Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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Integrated Geological and Geophysical Mapping of a Carbonatite-Hosting Outcrop in Siilinjärvi, Finland, Using Unmanned Aerial Systems
Mapping geological outcrops is a crucial part of mineral exploration, mine planning and ore extraction. With the advent of unmanned aerial systems (UAS) for rapid spatial and spectral mapping, opportunities arise in fields where traditional ground-based approaches are established and trusted, but fail to cover sufficient area or compromise personal safety. Multi-sensor UAS are a technology that change geoscientific research, but they are still not routinely used for geological mapping in exploration and mining due to lack of trust in their added value, missing expertise and guidance in the selection and combination of drones and sensors. To address these limitations and highlight the potential of using UAS in exploration settings, we present a UAS multi-sensor mapping approach based on the integration of drone-borne photography, multi- and hyperspectral imaging, and magnetics. Data are processed with conventional methods as well as innovative machine-learning algorithms and validated by geological field mapping, yielding a comprehensive and geologically interpretable product. As a case study, we chose the northern extension of the Siilinjärvi apatite mine in Finland, in a brownfield exploration setting with plenty of ground truth data available and a survey area that is only partly covered by vegetation. We conducted rapid UAS surveys from which we created a multi-layered dataset to investigate properties of the ore-bearing carbonatite-glimmerite body. Our resulting geologic map discriminates between the principal lithologic units and distinguishes ore-bearing from waste rocks. Structural orientations and lithological units are deduced based on high-resolution, hyperspectral image-enhanced point clouds. UAS-based magnetic data allow an insight into their subsurface geometry through modelling based on magnetic interpretation. We validate our results via ground survey including rock specimen sampling, geochemical and mineralogical analysis and spectroscopic point measurements. We are convinced that the presented non-invasive, data-driven mapping approach can complement traditional workflows in mineral exploration as a flexible tool. Mapping products based on UAS data increase efficiency and maximize safety of the resource extraction process, reduce expenses and incidental wastes.
Keywords: unmanned aerial vehicles; hyperspectral; multispectral; magnetic; geologic mapping; drones; UAV
Remote Sensing 12(2020)18, 2998
Live-cell Imaging with Aspergillus Fumigatus-specific fluorescent Siderophore Conjugates
Live-cell imaging allows to analyse the subcellular localisation dynamics of physiological processes with high spatial-temporal resolution in vivo. So far, only few fluorescent dyes have been custom-designed to facilitate species-specific live-cell imaging approaches in filamentous fungi. Therefore, we developed fluorescent dye conjugates based on the sophisticated iron acquisition system of Aspergillus fumigatus by chemical modification of the siderophore Triacetylfusarinine C (TAFC).
Various fluorophores (FITC, NBD, Ocean Blue, BODIPY 630/650, SiR, TAMRA and Cy5) were conjugated to Diacetylfusarinine C (DAFC). Gallium-68 labelling enabled in-vitro and in-vivo characterisations. LogD, uptake assays and growth assays were performed and complemented by live-cell imaging in different Aspergillus species.
Siderophore conjugates were specifically recognised by the TAFC transporter MirB and utilized in growth assays as an iron source. Fluorescence microscopy revealed uptake dynamics and differential subcellular accumulation patterns of all compounds inside fungal hyphae. [Fe]DAFC-NBD and -Ocean Blue accumulated in vacuoles, whereas [Fe]DAFC-BODIPY, -SiR and -Cy5 localised to mitochondria. [Fe]DAFC -FITC showed a uniform cytoplasmic distribution, whereas [Fe]DAFC-TAMRA was not internalised at all. Co-staining experiments with commercially available fluorescent dyes confirmed these findings.
Overall we developed a new class of fluorescent dyes varying in intracellular fungal targeting providing novel tools for live-cell imaging applications for Aspergillus fumigatus.
Keywords: Live-cell Imaging; Aspergillus Fumigatus; Fluorescence Microscopy; Siderophores; Fluorescent Dyes
Scientific Reports 10(2020), 15519
Data for: An analysis for detecting potential relocation of the inventory of dry storage containers during prolonged interim storage via changes in the wall temperature fields
Wagner, M.; Reinicke, S.
Geometry files of the performed simulations (ANSYS Fluent).
- An analysis for detecting potential relocation of the … (Id 30221) has used this (Id 31409) publication of HZDR-primary research data
Reseach data in the HZDR data repository RODARE
Publication date: 2020-08-06
Radiomics-based prediction of tumor phenotype from tumor microenvironment and medical imaging
Magnetic resonance imaging (MRI) and immunohistochemical tissue stainings are pivotal for radiotherapeutic workflows. Yet, recent efforts herald a paradigm shift: Radiomic methods are used to extract a large number of quantitative features from image data to detect high-dimensional patterns, which are correlated with relevant clinical endpoints. Preclinical experiments help to understand underlying mechanisms, yet require the backtranslation of clinically used methods and their application to a heterogeneous patient cohort. In the present preclinical experiment, we determine the tumor phenotype from MRI and tumor microenvironment (TME) features in a patient cohort of xenograft tumor models of the head and neck.
An artificial heterogeneous patient population was created by mixing two tumor models of different radiosensitivity (SAS & UT-SCC-14) in pooled cohort (N = 108) and exposure to one week of fractionated irradiation with photons and protons. After irradiation, contrast agent-enhanced T1-weighted 3D gradient-echo MRI scans were acquired, tumors were excised and characterized immunohistochemically regarding vascularity (CD31), hypoxia (Pimonidazole) and morphology (H&E). Approximately 200 quantitative features were extracted from MRI and light-microscopy image data with an automated medical image radiomics processor and trainable image segmentation, respectively. TME parameters were analyzed regarding effects of radiation with two-sided t-tests. A fully automated radiomic framework was used for feature selection, model generation using leave-one-out cross validation with the individual tumor model’s identity (i.e. its phenotype) as endpoint. Model performance was assessed through area under the curve (AUC).
The used image quantification methods allowed for robust feature extraction. No effects of radiation on the TME were detected except for changes in vessel-adjacent hypoxia. Radiomic analysis was able to predict the tumor model based on TME features (AUC = 0.86), MRI features (AUC = 0.90) or combined features (AUC = 0.86).
We demonstrated backtranslation of radiomic methods in a preclinical setting with multi-modal image data. Further analysis of automatically extracted MRI and TME features may allow for a more biologically informed interpretation of MRI data.
Keywords: Radiomics; Medical Imaging; Preclinical; Microenvironment; Hypoxia; Radiation
Virtual Meeting 2020, 18.-21.10.2020, (Virtual), (Virtual)
A convolutional neural network for fully automated blood SUV determination in oncological FDG-PET
Aim: The standardized uptake value (SUV) is widely used for quantitative evaluation in oncological FDG-PET but has well-known shortcomings as a measure of the tumor's glucose consumption. The standard uptake ratio (SUR) of tumor SUV and arterial blood SUV (BSUV) possesses an increased prognostic value but requires image-based BSUV determination, typically in the aortic lumen. However, accurate manual ROI delineation requires care and imposes an additional workload which makes the SUR approach less attractive for clinical routine. The goal of the present work was the development of a fully automated method for BSUV determination in whole-body PET/CT.
Methods: Automatic delineation of the aortic lumen was performed with a convolutional neural network (CNN), namely U-Net. 632 FDG PET/CT scans from 4 different sites were used for network training (N=208) and testing (N=424). For all scans, the aortic lumen was manually delineated, avoiding areas affected by motion-induced attenuation artifacts or potential spill-over from adjacent FDG-avid regions. Performance of the network was assessed using the fractional deviations of automatically and manually derived BSUVs in the test data.
Results: The trained U-Net yields BSUVs in close agreement with those obtained from manual delineation. Notably, using both CT and PET data as input for network training allows the trained network to derive unbiased BSUVs by detecting and excluding aorta segments affected by attenuation artifacts or spill-over. Comparison of manually (M) and automatically (A) derived BSUVs shows excellent concordance: the mean paired M-A difference in the 424 test cases is (mean +/- SD)=(0.2 +/- 3.1)% with a 95% confidence interval of [-6.6, 5.7]%. For a single test case the M-A difference exceeded 10%.
Conclusion: CNNs offer a viable approach for automatic BSUV determination. Our trained network exhibits a performance comparable to an experienced human observer and might already be considered suitable for supervised clinical use.
Keywords: FDG-PET; standardized uptake value; SUV; standardized uptake ratio; SUR; convolutional neural network
Nuklearmedizin 2020, 07.-09.07.2020, Online, Online
EANM’20 Congress, 22.-30.10.2020, Online, Online
A convolutional neural network for fully automated blood SUV determination to facilitate SUR computation in oncological FDG-PET
Purpose: The standardized uptake value (SUV) is widely used for quantitative evaluation in oncological FDG-PET but has well-known shortcomings as a measure of the tumor’s glucose consumption. The standard uptake ratio (SUR) of tumor SUV and arterial blood SUV (BSUV) possesses an increased prognostic value but requires image-based BSUV determination, typically in the aortic lumen. However, accurate manual ROI delineation requires care and imposes an additional workload which makes the SUR approach less attractive for clinical routine. The goal of the present work was the development of a fully automated method for BSUV determination in whole-body PET/CT.
Methods: Automatic delineation of the aortic lumen was performed with a convolutional neural network (CNN), using the U-Net architecture. 946 FDG PET/CT scans from several sites were used for network training (N = 366) and testing (N = 580). For all scans, the aortic lumen was manually delineated, avoiding areas affected by motion-induced attenuation artifacts or potential spill-over from adjacent FDG-avid regions. Performance of the network was assessed using the fractional deviations of automatically and manually derived BSUVs in the test data.
Results: The trained U-Net yields BSUVs in close agreement with those obtained from manual delineation. Comparison of manually and automatically derived BSUVs shows excellent concordance: the mean relative BSUV difference was (mean ± SD) = (-0.5± 2.2)% with a 95% confidence interval of [−5.1, 3.8]% and a total range of [-10.0, 12.0]%. For four test cases the derived ROIs were unusable (<1 ml).
Conclusion: CNNs are capable of performing robust automatic image-based BSUV determination. Integrating automatic BSUV derivation into PET data processing workflows will significantly facilitate SUR computation without increasing the workload in the clinical setting.
Keywords: FDG-PET; standardized uptake value; SUV; standardized uptake ratio; SUR; convolutional neural network
European Journal of Nuclear Medicine and Molecular Imaging 47(2020)Suppl. 1, S272-S273
Hierarchical Sparse Subspace Clustering (HESSC): An Automatic Approach for Hyperspectral Image Analysis
Hyperspectral imaging techniques are becoming one of the most important tools to remotely acquire fine spectral information on different objects. However, hyperspectral images (HSIs) require dedicated processing for most applications. Therefore, several machine learning techniques were proposed in the last decades. Among the proposed machine learning techniques, unsupervised learning techniques have become popular as they do not need any prior knowledge.
Specifically, sparse subspace-based clustering algorithms have drawn special attention to cluster the HSI into meaningful groups since such algorithms are able to handle high dimensional and highly mixed data, as is the case in real-world applications. Nonetheless, sparse subspace-based clustering algorithms usually tend to demand high computational power and can be time-consuming.
In addition, the number of clusters is usually predefined. In this paper, we propose a new hierarchical sparse subspace-based clustering algorithm (HESSC), which handles the aforementioned problems in a robust and fast manner and estimates the number of clusters automatically. In the experiment, HESSC is applied to three real drill-core samples and one well-known rural benchmark (i.e., Trento) HSI datasets. In order to evaluate the performance of HESSC, the performance of the new proposed algorithm is quantitatively and qualitatively compared to the state-of-the-art sparse subspace-based algorithms. In addition, in order to have a comparison with conventional clustering algorithms, HESSC’s performance is compared with K-means and FCM. The obtained clustering results demonstrate that HESSC performs well when clustering HSIs compared to the other applied clustering algorithms.
Keywords: hyperspectral images; subspace-based clustering; hierarchical structure; unsupervised learning; sparse representation; ensemble learning
Remote Sensing 12(2020)15, 2421
Magnetic properties of biogenic selenium nanomaterials
The properties of biogenic elemental selenium (BioSe) need to be studied in order to understand its environmental fate. In this paper, the magnetic properties of biogenic elemental selenium nanospheres (BioSe-Nanospheres) and nanorods (BioSe-Nanorods) obtained via the reduction of selenium(IV) using anaerobic granular sludge were investigated. The study indicated that the BioSe nanomaterials have a strong paramagnetic contribution with some ferromagnetic component due to the incorporation of Fe(III) (high spin and low spin species) as indicated by Electron Paramagnetic Resonance (EPR). X-Ray Photoelectron Spectroscopy (XPS) also confirmed the weak presence of Fe(III) and combined with EPR data, the Fe(III) availability through the nanomaterial was established. It is likely that Fe(III) being abundantly present in sludge got entrapped in the extracellular polymeric substances (EPS) coating the biogenic nanomaterials. The presence of Fe(III) in BioSe nanomaterials increases the mobility of Fe(III) and can have an effect on phytoplankton growth in the environment. Further, there is a potential to exploit the magnetic properties of BioSe nanomaterials in drug delivery system as well as in space refrigeration.
Environmental Science and Pollution Research (2021)
Thermal kinetics of free volume in porous spin-on dielectrics: exploring the network- and pore-properties
Comprehensive ex-situ and in-situ investigations of thermal curing processes in spin-on ultra-low-k thin films conducted by positron annihilation spectroscopy and Fourier transform infrared spectroscopies are presented. Positron annihilation lifetime spectroscopy of ex-situ cured samples reveals an onset of the curing process at about 200 °C, which advances with increasing curing temperature. Porogen agglomeration followed by diffusive migration to the surface during the curing process leads to the generation of narrow channels across the film thickness. The size of those channels is determined by a pore size distribution analysis of positron lifetime data. Defect kinetics during in-situ thermal curing has been investigated by means of Doppler broadening spectroscopy of the annihilation radiation, showing several distinct partially superposed and subsequent curing stages, i.e., moisture and residual organic solvents removal, SiOx network cross-linking, porogen decomposition, and finally creation of a stable porous structure containing micropore channels interconnecting larger mesopores formed likely due to micelle like interaction between porogen molecules, for curing temperatures not larger than 500 °C. Static (sequencing curing) states captured at specific temperature steps confirm the conclusions drawn during the dynamic (continuous curing) measurements. Moreover, the onset of pore inter-connectivity is precisely estimated as pore interconnectivity sets in at 380–400 °C.
Keywords: In-situ curing; Positron annihilation spectroscopy; Porogen removal; Porosimetry; FTIR; Dielectrics; Pore size distribution; Positronium
- Thermal kinetics of free volume in porous spin-on … (Id 31002) HZDR-primary research data are used by this (Id 31402) publication
Microporous and Mesoporous Materials 308(2020), 110457
Transition from steady to oscillating convection rolls in Rayleigh-Bénard convection under the influence of a horizontal magnetic field
In this study we consider the effect of a horizontal magnetic field on the Rayleigh-Bénard convection in a finite liquid metal layer contained in a cuboid vessel (200x200x40 mm^3) of aspect ratio Gamma = 5. Laboratory experiments are performed for measuring temperature and flow field in the low melting point alloy GaInSn at Prandtl number Pr = 0.03 and in a Rayleigh number range 2.3x10^4 < Ra < 2.6x10^5. The field direction is aligned parallel to one pair of the two side walls. The field strength is varied up to a maximum value of 320 mT (Ha = 2470, Q = 6.11x10^6, definitions of all non-dimensional numbers are given in the text). The magnetic field forces the flow to form two-dimensional rolls whose axes are parallel to the direction of the field lines. The experiments confirm the predictions made by Busse and Clever (J. Mécanique Théorique et Appliquée, 1983 ) who showed that the application of the horizontal magnetic field extends the range in which steady two-dimensional roll structures exist (‘Busse balloon’) towards higher Ra numbers. A transition from the steady to a time-dependent oscillatory flow occurs when Ra exceeds a critical value for a given Chandrasekhar number Q, which is also equivalent to a reduction of the ratio Q/Ra. Our measurements reveal that the first developing oscillations are clearly of two-dimensional nature, in particular a mutual increase and decrease in the size of adjacent convection rolls is observed without the formation of any detectable gradients in the velocity field along the magnetic field direction. At a ratio of Q/Ra = 1, the first 3D structures appear, which initially manifest themselves in a slight inclination of the rolls with respect to the magnetic field direction. Immediately in the course of this, there arise also disturbances in the spaces between adjacent convection rolls, which are advected along the rolls due to the secondary flow driven by Ekman pumping. The transition to fully-developed three-dimensional structures and then to a turbulent regime takes place with further lowering Q/Ra.
