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41396 Publications

Carbon monoxide-releasing molecules for biomedicinal applications

Kubeil, M.; Geri, S.; Mamat, C.; Stephan, H.

Carbon monoxide has been demonstrated to exhibit several beneficial effects on biological targets (anti-inflammatory, anti-proliferative, anti-apoptotic effects, causes vasodilation, etc.).1 Consequently, the development of CO releasing molecules (CORMs), that allows for controlled release of CO under physiological conditions, has therefore become a major field of scientific and medical interest.2,3 Considerable research interest has been drawn on light-activated CORMs (photoCORMs) which only release CO upon radiation with a certain energy. However, despite a large number of photoCORMs reported, relatively little information is available on the precise mechanism of CO release from most photoCORMs and even less compounds have been tested as anti-cancer agents in cells so far.
Herein, we report about the synthesis of ruthenium(II) dicarbonyl complexes functionalized with bidentate or tridentate (pyridyl, phenanthroline or diquinolyl) ligands and appending dyes for tuning the release properties as well as tracking the compound in cells. The mechanism of CO release in aqueous media (before and after light-activation) has been investigated. The photo-induced CO release kinetics of the Ru(II) photoCORMs, as well as in vitro studies in cancerous and healthy cell lines will be presented.4,5

References

[1] R. Motterlini, L. E. Otterbein, Nat. Rev. Drug Discov. 9 (2010) 728-743.
[2] U. Schatzschneider, Br. J. Pharmacol. 172 (2015) 1638-1650.
[3] F. Zobi, Future Med. Chem. (2013) 5, 175-188.
[4] M. Kubeil, R. R. Vernooij, C. Kubeil, B. R. Wood, B. Graham, H. Stephan, L. Spiccia, Inorg. Chem. 56 (2017) 5941-5952.
[5] M. Kubeil, T. Joshi, B. R. Wood, H. Stephan, ChemistryOpen (2019) 8, 637-642.

Acknowledgements

MK was supported by a Marie Curie International Outgoing Fellowship from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 627113.

Keywords: CORM; photoactivatable; ruthenium; in vitro studies

  • Lecture (Conference)
    3rd International Caparica Christmas Conference on Translational Chemistry, 01.-05.12.2019, Caparica, Lisboa, Portugal

Permalink: https://www.hzdr.de/publications/Publ-30115
Publ.-Id: 30115


Simulation and economic assessment of a small ammonia production plant using electricity purchased in the day-ahead market

Rodriguez Garcia, G.; Bergander, S.; Hampel, U.

Ammonia is one of the most highly produced chemicals in the world, being the source of all nitrogen-based fertilizers. Its conventional production relies on fossil fuels reforming as its source of hydrogen, cryogenic air separation for nitrogen, and the Haber-Bosch process for the ammonia synthesis itself. This route has made ammonia production responsible for the consumption of 1% of all energy worldwide, and for the emissions of 298 Mt CO2 eq./year. In a future where most energy comes from fluctuating sources, such as the one envisioned in the Energiewende, energy intensive industries like ammonia production would need to adapt its operation to mimic that of energy generation. A potential alternative for ammonia production is to obtain hydrogen and nitrogen from water electrolysis, and pressure swing adsorption (PSA) respectively. In our effort for the flexibilization of the chemical industry, we have designed a small ammonia production plant using these technologies. With it we intend to cover the fertilizing needs of a large German farm (1,000 ha), requiring a minimum production of 100 t NH3/year. As a first step, we purchased the electricity used for the water electrolyzer in the day-ahead market. The rest of the plant relied on a steady industrial supply. Our first results indicated the plant was not profitable. The main reason behind this are the capital investment in the intermediate hydrogen storage unit

  • Contribution to proceedings
    Oberlausitzer Energiesymposyum & Zittauer Energieseminar, 07.-08.11.2019, Zittau, Deutschland
    Sektorkopplung - eine Herausforderung, Zittau: Hochschule Zittau/Görlitz, 978-3-00-064125-1, 49-53

Permalink: https://www.hzdr.de/publications/Publ-30114
Publ.-Id: 30114


Correlative microscopy of lung epithelial in vitro model exposed to nanoparticles by using super-resolution optical and advanced ion/electron based techniques

Podlipec, R.; Klingner, N.; Heller, R.; Majaron, H.; Pelicon, P.; Strancar, J.; Borany, J.

Clear understanding of molecular events followed by lung epithelial cells/tissue response to inhaled nanoparticles is still lacking. As these interaction events in lungs eventually lead to diseases and potentially persistent inflammation [1,2], one urgently needs new and relevant investigation methods which could provide new insights into the key mechanisms of interaction. In our latest research we have thus focused on this toxicology problem first by developing an appropriate in vitro lung epithelial model and second by developing and implementing relevant advanced correlative imaging techniques capable of gathering more insight of interaction properties on scales well below optical resolution limit. In order to understand the mechanisms of molecular initiative events we have first performed live cell imaging using STED super-resolution microscopy by which few tens to hundred nm resolution was achieved locally. As the technique is incapable of providing resolution further down to nm and lacks the visualization of non-labeled surrounding structures and morphology, we thus introduced suitable complementary correlative microscopy techniques with high surface contrast, SEM and Helium Ion Microscopy (HIM). Main focus, besides sample and sample holder preparation for these high vacuum techniques, was dedicated to HIM measurements which in general are capable of providing better resolution and sensitivity compared to SEM [3]. From this ongoing study we briefly present the first interesting results of correlative microscopy combining optical, electron and ion based techniques on the epithelial cells exposed to TiO2 nanoparticles from micro to nano scale.
References:
1. Li, X., Jin, L. & Kan, H. Air pollution: a global problem needs local fixes. Nature 570, 437–439 (2019).
2. Underwood, E. The polluted brain. Science 355, 342–345 (2017).
3. Hlawacek, G. et Al. Helium Ion Microscopy. J. Vac. Sci. Technol. 32, (2014)

Keywords: Correlative microscopy; optical microscopy; helium ion microscopy; lung epithelium; in-vitro model; TiO2 nanoparticles

Related publications

  • Lecture (Conference)
    COMULIS & BioImaging Austria - CMI Conference 2019, Correlated Multimodal Imaging, 21.-22.11.2019, Vienna, Austria
  • Poster
    COMULIS & BioImaging Austria - CMI Conference 2019, 21.-22.11.2019, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-30111
Publ.-Id: 30111


Towards correlative live-cell imaging using super-resolution optical and ion/electron based techniques and development of special holders

Podlipec, R.; Sebastijanovic, A.; Vogel Mikus, K.; Pelicon, P.; Strancar, J.

Clear understanding of molecular phenomena of cells/tissue response after interacting with dangerous metal nanoparticles is still lacking. In our research we thus focus on highly relevant scientific/toxicology problem, which is understanding of the mechanisms of molecular initiative events between nanoparticles (typically smaller than 100 nm) and lung tissue cells during inhalation [1]. It is strongly believed that nanoparticles can trigger toxic effects with increasing risk for further cardiovascular diseases [2]. However, limited spatial resolution of optical microscopy, even in super-resolution mode, prevents visualization of interaction phenomena at smaller, nanometer scales which could reveal some of still unclear molecular events. In order to get better insight on the phenomena at such small scales one needs to introduce proper correlative microscopy techniques which in our case are electron (eSEM) and ion based (PIXE, HIM). Since these techniques are commonly employed in high vacuum and detection principles differ reasonably in comparison to optical imaging techniques, special sample holders have to be developed in order to perform efficient correlative microscopy on different submicron scales.
In this pilot study we first tested the performance of correlative microscopy on epithelial cells nebulized with TiO2 nanoparticles using optical, eSEM and RISE techniques, while in the second pilot study we developed the concept for robust special holder preparation in order to enable super-resolution optical imaging (STED) as well as ion based imaging on the same sample site. Despite integrating few to few tens micron sized layers consisting of Mylar foil, water and glass which introduce refractive index mismatches, we were able to improve confocal resolution by at least factor 2-3 using STED imaging. This was a proof-of-concept that we can perform high resolution optical imaging on these holders which can successfully be implemented as well in correlative electron/ion based imaging, thus giving the opportunity to gain better insight of the measured complex samples from nano to micro scale.

[1] Iztok Urbančič et al., “Nanoparticles Can Wrap Epithelial Cell Membranes and Relocate Them Across the Epithelial Cell Layer,” Nano Letters 18, 5294–5305.
[2] Robert D. Brook et al., “Air Pollution and Cardiovascular Disease: A Statement for Healthcare Professionals From the Expert Panel on Population and Prevention Science of the American Heart Association,” Circulation 109, 2655–2671

Keywords: Correlative microscopy; sammple holder; STED imaging; SEM; Helium Ion Microscopy; TiO2 nanoparticles; epithelial cells

Related publications

  • Lecture (Conference)
    89th IUVSTA Workshop, Biological and soft matter sample preparation for high resolution imaging by high vacuum techniques, 19.-24.05.2019, Zakopane, Poland
  • Poster
    89th IUVSTA Workshop, Biological and soft matter sample preparation for high resolution imaging by high vacuum techniques, 19.-24.05.2019, Zakopane, Poland

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Permalink: https://www.hzdr.de/publications/Publ-30110
Publ.-Id: 30110


Deep Learning Ensemble for Hyperspectral Image Classification

Chen, Y.; Wang, Y.; Gu, Y.; He, X.; Ghamisi, P.; Jia, X.

Deep learning models, especially deep convolutional neural networks (CNNs), have been intensively investigated for hyperspectral image (HSI) classification due to their powerful feature extraction ability. In the same manner, ensemble-based learning systems have demonstrated high potential to effectively perform supervised classification. In order to boost the performance of deep learning-based HSI classification, the idea of deep learning ensemble framework is proposed here, which is loosely based on the integration of deep learning model and random subspace-based ensemble learning. Specifically, two deep learning ensemble-based classification methods (i.e., CNN ensemble and deep residual network ensemble) are proposed. CNNs or deep residual networks are used as individual classifiers and random subspaces contribute to diversify the ensemble system in a simple yet effective manner. Moreover, to further improve the classification accuracy, transfer learning is investigated in this study to transfer the learnt weights from one individual classifier to another (i.e., CNNs). This mechanism speeds up the learning stage. Experimental results with widely used hyperspectral datasets indicate that the proposed deep learning ensemble system provides competitive results compared with state-of-the-art methods in terms of classification accuracy. The combination of deep learning and ensemble learning provides a significant potential for reliable HSI classification.

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Permalink: https://www.hzdr.de/publications/Publ-30109
Publ.-Id: 30109


Automatic Design of Convolutional Neural Network for Hyperspectral Image Classification

Chen, Y.; Zhu, K.; Zhu, L.; He, X.; Ghamisi, P.; Benediktsson, J. A.

Hyperspectral image (HSI) classification is a core task in the remote sensing community, and recently, deep learning-based methods have shown their capability of accurate classification of HSIs. Among the deep learning-based methods, deep convolutional neural networks (CNNs) have been widely used for the HSI classification. In order to obtain a good classification performance, substantial efforts are required to design a proper deep learning architecture. Furthermore, the manually designed architecture may not fit a specific data set very well. In this paper, the idea of automatic CNN for the HSI classification is proposed for the first time. First, a number of operations, including convolution, pooling, identity, and batch normalization, are selected. Then, a gradient descent-based search algorithm is used to effectively find the optimal deep architecture that is evaluated on the validation data set. After that, the best CNN architecture is selected as the model for the HSI classification. Specifically, the automatic 1-D Auto-CNN and 3-D Auto-CNN are used as spectral and spectral-spatial HSI classifiers, respectively. Furthermore, the cutout is introduced as a regularization technique for the HSI spectral-spatial classification to further improve the classification accuracy. The experiments on four widely used hyperspectral data sets (i.e., Salinas, Pavia University, Kennedy Space Center, and Indiana Pines) show that the automatically designed data-dependent CNNs obtain competitive classification accuracy compared with the state-of-the-art methods. In addition, the automatic design of the deep learning architecture opens a new window for future research, showing the huge potential of using neural architectures' optimization capabilities for the accurate HSI classification.

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Permalink: https://www.hzdr.de/publications/Publ-30108
Publ.-Id: 30108


UAVs as a Tool for Socially Acceptable Exploration of Waste Rock Dumps

Ajjabou, L.; Kirsch, M.; Lorenz, S.; Zimmermann, R.; Farci, A.; Viezzoli, A.; Gloaguen, R.

There is a growing demand for mineral resources worldwide, and yet industry is facing increasing obstacles in obtaining public acceptance for new exploration and mining projects. Numerous recent citizen protests highlight the public perception of ‘dirty’ mining projects and increase the reluctance of investors to finance explorations. Non-invasive exploration techniques can be defined as energy efficient, low-impact technologies. They assist in the detection and mapping of mineral deposits and improve exploration targeting with minimal environmental impact, while demonstrating that industry cares about reducing disturbance to the communities and environment in which they operate. However, it is increasingly understood that non-invasive technologies can help to maintain the social licence to operate and consequently lower the investment risk of exploration. To demonstrate this premise, we established an EU-funded research initiative called INFACT (Innovative, Non-Invasive and Fully Acceptable Exploration Technologies), which supports the development of innovative exploration and stakeholder engagement approaches. Our project will establish a set of permanent, accessible reference sites to trial and assess the technological and social performance of existing and emerging innovative, non-invasive exploration techniques like UAVs infrared hyperspectral imaging, magnetics, EM and radiometry.

  • Invited lecture (Conferences)
    First EAGE Workshop on Unmanned Aerial Vehicles, 02.-04.12.2019, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-30107
Publ.-Id: 30107


Newly synthesized fluorinated cinnamylpiperazines possessing low in vitro MAO-B binding

Jevtić, I. I.; Lai, T. H.; Penjišević, J. Z.; Dukic-Stefanovic, S.; Andrić, D. B.; Brust, P.; Kostić-Rajačić, S. V.; Teodoro, R.

Herein, we report on the synthesis and pharmacological evaluation of ten novel fluorinated cinnamylpiperazines as potential monoamine oxidase B (MAO-B) ligands. The designed derivatives consist of either cinnamyl or 2-fluorocinnamyl moieties connected to 2-fluoropyridylpiperazines. The three-step synthesis starting from commercially available piperazine afforded the final products in overall yields between 9 and 29%. An in vitro competitive binding assay using L-[3H]Deprenyl as radioligand was developed and the MAO-B binding affinities of the synthesized derivatives were assessed. Docking studies revealed that the compounds 8–17 were stabilized in both MAO-B entrance and substrate cavities, thus resembling the binding pose of L-Deprenyl. Although our results revealed that the novel fluorinated cinnamylpiperazines 8–17 do not possess sufficient MAO-B binding affinity to be eligible as positron emission tomography (PET) agents, the herein developed binding assay and the insights gained within our docking studies will certainly pave the way for further development of MAO-B ligands.

Keywords: MAO-B; positron emission tomography; piperazine; cinnamic acid

Permalink: https://www.hzdr.de/publications/Publ-30106
Publ.-Id: 30106


Multi-Source Hyperspectral Data Integration using Image Feature Extraction for Mineral Mapping

Lorenz, S.; Seidel, P.; Ghamisi, P.; Zimmermann, R.; Tusa, L.; Khodadadzadeh, M.; Contreras Acosta, I. C.; Gloaguen, R.

The fusion of remote sensing datasets for combined classifications has recently received great attention. Separate data acquisition and subsequent fusion allow for sensor-specific adjustments of experimental parameters and flexible sensor combinations. In mineral exploration, multi-sensor approaches are particularly promising to extend the range and accuracy of mineral phase detection. However, the time-efficient and accurate integration of data with differing resolution, field of view or acquisition modi remains challenging. This motivates us to promote a multi-source data integration based on efficient feature extraction strategies. An important pre-requisite for a successful integration is data co-registration. A workflow combining automated keypoint detection and matching provides an accurate and fast method to align multi-sensor datasets of different spatial sampling distances for a joint processing. For feature extraction, we employ innovative methods that consider both spatial and spectral aspects such as Orthogonal Total Variation Component Analysis (OTVCA). Besides the reduction of dimensionality and consequently processing time, the method allows the integration of textural and spectral information, such as short wave and long wave hyperspectral imagery or reflectance and luminescence data that are not directly interpretable with a single method. Application-relevant mineral assemblage classes such as alteration zones, ore zones or mineralized veins, become then discriminable as the spatio-spectral patterns are evident by extracting relevant features from all datasets. We use a Support Vector Machine with Radial Basis Function Kernel (SVM-RBF) to demonstrate the classification of mineralogical domains from such multi-source feature fused sets. We choose SVM as it is particularly robust when handling high-dimensional data with low number of training samples and against the heterogeneity of classes that is typical for mineralogical datasets. The optimal classification parameters are determined by five-fold cross- validation to ensure the best possible classification result with the given data. Training data required for the classification can be defined according to user knowledge, high resolution mineralogical analyses or spectral point measurements. The proposed multi-source data integration workflow shows to exceed the classification accuracy of single-source data and could be beneficial for many potential application fields in mineral exploration, mineral processing, recycling or food industry.

  • Lecture (Conference)
    10th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 24.-26.09.2019, Amsterdam, Nederland

Permalink: https://www.hzdr.de/publications/Publ-30105
Publ.-Id: 30105


Impact of Hydrogen-Rich Silicon Nitride Material Properties on Light-Induced Lifetime Degradation in Multicrystalline Silicon

Bredemeier, D.; Walter, D. C.; Heller, R.; Schmidt, J.

