pyka, T.; Schubert, M.

For liquid fraction investigations in a rotating packed bed (RPB) angular-resolved time-averaged gamma-ray computed tomography (GammaCT) is applied. Liquid is injected via different inlet geometries. This repository mainly contains the reconstructed CT data for the following configurations:

  • solid foam, 12 baffle liquid inlet
  • solid foam, 32 baffle liquid inlet
  • solid foam, single point liquid inlet
  • printed small zick-zack foam, multi point liquid inlet
  • printed small zick-zack foam, zero point liquid inlet
  • printed big zick-zack foam, multi point liquid inlet

Furthermore, the corresponding restructured sinogram raw data are included as well as diverse radiographic scans from different foam geometries that are used to arrange the RPB disc and the CT scanning plane as planar as possible and to define the vertically distributed scanning planes within the foams.

Keywords: Rotating Packed Bed; Process Intensivation; Computed Tomography

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-07-08
    DOI: 10.14278/rodare.1763

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Permalink: https://www.hzdr.de/publications/Publ-34851
Publ.-Id: 34851


Modeling COVID-19 Optimal Testing Strategies in Retirement Homes: An Optimization-based Probabilistic Approach

Davoodi Monfared, M.; Batista German, A. C.; Senapati, A.; Schlechte-Welnicz, W.; Calabrese, J.

Retirement Home facilities have been widely affected by the COVID-19 pandemic. The residents in these homes are usually elderly people with a high risk of mortality from being infected. Since they are in contact with each other, once an infection arrives at the facility, it propagates quickly. To prevent the outbreaks, it has been demonstrated that regular testing of the residents is the most practical approach. However, testing may result in extra time for the staff that performs the test as well as residents' discontent, which presents a trade-off between the time invested in testing, daily caring activities, and viral spread containment. We introduce a novel optimization approach for testing schedule strategies in retirement homes. We develop a mixed-integer linear programming model for balancing the staff’s workload while minimizing the expected detection time of a probable infection inside the facility. We present a probabilistic approach in conjunction with the optimization models to compute the risk of infection, including contact rates, incidence status, and the probability of infection of the residents. To tackle the combinatorial nature of the problem, we proved an efficient property, called symmetry property of optimal testing strategy and utilized it in proposing an enhanced local search algorithm. We perform several experiments with real-size instances and show that the proposed approach can derive optimal testing strategies.

Keywords: Retirement Home; Testing Strategy; COVID-19

  • Open Access Logo Lecture (Conference)
    ESPOO 2022, 03.-06.07.2022, Helsinki, Finland

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Permalink: https://www.hzdr.de/publications/Publ-34850
Publ.-Id: 34850


Pore network and solute flux pattern analysis towards improved predictability of diffusive transport in argillaceous host rocks

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

Clay rock formations are considered as host rocks for underground radioactive waste repositories. Reliable predictions of diffusive transport heterogeneity are critical for assessing the sealing capacity of argillaceous rocks. The predictive power of numerical approaches to flow field analysis and radionuclide migration depends on the quality of the underlying pore network geometry. Both sedimentary and diagenetic complexity are controlling factors.
In this study, we demonstrate a cross-scale approach to reconstruct the pore network geometries of the sandy facies of the Opalinus Clay rock. We identified diagenetic and sedimentary subfacies components based on the concentration of diagenetic carbonates and sulfides and grain size variability, and quantified their pore size distributions and pore network geometries. A viable approach for use in transport modeling is to combine μ-CT data segmentation followed by filling the resulting volumes with representative pore network geometries based on FIB-SEM data. The resulting generalized pore network geometries are applied in digital rock models to calculate effective diffusivities, using a combined upscaling workflow for transport simulations from nanometer to micrometer scales.
Positron emission tomography (PET) diffusion experiments validated the transport simulation results. We introduced a statistical treatment of the PET and μ-CT tomographic datasets based on the spatial variability of both PET tracer concentrations and rock density. The analyzed effective diffusivities confirmed the numerical results.
This study illustrates three important steps in migration analysis: (i) a workflow of general applicability for cross-scale identification of pore network data in argillaceous rocks, (ii) application of the pore network data for the numerical analysis of diffusive transport, and (iii) validation of numerical results via combined PET - μ-CT diffusion experiments. Although the conceptual approach is not feasible for large numbers of samples, it opens up a strong potential for generalization: the validated results of effective diffusivities can now be easily used in a variety of segmented geometries. This allows to efficiently test upscaling concepts for the continuum scale on this basis.

