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39008 Publications

Data publication: Optimal test-kit-based intervention strategy of epidemic spreading in heterogeneous complex networks

Ghosh, S.; Senapati, A.; Chattopadhyay, J.; Hens, C.; Ghosh, D.

This contains all the python script and related data required for reproducing the results presented in the article

Keywords: Infectious disease modelling; Test-kit; Complex network; Intervention strategy

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Permalink: https://www.hzdr.de/publications/Publ-34174
Publ.-Id: 34174


Optimal test-kit-based intervention strategy of epidemic spreading in heterogeneous complex networks

Ghosh, S.; Senapati, A.; Chattopadhyay, J.; Hens, C.; Ghosh, D.

We propose a deterministic compartmental model of infectious disease that considers the test kits as an important ingredient for the suppression and mitigation of epidemics. A rigorous simulation (with an analytical argument) is provided to reveal the effective reduction of the final outbreak size and the peak of infection as a function of basic reproduction number in a single patch. Furthermore, to study the impact of long and short-distance human migration among the patches, we consider heterogeneous networks where the linear diffusive connectivity
is determined by the network link structure. We numerically confirm that implementation of test kits in a fraction of nodes (patches) having larger degrees or betweenness centralities can reduce the peak of infection (as well as the final outbreak size) significantly. A next-generation matrix-based analytical treatment is provided to find out the critical transmission probability in the entire network for the onset of epidemics. Finally, the optimal intervention strategy is validated in two real networks: the global airport network and the transportation network of Kolkata, India.

Keywords: Infectious disease modelling; Test-kit; Complex network; Intervention strategy

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Permalink: https://www.hzdr.de/publications/Publ-34173
Publ.-Id: 34173


Data publication: Reservoir computing on epidemic spreading: A case study on COVID-19 cases

Ghosh, S.; Senapati, A.; Mishra, A.; Chattopadhyay, J.; Dana, S. K.; Hens, C.; Ghosh, D.

Python scripts and relevant data required for reproducing the figures in the article

Keywords: COVID-19; Mathematical modelling; Prediction; Machine Learning

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Permalink: https://www.hzdr.de/publications/Publ-34172
Publ.-Id: 34172


Reservoir computing on epidemic spreading: A case study on COVID-19 cases

Ghosh, S.; Senapati, A.; Mishra, A.; Chattopadhyay, J.; Dana, S. K.; Hens, C.; Ghosh, D.

A reservoir computing based echo state network (ESN) is used here for the purpose of predicting the spread
of a disease. The current infection trends of a disease in some targeted locations are efficiently captured by
the ESN when it is fed with the infection data for other locations. The performance of the ESN is first tested
with synthetic data generated by numerical simulations of independent uncoupled patches, each governed by the
classical susceptible-infected-recovery model for a choice of distributed infection parameters. From a large pool
of synthetic data, the ESN predicts the current trend of infection in 5% patches by exploiting the uncorrelated
infection trend of 95% patches. The prediction remains consistent for most of the patches for approximately 4 to 5
weeks. The machine’s performance is further tested with real data on the current COVID-19 pandemic collected
for different countries. We show that our proposed scheme is able to predict the trend of the disease for up to
3 weeks for some targeted locations. An important point is that no detailed information on the epidemiological
rate parameters is needed; the success of the machine rather depends on the history of the disease progress
represented by the time-evolving data sets of a large number of locations. Finally, we apply a modified version
of our proposed scheme for the purpose of future forecasting.

Keywords: COVID-19; Mathematical modelling; Prediction; Machine Learning

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Permalink: https://www.hzdr.de/publications/Publ-34171
Publ.-Id: 34171


Energy relaxation and electron-phonon coupling in laser-excited metals

Zhang, J.; Qin, R.; Zhu, W.; Vorberger, J.

The rate of energy transfer between electrons and phonons is investigated by a first principles framework for electron temperatures up to $T_e=50000$~K while considering the lattice at ground state. Two typical but differently complex metals are investigated, namely Aluminium and Copper. In order to reasonably take the electronic excitation effect into account, we adopt finite temperature density functional theory and linear response to determine the electron-temperature-dependent Eliashberg function and electron density of states. Of the three branch-dependent electron-phonon coupling strengths, the longitudinal acoustic mode plays a dominant role in the electron-phonon coupling for Aluminium for all temperatures considered here, but for Copper it only dominates above an electron temperature of $T_e=40000$~K. The second moment of the Eliashberg function and the electron phonon coupling constant at room temperature $T_e=315$~K show good agreement with other results. For increasing electron temperatures, we show the limits of the $T=0$ approximation for the Eliashberg function. Our present work provides a rich perspective on the phonon dynamics and this will help to improve insight into the underlying mechanism of energy flow in ultra-fast laser-metal interaction.

Keywords: electron-phonon; DFT; laser; laser-matter interaction; two-temperature model; relaxation; energy transfer

Permalink: https://www.hzdr.de/publications/Publ-34170
Publ.-Id: 34170


Development and Biological Evaluation of the First Highly Potent and Specific Benzamide-Based Radiotracer [¹⁸F]BA3 for Imaging of Histone Deacetylases 1 and 2 in Brain

Clauß, O.; Schäker-Hübner, L.; Wenzel, B.; Toussaint, M.; Deuther-Conrad, W.; Gündel, D.; Teodoro, R.; Dukic-Stefanovic, S.; Ludwig, F.-A.; Kopka, K.; Brust, P.; Hansen, F. K.; Scheunemann, M.

The degree of acetylation of lysine residues on histones influences the accessibility of DNA and, furthermore, the gene expression. Histone deacetylases (HDACs) are overexpressed in various tumour diseases, resulting in the interest in HDAC inhibitors for cancer therapy. The aim of this work is the development of a novel ¹⁸F-labelled HDAC1/2-specific inhibitor with a benzamide-based zinc-binding group to visualize these enzymes in brain tumours by positron emission tomography (PET). BA3, exhibiting high inhibitory potency for HDAC1 (IC50 = 4.8 nM) and HDAC2 (IC50 = 39.9 nM), and specificity towards HDAC3 and HDAC6 (specificity ratios >230 and >2080, respectively), was selected for radiofluorination. The two-step one-pot radiosynthesis of [¹⁸F]BA3 was performed in a TRACERlab FX2 N radiosynthesizer by a nucleophilic aliphatic substitution reaction. The automated radiosynthesis of [¹⁸F]BA3 resulted in a radiochemical yield of 1%, a radiochemical purity of >96% and a molar activity between 21 and 51 GBq/µmol (n = 5, EOS). For the characterization of BA3, in vitro and in vivo experiments were carried out. The results of these pharmacological and pharmacokinetic studies indicate a suitable inhibitory potency of BA3, whereas the applicability for non-invasive imaging of HDAC1/2 by PET requires further optimization of the properties of this compound.

Keywords: histone deacetylase inhibitor; HDAC1/2-specific; radiochemistry; fluorine-18 labelling; positron emission tomography (PET); brain-penetration; glioblastoma; glioma

Permalink: https://www.hzdr.de/publications/Publ-34169
Publ.-Id: 34169


Acquired resistance to irradiation or docetaxel is not associated with cross-resistance to cisplatin in prostate cancer cell lines

Donix, L.; Erb, H. H.; Peitzsch, C.; Dubrovska, A.; Pfeifer, M.; Thomas, C.; Fuessel, S.; Erdmann, K.

Purpose: Platinum chemotherapy can be considered to treat metastatic castration-resistant prostate cancer (mCRPC) with
features of neuroendocrine differentiation. However, platinum compounds are generally only applied after the failure of
multiple prior-line treatment options. This study investigated whether acquired resistance against ionizing radiation or doc-
etaxel chemotherapy—two commonly applied treatment modalities in prostate cancer—influences the cisplatin (CDDP)
tolerance in mCRPC cell line models.
Methods: Age-matched parental as well as radio- or docetaxel-resistant DU145 and PC-3 cell lines were treated with CDDP
and their sensitivity was assessed by measurements of growth rates, viability, apoptosis, metabolic activity and colony
formation ability.
Results: The data suggest that docetaxel resistance does not influence CDDP tolerance in all tested docetaxel-resistant cell
lines. Radio-resistance was associated with sensitization to CDDP in PC-3, but not in DU145 cells. In general, DU145 cells
tolerated higher CDDP concentrations than PC-3 cells regardless of acquired resistances. Furthermore, non-age-matched
treatment-naïve PC-3 cells exhibited significantly different CDDP tolerances.
Conclusion: Like patients, different mCRPC cell lines exhibit significant variability regarding CDDP tolerance. The presented
in vitro data suggest that previous radiation treatment may be associated with a moderate sensitization to CDDP in an isogenic
and age-matched setting. Therefore, previous radiotherapy or docetaxel chemotherapy might be no contraindication against
initiation of platinum chemotherapy in selected mCRPC patients.

Keywords: Cisplatin; Docetaxel; mCRPC; NEPC; Prostate cancer; Radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-34168
Publ.-Id: 34168


Efficient doping of TMDs using NH₃ plasma treatment

Li, Y.; Duan, J.; Helm, M.; Zhou, S.; Prucnal, S.

The precise control of dopant concentration and distribution in two-dimensional materials (2D), e.g. transition metal dichalcogenides (TMDs), is a major problem on the way to their successful application in modern nanoelectronics. Efficient doping can be achieved by substituting chalcogenide atoms with group V or VII atoms, intercalations or electrostatic doping. In the present work, both the optical and electrical properties of mechanically exfoliated 2D TMDs have been modified using NH₃ plasma treatment for 10 s followed by short-time annealing. After plasma treatment, the TMDs flakes were investigated by photoluminescence (PL) and Raman spectroscopies and current-voltage (I-V) characteristics. After NH₃ plasma treatment, the PL-peak intensity of the MoSe₂ monolayer degrades and shifts towards lower energy (higher wavelength) due to hydrogen doping. Annealing after plasma treatment releases hydrogen and the PL emission returns to normal. The same has been observed in Raman spectra. H-doping causes a shift of the main phonon modes due to the phonon-plasmon coupling, i.e. Fano effect. The I-V characteristics also clearly confirm the efficient hydrogen doping of the MoSe₂ monolayer. This work shows new insights into controllable doping in 2D materials.

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  • Poster
    European Materials Research Society 2021 Fall Meeting, 20.-23.09.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-34167
Publ.-Id: 34167


The design-construction interface of Ti₂.₅O₃ (010)/GaAs (001): minimizing the lattice mismatch and impeding ions diffusions

Zhou, Y.; Zhu, J.; Zhou, S.

Feasible interface lattice design is a really key issue for a high-quality hybrid of functional oxide thin films on GaAs semiconductor substrates. But interfacial defects induced by lattice mismatch cause the problem to become challenging. Here, we reported a novel sub-titanium oxide (Ti₂.₅O₃) thin film epitaxially grown on GaAs substrate using pulsed laser deposition, the high-quality Ti₂.₅O₃/GaAs heterostructure significantly reduced the lattice mismatch between titanium sub-oxides and the GaAs substrate. Besides, our work theoretically and experimentally demonstrated that high crystalline Ti₂.₅O₃ (010) film can be grown layer-by-layer on GaAs (001) substrate with highly compatible interfaces. Extremely low lattice mismatch values of 0.3% and 0.6% along different orientations can be achieved in combination with the notably suppressed formation of arsenic oxides (AsOx) and gallium oxides (GaOx) between Ti₂.₅O₃/GaAs interfaces. Owing to the favorable interface and high crystalline, integrated BaTiO₃(250 nm)/STO/Ti₂.₅O₃/GaAs heterostructure demonstrates hysteresis loops with a remnant polarization of 9.85 µC/cm² at 600 kV/cm and a small leakage current density of 1×10−5 A/cm² at -500 kV/cm. Not only the excellent performances pave the path for the further application of Ti₂.₅O₃/GaAs heterostructure in electronics, but also the unique strategy gives a good inspiration for coupling other functional oxides on GaAs with expected excellent performances.

Keywords: Ti₂.₅O₃/GaAs

  • Lecture (Conference) (Online presentation)
    European Materials Research Society 2021 Fall, 20.-23.09.2021, Online meeting, Germany

Permalink: https://www.hzdr.de/publications/Publ-34166
Publ.-Id: 34166


Lifetime measurements in 80Br and a new region for observation of chiral electromagnetic selection rule

Guoa, R. J.; Wang, S. Y.; Schwengner, R.; Xu, W. Z.; Qi, B.; Liu, C.; Rohilla, A.; Dönau, F.; Servene, T.; Schnare, H.; Reif, J.; Winter, G.; Käubler, L.; Prade, H.; Skoda, S.; Eberth, J.; Thomas, H. G.; Becker, F.; Fiedler, B.; Freund, S.; Kasemann, S.; Steinhardt, T.; Thelen, O.; Härtlein, T.; Ender, C.; Köck, F.; Reiter, P.; Schwalm, D.

Level lifetimes for the candidate chiral doublet bands of 80 Br were extracted
by means of the Doppler-shift attenuation method. The absolute transition
probabilities derived from the lifetimes agree well with the M 1 and E2 chiral
electromagnetic selection rules, and the calculations reported in the frame-
work of triaxial particle rotor model [S.Y. Wang et al., Phys. Lett. B 703
(2011) 40] also support firmly for the chirality in 80 Br. Such good agree-
ments among the experimental data, selection rules of chiral doublet bands
and theoretical calculations are rare and outstanding in researches of nuclear
chirality. Besides odd-odd Cs isotopes, odd-odd Br isotopes in the A ≈ 80
mass region represent another territory that exhibits the ideal selection rules
expected for chiral doublet bands.

Keywords: Nuclear Structure; Level lifetime measurements; Transition probabilities; Chiral bands

Permalink: https://www.hzdr.de/publications/Publ-34164
Publ.-Id: 34164


Modeling the oscillatory dynamics of gas bubbles growing at microelectrodes

Hossain, S. S.; Bashkatov, A.; Yang, X.; Mutschke, G.; Eckert, K.

The working mechanism of the recently observed bubble oscillation on microelectrodes is explained [1]. The force balance
includes contributions from a thermocapillary force and a Columb force on the charged bubble. Comparison between model predictions
and experimental measurements is presented.

  • Open Access Logo Contribution to proceedings
    The 25th International Congress of Theoretical and Applied Mechanics, 22.-27.08.2021, Milan, Italy
    25th International Congress of Theoretical and Applied Mechanics – Book of Abstracts
  • Open Access Logo Poster
    The 25th International Congress of Theoretical and Applied Mechanics, 22.-27.08.2021, Milan, Italy, 22.-27.08.2021, Milan, Italy

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Permalink: https://www.hzdr.de/publications/Publ-34163
Publ.-Id: 34163


Geostatistics for compositional data: from spatial interpolation to high dimensional prediction

Tolosana Delgado, R.; van den Boogaart, K. G.

Geostatistics is a name given to a series of statistical and machine learning tools devised to treat a spatially dependent variable with the goal of interpolating it. The key tool of classical geostatistics is the covariance function, capturing the covariance (matrix) between the variable (vector) observed at two locations in space. Pawlwowsky-Glahn and Olea (2004; "Geostatistical analysis for compositional data") already extended this framework to deal with spatially dependent compositional data, taking a logratio transformation, i.e. by means of the covariance function of the logratio transformed scores. Given a spatially dependent compositional data set, if we had available a model for the covariance function, it would be possible to predict the composition at a new location by means of multivariate multiple linear regression. The typical approach to obtain this covariance is to restrict it to be location-independent (but still depend on the lag difference between locations), and give it a parametric form. This vector of parameters is then either fitted via maximum likelihood, or else data-driven to specific collections of spread statistics of the sample. Similar approaches can be followed with compositions. Several such data driven methods have been proposed for compositions, which can be seen as choosing an \emph{oblique logratio} such that the covariance function becomes a diagonal matrix for all lags (and by extension, for all pairs of locations), with the resulting diagonal elements easily modelled separately. In this contribution we will discuss the several implications of these methodologies to obtain a parametric model for the covariance function, how to use this function to predict the composition at any location, the subcompositional properties of this predictor, and how this whole framework can be used beyond spatial statistics, to establish (almost) non-parametric predictive models for compositional responses with high dimensional regressors.

Keywords: variogram; auto-covariance; cross-covariance; minimum-maximum autocorrelation factors; kriging

  • Open Access Logo Contribution to proceedings
    CoDaWork2022: 9th International Workshop on Compositional Data Analysis, 28.06.-01.07.2022, Tolouse, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-34162
Publ.-Id: 34162


Flash lamp annealing for thin film processing

Rebohle, L.; Begeza, V.; Cherkouk, C.; Neubert, M.; Prucnal, S.; Hübner, R.; Zhou, S.

Flash lamp annealing is, like laser annealing, a non-equilibrium annealing method on the sub-second time scale which excellently meets the requirements of thin film processing: it allows the use of temperature-sensible substrates for thin films, leads to energy and cost savings compared to long-time annealing methods, and enables the formation of new materials in thermal non-equilibrium. Originally developed for microelectronics, flash lamp annealing has opened up new areas of application like thin films on glass, sensors, printed electronics, flexible electronics, batteries etc.

In this presentation, we shortly compare the pros and cons of flash lamp and laser annealing for thin film processing and discuss these issues at the example of thin semiconductor films on glass. In detail, the crystallization of amorphous Si on borosilicate glass, the crystallization of amorphous Ge on SiO2/Si substrates, and the formation of NiGe on different Ge substrates (amorphous, polycrystalline and monocrystalline) have been investigated. In all cases, the thin films were deposited by magnetron sputtering, followed by flash lamp annealing. The evolution of microstructure and its electrical properties was traced by corresponding characterization methods such as Raman spectroscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, sheet resistance and Hall effect measurements.

Keywords: flash lamp annealing; thin film; crystallization amorphous Ge; NiGe

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  • Lecture (Conference) (Online presentation)
    E-MRS Spring 2021, Symposium H, 31.05.-03.06.2021, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-34161
Publ.-Id: 34161


Liquid Distribution in Industrial Structured-Packed Columns via Gamma-Ray Computed Tomography

Berger, A.; Houghton, P.; Wilson, J.; Schubert, M.; Bieberle, A.

A 600-mm diameter test column was constructed and packed with 3 layers of aluminum Sulzer 500Y packing. Liquid maldistribution was studied using a mechanical mechanism for blocking two rows of distributor holes. Two-phase counter-current flow was studied using air and water. Surfactant was added to mimic fluids with low surface tension. Gamma-ray CT scans were performed over a range of liquid and vapor rates, and visualization of flow details with pixel size down to 1mm was demonstrated. Generally, liquid holdup approached a characteristic value moving down the column. The characteristic holdup increased with liquid and/or vapor rates, as expected. When a distributor blocking mechanism was deployed, the decreased liquid fraction in the under-irrigated area is easily detectable in cross-sectional tomographic scans of the topmost packing layer. Liquid holdup data and tomographic images show that liquid distribution recovers substantially from gross maldistribution after three packing layers in water and two layers with surfactant-water.

Keywords: Gamma Ray Tomography; Structured packing; Liquid distribution

  • Contribution to proceedings
    12th International Conference Distillation & Absorption, 18.-21.09.2022, Toulouse, France
    Proceedings of the 12th International Conference Distillation & Absorption

Permalink: https://www.hzdr.de/publications/Publ-34160
Publ.-Id: 34160


Decoating of Electrode Foils from EOL Lithium-Ion Batteries by Electrohydraulic Fragmentation

Lyon, T.; Mütze, T.; Peuker, U. A.

In order to ensure environmentally friendly mobility, electric drives are increasingly being used. As a result, the number of used lithium-ion batteries has been rising steadily for years. To ensure a closed recycling loop, these batteries must be recycled in an energy- and raw materialefficient manner. For this purpose, hydrometallurgical processes are combined with mechanical pretreatment, including disintegration by mills, crushers and/or shears. Alternatively, lectrohydraulic fragmentation (EHF) is also of great interest, as it is considered to have a selective fragmentation effect. For a better comparison, different application scenarios of EHF with other methods of mechanical process engineering for the treatment of lithium-ion batteries are investigated in the present study.

Keywords: electrohydraulic fragmentation; EHF; lithium-ion batteries; decoating; active material; black mass; granulator; recycling

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Permalink: https://www.hzdr.de/publications/Publ-34158
Publ.-Id: 34158


AMS with a 14 million volt accelerator – 53Mn and 60Fe measurements at ANU

Wallnera, A.; Fifield, L. K.; Froehlich, M. B.; Koll, D.; Martschini, M.; Pavetich, S.; Tims, S. G.; Schumann, D.; Slavkovská, Z.

