Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34730 Publications

Magnetische Kühlung

Gottschall, T.

es hat keine aussagefähiges Abstract vorgelegen

  • Lecture (others)
    Seniorenakademie der TU Dresden, 15.09.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32093
Publ.-Id: 32093


Advanced characterization of multicaloric materials in pulsed magnetic fields

Gottschall, T.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    JEMS 2020, 07.12.2020, Lissabon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-32092
Publ.-Id: 32092


Dynamics of Rising Bubbles in a Quiescent Slag Bath with Varying Thermo-Physical Properties

Reuter, M. A.; Obiso, D.; Schwittala, D. H.; Korobeinikov, I.; Meyer, B.; Richter, A.

The motion of bubbles in a liquid slag bath with temperature gradients is investigated by means of 3D fluid dynamic computations. The goal of the work is to describe the dynamics of the rising bubbles, taking into account the temperature dependency of the thermo-physical properties of the slag. Attention is paid to the modeling approach used for the slag properties and how this affects the simulation of the bubble motion. In particular, the usage of constant values is compared to the usage of temperature-dependent data, taken from models available in the literature and from in-house experimental measurements. Although the present study focuses on temperature gradients, the consideration of varying thermo-physical properties is greatly relevant for the fluid dynamic modeling of reactive slag baths, since the same effect is given by heterogeneous species and solid fraction distributions. CFD is applied to evaluate the bubble dynamics in terms of the rising path, terminal bubble shape, and velocity, the gas–liquid interface area, and the appearance of break-up phenomena. It is shown that the presence of a thermal gradient strongly acts on the gas–liquid interaction when the temperature-dependent properties are considered. Furthermore, the use of literature models and experimental data produces different results, demonstrating the importance of correctly modeling the slag’s thermo-physical properties.

Keywords: rising bubbles; liquid slag

Permalink: https://www.hzdr.de/publications/Publ-32091
Publ.-Id: 32091


Thermoelectric Performance of the Half-Heusler Phases RNiSb (R = Sc, Dy, Er, Tm, Lu): High Mobility Ratio between Majority and Minority Charge Carriers

Ciesielski, K.; Synoradzki, K.; Veremchuk, I.; Skokowski, P.; Szymanski, D.; Grin, Y.; Kaczorowski, D.

Deeper understanding of electrical and thermal transport is critical for further development of thermoelectric materials. Here we describe the thermoelectric performance of a group of rare-earth-bearing half-Heusler phases determined in a wide temperature range. Polycrystalline samples of ScNiSb, DyNiSb, ErNiSb, TmNiSb, and LuNiSb are synthesized by arc melting and densified by spark plasma sintering. They are characterized by powder x-ray diffraction and scanning electron microscopy. The physical properties are studied by means of heat-capacity and Hall-effect measurements performed in the temperature range from 2 to 300 K, as well as electrical-resistivity, Seebeck-coefficient, and thermal-conductivity measurements performed in the temperature range from 2 to 950 K. All the materials except TmNiSb are found to be narrow-gap intrinsic p-type semiconductors with rather light charge carriers. In TmNiSb, the presence of heavy holes with large weighted mobility is evidenced by the highest power factor among the series (17 mu W K-²cm(-¹) at 700 K). The experimental electronic relaxation time calculated with the parabolic band formalism is found to range from 0.8 x 10(-¹⁴) to 2.8 x 10(-¹⁴) s. In all the materials studied, the thermal conductivity is between 3 and 6 W m(-¹) K-¹ near room temperature (i.e., smaller than in other pristine d-electron half-Heusler phases reported in the literature). The experimental observation of the reduced thermal conductivity appears fully consistent with the estimated low sound velocity as well as strong point-defect scattering revealed by Debye-Callaway modeling. Furthermore, analysis of the bipolar contribution to the measured thermal conductivity yields abnormally large differences between the mobilities of n-type and p-type carriers. The latter feature makes the compounds examined excellent candidates for further optimization of their thermoelectric performance via electron doping.

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Permalink: https://www.hzdr.de/publications/Publ-32088
Publ.-Id: 32088


Discovery of high-performance thermoelectric copper chalcogenide using modified diffusion-couple high-throughput synthesis and automated histogram analysis technique

Deng, T.; Xing, T.; Brod, M. K.; Sheng, Y.; Qiu, P.; Veremchuk, I.; Song, Q.; Wei, T.-R.; Yang, J.; Snyder, G. J.; Grin, Y.; Chen, L.; Shi, X.

Discovery of novel high-performance materials with earth-abundant and environmentally friendly elements is a key task for civil applications based on advanced thermoelectric technology. Advancements in this area are greatly limited by the traditional trial-and-error method, which is both time-consuming and expensive. The materials genome initiative can provide a powerful strategy to screen for potential novel materials using high-throughput calculations, materials characterization, and synthesis. In this study, we developed a modified diffusion-couple high-throughput synthesis method and an automated histogram analysis technique to quickly screen high-performance copper chalcogenide thermoelectric materials, which has been well demonstrated in the ternary Cu-Sn-S compounds. A new copper chalcogenide with the composition of Cu₇Sn₃S₁₀ was discovered. Studies on crystal structure, band gap, and electrical and thermal transport properties were performed to show that it is a promising thermoelectric material with ultralow lattice thermal conductivity, moderate band gap, and decent electrical conductivity. Via Cl doping, the thermoelectric dimensionless figure of merit zT reaches 0.8 at 750 K, being among the highest values reported in Cu-Sn-S ternary materials. The modified diffusion-couple high-throughput synthesis method and automated histogram analysis technique developed in this study also shed light on the development of other advanced thermoelectric and functional materials.

Keywords: ultralow thermal conductivity; ternary; scattering; sulfides; Cu₂SnS₃; model

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  • Secondary publication expected from 30.07.2021

Permalink: https://www.hzdr.de/publications/Publ-32087
Publ.-Id: 32087


Robust Fermi-Surface Morphology of CeRhIn5 across the Putative Field-Induced Quantum Critical Point

Mishra, S.; Hornung, J.; Raba, M.; Klotz, J.; Förster, T.; Harima, H.; Aoki, D.; Wosnitza, J.; McCollam, A.; Sheikin, I.

We report a comprehensive de Haas–van Alphen (dHvA) study of the heavy-fermion material CeRhIn5 in magnetic fields up to 70 T. Several dHvA frequencies gradually emerge at high fields as a result of magnetic breakdown. Among them is the thermodynamically important β1 branch, which has not been observed so far. Comparison of our angle-dependent dHvA spectra with those of the non-4f compound LaRhIn5 and with band-structure calculations evidences that the Ce 4f electrons in CeRhIn5 remain localized over the whole field range. This rules out any significant Fermi-surface reconstruction, either at the suggested nematic phase transition at B* ≈ 30 T or at the putative quantum critical point at Bc ≃ 50 T. Our results rather demonstrate the robustness of the Fermi surface and the localized nature of the 4f electrons inside and outside of the antiferromagnetic phase.

Permalink: https://www.hzdr.de/publications/Publ-32086
Publ.-Id: 32086


Ternary MIn₂S₄ (M = Mn, Fe, Co, Ni) Thiospinels - Crystal Structure and Thermoelectric Properties

Wyzga, P.; Veremchuk, I.; Bobnar, M.; Hennig, C.; Leithe-Jasper, A.; Gumeniuk, R.

A combined structural, magnetic and thermoelectric study of polycrystalline ternary MIn₂S₄ (M = Mn, Fe, Co, Ni) thiospinels is presented. All compounds crystallize with MgAl₂O₄-type structure. Rietveld refinement analysis confirmed that the preferred crystallographic position of transition metal element changes from mainly tetrahedral 8a for Mn to exclusively octahedral 16d for Ni (i.e. increase of the inversion parameter). Magnetic susceptibility measurements revealed M-elements to possess 2+ oxidation state in MIn₂S₄. All these compounds order antiferromagnetically with Neel temperatures T-N ranging from 5-13 K. The studied thiospinels are n-type semiconductors with large values of electrical resistivity rho > 0.6 omega center dot m at room temperature. An increase of the inversion parameter leads to a reduction of the determined activation energies, as well as to a more disorder-like behavior of thermal conductivity. The highest thermoelectric Figure of merit ZT was observed for MIn₂S₄ with M = Fe, Ni, which adopt inverse spinel structure.

Keywords: Solid-phase synthesis; Spinel phases; Sulfur; X-ray diffraction; Thermoelectric perfomance; Tetrahedral site

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  • Secondary publication expected from 17.02.2021

Permalink: https://www.hzdr.de/publications/Publ-32084
Publ.-Id: 32084


Magnetoelastic study on the frustrated quasi-one-dimensional spin-1/2 magnet LiCuVO4

Miyata, A.; Hikihara, T.; Furukawa, S.; Kremer, R. K.; Zherlitsyn, S.; Wosnitza, J.

We investigated the magnetoelastic properties of the quasi-one-dimensional spin-1/2 frustrated magnet LiCuVO4. Longitudinal-magnetostriction experiments were performed at 1.5 K in high magnetic fields of up to 60 T applied along the b axis, i.e., the spin-chain direction. The magnetostriction data qualitatively resemble the magnetization results, and saturate at Hsat ≈ 54 T, with a relative change in sample length of ΔL/L ≈ 1.8 × 10−4. Remarkably, both the magnetostriction and the magnetization evolve gradually between Hc3 ≈ 48 T and Hsat, indicating that the two quantities consistently detect the spin-nematic phase just below the saturation. Numerical analyses for a weakly coupled spin-chain model reveal that the observed magnetostriction can overall be understood within an exchange-striction mechanism. Small deviations found may indicate nontrivial changes in local correlations associated with the field-induced phase transitions.

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Permalink: https://www.hzdr.de/publications/Publ-32083
Publ.-Id: 32083


Tuning of ferromagnetic behavior of GaN films by N ion implantation: an experimental and first principle-based study

Singh, P.; Ghosh, S.; Mishra, V.; Barman, S.; Barman, S. R.; Singh, A.; Kumar, S.; Li, Z.; Kentsch, U.; Srivastava, P.

Magnetic properties of N-ion implanted GaN films (150 nm) have been reported. It is found that GaN films grown by the MOCVD technique show strong room temperature ferromagnetic behavior, which can be tuned by implanting N-ions at different fluences (1×10¹⁵ to 5×10¹⁶ ions- cm⁻²). Presence of implanted N at interstitial sites of the GaN host matrix is indicated from the strain observed in GaN by analysis of XRD data. PL spectra show presence of different types of defects in the as deposited film and engineering of defects after N-ion implantation. XPS spectra of Ga 3d-core level and valence band reveal the bonding of implanted N with the host Ga and/or N. The origin of ferromagnetic behavior is ascribed to unpaired electrons created at N sites due to Ga vacancies. First principle-based calculations also confirm ferromagnetism due to Ga vacancies and the reduction of magnetic behavior in Ga deficient GaN with N-ion implantation at interstitial site. The systematic reduction in the saturation magnetic moment value after N-ion implantation is explained on the basis of pairing of the unpaired electrons due to the bond formation of interstitial N with Ga and N present in the host matrix.

Keywords: ion implantation; defects; ferromagnetism; nitrogen interstitials; tuning

Permalink: https://www.hzdr.de/publications/Publ-32080
Publ.-Id: 32080


Magnetic Refrigeration: From material to application

Gottschall, T.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences)
    31. Edgar Lüscher Seminar, 09.02.2020, Klosters, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-32079
Publ.-Id: 32079


Recent progress and future projects at HLD and LNCMI - Toulouse

Miyata, A.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    The 16th Japanese High Magnetic Field Forum, 03.12.2020, Tuhoku, Japan

Permalink: https://www.hzdr.de/publications/Publ-32078
Publ.-Id: 32078


Magnetoelastic coupling in frustrated magnets: The cases of LiCuVO4 and MnCr2S4

Miyata, A.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    ARHMF 2020 and KINKEN Materials Science School 2020 for Young Scientists, 02.12.2020, Tohoku, Japan

Permalink: https://www.hzdr.de/publications/Publ-32076
Publ.-Id: 32076


Pressure-tuned magnetic interactions in the triangular-lattice Quantum antiferromagnet Cs2CuCl4

Zvyagin, S.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    ARHMF 2020 and KINKEN Materials Science School 2020 for Young Scientists, 01.-03.12.2020, Tohoku, Japan

Permalink: https://www.hzdr.de/publications/Publ-32075
Publ.-Id: 32075


Spin dynamics in low-D spin systems: high-field ESR

Zvyagin, S.

es lag kein aussagefähiges Abstract vor

  • Invited lecture (Conferences) (Online presentation)
    Workshop on Neutrons and Complementary Techniques for Quantum Materials, 18.-21.08.2020, Oak Ridge, USA

Permalink: https://www.hzdr.de/publications/Publ-32073
Publ.-Id: 32073


Shaken and stirred: When Bond meets Suess-de Vries and Gnevyshev-Ohl

Stefani, F.; Stepanov, R.; Weier, T.

We argue that the most prominent temporal features of the solar dynamo, in particular the Hale cycle, the Suess de Vries cycle (associated with variations of the Gnevyshev-Ohl rule), Gleissberg-type cycles, and grand minima can be self-consistently explained by double synchronization with the 11.07-years periodic tidal forcing of the Venus-Earth-Jupiter system and the (mainly) 19.86-years periodic motion of the Sun around the barycenter of the solar system. In our numerical simulation, grand minima, and clusters thereof, emerge as intermittent and non periodic events on millennial time scales, very similar to the series of Bond events which were observed throughout the Holocene and the last glacial period. If confirmed, such an intermittent transition to chaos would prevent any long-term prediction of solar activity, notwithstanding the fact that the shorter-term Hale and Suess-de Vries cycles are clocked by planetary motion.

Keywords: solar cycle

  • Invited lecture (Conferences) (Online presentation)
    Virtual Nordic Dynamo Seminar, 15.09.2020, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-32072
Publ.-Id: 32072


Schwabe, Gleissberg, Suess-de Vries: Towards a consistent model of planetary synchronization of solar cycles

Stefani, F.; Giesecke, A.; Seilmayer, M.; Stepanov, R.; Weier, T.

Aiming at a consistent planetary synchronization model of both short-term and long-term solar cycles, we start with an analysis of Schove’s historical data of cycle maxima. Their deviations (residuals) from the average cycle duration of 11.07 years show a high degree of regularity, comprising a dominant 200 year period (Suess-de Vries cycle), and a few periods around 100 years (Gleissberg cycle). Encouraged by their robustness, we support previous forecasts of an upcoming grand minimum in the 21st century. To explain the long-term cycles, we enhance our tidally synchronized solar dynamo model by a modulation of the field storage capacity of the tachocline with the orbital angular momentum of the Sun, which is dominated by the 19.86-year periodicity of the Jupiter–Saturn synodes. This modulation of the 22.14-year Hale cycle leads to a 193-year beat period of dynamo activity which is indeed close to the Suess-de Vries cycle. For stronger dynamo modulation, the model produces additional peaks at typical Gleissberg frequencies, which seem to be explainable by the non-linearities of the basic beat process, leading to a bi-modality of the Schwabe cycle. However, a complementary role of beat periods between the Schwabe cycle and the Jupiter–Uranus/Neptune synodic cycles cannot be completely excluded.

Keywords: solar cycle

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  • Secondary publication expected from 28.09.2021

Permalink: https://www.hzdr.de/publications/Publ-32071
Publ.-Id: 32071


Evolution of a strong electrovortex flow in a cylindrical cell

Kolesnichenko, I.; Frick, P.; Eltishchev, V.; Mandrykin, S.; Stefani, F.

The mechanism of poloidal flow suppression in an electrovortex flow (EVF) is verified in a liquid metal experiment and supported by numerical simulations. Beyond a certain threshold of azimuthal forcing, a strong poloidal EVF flow develops only transiently, before the centrifugal forces of the slowly generated swirl compensate the EVF-driving forces. This result shows that EVFs can become of particular importance in large-scale liquid metal batteries, especially during the switch-on regime when the transient poloidal flows can be up to two orders of magnitude stronger than those expected in the saturated regime.

Keywords: electrovortex flow

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-32070
Publ.-Id: 32070


Overview of mico- and millifluidic prototyping and sensing approaches

Schütt, J.; Makarov, D.

Kick-Off Präsentation des HZDRs im Zuge des Projektstarts. Angesprochene Themengebiete umfassen die aktuellen und zukünftigen Arbeitsgebiete der Arbeitsgruppe "Fluid Sensorics".

Keywords: Fluidic Sensorics; SiNW FETs; Nano-capacitors; Planar Hall Effect Sensors

  • Lecture (others) (Online presentation)
    Initial Scientific Meeting, 12.11.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32069
Publ.-Id: 32069


Using Diffuse Scattering to Observe X-Ray-Driven Nonthermal Melting

Hartley, N.; Grenzer, J.; Huang, L.; Inubushi, Y.; Kamimura, N.; Katagiri, K.; Kodama, R.; Kon, A.; Lu, W.; Makita, M.; Matsuoka, T.; Nakajima, S.; Ozaki, N.; Pikuz, T.; Rode, A. V.; Sagae, D.; Schuster, A.; Tono, K.; Voigt, K.; Vorberger, J.; Yabuuchi, T.; McBride, E. E.; Kraus, D.