Keywords: Diffusive transport; Transport modeling; Positron emission tomography (PET); Opalinus Clay; Radionuclide migration; Nuclear waste

Permalink: https://www.hzdr.de/publications/Publ-34849
Publ.-Id: 34849


Viscous fingering in a non-Newtonian liquid radial displacement by surfactant (C14TAB)-polymer (Xanthnan Gum) interaction

Stergiou, Y.; Perrakis, A.; Keshavarzi, B.; Javadi, A.; Eckert, K.; Schwarzenberger, K.

We investigated a miscible displacement of a less viscous liquid by a more viscous shear-thinning liquid in a Hele-Shaw cell. Due to a coacervation
reaction between both liquids, a hydrodynamic instability appears in the form of inward viscous fingering. The liquids consisted of a solution of
the anionic biopolymer xanthan gum, as the injection liquid, which displaced a cationic surfactant (C14TAB) aqueous solution (Keshavarzi et al.,
2019). In the contact zone between the two solutions, the oppositely charged species form polymer-surfactant complexes due to electrostatic
interactions. The electrostatic and hydrophobic interactions between these complexes lead to a self-assembly process, forming a membrane
structure separated from the main solution. During the continuing radial displacement, a large variety of patterns can emerge which is attributed
to the rheological properties of the system involving viscosity gradients, the non-Newtonian nature of the displacing solution and the complex
rheology of the coacervate phase. Variation of the flow rate and gap width of the Hele-Shaw cell revealed distinct instability regimes and allowed
to identify main contributing mechanisms. These insights open the door for further investigation of fluid mechanics problems (i.e. Saffman-Taylor
instability) (Saffman & Taylor, 1958) in multiphase systems of complex rheology and its applications in engineering and technology.
References:
Keshavarzi, B., Langmuir. 2019, 35(42), 13624-13635.
Saffman, P., & Taylor, G. Proceedings of the Royal Society A: Mathematical, Physical. 1958, 245(1242), 312-329.
Acknowledgements: This work was supported by the German Aerospace Center (DLR) with funds provided by the Federal Ministry for
Economic Affairs and Energy (BMWi), Grant No. 50WM2061 (project ChemFront).

  • Lecture (Conference)
    Annual European Rheology Conference (AERC 2022), 26.-28.04.2022, Sevilla, Spain

Permalink: https://www.hzdr.de/publications/Publ-34847
Publ.-Id: 34847


Physics-Informed and Data-Driven Molecular Dynamics Simulations of Iron under Extreme Conditions

Ramakrishna, K.; Lokamani, M.; Nikolov, S.; Tranchida, J.; Wood, M.; Cangi, A.

We present a new Spectral Neighbor Analysis Potential (SNAP) machine-learning potential for large-scale molecular dynamics simulations of Iron. SNAP is a classical interatomic potential that expresses the energy of each atom as a linear function of selected bispectrum components of the neighbor atoms. The development of the SNAP potential entails three steps: (1) the creation of a training database comprised of a consistent and meaningful set of first-principles Density Functional Theory (DFT) data for Iron at a range of high pressures (0-400 GPa) and temperatures (0-6500 K); (2) the robust and physically guided training of the SNAP hyper-parameters based on DFT data using statistical data analysis; and (3) the validation of the SNAP potential in molecular dynamics simulations of Iron by evaluating transport properties at extreme conditions up to those prevalent in Earth's core.

Keywords: Warm dense matter; Matter under extreme conditions; Computational Physics

  • Poster
    Young Researcher's Workshop on Machine Learning for Materials 2022, 09.-13.05.2022, Trieste, Italy

Permalink: https://www.hzdr.de/publications/Publ-34846
Publ.-Id: 34846


Maskless magnetic patterning using cobalt and dysprosium focused ion beams

Lenz, K.; Pablo Navarro, J.; Klingner, N.; Hlawacek, G.; Samad, F.; Narkovic, R.; Hübner, R.; Pilz, W.; Meyer, F.; Mazarov, P.; Bischoff, L.; Lindner, J.