Keywords: Rayleigh-Benard convection; liquid metal; horizontal magnetic field; convection rolls; oscillatory instability
Physical Review Fluids 6(2021)2, 023502
- Original PDF 4 MB Secondary publication
Strengthening of ods silver wires
Wasserbäch, W.; Skrotzki, W.; Chekhonin, P.
The present work is part of an experimental program in which the mechanical behavior and the evolution of microstructure and texture of different industrially manufactured oxide-dispersion strengthened silver alloys upon different processing steps like hot-extrusion, cold-working and further annealing have been investigated. The investigations reveal that the incoherent oxide particles strongly influence the evolution of microstructure and texture during processing and consequently the deformation behavior at room temperature. Small oxide particles cause a high strengthening of the material but only a small change of the microstructure and texture. Increasing the oxide particle size subsequently reduces the strength and changes the original microstructure and texture in a more pronounced way. The yield strength at room temperature can be explained with a linear superposition of the Orowan stress for bypassing of oxide particles by dislocations and grain boundary strengthening according to Hall-Petch. The impact of texture of the materials on the yield strength is accounted for.
Keywords: Silver; Metal matrix composites; Cold-working; Strain hardening; Texture
Materialia 12(2020), 100818
- Secondary publication expected from 09.07.2021
Keap1 inhibition sensitizes head and neck squamous cell carcinoma cells to ionizing radiation via impaired non-homologous end joining and induced autophagy
The function of Keap1 (Kelch-like ECH-associated protein 1), a sensor of oxidative and electrophilic stress, in the radiosensitivity of cancer cells remains elusive. Here, we investigated the effects of pharmacological inhibition of Keap1 with ML344 on radiosensitivity, DNA double strand break (DSB) repair and autophagy in head and neck squamous cell carcinoma (HNSCC) cell lines. Our data demonstrate that Keap1 inhibition enhances HNSCC cell radiosensitivity. Despite elevated, Nrf2-dependent activity of non-homologous end joining (NHEJ)-related DNA repair, Keap1 inhibition seems to impair DSB repair through delayed phosphorylation of DNA-PKcs. Moreover, Keap1 inhibition elicited autophagy and increased p62 levels when combined with X-ray irradiation. Our findings suggest HNSCC cell radiosensitivity, NHEJ-mediated DSB repair and autophagy to be co-regulated by Keap1.
Keywords: HNSCC; radiosensitivity; Keap1; autophagy
Cell Death & Disease 11(2020)10, 887
c-Abl tyrosine kinase is regulated downstream of the cytoskeletal protein synemin in head and neck squamous cell carcinoma radioresistance and DNA repair
The intermediate filament synemin has been previously identified as novel regulator of cancer cell therapy resistance and DNA double strand break (DSB) repair. c-Abl tyrosine kinase is involved in both of these processes. Using PamGene technology, we performed a broad-spectrum kinase activity profiling in three-dimensionally, matrix grown head and neck cancer cell cultures. Upon synemin silencing, we identified 86 deactivated tyrosine kinases, including c-Abl, in irradiated HNSCC cells. c-Abl hyperphosphorylations on tyrosine (Y) 412 and threonine (T) 735 upon irradiation were significantly reduced after synemin inhibition prompting us to hypothesize that c-Abl tyrosine kinase is an important signaling component of the synemin-mediated radioresistance pathway. Simultaneous targeting of synemin and c-Abl resulted in similar radiosensitization and DSB repair compared with single synemin depletion suggesting synemin as an upstream regulator of c-Abl. Immunoprecipitation assays revealed a protein complex formation between synemin and c-Abl pre- and post-irradiation. Upon pharmacological inhibition of ATM, synemin/c-Abl protein-protein interactions were disrupted implying synemin function to depend on ATM kinase activity. Moreover, deletion of the ∆SH2 domain in c-Abl demonstrated a decrease in interaction indicating the dependency of the protein-protein interaction on this domain. Mechanistically, impairment of DNA repair seems to be related with radiosensitization upon synemin knockdown via regulation of non-homologous end joining, independent of c-Abl function. Our data generated in more physiological 3D cancer cell culture models suggest c-Abl as further key determinant of radioresistance downstream of synemin.
Keywords: Ionizing radiation; HNSCC; Synemin; DNA repair
International Journal of Molecular Sciences 21(2020)19, 7277
Comparative proton and photon irradiation combined with pharmacological inhibitors in 3D pancreatic cancer cultures
Pancreatic ductal adenocarcinoma (PDAC) is a highly therapy resistant tumor entity of unmet need. Over the last decades, radiotherapy has been considered as additional treatment modality to surgery and chemotherapy. Owing to radiosensitive abdominal organs, high precision proton beam radiotherapy has been regarded superior to photon radiotherapy. To further elucidate the potential of combination therapies, we employed a more physiological 3D, matrix-based cell culture model to assess tumoroid formation capacity after photon and proton irradiation. Additionally, we investigated proton and photon irradiation-induced phosphoproteomic changes for identifying clinically exploitable targets. Here, we show that proton irradiation elicits a higher efficacy to reduce 3D PDAC tumoroid formation and a greater extent of phosphoproteome alterations compared with photon irradiation. Targeting of proteins identified in the phosphoproteome that were uniquely altered by protons or photons failed to cause radiation type-specific radiosensitization. Targeting DNA repair proteins associated with non-homologous endjoing, however, revealed a strong radiosensitizing potential independent from the radiation type. In conclusion, our findings suggest proton irradiation to be potentially more effective in PDAC than photons without additional efficacy when combined with DNA repair inhibitors.
Keywords: PDAC; radiotherapy; proton beam irradiation; 3D cell culture; molecular targeting
Cancers 12(2020)11, 3126
Atomic-Scale Carving of Nanopores into a van der Waals Heterostructure with Slow Highly Charged Ions
The growing family of 2D materials led not long ago to combining different 2D layers and building artificial systems in the form of van-der-Waals heterostructures. Tailoring of heterostructure properties post-growth would greatly benefit from a modification technique with a monolayer precision. However, appropriate techniques for material modification with this precision are still missing. To achieve such control, slow highly charged ions appear ideal as they carry high amounts of potential energy, which is released rapidly upon ion neutralization at the position of the ion. The resulting potential energy deposition is thus limited to just a few atomic layers (in contrast to the kinetic energy deposition). Here, we irradiated a freestanding van-der-Waals MoS2/graphene heterostructure with 1.3 keV/amu xenon ions in high charge states of 38, which led to nm-sized pores that appear only in the MoS2 facing the ion beam, but not in graphene beneath the hole. Reversing the stacking order leaves both layers undamaged, which we attribute to the high conductivity and carrier mobility in graphene acting as a shield for the MoS2 underneath. Our main focus is here on monolayer MoS2, but we also analyzed areas with few-layer structures, and observed that the perforation is limited to the two topmost MoS2 layers, whereas deeper layers remain intact. Our results demonstrate that in addition to already being a valuable tool for materials processing, the usability of ion irradiation can be extended to mono(or bi-)layer manipulation of van-der-Waals heterostructures when also the localized potential energy deposition of highly charged ions is added to the toolbox.
Keywords: 2d material modification; ion beam surface modification; monolayer precision; van der Waals heterostructure
ACS Nano 14(2020)8, 10536-10543
The role of contaminations in ion beam spectroscopy with freestanding 2D materials: A study on thermal treatment
As surface-only materials, freestanding 2D materials are known to have a high level of contamination—mostly in the form of hydrocarbons, water, and residuals from production and exfoliation. For well-designed experiments, it is of particular importance to develop effective clean- ing procedures, especially since standard surface science techniques are typically not applicable. We perform ion spectroscopy with highly charged ions transmitted through freestanding atomically thin materials and present two techniques to achieve clean samples, both based on thermal treatment. Ion charge exchange and energy loss are used to analyze the degree of sample contamination. We find that even after cleaning, heavily contaminated spots remain on single layer graphene. The contamination coverage, however, clusters in strand-like structures leaving large clean areas. We present a way to discriminate clean from contaminated areas with our ion beam spectroscopy if the heterogeneity of the surface is increased sufficiently enough. We expect a similar discrimination to be necessary in most other experimental techniques.
Journal of Chemical Physics 153(2020), 014702
PIMC data for the nonlinear electronic density response in warm-dense matter (WDM)
This repository contains the PIMC raw data for the actual density response of the harmonically perturbed electron gas.
The data can be freely re-used. Please cite:
T. Dornheim, J. Vorberger, and M. Bonitz, Nonlinear Electronic Density Response in Warm Dense Matter, Phys. Rev. Lett. (in press), arXiv:2004.03229
Keywords: PIMC, density response, warm dense matter
- Nonlinear Electronic Density Response in Warm Dense Matter (Id 31377) has used this (Id 31390) publication of HZDR-primary research data
Reseach data in the HZDR data repository RODARE
Publication date: 2020-08-03
Trimeric uranyl(VI)–citrate forms Na+, Ca2+, and La3+ sandwich complexes in aqueous solution
Basile et al. (Chem. Commun., 2015, 51, 5306–5309) showed that a sodium ion is sandwiched by the uranyl(VI) oxygen atoms of two 3:3 uranyl(VI)–citrate complex molecules in single-crystals. By means of NMR spectroscopy supported by DFT calculation we provide unambiguous evidence for this complex to persist in aqueous solution above a critical concentration of 3 mM uranyl citrate. Unprecedented Ca2+ and La3+ coordination by a bis-(η3-uranyl(VI)-oxo) motif advances the understanding of uranium’s aqueous chemistry. As determined from 17O NMR, Ca2+ and especially La3+ cause strong O=U=O polarization which opens up new ways for uranyl(VI)-oxygen activation and functionalization.
Keywords: uranium; uranyl; U(VI); citric acid; NMR; DFT; spectroscopy; molecular structure
Chemical Communications 56(2020), 13133-13136
Tumor markers as an entry for SARS-CoV-2 infection?
Coronavirus disease 2019 (COVID-19), the highly contagious illness caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread across the globe, becoming one of the most challenging public health crisis of our times. SARS-CoV-2 can cause severe disease associated with multiple organ damage. Cancer patients have a higher risk of SARS-CoV-2 infection and death. While the virus uses angiotensin-converting enzyme 2 (ACE2) as the primary entry receptor, the recent experimental and clinical findings suggest that some tumor markers, including CD147 (Basigin), can provide a new entry for SARS-CoV-2 infection through binding to the viral spike (S) protein. In the absence of specific viral drugs, blocking of CD147 might be a way to prevent virus invasion. Identifying other target proteins is of high importance as targeting the alternative receptors for SARS-CoV-2 might open up a promising avenue for the treatment of COVID-19 patients, including those who have cancer.
Keywords: SARS-CoV-2; COVID-19; CD147; Basigin; Emmprin; spike protein
FEBS journal 287(2020)17, 3677-3680
Metal dissociation from humic colloids: Kinetics with time-dependent rate constants
The mobility of contaminant metals in aqueous subsurface environments is largely controlled by their interaction with humic substances as colloidal constituents of Dissolved Organic Matter. Transport models for predicting carrier-bound migration are based on a competitive partitioning process between solid surface and colloids. However, it has been observed that dissociation of multivalent metals from humic complexes is a slow kinetic process, which is even more impeded with increasing time of contact. Based on findings obtained in isotope exchange experiments, the convoluted time dependence of dissociation was fully described by a complex two-site approach, integrating rate “constants” that are in turn time-dependent. Thus, this study presents the treatment of a particular phenomenon: kinetics within kinetics. The analysis showed that the inertization process does not lead to irreversible binding. Consequently, thermodynamic concepts using equilibrium constants remain applicable in speciation and transport modeling if long time frames are appropriate.
Keywords: Colloids; Desorption; Humic complexes; Kinetic model; Metal binding; Natural organic matter
Chemosphere 275(2021), 130045
- Secondary publication expected from 22.02.2022
Quantitative isotopic fingerprinting of thallium associated with potentially toxic elements (PTEs) in fluvial sediment cores with multiple anthropogenic sources
Thallium (Tl) is a dispersed trace metal showing remarkable toxicity. Various anthropogenic activities may generate Tl contamination in river sediments, posing tremendous risks to aquatic life and human health. This paper aimed to provide insight into the vertical distribution, risk assessment and source tracing of Tl and other potentially toxic elements (PTEs) (lead, cadmium, zinc and copper) in three representative sediment cores from a riverine catchment impacted by multiple anthropogenic activities (such as steel-making and Pb-Zn smelting). The results showed high accumulations of Tl combined with associated PTEs in the depth profiles. Calculations according to three risk assessment methods by enrichment factor (EF), geoaccumulation index (Igeo) and the potential ecological risk index (PERI) all indicated a significant contamination by Tl in all the sediments. Furthermore, lead isotopes were analyzed to fingerprint the contamination sources and to calculate their quantitative contributions to the sediments using the IsoSource software. The results indicated that a steel-making plant was the most important contamination source (~56%), followed by a Pb-Zn smelter (~20%). The natural parental bedrock was found to contribute ~24%. The findings highlight the importance of including multiple anthropogenic sources for quantitative fingerprinting of Tl and related metals by the lead isotopic approach in complicated environmental systems.
Keywords: Thallium contamination; Spatial distribution; Pollution risk assessment; Multiple end-members; Isotopic tracing
Environmental Pollution 266(2020), 115252
gmGeostats: an R package for Geostatistics for Compositional Analysis with R
The package provides support for geostatistical analysis of multivariate data, in particular data with restrictions, e.g. positive amounts data, compositional data, distributional data, microstructural data, as occur in Geometallurgy. It includes descriptive analysis and modelling for such data, both from a two-point Gaussian perspective and multipoint perspective, in an unified integrated approach.
Keywords: R programming; Geostatistics; Compositional data analysis; 3D modelling; Uncertainty
Software in external data repository
Publication year 2020
Programming language: R
System requirements: multiplatform
License: CC BY-SA 4.0 | GPL (≥ 2)
Hosted on CRAN: Link to location
Data for: The influence of negatively charged silica nanoparticles on the surface properties of anionic surfactants: electrostatic repulsion or the effect of ionic strength?
The presence of negatively charged nanoparticles affects the surface activity of anionic surfactants in an aqueous phase. Recent studies suggest that electrostatic repulsive forces play an important role in increasing the surface activity of surfactants. However, the addition of nanoparticles also increases the ionic strength of the system, which has a significant impact on the surfactant's properties, e.g. its critical micelle concentration (CMC). To investigate how and to what extent electrostatic forces and ionic strength influence the behavior of ionic surfactants, the surface tension and elasticity of different solutions were measured using drop profile tensiometry as a function of the surfactant (SDBS), nanoparticle (silica) and salt (KNO3) concentration. It is observed that the surface activity of the surfactants is mainly influenced by the change in the system's ionic strength due to the presence of nanoparticles. Several characteristic parameters including the equivalent concentration of the surfactant, the CMC and the apparent partial molar area of the adsorbed surfactant are theoretically calculated and further employed to validate experimental observations. Both the nanoparticles and electrolyte decrease the CMC, while the equivalent concentration of the surfactant remains nearly constant. This paper presents a criterion to estimate the possible influence of such forces for nanoparticles of different sizes and mass fractions.
- The influence of negatively charged silica nanoparticles … (Id 30817) has used this (Id 31383) publication of HZDR-primary research data
Reseach data in the HZDR data repository RODARE
Publication date: 2020-01-09
All-THz pump-probe spectroscopy of the intersubband AC-Stark effect in a wide GaAs quantum well
We report the observation of the intersubband AC-Stark effect in a single wide GaAs/AlGaAs quantum well. In a three-level configuration, the n = 2 to n = 3 intersubband transition is resonantly pumped at 3:5 THz using a free-electron laser. The induced spectral changes are probed using THz time-domain spectroscopy with a broadband pulse extending up to 4 THz. We observe an Autler Townes splitting at the 1 -> 2 intersubband transition as well as an indication of a Mollow triplet at the 2 -> 3 transition, both evidencing the dressed states. For longer delay times, a relaxation of the hot-electron system with a time constant of around 420 ps is measured.