We present results from the SPring-8 Angstrom Compact free electron LAser facility, where we used a high intensity (∼10^20 W/cm2) x-ray pump x-ray probe scheme to observe changes in the ionic structure of silicon induced by x-ray heating of the electrons. By avoiding Laue spots in the scattering signal from a single crystalline sample, we observe a rapid rise in diffuse scattering and a transition to a disordered, liquidlike state with a structure significantly different from liquid silicon. The disordering occurs within 100 fs of irradiation, a timescale that agrees well with first principles simulations, and is faster than that predicted by purely inertial behavior, suggesting that both the phase change and disordered state reached are dominated by Coulomb forces. This method is capable of observing liquid scattering without masking
signal from the ambient solid, allowing the liquid structure to be measured throughout and beyond the phase change.

Permalink: https://www.hzdr.de/publications/Publ-32068
Publ.-Id: 32068


Design and performance characterisation of the HAPG von Hámos Spectrometer at the High Energy Density Instrument of the European XFEL

Preston, T. R.; Göde, S.; Schwinkendorf, J.-P.; Appel, K.; Brambrink, E.; Cerantola, V.; Höppner, H.; Makita, M.; Pelka, A.; Prescher, C.; Sukharnikov, K.; Schmidt, A.; Thorpe, I.; Toncian, T.; Amouretti, A.; Chekrygina, D.; Falcone, R. W.; Falk, K.; Fletcher, L. B.; Galtier, E.; Harmand, M.; Hartley, N.; Hau-Riege, S. P.; Heimann, P.; Huang, L.; Humphries, O. S.; Karnbach, O.; Kraus, D.; Lee, H. J.; Nagler, B.; Ren, S.; Schuster, A.; Smid, M.; Voigt, K.; Zhang, M.; Zastrau, U.

The von Hámos spectrometer setup at the HED instrument of the European XFEL is described in detail. The spectrometer is designed to be operated primarily between 5 and 15 keV to complement the operating photon energy range of the HED instrument. Four Highly Annealed Pyrolitic Graphite (HAPG) crystals are characterised with thicknesses of 40 μm or 100 μm and radius-of-curvature 50 mm or 80 mm, in conjunction with either an ePix100 or Jungfrau detector. The achieved resolution with the 50 mm crystals, operated between 6.5 and 9 keV, matches that reported previously: ~8 eV for a thickness of 40 μm, whereas, with an 80 mm crystal of thickness 40 μm, the resolution exceeds that expected. Namely, a resolution of 2 eV is demonstrated between 5–6 keV implying a resolving power of 2800. Therefore, we posit that flatter HAPG crystals, with their high reflectivity and improved resolving power, are a powerful tool for hard x-ray scattering and emission experiments allowing unprecedented measurements of collective scattering in a single shot.

Permalink: https://www.hzdr.de/publications/Publ-32067
Publ.-Id: 32067


A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

Fuchs, M.; Beyer, J.; Lorenz, S.; Sharma, S.; Renno, A.; Heitmann, J.; Gloaguen, R.

With the recurring interest on rare-earth elements (REE), laser-induced fluorescence (LiF) may provide a powerful tool for their rapid and accurate identification at different stages along their value chain. Applications to natural materials such as rocks could complement the spectroscopy-based toolkit for innovative, non-invasive exploration technologies. However, the diagnostic assignment of detected emission lines to individual REE remains challenging, because of the complex composition of natural rocks in which they can be found. The resulting mixed spectra and the large amount of data generated demand for automated approaches of data evaluation, especially in mapping applications such as drill core scanning. LiF reference data provide the solution for robust REE identification, yet they usually remain in the form of tables of published emission lines. We show that a complete reference spectra library could open manifold options for innovative automated analysis.

We present a library of high-resolution LiF reference spectra using the Smithsonian rare-earth phosphate standards for electron microprobe analysis.We employ three standard laser wavelengths (325 nm, 442 nm, 532 nm) to record representative spectra in the UV-visible to near-infrared spectral range (340–1080 nm). Excitation at all three laser wavelengths yielded characteristic spectra with distinct REE-related emission lines for EuPO4, TbPO4, DyPO4 and YbPO4. In the other samples, the high-energy excitation at 325 nm caused unspecific, broadband defect emissions. Here, lower energy laser excitation showed successful for suppressing non-REE-related emission. At 442 nm excitation, REE-reference spectra depict the diagnostic emission lines of PrPO4, SmPO4 and ErPO4. For NdPO4 and HoPO4 most efficient excitation was achieved with 532 nm. Our results emphasise on the possibility of selective REE excitation by changing the excitation wavelength according to the suitable conditions for individual REEs. Our reference spectra provide a database for transparent and reproducible evaluation of REE-bearing rocks. The LiF spectral library is available at https://zenodo.org/ and the registered DOI: http://doi.org/10.5281/zenodo.4054606 (Fuchs et al., 2020). It gives access to traceable data for manifold further studies on comparison of emission line positions, emission line intensity ratios and splitting into emission line sub-levels or can be used as reference or training data for automated approaches of component assignment.

Keywords: Laser-induced fluorescence; rare earth elements; exploration; spectral library

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Permalink: https://www.hzdr.de/publications/Publ-32066
Publ.-Id: 32066


alpaka-group/alpaka: alpaka 0.5.0: C++14

Worpitz, B.; Matthes, A.; Zenker, E.; Hübl, A.; Widera, R.; Bastrakov, S.; Ehrig, S.; Kelling, J.; Krude, J.; Stephan, J.; Werner, M.

The alpaka library is a header-only C++14 abstraction library for accelerator development.
The release 0.5.0 is providing support for AMD HIP and dropped support for C++11, CUDA 8, gcc 4.9 and boost < 1.65.1.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: OS: Linux, Windows, or OSX requirements: C++14 compiler, boost 1.65.1+
    License: MPL-2.0
    Hosted on GitHub: Link to location
    DOI: 10.5281/zenodo.3909421

Permalink: https://www.hzdr.de/publications/Publ-32062
Publ.-Id: 32062


αvβ3-Specific Gold Nanoparticles for Fluorescence Imaging of Tumor Angiogenesis

Pretze, M.; von Kiedrowski, V.; Runge, R.; Freudenberg, R.; Hübner, R.; Davarci, G.; Schirrmacher, R.; Wängler, C.; Wängler, B.

This paper reports on the development of tumor-specific gold nanoparticles (AuNPs) as theranostic tools intended for target accumulation and the detection of tumor angiogenesis via optical imaging (OI) before therapy is performed, being initiated via an external X-ray irradiation source. The AuNPs were decorated with a near-infrared dye, and RGD peptides as the tumor targeting vector for αvβ3-integrin, which is overexpressed in tissue with high tumor angiogenesis. The AuNPs were evaluated in an optical imaging setting in vitro and in vivo exhibiting favorable diagnostic properties with regards to tumor cell accumulation, biodistribution, and clearance. Furthermore, the therapeutic properties of the AuNPs were evaluated in vitro on pUC19 DNA and on A431 cells concerning acute and long-term toxicity, indicating that these AuNPs could be useful as radiosensitizers in therapeutic concepts in the future.

Keywords: gold nanoparticle; optical imaging; radiosensitizer; tumor angiogenesis; RGD peptide

Permalink: https://www.hzdr.de/publications/Publ-32061
Publ.-Id: 32061


Data for "Gold implanted germanium photoswitch for cavity dumping of a free-electron laser"

Rana, R.; Klopf, J. M.; Ciano, C.; Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.; Pashkin, O.

Measurements were carried out in ELBE 113 c lab. Free electron laser (FEL) pulses with a wavelength ranging from 6 to 90 µm from the FELBE laser operating at its maximum power level were used. Photoswitching of Ge and Ge:Au samples were carried out using a 1 kHz Ti:Sapphire Amplifier system at 800 nm. The data used in the paper is arranged in subfolders 1, 2, and 3. The description is as follows
1. Scheme of the experiment (used in Figure 1 and shows the idea of the experiment)
2. FEL pulse picking traces from photoswitched Ge and Ge: Au samples were recorded using an oscilloscope with 1 GHz bandwidth (Keysight InfiniiVision DSOX4104A).
Relevance: This data is used in Figures 2 and 3. This measurement showed the photoswitching attributes in both reflection and transmission geometry for the Ge and Ge: Au samples and suitability of Ge:Au sample for efficient cavity dumping.
3. Photoinduced reflectivity measurements for the Ge: Au sample as a function of the time delay between FEL pulses and the pulses from a kHz amplifier system is recorded. The fluence required to couple out FEL wavelengths with an efficiency of at least 50 % reflectivity and Matlab scripts used for simulation of photoinduced reflectivity for the same FEL wavelengths.
Relevance: This data is used in Figure 4 and shows the fluence requirements of the Ge:Au photoswitch and also a faster recovery time of sub-ns, much shorter than the FEL pulsing period of 77ns.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-07
    DOI: 10.14278/rodare.726

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-32060
Publ.-Id: 32060


Theory of three-magnon interaction in a vortex-state magnetic nanodot

Verba, R.; Körber, L.; Schultheiß, K.; Schultheiß, H.; Tiberkevich, V.; Slavin, A.

This repository contains the data used to determine the numerical threshold fields for three-magnon scattering in a vortex-state disk used in our paper "Theory of three-magnon interaction in a vortex-state magnetic nanodot" published in Physical Review B. 

For different excitation frequencies, we provide:

  • mumax3 simulation file and table containing the time-dependent magnetic energy for simulations where the microwave-field power is decreased over time
  • mumax3 file and resulting power spectrum for a continuous-wave excitation at a given microwave-field power above threshold
  • spatial mode profiles (magnitude/amplitude) to identify the modes taking part in the three-magnon splitting channel

Keywords: spin wave; theory; nonlinear; vortex; micromagnetic simulation

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-05-01
    DOI: 10.14278/rodare.724
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-32057
Publ.-Id: 32057


A Roadmap for 3D Metal Aerogels: Materials Design and Application Attempts

Jiang, X.; Du, R.; Hübner, R.; Hu, Y.; Eychmüller, A.

Armed with merits of the metals (e.g., electrical conductivity, catalytic activity, and plasmonic properties) and aerogels (e.g., monolithic structure, porous network, and large specific surface area), metal aerogels (MAs) have stood out as a new class of porous materials in the last decade. With unparalleled potential in electrocatalysis, plasmonics, and sensing, they are envisaged to revolutionize the energy- and detection-related application fields. However, MA development is severely retarded by the lack of a sufficient material basis. Suffering from the ambiguous understanding of formation mechanisms, big challenges remain for tailoring MAs for task-specific applications. By surveying state-of-the-art developments, this review strives to summarize design principles and arouse interest in broad scientific communities. Moreover, critical challenges and opportunities are highlighted to provide a research roadmap for this young yet promising field.

Permalink: https://www.hzdr.de/publications/Publ-32053
Publ.-Id: 32053


Magnetic Field Assisted Electrodeposition of Metal on Conically Structured Electrodes

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

Conical structures towards nanometer length scales are attractive for numerous applications including super-hydrophobic and electrocatalytic materials. Among the various methods of synthesizing arrays of micro- and nano-cones, electrochemical deposition techniques have been widely applied. We aim at enhancing the conical growth during deposition by applying an external magnetic field. Most of the magnetic field effects can be attributed to the Lorentz force and the magnetic gradient force [1]. If the magnetic field imposed on the electrochemical cell is well designed, the magnetic forces can generate an electrolyte flow which brings fresh electrolyte towards the tip of a cone, so that the local mass transfer would be enhanced and the conical growth would be supported.

We first performed analytical and numerical studies of electrodeposition on diamagnetic (Cu) and ferromagnetic (Fe) cones of mm size under the influence of a homogeneous vertical magnetic field. The beneficial structuring effects of the Lorentz force has already been shown for the Cu cone case [2]. The magnetization of the Fe cones causes additionally a strong magnetic gradient force near the cone tips and gives rise to a flow that can bring enriched electrolyte to the conical cathode. As the cathodes are placed at the bottom of the electrochemical cell, solutal buoyancy tends to bring upwards lighter electrolyte from the conical cathode and thus counteract the downward flow caused by the magnetic forces. Our results show that for the Cu cones, the Lorentz force becomes smaller than the buoyancy force after the first few seconds of the deposition, while the magnetic gradient force in case of the Fe cones keeps surpassing the buoyancy during the deposition.

Next, scaling studies on cones of sizes ranging from millimeter to micrometer allow to deliver insights into the magnetic field assisted electrodeposition towards micro- and nano-cones. As the cone size shrinks, the geometrical inhomogeneity decreases, and the current density gets more uniformly distributed on the cone, which is making the conical growth more difficult. Furthermore, the beneficial flow forced by the magnetic field near smaller cones suffers from higher wall friction. But this can be partially compensated by the larger magnetic gradients existing at smaller Fe cones, and the flow caused by the magnetic gradient force was found to decrease more slowly than the flow caused by other forces with the decreasing cone size. Such scaling behavior of the flow velocity corresponds well with a theoretical analysis of the Navier-Stokes equation. For a Fe cone with a radius of 10 micron under study here, the magnetic gradient force generates a beneficial downward flow with a velocity of about 5 micron per second. But in general the structuring effects during the deposition is much weaker than at larger length scales.

This work shows the potential of using the magnetic gradient force for growing ferromagnetic conical structures during electrodeposition. Optimization possibilities for conical growth at smaller scales by e.g. enhancing the cell current, applying stronger magnetic fields and pulsed electrodeposition will also be discussed.

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Permalink: https://www.hzdr.de/publications/Publ-32049
Publ.-Id: 32049


How range residency and long-range perception change encounter rates

Martinez-Garcia, R.; Fleming, C. H.; Seppelt, R.; Fagan, W. F.; Calabrese, J.

Encounter rates link movement strategies to intra- and inter-specific interactions, and therefore translate individual movement behavior into higher-level ecological processes. Indeed, a large body of interacting population theory rests on the law of mass action, which can be derived from assumptions of Brownian motion in an enclosed container with exclusively local perception. These assumptions imply completely uniform space use, individual home ranges equivalent to the population range, and encounter dependent on movement paths actually crossing. Mounting empirical evidence, however, suggests that animals use space non-uniformly, occupy home ranges substantially smaller than the population range, and are of- ten capable of nonlocal perception. Here, we explore how these empirically supported behaviors change pairwise encounter rates. Specifically, we derive novel analytical expressions for encounter rates under Ornstein-Uhlenbeck motion, which features non-uniform space use and allows individual home ranges to differ from the population range. We compare OU-based encounter predictions to those of Reflected Brownian Motion, from which the law of mass action can be derived. For both models, we further explore how the interplay between the scale of perception and home-range size affects encounter rates. We find that neglecting realistic movement and perceptual behaviors can lead to systematic, non-negligible biases in encounter-rate predictions.

Keywords: Ecological theory; Encounter rates; Movement ecology; Home ranges

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Permalink: https://www.hzdr.de/publications/Publ-32048
Publ.-Id: 32048


How optimal allocation of limited testing capacity changes epidemic dynamics

Calabrese, J.; Demers, J.

Insufficient testing capacity continues to be a critical bottleneck in the worldwide fight against COVID-19. Optimizing the deployment of limited testing resources has therefore emerged as a keystone problem in pandemic response planning. Here, we use a modified SEIR model to optimize testing strategies under a constraint of limited testing capacity. We define pre-symptomatic, asymptomatic, and symptomatic infected classes, and assume that positively tested individuals are immediately moved into quarantine. We further define two types of testing. Clinical testing focuses only on the symptomatic class. Non-clinical testing detects pre- and asymptomatic individuals from the general population, and an information parameter governs the degree to which such testing can be focused on high infection risk individuals. We then solve for the optimal mix of clinical and non-clinical testing as a function of both testing capacity and the information parameter. We find that purely clinical testing is optimal at very low testing capacities, supporting early guidance to ration tests for the sickest patients.
Additionally, we find that a mix of clinical and non-clinical testing becomes optimal as testing capacity increases. At high but empirically observed testing capacities, a mix of clinical testing and unfocused (information=0) non-clinical testing becomes optimal. We further highlight the dvantages of early implementation of testing programs, and of combining optimized testing with contact reduction interventions such as lockdowns, social distancing, and masking.

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Permalink: https://www.hzdr.de/publications/Publ-32047
Publ.-Id: 32047


Spin stress contribution to the lattice dynamics of FePt

von Reppert, A.; Willig, L.; Pudell, J.-E.; Zeuschner, S.; Sellge, G.; Ganss, F.; Hellwig, O.; Ander Arregi, J.; Uhlíř, V.; Crut, A.; Bargheer, M.

Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments. We show that the granular microstructure is essential to support the contractive out-of-plane stresses originating from in-plane expansion via the Poisson effect that add to the uniaxial contractive stress driven by spin disorder. We prove the spin contribution by saturating the magnetic excitations with a first laser pulse and then detecting the purely expansive response to a second pulse. The contractive spin stress is reestablished on the same 100-ps time scale that we observe for the recovery of the ferromagnetic order. Finite-element modeling of the mechanical response of FePt nanosystems confirms the morphology dependence of the dynamics.

Permalink: https://www.hzdr.de/publications/Publ-32043
Publ.-Id: 32043


Theory of three-magnon interaction in a vortex-state magnetic nanodot

Verba, R.; Körber, L.; Schultheiß, K.; Schultheiß, H.; Tiberkevich, V.; Slavin, A.