We present results for direct maskless magnetic patterning of ferromagnetic nanostructures using a special liquid metal alloy ion source for focused ion beam (FIB) systems. We used a Co36Nd64 alloy as the FIB source [1]. A Wien mass filter allows for quick switching between the ion species in the alloy without changing the FIB source. A 5000×1000×50 nm3 permalloy strip served as the sample. Using the FIB we implanted a 300-nm-wide track with Co ions (see Fig.1). We observed the Co-induced changes by measuring the sample with microresonator ferromagnetic resonance before and after the implantation. Structures as small as 30 nm can be implanted up to a concentration of 10 % near the surface. Such lateral resolution is hard to reach for other lithographic methods. This allows for easy magnetic modification of edge-localized spin waves.
In another set of samples, we implanted Dy ions to locally increase the damping in a stripe pattern of ~120-nm-wide strips with 400 nm periodicity on a total area of 1×1 mm². Thus, the Gilbert damping parameter can be easily increased by one order of magnitude with a lateral resolution of about 100 nm.
In contrast to electron beam lithography in combination with broad-beam ion implantation, the maskless FIB process does not require the cumbersome and difficult removal of the ion-hardened resist if optical measurements like BLS or TR-MOKE are needed.

Keywords: ferromagnetic resonance; focused ion beams; nanostructures; implantation

Related publications

  • Poster
    Magnonics 2022, 31.07.-04.08.2022, Oxnard, USA

Permalink: https://www.hzdr.de/publications/Publ-34845
Publ.-Id: 34845


Nonstationary spin waves under a uniform excitation in a confined permalloy microstrip directly imaged with STXM-FMR

Pile, S.; Stienen, S.; Lenz, K.; Narkovic, R.; Wintz, S.; Förster, J.; Mayr, S.; Buchner, M.; Weigand, M.; Ney, V.; Lindner, J.; Ney, A.

Spin waves are one of the options to replace the transfer of electronic charges in logic devices to make information processing faster and more efficient [1]. A fundamental understanding of the dynamic magnetic properties of confined rectangular strips is a prerequisite for the development of nanoscale computational devices. Planar microresonators/microantennas made it possible not only to measure spin wave dynamics in a single microstrip, but to apply synchrotron-based time-resolved scanning transmission microscopy (TR-STXM) [3] using a phase-locked ferromagnetic resonance (FMR) excitation scheme (STXM-FMR). STXM-FMR enables direct temporally resolved imaging of the spatial distribution of the precessing magnetization within the microstrip during FMR excitation with elemental selectivity. FMR modes in a single rectangular permalloy microstrip were directly imaged using STXM-FMR and the findings were corroborated by micromagnetic simulations showing a very good agreement [5]. Under uniform excitation in a single confined microstrip typically standing spin waves are expected, nevertheless all imaged spin waves are nonstationary at and off resonance.

Keywords: ferromagnetic resonance; x-ray transmission microscopy; nanostructures

  • Invited lecture (Conferences)
    NESY User Symposium 2022, 29.-30.09.2022, Leoben, Österreich

Permalink: https://www.hzdr.de/publications/Publ-34844
Publ.-Id: 34844


PET Imaging of Cholinergic Neurotransmission in Neurodegenerative Disorders

Tiepolt, S.; Meyer, P. M.; Patt, M.; Deuther-Conrad, W.; Hesse, S.; Barthel, H.; Sabri, O.

As a neuromodulator, the neurotransmitter acetylcholine plays an important role in cognitive, mood, locomotor, sleep/wake, and olfactory functions. In the pathophysiology of
most neurodegenerative diseases, such as Alzheimer disease (AD) or Lewy body disorder (LBD), cholinergic receptors, transporters, or enzymes are involved and relevant as
imaging targets. The aim of this review is to summarize current knowledge on PET imaging of cholinergic neurotransmission in neurodegenerative diseases. For PET imaging
of presynaptic vesicular acetylcholine transporters (VAChT), (-)-18F-fluoroethoxybenzovesamicol (18F-FEOBV) was the first PET ligand that could be successfully translated
to clinical application. Since then, the number of 18F-FEOBV PET investigations on patients with AD or LBD has grown rapidly and provided novel, important findings
concerning the pathophysiology of AD and LBD. Regarding the α4β2 nicotinic acetylcholine receptors (nAChRs), various second-generation PET ligands, such as 18F-nifene,
18F-AZAN, 18F-XTRA, (-)-18F-flubatine, and (+)-18F-flubatine, were developed and successfully translated to human application. In neurodegenerative diseases such as AD
and LBD, PET imaging of α4β2 nAChRs is of special value for monitoring disease progression and drugs directed to α4β2 nAChRs. For PET of α7 nAChR, 18F-ASEM and
11C-MeQAA were successfully applied in mild cognitive impairment and AD, respectively. The highest potential for α7 nAChR PET is seen in staging, in evaluating disease
progression, and in therapy monitoring. PET of selective muscarinic acetylcholine receptors (mAChRs) is still in an early stage, as the development of subtype-selective
radioligands is complicated. Promising radioligands to image mAChR subtypes M1 (11C-LSN3172176), M2 (18F-FP-TZTP), and M4 (11C-MK-6884) were developed and
successfully translated to humans. PET imaging of mAChRs is relevant for the assessment and monitoring of therapies in AD and LBD. PET of acetylcholine esterase activity
has been investigated since the 1990s. Many PET studies with 11C-PMP and 11C-MP4A demonstrated cortical cholinergic dysfunction in dementia associated with AD and
LBD. Recent studies indicated a solid relationship between subcortical and cortical cholinergic dysfunction and noncognitive dysfunctions such as balance and gait in LBD.
Taken together, PET of distinct components of cholinergic neurotransmission is of great interest for diagnosis, disease monitoring, and therapy monitoring and to gain insight
into the pathophysiology of different neurodegenerative disorders.

