Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

35836 Publications

ExploreQC: A toolbox for MRI quality control in the EPAD multicentre study

Lorenzini, L.; Ingala, S.; Wottschel, V.; Wink, A. M.; Kuijer, J.; Sudre, C. H.; Haller, S.; Molinuevo, J. L.; Gispert, J. D.; Cash, D. M.; Thomas, D. L.; Vos, S.; Petr, J.; Wolz, R.; Pernet, C.; Waldman, A.; Barkhof, F.; Mutsaerts, H. J. M. M.; Epad, C.

Magnetic Resonance Imaging (MRI) of the brain is prone to artefacts that may worsen image quality and subsequent analyses. Despite the growing number of large-scale multi-institutional imaging studies, standardized approaches for defining inclusion and exclusion criteria on the basis of image data quality are still lacking and quality assessment is often based on visual inspection. We introduce ExploreQC, a MATLAB-based toolbox which implements a semi-automatic pipeline to assess QC metrics, select the most relevant parameters, and to derive informed inclusion thresholds.

  • Open Access Logo Poster (Online presentation)
    Alzheimer's Association International Conference, 27.07.2020, Virtual, Virtual
    DOI: 10.1002/alz.041952
  • Open Access Logo Abstract in refereed journal
    Alzheimer's & Dementia 16(2020), e041952
    DOI: 10.1002/alz.041952

Permalink: https://www.hzdr.de/publications/Publ-31929
Publ.-Id: 31929


ASL perfusion MRI in the follow-up of pediatric brain tumors

Verschuren, S.; Petr, J.; Mutsaerts, H. J.; Plasschaert, S.; Wijnen, J.; Lequin, M.; Wiegers, E.

ASL perfusion MRI in the follow-up of pediatric brain tumors

  • Open Access Logo Poster (Online presentation)
    European Society for Magnetic Resonance in Medicine and Biology, 30.09.2020, Virtual, Virtual
    DOI: 10.1007/s10334-020-00876-y
  • Open Access Logo Abstract in refereed journal
    Magnetic Resonance Materials in Physics, Biology and Medicine 33(2020)Suppl 1, P02.01
    DOI: 10.1007/s10334-020-00876-y

Permalink: https://www.hzdr.de/publications/Publ-31928
Publ.-Id: 31928


Accumulation of ferromanganese crusts derived from carrier-free 10Be/9Be

Lachner, J.; Ploner, M.; Steier, P.; Sakaguchi, A.; Usui, A.

The occurrence of 10Be in natural archives is commonly used to date their formation and growth on time scales of million years. Accelerator Mass Spectrometry (AMS) can perform a direct measurement of the 10Be/9Be ratio. The carrier-free method, in which no 9Be carrier is added to the original sample, is especially suitable for 10Be/9Be ratio determination in the marine environment. By normalizing the 10Be content to 9Be, temporal variations of Be uptake processes into the archive are eliminated.

Here, we present a simple method for the chemical extraction of beryllium from ferromanganese (FeMn) crusts or nodules, the measurement procedure, and the first carrier-free 10Be/9Be measurements at the 3 MV AMS facility VERA. Several tests of chemical methods are discussed including different options to short-cut and accelerate the procedure for special cases. Results from FeMn crust 237KD from cruise VA13/2 in the Pacific ocean show the known 10Be/9Be distribution with depth that is commonly related to a changing growth rate of the archive. In this context we discuss the potential influence of diffusion and adsorption processes on the age models of FeMn crusts that are based on radioactive nuclides such as 10Be and 230Th. Including an open-system behavior for these isotopes in the description of their profiles allows interpreting the accumulation of crusts with a constant growth rate over millions of years and does not require the assumption of abrupt growth changes.

Keywords: 10Be; Carrier-free 10Be/9Be; AMS; VERA; Ferromanganese crusts

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31927
Publ.-Id: 31927


Material requirements for pulsed magnets at the HLD

Zherlitsyn, S.

es hat kein Abstrakt vorgelegen

  • Lecture (Conference) (Online presentation)
    2020 Virtual MRS Spring/ Fall Meeting, 27.11.-04.12.2020, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-31926
Publ.-Id: 31926


Antisite disorder in the battery material LiFePO4

Werner, J.; Neef, C.; Koo, C.; Zvyagin, S.; Ponomaryov, O.; Klingeler, R.

We report detailed magnetometry and high-frequency electron spin resonance (HF-ESR) measurements which allow detailed investigation on Li-Fe antisite disorder in single-crystalline LiFePO4, i.e., exchange of Fe2+ and Li+ ions. The data imply that magnetic moments of Fe2+ ions at Li positions do not participate in long-range antiferromagnetic order in LiFePO4 but form quasifree moments. Anisotropy axes of the magnetic moments at antisite defects are attached to the main crystallographic directions. The local character of these moments is confirmed by associated linear resonance branches detected by HF-ESR studies. Magnetic anisotropy shows up in significant zero-field splittings of Δ = 220(3) GHz, Δ` ∼ 50 GHz, and a highly anisotropic g factor, i.e., ga = 1.4, gb = 2.0, and gc = 6.3. We demonstrate a general method to precisely determine Fe-antisite disorder in LiFePO4 from magnetic studies which implies a density of paramagnetic Fe2+ ions at Li positions of 0.53%.

Permalink: https://www.hzdr.de/publications/Publ-31925
Publ.-Id: 31925


Elastic response to the first-order magnetization process of U3Cu4Ge4

Gorbunov, D.

Es hat kein Abstrakt vorgelegen.

  • Invited lecture (Conferences) (Online presentation)
    ARHMF2020 & KINKEN Materials Science School 2020 for Young Scientists, 01.-03.12.2020, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-31924
Publ.-Id: 31924


Data for: A UV laser test facility for precise measurement of gas parameters in gaseous detectors

Fan, X.

It contains the data measured by the device and the simulation data.

Keywords: UV laser

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-17
    DOI: 10.14278/rodare.684
    License: CC-BY-1.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31923
Publ.-Id: 31923


Biplots for Compositional Data Derived from Generalised Joint Diagonalization Methods

Mueller, U.; Tolosana Delgado, R.; Grunsky, E. C.; McKinley, J. M.

Biplots constructed from principal components of a compositional data set are an established means to explore its features. Principal Component Analysis (PCA) is also used to transform a set of spatial variables into spatially decorrelated factors. However, because no spatial structures are accounted for in the transformation the application of PCA is limited. In geostatistics and blind source separation a variety of different matrix diagonalization methods have been developed with the aim to provide spatially or temporally decorrelated factors. Just as PCA, many of these transformations are linear and so lend themselves to the construction of biplots. In this contribution we consider such biplots for a number of methods (MAF, UWEDGE and RJD transformations) and discuss how and if they can contribute to our understanding of relationships between the components of regionalized compositions. A comparison of the biplots with the PCA biplot commonly used in compositional data analysis for the case of data from the Northern Irish geochemical survey shows that the biplots from MAF and UWEDGE are comparable as are those from PCA and RJD. The biplots emphasize different aspects of the regionalized composition: for MAF and UWEDGE the focus is the spatial continuity, while for PCA and RJD it is variance explained. The results indicate that PCA and MAF combined provide adequate and complementary means for exploratory statistical analysis.

Keywords: Semivariogram matrices; Spatial decorrelation; Structural analysis; Geochemical data

Permalink: https://www.hzdr.de/publications/Publ-31922
Publ.-Id: 31922


Data for: Mapping the stray fields of a micromagnet using spin centers in SiC

Bejarano, M.; Trindade Goncalves, F. J.; Hollenbach, M.; Hache, T.; Hula, T.; Berencen, Y.; Faßbender, J.; Helm, M.; Astakhov, G.; Schultheiß, H.

We utilized the following methods to obtain the presented data: optically detected magnetic resonance (ODMR), photoluminescence spectroscopy, and micromagnetic simulations in Mumax3. The experimental data were obtained on the sample which is labeled as: "HPSI 4H-SiC 30 Magnon Q #2". On that sample we investigated magnetic ellipses, sized 8 micrometer x 2 micrometer, made of Permalloy, that lie on top of a silicon carbide substrate. The measured data for all measurements (including ALL parameters) are included in the uploaded primary data subdirectories. The uploaded data is organized in folders according to the figures in the paper. Each folder contains the experimental data, together with the MuMax3 definition files, all the possible possible scripts used for evaluation and all figures included in the paper. This is the final version with the reviewers' corrections.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-17
    DOI: 10.14278/rodare.682
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31921
Publ.-Id: 31921


CaTeNA – Climatic and Tectonic Natural Hazards in Central Asia Final virtual workshop September 24-25 2020

Barbosa, N.; Bloch, W.; Crosetto, S.; Haberland, C.; Jarihani, B.; Kakar, N.; Metzger, S.; Mohadjer, S.; Orunbaev, S.; Ratschbacher, L.; Schurr, B.; Strecker, M.; Wang, X.

CaTeNA – Climatic and Tectonic Natural Hazards in Central Asia – is an interdisciplinary, international project funded by the German Ministry of Education and Research to study natural hazards in Central Asia. Central Asia is one of the most tectonically active regions of the world and is influenced by both the west wind zone and monsoon. CaTeNA is examining the two most serious natural hazards arising from these conditions: Earthquakes and mass movements. The project goal is to better understand the underlying processes and triggering factors and to better estimate the resulting risks. For this purpose, CaTeNA localises tectonic faults and determines deformation rates and their changes. Focus is put on two of the most active fault systems, the Main Pamir Thrust and the Darvaz Fault crossing Tajikistan and Kyrgyzstan. We try to estimate recurrence intervals of large earthquakes and to understand their relationship to mass movements using paleo-seismology, geomorphology and remote sensing. The current deformation field is characterised and quantified using the methods of space geodesy and seismology. The results will be incorporated into the openly accessible Central Asian Tectonic Database developed within the project, making it accessible to the public, stakeholders and decision-makers. They form the basis for a more accurate estimation of the risk for earthquakes and landslides. Another important project goal is the development and implementation of a dynamic risk assessment for landslides, including high-resolution, model-based precipitation and snowmelt maps. This allows for improved estimation of the effects of geological hazards on inhabited areas and traffic infrastructure. Direct and efficient risk communication is achieved through interactive visualisation based on a dynamic multilingual web GIS platform. This is an essential step on the path to an early-warning system that takes into account the most important triggering factors. This data repository provides pdf files and recorded videos of talks presented during the final online workshop of the project.

Keywords: climatic natural hazard; tectonic natural hazard; coupling mechanism; central asia

  • Open Access Logo Lecture (others) (Online presentation)
    CaTeNA – Climatic and Tectonic Natural Hazards in Central Asia Final virtual workshop, 24.-25.09.2020, Potsdam, Germany
    DOI: 10.2312/gfz.catena.2020

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31920
Publ.-Id: 31920


Window-based morphometric indices as predictive variables for landslide susceptibility models

Barbosa, N.; Andreani, L.; Gloaguen, R.; Ratschbacher, L.

Identification of areas prone to landslides is essential to mitigate associated risks. This is usually achieved using landslide susceptibility models, which estimate landslide likelihood given local terrain conditions and the location of known past events. Detailed databases covering different conditioning factors are paramount to produce reliable susceptibility maps. However, thematic data from developing countries are scarce. As a result, susceptibility models often rely on morphometric parameters derived from widely-available digital elevation models. In most cases, simple parameters such as slope, aspect, and curvature, computed using a moving window of 3{$\times$}3 pixels, are used. Recently, the use of window-based morphometric indices as an additional input has increased. These rely on a user-defined observation window size. In this contribution, we examine the influence of observation window size when using window-based morphometric indices as core predictive variables for landslide susceptibility assessment. We computed a variety of models that include morphometric indices calculated with different window sizes, and compared the predictive capabilities and reliability of the resulting predictions. All models are based on the random forest algorithm. The results improved significantly when each window-based morphometric index was calculated with a different and meaningful observation window. The sensitivity analysis highlights both the highly-informative observation windows and the impact of their selection on the model performance. We also stress the importance of evaluating landslide susceptibility results using different adapted metrics for predictive performance and reliability.

Keywords: landslide susceptibility model; morphometric indices; observation window; random forest; Tajik-Tian Shan

Permalink: https://www.hzdr.de/publications/Publ-31918
Publ.-Id: 31918


Improving landslide susceptibility models using morphometric indices: Influence of the observation window in the reliability of the results.

Barbosa Mejia, L. N.; Andreani, L.; Gloaguen, R.

Estimation of landslide susceptibility in mountainous areas is a prerequisite for risk assessment and contingency planning. The susceptibility to landslide is modelled based on thematic layers of information such as geomorphology, hydrology, or geology, where detailed characteristics of the area are depicted. The growing use of machine learning techniques to identify complex relationships among a high number of variables decreased the time required to distinguish areas prone to landslides and increased the reliability of the results. However, numerous countries lack detailed thematic databases to feed in the models. As a consequence, susceptibility assessment often relies heavily on geomorphic parameters derived from Digital Elevation Models. Simple parameters such as slope, aspect and curvature, calculated under a moving window of 3x3-pixels are mostly used. Furthermore, advanced morphometric indices such as topographic position index or surface roughness are increasingly used as additional input parameters. These indices are computed under a bigger window of observation usually defined by the researcher and the goal of the study. While these indices proved to be useful in capturing the overall morphology of an entire slope profile or regional processes, little is known on how the selection of the moving window size is relevant and affects the output landslide susceptibility model.

In order to address this question, we analysed how the predicting capabilities and reliability of landslide susceptibility models were impacted by the morphometric indices and their window of observation. For this purpose, we estimate the landslide susceptibility of an area located in Tajikistan (SW Tien Shan) using a Random Forest algorithm and different input datasets. Predicting factors include commonly used 3x3-pixel morphometrics, environmental, geological and climatic variables as well as advanced morphometric indices to be tested (surface roughness, local relief, topographic position index, elevation relief ratio and surface index). Two approaches were selected to address the moving window size. First, we chose a common window of observation for all the morphometric indices based on the study area valley’s characteristics. Second, we defined an optimal moving window(s) for each morphometric index based on the importance ranking of models that include moving windows from a range of 300 to 15000 m for each index. A total of 20 models were iteratively created, started by including all the moving windows from all the indices. Predicting capabilities were evaluated by the receiver operator curve (ROC) and Precision-Recall (PR). Additionally, a measure of reliability is proposed using the standard deviation of 50 iterations. The selection of different moving windows using the feature importance resulted in better predicting capabilities models than assigning an optimal for all. On the other hand, using a single different moving window per morphometric index (eg. most important ranked by random forest) decreases the evaluating metrics (a drop of PR from 0.88 to 0.85). Landslide susceptibility models can thus be improved by selecting a variety of meaningful (physically and methodological) windows of observation for each morphometric index. A 3x3-pixel moving window is not recommended because it is too small to capture the morphometric signature of landslides.

Keywords: Landslide susceptibility; morphometry; machine learning; random forest

Permalink: https://www.hzdr.de/publications/Publ-31917
Publ.-Id: 31917


Impact of laser polarization on q-exponential photon tails in nonlinear Compton scattering

Kämpfer, B.; Titov, A.

Non-linear Compton scattering of ultra-relativistic electrons traversing high-intensity laser pulses generates also hard photons. These photon high-energy tails are considered for parameters in reach at the forthcoming experiments LUXE and E-320. We consider the invariant differential cross sections dσ/du between the IR and UV regions and analyze the impact of the laser polarization and find q-deformed exponential shapes. (The variable u is the light-cone momentum-transfer from initial electron to final photon.) Optical laser pulses of various durations are compared with the monochromatic laser beam model which uncovers the laser intensity parameter in the range ξ=1⋯10. Some supplementary information is provided for the azimuthal final-electron/photon distributions and the photon energy-differential cross sections.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31915
Publ.-Id: 31915


Improved accuracy in high-frequency AC transport measurements in pulsed high magnetic fields

Mitamura, Y.; Watanuki, R.; Kampert, W. A. G.; Förster, T.; Matsuo, A.; Onimaru, T.; Onozaki, N.; Amou, Y.; Wakiya, K.; Matsumoto, K. T.

We show theoretically and experimentally that accurate transport measurements are possible even within the short time provided by pulsed magnetic fields. For this purpose, a new method has been devised, which removes the noise component of a specific frequency from the Signal by taking a linear combination of the results of numerical phase detection using multiple integer periods. We also established a method to unambiguously determine the phase rotation angle in AC transport measurements using a frequency range of tens of kilohertz. We revealed that the dominant noise in low-frequency transport measurements in pulsed magnetic fields is the electromagnetic induction caused by mechanical vibrations of wire loops in inhomogeneous magnetic fields. These results strongly suggest that accurate transport measurements in short-pulsed magnets are possible when mechanical vibrations are well suppressed.

Permalink: https://www.hzdr.de/publications/Publ-31914
Publ.-Id: 31914


How Hyperspectral Image Unmixing and Denoising Can Boost Each Other

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

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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-16
    DOI: 10.14278/rodare.680
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31912
Publ.-Id: 31912


Multicaloric effects in metamagnetic Heusler Ni-Mn-In under uniaxial stress and magnetic field

Gràcia-Condal, A.; Gottschall, T.; Pfeuffer, L.; Gutfleisch, O.; Planes, A.; Manosa, L.