Keywords: AC Stark effect; Autler Townes splitting; high-field physics; intersubband transitions
Optics Express 28(2020), 25358-25370
Modelling of late side effects following cranial proton beam therapy
Dutz, A.; Lühr, A.; Agolli, L.; Bütof, R.; Valentini, C.; Troost, E. G. C.; Baumann, M.; Vermeren, X.; Geismar, D.; Lamba, N.; Lebow, E.; Bussière, M.; Daly, J.; Bussière, M.; Krause, M.; Timmermann, B.; Shih, H.; Löck, S.
The limited availability of proton beam therapy (PBT) requires individual treatment selection strategies that can be based on normal tissue complication probability (NTCP) models. We developed and externally validated NTCP models for common late side-effects following PBT in brain tumour patients to optimise patients’ quality of life.
Cohorts from three PBT centres (216 patients) were investigated for several physician-rated endpoints at 12 and 24 months after PBT: alopecia, dry eye syndrome, fatigue, headache, hearing and memory impairment, and optic neuropathy. Dose-volume parameters of associated normal tissues and clinical factors were used for logistic regression modelling in a development cohort. Statistically significant parameters showing high area under the receiver operating characteristic curve (AUC) values in internal cross-validation were externally validated. In addition, analyses of the pooled cohorts and of time-dependent generalised estimating equations including all patient data were performed.
In the validation study, mild alopecia was related to high dose parameters to the skin [e.g. the dose to 2% of the volume (D2%)] at 12 and 24 months after PBT. Mild hearing impairment at 24 months after PBT was associated with the mean dose to the ipsilateral cochlea. Additionally, the pooled analyses revealed dose-response relations between memory impairment and intermediate to high doses to the remaining brain as well as D2% of the hippocampi. Mild fatigue at 24 months after PBT was associated with D2% to the brainstem as well as with concurrent chemotherapy. Moreover, in generalised estimating equations analysis, dry eye syndrome was associated with the mean dose to the ipsilateral lacrimal gland.
We developed and in part validated NTCP models for several common late side-effects following PBT in brain tumour patients. Validation studies are required for further confirmation.
Keywords: NTCP models; brain tumours; late side-effects; proton beam therapy
Radiotherapy and Oncology 157(2021), 15-23
Practice recommendations for lung cancer radiotherapy during the COVID-19 pandemic: An ESTRO-ASTRO consensus statement
COVID-19 Rapid Letter
Radiotherapy and Oncology 147(2020), 227-228
Nonlinear Electronic Density Response in Warm Dense Matter
Warm dense matter (WDM)—an extreme state with high temperatures and densities that occurse.g. in astrophysical objects—constitutes one of the most active fields in plasma physics and materials science. These conditions can be realized in the lab by shock compression or laser excitation, and the most accurate experimental diagnostics is achieved with lasers and free electron lasers which is theoretically modeled using linear response theory. Here, we present first ab initio path integral Monte Carlo results for the nonlinear density response of correlated electrons in WDM and show that for many situations of experimental relevance nonlinear effects cannot be neglected.
Keywords: Warm dense matter; Nonlinear effects; path integral Monte Carlo
- PIMC data for the nonlinear electronic density response in … (Id 31390) HZDR-primary research data are used by this (Id 31377) publication
Physical Review Letters 125(2020)8, 085001
- Original PDF 450 kB Secondary publication
Imaging and Milling Resolution of Light Ion Beams from HIM and Liquid Metal Alloy Ion Source driven FIBs
The application of Focused Ion Beams (FIB) has become a well-established and promising technique for patterning and prototyping on the nm-scale in research and development. Light ions in the range of m = 1 … 28 u (hydrogen to silicon) are of increasing interest due to the available high beam resolution in the nm range and their special chemical and physical behavior in the substrate. In this work helium and neon ion beams from a Helium Ion Microscope (HIM) are compared with ion beams like beryllium, lithium, boron, carbon and silicon obtained from a mass separated FIB using Liquid Metal Alloy Ion Sources (LMAIS) with respect to their imaging and milling resolution.
Keywords: Focused Ion Beam; Helium Ion Microscope; Gas Field Ion Source; Liquid Metal Alloy Ion Sources; resolution
Beilstein Journal of Nanotechnology 11(2020), 1742-1749
Mapping the Future of Particle Radiobiology in Europe: The INSPIRE Project
Henthorn, N.; Sokol, O.; Durante, M.; de Marzi, L.; Pouzoulet, F.; Miszczyk, J.; Olko, P.; Brandenburg, S.; van Goethem, M.-J.; Barazzuol, L.; Tambas, M.; Langendijk, J. A.; Davídková, M.; Vondráček, V.; Bodenstein, E.; Pawelke, J.; Lomax, A. J.; Weber, D. C.; Dasu, A.; Stenerlöw, B.; Poulsen, P. R.; Sørensen, B. S.; Grau, C.; Sitarz, M. K.; Heuskin, A.-C.; Lucas, S.; Warmenhoven, J. W.; Merchant, M. J.; Mackay, R. I.; Kirkby, K. J.
Particle therapy is a growing cancer treatment modality worldwide. However, there still remains a number of unanswered
questions considering differences in the biological response between particles and photons. These questions, and probing of biological mechanisms in general, necessitate experimental investigation. The “Infrastructure in Proton International Research” (INSPIRE) project was created to provide an infrastructure for European research, unify research efforts on the topic of proton and ion therapy across Europe, and to facilitate the sharing of information and resources. This work highlights the radiobiological capabilities of the INSPIRE partners, providing details of physics (available particle types and energies), biology (sample preparation and post-irradiation analysis), and researcher access (the process of applying for beam time). The collection of information reported here is designed to provide researchers both in Europe and worldwide with the tools required to select the optimal center for their research needs. We also highlight areas of redundancy in capabilities and suggest areas for future investment.
Keywords: Proton theraphy; Radiotherapy; Radiobiology; Beamline; Irradiation
Frontiers in Physics 8(2020), 565055
Benchmark hyperspectral field and laboratory data against X-ray diffraction (XRD), Portable X-ray fluorescence (pXRF) and Scanning Electron Microscopy with Mineral Liberation Analysis (SEM-MLA) data.
A benchmarking databank based on different spectral, multiscale, multisensor exploration technologies was created. The benchmarking is composed of 63 rock samples from drill cores from a polymetallic (Cu-Zn-Pb) massive sulphide deposit in the Iberian Pyrite Belt. The samples had been analyzed by portable XRF, point hyperspectral spectrometer, portable FTIR, VNIR-SWIR imaging hyperspectral sensor and a LWIR imaging thermal hyperspectral sensor.
The mineralogical information from the boreholes will be complemented with mineral chemistry extracted from the spectral features of the alteration minerals that display chemical variations. The chemical variations in minerals generate shifts on the position of the metal-OH vibrational absorptions. This systematic variation can be recorded using the SWIR wavelength region of hyperspectral data. The shifts sometimes occur systematically with respect to ore deposits and hence mineral chemical information extracted from hyperspectral surveys can be used for mineral exploration. The mineral chemistry of the samples will be validated using scanning electron microscopy data integrated with the mineral liberation analysis (SEM-MLA).
In order to apply this type of research techniques aiming at a 3D model of the alteration areas of the entire deposit based on the hyperspectral data, it is essential to have the availability of drill cores along the whole extension of the mineral deposit. Consequently, the research was focused in a study area in the Southern Spain, the Elvira deposit of the MATSA–VALORIZA mining company, where 7 km of drill core were scanned with the hyperspectral sensors.
New exploration technologies (NEXT) is a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement nº 776804.
Keywords: Benchmarking; Hyperspectral; Drill core scanner; pFTIR; PXRF; VNIR - SWIR - LWIR
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Publication date: 2020-07-02
Advanced Sandwich Composite Cores for Patient Support in Advanced Clinical Imaging and Oncology Treatment
Ongoing advances in both imaging and treatment for oncology purposes have seen a significant rise in the use of not only the individual imaging modalities, but also their combination in single systems such as PET-CT and PET-MRI when planning for advanced oncology treatment, the most demanding of which is proton therapy. This has identified issues in the availability of suitable materials upon which to support the patient undergoing imaging and treatment owing to the differing requirements for each of the techniques. Sandwich composites are often selected to solve this issue but there is little information regarding optimum materials for their cores. In this paper we present a range of materials which are suitable for such purposes and evaluate the performance for use in terms of PET signal attenuation, proton beam stopping, MRI signal shading and X-Ray CT visibility. We find that Extruded Polystyrene offers the best compromise for patient support and positioning structures across all modalities tested, allowing for significant savings in treatment planning time and delivering more efficient treatment with lower margins.
Keywords: Composite; Core; Clinical imaging; PET; CT; MRI; Proton
Materials 13(2020)16, 3549
Brain geometry matters in Alzheimer disease progression: a simulation study
The Amyloid cascade hypothesis (ACH) for Alzheimer's disease (AD) is modeled over the whole brain tissue with a set of partial differential equations. Our results show that the amyloid plaque formation is critically dependent on the secretion rate of amyloid β(Aβ), which is proportional to the product of neural density and neural activity. Neural atrophy is similarly related to the secretion rate of Aβ. Due to a heterogeneous distribution of neural density and brain activity throughout the brain, amyloid plaque formation and neural death occurs heterogeneously in the brain. The geometry of the brain and microglia migration in the parenchyma bring more complexity into the system and result in a diverse amyloidosis and dementia pattern of different brain regions. Although the pattern of amyloidosis in the brain cortex from in-silico results is similar to experimental autopsy findings, they mismatch at the central regions of the brain, suggesting that ACH is not able to explain the whole course of AD without considering other factors, such as tau-protein aggregation or neuroinflammation.
Keywords: Neurdegenerative disease; Alzheimer's disease; Amyloid cascade hypothesis; mult-phase model
Contribution to WWW
Multiscale Tomographic Analysis for Micron-Sized Particulate Samples
The three-dimensional characterization of distributed particle properties in the micro- and nanometer range is essential to describe and understand highly specific separation processes in terms of selectivity and yield. Both performance measures play a decisive role in the development and improvement of modern functional materials. In this study, we mixed spherical glass particles (0.4–5.8 μm diameter) with glass fibers (diameter 10 μm, length 18–660 μm) to investigate a borderline case of maximum difference in the aspect ratio and a significant difference in the characteristic length to characterize the system over several size scales. We immobilized the particles within a wax matrix and created sample volumes suitable for computed tomographic (CT) measurements at two different magnification scales (X-ray micro- and nano-CT). Fiber diameter and length could be described well on the basis of the low-resolution micro-CT measurements on the entire sample volume. In contrast, the spherical particle system could only be described with sufficient accuracy by combining micro-CT with high-resolution nano-CT measurements on subvolumes of reduced sample size. We modeled the joint (bivariate) distribution of fiber length and diameter with a parametric copula as a basic example, which is equally suitable for more complex distributions of irregularly shaped particles. This enables us to capture the multidimensional correlation structure of particle systems with statistically representative quantities.
Keywords: multidimensional particle characterization; multiscale X-ray tomography; parametric copula; statistical image analysis
Microscopy and Microanalysis 26(2020)4, 676-688
Yu-Shiba-Rusinov bands in ferromagnetic superconducting diamond
The combination of different exotic properties in materials paves the way for the emergence of their new potential applications. An example is the recently found coexistence of the mutually antagonistic ferromagnetism and superconductivity in hydrogenated boron-doped diamond, which promises to be an attractive system with which to explore unconventional physics. Here, we show the emergence of Yu-Shiba-Rusinov (YSR) bands with a spatial extent of tens of nanometers in ferromagnetic superconducting diamond using scanning tunneling spectroscopy. We demonstrate theoretically how a two-dimensional (2D) spin lattice at the surface of a three-dimensional (3D) superconductor gives rise to the YSR bands and how their density-of-states profile correlates with the spin lattice structure. The established strategy to realize new forms of the coexistence of ferromagnetism and superconductivity opens a way to engineer the unusual electronic states and also to design better-performing superconducting devices.
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Publication date: 2020-05-25
Tailoring Magnetic Features in Zigzag-Edged Nanographenes by Controlled Diels–Alder Reactions
Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0=0.72; half-life, t1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y0=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.
- Tailoring Magnetic Features in Zigzag-Edged Nanographenes … (Id 31068) has used this (Id 31366) publication of HZDR-primary research data
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Publication date: 2020-05-25
HIF2α supports pro-metastatic behavior in pheochromocytomas/paragangliomas
Bechmann, N.; Moskopp, M. L.; Ullrich, M.; Calsina, B.; Wallace, P. W.; Richter, S.; Friedemann, M.; Langton, K.; Fliedner, S. M. J.; Timmers, H. J. L. M.; Nölting, S.; Beuschlein, F.; Fassnacht, M.; Preijbisz, A.; Pacak, K.; Ghayee, H. K.; Bornstein, S. R.; Dieterich, P.; Pietzsch, J.; Wielockx, B.; Robledo, M.; Qin, N.; Eisenhofer, G.
Mutations that drive the stabilization of hypoxia inducible factor 2α (HIF2α) and downstream pseudohypoxic signaling are known to predispose to the development of pheochromocytomas and paragangliomas (PPGLs). However, any role of HIF2α in predisposition to metastatic disease remains unclear. To assess such a role we combined gene-manipulations in pheochromocytoma cell lines with retrospective analyses of patient data and gene expression profiling in tumor specimens. Among 425 patients with PPGLs identified with mutations in tumor-susceptibility genes, those with tumors due to activation of pseudohypoxic pathways had a higher frequency of metastatic disease than those with tumors due to activation of kinase- signaling pathways, even without inclusion of patients with mutations in SDHB (18.6% vs. 4.3% in, p<0.0001). Three out of nine (33%) of patients with gain-of-function mutations in HIF2α had metastatic disease. In cell line studies, elevated expression of HIF2α enhanced cell proliferation and led to increased migration and invasion capacity. Moreover, HIF2α expression in HIF2α-deficient cells resulted in increased cell motility, diffuse cluster formation and emergence of pseudopodia indicating changes in cell adhesion and cytoskeletal remodeling. In a mouse liver metastasis model, HIF2α enhanced the metastatic load. Transcriptomics data revealed alterations in focal adhesion and extracellular matrix-receptor interactions in HIF2α-mutated PPGLs. Our translational findings demonstrate that HIF2α supports pro-metastatic behavior in PPGLs, though other factors remain critical for subsequent transition to metastasis. We identified LAMB1 and COL4A2 as new potential therapeutic targets for HIF2α-driven PPGLs. Identified HIF2α downstream targets might open a new therapeutic window for aggressive HIF2α-expressing tumors.
Endocrine-Related Cancer 27(2020)11, 625-640
- Secondary publication expected from 14.09.2021
Dynamics of Bubble Formation at Micro-orifices under Constant Gas Flow Conditions
Fine gas dispersion into a liquid is requested in a number of industrial applications. One way to achieve fine gas dispersion is to downsize the openings from which gas bubbles are generated. Accordingly, we have investigated the dynamics of bubble formation from submerged orifices ranging from 0.04 to 0.8 mm at a comprehensive range of gas flow rates for a system of air and deionized water. In this range of orifice size, we observe a different mechanism of bubble formation compared with millimeter-range orifices. We discuss the observations on the basis of temporal change of the bubble shape, bubble base expansion, and detachment criteria. At submillimeter orifices, the mechanism of bubble formation is highly influenced by the capillary pressure and the gas kinetic energy. The latter results in congregation of small bubbles in the vicinity of the orifice, even at very small gas flow rates. Moreover, we studied the evolution of individual forces applied to the surface of bubbles during their formation. We have found that the formation of bubbles at submillimeter orifices cannot be described with a quasi-static force balance. Finally, we present a bubbling regime map using relevant dimensionless numbers.