The AMS program at ANU’s Department of Nuclear Physics is based on a 14UD tandem accelerator which runs regularly above 14 MV with stable measurement conditions. This setup provides particle energies between ~24 MeV (actinides) and >200 MeV (e.g. 53Mn, 93Zr). The facility is equipped with a dedicated SNICS ion source, provides typically 155 keV beam injection energy and is capable of a simultaneous use of both gas and foil stripper. Dedicated beamlines feature multi-anode ionisation chambers, an ENGE gas-filled magnet and a 6m TOF flight path. Further, a new fast cycling system is now being implemented (see contribution by L.K. Fifield et al.) that will replace our slow cycling method.

The ANU has a strong focus in projects in environmental, safeguards and geological research with several nuclear astrophysics projects added recently as an additional major research topic. New isotopes recently introduced include 60Fe, 93Zr, 210Pb, 210mBi and 231Pa. We will give an overview of recent research activities and will summarize the performance of the different AMS setups. The potential of the ENGE setup for isobaric suppression will be exemplified for the two isotopes 60Fe and 53Mn. Measurement reproducibility and absolute detection efficiency will be compared.

Keywords: AMS; gas filled magnet; high energy aMS; ANU; 14UD

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry, 15.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-34157
Publ.-Id: 34157


A multi-parameter approach for recognition of anthropogenic noise in aeromagnetic data collected over populated areas: Erzgebirge, Germany

Morris, W.; Ugalde, H.; Kirsch, M.; Gloaguen, R.; Ibs-Von Seht, M.; Siemon, B.; Meyer, U.

Aeromagnetic data is routinely acquired by mineral exploration programs. The objective is to obtain a raster image of the spatial variations of magnetic field intensity, these variations are associated with mineralogical variations in the subsurface. When the survey is conducted in a populated area much of the signal, however may be associated with anthropogenic sources such as buildings and roads. Identification, and minimisation of the anthropogenic related signal then is essential to derive a useful product for geological mapping. In this work we examine a scalar magnetic dataset from Geyer, Saxony, and we apply five approaches for locating regions of anomalous anthropogenic signal: signal amplitude, absolute 4th difference, signal standard deviation, enhanced horizontal gradient, and curvedness. All are shown to produce similar responses, and the summation of the five results compares favorably with the standard Keating kimberlite (circular anomaly) approach for detecting anthropogenic signals. Complications arise when geological features produce signals of similar amplitude to anthropogenic sources. Differentiating the probable origin of any specific pattern can be assessed by using a 2D shape index and increased flight height. Verification of an anthropogenic anomaly is achieved by comparison of anomalous solution grids with GIS based reference data.

Keywords: Data processing; Magnetics; Noise

Permalink: https://www.hzdr.de/publications/Publ-34156
Publ.-Id: 34156


The radioactive nuclei 26Al and 60Fe in the Cosmos and in the solar system

Diehl, R.; Lugaro, M.; Heger, A.; Sieverding, A.; Tang, X.; Li, K. A.; Li, E. T.; Doherty, C. L.; Krause, M. G. H.; Wallner, A.; Prantzos, N.; Brinkman, H. E.; Den, H. J. W.; Wehmeyer, B.; Yagüe López, A.; Pleintinger, M. M. M.; Banerjee, P.; Wang, W.

The cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and this matter cycle requires the understanding of the physics of nuclear reactions, of the conditions at which the nuclear reactions are activated inside the stars and stellar explosions, of the stellar ejection mechanisms through winds and explosions, and of the transport of the ejecta towards the next cycle, from hot plasma to cold, star-forming gas. Due to the long timescales of stellar evolution, and because of the infrequent occurrence of stellar explosions, observational studies are challenging, as they have biases in time and space as well as different sensitivities related to the various astronomical methods. Here, we describe in detail the astrophysical and nuclear-physical processes involved in creating two radioactive isotopes useful in such studies, $^{26}\mathrm{Al}$ and $^{60}\mathrm{Fe}$ . Due to their radioactive lifetime of the order of a million years, these isotopes are suitable to characterise simultaneously the processes of nuclear fusion reactions and of interstellar transport. We describe and discuss the nuclear reactions involved in the production and destruction of $^{26}\mathrm{Al}$ and $^{60}\mathrm{Fe}$ , the key characteristics of the stellar sites of their nucleosynthesis and their interstellar journey after ejection from the nucleosynthesis sites. This allows us to connect the theoretical astrophysical aspects to the variety of astronomical messengers presented here, from stardust and cosmic-ray composition measurements, through observation of $\gamma$ rays produced by radioactivity, to material deposited in deep-sea ocean crusts and to the inferred composition of the first solids that have formed in the Solar System. We show that considering measurements of the isotopic ratio of $^{26}\mathrm{Al}$ to $^{60}\mathrm{Fe}$ eliminate some of the unknowns when interpreting astronomical results, and discuss the lessons learned from these two isotopes on cosmic chemical evolution. This review paper has emerged from an ISSI-BJ Team project in 2017–2019, bringing together nuclear physicists, astronomers, and astrophysicists in this inter-disciplinary discussion.

Keywords: radioactive nuclei; interstellar medium; 60Fe; 26Al; 244Pu; accelerator mass spectrometry; review

Permalink: https://www.hzdr.de/publications/Publ-34155
Publ.-Id: 34155


High-field charge transport in InGaAs nanowires

Rana, R.; Balaghi, L.; Fotev, I.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, O.

Charge transport in GaAs/InGaAs nanowires is studied using high-field terahertz pulses. With increasing terahertz field, the plasmon resonance redshifts and loses its spectral weight. The results provide evidence for inhomogeneous intervalley scattering across the nanowire.

Keywords: Intense Terahertz pulses; Nanowires; Plasmon

  • Poster (Online presentation)
    CLEO: Applications and Technology 2021, 09.-14.05.2021, San Jose, California, United States

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Permalink: https://www.hzdr.de/publications/Publ-34154
Publ.-Id: 34154


Biokollektoren - Die innovative Lösung für das Recycling der Zukunft

Lederer, F.

Die Nachwuchsforschergruppe BioKollekt entwickelt derzeit ein neues, effizientes Recyclingverfahren für Hochtechnologiemetalle aus EoLEP. Dabei wird der „Proof-of-Principle“ am Beispiel der Energiesparlampe und dem darin enthaltenen Leuchtpulver erbracht. Dieses besteht aus Selten-Erd-Element (SEE)-haltigen Partikeln, welche im Moment noch nicht voneinander getrennt und daher nicht wiederverwendet werden können. An dieser Stelle kommt die Biologie zum Recycling. Unsere biologischen Bausteine sind SEE-erkennende Peptide, also kurze Eiweißketten. Peptide sind aus Aminosäuren aufgebaut, wovon es in der Natur mehr als 20 verschiedene gibt. Die unterschiedliche Zusammensetzung der Peptide bestimmt darüber, ob ein Zielmaterial erkannt wird oder nicht. Der Gruppe BioKollekt ist es gelungen, für die SEE-haltigen Partikel des Leuchtpulvers stark bindende Peptide mit Hilfe des Phage Surface Display (PSD) zu finden. Das Verfahren an sich ist bereits lange bekannt. Der Erfinder dieser Methode erhielt 2018 dafür den Chemienobelpreis. Er öffnete damit den Weg für die Entwicklung neuer medizinischer Ansätze aber eben auch für das gezielte Finden von Peptiden für das Recycling von SEE aus Leuchtpulver.

Keywords: Biokollektoren; Phagendisplay; Peptide; Seltene Erden; Recycling; Kreislaufwirtschaft

  • Open Access Logo Technik in Bayern 03/2021(2021), 12-13

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Permalink: https://www.hzdr.de/publications/Publ-34153
Publ.-Id: 34153


X-ray Free Electron Laser-Induced Synthesis of ε-Iron Nitride at High Pressures

Hwang, H.; Kim, T.; Cynn, H.; Vogt, T.; Husband, R. J.; Appel, K.; Bähtz, C.; Ball, O. B.; Baron, M. A.; Briggs, R.; Bykov, M.; Bykova, E.; Cerantola, V.; Chantel, J.; Coleman, A. L.; Dattlebaum, D.; Dresselhaus-Marais, L. E.; Eggert, J. H.; Ehm, L.; Evans, W. J.; Fiquet, G.; Frost, M.; Glazyrin, K.; Goncharov, A. F.; Jenei, Z.; Kim, J.; Konôpková, Z.; Mainberger, J.; Makita, M.; Marquardt, H.; McBride, E. E.; McHardy, J. D.; Merkel, S.; Morard, G.; O’Bannon Iii, E. F.; Otzen, C.; Pace, E. J.; Pelka, A.; Pépin, C. M.; Pigott, J. S.; Prakapenka, V. B.; Prescher, C.; Redmer, R.; Speziale, S.; Spiekermann, G.; Strohm, C.; Sturtevant, B. T.; Velisavljevic, N.; Wilke, M.; Yoo, C.-S.; Zastrau, U.; Liermann, H.-P.; McMahon, M. I.; Stewart McWilliams, R.; Lee, Y.

The ultrafast synthesis of ε-Fe3N1+x in a diamond-anvil cell (DAC) from Fe and N2 under pressure was observed using serial exposures of an X-ray free electron laser (XFEL). When the sample at 5 GPa was irradiated by a pulse train separated by 443 ns, the estimated sample temperature at the delay time was above 1400 K, confirmed by in situ transformation of α- to γ-iron. Ultimately, the Fe and N2 reacted uniformly throughout the beam path to form Fe3N1.33, as deduced from its established equation of state (EOS). We thus demonstrate that the activation energy provided by intense X-ray exposures in an XFEL can be coupled with the source time structure to enable exploration of the time-dependence of reactions under high-pressure conditions.

Keywords: Iron; X-rays; Chemical reactions; Nitrogen; Diffraction

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Permalink: https://www.hzdr.de/publications/Publ-34149
Publ.-Id: 34149


Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL)

Liermann, H. P.; Konôpková, Z.; Appel, K.; Prescher, C.; Schropp, A.; Cerantola, V.; Husband, R. J.; McHardy, J. D.; McMahon, M. I.; McWilliams, R. S.; Pépin, C. M.; Mainberger, J.; Roeper, M.; Berghäuser, A.; Damker, H.; Talkovski, P.; Foese, M.; Kujala, N.; Ball, O. B.; Baron, M. A.; Briggs, R.; Bykov, M.; Bykova, E.; Chantel, J.; Coleman, A. L.; Cynn, H.; Dattelbaum, D.; Dresselhaus-Marais, L. E.; Eggert, J. H.; Ehm, L.; Evans, W. J.; Fiquet, G.; Frost, M.; Glazyrin, K.; Goncharov, A. F.; Hwang, H.; Jenei, Z.; Kim, J.-Y.; Langenhorst, F.; Lee, Y.; Makita, M.; Marquardt, H.; McBride, E. E.; Merkel, S.; Morard, G.; Obannon, E. F.; Otzen, C.; Pace, E. J.; Pelka, A.; Pigott, J. S.; Prakapenka, V. B.; Redmer, R.; Sanchez-Valle, C.; Schölmerich, M.; Speziale, S.; Spiekermann, G.; Sturtevant, B. T.; Toleikis, S.; Velisavljevic, N.; Wilke, M.; Yoo, C.-S.; Baehtz, C.; Zastrau, U.; Strohm, C.

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump–probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Keywords: diamond anvil cells; x-ray free electron lasers; high precision x-ray diffraction; finite element modeling

Permalink: https://www.hzdr.de/publications/Publ-34147
Publ.-Id: 34147


Exchange and anisotropy-driven effects in antiferromagnetic spin chains

Pylypovskyi, O.

Antiferromagnets (AFMs) represent a class of materials with complex magnetic subsystem involving more than one ferromagnetically ordered sublattice. Such properties as high resonance frequencies in THz range, negligible net magnetic moment and respective weak stray fields, strong spin-orbit interaction make them promising for applications. The field of curvilinear magnetism offers additional degrees of freedom to tailor chiral and anisotropic responses of magnets and is well-established for ferromagnetic materials. Curvilinear AFMs possess additional features, important for for spintronic and spin-orbitronic applications [1].

The simplest curvilinear AFM is a spin chain arranged along flat or space curve. This geometry is characterized by the scalar functions of curvature K(s) and torsion T(s) with s being a coordinate along the curve. In the absence of intrinsic anisotropy, the dipolar interaction renders the tangential direction as the hard axis of the anisotropy [2]. Competition of this geometry-tracking interaction with the nearest-neighbor exchange leads to the emergence of additional anisotropic and chiral energy terms, whose coefficients are determined by K and T only. The geometry-driven anisotropic term brings about the easy axis determining direction of the order parameter within the dipole-driven easy-plane. The geometry-driven inhomogeneous Dzyaloshinskii-Moriya interaction (DMI) renders the curvilinear spin chain as a chiral helimagnet. For example, the spin chain along the helix with the given radius and pitch possesses one of two magnetic states depending on the geometrical parameters. For a dominating curvature K, the ground state is the homogeneous in the local reference frame, while for the dominating torsion T, the ground state is helicoidal. In contrast to ferromagnetic nanowires [3], there is no critical curvature, separating the ground states in the limiting case of small torsion. This reflects the presence of the only one ground state along the binormal direction for the spin chains along the flat curves [2].

The local variation of the anisotropy axis can result in the non-collinearity of the neighboring spins in curvilinear chains. 1D AFMs exhibit the parity-breaking effect, which forbids to exchange sublattices once they are selected. This leads to the emergent magnetization at non-collinear AFM textures [4]. Therefore, in any spin chain arranged along the space curve, there is a weak ferromagnetism proportional to the curvature and torsion of the curve [5].

In the presence of strong intrinsic anisotropy in AFM spin chain with the anisotropy axis following the tangential direction, one can observe the effects of geometry proportional to the anisotropy constant and curvature K [5]. Both models of the single- and inter-ion anisotropies lead to the tilt of the anisotropy axes, which is pronounced in the spin-flop phase. In addition, the single-ion anisotropy leads to the emergence of the additional anisotropic term of the homogeneous DMI symmetry. The latter is described by the tensor product of the ferro- and antiferromagnetic order parameters, which scales with K.

References

[1] V. Baltz, A. Manchon, M. Tsoi et al, Rev. Mod. Phys. Vol. 90, P. 015005 (2018); H. Yan, Z. Feng, P. Qin et al, Avd. Mat. Vol. 32, P. 1905603 (2020); D. D. Sheka, Appl. Phys. Lett. Vol. 118, P. 230502 (2021).
[2] O. V. Pylypovskyi, D. Y. Kononenko, K. V. Yershov et al, Nano Lett. Vol. 20, P. 8157 (2020).
[3] D. D. Sheka, V. P. Kravchuk, K. V. Yershov, Y. Gaididei, Phys. Rev. B Vol. 92, P. 054417 (2015).
[4] N. Papanicolaou, Phys. Rev. B Vol. 51, P. 15062 (1995); E. G. Tveten, T. Mueller, J. Linder et al, Phys. Rev. B Vol. 93, P. 104408 (2016).
[5] O. V. Pylypovskyi, Y. A. Borysenko, J. Fassbender et al, Appl. Phys. Lett., Vol. 118, P. 182405 (2021)

Keywords: antiferromagnetism; curvilinear magnetism

  • Invited lecture (Conferences) (Online presentation)
    Yuri Gaididei memorial workshop, 02.-03.02.2022, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34146
Publ.-Id: 34146


Computer simulations of magnetic nanoarchitectures

Pylypovskyi, O.

Computer simulations of strongly non-linear systems with many degrees of freedom represent an important tool for physicists in both, theory an experiment. These systems are typical for the modern nanomagnetism, which leads to the development of plenty of special computational tools. Here, we consider an investigation of ferro- and antiferromagnetic nanoarchitectures, properties of magnetic solitons and numerical tools to address them.

Keywords: nanomagnetism; numerics

  • Invited lecture (Conferences) (Online presentation)
    Winter school on theoretical physics, 20.01.2022, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34145
Publ.-Id: 34145


CFD simulation of a heat pipe using the homogeneous model

Höhne, T.

Heat-pipes are important in many industrial applications improving the thermal performance of heat exchangers and increasing energy savings. Computational Fluid Dynamics (CFD) were used to simulate the steam/water two-phase flow and heat transfer processes of a heat-pipe. The novelty of the study is that the evaporation, condensation and phase change processes were modelled using a homogeneous multiphase model and implemented source terms inspired by the Lee phase change model. The 3D CFD simulations could reproduce the heat and mass transfer processes in comparison with experiments from the literature. Reasonable good agreement was not only observed between CFD temperature profiles in relation with experimental data but also in comparing the thermal performance of the heat-pipe. It was found that the heating power should not increase above 1000 W for the analyzed type of heat-pipe design using copper material. In future, the use of the improved advanced numerical models is planned.

Keywords: Two-phase flow; Boiling; CFD; Condensation; Heat-pipe

Permalink: https://www.hzdr.de/publications/Publ-34144
Publ.-Id: 34144


Electron spin- and photon polarization-resolved probabilities of strong-field QED processes

Chen, Y.-Y.; Hatsagortsyan, K. Z.; Keitel, C. H.; Shaisultanov, R.

A derivation of fully polarization-resolved probabilities is provided for high-energy photon emission and electron-positron pair production in ultrastrong laser fields. The probabilities resolved in both electron spin and photon polarization of incoming and outgoing particles are indispensable for developing QED Monte Carlo and QED-Particle-in-Cell codes, aimed at the investigation of polarization effects in nonlinear QED processes in ultraintense laser-plasma and laser-electron beam interactions, and other nonlinear QED processes in external ultrastrong fields, which involve multiple elementary processes of a photon emission and pair production. The quantum operator method introduced by Baier and Katkov is employed for the calculation of probabilities within the quasiclassical approach and the local constant field approximation. The probabilities for the ultrarelativistic regime are given in a compact form and are suitable to describe polarization effects in strong laser fields of arbitrary configuration, rendering them very well suited for applications.

Permalink: https://www.hzdr.de/publications/Publ-34143
Publ.-Id: 34143


Data publication: Collapse of Coherent Large Scale Flow in Strongly Turbulent Liquid Metal Convection

Schindler, F.; Eckert, S.; Zürner, T.; Schumacher, J.; Vogt, T.

Rawdata on which the publication is based on. .BDD binary files for Ultrasound measurements. .dat: direct temperature measurement data.

Keywords: Rayleigh-Benard Convection; liquid metal; low Pr; cylinder; Aspect Ratio 0.5; Ultrasound Doppler Velocimetry

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Permalink: https://www.hzdr.de/publications/Publ-34142
Publ.-Id: 34142


Ion implantation and Subsecond annealing: a versatile approach for hyperdoping semiconductors

Zhou, S.

Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. For example, Ga hyperdoped Ge reveals superconductivity and Mn hyperdoped GaAs represents a typical ferromagnetic semiconductor. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. However, being applied to hyperdoping, the annealing duration has to be shortenedto millisecond or even nanosecond. The intrinsic physical parameters related to dopants and semiconductors (e.g. Solubility, diffusivity, melting point and thermal conductivity) have to be considered to choose the right annealing time regime. In this talk, we propose that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. The examples include magnetic semiconductors [1-5], highly mismatched semiconductor alloys (Ge1-xSnx [6] and GaAs1-xNx [7]), n++ Ge [8, 9] and chalcogen doped Si [10-12].

[1] M. Khalid, et al., Phys. Rev. B 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001(2015).
[3] S. Prucnal, et al., Phys. Rev. B 92, 222407 (2015).
[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[5] Y. Yuan, et al., Phys. Rev. Mater. 1, 054401 (2017).
[6] K. Gao, et al., Appl. Phys. Lett.,105, 042107 (2014).
[7] K. Gao, et al., Appl. Phys. Lett.,105, 012107 (2014).
[8] S. Prucnal, et al., Sci.Reports 6, 27643(2016).
[9] S. Prucnal, et al., Semicond. Sci. Technol. 32 115006 (2017).
[10] S. Zhou, et al., Sci. Reports 5, 8329(2015).
[11] Y. Berencén, et al., Adv. Mater. Inter. 5, 1800101 (2018).
[12] M. Wang, et al., Phys. Rev. Applied. 10, 024054 (2018).