The world’s growing hunger for artificial cold, on the one hand, and the ever more stringent climate targets, on the other, pose an enormous challenge to mankind. Novel, efficient, and environmentally friendly refrigeration technologies based on solid-state refrigerants can offer a way out of the problems arising from climate-damaging substances used in conventional vapor-compressors. Multicaloric materials stand out because of their large temperature changes, which can be induced by the application of different external stimuli such as a magnetic, electric, or a mechanical field. Despite the high potential for applications and the interesting physics of this group of materials, few studies focus on their investigation by direct methods. In this paper, we report on the advanced characterization of all relevant physical quantities that determine the multicaloric effect of a Ni-Mn-In Heusler compound. We have used a purpose-designed calorimeter to determine the isothermal entropy and adiabatic temperature changes resulting from the combined action of magnetic field and uniaxial stress on this metamagnetic shape-memory alloy. From these results, we can conclude that the multicaloric response of this alloy by appropriate changes of uniaxial stress and magnetic field largely outperforms the caloric response of the alloy when subjected to only a single stimulus. We anticipate that our findings can be applied to other multicaloric materials, thus inspiring the development of refrigeration devices based on the multicaloric effect

Permalink: https://www.hzdr.de/publications/Publ-31911
Publ.-Id: 31911


Field-Modulated Anomalous Hall Conductivity and Planar Hall Effect in Co3Sn2S2 Nanoflakes

Yang, S.-Y.; Noky, J.; Gayles, J.; Dejene, F. K.; Sun, Y.; Doerr, M.; Scurschii, I.; Felser, C.; Nawaz Ali, M.; Liu, E.; Parkin, S. S. P.

Time-reversal-symmetry-breaking Weyl semimetals (WSMs) have attracted great attention recently because of the interplay between intrinsic magnetism and topologically nontrivial electrons. Here, we present anomalous Hall and planar Hall effect studies on Co3Sn2S2 nanoflakes, a magnetic WSM hosting stacked Kagome lattice. The reduced thickness modifies the magnetic properties of the nanoflake, resulting in a 15-time larger coercive field compared with the bulk, and correspondingly modifies the transport properties. A 22% enhancement of the intrinsic anomalous Hall conductivity (AHC), as compared to bulk material, was observed. A magnetic field-modulated AHC, which may be related to the changing Weyl point separation with magnetic field, was also found. Furthermore, we showed that the PHE in a hard magnetic WSM is a complex interplay between ferromagnetism, orbital magnetoresistance, and chiral anomaly. Our findings pave the way for a further understanding of exotic transport features in the burgeoning field of magnetic topological phases.

Permalink: https://www.hzdr.de/publications/Publ-31910
Publ.-Id: 31910


HIF2alpha-associated pseudohypoxia promotes radioresistance in pheochromocytoma: insights from 3D models

Seifert, V.; Richter, S.; Bechmann, N.; Bachmann, M.; Ziegler, C. G.; Pietzsch, J.; Ullrich, M.

Pheochromocytomas and paragangliomas (PCCs/PGLs) are rare neuroendocrine tumors arising from chromaffin tissue located in the adrenal or in ganglia of the sympathetic or parasympathetic nervous system. Treatment of non-resectable or metastatic PCCs/PGLs is still limited to palliative measures, including somatostatin type 2 receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE as one of the most effective approaches to date. Nevertheless, metabolic and molecular determinants of radiation response in PCCs/PGLs have not yet been characterized. This study investigates the effects of hypoxia-inducible factor 2 alpha (HIF2α) on the susceptibility of PCCs/PGLs to radiation treatments using spheroids grown from genetically engineered mouse pheochromocytoma (MPC) cells. Expression of Hif2α was associated with significantly increased resistance of MPC spheroids to external X-ray irradiation and exposure to beta particle-emitting [177Lu]LuCl3 compared to Hif2α-deficient controls. Exposure to [177Lu]LuCl3 provided increased long-term control of MPC spheroids compared to single-dose external X-ray irradiation. This study provides first experimental evidence that HIF2α-associated pseudohypoxia contributes to a radioresistant phenotype of PCCs/PGLs. Furthermore, external irradiation and [177Lu]LuCl3 exposure of MPC spheroids provide surrogate models for radiation treatments to further investigate metabolic and molecular determinants of radiation responses in PCCs/PGLs and to evaluate effects of neo-adjuvant, in particular, radiosensitizing treatments in combination with targeted radionuclide therapies.

Keywords: paraganglioma; radionuclide therapy; lutetium-177; spheroid control dose; SCD50; spheroid re-growth; irradiation; X-ray; radioresistance

Permalink: https://www.hzdr.de/publications/Publ-31909
Publ.-Id: 31909


Nanometer-Thick Bismuth Nanocrystal Films for Sensoric Applications

Pilidi, A.; Tzanis, A.; Helm, T.; Arfanis, M.; Falaras, P.; Speliotis, T.

The present article is concerned with investigations of the structural, surface morphological, and magnetotransport properties of DC magnetron-sputtered nanometer-thick Bi nanocrystal films on Si(111) substrates. Crystal structure and surface morphology were studied with X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, and atomic force microscopy. For the samples deposited at the melting point of Bi, 271 °C, equilibrium crystals formed and according to Wulff theorem acquire a specific shape determined by the surface tension. These crystals were investigated for different film thicknesses and deposition temperatures varying from 25 to 300 °C. Furthermore, magnetotransport characterization was carried out in steady and pulsed magnetic fields of up to 9 and 70 T, respectively. At low temperatures, clear weak antilocalization behavior is observed, attributed to 2D conduction channels. A nonlinear Hall resistance is also confirmed, ascribed to the coexistence of two types of carriers (p and n). This study contributes to the elucidation of the transport properties of the Bi thin films and opens new perspectives for their exploitation in modern applications such as sensorics.

Permalink: https://www.hzdr.de/publications/Publ-31908
Publ.-Id: 31908


Allianz Initiative: Positionspapier Digitale Dienste für die Wissenschaft – wohin geht die Reise?

Konrad, U.; Förstner, K.; Reetz, J.; Wannemacher, K.; Kett, J.; Mannseicher, F.

Aufgrund des informationstechnologischen Fortschritts, der immer stärkeren, domänenübergreifenden Vernetzung in Wissenschaft und Forschung sowie der Notwendigkeit, gemeinsam Dienste und Ressourcen zu nutzen, werden von den Akteuren in Forschung und Wissenschaft zunehmend verteilte digitale Dienste verwendet. Der Fokus dieser Handreichung liegt auf den wissenschaftlichen Informationsdiensten, zu denen man u. a. Werkzeuge für kollaboratives Arbeiten, für die Aufbereitung und Analyse von Daten sowie Dienste zum wissenschaftlichen Publizieren, aber auch Dienste für die Entwicklung von Forschungssoftware zählen kann. Dabei zielen die Fragen nach der Art der geforderten bzw. wirklich verwendeten Diensten, der Vor- und Nachteile der gegenwärtigen Nutzung sowie der eigenverantwortlichen Bereitstellung dieser Dienste unter dem Aspekt der (finanziellen) Ressourcen-
Effizienz.

Keywords: Research Software; Open Science; Open Source; Digital Transformation; Information Technology

Permalink: https://www.hzdr.de/publications/Publ-31907
Publ.-Id: 31907


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

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

Hyperspectral images (HSIs) provide detailed spectral information through hundreds of (narrow) spectral channels (also known as dimensionality or bands), which can be used to accurately classify diverse materials of interest. The increased dimensionality of such data makes it possible to significantly improve data information content but provides a challenge to conventional techniques (the so-called curse of dimensionality) for accurate analysis of HSIs. Feature extraction (FE), a vibrant field of research in the hyperspectral community, evolved through decades of research to address this issue and extract informative features suitable for data representation and classification. The advances in FE were inspired by two fields of research—the popularization of image and signal processing along with machine (deep) learning—leading to two types of FE approaches: the shallow and deep techniques. This article outlines the advances in these approaches for HSI by providing a technical overview of state-of-the-art techniques, offering useful entry points for researchers at different levels (including students, researchers, and senior researchers) willing to explore novel investigations on this challenging topic. In more detail, this article provides a bird’s eye view of shallow [both supervised FE (SFE) and unsupervised FE (UFE)] and deep FE approaches, with a specific focus on hyperspectral FE and its application to HSI classification. Additionally, this article compares 15 advanced techniques with an emphasis on their methodological foundations and classification accuracies. Furthermore, to push this vibrant field of research forward, an impressive amount of code and libraries are shared on GitHub, which can be found in [131].

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-16
    DOI: 10.14278/rodare.678

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31906
Publ.-Id: 31906


Oscillatory thermal-inertial flows in liquid metal rotating convection

Vogt, T.; Horn, S.; Aurnou, J.

We present the first detailed thermal and velocity field characterization of convection in a rotating cylindrical tank of liquid gallium, which has thermophysical properties similar to those of planetary core fluids. Our laboratory experiments, and a closely associated direct numerical simulation, are all carried out in the regime prior to the onset of steady convective modes. This allows us to study the oscillatory convective modes, sidewall modes and broadband turbulent flow that develop in liquid metals before the advent of steady columnar modes. Our thermo-velocimetric measurements show that strongly inertial, thermal wind flows develop, with velocities reaching those of comparable non-rotating cases. Oscillatory bulk convection and wall modes coexist across a wide range of our experiments, along with strong zonal flows that peak in the Stewartson layer, but that extend deep into the fluid bulk in the higher supercriticality cases. The flows contain significant time-mean helicity that is anti-symmetric across the midplane, demonstrating that oscillatory liquid metal convection contains the kinematic components to sustain system-scale dynamo generation.

Permalink: https://www.hzdr.de/publications/Publ-31905
Publ.-Id: 31905


Data for: "Multi Optical Sensor Fusion for Mineral Mapping of Core Samples"

Rasti, B.; Ghamisi, P.; Seidel, P.; Lorenz, S.; Gloaguen, R.

Geological objects are characterized by a high complexity inherent to a strong compositional variability at all scales and usually unclear class boundaries. Therefore, dedicated processing schemes are required for the analysis of such data for mineral mapping. On the other hand, the variety of optical sensing technology reveals different data attributes and therefore multi-sensor approaches are adapted to solve such complicated mapping problems. In this paper, we devise an adapted multi-optical sensor fusion (MOSFus) workflow which takes the geological characteristics into account. The proposed processing chain exhaustively covers all relevant stages, including data acquisition, preprocessing, feature fusion, and mineral mapping. The concept includes i) a spatial feature extraction based on morphological profiles on RGB data with high spatial resolution, ii) a specific noise reduction applied on the hyperspectral data that assumes mixed sparse and Gaussian contamination and iii) a subsequent dimensionality reduction using a sparse and smooth low rank analysis. The feature extraction approach allows to fuse heterogeneous data at variable resolutions, scales, and spectral ranges as well as improve classification substantially. The last step of the approach, an SVM classifier, is robust to unbalanced and sparse training sets and is particularly efficient with complex imaging data. We evaluate the performance of the procedure with two different multi-optical sensor datasets. The results demonstrate the superiority of this dedicated approach over common strategies.

Keywords: Multi-sensor data; optical sensor; hyperspectral; hyperspectral mixed sparse and Gaussian noise reduction (HyMiNoR); spectral imaging; data fusion; feature extraction; dimensionality reduction; support vector machine (SVM); sparse and smooth low-rank analysis (SSLRA); orthogonal total variation component analysis (OTVCA); mineral exploration

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-07-05
    DOI: 10.14278/rodare.632
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31904
Publ.-Id: 31904


Flow Control Based on Feature Extraction in Continuous Casting Process

Abouelazayem, S.; Glavinic, I.; Wondrak, T.; Hlava, J.

The flow structure in the mold of a continuous steel caster has a significant impact on the quality of the final product. Conventional sensors used in industry are limited to measuring single variables such as the mold level. These measurements give very indirect information about the flow structure. For this reason, designing control loops to optimize the flow is a huge challenge. A solution for this is to apply non-invasive sensors such as tomographic sensors that are able to visualize the flow structure in the opaque liquid metal and obtain information about the flow structure in the mold. In this paper, ultrasound Doppler velocimetry (UDV) is used to obtain key features of the flow. The preprocessing of the UDV data and feature extraction techniques are described in detail. The extracted flow features are used as the basis for real time feedback control. The model predictive control (MPC) technique is applied, and the results show that the controller is able to achieve optimum flow structures in the mold. The two main actuators that are used by the controller are the electromagnetic brake and the stopper rod. The experiments included in this study were obtained from a laboratory model of a continuous caster located at the Helmholtz-Zentrum Dresden Rossendorf (HZDR).

Keywords: industrial control; industrial process tomography; model predictive control; ultrasound doppler velocimetry

Permalink: https://www.hzdr.de/publications/Publ-31903
Publ.-Id: 31903


A UV laser test facility for precise measurement of gas parameters in gaseous detectors

Fan, X.; Naumann, L.; Siebold, M.; Stach, D.; Kämpfer, B.

This work is devoted to the development of a UV laser test facility for calibration of gaseous detectors. We applied multiple methods to achieve a micrometer scale accuracy for the laser test facility and provide dedicated investigations for laser ionization in the gaseous detector. With the well-controlled laser ionization and remote DAQ system, we can operate the calibration of gaseous detectors and precise measurement of gas parameters at the micrometer scale related to the detector’s field geometry.

Keywords: UV Laser

Related publications

Downloads:

  • Secondary publication expected from 04.12.2021

Permalink: https://www.hzdr.de/publications/Publ-31902
Publ.-Id: 31902


Geometrically driven chiral effects in curvilinear antiferromagnetic spin chains

Pylypovskyi, O.; Kononenko, D.; Yershov, K.; Roessler, U.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Antiferromagnets are technologically promising materials for spintronic and spinorbirtonic devices [1]. An efficient manipulation of antiferromagnetic textures requires the presence of the Dzyaloshinskii-Moriya interaction (DMI), which is present in crystals of special symmetry, and thus limits the number of available materials. In contrast to antiferromagnets, it is already established that in ferromagnetic thin films and nanowires chiral responses can be tailored relying on curvilinear geometries [2].

Here, we explore curvature effects in curvilinear antiferromagnets [3]. We demonstrate theoretically that intrinsically achiral curvilinear antiferromagnetic spin chains behave as a biaxial chiral helimagnet with a curvature-tunable anisotropy and DMI. In contrast to ferromagnetic spin chains, this system possesses the hard-axis anisotropy stemming from the dipolar interaction, which allows to observe the effects of geometry even in chains with small curvature and torsion. The geometry-driven easy axis anisotropy determines the homogeneous antiferromagnetic state at low curvatures and the gap for spin waves. The geometry-driven DMI determines the helimagnetic phase transition and leads to the appearance of the region with the negative group velocity at the dispersion curve.

[1] V. Baltz et al., Rev. Mod. Phys. 90, 015005 (2018)
[2] R. Streubel et al., J. Phys. D.: Appl. Phys. 49, 363001 (2016)
[3] O. V. Pylypovskyi, D. Y. Kononenko et al., Nano Lett. 20, 8157 (2020)

  • Contribution to proceedings
    Magnetism at the Nanoscale: Imaging ‐ Fabrication – Physics, 06.-08.01.2021, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31901
Publ.-Id: 31901


Parallel computing of elastic magnetic systems at the nanoscale

Tomilo, A.; Pylypovskyi, O.; Yershov, K.; Sheka, D.

Intensive research in the area of nanoscaled physics opens new possibilities for the construction and fabrication of nanoscale devices. A numerical experiment is a powerful tool to analyze complex systems and flexibly check analytical predictions in addition to experimental validation. Therefore usage of parallel
calculation is required to decrease the time of simulation.

  • Contribution to proceedings
    Sixth International Conference on High Performance Computing (HPC-UA 2020), 06.-07.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31900
Publ.-Id: 31900


Stabilization of Skyrmion States by a Gradient of Curvature in Ferromagnetic Shells

Pylypovskyi, O.; Makarov, D.; Kravchuk, V.; Saxena, A.; Sheka, D.

Skyrmions represent a class of chiral magnetic textures with unique properties relevant for spintronic and spin-orbitronic applications [1]. Geometrical curvature can be used as an efficient mean to tailor chiral and anisotropic responses of thin ferromagnetic shells [2-4]. This was recently confirmed by quantifying the strength of the Dzyaloshinskii-Moriya interaction (DMI) in curved nanostripes [5]. Furthermore, there are numerous predictions of the stabilization of curvature-driven of small-radius skyrmions in spherical shells [6] and an appearance of skyrmion lattices as the ground state in intrinsically chiral curvilinear thin films [7].

Here, we demonstrate a new pathway of stabilizing Neel skyrmion and skyrmionium states relying on the gradient of curvature using a magnetic thin film hosting a circular nanoindentation [8]. These skyrmion states can be formed in a material even without an intrinsic DMI. We propose a physical picture of this effect, which is related to the pinning of a chiral magnetic domain wall at the bend of a nanoindentation. Geometry of the film is described by two principal curvatures k1(r), describing film geometry in radial direction, and k2(r) inversely proportional to the distance from origin. In this respect, the spatial inhomogeneity of the curvature-induced DMI governing by k1(r) is responsible for the stabilization of the skyrmion state. The lateral dimensions of the stabilized chiral magnetic textures are varied in a broad range by engineering the size of the nanoindentation. We describe the stability condition of skyrmion states. Furthermore, on the fundamental side, we put forth a general analytical framework allowing us to map a complex problem of the description of a magnetic texture at a surface of revolution to a standard planar problem with modified constants of DMI and magnetic anisotropy. In this respect, our model predicts a new mechanism of pinning of magnetic domain walls in planar ferromagnetic films with intrinsic DMI on inhomogeneities of the DMI.

[1] A. Fert, N. Reyren, V. Cros, Nat. Rev. Mater., Vol. 2, 17031 (2017)
[2] R. Streubel, P. Fischer, F. Kronast et al., J. Phys. D: Appl. Phys. Vol. 49, 363001 (2016)
[3] O. Pylypovskyi, V. Kravchuk, D. Sheka et al., Phys. Rev. Lett. Vol. 114, 197204 (2015)
[4] Y. Gaididei, A. Goussev, V. Kravchuk et al., J. Phys. A: Mat. and Theor. Vol. 50, 385401 (2017)
[5] Volkov, Kakay, Kronast et al., Phys. Rev. Lett. Vol. 123, 077201 (2019)
[6] V. Kravchuk, U. K. Röβler, O. M. Volkov et al., Phys. Rev. B. 94, 144402 (2016)
[7] V. Kravchuk, D. Sheka, A. Kákay et al., Phys. Rev. Lett. Vol. 120, 067201 (2018)
[8] O. Pylypovskyi, D. Makarov, V. Kravchuk et al., Phys. Rev. Appl. Vol. 10, 064057 (2018)

  • Contribution to proceedings
    2020 Virtual MRS Fall Meeting, 28.11.-04.12.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31899
Publ.-Id: 31899


Experimental observation of exchange-driven chiral effects in parabolic stripes

Volkov, O.