Keywords: Bubble Formation; Submillimeter Orifices; Bubbling Regime; Bubbling Dynamics; Stainless Steel Orifice
- Dynamics of Bubble Formation at Micro-orifices under … (Id 30717) HZDR-primary research data are used by this (Id 31363) publication
International Journal of Multiphase Flow 132(2020), 103407
Sorption of Europium on Diatom Biosilica as Model of a “Green” Sorbent for f-Elements
Removing f-elements from anthropogenically contaminated sites is a challenging, but ecologically important task. Some of these elements are not only radioactive, but also chemically toxic and can spread through various pathways in the environment. The present work investigates f-element sorption on biogenic silica, which may be a promising “green” material for remediation. Commercially available diatomaceous earth (DE) and the cleaned cell walls of the diatom species Stephanopyxis turris (S.t.) and Thalassiosira pseudonana (T.p.) are compared with artificial mesocellular foam (MCF) as porous silica reference material. Trivalent europium was chosen as model sorptive for chemically similar trivalent actinides. Accordingly, Eu(III) in concentrations of 10-3 M and 10-5 M was sorbed on the four silica materials at varying pH values. The zeta potentials of the implemented sorbents under the same conditions were determined. In addition, the sorption reaction and the aqueous speciation of Eu(III) in the (bio)silica suspensions were modeled using the Diffuse Double Layer (DDL) model. With time-resolved laser-induced fluorescence spectroscopy (TRLFS), two different uptake mechanisms can be discerned, surface adsorption and incorporation/precipitation.
Keywords: biosilica; diatoms; europium; fluorescence; sorption
Applied Geochemistry 126(2021), 104823
- Secondary publication expected from 14.11.2021
Magnetocaloric effect in GdNi2 for cryogenic gas liquefaction studied in magnetic fields up to 50 T
Natural gases have played a significant role in different sectors of the global economy. Recent analyses have shown that the world’s gas consumption doubled over the last three decades; further growth of the gas consumption is predicted, rising to be 23%–28% of the total primary energy demand by 2030. Therefore, liquefaction of natural gases rapidly gains global importance. In this context, magnetic refrigeration emerges as a modern energy-saving technique, which is an alternative to the traditional gas-compression refrigeration. This paper is devoted to the study of the magnetocaloric effect in magnetic fields up to 10 T on a representative of the Laves phase alloys, GdNi2, which is considered as a perspective material for liquefaction of natural gases. For a magnetic field change of 10 T, the magnetic entropy change ΔSm≈−17 J/kg K and the adiabatic temperature change ΔTad ≈ 6.8 K was attained around Curie temperature TC = 70 K. The maximal value of the adiabatic temperature change measured directly in pulsed magnetic fields up to 50 T is ΔTad ≈ 15 K.
Journal of Applied Physics 127(2020), 233906
Effect of uniaxial stress on the electronic band structure of NbP
Schindler, C.; Noky, J.; Schmidt, M.; Felser, C.; Wosnitza, J.; Gooth, J.
The Weyl semimetal NbP exhibits a very small Fermi surface consisting of two electron and two hole pockets, whose fourfold degeneracy in k space is tied to the rotational symmetry of the underlying tetragonal crystal lattice. By applying uniaxial stress, the crystal symmetry can be reduced, which successively leads to a degeneracy lifting of the Fermi-surface pockets. This is reflected by a splitting of the Shubnikov–de Haas frequencies when the magnetic field is aligned along the c axis of the tetragonal lattice. In this study, we present the measurement of Shubnikov–de Haas oscillations of single-crystalline NbP samples under uniaxial tension, combined with state-of-the-art calculations of the electronic band structure. Our results show qualitative agreement between calculated and experimentally determined Shubnikov–de Haas frequencies, demonstrating the robustness of the band-structure calculations upon introducing strain. Furthermore, we predict a significant shift of the Weyl points with increasing uniaxial tension, allowing for an effective tuning to the Fermi level at only 0.8% of strain along the a axis.
Physical Review B 102(2020), 035132
Adding CUDA® Support to Cling: JIT Compile to GPUs
Jupyter Notebooks are omnipresent in the modern scientist's and engineer's toolbox just as CUDA C++ is in accelerated computing. We present the first implementation of a CUDA C++ enabled read-eval-print-loop (REPL) that allows to interactively "script" the popular CUDA C++ runtime syntax in Notebooks. With our novel implementation, based on LLVM, Clang and CERN's C++ interpreter Cling, the modern CUDA C++ developer can work as interactively and productively as (I)Python developers while keeping all the benefits of the vast C++ computing and library ecosystem coupled with first-class performance.
Keywords: Cling; CUDA; Jupyter Notebook; interactive C++; LLVM; interactive simulation; rapid prototyping
2020 Virtual LLVM Developers' Meeting, 06.-08.10.2020, Virtuell, USA
Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation
Konstantinovic, M. J.; Ulbricht, A.; Brodziansky, T.; Castin, N.; Malerba, L.
Origin-files, data for figure 3 and figure 4 of publication in J. Nucl. Mater.
Keywords: Neutron irradiation, FeCr alloys and steels
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Publication date: 2020-07-21
Evaluation of Recyclability of a WEEE Slag by Means of Integrative X-Ray Computer Tomography and SEM-Based Image Analysis
Waste of electrical and electronic equipment (WEEE) is one of the fastest growing waste streams globally. Therefore, recycling of the valuable metals of this stream plays a vital role in establishing a circular economy. The smelting process of WEEE leads to significant amounts of valuable metals and rare earth elements (REEs) trapped in the slag phase. The effective manipulation of this phase transfer process necessitates detailed understanding and effective treatment to minimize these contents. Furthermore, an adequate process control to bring these metal contents into structures that make recycling economically applicable is required. Within the present study, a typical slag from a WEEE melting process is analyzed in detail. Therefore, the material is investigated with the help of X-ray computed tomography (XCT) and scanning electron microscopy (SEM)-based mineralogical analysis (MLA) to understand the typical structures and its implications for recycling. The influencing factors are discussed, and further processing opportunities are illustrated.
Keywords: waste of electrical and electronic equipment; X-ray computed tomography; mineral liberation analysis
Minerals 10(2020)4, 309
Spectral X-ray Computed Micro Tomography: 3-dimensional chemical imaging
We present a new approach to 3-dimensional chemical imaging based on computed tomography (CT), which allows a reconstruction of the internal elemental chemistry. The method uses a conventional laboratory based CT scanner combined with a semiconductor detector (CdTe). Based on the X-ray absorption spectrum, elements in a sample can be distinguished by their K-edge energy, which is specific. Different experiments have been preformed to test the performance of the system i.e. single pure element particle measurements, element differentiation in mixtures, and mineral differentiation in a gold ore sample. The results show that the method is able to distinguish elements in the samples with K-edges in the range of 20 to 160 keV, which corresponds to an elemental range from Ag to U. Furthermore, the spectral information allows a distinction between materials, which show no variation in contrast in the reconstructed CT image.
Keywords: X-ray computed tomography; Spectral X-ray tomography; Photon counting detector; 3D imaging
- Data for: Spectral X-ray Computed Micro Tomography … (Id 31653) HZDR-primary research data are used by this (Id 31354) publication
X-Ray Spectrometry (2021), 1-14
CFD Modeling and Experimental Validation of Top-Submerged-Lance Gas Injection in Liquid Metal
Reuter, M. A.; Akashi, M.; Kriebitzsch, S.; Meyer, B.; Obiso, D.; Eckert, S.; Richter, A.
In the present work, the dynamics of a downward gas injection into a liquid metal bath is studied using a numerical modeling approach, and validated with experimental data. As in a top-submerged-lance (TSL) smelter, gas is injected through the lance into the melt. By this means, the properties of the liquid are closer to the actual industrial process than the typically used water/glycerol–air/helium systems. The experimental activity was carried out in a quasi-2D vessel (144 x 144 x 12 mm3) filled with GaInSn, a metal alloy with eutectic at room temperature. Ar was used as the inert gas. The structure and behavior of the gas phase were visualized and quantitatively analyzed by X-ray radiography and high-speed imaging. Computational Fluid Dynamics (CFD) was applied to simulate the multiphase flow in the vessel and the Volume Of Fluid (VOF) model chosen to track the interface using a geometric reconstruction of the interface. Three different vertical lance positions were investigated, applying a gas flow rate of Qgas = 6850 cm³/min: The CFD model is able to predict the bubble detachment frequency, the average void fraction distributions, and the bubble size and hydrodynamic behavior, demonstrating its applicability to simulate such complex multiphase systems. The use of numerical models also provides a deep insight into fluid dynamics to study particular phenomena such as bubble break-up and free surface oscillations.
Keywords: top-submerged-lance (TSL),; X-ray,; Computational Fluid Dynamics (CFD),; Volume Of Fluid (VOF),
Metallurgical and Materials Transactions B 51(2020), 1509-1525
Engineering telecom single-photon emitters in silicon for scalable quantum photonics
We create and isolate single-photon emitters with a high brightness approaching 10⁵ counts per second in commercial silicon-on-insulator (SOI) wafers. The emission occurs in the infrared spectral range with a spectrally narrow zero phonon line in the telecom O-band and shows a high photostability even after days of continuous operation. The origin of the emitters is attributed to one of the carbon-related color centers in silicon, the so-called G center, allowing purification with the ¹²C and ²⁸Si isotopes. Furthermore, we envision a concept of a highly-coherent scalable quantum photonic platform, where single-photon sources, waveguides and detectors are integrated on the same SOI chip. Our results provide a route towards the implementation of quantum processors, repeaters and sensors compatible with the present-day silicon technology.
Keywords: Signe photon source; telecommunication window; silicon photonics; quantum communication; color centers
Optics Express 28(2020), 26111-26121
Investigation of inter-fraction target motion variations in the context of pencil beam scanned proton therapy in non-small cell lung cancer patients
Den Otter, L. A.; Anakotta, R. M.; Weessies, M.; Roos, C. T. G.; Sijtsema, N. M.; Muijs, C. T.; Dieters, M.; Wijsman, R.; Troost, E. G. C.; Richter, C.; Meijers, A.; Langendijk, J. A.; Both, S.; Knopf, A.-C.
Purpose: For locally advanced-stage non-small cell lung cancer (NSCLC), inter-fraction target motion variations during the whole time span of a fractionated treatment course are assessed in a large and representative patient cohort. The primary objective is to develop a suitable motion monitoring strategy for pencil beam scanning proton therapy (PBS-PT) treatments of NSCLC patients during free breathing. Methods: Weekly 4D computed tomography (4DCT; 41 patients) and daily 4D cone beam computed tomography (4DCBCT; 10 of 41 patients) scans were analyzed for a fully fractionated treatment course. Gross tumor volumes (GTVs) were contoured and the 3D displacement vectors of the centroid positions were compared for all scans. Furthermore, motion amplitude variations in different lung segments were statistically analyzed. The dosimetric impact of target motion variations and target motion assessment was investigated in exemplary patient cases. Results: The median observed centroid motion was 3.4 mm (range: 0.2–12.4 mm) with an average variation of 2.2 mm (range: 0.1–8.8 mm). Ten of 32 patients (31.3%) with an initial motion <5 mm increased beyond a 5-mm motion amplitude during the treatment course. Motion observed in the 4DCBCT scans deviated on average 1.5 mm (range: 0.0–6.0 mm) from the motion observed in the 4DCTs. Larger motion variations for one example patient compromised treatment plan robustness while no dosimetric influence was seen due to motion assessment biases in another example case. Conclusions: Target motion variations were investigated during the course of radiotherapy for NSCLC patients. Patients with initial GTV motion amplitudes of < 2 mm can be assumed to be stable in motion during the treatment course. For treatments of NSCLC patients who exhibit motion amplitudes of > 2 mm, 4DCBCT should be considered for motion monitoring due to substantial motion variations observed. ©2020 The Authors. Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.
Keywords: free breathing; lung cancer; moving target; spencil beam scanning proton therapy; inter-fractional motion monitoring
Medical Physics 47(2020)9, 3835-3844
Adenosine/A2B Receptor Signaling Ameliorates the Effects of Aging and Counteracts Obesity
Gnad, T.; Navarro, G.; Lahesmaa, M.; Reverte-Salisa, L.; Copperi, F.; Cordomi, A.; Naumann, J.; Hochh€Auser, A.; Haufs-Brusberg, S.; Wenzel, D.; Suhr, F.; Zenius Jespersen, N.; Scheele, C.; Tsvilovskyy, V.; Brinkmann, C.; Rittweger, J.; Dani, C.; Kranz, M.; Deuther-Conrad, W.; Eltzschig, H. K.; Niemi, T.; Taittonen, M.; Brust, P.; Nuutila, P.; Pardo, L.; Fleischmann, B. K.; Bleuher, M.; Franco, R.; Bloch, W.; Virtanen, K. A.; Pfeifer, A.
The combination of aging populations with the obesity pandemic results in an alarming rise in non-communicable diseases. Here, we show that the enigmatic adenosine A2B receptor (A2B) is abundantly expressed in skeletal muscle (SKM) as well as brown adipose tissue (BAT) and might be targeted to counteract age-related muscle atrophy (sarcopenia) as well as obesity. Mice with SKM-specific deletion of A2B exhibited sarcopenia, diminished muscle strength, and reduced energy expenditure (EE), whereas pharmacological A2B activation counteracted these processes. Adipose tissue-specific ablation of A2B exacerbated age-related processes and reduced BAT EE, whereas A2B stimulation ameliorated obesity. In humans, A2B expression correlated with EE in SKM, BAT activity, and abundance of thermogenic adipocytes in white fat. Moreover, A2B agonist treatment increased EE from human adipocytes, myocytes, and muscle explants. Mechanistically, A2B forms heterodimers required for adenosine signaling. Overall, adenosine/A2B signaling links muscle and BAT and has both anti-aging and anti–obesity potential.
Cell Metabolism 32(2020), 56-70
Advanced flow profiler for two-phase flow imaging on distillation trays
A profound knowledge of the two-phase cross-flow on large-scale distillation trays is pivotal to their efficient design and operation. For such trays, a novel flow profiler comprising of multiple dual-tip probes for simultaneous local conductivity measurements is proposed in this work. The profiler is applied for a DN800 air/water column simulator equipped with sieve trays. 3D distribution of liquid holdup and tracer-based liquid flow in the two-phase dispersion are assessed in high resolution. Non-uniform holdup is found along the dispersion height. Contrarily, the liquid flow is largely uniform and symmetric with respect to the tray centerline. Prior to measurements, the profiler design, electronic scheme, measurement principle and data processing schemes are described.
Keywords: column tray; two-phase cross-flow; 3D flow imaging; conductivity measurement; liquid holdup; tracer dispersion
Chemical Engineering Science (2021)
- Secondary publication expected from 08.11.2021
Numerical study of the appearance of short-circuits in liquid metal batteries
The report gives an overview on small-scale interface instabilities in liquid metal batteries.
École normale supérieure Paris-Saclay, 2020
Magnetoelectric coupling in a frustrated spinel studied using high-field scanning probe microscopy
Rossi, L.; Brüning, D.; Ueda, H.; Scurschii, I.; Lorenz, T.; Bryant, B.
Below its Neél temperature, the frustrated magnet CdCr2O4 exhibits an antiferromagnetic spin-spiral ground state. Such states can give rise to a sizable magnetoelectric coupling. In this report, we measure the electric polarization induced in single-crystalline CdCr2O4 by large applied magnetic field. Because the detection of a macroscopic polarization is hindered by the structural domains in the tetragonal spin-spiral phase, we have pioneered an alternative method of measuring polarization induced by high magnetic fields, using electrostatic force microscopy. This method enables us to measure polarization from nanoscale areas of the sample surface, as well as imaging how charge inhomogeneities change with magnetic field.