The root cause of “Light and Elevated Temperature Induced Degradation” (LeTID) of the carrier lifetime in multicrystalline silicon (mc-Si) wafers is investigated by depositing hydrogen-rich silicon nitride (SiN x :H) films of different compositions on boron-doped mc-Si wafers. The extent of LeTID observed in mc-Si after rapid thermal annealing (RTA) shows a positive correlation with the amount of hydrogen introduced from the SiN x :H layers into the bulk. The concentration of in-diffused hydrogen is quantified via measuring the resistivity change due to the formation of boron–hydrogen pairs in boron-doped float-zone silicon wafers processed in parallel to the mc-Si wafers. The measurements clearly show that the in-diffusion of hydrogen into the silicon bulk during RTA depends on both the atomic density of the SiN x :H film as well as the film thickness. Importantly, the impact of SiN x :H film properties on LeTID shows the same qualitative dependence as the hydrogen content in the silicon bulk, providing evidence that hydrogen is involved in the LeTID defect activation process.

Keywords: carrier lifetime; hydrogen; LeTID defects; light-induced lifetime degradation; silicon nitride; ulticrystalline silicon

Related publications

Permalink: https://www.hzdr.de/publications/Publ-30103
Publ.-Id: 30103


Improvement of Euler-Euler simulation of two-phase flow by particle-center-averaged method

Lyu, H.; Schlegel, F.; Rzehak, R.; Lucas, D.

Current Euler-Euler modeling based on phase-averages shows inconsistencies since the finite size of the bubbles is not properly accounted for. As a result, nonphysical gas concentration can appear in the center or the near wall region of a pipe if the bubble diameter is larger than the mesh size (Tomiyama, Shimada et al. 2003). In addition, mesh independent solutions may not exist in these cases.
By employing particle-center-averages (Prosperetti 1998), these inconsistencies can be remedied and mesh independent solutions are obtained. In this approach, the number density of bubble centers is the primary variable. This requires an additional wall-contact force to ensure that bubble centers cannot come arbitrarily close to walls (Lucas, Krepper et al. 2007). The gas volume fraction can be calculated from the number density by a convolution (Kitagawa, Murai et al. 2001) with a kernel that has a support corresponding to the extent of a bubble. In addition, the derivation shows explicitly that bubbles respond to pressure and stress of the continuous liquid phase such that no additional closure models for the gas phase pressure or stress are required.
In the present contribution, the convolution method is replaced by a diffusion-based method (Sun and Xiao 2015), which is much easier to implement in CFD codes using unstructured meshes like OpenFOAM. A physically motivated model for the wall-contact force is introduced. The remedy of the issues with the conventional phase-averaged two-fluid model is demonstrated using a simplified two-dimensional test case. Furthermore, comparison is made for real pipe flow cases where experimental data are available.

References
Kitagawa, A., Y. Murai and F. Yamamoto (2001). "Two-way coupling of Eulerian–Lagrangian model for dispersed multiphase flows using filtering functions." International journal of multiphase flow 27(12): 2129-2153.
Lucas, D., E. Krepper and H.-M. Prasser (2007). "Use of models for lift, wall and turbulent dispersion forces acting on bubbles for poly-disperse flows." Chemical Engineering Science 62(15): 4146-4157.
Prosperetti, A. (1998). Ensemble averaging techniques for disperse flows. Particulate Flows, Springer: 99-136.
Sun, R. and H. Xiao (2015). "Diffusion-based coarse graining in hybrid continuum–discrete solvers: Theoretical formulation and a priori tests." International Journal of Multiphase Flow 77: 142-157.
Tomiyama, A., N. Shimada and H. Asano (2003). Application of Number Density Transport Equation for the Recovery of Consistency in Multi-Field Model. ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference, American Society of Mechanical Engineers.

Keywords: Particle-center-averaged method; Number density of bubble centers; Bubble dimension; Diffusion equation; Deformation force model; Equation of motion

  • Contribution to proceedings
    14th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 12.-14.10.2020, Trondheim, Norway
    Proceedings from the 14th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, Norway: SINTEF Academic Press, 978-82-536-1684-1

Permalink: https://www.hzdr.de/publications/Publ-30102
Publ.-Id: 30102


Reduction of respiratory pancreas motion using an MRI and proton therapy compatible abdominal corset

Schneider, S.; Stefanowicz, S.; Jentsch, C.; Lohaus, F.; Valentini, C.; Platzek, I.; Troost, E. G. C.; Hoffmann, A. L.

Objectives:

An MRI- and particle therapy compatible patient-individualized abdominal corset was developed and its efficacy to reduce respiratory-induced pancreas motion was evaluated by orthogonal 2D-cine and 4D-MRI.

Patients & Methods:

Nine patients (6 female; average age 72.9±9.6 years) with tumors of the pancreas (7), gallbladder (1), or liver (1) provided written informed consent to be scanned on a 3T MRI scanner (Philips Healthcare) by means of orthogonal 2D-cine and 4D-MRI, without and with a patient-individualized abdominal corset, respectively. A polyethylene (PE) abdominal corset (ORD Dresden GmbH) was customized based on an optical 3D-surface scan (Artec Eva®). For MR imaging the patients were positioned supine on a flat tabletop using an anterior coil holder to avoid compression of the chest wall. For 2D-cine MRI, coronal and sagittal slices were selected to image the pancreatic head. The 4D-MRI dataset was reconstructed by retrospectively resorting a multi-slice 2D acquisition into 10 respiratory phases. Pancreas motion was determined as center-of-mass displacement in three orthogonal directions (inferior-superior (IS), anterior-posterior (AP), left-right (LR)).

Results and Conclusion:

MRI revealed predominant motion in IS direction, which was reduced by 42% (p<0.05) in both 2D-cine (5.0±3.7 mm without corset; 3.8±1.1 mm with corset) and 4D-MRI (8.6±3.7 mm without corset; 5.0±2.4 mm with corset) through the corset which furthermore reduced the motion variability by 40% (p<0.01). The corset had no effect on motion in AP and LR direction. This confirms earlier results obtained with a custom-made polyurethane corset [1]. However, the homogeneous material properties of PE allow the corset to be integrated in PT without increasing range uncertainties. Pancreas motion in IS direction can be significantly reduced in patients scheduled for PT by an individualized abdominal corset.

[1] Heerkens et al, Phys Imaging Radiat Oncol 2017; 2:7–10.

Keywords: MR guided radiation therapy; abdominal compression; time resolved MRI; 4D MRI

  • Lecture (Conference)
    8th MR in RT Symposium 2021, 19.-21.04.2021, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30101
Publ.-Id: 30101


Numerical simulation of mass transfer enhancement in liquid metal batteries by means of electro-vortex flow

Weber, N.; Nimtz, M.; Personnettaz, P.; Weier, T.; Sadoway, D.

Mass transfer is of paramount importance for an efficient operation of liquid metal batteries. We show for the first time that electrodynamically driven flow can indeed improve mixing of liquid electrodes, and reduces concen tration polarisation substantially. Simulating the discharge of a realistic Li||Bi cell at 1 A/cm², the corresponding overpotential reduces by up to 62%. Moreover, the formation of intermetallic phases is delayed, which improves
capacity usage. Finally, we demonstrate that vertical magnetic fields – which are originating from external sources – change the flow structure entirely, and will homogenise the positive electrode even better.

Permalink: https://www.hzdr.de/publications/Publ-30100
Publ.-Id: 30100


Electrochemical simulation of liquid metal batteries

Weber, N.; Personnettaz, P.; Weier, T.

Liquid metal batteries (LMBs) consist of a stable density stratification of two liquid metal electrodes, separated by a molten salt electrolyte. Discharing the cell, the anode metal dissolves in the cathode metal. Due to slow diffusion, concentration layers develop especially at high current densities, and lead to considerable concentration polarisation. As the density difference between the anode and cathode metal is usually large, the formed density stratification is often very stable. The talk will describe how to simulate the electric potential, current density and Lorentz force in a liquid metal battery. Finally, it will be shown that electrodynamically driven flow is able to mix the cathode alloy of an LMB, thus reducing concentration polarisation. A 10 cm Li||Bi cell, studied experimentally by Ning et al., will be used as reference case.

  • Lecture (Conference)
    14th WCCM & ECCOMAS Congress, 11.-15.01.2021, Paris, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-30099
Publ.-Id: 30099


Advanced modelling of complex boron dilution transients in PWRs – Validation of ATHLET 3D-Module against the experiment ROCOM E2.3

Diaz Pescador, E.; Grahn, A.; Kliem, S.; Schäfer, F.; Höhne, T.

Inherent boron dilution in PWRs constitutes one of the key issues in nuclear safety research. This issue has been therefore widely investigated analytically and experimentally through several test facilities in Germany. Besides the knowledge gained on the matter, the experimental research has contributed to the creation of large databases for the validation of computational tools used in accident analyses such as system and computational fluid dynamic (CFD) codes. In Part I of a series of two papers, the multidimensional features of the thermal-hydraulic system code ATHLET are assessed based on the experimental results from the boron dilution experiment E2.3 carried out at the ROCOM test facility. In Part II, a code to code evaluation is performed against the CFD code ANSYS CFX. The aim of the present paper is twofold: first to validate the 3D-Module of ATHLET as well as the “Profile Model I” boron transport model concerning the transport and thermal mixing in the developed multidimensional vessel during the progression of a complex boron dilution event. The obtained results with ATHLET 3.1A are satisfactory and meet the validation exercise goals, especially concerning the calculation of the average boron concentration. However, the limitations of the code to simulate thermal mixing in the cold legs lead to few deviations concerning the calculation of the minimum boron concentration.

Keywords: ATHLET; ROCOM E2.3; thermal mixing; boron dilution; validation exercise

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30098
Publ.-Id: 30098


Modelling of fluid mixing in reactor circuits with the thermal-hydraulic system code ATHLET

Diaz Pescador, E.

Modelling of fluid mixing in reactor circuits with the thermal-hydraulic system code ATHLET

  • Lecture (Conference)
    51. Kraftwerkstechnisches Kolloquium, 22.-23.10.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-30097
Publ.-Id: 30097


Thermal-hydraulic insights during a main steam line break in a generic PWR KONVOI reactor with ATHLET 3.1A

Diaz Pescador, E.; Schäfer, F.; Kliem, S.

The present paper gathers the main insights obtained during the numerical simulation of a 10 % main steam line break (MSLB) in a generic German PWR KONVOI reactor with the thermal-hydraulic system code ATHLET 3.1 A. The contents of this paper are focused first on the transient thermal-hydraulic calculation during affected steam generator (SG) 1 boil-off and subsequently on the multidimensional fluid mixing study of the overcooled water stream and the coolant in the reactor pressure vessel. With this aim, the boundary conditions from the test PKL G3.1, carried out at the PKL test facility in the framework of the OECD/PKL-II project, are implemented in the simulation over the plant nominal parameters from the KONVOI reactor. The thermal-hydraulic and fluid mixing results obtained in the simulations are qualitatively assessed against suitable experimental data from the PKL and ROCOM test facilities, showing a good agreement between simulation and test behaviour.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30096
Publ.-Id: 30096


Local liquid fraction measurement in annular two-phase flow using x-ray microtomography

Porombka, P.; Boden, S.; Lucas, D.

Annular-dispersed two-phase flow in pipes consists of a thin wavy liquid film covering the pipe wall and a gas core with entrained liquid droplets. Knowledge of the film thickness and entrained liquid fraction is of importance in numerous industrial applications, such as the thermal design of heat exchangers.
The application of X-ray microtomography to obtain these parameters in case of small diameter pipes is presented here. The three-dimensional, time-averaged liquid fraction distribution has been measured in air-water annular flow in a horizontal pipe. In combination with pressure drop measurements, the film and entrained liquid mass flow rates are derived using a simple annular flow model. The portrayed method may also serve as a basis for the validation of computational fluid dynamics simulations of annular flow.

Keywords: horizontal annular flow; X-ray microtomography; droplet entrainment

  • Lecture (Conference)
    10th International Conference on Multiphase Flow, 19.-24.05.2019, Rio de Janeiro, Brazil

Permalink: https://www.hzdr.de/publications/Publ-30095
Publ.-Id: 30095


PREDICT – Predictive Geometallurgy

Bachmann, K.; Tolosana Delgado, R.; Wopat, K.; Smith, A.; Gutzmer, J.

The long‐term availability of minerals and metals from primary (i.e. geogenic) and secondary (i.e. recycling) resources is not only the key to most economic activity, but also to the realization of important societal developments, such as the transition to a renewables‐based energy system and the rollout of e‐mobility. Due to several factors, the utilization of raw materials from geogenic sources will continue to form an essential part of the raw materials supply for a growing global population. In order to develop a highly skilled work force, to develop novel approaches for raw materials utilization, approaches that deploy resource‐ and energy‐efficient technologies for the delineation, extraction and beneficiation of mineral resources, while at the same time minimizing environmental risks, the Helmholtz International Research School for Predictive Geometallurgy (PREDICT) provides the first‐ever training programme dedicated to predictive geometallurgy and adaptive processing. PREDICT has pooled the interdisciplinary and intersectoral expertise of leading German and South African research institutes, world‐leading mining and metallurgical companies, covering all the links in the raw materials chain from exploration to mineral beneficiation and mine planning. PREDICT not only develops cuttingedge methodologies to take geometallurgical resource potential models to an entire new level but also implements and tests an optimal adaptive processing approach for a beneficiation plant model. In addition, we will combine both models by establishing feedback loops for model reconciliation.
Furthermore, PREDICT will close the loop by implementation of the model results in a simulation‐based mine‐planning block model.

  • Invited lecture (Conferences)
    Helmholtz International Research School Selection Meeting, 29.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30094
Publ.-Id: 30094


Modelling of complex boron dilution transients in PWRs—Validation of CFD simulation with ANSYS CFX against the ROCOM E2.3 experiment

Grahn, A.; Diaz Pescador, E.; Kliem, S.; Schäfer, F.; Höhne, T.

This part of a series of two papers compares CFD simulation results of a boron dilution scenario with experimental results. The simulation was carried out with ANSYS CFX using the SST turbulence scheme, experimental data were produced in the ROCOM test facility, experiment E2.3. The main features of the scenario are asymmetric, transient mass flow conditions in the affected loops 1 and 2 of a KONVOI-type reactor vessel and reduced density of the underborated coolant slugs fed into the reactor trough the cold legs of both loops. The CFD simulation was able to capture the density stratification in the loops affected by underboration and the mixing in the downcomer and in the lower plenum. Good agreement with the experiment was obtained for the temporal evolution of average boron concentration in several measuring sections of the reactor vessel and of the boron distribution in the core inlet. In general, minimal values of boron concentration were found to be lower in the simulation than in the experiment.

Keywords: Boron dilution; ROCOM; ANSYS CFX; Validation

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Permalink: https://www.hzdr.de/publications/Publ-30093
Publ.-Id: 30093


Predictive geometallurgical modelling

Bachmann, K.