Broken magnetic symmetry is a key aspect in condensed matter physics and in particular in magnetism. It results in the appearance of chiral effects, e.g. topological Hall effect [1] and non-collinear magnetic textures including chiral domain walls and skyrmions [2,3]. These chiral structures are in the heart of novel concepts for magnonics [4], antiferromagnetic spintronics [5], spin-orbitronics [6] and oxitronics [7]. The main origin of the chiral symmetry breaking and thus for the magnetochiral effects in magnetic materials is associated to an antisymmetric exchange interaction, the intrinsic Dzaloshinskii-Moriya interaction (DMI). At present, tailoring of DMI is done rather conventionally by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers. A viable alternative to the conventional material screening approach can be the exploration of the interplay between geometry and topology. This interplay is of fundamental interest throughout many disciplines in condensed matter physics, including thin layers of superconductors [8] and superfluids [9], nematic liquid crystals [10], cell membranes [11], semiconductors [12]. In the emergent field of curvilinear magnetism chiral effects are ssociated to the geometrically broken inversion symmetries [13]. Those appear in curvilinear architectures of even conventional materials. There are numerous exciting theoretical predictions of exchange and magnetostatically-driven curvature effects, which do not rely on any specific modification of the
intrinsic magnetic properties, but allow to create non-collinear magnetic textures in a controlled manner by tailoring local curvatures and shapes [14,15]. Until now the predicted chiral effects due to curvatures remained a neat theoretical abstraction. Here, we demonstrate the very first experimental confirmation of the existence of the curvature-induced chiral interaction with exchange origin in a conventional soft ferromagnetic material [16]. It is experimentally explored the theoretical predictions, that the magnetisation reversal of flat parabolic stripes shows a two step process. At the first switching event, a domain wall pinned by the curvature induced exchange-driven DMI is expelled leading to a magnetisation state homogeneous along the parabola’s long axis. Measuring the depinning field enables to quantify the effective exchange-driven DMI interaction constant. The magnitude of the effect can be tuned by the parabola’s curvature. It is found that the strength of the exchange-induced DMI interaction for the experimentally realised geometries is remarkably strong, namely ≈ 0.4 mJ/m 2 , compared the surface induced DMI. The presented study legitimates the predictive power of full-scale micromagnetic simulations to design the properties of ferromagnets through their geometry, thus stabilising chiral textures.

[1] N. Nagaosa, et al., Nature Nanotech. 8, 899 (2013)
[2] U. K. Rößler, et al., Nature 442, 797 (2006)
[3] A. Fert, et al., Nature Rev. Mat. 2, 17031 (2017)
[4] A. V. Chumak, et al., Nature Physics 11, 453 (2015)
[5] T. Jungwirth, et al., Nature Nanotech. 11, 231 (2016)
[6] I. M. Miron, et al., Nature 476, 189 (2011)
[7] V. Garcia, et al., Nature 460, 81 (2009)
[8] J. Tempere, et al., Phys. Rev. B 79, 134516 (2009)
[9] H. Kuratsuji, Phys. Rev. E 85, 031150 (2012)
[10] T. Lopez-Leon, et al., Nature Physics 7, 391 (2011)
[11] H. T. McMahon, et al., Nature 438, 590 (2005)
[12] C. Ortix, Phys. Rev. B 91, 245412 (2015)
[13] Y. Gaididei, et al., Phys. Rev. Lett. 112, 257203 (2014)
[14] J. A. Otálora, et al., Phys. Rev. Lett. 117, 227203 (2016)
[15] V. P. Kravchuk, et al., Phys. Rev. Lett. 120, 067201 (2018)
[16] O. M. Volkov, et al., Phys. Rev. Lett. 123, 077201 (2019)

Keywords: Ferromagnetism; Curvilinear magnetism

  • Contribution to proceedings
    2020 MRS Virtual Spring/Fall Meeting & Exhibit, 27.11.-04.12.2020, Boston, Massachusetts, USA
    Proceedings of the 2020 MRS Virtual Spring/Fall Meeting & Exhibit

Permalink: https://www.hzdr.de/publications/Publ-31898
Publ.-Id: 31898


Domain Wall Tilt and Enhancement of the Walker Limit in Stripes with Dzyaloshinskii-Moriya Interaction and Perpendicular Anisotropy

Pylypovskyi, O.; Kravchuk, V.; Volkov, O.; Faßbender, J.; Sheka, D.; Makarov, D.

The efficiency of manipulation of domain walls and skyrmions in ferromagnetic racetracks with perpendicular anisotropy determines perspectives of development of data storage and logic devices relying on spintronic and spin-orbitronic concepts [1, 2]. The domain wall dynamics is dependent on its orientation with respect to the racetrack axis. In-plane fields [3], edge roughness [4] and current [5] result in the domain wall tilt in samples, possessing Dzyaloshinskii-Moriya interaction (DMI). Here, we show theoretically, that the tilt can appear in equilibrium and describe the domain wall dynamics under the action of external field. We consider a thin biaxial stripe with DMI of interfacial type [6]. The main easy axis of anisotropy is perpendicular to the plane, and the direction of the second easy axis lies in the stripe plane under the angle α to the stripe axis. While the shape anisotropy results in α = 0, a general case α ≠ 0 can appear under the influence of other effects, e.g crystalline structure [7]. While the second easy axis defines the preferable in-plane magnetization within the domain wall, the DMI forces the domain wall being perpendicular to the magnetization gradient. The competition between these two energy contributions and the domain wall tension results in the unidirectional tilt of the whole domain wall. If the DMI is weak enough, there is an additional metastable domain wall state, tilted into the opposite direction. The symmetry break is observed not only for static magnetization texture, but also in the domain wall dynamics under the action of external magnetic field. The domain wall reveals fast and slow motion regimes for the opposite signs of A. The maximum of the Walker field and Walker velicities is determined by the angle A of the second easy axis anisotropy and does not coincide with a shape-induced anisotropy direction A=0. The domain wall possesses the switch of the magnetization direction inside the domain wall in the slow motion regime, which results in the faster motion.

[1] K.-S. Ryu, L. Thomas, S.-H. Yang et al., Nat. Nanotech., Vol. 8, 527 (2013)
[2] O. Pylypovskyi, D. Sheka, V. Kravchuk et al., Sci. Rep. Vol. 6, 23316 (2016)
[3] C. Muratov, V. Slastikov, A. Kolesnikov et al., Phys. Rev. B. Vol. 96, 134417 (2017)
[4] E. Martinez, S. Emori, N. Perez et al. J. Appl. Phys. Vol. 115, 213909 (2014)
[5] O. Boulle, S. Rohart, L. Buda-Prejbeanu et al., Phys. Rev. Lett. Vol. 111, 217203 (2013)
[6] O. Pylypovskyi, V. Kravchuk, O. Volkov et al., J. Phys. D. (2020), DOI:10.1088/1361-6463/ab95bd
[7] M. Heide, G. Bihlmayer, S. Blügel, Pys. Rev. B, Vol. 78, p. 140403 (2008).

  • Contribution to proceedings
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31897
Publ.-Id: 31897


Curvature-driven Chiral Effects in Nanomagnetism

Volkov, O.

The structural inversion symmetry plays an important role in low-dimensional nanomagnets, due to its strong influence on magnetic and electrical properties. It can lead to the appearance of chiral effects, such as the topological Hall effect [1], or to the formation of chiral noncollinear magnetic textures, as skyrmions [2] and chiral domain walls (DWs) [3]. These chiral structures can be the key components for realizing novel concepts for magnonics [4], antiferromagnetic spintronics [5], spin-orbitronics [6], and oxitronics [7]. So far, the main chiral symmetry breaking effect considered as being the origin for the presence of chiral noncollinear magnetic textures is the intrinsic Dzyaloshinskii-Moriya interaction (DMI) [8,9], which appears in certain magnetic crystals in which the unit cell lacks inversion symmetry, such as the gyrotropic magnetic crystals, or appear typically in ultrathin films or bilayers due to the inversion symmetry breaking on the film interface [3]. At present, tailoring of DMI is done by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers.

A viable alternative to the conventional material screening approach can be the exploration of the interplay between geometry and topology. This interplay is of fundamental interest throughout many disciplines in condensed matter physics, including thin layers of superconductors [10] and superfluids [11], nematic liquid crystals [12], cell membranes [13], semiconductors [14]. In the emergent field of curvilinear magnetism chiral effects are associated to the geometrically broken inversion symmetries [15]. Those appear in curvilinear architectures of even conventional materials. There are numerous exciting theoretical predictions of exchange- and magnetostatically-driven curvature effects, which do not rely on any specific modification of the intrinsic magnetic properties, but allow to create non-collinear magnetic textures in a controlled manner by tailoring local curvatures and shapes [16,17]. Until now the predicted chiral effects due to curvatures remained a neat theoretical abstraction.

Very recently, we provided the very first experimental confirmation of the existence of the curvature-induced chiral interaction with exchange origin in a conventional soft ferromagnetic material. It is experimentally explored the theoretical predictions, that the magnetisation reversal of flat parabolic stripes shows a two step process [18,19]. At the first switching event, a domain wall pinned by the curvature induced exchange-driven DMI is expelled leading to a magnetisation state homogeneous along the parabola's long axis. Measuring the depinning field enables to quantify the effective exchange-driven DMI interaction constant. The magnitude of the effect can be tuned by the parabola's curvature. It is found that the strength of the exchange-induced DMI interaction for the experimentally realised geometries is remarkably strong, namely ~0.4 mJ/m2, compared the surface induced DMI. The presented study legitimates the predictive power of full-scale micromagnetic simulations to design the properties of ferromagnets through their geometry, thus stabilising chiral textures. We explore these curvilinear magnetic thin films for the realization of novel artificial magnetoelectric materials based on curvilinear helimagnets embedded in piezoelectric matrix [20], to enable the geometrical tuning of the magnetochirality in curvilinear 1D architectures [21], tailoring of magnetic states in flat nanospirals [22] and as components of shapeable magnetoelectronics for interactive wearables [23].

[1] N. Nagaosa, et al., Nature Nanotech. 8, 899 (2013)
[2] U. K. Rößler, et al., Nature 442, 797 (2006)
[3] A. Fert, et al., Nature Rev. Mat. 2, 17031 (2017)
[4] A. V. Chumak, et al., Nature Physics 11, 453 (2015)
[5] T. Jungwirth, et al., Nature Nanotech. 11, 231 (2016)
[6] I. M. Miron, et al., Nature 476, 189 (2011)
[7] V. Garcia, et al., Nature 460, 81 (2009)
[8] I. Dzyaloshinsky, J. Phys. Chem. Solids 4, 241 (1958).
[9] T. Moriya, Phys. Rev. Lett. 4, 228 (1960).
[10] J. Tempere, et al., Phys. Rev. B 79, 134516 (2009)
[11] H. Kuratsuji, Phys. Rev. E 85, 031150 (2012)
[12] T. Lopez-Leon, et al., Nature Physics 7, 391 (2011)
[13] H. T. McMahon, et al., Nature 438, 590 (2005)
[14] C. Ortix, Phys. Rev. B 91, 245412 (2015)
[15] Y. Gaididei, et al., Phys. Rev. Lett. 112, 257203 (2014)
[16] J. A. Otálora, et al., Phys. Rev. Lett. 117, 227203 (2016)
[17] V. P. Kravchuk, et al., Phys. Rev. Lett. 120, 067201 (2018)
[18] O. Volkov et al., PRL 123, 077201 (2019).
[19] O. Volkov et al., PSS-RRL 13, 1800309 (2019).
[20] O. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).
[21] O. Volkov et al., Scientific Reports 8, 866 (2018).
[22] M. Nord, et al., Small 1904738 (2019).
[23] J. Ge, et al., Nature Comm. 10, 4405 (2019).

Keywords: Ferromagnetism; Curvilinear magnetism; Chiral effects

  • Invited lecture (Conferences) (Online presentation)
    MMM 2020 Virtual Conference, 02.-06.11.2020, Palm Beach, Florida, USA

Permalink: https://www.hzdr.de/publications/Publ-31896
Publ.-Id: 31896


Effects of Geometry on Curvilinear Spin Chains

Kononenko, D.; Pylypovskyi, O.; Yershov, K.; Roessler, U.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Curvilinear magnetism is of great fundamental and practical interest whose rapid development is inspired by novel experimental technologies and wide potential applications [1]. A general approach for description of curvilinear ferromagnets [2] has been recently developed and used for thin wires and shells uncovering magnetochiral effects in statics and dynamics [1,3]. Besides intensive research of ferromagnetic materials, their antiferromagnetically ordered (AFM) counterparts are promising candidates for spintronics applications by their low sensitivity to external fields and ultra high eigenfrequencies [4]. Here, we present a general approach for description of AFM textures in curvilinear spin chains [5]. We show that the magnetic dipole-dipole interaction in these systems can be reduced to a hard-axis anisotropy along the chain. Lagrangian of the curvilinear AFM spin chain in continuum limit corresponds to the biaxial chiral helimagnet. Helix geometry shows existence of two equilibrium magnetic states depending on values of curvature and torsion: (i) homogeneous state in the local reference frame, it is typical for helices with the curvature larger than torsion; and (ii) periodic state is quasi-homogeneous in the laboratory reference frame. For specific case of the AFM flat chain there is the only ground state, with the order parameter being oriented perpendicular to the chain plane. We show that in curvilinear system transverse and longitudinal magnon modes in the AFM helix and ring are coupled due to geometry-induced Dzyaloshinskii–Moriya interaction.

[1] R. Streubel, J. Lee, D. Makarov et al, J. Phys. D, 49, 363001, (2016); A. Fernández-Pacheco et al, Nat. Comm., Vol. 8, p. 15756 (2017).
[2] Y. Gaididei, V. P. Kravchuk, D. D. Sheka, Phys. Rev. Lett. 112, 257203 (2014); D. D. Sheka, V. P. Kravchuk, Y. Gaididei, J. Phys. A, Vol. 48, p. 125202 (2015).
[3] O. V. Pylypovskyi, D. D. Sheka, V. P. Kravchuk et al, Sci. Rep. Vol. 6, p. 23316 (2016); O. V. Pylypovskyi, D. Makarov, V. P. Kravchuk et al, Phys. Rev. Applied, Vol. 10, p. 064057 (2018)
[4] V. Balz, A. Manchon, M. Tsoi et al, Rev. Mod. Phys., Vol. 90, p. 015005 (2018)
[5] D. Y. Kononenko, O. V. Pylypovskyi, K. V. Yershov et al., arXiv:2005.05835 (2020)

  • Contribution to proceedings
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31895
Publ.-Id: 31895


Magnetostatics-Induced Symmetry Breaking Effects in Curvilinear Shells

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

The behavior of any physical system is governed by the order parameter, determined by the geometry of the physical space of the object, namely their dimensionality and curvature. Usually, the effects of curvature are identified using local interactions only, e.g. local spin-orbit- or curvature-induced Rashba and Dzyaloshinskii-Moriya interactions in condensed matter [1]. Lack of the framework, involving both, local and non-local interactions impedes the description of the essentially micromagnetic textures like magnetic domains, skyrmion-bubbles and vortices. Here, we present a micromagnetic theory of curvilinear ferromagnetic shells [2]. New chiral effects, originating from the magnetostatic interaction, can appear in such systems. They manifest themselves even in statics and are essentially nonlocal. This is in contrast to conventional Dzyaloshinskii--Moriya interaction (material intrinsic or curvature-induced, stemming from the exchange). The physical origin is in a non-zero mean curvature of a shell and non-equivalence between the top and bottom surfaces of the shell. To describe the new effects, we split a conventional volume magnetostatic charge into two terms: (i) magnetostatic charge, governed by the tangent to the sample’s surface, and (ii) geometrical charge, given by the normal component of magnetization and the mean curvature. We classify the interplay between the symmetry of the shell, its local curvature and magnetic textures and apply the proposed formalism to analyze magnetic textures in corrugated shells with perpendicular anisotropy.

[1] R. Streubel, J. Lee, D. Makarov et al, J. Phys. D, 49, 363001, (2016);
[2] O. V. Pylypovskyi, D. D. Sheka, V. P. Kravchuk et al, Sci. Rep. Vol. 6, p. 23316 (2016); O. M. Volkov, D. D. Sheka, Y. Gaididei et al, Sci. Rep. Vol. 8, p. 866 (2018).
[3] D. D. Sheka, O. V. Pylypovskyi, P. Landeros et al., Comm. Phys. 3, 128 (2019), DOI:10.1038/s42005-020-0387-2

  • Contribution to proceedings
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual Conference, Virtual Conference

Permalink: https://www.hzdr.de/publications/Publ-31894
Publ.-Id: 31894


From stripes to bubbles: Deterministic transformation of magnetic domain patterns in Co/Pt multilayers induced by laser helicity

Novakovic-Marinkovic, N.; Mawass, M.-A.; Volkov, O.; Makushko, P.; Dieter Engel, W.; Makarov, D.; Kronast, F.

The optical control of magnetism offers an attractive possibility to manipulate small magnetic domains for prospective memory devices on ultrashort time scales. Here, we report on the local deterministic transformation of the magnetic domain pattern from stripes to bubbles in out-of-plane magnetized Co/Pt multilayers controlled only by the helicity of ultrashort laser pulses. Relying on the experimentally determined average size of stripe domains and the magnetic layer thickness, we calculate the temperature and characteristic fields at which the stripe-bubble transformation occurs. Furthermore, we demonstrate that in the narrow range of the laser power, the helicity induces a drag on domain walls.