Applied Physics Letters 116(2020), 262901
A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar
The mobility of heavy metal contaminants and radionuclides in the environment is directly controlled by their interactions with charged mineral surfaces, hence an assessment of their potential toxicity, e.g. in the context of nuclear waste disposal sites, requires understanding of sorption processes on the molecular level. Here, we investigate the sorption of a variety of rare earth elements (REE) and trivalent actinides (Am, Cm) on K-feldspar using batch sorption and column transport experiments, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and a surface complexation model. Initially, a reliable pKa for K-feldspar’s surface deprotonation reaction was determined as 2.5 ± 0.02, in excellent agreement with a measured pHIEP of 2.8. Batch sorption experiments over a broad range of experimental conditions in terms of mineral grain size, pH, [M3+], ionic radius, solid/liquid ratio, ionic strength, and equilibration procedures were carried out to quantify macroscopic immobilization. Similar pH-dependent uptake behavior was found for all investigated trivalent REE and actinides. In parallel, spectroscopic investigations provided insight into surface speciation. Cm TRLFS spectra indicate the formation of three inner-sphere sorption complexes with increasing hydrolysis. Additionally, a ternary K-feldspar/Cm/silicate complex was found for pH > 10, and batch and spectroscopic data at low pH (< 4) point to small amounts of outer sphere sorption complexes. Based on TRLFS data, batch sorption, and titration data, a generic geochemical sorption model was developed, that describes sorption edges for all investigated M3+/K-feldspar systems satisfactorily. The derived stability constants for the binary sorption complexes (logK1-4 = −3.6, −7.7, −11.5, and −17.4, respectively) are in good agreement with previous studies on similar systems, and could successfully be used to reproduce literature data. The stability constants obtained for the surface complexes were included into the database for the Smart Kd-concept, which will further improve the safety assessment of potential repositories for radioactive waste.
Keywords: sorption; trivalent metal ions; actinides; K-feldspar; surface complexation model; TRLFS
Journal of Colloid and Interface Science 591(2021), 490-499
Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation
Konstantinovic, M. J.; Ulbricht, A.; Brodziansky, T.; Castina, N.; Malerba, L.
Vacancy-solute clustering in neutron irradiated Fe-Cr alloys with various concentrations of Cr and minor solutes (Ni, Si and P) were studied by using
coincidence Doppler broadening spectroscopy and small angle neutron scattering techniques. The results from both experiments, supported by an object kinetic Monte Carlo model, show in a very consistent way the existence and formation of vacancy-CrNiSiP clusters that play detrimental role in irradiation hardening. Similar solute cluster number density of about 30 to 50 x10^16cm-3 and an average diameter of about 1 nm were estimated for all alloys containing minor solutes, irrespectively of the chromium content. In Fe9Cr ferritic and Fe9Cr ferritic/martensitic alloys, with significantly reduced concentration of minor solute elements, the main defects are vacancy clusters, with an average cluster size size of about 10 and 2 vacancies, respectively. Large concentration of alpha'-precipitates was observed in Fe14Cr(NiSiP). However, both vacancy clusters and alpha'-precipitates provide significantly less impact to hardening in comparison to vacancy-CrNiSiP clusters. The fact that vacancy clustering in Fe9Cr ferritic alloy resembles that of pure iron suggests that Cr solutes may play lesser role in irradiation hardening of ferritic alloys and steels than previously believed.
Keywords: Neutron irradiation; FeCr alloys; Steels
- Vacancy-solute clustering in Fe-Cr alloys after neutron … (Id 31356) HZDR-primary research data are used by this (Id 31344) publication
Journal of Nuclear Materials 540(2020), 152341
- Secondary publication expected from 24.07.2021
Uranium(VI) toxicity in tobacco BY-2 cell suspension culture - a physiological study
For the first time, the physiological and cellular responses of Nicotiana tabacum (BY-2) cells to uranium (U) as an abiotic stressor was studied in a multi analytic approach combining biochemical analysis, thermodynamic modeling and spectroscopic studies. It was focused on the determination of the U threshold toxicity in tobacco BY-2 cells, the influence of U on the homeostasis of micro-macro essential nutrients as well as the effect of Fe starvation on U bioassociation in cultured BY-2 cells. Our findings showed that U interferes with the homeostasis of essential elements. The interaction of U with BY-2 cells showed a time and concentration dependent kinetic. Under Fe deficiency, less U was detected in the cells compared to Fe sufficient conditions. Interestingly, blocking of Ca channels by gadolinium chloride caused a decrease in U concentration in BY-2 cells. Spectroscopic studies evidenced changes in the U speciation in the culture media with increasing exposure time under Fe sufficient and deficient conditions. Thusly, different stress response reactions related to the Fe metabolism are assumed. It is suggested that U toxicity in BY-2 cells is highly dependent on the existence of other micro-macro elements as showed by negative synergistic effects of U and Fe on the viability of cells.
Keywords: Nicotiana tabacum cells; uranium; toxicity; physiology; bioavailability; Fe starvation; speciation; plants; plant cells
Ecotoxicology and Environmental Safety 211(2021), 111883
Band Bending and Valence Band Quantization at Line Defects in MoS2
The variation of the electronic structure normal to 1D defects in quasi-freestanding MoS2, grown by molecular beam epitaxy, is investigated through high resolution scanning tunneling spectroscopy at 5K. Strong upward bending of valence and conduction bands toward the line defects is found for the 4|4E mirror twin boundary and island edges but not for the 4|4P mirror twin boundary. Quantized energy levels in the valence band are observed wherever upward band bending takes place. Focusing on the common 4|4E mirror twin boundary, density functional theory calculations give an estimate of its charging, which agrees well with electrostatic modeling. We show that the line charge can also be assessed from the filling of the boundary-localized electronic band, whereby we provide a measurement of the theoretically predicted quantized polarization charge at MoS2 mirror twin boundaries. These calculations elucidate the origin of band bending and charging at these 1D defects in MoS2. The 4|4E mirror twin boundary not only impairs charge transport of electrons and holes due to band bending, but holes are additionally subject to a potential barrier, which is inferred from the independence of the quantized energy landscape on either side of the boundary.
Keywords: 2D materials; Line defects; first-principles calculations
ACS Nano 14(2020), 9176-9187
- Secondary publication expected from 30.06.2021
Strain robust spin gapless semiconductors/half-metals in transition metal embedded MoSe2 monolayer
The realization of spin gapless semiconductor (SGS) and half-metal (HM) behavior in two-dimensional (2D) transition metal (TM) dichalcogenides is highly desirable for their applications in spintronic devices. Here, using density functional theory calculations, we demonstrate that Fe, Co, Ni substitutional impurities can not only induce magnetism in MoSe2 monolayer, but also convert the semiconducting MoSe2 to SGS/HM system. We also study the effects of mechanical strain on the electronic and magnetic properties of the doped monolayer. We show that for all TM impurities we considered, the system exhibits the robust SGS/HM behavior regardless of biaxial strain values. Moreover, it is found that the magnetic properties of TM–MoSe2 can effectively be tuned under biaxial strain by controlling the spin polarization of the 3d orbitals of Fe, Co, Ni atoms. Our findings offer a new route to designing the SGS/HM properties and modulating magnetic characteristics of the TM–MoSe2 system and may also facilitate the implementation of SGS/HM behavior and realization of spintronic devices based on other 2D materials.
Keywords: 2D materials; first-principles simulations; magnetism
Journal of Physics: Condensed Matter 32(2020), 365305
- Secondary publication expected from 17.06.2021
Reversible crystalline-to-amorphous phase transformation in monolayer MoS under grazing ion irradiation
By combining scanning tunneling microscopy, low-energy electron diffraction, photoluminescence and Raman spectroscopy experiments with molecular dynamics simulations, a comprehensive picture of the structural and electronic response of a monolayer of MoS2 to 500 eV Xe+ irradiation is obtained. The MoS2 layer is epitaxially grown on graphene/Ir(1 1 1) and analyzed before and after irradiation in situ under ultra-high vacuum conditions. Through optimized irradiation conditions using low-energy ions with grazing trajectories, amorphization of the monolayer is induced already at low ion fluences of 1.5 × 1014 ions cm−2 and without inducing damage underneath the MoS2 layer. The crystalline-to-amorphous transformation is accompanied by changes in the electronic properties from semiconductor-to-metal and an extinction of photoluminescence. Upon thermal annealing, the re-crystallization occurs with restoration of the semiconducting properties, but residual defects prevent the recovery of photoluminescence.
Keywords: 2D materilas; irradiation; atomistic simulations; defects
2D Materials 7(2020), 025005
- Final Draft PDF 12,4 MB Secondary publication
Increasing the Diversity and Understanding of Semiconductor Nanoplatelets by Colloidal Atomic Layer Deposition
Nanoplatelets (NPLs) are a remarkable class of quantum confined materials with size-dependent optical properties, which are determined by the defined thickness of the crystalline platelets. To increase the variety of species, the colloidal atomic layer deposition method is used for the preparation of increasingly thicker CdSe NPLs. By growing further crystalline layers onto the surfaces of 4 and 5 monolayers (MLs) thick NPLs, species from 6 to 13 MLs are achieved. While increasing the thickness, the heavy-hole absorption peak shifts from 513 to 652 nm, leading to a variety of NPLs for applications and further investigations. The thickness and number of MLs of the platelet species are determined by high-resolution transmission electron microscopy (HRTEM) measurements, allowing the interpretation of several contradictions present in the NPL literature. In recent years, different assumptions are published, leading to a lack of clarity in the fundamentals of this field. Regarding the ongoing scientific interest in NPLs, there is a certain need for clarification, which is provided in this study.
Keywords: CdSe; colloidal atomic layer deposition; nanoplatelets
Physica Status Solidi (RRL) (2020), 2000282
Unraveling Structure and Device Operation of Organic Permeable Base Transistors
Organic permeable base transistors (OPBTs) are of great interest for flexible electronic circuits, as they offer very large on-current density and a record-high transition frequency. They rely on a vertical device architecture with current transport through native pinholes in a central base electrode. This study investigates the impact of pinhole density and pinhole diameter on the DC device performance in OPBTs based on experimental data and TCAD simulation results. A pinhole density of NPin = 54 μm−2 and pinhole diameters around LPin = 15 nm are found in the devices. Simulations show that a variation of pinhole diameter and density around these numbers has only a minor impact on the DC device characteristics. A variation of the pinhole diameter and density by up to 100% lead to a deviation of less than 4% in threshold voltage, on/off current ratio, and sub-threshold slope. Hence, the fabrication of OPBTs with reliable device characteristics is possible regardless of statistical deviations in thin film formation.
Keywords: organic permeable base transistors; organic electronics; technology computer-aided design simulation
Advanced Electronic Materials 6(2020)7, 2000230
Phase coherence and phase jumps in the Schwabe cycle
Guided by the working hypothesis that the Schwabe cycle of solar activity is synchronized by the 11.07 years alignment cycle of the tidally dominant planets Venus, Earth and Jupiter, we reconsider the phase diagrams of sediment accumulation rates in lake Holzmaar, and of methanesulfonate (MSA) data in the Greenland ice core GISP2, which are available for the period 10000-9000 cal. BP. Since some half-cycle phase jumps appearing in the output signals are, very likely, artifacts of applying a biologically substantiated transfer function, the underlying solar input signal with a dominant 11.04 years periodicity can be considered as mainly phase-coherent over the 1000 years period in the early Holocene. For more recent times, we show that the re-introduction of a hypothesized “lost cycle” at the beginning of the Dalton minimum would lead to a real phase jump. Similarly, by analyzing various series of 14C and 10Be data and comparing them with Schove’s historical cycle maxima, we support the existence of another “lost cycle” around 1565, also connected with a real phase jump. Viewed synoptically, our results lend greater plausibility to the starting hypothesis of a tidally synchronized solar cycle, which at times can undergo phase jumps, although the competing explanation in terms of a non-linear solar dynamo with increased coherence cannot be completely ruled out.
Keywords: Solar cycle; Synhcronization
Astronomische Nachrichten 341(2020)6-7, 600-615
Data set on DBTTs from SPT and CVN
The data set is related to a manuscript entitled "Use of the small punch test for the estimation of ductile-to-brittle transition temperature shift of irradiated steels". Contents raw data of small punch tests, evaluation data of small punch tests and Charpy impact tests, correlation and regression analysis.
Keywords: small punch test; Charpy impact test; ductile-to-brittle-transition temperature; reactor pressure vessel steel; neutron irradiation
- Use of the small punch test for the estimation of … (Id 31333) has used this (Id 31334) publication of HZDR-primary research data
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-16
Use of the small punch test for the estimation of ductile-to-brittle transition temperature shift of irradiated steels
The small punch test is evaluated as a screening procedure for irradiation embrittlement of reactor pressure vessel steels. In particular, the correlation between ductile-to-brittle transition temperatures obtained from this small specimen test technique and from the standard Charpy impact test is investigated. Small punch tests and Charpy impact tests at different temperatures were performed on various steels including materials from original reactor pressure vessels in the unirradiated, neutron irradiated and annealed condition. It is demonstrated that the small punch test is a reliable and effective supportive means for the estimation of the irradiation-induced shift of the ductile-to-brittle transition temperature. It was found that a tanh-fit of the normalized small punch energy in dependence of temperature is preferable in comparison to the two-curve fit of the total small punch energy.
Keywords: small punch test; ductile-to-brittle-transition temperature; reactor pressure vessel steel; neutron irradiation; annealing
- Data set on DBTTs from SPT and CVN (Id 31334) HZDR-primary research data are used by this (Id 31333) publication
Nuclear Materials and Energy 26(2021), 100918
Magnetic separation of rare-earth ions: Transport processes and pattern formation
Despite the relevance of the Kelvin force in many physical and electrochemical systems involving magnetic species, the underlying convective flows are scarcely understood. For that purpose, we simulate a simplified rare-earth system in the presence of competing Kelvin and gravity forces. The results are experimentally validated using interferometry and microscopic particle image velocimetry. Based on the excellent agreement of numerical and experimental results, the underlying mechanism of ions' magnetic separation can be explained, which paves the way for a prospective application in rare-earth beneficiation.
Keywords: magnetic separation; rare-earth ions; solutomagnetic convection; magnetophoresis; interferometer; Pattern formation; Rayleigh-Taylor instability; Rayleigh-Bénard convection; Paramagnetism
Physical Review Fluids 6(2021)2, L021901
- Original PDF 1,7 MB Secondary publication
DGN-Handlungsempfehlung (S1-Leitlinie): PSMA-Liganden-PET/CT in der Diagnostik des Prostatakarzinoms
Afshar-Oromieh, A.; Eiber, M.; Fendler, W.; Schmidt, M.; Rahbar, K.; Ahmadzadehfar, H.; Umutlu, L.; Hadaschik, B.; Hakenberg, O. W.; Formara, P.; Kurth, J.; Neels, O.; Wester, H. J.; Schwaiger, M.; Kopka, K.; Haberkorn, U.; Hermann, K.; Krause, B. J.
Das Ziel der vorliegenden Leitlinie ist es, den Arzt bei der Indikationsstellung, der standardisierten Durchführung, der Interpretation und der Dokumentation der Befunde einer Positronen-Emissions-Tomographie/Computertomographie (PET/CT) mit PSMA-Liganden bei Patienten mit Prostatakarzinom zu unterstützen. Es werden Empfehlungen zu Patientenselektion, Bilderfassung, Interpretation und Befundung ausgesprochen sowie Limitationen der PSMA-Liganden-PET/CT präsentiert. Die Leitlinie basiert auf einer Zusammenführung wissenschaftlicher Veröffentlichungen, Empfehlungen der Autoren und evidenzbasierter Daten.
- PSMA-Liganden-PET/CT in der Diagnostik des Prostatakarzinoms 10(2019) 031-055
Safety Cases for Design-Basis Accidents in LWRs Featuring Passive Systems Part 2 - Numerical Investigations
Buchholz, S.; Bonfigli, G.; Schäfer, F.; Kaczmarkiewicz, N.; Schuster, C.; Sporn, M.
This paper deals with the improvement and validation of numerical tools for the simula-tion of design basis accidents in nuclear power plants equipped with passive safety sys-tems. Numerical models are implemented in the framework of the 1-D thermal-hydraulic system code ATHLET developed by GRS. Experimental reference data for the validation were obtained at the INKA test facility, a model of the KERENA reactor, reproducing the passive safety systems nearly at full scale.
The validation effort focuses firstly on the accuracy of the models for the single passive components, and secondly on the ability of the numerical simulation to reproduce the in-teraction of all components of the KERENA design under realistic conditions as repro-duced in the INKA test facility. Thermal-hydraulic models are presented and validated for two passive components of the KERENA reactor: the passive pressure pulse trans-mitter and the pressure-controlled flooding valve. Finally, the full model of the INKA fa-cility, including these and other passive components, is discussed and numerical results for simulations reproducing three different design basis accidents are validated by com-parison with the corresponding experimental data.