We use vector Hamiltonian formalism (VHF) to study theoretically three-magnon parametric interaction (or three-wave splitting) in a magnetic disk existing in a magnetic vortex ground state. The three-wave splitting in a disk is found to obey two selection rules: (i) conservation of the total azimuthal number of the resultant spin-wave modes, and (ii) inequality for the radial numbers of interacting modes, if the mode directly excited by the driving field is radially symmetric (i.e. if the azimuthal number of the directly excited mode is m=0). The selection rule (ii), however, is relaxed in the "small" magnetic disks, due to the influence of the vortex core. We also found, that the efficiency of the three-wave interaction of the directly excited mode strongly depends on the azimuthal and radial mode numbers of the resultant modes, that becomes determinative in the case when several splitting channels (several pairs of resultant modes) simultaneously approximately satisfy the resonance condition for the splitting. The good agreement of the VHF analytic calculations with the experiment and micromagnetic simulations proves the capability of the VHF formalism to predict the actual splitting channels and the magnitudes of the driving field thresholds for the three-wave splitting.

Keywords: spin wave; nonlinear; three-magnon interaction; theory; micromagnetic simulation; vortex

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Permalink: https://www.hzdr.de/publications/Publ-32042
Publ.-Id: 32042


Circular by Design (CbD) - Ressourcenwende über nachhaltiges Produktdesign am Fallbeispiel Kühl-/Gefriergeräte

Raatz, S.; Heibeck, M.; Bickel, M.; Liedtke, C.; Tochtrop, C.; Schliack, M.; Förster, S.; Wächter, M.; Irmer, J.

Das Ziel von „Circular by Design“ besteht in der Entwicklung eines kreislauffähigen Produktdesigns für Kühl-/Gefriergeräte, das neben Energieeffizienz auch auf Ressourceneffizienz hin optimiert ist. Mit dem durch das BMBF geförderten Projekt soll die tatsächlich machbare Umsetzung von zirkulärem Design, zum einen mit dem Fokus auf Repair/Reuse und zum anderen auf möglichst geschlossene Recyclingpfade, demonstriert werden.
Die Zusammenführung der Ressourceneffizienzanalyse mit dem technologieorientierten und simulationsbasierten „Design for Recycling“-Modell soll künftig die Vorhersage eines für eine vollständige Kreislaufführung geeigneten Produktdesigns erlauben. Es werden die derzeitigen Verluste beim Erfassen und Recycling eines Kühl-/Gefriergerätes auf verschiedenen Ebenen quantifiziert, Ressourceneffizienzpotentiale dargestellt und auf dieser Basis ein Produktdesign entwickelt, dessen Materialzusammensetzung ein möglichst vollständiges Recycling sowie Reuse erlaubt.

Keywords: Recyclingfähigkeit; zirkuläres Produktdesign; metallische Rohstoffe; Ressourceneffizienz; Kreislaufwirtschaft; Kühl-/Gefriergeräte; Nachhaltigkeit; Substitution; Sekundäre Rohstoffe

  • Contribution to proceedings
    Recy & DepoTech 2020, 18.-20.11.2020, Leoben, Österreich
    Circular by Design (CbD) - Ressourcenwende über nachhaltiges Produktdesign am Fallbeispiel Kühl-/Gefriergeräte, Wien: aVW Abfallverwertungstechnik & Abfallwirtschaft, 978-3-200-07190-2, 799-804

Permalink: https://www.hzdr.de/publications/Publ-32041
Publ.-Id: 32041


Strongly coupled electron liquid: Ab initio path integral Monte Carlo simulations and dielectric theories

Dornheim, T.; Sjostrom, T.; Tanaka, S.; Vorberger, J.

Data used in the paper

Strongly coupled electron liquid: Ab initio path integral Monte Carlo simulations and dielectric theories

Tobias Dornheim, Travis Sjostrom, Shigenori Tanaka, and Jan Vorberger

Phys. Rev. B 101, 045129 – Published 27 January 2020

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-05
    DOI: 10.14278/rodare.709
    License: CC-BY-1.0

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Permalink: https://www.hzdr.de/publications/Publ-32038
Publ.-Id: 32038


New instrumentation to enable novel imaging modalities using sub-50 keV transmitted helium ions

Mousley, M.; Eswara, S.; de Castro, O.; Bouton, O.; Serralta Hurtado De Menezes, E.; Klingner, N.; Koch, C.; Hlawacek, G.; Wirtz, T.

Helium ions offer an alternative imaging probe to electrons, with a smaller de Broglie wavelength at the same energy [1] [2][3]. Furthermore, the ability for neutralisation means that images can be formed by collecting only post-sample neutrals or both neutrals and transmitted ions. A comparison between the two can map where ions are more easily neutralised and offers an alternative contrast mechanism not possible with electrons. Transmission helium ion imaging is quite an understudied field and more experiments are required to fully assess the possibilities and benefits with this new microscopy. With this aim in mind, a prototype transmission helium ion microscope (THIM) has been constructed at the Luxembourg -Institute of Science and Technology (LIST) (Figure 1). The ion source is a duoplasmatron operated at 10-20 keV with a minimum beam spot size of 100 µm and a beam current of 0.1-2 nA . A microchannel plate (MCP) located behind the sample converts the transmitted ion signal to an electron shower which then hits a phosphor screen for direct transmission imaging with a stationary beam [4]. The detector is placed over 50 cm away from the sample. Imaging of crystalline powders showed unexpectedly large charging and deformation of the beam, producing collections of spots (Figure 2). Scanning transmission ion microscopy (STIM) can also be conducted if the phosphor screen is replaced with a metal anode plate. As the beam is scanned over the sample surface, the current from the plate is measured and gives the intensity at each pixel in the STHIM image. A secondary electron detector in front of the sample is used to record secondary electron images at the same time as STIM imaging (Figure 1). Post sample deflectors blank all ions in transmission, such that only neutral atoms are imaged and the fraction of neutralised ions can be estimated. Electrostatic blanking and using the anode plate current as a stop signal allows one to determine the energy of transmitted particles by measuring their time of flight (TOF). In addition, a position sensitive delay line detector has recently been installed, to add position sensitivity to the TOF measurements. This allows both the trajectory and energy of and ion to be measured at the same time, providing a more complete record of the transmission through the sample.

On a separate prototype machine, the ‘NPScope’ instrument, which combines a gas field ion source with a transmission delay line detector, STIM can be performed with nanometre spot size. This enables parallel bright and dark field imaging using the same detector (Figure 3).

Keywords: helium ion imaging; Scanning transmission ion microscopy

  • Lecture (Conference) (Online presentation)
    Virtual Early Career European Microscopy Congress 2020, 24.-26.11.2020, København, Danmark

Permalink: https://www.hzdr.de/publications/Publ-32036
Publ.-Id: 32036


Gold implanted germanium photoswitch for cavity dumping of a free-electron laser

Rana, R.; Klopf, J. M.; Ciano, C.; Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.; Pashkin, O.

We present a plasma switch based on gold implanted germanium (Ge:Au) as a potential candidate for efficient cavity dumping of a free-electron laser (FEL). Ge:Au has a sub-nanosecond carrier lifetime – much shorter than the FEL pulsing period of 77 ns – and demonstrates a high photoinduced reflectivity in a broad range of infrared wavelengths from 6 to 90 µm. The Ge:Au plasma switch exhibits negligible absorption of the FEL radiation in the ʻoff ʼ state and requires only moderate thermoelectric cooling for incident FEL power of several Watts. A reflectivity level of more than 50 % in the ‘on’ state is achieved over the entire spectral range of this study. The corresponding optical pump fluence exhibits a linear relationship with the FEL frequency. This scaling is corroborated by our simulations highlighting the role of a finite sub-µm thickness of the photoinduced reflecting plasma layer. The demonstrated device is promising for the realization of the FEL cavity dumping for experiments that simultaneously require higher pulse energy and lower average power.

Keywords: Intense Terahertz pulses; Free Electron Laser; Cavity dumping; Optical switch

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Permalink: https://www.hzdr.de/publications/Publ-32035
Publ.-Id: 32035


Data for "Observation of strong magneto plasmonic nonlinearity in bilayer graphene discs"

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

Data, Labbook notes and some presentations to the pblication topic

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-04
    DOI: 10.14278/rodare.703

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Permalink: https://www.hzdr.de/publications/Publ-32034
Publ.-Id: 32034


Data for: Fusion of Dual Spatial Information for Hyperspectral Image Classification

Duan, P.; Ghamisi, P.; Kang, X.; Rasti, B.; Li, S.; Gloaguen, R.

The inclusion of spatial information into spectral classifiers for fine-resolution hyperspectral imagery has led to significant improvements in terms of classification performance. The task of spectral-spatial hyperspectral image classification has remained challenging because of high intraclass spectrum variability and low interclass spectral variability. This fact has made the extraction of spatial information highly active. In this work, a novel hyperspectral image classification framework using the fusion of dual spatial information is proposed, in which the dual spatial information is built by both exploiting pre-processing feature extraction and post-processing spatial optimization. In the feature extraction stage, an adaptive texture smoothing method is proposed to construct the structural profile (SP), which makes it possible to precisely extract discriminative features from hyperspectral images. The SP extraction method is used here for the first time in the remote sensing community. Then, the extracted SP is fed into a spectral classifier. In the spatial optimization stage, a pixel-level classifier is used to obtain the class probability followed by an extended random walker-based spatial optimization technique. Finally, a decision fusion rule is utilized to fuse the class probabilities obtained by the two different stages. Experiments performed on three data sets from different scenes illustrate that the proposed method can outperform other state-of-the-art classification techniques. In addition, the proposed feature extraction method, i.e., SP, can effectively improve the discrimination between different land covers.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-19
    DOI: 10.14278/rodare.686

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Permalink: https://www.hzdr.de/publications/Publ-32033
Publ.-Id: 32033


Data for: Remote Sensing Image Classification Using Subspace Sensor Fusion

Rasti, B.; Ghamisi, P.

The amount of remote sensing and ancillary datasets captured by diverse airborne and spaceborne sensors has been tremendously increased, which opens up the possibility of utilizing multimodal datasets to improve the performance of processing approaches with respect to the application at hand. However, developing a generic framework with high generalization capability that can effectively fuse diverse datasets is a challenging task since the current approaches are usually only applicable to two specific sensors for data fusion. In this paper, we propose an accurate fusion-based technique called SubFus with capability to integrate diverse remote sensing data for land cover classification. Here, we assume that a high dimensional multisensor dataset can be represented fused features that live in a lower-dimensional space. The proposed classification methodology includes three main stages. First, spatial information is extracted by using spatial filters (i.e., morphology filters). Then, a novel low- rank minimization problem is proposed to represent the multisensor datasets in subspaces using fused features. The fused features in the lower-dimensional subspace are estimated using a novel iterative algorithm based on the alternative direction method of multipliers. Third, the final classification map is produced by applying a supervised spectral classifier (i.e., random forest) on the fused features. In the experiments, the proposed method is applied to a three-sensor (RGB, multispectral LiDAR, and hyperspectral images) dataset captured over the area of the University of Houston, the USA, and a two-sensor (hyperspectral and LiDAR) dataset captured over the city of Trento, Italy. The land-cover maps generated using SubFus are evaluated based on classification accuracies. Experimental results obtained by SubFus confirm considerable improvements in terms of classification accuracies compared with the other methods used in the experiments. The proposed fusion approach obtains 85.32% and 99.25% in terms of overall classification accuracy on the Houston (the training portion of the dataset distributed for the data fusion contest of 2018) and trento datasets, respectively.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-01
    DOI: 10.14278/rodare.688

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Permalink: https://www.hzdr.de/publications/Publ-32032
Publ.-Id: 32032


The Road to Exascale

Stephan, J.

Exascale is the next big step in the field of high-performance computing. However, the hardware configurations of supercomputers around the world are becoming increasingly heterogeneous. Programmers have to take into account varying processor architectures (x86, ARM, RISC-V, ...) as well as different accelerator types (multicore CPUs, GPUs, FPGAs, ...) and the accompanying tools. Our goal is a portable stack of C++ libraries and tools. Together they shall form an ecosystem which abstracts away the differences between hardware configurations without sacrificing performance.

Keywords: alpaka; C++; heterogeneous computing; heterogeneous programming; HPC; hardware abstraction

  • Open Access Logo Poster
    Polish delegation meeting, 29.09.2020, Görlitz, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-32031
Publ.-Id: 32031


Four-Frequency Solution in a Magnetohydrodynamic Couette Flow as a Consequence of Azimuthal Symmetry Breaking

Garcia, F.; Seilmayer, M.; Giesecke, A.; Stefani, F.

The occurrence of magnetohydrodynamic quasiperiodic flows with four fundamental frequencies in differentially rotating spherical geometry is understood in terms of a sequence of bifurcations breaking the azimuthal symmetry of the flow as the applied magnetic field strength is varied. These flows originate from unstable periodic and quasiperiodic states with broken equatorial symmetry, but having fourfold azimuthal symmetry. A posterior bifurcation gives rise to twofold symmetric quasiperiodic states, with three fundamental frequencies, and a further bifurcation to a four-frequency quasiperiodic state which has lost all the spatial symmetries. This bifurcation scenario may be favored when differential rotation is increased and periodic flows with m-fold azimuthal symmetry, m being a product of several prime numbers, emerge at sufficiently large magnetic field.

Keywords: Astrophysical fluid dynamics; Bifurcations; Chaos; Flow instability; Geophysical fluid dynamics; Magnetohydrodynamics

Permalink: https://www.hzdr.de/publications/Publ-32030
Publ.-Id: 32030


Laser produced electromagnetic pulses: generation, detection and mitigation

Consoli, F.; Tikhonchuk, V. T.; Bardon, M.; Bradford, P.; Carrol, D. C.; Cikhardt, J.; Cipriani, M.; Clarke, R. J.; Cowan, T. E.; Danson, C. N.; de Angelis, R.; de Marco, M.; Dubois, J.-L.; Etchessahar, B.; Laso Garcia, A.; Hillier, D. I.; Weiman, J.; Kmetik, V.; Krasa, J.; Li, Y.; Lubrano, F.; McKenna, P.; Metzkes-Ng, J.; Poye, A.; Prencipe, I.; Raczka, P.; Smith, R. A.; Vrana, R.; Woolsey, N. C.; Zemaityte, E.; Zhang, Y.; Zhang, Z.; Zielbauer, B.; Neely, D.; Honsa, A.

This paper provides an up-to-date review of the problems related to the generation, detection and mitigation of strong electromagnetic pulses created in the interaction of high-power, high-energy laser pulses with different types of solid targets. It includes new experimental data obtained independently at several international laboratories. The mechanisms of electromagnetic field generation are analyzed and considered as a function of the intensity and the spectral range of emissions they produce. The major emphasis is put on the GHz frequency domain, which is the most damaging for electronics and may have important applications. The physics of electromagnetic emissions in other spectral domains, in particular THz and MHz, is also discussed. The theoretical models and numerical simulations are compared with the results of experimental measurements, with special attention to the methodology of measurements and complementary diagnostics. Understanding the underlying physical processes is the basis for developing techniques to mitigate the electromagnetic threat and to harness electromagnetic emissions, which may have promising applications.

Keywords: Electromagnetic Pulses; High-Power Lasers; Diagnostics; Mitigation Techniques

Permalink: https://www.hzdr.de/publications/Publ-32029
Publ.-Id: 32029


Deep model simulation of polar vortices in gas giant atmospheres

Garcia, Ferran; Chambers, Frank R. N.; Watts, Anna L.

The Cassini and Juno probes have revealed large coherent cyclonic vortices in the polar regions of Saturn and Jupiter, a dramatic contrast from the east–west banded jet structure seen at lower latitudes. Debate has centred on whether the jets are shallow, or extend to greater depths in the planetary envelope. Recent experiments and observations have demonstrated the relevance of deep convection models to a successful explanation of jet structure, and cyclonic coherent vortices away from the polar regions have been simulated recently including an additional stratified shallow layer. Here we present new convective models able to produce long-lived polar vortices. Using simulation parameters relevant for giant planet atmospheres we find flow regimes of geostrophic turbulence (GT) in agreement with rotating convection theory. The formation of large-scale coherent structures occurs via 3D upscale energy transfers. Our simulations generate polar characteristics qualitatively similar to those seen by Juno and Cassini: They match the structure of cyclonic vortices seen on Jupiter; or can account for the existence of a strong polar vortex extending downwards to lower latitudes with a marked spiral morphology, and the hexagonal pattern seen on Saturn. Our findings indicate that these vortices can be generated deep in the planetary interior. A transition differentiating these two polar flows regimes is described, interpreted in terms of force balances and compared with shallow atmospheric models characterizing polar vortex dynamics in giant planets. In addition, heat transport properties are investigated, confirming recent scaling laws obtained with reduced models of GT.