Keywords: Ferromagnetism; Magnetic domains; Magnetization switching; Ultrafast megnetic effects; Multilayer thin films

Permalink: https://www.hzdr.de/publications/Publ-31893
Publ.-Id: 31893


PET measured hypoxia and MRI parameters in re-irradiated head and neck squamous cell carcinomas: findings of a prospective pilot study

Rogasch, J.; Beck, M.; Stromberger, C.; Hofheinz, F.; Ghadjar, P.; Wust, W.; Budach, V.; Amthauer, H.; Tinhofer, I.; Furth, C.; Walter-Rittel, T.; Zschaeck, S.

Background: Tumor hypoxia measured by dedicated tracers like [18F]fluoromisonidazole (FMISO) is a well-established prognostic factor in head and neck squamous cell carcinomas (HNSCC) treated with definitive chemoradiation (CRT). However, prevalence and characteristics of positron emission tomography (PET) measured hypoxia in patients with relapse after previous irradiation is missing. Here we report imaging findings of a prospective pilot study in HNSCC patients treated with re-irradiation.

Methods: In 8 patients with recurrent HNSCC, diagnosed at a median of 18 months after initial radiotherapy/CRT, [18F]fluorodeoxyglucose (FDG)-PET/CT (n=8) and FMISO-PET/MRI (n=7) or FMISO-PET/CT (n=1) were performed. Static FMISO-PET was performed after 180 min. MRI sequences in PET/MRI included diffusion-weighted imaging with apparent diffusion coefficient (ADC) values and contrast enhanced T1w imaging (StarVIBE). Lesions (primary tumor recurrence, 4; cervical lymph node, 1; both, 3) were delineated on FDG-PET and FMISO-PET data using a background-adapted threshold-based method. SUVmax and SUVmean in FDG- and FMISO-PET were derived, as well as maximum tumor-to-muscle ratio (TMRmax) and hypoxic volume with 1.6-fold muscle SUVmean (HV1.6) in FMISO-PET. Intensity of lesional contrast enhancement was rated relative to contralateral normal tissue. Average ADC values were derived from a 2D region of interest in the tumor.

Results: In FMISO-PET, median TMRmax was 1.7 (range: 1.1-1.8). Median HV1.6 was 0.05 ml (range: 0-7.3 ml). Only in 2/8 patients, HV1.6 was ≥1.0 ml. In FDG-PET, median SUVmax was 9.3 (range: 5.0-20.1). On contrast enhanced imaging four lesions showed decreased and four lesions increased contrast enhancement compared to non-pathologic reference tissue. Median average ADC was 1,060 ×106 mm2/s (range: 840-1,400 ×106 mm2/s).

Conclusions: This pilot study implies that hypoxia detectable by FMISO-PET may not be as prevalent as expected among loco-regional recurrent HNSCC. ADC values were only mildly reduced, and contrast enhancement was variable. The results require confirmation in larger sample sizes.

Keywords: radiotherapy; head and neck squamous cell carcinoma; hypoxia; FMISO; FDG; PET

Permalink: https://www.hzdr.de/publications/Publ-31892
Publ.-Id: 31892


Depth distribution of irradiation-induced dislocation loops in an Fe-9Cr model alloy irradiated with Fe ions: The effect of ion energy

Vogel, K.; Chekhonin, P.; Kaden, C.; Hernández-Mayoral, M.; Akhmadaliev, S.; Bergner, F.

It is generally accepted that the microstructure of ion-irradiated Fe-based alloys does not only depend on the local level of displacement damage and the initial microstructure. Other factors such as the vicinity of a surface and the injected ions also play a role and may give rise to peculiar depth dependencies of the irradiated microstructure. Some investigators reported a band-like appearance indicating depth ranges of relatively uniform microstructure clearly distinguished from other ranges. Clarification is important for at least two purposes: first, to identify a depth range suitable for gaining meaningful information about the behaviour of materials exposed to neutron irradiation and, second, to correctly interpret results obtained by methods, such as nanoindentation, that integrate over extended depth ranges. A variation of the ion energy is expected to gain additional insight. In this work, two samples of Fe-9%Cr were irradiated at 300 °C with Fe2+ ions, one sample using 1 MeV ions and another sample using 5 MeV ions. Calculations using the binary collision code SRIM indicate displacement damage peaks at depths of 0.3 and 1.3 µm for ion energies of 1 and 5 MeV, respectively. The depth distribution of irradiation-induced dislocation loops was studied by cross-sectional scanning transmission electron microscopy (STEM). Loops visible in the STEM images were found to be arranged within two bands with the positions of these bands depending on the profiles of displacement damage and injected interstitials. The first and second band exhibit noticeably different number densities and mean sizes of the loops. For the 5 MeV irradiation, an extended range between the sample surface and the first band was observed, where decoration of pre¬existing line dislocations with loops is dominant. This microstructure resembles cases reported for neutron irradiation. For the 1 MeV irradiation, such a range does not exist. Estimates characterizing the loop size and number density in the distinct depth ranges are provided.

Keywords: Fe-9Cr; Ion irradiation; Scanning TEM; Dislocation loops

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31891
Publ.-Id: 31891


Dataset for the publication "Depth distribution of irradiation-induced dislocation loops in an Fe-9Cr model alloy irradiated with Fe ions: The effect of ion energy"

Vogel, K.; Chekhonin, P.; Bergner, F.

The dataset covers the raw/processed data required to reproduce the findings derived in the publication "Depth distribution of irradiation-induced dislocation loops in an Fe-9Cr model alloy irradiated with Fe ions: The effect of ion energy" by K. Vogel, P. Chekhonin, C. Kaden, M. Hernández-Mayoral, S. Akhmadaliev and F. Bergner. The whole set of original figures included in the publication is included as TIFF files. Supplementary material is provided as follows:

  • G385_xMeV_loop_count.pptx: Powerpoint files related to the estimation of the loop concentrations for the 1 MeV and 5 MeV irradiations,
  • Image_FIB_Position_Final.pptx: Powerpoint file showing the way how the 5 MeV FIB lamella was taken,
  • Loop_size_xMeV_Slicey.xlsx: Excel files related to the sizing of loops utilized to derive the histograms of the loops sizes,
  • Thickness_Profile_CBED_5MeV.xlsx: Thickness measurement for 5 MeV using the method of CBED.

Keywords: Fe-9Cr; Ion irradiation; Cross-sectional scanning transmission electron microscopy (STEM)

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-15
    DOI: 10.14278/rodare.670

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31890
Publ.-Id: 31890


Data for: "MicroTCA.4 based low level RF for continuous wave mode operation at the ELBE accelerator"

Kuntzsch, M.; Steinbrück, R.; Zenker, K.

This data is used in the publication "MicroTCA.4 based low level RF for continuous wave mode operation at the ELBE accelerator". The README.md includes all the information about which data set was used for which figure. The paper only shows the raw  data and numbers deduced from the data. No post processing like cleaning was done.

Keywords: ELBE; ChimeraTK; MicroTCA.4; LLRF; OPC UA

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-09
    DOI: 10.14278/rodare.630

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31889
Publ.-Id: 31889


The effect of the particle parameters of morphology and wettability in ultrafine particle flotation and froth fractionation

Sygusch, J.; Rudolph, M.

Froth flotation is well-established and efficient in the selective separation of valuable particles from unwanted material with sizes ranging from 10 µm to 200 µm. However, when it comes to the separation of ultrafine particles (< 10 µm) there are still some challenges, or rather opportunities. This research is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart” aiming at developing a method for the separation of ultrafine particles based on multiple particle properties. Amongst such properties are wettability, morphology (shape or roughness) and size with applications not only in mineral processing but in general chemical engineering.
In order to study the effect of particle morphology on ultrafine particle flotation, three differently shaped fractions are used for testing, e.g. spherical particles, elongated particles and irregularly shaped particle fragments. Said particles are analysed for their wettability, which is varied by esterification using alcohols with differing alkyl chain lengths, through contact angle measurements. The particle size and shape properties are assessed by a combination of scanning electron microscopy, laser diffraction and optical microscopy.
Flotation tests are carried out using a novel flotation device that was designed especially for the flotation of ultrafine particles, combining advantages from machine-type froth flotation and column flotation.
Besides introducing a new concept of ultrafine particle flotation and froth fractionation, the study is contributing to the common understanding of flotation and the impact of different complex particle properties.

Keywords: Ultrafine particles; Flotation; Surface modification; Esterification of glass; Hydrophobisation

  • Contribution to proceedings
    International Mineral Processing Congress 2020, 18.-22.10.2020, Cape Town, South Africa
    Proceedings of the International Mineral Processing Congress 2020

Permalink: https://www.hzdr.de/publications/Publ-31885
Publ.-Id: 31885


Numerical ferromagnetic resonance experiments in nano-sized elements

Kai, W.; Körber, L.; Stienen, S.; Lindner, J.; Farle, M.; Kákay, A.

This dataset contains the raw data for our paper "Numerical ferromagnetic resonance experiments in nano-sized elements" published in IEEE Magnetic Letters. It is organized in folders according to the figures in the paper. Each folder contains the experimental and numerical data, together with the MuMax3 definition files and possible scripts used for evaluation.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-14
    DOI: 10.14278/rodare.666
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31884
Publ.-Id: 31884


High denticity oxinate-linearbackbone chelating ligand for diagnostic radiometal ions [111In]In3+ and [89Zr]Zr4+

Southcott, L.; Wang, X.; Wharton, L.; Yang, H.; Radchenko, V.; Kubeil, M.; Stephan, H.; Jaraquemada-Pelaez, M.; Orvig, C.

Advances in nuclear medicine depend on chelating ligands that form highly stable and kinetically inert complexes with relevant radiometal ions for use in diagnosis or therapy. A new potentially decadentate ligand, H5decaox, was synthesised to incorporate two 8-hydroxyquinoline moieties on either end of a diethylene triamine backbone decorated with three carboxylic acids, one at each N atom of the backbone. Metal complexation was assessed using nuclear magnetic resonance (NMR) spectroscopy and high-resolution massspectrometry (HR-MS) with In3+, Zr4+ and La3+. Solution thermodynamic studies provided the stepwise protonation constants and metal formation constants, indicating a high affinity for both In3+ and Zr4+ (pIn = 32.3 and pZr = 34.7), and density functional theory (DFT) calculations provided insight to the coordination environments with either metal ion.Concentration dependent radiolabeling experiments with [111In]InCl3 and [89Zr]ZrCl4 showed promise as quantitative radiolabeling (>95%) occurred at micromolar concentrations, under mild, near-physiological conditions of pH 7 and room temperature for 30 minutes. Serum stability of both radiometal complexes was investigated and the
[111In]In(decaox) complex remained 91% intact after 24 hours while the [89Zr]Zr(decaox) complex was 86% intact over the same time, comparable to other chelating ligands previously assessed with the same methods. The high radiolabeling yields, limited serum protein transchelation and structural insight of [89Zr]Zr(decaox) complex suggests a promising fit between the oxinate-containing ligand and the Zr4+ ion, setting the stage for further investigations with a functionalised version of the chelator for its potential in PET imaging.

Permalink: https://www.hzdr.de/publications/Publ-31883
Publ.-Id: 31883


A metabolic switch regulates the transition between growth and diapause in C. elegans

Penkov, S.; Raghuraman, B. K.; Erkut, C.; Oertel, J.; Galli, R.; Ackerman, E. J. M.; Vorkel, D.; Verbavatz, J. M.; Koch, E.; Fahmy, K.; Shevchenko, A.; Kurzchalia, T. V.

Background Metabolic activity alternates between high and low states during different stages of an organism's life cycle. During the transition from growth to quiescence, a major metabolic shift often occurs from oxidative phosphorylation to glycolysis and gluconeogenesis. We use the entry of Caenorhabditis elegans into the dauer larval stage, a developmentally arrested stage formed in response to harsh environmental conditions, as a model to study the global metabolic changes and underlying molecular mechanisms associated with growth to quiescence transition. Results Here, we show that the metabolic switch involves the concerted activity of several regulatory pathways. Whereas the steroid hormone receptor DAF-12 controls dauer morphogenesis, the insulin pathway maintains low energy expenditure through DAF-16/FoxO, which also requires AAK-2/AMPK alpha. DAF-12 and AAK-2 separately promote a shift in the molar ratios between competing enzymes at two key branch points within the central carbon metabolic pathway diverting carbon atoms from the TCA cycle and directing them to gluconeogenesis. When both AAK-2 and DAF-12 are suppressed, the TCA cycle is active and the developmental arrest is bypassed. Conclusions The metabolic status of each developmental stage is defined by stoichiometric ratios within the constellation of metabolic enzymes driving metabolic flux and controls the transition between growth and quiescence.

Keywords: microcalorimetry

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31882
Publ.-Id: 31882


Laser-plasma proton acceleration with a combined gas-foil target

Levy, D.; Bernert, C.; Rehwald, M.; Andriyash, I. A.; Assenbaum, S.; Kluge, T.; Kroupp, E.; Obst-Huebl, L.; Pausch, R.; Schulze-Makuch, A.; Zeil, K.; Schramm, U.; Malka, V.

Laser-plasma proton acceleration was investigated in the target normal sheath acceleration regime with a target composed of a gas layer and a thin foil. The laser's shape, duration, energy and frequency are modified as it propagates in the gas, altering the laser-solid interaction leading to proton acceleration. The modified properties of the laser were assessed by both numerical simulations and by measurements. The 3D particle-in-cell simulations have shown that a nearly seven-fold increase in peak intensity at the foil plane is possible. In the experiment, maximum proton energies showed high dependence on the energy transmission of the laser through the gas and a lesser dependence on the size and shape of the pulse. At high gas densities, where high intensity was expected, laser energy depletion and pulse distortion suppressed proton energies. At low densities, with the laser focused far behind the foil, self-focusing was observed and the gas showed a positive effect on proton energies. The promising results of this first exploration motivate further study of the target.

Keywords: laser plasma; TNSA; self focusing; PIConGPU

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31881
Publ.-Id: 31881


Status Report of GaN photocathode

Schaber, J.; Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.

Particle accelerators are always looking for new materials which can promise high quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance. Semiconductors such as GaN as novel materials for photocathodes are showing an enormous potential.
Activated with a thin alkali metal layer, like caesium (Cs), p-GaN has the ability to lower the surface work function to produce a negative electron affinity (NEA). Requirements on the instrumentation is to avoid any oxygen contamination before, during and after the activation with caesium, so the activation process takes place in a UHV chamber.
At the beginning of 2020 the first activation of GaN on sapphire substrate was successfully done and meanwhile more activations could be implemented. The activation process is influenced by many parameters like Cs-flux, heat-cleaning temperature, conductivity, anode material, vacuum and the substrate. All of these parameters have an influence on the photocathodes quality and its lifetime, which are studied and compared.

Keywords: GaN photocathode; III-V semiconductor; caesium activation; NEA cathode; Quantum efficiency

  • Open Access Logo Lecture (others) (Online presentation)
    High Brightness Electron beams generated from novel THermal resistant photocathodes (BETH) 2nd Collaboration Meeting, 10.07.2020, Siegen, Deutschland

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31880
Publ.-Id: 31880


Status Report of ELBE and GaN

Xiang, R.; Teichert, J.; Arnold, A.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.; Schaber, J.

The SRF Gun has been running stabile using a magnesium cathode in the last year. Over 200 hours beam time have been provided in CW operation in 2019.
The magnesium bulk cathodes work routinely in ELBE and are polished and chemical cleaned before inserting them into the SRF Gun II, where they are again cleaned with an UV drive laser. Magnesium cathodes derives usually quantum effeciencies (QE) between 0.3 to 0.5% in SRF Gun II and offer a low risk of contaminations and an extreme long lifetime. The UV drive laser cleaning can be repeated several times to guarantee an high quality working cathode.
However, the particle accelerator community is always looking for new materials which can promise high quantum efficiency, a long lifetime and good vacuum stability, fast response time and low thermal emittance. Semiconductors such as GaN as novel materials for photocathodes are showing an enormous potential.
GaN is a semi-conductive material and well known for its high QE when illuminated with UV light. For the activation only caesium is required.
At the beginning of 2020 the first activation of GaN on sapphire substrate was successfully done. At first the GaN is heat treated at 610°C for 15 min and then activated with caesium to form a negative electron affinity surface. With 0.5 % quantum efficiency the first activation is all in all a successfully step for further promising GaN photocathodes.

Keywords: GaN; photocathode; SRF Gun; III-V semiconductor photocathode; Mg cathode

  • Open Access Logo Lecture (others)
    High Brightness Electron beams generated from novel THermal resistant photocathodes (BETH) Meeting, 20.-21.01.2020, Siegen, Deutschland

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31879
Publ.-Id: 31879


C. elegans possess a general program to enter cryptobiosis that allows dauer larvae to survive different kinds of abiotic stress

Gade, V. R.; Traikov, S.; Oertel, J.; Fahmy, K.; Kurzchalia, T. V.

All organisms encounter abiotic stress but only certain organisms are able to cope with extreme conditions and enter into cryptobiosis (hidden life). Previously, we have shown that C. elegans dauer larvae can survive severe desiccation (anhydrobiosis), a specific form of cryptobiosis. Entry into anhydrobiosis is preceded by activation of a set of biochemical pathways by exposure to mild desiccation. This process called preconditioning induces elevation of trehalose, intrinsically disordered proteins, polyamines and some other pathways that allow the preservation of cellular functionality in the absence of water. Here, we demonstrate that another stress factor, high osmolarity, activates similar biochemical pathways. The larvae that acquired resistance to high osmotic pressure can also withstand desiccation. In addition, high osmolarity significantly increases the biosynthesis of glycerol making larva tolerant to freezing. Thus, to survive abiotic stress, C. elegans activates a combination of genetic and biochemical pathways that serve as a general survival program.

Keywords: calorimetry; anhydrobiosis; metabolic monitoring; osmmotic stress

Permalink: https://www.hzdr.de/publications/Publ-31878
Publ.-Id: 31878


Current status of the simulations on Wu et al. using fbpic and PIConGPU

Pausch, R.; Döpp, A.

A brief summary to drive a discussion regarding the Wu et al. paper and a possible reply to it.