Keywords: Passive Safety Systems; passive pressure pulse transmitter; passive core flooding sys-tem; ATHLET; AC2; INKA; KERENA
Nuclear Engineering and Design 372(2021), 110996
Safety Cases for Design-Basis Accidents in LWRs Featuring Passive Systems Part 1 - Experimental Investigations
Mull, T.; Wagner, T.; Bonfigli, G.; Buchholz, S.; Schäfer, F.; Schleicher, E.; Schuster, C.; Sporn, M.
This paper presents results from a series of integral tests performed at Framatome’s INKA test facility in Karlstein (Germany) which simulates a KERENA boiling water reac-tor (BWR). The scope of the test series was on the behaviour of and interaction be-tween the different passive systems and components under the conditions of extended loss of alternating power (ELAP). These SBO-like conditions were aggravated in three out of four tests by parallel LOCA (Loss of Coolant Accident). The scenarios of all four tests fully correspond to Design Basic Conditions (DBC). They were: main steam line break, feed water line break, reactor pressure vessel (RPV) bottom leak and station blackout (SBO, non-LOCA).
In the tests, the passive systems integrated in KERENA and INKA, respectively, have fulfilled their design functions fully satisfactorily and as follows:
The Passive Pressure Pulse Transmitter (PPPT) triggered the RPV depressurization without delay. The Emergency Condenser (EC) system removed decay heat along with stored energy from the RPV to the containment. The Containment Cooling Condenser (CCC) system forwarded said power to a heat sink outside of the containment. The passive containment pressure suppression system kept the containment pressure within the design range, partially displacing surplus thermal energy from the drywell to the wetwell, in particular in the early phases after occurrence of LOCA. The passive core flooding system replenished the coolant inventory of the RPV thereby ensuring water levels in the RPV which are fully sufficient for core cooling.
Moreover, the systems have cooperated as anticipated by the designers, quietly and without perturbing each other.
Hence the test results, which are reported and discussed more in detail within this pa-per, soundly confirm the underlying design and its passive features.
Said tests were carried out as a part of the joint research project EASY (Evidence of Design Basis Accidents Mitigation solely with passive safety Systems), the overarching objective of which was the development and validation of the code system AC2 of GRS (Gesellschaft für Anlagen- und Reaktorsicherheit gGmbH).
Keywords: INKA, KERENA, BWR, DBC, Passive Safety Systems
Nuclear Engineering and Design (2021)
Nature of Magnetic Excitations in the High-Field Phase of α-RuCl3
We present comprehensive electron spin resonance (ESR) studies of in-plane oriented single crystals of α-RuCl3, a quasi-two-dimensional material with honeycomb structure, focusing on its high-field spin dynamics. The measurements were performed in magnetic fields up to 16 T, applied along the  and  directions. Several ESR modes were detected. Combining our findings with recent inelastic neutronand Raman-scattering data, we identified most of the observed excitations. Most importantly, we show that the low-temperature ESR response beyond the boundary of the magnetically ordered region is dominated by single- and two-particle processes with magnons as elementary excitations. The peculiarities of the excitation spectrum in the vicinity of the critical field are discussed.
Physical Review Letters 125(2020), 037202
- Original PDF 912 kB Secondary publication
Earthquake-induced deformation structures in glacial sediments—evidence on fault reactivation and instability at the Vaalajärvi fault in northern Fennoscandia
Late and postglacial reverse faults and seismically-induced landslides are characteristic features of deglaciated terrain in the northern Fennoscandia. The main focus of this study was to investigate the rupturing history of the reverse Vaalajärvi fault complex in Sodankylä, Finland, based on remote sensing, on-site geophysics and sedimentology in excavations trenched across the faulted terrain. In addition to the previously known NNW–SSE-trending Vaalajärvi segment, we discovered six new SW–NE-trending fault segments that probably belong to the same Vaalajärvi ‘postglacial’ fault complex. Our analysis indicate that the Vaalajärvi fault segment was triggered by stress change caused by ruptures on the surrounding SW–NE-trending reverse faults. In total, at least two to three slip events have taken place in different segments of the Vaalajärvi complex since the Early Weichselian with the most recent event(s) being postglacial in timing. By using the scaling laws of fault surface rupture length and offset and under different scenarios of which segments or systems ruptured in a single or separate event, we estimate that the Vaalajärvi complex potentially hosted an earthquake that ranged between Mw ≈ 6.7–7.0. This magnitude is comparable to the landslide-inferred magnitudes in the Vaalajärvi area.
Keywords: Postglacial fault; Paleoseismology; Moment magnitude; LiDAR; Vaalajärvi; Finland
Journal of Seismology 24(2020)3, 549-571
- Secondary publication expected from 21.04.2021
Halogen Bonded Assemblies of Arylene-imides and -diimides: Insight from Electronic, Structural and Computational studies
Mandal, K.; Bansal, D.; Kumar, Y.; Khan, R.; Shukla, J.; Mukhopadhyay, P.
Halogen bonding interactions in electron deficient π-scaffolds has largely been underexplored. Herein, we have studied the halogen bonding properties of arylene-imide/-diimide-based electron deficient scaffolds. We probed the influence of: scaffold size, e.g. from small phthalimide (PTMI), moderately-sized pyromelliticdiimide (PMDI) or naphthalenediimides (NDIs) to large perylenediimide (PDI); axial-group modifications; varied number of halogens, etc. on the halogen bonding and its self-assembly in a set of nine molecules. The structural modification leads to tunable optical as well as redox property. Gratifyingly, we realized single crystals of all the nine systems, which revealed Br∙∙∙O, Br∙∙∙Br or Br∙∙∙π halogen bonding interactions, with few systems capable of forming all the three-types. These interactions lead to halogen bonded rings (up to 12-membered), which propagate to form stacked 1D-, 2D- or corrugated sheets. We also identified few outliers, e.g. molecule which prefer C-H∙∙∙O hydrogen bonding over halogen bonding; or a non-centrosymmetric organization over the centrosymmetric ones. Computational studies based on Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) analysis provided
further insight into the halogen bonding interactions. This study can lead to a predictive design tool-box to further explore related systems on surfaces reinforced by these weak directional forces.
Chemistry - A European Journal 26(2020)46, 10607-10619
Benchmarking of Computational Fluid Dynamics Codes for Reactor Vessel Design
Computational Fluid Dynamics (CFD) codes have reached a level of maturity, at least for single-phase applications, to be utilized in the design process of Nuclear Power Plant (NPP) components, such that advanced NPPs over the past years have increasingly utilized CFD codes in their design. A recently completed Cooperative Research Project (CRP) addressed the application of CFD codes to the process of optimizing the design of components in Pressurized Water-cooled Reactors (PWRs). Following several initiatives within the IAEA where CFD codes have been applied to situations of interest in nuclear reactor technology, this CRP aimed to contribute to a consistent application of CFD codes by establishing a common platform to assess their capabilities and level of qualification.
Eleven participant organizations from nine Member States performed simulations against four “CFD-grade” experiments performed to investigate key phenomena for CFD simulations. Two are based on test data from the ROCOM (ROssendorf COolant Mixing) facility at HZDR in Germany, and another two are based on rod-bundle experiments in the OFEL (Omni Flow Experimental Loop) facility at KAERI in Korea.
This paper outlines the objectives of the CRP, provides a description of the test facilities and experiments, and discusses selected results obtained for the four above benchmark exercises.
Keywords: Computational Fluid Dynamics; Reactor Design; CFD benchmark
Wien: IAEA, 2020
Protecting-Group-Directed Diastereo- and Enantioselective Approach to Substituted Chiral Tetrahydropyrroloquinolines.
Chaudhari, T.; Mallampudi, N.; Bansal, D.; Mohapatra, D.; Tandon, V.
A novel synthetic method for chiral tricyclic tetrahydropyrroloquinolines following a protecting‐group‐directed domino reaction consisting of Michael addition and Mannich cyclization under mild reaction conditions was developed.
European Jounal of Organic Chemistry 18(2020), 2771-2780
Evaluation of tube size variations to improve resolution in tube-of-response based image reconstruction for ⁶⁸Ga PET
Ga68-labeled tracers like Ga68-PSMA or Ga68-DOTATOC play a relevant role in clinical PET, but the substantial positron range of Ga68 (mean/max range in water: 2.7/8 mm) deteriorates spatial resolution. Integration of isotope-specific resolution recovery into iterative reconstruction should therefore be considered. In our in-house PET image reconstruction – THOR – this is possible by adjusting the tube diameter in the used tube-of-response projector. We have, therefore, investigated the potential of tube diameter optimization on achievable image resolution for Ga68.
We performed measurements with a resolution phantom at three different target-to-background ratios (20:1, 10:1, 5:1) for F18 and Ga68, respectively (Philips Ingenuity-TF PET/MR). All measurements were reconstructed with the vendor reconstruction as well as with THOR using different tube diameters and voxel sizes (2mm, 4mm). Image resolution, noise level, and magnitude of Gibbs artifacts (GA) were derived. The optimal tube diameters for F18 and Ga68 were determined respectively and applied to exemplary clinical Ga68 PSMA data.
The vendor reconstruction yields a resolution (FWHM) of [6.7+/-0.2] mm for Ga68 which is ~10% worse than for F18 while THOR yielded [5.0+/-0.4] mm using the default – F18-optimized – tube size which is ~14% worse than for F18. Increasing the tube diameter in THOR by up to 30% is possible for Ga68 (but not for F18) without causing notable GAs. This improves the achieved resolution by ~8% to ~4.6 mm. This is only slightly worse than the THOR result for F18 and much better than the resolution achievable for Ga68 with the vendor reconstruction. First clinical examples also demonstrate the beneficial effects of an isotope-specific tube size, exhibiting visually superior image quality.
Our preliminary results indicate that an isotope-dependent tube diameter does improve image resolution for challenging isotopes like Ga-68 without introducing notable GAs that often plaque resolution recovery attempts.
Keywords: positron emission tomography; PET; Ga68; positron range; image reconstruction; tube-of-response; nuclear medicine
58. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 07.07.2020, Leipzig, Deutschland
Multi Geometry Critical Heat Flux Observation facility (MORENA): Investigation of Critical Heat Flux (CHF) at 3 K and 5 K subcooled flow boiling - Infrared thermography (IR) data set
Experiments have been conducted to investigate the boiling heat transfer and local development of Critical Heat Flux (CHF) at subcooled flow boiling in a heated vertical tube. This data set contains the raw and processed Infrared thermography (IR) data along with measured operational data of the experimental facility for 3 K and 5 K subcooled flow boiling.
Keywords: Critical Heat Flux (CHF); Subcooled flow boiling; Infrared thermography
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-14
Berührungslose induktive Strömungstomographie für Modelle des kontinuierlichen Stranggießens von Stahl
Das Stranggießen von Stahl ist mit 96% Marktanteil das weltweit wichtigste Verfahren zur Stahlherstellung. Im Gießprozess beeinflusst das Strömungsprofil in der Kokille entscheidend die Qualität des resultierenden Stahls. Um eine möglichst optimale Strömung zu erhalten, werden Aktuatoren eingesetzt, die die Strömung kontaktlos mithilfe der Lorentzkraft beeinflussen. Diese Aktuatoren würden auch eine Regelung der Strömung ermöglichen, wenn eine geeignete Messtechnik vorhanden wäre. Allerdings messen bisher verfügbare Messtechniken für heiße Schmelzen vor allem lokal in der Nähe der Randgebiete der Strömung und sind oft in ihrer zeitlichen Auflösung limitiert. Eine neue infrage kommende Messtechnik ist die berührungslose induktive Strömungstomographie (contactless inductive flow tomography, CIFT), die aus der gemessenen strömungsinduzierten Verzerrung eines angelegten Magnetfeldes die dreidimensionale Strömung rekonstruieren kann.
In dieser Arbeit wird anhand eines 1:8-Labormodells einer Stranggusskokille und numerischen Simulationen untersucht, ob CIFT bei Anlagen mit elektromagnetischen Bremsen eingesetzt werden kann. Besondere Herausforderungen entstehen aufgrund der Verzerrung des CIFT-Anregungsmagnetfeldes durch die ferromagnetische Bremse, der großen Dynamik von 6 Größenordnungen zwischen dem Magnetfeld der Bremse und dem strömungsinduzierten Magnetfeld sowie intrinsischen Strömungsoszillationen mit einer charakteristischen Frequenz im Bereich der üblicherweise verwendeten CIFT-Anregungsfrequenzen. Es wird dargelegt, dass sich CIFT in derartigen Aufbauten einsetzen lässt, wenn (a) eine geeignete Anregungsmagnetfeldstruktur erzeugt werden kann, (b) gradiometrische Induktionsspulen als Magnetfeldsensoren eingesetzt werden und (c) die Anregungsfrequenz in einem optimalen, schmalen Bereich gewählt wird. Diese Messungen werden erst durch in dieser Arbeit angefertigte theoretische und experimentell validierte Analysen der Induktionsspulen möglich, wofür Schwerpunkte auf deren Modellierung, Design und Messunsicherheit gelegt wurden. Außerdem werden für dieses Stranggussmodell erstmals experimentelle Ergebnisse mit horizontal anstatt vertikal orientierten Anregungsmagnetfeldern präsentiert.
Um die Skalierbarkeit von CIFT in Richtung industrieller Anlagen zu demonstrieren, werden zum einen neue Rekonstruktionen in einem heißen 1:2-Labormodell einer Kokille vorgestellt. Andererseits wird die in industriellen Kokillen typischerweise aufgebrachte ferromagnetische Nickelbeschichtung und ihre Auswirkung auf CIFT mit numerischen Simulationen quantifiziert. Diese Beschichtung stellt aufgrund ihrer zeitlich und räumlich schwankenden Permeabilität eines der größten Hindernisse für die Anwendung von CIFT im industriellen Stahlguss dar. Für dieses Szenario werden neue Anregungsgeometrien untersucht und erste Rekonstruktionen gezeigt.
Keywords: CIFT; contactless inductive flow tomography; kontinuierliches Stranggießen; magnetische Bremse
TU Dresden, 2020
Mentor: Prof. Dr.-Ing. Dr. h.c. habil. Uwe Hampel
Superconductivity with broken time-reversal symmetry inside a superconducting s-wave state
Grinenko, V.; Sarkar, R.; Kihou, K.; Lee, C. H.; Morozov, I.; Aswartham, S.; Büchner, B.; Chekhonin, P.; Skrotzki, W.; Nenkov, K.; Hühne, R.; Nielsch, K.; Drechsler, S.-L.; Vadimov, V. L.; Silaev, M. A.; Volkov, P. A.; Eremin, I.; Luetkens, H.; Klauss, H.-H.
In general, magnetism and superconductivity are antagonistic to each other. However, there are several families of superconductors in which superconductivity coexists with magnetism, and a few examples are known where the superconductivity itself induces spontaneous magnetism. The best known of these compounds are Sr2RuO4 and some non-centrosymmetric superconductors. Here, we report the finding of a narrow dome of an s + is' superconducting phase with apparent broken time-reversal symmetry (BTRS) inside the broad s-wave superconducting region of the centrosymmetric multiband superconductor Ba1−xKxFe2As2 (0.7 ≲ x ≲ 0.85). We observe spontaneous magnetic fields inside this dome using the muon spin relaxation (μSR) technique. Furthermore, our detailed specific heat study reveals that the BTRS dome appears very close to a change in the topology of the Fermi surface. With this, we experimentally demonstrate the likely emergence of a novel quantum state due to topological changes of the electronic system
Nature Physics 16(2020), 789-794
Femtosecond laser produced periodic plasma in a colloidal crystal probed by XFEL radiation
Mukharamova, N.; Lazarev, S.; Meijer, J.-M.; Gorobtsov, O. Y.; Singer, A.; Chollet, M.; Bussmann, M.; Dzhigaev, D.; Feng, Y.; Garten, M.; Huebl, A.; Kluge, T.; Kurta, R. P.; Lipp, V.; Santra, R. J.; Sikorski, M.; Song, S.; Williams, G.; Zhu, D.; Ziaja-Motyka, B.; Cowan, T. E.; Petukhov, A. V.; Vartanyants, I. A.