Keywords: convection; turbulence; software: simulations; planets and satellites: gaseous planets

  • Monthly Notices of the Royal Astronomical Society 499(2020)4, 4
    Online First (2020) DOI: 10.1093/mnras/staa2962

Permalink: https://www.hzdr.de/publications/Publ-32028
Publ.-Id: 32028


Bremsstrahlung emission and plasma characterization driven by moderately relativistic laser-plasma interactions

Singh, S. K.; Armstrong, C.; Kang, N.; Ren, L.; Liu, H.; Hua, N.; Rusby, D. R.; Klimo, O.; Versaci, R.; Zhang, Y.; Sun, M.; Zhu, B.; Lei, A.; Ouyang, X.; Lancia, L.; Laso Garcia, A.; Wagner, A.; Cowan, T. E.; Schlegel, T.; Weber, S.; McKenna, P.; Neely, D.; Tikhonchuk, V. T.; Kumar, D.; Zhu, J.

Relativistic electrons generated by the interaction of petawatt-class short laser pulses with solid targets can be used to generate bright X-rays via bremsstrahlung. The efficiency of laser energy transfer into these electrons depends on multiple parameters including focused intensity and pre-plasma level. This paper describes the experimental results from the interaction of a high intensity petawatt-class glass laser with solid targets at a maximum intensity of 10^19 W/cm^2. In-situ measurements of specularly reflected light were used to provide an upper bound of laser absorption and to characterize focused laser intensity, the pre-plasma level and the generation mechanism of second harmonic light. The measured spectrum of electrons and bremsstrahlung radiation provide information about the efficiency of laser energy transfer.

Keywords: Plasma Physics; Bremsstrahlung; High intensity laser

Permalink: https://www.hzdr.de/publications/Publ-32027
Publ.-Id: 32027


Chaotic wave dynamics in weakly magnetized spherical Couette flows

Garcia Gonzalez, F.; Seilmayer, M.; Giesecke, A.; Stefani, F.

Direct numerical simulations of a liquid metal filling the gap between two concentric spheres are presented. The flow is governed by the interplay between the rotation of the inner sphere (measured by the Reynolds number Re) and a weak externally applied axial magnetic field (measured by the Hartmann number Ha). By varying the latter, a rich variety of flow features, both in terms of spatial symmetry and temporal dependence, is obtained. Flows with two or three independent frequencies describing their time evolution are found as a result of Hopf bifurcations. They are stable on a sufficiently large interval of Hartmann numbers where regions of multistability of two, three, and even four types of these different flows are detected. The temporal character of the solutions is analyzed by means of an accurate frequency analysis and Poincaré sections. An unstable branch of flows undergoing a period doubling cascade and frequency locking of three-frequency solutions is described as well.

  • Chaos: An Interdisciplinary Journal of Nonlinear Science 30(2020), 043116
    Online First (2020) DOI: 10.1063/1.5140577

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Permalink: https://www.hzdr.de/publications/Publ-32025
Publ.-Id: 32025


Untersuchungen zur Optimierung der Selektivität bei der Extraktion von Indium durch gezielte Komplexbildung

Göthel, J.

Indium kann sekundärmetallurgisch aus der Prozessierung von Schlacken, Flugstäuben und metallischen Zwischenprodukten aus der Zinkdarstellung gewonnen werden. Eine weitere Möglichkeit der Indiumgewinnung stellt sich in der Aufbereitung von Rückständen des Bergbaus durch Biolaugungsprozesse dar. Höhere Konzentrationen an Eisen und Zink sind in den gewinnbaren Laugen im Vergleich zu sehr niedrigen Indiumkonzentrationen häufig präsent. Ein Trenn- und Aufbereitungsverfahren für die Verarbeitung von hydro-metallurgischen Prozesslösungen und die Gewinnung von Einsatzstoffen aus diesen wird durch Ionenaustauscherharze realisiert. Sowohl kationische als auch anionische feste Ionenaustauscherharze zeigen für Indium in sauren wässrigen Lösungen eine Affinität für die Indiumadsorption. Hinsichtlich der selektiven Adsorption von Indium gegenüber Eisen und Zink mittels festen Anionenaustauschern wurde der Einfluss der selektiven Komplexbildung von Indium durch die Zugabe von Iod in der Form von Kaliumiodid auf die Adsorption untersucht. Als Referenzsystem wurde die Indiumadsorption an festen Kationen-austauscherharzen gewählt. Die selektive Adsorption für Indium wurde aus einer vereinfachten Modelllösung der Biolaugungslösung des „ReMining“-Projektes hinsichtlich der Faktorgrößen des pH-Wertes, der Kaliumiodid- und Indiumadsorption im kleineren Maßstab im Becherglas untersucht. Die bestimmten Optima wurden auf die Prozessierung der realen Biolaugungslösung in Ionenaustauschersäulen angewandt. Indium kann in vergleichbaren quantitativen Mengen sowohl als anionischer Komplex ([InI4]-) von den getesteten Anionenaustauscherharzen A 111 und A 500 als auch von dem Kationenaustauscherharz MTS 9300 als Kation In3+ durch Adsorption aus der Modell- und Biolaugungslösung extrahiert werden. Beide Ionenaustauscher zeigen höchste Selektivitäten gegenüber Eisen, Arsen und Aluminium. Der Vergleich der Konzentrationsverhältnisse von Feed und dem Eluat zeigt, dass Eisen zu ~ 700 Mal mehr wie Indium (Fe/In = ~ 700) im Feed vorhanden ist und nach dem Ionenaustausch ~ 0,7 Mal so viel wie Indium (Fe/In = ~ 0,7) im Eluat verbleibt. Kupfer und Cadmium konnten von dem Anionenaustauscherharz A 111 nicht mit destilliertem Wasser und 0,1 M Schwefelsäure eluiert werden. In der Gesamtbetrachtung der selektiven Adsorption und Eluation von Indium aus der realen Biolaugungslösung ist das Kationenaustauscherharz MTS 9300 dem Anionenaustauscherharz A 111 vorzuziehen.

  • Diploma thesis
    TU Bergakademie Freiberg, 2020
    Mentor: Toni Helbig/Arite Werner

Permalink: https://www.hzdr.de/publications/Publ-32023
Publ.-Id: 32023


A bimodal soft electronic skin for tactile and touchless interaction in real time

Ge, J.; Wang, X.; Drack, M.; Volkov, O.; Liang, M.; Canon Bermudez, G. S.; Wang, C.; Zhou, S.; Faßbender, J.; Kaltenbrunner, M.; Makarov, D.

The transformative emergence of smart electronics, human-friendly robotics and supplemented or virtual reality will revolutionize the interplay with our surrounding. The complexity that is involved in the manipulation of objects in these emerging technologies is dramatically increased, which calls for electronic skins (e-skin) that can conduct tactile and touchless sensing events in a simultaneous and unambiguous way. Integrating multiple functions in a single sensing unit offers the most promising path towards simple, scalable and intuitive-to-use e-skin architectures. However, by now, this path has always been hindered by the confusing overlap of signals from different stimuli.
Here, we put forward the field of soft, flexible electronics by developing a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [1]. For the first time, the electric signals from tactile and touchless interactions are intrinsically separated into two different regions, allowing the m-MEMS, a single sensor unit, to unambiguously distinguish the two modes without knowing the signal history.
Owing to its intrinsic magnetic functionality, our complaint m-MEMS platform is able to discriminate magnetic vs. non-magnetic objects already upon touchless interaction. With this intrinsic selectivity, we address the long-standing problem in the field of touchless interaction – namely, the issue of interference with objects, which are irrelevant or even disturbing the interaction process. In addition, the interaction process is programmable. The sensitivity of the two interaction modes could be tuned by adjusting the magnetic field of the objects able to meet the requirements of different interaction tasks.
By using tactile and touchless sensing functions simultaneously, our m-MEMS e-skins enable complex interactions with a magnetically functionalized physical object that is supplemented with content data appearing in the virtual reality. We demonstrated data selection and manipulation with our m-MEMS e-skins leading to the realization of a multi-choice for augmented reality through three dimensional (3D) touch. Beyond the field of augmented reality, our m-MEMS will bring great benefits for healthcare, e.g. to ease surgery operations and manipulation of medical equipment, as well as for humanoid robots to overcome the challenging task of grasping.

[1] J. Ge, X. Wang, M. Drack, O. Volkov, M. Liang, G. S. Cañón Bermúdez, R. Illing, C. Wang, S. Zhou, J. Fassbender, M. Kaltenbrunner, and D. Makarov. A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Lecture (Conference) (Online presentation)
    2020 MRS Fall Meeting, 02.12.2020, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-32022
Publ.-Id: 32022


Flexible highly compliant magnetoelectronics

Canon Bermudez, G. S.; Ge, J.; Faßbender, J.; Kaltenbrunner, M.; Makarov, D.

Mechanical flexibility and even stretchability of functional elements is a key enabler of numerous applications including wearable electronics, healthcare and medical appliances. The magnetism community developed the family of high-performance shapeable magnetoelectronics [1], which contain flexible [2-4], printable [5-7], stretchable [8-11] and even mechanically imperceptible [12-16] magnetic field sensorics. The technology relies on a smart combination of thin inorganic functional elements prepared directly on flexible or elastomeric supports. The concept of shapeable magnetoelectronics is explored for various applications ranging from automotive [17] through consumer electronics and point of care [2,18] to virtual and augmented reality [14-16] applications.
Here, we will focus on the use of compliant magnetosensitive skins [14-16] for augmented reality systems. We demonstrate that e-skin compasses [14] allow humans to orient with respect to earth’s magnetic field ubiquitously. The biomagnetic orientation enables the realization of a touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins (Fig. 1).
This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [16] (Fig. 2). We demonstrate data selection and manipulation with our m-MEMS e-skins leading to the realization of a multi-choice menu for augmented reality through three dimensional (3D) touch. Beyond the field of augmented reality, our m-MEMS will bring great benefits for healthcare, e.g. to ease surgery operations and manipulation of medical equipment, as well as for humanoid robots to overcome the challenging task of grasping.
[1] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[2] G. Lin, D. Makarov et al., Lab Chip 14, 4050 (2014).
[3] N. Münzenrieder, D. Makarov et al., Adv. Electron. Mater. 2, 1600188 (2016).
[4] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1274 (2015).
[5] D. Makarov et al., ChemPhysChem (Review) 14, 1771 (2013).
[6] D. Karnaushenko, D. Makarov et al., Adv. Mater. 24, 4518 (2012).
[7] D. Karnaushenko, D. Makarov et al., Adv. Mater. 27, 880 (2015).
[8] M. Melzer, D. Makarov et al., J. Phys. D: Appl. Phys. (Review) 53, 083002 (2020).
[9] M. Melzer, D. Makarov et al., Nano Lett. 11, 2522 (2011).
[10] M. Melzer, D. Makarov et al., Adv. Mater. 24, 6468 (2012).
[11] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1333 (2015).
[12] M. Melzer, D. Makarov et al., Nat. Commun. 6, 6080 (2015).
[13] P. N. Granell, D. Makarov et al., npj Flexible Electronics 3, 3 (2019).
[14] G. S. Cañón Bermúdez, D. Makarov et al., Nature Electronics 1, 589 (2018).
[15] G. S. Cañón Bermúdez, D. Makarov et al., Science Advances 4, eaao2623 (2018).
[16] J. Ge, D. Makarov et al., Nature Communications 10, 4405 (2019).
[17] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1274 (2015).
[18] G. Lin, D. Makarov et al., Lab Chip (Review) 17, 1884 (2017).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Lecture (Conference) (Online presentation)
    65th Annual Conference on Magnetism and Magnetic Materials, 03.11.2020, Palm Beach, USA

Permalink: https://www.hzdr.de/publications/Publ-32021
Publ.-Id: 32021


Curvilinear magnetism: From curvature induced magnetochirality to shapeable magnetoelectronics

Makarov, D.

Non-collinear magnetic textures like spin spirals, chiral domain walls or skyrmions are typically stabilized by the intrinsic spin-orbit induced Dzyaloshinskii-Moriya interaction (DMI) [1]. Curvature effects emerged as a novel mean to design chiral magnetic responses relying on extrinsic parameters, i.e. geometrical curvature of thin films [2-4]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [5-7]. Vast majority of activities are dedicated to curved ferromagnets, where recent achievements include the development of the theory of curvilinear micromagnetism [3] and the first experimental confirmation of curvature-driven chiral effects stemming from the exchange interaction [4]. Only very recently, the focus was put also on curvilinear antiferromagnets. Pylypovskyi et al. [8] demonstrated that intrinsically achiral one-dimensional curvilinear antiferromagnets behave as a chiral helimagnet with geometrically tunable DMI and orientation of the Neel vector.
The application potential of 3D-shaped magnetic thin films is currently being explored as mechanically shapeable magnetic field sensors [9] for automotive applications, magnetoelectrics for memory devices, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics [10-12].
The fundamentals as well as application relevant aspects of curvilinear ferro- and antiferromagnets will be covered in this presentation.

References

[1] D. Sander, DM et al., J. Phys. D 50, 363001 (2017)
[2] R. Streubel, DM et al., J. Phys. D 49, 363001 (2016)
[3] D. Sheka, DM et al., Communications Physics 3, 128 (2020)
[4] O. M. Volkov, DM et al., Phys. Rev. Lett. 123, 077201 (2019)
[5] V. Kravchuk, DM et al., Phys. Rev. Lett. 120, 067201 (2018)
[6] O. Pylypovskyi, DM et al., Phys. Rev. Appl. 10, 064057 (2018)
[7] O. Pylypovskyi, DM et al., Phys. Rev. Lett. 114, 197204 (2015)
[8] O.Pylypovskyi, DM et al., Nano Lett. (2020) doi:10.1021/acs.nanolett.0c03246
[9] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)
[10] S. Canon Bermudez, DM et al., Science Advances 4, eaao2623 (2018)
[11] S. Canon Bermudez, DM et al., Nature Electronics 1, 589 (2018)
[12] J. Ge, DM et al., Nature Communications 10, 4405 (2019).

Keywords: curvilinear magnetism; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    736. WE-Heraeus-Seminar "Magnetism at the Nanoscale: Imaging ‐ Fabrication – Physics", 06.01.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-32012
Publ.-Id: 32012


Implantable Highly Compliant Devices for Heating of Internal Organs

Makarov, D.

Recent advances in the field of flexible electronics have opened the door for this technology to deeply impact the health care sector. The development of sensors and actuators which are lightweight and mechanically compliant enables them to be used for continuous health monitoring, on-site therapies or soft chirurgical ads. The key feature of these novel gadgets is their ability to provide targeted treatment and diagnosis without constraining the natural motion of the body or its internal organs.
Though many of these flexible diagnostic or therapeutic devices have been successfully demonstrated already, cancer treatment remains relatively unexplored in this field. In particular, hepatocellular carcinoma (HCC, liver cancer) is one of the leading causes of cancer related mortalities worldwide with a constantly growing incidence. Numerous efforts have been devoted to the development of targeted cancer treatments which selectively destroy cancer cells and spare the healthy tissue.
We propose and develop an implantable, multifunctional and highly compliant device for targeted thermal treatment of cancerous tissues [1]. The device is fabricated on a 6-µm-thick polymeric foil, which seamlessly conforms to the soft liver tissue and allows for precisely controlled joule heating without on-site rigid parts. Its high mechanical compliance provides stable readings even upon severe mechanical deformations, enabling temperature accuracies of 0.1°C at bending radii of 2.5 mm, characteristic for mouse liver tissues. This heating device can treat tissue over the whole range of temperatures leading to fever, hyperthermia and ablation, while using a driving current as low as 10 mA. We demonstrate the electro-thermal and mechanical characterization of the devices and study various heat impact scenarios on normal and cancerous tissue using autochthonous murine HCC models.
Due to their high mechanical compliance, stability and thermal treatment versatility, the here developed devices can become a complement or alternative solution to radio frequency ablation (RFA) techniques for cancer treatment.

[1] G. S. Cãnón Bermudez, A. Kruv, T. Voitsekhivska, I. Hochnadel, A. Lebanov, A. Potthoff, J. Fassbender, T. Yevsa, and D. Makarov, “Implantable Highly Compliant Devices for Heating of Internal Organs: Toward Cancer Treatment”. Adv. Eng. Mater. 21, 1900407 (2019).

Keywords: flexible electronics; cancer treatment

  • Invited lecture (Conferences) (Online presentation)
    International Conference on Advances in Biological Science and Technology (ICABST2020), 28.10.2020, Sanya, China

Permalink: https://www.hzdr.de/publications/Publ-32011
Publ.-Id: 32011


Flexible magnetic field sensors

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. We put forth the concept of shapeable magnetoelectronics [2] for various applications ranging from automotive [3-5] through consumer electronics to virtual and augmented reality [6-9] applications. These activities impact several emerging research fields of smart skins, soft robotics and human-machine interfaces. In this talk, recent fundamental and technological advancements in this research field will be reviewed.