Related publications

  • Lecture (others) (Online presentation)
    Invited talk at Brandenburgische Technische Universität Cottbus-Senftenberg, 25.11.2021, Cottbus, Germany
  • Lecture (Conference)
    2021 Spring Meeting of the European Materials Research Society (E-MRS), 31.05.-04.06.2021, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-34141
Publ.-Id: 34141


Tailoring oxide thin films by ion beam

Zhou, S.

Complex oxides host a multitude of novel phenomena in condensed matter physics, such as various forms of multiferroicity, colossal magnetoresistance, quantum magnetism and superconductivity. Defect engineering via ion irradiation can be a useful knob to control these physical properties for future practical applications. Two prominent effects are disorder and uniaxial strain. Particularly, the uniaxial strain, manifesting as the elongation of the out-of-plane lattice spacing, is not limited to available substrates, the conventional and well-known strain engineering approach. In this talk, I will introduce the basics of ion irradiation and its applications to oxide thin films, including the modification of magnetic properties of NiCo2O4 [1], SrRuO3 [2], the magneto-transport properties of rare-earth nickelates [3] and SrRuO3 [4] and the structural properties of BiFeO3 [5]. It is worth to note that ion beam technology has been well developed for microelectronics. Once the principle of concept is approved, the approach can be easily scaled up and integrated to the industry production line.

References:

[1] P. Pandey, Y. Bitla, M. Zschornak, M. Wang, C. Xu, J. Grenzer, D. C. Meyer, Y. Y. Chin, H. J. Lin, C. T. Chen, S. Gemming, M. Helm, Y. H. Chu, S. Zhou, APL Materials 6 (2018) 066109 (2018).
[2] C. A. Wang, C. Chen, C-H. Chang, H-S, Tsai, P. Pandey, C. Xu, R. Böttger, D. Y. Chen, Y-J Zeng, X. S. Gao, M. Helm, S. Q. Zhou, ACS Appl. Mater. Interfaces 10 (2018) 27472-27476.
[3] C. A. Wang, C-H, Chang, A. Huang, P-C. Wang, P-C. Wu, L. Yang, C. Xu, P. Pandey, M. Zeng, R. Böttger, H-T. Jeng, Y-J. Zeng, M. Helm, Y-H. Chu, R. Ganesh, and S. Q. Zhou, Phys. Rev. Materials 3 (2019) 053801
[4] C. A. Wang, C-H Chang, A. Herklotz, C. Chen, F. Ganss, U. Kentsch, D. Y. Chen, X. S. Gao, Y-J. Zeng, O. Hellwig, M. Helm, S. Gemming, Y-H. Chu, and S. Q. Zhou, Adv. Electron. Mater. 6 (2020) 2000184.
[5] C. Chen, C. Wang, X. Cai, C. Xu, C. Li, J. Zhou, Z. Luo, Z. Fan, M. Qin, M. Zeng, X. Lu, X. Gao, U. Kentsch, P. Yang, G. Zhou, N. Wang, Y. Zhu, S. Zhou, D. Chen, J. Liu, Nanoscale 11 (2019) 8110-8118.

Related publications

  • Invited lecture (Conferences) (Online presentation)
    2nd International Workshop on Advanced Magnetic Oxides, 24.-26.11.2021, Aveiro, PORTUGAL
  • Invited lecture (Conferences) (Online presentation)
    10th Vacuum and Surface Sciences Conference of Asia and Australia, 11.-14.10.2021, Shanghai, China
  • Lecture (Conference)
    22nd International Conference on Ion Beam Modification of Materials, 10.-15.07.2022, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-34140
Publ.-Id: 34140


Simulation-Based Inference for Beam Parameter Inversion

Steinbach, P.; Hartmann, G.

In this talk, I'd like to present modern machine learning tools for estimating the posterior of the inverse problem exposed in a beam control setting. That is, given an experimental beam profile, I'd like to demonstrate tools that help to estimate which simulation parameters might have produced a similar beam profile with high likelihood.

We summarize preliminary findings bound to optimize a xray beamline located at a synchrotron accelerator. With this, we hope to tackle the challenge to characterize beam quality with minimal invasion as possible. The basis of my discussion will be a surrogate model that emulates experimental conditions of beam profile knife-edge scans. We hope that this discussion is of interest to this accelerator physics community at LPA.

Keywords: laser-plasma acceleration; simulation based inference; machine learning; modelling

  • Open Access Logo Poster (Online presentation)
    LPA Online Workshop on Control Systems and Machine Learning 24-27 January 2022, 24.-28.01.2022, online, www
    DOI: 10.6084/m9.figshare.19071641.v1

Permalink: https://www.hzdr.de/publications/Publ-34139
Publ.-Id: 34139


Selektion hochaffiner Peptide zur Bindung von f-Elementen und deren physikochemische Charakterisierung

Claus, G.

Das wesentliche Ziel der vorliegenden Arbeit bestand darin, hochaffine Peptide zur Bindung des Lanthanoides Europium zu selektieren, zu identifizieren und hinsichtlich ihrer Affinität zu charakterisieren. Die Elemente der Seltenen Erden (REE) sind aufgrund ihrer besonderen Eigenschaften von enormer Wichtigkeit in Zeiten der modernen Technologie. Die Selektion von Peptid-Biosorbenzien mit hoher REE-Affinität würde den ersten Schritt bilden, um die Herstellung von sogenannten Biokollektoren zu verwirklichen. Diese sollen zukünftig für das Recycling von Seltenen Erdmetallen wie Europium aus Elektroschrott oder für deren Extraktion aus primären Rohstoffgemischen angewendet werden.
Für die Realisierung dieser Zielstellung kam zunächst die Technik des Phage Surface Display zum Einsatz, mit dessen Hilfe gut bindende Phagenvarianten über mehrere Runden einer Affinitätsselektion angereichert und schließlich mittels Sanger-Sequenzierung identifiziert wurden. Die ermittelten Peptidsequenzmotive wurden in einem kompetitiven Bindeversuch weiter reduziert und die daraus resultierten besten Binder in Einzelbindeversuchen sowie in der zeitaufgelösten Laser-induzierten Fluoreszenz-spektroskopie (TRLFS) auf ihre Bindungsaffinität für Europium-Ionen hin untersucht. Die EF-Hand 4 des Calmodulins diente als Modellsystem zur Bestimmung der Bindungsparameter unter Verwendung der TRLFS sowie der isothermen Titrationskalorimetrie (ITC).
Die am stärksten gebundenen Peptidmotive sind durch eine hohe Anzahl an basischen Aminosäuren (AS), insbesondere Histidin, wie auch durch eine vergleichsweise hohe Anzahl an hydrophoben Resten und einen relativ geringen Anteil an sauren AS charakterisiert. Die Histidine deuteten aufgrund der freien Elektronenpaare ihrer Stickstoffatome auf eine vielversprechende Europium-Komplexierung hin. In der TRLFS stellte sich jedoch heraus, dass keines der sechs ausgewählten und synthetisierten Peptide die Europium-Ionen komplexiert. Auch in den Einzelbindeversuchen zeigte keiner der selektierten Phageneinzelklone eine gegenüber dem Phagenwildtyp verbesserte Bindung an die Zielmoleküle. Mögliche Gründe dafür werden diskutiert und sollen in fortführenden Versuchen überprüft werden.
Die TRLFS- sowie ITC-basierten Modelluntersuchungen der EF-Hand 4 des Calmodulins ergaben zwei Komplexspezies mit einer 1:1- und einer 1:2-Stöchiometrie. Es wurde die Parallele Faktoranalyse angewandt, um die Einzelkomponenten aus den experimentellen TRLFS-Spektren zu extrahieren und ihre Bindungsaffinität zu bestimmen. Anhand der ermittelten Dissoziationskonstanten von 5,66*10-6 M bzw. 1,00*10-4 M für den 1:1- bzw. 1:2-Eu(III)-EF-Hand-4-Komplex konnte eine hohe Affinität der EF-Hand 4 für Europium-Ionen nachgewiesen werden. Dies steht grundsätzlich in Übereinstimmung mit den Ergebnissen der Komplexbildungsstudie zum Calmodulin (Drobot et al. 2019). Eine Ausnahme bildet jedoch der 1:2-Eu(III)-EF-Hand-4-Komplex, da er in dieser Form nicht im nativen Calmodulin-Protein vorkommt.
Die wesentliche Fragestellung, ob es Peptidmotive gibt, die noch besser an Europium-Ionen binden als die EF-Hände des Calmodulins, kann in der vorliegenden Arbeit nicht beantwortet werden. Aufgrund dessen sollte zukünftig das Peptidmotiv der EF-Hand 4 modifiziert und weiter optimiert werden, um eine noch höhere Europium-Affinität zu erhalten und somit dem Anwendungsziel, dem Recycling oder der Extraktion von Europium aus Elektroschrott bzw. primären Rohstoffquellen, einen Schritt näher zu kommen.

Keywords: Phage Surface Display; Biopanning; Europium; f-Elemente; TRLFS; Peptide

  • Master thesis
    TU Dresden/ IHI Zittau, 2020
    Mentor: Dr. Björn Drobot
    143 Seiten

Permalink: https://www.hzdr.de/publications/Publ-34138
Publ.-Id: 34138


Blaubeuren, Cloppenburg, and Machtenstein—Three recently recognized H-group chondrite finds in Germany with distinct terrestrial ages and weathering effects

Bischoff, A.; Storz, J.; Barrat, J.-A.; Heinlein, D.; Jull, A. J. T.; Merchel, S.; Pack, A.; Rugel, G.

In the last 7 years, three meteorites (Blaubeuren, Cloppenburg, and Machtenstein) found in Germany were identified as
chondrites. Two of these rocks had been recovered from the impact sites decades ago but not considered to be meteorites.
The aim of this study is to fully characterize these three meteorites. Based on the compositional data on the silicates, namely
olivine and low-Ca pyroxene, these meteorites fit nicely within the H-group ordinary chondrites. The brecciated texture of
Blaubeuren and Cloppenburg (both H4-5) is perfectly visible, whereas that of Machtenstein, officially classified as an H5
chondrite, is less obvious but was detected and described in this study. Considering chondrites in general, brecciated rocks
are very common rather than an exception. The bulk rock degree of shock is S2 for Blaubeuren and Machtenstein and S3
for Cloppenburg. All samples show significant features of weathering. They have lost their original fusion crust and more
than half (W3) or about half (W2-3) of their original metal abundances. The oxygen isotope compositions of the three
chondrites are consistent with those of other H chondrites; however, the Cloppenburg values are heavily disturbed and
influenced by terrestrial weathering. This is supported by the occurrence of the very rare hydrated iron phosphate mineral
vivianite (Fe2+Fe2+2[PO4]2·8H2O), which indicates that the chondrite was weathered in a very wet environment. The
terrestrial ages of Blaubeuren (~9.2 ka), Cloppenburg (~5.4 ka), and Machtenstein (~1.8 ka) show that these chondrites are
very similar in their degree of alteration and terrestrial age compared to meteorite finds from relatively wet terrestrial
environments. They still contain abundant metal, although, as noted, the oxygen isotope data indicate substantial weathering
of Cloppenburg. The bulk compositions of the three meteorites are typical for H chondrites, although terrestrial alteration has
slightly modified the concentrations, leading in general to a loss of Fe, Co, and Ni due to preferential alteration of metals and
sulfides. As exceptions, Co and Ni concentrations in Machtenstein, which has the shortest terrestrial age, are typical for H
chondrites. The chemical data show no enrichments in Ba and Sr, as is often observed in different meteorite groups of
desert finds.

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Permalink: https://www.hzdr.de/publications/Publ-34136
Publ.-Id: 34136


A rigorous single period micromagnetic model of stripe domains - comparison with analytics and experiment

Deussner, S.; Süss, D.; Abert, C.; Bruckner, F.; Fähler, S.; Heistracher, P.; Reichel, L.; Neu, V.

Stripe domains in thin films form through a complex competition of perpendicular anisotropy and demagnetizing energy and are still lacking a complete micromagnetic description, despite being investigated since 50 years. This work elucidates the formation of stripe domains with a special focus on the dependence of stripe domain width on film thickness with varying ratio of the two major energy contributions. An overview and review of the most established analytical models for the calculation of this dependency is given with respect to existing experimental data as well as to new experimental data on epitaxial Fe-Co-C films with perpendicular anisotropy. Since the analytical models are limited in their predictive power and compatibility in terms of the suitable material parameter range, an effcient but rigorous micromagnetic simulation method was developed, which proved to be comparable or better than
previous models in describing experimental finding, especially for films with strongly dominating demagnetizing. Comprehensive simulations where performed to determine thickness dependent stripe width for various material parameters which can serve as a benchmark for analytical theories or can be used directly for comparison with experimental results. At a given combination of exchange constant and saturation polarization there exists a specifc thickness at which the stripe width is independent of the uniaxial anisotropy.

Keywords: Stripe domains; perpendicular anisotropy; thin magnetic films

Permalink: https://www.hzdr.de/publications/Publ-34134
Publ.-Id: 34134


Data publication: Data-Driven Quest for Two-Dimensional Non-van der Waals Materials

Friedrich, R.; Ghorbani-Asl, M.; Curtarolo, S.; Krasheninnikov, A. V.

This dataset includes the primary research data for the publication "Data-Driven Quest for Two-Dimensional Non-van der Waals Materials", https://doi.org/10.1021/acs.nanolett.1c03841.

Keywords: 2D materials; exfoliation; data-driven research; computational materials science; high-throughput computing

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Permalink: https://www.hzdr.de/publications/Publ-34133
Publ.-Id: 34133


Data publication: Three-dimensional distribution of platinum group minerals in natural MSS-ISS ores from the Norilsk 1 Deposit, Russia

Sittner, J.; Brovchenko, V.; Siddique, A.; Buyse, F.; Boone, M.; Renno, A.; Cnudde, V.; Merkulova, M.; Sluzhenikin, S.

Datensatz zur 2D und 3D Verteilung von Platin Gruppen Mineralen (PGM) . Außerdem verschiedene spektren welche mittels spektraler tomographie gemessen wurden. Außerdem enthält der Datensatz 3-dimensionale Parameter einzelner PGMs in den Proben.

Keywords: Norilsk; Platinum Group Minerals; X-ray computed tomography; Spectral X-ray computed tomography; 3D imaging; SEM-EDS

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Permalink: https://www.hzdr.de/publications/Publ-34132
Publ.-Id: 34132


Impedance characterization of particles one by one using a nanosensor electronic platform

Sandoval Bojorquez, D. I.; Oliveros Mata, E. S.; Schütt, J.; Bachmann, M.; Baraban, L.

Impedance cytometry represents a technique that allows the electronic characterization of colloids and living cells in a highly miniaturized way. In contrast with impedance spectroscopy, the measurements are performed at a fixed frequency, providing real-time monitoring of the species traveling over the sensor. By measuring the electrical properties of particles in suspension, the dielectric characteristics (electric conductivity and capacitance) of both cells and particles can be readily determined. During the last years, this technique has been broadly investigated; however, it is still not trivial to differentiate particles of similar size based on their dielectric characteristics. A way to increase the discrimination abilities of this technique could be the integration of nanostructures into the impedance platforms. In this work, we present the impedance cytometry study of particles using microfluidic channels aligned over interdigitated gold nanowire structures as our impedimetric sensor. The characterization of particles of different sizes and their comparison with particles of different compositions will provide an understanding of the correlation between the electrical signal and the own characteristics of each particle. This approach is an attractive element for label-free detection platforms that can be integrated into lab-on-a-chip systems, and that can be further implemented for single-cell analysis.

  • Open Access Logo Poster (Online presentation)
    8th International Symposium on Sensor Science, 20.-26.05.2021, Dresden, Germany
    DOI: 10.3390/I3S2021Dresden-10110

Permalink: https://www.hzdr.de/publications/Publ-34131
Publ.-Id: 34131


TOMOCON Continuous Casting Demonstration

Glavinic, I.; Wondrak, T.; Eckert, S.

More than 95% of steel produced in the entire world is produced by continuous casting. Flow condition in the mould, where the initial solidification occurs, are important for the end quality of the product. It is important to understand these conditions and react accordingly. The process is modeled at the mini-LIMMCAST facility which is operated with a eutectic alloy of GaInSn. The flow in the mould is monitored with Contactless Inductive Flow Tomography (CIFT) and the flow is influenced with an Electromagnetic Brake (EMBr). The EMBr has a great influence on the CIFT measurement system which needs to be compensated. The video explains basics of continuous casting and the experimental setup; it highlights the challenges and implemented solutions, and gives and outlook to the related research.

Keywords: Contactless inductive flow tomography; Continuous casting; Electromagnetic Brake

  • Communication & Media Relations
    Video 06.10.2021

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Permalink: https://www.hzdr.de/publications/Publ-34130
Publ.-Id: 34130


Ultrasound Image Velocimetry with Adaptive Beamforming for Modal Measurements in Liquid Metal Convection

Weik, D.; Nauber, R.; Büttner, L.; Czarske, J.; Räbiger, D.; Singh, S.; Vogt, T.; Eckert, S.

Coherent plane wave compounding allows to enhance the spatial resolution by maintaining high frame rates. Furthermore, by means of a phased array probe with adaptive beamforming, the imaging plane can be extended to the sides of the probe, although using a flat array. This approach is adapted and demonstrated for observing liquid metal convection in magnetohydrodynamic (MHD) model experiments, where high penetration depths of up to 200 mm are required, the access is limited due to the experimental conditions and the decomposition of oscillation modes requires sufficient spatial and temporal resolution. As a result of adapting ultrafast Ultrasound Imaging Velocimetry in this paper, a two component flow regime can be obtained in the conducted model experiment for penetration dephts of up to 100 mm with a spatial resolution of 2.7 mm and a temporal resolution of 2 Hz. The full penetration depth of 200 mm can be obtained with axial velocities only and a reduced spatial and temporal resolution. This allows a planar observation of turbulent and oscillating flow patterns in MHD convection experiments without elaborate fluid simulations.

Keywords: Phased arrays,Ultrasonic imaging,Magnetohydrodynamics,Array signal processing,Liquid Metals,Imaging

  • Contribution to proceedings
    2021 IEEE International Ultrasonics Symposium (IUS), 11.-16.09.2021, Xi'an, China
    Proceedings of the 2021 IEEE International Ultrasonics Symposium (IUS)
    DOI: 10.1109/IUS52206.2021.9593429

Permalink: https://www.hzdr.de/publications/Publ-34129
Publ.-Id: 34129


Data publication: Dynamics and length scales in vertical convection of liquid metals

Zwirner, L.; S. Emran, M.; Schindler, F.; Singh, S.; Eckert, S.; Vogt, T.; Shishkina, O.

The dataset consists of raw data from experiments run for aspect ratio 3 cuboid alone.

Keywords: Convection in cavities

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-34128
Publ.-Id: 34128


Dysprosium Liquid Metal Alloy Ion Source For Magnetic Nanostructures

Bischoff, L.; Klingner, N.; Mazarov, P.; Lenz, K.; Narkovic, R.; Pilz, W.; Meyer, F.

Focused Ion Beam (FIB) processing has been established as a well-suited and promising technique in R&D in nearly all fields of nanotechnology for patterning and prototyping on the μm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent an alternative to expand the FIB application fields beside all other source concepts. Especially ions from the rare earth (RE) element Dy is very interesting for local modification of magnetic properties like RE-induced damping in metallic alloys. So various alloys for source preparation were investigated. A promising solution was found in a Cu30Dy70 based LMAIS which should be introduced in more detail.

Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Source; Dysprosium; magnetic properties

Related publications

  • Journal of Vacuum Science & Technology B 40(2022)5, 052802-1-052802-6
    DOI: 10.1116/6.0001837

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  • Secondary publication expected from 10.08.2023

Permalink: https://www.hzdr.de/publications/Publ-34127
Publ.-Id: 34127


Interdigitated gold nanowires for impedimetric detection of SARS-CoV-2 antibodies

Sandoval Bojorquez, D. I.; Palestina Romero, B.; Oliveros Mata, E. S.; Laube, M.; Bachmann, M.; Baraban, L.

In the current COVID-19 pandemic that we are facing, it has become evident that the development of biosensors that can aid in the different stages of screening and surveillance: infection, disease progression and recovery, is extremely important. We developed a system that can be used for the detection of SARS-CoV-2 antibodies that are present during and after the infection. Our sensor chips were composed of six sensing devices, each of these containing interdigitated gold nanowires. The surfaces of the mentioned nanowires were functionalized with proteins of the SARS-CoV-2 so that the antibodies present in solution can bind to them. The detection of such antigen-antibody binding events was performed using the impedance spectroscopy technique. For this purposes, an AC signal over a range of frequencies (20 Hz-1 MHz) was applied to the sensor chips and the changes in impedance and phase were measured. The change in the overall impedance of the system was correlated to antigen-antibody binding events. The developed sensing system is a versatile platform that could be easily adapted to detect relevant target-analyte pairs in different diseases.