The modern mining industry faces a number of important technical challenges, such as declining ore grades, complex mineral associations, fine-grain size and increasing geological variability. To meet these challenges geometallurgical models are constructed to quantita-tively predict how ores will behave during extraction and beneficiation. Current geometal-lurgical programs carried out by industry, focus on the definition of larger spatial domains that have similar characteristics. However, a consequent application and further develop-ment of geometallurgical programs should lead to an implementation of spatially more highly resolved geometallurgical resource models that are truly predictive for each mined block (including uncertainty), in order to improve raw material quality control and the process efficiency of mining operations. Such an approach would also enable the targeted recovery of by-products, which may generate significant additional revenue and improve overall efficiency. In order to construct relevant resource models, detailed quantitative information on the spatial distribution and geometallurgical behaviour of the by-products within the deposit is crucial.
The aim of this thesis is the development and creation of a predictive geometallurgical model by means of a case study and the presentation of the resulting advantages for the extraction of ores. Based on this, a general structure for the development of predictive geo-metallurgical models is developed, which can be applied to different types of commodities, as well as by-products, is cost-efficient, able to adapt to future data, and predicts metallurgi-cal parameters. As the case study serves the Thaba Chromium Mine in the western Bushveld Complex (South Africa), which is operated by Cronimet Chrome Mining SA (Pty) Ltd. In par-ticular, this thesis focusses on four distinct chromitite seams of the Lower and Middle Groups (LG and MG) at Thaba Mine, namely the LG-6, LG-6A, MG-1 and MG-2, which are considered as target seams for an open-cast and future underground mining scenario.
In order to understand the geological and geochemical architecture of the Thaba Mine deposit and as a foundation of the predictive geometallurgical model, an extensive geo-chemical dataset as well as logging and drill core data provided by Cronimet was evaluated and a 3D geological model was developed. A statistical assessment was performed to evalu-ate the variability within and between the chromitite seams and to separate the mine lease area into distinct geochemical clusters. The distribution of the samples belonging to the dif-ferent geochemical clusters was then transposed onto the geology of the mine lease area. This allowed the definition of spatial domains. These spatial domains, recognized by the as-sessment of assay data only, are then validated by mineralogical attributes; implications for mineral beneficiation are tested and verified.
According to this assessment, the chromitites of the Thaba Mine area can be subdivided into three distinct geochemical domains, domains that constitute the suitable foundation for a geometallurgical model. An extensive supergene altered domain or weathered domain is distinguished from a domain affected by hydrothermal alteration. The latter domain occurs below the depth of modern weathering, but in obvious proximity to faults and around a prominent dunite pipe. The third domain is represented by ores least affected by post-magmatic alteration processes. This domain occupies the centre of fault blocks below the extent of modern weathering.
Furthermore, the geochemical data is used to develop a tailored and easy-to-use multi-variate classification scheme for the chromitite layers in the Thaba Mine, based on a com-prehensive classification routine for the LG and MG chromitites. This routine allows a clear attribution with known uncertainty of all relevant chromitite layers. It comprises of a hierar-chical discrimination approach relying on linear discriminant analysis and involves five dis-tinct steps. Overall classification results for unknown samples belonging to one of the layers are 81 %. The approach may, however, be extended across the entire Bushveld, provided that an appropriate geochemical data set is available.
For detailed characterization of the mineral assemblages in the chromitite ores, selected core samples of the target layers were analysed in detail by various analytical methods, such as Mineral Liberation Analysis and Electron Probe Microanalysis. Therefore, we extended the common measurement protocols for electron probe microanalysis to ensure applicability to a wider range of PGM compositions and its overall accuracy as well as consistency. Based on the results two distinct major mineral assemblages are defined: The first assemblage is rich in platinum group element-sulphides, along with variable proportions of malanite/ cu-prorhodsite and alloys of Fe and Sn. The associated base metal sulphides are dominated by chalcopyrite and pentlandite, along with pyrite and subordinate millerite/ violarite. Associ-ated silicates are mainly primary magmatic orthopyroxene and plagioclase. The second as-semblage is rich in platinum group element-sulpharsenides and -arsenides as well as -antimonides and -bismuthides, which are associated with a base metal sulphide assemblage dominated by pentlandite and Co-rich pentlandite. The assemblage is also marked by an abundance of alteration minerals, such as talc, serpentine and/or carbonates, which are closely associated with the platinum group minerals. Statistical evaluation reveals that these two mineral assemblages cannot be attributed to their derivation from different chromitite layers, but document the effects of pervasive hydrothermal alteration.
The knowledge of the detailed mineralogical investigation was transferred to a large da-taset comprising similar mineralogical data for unweathered ore of the deposit. Hence, it was possible to identify seven distinct ore types via statistical assessment, subsequently val-idated through beneficiation tests of drill core material. In addition, metallurgical test work for large batch samples of the weathered domain was carried out. Furthermore, beneficia-tion tests were aligned with process chemistry and mineralogy to monitor the results.
The predictive geometallurgical model aims to express the recoverability of PGE as by-product from the chromite processing stream. Within this context, the weathered ores were regarded as a single domain, as chromite ores from this oxidized zone were consistently found to have very low PGE recoveries. Any attempt to recover PGE by flotation from this zone appears to be challenging. For unweathered ores, the approach towards a predictive geometallurgical model needs to be somewhat more complex. The following steps were performed:
(i) Building a predictive model of the recoverability of PGE as a function of chemical composition, i.e. establish a chemical proxy for PGE recoverability;
(ii) Performing a geostatistical modelling of the geochemical dataset, i.e. interpolation through cokriging, and
(iii) Combining step (i) and (ii) to generate a spatially-resolved geometallurgical model able to predict the potential to recover PGE by flotation in terms of probabilities.
The resultant predictive, spatially-resolved geometallurgical model displays the PGE pro-cessing potential in terms of probabilities and therefore incorporates uncertainty.
Based on the work flow applied in this study, a more generic framework towards a predictive geometallurgical model can be proposed that can be applied to different commodities, is able to adapt to future data, and predicts metallurgical parameters, e.g. the recoverability of an ore as probabilities (and therefore including uncertainty). Furthermore, the model can be applied to main as well as by-product and therefore represents a holistic modelling approach. Most of the modelled parameters are derived from primary ore properties (e.g. rock or particle stream), e.g. modal mineralogy, mineral association, densities, etc., combined with a minimum of empirical test work.

  • Doctoral thesis
    TU Bergakademie Freiberg, 2020
    Mentor: Dr. Jens Gutzmer, Dr. Raimon Tolosana-Delgado

Permalink: https://www.hzdr.de/publications/Publ-30092
Publ.-Id: 30092


A First Order Geometallurgical Model for PGEs in a Chromite Ore

Bachmann, K.

In the effort to become more sustainable the mining industry currently faces a number of important challenges. One important direction of change would be to achieve a more holistic use of mineral resources, i.e., by considering the efficient extraction and beneficiation of all possible valuable constituents – rather than only focusing on the major commodity. Thus, geometallurgical models need to be adapted accordingly. Instead of only centring on the efficient extraction and beneficiation of a single (economically most relevant) commodity, future geometallurgical models should be expanded to consider all potential products.
In the present contribution, a generic framework is proposed that can be applied to a large variety of different commodities; it is able to adapt to future data, predicts metallurgical parameters, e.g. the recoverability of an ore as probabilities, and can be extended to include environmental footprint calculations. Most of the parameters are derived from primary ore properties (e.g. rock or particle streams), e.g. modal mineralogy, mineral association, densities, etc., combined with a minimum of conventional test work. The work flow is demonstrated with a case study, in which the beneficiation potential of PGE as a by-product in an existing chromite mine in the Bushveld Complex of South Africa is considered. All available data were incorporated in a geological block model and interpreted to form geometallurgical domains of sufficient size to be considered during mine planning. The resultant predictive, spatially-resolved geometallurgical model displays the PGE processing potential in terms of probabilities and therefore incorporates uncertainty. The viability of the geometallurgical model relates well to the original geological architecture, is cost- and time-effective and highly versatile to form a foundation for further use and development during exploitation.

  • Invited lecture (Conferences)
    Workshop on Geometallurgy - SGA 2019, 26.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30091
Publ.-Id: 30091


Imaging and writing magnetic domains in the non-collinear antiferromagnet Mn₃Sn

Reichlova, H.; Janda, T.; Godinho, J.; Markou, A.; Kriegner, D.; Schlitz, R.; Zelezny, J.; Soban, Z.; Bejarano, M.; Schultheiß, H.; Nemec, P.; Jungwirth, T.; Felser, C.; Wunderlich, J.; Goennenwein, S.

Non-collinear antiferromagnets are revealing many unexpected phenomena and they became crucial for the field of antiferromagnetic spintronics. To visualize and prepare a well-defined domain structure is of key importance. The spatial magnetic contrast, however, remains extraordinary difficult to be observed experimentally. Here, we demonstrate a magnetic imaging technique based on a laser induced local thermal gradient combined with detection of the anomalous Nernst effect. We employ this method in one the most actively studied representative of this class of materials - Mn₃Sn. We undoubtedly proof that the observed contrast is of magnetic origin. We further show an algorithm to prepare a well defined domain pattern at room temperature based on heat assisted recording principle. Our study opens a prospect to study spintronics phenomena in non-collinear antiferromagnets with spatial resolution.

Keywords: Information Storage; Magnetic properties and materials; Spintronics; Surfaces, interfaces and thin films

Permalink: https://www.hzdr.de/publications/Publ-30090
Publ.-Id: 30090


Magnetization dynamics in synthetic antiferromagnets: the role of dynamical energy and mutual spin-pumping

Sorokin, S.; Gallardo, R.; Fowley, C.; Lenz, K.; Titova, A.; Dennehy, G.; Atcheson, G.; Rode, K.; Faßbender, J.; Lindner, J.; Deac, A. M.

We investigate magnetization dynamics in asymmetric interlayer exchange coupled Py/Ru/Py trilayers using both vector network analyzer-based and electrically-detected ferromagnetic resonance techniques. Two different ferromagnetic resonance modes, in-phase and out-of-phase, are observed across all three regimes of the static magnetization configurations, through antiparallel alignment at low fields, the spin-flop transition at intermediate fields and the parallel alignment at high fields. The non-monotonic behavior of the modes as a function of the external field is explained in detail by analyzing the interlayer exchange and Zeeman energies, and is found to be solely governed by the interplay of their dynamical components. In addition, the linewidths of both modes were determined across the three regimes and the different behaviors of the linewidths versus external magnetic field are attributed to mutual spin pumping induced in the samples. Interestingly, the difference between the linewidths of the out-of-phase and in-phase modes decreases at the spin-flop transition and is reversed between the antiparallel and parallel aligned magnetization states.

Keywords: spin-pumping; magnetoresistance; interlayer exchange coupling; synthetic antiferromagnets; magnetization dynamics; ferromagnetic resosnance; electrically-detected ferromagnetic resonance

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Permalink: https://www.hzdr.de/publications/Publ-30089
Publ.-Id: 30089


Inertiale Lage- und Bewegungsverfolgung für instrumentierte Strömungsfolger zur Strömungscharakterisierung in Bioreaktoren

Buntkiel, L.; Reinecke, S.; Hampel, U.

Zur Untersuchung der ablaufenden Prozesse in großen Behältern, wie z. B. Biogasfermentern, Bioreaktoren und Belebtschlammbecken, wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt [1],[2]. Bisher wurden damit die Strömungsverhältnisse mit probabilistischen Auswertemethoden ausschließlich basierend auf der Messung der vertikalen Position als Funktion des hydrostatischen Drucks charakterisiert und Parameter einfacher Prozessmodelle für Anlagen im Labor- und Pilotmaßstab bestimmt.
Derzeit wird das Konzept des Sensorsystems mit dem Ziel weiterentwickelt, eine räumliche Lage- und Bewegungsverfolgung für Bioreaktoren basierend auf Inertialsensoren zu realisieren. Dies umfasst sowohl die dafür zu qualifizierenden Sensoren für Beschleunigung, Drehrate, Magnetfeld sowie Umgebungsdruck als auch die Softsensor-Algorithmen zur Bestimmung der Lage und der Bewegung. Damit sollen zukünftig Auftriebsmanöver der Sensorpartikel autonom ablaufen und die räumliche Strömungscharakterisierung erfolgen.
Im Beitrag werden drei Softsensor-Algorithmen zur Bewegungsverfolgung vorgestellt und verglichen. Diese sind ein linearisiertes Kalman-Filter (Error State Kalman Filter ESKF) und zwei nichtlineare Komplementärfilter (Direct und Passive Complementary Filter DCF, PCF) nach [3]. Diese Algorithmen wurden mit praxisrelevanten simulierten Strömungsbewegungen (siehe Abb. 1) unter Berücksichtigung von Unsicherheiten der Sensoren und realen Sensordaten analysiert. Die Simulationsergebnisse zeigen, dass durch die genaue Lagebestimmung, die Beschleunigung permanent im Koordinatensystem des Behälters nahezu driftfrei bestimmt wird (Abb. 1 und 2). Der Beitrag führt einen umfassenden Vergleich anhand simulierter und gemessener Referenztrajektorien von drei qualifizierten, kommerziellen Inertialsensoreinheiten und diskutiert die relevanten Implikationen für die Auslegung des Sensorsystems.

Keywords: Strömungsfolger; Bioreaktor; Inertialnavigation

  • Open Access Logo Contribution to proceedings
    14. Dresdner Sensor-Symposium, 02.-04.12.2019, Dresden, Deutschland
    Inertiale Lage- und Bewegungsverfolgung für instrumentierte Strömungsfolger zur Strömungscharakterisierung in Bioreaktoren, 978-3-9819376-1-9, 52-58
    DOI: 10.5162/14dss2019/3.5
  • Lecture (Conference)
    14.Dresdner Sensor-Symposium, 02.-04.12.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30088
Publ.-Id: 30088


Demonstration of X-ray Thomson scattering as diagnostics for miscibility in warm dense matter

Frydrych, S.; Vorberger, J.; Hartley, N.; Schuster, A.; Ramakrishna, K.; Saunders, A. M.; van Driel, T.; Falcone, R. W.; Fletcher, L. B.; Galtier, E.; Gamboa, E. J.; Glenzer, S. H.; Granados, E.; Macdonald, M. J.; Mackinnon, A. J.; Mcbride, E. E.; Nam, I.; Neumayer, P.; Pak, A.; Voigt, K.; Roth, M.; Sun, P.; Gericke, D. O.; Döppner, T.; Kraus, D.

The gas and ice giants in our solar system can be seen as a natural laboratory for the physics of highly compressed matter at temperatures of a few thousand kelvins. In turn, our understanding of their structure and evolution depends critically on our ability to model such matter. One key aspect is the miscibility of the elements in their interiors. Here, we demonstrate the feasibility of X-ray Thomson scattering to quantify the degree of species separation in a 1:1 carbon-hydrogen mixture at a pressure of ~150GPa and a temperature of ~5,000 K. Our measurements provide absolute values of the structure factor that encodes the microscopic arrangement of the particles. From these data, we find a lower limit of 24+6-7 % of the carbon atoms forming isolated carbon clusters. In principle, this procedure can be employed for investigating the miscibility behaviour of any binary mixture at the high-pressure environment of planetary interiors, in particular, for non-crystalline samples where it is difficult to obtain conclusive results from X-ray diffraction. Moreover, this method will enable unprecedented measurements of mixing/demixing kinetics in dense plasma environments, e.g., induced by chemistry or hydrodynamic instabilities.

Permalink: https://www.hzdr.de/publications/Publ-30087
Publ.-Id: 30087


Ionization in high-density plasmas: an ab initio study for carbon at Gbar pressures

Bethkenhagen, M.; Witte, B. B. L.; Röpke, G.; Döppner, T.; Kraus, D.; Glenzer, S. H.; Redmer, R.

We apply density functional theory molecular dynamics (DFT-MD) simulations to calculate the ionization degree of plasmas in the warm dense matter regime. Standard descriptions of the ionization potential depression (IPD) have been challenged recently by experiments approaching unprecedentedly high densities indicating that improved IPD models are required to describe warm dense matter. We propose a novel ab initio method to calculate the ionization degree directly from the dynamic electrical conductivity using the Thomas-Reiche-Kuhn (TRK) sum rule. This approach is demonstrated for carbon at a temperature of 100 eV and pressures in the Gbar range. We find substantial deviations from widely applied IPD models like Stewart-Pyatt and Ecker-Kröll implying that condensed matter and quantum effects like band structure and Pauli blocking need to be included explicitly in ionization models. Our results will help to precisely model matter under conditions occurring, e.g., during inertial confined fusion implosions or inside astrophysical objects such as brown dwarfs and low-mass stars.

Permalink: https://www.hzdr.de/publications/Publ-30086
Publ.-Id: 30086


Exploring THz-driven dynamics on sub-cycle timescales at the TELBE facility

Deinert, J.-C.; Green, B. W.; Ilyakov, I.; Awari, N.; Wang, Z.; Germanskiy, S.; Chen, M.; Bawatna, M.; Gensch, M.; Kovalev, S.

The TELBE Terahertz (THz) facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) offers narrowband high-field high-repetition rate THz radiation for driving low-energy excitations in matter in the spectral region between 0.1 THz and 1.5 THz [1]. In combination with our pulse-resolved data acquisition and the numerous available probing techniques based on table-top laser systems, we can resolve THz-driven dynamics with few 10 fs time resolution and high dynamic range of up to 120 dB [2]. This makes TELBE a unique facility for exploring low-energy THz excitations offering (resonant) access to a multitude of fundamental modes, e.g., lattice vibrations, molecular rotations, spin precession and the motion of free electrons [3]. Recently, we demonstrated THz high harmonic generation (HHG) in the model 2D material graphene [4]. Here, the ultrafast collective thermal response of free background electrons near the Dirac point [5] enables very efficient generation of harmonics in the technologically relevant THz frequency range. We further show that the underlying principle of the collective response can be generalized to other 2D and 3D Dirac materials, such as CdAs. The crucial role of doping in graphene can be exploited by, e.g. electrochemical gating, which allows tuning of the HHG efficiency by almost two orders of magnitude. The corresponding setup for phase-resolved nonlinear THz spectroscopy further enables a novel technique: Higgs spectroscopy, which offers new ways for understanding unconventional superconductivity. Using this technique, we recently discovered a new collective mode distinct from the heavily damped Higgs mode in different families of cuprates [6]. Our results establish Higgs spectroscopy as a new approach to uncover interactions directly relevant to superconductivity.
In this contribution, I will also discuss experiments on the selective THz control of magnetic properties in a number of different materials [7], which is enabled by probing techniques, such as Faraday Rotation or MOKE, using the NIR and UV output from our table-top sources.
[1] B. Green et al., Sci. Rep. 6, 22256 (2016)
[2] S. Kovalev et al., Struct. Dyn. 4, 024301 (2017)
[3] T. Kampfrath et al. Nat. Photonics 7, 680–690 (2013)
[4] H. Hafez et al., Nature 561, 507 (2018)
[5] Z. Mics et al., Nature Communications 6, 7655 (2015)
[6] H. Chu et al., arXiv preprint, arXiv:1901.06675 (2019)
[7] S. Kovalev et al., J. Phys. D: Appl. Phys. 51, 114007 (2018)

Keywords: Terahertz; pump-probe; nonlinear dynamics; high harmonic generation; graphene; Dirac materials; superradiance

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  • Invited lecture (Conferences)
    10th International Workshop on Infrared Microscopy and Spectroscopy with Accelerator Based Sources WIRMS 2019, 24.09.2019, Ubatuba, Brasil

Permalink: https://www.hzdr.de/publications/Publ-30085
Publ.-Id: 30085


Ultrafast Photoelectron Spectroscopy - How to Make Movies of Elementary Electronic Processes

Deinert, J.-C.

How does functionality in quantum devices emerge? The answer lies in the numerous elementary processes, the interactions and correlations of (quasi-)particles that happen on timescales of femtoseconds. Thorough understanding of these processes can eventually lead to more efficient OLEDs, faster microprocessors, and other functional materials. A complex, but highly insightful method to access the required spectral and dynamic information in solid state systems is time- and angle-resolved photoemission spectroscopy. This lecture attempts to give an overview on this powerful technique for exploring non-equilibrium properties of matter. This includes discussions of elementary scattering processes, experimental techniques, and latest results on optoelectronic systems and correlated materials.