Keywords: PIConGPU; LWFA; PWFA; fbpic

  • Lecture (others)
    hybrid meeting, 06.02.2020, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-31877
Publ.-Id: 31877


Data for: "First-principles modeling of plasmons in aluminum under ambient and extreme conditions"

Ramakrishna, K.; Cangi, A.; Dornheim, T.; Vorberger, J.

The numerical modeling of plasmon behavior is crucial for an accurate interpretation of inelastic scattering diagnostics in many experiments. We highlight the utility of linear-response time-dependent density functional theory (LR-TDDFT) as an appropriate first-principles framework for a consistent modeling of plasmon properties. We provide a comprehensive analysis of plasmons from ambient throughout warm dense conditions and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon width. We compare them with experimental measurements in aluminum accessible via x-ray Thomson scattering and with other dielectric models such as the Lindhard model, the Mermin approach based on parametrized collision frequencies, and the dielectric function obtained using static local field corrections of the uniform electron gas parametrized from path integral Monte Carlo simulations both at the ground state and at finite temperature. We conclude with the remark that the common practice of extracting and employing plasmon dispersion relations and widths is an insufficient procedure to capture the complicated physics contained in the dynamic structure factor in its full breadth.

Keywords: Warm dense matter

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-25
    DOI: 10.14278/rodare.331
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31876
Publ.-Id: 31876


Probing ultrafast magnetic-field generation by current filamentation instability in femtosecond relativistic laser-matter interactions

Raj, G.; Kononenko, O.; Gilljohann, M. F. F.; Doche, A.; Davoine, X.; Caizergues, C.; Chang, Y.-Y.; Couperus Cabadağ, J. P.; Debus, A.; Ding, H.; Förster, M.; Goddet, J.-P.; Heinemann, T.; Kluge, T.; Kurz, T.; Pausch, R.; Rousseau, P.; San Miguel Claveria, P.; Schöbel, S.; Siciak, A.; Steiniger, K.; Tafzi, A.; Yu, S.; Hidding, B.; Martinez De La Ossa, A.; Irman, A.; Karsch, S.; Döpp, A.; Schramm, U.; Gremillet, L.; Corde, S.

The current filamentation instability is a key phenomenon underpinning various processes in astrophysics, laboratory laser-plasma, and beam-plasma experiments. Here we show that the ultrafast dynamics of this instability can be explored in the context of relativistic laser-solid interactions through deflectometry by low-emittance, highly relativistic electron bunches from a laser wakefield accelerator. We present experimental measurements of the femtosecond timescale generation of strong magnetic-field fluctuations, with a measured line-integrated B field of 2.70±0.39kTμm. Three-dimensional, fully relativistic particle-in-cell simulations demonstrate that such fluctuations originate from the current filamentation instability arising at submicron scales around the irradiated target surface, and that they grow to amplitudes strong enough to broaden the angular distribution of the probe electron bunch a few tens of femtoseconds after the laser pulse maximum. Our results open a branch of physics experiments investigating the femtosecond dynamics of laser-driven plasma instabilities by means of synchronized, wakefield-accelerated electron beams.

Keywords: current filamentation; laser plasma

Permalink: https://www.hzdr.de/publications/Publ-31875
Publ.-Id: 31875


Review on the Compositional Variation of Eudialyte-Group Minerals in the Ilímaussaq Complex (South Greenland)

Marks, M. A. W.; Eggenkamp, H. G. M.; Atanasova, Petya; Mundel, F.; Kümmel, S.; Hagen, M.; Wenzel, T.; Markl, G.

We review the compositional variation of eudialyte-group minerals (EGM) from the Ilímaussaq complex in South Greenland. Investigated samples cover all major rock units and associated pegmatites and aplites. The whole data set (>3000 analyses from>250 samples) exhibits variable XMn (0.1–0.5), REE (0.2–1.7 apfu), Nb (0.1–0.4), and Cl contents (0.4–1.6 apfu). Most EGM compositions are Na-rich (13–15 apfu), while deviations to Na-rich but also to Na-poor compositions occur because of a combination of primary features (peralkalinity, water activity) and secondary alteration. During magma evolution, REE contents in EGM cores generally increase and reach their highest contents in the most evolved rock units of the complex. This points to the moderate compatibility of REE in EGM and a bulk D (cEGM/cmelt) value of <1 during magma differentiation. Chlorine contents in EGM cores continuously decrease, and are lowest at the rims of individual crystals, suggesting a continuous decrease of Cl activity in the magmas by large-scale EGM and sodalite extraction during the orthomagmatic stage and water enrichment during the late-magmatic stage. The overall variations of XMn across stratigraphy are only minor and likely influenced bythe co-crystallization of sodic pyroxene and amphibole (c.f. aegirine, arfvedsonite) and local phaseproportions. Similarly, Nb and Ti contents are influenced by co-crystallizing aenigmatite, rinkite, and others. Their presence buffers Ti and Nb contents to rather constant and low values, while their absence may cause variable enrichment on a local scale. Very low Sr contents (<0.1 apfu) in magmatic EGM from Ilímaussaq are related to the basaltic nature of the parental magmas of the complex, as large-scale plagioclase fractionation occurred prior to the formation of the Ilímaussaq magmas, effectively removing Sr from the system. This is in line with very strong negative Eu anomalies in EGM from Ilímaussaq. Consistently, Sr contents in EGM from alkaline complexes, for which foiditic parental magmas are assumed, are much higher and, in such cases, negative Eu anomalies aregenerally absent.

Keywords: Ilimaussaq; differentiation; eudialyte-group minerals; mineral chemistry

Permalink: https://www.hzdr.de/publications/Publ-31874
Publ.-Id: 31874


PIConGPU - a highly-parallel 3D3V particle-in-cell code

Pausch, R.; Bastrakov, S.; Debus, A.; Garten, M.; Huebl, A.; Marre, B.-E.; Meyer, F.; Steinger, K.; Widera, R.; Bussmann, M.

This talk will introduce the basic concepts of how particle-in-cell codes model plasma dynamics and discuss their implementation in the open-source code PIConGPU, focusing on how parallelism can be exploited to enable efficient scaling on today's largest HPC systems. Furthermore, the problem of IO limitations with larger simulations is discussed and the plugin method for in-situ data analysis in PIConGPU is presented to overcome these limitations. Finally, an overview of different physics cases simulated with PIConGPU is presented, ranging from small-scale laser-plasma accelerators to plasma jets in astrophysics.

Keywords: PIConGPU; LWFA; TNSA; alpaka; ISAAC; KHI

  • Lecture (others) (Online presentation)
    CASUS Seminar, 08.09.2020, Görlitz, Deutschland
  • Lecture (others)
    Seminar Series 'Hardware & Numerics', 24.11.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31873
Publ.-Id: 31873


Changes in Halogen (F, Cl, Br, and I) and S Ratios inRock-Forming Minerals as Monitors for MagmaticDifferentiation, Volatile-Loss, and HydrothermalOverprint: The Case for Peralkaline Systems

Eggenkamp, H. G. M.; Marks, M. A. W.; Atanasova, Petya; Wenzel, T.; Markl, G.

We determined the halogen (F, Cl, Br, and I) and sulfur (S) concentrations in Cl-rich rock-forming minerals from five peralkaline complexes. We investigated sodalite (N=42), eudialyte-group minerals (N=84), and tugtupite (N=8) from representative rock samples derived from Ilímaussaq (South Greenland), Norra Kärr (Sweden), Tamazeght (Morocco), Lovozero, and Khibina (Russian Federation). Taken together, sodalite and eudialyte-group minerals dominate the Cl and Br budget of the investigated rocks. For F, however, several other phases (e.g., amphibole, fluorite, villiaumite, and minerals of the rinkite group and the apatite supergroup) are additional sinks, and parts of the S may be scavenged in generally rare sulfides. The investigated minerals contain Cl at the wt.% level, F and S concentrations are in the hundreds to thousands of μg/g-range, Br is less common (0.2–200μg/g) and I is rare (mostly well below 1μg/g). Normalized to Cl, sodalite prefers Br relative to eudialyte-group minerals, while F is always enriched in the latter. Our data show that both F and S may represent important components in eudialyte-group minerals, sometimes at similar levels as Cl, which normally dominates. Sulfur reveals redox-dependent behavior: Under reduced crystallization conditions, S is more compatible in eudialyte-group minerals (EGM) than in sodalite, which flips to the opposite under water-rich and presumably more oxidized conditions. We investigate the applicability of F/Cl, Br/Cl, and S/Cl ratios in these minerals in peralkaline systems to better understand the interplay of magmatic differentiation, fluid loss and hydrothermal overprint. Similar to apatite in metaluminous systems, fractionation of sodalite, and eudialyte-group minerals in peralkaline magmas leads to decreasing Br/Cl ratios. The data presented in this study bear implications for the mineral chemistry and compositional variation of sodalite and especially EGM in general. Volatile components in EGM that are not normally considered, such as F and S, can reach concentrations of thousands of μg/g. Especially in the case of F, with its low atomic weight, the results obtained in this study indicate that it is very significant for formulae calculations, neutral charge-balance, and similar aspects at such concentration levels. This study demonstrates that halogen contents and ratios are sensitive monitors for a variety of processes in magmatic-hydrothermal systems, including magmatic fractionation, volatile loss, and fluid–rock interaction.

Keywords: eudialyte group minerals; sodalite; tugtupite; chloride; fluoride; bromide; sulfur; Ilímaussaq; peralkaline rocks

Permalink: https://www.hzdr.de/publications/Publ-31872
Publ.-Id: 31872


Design study for a compact laser-driven source for medical x-ray fluorescence imaging

Brümmer, T.; Debus, A.; Pausch, R.; Osterhoff, J.; Grüner, F.

Thomson scattering sources with their hard x-ray pencil beams represent a promising candidate to drive high-resolution X-ray Fluorescence Imaging (XFI). As XFI is a scanning imaging modality, it specifically requires pencil-beam geometries along with a high beam mobility. In combination with laser-wakefield acceleration (LWFA) such sources could provide the compactness needed for a future transition into clinical application. A sufficient flux within a small bandwidth could enable in-vivo high-sensitivity XFI for early cancer diagnostics and pharmacokinetic imaging. We thus report on a specific all-laser driven source design directed at increasing the photon number within the bandwidth and opening angle defined by XFI conditions. Typical parameters of driver lasers and electron bunches from LWFA are utilized and controlled within realistic parameter regions on the basis of appropriate beam optics. An active plasma lens is implemented for chromatic focal control of the bunch. Source performance limits are identified and compared to existing x-ray sources with regard to their potential to be implemented in future clinical XFI.

Keywords: Thomsons scattering; x-ray; light source; ClaRa2

Permalink: https://www.hzdr.de/publications/Publ-31871
Publ.-Id: 31871


Uranium(VI) reduction by a sulphate-reducing microorganism in Opalinus Clay pore water

Hilpmann, S.; Drobot, B.; Steudtner, R.; Bok, F.; Stumpf, T.; Cherkouk, A.

1 Introduction
Clay formations are potential host rocks for the long-term storage of high-level radioactive waste in a deep geological repository in Germany, besides salt and crystalline rock. A multi-barrier system is fa-vored, consisting of the technical (container with the waste), the geotechnical (sealing and backfilling material, e.g. bentonite) and the geological barrier (host rock) to isolate it from the biosphere.
Different studies showed that sulphate-reducing microorganisms, especially Desulfosporosinus species, occur in various clay formations, as well as in bentonite [1,2]. Desulfosporosinus hippei DSM 8344 is an anaerobic spore-forming microorganism isolated from permafrost soil [3] and a close phylogenetic relative of the Desulfosporosinus species detected in clay formations. Therefore, this strain was selected to study the reduc-tion of uranium(VI) to the less mobile uranium(IV).

2 Results
A time-dependent experiment in artificial Opalinus Clay pore water [4] (100 µM uranium(VI), pH 5.5) revealed a 95 % removal of uranium from the supernatant within 24 h. The corresponding microscopy of live/dead stained cells showed the formation of agglomerates and an increasing number of dead cells within the incubation time. The black colouring of the agglomerates already provided hints of the occur-ring reduction of uranium(VI).
Different aqueous species including uranyl(VI) lactate and uranyl(VI) carbonate complexes are present in the supernatant, as determined by time-resolved laser-induced luminescence spectroscopy. The assign-ment of the different species was possible by comparison with reference spectra. While the amount of the uranyl(VI) lactate complex decreased with the incubation time, the uranyl(VI) carbonate fraction re-mained almost constant. This leads to the assumption, that the cells reduce only the uranyl(VI) lactate complex. This conclusion can be supported by the fact that the reduction process did not take place in bicarbonate buffer, where the uranyl(VI) carbonate complexes are dominant, using the same microor-ganism.
The comparison of the UV/VIS band positions of the dissolved cell pellets with the spectra of pure uranium(IV) and uranyl(VI) samples provides clear evidence of the formed uranium(IV). Furthermore, bands of uranyl(VI) occur in the spectrum, as well. Therefore, a combination of a sorption and reduction processes is assumed. These findings offer new insights into the microbe-actinide interactions relevant to high-level radioactive waste disposal in clay rock.

The authors gratefully acknowledge the funding provided by the German Federal Ministry of Education and Research (BMBF) (Grant 02NUK053E) and The Helmholtz Association (Grant SO-093).

References
[1] A. Bagnoud et al., “Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock”, Nat. Commun. 7, 1–10 (2016)
[2] N. Matschiavelli et al., “The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C”, Environ. Sci. Technol. 53, 10514–10524 (2019).
[3] A. Vatsurina et al., “Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost”, Int. J. Syst. Evol. Microbiol. 58, 1228–1232 (2008).
[4] P. Wersin et al. “Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland”, Appl. Geochemistry 26, 931–953 (2011).

Keywords: uranium(VI) reduction; sulphate-reducing bacteria; clay rock

  • Lecture (Conference) (Online presentation)
    Tage der Standortauswahl Freiberg 2021, 11.-12.02.2021, Freiberg, Deutschland
  • Poster (Online presentation)
    Tage der Standortauswahl Freiberg 2021, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31870
Publ.-Id: 31870


Wire-mesh sensor data set of gas-water flow in a horizontal pipe

de Assis Dias, F.; Pipa, D. R.; Morales, R. E. M.; Da Silva, M. J.

Wire-mesh sensor raw data of gas-water pipe flow. The experiments were performed at the Federal University of Paraná in a setup located at the NUEM (Núcleo de Escoamento Multifásico). The flow loop is composed of a horizontal pipe of 26 mm inner diameter and 9 m long. The data set are measurements of wire-mesh sensors with the following resolutions: 12x12, 8x8, 6x6, 4x4 and 2x2.

Keywords: wire-mesh sensor; multiphase flow

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-14
    DOI: 10.14278/rodare.659

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31869
Publ.-Id: 31869


First-principles modeling of plasmons in aluminum under ambient and extreme conditions

Ramakrishna, K.; Cangi, A.; Dornheim, T.; Vorberger, J.

The numerical modeling of plasmon behavior is crucial for an accurate interpretation of inelastic scattering diagnostics in many experiments. We highlight the utility of linear-response time-dependent density functional theory (LR-TDDFT) as an appropriate first-principles framework for a consistent modeling of plasmon properties. We provide a comprehensive analysis of plasmons from ambient throughout warm dense conditions and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon width. We compare them with experimental measurements in aluminum accessible via x-ray Thomson scattering and with other dielectric models such as the Lindhard model, the Mermin approach based on parametrized collision frequencies, and the dielectric function obtained using static local field corrections of the uniform electron gas parametrized from path integral Monte Carlo simulations both at the ground state and at finite temperature. We conclude with the remark that the common practice of extracting and employing plasmon dispersion relations and widths is an insufficient procedure to capture the complicated physics contained in the dynamic structure factor in its full breadth.

Keywords: Warm dense matter

Related publications

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31868
Publ.-Id: 31868


Attenuating the fermion sign problem in path integral Monte Carlo simulations using the Bogoliubov inequality and thermodynamic integration

Dornheim, T.; Invernizzi, M.; Hirshberg, B.; Vorberger, J.

Accurate thermodynamic simulations of correlated fermions using path integral Monte Carlo (PIMC) methods are of paramount importance for many applications such as the description of ultracold atoms, electrons in quantum dots, and warm-dense matter. The main obstacle is the fermion sign problem (FSP), which leads to an exponential increase in computation time both with increasing the system-size and with decreasing temperature. Very recently, Hirshberg et al.[J. Chem. Phys. 152, 171102 (2020)] have proposed to alleviate the FSP based on the Bogoliubov inequality. In the present work, we extend this approach by adding a parameter that controls the perturbation, allowing for an extrapolation to the exact result. In this way, we can also use thermodynamic integration to obtain an improved estimate of the fermionic energy. As a test system, we choose electrons in 2D and 3D quantum dots and find in some cases a speed-up exceeding 10^ 6, as compared to standard PIMC, while retaining a relative accuracy of ~0.1%. Our approach is quite general and can readily be adapted to other simulation methods.

Permalink: https://www.hzdr.de/publications/Publ-31866
Publ.-Id: 31866


Finite-size effects in the reconstruction of dynamic properties from ab initio path integral Monte Carlo simulations

Dornheim, T.; Vorberger, J.

We systematically investigate finite-size effects in the dynamic structure factor S(q,ω) of the uniform electron gas obtained via the analytic continuation of ab initio path integral Monte Carlo data for the imaginary-time density–density correlation function F(q,τ). Using the recent scheme by Dornheim et al. [Phys. Rev. Lett. 121, 255001 (2018)], we find that the reconstructed spectra are not afflicted with any finite-size effects for as few as N=14 electrons both at warm dense matter (WDM) conditions and at the margins of the strongly correlated electron liquid regime. Our results further corroborate the high quality of our current description of the dynamic density response of correlated electrons, which is of high importance for many applications in WDM theory and beyond.

