Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34800 Publications

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

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

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

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

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


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

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

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

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


Fusion of Dual Spatial Information for Hyperspectral Image Classification

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

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

Related publications

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


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

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

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

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


Classification of Hyperspectral and LiDAR Data Using Coupled CNNs

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

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

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  • Secondary publication expected from 06.02.2021

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


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

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

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

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


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

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

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

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


Multilevel Structure Extraction-Based Multi-Sensor Data Fusion

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

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

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


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

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

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

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


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

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

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

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


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

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

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

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

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


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

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

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

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

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

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

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

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

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

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


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

Kupka, N.

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

Keywords: froth flotation; scheelite; depressants; automated mineralogy

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

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


Uploading data to the HepDATA repository with Python using hepdata_lib

Müller, S.

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

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

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


LLAMA: Compile time automatic memory layout optimization

Gruber, B. M.

Write code once and perform well on many systems.

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

Downloads:

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


Cryogenic Liquid Jets for High Repetition Rate Discovery Science

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

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

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

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


Comparison of experimental STEM conditions for fluctuation electron microscopy

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

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

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

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


Implementation of the academic image processing pipeline ExploreASL in an outpatient center using IntelliSpace Discovery

Ganji, S.; Pinter, N.; Petr, J.; Ajtai, B.; Fritz, J.; Mechtler, L.; Husain, S.; Fischer, A.; Barkhof, F.; Mutsaerts, H.

The use of standardized image processing pipelines is continuously increasing in radiological research with developments in computing power, image processing, and machine learning techniques. Early integration of academic processing methods into clinical research workflow would accelerate the translation of promising novel MRI techniques into the clinic. However, the integration of such tools is both resource and time consuming. While most of neurological imaging takes place in outpatient centers, resource and workflow limitations of such clinics do not allow for the application of advanced image analysis. Here, we present the integration the “ExploreASL” into the PACS-connected research platform IntelliSpace Discovery.

  • Poster
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual
  • Contribution to proceedings
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-31936
Publ.-Id: 31936


Treatment efficacy of asymptomatic carotid artery stenosis patients evaluated by clinically applicable hemodynamic MRI and cognitive testing

Kaczmarz, S.; Göttler, J.; Petr, J.; Sollmann, N.; Schmitzer, L.; Hock, A.; Hansen, M.; Mouridsen, K.; Zimmer, C.; Hyder, F.; Preibisch, C.

Hemodynamic MRI is highly promising to improve treatment decisions in asymptomatic internal carotid artery stenosis (ICAS). However, treatment efficacy evaluations require clinically applicable techniques, such as dynamic susceptibility contrast (DSC) and resting-state BOLD-based evaluations of amplitude of low-frequency fluctuations (ALFF). We present data from 16 asymptomatic ICAS patients before and after treatment and 17 age-matched healthy controls measuring cerebral blood volume (CBV) and capillary transit-time heterogeneity (CTH) by DSC and ALFF with additional cognitive testing. We hypothesized recovery of hemodynamic impairments after revascularization. Our results confirmed this hypothesis for all parameters. Interestingly, at the same time cognitive function remained impaired

  • Lecture (Conference) (Online presentation)
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual
  • Contribution to proceedings
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-31935
Publ.-Id: 31935


Measurement of intra- and extra-neurite perfusion by combining ASL with the NODDI DWI model

Asllani, I.; Plaindoux, A.; Petr, J.; Woods, J.; van Osch, M.; Cercignani, M.

Intra- and extra-neurite perfusion in gray and white matter were estimated by applying a spatial linear regression algorithm on ASL images using the micro-structural anatomical information derived from the NODDI analysis of the DWI data. Baseline ASL images were acquired with 4 post-labeling delay (PLD) values in order to test the hypothesis of redistribution of ASL signal across the micro-compartments with increasing PLD. Motor activation was used to investigate the sensitivity of the method for detecting changes in perfusion at the micro-structural level.