[1] R. Streubel, D. Makarov et al., J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[3] M. Melzer, D. Makarov et al., Adv. Mater. 27, 1274 (2015).
[4] I. J. Mönch, D. Makarov et al., IEEE Trans. Magn. 51, 4004004 (2015).
[5] D. Ernst, D. Makarov et al., IEEE Proceedings of the 37th International Spring Seminar on Electronics Technology (ISSE), pp. 125-129 (2014). doi:10.1109/ISSE.2014.6887577
[6] G. S. Cañón Bermúdez, D. Makarov et al., Science Advances 4, eaao2623 (2018).
[7] G. S. Cañón Bermúdez, D. Makarov et al., Nature Electronics 1, 589 (2018).
[8] P. N. Granell, D. Makarov et al., npj Flexible Electronics 3, 3 (2019).
[9] J. Ge, D. Makarov et al., Nature Communications 10, 4405 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    MSM2020: 15th International Conference Mechatronic Systems and Materials, 01.07.2020, Bialystok, Poland

Permalink: https://www.hzdr.de/publications/Publ-32010
Publ.-Id: 32010


Mechanically compliant magnetic field sensor technologies

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-7]. In this respect, we will present technological platforms allowing to realize not only mechanically imperceptible electronic skins, which enable perception of the geomagnetic field (e-skin compasses) [6], but also enable sensitivities down to ultra-small fields of sub-200 nT [8]. We demonstrate that e-skin compasses allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactive devices for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins. This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [7]. Those devices are crucial for interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly compliant integrated feedback system as well as in medicine for physicians and surgeons. In this talk, recent fundamental and technological advancements in this novel research field will be reviewed.

[1] R. Streubel, DM et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander, DM et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov, DM et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez, DM et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez, DM et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] J. Ge, DM et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[8] P. Granell, DM et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).

Keywords: flexible electronics; shapeable magnetoelectronics

  • Lecture (others) (Online presentation)
    Seminar at the Karlsruhe Institute of Technology, 13.10.2020, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-32009
Publ.-Id: 32009


From curvilinear magnetism to shapeable magnetoelectronics

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-4]. On the other hand, we explore the application potential of 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [5] for automotive but also virtual and augmented reality appliances [6-8]. In this respect, we will present technological platforms allowing to realize not only mechanically imperceptible electronic skins, which enable perception of the geomagnetic field (e-skin compasses) [7], but also enable sensitivities down to ultra-small fields of sub-200 nT [9]. We demonstrate that e-skin compasses allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactive devices for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins. This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [8]. Those devices are crucial for interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly compliant integrated feedback system as well as in medicine for physicians and surgeons. In this talk, recent fundamental and technological advancements in this novel research field will be reviewed.

[1] R. Streubel, DM et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander, DM et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov, DM et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] V. P. Kravchuk, DM et al., Multiplet of Skyrmion states on a curvilinear defect: Reconfigurable Skyrmion lattices. Phys. Rev. Lett. 120, 067201 (2018).
[5] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[6] G. S. Cañón Bermúdez, DM et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[7] G. S. Cañón Bermúdez, DM et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[8] J. Ge, DM et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[9] P. Granell, DM et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).

Keywords: curvilinear magnetism; shapeable magnetoelectronics

  • Lecture (others)
    Seminar at the Johannes Kepler University Linz, 12.08.2020, Linz, Austria

Permalink: https://www.hzdr.de/publications/Publ-32008
Publ.-Id: 32008


Curvilinear Magnetism: Fundamentals and Applications

Makarov, D.

There is one aspect, which is in common to the majority of fundamentally appealing and technologically relevant novel magnetic materials, namely their non-collinear magnetic textures like spin spirals, chiral domain walls or skyrmions [1]. These textures are typically driven by the Dzyaloshinskii-Moriya interaction (DMI). Recently, curvature effects emerged as a novel mean to design chiral magnetic properties by relying on extrinsic parameters, e.g. geometry of thin films [2]. In particular, novel effects occur when the magnetization is modulated by curvature leading to new magnetization configurations and is implications on the spin dynamics due to topological constraints. Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films [3-5] and nanowires [6,7]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [8,9]. The application potential of 3D-shaped objects is currently being explored as mechanically reshapeable magnetic field sensorics [10] for flexible interactive electronics [11-13], magnetic field sensors [14-18], curvilinear magnetoelectrics for memory devices [19], spin-wave filters and high-speed racetrack memory devices [20]. To advance in this research field, novel theoretical methods and fabrication/characterization techniques [21-24]. The fundamentals as well as application relevant aspects of curvilinear nanomagnets will be covered in this presentation.

[1] D. Sander, DM et al., “The 2017 Magnetism Roadmap”, J. Phys. D 50, 363001 (2017).
[2] R. Streubel, DM et al., “Magnetism in curved geometries”, J. Phys. D 49, 363001 (2016).
[3] Y. Gaididei et al., “Curvature Effects in Thin Magnetic Shells”, Phys. Rev. Lett. 112, 257203 (2014).
[4] V. Kravchuk, DM et al., “Multiplet of Skyrmion States on a Curvilinear Defect: Reconfigurable Skyrmion Lattices”, Phys. Rev. Lett. 120, 067201 (2018).
[5] O. V. Pylypovskyi, DM et al., “Chiral Skyrmion and Skyrmionium States Engineered by the Gradient of Curvature”, Phys. Rev. Appl. 10, 064057 (2018).
[6] O. M. Volkov, DM et al., “Mesoscale Dzyaloshinskii-Moriya interaction: geometrical tailoring of the magnetochirality”, Scientific Reports 8, 866 (2018).
[7] O. M. Volkov, DM et al., “Experimental observation of exchange-driven chiral effects in curvilinear magnetism”, Phys. Rev. Lett. 123, 077201 (2019).
[8] O. V. Pylypovskyi, DM et al., “Coupling of Chiralities in Spin and Physical Spaces: The Möbius Ring as a Case Study”, Phys. Rev. Lett. 114, 197204 (2015).
[9] J. A. Otalora et al., “Curvature-Induced Asymmetric Spin-Wave Dispersion”, Phys. Rev. Lett. 117, 227203 (2016).
[10] D. Makarov et al., “Shapeable magnetoelectronics”, Appl. Phys. Rev. 3, 011101 (2016).
[11] S. Canon Bermudez, DM et al., “Magnetosensitive e-skins with directional perception for augmented reality”, Science Advances 4, eaao2623 (2018).
[12] S. Canon Bermudez, DM et al., “Electronic-skin compasses for geomagnetic field driven artificial magnetoreception and interactive electronics”, Nature Electronics 1, 589 (2018).
[13] J. Ge, DM et al., “A bimodal soft electronic skin for tactile and touchless interaction in real time”, Nature Comm. 10, 4405 (2019).
[14] D. Karnaushenko, DM et al., “Self-assemled on-chip integrated giant magneto-impedance sensorics”, Adv. Mater. 27, 6582 (2015).
[15] G. Lin, DM et al., “A highly flexible and compact magnetoresistive analytic device”, Lab Chip 14, 4050 (2014).
[16] N. Münzenrieder, DM et al., “Entirely flexible on-site conditioned magnetic sensorics”, Adv. Electron. Mater. 2, 1600188 (2016).
[17] C. Becker et al., “Self-assembly of highly sensitive 3D magnetic field vector angular encoders”, Science Advances 5, eaay7459 (2019).
[18] M. Kondo et al., “Imperceptible magnetic sensor matrix system integrated with organic driver and amplifier circuits”, Science Advances 6, eaay6094 (2020)
[19] O. M. Volkov, DM et al., “Concept of artificial magnetoelectric materials via geometrically controlling curvilinear helimagnets”, J. Phys. D: Appl. Phys. 52, 345001 (2019).
[20] M. Yan et al., “Beating the Walker Limit with Massless Domain Walls in Cylindrical Nanowires”, Phys. Rev. Lett. 104, 057201 (2010).
[21] R. Streubel, DM et al., “Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies”, Nature Comm. 6, 7612 (2015).
[22] T. Kosub, DM et al., “Purely antiferromagnetic magnetoelectric random access memory”, Nature Comm. 8, 13985 (2017).
[23] M. Huth et al., “Focused electron beam induced deposition meets materials science”, Microelectron. Engineering 185-186, 9 (2018).
[24] M. Nord, DM et al., “Strain Anisotropy and Magnetic Domains in Embedded Nanomagnets”, Small 15, 1904738 (2019).

Keywords: curvilinear magnetism; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    The 2020 Magnetism and Magnetic Materials Conference, 04.11.2020, Palm Beach, USA

Permalink: https://www.hzdr.de/publications/Publ-32007
Publ.-Id: 32007


Overview of recent advances in flexible highly compliant magnetoelectronics

Makarov, D.

Recent rapid advances and eagerness of portable consumer electronics stimulate the development of functional elements towards being lightweight, flexible, and wearable. Next generation flexible appliances aim to become fully autonomous and will require ultra-thin and flexible navigation modules, body tracking and relative position monitoring systems. Key building blocks of navigation and position tracking devices are magnetic field sensors. In this presentation, recent developments in the emerging field of flexible magnetic field sensorics and its applications in printed electronics, eMobility, virtual and augmented reality settings will be reviewed.

Keywords: flexible electronics; shapeable magnetoelectronics

  • Invited lecture (Conferences) (Online presentation)
    2020 IEEE Electron Devices Technology and Manufacturing Conference (EDTM), 06.04.2020, Penang, Malaysia

Permalink: https://www.hzdr.de/publications/Publ-32006
Publ.-Id: 32006


Coding and decoding stray magnetic fields for multiplexing kinetic bioassay platform

Liu, Y.; Lin, G.; Chen, Y.; Mönch, J. I.; Makarov, D.; Walsh, B. J.; Jin, D.

Polymer microspheres can be fluorescently-coded for multiplexing molecular analysis, but their usage has been limited by the fluorescent quenching and bleaching and crowded spectral domain with issues of cross-talks and background interference. Each bioassay step of mixing and separation of analytes and reagents require off-line particle handling procedures. Here, we report stray magnetic fields can code and decode a collection of hierarchically-assembled beads. By the microfluidic assembling of mesoscopic superparamagnetic cores, diverse and non-volatile stray magnetic field response can be built in the series of microscopic spheres, dumbbells, pears, chains and triangles. Remarkably, the set of stray magnetic field fingerprints are readily discerned by a compact giant magnetoresistance sensor for parallelised screening of multiple distinctive pathogenic DNAs. This opens up the magneto-multiplexing opportunity and could enable streamlined assays to incorporate magneto-mixing, washing, enrichment and separation of analytes.
This strategy therefore suggests a potential point-of-care testing solution for efficient kinetic assay.

Keywords: magnetic field sensor; microfluidics; bioassays

Permalink: https://www.hzdr.de/publications/Publ-31999
Publ.-Id: 31999


L10 Ordered Thin Films for Spintronic and Permanent Magnet Applications

Hafarov, A.; Prokopenko, O.; Sidorenko, S.; Makarov, D.; Vladymyrskyi, I.

Materials with strong perpendicular magnetic anisotropy (PMA) are fundamentally appealing and also relevant for numerous applications especially reconsidering their practical relevance for the enhancement of the energy product for thin film based permanent magnets and realization of energy efficient and miniaturized spintronic devices. In contrast to materials exhibiting PMA due to surface anisotropy, these applications would benefit from thin films where PMA stems from a strong uniaxial magnetocrystalline anisotropy (Ku). In this regard, magnetic thin films with chemically ordered L10 structure, representing alternation of A and B atomic planes along the c direction, are considered as most promising due to the high Ku values and finely tunable magnetic properties. Typical representatives of L10 structures are ordered binary phases, e.g. FePt, FePd, MnAl, MnGa, or NiFe, etc. phases. In the case when the c axes of the L10 structure is normal to the film plane, remarkably strong PMA could can be achieved. Another important property of L10 structures is their thermodynamic stability providing resistance of corresponding devices against thermal processing. Here, we will review the application prospects of L10 ordered magnetic thin films for spintronic and permanent magnet technologies.

Keywords: L10 alloys; perpendicular magnetic anisotropy

  • Book chapter
    A. Kaidatzis, S. Sidorenko, I. Vladymyrskyi, D. Niarchos: Modern Magnetic and Spintronic Materials. NATO Science for Peace and Security Series B: Physics and Biophysics, Dordrecht: Springer, 2020, 978-94-024-2033-3
    DOI: 10.1007/978-94-024-2034-0_4

Permalink: https://www.hzdr.de/publications/Publ-31998
Publ.-Id: 31998


Influence of a low-Z thin substrate on a microwire hard x-ray source driven by a picosecond laser pulse for point-projection x-ray radiography

Meng-Ting, L.; Guang-Yue, H.; Huang, L.; Jian, Z.

In the point-projection hard x-ray radiography of dense matter, for example, an inertial confinement fusion implosion capsule at stagnation time, a picosecond laser driven gold microwire is used to produce a short pulse point, bremsstrahlung hard x-ray source. The microwire was held by a low-Z CH thin substrate commonly used to promote experimental performance. We explored the influence of the low-Z thin substrate on the microwire bremsstrahlung hard x-ray source via particle-in-cell and Monte Carlo simulations. It was shown that both of the microwires, with or without the low-Z thin substrate, could emit more intense hard x-ray radiation than the radiator buried in the equal-density substrate, which benefited from efficient electron recirculation. The freestanding microwire exhibited further enhanced electron recirculation compared to that with the low-Z thin substrate, while the increased hot electrons were only present for the energetic electrons of >1 MeV. Thus, the freestanding microwire could produce significantly more intense MeV gamma x-ray emission with respect to that with the substrate, but an ignorable increment was exhibited at the softer x-ray emission of 10–200 keV. These results provided valuable insights into the design of backlighter targets in point-projection x-ray radiography, such as a freestanding microwire being preferred in MeV gamma-ray radiography, while the microwire with the CH thin substrate could be used in the 10–200 keV hard x-ray Compton radiography of an implosion capsule.

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  • Secondary publication expected from 24.12.2021

Permalink: https://www.hzdr.de/publications/Publ-31997
Publ.-Id: 31997


PIConGPU Performance and Scaling Results on Summit

Widera, R.; Bastrakov, S.; Debus, A.; Garten, M.; Pausch, R.; Steiniger, K.; Bussmann, M.; Hübl, A.

This talk present recent performance and scaling results of Particle-in-Cell code PIConGPU on the Summit supercomputer. PIConGPU is an open-source plasma simulation code for the Exascale era. It implements a wide range of core Particle-in-Cell numerical schemes and extensions, in-situ diagnostics, and high-performance I/O. Using single-source programming approach powered by alpaka library, PIConGPU runs on a variety of modern hardware, including both CPUs and GPUs. We demonstrate that it scales from a single workstation up to the full Summit supercomputer.

Keywords: Large-scale computing; Scalability; GPGPU; Plasma simulation; Particle-in-Cell

  • Lecture (Conference) (Online presentation)
    Supercomputing Frontiers Europe 2020, 23.-25.03.2020, Warszawa, Polska

Permalink: https://www.hzdr.de/publications/Publ-31996
Publ.-Id: 31996


Pedal to the Metal: Designing a Scalable Particle-in-Cell Code PIConGPU

Bastrakov, S.; Widera, R.; Debus, A.; Garten, M.; Pausch, R.; Steiniger, K.; Hübl, A.; Bussmann, M.

PIConGPU is an open-source Particle-in-Cell simulation code for the Exascale era. It implements a wide range of core Particle-in-Cell numerical schemes and extensions, in-situ diagnostics, and high-performance I/O. With a single source code base, PIConGPU runs on a variety of modern hardware, including both CPUs and GPUs, and scales from a single workstation up to the largest supercomputers. Following up the two recent talks concerning physical and numerical features of PIConGPU, this talk will focus on the computer science and software design aspects of the code and the underlying software stack. The talk concerns PIConGPU core data structures, typical patterns of parallel processing, and software design approach to enable efficient and scalable single-source implementation. It also presents performance and scaling results on the Summit supercomputer.

Keywords: Particle-in-Cell; plasma simulation; scalable computing; single-source programming; PIConGPU; alpaka

  • Lecture (others)
    CASUS Seminar, 01.10.2020, Görlitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31995
Publ.-Id: 31995


alpaka Parallel Programming - Online Tutorial

Stephan, J.; Bastrakov, S.; Widera, R.; Ehrig, S.; Bussmann, M.

Alpaka (Abstraction Library for Parallel Kernel Acceleration) provides a library and tools for programming compute accelerators on a device agnostic level. This online tutorial will give an introduction to Alpaka combined with online exercises.

Keywords: alpaka; parallel programming; accelerators; C++

  • Open Access Logo Lecture (others) (Online presentation)
    alpaka Parallel Programming - Online Tutorial, 29.06.-03.07.2020, Genf, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-31993
Publ.-Id: 31993


Lessons Learned Developing Frameworks with SYCL

Stephan, J.

alpaka is a header-only C++ library for developing portable high-performance programs. Much like SYCL, it aims to abstract away the differences between accelerator types and vendors. In 2019 an experimental SYCL backend was developed in order to target FPGAs. In my talk I will focus on the challenges I faced during the SYCL backend development as well as conceptual differences between SYCL and other heterogeneous programming platforms.