Keywords: Photoelectron spectroscopy; ultrafast; electronic structure; band structure; phase transitions; pump-probe

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  • Invited lecture (Conferences)
    Ultrafast Science: Lasers, Fundamentals and Spectroscopy (SoSe 2019) Guest Lecture, 16.05.2019, Bielefeld, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30084
Publ.-Id: 30084


Terahertz high harmonic generation in Dirac materials

Deinert, J.-C.; Kovalev, S.; Hafez, H.; Chen, M.; Green, B. W.; Bawatna, M.; Germanskiy, S.; Awari, N.; Wang, Z.; Ilyakov, I.; Turchinovich, D.; Gensch, M.

The exploration of nonlinear optical phenomena has not only deepened the understanding of light-matter interaction, but it also enabled novel technologies that make use of the resulting synthesis of electromagnetic radiation at new frequencies. Whereas the nonlinear responses of matter in the microwave and optical regimes are well explored, research addressing the intermediate Terahertz (THz) regime is still largely in its infancy, despite its high technological relevance, e.g. for novel high-speed (opto-)electronics.
For these future applications in the THz range, graphene is a highly promising material, because of the unique optical properties originating from its prototypical Dirac-type electronic structure. Soon after its discovery, there have multiple predictions of efficient harmonic generation in the THz range [1, 2], but experimental evidence has remained incomplete. Recently, we experimentally demonstrated the highly efficient THz harmonics generation (HG) in a single layer graphene sample (up to 7th order) at ambient conditions upon excitation with a moderate THz field of only 85 kV/cm (see Fig. 1) [3]. Our observations have been successfully described by a thermodynamic model, which clearly explains the experimentally observed crucial role of the graphene doping level for THz HG [3, 4]. By using gated graphene samples and multilayer structures, we are able to predictably modify the HG efficiency and thereby corroborate the thermodynamic model.

In addition, we employed the same experimental scheme to other Dirac materials, such as topological insulators and Dirac/Weyl semimetals, showing that THz HG is a rather universal phenomenon based on the linear band dispersion in the vicinity of the Dirac point.

[1] S. Mikhailov et al., Microelectron. J. 40 (2009) 712.
[2] I. Al-Naib, Phys. Rev. B, 90 (2014) 245423
[3] H. Hafez, S. Kovalev et al., Nature, 561 (2018) 507
[4] Z. Mics et al., Nat. Commun., 6 (2015) 7655

Keywords: Graphene; Dirac materials; high harmonic generation; terahertz

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  • Lecture (Conference)
    Graphene 2019, 26.06.2019, Roma, Italia

Permalink: https://www.hzdr.de/publications/Publ-30083
Publ.-Id: 30083


Investigation of ⁵⁴Fe(n,gamma)⁵⁵Fe and ³⁵Cl(n,gamma)³⁶Cl reaction cross sections at keV energies by Accelerator Mass Spectrometry

Slavkovská, Z.; Wallner, A.; Reifarth, R.; Pavetich, S.; Brückner, B.; Al-Khasawneh, K.; Merchel, S.; Volknandt, M.; Weigand, M.

Activations with neutrons in the keV energy range were routinely performed at the Karlsruhe Institute of Technology (KIT) in Germany in order to simulate stellar conditions for neutron-capture cross sections. A quasi-Maxwell-Boltzmann neutron spectrum of kT = 25 keV, being of interest for the astrophysical s-process, was produced by the ⁷Li(p,n) reaction utilizing a 1912 keV proton beam at the Karlsruhe Van de Graaff accelerator. Activated samples resulting in long-lived nuclear reaction products with half-lives in the order of yr - 100 Myr were analyzed by Accelerator Mass Spectrometry (AMS). Comparison of this data to cross sections from Time-of-Flight (ToF) measurements showed that the selected AMS data is systematically lower than the ToF data. To investigate this discrepancy, ⁵⁴Fe(n,gamma)⁵⁵Fe and ³⁵Cl(n,gamma)³⁶Cl reaction cross sections were newly measured at the Frankfurt Neutron Source (FRANZ) in Germany. To complement the existing data, an additional neutron activation of ⁵⁴Fe and ³⁵Cl at a proton energy of 2 MeV was performed. The results will give implications for the stellar environment at kT = 90 keV, reaching the yet not experimentally explored high-energy s-process range. AMS measurements of the activated samples are scheduled.

Keywords: AMS; nuclear reactions; s-process

Permalink: https://www.hzdr.de/publications/Publ-30082
Publ.-Id: 30082


Definition of geochemical domains in a chromite mine, Bushveld Complex, South Africa

Bachmann, K.; Menzel, P.; Tolosana Delgado, R.; Gutzmer, J.

The Lower and Middle Group chromitites of the Bushveld Complex are the source of a very large portion of the global chrome supply. Yet, the effectiveness of chromite beneficiation circuits is highly sensitive to mineralogical and textural variations in feed composition. The use of geochemical proxies, based on data acquired routinely during the exploration and mining process may provide a cost- and time-efficient alternative to more time-consuming and expensive mineralogical analyses. Such an approach is presented in this study, which focuses on the LG-6, LG-6A, MG-1 and MG-2 chromitite seams at the Thaba mine located on the western limb of the Bushveld Complex. According to a sound statistical assessment, the chromitites of the Thaba mine area can be subdivided into three distinct domains, domains that constitute the suitable fundament for a geometallurgical model. Accordingly, a least altered (orthomagmatic) domain is distinguished from a supergene altered domain and a domain affected by widespread hydrothermal alteration. The latter domain occurs below the depth of modern weathering, but in obvious proximity to faults and around a prominent dunite pipe. The orthomagmatic domain is represented by ores least affected by post-magmatic alteration processes. This domain occupies the centre of fault blocks below the extent of modern weathering.

  • Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30081
Publ.-Id: 30081


Lower Group and Middle Group chromitites of the Bushveld Complex – the effect of weathering on the distribution of platinum-group elements

Junge, M.; Bachmann, K.; Oberthür, T.; Groshev, N. Y.

The Bushveld Complex in South African contains vast resources of Cr, PGE and V. Currently, the Merensky Reef, the Platreef and the UG-2 chromitite seam are the major mining targets for PGE, although chromitites of the Lower Group (LG) and Middle Group (MG) may also contain concentrations up to several ppm PGE.
In a suite of chromitite samples from the Thaba Mine in the western Bushveld Complex it was shown that Pt concentrations in weathered chromitite seams (LG-6 to MG-4) generally exceed those of Pd. However, differences are observed by comparing individual chromitite seams as total PGE concentrations of weathered chromitites from the LG-6 to MG-4 range between 760 and 1300 ppb. Elevated concentrations of Pt and Pd are also present in hanging and footwalls of chromitite seams (median 333 ppb Pt). The PPGE (Rh, Pt, Pd) contents of weathered ores are generally lower than those of the pristine ores. The IPGE (Os, Ir, Ru) are very similar in both pristine and weathered ores. Particularly, Ru concentration are in the same range as the pristine ores.
Platinum concentrations increase from LG-6 to MG-4, whereas Pd remains at near-constant levels, resulting in a strong increase of the Pt/Pd ratio from 2.2 to 15.3. Platinum, largely remains within the chromitite seams and is only locally mobilized within the chromitites and their surrounding hanging and footwalls, whereas a large proportion of the Pd is leached out. Weathering causes mobilization of Pt and Pd out of the chromitites, locally into the hanging and footwall. The general decrease (in particular of Pd) can also be observed by comparing the average Pt/Pd ratio of pristine chromitites from the Thaba Mine. The IPGE are generally less affected by weathering processes which may be explained by the fact that laurite [(Ru,Os,Ir)S2] commonly occurs as inclusions in chromite, and PGM incorporated in chromite are largely unaffected by weathering processes.

  • Contribution to proceedings
    GeoMünster 2019, 22.-25.09.2019, Münster, Germany

Permalink: https://www.hzdr.de/publications/Publ-30080
Publ.-Id: 30080


Platinum-group elements in weathered Lower Group and Middle Group chromitites of the Bushveld Complex

Junge, M.; Bachmann, K.; Oberthür, T.

All major sources of economically important platinum-group elements (PGE) are associated with sulfides and chromite in mafic-ultramafic rocks. The Bushveld Complex in South Africa is the largest PGE deposit worldwide. Chromitites of the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex hold PGE contents of a few ppm. However, these chromitites are mainly mined for chromium only and extraction of PGE as a by-product is limited. Surface weathering in the area of the Bushveld Complex is up to 50 m down from surface. Attempts to recover Pt and Pd from these weathered ores lead to recoveries of <30 %, despite that Pt and Pd concentrations are similar in pristine and weathered ores. The recovery of PGE from near-surface chromitites of the LG and MG would increase the resource efficiency of current mining operations.. Therefore, an efficient utilization of these ores requires geochemical and mineralogical characterization of the PGE within these ores and the development of novel approaches of mineral beneficiation.

  • Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30079
Publ.-Id: 30079


From tailings to valuable resources: the use of predictive geometallurgy to quantify the feasibility of tailings reprocessing

Pereira, L.; Frenzel, M.; Khodadadzadeh, M.; Tolosana Delgado, R.; Büttner, P.; Birtel, S.; Gutzmer, J.

The tailings of industrial mineral production are a major environmental and financial burden for mining operations. Because most historic and current beneficiation plants extract only one – or few – commodities contained in the ore, tailings dams should be regarded as anthropogenic ore deposits, i.e., potential sources of raw materials. Their recovery would have a number of associated benefits: effectively reducing the waste volume as well as the environmental burden whilst simultaneously increasing the efficiency of metal / mineral production from a non-renewable resource. In some cases, this may be achieved at minimal cost, since raw materials in tailings dams are already mined, milled and deposited at surface.
Yet, most tailings are low-grade resources; technologies applied in beneficiating tailings need to be well-selected and highly efficient. For this purpose, a sound understanding of the beneficiation characteristics of such tailings needs to be developed. With the latest advances of mineral characterization and data mining techniques, the Helmholtz Institute Freiberg for Resource Technology has been developing a framework that enables predictive geometallurgical studies of tailings materials. This presentation will illustrate three particular parts of this framework, namely (i) resource models that account for mineral processing properties, (ii) economic evaluation of by-product recovery in early stages of projects, and (iii) the use of single particles’ information for modelling mineral processing units. By combining these techniques, we are able to quantify the potential of transforming tailings into valuable resources.

  • Invited lecture (Conferences)
    SIMEXMIN, 04.-07.07.2021, Ouro Preto, Brazil

Permalink: https://www.hzdr.de/publications/Publ-30078
Publ.-Id: 30078


Spectral tomography - 3D mineral classification

Da Assuncao Godinho, J. R.; Renno, A.; de Schryver, T.; Masschaele, B.

A new analytical tool for mineral analysis will be introduced: Laboratory-based Spectral 3D X-ray Computed Tomography (Sp-CT). Results from a spectral imaging detector, prototype installed inside a TESCAN CoreTOM micro-CT system, will be presented and discussed in the context of mineralogical and chemical analysis of geological materials. The technique will be demonstrated to allow:

a) 3D mineral classification from the transmitted energy spectrum characteristic of a mineral phase.
b) Quick bulk chemical quantification of heavy elements with K-edge > 20 keV at high concentrations that are difficult to analyse by other methods.
c) Reducing common CT artefacts such as scattering and beam hardening, as well as improved contrast by selectively choose the most convenient energy range.
The advantages of Sp-CT will open new possibilities in geometallurgy and minerals processing research to move from the predominant 2D based image characterization towards more representative 3D characterization. These are fundamental steps to enable automated and routine 3D characterization that ultimately has the potential to provide faster and lower cost analysis to, for example, the mining industry, as well as more comprehensive rock characterization technique for Earth sciences research.

  • Open Access Logo Poster
    Goldschmidt 2019, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-30077
Publ.-Id: 30077


High energy ion beams as a powerful tool for the analysis of the elemental composition of thin layers

Munnik, F.

Keywords: Ion Beam Analysis

Related publications

  • Lecture (others)
    Kolloquium am Ferdinand-Braun-Institut, Berlin, 29.11.2019, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-30076
Publ.-Id: 30076


Volume quantification in interphase voxels of ore minerals using 3D imaging

Da Assuncao Godinho, J. R.; Kern, M.; Renno, A.; Gutzmer, J.

This contribution presents and validates a new method to correct for the main limitations of volume quantification using X-ray computed tomography: limited spatial resolution and lack of mineralogical classification. The volume of a phase of interest (cassiterite, SnO2) is calculated using the intensity of voxels at interphases, which are typically the regions of main uncertainty in 3D imaging. Instead of traditional segmentation methods that define boundaries between phases, our method considers interphases as regions that can be several voxels across. The method is validated using a feedback loop between 2D scanning electron microscopy-based image analysis and bulk chemical analysis where the advantages of each technique are used to correct for the limitations of another. The percent of cassiterite derived from our method are within 10% deviation from those measured by scanning electron microscopy-based image analysis and bulk chemical analysis, when the P50 of the particle size distribution is at least 5 times the voxel size of the scan, which is a better agreement than results derived from other segmentation methods. Therefore, our method reduces the uncertainty of volume quantification and lowers the limit of grain sizes for which volumes can be reliably measured using computed tomography. The reduced uncertainty and bias can contribute to broadening the application of 3D imaging to mineral engineering as complementary to well established techniques.

Keywords: Partial volume effect; Computed tomography; Mineral processing; Raw materials; X-ray imaging; Geometallurgy

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Permalink: https://www.hzdr.de/publications/Publ-30075
Publ.-Id: 30075


Conductivity influence on interfacial waves in liquid metal batteries and related two-layer systems

Weier, T.; Grants, I.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Stefani, F.; Weber, N.

Fluid flows in liquid metal batteries can be generated by a number of effects. We start with a short overview of different driving mechanisms and then address questions specific to the metal pad role instabilities in three-layer systems. We focus on the role of the conductivity distribution in the cell, noting at the same time that interfacial tension should be considered as well for smaller cells. Following this discussion, numerical results on the excitation of interfacial waves in two-layer liquid metal systems with miscibility gaps bearing an interface normal electric current are presented. Confirming recent results from the literature, we find that magnetic damping plays a decisive role for strong vertical magnetic fields. In addition, boundary conditions for the electric field strongly influence critical currents and growth rates.

Keywords: liquid metal batteries; interfacial waves; sloshing

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Permalink: https://www.hzdr.de/publications/Publ-30074
Publ.-Id: 30074


Improvement of luminescence properties of n-GaN using TEGa precursor

Hubáčeka, T.; Hospodková, A.; Kuldová, K.; Slavická Zíková, M.; Pangrác, J.; Čížek, J.; Liedke, M. O.; Butterling, M.; Wagner, A.; Hubík, P.; Hulicius, E.

The aim of this work is to compare and improve optical and structural properties of GaN layers prepared using TMGa or TEGa precursors. MOVPE grown GaN buffer layers on sapphire substrates are usually grown from TMGa precursor at the temperatures above 1000 °C. These layers contain deep and shallow acceptor levels which are responsible for blue and yellow defect bands in luminescent spectra. Both defect bands are detrimental for all major nitride device applications. Especially n-doped GaN layers suffer from strong yellow defect bands. In this work, it is shown that yellow band photoluminescence intensity can be suppressed by using TEGa precursor during the growth of n–doped GaN layers. Different kinds of growth parameters, such as growth temperature or growth rate, have been studied. It is also shown that the change of carrier gas (H2 or N2) has very strong influence on the layer quality. H2 carrier gas increased intensity of yellow band in sample grown from TEGa precursor while N2 carrier gas had the same effect for sample grown from TMGa precursor. Variable energy positron annihilation spectroscopy showed creation of single VGa in H2 atmosphere and clustering of VGa to big complexes ((VGa)3(VN)n) in N2 atmosphere.

Keywords: MOVPE; TEGa precursor; n-GaN; yellow band; VGa defect

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Permalink: https://www.hzdr.de/publications/Publ-30073
Publ.-Id: 30073


Enhanced flux pinning isotropy by tuned nanosized defect network in superconducting YBa2Cu3O6+x films

Khan, M. Z.; Rivasto, E.; Tikkanen, J.; Rijckaert, H.; Malmivirta, M.; Liedke, M. O.; Butterling, M.; Wagner, A.; Huhtinen, H.; van Driessche, I.; Paturi, P.