  • Lecture (Conference) (Online presentation)
    SelectBIO conference Point-of-Care, Biosensors & Mobile Diagnostics Europe 2021, 28.-30.06.2021, Rotterdam, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-34125
Publ.-Id: 34125


The resources, exergetic and environmental footprint of the silicon photovoltaic circular economy: Assessment and opportunities

Neill, B.; Lucero, C.-B.; Magnus, F.; Rutger, S.; Reuter, M.

The photovoltaic industry has shown vigorous growth over the last decade and will continue on its trajectory to reach terawatt-level deployment by 2022–2023 and an estimated 4.5 TW by 2050. Presently, its elaboration is driven primarily by cost reduction. Growth will, however, be fuelled by the consumption of various resources, bringing with it unavoidable losses and environmental, economic, and societal impacts. Additionally, strong deployment growth will be trailed by waste growth, which needs to be managed, to support Sustainable Development and Circular Economy (CE). A rigorous approach to quantifying the resource efficiency, circularity and sustainability of complex PV life cycles, and exploring opportunities for partially sustaining industry growth through the recovery of high-quality secondary resources is needed. We create a high-detail digital twin of a Silicon PV life cycle using process simulation. The scalable, predictive simulation model accounts for the system's non-linearities by incorporating the physical and thermochemical principles that govern processes down to the unit operation level. Neural network-based surrogate functions are subsequently used to analyse the system's response to variations in end-of-life and kerf recycling in terms of primary resource and power consumption, PV power generation capacity, and CO2 emission. Applying the second law of thermodynamics, opportunities for improving the sustainability of unit operations, the larger processes they are the building blocks of, and the system as a whole are pinpointed, and the technical limits of circularity highlighted. We show the significant effects changes in technology can have on the conclusions drawn from such analyses.

Keywords: Silicon photovoltaics; Circular Economy; Digital twin simulation; Neural networks Exergy

Permalink: https://www.hzdr.de/publications/Publ-34124
Publ.-Id: 34124


2.2 - Mit UWB-Lokalisierung gekoppelte inertiale Lage- und Bewegungsverfolgung für instrumentierte Strömungsfolger

Buntkiel, L.; Heller, A.; Budelmann, C.; Reinecke, S.; Hampel, U.

Zur räumlichen Vermessung von Prozessparametern und zur Strömungscharakterisierung in großen Behältern, wie z. B. Biogasfermentern und Belebtschlammbecken wurde am HZDR das Konzept strömungsfolgender Sensoren entwickelt. Alle derzeit verfügbaren oder in Entwicklung befindlichen instrumentierten Strömungsfolger nutzen zur Strömungsanalyse lediglich vertikale Positionsprofile, gemessen über den hydrostatischen Druck. Für eine weitere Analyse und Optimierung von Prozessen in großen Behältern soll deshalb der sog. Sensorpartikel aus derart weiterentwickelt werden, dass eine dreidimensionale Rekonstruktion der Trajektorie des Sensorpartikels im Behälter durchgeführt werden kann. Dazu wurde das System um eine inertiale Messeinheit und ein auf Ultrabreitbandfunktechnologie (Ultra-Wide-Band, UWB) basierendes Lokalisierungssystem erweitert. Im Beitrag wird das Sensorsystem vorgestellt und daran anschließend die Problematik der Bewegungsverfolgung mit limitierter Sensorik eingeführt, sowie die Bewegungsverfolgung basierend auf inertialer Sensorik und UWB-Lokalisierung präsentiert. Abschließend wird der gesamte Ablauf beispielhaft für ausgewählte Szenarien gezeigt.

  • Open Access Logo Contribution to proceedings
    15. Dresdner Sensor-Symposium 2021, 06.-08.12.2021, Online, Deutschland, Wunstorf: AMA Service GmbH, 978-3-9819376-5-7, 22-27
    DOI: 10.5162/15dss2021/2.2
  • Lecture (Conference) (Online presentation)
    15. Dresdner Sensor-Symposium 2021, 06.-08.12.2021, Online, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-34118
Publ.-Id: 34118


GDPR compliant reuse of medical data : encouraging patients to contribute to research (video)

Warnert, E.; Beun, S.; Broeckx, N.; Keil, V.; Maumet, C.; Oliver, K.; Petr, J.; Pinto, J.; van Driessche, K.; Wamelink, I.; Clement, P.

Data acquired for clinical purposes are often unreachable for scientific research. The General Data Protection Regulation
(GDPR) in the EU introduced new safeguards to ensure patient privacy, including the transparency principle that states that
information about data protection should be easily accessible in a concise and clear way, using plain language.1,2,3 Patients
are often unaware that they can become active participants in the scientific process by allowing the reuse of their medical
data and that privacy protection rules guarantee safe data-sharing.
Having these challenges in mind, the European Cooperation in Science and Technology (COST) Action ‘Glioma MR Imaging
2.0’ (GliMR; glimr.eu) has developed an animation video that can be used to inform patients. GliMR is a network of clinicians,
researchers and other stakeholders, that attempts to streamline and improve the diagnosis, prognosis, follow-up, and
evaluation of treatment of brain tumours using advanced MRI techniques.4 Previously, a joint-initiative from GliMR and the
Open Brain Consent resulted in the development of a GDPR-compliant template consent form and associated data user
agreement.5 These templates are valuable tools to inform patients and healthy volunteers about data usage and sharing
related privacy regulations, and facilitate the collection of consent. Unfortunately, patients are only exposed to this
information when recruited specifically for scientific studies.
Therefore, GliMR released an animation video as a tool for communication towards patients, which can be used as part of
the data protection strategy within hospitals and healthcare institutions across Europe.

  • Open Access Logo Contribution to proceedings
    MRI Together 21, 13.12.2021, Virtual, Virtual

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Permalink: https://www.hzdr.de/publications/Publ-34117
Publ.-Id: 34117


Medical data in science : patient information matters!

Warnert, E.; Beun, S.; Broeckx, N.; Keil, V. C.; Maumet, C.; Oliver, K.; Petr, J.; Pinto, J.; van Driessche, K.; Wamelink, I.; Clement, P.

Patient data is crucial to discover more about illnesses and develop new treatments. Your medical data can be used for such purposes but your privacy is always protected. By sharing your medical data, you can make a difference!

  • Open Access Logo Other report
    glimr.eu/gdpr-video: European Cooperation in Science and Technology (COST) Action ‘Glioma MR Imaging 2.0’ (GliMR), 2021
    DOI: 10.13140/RG.2.2.26796.80008

Permalink: https://www.hzdr.de/publications/Publ-34116
Publ.-Id: 34116


ml_kennewick: First release of ML modeling framework

Fan, K.; Dhammapala, R.; Harrington, K.; Lamastro, R.; Lamb, B.; Lee, Y. H.

This is the first release of the machine learning modeling framework for O3 predictions at Kennewick, WA, U.S.

Keywords: machine learning; air quality forecasts; ozone; random forest; multiple linear regression

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34114
Publ.-Id: 34114


Ressourcentechnologie: Neue Akzente durch gerichtete Evolution

Schönberger, N.; Matys, S.; Lederer, F.; Braun, R.; Pollmann, K.

Directed evolution is achieved by mimicking natural selection. It allows the optimization of certain biomolecules with desired properties such as functionality or structure. The concept is realized by the Phage Surface Display. The method can be used to isolate biomolecules, such as peptides, that natural evolution has not created. In resource technology, the phage surface display has applications in the development of new high-affinity and environmentally friendly agents, for the extraction or recycling of valuable raw materials.

Permalink: https://www.hzdr.de/publications/Publ-34113
Publ.-Id: 34113


Towards a dynamic compression facility at the ESRF

Sévelin-Radiguet, N.; Torchio, R.; Berruyer, G.; Gonzalez, H.; Pasternak, S.; Perrin, F.; Occelli, F.; Pépin, C.; Sollier, A.; Kraus, D.; Schuster, A.; Voigt, K.; Zhang, M.; Amouretti, A.; Boury, A.; Fiquet, G.; Guyot, F.; Harmand, M.; Borri, M.; Groves, J.; Helsby, W.; Branly, S.; Norby, J.; Pascarelli, S.; Mathon, O.

Results of the 2018 commissioning and experimental campaigns of the new High Power Laser Facility on the Energy-dispersive X-ray Absorption Spectroscopy (ED-XAS) beamline ID24 at the ESRF are presented. The front-end of the future laser, delivering 15 J in 10 ns, was interfaced to the beamline. Laser-driven dynamic compression experiments were performed on iron oxides, iron alloys and bismuth probed by online time-resolved XAS.

Keywords: dynamic compression; laser-shock compression; time-resolved X-ray absorption spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-34112
Publ.-Id: 34112


Single-shot XAS on laser shock compressed Fe-rich alloys: Fe-Ni, Fe-Si and Fe oxides

Voigt, K.; Amouretti, A.; Sévelin-Radiguet, N.; Torchio, R.; Berruyer, G.; Gonzalez, H.; Pasternak, S.; Perrin, F.; Occelli, F.; Pépin, C.; Sollier, A.; Schuster, A.; Zhang, M.; Boury, A.; Fiquet, G.; Guyot, F.; Harmand, M.; Borri, M.; Groves, J.; Helsby, W.; Pascarelli, S.; Mathon, O.; Kraus, D.

Deep inside planets extreme material states can be found: pressures up to hundreds of GPa and temperatures up to thousands and ten thousands of K are common. From all planets, the Earth is most investigated, but open questions e.g. regarding the crystallographic structure and composition of the core material remain. The Earth’s core consists mostly of iron, supposedly in an alloy with a substantial amount of nickel. However, results from seismological studies suggest the presence of lighter elements (like H, C, O ,Si and S), too. Not only for geophysics but also for modelling terrestrial planets found in extrasolar systems, the study of the high-pressure high-temperature phase diagram of iron and its alloys is of importance.
Bright X-ray sources in combination with high-power optical laser provide unique possibilities for creating and probing such extreme material states and their properties in the laboratory. In 2018, the High Power Laser Facility (HPLF) at the European Synchrotron Radiation Facility (ESRF) has started to be established. High quality X-ray absorption spectroscopy of dynamically compressed matter together with additional shock diagnostics will give insight into structural and electronic changes of the material as well as will give information about generated temperatures and pressures. This talk presents results from first commissioning experiments at this new outstanding facility, where laser shock compressed high-energy-density states of iron and its alloys with nickel and silicon have been investigated via single-shot X-ray absorption spectroscopy at the iron K edge.

Keywords: dynamic compression; laser-shock compression; time-resolved X-ray absorption spectroscopy; Fe alloys

  • Invited lecture (Conferences) (Online presentation)
    3rd workshop on Studies of Dynamically Compressed Matter with X-rays, 14.-15.01.2021, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-34111
Publ.-Id: 34111


Investigation of Sensor-Based sorting and selective comminution for pre-concentration of an unusual parisite-rich REE ore, South Namxe, Vietnam

Cardenas Vera, A. F.; Hesse, M.; Möckel, R.; Merker, G.; Heinig, T.; Quang, V. P.

The South Namxe deposit in Vietnam contains unusually high quantities of parisite, in addition to minor quantities of other fluorocarbonates, such as synchysite and bastnaesite. Together these minerals constitute the main REE-bearing minerals. This carbonatite-related deposit presents tabular (dykes) or lens-form ore bodies, up to several tens of meters wide and tens
to hundreds of meters in length, that are hosted in Permian limestone and Triassic basalts. The main gangue minerals in the ore bodies are from the barite-celestine solid solution series, ankerite and calcite. It was considered necessary to assess the different grain characteristics presented by the presence of parisite intergrowths and its association with minerals of the
barite-celestine solid solution series to structure a probable initial beneficiation strategy. Mineral liberation analysis revealed that an optimal liberation particle size between 45 µm and 90 µm could be achieved without overgrinding the material. Additionally, it showed a strong mineral association between fluorocarbonates, baryto-celestine, and calcite. Grinding below
100 µm is necessary. One substantial energy saving potential is removing the host rock prior to grinding. The potential for pre-concentration with sensor-based sorting and selective comminution is investigated in a pre-study. Sensor-based sorting using X-ray transmission resulted in an enrichment of REE by a factor of 4, a reduction of the mass stream down to
approximately 30%, and a loss of rare earths below 2%. Selective comminution using a pin mill, at a circumferential speed of 20 m/s, yielded a recovery of 96.5% of REE minerals and allowed rejection of 27% of barren material. This shows that both selective comminution and sensor-based sorting can be considered as complementary beneficiation steps when processing these REE ores.

Keywords: Mineral Liberation; Parisite; Selective Comminution; Sensor-Based Sorting; X-ray Transmission

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-34108
Publ.-Id: 34108


TetraX: Finite-Element Micromagnetic-Modeling Package

Körber, L.; Quasebarth, G.; Hempel, A.; Zahn, F.; Otto, A.; Westphal, E.; Hertel, R.; Kakay, A.

This repository holds the first release of TetraX. The recent version is found at gitlab.hzdr.de/micromagnetic-modeling/tetrax

TetraX is a package for finite-element-method (FEM) micromagnetic modeling of magnetization statics and dynamics with the aim to provide user friendly and flexible workflows. Apart from energy minimizers and an LLG solver, it provides implementations of several FEM dynamic-matrix approaches to numerically calculate the normal modes and associated frequencies for magnetic specimen of different geometries such as confined samples, infinitely long waveguides, or infinitely extended multilayers. Next to support for ferromagnets, TetraX will also provide the first full micromagnetic package for antiferromagnets.

TetraX is a package for finite-element-method (FEM) micromagnetic modeling of magnetization statics and dynamics with the aim to provide user friendly and flexible workflows. Apart from energy minimizers and an LLG solver, it provides implementations of several FEM dynamic-matrix approaches to numerically calculate the normal modes and associated frequencies for magnetic specimen of different geometries such as confined samples, infinitely long waveguides, or infinitely extended multilayers. Next to support for ferromagnets, TetraX will also provide the first full micromagnetic package for antiferromagnets.

Keywords: python; Micromagnetic simulations; micromagnetic modeling; magnetization dynamics; numeric

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-34107
Publ.-Id: 34107


Dynamics and length scales in vertical convection of liquid metals

Zwirner, L.; S. Emran, M.; Schindler, F.; Singh, S.; Eckert, S.; Vogt, T.; Shishkina, O.

Using complementary experiments and direct numerical simulations, we study turbulent thermal convection of a liquid metal (Prandtl number Pr≈0.03) in a box-shaped container, where two opposite square sidewalls are heated/cooled. The global response characteristics like the Nusselt number Nu and the Reynolds number Re collapse if the side height 𝐿 is used as the length scale rather than the distance 𝐻 between heated and cooled vertical plates. These results are obtained for various Rayleigh numbers 5×103≤Ra𝐻≤108 (based on 𝐻) and the aspect ratios 𝐿/𝐻=1,2,3 and 5. Furthermore, we present a novel method to extract the wind-based Reynolds number, which works particularly well with the experimental Doppler-velocimetry measurements along vertical lines, regardless of their horizontal positions. The extraction method is based on the two-dimensional autocorrelation of the time–space data of the vertical velocity.

Keywords: Convection in cavities

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Permalink: https://www.hzdr.de/publications/Publ-34106
Publ.-Id: 34106


Nonlinear response of semiconductor systems under intense THz excitation

Pashkin, O.

Intense narrowband terahertz pulses from the FELBE free-electron laser facility are utilized to study nonlinear excitation regimes of various degrees of freedom in semiconductors. In this talk we present several recent examples including plasmons in InGaAs nanowires, intersubband transitions in Ge/SiGe quantum wells, and impurity transitions in boron doped Si.

Related publications

  • Invited lecture (Conferences) (Online presentation)
    The 10th International Symposium on Ultrafast Phenomena and Terahertz Waves (ISUPTW 2021), 16.-19.06.2021, Chengdu, China
  • Lecture (Conference)
    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-34105
Publ.-Id: 34105


Development of a system for the design and synthesis of tailor-made peptides for the treatment of polymers prior to plastic metallization, highlight presentation Euromat 2021

Kießlich, T.

Increasing demands in environmental protection and environmentally friendly solutions are important market drivers for the development of sustainable chemicals. Chromium (VI) is used in electroplating technology to pretreat polymers in order to achieve good metallization. However, it´s applications of now require special permits. This is an EU strategy to prevent the use of dangerous and unhealthy Reduce substances. Finding replacements with conventional chemicals is increasingly difficult. In order to change the chemistry and microstructure of polymer surfaces at suitable temperatures and process times, very reactive chemicals are required, which pose a high risk. Currently available alternative chromium (VI) -free technologies for polymer preconditioning have not yet been able to meet the industrial requirements.
One strategy to solve this problem is to focus on very specific and selective reactions. The main aim of this work is to develop a biological system that enables the development and synthesis of tailor-made, selective polymer-binding peptides. The system is based on what is known as phage display technology (PSD).
PSD generally uses a library of about 109 phages with various peptides fused to the phage coat proteins. All the phages in the library are unique. Phage particles are incubated with the substrate (polymer) in three biopanning cycles. Only a few phages bind to surfaces or via their envelope peptides particles, most have no affinity and will not bind. Unbound phage particles are removed when the target materials are washed. Finally, the attached phage particles are eluted. The eluted phage are amplified and purified in Escherichia coli cells. After the last cycle of biopanning, there are only a few individual phages left that have exceptionally high surface affinity. The phage particles are used for subsequent sequencing, modification and application.
The peptides that are expressed by the selected phages are then characterized with regard to their sequence, their binding motif and their interaction with the target material.
In parallel, new, improved and adapted phage libraries are constructed that minimize the proportion of wild-type phages. These constructed libraries are used for further biopanning experiments and the results are compared with commercial libraries.

Keywords: phage surface display; biopanning; resourche recovery; polymers; biotechnology

  • Lecture (Conference) (Online presentation)
    Euromat 2021, 13.-17.09.2021, Genf, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-34104
Publ.-Id: 34104


Experimental and Numerical Investigations for an Advanced Modeling of Two-Phase Flow and Mass Transfer on Column Trays

Vishwakarma, V.

Distillation is the leading thermal separation technology that is carried out in many industrial tray columns worldwide. Although distillation columns are expensive in terms of cost and energy, they will remain in service due to unavailability of any equivalent industrially-viable alternative. However, rising energy costs and urgent needs to reduce greenhouse gas emissions demand improvements in the energy efficiency of separation processes, globally. This can be achieved by tuning the dynamics of the evolving two-phase dispersion on column trays via design modification and revamping. Thus, it becomes necessary to understand how the two phases evolve over the tray and how they link to tray efficiency for given tray designs, systems and operating conditions. Only then, the cost and energy reduction can be achieved by strategically iterating the tray design and revamps with respect to the resulting tray efficiency. To pursue this strategy, accurate prediction of the separation efficiency based on flow and mixing patterns on the trays is an important prerequisite.

In this thesis, the mathematical models relying on flow and mixing patterns for predicting the tray efficiencies were reviewed. These models were developed based on the analyses of two-phase flow, crossflow hydraulics and mass transfer over the trays. Several limitations in the existing models were identified that could lead to inaccurate tray efficiency predictions. First, the conventional models do not account for any variation in the local two-phase flow in their formulation. These models rather consider a homogeneous flow scenario based on flow monitoring at the tray boundaries only, which indicates a black box efficiency estimation. Second, the existing models do not consider any vapor flow maldistribution, which can be detrimental to the tray efficiency. In response to these limitations, a new model based on refinement of the conventional residence time distribution (RTD) model (referred to as the ‘Refined RRTD model’) was proposed. The new model involves geometric partitioning of the tray into compartments along the flow path length, which permits computing the tray efficiency through quantification of the efficiency of the individual compartments. The proposed model ensures that the fluid dynamics of each compartment contribute towards the overall tray efficiency, which specifically targets the black box prediction of the tray efficiency by the conventional models. The tray discretization further aids in analyzing the impact of vapor flow maldistribution on the tray efficiency. In the initial assessment, the new model capabilities were demonstrated in appropriate case studies after theoretical validation of the model for the limiting cases of the two-phase flows. For the experimental validation of the new model, a full hydrodynamic and mass transfer description of the two-phase dispersion specific to the tray operation is indispensable. Because of the inherently complex dispersion characteristics, significant advancements in the imaging and efficiency modeling methods were required.