Keywords: acetylcholine; Alzheimer disease; Lewy body disorder; neurodegenerative disorde; neurology; PET

Permalink: https://www.hzdr.de/publications/Publ-34841
Publ.-Id: 34841


New analytical tools for studying habitat selection in terrestrial mammals

Alston, J.; Fleming, C. H.; Calabrese, J.

The study of habitat selection is a foundational component of basic and applied animal ecology. Today, habitat selection in mammals is primarily studied using resource selection functions, a class of models that uses logistic regression to compare “used” to “available” habitat. However, these models have several statistical problems, including rampant pseudoreplication from failing to account for autocorrelation in modern animal movement data, no clear guidelines for sampling available habitat, and large amounts of numerical error from sampling too few available points. These problems are widely acknowledged but have no generally accepted solutions, so we propose three new methods for addressing them: likelihood weighting, Gaussian availability sampling, and numerical convergence checks. We demonstrate the practical advantages of these methods over conventional approaches using simulations and empirical data on a water mongoose (Atilax paludinosus), a caracal (Caracal caracal), and a serval (Leptailurus serval), and briefly demonstrate how to apply our methods to animal tracking data using the ‘ctmm’ R package. Broad uptake of these methods could substantially improve our estimates of habitat selection in mammals.

  • Lecture (Conference)
    American Society of Mammalogists Annual Meeting, 16.-21.06.2022, Tucson, AZ, USA

Permalink: https://www.hzdr.de/publications/Publ-34830
Publ.-Id: 34830


Data publication: Curvilinear spin-wave dynamics beyond the thin-shell approximation: Magnetic nanotubes as a case study

Körber, L.; Verba, R.; Otálora, J. A.; Kravchuk, V.; Lindner, J.; Faßbender, J.; Kakay, A.

This dataset contains the numerical data for our publication "Curvilinear spin-wave dynamics beyond the thin-shell approximation: Magnetic nanotubes as a case study" published in Physical Review B. The data consists of dispersion, magnetization ground states and mode profiles of spin waves in vortex-state magnetic nanotubes of different thicknesses, and has been calculated with the TetraX micromagnetic modeling package. All calculations are described within each subfolder by a jupyter notebook.

Keywords: spin waves; nanotubes; curvilinear magnetism; curvature effects; micromagnetic modeling; tetrax; nonreciprocity

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-06-23
    DOI: 10.14278/rodare.1749
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-34826
Publ.-Id: 34826


Magnetic-field-assisted electrodeposition at conically structured metal layers

Huang, M.