Permalink: https://www.hzdr.de/publications/Publ-31865
Publ.-Id: 31865


Effective Static Approximation: A Fast and Reliable Tool for Warm-Dense Matter Theory

Dornheim, T.; Cangi, A.; Ramakrishna, K.; Böhme, M.; Tanaka, S.; Vorberger, J.

We present an effective static approximation (ESA) to the local field correction (LFC) of the electron gas that enables highly accurate calculations of electronic properties like the dynamic structure factor S(q,ω), the static structure factor S(q), and the interaction energy v. The ESA combines the recent neural-net representation by T. Dornheim et al., [J. Chem. Phys. 151, 194104 (2019)] of the temperature-dependent LFC in the exact static limit with a consistent large wave-number limit obtained from quantum Monte Carlo data of the on-top pair distribution function g(0). It is suited for a straightforward integration into existing codes. We demonstrate the importance of the LFC for practical applications by reevaluating the results of the recent x-ray Thomson scattering experiment on aluminum by Sperling et al. [Phys. Rev. Lett. 115, 115001 (2015)]. We find that an accurate incorporation of electronic correlations in terms of the ESA leads to a different prediction of the inelastic scattering spectrum than obtained from state-of-the-art models like the Mermin approach or linear-response time-dependent density functional theory. Furthermore, the ESA scheme is particularly relevant for the development of advanced exchange-correlation functionals in density functional theory.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31864
Publ.-Id: 31864


Pump-probe response of correlated materials under high pressures

Pashkin, O.

Time-resolved optical spectroscopy is a very powerful tool for studying the photoinduced phase transitions and ultrafast dynamics in strongly correlated electronic systems. We reinforce this method by combining it with the high-pressure technique which allows to tune the strength of electronic correlations and Fermi surface nesting in a system. Several application examples for the investigation of the pressure-induced phenomena such as the metallization in VO2 and the suppression of the charge-density wave in CeTe3 and the spin-density wave in BaFe2As2 will be discussed.

  • Lecture (others) (Online presentation)
    Elasto-Q-Mat Colloquia, 10.12.2020, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31863
Publ.-Id: 31863


Protein-Assisted Room-Temperature Assembly of Rigid, Immobile Holliday Junctions and Hierarchical DNA Nanostructures

Ramakrishnan, S.; Subramaniam, S.; Kielar, C.; Grundmeier, G.; Stewart, A. F.; Keller, A.

Immobile Holliday junctions represent not only the most fundamental building block of structural DNA nanotechnology but are also of tremendous importance for the in vitro investigation of genetic recombination and epigenetics. Here, we present a detailed study on the room-temperature assembly of immobile Holliday junctions with the help of the single-strand annealing protein Red beta. Individual DNA single strands are initially coated with protein monomers and subsequently hybridized to form a rigid blunt-ended four-arm junction. We investigate the efficiency of this approach for different DNA/protein ratios, as well as for different DNA sequence lengths. Furthermore, we also evaluate the potential of Red beta to anneal sticky-end modified Holliday junctions into hierarchical assemblies. We demonstrate the Red beta-mediated annealing of Holliday junction dimers, multimers, and extended networks several microns in size. While these hybrid DNA-protein nanostructures may find applications in the crystallization of DNA-protein complexes, our work shows the great potential of Red beta to aid in the synthesis of functional DNA nanostructures under mild reaction conditions.

Keywords: DNA nanotechnology; Holliday junctions; atomic force microscopy; single-strand annealing proteins

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31862
Publ.-Id: 31862


Alginite rock as effective demulsifier to separate water from various crude oil emulsions

Ahmed, S. S.; Hippmann, S.; Roode-Gutzmer, Q. I.; Fröhlich, P.; Bertau, M.

Due to environmental restriction laws in oil production and processing, there is a high demand for the oil industry to reduce the use of chemical demulsifiers and to employ safer, less toxic materials. The purpose of this research is to investigate whether Alginite, a naturally occurring and abundant oil-shale rock, can be utilised as an alternative, environmentally friendly and low-cost material to demulsify various water-in-crude oil emulsions (W/O). Three W/O emulsions were prepared using saline water with respectively light, medium and heavy crude oils. The properties of the crude oils were analysed and the effectiveness of Alginite to demulsify the corresponding W/O emulsions was investigated. The results confirm that naturally occuring Alginite exhibits exceptional water-removing capacity even from emulsions containing heavy crude oil, leaving only < 1.0 wt.-% water in the remaining demulsified oil, which satisfies the required specification for industrial applications. Alginite was shown to reduce viscosity and to deform the dispersed phase in W/O emulsions even in the absence of flow. The results of this work indicate that Alginite is of significant interest in petroleum research, in industrial oil processing as well as in environmental remediation.

Keywords: Alginite rock; natural demulsifier; crude oil; viscosity; water droplet

Permalink: https://www.hzdr.de/publications/Publ-31861
Publ.-Id: 31861


Solventextraktion von Rhenium und Molybdän - Trennung durch selektive Reextraktion

Göthel, J.

Die Anwendungen der Solventextraktion finden sich in der anorganischen, organischen und analytischen Chemie, in den pharmazeutischen und biochemischen Industrien sowie in der Abfallbehandlung und ist eine der groß angelegten industriellen Trennungs-verfahren. In der metallurgischen Aufbereitung von Rohstoffen ist die Solventextraktion durch die Interdisziplinarität von hydrometallurgischer Verfahrenstechnik und anorganisch-organischer Chemie geprägt. Bei der Extraktion anionischer Metallspezies aus wässriger Lösung finden unter anderem aliphatische Amine eine breite Anwendung. Die wirtschaftsstrategischen Refraktärmetalle Rhenium und Molybdän wurden in den 1980er Jahren hinsichtlich ihrer selektiven Trennung durch eine Kombination von sekundären Aminen (R2NH) als Extraktionsmittel und Phosphinoxid (R3PO) als Additiv beschrieben. Bisher wurden keine Untersuchungen des Extraktionssystems gegenüber Eisen (III), der Coextraktion vom Mo (VI) und Re (VII) aus stark verdünnten Lösungen und dem Vergleich zu anderen sekundären Aminen durchgeführt sowie den Einfluss des Lösungsmittels untersucht (vgl. KÄHLER und GOCK). Die Untersuchungen zum System Rhenium und Molybdän im Rahmen dieser experimentellen Studienarbeit haben gezeigt, dass das Additiv TOPO mit dem Extraktionsmittel DTDA die Extraktion von Rhenium verbessert. Das Extraktionsmittel DTDA führt aufgrund seiner langkettigen Alkylreste im Vergleich zu DOA zu größeren Extraktionsergebnissen. Mit dem Extraktionsmittel DOA treten vermehrt dritte Phasen bei der Extraktion auf. Das Extraktionssystem zeichnet sich durch eine Gesamtbeladungs-kapazität aus, wobei Sulfatspezies und auch Wasser coextrahiert werden können. Das Lösungsmittel Chloroform verschlechtert die Extraktion von Rhenium durch seine abschirmenden polaren Wechselwirkungen und der Konkurrenzsituation bei der Ausbildung von Wasserstoffbrückenbindungen. Molybdän scheint für die Extraktion keine signifikante Abhängigkeit vom Lösungsmittel (Kerosin, Toluol und Chloroform) zu zeigen. Molybdän und Rhenium lassen sich selektiv von Kupfer und Zink extrahieren, jedoch nicht von Eisen (III). Eisen kann mit Salzsäure zu über 60 % von der beladenen Organik unter Verlust von Molybdän gewaschen werden. Mittels Schwefelsäure kann Eisen vollständig von der Organik, aber mit noch höheren Molybdänüberführungen, gewaschen werden. Eine befriedigende Trennung ergibt sich nicht. Rhenium kann von Molybdän selektiv unter dem Einfluss von TOPO bereits bei geringen TOPO-Konzentrationen reextrahiert werden. Diese Selektivität zeigt sich deutlicher im Lösungsmittel Chloroform als im Lösungsmittel Kerosin.

  • Other
    TU Bergakademie Freiberg, 2020
    Mentor: Toni Helbig

Permalink: https://www.hzdr.de/publications/Publ-31858
Publ.-Id: 31858


Accelerating Finite-temperature Kohn-Sham Density Functional Theory with Deep Neural Networks

Ellis, J. A.; Cangi, A.; Modine, N. A.; Stephens, J. A.; Thompson, A. P.; Rajamanickam, S.

Output from electronic structure code (Quantum Espresso) that serves as training data for the machine-learning workflow of the related scientific publication (https://arxiv.org/abs/2010.04905).

Keywords: machine learning; neural networks; materials science; density functional theory

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-11
    DOI: 10.14278/rodare.645

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31857
Publ.-Id: 31857


Defects in Functional Materials

Ling, F. C.-C.; Zhou, S.; Kuznetsov, A.

The research of functional materials has attracted extensive attention in recent years, and its advancement nitrifies the developments of modern sciences and technologies like green sciences and energy, aerospace, medical and health, telecommunications, and information technology. The present book aims to summarize the research activities carried out in recent years devoting to the understanding of the physics and chemistry of how the defects play a role in the electrical, optical and magnetic properties and the applications of the different functional materials in the fields of magnetism, optoelectronic, and photovoltaic etc.

  • Book (Editorship)
    Singapore: World Scientific Publishing Co., 2020
    ISBN: 978-981-120-316-9
    DOI: 10.1142/11352

Permalink: https://www.hzdr.de/publications/Publ-31856
Publ.-Id: 31856


Making 2D topological polymers a reality

Jing, Y.; Heine, T.

First-principles calculations predicted electronic topological properties for 2D honeycomb–kagome polymers, which have been now confirmed experimentally thanks to improvements in on-surface synthesis.

Keywords: 2D polymers; topological polymers

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31854
Publ.-Id: 31854


Benchmark of Simplified Time-Dependent Density Functional Theory for UV–Vis Spectral Properties of Porphyrinoids

Batra, K.; Zahn, S.; Heine, T.

Time-dependent density functional theory is thoroughly benchmarked for the predictive calculation of UV–vis spectra of porphyrin derivatives. With the aim to provide an approach that is computationally feasible for large-scale applications such as biological systems or molecular framework materials, albeit performing with high accuracy for the Q-bands, the results given by various computational protocols, including basis sets, density-functionals (including gradient corrected local functionals, hybrids, double hybrids and range-separated functionals), and various variants of time-dependent density functional theory, including the simplified Tamm–Dancoff approximation, are compared. An excellent choice for these calculations is the range-separated functional CAM-B3LYP in combination with the simplified Tamm–Dancoff approximation and a basis set of double-ζ quality def2-SVP (mean absolute error [MAE] of ≈0.05 eV). This is not surpassed by more expensive approaches, not even by double hybrid functionals, and solely systematic excitation energy scaling slightly improves the results (MAE ≈0.04 eV).

Keywords: density functional theory; UV–Vis; porphyrinoids; spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-31853
Publ.-Id: 31853


Blue Phosphorene Bilayer Is a Two-Dimensional Metal and an Unambiguous Classification Scheme for Buckled Hexagonal Bilayers

Arcudia, J.; Kempt, R.; Eduardo Cifuentes-Quintal, M.; Heine, T.; Merino, G.

High-level first-principles computations predict blue phosphorene bilayer to be a two-dimensional metal. This structure has not been considered before and was identified by employing a block-diagram scheme that yields the complete set of five high-symmetry stacking configurations of buckled honeycomb layers, and allows their unambiguous classification. We show that all of these stacking configurations are stable or at least metastable both for blue phosphorene and gray arsenene bilayers. For blue phosphorene, the most stable stacking arrangement has not yet been reported, and surprisingly it is metallic, while the others are indirect band gap semiconductors. As it is impossible to interchange the stacking configurations by translations, all of them should be experimentally accessible via the transfer of monolayers. The metallic character of blue phosphorene bilayer is caused by its short interlayer distance of 3.01 Å and offers the exceptional possibility to design single elemental all-phosphorus transistors.

Keywords: 2D materials; phosphorus; nanoelectronics; first-principles calculations

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31852
Publ.-Id: 31852


RBS raw data for publication "Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth"

Schöffmann, P.; Pütter, S.; Schubert, J.; Zander, W.; Barthel, J.; Zakalek, P.; Waschk, M.; Heller, R.; Brückel, T.

RBS raw date for publication "Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth"

Simulation results using SIMNRA included as well

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-11-06
    DOI: 10.14278/rodare.657
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31851
Publ.-Id: 31851


Tuning the Co/Sr stoichiometry of SrCoO2.5 thin films by RHEED assisted MBEgrowth

Schöffmann, P.; Pütter, S.; Schubert, J.; Zander, W.; Barthel, J.; Zakalek, P.; Waschk, M.; Heller, R.; Brückel, T.

Strontium cobaltite (SrCoO2.5+δ, SCO) is a fascinating material because of its topotactic structural phase transition caused by a change in oxygen stoichiometry. In the brownmillerite phase (δ = 0) it is an insulating antiferromagnet whereas in the perovskite phase (δ = 0.5) it is a conducting ferromagnet. In contrast, the impact of the varying Co/Sr stoichiometry on the structure has not yet been studied in SCO thin films. Using molecular beam epitaxy we have fabricated SCO thin films of varying Co/Sr stoichiometry. Films with Co excess exhibit a brownmillerite crystal structure with CoO precipitates within the thin film and on the surface. Co deficient films are amorphous. Only for 1:1 stoichiometry a pure brownmillerite structure is present. We find a clear dependence of the Reflection High Energy Electron Diffraction (RHEED) pattern of these thin films on the stoichiometry. Interestingly, RHEED is very sensitive to a Co excess of less than 12% while x-ray diffraction fails to reveal that difference. Hence, using RHEED, the stoichiometry of SCO can be evaluated and tuned in-situ to a high degree of precision, which allows for a quick adjustment of the growth parameters during a sample series.

Keywords: This films; SrCoO; Rutherford Backscattering; RHEED; MBE; growth

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31850
Publ.-Id: 31850


MEIS raw data and maps for publication "Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films"

Selau, F. F.; Trombini, H.; Marmitt, G. G.; de Andrade, A. M. H.; Morais, J.; Grande, P. L.; Alencar, I.; Vos, M.; Heller, R.

MEIS raw data and maps for publication "Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films"

Including stiched spectra and 2D ESTAT maps

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-14
    DOI: 10.14278/rodare.655
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31849
Publ.-Id: 31849


Stopping and straggling of 60–250-keV backscattered protons on nanometric Pt films

Selau, F. F.; Trombini, H.; Marmitt, G. G.; de Andrade, A. M. H.; Morais, J.; Grande, P. L.; Alencar, I.; Vos, M.; Heller, R.

The stopping power and straggling of backscattered protons on nanometric Pt films were measured at low to medium energies (60–250 keV) by using the medium-energy ion scattering technique. The stopping power results are in good agreement with the most recent measurements by Primetzhofer Phys. Rev. B 86, 094102 (2012) and are well described by the free electron gas model at low projectile energies. Nevertheless, the straggling results are strongly underestimated by well-established formulas up to a factor of two. Alternatively, we propose a model for the energy-loss straggling that takes into account the inhomogeneous electron-gas response, based on the electron-loss function of the material, along with bunching effects. This approach yields remarkable agreement with the experimental data, indicating that the observed enhancement in energy-loss straggling is due to bunching effects in an inhomogeneous electron system. Nonlinear effects are of minor importance for the energy-loss straggling.

Keywords: Stopping cross sections; Rutherford Backscattering; Medium Energy Ion Scattering; Energy Straggling

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31848
Publ.-Id: 31848


RBS raw data for publication "Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites"

Zehner, J.; Soldatov, I.; Schneider, S.; Heller, R.; Khojasteh, N. B.; Schiemenz, S.; Fähler, S.; Nielsch, K.; Schäfer, R.; Leistner, K.

RBS raw data for publication "Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites"

Simulation results using SIMNRA are included as well

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-16
    DOI: 10.14278/rodare.653
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31847
Publ.-Id: 31847


Voltage‐Controlled Deblocking of Magnetization Reversal in Thin Films by Tunable Domain Wall Interactions and Pinning Sites

Zehner, J.; Soldatov, I.; Schneider, S.; Heller, R.; Khojasteh, N. B.; Schiemenz, S.; Fähler, S.; Nielsch, K.; Schäfer, R.; Leistner, K.

High energy efficiency of magnetic devices is crucial for applications such as data storage, computation, and actuation. Redox‐based (magneto‐ionic) voltage control of magnetism is a promising room‐temperature pathway to improve energy efficiency. However, for ferromagnetic metals, the magneto‐ionic effects studied so far require ultrathin films with tunable perpendicular magnetic anisotropy or nanoporous structures for appreciable effects. This paper reports a fully reversible, low voltage‐induced collapse of coercivity and remanence by redox reactions in iron oxide/iron films with uniaxial in‐plane anisotropy. In the initial iron oxide/iron films, Néel wall interactions stabilize a blocked state with high coercivity. During the voltage‐triggered reduction of the iron oxide layer, in situ Kerr microscopy reveals inverse changes of coercivity and anisotropy, and a coarsening of the magnetic microstructure. These results confirm a magneto‐ionic deblocking mechanism, which relies on changes of the Néel wall interactions, and of the microstructural domain‐wall‐pinning sites. With this approach, voltage‐controlled 180° magnetization switching with high energy‐efficiency is achieved. It opens up possibilities for developing magnetic devices programmable by ultralow power and for the reversible tuning of defect‐controlled materials in general.

Keywords: iron films; magnetic domains; magnetoelectrics; magneto‐ionic mechanisms

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31846
Publ.-Id: 31846


RBS raw data for publication "High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy "

Bommanaboyena, S. P.; Bergfeldt, T.; Heller, R.; Kläui, M.; Jourdan, M.

RBS raw data for publication "High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy "

Simulation results using SINRA are included as well.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-22
    DOI: 10.14278/rodare.651
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31845
Publ.-Id: 31845


High quality epitaxial Mn2Au (001) thin films grown by molecular beam epitaxy

Bommanaboyena, S. P.; Bergfeldt, T.; Heller, R.; Kläui, M.; Jourdan, M.