In this thesis, a DN800 column simulator equipped with two sieve trays (each with 13.55% fractional free area) was used with air and tap water as the working fluids. Deionized water was used as a tracer. The gas loadings in the column in terms of 𝐹-factor were 1.77 Pa0.5 and 2.05 Pa0.5, whereas the weir loadings were 2.15 m3m-1h-1, 4.30 m3m-1h-1 and 6.45 m3m-1h-1. An advanced multiplex flow profiler comprising 776 dual-tip conductivity probes for simultaneous conductivity measurements was introduced for hydrodynamic characterization. The spatial resolution of the profiler based on the inter-probe distance was 21 mm × 24 mm, whereas the temporal resolution was 5000 Hz. The design characteristics of the new profiler, electronic scheme, measurement principle, reference framework, and data processing schemes are explained in detail. By analyzing the two-phase dispersion data gathered by the profiler at multiple elevations above the tray, the effective froth height distributions were obtained for the first time based on a newly proposed approach. Uniform froth heights were seen over the majority of the tray deck, whereas both minimum and maximum froth heights were detected immediately after the tray inlet. Based on threshold-based calculation (accompanied by γ-ray CT scans), 3D time-averaged liquid holdup distributions were visualized for the first time, too. Homogeneous liquid holdup distributions were observed at multiple elevations above the deck with the highest holdups occurring near the average effective froth heights. The detailed flow and mixing patterns of the liquid in the two-phase dispersion were retrieved via tracer monitoring. With respect to tray centerline, axisymmetric liquid flow and mixing patterns were detected with parabolic velocity distributions near the tray inlet. The liquid velocities over the remaining tray deck were nearly uniform for the prescribed loadings. Eventually, the RRTD model was applied by discretizing the tray geometrically, and accordingly employing the available hydrodynamic data. The conventional models often applied in the literature were also evaluated with the new model.

For evaluating the model predictions, a new system add-on for the existing air-water column facility was proposed for direct efficiency measurements. The air-led stripping of isobutyl acetate from the aqueous solution is a safe and viable approach that overcomes numerous limitations posed by the existing chemical systems. Based on liquid sampling at different tray locations, the liquid concentration distributions were obtained at each operating condition via UV spectroscopy. The tray and point efficiencies as well as stripping factors were calculated from those distributions. Because of the low liquid diffusivity and high liquid backmixing, low efficiencies were observed at the given loadings. The model predictions were consistent with the experimental counterparts (even for the extrapolated values of the involved parameters), because of the uniform liquid flow and mixing in the compartments. For the given predictions, those corresponding to the new RRTD model were the most accurate. Additional hydrodynamic and efficiency data are needed for more conclusive evidence regarding the promise of the RRTD model.

Keywords: column tray; two-phase crossflow; efficiency prediction model; 3D liquid holdup; tracer-response analysis; tray efficiency calculation

  • Doctoral thesis
    TU Dresden, 2021

Permalink: https://www.hzdr.de/publications/Publ-34102
Publ.-Id: 34102


Voltage‐driven motion of oxygen and nitrogen ions: role of defects in magneto‐ionics

Liedke, M. O.; Butterling, M.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.; Menéndez, E.; de Rojas, J.; Sort, J.

Nowadays magnetoelectronic devices are still controlled by electric currents, a scheme which suffers from energy losses due to heat dissipation. Employing electrical fields as a substitution of
currents can strongly reduce ohmic losses and is expected to be crucial for energy-efficient applications. Here, a voltage-induced ionic motion (magneto-ionics) is proposed to control the magnetic properties. In traditional magneto-ionic systems oxygen or lithium are exploited as transport
ions and, only recently, nitrogen. We will demonstrate magneto-ionic effects in single-layer iron
and cobalt nitride films. Their microstructural and magnetic properties are evaluated and compared with previously studied oxides using positron annihilation spectroscopy and magnetometry
techniques. The electrolyte-gated ionic migration enables switching between paramagnetic and
ferromagnetic states. The role of vacancies and their agglomerations at grain boundaries are emphasized as diffusion channels, which allow for a fast migration and large incorporation of the
ionic species.

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; magneto-ionics; oxide; nitride

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  • Poster (Online presentation)
    MML-Workshop 2021 - "From Matter to Materials and Life", 22.-24.11.2021, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-34100
Publ.-Id: 34100


Three-dimensional distribution of platinum group minerals in natural MSS-ISS ores from the Norilsk 1 Deposit, Russia

Sittner, J.; Brovchenko, V.; Siddique, A.; Buyse, F.; Boone, M.; Renno, A.; Cnudde, V.; Merkulova, M.; Sluzhenikin, S.

The Mt. Rudnaya Mss-Iss fine-grained ores from a NE termination of Norilsk 1 deposit were analyzed using a combination of X-ray computed micro tomography, spectral X-ray computed micro tomography and scanning electron microscopy to achieve both, 2D and 3D data. The ores consist of a copper-rich Iss composed of tiny lamellar intergrowths of cubanite and chalcopyrite solid solutions, which form up to 4-mm distinct globules surrounded by an Iss-Mss matrix. Our X-ray computed micro tomography results provide 3D textural evidence of a possible natural sulfide-sulfide liquid immiscibility between Cu-rich and Cu-poor sulfide liquids. The platinum-group minerals (PGM) distribution shows that 20.6 Vol.-% of all PGMs occur in the Iss-Mss matrix and 79.4 Vol.-% in the Iss globules. We believe that this distributional behavior is due to the fact that the platinum group elements (PGE) cannot be dissolved in Iss, which led to the formation of the large PGM grains, which are up to 120 μm on their longest axis. The initial enrichment of Iss with PGEs was controlled by differences in the partition coefficients of platinum and palladium Cu-poor and Cu-rich liquids.

Keywords: Norilsk; Platinum Group Minerals; X-ray computed tomography; Spectral X-ray computed tomography; 3D imaging; SEM-EDS

Permalink: https://www.hzdr.de/publications/Publ-34099
Publ.-Id: 34099


Vacancy kinetics during magnetic phase transitions

Liedke, M. O.; Butterling, M.; Ehrler, J.; Eggert, B.; Griggs, W.; Anwar, M. S.; Bali, R.; Thomson, T.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.

Two model magnetic systems, FeAl and FeRh, will be discussed in terms of defect kinetics during magnetic phase transitions. Open volume defects have been investigated with Doppler broadening and positron annihilation lifetime spectroscopy techniques using continuous [1] and pulsed [2] slow positron beams, respectively.
The first system, FeAl, exhibits the so-called disorder induced ferromagnetism, where anti-site disorder promotes ferromagnetic A2 phase over paramagnetic ordered B2 phase. The overall control of the phase transition is given by ion irradiation and annealing [1,3]. The main physical origin correlates strongly with the anti-site disorder [4], however the concentration and size of open volume defects is crucial for kinetics of the reordering processes. It will be shown that Fe and Al mono-vacancies introduced by Ne+ irradiation increase the A2 → B2 ordering rate, whereas triple defects and vacancy clusters are stable during annealing. The ordering is achieved through the diffusion of Al and Fe atoms which is mediated by vacancies, and the splitting of vacancy clusters and triple defects into single vacancies during irradiation allows control of the A2 → B2 re-ordering rates, strongly accelerating thermal diffusion [3]. These results provide insights into thermal reordering processes in binary alloys, and the consequent effect on magnetic behavior.
The second system investigated, FeRh, shows a first-order metamagnetic transition from a low temperature antiferromagnetic to a high temperature ferromagnetic phase at about 370 K. During this transition the local Fe magnetic moments align ferromagnetically while the Rh atoms acquire a moment of approximately 1 μB. Moreover, the lattice volume expands by about 1%. The phase transition can also be induced by ion or laser irradiation which drives a disorder-induced mechanism where so-called static disorder plays a key role. It can occur in the form of mono-vacancies, vacancy clusters, grain boundaries or as anti-site disorder, which lead to the formation of ferromagnetism. It will be demonstrated that ion irradiation damages the film structure introducing open volume defects, where concentration scales with ion fluence. Moreover, defect kinetics during thermal annealing across the antiferromagnetic-ferromagnetic phase transition critical temperature will be discussed in detail.

[1] M.O. Liedke, W. Anwand, R. Bali et al., J. Appl. Phys. 117 (2015) 163908.
[2] A. Wagner, M. Butterling, M.O. Liedke et al., AIP Conf. Proc. 1970 (2018), 040003.
[3] J. Ehrler, M.O. Liedke, J. Čížek et al., Acta Mater. 176 (2019) 167.
[4] R. Bali, S. Wintz, F. Meutzner et al., Nano Lett. 14 (2014) 435.

* The Impulse- and Networking Fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox), and the Helmholtz Energy Materials Characterization Platform (03ET7015) are acknowledged.

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; FeRh; FeAl

Related publications

  • Lecture (Conference) (Online presentation)
    Int. Workshop on Positron Studies of Defects-2021, 01.-05.03.2021, Mumbai, India

Permalink: https://www.hzdr.de/publications/Publ-34098
Publ.-Id: 34098


Oxygen vs. Nitogen Magneto-ionics

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

Voltage-controlled magnetism, where magnetic properties are controlled via an applied electricfield instead of current, could represent a significant increase in energy savings in future magnetically actuateddevices. Practically, however, this approach faces several important obstacles, such as thickness limitations inelectrically charged metallic films, mechanical failure in strain-mediated piezoelectric/magnetostrictive devices,and a lack of room-temperature multiferroics. Voltage-driven ionic motion (magneto-ionics) may provide a pathforward by avoiding many of these drawbacks, in addition to its own interesting magnetoelectric phenomena.Nevertheless, translating magneto-ionics into real world devices requires significant improvements in magneto-ionic rates, cyclability, and magnetization. Here, we report on the development of magneto-ionics in single-layer, semiconducting transition metal oxides and nitrides, and the subsequent enhancements in theirperformance. We first present electrolyte-gated and defect-mediated O transport in single-layer, paramagneticCo
O
at room temperature (i.e. without thermal assistance), which allows voltage-controlled magneticswitching (referred to here as ON-OFF ferromagnetism: Fig. 1) via internal reduction/oxidation processes
.Negative bias partially reduces Co
O
to Co, resulting in films with Co- and O-rich areas (ferromagnetism: ON).Positive bias re-oxidizes Co back to Co
O
(paramagnetism: OFF). We show that the bias-induced motion of Ois caused by mixed vacancy clusters, with O motion promoted at grain boundaries and assisted by thedevelopment of O-rich diffusion channels. The generated ferromagnetism is shown to be stable, and easilyerased by sufficient positive bias. This voltage-induced process is demonstrated to be compositionally,structurally, and magnetically reversible and self-contained, as no oxygen reservoir besides Co
O
is needed.We then show that room-temperature magneto-ionic effects in electrolyte-gated paramagnetic Co
O
films canbe significantly increased, both in terms of generated magnetization (6 times larger) and speed (35 timesfaster), if the electric field is applied using an electrochemical capacitor configuration (utilizing an underlyingconducting buffer layer: Fig. 2) instead of electric-double-layer transistor-like configuration (placing the electriccontacts at the side of the semiconductor)
. In addition to gains in speed, magnetization measurements showa marked increase in the squareness ratio and a decrease in the switching field distribution of the hysteresisloops in Co
O
biased in the capacitor configuration, the result of the formation of more uniform ferromagneticregions. These results are attributed to the uniform electric field applied throughout the film, as confirmed byCOMSOL simulations. As the measured films are quite thick, further miniaturization promises even greatermagneto-ionic rates. We then demonstrate room-temperature voltage-driven nitrogen magneto-ionics (i.e., Ntransport) by electrolyte-gating of a CoN film
. Nitrogen magneto-ionics in CoN is compared to oxygenmagneto-ionics in Co
O
, in films using an electrochemical capacitor configuration. Both materials are shownto be nanocrystalline (face-centered cubic structure), and show reversible voltage-driven ON-OFFferromagnetism (Fig. 1). Nitrogen transport is found to occur uniformly throughout the film, creating a plane-wave-like migration front, without assistance of diffusion channels. Nitrogen magneto-ionics also requires lowerthreshold voltages and exhibits enhanced rates and cyclability, due to the combination of a lower criticalelectric field required to overcome the energy barrier for ion diffusion and the lower electronegativity of nitrogenwith respect to oxygen, consistent with
ab initio
calculations contrasting N vs. O motion in cobalt stacks. Theseresults place nitrogen magneto-ionics as a robust alternative for efficient voltage-driven effects and, along withoxygen magneto-ionics, may enable the use of magneto-ionics in devices that require endurance and moderate speeds of operation, such as brain-inspired/stochastic computing or magnetic micro-electro-mechanical systems.
References:
[1] A. Quintana, E. Menéndez, M. O. Liedke et al., ACS Nano, Vol. 12, p. 10291 (2018)
[2] J. de Rojas, A. Quintana, A. Lopeandía et al., Advanced Functional Materials, Vol. 30, p. 2003704 (2020)
[3] J. de Rojas, A. Quintana, A. Lopeandía et al., Nature Communications, Vol. 11, p. 5871 (2020)
KEYWORDS:
magneto-ionics, voltage-controlled magnetism, oxygen, nitrogen.
IMAGE CAPTION:
Fig. 1. Hysteresis loops (M vs. H) of as-prepared, negatively-biased, and positively-biased CoN films atmagneto-ionic activation voltages.
Fig. 2. A schematic of the electrochemical capacitor configuration used to bias cobalt-oxide (Co
O
) andcobalt-nitride (CoN) films.

Related publications

  • Lecture (Conference)
    INTERMAG 2021, 26.-30.04.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-34097
Publ.-Id: 34097


Precipitation stripping of nanometrical particles for the recovery of vanadium

Kelly, N.; Helbig, T.; Ebert, D.; Möckel, R.; Chekhonin, P.; O'Toole, N.; Sanchez Loredo, M. G.

The demand for strategic metals such as chromium and vanadium is predicted to rise in the future. These metals can currently be found in the slag by-products of certain steel production processes. To help meet the rising demand, the CHROMIC project seeks to develop a hydrometallurgical process for the recovery and purification of these valuable resources. Various methods are being investigated for separation of the metal value from the resulting alkaline leach feeds, including solvent extraction.
In case of the recovery of vanadium an interesting modification of the conventional solvent extraction process is the addition of a crystallization operation (precipitation stripping). The extraction was carried out using an Aliquat 336 solution in n-octanol/kerosene as extractant. Precipitation stripping was carried out using metal salt dissolved in a concentrated chloride solution. For some experiments, polyvinylpyrrolidone was used as stabilizer in order to avoid agglomeration and control growth. The metal vanadate particles are nanometrical in size, with morphologies varying from nanowires to spherical particles.

  • Poster (Online presentation)
    International Conference on Resource Chemistry, 08.-09.03.2021, online (ursprünglich Darmstadt), Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34096
Publ.-Id: 34096


The radiolabeling of silicon rhodamines for multimodal PET/ SPECT- and NIR optical imaging

Kanagasundaram, T.; Laube, M.; Carsten, S. K.; Stadlbauer, S.; Pietzsch, J.; Kopka, K.

Objectives: The combination of non-invasive molecular imaging (PET/SPECT)- and optical imaging (OI) techniques for tumor identification and resection are emerging. This powerful strategy promises to precisely differentiate between healthy and affected tumor tissues which is of most relevance for preoperative planning (prestaging) followed by R0-tumor resection via image-guided intraoperative surgery. The goal of this work is the development of radiolabeled near-infrared (NIR) fluorophores for PET/SPECT and optical imaging. The fluorophores were prepared for radiolabeling with the positron emitter fluorine-18 and with the gamma emitter iodine-123 for SPECT imaging with the aim to elucidate their potential as imaging agents for the detection of tumor tissues. Moreover, the radiolabeled dyes are intended to be bioconjugated to the PSMA-1007 binding motif, as a generic prominent tumor targeting vector for enrichment in prostate tumors (1).
Methods: We have developed fluorophores belonging to the silicon rhodamine (SiR) family with optical properties in the NIR spectral range (2). The photostable fluorophores have been characterized using NMR-, UV/VIS/NIR-spectroscopy and mass spectrometry. Furthermore the SiRs were radiolabeled by using the approach for copper-mediated radiolabeling of arylboronic acids, functioning as precursors both for fluorine-18 and iodine-123 labeling (3). The radiolabeling conditions were optimized based on radiochemical conversions (RCC) as analyzed by using radio-HPLC and radio-TLC. The model and lead compound [18F]F-SiR was isolated by radio-HPLC followed by SPE for further in vitro experiments, e.g. in vitro stability was determined in human serum.
Results: Novel boronic acid functionalized SiRs with chemical yields up to 68% were received via multistep organic syntheses. The blue dyes show high extinction coefficients up to 95.000 M-1cm-1, quantum yields of 0.33 and high photo stability making them useful for NIR optical imaging. After careful optimization of the radiolabeling conditions, [18F]F-SiR was obtained in isolated radiochemical yields of up to 31% and a molar activity of 70 GBq/µmol. Moreover, radioiodination experiments led to [123I]I-SiRs with radiochemical conversions higher than 90% (figure 1).
Demonstrated by human serum stability, the lead fluorophore [18F]F-SiR showed promising performance for in vitro and in vivo experiments.
The current work is focused on the synthesis of 18F/123I-radiolabeled SiRs and their reference analogs containing an active ester for bioconjugation with prominent biological vectors (e.g. PSMA-1007 motif) to perform first proof-of-concept studies.
Conclusions: The very first radiolabeled NIR fluorophores based on the SiR lead structure were synthesized and their labeling efficiencies for radiofluorination and radioiodination were evaluated. Ideal optical- and radiolabeling properties show promising features for further bioconjugation with prominent target vectors (e.g. PSMA-1007 binding motif) and biological evaluation of the novel SiR-PSMA-1007 conjugates in vitro and in vivo.
Acknowledgements:
This project is supported by the Wilhelm Sander-Stiftung for a grant on dual-labeled tumor tracers, grant number 2018.024.1.
References:
(1) K. Kopka et al., J. Nucl. Med. 2015, 56, 914–920.
(2) T. Nagano et al., J. Am. Chem. Soc. 2012, 134, 5029–5031.
(3) B. Neumaier et al., Chem. Eur. J. 2017, 23, 3251–3556.

Keywords: PET/SPECT Imaging; Optical Imaging; Organic Chemistry; Si-Rhodamines; Radiochemistry

Permalink: https://www.hzdr.de/publications/Publ-34095
Publ.-Id: 34095


Physics and Theory of Defects in 2D Materials: The Role of Reduced Dimensionality

Komsa, H.-P.; Krasheninnikov, A.

Similar to their bulk counterparts, most crystalline two-dimensional materials (2DMs) have defects and impurities. Even when the formation energy of defects in a 2D system is high, so that the equilibrium defect concentration is negligible (as, e.g., in graphene in a wide range of temperatures), the defects can appear due to the interaction with the environment, as 2DMs have a very high surface-to-volume ratio. Moreover, any species on the surface of 2DMs can have strong effect on the material properties, while most species found on the surfaces of bulk systems are normally completely ignored in the context of point and line defects. Defects can have both detrimental and beneficial effects on the properties of 2DMs, as in the case of the bulk systems. Specifically, defects can deteriorate the electronic, optical and mechanical characteristics of 2DMs, and at the same time, add new functionalities, e.g., magnetism, or improve their catalytic performance. The reduced dimensionality of 2DMs, however, modifies the influence of defects on the materials properties. The geometry of 2DMs also makes it possible to deliberately introduce defects with nearly atomic spatial resolution using focused ion and electron beams and also helps in imaging the defects using scanning probe and transmission electron microscopy. At the same time, the reduced dimensionality of 2DMs also requires to modify the theoretical approaches aimed at assessing the formation energy of defects to account for the environment and much weaker screening of electrical point charges when defects are not neutral. In this chapter, we give a brief overview of the types of defects in 2DMs and bulk systems with the main focus on the differences originating from the reduced dimensionality of the former. We also discuss the changes which should be made in the theoretical description of point and line defects and give examples of the calculations for 2DMs with defects.