With the rapid development of short-pulse intense laser sources, studies of matter under extreme irradiation conditions enter further unexplored regimes. In addition, an application of X-ray Free-Electron Lasers (XFELs) delivering intense femtosecond X-ray pulses, allows to investigate sample evolution in IR pump - X-ray probe experiments with an unprecedented time resolution. Here we present a detailed study of the periodic plasma created from the colloidal crystal. Both experimental data and theory modeling show that the periodicity in the sample survives to a large extent the extreme excitation and shock wave propagation inside the colloidal crystal. This feature enables probing the excited crystal, using the powerful Bragg peak analysis, in contrast to the conventional studies of dense plasma created from bulk samples for which probing with Bragg diffraction technique is not possible. X-ray diffraction measurements of excited colloidal crystals may then lead towards a better understanding of matter phase transitions under extreme irradiation conditions.
Scientific Reports 10(2020), 10780
The fate of anthropogenic nanoparticles, nTiO2 and nCeO2, in waste water treatment
Lange, T.; Schneider, P.; Schymura, S.; Franke, K.
Wastewater treatment is one of the main end-of-life scenarios, as well as a possible reentry point into the environment, for anthropogenic nanoparticles (NP). These can be released from consumer products such as sunscreen or antibacterial clothing, from health-related applications or from manufacturing processes such as the use of polishing materials (nCeO2) or paints (nTiO2). The use of NP has dramatically increased over recent years and initial studies have examined the possibility of toxic or environmentally hazardous effects of these particles, as well as their behavior when released. This study focuses on the fate of nTiO2 and nCeO2 during the wastewater treatment process using lab scale wastewater treatment systems to simulate the NP mass flow in the wastewater treatment process. The feasibility of single particle mass spectroscopy (sp-ICP-MS) was tested to determine the NP load. The results show that nTiO2 and nCeO2 are adsorbed to at least 90 percent of the sludge. Furthermore, the results indicate that there are processes during the passage of the treatment system that lead to a modification of the NP shape in the effluent, as NP are observed to be partially smaller in effluent than in the added solution. This observation was made particularly for nCeO2 and might be due to dissolution processes or sedimentation of larger particles during the passage of the treatment system.
Keywords: synthetic nanoparticles; nTiO₂ and nCeO₂; waste water treatment; sp-ICP-MS nanoparticles tracking
Water 12(2020)9, 2509
Polarization tunability in multiferroic DyMn2O5: Influence of Y and Eu co-doping and 3d-4f exchange
Yang, L.; Wang, Changan; Zeng, M.; Hou, Z.; Fan, Z.; Chen, D.; Qin, M.; Lu, X.; Li, Q.; Gao, X.
Coupling effects among spin, charge, and lattice in a strongly correlated system are critical for next generation spintronic and data storage devices. However, the complex effects are elusive and difficult to distinguish their contributions to polarization modulation. Here we tailored the polarization by co-doping of non-magnetic Y and Eu at A-sites in DyMn2O5. The structure, specific heat, magnetism, and ferroelectricity of the polycrystalline Dy1-x(Eu0.24Y0.76)xMn2O5 ceramics were comprehensively explored. Interestingly, the co-doping does not cause lattice distortion of DyMn2O5, and all the ceramics are orthorhombic structures, while the independent Dy3+ spin order and the Dy3+-Mn3+ coupling can be suppressed. With increasing the co-doping content x, the spins related properties associated with the Dy3+-Mn4+-Dy3+ sub-lattice are progressively inhibited, while they keep less disturbance in the Mn3+-Mn4+-Mn3+ block. Moreover, the spin coupling of Dy3+-Mn3+ ions is stronger again the magnetic field than that of Dy3+-Mn3+. Our results enhance the understanding of ferrielectricity in DyMn2O5, and provide a method for controlling the polarization in the multiferroic manganite coexisting 3d and 4f elements.
Keywords: DyMn2O5; Multiferroicity; Ferrielectricity; Manganite
Solid State Communications 307(2020), 113809
Probing the local atomic structure of In and Cu in sphalerite by XAS spectroscopy enhanced by reverse Monte-Carlo algorithm
Trigub, A. L.; Trofimov, N. D.; Tagirov, B. R.; Nickolsky, M. S.; Kvashnina, K. O.
The distortion of the atomic structure around In and Cu atoms in sphalerite ZnS was explored by reverse Monte Carlo (RMC) method applied to the Extended x-ray absorption fine structure (EXAFS) interpretation. Parameters of the local atomic structure (interatomic distances) around dopants in synthetic In- and In-Cu-bearing sphalerites were determined by fitting In and Cu K-edge EXAFS spectra using evolutionary algorithm (EA) of the RMC method. These data were complemented with quantum chemical Density Functional Theory (DFT) calculations and theoretical modeling of XANES spectra. The RMC-EXAFS method showed that the three coordination shells of In-bearing sphalerite are characterized by almost symmetrical Gaussian type peaks, which shapes are close to the one of pure sphalerite. This shape of the peaks is characteristic of symmetrical undisturbed structural environment of In in the sphalerite solid solution which is formed via the charge compensation schemes 3Zn2+↔2In3++□, where □ is a Zn vacancy. However, in case of (In,Cu)-bearing sphalerites formation of solid solution state follows the charge compensation scheme 2Zn2+↔Cu++In3+. In this case some splitting of the RDF peaks are observed, the splitting rate correlates with impurities concentrations. In contrast to In, the local atomic structure around Cu is not symmetric. The 2nd coordination shell around Cu (which consists of 12 metal atoms) can be described by three distinct Gaussian contributions. This splitting of interatomic distances in the 2nd coordination shell points out on the significant distortion of the ZnS crystal structure around Cu. The theoretical calculation of Cu K-edge XANES based on the distorted structural environment near Cu provides better agreement with the experiment than the symmetrical atomic model. According to our DFT calculations, considerable splitting of the 2nd coordination shell (up to 0.1 Å for Cu) occurs in the case of close positions of the impurity atoms or the Zn vacancy. The DFT calculations showed that the geometries with the close arrangement (clustering) of the impurities – In and Cu atoms, or the In atom and a vacancy, are energetically more favorable than the random distribution of the defects. However, as no heavy In atoms were detected in the 2nd shell of Cu, and the 2nd shell of In is almost undisturbed, we conclude that the defects are distributed randomly (or at least not close to each other). The disagreement of RMC-EXAFS fittings with results of DFT calculations, according to which the closest arrangement of dopants is the most stable configuration, can be explained by the presence of other defects of the sphalerite crystal lattice which were not considered in the DFT calculations.
Minerals 10(2020)10, 841
Modelling thermal-hydraulic effects of zinc borate deposits in the PWR core after LOCA - Experimental strategies and test facilities
The German software tool ATHLET (Analysis of THermohydraulics of Leaks and Transients) is continuously being developed for the simulation of the nuclear power plant behaviour in the event of transients and accidents. The focus of a current joint research project named „ATHLET Modul Zinkborat“ (AZora) is the development and validation of an ATHLET module on the basis of the current state of research on chemical long-term effects according to PWR LOCA. The module is intended to simulate thermohydraulic effects of zinc borate precipitations in the reactor core originating from long-term corrosion processes in the reactor sump during sump recirculation operation after postulated loss-of-coolant accidents in PWR. To develop and validate the sub-models, generic experiments at lab-scale as well as at semi-technical scale are planned to be carried out in unique test facilities. The structure of the module as well as the experimental strategies and the related facilities are described in the article.
Keywords: loss-of-coolant accident; LOCA; pressurized water reactor; nuclear safety research; zinc borate; corrosion; simulation; chemical effects
- atw - International Journal for Nuclear Power 65(2020)6/7, 341-345
- Secondary publication expected from 09.07.2021
Numerical simulations of short-circuits appearance in liquid metal batteries
The mid-term report gives an overview on S. Bénards work at HZDR concerning local short-circuits in liquid metal batteries.
Paris: École normale supérieure Paris-Saclay, 2020
Microfocus X-ray tomography data set of boiling flow in vertical rod bundle with spacer grid at constant heat flux condition
The test section of the rod bundle experimental facility at HZDR consists of a vertically aligned PMMA channel with an upward flow of the working fluid. The cross-section of the channel is quadratic (inner edge length: 37 mm) and contains nine directly electrically heated rods (material: titanium-alloy, diameter: 10 mm, wall thickness: 0.3 mm) which are arranged in an orthogonal 3 by 3 matrix (rod axis distance: 12.8 mm). Circa 190 mm downstream of the start of the heating zone a 30 mm long spacer for the rods with tilted flow guiding vanes is mounted. These vanes are aimed to increase lateral flow velocities within the subchannels. Working fluid was octafluorocyclobutane (CAS 115-25-3, RC318). The experimental facility is comprehensively instrumented for measurement of flow, temperature and pressure/pressure difference. For non-invasive three-dimensional high-resolution measurement of a temporally averaged volumetric void fraction within the working fluid flowing around the heating rods in the subchannels an X-ray computer tomography measurement system was set up.
The presented dataset contains measurement data of the experimental facility's instrumentation and tomographic void fraction data of experiments with four different configurations of the flow guiding vanes (without vanes, 20°, 29°, 40°) for four different flow velocities between 0.4 m/s and 1.3 m/s at a heat flow density of 85.7 kW/m².
Keywords: X-Ray Computed Tomography; Phase fraction; Rod bundle; Boiling flow
Reseach data in the HZDR data repository RODARE
Publication date: 2020-07-08
Validierung eines Open-source-Modells für die Simulation von PEM-Brennstoffzellen und Anwendung auf eine luftatmende Brennstoffzelle
Die vorliegende Arbeit beschäftigt sich mit der dreidimensionalen und mehrphasigen CFD-Simulation von PEM-Brennstoffzellen. Dabei wird die Validierung eines in OpenFOAM implementierten Modells zur Gesamtzellensimulation anhand von drei, von verschiedenen Forschungsgruppen vorgestellten, Experimenten durchgeführt.
Aufbauend auf der Modellvalidierung wird die Anwendbarkeit des Modells auf eine luft-atmende Brennstoffzelle überprüft. In diesem Zusammenhang wird der Einfluss der Orientierung auf die Transportprozesse in einer luftatmenden Brennstoffzelle mit zylindrischer Form untersucht. Dafür wird sowohl die Brennstoffzelle, als auch deren Umgebung beachtet. Die bei variierender Orientierung auftretenden Unterschiede von Naturkonvektion, Temperatur und Massenverteilung von Wasser und Sauerstoff werden dargestellt und diskutiert. Zusätzlich wird auf die Grenzen des verwendeten Modells und mögliche Verbesserungen hingewiesen.
TU Dresden, 2020
Heavy ion irradiation damage in Zr3(Al0.9Si0.1)C2 MAX phase
Qarra, H. H.; Knowles, K. M.; Vickers, M. E.; Zapata-Solvas, E.; Akhmadaliev, S.
A Zr3(Al0.9Si0.1)C2 MAX phase-based ceramic with 22 wt.% ZrC and 10 wt.% Zr5Si3 has been irradiated with 52 MeV I9+ ions at room temperature, achieving a maximum dose of 8 displacements per atom (dpa). The response of this MAX phase-rich material to irradiation has been studied using scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. Post-irradiation examination of the material revealed a number of crystalline changes to the MAX phase. At low doses, Zr3(Al0.9Si0.1)C2 maintained a high degree of crystallinity, while at the highest doses, its degree of crystallinity was reduced significantly. A number of radiation-induced phase transformations were observed, including the decomposition of Zr3(Al0.9Si0.1)C2 into ZrC and other phases, and the formation of β-Zr3(Al,Si)C2, a MAX phase with a rearranged stacking sequence. Microstructural examination revealed that the majority of the extended defects in Zr3(Al0.9Si0.1)C2 lie in the (0001) basal planes. Analysis of X-ray diffraction profiles after heat treating the 8 dpa-irradiated material for 1 h at 300 °C and at 600 °C showed that there were only subtle changes to the profiles relative to that of the 8 dpa-irradiated material which had not been heat treated. Overall, the experimental results of this study show that the Zr3(Al0.9Si0.1)C2 MAX phase responds less well to irradiation relative to other MAX phases irradiated with high energy heavy ions at room temperature.
Journal of Nuclear Materials 540(2020), 152360
Two types of alternating spin-1/2 chains and their field-induced transitions in ε-LiVOPO4
Mukharjee, P. K.; Ranjith, K. M.; Baenitz, M.; Scurschii, I.; Tsirlin, A. A.; Nath, R.
Thermodynamic properties, 31P nuclear magnetic resonance (NMR) measurements, and density-functional band-structure calculations for ε-LiVOPO4 are reported. This quantum magnet features a singlet ground state and comprises two types of alternating spin-1/2 chains that manifest themselves by the double maxima in the susceptibility and magnetic specific heat, and by the two-step magnetization process with an intermediate 1/2-plateau. From thermodynamic data and band-structure calculations, we estimate the leading couplings of J1 ≃ 20 K and J2 ≃ 60 K and the alternation ratios of α1 = J’1/J1 ≃ 0.6 and α2 = J’2/J2 ≃ 0.3 within the two chains, respectively. The zero-field spin gap Δ0/kB ≃ 7.3 K probed by thermodynamic and NMR measurements is caused by the J1-J’1 spin chains and can be closed in the applied field of μ0Hc1 ≃ 5.6 T, giving rise to a field-induced long-range order. The NMR data reveal predominant three-dimensional spin-spin correlations at low temperatures. Field-induced magnetic ordering transition observed above Hc1 is attributed to the Bose-Einstein condensation of triplons in the sublattice formed by the J1-J’1 chains with weaker exchange couplings.
Physical Review B 101(2020), 224403
Polar structure formation in solid solution of strontium substituted fluorapatite-gelatin composites: from structural and morphogenetic aspects to pyroelectric properties
Knaus, J.; Sommer, M.; Duchstein, P.; Gumeniuk, R.; Akselrud, L. G.; Sturm, S.; Auffermann, G.-D.; Hennig, C.; Zahn, D.; Hulliger, J.; Sturm, E. V.
Strontium substituted apatite-(CaF)-gelatin composites have been synthesized within a gelatin gel using the dou-ble diffusion technique. All experimental parameters were kept constant while systematically varying the strontium/ calcium molar ratio in solution. The effect of the presence of strontium ions in the growth solution on composition, morphogenesis and morphology as well as pyroelectric properties of synthetic aggregates was systemically analyzed. It was shown that stron-tium ions significantly inhibit the growth process of composite aggregates and increase growth anisotropy along , which were also confirmed and explained by molecular dynamic simulations. Furthermore, it was observed the promotion of the crystal branching processes and spherulite formation. Pyroelectric microscopy (SPEM) measurements on mixed substi-tuted apatite-(CaSrF)-gelatin composite aggregates showed an increase in polar properties, suggesting a lowering of the crys-tal symmetry. This was verified by Rietveld refinement of synchrotron pXRD, which revealed the non-centrosymmetric P63apatite crystal structure. These data could shed new light on understanding piezoelectric and pyroelectric properties of apa-tite based biological hard tissues.
Chemistry of Materials 32(2020)19, 8619-8632
ROBL-II at ESRF: A synchrotron toolbox for actinide research
Scheinost, A.; Claußner, J.; Exner, J.; Feig, M.; Findeisen, S.; Hennig, C.; Kvashnina, K.; Naudet, D.; Prieur, D.; Roßberg, A.; Schmidt, M.; Qiu, C.; Colomp, P.; Cohen, C.; Dettona, E.; Dyadkin, V.; Stumpf, T.