The recently discovered phenomenon of Néel spin-orbit torque in antiferromagnetic Mn2Au [Bodnar et al., Nat. Commun. 9, 348 (2018); Meinert et al., Phys. Rev. Appl. 9, 064040 (2018); Bodnar et al., Phys. Rev. B 99, 140409(R) (2019)] has generated huge interest in this material for spintronics applications. In this paper, we report the preparation and characterization of high quality Mn2Au thin films by molecular beam epitaxy and compare them with magnetron sputtered samples. The films were characterized for their structural and morphological properties using reflective high-energy electron diffraction, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and temperature dependent resistance measurements. The thin film composition was determined using both inductively coupled plasma optical emission spectroscopy and Rutherford backscattering spectrometry techniques. The MBE-grown films were found to show a superior smooth morphology and a low defect concentration, resulting in reduced scattering of the charge carriers.

Keywords: Atomic force microscopy; Electron diffraction; Epitaxy; Inductively coupled plasma atomic emission spectroscopy; Thin films; Rutherford backscattering spectrometry

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31844
Publ.-Id: 31844


Explicit algebraic relation for calculating Reynolds normal stresses in flows dominated by bubble-induced turbulence

Ma, T.; Lucas, D.; Bragg, A. D.

Two new algebraic turbulence models for flows dominated by bubble-induced turbulence (BIT) are presented. They combine different elements of existing models that are considered superior to their alternatives. Both models focus on the core region of a channel flow, where the flow can be assumed to be in local equilibrium and the void fraction is approximately homogeneous. The first model, referred to as the algebraic Reynolds normal stress model, is derived from the differential Reynolds stress model of Ma et al. [J. Fluid Mech. 883, A9 (2020)]. The second model utilizes the original two-equation turbulence model for bubbly flows [Ma et al., Phys. Rev. Fluids 2, 034301 (2017)] to achieve algebraic expressions for k and ε in BIT-dominated cases. If both models are combined, it results in a purely algebraic (i.e. not involving any differential equations), explicit relation for the Reynolds normal stresses, which depends only on the mean flow parameters, namely, the mean gas void fraction and mean liquid and gas velocities. We find that the model can well predict the Reynolds normal stresses, compared with direct numerical simulation and experimental data.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31843
Publ.-Id: 31843


RBS raw data for publication "Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy "

Bergmann, U.; Apelt, S.; Khojasteh, N. B.; Heller, R.

RBS raw data for publication "Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy "

Simulation results using SIMNRA-Code also included

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-06-08
    DOI: 10.14278/rodare.649
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31842
Publ.-Id: 31842


Solid–liquid interface analysis with in‐situ Rutherford backscattering and electrochemical impedance spectroscopy

Bergmann, U.; Apelt, S.; Khojasteh, N. B.; Heller, R.

A novel Rutherford backscattering spectrometry (RBS) method is presented to investigate the interface between a solid surface and a surrounding liquid. The introduced measurement system allows to observe and quantify adsorption at the solid–liquid interface and the formation of the electrochemical double layer (EDL). BaCl2 as a bicomponent electrolyte and a Si3N4 membrane surface are chosen as a model system to prove the capabilities of the setup. The results of these RBS measurements are combined with electrochemical impedance spectroscopy (EIS) to validate the findings for the solid–liquid interface under study. Complementary results and discrepancies regarding the formation of the EDL are discussed.
Author keywords: electrochemical double layer, electrochemical impedance spectroscopy, Rutherford backscattering spectroscopy, silicon nitride

Keywords: Rutherford backscattering spectrometry; electrochemical double layer; electrochemical impedance spectroscopy; point of zero charge

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31841
Publ.-Id: 31841


RBS Raw data for publication: ""Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas"

Mientus, R.; Weise, M.; Seeger, S.; Heller, R.; Ellmer, K.

Raw data for pub. "Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas"

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-26
    DOI: 10.14278/rodare.647
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31840
Publ.-Id: 31840


Tantalum recycling from pyrometallurgical residues (Tantalrecycling aus pyrometallurgischen Rückständen)

Reuter, M.; Taube, M. C.; Adamczyk, B.; Adam, C.; Feldmann, I.; Ostermann, M.; Stelter, M.

An existing pyrometallurgical process for tantalum and niobium recovery, mainly from low grade pyrometallurgical residues, was investigated. Melting experiments were carried out in a pilot-scale electric arc furnace to study the material system during the reduction process caused by blowing coke into the liquid mineral melt. During the pyrometallurgical treatment refractory metals such as tantalum and niobium are converted into their carbides and enriched in the molten iron-based metal phase.Titanium is also enriched in the metal phase as an unwanted accompanying element, but most of it remains in oxidic form in the slag and is mainly bound in the mineral perovskite. Cooled down slag samples were analysed using XRF, XRD, SEM and EDX to investigate the formation of mineral phases rich in tantalum during various stages of the reduction process. The results show that the settling of the tantalum-rich iron droplets in the molten slag into the metal phase may play a greater role for the kinetics than the actual reduction reaction caused by blowing in coke.

Keywords: tantalum; niobium; pyrometallurgical

  • World of Metallurgy - Erzmetall 73(2020)4, 196-205

Permalink: https://www.hzdr.de/publications/Publ-31839
Publ.-Id: 31839


Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas

Mientus, R.; Weise, M.; Seeger, S.; Heller, R.; Ellmer, K.

By reactive magnetron sputtering from a ceramic SnO2:Ta target onto unheated substrates, X-ray amorphous SnO:Ta films were prepared in gas mixtures of Ar/O2(N2O, H2O). The process windows, where the films exhibit the lowest resistivity values, were investigated as a function of the partial pressure of the reactive gases O2, N2O and H2O. We found that all three gases lead to the same minimum resistivity, while the width of the process window is broadest for the reactive gas H2O. While the amorphous films were remarkably conductive (ρ ≈ 5 × 10−3 Ωcm), the films crystallized by annealing at 500 °C exhibit higher resistivities due to grain boundary limited conduction. For larger film thicknesses (d ≳ 150 nm), crystallization occurs already during the deposition, caused by the substrate temperature increase due to the energy influx from the condensing film species and from the plasma (ions, electrons), leading to higher resistivities of these films. The best amorphous SnO2:Ta films had a resistivity of lower than 4 × 10−3 Ωcm, with a carrier concentration of 1.1 × 1020 cm−3, and a Hall mobility of 16 cm2/Vs. The sheet resistance was about 400 Ω/□ for 100 nm films and 80 Ω/□ for 500 nm thick films. The average optical transmittance from 500 to 1000 nm is greater than 76% for 100 nm films, where the films, deposited with H2O as reactive gas, exhibit even a slightly higher transmittance of 80%. These X-ray amorpous SnO2:Ta films can be used as low-temperature prepared transparent and conductive protection layers, for instance, to protect semiconducting photoelectrodes for water splitting, and also, where appropriate, in combination with more conductive TCO films (ITO or ZnO).

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31838
Publ.-Id: 31838


Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Kaden, P.; Kupka, N.

NMR dataset to the publication:
Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Keywords: NMR; acidified water glass; scheelite calcite separation; froth flotation; mechanism

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-07-22
    DOI: 10.14278/rodare.641

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31837
Publ.-Id: 31837


Timing and correlation of glacial and glaciofluvial sediments in the German Alpine Foreland

Hofmann, F.; Hildebrandt, D.; Merchel, S.; Rugel, G.; Lachner, J.; Friedrich, A. M.

Multiple periods of advance and retreat of piedmont glaciers in the German Alpine Foreland due to changing climatic conditions were classically defined by Penck and Brückner in 1909. However, a robust absolute chronology has not yet been established. Age assignments in previous studies have mostly been based on the interpretation of terrace deposits as a result of periods of glacier advance and retreat and correlation with periods of globally low temperatures. Intercorrelation between these discontinuous deposits has mainly been done by using morphological, petrographical, and hypsometric characteristics. We measure absolute cosmogenic ³⁶Cl exposure ages of glacial erratics and ¹⁰Be/²⁶Al isochron burial ages of till and glaciofluvial deposits, which have previously been interpreted as Würmian (ultimate) and Rissian (penultimate glacial period). This establishes an absolute chronology for these periods and enables the correlation of moraines, which are direct products of advancing and retreating glaciers, with indirect glaciofluvial deposits in the foreland. The absolute chronology of this study sheds light on the development of Central European climatic trends and enables the correlation to global climate.

Keywords: AMS; cosmogenic radionuclide; dating; burial age; glacier; climate; exposure age

  • Poster (Online presentation)
    American Geophysical Union (AGU) Fall Meeting, 01.-17.12.2020, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-31836
Publ.-Id: 31836


Nanoscale‐Confined Terahertz Polaritons in a van der Waals Crystal

de Oliveira, T. V. A. G.; Nörenberg, T.; Álvarez‐Pérez, G.; Wehmeier, L.; Taboada‐Gutiérrez, J.; Obst, M.; Hempel, F.; Lee, E. J. H.; Klopf, J. M.; Errea, I.; Nikitin, A. Y.; Kehr, S. C.; Alonso‐González, P.; Eng, L. M.

Electromagnetic field confinement is crucial for nanophotonic technologies, since it allows for enhancing light–matter interactions, thus enabling light manipulation in deep sub‐wavelength scales. In the terahertz (THz) spectral range, radiation confinement is conventionally achieved with specially designed metallic structures—such as antennas or nanoslits—with large footprints due to the rather long wavelengths of THz radiation. In this context, phonon polaritons—light coupled to lattice vibrations—in van der Waals (vdW) crystals have emerged as a promising solution for controlling light beyond the diffraction limit, as they feature extreme field confinements and low optical losses. However, experimental demonstration of nanoscale‐confined phonon polaritons at THz frequencies has so far remained elusive. Here, it is provided by employing scattering‐type scanning near‐field optical microscopy combined with a free‐electron laser to reveal a range of low‐loss polaritonic excitations at frequencies from 8 to 12 THz in the vdW semiconductor α‐MoO3. In this study, THz polaritons are visualized with: i) in‐plane hyperbolic dispersion, ii) extreme nanoscale field confinement (below λo ⁄75), and iii) long polariton lifetimes, with a lower limit of >2 ps.

Keywords: THz; FEL; s-SNOM; phonon polaritons; field confinement

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31835
Publ.-Id: 31835


68Ga, 44Sc and 177Lu-labeled AAZTA5-PSMA-617: synthesis, radiolabeling, stability and cell binding compared to DOTA-PSMA-617 analogues

Sinnes, J.; Bauder-Wüst, U.; Schäfer, M.; Moon, E.; Kopka, K.; Rösch, F.

Background: The AAZTA chelator and in particular its bifunctional derivative AAZTA5 was recently investigated to demonstrate unique capabilities to complex diagnostic and therapeutic trivalent radiometals under mild conditions. This study presents a comparison of 68Ga, 44Sc and 177Lu-labeled AAZTA5-PSMA-617 with DOTA-PSMA-617 analogues. We evaluated the radiolabeling characteristics, in vitro stability of the radiolabeled compounds and evaluated their binding affinity and internalization behavior on LNCaP tumor cells in direct comparison to the radiolabeled DOTA-conjugated PSMA-617 analogs.
Results: AAZTA5 was synthesized in a five-step synthesis and coupled to the PSMA-617 backbone on solid phase. Radiochemical evaluation of AAZTA5-PSMA-617 with 68Ga, 44Sc and 177Lu achieved quantitative radiolabeling of > 99% after less than 5 min at room temperature. Stabilities against human serum, PBS buffer and EDTA and DTPA solutions were analyzed. While there was a small degradation of the 68Ga complex over 2 h in human serum, PBS and EDTA/DTPA, the 44Sc and 177Lu complexes were stable at 2 h and remained stable over 8 h and 1 day. For all three compounds, i.e. [natGa]Ga-AAZTA5-PSMA-617, [natSc]Sc-AAZTA5-PSMA-617 and [natLu]Lu-AAZTA5-PSMA-617, in vitro studies on PSMA-positive LNCaP cells were performed in direct comparison to radiolabeled DOTA-PSMA-617 yielding the corresponding inhibition constants (Ki). Ki values were in the range of 8-31 nM values which correspond with those of [natGa]Ga-DOTA-PSMA-617, [natSc]Sc-DOTA-PSMA-617 and [natLu]Lu-DOTA-PSMA-617, i.e. 5-7 nM, respectively. Internalization studies demonstrated cellular membrane to internalization ratios for the radiolabeled 68Ga, 44Sc and 177Lu-AAZTA5-PSMA-617 tracers (13-20%IA/10^6 cells) in the same range as the ones of the three radiolabeled DOTA-PSMA-617 tracers (17-20%IA/10^6 cells) in the same assay.
Conclusions: The AAZTA5-PSMA-617 structure proved fast and quantitative radiolabeling with all three radiometal complexes at room temperature, excellent stability with 44Sc, very high stability with 177Lu and medium stability with 68Ga in human serum, PBS and EDTA/DTPA solutions. All three AAZTA5-PSMA-617 tracers showed binding affinities and internalization ratios in LNCaP cells comparable with that of radiolabeled DOTA-PSMA-617 analogues. Therefore, the exchange of the chelator DOTA with AAZTA5 within the PSMA-617 binding motif has no negative influence on in vitro LNCaP cell binding characteristics. In combination with the faster and milder radiolabeling features, AAZTA5-PSMA-617 thus demonstrates promising potential for in vivo application for theranostics of prostate cancer.

Keywords: AAZTA; AAZTA5-PSMA-617; Gallium-68; Lutetium-177; PET; PSMA-617; Scandium-44; Theranostics

Permalink: https://www.hzdr.de/publications/Publ-31834
Publ.-Id: 31834


UAS-Based Hyperspectral Environmental Monitoring of Acid Mine Drainage Affected Waters

Flores Rojas, H. M.; Lorenz, S.; Jackisch, R.; Tusa, L.; Contreras Acosta, I. C.; Zimmermann, R.; Gloaguen, R.

The exposure of metal sulfides to air or water, either produced naturally or due to mining activities, can result in environmentally damaging acid mine drainage (AMD). This needs to be accurately monitored and remediated. In this study, we apply high-resolution unmanned aerial system (UAS)-based hyperspectral mapping tools to provide a useful, fast, and non-invasive method for the monitoring aspect. Specifically, we propose a machine learning framework to integrate visible to near-infrared (VNIR) hyperspectral data with physicochemical field data from water and sediments, together with laboratory analyses to precisely map the extent of acid mine drainage in the Tintillo River (Spain). This river collects the drainage from the western part of the Rio Tinto massive sulfide deposit and discharges large quantities of acidic water with significant amounts of dissolved metals (Fe, Al, Cu, Zn, amongst others) into the Odiel River. At the confluence of these rivers, different geochemical and mineralogical processes occur due to the interaction of very acidic water (pH 2.5–3.0) with neutral water (pH 7.0–8.0). This complexity makes the area an ideal test site for the application of hyperspectral mapping to characterize both rivers and better evaluate contaminated water bodies with remote sensing imagery. Our approach makes use of a supervised random forest (RF) regression for the extended mapping of water properties, using the samples collected in the field as ground-truth and training data. The resulting maps successfully estimate the concentration of dissolved metals and related physicochemical properties in water, and trace associated iron species (e.g., jarosite, goethite) within sediments. These results highlight the capabilities of UAS-based hyperspectral data to monitor water bodies in mining environments, by mapping their hydrogeochemical properties, using few field samples. Hence, we have demonstrated that our workflow allows the rapid discrimination and mapping of AMD contamination in water, providing an essential basis for monitoring and subsequent remediation.

Keywords: hyperspectral; remote sensing; machine learning; unmanned aerial system; acid mine drainage; random forest regression; post-mining

Permalink: https://www.hzdr.de/publications/Publ-31833
Publ.-Id: 31833


Online Detuning Computation and Quench Detection for Superconducting Resonators

Bellandi, A.; Butkowski, Ł.; Dursun, B.; Eichler, A.; Gümüs, C.; Kuntzsch, M.; Nawaz, A.; Pfeiffer, S.; Schlarb, H.; Schmidt, C.; Zenker, K.; Branlard, J.

Superconducting cavities are responsible for beam acceleration in superconducting linear accelerators. Challenging cavity control specifications are necessary to reduce RF costs and to maximize the availability of the accelerator. Cavity detuning and bandwidth are two critical parameters to monitor when operating particle accelerators. Cavity detuning is strongly related to the power required to generate the desired accelerating gradient. Cavity bandwidth is related to the cavity RF losses.
A sudden increase in bandwidth can indicate the presence of a quench or multipacting event. Therefore, calculating these parameters in real-time in the low-level RF system is highly desirable. A real-time estimation of the bandwidth allows a faster response of the machine protection system in case of quench events, whereas the estimation of cavity detuning can be used to drive piezoelectric tuner-based resonance control algorithms. In this proceeding, a new FPGA-based estimation component is presented. Such a component is designed to be used either in continuous wave or pulsed operation mode with loaded quality factors between 10^6 and 10^8 . Results of this component with FLASH, EuXFEL, CMTB, and ELBE are presented.

Keywords: Particle accelerators; Parameter estimation; Superconducting cavities; ELBE

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31832
Publ.-Id: 31832


Curvilinear One-Dimensional Antiferromagnets

Pylypovskyi, O.; Kononenko, D. Y.; Yershov, K.; Rößler, U. K.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Antiferromagnets host exotic quasiparticles, support high frequency excitations and are key enablers of the prospective spintronic and spin−orbitronic technologies. Here, we propose a concept of a curvilinear antiferromagnetism where material responses can be tailored by a geometrical curvature without the need to adjust material parameters. We show that an intrinsically achiral one-dimensional (1D) curvilinear antiferromagnet behaves as a chiral helimagnet with geometrically tunable Dzyaloshinskii−Moriya interaction (DMI) and orientation of the Né el vector. The curvature-induced DMI results in the hybridization of spin wave modes and enables a geometrically driven local minimum of the low-frequency branch. This positions curvilinear 1D antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spin−orbitronics and fundamental discoveries in the formation of coherent magnon condensates in the momentum space.