Keywords: 2D materials; Defects

Related publications

  • Book chapter
    Rafik Addou, Luigi Colombo: Defects in Two-Dimensional Materials, Elsevier: Elsevier, 2022, 032390310X, 9780323903103, 7-41
    DOI: 10.1016/B978-0-12-820292-0.00008-2

Permalink: https://www.hzdr.de/publications/Publ-34094
Publ.-Id: 34094


In situ study of solidification patterns of a ternary Ga-In-Bi alloy in presence of melt convection

Shevchenko, N.; Budenkova, O.; Birjukovs, M.; Chichignoud, G.; Eckert, S.

In situ real-time observations, which are important in studies of binary alloy systems for verification of theoretical hypotheses, are scarce for ternary and multi-component alloys. This work is devoted to in situ visualization of solidification patterns observed during bottom-up solidification of a Ga-In-Bi alloy in a Hele-Shaw cell under buoyancy-driven convection. The investigations are based on a combination of micro-focus X-ray radiography and advanced image processing techniques. A model ternary system is selected from the family of low-temperature metallic alloys with working temperatures below 100 °C. The phase diagram of the ternary Ga-In-Bi system indicates the appearance of an indium-based primary solid phase and only a minor amount of intermetallic phase for concentrations chosen within this study.
Our observations show complex and strongly disoriented solidification patterns with curved primary and secondary branches. By studying the solidification dynamics we establish that some grains exhibit a morphology that is rather similar to the "seaweed" pattern. The appearance of seaweed grains is usually related to the low anisotropy of the surface energy of metal crystals that can be relatively easy modified by the presence of another element. We focus on the role of melt flow in transition from dendritic arrays to seaweed structures in this ternary system. Morphological analysis and comparison of dendritic and seaweed patterns are performed using a new X-ray image processing approach.

Keywords: Ternary alloy; in situ X-ray imaging; solidification; seaweed pattern; melt convection

  • Lecture (Conference)
    6th International Conference on Advances in Solidification Processes, 20.-24.06.2022, Le Bischenberg, France

Permalink: https://www.hzdr.de/publications/Publ-34093
Publ.-Id: 34093


Potential of industrial hemp (Cannabis sativa L.) for bioenergy production in Canada: Status, challenges and outlook

Parvez, A. M.; David Lewis, J.; Afzal, M. T.

Climate change from carbon emissions and rising energy demands poses a serious threat to global sustainability. This issue is particularly noticeable in Canada where per capita energy demands are high and fossil fuels are used. Industrial hemp can be used for bioenergy production as an alternative to fossil fuels to capture and utilize carbon, with applications in various markets at high values. Despite this, industrial hemp has faced legal barriers that have hampered its viability. This review describes industrial hemp, its status in global markets, its performance as bioenergy feedstock, and potential in Canada, so research can target gaps in available knowledge. Numerous bioenergy applications for industrial hemp exist; the production of bioethanol and biodiesel from industrial hemp has strong potential to reduce greenhouse gas emissions and improve the Canadian economy. The current study found that industrial hemp can compete with many energy crops in global markets as a feedstock for many bioenergy products with solid hemp yielding 100 GJ/ha/y, allowing for economical emissions reductions for example in coal/biochar blends that can reduce emissions by 10%, and in co-production of bioethanol and grain, generating $2632/ha/y. This work also suggests industrial hemp has unique potential for growth in Canada, though processing facilities are severely lacking, and hemp growing has some negative environmental impacts related to fertilizer use. Responsible growth could be realized through incentivizing or subsidizing processing facility investment, implementing co-production where possible, and funding research to improve conversion, harvesting and polygeneration processes.

Keywords: Canada; Industrial hemp; Second-generation biofuel

Permalink: https://www.hzdr.de/publications/Publ-34091
Publ.-Id: 34091


Predicting Concurrent Structural Mechanical Mechanisms During Microstructure Evolution

Soar, P.; Kao, A.; Shevchenko, N.; Eckert, S.; Djambazov, G.; Pericleous, K.

The interdependence between structural mechanics and microstructure solidification has been widely observed experimentally as a factor leading to undesirable macroscopic properties and casting defects. Despite this, numerical modelling of microstructure solidification often neglects this interaction and is therefore unable to predict key mechanisms such as the development of misoriented grains. This paper presents a numerical method coupling a Finite Volume Structural Mechanics Solver to a Cellular Automata Solidification Solver, where gravity or pressure-driven displacements alter the local orientation and thereby growth behaviour of the solidifying dendrites. Solutions obtained using this model are presented which show fundamental behaviours observed in experiments. The results show that small, localised deformations can lead to significant changes in crystallographic orientation of a dendrite and ultimately affect the overall microstructure development.

Keywords: Structural mechanics; Microstructure solidification; Cellular Automata Solidification; Numerical method; Dendrites

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Permalink: https://www.hzdr.de/publications/Publ-34090
Publ.-Id: 34090


Sorption enhanced gasification (SEG) of biomass for tailored syngas production with in-situ CO2 capture: Current status, process scale-up experiences and outlook

Parvez, A. M.; Hafner, S.; Hornberger, M.; Schmid, M.; Scheffknecht, G.

Sorption Enhanced Gasification (SEG) is being considered as a promising solid fuel conversion and carbon capture and sequestration technology since it can produce tailored syngas coupled with in-situ CO2 capture. Over the years, considerable research has been conducted with high grade biomass in laboratory and pilot scale facilities targeting technical and process scale-up viabilities of the SEG process. SEG has successfully been tested at semi industrial scale which demonstrates further scale-up potential (e.g. commercial demonstration plant) of this innovative technology. The results showed that the operation window of SEG laid at a gasification temperature ranging from 600 °C to 750 °C. By optimizing the process parameters, H2-rich syngas (>70 vol %db) and desired H2/CO ratios can be attained. Also, the total tar content of the optimized process is reported to be low compared to those obtained from classical fluidized bed gasification processes. So far, wood is mostly used as the feedstocks while tests with wastes including solid recovered fuels (SRFs) have also been conducted. Cheap and readily available natural sorbents (such as limestone) enable a satisfactory operation, however, issues associated with attrition and deactivation still need to be addressed. Accordingly, natural sorbents with improved properties, synthetic CaO-based sorbents as well as pre-treated natural sorbents are considered to overcome these limitations. This paper therefore discusses the current status of the SEG technology with an emphasis on its industrial applications for flexible syngas production with in-situ CO2 reduction. Moreover, challenges, process scale-up experiences and research gaps for the commercialization of this novel technology are identified in this review.

Keywords: Sorption enhanced gasification; Biomass; In-situ CO2 capture; Limestone/CaO sorbent; Carbon capture and sequestration

Permalink: https://www.hzdr.de/publications/Publ-34089
Publ.-Id: 34089


Microbial consortium: A promising strategy for bioleaching of metals from industrial wastes

Chakankar, M. V.; Hocheng, H.

Advances in biohydrometallurgical technology have made it possible to utilize the microorganisms and their metabolites in the recovery and resource recycling of metals from secondary sources like industrial wastes. Various strategies have been developed to apply these microorganisms to improve the efficiency of the method. Use of microbial consortia is one of the promising strategies. Microbial consortia can be applied in various approaches and this chapter discusses the current applications and some promising emerging technologies that can assist in enhancing the bioleaching performance. Furthermore, interesting applications of microbial consortia for metal recovery from different industrial wastes are described along with the role of consortia and mechanisms involved.

Keywords: Microbial consortia; bioleaching; industrial waste; metal

  • Book chapter
    Christon J Jurst: Microbial Metabolism of Metals and Metalloids, Germany: Springer, 2022, 978-3-030-97184-7, 109-134

Permalink: https://www.hzdr.de/publications/Publ-34088
Publ.-Id: 34088


Radiomics-based tumor phenotype determination based on medical imaging and tumor microenvironment in a preclinical setting

Müller, J.; Leger, S.; Zwanenburg, A.; Suckert, T.; Lühr, A.; Beyreuther, E.; von Neubeck, C.; Krause, M.; Löck, S.; Dietrich, A.; Bütof, R.

Background and purpose: Radiomics analyses have been shown to allow for the prediction of clinical outcomes of radiotherapy based on medical imaging-derived biomarkers. However, the biological meaning attached to such image features often remains unclear, thus hindering the clinical translation of radiomics analysis. In this manuscript, we describe a preclinical radiomics trial, which attempts to establish correlations between the expression of histological tumor microenvironment (TME)- and magnetic resonance imaging (MRI)-derived image features.
Materials & Methods: 114 mice were transplanted with the radioresistant and radiosensitive head and neck squamous cell carcinoma cell lines SAS and UT-SCC-14, respectively. The models were irradiated with five fractions of protons or photons using different doses. Post-treatment T1-weighted MRI and histopathological evaluation of the TME was conducted to extract quantitative features. We performed radiomics analysis with leave-one-out cross validation to identify the features most strongly associated with the tumor’s phenotype. Performance was assessed using the area under the curve (AUCValid) and F1-score. Furthermore, we analyzed correlations between TME- and MRI features using the Spearman correlation coefficient ρ.
Results: TME and MRI-derived features showed good performance (AUCValid, TME = 0.72, AUCValid, MRI = 0.85, AUCValid, Combined = 0.85) individual tumor phenotype prediction. We found correlation coefficients of ρ = - 0.46 between hypoxia-related TME features and texture-related MRI features. Tumor volume was a strong confounder for MRI feature expression.
Conclusion: We demonstrated a preclinical radiomics implementation and notable correlations between MRI- and TME hypoxia-related features. Developing additional TME features may help to further unravel the underlying biology.

Permalink: https://www.hzdr.de/publications/Publ-34087
Publ.-Id: 34087


Development of the bioionflotation process using rhamnolipid for metal recovery from industrial wastewaters

Chakankar, M. V.; Oestreich, A.; Pollmann, K.; Rudolph, M.

Recovery of critical metals like Gallium (Ga) from industrial wastewaters helps in resource recycling and reducing environmental burden. Low concentration of target metals and high concentration of unwanted metals makes such a recovery challenging. Ion flotation is a promising separation and recovery process in this regards. However, low selectivity and secondary pollution by used chemicals limits its practical application. Rhamnolipid is microbial biosurfactant having both hydrophilic and hydrophobic moieties. High surface activity and metal complexing ability makes rhamnolipid a molecule of interest for their application in bioionflotation for selective recovery of metals from wastewaters. When applied as a flotation reagent, rhamnolipid plays a dual role of frother and ion collector. Our objective is to provide an insight into the role of rhamnolipid in the process and its efficiency for removal of Ga by bioionflotation. The results of these investigations provide an insight into the process fundamentals and form the basis for development of the bioionflotation process for resource recovery from wastewaters.

Keywords: Rhamnolipid; Bioionflotation; Metal; Wastewater; Gallium

  • Lecture (Conference)
    ACS Spring 2022, 20.-24.03.2022, San Diego, CA, United States of America

Permalink: https://www.hzdr.de/publications/Publ-34086
Publ.-Id: 34086


Significance of pulmonary endothelial injury and the role of cyclooxygenase-2 and prostanoid signaling

Nickl, R.; Hauser, S.; Pietzsch, J.; Richter, T.

The endothelium plays a key role in the dynamic balance of hemodynamic, humoral and inflam-matory processes in the human body. Its central importance and the resulting therapeutic concepts are the subject of ongoing research efforts and form the basis for the treatment of numerous dis-eases. The pulmonary endothelium is an essential component for the gas exchange in humans. Pulmonary endothelial dysfunction has serious consequences for the oxygenation with the poten-tial of consecutive multiple organ failure. Therefore, we provide an overview of pulmonary endo-thelial dysfunction due to viral, bacterial and fungal infections, ventilator induced injury or aspi-ration in a medical context. The elucidation of the underlying causes and mechanisms of damage and repair results in new therapeutic approaches. Specific emphasis is placed on the processes leading to the induction of cyclooxygenase-2 and downstream prostanoid-based signaling path-ways associated with this enzyme.

Keywords: acute respiratory distress; cyclooxygenases; eicosanoids; endothelial permeability; endothelial barrier dysfunction; lung endothelium; lung infection; lung inflammation; prostanoid receptors; traditional non-steroidal anti-inflammatory drugs (tNSAIDs)

Permalink: https://www.hzdr.de/publications/Publ-34085
Publ.-Id: 34085


Improvement of wire-mesh sensor accuracy via adapted circuit design and integrated energy loss measurement

de Assis Dias, F.; Wiedemann, P.; Schleicher, E.; Da Silva, M. J.; Hampel, U.

We reviewed the electronic principles and design of the wire-mesh sensor with respect to inherent energy losses. From the analysis we derived a new circuit design with an optimized amplifier circuit and extended the sensor by an extra transmitter electrode embedded into the dielectric construction material. The latter allows an inherent determination of the energy losses that cannot be suppressed by circuit optimization only. Experimental analysis showed that we achieve an improvement in measurement accuracy with respect to the local and average phase fractions. Deviations in a single crossing point are reduced from more than 30% down to less than 5% and deviations in the average phase fraction are reduced from more than 15% down to less than 2%.

Keywords: wire-mesh sensor; multiphase flow; impedance measurement; energy loss

Permalink: https://www.hzdr.de/publications/Publ-34084
Publ.-Id: 34084


Experimental investigations of hard x-ray source produced by picosecond laser-irradiated solid target

Li, M.-T.; An, H.-H.; Hu, G.-Y.; Xiong, J.; Lei, A.-L.; Xie, Z.-Y.; Wang, C.; Wang, W.; Zhang, Z.-C.; Huang, L.

Measurements of Kα line and bremsstrahlung continuous x-ray emission from high-intensity laser-irradiated thin targets are presented. The experiments were performed at the SG-II UP Petawatt laser. Self-standing Sn foils varying thicknesses and Sn foils backed by the thick substrate were irradiated by the laser pulses up to 300 J of energy with peak intensity higher than 10^18 W/cm^2. A transmission curved crystal spectrometer and a filter-stack spectrometer were used to measure the Kα line and bremsstrahlung x-ray spectral distribution, respectively. Both Kα and 70–200 keV x-ray yields decrease 3- to 5-fold for target backed by the substrate. 2- to 4-fold reduction of Kα and 70–200 keV x-ray yields for the 8.5 μm targets relative to 50 μm targets was observed. Moreover, a significant background x-ray emission generated from the target holder reduces the ratio of signal to noise. Adopting a low-Z material holder can mitigate the x-ray background noises. This study is instructive to optimize target design for the high-intensity laser-driven Kα or continuous x-ray sources.

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Permalink: https://www.hzdr.de/publications/Publ-34083
Publ.-Id: 34083


Collapse of Coherent Large Scale Flow in Strongly Turbulent Liquid Metal Convection

Schindler, F.; Eckert, S.; Zürner, T.; Schumacher, J.; Vogt, T.

The large-scale flow structure and the turbulent transfer of heat and momentum are directly measured in highly turbulent liquid metal convection experiments for Rayleigh numbers varied between $4 \times 10^5$ and $\leq 5 \times 10^9$ and Prandtl numbers of $0.025~\leq~Pr~\leq ~0.033$. Our measurements are performed in two cylindrical samples of aspect ratios $\Gamma =$ diameter/height $= 0.5$ and 1 filled with the eutectic alloy GaInSn. The reconstruction of the three-dimensional flow pattern by 17 ultrasound Doppler velocimetry sensors detecting the velocity profiles along their beamlines in different planes reveals a clear breakdown \FIN{of coherence} of the large-scale circulation for $\Gamma = 0.5$. As a consequence, the scaling laws for heat and momentum transfer inherit a dependence on the aspect ratio. We show that this breakdown of coherence is accompanied with a reduction of the Reynolds number $Re$. The scaling exponent $\beta$ of the power law $Nu\propto Ra^{\beta}$ crosses \FIN{eventually} over from $\beta=0.221$ to 0.124 when the liquid metal flow at $\Gamma=0.5$ reaches $Ra\gtrsim 2\times 10^8$ \FIN{and the coherent large-scale flow is completely collapsed}.

Keywords: Rayleigh-Benard Convection; liquid metal; low Pr; cylinder; Ultrasound Doppler Velocimetry; large scale flow structure

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Permalink: https://www.hzdr.de/publications/Publ-34082
Publ.-Id: 34082


Dynamics of hot refluxing electrons in ultra-short relativistic laser foil interactions

Huang, L.; Molodtsova, M.; Ferrari, A.; Laso García, A.; Toncian, T.; Cowan, T.

We investigate the dynamics of hot refluxing electrons in the interaction of an ultra-short relativistic laser pulse with a thin foil target via particle-in-cell (PIC) simulations, that is governed by the multidimensional spatio-temporal evolution of self-generated sheath field. The comparison of time-integrated energy spectra of refluxing and escaping electrons indicates the refluxing efficiency is higher than 95\% in average for each bounce. The characteristics of wide transverse spatial distribution and energy-resolved angular distribution caused by the refluxing electrons show a direct correlation with the angular-dependent photon yield of Bremsstrahlung emission, as verified by the hybrid simulations of coupling the PIC results with Monte-Carlo particle transport code. We further clarify the energy dissipation mechanisms of refluxing electrons through the recirculation in the thin target under the electron-refluxing dominated regime, and conclude that the self-generated sheath field plays a dominant role over the competing processes such as the radiation loss, collisional stopping and anomalous inhibition via the resistive field. The lifetime of recirculation is calculated to be few hundred femtoseconds, that is one order of magnitude shorter than the time scale of collisional dissipation, while one order of magnitude longer than the laser pulse duration. The results could provide useful insight to understand the hot electron transport and stopping, secondary radiation generation and ion acceleration in the high energy density plasmas.

Keywords: ultra-short relativistic laser pulse; particle-in-cell; refluxing electrons; high energy density plasmas; plasma physics

Permalink: https://www.hzdr.de/publications/Publ-34080
Publ.-Id: 34080


Evolution of Molecular Binding in Mechanically controlled Break-Junctions

Lokamani, M.; Günther, F.; Kelling, J.; Gemming, S.

Mechanically controllable break junctions (MCBJs) are devices, in which the electrical properties of single molecules can be investigated with extreme precision using atomically structured metallic electrodes. The current-voltage (IV) characteristics in such junctions are considerably affected by the binding positions of the anchoring groups on the tip-facets and the configuration of the molecule. Hence, characterizing the electronic transport properties during a single tip-tip opening provides interesting insights in to the tip-molecule interaction.
In this contribution/talk, we present a novel, high-throughput approach to reproduce the time evolution of the electronic transport characteristics. For this, we performed transport calculations using the self-consistent charge scheme of the density-functional-based tight binding (SCC-DFTB)[1] approach and the Green’s function formalism. In particular, we evaluated the energy level E0 and the coupling Γ of the dominating transport channel using the single level model[2]. In contrast to standard approaches, we consider not just one molecule orientation but many thermodynamically relevant configurations. The obtained parameters were averaged using statistical weights obtained from Metropolis simulation considering up to 80.000 different configurations for selected tip-tip distances. The dependence of the averaged quantities with respect to the tip-tip separation reveals characteristic features also observed in experiments for similar molecular systems.
Our approach allows us to relate these features to binding-site and molecule-curvature effects and therefore provides a better interpretation of the experimental results.

1. M. Elstner, D. Porezag, G. Jungnickel, J. Elsner, M. Haugk, T. Frauenheim, S. Suhai, and G. Seifert, Self-consistent-charge density-functional tight-binding method for simulations of complex materials properties, Phys. Rev. B 58, 7260 (1998)
2. Cuevas, J. C.; Scheer, E. In Molecular Electronics: An Introduction to Theory and Experiment; Reed, M., Ed.; World Scientific Series in Nanoscience and Nanotechnology, Vol. 1; World Scientific: Singapore,Hackensack, NJ, 201

Keywords: mechanically controlled break junctions; high-throughput simulations

  • Open Access Logo Lecture (others)
    Seminar Theorie, Modellierung, Simulation https://www.tu-chemnitz.de/physik/TQPS/TheorieSeminar.html, 15.09.2021, Chemnitz, Germany

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Permalink: https://www.hzdr.de/publications/Publ-34079
Publ.-Id: 34079


Forming Federal Communities

Lokamani, M.; Erxleben, F.; Knodel, O.; Juckeland, G.

Forming Federal Communities
Building Research Collaboration Networks

Keywords: Federal Communities; Research Collaboration Networks

  • Open Access Logo Lecture (Conference) (Online presentation)
    TEACH - Talk about Education Across Communities in Helmholtz, 07.-10.12.2021, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-34078
Publ.-Id: 34078


Dynamics of H2 Bubbles Growing at Microelectrodes

Bashkatov, A.; Hossain, S. S.; Yang, X.; Mutschke, G.; Eckert, K.