Keywords: SYCL; alpaka; parallel programming; C++

  • Open Access Logo Lecture (others) (Online presentation)
    SYCL Summer Sessions 2020, 31.08.-04.09.2020, London, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-31992
Publ.-Id: 31992


Mirror twin boundaries in MoSe₂ monolayers as one dimensional nanotemplates for selective water adsorption

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

Water adsorption on transition metal dichalcogenides and other 2D materials is generally governed by weak van der Waals interactions. This results in a hydrophobic character of the basal planes, and defects may play a significant role in water adsorption and water cluster nucleation. However, there is a lack of detailed experimental investigations on water adsorption on defective 2D materials. Here, by combining low-temperature scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations, we study in that context the well-defined mirror twin boundary (MTB) networks separating mirror-grains in 2D MoSe2. These MTBs are dangling bond-free extended crystal modifications with metallic electronic states embedded in the 2D semiconducting matrix of MoSe2. Our DFT calculations indicate that molecular water also interacts similarly weak with these MTBs as with the defect-free basal plane of MoSe2. However, in low temperature STM experiments, nanoscopic water structures are observed that selectively decorate the MTB network. This localized adsorption of water is facilitated by functionalization of the MTBs by hydroxyls formed by dissociated water. Hydroxyls may form by dissociating of water at undercoordinated defects or adsorbing of radicals from the gas phase in the UHV chamber. Our DFT analysis indicates that the metallic MTBs adsorb these radicals much stronger than on the basal plane due to charge transfer from the metallic states into the molecular orbitals of the OH groups. Once the MTBs are functionalized with hydroxyls, molecular water can attach to them, forming water channels along the MTBs. This study demonstrates the role metallic defect states play in the adsorption of water even in the absence of unsaturated bonds that have been so far considered to be crucial for adsorption of hydroxyls or water.

Keywords: van der Waals materials; water adsorption; defect engineering; hydroxylation; metallic defect states; molecular scale adsorption template

Permalink: https://www.hzdr.de/publications/Publ-31988
Publ.-Id: 31988


Geological Remote Sensing

Booysen, R.; Gloaguen, R.; Lorenz, S.; Zimmermann, R.; Nex, P.

Remote sensing is commonly defined either as the data acquisition about an object or a process at a distance or the scanning of the Earth by satellite or high-flying aircraft. In the present article, we will consider all the relevant sensors and techniques that allow the imaging, measurement and monitoring of the Earth’s surface from a distance greater than 10 m.

Permalink: https://www.hzdr.de/publications/Publ-31986
Publ.-Id: 31986


Crystallization of optically thick films of CoxFe80−xB20: Evolution of optical, magneto-optical, and structural properties

Sharma, A.; Hoffmann, M. A.; Matthes, P.; Hellwig, O.; Kowol, C.; Schulz, S. E.; Zahn, D. R. T.; Salvan, G.

CoFeB alloys are highly relevant materials for spintronic applications. In this work, the crystallization of CoFeB alloys triggered by thermal annealing was investigated by x-ray diffraction techniques and scanningelectron microscopy, as well as spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy forannealing temperatures ranging from 300 to 600◦C. The transformation of∼100-nm-thick CoxFe(80−x)B20filmsfrom amorphous to polycrystalline was revealed by the sharpening of spectral features observed in optical andmagneto-optical dielectric functions spectra. The influence of B on the dielectric function was assessed bothexperimentally and by optical modeling. By analyzing the Drude component of the optical dielectric function,a consistent trend between the charge-carrier scattering time/resistivity and the annealing temperature wasobserved, in agreement with the electrical investigations by means of the four-point-probe method.

Permalink: https://www.hzdr.de/publications/Publ-31984
Publ.-Id: 31984


Manipulating the Energy Balance of Perpendicular-Anisotropy Synthetic Antiferromagnets by He+-Ion Irradiation

Koch, L.; Samad, F.; Lenz, M.; Hellwig, O.

He+-ion irradiation enables controlled postdeposition modification of layered magnetic thin-film sys-tems. The degree of modification and its depth profile can be tuned by the irradiation dose and energy.Here, we use magnetometry and magnetic force microscopy to explore the impact of gentle He+-ion irra-diation on synthetic antiferromagnets, consisting of ferromagnetic Co/Pt multilayers with perpendicularmagnetic anisotropy, which are antiferromagnetically (AF) coupled via Ru interlayers. This system showsa rich variety of magnetic domain patterns due to the strong competition between different magnetic ener-gies. We show that AF interlayer exchange and perpendicular interface anisotropy energy are graduallyreduced by the ion irradiation while the demagnetization energy is mainly preserved, which thus results inmultiple successive magnetic-phase transitions.

Permalink: https://www.hzdr.de/publications/Publ-31983
Publ.-Id: 31983


Algorithms for the Exploration of an Automated STM DAQ Hardware Development Process based on Continuous Integration for the Mu2e Experiment

Ufer, R.; Voigt, M.; Müller, S.; Knodel, O.

This project contains the source code for the evaluation of an automated process which converts algorithms written in C/C++ to Data Acquisition (DAQ) hardware cores on Field Programmable Gate Arrays (FPGAs) using Continuous Integration (CI). The cores are building blocks of the DAQ for the Stopping-Target-Monitor of the MU2E experiment currently in construction at FERMILAB (USA). The MU2E experiment will search for Charged Lepton Flavor Violation (CLFV) looking for the direct decay of a muon into an electron.

Keywords: Data Management; DAQ; FPGA; Mu2e

  • Software in the HZDR data repository RODARE
    Publication date: 2021-01-07
    DOI: 10.14278/rodare.720
    License: BSD-3-Clause

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Permalink: https://www.hzdr.de/publications/Publ-31982
Publ.-Id: 31982


Edge localization of spin waves in antidot multilayers with perpendicular magnetic anisotropy

Pan, S.; Mondal, S.; Zelent, M.; Szwierz, R.; Pal, S.; Hellwig, O.; Krawczyk, M.; Barman, A.

We study the spin-wave dynamics in nanoscale antidot lattices based on Co/Pd multilayers with perpendicularmagnetic anisotropy. Using time-resolved magneto-optical Kerr effect measurements we demonstrate that thevariation of the antidot shape introduces significant change in the spin-wave spectra, especially in the lowerfrequency range. By employing micromagnetic simulations we show that additional peaks observed in themeasured spectra are related to narrow shell regions around the antidots, where in-plane domain structures areformed. This is because the magnetic anisotropy in these regions is reduced due to the Ga(+)ion irradiation duringthe focused ion beam milling process of the antidot fabrication. The results point at possibilities for exploitationof localized spin waves in out-of-plane magnetized thin films, which are easily tunable and suitable for magnonicapplications.

Permalink: https://www.hzdr.de/publications/Publ-31981
Publ.-Id: 31981


UAS-based hyperspectral and magnetic mineral exploration targeting Ni-PGE mineralization on Northern Disko Island, West Greenland

Jackisch, R.; Zimmermann, R.; Heincke, B.; Karinen, A.; Salmirinne, H.; Pirtijärvi, M.; Lorenz, S.; Madriz Diaz, Y. C.; Gloaguen, R.

Geologic mapping in arctic regions faces demanding challenges, from accessibility to weather, light and infrastructure conditions. Field expeditions need to cover substantial area, and mostly are supported by satellite and airborne data. While named methods offer large-scaled insights, they often lack the required resolution for precise ground investigations. The rise of unmanned aerial systems (UAS) as new state-of-the-art platform in geoscience provides the means needed to close that scale gap.

Fieldwork within the frame of the EIT project MULSEDRO focused on the Paleocene flood basalt province of Disko Island (West Greenland). On the example of the Qullissat area, we demonstrate how UAS can bring new insights into strategies for magmatic Ni-PGE exploration in the area. Mineralization is associated to basalt sills of the Asuk Member, emplaced locally in coal-bearing cretaceous sandstones. We conducted photogrammetric outcrop modelling, interpretation of orthoimagery, multi- and hyperspectral based lithological classification and analysis of magnetic data. While magnetics give the location, orientation and subsurface extension of the basaltic sills, spectral imaging, in particular with focus on the iron absorption feature, reveals mineral proxies due to sulphide weathering. A total of 216 line-km for magnetics and 18.5 km2 of multi- and hyperspectral data was covered.

First results show that integration of drone-borne spectroscopic and magnetic data highlights potential local mineralization. Based on our results, possible indications for mineralization are linear features in the first vertical derivative of the magnetic data and specific iron absorptions in the spectral data. Resulting maps are validated using handheld spectroscopy, ground magnetics, susceptibility measurements, combined with geochemistry and mineralogy of rock samples examined in the laboratory. Conclusively, the study solidifies UAS as highly valuable tool for exploration.

Keywords: unmanned aerial vehicles; magnetics; multispectral; hyperspectral; Greenland

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Permalink: https://www.hzdr.de/publications/Publ-31977
Publ.-Id: 31977


Science Blog: Game of drones – unmanned aerial vehicles in mineral exploration and geological mapping

Salmirinne, H.; Heincke, B.; Jackisch, R.; Saartenoja, A.

Over the last ten years, unmanned aerial vehicles (UAV), commonly called drones, and related systems have rapidly developed. Everyman’s drones are available on store shelves to take photos and videos of holidays, one’s own house and garden, and for many other private reasons. With the general advances in robotics and digitalization, drones have also been increasingly utilized for various commercial applications. This trend can additionally be seen in geosciences. A key question arising for many geoscience applications is whether drones could be used as platforms to carry out more demanding surveys with remote sensing and geophysical sensors that have traditionally been mounted on aircraft or have been carried by workers on the ground. The answer is yes, drones can be used, although the integration of such sensors on drones is not straightforward. The methods themselves are typically well developed, but drones as an aspiring platform pose challenges for operating sensors and performing measurement procedures in proper ways. In particular, the need for small and lightweight sensors with a low power consumption for UAV platforms plays an important role, because they allow flexible low-cost measurements to be performed without a long preparation phase. Another aspect is that legislation, which varies from country to country, affects drone operations. Therefore, it is often difficult in practice for drone-operating companies to provide international services, and it is generally easier to obtain permission for small drones flying at low altitude only. To find a remedy for this, a common EU-wide regulation is currently in preparation. EU drone regulation (EU) 2019/947 defines the rules and procedures for different types of drone operations and is intended to be applied according to the transition period of the regulation on 31 December 2020.

In recent years, many groups all over the world – both in academia and industry – have worked on the integration of various sensor types on drones that are relevant for geological mapping and mineral exploration. Drone-borne survey systems are considered to be especially appropriate for small to medium-sized surveys that are smaller than those carried out with traditional aircraft, but larger than ground-based surveys. The goal of many companies is to offer drone-based services for this market niche.

Keywords: unmanned aerial vehicles; mineral mapping; hyperspectral imaging; magnetics

Permalink: https://www.hzdr.de/publications/Publ-31976
Publ.-Id: 31976


Component Decomposition-Based Hyperspectral Resolution Enhancement for Mineral Mapping

Duan, P.; Lai, J.; Ghamisi, P.; Kang, X.; Jackisch, R.; Kang, J.; Gloaguen, R.

Combining both spectral and spatial information with enhanced resolution provides not only elaborated qualitative information on surfacing mineralogy but also mineral interactions of abundance, mixture, and structure. This enhancement in the resolutions helps geomineralogic features such as small intrusions and mineralization become detectable. In this paper, we investigate the potential of the resolution enhancement of hyperspectral images (HSIs) with the guidance of RGB images for mineral mapping. In more detail, a novel resolution enhancement method is proposed based on component decomposition. Inspired by the principle of the intrinsic image decomposition (IID) model, the HSI is viewed as the combination of a reflectance component and an illumination component. Based on this idea, the proposed method is comprised of several steps. First, the RGB image is transformed into the luminance component, blue-difference and red-difference chroma components (YCbCr), and the luminance channel is considered as the illumination component of the HSI with an ideal high spatial resolution. Then, the reflectance component of the ideal HSI is estimated with the downsampled HSI image and the downsampled luminance channel. Finally, the HSI with high resolution can be reconstructed by utilizing the obtained illumination and the reflectance components. Experimental results verify that the fused results can successfully achieve mineral mapping, producing better results qualitatively and quantitatively over single sensor data.

Keywords: hyperspectral image; mineral mapping; resolution enhancement; intrinsic image decomposition

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Permalink: https://www.hzdr.de/publications/Publ-31975
Publ.-Id: 31975


Thermal treatment of materials on short time scales

Rebohle, L.; Prucnal, S.; Cherkouk, C.; Berencen, Y.; Skorupa, I.

Important technological developments of our time such as the energy transition or digitalization require new materials and more efficient manufacturing processes. The processes of ultra-short time annealing such as flash lamp annealing (FLA) and laser annealing have the potential to make an important contribution. During such processes high temperatures are applied for very short times (nano- to milliseconds), so that only near surface regions of the material are exposed to the maximum temperature. Compared to conventional thermal treatments, ultra-short time annealing enables energy and process time savings, the use of temperature-sensitive substrates, and the synthesis of new materials in thermal non-equilibrium.
The talk is divided into two parts. After an introduction, the first part discusses the main features of FLA in comparison with other short time annealing techniques, namely rapid thermal annealing and laser annealing. Special focus is set on temperature and its determination, as this is a complex and challenging issue on short time scales. The second part deals with various examples of applying FLA to materials, ranging from semiconductor applications over printed electronics to energy materials for batteries.

Keywords: ultra-short time annealing; flash lamp annealing; ion implantation; energy materials; lithium ion battery

  • Lecture (others)
    Kooperationstreffen Universität Lublin, 08.10.2020, Lublin, Polen

Permalink: https://www.hzdr.de/publications/Publ-31974
Publ.-Id: 31974


BlitzLab – ein Helmholtz Innovation Lab

Rebohle, L.; Cherkouk, C.; Folgner, C.; Prucnal, S.; Schumann, T.; Krüger, S.

Der Vortrag stellt das Helmholtz Innovation Lab blitzlab vor und geht danach auf die Blitzlampenausheilung als ein innovatives Verfahren zur thermischen Behandlung von Materialien und Werkstoffen ein.

Keywords: Helmholtz Innovation Lab blitzlab; flash lamp annealing; ultra-short annealing

  • Lecture (others)
    Arbeitstreffen am IMWS, 30.09.2020, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31973
Publ.-Id: 31973


Data for: The structure in warm dense carbon

Vorberger, J.; Plageman, K.-U.; Redmer, R.

The structure of the fluid carbon phase in the pressure region of the graphite, diamond, and BC8 solid phases is investigated. We find increasing coordination numbers with an increase in density. From zero to 30 GPa, the liquid shows a decrease of packing efficiency with increasing temperature. However, for higher pressures, the coordination number increases with increasing temperature. Up to 1.5 eV and independent of the pressure up to 1500 GPa, a double-peak structure in the ion structure factors exists, indicating persisting covalent bonds. Over the whole pressure range from zero to 3000 GPa, the fluid structure and properties are strongly determined by such covalent bonds.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-06
    DOI: 10.14278/rodare.716
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31971
Publ.-Id: 31971


Nanosensor-Based Real-Time Monitoring of Stress Biomarkers in Human Saliva Using a Portable Measurement System

Klinghammer, S.; Voitsekhivska, T.; Licciardello, N.; Kim, K.; Baek, C.-K.; Cho, H.; Wolter, K.-J.; Kirschbaum, C.; Baraban, Larysa; Cuniberti, G.

Small molecules with no or little charge are considered to have minimal impact on signals measured by field effect transistor (FET) sensors. This fact typically excludes steroids from the family of analytes, detected by FETs. We present a portable multiplexed platform based on an array of nanowire sensors for label-free monitoring of daytime levels of the stress hormone cortisol in saliva samples, obtained from multiple donors. To achieve an effective quantification of the cortisol with FETs, we rely on the specific DNA aptamer sequences as receptors, bringing the complex “target-receptor” closer to the nanowire surface. Upon binding, cortisol induces conformational changes of negatively charged aptamers, wrapping it into a close proximity to the silicon nanowires, to efficiently modulate their surface potential. Thus, the sensors allow for a real-time assessment of the steroid biomarkers at low nanomolar concentration. The measurement platform is designed in a building-block concept, consisting of a modular measuring unit and a customizable biochip board, and operates using a complementary metal-oxide-semiconductor-integrated multiplexer. The platform is capable of continuous and simultaneous measurement of samples from multiple patients. Cortisol levels detected with the presented platform agreed well with the results obtained with a commercial high-sensitivity immunoassay

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  • Secondary publication expected from 03.12.2021

Permalink: https://www.hzdr.de/publications/Publ-31970
Publ.-Id: 31970


Laser-driven ion accelerators for applications in radiobiology

Metzkes-Ng, J.

Laser-driven plasmas – generated in the interaction of a focused high power laser pulse with a solid surface – can sustain electrical field strengths of ~TV/m, allowing for compact and efficient particle acceleration of proton pulses with up to 100 MeV kinetic energies on ~µm spatial scales. The particle pulses feature a picosecond pulse duration at the source and extremely high pulse currents and dose, making them an ideal tool for laboratory-scale high dose-rate radiobiology research.
At the Draco Petawatt laser source, we have established and now successfully operate a source-to-sample just meter-scale setup for high dose-rate in vivo radiobiological studies based on a laser-driven proton source and a compact, versatile pulsed high-field magnetic beamline.
The setup development and preliminary experimental results will be presented, also intending to foster collaborations within HZDR for a wide range of high dose-rate applications.

Keywords: laser-driven proton acceleration; high dose-rate radiobiology

  • Lecture (others)
    HZDR Research Talk, 14.10.2020, Dresden, Deutschland
  • Lecture (others) (Online presentation)
    3rd Laser-Plasma Summer School (LAPLASS_3), 14.-18.09.2020, Salamanca, Spanien

Permalink: https://www.hzdr.de/publications/Publ-31969
Publ.-Id: 31969


Deep point embedding for urban classification using ALS point clouds: A new perspective from local to global

Huang, R.; Xu, Y.; Hong, D.; Yao, W.; Ghamisi, Pedram; Stilla, U.