Striving to improve the critical current density Jc of superconducting YBa 2 Cu 3 o 6+x (YBCO) thin films via enhanced vortex pinning, the interplay between film growth mechanisms and the formation of nanosized defects, both natural and artificial, is systematically studied in undoped and BaZrO 3 (BZO)-doped YBCO thin films. The films were grown via pulsed laser deposition (PLD), varying the crystal grain size of the targets in addition to the dopant content. The microstructure of the PLD target has been observed to have a great impact on that of the deposited thin films, including the formation of vortex pinning centers, which has direct implications on the superconducting performance, especially on the isotropy of flux pinning properties. Based on experimentally measured angular dependencies of Jc, coupled with a molecular dynamics (MD) simulation of flux pinning in the YBCO films, we present a quantitative model of how the splay and fragmentation of BZO nanorods artifically introduced into the YBCO film matrix explain the majority of the observed critical current anisotropy. To obtain the freedom to engineer future high-temperature superconductor (HTS) applications for desired operating magnetic field and temperature ranges, it is necessary to optimize the vortex pinning landscape for an enhanced, isotropic flux pinning performance 1-6. In addition to naturally formed crystalline defects, which typically have spatial dimensions distinctly below the superconducting coherence length, defect-engineering with artificially produced pinning centers (APCs) with dimensionalities of 1D-3D have been observed to be extremely effective 7-10. However, the complex nucleation process of YBCO during PLD process, that leads to growth island size variation, and the manner in which this could affect the size and distribution of the nanoscale structural defects is chiefly neglected. Especially, a clear gap exists in the current literature regarding how ordered arrays of nanoscale defects can also influence and regulate the distribution and growth of more effective APCs and thus decrease the anisotropy by allowing vortices to be trapped in a wider angular range 11. Partly, the clear lack of information on the subject is arguably be due to the rather general assumption that during PLD process, the film growth method of our choice, the target material is largely decomposed on the atomic level, and thus its properties should not have an effect on the formation and nucleation of particles on the substrate surface. This assumption, which our studies have led us to challenge, would precariously force one to downplay the potential importance of target microstructure on the functional properties of derived films. The angular dependence of the J c has an excellent physical importance providing an approach to the problem of flux pinning and vortex dynamics anisotropy in HTSs, both from the experimental and theoretical point of view. For instance, in the angular dependent critical current plots, one can easily observe how the various types of pinning centers such as correlated linear, columnar or planar defects and, on the other hand, defects based on growth mechanisms together with YBCO's intrinsic pinning can dramatically alter the angular dependence of J c (B) 4. For understanding the origin of angular dependent flux pinning J c (θ), experimental tools like transmission electron microscopy (TEM) are often exploited to probe the structural properties and features, such as the defects naturally formed during the film growth, as well as the size, shape, orientation and distribution of the artificially produced and self-assembled pinning centers 5,12,13. However, methods like positron annihilation spectroscopy,

Keywords: superconductivity; YBa2Cu3O6; YBCO; positron annihilation spectroscopy; PAS

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Permalink: https://www.hzdr.de/publications/Publ-30072
Publ.-Id: 30072


An Integrated Multi-Sensor System for the In-Line Monitoring of Material Streams

Seidel, P.; König, S.; Lorenz, S.; Sudharshan, V.; Shaik Fareedh, J.; Zimmermann, R.; Ghamisi, P.; Kaever, P.; Gloaguen, R.; Reuter, M.

We present an innovative multi-sensor system, based on non-invasive optical spectroscopy for the characterization of material streams. The novel hardware and software set-ups are explained in detail and first results from RGB stereoscopy and object detection are shown.

  • Contribution to proceedings
    IEEE Sensors 2019, 27.-30.10.2019, Montreal, Canada
    Proceedings of IEEE Sensors 2019

Permalink: https://www.hzdr.de/publications/Publ-30069
Publ.-Id: 30069


Structural, magnetic and magnetocaloric properties of NdPrFe14B and its hydrides

Tereshina, I.; Kaminskaya, T.; Ivanov, L.; Politova, G.; Drulis, H.; Gorbunov, D.; Paukov, M.; Tereshina-Chitrova, E.; Andreev, A.

A systematic study of the influence of interstitial hydrogen on the structure, morphology of surface, magnetic and magnetothermal properties in multicomponent (Nd0.5Pr0.5)2Fe14BHx (x = 0; 2.7; 4.3) are reported. Partial substitution of Pr for Nd allows a decrease of the spin-reorientation transition temperature from 135 K for Nd2Fe14B to 73 K for (Nd0.5Pr0.5)2Fe14B. Hydrides (Nd0.5Pr0.5)2Fe14BHx crystallize in a tetragonal crystal structure (space group P42/mnm) of the Nd2Fe14B-type. Both lattice constants and unit cell volume increase upon hydrogen absorption. It was also found that the surface of the hydrogenated sample was very severely damaged by the introduction of hydrogen. Magnetic studies of both initial compound and the hydrides were performed on bulk and powder samples in static and pulsed magnetic fields up to 14 and 58 T, respectively. Hydrogenation has a significant effect on magnetic properties of a multicomponent alloy (Nd0.5Pr0.5)2Fe14B: Curie temperature and saturation magnetization increase, while temperature of SRT decreases (TSRT = 63 K for (Nd0.5Pr0.5)2Fe14BHx with x = 2.7 and 4.3). The magnetocaloric effect (MCE) in the range of spin-reorientation transition also decreases significantly. We analyzed magnetic properties of (Nd0.5Pr0.5)2Fe14BHx and compare them with that of Nd2Fe14BHx. Magnetic phase diagrams are constructed.

Permalink: https://www.hzdr.de/publications/Publ-30068
Publ.-Id: 30068


Evidence of one-dimensional magnetic heat transport in the triangular-lattice antiferromagnet Cs2CuCl4

Schulze, E.; Arsenijevic, S.; Opherden, L.; Ponomaryov, O.; Wosnitza, J.; Ono, T.; Tanaka, H.; Zvyagin, S.

We report on low-temperature heat-transport properties of the spin-1/2 triangular-lattice antiferromagnet Cs2CuCl4. Broad maxima in the thermal conductivity along the three principal axes, observed at about 5 K, are interpreted in terms of the Debye model, including the phonon umklapp scattering. For thermal transport along the b axis, we found a pronounced field-dependent anomaly, close to the transition into the three-dimensional long-range-ordered state. No such anomalies were found for the transport along the a and c directions.We argue that this anisotropic behavior is related to an additional heat-transport channel through magnetic excitations, that can best propagate along the direction of the largest exchange interaction. In addition, peculiarities of the heat transport of Cs2CuCl4 in magnetic fields up to the saturation field and above are discussed.

Permalink: https://www.hzdr.de/publications/Publ-30067
Publ.-Id: 30067


Effects of current distribution on mass transport in the positive electrode of a liquid metal battery

Personnettaz, P.; Landgraf, S.; Nimtz, M.; Weber, N.; Weier, T.

Liquid metal electrodes are one of the key components of different electrical energy storage technologies. The understanding of transport phenomena in liquid electrodes is mandatory in order to ensure efficient operation. In the present study we focus our attention on the positive electrode of the Li||Bi liquid metal battery. Starting from a real experimental setup, we numerically investigate the charge transfer in a molten salt electrolyte and the mass transport in the positive electrode. The two phenomena are tightly coupled, because the current distribution influences the concentration field in the positive electrode. The cell is studied during charging when compositional convection becomes apparent. First results of compositional convection from a non-uniform current distribution are presented, highlighting its capability to affect the flow in the positive electrode and the cell performance.

Keywords: Liquid metal electrode; mass transport; OpenFOAM; liquid metal battery

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Permalink: https://www.hzdr.de/publications/Publ-30066
Publ.-Id: 30066


The effect of microwave’s location in a comminution circuit on improving grindability of a porphyry copper deposit

Gholami, H.; Bahram, B.; Hassanzadehmahaleh, A.; Mehdilo, A.; Jabbari, M. R.

The present work initially studies the impact of a laboratory microwave (MW)’s location (before and after a jaw crusher) on grindability of a copper ore. Additionally, the role of MW’s radiation time (15–150 sec) and grinding time (13, 15 and 17 min) on the produced particle size distribution (PSD), mineral liberation degree (LD) and energy consumption are investigated. relative work index (RWI), standard Bond work index (Wi), and grindability index (GI) together with the breakage and selection functions were utilized to assess the grinding efficiency and its kinetics of the untreated and MW-pretreated (at a constant power of 0.9 kW) samples. Bond work indices were obtained 13.70, 13.04 and 10.86 kWh/t for the untreated, MW-treated uncrushed and MW-treated crushed samples, respectively. Besides, the results confirmed that the microwave pretreatment was comparatively effective at the shortest grinding time (13 min). Furthermore, locating the microwave after the crushing stage indicated substantial improvements in the sample’s grindability and its kinetics rate. The product size (P80) of the MW-treated crushed sample (13 min, 0.9 kW, 150 sec) showed enhancements of 27% and 17% in comparison with the un-microwaved and MW-treated uncrushed samples. Finally, the comparative GIs acquired in the entire spectrum of the particle range were reasonably higher if the microwave was located after the jaw crusher, particularly for the coarse fraction sizes.

Keywords: Microwave irradiation; grinding kinetics; copper complex ore; liberation degree; untreated and microwave-treated

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Permalink: https://www.hzdr.de/publications/Publ-30065
Publ.-Id: 30065


Effect of microwave system location on floatability of chalcopyrite and pyrite in a copper ore processing circuit

Gholami, H.; Rezai, B.; Mehdilo, A.; Hassanzadehmahaleh, A.; Yarahmadi, M. R.

The present work aims at investigating the effect of microwave local positions (i.e. before crushing (BC), after crushing (AC) and after milling (AM)) on microwave-assisted flotation of chalcopyrite and pyrite in a porphyry copper complex deposit. Individual given samples for each state were pre-treated with a variable power microwave at a power level of 90 to 900W for 15, 30, and 60s. Furthermore, froth floatation experiments were carried out using a laboratory mechanical Denver flotation cell on both microwave-treated and untreated samples. Particle surface properties were characterized by a scanning electron microscopy (SEM) and an energy-dispersive X-ray spectroscopy (EDX) analysis. The results showed that the chalcopyrite and pyrite floatabilities increased monotonically by rising the exposure time and power level for the uncrushed preconditioned samples (BC) due to the enhancement of mineral liberation degrees together with the formation of sulphide species and polysulphides on the mineral surfaces. However, flotation results of treated samples for the crushed one (AC) revealed an optimum range. Formation of intensive oxide layers on the mineral surfaces of milled samples (AM) led to a substantial reduction in their recoveries by increasing the microwave’s power level and the sample’s exposure time. The results obtained from mineral’s floatabilities in recleaner stage showed that the microwave-assisted sample at 900W for 30s at BC state favourably provided 5% higher S.E.’s than that of the untreated sample. Finally, it was concluded that the microwave pretreatment of samples induced the best floatability responses if it located before the crusher.

Keywords: Microwave technology; Chalcopyrite; Pyrite; Comminution circuit; Separation efficiency

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Permalink: https://www.hzdr.de/publications/Publ-30064
Publ.-Id: 30064


Diffusion and Interaction of In and As Implanted into SiO2 Films

Tyschenko, I. E.; Voelskow, M.; Mikhaylov, A. N.; Tetelbaum, D. I.

By means of Rutherford backscattering spectrometry, electron microscopy, and energy-dispersive X-ray spectroscopy, the distribution and interaction of In and As atoms implanted into thermally grown SiO2 films to concentrations of about 1.5 at % are studied in relation to the temperature of subsequent annealing in nitrogen vapors in the range of T = 800–1100°C. It is found that annealing at T = 800–900°C results in the segregation of As atoms at a depth corresponding to the As+-ion range and in the formation of As nanoclusters that serve as sinks for In atoms. An increase in the annealing temperature to 1100°C yields the segregation of In atoms at the surface of SiO2 with the simultaneous enhanced diffusion of As atoms. The corresponding diffusion coefficient is DAs = 3.2 × 10–14 cm2 s–1.

Keywords: As; diffusion; In; ion implantation; silicon oxide

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Permalink: https://www.hzdr.de/publications/Publ-30063
Publ.-Id: 30063


Deep Learning for Hyperspectral Image Classification: An Overview

Li, S.; Song, W.; Fang, L.; Chen, Y.; Ghamisi, P.; Benediktsson, J. A.

Hyperspectral image (HSI) classification has become a hot topic in the field of remote sensing. In general, the complex characteristics of hyperspectral data make the accurate classification of such data challenging for traditional machine learning methods. In addition, hyperspectral imaging often deals with an inherently nonlinear relation between the captured spectral information and the corresponding materials. In recent years, deep learning has been recognized as a powerful feature-extraction tool to effectively address nonlinear problems and widely used in a number of image processing tasks. Motivated by those successful applications, deep learning has also been introduced to classify HSIs and demonstrated good performance. This survey paper presents a systematic review of deep learning-based HSI classification literature and compares several strategies for this topic. Specifically, we first summarize the main challenges of HSI classification which cannot be effectively overcome by traditional machine learning methods, and also introduce the advantages of deep learning to handle these problems. Then, we build a framework that divides the corresponding works into spectral-feature networks, spatial-feature networks, and spectral-spatial-feature networks to systematically review the recent achievements in deep learning-based HSI classification. In addition, considering the fact that available training samples in the remote sensing field are usually very limited and training deep networks require a large number of samples, we include some strategies to improve classification performance, which can provide some guidelines for future studies on this topic. Finally, several representative deep learning-based classification methods are conducted on real HSIs in our experiments.

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Permalink: https://www.hzdr.de/publications/Publ-30062
Publ.-Id: 30062


Cascaded Recurrent Neural Networks for Hyperspectral Image Classification

Hang, R.; Liu, Q.; Hong, D.; Ghamisi, P.

By considering the spectral signature as a sequence, recurrent neural networks (RNNs) have been successfully used to learn discriminative features from hyperspectral images (HSIs) recently. However, most of these models only input the whole spectral bands into RNNs directly, which may not fully explore the specific properties of HSIs. In this paper, we propose a cascaded RNN model using gated recurrent units to explore the redundant and complementary information of HSIs. It mainly consists of two RNN layers. The first RNN layer is used to eliminate redundant information between adjacent spectral bands, while the second RNN layer aims to learn the complementary information from nonadjacent spectral bands. To improve the discriminative ability of the learned features, we design two strategies for the proposed model. Besides, considering the rich spatial information contained in HSIs, we further extend the proposed model to its spectral-spatial counterpart by incorporating some convolutional layers. To test the effectiveness of our proposed models, we conduct experiments on two widely used HSIs. The experimental results show that our proposed models can achieve better results than the compared models.

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Permalink: https://www.hzdr.de/publications/Publ-30061
Publ.-Id: 30061


Hyperspectral Image Classification with Multi-Scale Feature Extraction

Bing, T.; Nanying, L.; Leyuan, F.; Danbing, H.; Ghamisi, P.

Spectral features cannot effectively reflect the differences among the ground objects and distinguish their boundaries in hyperspectral image (HSI) classification. Multi-scale feature extraction can solve this problem and improve the accuracy of HSI classification. The Gaussian pyramid can effectively decompose HSI into multi-scale structures, and efficiently extract features of different scales by stepwise filtering and downsampling. Therefore, this paper proposed a Gaussian pyramid based multi-scale feature extraction (MSFE) classification method for HSI. First, the HSI is decomposed into several Gaussian pyramids to extract multi-scale features. Second, we construct probability maps in each layer of the Gaussian pyramid and employ edge-preserving filtering (EPF) algorithms to further optimize the details. Finally, the final classification map is acquired by a majority voting method. Compared with other spectral-spatial classification methods, the proposed method can not only extract the characteristics of different scales, but also can better preserve detailed structures and the edge regions of the image. Experiments performed on three real hyperspectral datasets show that the proposed method can achieve competitive classification accuracy.

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Permalink: https://www.hzdr.de/publications/Publ-30060
Publ.-Id: 30060


Crystallization of colourless hexanitratoneptunate(IV) with anhydrous H+ countercations trapped into hydrogen bond polymer with diamide linkers

Takao, K.; März, J.; Matsuoka, M.; Mashita, T.; Kazama, H.; Tsushima, S.

Colourless crystalline compounds of centrosymmetric [Np(NO3)6]2− were yielded from 3 M HNO3 aq under presence of double-headed 2-pyrrolidone derivatives (L). In the obtained crystal structures, H+ was also involved as a countercation to compensate the negative charge of [Np(NO3)6]2−, where initial hydration around H+ was fully removed during crystallization despite its strongest hydration enthalpy. Instead, such an anhydrous H+ was captured by L to form a [H+···L]n hydrogen bond polymer. In [Np(NO3)6]2−, Np4+ centre is twelve-coordinated with 6 bidentate NO3−, and therefore, present in an icosahedral geometry bearing inversion centre. In such a centrosymmetric system, any f-f transitions stemming from 5f3 electronic configuration of Np4+ are electric-dipole forbidden. This is the reason why the compounds currently obtained were colourless unlike ordinary Np(IV) species with olive-green.

Permalink: https://www.hzdr.de/publications/Publ-30059
Publ.-Id: 30059


Spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy study of thermally treated Co60Fe20B20 thin films

Hoffmann, M.; Sharma, A.; Matthes, P.; Okano, S.; Hellwig, O.; Ecke, R.; Zahn, D.; Salvan, G.; Schulz, S.

We report the optical and magneto-optical properties of amorphous and crystalline Co60Fe20B20 films with thicknesses in the range of 10 nm to 20 nm characterized using spectroscopy ellipsometry (SE) and magneto-optical Kerr effect (MOKE) spectroscopy. We derived the spectral dependence of the dielectric tensor from experimental data for samples prior and after annealing in vacuum. The features of the dielectric function can be directly related to the transitions between electronic states and the observed changes upon annealing can be ascribed to an increase of the crystalline ordering of CoFeB.

Keywords: CoFeB; spectroscopic ellipsometry; magneto-optical Kerr effect spectroscopy; x-ray diffraction

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Permalink: https://www.hzdr.de/publications/Publ-30057
Publ.-Id: 30057


Studies on the interaction of plant cells with U(VI) and Eu(III) and on stress-induced metabolite release

Jessat, J.

Uranium(VI) and Europium(III) can interact with Brassica napus suspension cell cultures. This can lead to bioassociation (immobilisation of metals due to the cell metabolism), which is discussed in more detail here. Heavy metal stress can also lead to the formation of protective metabolites by the plant cells, whose complex formation behaviour with U(VI) has been investigated.