Micro- and nano-sized conical structures possess specific magnetic, superhydrophobic and electrocatalytic properties and are therefore attractive for numerous applications. Among the various methods of manufacturing such structured layers, electrodeposition appears a simple and inexpensive method. Beside the use of capping agents, the application of magnetic fields could support the local growth of cones on a non-templated planar electrode.
This dissertation investigates electrodeposition at conically structured metal layers in external magnetic fields. Depending on the direction and the intensity of the magnetic field, the Lorentz force and the magnetic gradient force can generate electrolyte flow and bring electrolyte enriched with metal ions towards the cone tips. As a result, the local deposition rate is increased and conical growth is promoted. In order to obtain a basic understanding of the magnetic field effects, systematic numerical and theoretical investigations are performed for electrodeposition at mm-sized cones of different materials, shapes and arrangements under different electrochemical and magnetic conditions. If a uniform external magnetic field is oriented parallel to the cone axis, the magnetic gradient force enabled by the magnetization of ferromagnetic cones provides a strong support for conical growth, thereby often dominating over the Lorentz force and the buoyancy force arising from electrode reactions. This supporting effect is only slightly mitigated when neighboring cones are getting closer. The numerical results shown are validated by experimental data for different configurations and deposition parameters.
In order to explore the prospects of magnetic fields to enhance the growth of smaller, micro- and nanometer sized conical structures, scaling laws of the local flows driven by the magnetic forces are derived numerically and confirmed analytically for shrinking cone sizes. Although the magnetic gradient force can generate a beneficial flow at ferromagnetic cones, the small flow region and the nearly constant thickness of the concentration boundary layer limit the support of the magnetic field. Enhancements of the structuring effect are observed for pulsed deposition and, despite only moderately, at higher magnetic field intensities. Furthermore, a simplified modeling approach is developed to simulate the growth mechanism of nano-cones with respect to the influence of capping agents.
Experimental results of the electrodeposition of Ni cones in magnetic fields obtained by partners in Krakow are analyzed by performing simulations of both the global cell flow and the local flows generated by magnetic fields of different orientations. This two-step approach provides an interpretation of the experimental results, and gives a deeper insight on how the capping agent influences the local growth.
Finally, the impact of the hydrogen side reaction on the electrodeposition in magnetic fields is considered. The numerical results indicate that hydrogen bubbles sitting at the cone tips may damp conical growth, while the magnetic-field-driven flow imposes a weak stabilizing force on the bubble.

Keywords: Metal electrodeposition; Nano-structured catalyst; Lorentz force; Magnetic gradient force; Numerical simulation; Magnetic field

  • Doctoral thesis
    TU Dresden, 2022
    Mentor: Dr. Gerd Mutschke, Prof. Kerstin Eckert

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Permalink: https://www.hzdr.de/publications/Publ-34824
Publ.-Id: 34824


Nonlinear THz spectroscopy of two-dimensional systems

Helm, M.

Nonlinear THz spectroscopy of two-dimensional systems (pump-probe in graphene, with and without magnetic field, dressed microcavity polaritons).

Keywords: THz; free-electron laser; graphene; Landau levels; polariton

  • Invited lecture (Conferences)
    Workshop on "Semiconductors,nanostructures, 2D systems, and Dirac matter", 20.-22.06.2022, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-34823
Publ.-Id: 34823


Liquid flow morphology investigation in structured packings for offshore applications using a novel flow imaging sensor

Mamedov, T.; Schleicher, E.; Schubert, M.; Ehlert, T.; Kenig, E. Y.; Hampel, U.

Environmental and economic constraints for oil and gas production necessitate the development of cost-effective operating facilities in the modern offshore industry. For this reason, floating production systems are increasingly used to operate oil and gas fields in deepwater locations, whereby high submarine pipeline expenditures of fixed offshore platforms are eliminated. Apart from economic advantages, floating production systems maintain a safe operation and continuous production under severe ocean conditions, i.e. cyclones, huge waves and floating icebergs. Whilst traditional fossil energy sources are continuously losing their dominance, liquefied natural gas (LNG) is gaining popularity in the energy market owing to the comparatively lower greenhouse gas emissions. For LNG production, Floating Production Storage and Offloading (FPSO) units combine the feature of onshore LNG plants and that of storage tankers in a single large marine vessel. Thus, the number of FPSOs for LNG production has been growing in the offshore industry. The design principles for land-based process units cannot be directly applied to FPSO topside equipment because of wind-generated wave effects. Separation columns are more susceptible to the motion impact than most of the onboard process equipment, and consequent product quality losses represent the main concern.
Separation columns with structured packings are mostly used on floating platforms due to their low pressure drop, high capacity and performance. To study the dynamics of the flow morphology in the packing and the corresponding mass transfer performance, a structured packing column is embarked on a hexapod motion simulator, which mimics the six-degree-of-freedom ship motion (cf. Fig. 1). The process of air dehumidification by triethylene glycol (TEG) solutions is used as an example. A novel flow imaging sensor was developed to visualize the flow morphology dynamics evolving on the corrugated sheets of the structured packing (Fig. 2). The sensor detects most relevant morphologies, i.e. unwetted, partially and fully wetted channels and their corresponding film thicknesses on the packing sheets for the tilted and moving column allowing a comparison with the vertically oriented configuration.
At a later step, along with the fluid dynamics, the separation performance of air dehumidification and the liquid desiccant regeneration processes will be evaluated. The experimental data will be used to develop a new modelling approach for floating structured packing columns based on hydrodynamic analogies between complex flow patterns in real columns and simplified fluid-dynamic elements.