Semantic interpretation of the 3D scene is one of the most challenging problems in point cloud processing, which also deems as an essential task in a wide variety of point cloud applications. The core task of semantic interpretation is semantic labeling, namely, obtaining a unique semantic label for each point in the point cloud. Despite several reported approaches, semantic labeling continues to be a challenge owing to the complexity of scenes, objects of various scales, and the non-homogeneity of unevenly distributed points. In this paper, we propose a novel method for obtaining semantic labels of airborne laser scanning (ALS) point clouds involving the embedding of local context information for each point with multi-scale deep learning, nonlinear manifold learning for feature dimension reduction, and global graph-based optimization for refining the classification results. Specifically, we address the tasks of learning discriminative features and global labeling smoothing. The key contribution of our study is threefold. First, a hierarchical data augmentation strategy is applied to enhance the learning of deep features based on the PointNet++ network and simultaneously eliminate the artifacts caused by division and sampling while dealing with large-scale datasets. Subsequently, the learned hierarchical deep features are globally optimized and embedded into a low-dimensional space with a nonlinear manifold-based joint learning method with the removal of redundant and disturbing information. Finally, a graph-structured optimization based on the Markov random fields algorithm is performed to achieve global optimization of the initial classification results that are obtained using the embedded deep features by constructing a weighted indirect graph and solving the optimization problem with graph-cuts. We conducted thorough experiments on ALS point cloud datasets to assess the performance of our framework. Results indicate that compared to other commonly used advanced classification methods, our method can achieve high classification accuracy. The overall accuracy (OA) of our approach on the ISPRS benchmark dataset can scale up to 83.2% for classifying nine semantic classes, thereby outperforming other compared point-based strategies. Additionally, we evaluated our framework on a selected portion of the AHN3 dataset, which provided OA up to 91.2%.

Permalink: https://www.hzdr.de/publications/Publ-31968
Publ.-Id: 31968


Texture-Aware Total Variation-Based Sun Glint Removal of Hyperspectral Images

Duan, P.; Lai, J.; Kang, J.; Kang, X.; Ghamisi, Pedram; Li, S.

Sun glint in hyperspectral images (HSIs) leads to undesirable spectral interference, which severely affects subsequent image interpretation, such as environmental monitoring of coastal areas. Sun glint removal methods aim to recover a high quality image without sun glint from the original image. Most methods depend on an assumption that the near infrared band is strongly absorbed by water. However, this assumption is not always reliable because the infrared radiation in shallow or turbid water can be reflected back by the seabed or sediment, rather than being fully absorbed. Therefore, the reflected infrared radiation still contains sun glint and these methods cannot sufficiently remove sun glint from HSIs. To address this problem, a texture-aware total variation (TATV)-based method is proposed to remove sun glint from HSIs. The original HSI first is formulated as a desired clean image and a sun glint image. Then, in order to remove the sun glint, we propose a variational model where the different spectral characteristics of sun glint and other surrounding materials are considered. Specifically, we propose a texture-aware total variation regularized method to heavily penalize the variation of the sun glint areas. Experiments performed on simulated and real data sets demonstrate that our method can greatly outperform other state-of-the-art methods in removing sun glint.

  • ISPRS Journal of Photogrammetry and Remote Sensing 166(2020), 10.1016/j.isprsjprs.2020.06.009

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  • Secondary publication expected from 08.07.2021

Permalink: https://www.hzdr.de/publications/Publ-31967
Publ.-Id: 31967


Machine learning information fusion in Earth observation: A comprehensive review of methods, applications and data sources

Salcedo-Sanz, S.; Ghamisi, P.; Piles, M.; Werner, M.; Cuadra, L.; Moreno-Martínez, A.; Izquierdo-Verdiguier, E.; Muñoz-Marí, J.; Amirhosein, M.; Camps-Valls, G.

This paper reviews the most important information fusion data-driven algorithms based on Machine Learning (ML) techniques for problems in Earth observation. Nowadays we observe and model the Earth with a wealth of observations, from a plethora of different sensors, measuring states, fluxes, processes and variables, at unprecedented spatial and temporal resolutions. Earth observation is well equipped with remote sensing systems, mounted on satellites and airborne platforms, but it also involves in-situ observations, numerical models and social media data streams, among other data sources. Data-driven approaches, and ML techniques in particular, are the natural choice to extract significant information from this data deluge. This paper produces a thorough review of the latest work on information fusion for Earth observation, with a practical intention, not only focusing on describing the most relevant previous works in the field, but also the most important Earth observation applications where ML information fusion has obtained significant results. We also review some of the most currently used data sets, models and sources for Earth observation problems, describing their importance and how to obtain the data when needed. Finally, we illustrate the application of ML data fusion with a representative set of case studies, as well as we discuss and outlook the near future of the field.

Permalink: https://www.hzdr.de/publications/Publ-31966
Publ.-Id: 31966


Deep Metric Learning Based on Scalable Neighborhood Components for Remote Sensing Scene Characterization

Kang, J.; Fernandez-Beltran, R.; Ye, Z.; Tong, X.; Ghamisi, P.; Plaza, A.

With the development of convolutional neural networks (CNNs), the semantic understanding of remote sensing (RS) scenes has been significantly improved based on their prominent feature encoding capabilities. While many existing deep-learning models focus on designing different architectures, only a few works in the RS field have focused on investigating the performance of the learned feature embeddings and the associated metric space. In particular, two main loss functions have been exploited: the contrastive and the triplet loss. However, the straightforward application of these techniques to RS images may not be optimal in order to capture their neighborhood structures in the metric space due to the insufficient sampling of image pairs or triplets during the training stage and to the inherent semantic complexity of remotely sensed data. To solve these problems, we propose a new deep metric learning approach, which overcomes the limitation on the class discrimination by means of two different components: 1) scalable neighborhood component analysis (SNCA) that aims at discovering the neighborhood structure in the metric space and 2) the cross-entropy loss that aims at preserving the class discrimination capability based on the learned class prototypes. Moreover, in order to preserve feature consistency among all the minibatches during training, a novel optimization mechanism based on momentum update is introduced for minimizing the proposed loss. An extensive experimental comparison (using several state-of-the-art models and two different benchmark data sets) has been conducted to validate the effectiveness of the proposed method from different perspectives, including: 1) classification; 2) clustering; and 3) image retrieval. The related codes of this article will be made publicly available for reproducible research by the community.

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  • Secondary publication expected from 12.12.2021

Permalink: https://www.hzdr.de/publications/Publ-31965
Publ.-Id: 31965


An Efficient Deep Unsupervised Superresolution Model for Remote Sensing Images

Sheikholeslami, M. M.; Nadi, S.; Naeini, A. A.; Ghamisi, P.

Superresolution (SR) has provided an effective solution to the increasing need for high-resolution images in remote sensing applications. Among various SR methods, deep learning-based SR (DLSR) has made a significant breakthrough. However, supervised DLSR methods require a considerable amount of training data, which is hardly available in the remote sensing field. To address this issue, some research works have recently proposed and revealed the capability of deep learning in unsupervised SR. This article presents an efficient unsupervised SR (EUSR) deep learning model using dense skip connections, which boosts the reconstruction performance in parallel with the reduction of computational burden. To do this, several blocks containing densely connected convolutional layers are implemented to increase the depth of the model. Some skip connections also concatenate feature maps of different blocks to enable better SR performance. Moreover, a bottle-neck block abstracts the feature maps in fewer feature maps to remarkably reduce the computational burden. According to our experiments, the proposed EUSR leads to better results than the state-of-the-art DLSR method in terms of reconstruction quality with less computational burden. Furthermore, results indicate that the EUSR is more robust than its rival in dealing with images of different classes and larger sizes.

  • Open Access Logo IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 13(2020), 1937-1945
    DOI: 10.1109/JSTARS.2020.2984589

Permalink: https://www.hzdr.de/publications/Publ-31964
Publ.-Id: 31964


COVID-19 Outbreak Prediction with Machine Learning

Ardabili, S. F.; Mosavi, A.; Ghamisi, Pedram; Ferdinand, F.; Varkonyi-Koczy, A. R.; Reuter, U.; Rabczuk, T.; Atkinson, P. M.

Several outbreak prediction models for COVID-19 are being used by officials around the world to make informed decisions and enforce relevant control measures. Among the standard models for COVID-19 global pandemic prediction, simple epidemiological and statistical models have received more attention by authorities, and these models are popular in the media. Due to a high level of uncertainty and lack of essential data, standard models have shown low accuracy for long-term prediction. Although the literature includes several attempts to address this issue, the essential generalization and robustness abilities of existing models need to be improved. This paper presents a comparative analysis of machine learning and soft computing models to predict the COVID-19 outbreak as an alternative to susceptible–infected–recovered (SIR) and susceptible-exposed-infectious-removed (SEIR) models. Among a wide range of machine learning models investigated, two models showed promising results (i.e., multi-layered perceptron, MLP; and adaptive network-based fuzzy inference system, ANFIS). Based on the results reported here, and due to the highly complex nature of the COVID-19 outbreak and variation in its behavior across nations, this study suggests machine learning as an effective tool to model the outbreak. This paper provides an initial benchmarking to demonstrate the potential of machine learning for future research. This paper further suggests that a genuine novelty in outbreak prediction can be realized by integrating machine learning and SEIR models.

Permalink: https://www.hzdr.de/publications/Publ-31963
Publ.-Id: 31963


COVID-19 Pandemic Prediction for Hungary; A Hybrid Machine Learning Approach

Pinter, G.; Felde, I.; Mosavi, A.; Ghamisi, Pedram; Gloaguen, R.

Several epidemiological models are being used around the world to project the number of infected individuals and the mortality rates of the COVID-19 outbreak. Advancing accurate prediction models is of utmost importance to take proper actions. Due to the lack of essential data and uncertainty, the epidemiological models have been challenged regarding the delivery of higher accuracy for long-term prediction. As an alternative to the susceptible-infected-resistant (SIR)-based models, this study proposes a hybrid machine learning approach to predict the COVID-19, and we exemplify its potential using data from Hungary. The hybrid machine learning methods of adaptive network-based fuzzy inference system (ANFIS) and multi-layered perceptron-imperialist competitive algorithm (MLP-ICA) are proposed to predict time series of infected individuals and mortality rate. The models predict that by late May, the outbreak and the total morality will drop substantially. The validation is performed for 9 days with promising results, which confirms the model accuracy. It is expected that the model maintains its accuracy as long as no significant interruption occurs. This paper provides an initial benchmarking to demonstrate the potential of machine learning for future research.

Permalink: https://www.hzdr.de/publications/Publ-31962
Publ.-Id: 31962


Remote Sensing Image Classification Using Subspace Sensor Fusion

Rasti, B.; Ghamisi, P.

The amount of remote sensing and ancillary datasets captured by diverse airborne and spaceborne sensors has been tremendously increased, which opens up the possibility of utilizing multimodal datasets to improve the performance of processing approaches with respect to the application at hand. However, developing a generic framework with high generalization capability that can effectively fuse diverse datasets is a challenging task since the current approaches are usually only applicable to two specific sensors for data fusion. In this paper, we propose an accurate fusion-based technique called SubFus with capability to integrate diverse remote sensing data for land cover classification. Here, we assume that a high dimensional multisensor dataset can be represented fused features that live in a lower-dimensional space. The proposed classification methodology includes three main stages. First, spatial information is extracted by using spatial filters (i.e., morphology filters). Then, a novel low- rank minimization problem is proposed to represent the multisensor datasets in subspaces using fused features. The fused features in the lower-dimensional subspace are estimated using a novel iterative algorithm based on the alternative direction method of multipliers. Third, the final classification map is produced by applying a supervised spectral classifier (i.e., random forest) on the fused features. In the experiments, the proposed method is applied to a three-sensor (RGB, multispectral LiDAR, and hyperspectral images) dataset captured over the area of the University of Houston, the USA, and a two-sensor (hyperspectral and LiDAR) dataset captured over the city of Trento, Italy. The land-cover maps generated using SubFus are evaluated based on classification accuracies. Experimental results obtained by SubFus confirm considerable improvements in terms of classification accuracies compared with the other methods used in the experiments. The proposed fusion approach obtains 85.32% and 99.25% in terms of overall classification accuracy on the Houston (the training portion of the dataset distributed for the data fusion contest of 2018) and trento datasets, respectively.

Related publications

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  • Secondary publication expected from 01.12.2021

Permalink: https://www.hzdr.de/publications/Publ-31961
Publ.-Id: 31961


Support Vector Machine Versus Random Forest for Remote Sensing Image Classification: A Meta-Analysis and Systematic Review

Sheykhmousa, M.; Mahdianpari, M.; Ghanbari, H.; Mohammadimanesh, F.; Ghamisi, P.; Homayouni, S.

Several machine-learning algorithms have been proposed for remote sensing image classification during the past two decades. Among these machine learning algorithms, Random Forest (RF) and Support Vector Machines (SVM) have drawn attention to image classification in several remote sensing applications. This article reviews RF and SVM concepts relevant to remote sensing image classification and applies a meta-analysis of 251 peer-reviewed journal papers. A database with more than 40 quantitative and qualitative fields was constructed from these reviewed papers. The meta-analysis mainly focuses on 1) the analysis regarding the general characteristics of the studies, such as geographical distribution, frequency of the papers considering time, journals, application domains, and remote sensing software packages used in the case studies, and 2) a comparative analysis regarding the performances of RF and SVM classification against various parameters, such as data type, RS applications, spatial resolution, and the number of extracted features in the feature engineering step. The challenges, recommendations, and potential directions for future research are also discussed in detail. Moreover, a summary of the results is provided to aid researchers to customize their efforts in order to achieve the most accurate results based on their thematic applications.

  • Open Access Logo IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 13(2020), 6308-6325
    DOI: 10.1109/JSTARS.2020.3026724

Permalink: https://www.hzdr.de/publications/Publ-31960
Publ.-Id: 31960


Data Science in Economics: Comprehensive Review of Advanced Machine Learning and Deep Learning Methods

Nosratabadi, S.; Mosavi, A.; Duan, P.; Ghamisi, Pedram; Filip, F.; Band, S. S.; Reuter, U.; Gama, J.; Gandomi, A. H.

This paper provides a comprehensive state-of-the-art investigation of the recent advances in data science in emerging economic applications. The analysis is performed on the novel data science methods in four individual classes of deep learning models, hybrid deep learning models, hybrid machine learning, and ensemble models. Application domains include a broad and diverse range of economics research from the stock market, marketing, and e-commerce to corporate banking and cryptocurrency. Prisma method, a systematic literature review methodology, is used to ensure the quality of the survey. The findings reveal that the trends follow the advancement of hybrid models, which outperform other learning algorithms. It is further expected that the trends will converge toward the evolution of sophisticated hybrid deep learning models.

Permalink: https://www.hzdr.de/publications/Publ-31959
Publ.-Id: 31959


Fusion of Dual Spatial Information for Hyperspectral Image Classification

Duan, P.; Ghamisi, P.; Kang, X.; Rasti, B.; Li, S.; Gloaguen, R.

The inclusion of spatial information into spectral classifiers for fine-resolution hyperspectral imagery has led to significant improvements in terms of classification performance. The task of spectral-spatial hyperspectral image classification has remained challenging because of high intraclass spectrum variability and low interclass spectral variability. This fact has made the extraction of spatial information highly active. In this work, a novel hyperspectral image classification framework using the fusion of dual spatial information is proposed, in which the dual spatial information is built by both exploiting pre-processing feature extraction and post-processing spatial optimization. In the feature extraction stage, an adaptive texture smoothing method is proposed to construct the structural profile (SP), which makes it possible to precisely extract discriminative features from hyperspectral images. The SP extraction method is used here for the first time in the remote sensing community. Then, the extracted SP is fed into a spectral classifier. In the spatial optimization stage, a pixel-level classifier is used to obtain the class probability followed by an extended random walker-based spatial optimization technique. Finally, a decision fusion rule is utilized to fuse the class probabilities obtained by the two different stages. Experiments performed on three data sets from different scenes illustrate that the proposed method can outperform other state-of-the-art classification techniques. In addition, the proposed feature extraction method, i.e., SP, can effectively improve the discrimination between different land covers.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31957
Publ.-Id: 31957


Spatial Analysis of Seasonal Precipitation over Iran: Co-Variation with Climate Indices

Dehghani, M.; Salehi, S.; Mosavi, A.; Nabipour, N.; Shamshirband, S.; Ghamisi, P.

Temporary changes in precipitation may lead to sustained and severe drought or massive floods in different parts of the world. Knowing the variation in precipitation can effectively help the water resources decision-makers in water resources management. Large-scale circulation drivers have a considerable impact on precipitation in different parts of the world. In this research, the impact of El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO) on seasonal precipitation over Iran was investigated. For this purpose, 103 synoptic stations with at least 30 years of data were utilized. The Spearman correlation coefficient between the indices in the previous 12 months with seasonal precipitation was calculated, and the meaningful correlations were extracted. Then, the month in which each of these indices has the highest correlation with seasonal precipitation was determined. Finally, the overall amount of increase or decrease in seasonal precipitation due to each of these indices was calculated. Results indicate the Southern Oscillation Index (SOI), NAO, and PDO have the most impact on seasonal precipitation, respectively. Additionally, these indices have the highest impact on the precipitation in winter, autumn, spring, and summer, respectively. SOI has a diverse impact on winter precipitation compared to the PDO and NAO, while in the other seasons, each index has its special impact on seasonal precipitation. Generally, all indices in different phases may decrease the seasonal precipitation up to 100%. However, the seasonal precipitation may increase more than 100% in different seasons due to the impact of these indices. The results of this study can be used effectively in water resources management and especially in dam operation.