Keywords: canola; plants; uranium; europium; metabolites; WiN; Women in Nuclear; bioassociation; heavy metal; plant cells; suspension cell cultures

  • Invited lecture (Conferences)
    Finale der WiN Preisverleihung, 11.10.2019, Karlstein/Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30056
Publ.-Id: 30056


Femtosecond X-ray induced changes of the electronic and magnetic response of solids from electron redistribution

Higley, D.; Reid, A.; Chen, Z.; Le Guyader, L.; Hellwig, O.; Lutman, A.; Liu, T.; Shafer, P.; Chase, T.; Dakovski, G.; Mitra, A.; Yuan, E.; Schlappa, J.; Dürr, H.; Schlotter, W.; Stöhr, J.

Resonant X-ray absorption, where an X-ray photon excites a core electron into an unoccupiedvalence state, is an essential process in many standard X-ray spectroscopies. With increasingX-ray intensity, the X-ray absorption strength is expected to become nonlinear. Here, wereport the onset of such a nonlinearity in the resonant X-ray absorption of magnetic Co/Pdmultilayers near the Co L3edge. The nonlinearity is directly observed through the change ofthe absorption spectrum, which is modified in less than 40 fs within 2 eV of its threshold.This is interpreted as a redistribution of valence electrons near the Fermi level. For ourmagnetic sample this also involves mixing of majority and minority spins, due to sampledemagnetization. Ourfindings reveal that nonlinear X-ray responses of materials may alreadyoccur at relatively low intensities, where the macroscopic sample is not destroyed, providinginsight into ultrafast charge and spin dynamics.

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Permalink: https://www.hzdr.de/publications/Publ-30055
Publ.-Id: 30055


Critical behavior of intercalated quasi-van der Waals ferromagnet Fe0.26TaS2

Zhang, C.; Yuan, Y.; Wang, M.; Li, P.; Zhang, J.; Wen, Y.; Zhou, S.; Zhang, X. X.

In the present work, single-crystalline quasi-van der Waals ferromagnet Fe0.26TaS2 was successfully synthesized with Fe atoms intercalated at ordered positions between TaS2 layers. Its critical behavior was systematically studied by measuring the magnetization around ferromagnetic to paramagnetic phase transition temperature, TC∼100.7K, under different magnetic fields. The critical exponent β for the spontaneous magnetization below TC, γ for the inverse initial susceptibility above TC, and δ for the magnetic isotherm at TC were determined with modified Arrott plots, the Kouvel-Fisher method, the Widom scaling law, and critical isotherm analysis, and found to be the following values: β=0.459(6),γ=1.205(11), and δ=3.69(1). The obtained critical exponents are self-consistent and follow the scaling equation, indicating the reliability and intrinsicality of these parameters. A close analysis within the framework of renormalization group theory reveals that the spin coupling inside Fe0.26TaS2 crystal is of the three-dimensional Heisenberg ({d:n}={3:3}) type with long-range magnetic interaction and that the exchange interaction decays with distance as J(r)∼r-4.71

Keywords: quasi-van der Waals ferromagnet; critical behavior; three-dimensional Heisenberg

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Permalink: https://www.hzdr.de/publications/Publ-30054
Publ.-Id: 30054


New tools for calibrating diffraction setups

Kieffer, J.; Vals, V.; Blanc, N.; Hennig, C.

This work presents new calibration tools in the pyFAI suite for processing scattering experiments acquired with area detectors: a new graphical user interface for calibrating the detector position in a scattering experiment performed with a fixed, large area detector as well as a library to be used in Jupyter notebooks for calibrating the motion of a detector on a goniometer arm (or any other moving table) to perform diffraction experiments.

Keywords: powder diffraction; detector calibration; pyFAI

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Permalink: https://www.hzdr.de/publications/Publ-30053
Publ.-Id: 30053


Bio-Fishing for Rare Earth Recycling

Lederer, F.

Rare earth elements (REE) are a group of seventeen elements consisting of scandium, yttrium as well as what are known as lanthanides. These elements are found only in a few regions worldwide in quantities worth mining. REEs are considered key components in the high-tech industry and are utilized, for example, in wind turbines, smartphones and energy-saving lamps.

  • G.I.T. Laboratory Journal 23(2019)5, 30-31

Permalink: https://www.hzdr.de/publications/Publ-30051
Publ.-Id: 30051


Two-Dimensional Noble-Metal Dichalcogenides and Phosphochalcogenides

Kempt, R.; Kuc, A. B.; Heine, T.

Noble-metal chalcogenides, dichalcogenides and phosphochalcogenides are an emerging class of two- dimensional materials. Their properties can be broadly tuned via quantum confinement (number of layers) and defect engineering, including metal-to-semiconductor transitions, magnetic ordering, and topological surface states. They possess various polytypes, often of similar formation energy, which can be assessed by selective synthesis approaches. They excel in mechanical, optical and chemical sensing applications, and feature long-term air- and moisture stability. In this review, we summarize the recent progress in the field of noble metal chalcogenides and phosphochalcogenides and highlight the structural complexity and its impact on applications.

Permalink: https://www.hzdr.de/publications/Publ-30050
Publ.-Id: 30050


Bio-compatible flotation of Chlorella vulgaris: Study of zeta potential and flotation efficiency

Matho, C.; Schwarzenberger, K.; Eckert, K.; Keshavarzi, B.; Walther, T.; Steingroewer, J.; Krujatz, F.

The energy-intensive dewatering of algae biomass, the first step of most downstream processes, remains one of the big challenges for economically relevant photoautotrophic bioprocesses. Due to its scalability and easy construction, froth flotation using the interactions between cells and bubbles shows considerable potential for this type of cost-efficient initial dewatering step. Comprehensive knowledge on both the physico-chemical conditions and the cellular surface properties are an important precondition to harvest cells by flotation. This study investigates the impact of changing the medium composition, specifically varying the pH and adding (bio-) collectors, on the zeta potential of Chlorella vulgaris SAG 211-1b. Decreasing the pH value from physiological to acidic conditions (pH 1–1.5) resulted in a strongly reduced cellular zeta potential. As validated by dispersed-air flotation, this yields a significantly enhanced cell recovery R > 95 %. The impact of the synthetic collector cetyltrimethylammonium bromide and the biopolymer chitosan on the cellular zeta potential and flotation performance was studied, resulting in a 3.3-fold decrease in the surfactant dose when chitosan was used . The basic mechanisms of cell-chitosan interaction were analysed in terms of particle size distribution and surface tension measurements, revealing interactions between flocculation and adsorption during the dispersed-air flotation of C.vulgarisSAG 211-1b.

Keywords: Chlorella vulgaris; Flotation; Zeta potential; Dispersed-air flotation; Chitosan; CTAB

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Permalink: https://www.hzdr.de/publications/Publ-30048
Publ.-Id: 30048


Wie uns die Biologie beim Recycling von Elektroschrott hilft

Lederer, F.

Gold, Kupfer, Palladium und Seltene Erden sind wichtige Bestandteile von Smartphones und anderen Geräten unseres täglichen Lebens. Jedes dieser Metalle erfüllt ganz gezielt Aufgaben im Gerät und ist daraus nicht wegzudenken. Ihre Gewinnung aus den Bergbauminen dieser Erde ist häufig mit enormen Schäden für Mensch und Natur verbunden. Die Verwendung von recycelten Metallen bietet dazu eine deutlich umweltfreundlichere Alternative. Da die Metalle aber in sehr kleinen Mengen und fein verteilt im Gerät verbaut sind, ist ihr Recycling häufig nicht wirtschaftlich. Hier können neue biologische Recyclingwege Abhilfe leisten. Forscher des Helmholtz Instituts Freiberg für Ressourcentechnologie arbeiten an der Entwicklung von Metallspezifischen Antikörpern, welche gezielt ein Wertmetall nach dem anderen auch in kleinsten Konzentrationen in Form von Bioangeln aus einem Metallgemisch herausfischen können.

Keywords: Recycling; Elektroschrott; Bioangeln

  • Lecture (others)
    Campus Talks - Forschung auf den Punkt gebracht, 19.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30047
Publ.-Id: 30047


Metallgewinnung durch Mikrobiologie - Biologisch assistierte Prozesse in der Rohstofftechnologie

Lederer, F.

Präsentation der Arbeiten der Abteilung Biotechnologie des Helmholtz Institut Freiberg für Ressourcentechnologie sowie der Arbeiten der Nachwuchsforschergruppe BioKollekt

Keywords: Biokollektoren; Peptide; Recycling

  • Lecture (others)
    Institutskolloquium, 25.09.2019, Waldheim, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30046
Publ.-Id: 30046


BioKollekt - A biobased material recycling process promotes circular economy

Lederer, F.; Pollmann, K.

Recycling high-value products is a pivotal part of a circular economy. Current high-tech products contain a highly complex mixture of elements in low concentrations. Elements in these mixtures usually possess similar chemical and physical properties, which poses technical difficulties when considering a potential recycling process. Currently, only 22% terbium, 1% cerium and 1% lanthanum used in electronic devices like fluorescent light bulbs is recycled.1 A large proportion of these precious elements is lost. There is a need for novel techniques to be developed in order to recycle elements that are in low concentrations and in a complex matrix. Junior research group BioKollekt has begun the design and development of highly selective bio-based collector materials for a more sustainable recycling process of these elements. Biological peptide structures were identified in a highly competitive process for their selectivity and affinity for the fluorescent phosphor lanthanum phosphate doped with cerium and terbium (LAP). LAP-selective binding peptides coupled to a carrier material could be used in the future as separation tools for the selective recycling of LAP from lamp phosphors of fluorescent light bulbs. The BioKollekt approach uses LAP as a “proof of principle” to show the efficiency of biocollector materials. Figure 1 demonstrates the BioKollekt concept. The identification of highly selective biomolecules for preferred target materials (step 1) has been already achieved. In the second step, carrier materials (e.g. hydrophobic beads) will be functionalized with material binding-selective peptides. Biocollectors will interact selectively with their target material in a separation process (step 3-4). Finally, the target material and biocollector will be recycled and reused (step 5). The talk will present the BioKollekt concept and its achievements.

Keywords: Recycling; Peptides; Fluorescent Phosphor; Lanthanum

  • Invited lecture (Conferences)
    European Congress and Exhibition on Advanced Matertials and Processes (EUROMAT 2019), 01.-05.09.2019, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-30044
Publ.-Id: 30044


Distinct defect appearance in Gd implanted polar and nonpolar ZnO surfaces in connection to ion channeling effect

Jagerová, A.; Malinský, P.; Mikšová, R.; Nekvindová, P.; Cajzl, J.; Akhmadaliev, S.; Holý, V.; Macková, A.

(0001) c-plane, (11-20) a-plane, and m-plane (10-10) ZnO bulk crystals were implanted with 400-keV Gd+ ions using fluences of 5 × 1014, 1 × 1015, 2.5 × 1015, and 5 × 1015 cm-2. Structural changes during the implantation and subsequent annealing were characterized by Rutherford backscattering spectrometry in channeling mode (RBS-C); the angular dependence of the backscattered ions (angular scans) in c-, a-, and m-plane ZnO was realized to get insight into structural modification and dopant position in various crystallographic orientations. X-ray diffraction (XRD) with mapping in reciprocal space was also used for introduced defect identification. Defect-accumulation depth profiles exhibited differences for c-, a-, and m-plane ZnO, with the a-plane showing significantly lower accumulated disorder in the deeper layer in Zn-sublattice, accompanied by the preservation of ion channeling phenomena in a-plane ZnO. Enlargement of the main lattice parameter was evidenced, after the implantation, in all orientations. The highest was evidenced in a-plane ZnO. The local compressive deformation was seen with XRD analysis in polar (c-plane) ZnO, and the tensile deformation was observed in nonpolar ZnO (a-plane and m-plane orientations) being in agreement with RBS-C results. Raman spectroscopy showed distinct structural modification in various ZnO orientations simultaneously with identification of the disordered structure in O-sublattice. Nonpolar ZnO showed a significant increase in disorder in O-sublattice exhibited by E2(high) disappearance and enhancement of A1(LO) and E1(LO) phonons connected partially to oxygen vibrational modes. The lowering of the E2(low) phonon mode and shift to the lower wavenumbers was observed in c-plane ZnO connected to Zn-sublattice disordering. Such observations are in agreement with He ion channeling, showing channeling effect preservation with only slight Gd dopant position modification in a-plane ZnO and the more progressive diminishing of channels with subsequent Gd movement to random position with the growing ion fluence and after the annealing in c-plane and m-plane ZnO.

Keywords: doped c-, a- plane and m-plane ZnO; damage accumulation asymmetry; rare-earth ion implantation; RBS channelling; damage-depth profiling

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Permalink: https://www.hzdr.de/publications/Publ-30043
Publ.-Id: 30043


Introducing the periventricular region as a novel organ at risk in proton treatment planning of gliomas

Eulitz, J.; Raschke, F.; Troost, E. G. C.; Thiele, J.; Makocki, S.; Menkel, S.; Appold, S.; Enghardt, W.; Krause, M.; Lühr, A.

The periventricular region (PVR) has been shown to have an increased susceptibility to dose-dependent brain injury after proton therapy of gliomas (Eulitz 2019, Harrabi 2019). However, the PVR has not been considered in proton treatment planning so far. Here, we present an approach for incorporating the PVR as a novel organ at risk in proton treatment planning.

The PVR was defined as a 4 mm uniformly expanded margin around the ventricular system. The PVR tolerance dose was estimated as the observed near-min dose derived within late post-treatment radiation-associated contrast-enhancements (CE) on T1wCE-follow up images. All grade II/III glioma patients treated between 2014 and 2018 with (adjuvant) proton radio(chemo)therapy to 54/60 Gy(RBE), respectively, were analyzed. Retrospective PVR-sparing treatment planning was performed for 11 (4/7) consecutive glioma patients (Fig.1). Patient-wise comparison to the clinically delivered plans considered the near-max dose D2% and the volume Vx that received more than x% of prescribed dose in PVR tissue outside the target boost volume.

The median distance of the observed CE lesion centers to the cerebral ventricles was 2.5 mm. The median and near-min CE lesion dose was 57.6 Gy(RBE) and 53.0 Gy(RBE), respectively. PVR-sparing treatment planning reduced D2% and V90% by 4.3 (±1.4)% and 53.2 (±22.4)%, respectively, while maintaining clinical goals (Fig.1).

PVR-sparing in treatment planning is a promising approach to reduce late brain injury. In many cases this should be possible without compromising target coverage and field homogeneity. Further experience will improve the arrangement of PVR-sparing in the priority order of planning goals.

Keywords: Proton Therapy; Gliomas; Periventricular Region

  • Contribution to proceedings
    PTCOG - 59th Annual Conference of the Particle-Therapy Co-operative Group, 09.-14.05.2020, Taipei, Taiwan

Permalink: https://www.hzdr.de/publications/Publ-30042
Publ.-Id: 30042


Overexpression of the adenosine A2A receptor in murine heart assessed by PET imaging with [18F]FLUDA

Gündel, D.; Lai, T. H.; Dukic-Stefanovic, S.; Toussaint, M.; Deuther-Conrad, W.; Teodoro, R.; Boknik, P.; Gergs, U.; Neumann, J.; Brust, P.

Introduction
The impact of adenosine A2A receptors (A2AR) in heart diseases is discussed diversely and only a few preclinical models are available. Therefore, we generated a transgenic mouse (TG) model with heart-specific overexpression of the human A2AR (hA2AR). The overexpressed hA2AR exhibited a cardioprotective, but proarrhythmic function, and A2AR agonists exerted a positive inotropic effect in vitro [1, 2]. Here, we show, that our new radioligand [18F]FLUDA can be used to assess hA2AR overexpression in murine heart by PET and to proof specific A2AR binding in human atrial samples by autoradiography.

Methods
FVB/N mice overexpressing the hA2AR under control of a α-MHC promotor were studied. Receptor autoradiography was used to determine Kd and Bmax of [18F]FLUDA in hearts of WT and TG mice (n=3). A 90 min dynamic µPET acquisition was performed to determine the biodistribution of [18F]FLUDA (7.4±3.4 MBq i.v.; Am=23-154 GBq/µmol) in wildtype (WT) and TG (n=3-5) after preinjection of vehicle or the A2AR antagonist tozadenant (2.5 mg/kg bw). The PET images were attenuation corrected by a T1-weighted MRI and list mode data were reconstructed (dynamic, 3D-OSEM algorithm). For activity quantification in tissues VOIs were determined by MRI images (Fig. 2A). In addition, the impact of 1µM FLUDA on the force of contraction (FOC) in isolated electrically driven atrial preparation was investigated.

Results
In vitro autoradiography of [18F]FLUDA in cryosections of hearts (Fig. 1) revealed a KD of 5.9 ± 1.6 nM and Bmax of 455 ± 78 fmol/mg protein in TG, whereas in WT the receptor density was too low for exact quantification. Using ZM241385 as competitor 36.3 ± 5.3 % specific binding of [18F]FLUDA was demonstrated in normal human atrial samples. PET/MR analyses revealed a 26 % (p<0.05) higher SUV ratio (SUVR) of myocard/blood (Fig.2B) in TG vs. WT mice. In TG mice the SUVR was reduced by tozadenant pre-treatment by 6 % (p<0.05) while no change in WT was observed. In electrically driven atrial preparations of TG (but not WT), FLUDA reduced the increase of FOC after CGS 2180 stimulation by about 20% (p<0.05), indicating a functional antagonism of FLUDA at the human cardiac A2AR.

Conclusion
FVB/N mice overexpressing the hA2AR are a useful model for non-invasive investigation of this receptor function with [18F]FLUDA PET. The demonstration of specific radiotracer binding in the human heart provides evidence that [18F]FLUDA might be a suitable radiotracer for assessment the A2AR status of human heart with PET. Our next steps will focus on the disease-related changes of the A2AR expression in human atrial samples with [18F]FLUDA.