  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Hochdruckverfahrenstechnik, 02.-03.05.2022, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34818
Publ.-Id: 34818


Optimization and preliminary design of a high-temperature, low pressure-ratio sCO2-compressor for a wide operating range

Rath, S.; Unger, S.; Hampel, U.; Gampe, U.

Power cycles based on supercritical carbon dioxide (sCO2) promise higher thermal efficiencies and more compact components than conventional technologies. Within the CARBOSOLA project, funded by the German Federal Ministry for Economic Affairs and Energy, a large-scale experimental facility is being set up by a consortium of scientific and industrial partners to actively contribute to the development of sCO2 technology. The first expansion stage provides a circulation of the sCO2 flow without expansion devices in the test loop. Thereby the compressor is intended to compensate for pressure losses and consequently for low pressure differences. In addition to that, a preferably wide operating range, regarding temperature and pressure, shall provide a high degree of flexibility of the test rig.
This work presents the design optimization of the impeller aiming at a wide operating range in compliance with the boundary conditions set for the test rig and the use of sCO2. For this purpose, a hybrid approach is used, combining parametric three-dimensional modeling with a one-dimensional performance criterion for operating range estimation. A large number of impeller designs have been simulated numerically within an optimization procedure using a genetic algorithm. On this basis, several designs have been selected and compared against each other. The evaluation includes sets of performance lines and the validation of the one-dimensional criterion used for optimization.

  • Open Access Logo Contribution to proceedings
    7th International sCO2 Power Cycles Symposium, 21.-24.02.2022, San Antonio, Texas, USA
    Optimization and preliminary design of a high-temperature, low pressure-ratio sCO2-compressor for a wide operating range
  • Open Access Logo Poster
    Optimization and preliminary design of a high-temperature, low pressure-ratio sCO2-compressor for a wide operating range, 21.-24.02.2022, San Antonio, Texas, USA

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Permalink: https://www.hzdr.de/publications/Publ-34817
Publ.-Id: 34817


Application of laser-induced nanostructured metal surfaces

Lorenz, P.; Zajadacz, J.; Bez, E. A.; Marquardt, F.; Franz, R.; Lecrivain, G.; Peter, S.; Hommes, G.; Ehrhardt, M.; Himmerlich, M.; Zimmer, K.

Nature teaches that nanostructured surfaces show a variety of beneficial macroscopic effects. The laser texturing of metal surfaces allows the fast, defined, and adjustable large-area nano- and micro surface structuring using ultrashort laser pulses. Such hierarchical structures comprising of determined micro patterns and self-organized nanostructures allow the customization of metal surface properties for applications in accelerators, optics, and fluidics. Here, the laser exposure of superhydrophobic SSt can cause a localized modification of the surface tension which enables the guiding and pining of water droplets which was studied using high-speed optical imaging.
The laser-induced micro- and nano structuring and the chemical modification of the metal surfaces allows the fast and defined adjustment of the macroscopic properties of metals with manifold applications.

  • Lecture (Conference)
    16th International Conference on Laser Ablation, 24.-29.04.2022, Matsue, Japan

Permalink: https://www.hzdr.de/publications/Publ-34812
Publ.-Id: 34812


Modulating properties by light ion irradiation: From novel functional materials to semiconductor power devices

Yuan, Y.; Zhou, S.; Wang, X.

In this review, the application of light ion irradiation is discussed for tailoring novel functional materials and for improving the performance in SiC or Si based electrical power devices. The deep traps and electronic disorder produced by light ion irradiation can modify the electrical, magnetic, and optical properties of films (e.g., dilute ferromagnetic semiconductors and topological materials). Additionally, benefiting from the high reproducibility, precise manipulation of functional depth and density of defects, as well as the flexible patternability, the helium or proton ion irradiation has been successfully employed in improving the dynamic performance of SiC and Si based PiN diode power devices by reducing their majority carrier lifetime, although the static performance is sacrificed due to deep level traps. Such a trade-off has been regarded as the key point to compromise the static and dynamic performances of power devices. As a result, herein the light ion irradiation is highlighted in both exploring new physics and optimizing the performance in functional materials and electrical devices.