Recently a new phenomenon of long-lasting position oscillations of hydrogen gas bubbles produced via electrolysis at horizontally installed microelectrodes has been found. The bubbles grow until their detachment when buoyancy exceeds the retarding forces. The phenomenon itself consists in multiple bubble returns to the electrode. It was found that the mother bubble sits on and is fed by a carpet of small bubbles. The dynamics of the growing bubble was systematically studied and found to be strongly dependent on the cathodic potential and electrolyte concentration.

Keywords: electrolysis; hydrogen bubble; oscillations; electric force

  • Lecture (Conference) (Online presentation)
    ISE Annual 72nd meeting, 29.08.-03.09.2021, Jeju Island, Korea
  • Lecture (Conference) (Online presentation)
    The 25th International Congress of Theoretical and Applied Mechanics (25th ICTAM), 22.-27.08.2021, Milano, Italy

Permalink: https://www.hzdr.de/publications/Publ-34077
Publ.-Id: 34077


The QED four – photon amplitudes off-shell: part 1

Ahmadiniaz, N.; Lopez-Arcos, C.; Lopez-Lopez, M. A.; Schubert, C.

The QED four-photon amplitude has been well-studied by many authors, and on-shell is treated in many textbooks. However, a calculation with all four photons off-shell is presently still lacking, despite of the fact that this amplitude appears off-shell as a subprocess in many different contexts, in vacuum as well as with some photons connecting to external fields. The present paper is the first in a series of four where we use the worldline formalism to obtain this amplitude explicitly in terms of hypergeometric functions, and derivatives thereof, for both scalar and spinor QED. The formalism allows us to unify the scalar and spinor loop calculations, to avoid the usual breaking up of the amplitude into three inequivalent Feynman diagrams, and to achieve manifest transversality as well as UV finiteness at the integrand level by an optimized version of the integration-by-parts procedure originally introduced by Bern and Kosower for gluon amplitudes. The full permutation symmetry is maintained throughout, and the amplitudes get projected naturally into the basis of five tensors introduced by Costantini et al. in 1971. Since in many applications of the “four-photon box” some of the photons can be taken in the low-energy limit, and the formalism makes it easy to integrate out any such leg, apart from the case of general kinematics (part 4) we also treat the special cases of one (part 3) or two (part 2) photons taken at low energy. In this first part of the series, we summarize the application of the worldline formalism to the N-photon amplitudes and its relationto Feynman diagrams, derive the optimized tensor-decomposed integrands of the four-photon amplitudes in scalar and spinor QED, and outline the computational strategy tobe followed in parts 2 to 4. We also give an overview of the applications of the four-photon amplitudes, with an emphasis on processes that naturally involve some off-shell photons, either because external fields are involved or we use the amplitude as a building block for higher-order process. The case where all photons are taken at low energy (the “Euler-Heisenberg approximation”) is simple enough to be doable for arbitrary photon numbers,and we include it here for completeness

Keywords: Four-photon amplitude; Worldline formalism; Bern-Kosower formalism

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Permalink: https://www.hzdr.de/publications/Publ-34076
Publ.-Id: 34076


Non-perturbative gauge transformations of arbitrary fermion correlation functions inquantum electrodynamics

Nicasio, J.; Edwards, J. P.; Schubert, C.; Ahmadiniaz, N.

We study the transformation of the dressed electron propagator and the general N-point functions under a change in the covariant gauge of internal photon propagators. We re-establish the well known Landau-Khalatnikov-Fradkin transformation for the propagator and generalise it to arbitrary correlation functions in configuration space, finding that it coincides with the analogous result for scalar fields. We comment on the consequences for perturbative application in momentum-space.

Keywords: LKF transformations; Worldline formalism; Dressed fermion propagator

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Permalink: https://www.hzdr.de/publications/Publ-34075
Publ.-Id: 34075


Color-kinematics duality from the Bern-Kosower formalism

Ahmadiniaz, N.; Balli, F. M.; Lopez-Arcos, C.; Quintero Velez, A.; Schubert, C.

Berends-Giele currents are fundamental building blocks for on-shell amplitudes in non-abelian gauge theory. We present a novel procedure to construct them using the Bern-Kosower formalism forone-loop gluon amplitudes. Applying the pinch procedure of that formalism to a suitable special casethe currents are naturally obtained in terms of multi-particle fields and obeying color-kinematics duality. As a feedback to the Bern-Kosower formalism, we outline how the
multi-particle polarisations and field-strength tensors can be used to significantly streamline the pinch procedure

Keywords: Berends-Giele currents; on-shell amplitudes; Bern-Kosower formalism

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Permalink: https://www.hzdr.de/publications/Publ-34074
Publ.-Id: 34074


Numerical simulation of tidal synchronization of the Large-Scale Circulation in Rayleigh-Bénard Convection with aspect ratio 1

Röhrborn, S.; Jüstel, P.; Galindo, V.; Stefani, F.; Stepanov, R.

A possible explanation for the apparent phase stability of the 11.07-year Schwabe cycle of the solar dynamo was the subject of a series of recent papers [1, 2, 3]. The synchronization of the helicity of an instability with azimuthal wavenumber m=1 by a tidal m=2 perturbation played a key role here. To analyze this type of interaction in a paradigmatic set-up, we study a thermally driven Rayleigh-Bénard Convection (RBC) of a liquid metal under the influence of a tide-like electromagnetic forcing. As shown previously, the time-modulation of this forcing emerges as a peak frequency in the m=2 mode of the radial flow velocity component. In this paper we present new numerical results on the interplay between the Large Scale Circulation (LSC) of a RBC flow and the time modulated electromagnetic forcing.

Keywords: Magnetohydrodynamics; Rayleigh-Bénard convection; liquid metal flow; electromagnetic forcing; CFD

  • Open Access Logo Lecture (Conference)
    RMHD-2021, 20.-22.09.2021, Perm, Russia Federation
  • Open Access Logo Magnetohydrodynamics 58(2022)3, 285-292
    DOI: 10.22364/mhd.58.3.5
    arXiv: 2209.07173

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Permalink: https://www.hzdr.de/publications/Publ-34073
Publ.-Id: 34073


Manifest colour-kinematics duality and double-copy in the string-based formalism

Ahmadiniaz, N.; Balli, F. M.; Corradini, O.; Lopez-Arcos, C.; Quintero Velez, A.; Schubert, C.

The relation for the gravity polarisation tensor as the tensor product of two gluon polarisation vectors has been well-known for a long time, but a version of this relation for multi-particle fields is presently still not known. Here we show that in order for this to happen we first have to ensure that the multi-particle polarisations satisfy color-kinematics duality. In previous work, it has been show that this arises naturally from the Bern-Kosower formalism for one-loop gluon amplitudes, and here we show that the tensor product for multi-particle fields arise naturally in the Bern-Dunbar-Shimada formalism for one-loop gravity amplitudes. This allows us to formulate a new prescription for double-copy gravity Berends-Giele currents,and to obtain both the colour-dressed Yang-Mills Berends-Giele currents in the Bern-Carrasco-Johanssongauge and the gravitational Berends-Giele currents explicitly. An attractive feature of our formalism is that it never becomes necessary to determine gauge transformation terms. Our double-copy prescription can also be applied to other cases, and to make this point we derive the double-copy perturbers for α′-deformed gravity and the bi-adjoint scalar model

Keywords: Bern-Dunbar-Shimada formalism; Berends-Giele currents; color-kinematics duality; gravity amplitudes

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Permalink: https://www.hzdr.de/publications/Publ-34072
Publ.-Id: 34072


Analyzing a modulated electromagnetic m=2 forcing and its capability to synchronize the Large Scale Circulation in a Rayleigh-Bénard cell of aspect ratio Г = 1

Röhrborn, S.; Jüstel, P.; Galindo, V.; Gundrum, T.; Schindler, F.; Stefani, F.; Stepanov, R.; Vogt, T.

The synchronization of the helicity of an instability with azimuthal wavenumber m = 1 by a weak tidal m = 2 perturbation might play a key role in explaining the phase-stable Schwabe cycle of the solar dynamo [1]. In order to elucidate this type of interaction, we study a thermally driven Rayleigh-Bénard Convection (RBC) under a tide-like influence. We focus first on the generation of the m = 2 mode flow by an electromagnetic forcing, and second on its low-frequency modulation. In the last part, we present preliminary results on the interaction of this perturbation with the sloshing/torsional motion of the Large Scale Circulation (LSC) of an RBC flow. While the main focus of the paper is on the numerical side, some comparisons with experimental results are also made.

Keywords: Magnetohydrodynamics; Rayleigh-Bénard convection; liquid metal flow; electromagnetic forcing; CFD

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  • Secondary publication expected from 24.05.2023

Permalink: https://www.hzdr.de/publications/Publ-34071
Publ.-Id: 34071


Worldline master formulas for the dressed electron propagato, part 2: on-shell amplitudes

Ahmadiniaz, N.; Banda Guzman, V. M.; Bastianelli, F.; Corradini, O.; Edwards, J. P.; Schubert, C.

In the first part of this series, we employed the second-order formalism and the“symbol” map to construct a particle path-integral representation of the electron propagator in a background electromagnetic field, suitable for open fermion-line calculations. Its main advantages are the avoidance of long products of Dirac matrices, and its ability to unify whole sets of Feynman diagrams related by permutation of photon legs along the fermion lines. We obtained a Bern-Kosower type master formula for the fermion propagator, dressedwithNphotons, in terms of the “N-photon kernel,” where this kernel appears also in“subleading” terms involving only N−1 of the N-photons.In this sequel, we focus on the application of the formalism to the calculation of on-shell amplitudes and cross-sections. Universal formulas are obtained for the fully polarised matrix elements of the fermion propagator dressed with an arbitrary number of photons, as well as for the corresponding spin-averaged cross-sections. A major simplification of the on-shell case is that the subleading terms drop out, but we also pinpoint other, less obvious simplifications. We use integration by parts to achieve manifest transversality of these amplitudes at the integrand level and exploit this property using the spinor helicity technique. We give a simple proof of the vanishing of the matrix element for all “+” photon helicities in the massless case and find a novel relation between the scalar and spinor spin-averaged cross-sections in the massive case. Testing the formalism on the standard linear Comptonscattering process, we find that it reproduces the known results with remarkable efficiency. Further applications and generalisations are pointed out.

Keywords: On-shell amplitudes; Dressed fermion propagator; Worldline formalism

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Permalink: https://www.hzdr.de/publications/Publ-34069
Publ.-Id: 34069


Sauter-Schwinger effect for colliding laser pulses

Kohlfürst, C.; Ahmadiniaz, N.; Oertel, J.; Schützhold, R.

We study electron-positron pair creation by the electromagnetic field of two colliding laser pulses as described by the vector potential
A(t,r) = [f(ct−x) +f(ct+x)]ey. Employing the world-line instanton technique as well as a generalized WKB approach, we find that the pair creation rate along the symmetry axisx= 0(where one would expect the maximum contribution) displays the same exponential dependence as for a purely time-dependent electric field A(t) = 2f(ct)ey. The pre-factor in front of this exponential does also contain corrections due to focusing or de-focusing effects induced by the spatially inhomogeneous magnetic field. We compare our analytical results to numerical simulations using the Dirac-Heisenberg-Wigner method and find good agreement.

Keywords: Sauter-Schwinger effect; WKB; Worldline instanton; Numerical analysis

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Permalink: https://www.hzdr.de/publications/Publ-34066
Publ.-Id: 34066


Tadpole contribution to magnetic photon-graviton conversion

Ahmadiniaz, N.; Bastianelli, F.; Karbstein, F.; Schubert, C.

Photon-graviton conversion in a magnetic field is a process that is usually studied at tree-level, but the one-loop corrections due to scalars and spinors have also been calculated. Differently from the tree-level process, at one-loop one finds the amplitude to depend on the photon polarization, leading to dichroism. However, previous calculations overlooked tadpole contribution of the type that was considered to be vanishing in QED for decades but erroneously so, as shown by H. Gies and one of the authors in 2016. Here we compute this missing diagram in closed form and show that it does not contribute to dichroism.

Keywords: Photon-Graviton amplitude; Worldline formalism; Tadpole contribution

  • Open Access Logo Contribution to proceedings
    Sixteenth Marcel Grossmann Meeting, 05.-10.07.2021, Virtual meeting, Italy
    Proceedings of the Sixteenth Marcel Grossmann Meeting
  • Open Access Logo Contribution to proceedings
    Sixteenth Marcel Grossmann Meeting, 05.-10.07.2021, Virtual Meeting, Virtual Meeting
    Tadpole contribution to magnetic photon-graviton conversion: WORLD SCIENTIFIC, 978-981-126-976-9, 4393-4400
    DOI: 10.1142/13149
    arXiv: https://arxiv.org/pdf/2111.01980.pdf

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Permalink: https://www.hzdr.de/publications/Publ-34065
Publ.-Id: 34065


Data publication: Bubble Formation from Sub-millimetre Orifices

Mohseni, E.

This is the data used in the thesis "Bubble Formation from Sub-millimetre Orifices".

Keywords: Bubble formation; Sub-millimetre orifice; Bubble dynamics; Modelling; Bubble in-rush; Controlled bubble formation

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Permalink: https://www.hzdr.de/publications/Publ-34063
Publ.-Id: 34063


Bubble Formation from Sub-millimetre Orifices

Mohseni, E.

Efficient contacting of gas and liquid is an important problem in many industrial processes. Examples can be found (bio-) chemical engineering, medicine, water and wastewater treatment among others. To operate these processes in a more efficient manner, usually the gas phase is dispersed into the continuous phase in the form of bubbles. In this case, it is often required to reduce the bubble size to enhance the mass transfer. This is often done by scaling down the opening from which bubbles are generated. Hence, gas bubble generation from sub-millimetre orifices has been an interesting topic in research and technology. The present thesis is an endeavour to bring more physical insights on the mechanism of bubble formation and detachment from sub-millimetre orifices as this phenomenon is not yet well-understood.

Formation of bubbles from a submerged orifice depends on various parameters such as orifice diameter dor, gas flow rate Q, volume of the gas reservoir upstream of the orifice Vc and others. On the basis of these parameters, the bubble growth dynamics, bubbling regime, and bubble volume strongly vary. To further advance the fundamental understanding of the bubble formation at sub-millimetre orifices, two series of experiments were conducted, and the nfluence of the design parameters namely dor, Q, and Vc were investigated in detail. In the experiments, pressurized air is used to generate bubbles in eionized water using stainless-steel orifices in the range of 0.03 mm< dor <1 mm. Based on the findings of these experiments, a mechanism is designed to control the formation process and therefore the bubble volume. Accordingly, in a separate series of experiments, periodic modulations in the gas reservoir is utilised to control the formation and detachment of bubbles from the orifice.

In the first series of experiments, the influence of dor and Q on bubble formation dynamics are investigated. It is observed that the mechanism of bubble formation is not uniform throughout the sub-millimetre range. For orifices with dor > 0.4 mm, the bubble volume Vb progressively increases with both dor and Q. For smaller orifices, however, Vb is determined by the number of subsequent bubbles that merge with the leading bubble after its departure. This is eferred to as in-rush bubbling and it even occurs in the lowest range of Q, at which larger orifices generate bubbles with a single detachment. The bubble formation from orifices with dor < 0.4 mm is highly affected by the gas kinetic energy. Hence, in the balance of forces acting on the bubble, the gas momentum force and the liquid inertia force substantially contribute to the bubble growth rate and therefore Vb.

In the second series of experiments the influence of Vc on bubble formation is investigated. Experimental results showed that, by increasing Vc, the magnitude of the pressure variations in the gas reservoir reduces. Moreover, enlarging the gas reservoir, not only results in a variable gas flux q into the bubble, but also the average gas flux elevates with Vc. Consequently, larger bubbles at lower bubbling frequencies are generated. The impact of Vc on bubble formation for dor < 0.4 mm is, however, limited as the gas kinetic energy readily affects the bubble formation. According to the findings of the first two series of experiments, new models are developed to calculate Vb. The models agree well with experimental results. Moreover, new correlations for bubble detachment are delivered which correlate the non-spherical bubble shape from the observations in the experiments to the spherical bubble volumes calculated from the models.

Last but not least, a control mechanism by means of continuous pressure modulation of the gas phase in the reservoir upstream of the orifice is experimentally investigated. The modulation comes from a loudspeaker, which is mounted in the gas reservoir. The modulation propagates through the pipe to an orifice with a 0.5 mm diameter. Consequently, the onset and termination of the formation process is forced by each successive compression and rarefaction of the acoustic waves. Using the control mechanism, the bubble diameter can be reduced by a factor of four of that generated by uncontrolled formation process. Studying the force balance on the bubble revealed that the detachment of the bubble in the controlled method is determined by the hydrodynamic forces. Moreover, applicability of the Rayleigh-Plesset equation for calculation of the bubble size is examined for the presented bubble generator.

Keywords: Bubble formation; Sub-millimetre orifice; Bubble dynamics; Modelling; Bubble in-rush; Controlled bubble formation

  • Doctoral thesis
    TU Dresden, 2021
    Mentor: Prof. Dr.–Ing. habil. Dr. h.c. Uwe Hampel
    202 Seiten

Permalink: https://www.hzdr.de/publications/Publ-34062
Publ.-Id: 34062


Motion reversals of rising electrogenerated hydrogen bubbles

Bashkatov, A.; Babich, A.; Yang, X.; Boenke, J.; Hossain, S. S.; Mutschke, G.; Eckert, K.

The growth of hydrogen bubbles in water electrolysis is of high practical relevance due to the prominent role of hydrogen in the future energy system. The dynamics even of a single bubble is already multifaceted and is associated with several interdisciplinary phenomena such as Marangoni convection [1, 2], bubble-microlayer interaction [3, 4] and electric forces on the bubbles [4,5].

In this contribution, the dynamics of a single hydrogen bubble was studied during water electrolysis at a horizontal Pt microelectrode in an acidic environment. A new phenomenon was observed. It consists of the ability of already detached hydrogen bubbles, expected to continue buoyant rise, to reverse the direction of motion and to return to the electrode from relatively large distances (350 μm). The phenomenon was systematically studied at different cathodic potentials and electrolyte concentrations by using high-speed microscopic shadowgraphy and electric current measurements.

Acknowledgment
This project is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry of Economics and Technology (BMWi) due to the enactment of the German Bundestag under Grant No. DLR 50WM2058 (project MADAGAS II).

Keywords: Hydrogen evolution; Electrolysis; Microelectrode; Microbubbles

  • Poster (Online presentation)
    18th Multiphase Flow Conference and Short Course, 08.-11.11.2021, Helmholtz-Zentrum Dresden-Rossendorf, Germany

Permalink: https://www.hzdr.de/publications/Publ-34061
Publ.-Id: 34061


MADAGAS II - Untersuchungen zum Einfluss von Marangoni-Konvektion und Doppelschicht-Effekten auf die Ablösung von Gasblasen an Mikroelektroden

Eckert, K.; Mutschke, G.

Für die Energiewende spielen Technologien zur Erzeugung von Wasserstoff aus regenerativen Energiequellen eine wichtige Rolle. Bei der Elektrolyse zur Spaltung von Wasser beeinflusst das Verhalten der entstehenden Wasserstoff- und Sauerstoffblasen ganz wesentlich die Prozesseffizienz. Jedoch ist die Dynamik der Gasblasen noch nicht vollständig verstanden. Erst unlängst wurde in der Literatur auf den möglichen Einfluss kapillarer und elektrischer Kräfte hingewiesen.
In unserem Projekt beschäftigen wir uns im Detail mit der Dynamik von bei der Elektrolyse an Mikroelektroden entstehenden Wasserstoffblasen. Wir untersuchen die auf die Blasen wirkenden elektrischen Kräfte, um diese genauer zu quantifizieren, sowie ebenfalls den Einfluss von Marangonieffekten und Koaleszenzphänomenen. Wir verwenden optische Hochgeschwindigkeits- und elektrochemische Methoden, um die schnelle Dynamik der Blasen in unseren Testzellen zu erfassen, und komplementieren die Untersuchungen mit numerischen Simulationen.
Zur Durchführung der Elektrolyse-Experimente in unseren Testzellen nutzen wir ebenfalls Parabelflüge, bei denen periodisch Phasen der Schwerelosigkeit und der Hypergravitation auftreten. Hierdurch können die genannten Effekte genauer und selektiv untersucht werden, da die Schwerebeschleunigung die Dynamik der Gasblasen wesentlich beeinflusst. Ebenfalls können hierbei Erkenntnisse zur Verbesserung der Ablösung von Gasblasen in Raumfahrt-Anwendungen gewonnen werden.