Acknowledgments
The authors thank the European Regional Development Fund and Sächsische Aufbaubank (SAB) for financial support (project no. 100226753).

Keywords: [18F]FLUDA, adenosine, A2AR, heart

References
1. Boknik P, Drzewiecki K, Eskandar J, et al (2018) Phenotyping of mice with heart specific overexpression of A2A-adenosine receptors: Evidence for cardioprotective effects of A2A-adenosine receptors. Front Pharmacol 9:1–12. https://doi.org/10.3389/fphar.2018.00013
2. Boknik P, Drzewiecki K, Eskandar J, et al (2019) Evidence for arrhythmogenic effects of A2A-adenosine receptors. Front Pharmacol 10:1–12. https://doi.org/10.3389/fphar.2019.01051


Fig. 1: Representative autoradiography of 20 µm cryosections of a FVB/N mouse heart overexpressing the human adenosine A2AR (A2AR-TG), showing the total binding of [18F]FLUDA (left) and the non-homologous competition of [18F]FLUDA with the A2AR specific antagonist ZM241385 (right).


Fig. 2: A) Representative MR image (left), PET image (middle) and merged overlay (right) of one slice in the short axis orientation of TG mouse heart used for the determination of VOIs.; B) standardized uptake value ratio (SUVR) of myocard over blood under baseline (veh – vehicle) and blocking conditions (toz- tozadenant) in wildtype (WT) and myocard specific hA2AR overexpressing mice (TG); n=3-5, *p≤0.05 WT vs. TG and #p≤0.05 veh vs. toz.

Keywords: [18F]FLUDA; adenosine; A2AR; heart

  • Lecture (Conference) (Online presentation)
    15th European Molecular Imaging Meeting, 24.-27.03.2020, Thessaloniki, Griechenland

Permalink: https://www.hzdr.de/publications/Publ-30041
Publ.-Id: 30041


Non-invasive assessment of the A2A adenosine receptor expression in the murine heart with [18F]FLUDA by positron-emission tomography (PET)

Gündel, D.; Lai, T. H.; Dukic-Stefanovic, S.; Toussaint, M.; Deuther-Conrad, W.; Teodoro, R.; Boknik, P.; Gergs, U.; Neumann, J.; Brust, P.

Question
We have shown that A2A adenosine receptors (A2A-AR) are functionally active in human hearts. Moreover, we generated a transgenic mouse model with heart specific overexpression of the human A2A-AR (TG), which responded to agonists with a positive inotropic effect in vitro. Overexpressed A2A-AR were cardioprotective but also proarrhythmic in TG (Boknik et al. Front Pharmacol 2018, 2019). Here, we focused on the question if a cardiac A2A-AR expression could be assessed in vivo utilizing PET imaging in this model.

Methods
The impact of FLUDA (7-(3-(4-(2-(fluoro)ethoxy-1,1,2,2-d4)phenyl)propyl)-2-(furan-2-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine; patent: DE 10 2019 116 986.0) on the force of contraction (FOC) in isolated electrically driven (1 Hz) atrial preparation after stimulation with the A2A–AR-agonist CGS 2180 (10 µM, in the presence of the A1A-AR antagonist DPCPX 1 µM) was measured. On cryosections of mouse hearts the KD and Bmax values of [18F]FLUDA were determined by autoradiography. A small animal PET/MRI scanner (nanoscan, Mediso) was used for in vivo imaging of mice under isoflurane anaesthesia. [18F]FLUDA (7.4±3.4 MBq) was applied via the tail vein 20 s after starting the 90-minute PET measurement. A2A-AR specificity of [18F]FLUDA was determined by application of 2.5 mg/kg body weight Tozadenant 10 minutes prior to tracer administration.

Results
FLUDA was able to reduce (p<0.05) the increase of FOC after CGS 2180 stimulation by about 20 % (p<0.05) in isolated electrically driven atrial preparation in TG (but not WT), indicating a functional antagonism of FLUDA at the human cardiac A2A-AR. By in vitro autoradiography of [18F]FLUDA a KD (5.9±1.6 nM) and Bmax (455±78 fmol/mg protein) could be determined in the A2A-AR-TG hearts, whereas in the control hearts the receptor density was below the detection limit. Using PET/MR, an SUV ratio (SUVR) myocardial/cardiac ventricle of ≥1,0 was determined for the A2A-AR-TG animals at 15-30 min p.i.. Tozadenant reduced SUVR by 6 % (p<0.05).

Conclusion
These data suggest that A2A-AR can be in principle quantified in vivo in the heart.

Keywords: A2A-AR; [18F]FLUDA; adenosine; heart

  • Poster
    5th German Pharm-Tox Summit, 02.-05.03.2020, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30040
Publ.-Id: 30040


[18F]FLUDA ist geeignet eine kardiale Überexpression des Adenosin-A2A-Rezeptors (A2AR) in der Maus nachzuweisen

Gündel, D.; Lai, T. H.; Dukic-Stefanovic, S.; Toussaint, M.; Deuther-Conrad, W.; Teodoro, R.; Boknik, P.; Gergs, U.; Neumann, J.; Brust, P.

A2AR-Liganden sind bei ischämischen Reperfusionsschäden kardioprotektiv wirksam (1). Somit ist eine Diagnose der kardialen A2AR-Verfügbarkeit für die Behandlung von Patienten mit koronaren Erkrankungen bedeutsam. Unser Ziel war es, anhand eines transgenen Mausmodells mit einer kardialen Überexpression des humanen A2AR das Potential von [18F]FLUDA als potentielles Radiopharmakon für die Darstellung des A2AR zu evaluieren.
Es wurden 4-6 Monate alte FVB/N Mäuse mit einer Kardiomyozyten-spezifischen Überexpression des humanen A2AR (A2AR TG) bzw. Kontrolltiere untersucht. Die Bestimmung der KD- und Bmax-Werte von [18F]FLUDA erfolgte autoradiographisch an Kryoschnitten von Herzexplantaten. Die In-vivo-Untersuchungen fanden unter Isoflurannarkose in einem Kleintier-PET/MRT-Scanner (nanoscan, Mediso) statt. [18F]FLUDA (7,4±3,4 MBq) wurde i.v. über die Schwanzvene 20 s nach Start der 90-minütigen PET-Messung appliziert. Die A2AR-Spezifität von [18F]FLUDA wurde durch Applikation von 2,5 mg/kg Tozadenant 10 min vor der Tracer Gabe bestimmt. Für die anatomische Korrelation und Schwächungskorrektur der PET-Aufnahmen erfolgte eine T1-gewichtete MRT. Die dynamische Rekonstruktion der Listenmodus-Daten erfolgte durch einen 3D-OSEM-Algorithmus. Die Quantifizierung der aufgenommenen Aktivität erfolgte mit PMOD.
Mittels In-vitro-Autoradiografie von [18F]FLUDA konnten in den A2AR-TG Herzen die Rezeptorparameter KD (5,9 ± 1,6 nM) und Bmax (455 ± 78 fmol/mg Protein) bestimmt werden, während in den Herzen der Kontroll-Tiere die Rezeptordichte unter der Nachweisgrenze lag. Mittels PET/MR wurde 15–30 min p.i. für die A2A-R TG Tiere ein SUV-Verhältnis (SUVR) Myokard/Herzventrikel von ≥1,0 bestimmt. Tozadenant verminderte das SUVR um 6 % (p < 0.05).
[18F]FLUDA ist ein vielversprechender Radiotracer zur Untersuchung der A2AR Verfügbarkeit im Herzen.
(1) Boknik P, et al., Front Pharmacol. 2018; 9:1–12.

Keywords: [18F]FLUDA; adenosine; A2AR; heart

  • Lecture (Conference) (Online presentation)
    58. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 22.-25.04.2020, Leipzig, Leipzig
    DOI: 10.1055/s-0040-1708154

Permalink: https://www.hzdr.de/publications/Publ-30036
Publ.-Id: 30036


Multiconfigurational calculations of ground and excited states of actinide complexes

Kloditz, R.; Patzschke, M.; Stumpf, T.

Multiconfigurational wavefunction based methods are the state of the art methods to quantitatively compute excited state energies and transition moments for heavy element systems where the inclusion of electron correlation and relativistic effects is crucial. Since the advent of these methods, e.g. the complete active-space self-consistent field (CASSCF) method and the density-matrix renormalization group (DMRG) method, it is possible to accurately interpret and predict the UV-Vis spectra of these heavy element systems.
In this talk the CASSCF and DMRG methods are introduced and used to simulate the UV-Vis spectrum of the Uranium-bissalen complex. The active space is set up and varied to accurately describe the wavefunction. CASPT2 and RASSI are used to obtain quantitative results for excited state energies and transition moments.

Keywords: CASSCF; DMRG; Actinides; Excited states; Correlation

  • Invited lecture (Conferences)
    Arbeitsgruppenseminar des AK Thomas Heine (TU Dresden), 26.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30035
Publ.-Id: 30035


Revealing the metal-ligand bonding character in tetravalent f-element complexes with Schiff-base ligands

Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.

The contribution of the f-orbitals to chemical bonding leads to the rich chemistry of the actinides. This is in contrast to the lanthanides, where it is known that this contribution is less important. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study compares the different bonding behavior of tetravalent actinides and lanthanides with the Schiff base salen by means of real-space bonding analysis. Our approach makes use of the quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) analysis and density differences complemented by natural population analysis (NPA). Especially the local properties at the bond critical points, for instance charge, density, ellipticity and others, can be used to characterize a bond’s order, strength, and covalent contribution.
First results reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker. The delocalization index, density and Laplacian reveal a significant increase of covalency for Pa to Pu compared to Th and Ce being an indicator of the contribution of the f-electrons. Tetravalent Ce as a lanthanide analogue of Th is expected to show a similar bonding behavior, but, surprisingly, this is not the case for all investigated bonding properties.
This detailed analysis of the electronic properties of actinide compounds will help to improve understanding of their behavior in the environment as well as in technical processes and leads to the possibility to predict properties of unknown complexes.

Keywords: DFT; QTAIM; DMRG; Actinides; Quantum chemistry; Bonding

  • Poster
    European Summerschool of Quantum Chemistry, 08.-21.09.2019, Palermo, Italien
  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30034
Publ.-Id: 30034


Insights into the excited states of 5f systems: Protactinium and Uranium

Kloditz, R.; Patzschke, M.; Stumpf, T.

The calculation of the excited states of actinide systems is a challenging task because of the delicate influence of electron correlation and relativistic effects. Density functional theory is not applicable for obtaining quantitative results, hence multiconfigurational wavefunction based methods have to be used. State of the art is a combination of spinfree CASSCF and CASPT2/NEVPT2 and a following inclusion of spin-orbit coupling.
This talk presents quantitative excited state energy calculations of simple Protactinium and Uranium systems in comparison with qualitative group-theoretical considerations.

Keywords: CASSCF; Actinides; Excited states; Group theory

  • Invited lecture (Conferences)
    Arbeitsgruppenseminar des AK Markus Reiher (ETH Zürich), 10.07.2019, Zürich, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-30033
Publ.-Id: 30033


Analysis of the metal-ligand bonding character in tetravalent f-element complexes with Schiff-base ligands

Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.

The contribution of the f-orbitals to chemical bonding leads to the rich chemistry of the actinides. This is in contrast to the lanthanides, where it is known that this contribution is less important. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study compares the different bonding behavior of tetravalent actinides and lanthanides with the Schiff base salen by means of real-space bonding analysis. Our approach makes use of the quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) analysis and density differences complemented by natural population analysis (NPA). Especially the local properties at the bond critical points, for instance charge, density, ellipticity and others, can be used to characterize a bond’s order, strength, and covalent contribution.
First results reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker. The delocalization index, density and Laplacian reveal a significant increase of covalency for Pa to Pu compared to Th and Ce being an indicator of the contribution of the f-electrons. Tetravalent Ce as a lanthanide analogue of Th is expected to show a similar bonding behavior, but, surprisingly, this is not the case for all investigated bonding properties.
This detailed analysis of the electronic properties of actinide compounds will help to improve understanding of their behavior in the environment as well as in technical processes and leads to the possibility to predict properties of unknown complexes.

Keywords: Actinides; DFT; QTAIM; bonding; covalency; quantum chemistry

  • Poster
    Molecular Quantum Mechanics, 30.06.-05.07.2019, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30032
Publ.-Id: 30032


Towards multiscale and multisource remote sensing mineral exploration using RPAS: A case study in the Lofdal Carbonatite-Hosted REE Deposit, Namibia

Booysen, R.; Zimmermann, R.; Lorenz, S.; Gloaguen, R.; Nex, P. A. M.; Andreani, L.; Möckel, R.

Traditional exploration techniques usually rely on extensive field work supported by geophysical ground surveying. However, this approach can be limited by several factors such as field accessibility, financial cost, area size, climate, and public disapproval. We recommend the use of multiscale hyperspectral remote sensing to mitigate the disadvantages of traditional exploration techniques. The proposed workflow analyzes a possible target at different levels of spatial detail. This method is particularly beneficial in inaccessible and remote areas with little infrastructure, because it allows for a systematic, dense and generally noninvasive surveying. After a satellite regional reconnaissance, a target is characterized in more detail by plane-based hyperspectral mapping. Subsequently, Remotely Piloted Aircraft System (RPAS)-mounted hyperspectral sensors are deployed on selected regions of interest to provide a higher level of spatial detail. All hyperspectral data are corrected for radiometric and geometric distortions. End-member modeling and classification techniques are used for rapid and accurate lithological mapping. Validation is performed via field spectroscopy and portable XRF as well as laboratory geochemical and spectral analyses. The resulting spectral data products quickly provide relevant information on outcropping lithologies for the field teams. We show that the multiscale approach allows defining the promising areas that are further refined using RPAS-based hyperspectral imaging. We further argue that the addition of RPAS-based hyperspectral data can improve the detail of field mapping in mineral exploration, by bridging the resolution gap between airplane- and ground-based data. RPAS-based measurements can supplement and direct geological observation rapidly in the field and therefore allow better integration with in situ ground investigations. We demonstrate the efficiency of the proposed approach at the Lofdal Carbonatite Complex in Namibia, which has been previously subjected to rare earth elements exploration. The deposit is located in a remote environment and characterized by difficult terrain which limits ground surveys.

Keywords: Carbonatite complex; Hyperspectral sensors; Mineral exploration; Multiscale; Namibia; Remotely Piloted Aircraft System

Permalink: https://www.hzdr.de/publications/Publ-30031
Publ.-Id: 30031


Active Targeting of Dendritic Polyglycerols for Diagnostic Cancer Imaging

Kritee, P.; Neuber, C.; Zarschler, K.; Wodtke, J.; Meister, S.; Rainer, H.; Pietzsch, J.; Stephan, H.

Active tumor targeting involves the decoration of nanomaterials (NM) with oncotropic vector biomolecules that selectively recognize certain antigens on malignant cells or in the tumor microenvironment. This strategy can facilitate intracellular uptake of NM through specific interactions such as receptor-mediated endocytosis and can lead to prolonged retention in the malignant tissues by preventing rapid efflux from the tumor. Here, the design of actively targeting, renally excretible bimodal dendritic polyglycerols (dPGs) for diagnostic cancer imaging is described. Single-domain antibodies (sdAb) specifically binding to the epidermal growth factor receptor (EGFR) are employed herein as targeting warheads owing to their small size and high affinity for their corresponding antigen. The dPGs equipped with EGFR-targeting feature are compared head-to-head with their non-targeting counterparts in terms of interaction with EGFR-overexpressing cells in vitro as well as accumulation at receptor-positive tumors in vivo. Experimental results reveal a higher specificity and preferential tumor accumulation for the α-EGFR dPGs, resulting from the introduction of active targeting capabilities on their backbone. These results highlight the potential for improving the tumor uptake properties of dPGs by strategic use of sdAb functionalization, which could ultimately prove useful to the development of ultrasmall NM with highly specific tumor accumulation.

Keywords: polymeric nanoparticles; targeting; single-domain antibodies; multimodality imaging; optical imaging; positron emission tomography

Permalink: https://www.hzdr.de/publications/Publ-30029
Publ.-Id: 30029


New detection system for transmission imaging in the helium ion microscope

Serralta Hurtado De Menezes, E.; Klingner, N.; de Casto, O.; Duarte Pinto, S.; Bebeacua, C.; Findeisen, S.; Bouton, O.; Wirtz, T.; Hlawacek, G.

Transmission imaging in the helium ion microscope allows to measure mass-thickness contrast and reveal crystallographic information. We recently customized a microchannel plate followed by a delay line readout structure especially for this application. This system can correlate the scanning transmission ion image to the angular distribution of the transmitted ions. An in-vacuum linear support is used to place the detector at different distances from the sample, adjusting the maximum collection angle. Post-processing allows the reconstruction of images for selected scattering angles. The first results show images with nanometer resolution, material contrast, and identification of sub-surface features in biological tissues. This work has been supported by the H2020 Project npSCOPE under grant number 720964.

Keywords: Helium Ion Microscopy; Scanning Transmission Ion Imaging; HIM; STIM

Related publications

  • Lecture (Conference)
    The 3rd International Workshop of the PicoFIB Network, 20.01.2020, Sheffield, United Kingdom
  • Lecture (Conference)
    DPG Spring Meeting of the Condensed Matter Section (SKM), 15.-20.03.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30028
Publ.-Id: 30028


X-ray absorption near edge spectroscopy study of warm dense MgO

Bolis, R.; Hernandez, J.-A.; Recoules, V.; Guarguaglini, M.; Dorchies, F.; Jourdain, N.; Ravasio, A.; Vinci, T.; Brambrink, E.; Ozaki, N.; Bouchet, J.; Remus, F.; Musella, R.; Mazevet, S.; Hartley, N.; Guyot, F.; Benuzzi-Mounaix, A.