Keywords: antiferromagnetism; curvilinear spin chain; Dzyaloshinskii-Moriya interaction; spin-orbitronics

Permalink: https://www.hzdr.de/publications/Publ-31831
Publ.-Id: 31831


Data Fusion Using a Multi-Sensor Sparse-Based Clustering Algorithm

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

The increasing amount of information acquired by imaging sensors in Earth Sciences results in the availability of a multitude of complementary data (e.g., spectral, spatial, elevation) for monitoring of the Earth’s surface. Many studies were devoted to investigating the usage of multi-sensor data sets in the performance of supervised learning-based approaches at various tasks (i.e., classification and regression) while unsupervised learning-based approaches have received less attention. In this paper, we propose a new approach to fuse multiple data sets from imaging sensors using a multi-sensor sparse-based clustering algorithm (Multi-SSC). A technique for the extraction of spatial features (i.e., morphological profiles (MPs) and invariant attribute profiles (IAPs)) is applied to high spatial-resolution data to derive the spatial and contextual information. This information is then fused with spectrally rich data such as multi- or hyperspectral data. In order to fuse multi-sensor data sets a hierarchical sparse subspace clustering approach is employed. More specifically, a lasso-based binary algorithm is used to fuse the spectral and spatial information prior to automatic clustering. The proposed framework ensures that the generated clustering map is smooth and preserves the spatial structures of the scene. In order to evaluate the generalization capability of the proposed approach, we investigate its performance not only on diverse scenes but also on different sensors and data types. The first two data sets are geological data sets, which consist of hyperspectral and RGB data. The third data set is the well-known benchmark Trento data set, including hyperspectral and LiDAR data. Experimental results indicate that this novel multi-sensor clustering algorithm can provide an accurate clustering map compared to the state-of-the-art sparse subspace-based clustering algorithms.

Keywords: multi-sensor data fusion; subspace-based clustering; sparse representation; hierarchical representation; remote sensing

Permalink: https://www.hzdr.de/publications/Publ-31830
Publ.-Id: 31830


A New Spectral-Spatial Subspace Clustering Algorithm For Hyperspectral Image Analysis

Rafiezadeh Shahi, K.; Ghamisi, P.; Jackisch, R.; Khodadadzadeh, M.; Lorenz, S.; Gloaguen, R.

In the past decade, hyperspectral imaging techniques have been widely used in various applications to acquire high spectral-spatialresolution images from different objects and materials. Although hyperspectral images (HSIs) are useful tools to obtain valuableinformation from different materials, the processing of such data is challenging due to several reasons such as the high dimension-ality and redundancy of the feature space. Therefore, advanced machine learning algorithms have been developed to analyse HSIs.Among the developed algorithms, unsupervised learning techniques have become popular since they are capable of processing HSIswithout having prior knowledge. Generally, unsupervised learning algorithms analyse HSIs based on spectral information. How-ever, in many applications, spatial information plays an eminent role, in particular when the input data is of high spatial resolution.In this study, we propose a new clustering approach by utilizing the sparse subspace-based concept within the hidden Markov ran-dom field (HMRF) structure to process HSIs in an unsupervised manner. The qualitative analyses of the obtained clustering resultsshow that the proposed spectral-spatial clustering algorithm outperforms the sparse subspace-based clustering algorithm that onlyuses spectral information.

Keywords: Hyperspectral image analysis; Subspace clustering; Sparse representation; Hidden Markov random field; UAV data

  • Open Access Logo Lecture (Conference) (Online presentation)
    ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 30.08.-02.09.2020, Nice, France
    DOI: 10.5194/isprs-annals-V-3-2020-185-2020

Permalink: https://www.hzdr.de/publications/Publ-31829
Publ.-Id: 31829


Geochemical and mineralogical characterisation of Historic Zn-Pb Mine Waste, Plombières, East Belgium

Bevandic, S.; Blannin, R.; Vander Auwera, J.; Delmelle, N.; Caterina, D.; Nguyen, F.; Muchez, P.

Mine wastes and tailings derived from historical processing may contain significant contents of valuable metals due to processing being less efficient in the past. The Plombières tailings pond in eastern Belgium was selected as a case study to determine mineralogical and geochemical characteristics of the different mine waste materials found at the site. Four types of material were classified: soil, metallurgical waste, brown tailings and yellow tailings. The distribution of the mine wastes was investigated with drill holes, pit-holes and geophysical methods. Samples of the materials were assessed with grain size analysis, mineralogical and geochemical techniques. The mine wastes dominantly consist of SiO2, Al2O3 and Fe2O3. The cover material, comprising soil and metallurgical waste is highly heterogeneous in terms of mineralogy, geochemistry and grain size. The metallurgical waste has a high concentration of metals (Zn: 0.1 to 24 wt% and Pb: 0.1 to 10.1 wt%). In the tailings materials, Pb and Zn vary from 10 ppm to 8.5 wt% and from 51 ppm to 4 wt%, respectively. The mining wastes comprises mainly quartz, amorphous phases and phyllosilicates, with minor contents of Fe-oxide, Pb- and Zn-bearing minerals. Based on the mineralogical and geochemical properties, the different potential applications of the four waste material types were determined. Additionally, the theoretical economic potential of Pb and Zn in the mine wastes was established.

Permalink: https://www.hzdr.de/publications/Publ-31828
Publ.-Id: 31828


The 2021 Magnonics Roadmap

Barman, A.; Gubbiotti, G.; Ladak, S.; Adeyeye, A. O.; Krawczyk, M.; Gräfe, J.; Chumak, A. V.; Khitun, A.; Nikonev, D.; Young, I. A.; Vasyuchka, V. I.; Hillebrands, B.; Nikitov, S. A.; Yu, H.; Grundler, D.; Sadovnikov, A. V.; Grachev, A. A.; Sheshukova, S. E.; Duquesne, J.-Y.; Marangolo, M.; Csaba, G.; Porod, W.; Demidov, V. E.; Urazhdin, S.; Demokritov, S. O.; Albisetti, E.; Petti, D.; Bertacco, R.; Schultheiß, H.; Kruglyak, V. V.; Poimanov, V. D.; Sahoo, S.; Sinha, J.; Moriyama, T.; Mizukami, S.; Yang, H.; Münzenburg, M.; Landeros, P.; Gallardo, R. A.; Carlotti, G.; Kim, J.-V.; Stamps, R. L.; Camley, R. E.; Rana, B.; Otani, Y.; Yu, W.; Yu, T.; Bauer, G. E. W.; Back, C.; Uhrig, G. S.; Dobrovolskiy, O. V.; van Dijken, S.; Budinska, B.; Qin, H.; Adelmann, C.; Cotofana, S.; Naeemi, A.; Zingsem, B. W.; Winklhofer, M.

Magnonics is a rather young physics research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. After several papers and review articles published in the last decade, with a steadily increase in the number of citations, we are presenting the first Roadmap on Magnonics. This a collection of 22 sections written by leading experts in this field who review and discuss the current status but also present their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and the interconnections to standard electronics. In this respect, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This Roadmap represents a milestone for future emerging research directions in magnonics and hopefully it will be followed by a series of articles on the same topic.

Keywords: magnonics; spin waves; roadmap; spin textures; skyrmions; computing

Permalink: https://www.hzdr.de/publications/Publ-31827
Publ.-Id: 31827


MicroTCA.4 based low level RF for continuous wave mode operation at the ELBE accelerator

Gümüş, Ç.; Hierholzer, M.; Kuntzsch, M.; Pfeiffer, S.; Schmidt, C.; Steinbrück, R.; Zenker, K.; Michel, P.; Schlarb, H.; Schurig, R.

At the superconducting linear accelerator ELBE electrons with an energy of up to 40 MeV can be generated. ELBE is operated in continuous wave mode. The acceleration is achieved using superconducting RF cavities, which are driven by an analogue low level RF system and solid state based RF amplifiers. The analogue low level RF system was transformed to a digital system based on the MicroTCA standard. It is in user operation since 2020. Here the new digital system and its integration in the ELBE control system is described. Furthermore, the system is characterised by noise measurements, which result in a RMS field stability of the digital low level RF system of 0.01 ◦ in phase and 0.005 % in amplitude. In addition, an algorithm for compensating long term drifts is presented and characterised.

Keywords: ELBE; ChimeraTK; MicroTCA.4; LLRF; OPC UA

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31825
Publ.-Id: 31825


Multi-scale, multi-sensor data integration for automated 3-D geological mapping

Thiele, S. T.; Lorenz, S.; Kirsch, M.; Contreras Acosta, I. C.; Tusa, L.; Herrmann, E.; Möckel, R.; Gloaguen, R.

Enhanced digital outcrop models attributed with hyperspectral reflectance data, or hyperclouds, provide a flexible, three-dimensional medium for data-driven mapping of geological exposures, mine faces or cliffs. In this contribution we present an open-source python workflow, hylite, for creating hyperclouds by seamlessly fusing geometric information with data from a variety of hyperspectral imaging sensors and applying necessary atmospheric and illumination corrections. These rich datasets can be analysed using a variety of techniques, including minimum wavelength mapping and spectral indices to accurately map geological objects from a distance. Reference spectra from spectral libraries, ground or laboratory measurements can also be included to derive supervised classifications using machine learning techniques. We demonstrate the potential of the hypercloud approach by integrating hyperspectral data from laboratory, tripod and unmanned aerial vehicle acquisitions to automatically map relevant lithologies and alterations associated with volcanic hosted massive sulphide (VHMS) mineralisation in the Corta Atalaya open-pit, Spain. These analyses allow quantitative and objective mineral mapping at the outcrop and open-pit scale, facilitating quantitative research and smart-mining approaches. Our results highlight the seamless sensor integration made possible with hylite and the power of data-driven mapping approaches applied to hyperclouds. Significantly, we also show that random forests (RF) trained only on laboratory data from labelled hand-samples can be used to map outcrop scale data.

Permalink: https://www.hzdr.de/publications/Publ-31823
Publ.-Id: 31823


Liquid Metal Batteries for cheap stationary electricity storage

Weber, N.; Weier, T.

Liquid metal batteries are discussed as cheap stationary energy storage. Built as a stable density stratification of two liquid metals separated by a molten salt, they offer excellent charge transfer kinetics, extreme current densities and a very long lifetime. Using earth-abundant and cheap raw materials allows potentially reaching a storage price of 1-5 ct/kWh/cycle.
The talk will give an overview of LMB research at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Special focus will be given to the Li-Bi and Na-Bi systems, and the importance of fluid dynamics for the efficient and safe operation of the cells. Finally, an outlook on the Horizon 2020 project “Solstice”, which aims in developing Na-Zn molten salt batteries, will be given.

  • Open Access Logo Lecture (Conference)
    I Meeting on Energy Conversion and Storage Electrochemical Devices, 28.-29.01.2021, Madrid, Spanien

Permalink: https://www.hzdr.de/publications/Publ-31822
Publ.-Id: 31822


Acidified water glass in the selective flotation of scheelite from calcite, part II: species in solution and related mechanism of the depressant

Kupka, N.; Kaden, P.; Jantschke, A.; Schach, E.; Rudolph, M.

Sodium silicate is one of the main depressants against calcite and fluorite in the scheelite flotation industry. In the first part of this article, the authors acidified sodium silicate (AWG) with three acids (sulfuric, oxalic and hydrochloric) to improve its performance. Results showed that acidified water glass outperforms alkaline water glass in terms of selectivity: it increases mainly the grade by further depressing silicates and calcium-bearing minerals. In most cases, AWG requires lower dosages to do so. The effect of acidified water glass is evaluated through Mineral Liberation Analysis (MLA), froth analysis, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy in order to hypothesize its mechanism. MLA shows that AWG affects silicates and sulfides more intensely than semi-soluble salt-type minerals. Froth observations indicate other species in solution associated to the acid having an impact on the flotation results. Raman spectroscopy and NMR measurements indicate that the solution undergoes deep depolymerization when water glass is acidified. Lower molecular weight silica species, specifically Si-O monomers such as SiO(OH)3- will be responsible for the depression of the gangue minerals and are the drivers of the selectivity of AWG, more than orthosilicic acid. Depolymerization is more or less effective depending on the mass ratio of the acid to water glass and depending on the acid.

Keywords: acidified water glass; scheelite calcite separation; froth flotation; mechanism; mineral processing

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31821
Publ.-Id: 31821


Coordination of Trivalent Lanthanum and Cerium, and Tetravalent Cerium and Actinides (An = Th(IV), U(IV), Np(IV)) by a 4-Phosphoryl 1H-Pyrazol-5-olate Ligand in Solution and the Solid State

Kaden, P.; Roßberg, A.

This dataset is a subset of the complete data used in the original publication. It contains NMR and XAS data and there simulation. Based on this original data, conlcusions are drawn in the linked publication. For the full data, please refer to the corresponding author of the full publication.

Abstract of the publication:

Structural investigations of three actinide(IV) 4-phosphoryl 1H-pyrazol-5-olate complexes (An = Th(IV), U(IV), Np(IV)) and their cerium(IV) analogue display the same metal coordination in the solid state. The mononuclear complexes show the metal centre in a square antiprismatic coordination geometry composed by the two O-donor atoms of four deprotonated ligands. Detailed solid state analysis of the U(IV) complex shows that in dependence of the solvent used altered arrangements are observable, resulting in a change in the coordination polyhedron of the U(IV) metal centre to bi-capped trigonal prismatic. Further, single crystal analyses of the La(III) and Ce(III) complexes show that the ligand can also act as a neutral ligand by protonation of the pyrazoyl moiety. All complexes were comprehensively characterized by NMR, IR and Raman spectroscopy. A single resonance in each of the 31P NMR spectra for the La(III), Ce(III), Ce(IV), Th(IV) and Np(IV) complex indicates the formation of highly symmetric complex species in solution. Extended X-ray absorption fine structure (EXAFS) investigations provide evidence for the same local structure of the U(IV) and Np(IV) complex in toluene solution, confirming the observations made in the solid state.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-12-11
    DOI: 10.14278/rodare.643

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31820
Publ.-Id: 31820


Uncertainties in quantitative mineralogical studies using scanning electron microscope-based image analysis

Blannin, R.; Frenzel, M.; Tusa, L.; Birtel, S.; Ivășcanu, P.; Baker, T.; Gutzmer, J.

Scanning electron microscope-based automated mineralogy studies are readily associated with quantitative results, providing one of the foundations for geometallurgical studies. Despite the importance of quantitative data for such studies, and efforts to reduce statistical errors, the reporting of uncertainties is rare. This contribution illustrates how bootstrap resampling can be used to provide robust estimates of statistical uncertainties for the modal mineralogy, metal deportment and all relevant textural attributes of a sample, or series of samples. Based on a case study of the Bolcana Au-Cu porphyry deposit in the South Apuseni Mountains, Romania, the impact of insufficient sampling statistics on quantitative mineralogical studies is illustrated. Quantitative analyses of the mineralogy and microfabric of milled ore samples from seven 40 m drill core intervals from the Bolcana Prospect were conducted using a Mineral Liberation Analyser (MLA), complemented by electron probe micro-analysis. Bootstrap resampling was then applied to assess how many grain mount surfaces should be analysed to achieve statistically robust results for both Cu and Au mineralogy, deportment and textural attributes. Despite variable mineralogy, grades and mineralisation styles, estimated statistical uncertainties on Cu deportment are consistently low. In contrast, uncertainties for Au deportment are so high that most reported values for important characteristics are statistically meaningless. This is mainly attributed to the pronounced nugget effect for Au mineralisation, exacerbated by the small sample size analysed by MLA. An unfeasible number of measurements would be necessary to provide robust figures for the deportment of minor/trace elements and minerals, along with other tangible mineralogical properties, such as mineral associations. The results of this case study demonstrate that statistical uncertainties need to be carefully incorporated when considering the results of automated mineralogical studies and their impact on geometallurgical models. This is particularly relevant for studies of precious metal ores.

Keywords: Geometallurgy; Automated mineralogy; Nugget effect; Uncertainty estimation; Bootstrap resampling

Permalink: https://www.hzdr.de/publications/Publ-31819
Publ.-Id: 31819


Zero Net Flux MRI Turbulence in Disks: Sustenance Scheme and Magnetic Prandtl Number Dependence

Mamatsashvili, G.; Chagelishvili, George; Pessah, Martin E.; Stefani, F.; Bodo, Gianluigi

We investigate sustenance and dependence on magnetic Prandtl number (Pm) for magnetorotational instability (MRI)-driven turbulence in Keplerian disks with zero net magnetic flux using standard shearing box simulations. We focus on the turbulence dynamics in Fourier space, capturing specific/noncanonical anisotropy of nonlinear processes due to disk flow shear. This is a new type of nonlinear redistribution of modes over wavevector orientations in Fourier space—the nonlinear transverse cascade—which is generic to shear flows and fundamentally different from the usual direct/inverse cascade. The zero flux MRI has no exponentially growing modes, so its growth is transient, or nonmodal. Turbulence self-sustenance is governed by constructive cooperation of the transient growth of MRI and the nonlinear transverse cascade. This cooperation takes place at small wavenumbers (on the flow size scales) referred to as the vital area in Fourier space. The direct cascade transfers mode energy from the vital area to larger wavenumbers. At large Pm, the transverse cascade prevails over the direct one, keeping most of modes' energy contained in small wavenumbers. With decreasing Pm, however, the action of the transverse cascade weakens and can no longer oppose the action of the direct cascade, which more efficiently transfers energy to higher wavenumbers, leading to increased resistive dissipation. This undermines the sustenance scheme, resulting in the turbulence decay. Thus, the decay of zero net flux MRI turbulence with decreasing Pm is attributed to the topological rearrangement of the nonlinear processes when the direct cascade begins to prevail over the transverse cascade.

Keywords: Stellar accretion disks; Magnetohydrodynamics; Plasma astrophysics; Magnetic fields; Interplanetary turbulence; Instabilities

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31818
Publ.-Id: 31818


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