Keywords: Elektrolyse; Wasserstoff

  • Poster
    1. Mitteldeutscher Wasserstoffkongress und 7. HYPOS-Forum, 02.-04.11.2021, Leuna, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34060
Publ.-Id: 34060


Cellular plasticity upon proton irradiation determines tumor cell radiosensitivity

Schniewind, I.; Hadiwikarta, W. W.; Grajek, J.; Poleszczuk, J.; Richter, S.; Peitzsch, M.; Müller, J.; Klusa, D.; Beyreuther, E.; Löck, S.; Lühr, A.; Frosch, S.; Groeben, C.; Sommer, U.; Krause, M.; Dubrovska, A.; von Neubeck, C.; Kurth, I.; Peitzsch, C.

Novel particle therapy was implemented into standard-of-care for cancer patients during the
last years. However, experimental studies investigating cellular and molecular mechanisms
are lacking and prognostic biomarker are urgently needed. Cancer stem cell
(CSC)-related biomarkers such as aldehyde dehydrogenase (ALDH) are known to cellular radiosensitivity by affecting defense against reactive
oxygen species, DNA damage repair and cell survival. Within a previous study, we found that ionizing radiation itself enriches for
ALDH-positive CSCs.
Within the present study, we investigated CSC marker dynamics in prostate cancer, head and neck cancer and glioblastoma cells upon proton beam irradiation. We found that proton irradiation has an increased CSC targeting potential, reduced methylation of activating histone marks and
a lower induction of cellular senescence compared to conventional photon irradiation. Interestingly, mathematical modeling
indicated to differences in plasticity rates among ALDH-positive CSCs and ALDH-negative cancer cells between the two irradiation types.

Permalink: https://www.hzdr.de/publications/Publ-34059
Publ.-Id: 34059


Reduced Hall carrier density in the overdoped strange metal regime of cuprate superconductors

Putzke, C.; Benhabib, S.; Tabis, W.; Ayres, J.; Wang, Z.; Malone, L.; Licciardello, S.; Lu, J.; Kondo, T.; Takeuchi, T.; Hussey, N. E.; Cooper, J. R.; Carrington, A.

Efforts to understand the microscopic origin of superconductivity in the cuprates are dependent on knowledge of the normal state. The Hall number in the low-temperature, high-field limit nH(0) has a particular importance because, within conventional transport theory, it is simply related to the number of charge carriers, so its evolution with doping gives crucial information about the nature of the charge transport. Here we report a study of the high-field Hall coefficient of the single-layer cuprates Tl2Ba2CuO6+δ (Tl2201) and (Pb/La)-doped Bi2Sr2CuO6+δ (Bi2201), which shows how nH(0) evolves in the overdoped—so-called strange metal—regime of cuprates. We find that nH(0) increases smoothly from p to 1 + p, where p is the number of holes doped into the parent insulating state, over a wide range of doping. The evolution of nH correlates with the emergence of the anomalous linear-in-temperature term in the low-temperature in-plane resistivity. The results could suggest that quasiparticle decoherence extends to dopings well beyond the pseudogap regime.

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Effect of neutron flux on irradiation-induced microstructure and hardening of reactor pressure vessel steel

Ulbricht, A.; Hernández-Mayoral, M.; Oñorbe, E.; Etienne, A.; Radiguet, B.; Hirschmann, E.; Wagner, A.; Hein, H.; Bergner, F.

Existing knowledge about the effect of neutron irradiation on the mechanical properties of reac-tor pressure vessel steels under reactor service conditions relies to a large extent on accelerated irradiations realized by exposing steel samples to a higher neutron flux. A deep understanding of flux effects is, therefore, vital for gaining service-relevant insight on the mechanical property degradation. Existing studies on flux effects often suffer from incomplete descriptions of the ir-radiation-induced microstructure. Our study aims at giving a detailed picture of irradia-tion-induced nanofeatures by applying complementary methods using atom probe tomography, positron annihilation, small-angle neutron scattering and transmission electron microscopy. The characteristics of the irradiation-induced nanofeatures and the dominant factors responsible for the observed increase of Vickers hardness are identified. The results rationalize why pronounced flux effects on the nanofeatures, in particular on solute atom clusters, only give rise to small or moderate flux effects on hardening.

Keywords: reactor pressure vessel steel; neutron irradiation; flux effect; microstructure; atom probe tomography; positron annihilation spectroscopy; small-angle neutron scattering; TEM

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Permalink: https://www.hzdr.de/publications/Publ-34055
Publ.-Id: 34055


Stretchable Printed Magnetic Sensors Based on Giant Magnetoresistive Microflakes for On-Skin Electronic Interfaces

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

On-demand fabrication of electronic devices is expected to be enabled by high throughput printing technologies1. Due to the simplified processing, printing is particularly attractive for flexible and stretchable electronics that are typically fabricated over polymeric soft substrates2. Wide research efforts are directed towards the development of conductive pastes with reliable electrical and mechanical properties.

Sensing pastes able to detect external stimuli are central for the operation of on-skin electronic interfaces. Among others, magnetic sensors are less prone to mechanical failure due to their touchless nature3. Solution processable pastes for magnetic sensing typically consist of composites of magnetoresistive micro- or nanoparticles embedded in polymeric binders4-7. Despite the research progress on printable magnetic sensors, until now there were no reports of printed magnetic sensors showing stable response after typical skin deformations: bending and stretching.

Here, we will show the fabrication and implementation of skin-compliant printed magnetic field sensors. These rely on microflakes obtained from a giant magnetoresistive (GMR) multilayer [Py/Cu]30 stacks. The microflakes were embedded on a poly(styrene-butadiene-styrene) copolymer (SBS) matrix that enables stretchability and high adherence properties. The stretchable printed magnetic sensors were obtained after dispensing the GMR paste over an ultrathin (3-µm-thick) Mylar substrate. We demonstrated stable sensing and mechanical performance even at 100% strain and 16 µm bending deformations, representing two orders of magnitude of performance enhancement with respect to previous works. The obtained sensors showed maximum sensitivity at 0.88 mT, which is compatible with the 40 mT safety threshold established by the World Health Organization7. These characteristics enabled a safe and conformal integration of the sensor for on-skin interactive electronics applications. We showed the use of the printed sensor platform for navigating through documents and digital maps. We foresee that the future development of this technology for user-specific fabrication of human-machine touchless interfaces with task-specific capabilities and integration8.
1 J.S. Chang, A.F. Facchetti and R. Reuss., IEEE Trans. Emerg. Sel. Topics Circuits Syst., Vol. 7, p.7 (2017)
2 Q. Huang and Yong Zhu., Adv Mater. Technol., Vol. 4, p.1800546 (2019)
3 S. Zuo, H. Heidari and D. Farina. Adv Mater. Technol., Vol. 5, p.2000185 (2020)
4 D. Karnaushenko, D. Makarov and M. Stöber, Adv. Mater., Vol.27, p.880 (2015)
5 J. Meyer, T. Rempel and M. Schäfers, Smart Mater. Struct., Vol. 22, p.025032 (2013)
6 B. Cox, D. Davis, N. Crews, Sens. Actuators, A, Vol. 203, p.335 (2013)
7 E.S. Oliveros Mata, G.S. Cañón Bermúdez and M. Ha,. Appl. Phys. A, Vol. 127, p.280 (2021)
8 Static Fields. World Health Organization. (2006)
9 M. Ha, E.S. Oliveros Mata and G. S. Cañón Bermúdez, Adv. Mater. Vol. 33, p.2005521 (2021)

  • Lecture (Conference)
    2022 Joint MMM-Intermag Conference, 10.-14.01.2022, New Orleans, United States

Permalink: https://www.hzdr.de/publications/Publ-34054
Publ.-Id: 34054


Printable Magnetoresistive Sensors for On-Skin Interactive Electronics

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

Ultra-portable, imperceptible[1], and shapeable[2] devices are expected to be widespread due to the emergence of flexible electronics as an industrial technology. Printing is an affordable and high throughput method to process electronics in soft substrates that is still to be optimized to deliver electrically and mechanically reliable electronic devices[3].

In particular, printable magnetoresistive pastes have been developed as an alternative single-step fabrication method to obtain magnetic field sensors [4]. These pastes usually consist of composites of magnetic particles embedded in a non-magnetic matrix[5,6]. Particle-based pastes can achieve large magnetoresistance ratios at the expense of high resistivity and noise levels[5-7]. We previously reported magnetoresistive pastes based on microflakes as an alternative to overcome the problems presented in particle-based pastes[8,9]. Magnetoresistive flakes were produced after the delamination of thin-film stacks from a deposited sacrificial layer. With this technology, it was showed that flakes-based Co/Cu printed sensors exhibit low resistance and 37% GMR response at moderate magnetic fields (500 mT)[9].

Despite the advances in printable magnetic sensors, there are no reports of systems that show good sensitivity at low magnetic fields relevant for safe integration into consumer and wearable electronics. Electronics with magnetic components have to perform below the WHO limit of continuous exposure to magnetic fields (<40mT) to comply with this health standard[10]. Especially for on-skin electronics that experience considerable strain, there are not examples of magnetic printed sensors that deliver steady sensing behaviour after stretching.

Here, we will present low-noise printable magnetic field sensors sensitive down to sub-mT, which are mechanically stretchable after printing. We demonstrate the fabrication of printable sensors in ultrathin foils (3-μm-thick Mylar) based on magnetoresistive pastes that can undergo 100 % strain and 16 μm bending radius maintaining stable sensing and mechanical performance. The pastes are composites of poly(styrene-butadiene-styrene) copolymer (SBS) with embedded magnetoresistive microflakes. Using [Py/Cu]30 and [Ta/Py] flakes, we obtained printed giant (GMR)[11] and anisotropic (AMR)[12] magnetoresistive-based sensors, respectively. We address the key role of SBS to enable an enhancement of two orders of magnitude improvement in bendability and sensitivity at low magnetic fields.

Due to the good performance at low fields, reduced noise levels and high compliance, we will show the direct lamination of the printed sensors as an on-skin interactive device for scrolling through documents or digital maps. We envision that the proposed magnetic sensors will enable printing on-demand utilities for physical activity tracking systems or human-machine interfaces that can improve and even expand our sensing capabilities.

[1] M. Melzer et al., Nat. Commun. 6, 6080 (2015)
[2] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)
[3] Q. Huang et al., Adv. Mater. Technol. 4, 1800546 (2019)
[4] D. Makarov et al., ChemPhysChem 14, 1771 (2013)
[5] J. Meyer et al., Smart Mater. Struct. 22, 025032 (2013)
[6] J. L. Mietta et al., Langmuir 28, 6985 (2012)
[7] L. Ding et al., ACS Appl. Mater. Interfaces 12, 20955 (2020)
[8] D. Karnaushenko et al., Adv. Mater. 24, 4518 (2012)
[9] D. Karnaushenko et al., Adv. Mater. 27, 880 (2015)
[10] World Health Organization, Static fields (2006)
[11] M. Ha et al., (2020) [Submitted]
[12] E. S. Oliveros Mata et al., (2020) [Submitted]

  • Lecture (Conference) (Online presentation)
    2021 MRS Spring Meeting and Exhibit, 17.-23.04.2021, Seatle, United States

Permalink: https://www.hzdr.de/publications/Publ-34053
Publ.-Id: 34053


Supervised folding of origami soft actuators enabled by magnetic e-skins

Oliveros Mata, E. S.; Ha, M.; Canon Bermudez, G. S.; Liu, J. A.-C.; Evans, B. A.; Tracy, J. B.; Makarov, D.

Reconfigurable[1], soft[2], and lightweight[3] actuators are expected to be implemented in robotic systems biomimicking the multifunctional and adaptive capabilities of living organisms. The integration of sensing elements in soft actuators enables smart motion events increasing reliability, efficiency, and safe integration in diverse environments[4]. Specifically, for origami-based systems[5], the tracking of the orientation and the readiness of the folding is important to achieve reliable assembly of the structures.
Integration of sensing elements with soft actuators is typically addressed with stimuli-responsive materials[6] and commercial sensors[7] that lack feedback capabilities and high compliancy, respectively. Recent approaches measuring strain[8], curvature[9], and optical[10] signals have been demonstrated for localized single folding in soft actuators. Until recently, there were no reports of an onboard sensing platform that enables the folding of multiple flaps as needed for origami.
Here, we will show the integration of flexible e-skins on magnetic actuators for supervision of the sequence and folding assembly of hinges defined on the fly. Highly compliant magnetic sensors (GMR and Hall effect) were laminated into ultrathin magnetic origami actuators enabling the detection of the readiness for actuation, the orientation, and the hinge folding process. The actuator, a magnetic composite based on a shape memory polymer with embedded NdFeB microparticles, actuates during a light softening and magnetic stimuli sequence[11]. We optimized the thickness (60 µm) and composition (NdFeB - 40 wt%) of the composite to achieve the 180 deg basic fold for origami structures. The capabilities of the system with laminated sensing e-skin were demonstrated after self-guided assembly of the origami platform with multiple hinges into box- and boat-like layouts[12]. We envision that further development of alike self-supervised systems will bring closer the realization of adaptive mechatronic soft systems for different environments and even remote applications.

[1] H. Song et al., Nano Lett. 20, 5185 (2020)
[2] Y.F. Zhang et al., Adv. Func. Mater. 29, 1806698 (2019)
[3] C. Lu et al., Materials 13, 656 (2020)
[4] S. Cheng et al., Adv. Mater. Interfaces 6, 1900985 (2019)
[5] M. Taghavi et al., Sci. Robot. 3, (2018)
[6] L. Hines et al., Adv. Mater. 29, 1603483 (2017)
[7] M. Salerno et al., Sens. Actuators, A 265, 70 (2017)
[8] S. Mousavi et al., ACS App. Mater. Interfaces 12, 15631 (2020)
[9] A. Koivikko et al., IEEE Sens. J. 18, 223 (2018)
[10] C. Wang et al., Adv. Mater. 30, 1706695 (2018)
[11] J. A.-C. Liu et al., Sci. Adv. 5, eaaw2897 (2019)
[12] M. Ha, E.S. Oliveros Mata et al., Adv. Mater. 2008751 (2021)

  • Lecture (Conference) (Online presentation)
    2021 MRS Fall Meeting and Exhibition, 06.-08.12.2021, Boston, United States

Permalink: https://www.hzdr.de/publications/Publ-34052
Publ.-Id: 34052


Stretchable Printed Giant Magnetoresistive Sensors for On-Skin Interactive Electronics

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

Printed electronics are expected to be implemented as a set of industrial technologies that will facilitate the on-demand fabrication of imperceptible[1] and shapeable[2] devices. Conductive pastes are typically composed of polymeric matrices with embedded conductive fillers. The properties of the fillers can be exploited to deliver functional devices as printed transistors[3], displays[4] and sensors[5]. The smart integration of such elements will allow task-specific integration in consumer electronics and even personalized wearable devices.
Aiming to develop on-skin printed interfaces, it is necessary to ponder mechanical, performance, and health safety considerations. Integrating magnetic sensors on interactive platforms is attractive due to their touchless, action-at-distance nature, which increases the reliability of the devices[6]. In the past, solution processable magnetic field sensors have been fabricated from composite pastes embedding magnetic particles. Among the previous reports on printable magnetic sensors, there are not examples of devices able to maintain high performance sensing during usual skin deformations[7]. Concomitantly, there is a lack of research on skin-compliant printed magnetic sensors able to perform below the 40 mT safety continuous exposure threshold established by the World Health Organization[8].
Here, we will present the fabrication and implementation of stretchable printed magnetic field sensors. They are based on composite pastes with embedded flakes of [Py/Cu]30 Giant Magnetoresistance (GMR) thin-film stacks. We demonstrated printed GMR sensors on ultrathin (3-µm-thick Mylar) foils which are skin compliant, and with maximum sensitivity at 0.88 mT. The stretchable sensors maintained stable sensing performance at 16 µm bending radius and 100 % strain which corresponds to two orders of magnitude increase with respect to previous reports. We demonstrate the implementation of the technology on interactive applications after laminating the printed sensors on the user's skin to navigate through digital maps and scroll through text documents. The ability of the sensor to comply with the skin creases and deformations, and to detect field changes in the safe threshold limit, place this technology as a prospective method for fabricating on-demand printed human-machine interfaces[9].

[1] M. Melzer et al., Nat. Commun. 6, 6080 (2015)
[2] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)
[3] J.A. Lim et al., Adv. Func. Mater. 20, 3292 (2010)
[4] S. Cho et al. ACS Appl. Mater. Interfaces 9, 44096 (2017)
[5] X. Wang et al. ACS Appl. Mater. Interfaces 10, 7371 (2018)
[6] P. Makushsko et al., Adv. Func. Mater, 2101089 (2021)
[7] E.S. Oliveros Mata, et al. Appl. Pys. A 127, 280 (2021)
[8] Static Fields. World Health Organization. (2006)
[9] M. Ha, E.S. Oliveros Mata, et al. Adv. Mater. 33, 2005521 (2021)

  • Lecture (Conference) (Online presentation)
    2021 MRS Fall Meeting and Exhibit, 06.-08.12.2021, Boston, United States

Permalink: https://www.hzdr.de/publications/Publ-34051
Publ.-Id: 34051


Gezieltes Herauslösen von Substanzen aus Roh-und Reststoffen mit biologisch basierten Aufbereitungstechnologien Identifizierung und Verwendung von Material spezifischen Biomaterialien in der Ressourcenrückgewinnung

Lederer, F.

Gezieltes Herauslösen von Substanzen aus Roh-und Reststoffen mit biologisch basierten Aufbereitungstechnologien
Identifizierung und Verwendung von Material spezifischen Biomaterialien in der
Ressourcenrückgewinnung

Keywords: Biotechnologie; Biolaugung; Bioflotation; Biokollekt

  • Invited lecture (Conferences) (Online presentation)
    Vorlesung Gezieltes Herauslösen von Substanzen aus Roh-und Reststoffen, 17.01.2022, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-34050
Publ.-Id: 34050


Generation of arbitrarily polarized GeV lepton beams via nonlinear Breit-Wheeler process

Xue, K.; Guo, R.-T.; Wan, F.; Shaisultanov, R.; Chen, Y.-Y.; Xu, Z.-F.; Ren, X.-G.; Hatsagortsyan, K. Z.; Keitel, C. H.; Li, J.-X.

Generation of arbitrarily spin-polarized lepton (here refer in particular to electron and positron) beams has been investigated in the single-shot interaction of high-energy polarized γ photons with an ultraintense asymmetric laser pulse via nonlinear Breit-Wheeler (BW) pair production. We develop a fully spin-resolved semi-classical Monte Carlo method to describe the pair creation and polarization in the local constant field approximation. In nonlinear BW process the polarization of created pairs is simultaneously determined by the polarization of parent γ photons, the polarization and asymmetry of scattering laser field, due to the spin angular momentum transfer and the asymmetric spin-dependent pair production probabilities, respectively. In considered all-optical method, dense GeV lepton beams with average polarization degree up to about 80% (adjustable between the transverse and longitudinal components) can be obtained with currently achievable laser facilities, which could be used as injectors of the polarized e+e− collider to search for new physics beyond the Standard Model.

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Publ.-Id: 34049


Photon polarization effects in polarized electron-positron pair production in a strong laser field

Dai, Y.-N.; Shen, B.-F.; Li, J.-X.; Shaisultanov, R.; Hatsagortsyan, K. Z.; Keitel, C. H.; Chen, Y.-Y.

Deep understanding of the impact of photon polarization on pair production is essential for the efficient generation of laser-driven polarized positron beams and demands a complete description of polarization effects in strong-field QED processes. Employing fully polarization-resolved Monte Carlo simulations, we investigate correlated photon and electron (positron) polarization effects in the multiphoton Breit–Wheeler pair production process during the interaction of an ultrarelativistic electron beam with a counterpropagating elliptically polarized laser pulse. We show that the polarization of e−e+ pairs is degraded by 35% when the polarization of the intermediate photon is resolved, accompanied by an ∼13% decrease in the pair yield. Moreover, in this case, the polarization direction of energetic positrons at small deflection angles can even be reversed when high-energy photons with polarization parallel to the laser electric field are involved.

  • Open Access Logo Matter and Radiation at Extremes 7(2022), 014401
    Online First (2021) DOI: 10.1063/5.0063633

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Publ.-Id: 34048


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