  • Poster (Online presentation)
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual
  • Contribution to proceedings
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-31934
Publ.-Id: 31934


The long road from invention to implementation a pan-European neuroradiological survey on quantitative MRI techniques in clinical practice

Keil, V.; Smits, M.; Thust, S.; Petr, J.; Solymosi, L.; Manfrini, E.

This pan-European online survey study revealed that clinically working Neuroradiologists appreciate the additional diagnostic accuracy rendered by quantitative MRI techniques. However, the clinical implementation of many techniques is hampered by a lack of knowledge on how to acquire, post-process and interpret results of multiple quantitative MRI techniques including ASL, CEST/APT, IVIM and others. With exception of DSC and DWI in tumor imaging and stroke, the number of indications is also still limited especially regarding head/neck Radiology and neurodegenerative diseases.

  • Lecture (Conference) (Online presentation)
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual
  • Contribution to proceedings
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-31933
Publ.-Id: 31933


Differences in quantitative glioma perfusion imaging with ASL and DSC: validation with 15O-H2O PET

Petr, J.; Verburg, N.; Kuijer, J.; Koopman, T.; Keil, V.; Warnert, E.; Barkhof, F.; van den Hoff, J.; Boellaard, R.; de Witt Hamer, P.; Mutsaerts, H.

While agreement between ASL, DSC, and PET perfusion is well established in healthy volunteers, an analogous comparison in gliomas is still missing and more challenging. We compared ASL and DSC perfusion measurements with the gold-standard of 15 O-H 2 O-PET perfusion measurements in eight patients diagnosed with gliomas. We showed the importance of normalization to the contralateral hemisphere, and identified several examples of different regional perfusion as assessed with ASL and DSC and interpreted them using the PET reference.

  • Lecture (Conference) (Online presentation)
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual
  • Contribution to proceedings
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-31932
Publ.-Id: 31932


Arterial spin labeling signal in the Sagittal Sinus as hemodynamic proxy parameter in patients with sickle cell disease

Afzali-Hashemi, L.; Vaclavu, L.; Petr, J.; Wood, J.; Biemond, B.; Nederveen, A.; Mutsaerts, H.

Higher sagittal sinus signal is present in the ASL images of patients with sickle cell disease (SCD). The purpose of this study was to assess if the signal in the sagittal sinus is correlated with clinical parameters and if this is affected by the vasoactive stimulus. The sagittal sinus signal was measured in patients with SCD and in healthy controls. Signal in sagittal sinus of the SCD patients were significantly correlated with clinical parameters including

  • Poster
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual
  • Contribution to proceedings
    ISMRM 28th Annual Meeting & Exhibition, 14.08.2020, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-31931
Publ.-Id: 31931


Nonlinear plasmonic response in GaAs/InGaAs core/shell nanowires.

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

We show nonlinear plasmonic response in GaAs/In0.2Ga0.8As nanowires using high field terahertz pulses. With increasing THz field, plasmon resonance is redshifted, and spectral weight decreases indicating an inhomogeneous intervalley electron scattering across the nanowire.

Keywords: Intense Terahertz pulses; Nanowires; Plasmon

  • Poster (Online presentation)
    The 22nd International Conference on Ultrafast Phenomena (UP 2020), 16.-19.11.2020, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-31930
Publ.-Id: 31930


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

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  • Secondary publication expected from 15.03.2021

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

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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.

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

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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

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


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

Barbosa Mejia, Laura Natalie; Andreani, Louis; Gloaguen, Richard

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 non-linear 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.

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.

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

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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


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].

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

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


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

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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

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


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


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


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


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)

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

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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

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

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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.

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

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


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

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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

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


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

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

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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


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

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

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


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.

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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

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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

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

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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

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  • Secondary publication expected

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

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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

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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

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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 Andr, 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

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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 Andr; 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

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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

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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

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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

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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

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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.

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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

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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

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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).

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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

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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

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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


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


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