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  • Secondary publication expected from 01.06.2023

Permalink: https://www.hzdr.de/publications/Publ-34811
Publ.-Id: 34811


A high-k Cu-doped ZnO film formed via Ga-ion implantation: The acceptor-donor co-doping approach

Shi, Y.-L.; Huang, D.; Kentsch, U.; Zhou, S.; Chi-Chung Ling, F.

Dielectric thin films having high permittivity (high-k) and low dielectric loss is essential for developing high performance capacitive devices like metal oxide field effect transistor or thin film transistor. Ga ion implantation performed on Cu-doped ZnO film fabricated by pulsed laser deposition with optimized doping concentrations and post-implantation annealing yielded film having high permittivity and low dielectric loss (ε = 87 and tan δ = 0.17 at the frequency of 1 kHz). Moreover, the permittivity exhibits good stability over a wide range of frequency from 20 Hz to 10 MHz. The high-k film was characterized by detailed dielectric studies, including frequency dependence of permittivity and dielectric loss, complex electrical modulus analysis, impedance spectroscopy and ac conductivity. The enhancement of the permittivity was attributed to the correlated potential barrier hopping of electrons between the neighboring acceptor-donor defect complex states in the band gap created by the co-doping, thus acting as electric dipoles polarizing the film. This work opens up future possibility for ‘dielectric engineering’. The three-dimensional dielectric spatial profile can be controlled via the selective area ion implantation with the depth controlled by the ion implantation energy.

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  • Secondary publication expected from 22.04.2023

Permalink: https://www.hzdr.de/publications/Publ-34810
Publ.-Id: 34810


Tunable structural colors in all-dielectric photonic crystals using energetic ion beams

Li, J.; Zhang, K.; Pang, C.; Zhao, Y.; Zhou, H.; Chen, H.; Lu, G.; Liu, F.; Wu, A.; Du, G.; Akhmadaliev, S.; Zhou, S.; Chen, F.

The modulation of structural color through various methods has attracted considerable attention. Herein, a new modulation method for the structural colors in all-dielectric photonic crystals (PCs) using energetic ion beams is proposed. One type of periodic PC and two different defective PCs were experimentally investigated. Under carbon-ion irradiation, the color variation primarily originated from the blue shift of the optical spectra. The varying degrees of both the reflection and transmission structural colors mainly depended on the carbon-ion fluences. Such nanostructures are promising for tunable color filters and double-sided chromatic displays based on PCs.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34809
Publ.-Id: 34809


In-Plane Oriented Two-Dimensional Conjugated Metal–Organic Framework Films for High-Performance Humidity Sensing

Park, S.; Zhang, Z.; Qi, H.; Liang, B.; Mahmood, J.; Noh, H.-J.; Hambsch, M.; Wang, M.; Wang, M.; Hoang Ly, K.; Wang, Z.; Weidinger, I. M.; Zhou, S.; Baek, J.-B.; Kaiser, U.; Mannsfeld, S. C. B.; Feng, X.; Dong, R.

Two-dimensional conjugated metal–organic frameworks (2D c-MOFs) have emerged as a new generation of conducting MOFs for electronics. However, controlled synthesis of thin-film samples with high crystallinity and defined layer orientation, which is beneficial for achieving high-performance devices and reliable structure–property relationship, has remained a challenge. Here, we develop a surfactant-directed two-step synthesis of layered 2D c-MOF films based on benzene and triphenylene ligands linked by copper-bis(diimino) complexes (HIB-Cu and HITP-Cu, respectively). The achieved layered 2D c-MOF films are featured as free-standing, in-plane oriented, and polycrystalline films with domain size up to ∼8000 nm2 and a tunable thickness in the range of 8–340 nm. Benefiting from the intrinsic electrical conductivity and quasi-one-dimensional pore channels, a HIB-Cu film based chemiresistive sensor is constructed, displaying effective humidity sensing with a response as fast as ∼21 s, superior to the reported MOF-powder-based chemiresistive sensors (in the orders of minutes).

Permalink: https://www.hzdr.de/publications/Publ-34808
Publ.-Id: 34808


Single-crystal epitaxial europium iron garnet films with strain-induced perpendicular magnetic anisotropy: Structural, strain, magnetic, and spin transport properties

Guo, M. X.; Cheng, C. K.; Liu, Y. C.; Wu, C. N.; Chen, W. N.; Y. Chen, T.; Wu, C. T.; Hsu, C. H.; Zhou, S.; Chang, C. F.; Tjeng, L. H.; Lee, S. F.; Pai, C. F.; Hong, M.; Kwo, J.