ROBL-II provides four different experimental stations to investigate actinide and other alpha- and beta-emitting radionuclides at the new EBS storage ring of ESRF within an energy range of 3 to 35 keV. The XAFS station consists of a highly automatized, high sample throughput installation in a glovebox, to measure EXAFS and conventional XANES of samples routinely at temperatures down to 10 K, and with a detection limit in the sub-ppm range. The XES station with its 5 bent-crystal analyzer, Johann-type setup with Rowland circles of 1.0 and 0.5 m radii provides high-energy resolution fluorescence detection (HERFD) for XANES, XES, and RIXS measurements, covering both actinide L and M edges together with other elements accessible in the 3 to 20 keV energy range. The 6-circle heavy duty goniometer of XRD-1 is equipped for both high-resolution powder diffraction as well as surface-sensitive CTR and RAXR techniques. Single crystal diffraction, powder diffraction with high temporal resolution, as well as X-ray tomography experiments can be performed at a Pilatus 2M detector stage. Elaborate radioprotection features enable a safe and easy exchange of samples between the four different stations to allow the combination of several methods for an unprecedented level of information on radioactive samples for both fundamental and applied actinide and environmental research.
Keywords: XAFS; XANES; XES; XRD; RIXS; RAXR; CTR; actinides
Journal of Synchrotron Radiation 28(2021), 333-349
Scanning transmission imaging in the helium ion microscope with a position-sensitive detector
The helium ion microscope (HIM) is an instrument for high-resolution imaging, nanofabrication, composition analysis, and material modification at the nanometer scale . The npSCOPE instrument is a unique HIM prototype with three special add-ons, namely: secondary ion mass spectroscopy (SIMS), cryo-microscopy, and scanning transmission helium ion microscopy (STHIM).
In this work, we focus on STHIM. Our STHIM detection system is based on a position- and time-sensitive detector comprising a microchannel plate and a delay line readout structure. A dedicated software interface for data acquisition and post-processing allows the reconstruction of images for selected scattering directions, and the visualization of different contrast regimes for a given sample. Using STHIM, we analyzed material contrast for layered films of various thicknesses and materials. Channeling contrast in transmission for poly- and single-crystalline materials is also detected. In the case of biological samples, STHIM provides a way of identifying sub-surfaces structures that can help to localize nanomaterials for toxicology studies, as shown in Figure 1.
Keywords: Helium Ion Microscopy; Scanning transmission ion microscopy
CMD2020GEFES, 31.08.-04.09.2020, Madrid, España
Virtual Early Career European Microscopy Congress 2020, 24.-26.11.2020, København, Danmark
Developments in nuclear medicine – new radioisotopes in use and associated challenges: proceedings of a scientific seminar held in Luxembourg on 13 November 2019
The European Commission organises every year, in cooperation with the Group of Experts referred to in Article 31 of the Euratom Treaty, a scientific seminar on emerging issues in radiation protection – generally addressing new research findings with potential policy and/or regulatory implications. Leading scientists are invited to present the status of scientific knowledge in the selected topic.
Based on the outcome of the scientific seminar, the Group of Experts referred to in Article 31 of the Euratom Treaty may recommend research, regulatory or legislative initiatives. The European Commission takes into account the conclusions of the Experts when setting up its radiation protection programme. The Experts' conclusions are valuable input to the process of reviewing and potentially revising European radiation protection legislation.
Keywords: Conference proceedings; Energy research; Nuclear accident; Nuclear medicine; Public health; Radiation exposure; Radiation protection
Contribution to proceedings
EU Scientific Seminar November 2019, 13.11.2019, Luxembourg, Luxembourg
Proceedings of EU Scientific Seminar November 2019, 978-92-76-27010-2
Direct Characterisation of Solute Transport inUnsaturated Porous Media using 4D X-raySynchrotron Microtomography
Sharul, H.; Vahid, J.-N.; Nikolaos, K. K.; Da Assuncao Godinho, J. R.; Nghia, T. V.; Senyou, A.; Arash, A.; Holger, S.
Solute transport in unsaturated porous materials is a complex pro-cess, which exhibits some distinct features differentiating it fromtransport under saturated conditions. These features emerge mostlydue to the different transport time scales at different regions of theflow network, which can be classified into flowing and stagnantregions, predominantly controlled by advection and diffusion, re-spectively. Under unsaturated conditions, the solute breakthroughcurves show early arrivals and very long tails, and this type of trans-port is usually referred to as non-Fickian. This is the first studywhich directly characterise transport through an unsaturated porousmedium in three spatial dimensions at the resolution of 3.25μm andthe time resolution of 6s. Using advanced high-speed, high spa-tial resolution, synchrotron-based X-Ray Computed Microtomogra-phy (sCT) we obtained the first detailed information on solute trans-port through a glass-bead packing at different saturations. A largeexperimental dataset (>50TB) was produced, while imaging the evo-lution of the solute concentration with time at any given point withinthe field of view. We show that the fluids’ topology has a critical sig-nature on the non-Fickian transport, which has not been addressedin the theories of transport through unsaturated porous media. Wedemonstrate that the "fully-mixing" assumption at pore scale is notvalid, due to the significant impact of the no-slip boundary of thesolid walls. Results demonstrate that dispersivity, as a major trans-port parameter, is changing with saturation, being two-fold larger atsmaller saturations compared to that at high saturations.
Keywords: contaminant transport; X-ray microtomography; stagnant saturation; non-Fickian transport; unsaturated flow
Proceedings of the National Academy of Sciences of the United States of America 117(2020)38, 23443-2344
Magnetization dynamics and mutual spin-pumping in SAFs
Some of the file are auxiliary or analisys files for faster display of the main results (like .opj, .ods files). Main raw data files are in the archives.
Keywords: Magnetization dynamics; Spin-pumping; SAFs, SAF; synthetic antiferromagnets; coupled magnetic trilayers; magnetic multilayers; ferromagnetic resonance; electrically-detected ferromagnetic resonance; FMR; ED-FMR; ST-FMR
- Magnetization dynamics in synthetic antiferromagnets: the … (Id 30089) is supplemented by this (Id 31295) publication
Reseach data in the HZDR data repository RODARE
Publication date: 2019-12-09
The influence of an applied magnetic field on the self-assembly of magnetic nanogels
Using Langevin dynamics simulations, we investigate the self-assembly of magnetic nanogels in the presence of applied magnetic fields of moderate strength. We find that even weak fields lead to drastic changes in the structure factors of both, the embedded magnetic nanoparticles and of whole nanogel particles. Nanogels assemble by uniting magnetic particle clusters forming inter-gel bridges. At zero field the average amount of such bridges for a pair of nanogels is close to one, whereas even for weak fields it fastly doubles. Rapid growth of cluster size at low values of the applied field is followed by a broad region of slow increase, caused by the mechanical constraints imposed the polymer matrix. The influence of the latter manifests itself in both, the slow growth of the magnetisation curve at intermediate fields and the slow decay of the total Zeeman energy.
Keywords: Magnetic nanogels; Self-assembly; Molecular dynamics
Journal of Molecular Liquids 307(2020), 112902
Contribution to WWW
arXiv:2004.00725 [cond-mat.soft]: https://arxiv.org/abs/2004.00725
- Secondary publication expected from 01.06.2021
Diffusion of single active-dipolar cubes in applied fields
“Active matter” refers to a class of out-of-equilibrium systems whose ability to transform environmental energy to kinetic energy is sought after in multiple fields of science and at very different length scales. At microscopic scales, an important challenge lies in overpowering the particles reorientation due to thermal fluctuations, especially in nano-sized systems, to create non-random, directed motion, needed for a wide range of possible applications. In this article, we employ molecular dynamics simulations to show that the diffusion of a self-propelling dipolar nanocube can be enhanced in a pre-defined direction with the help of a moderately strong applied magnetic field, overruling the effect of the thermal fluctuations. Furthermore, we show that the direction of diffusion is given by the orientation of the net internal magnetisation of the cube. This can be used to determine experimentally the latter in synthetically crafted active cobalt ferrite nanocubes.
Keywords: Active matter; Magnetic cubes; Molecular dynamics
Journal of Molecular Liquids 304(2020), 112688
Contribution to WWW
arXiv:2002.04299 [cond-mat.soft]: https://arxiv.org/abs/2002.04299
Measuring FORCs diagrams in computer simulations as a mean to gain microscopic insight
FORCs (first-order reversal curves) diagrams prove to be an efficient experimental technique to investigate magnetic interactions in complex systems. In experiments, as a rule, it is difficult to relate actual microstructural changes to the evolution of FORCs diagrams. Here, using Molecular Dynamics simulations, we calculate FORCs for two simple models of a magnetic elastomer. The simplicity of these models allows to relate directly both, the rigidity of the matrix and the magnetoelastic coupling to the shape and intensity of FORCs diagrams.
Keywords: FORC Molecular dynamics; Magnetic elastomers; Magneto-elastic coupling
Journal of Magnetism and Magnetic Materials 501(2020), 166393
- Secondary publication expected from 01.05.2021
Unknotting of quasi-two-dimensional ferrogranular networks by in-plane homogeneous magnetic fields
Our ongoing research addresses, by means of experiments and computer simulations, the aggregation process that takes place in a shaken granular mixture of glass and magnetized ferrous alloy beads when the shaking amplitude is suddenly decreased. After this quenching, the magnetized beads form a transient network that coarsens in time into compact clusters, following a viscoelastic phase separation. Here we focus on the quasi-two-dimensional case, analyzing in computer simulations the effects of a magnetic field parallel to the system plane. Our results evidence that the field drastically changes the structure of the forming network: chains and elongated clusters parallel to the field are favored whereas perpendicular connecting structures tend to be suppressed, leading to the unknotting of the networks which are observed at zero field. Importantly, we found that moderate field strengths lead to the formation of larger clusters at intermediate time intervals than in the case of weak and strong fields. Moreover, the latter tend to limit the overall growth of the clusters at longer time scales. These results may be relevant in different systems governed by similar magnetically driven aggregation processes as, for example, in the formation of iron-rich planetesimals in protoplanetary discs or for magnetic separation systems.
Keywords: Ferrogranulate mixture; Field induced network unknotting; Susceptible dipolar hard spheres; Langevin dynamics simulations; Viscoelastic phase separation; Transient network
Journal of Magnetism and Magnetic Materials 499(2020), 166182
Contribution to WWW
arXiv:1910.00317 [cond-mat.soft]: https://arxiv.org/abs/1910.00317
The influence of crosslinkers and magnetic particle distribution along the filament backbone on the magnetic properties of supracolloidal linear polymer-like chains
Diverse polymer crosslinking techniques allow the synthesis of linear polymer-like structures whose monomers are colloidal particles. In the case where all or part of these colloidal particles are magnetic, one can control the behaviour of these supracolloidal polymers, known as magnetic filaments (MFs), by applied magnetic fields. However, the response of MFs strongly depends on the crosslinking procedure. In the present study, we employ Langevin dynamics simulations to investigate the influence of the type of crosslinking and the distribution of magnetic particles within MFs on their response to an external magnetic field. We found that if the rotation of the dipole moment of particles is not coupled to the backbone of the filament, the impact of the magnetic content is strongly decreased.
Keywords: Supracolloidal magnetic polymers; Magnetisation; Crosslinking methods; Langevin dynamics simulations
Journal of Magnetism and Magnetic Materials 497(2020), 166029
Contribution to WWW
arXiv:1910.11607 [cond-mat.soft]: https://arxiv.org/abs/1910.11607
Suspensions of magnetic nanogels at zero field: Equilibrium structural properties
Magnetic nanogels represent a cutting edge of magnetic soft matter research due to their numerous potential applications. Here, using Langevin dynamics simulations, we analyse the influence of magnetic nanogel concentration and embedded magnetic particle interactions on the self-assembly of magnetic nanogels at zero field. For this, we calculated radial distribution functions and structure factors for nanogels and magnetic particles within them. We found that, in comparison to suspensions of free magnetic nanoparticles, where the self-assembly is already observed if the interparticle interaction strength exceeds the thermal fluctuations by approximately a factor of three, self-assembly of magnetic nanogels only takes place by increasing such ratio above six. This magnetic nanogel self-assembly is realised by means of favourable close contacts between magnetic nanoparticles from different nanogels. It turns out that for high values of interparticle interactions, corresponding to the formation of internal rings in isolated nanogels, in their suspensions larger magnetic particle clusters with lower elastic penalty can be formed by involving different nanogels. Finally, we show that when the self-assembly of these nanogels takes place, it has a drastic effect on the structural properties even if the volume fraction of magnetic nanoparticles is low.
Keywords: Magnetic nanogels; Magnetic self-assembly; Langevin dynamics; Structure factor
Journal of Magnetism and Magnetic Materials 498(2020), 166152
Contribution to WWW
arXiv:1911.06031 [cond-mat.soft]: https://arxiv.org/abs/1911.06031v1
The structure of clusters formed by Stockmayer supracolloidalmagnetic polymers
Unlike Stockmayer fluids, that prove to undergo gas-liquid transition on cooling, the system of dipolar hard or soft spheres without any additional central attraction so far has not been shown to have a critical point. Instead, in the latter, one observes diverse self-assembly scenarios. Crosslinking dipolar soft spheres into supracolloidal magnetic polymer-like structures (SMPs) changes the self-assembly behaviour. Moreover, aggregation in systems of SMPs strongly depends on the constituent topology. For Y- and X-shaped SMPs, under the same conditions in which dipolar hard spheres would form chains, the formation of very large loose gel-like clusters was observed (E. Novak et al., J. Mol. Liq. 271, 631 (2018)). In this work, using molecular dynamics simulations, we investigate the self-assembly in suspensions of four topologically different SMPs --chains, rings, X and Y-- whose monomers interact via Stockmayer potential. As expected, compact drop-like clusters are formed by SMPs in all cases if the central isotropic attraction is introduced, however, their shape and internal structure turn out to depend on the SMPs topology.
European Physical Journal E 42(2019), 158
- Final Draft PDF 634 kB Secondary publication
Particle Surfaces to Study Macrophage Adherence, Migration, and Clearance
Septiadi, D.; Lee, A.; Spuch‐Calvar, M.; Lee, M. T.; Spiaggia, G.; Abdussalam, W.; Rodriguez‐Lorenzo, L.; Taladriz‐Blanco, P.; Rothen‐Rutishauser, B.; Petri‐Fink, A.
Nanoparticle adsorption to substrates pose a unique challenge to understand uptake mechanisms as it involves the organization of complex cytoskeletal components by cells to perform endocytosis/phagocytosis. In particular, it is not well‐understood from a cell mechanics perspective how the adhesion of particles on substrate will influence the ease of material clearance. By using a particle model, key contributing factors underlying cell adhesion on nonporous silica particle surfaces, migration and engulfment, are simulated and studied. Following a 24 h incubation period, monocyte‐derived macrophages and A549 epithelial cells are able to adhere and remove particles in their local vicinity through induction of adhesive pulling arise from cell traction forces and phagocytic/endocytic mechanisms, in a size‐dependent manner. It is observed that such particle‐decorated surfaces can be used to address the influence of surface topography on cell behavior. Substrates which presented 480 nm silica particles are able to induce greater development and maturation of focal adhesions, which play an important role in cellular mechanoregulation. Moreover, under a chemotactic influence, in the presence of 30% fetal bovine serum, macrophages are able to uptake the particles and be directed to translocate along a concentration gradient, indicating that local mechanical effects do not substantially impair normal physiological functions.
Advanced Functional Materials 30(2020)34, 2002630
Atomistic simulation of PDADMAC/PSS oligoelectrolyte multilayers: overall comparison of tri- and tetra-layer systems
By employing large-scale molecular dynamics simulations of atomistically resolved oligoelectrolytes in aqueous solutions, we study in detail the first four layer-by-layer deposition cycles of an oligoelectrolyte multilayer made of poly(diallyl dimethyl ammonium chloride)/poly(styrene sulfonate sodium salt) (PDADMAC/PSS). The multilayers are grown on a silica substrate in 0.1 M NaCl electrolyte solutions and the swollen structures are then subsequently exposed to varying added salt concentration. We investigated the microscopic properties of the films, analyzing in detail the differences between three- and four-layer systems. Our simulations provide insights into the early stages of growth of a multilayer, which are particularly challenging for experimental observations. We found rather strong complexation of the oligoelectrolytes, with fuzzy layering of the film structure. The main charge compensation mechanism is for all cases intrinsic, whereas extrinsic compensation is relatively enhanced for the layer of the last deposition cycle. In addition, we quantified other fundamental observables of these systems, such as the film thickness, water uptake, and overcharge fractions for each deposition layer.
Soft Matter 15(2019), 9437-9451
- Final Draft PDF 3,2 MB Secondary publication
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