Permalink: https://www.hzdr.de/publications/Publ-31956
Publ.-Id: 31956


Classification of Hyperspectral and LiDAR Data Using Coupled CNNs

Hang, R.; Li, Z.; Ghamisi, P.; Hong, D.; Xia, G.; Liu, Q.

In this article, we propose an efficient and effective framework to fuse hyperspectral and light detection and ranging (LiDAR) data using two coupled convolutional neural networks (CNNs). One CNN is designed to learn spectral-spatial features from hyperspectral data, and the other one is used to capture the elevation information from LiDAR data. Both of them consist of three convolutional layers, and the last two convolutional layers are coupled together via a parameter-sharing strategy. In the fusion phase, feature-level and decision-level fusion methods are simultaneously used to integrate these heterogeneous features sufficiently. For the feature-level fusion, three different fusion strategies are evaluated, including the concatenation strategy, the maximization strategy, and the summation strategy. For the decision-level fusion, a weighted summation strategy is adopted, where the weights are determined by the classification accuracy of each output. The proposed model is evaluated on an urban data set acquired over Houston, USA, and a rural one captured over Trento, Italy. On the Houston data, our model can achieve a new record overall accuracy (OA) of 96.03%. On the Trento data, it achieves an OA of 99.12%. These results sufficiently certify the effectiveness of our proposed model.

Downloads:

  • Secondary publication expected from 06.02.2021

Permalink: https://www.hzdr.de/publications/Publ-31955
Publ.-Id: 31955


Spatial hazard assessment of the PM10 using machine learning models in Barcelona, Spain

Choubin, B.; Abdolshahnejad, M.; Moradi, E.; Querol, X.; Mosavi, A.; Shamshirband, S.; Ghamisi, P.

Air pollution, and especially atmospheric particulate matter (PM), has a profound impact on human mortality and morbidity, environment, and ecological system. Accordingly, it is very relevant predicting air quality. Although the application of the machine learning (ML) models for predicting air quality parameters, such as PM concentrations, has been evaluated in previous studies, those on the spatial hazard modeling of them are very limited. Due to the high potential of the ML models, the spatial modeling of PM can help managers to identify the pollution hotspots. Accordingly, this study aims at developing new ML models, such as Random Forest (RF), Bagged Classification and Regression Trees (Bagged CART), and Mixture Discriminate Analysis (MDA) for the hazard prediction of PM10 (particles with a diameter less than 10 µm) in the Barcelona Province, Spain. According to the annual PM10 concentration in 75 stations, the healthy and unhealthy locations are determined, and a ratio 70/30 (53/22 stations) is applied for calibrating and validating the ML models to predict the most hazardous areas for PM10. In order to identify the influential variables of PM modeling, the simulated annealing (SA) feature selection method is used. Seven features, among the thirteen features, are selected as critical features. According to the results, all the three-machine learning (ML) models achieve an excellent performance (Accuracy > 87% and precision > 86%). However, the Bagged CART and RF models have the same performance and higher than the MDA model. Spatial hazard maps predicted by the three models indicate that the high hazardous areas are located in the middle of the Barcelona Province more than in the Barcelona’s Metropolitan Area.

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Permalink: https://www.hzdr.de/publications/Publ-31953
Publ.-Id: 31953


Invariant Attribute Profiles: A Spatial-Frequency Joint Feature Extractor for Hyperspectral Image Classification

Hong, D.; Wu, X.; Ghamisi, P.; Chanussot, J.; Yokoya, N.; Zhu, X. X.

So far, a large number of advanced techniques have been developed to enhance and extract the spatially semantic information in hyperspectral image processing and analysis. However, locally semantic change, such as scene composition, relative position between objects, spectral variability caused by illumination, atmospheric effects, and material mixture, has been less frequently investigated in modeling spatial information. Consequently, identifying the same materials from spatially different scenes or positions can be difficult. In this article, we propose a solution to address this issue by locally extracting invariant features from hyperspectral imagery (HSI) in both spatial and frequency domains, using a method called invariant attribute profiles (IAPs). IAPs extract the spatial invariant features by exploiting isotropic filter banks or convolutional kernels on HSI and spatial aggregation techniques (e.g., superpixel segmentation) in the Cartesian coordinate system. Furthermore, they model invariant behaviors (e.g., shift, rotation) by the means of a continuous histogram of oriented gradients constructed in a Fourier polar coordinate. This yields a combinatorial representation of spatial-frequency invariant features with application to HSI classification. Extensive experiments conducted on three promising hyperspectral data sets (Houston2013 and Houston2018) to demonstrate the superiority and effectiveness of the proposed IAP method in comparison with several state-of-the-art profile-related techniques. The codes will be available from the website: https://sites.google.com/view/danfeng-hong/data-code.

Permalink: https://www.hzdr.de/publications/Publ-31952
Publ.-Id: 31952


Multilevel Structure Extraction-Based Multi-Sensor Data Fusion

Duan, P.; Kang, X.; Ghamisi, P.; Liu, Y.

Multi-sensor data on the same area provide complementary information, which is helpful for improving the discrimination capability of classifiers. In this work, a novel multilevel structure extraction method is proposed to fuse multi-sensor data. This method is comprised of three steps: First, multilevel structure extraction is constructed by cascading morphological profiles and structure features, and is utilized to extract spatial information from multiple original images. Then, a low-rank model is adopted to integrate the extracted spatial information. Finally, a spectral classifier is employed to calculate class probabilities, and a maximum posteriori estimation model is used to decide the final labels. Experiments tested on three datasets including rural and urban scenes validate that the proposed approach can produce promising performance with regard to both subjective and objective qualities.

Permalink: https://www.hzdr.de/publications/Publ-31951
Publ.-Id: 31951


High-Rankness Regularized Semi-Supervised Deep Metric Learning for Remote Sensing Imagery

Kang, J.; Fernández-Beltrán, R.; Ye, Z.; Tong, X.; Ghamisi, P.; Plaza, A.

Deep metric learning has recently received special attention in the field of remote sensing (RS) scene characterization, owing to its prominent capabilities for modeling distances among RS images based on their semantic information. Most of the existing deep metric learning methods exploit pairwise and triplet losses to learn the feature embeddings with the preservation of semantic-similarity, which requires the construction of image pairs and triplets based on the supervised information (e.g., class labels). However, generating such semantic annotations becomes a completely unaffordable task in large-scale RS archives, which may eventually constrain the availability of sufficient training data for this kind of models. To address this issue, we reformulate the deep metric learning scheme in a semi-supervised manner to effectively characterize RS scenes. Specifically, we aim at learning metric spaces by utilizing the supervised information from a small number of labeled RS images and exploring the potential decision boundaries for massive sets of unlabeled aerial scenes. In order to reach this goal, a joint loss function, composed of a normalized softmax loss with margin and a high-rankness regularization term, is proposed, as well as its corresponding optimization algorithm. The conducted experiments (including different state-of-the-art methods and two benchmark RS archives) validate the effectiveness of the proposed approach for RS image classification, clustering and retrieval tasks. The codes of this paper are publicly available.

Permalink: https://www.hzdr.de/publications/Publ-31950
Publ.-Id: 31950


A Multi-Sensor Fusion Framework Based on Coupled Residual Convolutional Neural Networks

Li, H.; Ghamisi, P.; Rasti, B.; Wu, Z.; Shapiro, A.; Schultz, M.; Zipf, A.

Multi-sensor remote sensing image classification has been considerably improved by deep learning feature extraction and classification networks. In this paper, we propose a novel multi-sensor fusion framework for the fusion of diverse remote sensing data sources. The novelty of this paper is grounded in three important design innovations: 1- a unique adaptation of the coupled residual networks to address multi-sensor data classification; 2- a smart auxiliary training via adjusting the loss function to address classifications with limited samples; and 3- a unique design of the residual blocks to reduce the computational complexity while preserving the discriminative characteristics of multi-sensor features. The proposed classification framework is evaluated using three different remote sensing datasets: the urban Houston university datasets (including Houston 2013 and the training portion of Houston 2018) and the rural Trento dataset. The proposed framework achieves high overall accuracies of 93.57%, 81.20%, and 98.81% on Houston 2013, the training portion of Houston 2018, and Trento datasets, respectively. Additionally, the experimental results demonstrate considerable improvements in classification accuracies compared with the existing state-of-the-art methods.

Permalink: https://www.hzdr.de/publications/Publ-31949
Publ.-Id: 31949


Creation of Gold Nanoparticles in ZnO by Ion Implantation–DFT and Experimental Studies

Cajzl, J.; Jeníčková, K.; Nekvindová, P.; Michalcová, A.; Veselý, M.; Macková, A.; Malinský, P.; Jágerová, A.; Mikšová, R.; Akhmadaliev, S.

Three different crystallographic orientations of the wurtzite ZnO structure (labeled as c-plane, a-plane and m-plane) were implanted with Au + ions using various energies and fluences to form gold nanoparticles (GNPs). The ion implantation process was followed by annealing at 600°C in an oxygen atmosphere to decrease the number of unwanted defects and improve luminescence properties. With regard to our previous publications, the paper provides a summary of theoretical and experimental results, i.e., both DFT and FLUX simulations, as well as experimental results from TEM, HRTEM, RBS, RBS/C, Raman spectroscopy and photoluminescence. From the results, it follows that in the ZnO structure, implanted gold atoms are located in random interstitial positions—experimentally, the amount of interstitial gold atoms increased with increasing ion implantation fluence. During ion implantation and subsequent annealing, the metal clusters and nanoparticles with sizes from 2 to 20 nm were formed. The crystal structure of the resulting gold was not cubic (confirmed by diffraction patterns), but it had a hexagonal close-packed (hcp) arrangement. The ion implantation of gold leads to the creation of Zn and O interstitial defects and extended defects with distinct character in various crystallographic cuts of ZnO, where significant O-sublattice disordering occurred in m-plane ZnO.

Keywords: gold; ZnO; nanoparticles; ion implantation; luminescence; DFT; RBS

Permalink: https://www.hzdr.de/publications/Publ-31948
Publ.-Id: 31948


ComputationalRadiationPhysics/picongpu: Perfectly Matched Layer (PML) and Bug Fixes

Hübl, A.; Widera, R.; Worpitz, B.; Pausch, R.; Burau, H.; Garten, M.; Starke, S.; Grund, A.; Debus, A.; Matthes, A.; Bastrakov, S.; Steiniger, K.; Göthel, I.; Rudat, S.; Kelling, J.; Bussmann, M.

This release adds a new field absorber for the Yee solver, convolutional perfectly matched layer (PML). Compared to the still supported exponential damping absorber, PML provides better absorption rate and much less spurious reflections.

We added new plugins for computing emittance and transition radiation, particle rendering with the ISAAC plugin, Python tools for reading and visualizing output of a few plugins.

The release also adds a few quality-of-life features, including a new memory calculator, better command-line experience with new options and bash-completion, improved error handling, cleanup of the example setups, and extensions to documentation.

Please refer to our ChangeLog for a full list of features, fixes and user interface changes before getting started.

Thanks to Igor Andriyash, Sergei Bastrakov, Xeinia Bastrakova, Andrei Berceanu, Finn-Ole Carstens, Alexander Debus, Jian Fuh Ong, Marco Garten, Axel Huebl, Sophie Rudat (Koßagk), Anton Lebedev, Felix Meyer, Pawel Ordyna, Richard Pausch, Franz Pöschel, Adam Simpson, Sebastian Starke, Klaus Steiniger, René Widera for contributions to this release!

Keywords: PIConGPU; Particle-in-Cell; Laser; Plasma

  • Software in external data repository
    Publication year 2020
    Programming language: C++, Python, Shell, CMake, Dockerfile, Awk
    System requirements: Computer
    License: GPLv3+, LGPLv3+, CC-BY 4.0 (Link to license text)
    Hosted on https://github.com/ComputationalRadiationPhysics/picongpu:
    DOI: 10.5281/zenodo.3875374

Permalink: https://www.hzdr.de/publications/Publ-31947
Publ.-Id: 31947


Depressants in scheelite flotation - Mechanism of sodium carbonate and acidified water glass and the application of process mineralogy

Kupka, N.

The European Union classified tungsten as a Critical Raw Material already in 2011, due to its high economic importance and high supply risk. Tungsten occurs under two main mineral forms, scheelite (CaWO4) and wolframite ((Fe,Mn)WO4), with scheelite’s importance increasing as wolframite resources are progressively depleting. Interest in scheelite is growing fast, as publications show: 15 % of all publications on scheelite flotation since the 1950s were published in 2019. A polar salt type mineral, scheelite is semi-soluble and exhibits a negative charge, almost regardless of the flotation conditions. It is mostly hydrophilic but can easily be floated using chemical reagents, usually at a high pH of 9 to 10. Scheelite flotation has run into serious difficulties when it is associated to a carbonaceous gangue. Other calcium-bearing minerals, such as calcite (CaCO3), apatite (Ca-phosphate) and fluorite (CaF2) all exhibit similar flotation properties and are therefore classified as semi-soluble salt-type minerals. These minerals will tend to float better than scheelite under the same circumstances and not only increase reagent consumption but heavily contaminate the concentrate, making it harder and more expensive to process for the smelter. Several depressants can be used to remedy this problem, the most used one being sodium silicate. However, this reagent is imperfect and its effect can be improved by modifying it or by combining it with other depressants. As a consequence, the focus of this work is to understand the mechanism of two important depressants in scheelite flotation, sodium carbonate and acidified sodium silicate, and linking said mechanism to mineralogy. A third depressant, colloidal silica, is studied from a performance point of view.

Keywords: froth flotation; scheelite; depressants; automated mineralogy

  • Doctoral thesis
    TUBAF, 2020
    Mentor: Prof. Urs Peuker
    174 Seiten

Permalink: https://www.hzdr.de/publications/Publ-31943
Publ.-Id: 31943


Uploading data to the HepDATA repository with Python using hepdata_lib

Müller, S.

Presentation at the "STRONG2020 Meeting on the Hadronic Cross Section database"

  • Lecture (Conference) (Online presentation)
    STRONG2020 Meeting on the hadronic Cross Section database, 18.12.2020, Pisa, Italy

Permalink: https://www.hzdr.de/publications/Publ-31942
Publ.-Id: 31942


LLAMA: Compile time automatic memory layout optimization

Gruber, B. M.

Write code once and perform well on many systems.

  • Open Access Logo Poster
    Polish delegation meeting, 29.09.2020, Görlitz, Germany

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Permalink: https://www.hzdr.de/publications/Publ-31941
Publ.-Id: 31941


Cryogenic Liquid Jets for High Repetition Rate Discovery Science

Curry, C. B.; Schoenwaelder, C.; Goede, S.; Kim, J. B.; Rehwald, M.; Treffer, F.; Zeil, K.; Glenzer, S. H.; Gauthier, M.

This protocol presents a detailed procedure for the operation of continuous, micron-sized cryogenic cylindrical and planar liquid jets. When operated as described here, the jet exhibits high laminarity and stability for centimeters. Successful operation of a cryogenic liquid jet in the Rayleigh regime requires a basic understanding of fluid dynamics and thermodynamics at cryogenic temperatures. Theoretical calculations and typical empirical values are provided as a guide to design a comparable system. This report identifies the importance of both cleanliness during cryogenic source assembly and stability of the cryogenic source temperature once liquefied. The system can be used for high repetition rate laser-driven proton acceleration, with an envisioned application in proton therapy. Other applications include laboratory astrophysics, materials science, and next-generation particle accelerators.

  • Open Access Logo Journal of Visualized Experiments 159(2020), e61130
    DOI: 10.3791/61130

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Permalink: https://www.hzdr.de/publications/Publ-31939
Publ.-Id: 31939


Comparison of experimental STEM conditions for fluctuation electron microscopy

Radic, D.; Hilke, S.; Peterlechner, M.; Posselt, M.; Wilde, G.; Bracht, H.

Variable-resolution fluctuation electron microscopy (VR-FEM) data from measurements on amorphous silicon and PdNiP have been obtained at varying experimental conditions. Measurements have been conducted at identical total electron dose and with an identical electron dose normalized to the respective probe size. STEM probes of different sizes have been created by variation of the semi-convergence angle or by defocus. The results show that defocus yields a reduced normalized variance compared to data from probes created by convergence angle variation. Moreover, the trend of the normalized variance upon probe size variation differs between the two methods. Beam coherence, which affects FEM data, has been analyzed theoretically using geometrical optics on a multi-lens setup and linked to the illumination conditions. Fits to several experimental beam profiles support our geometrical optics theory regarding probe coherence. The normalized variance can be further optimized if one determines the optimal exposure time for the nanobeam diffraction patterns.

Keywords: amorphous materials; coherence; fluctuation electron microscopy; medium-range order; nanobeam diffraction

Permalink: https://www.hzdr.de/publications/Publ-31938
Publ.-Id: 31938


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