Single-crystal europium iron garnet (EuIG) thin films were epitaxially grown on gadolinium gallium garnet (GGG)(001) substrates using off-axis sputtering and showed strain-induced perpendicular magnetic anisotropy (PMA). By varying the sputtering conditions, we have tuned the europium/iron (Eu/Fe) composition ratios in the films to tailor the film strains. The films exhibited an extremely smooth, particle-free surface with a root-mean-square roughness as low as 0.1 nm, as observed by atomic force microscopy. High-resolution x-ray diffraction analysis and reciprocal space maps showed pseudomorphic film growth, a very smooth film/substrate interface, excellent film crystallinity with a rocking curve of 0.012° (ω scans), and an in-plane compressive strain without relaxation. In addition, spherical aberration-corrected scanning transmission electron microscopy showed an atomically abrupt interface between the EuIG film and GGG. The saturation magnetization (Ms) and coercive field (Hc) were measured using a vibrating sample magnetometer. The square-shaped out-of-plane M-H loops in conjunction with angle-dependent x-ray magnetic dichroism demonstrated the PMA in the films. The spin Hall magnetoresistance on Pt/EuIG samples was measured to obtain the PMA field strength (H⊥), which increases from 4.21 to 18.87 kOe with the increasing Eu/Fe ratio and in-plane compressive strain. We also measured spin transport in the Pt/EuIG bilayer structure and directly obtained the real part of spin mixing conductance to be 3.48×10^14Ω–1m–2. We demonstrated current-induced magnetization switching with a low critical switching current density of 3.5×10^6A/cm2, showing excellent potential for low-dissipation spintronic devices.

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Permalink: https://www.hzdr.de/publications/Publ-34806
Publ.-Id: 34806


Atomically Thin Delta-Doping of Self-Assembled Molecular Monolayers by Flash Lamp Annealing for Si-Based Deep UV Photodiodes

Chang, S.; He, J.; Prucnal, S.; Zhang, J.; Zhang, J.; Zhou, S.; Helm, M.; Dan, Y.

Delta doping (δ-doping) can find a wide range of applications in advanced metal oxide semiconductor field effect transistors, deep UV photodetectors, quantum devices, and others. In this work, we formed a δ-doping layer in silicon by employing flash lamp annealing to treat the PCl3 monolayers grafted on silicon surfaces. The δ-doping layer is atomically thin (<1 nm). Low-temperature Hall measurements show that the δ-doping layer is in a metallic state and exhibits a weak localization phenomenon, implying that a two-dimensional electron gas is formed. When we form such an n-type δ-doping layer on a highly doped p-type Si substrate, a highly sensitive solar-blind UV photodetector is created, which traditionally was only possible by using wide band gap semiconductors such as gallium nitride (GaN) or silicon carbide (SiC).

  • ACS Applied Materials and Interfaces 14(2022)26, 30000-30006
    Online First (2022) DOI: 10.1021/acsami.2c04002

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  • Secondary publication expected from 06.06.2023

Permalink: https://www.hzdr.de/publications/Publ-34805
Publ.-Id: 34805


Two decades of CW SRF operation at ELBE

Arnold, A.

ELBE is a compact, accelerator-driven photon and particle source. The variety of secondary radiation being offered extends from high-energy gamma rays to infrared and THz radiation as well as from neutrons to positrons and electrons. Since 2001 ELBE is operated as a user facility, providing more than 5500 hours of beamtime with an efficiency of more than 90% each year. The electron accelerator is based on four superconducting 9-cell TESLA cavities that are driven in CW operation to accelerate an average current of 1 mA up to beam energies of 40 MeV.

The the talk will summarize our experiences of operating TESLA cavities over two decades in CW. In detail, this includes the cavity performance and attempts to improve it, as well as investigations on their limitations. Additionally, we will discuss several issues that are related to the high average RF as well as beam power and we will present appropriate measures to protect the machine. In this regard we will also report on long-term experiences with our 10kW 1.3 GHz solid state power amplifiers and introduce a resonant ring for RF component tests at CW power levels up to 100 kW.

Keywords: ELBE; CW SRF; TESLA cavity

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    e-LINAC Reliability Workshop (ERW), 09.-10.05.2022, Vancouver, Canada

Permalink: https://www.hzdr.de/publications/Publ-34802
Publ.-Id: 34802


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