We report time-resolved X-ray Absorption Near Edge Spectroscopy (XANES) measurements of warm dense MgO. We used a high power nanosecond pulse to drive a strong uniform shock wave into an MgO sample, and a picosecond pulse to generate a broadband X-ray source near the Mg K-edge. We used this setup to obtain XANES spectra across a large area of the phase diagram, with densities up to 6.8 g/cc and temperatures up to 30 000 K, conditions at which no prior investigations of electronic and ionic structure exist. Our XANES results, together with quantum molecular dynamic simulations, demonstrate that the sample metallizes due to the bandgap closure as it melts, after which it shows typical behavior for a disordered ionic liquid.

Keywords: Lasers; Metallization process; Band gap; Laser plasma interactions; Shock waves; High-density liquid; X-ray absorption spectroscopy; Phase transitions

Downloads

Permalink: https://www.hzdr.de/publications/Publ-30026
Publ.-Id: 30026


NORM research and strategy at the HZDR, Germany

Arnold, T.

The presentation gives an overview of the NORM research at the HZDR

Keywords: NORM; radioecology; uranium; research; strategy

  • Invited lecture (Conferences)
    Cores Symposium on Radon and NORM – regulatory aspects, scientific achievements and research needs, 03.-04.09.2019, Helsinki, Finland

Permalink: https://www.hzdr.de/publications/Publ-30025
Publ.-Id: 30025


CFD simulation of multiphase flow in evaporators

Schlottke, J.; Kühnel, W.; Porombka, P.; Lucas, D.

Inside evaporators of air-conditioning systems, uneven mass flow distribution of refrigerant leads to a loss of efficiency and finally a reduction of comfort in passenger compartments. The distribution is influenced by the flow field and two-phase distribution (flow pattern) in various elements, comprising developing and developed two-phase flow in straight and angled ducts, headers, flat tubes and the connection between these.
This talk presents on-going efforts to predict this type of flow with CFD.
In a first step, extensive experimental investigations on generic geometries are done using advanced measurement techniques. This data are then used to develop and validate numerical models capable of reproducing the relevant physics.
Important two-phase phenomena are: multiple regimes (continuous-disperse + separated flow), wall films, stripping/impingement, particle size distribution, two-phase heat transfer, boiling/condensation. In a final step, the developed modeling strategy is applied to real evaporators.
In comparing simulation results to experimental data, we find both good agreement as well as discrepancies which confirm that there is still more work on developing appropriate models to do.

Keywords: evaporator; CFD; flow distribution; air-conditioning systems; Euler-Euler method

  • Lecture (Conference)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30024
Publ.-Id: 30024


The Inverse Trans Influence in a novel Uranium(IV)bis(carbene) Complex

Köhler, L.; Patzschke, M.; März, J.; Stumpf, T.

The trans influence is an extensively investigated electronic concept in transition metal chemistry. It can be defined as the extent to which a bond in trans position to a ligand L is weakened.[1,2] In contrast, f-block elements exhibit an opposite effect, meaning a bond shortening and thus strengthening can be observed in the trans position to a strongly donating ligand. This is established as the inverse trans influence (ITI),[3–5] and is commonly assumed to be most prominent for actinides in high oxidation states.
A novel UIVbis(carbene) complex [UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) was synthesized by salt metathesis from UCl4 in the presence of iPrImHCl and TMSA. In the complex, the U centre is surrounded by two carbenes, three chloro- and one TMSA-ligand. The U–Cl bond in trans position to the TMSA is slightly shorter (0.01 Å) compared to the other U–Cl bonds, indicating an TMSA-induced ITI. However, this change is very small. For comparison, a structural optimization based on the SC-XRD data of 1 was carried out using tetravalent tungsten as a d-block analogue, because of its similar ionic radius to UIV. Tungsten’s transition metal behaviour should result in a trans influence. In the WIVbis(carbene) complex 2, the W–Cl bond trans to the TMSA ligand is indeed 0.05 Å longer than the other W–Cl bonds. This large change expresses the existence of a strong trans influence in 2 and hence ITI in 1.
References:
[1] A. Pidcock, R. E. Richards, L. M. Venanzi, J. Chem. Soc. Inorg. Phys. Theor. 1966, 0, 1707–1710.
[2] T. G. Appleton, H. C. Clark, L. E. Manzer, Coord. Chem. Rev. 1973, 10, 335–422.
[3] R. G. Denning, J. Phys. Chem. A 2007, 111, 4125–4143.
[4] H. S. La Pierre, K. Meyer, Inorg. Chem. 2013, 52, 529–539.
[5] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.

Keywords: uranium carbene complex; inverse trans influence; ITI; tungsten carbene complex

  • Lecture (Conference)
    Tagung Gesellschaft Deutscher Chemiker, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30023
Publ.-Id: 30023


Actinid-Komplexe mit N-heterocyclischen Carbenen

Köhler, L.; Patzschke, M.; März, J.; Stumpf, T.

The inverse trans influence (ITI) is an effect well-known to occur in high valent U(V/VI) complexes. It appears as a shortening of the M–L bond in trans position to a strongly donating ligand. The effect can be explained by electron density donation from the strong ligand to the metal center, which fills up the electron hole formed through electron density transfer from semi-core 6p to vacant 5f orbitals.[1,2] This results in the observed contraction and strengthening of the bond trans to the donating ligand.
To compare the ITI in UIV and UV complexes, the U compounds UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) and [UV(TMSI)Cl₅, but is in the same range as the other chloro ligands. The absence of a notable ITI can be attributed to intermolecular interactions in the crystal structure of 2. Structure optimization of the molecular UV complex dianion by DFT yield a U–Cl5 bond length of 2.55 Å, shorter than any other U–Cl bond by 0.02 Å. The difference between experiment and theory results from a great number of electrostatic interactions and hydrogen bonding between the complex dianion and the carbene counterions in 2. Similar intermolecular interactions are not present in the crystal structure of 1, which is why the ITI could be observed for this compound.
The results demonstrate that the ITI affects complex structures for both, UIV and UV compounds, but additional effects, such as the intermolecular network observed in the structure of 2 can surpass its relatively small structural contribution.

References
[1] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.
[2] B. Kosog, H. S. La Pierre, F. W. Heinemann, S. T. Liddle, K. Meyer, J. Am. Chem. Soc. 2012, 134, 5284–5289.

Keywords: carbenes; inverse trans influence; ITI; uranium(V) complex

  • Invited lecture (Conferences)
    Finale der WiN Preisverleihung, 11.10.2019, Karlstein/Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30022
Publ.-Id: 30022


The Inverse Trans Influence in U(IV/V) complexes

Köhler, L.; Patzschke, M.; März, J.; Stumpf, T.

The inverse trans influence (ITI) is an effect well-known to occur in high valent U(V/VI) complexes. It appears as a shortening of the M–L bond in trans position to a strongly donating ligand. The effect can be explained by electron density donation from the strong ligand to the metal center, which fills up the electron hole formed through electron density transfer from semi-core 6p to vacant 5f orbitals.[1,2] This results in the observed contraction and strengthening of the bond trans to the donating ligand.
To compare the ITI in UIV and UV complexes, the U compounds UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) and [UV(TMSI)Cl₅, but is in the same range as the other chloro ligands. The absence of a notable ITI can be attributed to intermolecular interactions in the crystal structure of 2. Structure optimization of the molecular UV complex dianion by DFT yield a U–Cl5 bond length of 2.55 Å, shorter than any other U–Cl bond by 0.02 Å. The difference between experiment and theory results from a great number of electrostatic interactions and hydrogen bonding between the complex dianion and the carbene counterions in 2. Similar intermolecular interactions are not present in the crystal structure of 1, which is why the ITI could be observed for this compound.
The results demonstrate that the ITI affects complex structures for both, UIV and UV compounds, but additional effects, such as the intermolecular network observed in the structure of 2 can surpass its relatively small structural contribution.

References
[1] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.
[2] B. Kosog, H. S. La Pierre, F. W. Heinemann, S. T. Liddle, K. Meyer, J. Am. Chem. Soc. 2012, 134, 5284–5289.

Keywords: inverse trans influence; ITI; uranium(V); carbenes

  • Lecture (Conference)
    Journées des Actinides, 14.-18.04.2019, Erice, Italien

Permalink: https://www.hzdr.de/publications/Publ-30021
Publ.-Id: 30021


Precise image-guided proton irradiation of mouse brain sub-volumes

Suckert, T.; Müller, J.; Beyreuther, E.; Brüggemann, A.; Bütof, R.; Dietrich, A.; Gotz, M.; Haase, R.; Schürer, M.; Tillner, F.; von Neubeck, C.; Krause, M.; Lühr, A.

Introduction
Due to the beneficial inverse physical depth-dose profile, proton radiotherapy (RT) offers the potential to reduce normal tissue toxicity by depositing the maximum dose within the tumor volume while sparing the surrounding tissue. However, range uncertainties and necessary clinical safety margins in combination with varying relative biological effectiveness (RBE) may result in a critical dose in tumor-surrounding normal tissue. Dedicated preclinical studies have been proposed to assess and better understand potential adverse effects of proton RT using image-guided proton irradiation of mouse brain. Here, we present the entire workflow from pre-treatment imaging, over treatment planning, mouse brain irradiation as established at the University Proton Therapy Center Dresden as well as first results from subsequent DNA damage analysis.

Materials & Methods
An experimental setup was designed and characterized to shape proton beams with 7 mm range in water and 3 mm diameter allowing for irradiation of the mouse brain´s right hemisphere. To simulate the dose distributions in vivo, a Monte Carlo model of the proton beam was designed in the simulation toolkit TOPAS, experimentally commissioned and validated. Cone-beam computed tomography (CT) and orthogonal X-ray imaging were used to delineate the hippocampus as target and position the mice at the proton beam. Mouse brains of C3H and C57BL/6 mice were irradiated with 4 Gy or 8 Gy in a single fraction and excised at different timepoints after irradiation. The number of remaining DNA double-strand break repair proteins was visualized by staining brain sections for cell nuclei and H2AX. Imaged sections were analyzed with an automated and validated processing pipeline to provide quantitative data on spatially resolved radiation damage distributions.
Results
Animals were planned and treated for proton irradiation of the right hippocampus with a proton beam stopping in the center of the brain. The analysis of irradiated brain sections revealed well-delimited sub-volumes of pronounced DNA damage in the right brain hemisphere. The registration of the brain sections with the CT anatomy revealed that the measured DNA damage pattern were in good spatial agreement with the planned dose distributions simulated in individual mouse brains. The cellular radiation response could be correlated with dose and LET on a sub-milimeter scale.
Conclusion:
Image-guided proton irradiation of mouse brains was established with a clinically oriented workflow that facilitates (back-) translational studies. The geometric accuracy, detailed Monte Carlo dose simulations and cell-based assessment enable a biologically and spatially resolved analysis of radiation response and RBE.

  • Lecture (Conference)
    5th Conference on Small Animal Precision Image-guided Radiotherapy, 21.-23.03.2022, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30020
Publ.-Id: 30020


Trivalent Lanthanide and Actinide Incorporation into Zirconium(IV) Oxide – Spectroscopic Investigations of Defect Fluorite Structures

Eibl, M.; Shaw, S.; Hennig, C.; Morris, K.; Stumpf, T.; Huittinen, N. M.

The incorporation of trivalent lanthanides and actinides into zirconia (ZrO₂) was studied using PXRD and spectroscopic methods (EXAFS, TRLFS). In highly doped cubic zirconia three Eu(III) incorporation species could be found using TRLFS. A surface associated species with an excitation maximum of 578.1 nm and two bulk incorporation species with excitation maxima at 579.0 and 579.7 nm were found.

  • Lecture (Conference)
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30019
Publ.-Id: 30019


Trivalent Lanthanide and Actinide Incorporation into Zirconium(IV) Oxide – Spectroscopic Investigations of Defect Fluorite Structures

Eibl, M.; Shaw, S.; Hennig, C.; Morris, K.; Stumpf, T.; Huittinen, N. M.

The incorporation of trivalent lanthanides and actinides into zirconia (ZrO₂) was studied using PXRD and spectroscopic methods (EXAFS, TRLFS). In highly doped cubic zirconia three Eu(III) incorporation species could be found using TRLFS. A surface associated species with an excitation maximum of 578.1 nm and two bulk incorporation species with excitation maxima at 579.0 and 579.7 nm were found.

  • Lecture (Conference)
    17th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere., 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-30018
Publ.-Id: 30018


Experimental investigation of ghosting artefacts in in-beam MRI during proton pencil beam scanning

Gantz, S.; Hietschold, V.; Hoffmann, A. L.

Introduction
The integration of real-time MRI is expected to improve the targeting precision of proton therapy. We have developed a first prototype setup of an in-beam MRI scanner at a proton pencil beam scanning (PBS) beam line. The aim of this study was to investigate the effects of the dynamic magnetic fringe fields of the PBS beam steering magnets on the MR image quality during simultaneous irradiation and MR image acquisition.
Materials and methods
A 0.22 T open MR scanner was positioned in front of the horizontal PBS research beam line. 2D planar dose spot application was achieved by magnetic beam steering in horizontal and vertical direction through a pair of fast scanning magnets.
A proton pencil beam of 220 MeV was subsequently scanned along a horizontal and vertical central line in the MR imaging field. The irradiation time matched the acquisition time of a single-slice gradient echo sequence, while imaging a homogeneous transversal slice of the ACR Small Phantom. The image quality was evaluated qualitatively and compared to reference images acquired without beam scanning.
Results and conclusions
MR images acquired during vertical beam scanning showed no visual differences to reference images, whereas images acquired during horizontal beam scanning showed coherent ghosting artefacts in phase encoding direction. The artefacts exhibit a systematic behavior in which the number of ghosts is inversely proportional to the number of dose spots scanned. The phase maps of the k-space data prove that the artefacts are caused by phase offsets between adjacent lines, which result from changes in the MR resonance frequency due to the dynamic fringe fields of the beam scanning magnets in the PBS nozzle.
Now the origin of the ghosting artefacts is well understood, appropriate means for magnetic shielding or k-space data post-processing have to be implemented and studied to eliminate these artefacts.

Keywords: MRI; proton therapy

  • Contribution to proceedings
    8th MR in RT Symposium 2021, 19.-21.04.2021, Heidelberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-30017
Publ.-Id: 30017


CFD simulation of flashing phenomena

Liao, Y.

Due to its relevance for technical applications, experimental and theoretical investigation on flashing flows through nozzles and tubes has gained great attention. Most of them have focused on area-averaged quantities such as mass flow rate and pressure drop, while little attention has been paid to the internal flow structure and interfacial exchanging processes. More recently, computational fluid dynamics is frequently utilized to explore the phase distribution in the flashing flows. Various gas-liquid mixture or two-fluid models have been proposed in the literature. However, knowledge on the non-equilibrium effects, interphase transfer as well as bubble dynamics under different flashing conditions is still insufficient, and a general and precise definition of the problem in numerical simulations remains a challenge. A broad consensus on the numerical methods for flashing flows is not available. Guidelines for selecting an appropriate model are desirable, which is, however, not an easy task due to the complex physics and lack of insights. The talk is focused on the elucidation of important interfacial processes such as interfacial area density, interfacial heat transfer, bubble nucleation, coalescence and breakup as well as available modelling approaches. Numerical simulations for various flashing scenarios, i.e. converging-diverging flow, pipe-blowdown, natural circulation loop and pressure release transient, are presented. The influence of chosen numerical methods is discussed, especially the mixture model versus two-fluid ones and mono-disperse versus poly-disperse approaches. Progresses towards developing a general framework for modelling of complex gas-liquid flows are demonstrated.

Keywords: Flashing flow; Numerical simulation; Phase change; Mono-disperse approach; Poly-disperse approach

  • Lecture (Conference)
    17th Multiphase Flow Conference & Short Course, 11.-15.11.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-30016
Publ.-Id: 30016


Accuracy and robustness of 4D logfile-based dose reconstruction and start of clinical application

Spautz, S.; Meijers, A.; Jakobi, A.; Peters, N.; Knopf, A.-C.; Troost, E. G. C.; Richter, C.; Stützer, K.

Introduction: We established a 4D logfile-based dose reconstruction for monitoring and potential intervention during intensity-modulated proton therapy (IMPT) of moving tumors. Before clinical application, we assessed the validity of reconstructed doses and the sensitivity against changes of selected input parameters by phantom experiments.
Material/Methods: A dynamic thorax phantom (CIRS, USA) with a soft-tissue target and radiochromic film insert was imaged by 4DCT and irradiated with either quasi-monoenergetic fields or 4D optimized proton plans. The surrogate signal (ANZAI, Japan) of the regular motion was recorded in synchronization with the machine logfiles. Reconstructions were performed with different dose grid resolutions (1mm/3mm), deformable image registrations (DIR; manually defined or automatically generated vector-fields) and artificial asynchronies between machine and motion logfiles.
Results: Characteristic dose patterns on radiochromic films were well reconstructed (Fig.1A). Gamma pass rates (2mm, 2%) for extracted characteristic profiles of the reconstructed and measured doses were >98% under static conditions, ranged between 99% and 86% for 5mm motion depending on applied reconstruction parameters, especially the DIR, and were about 80% for 30mm motion due to the predominant residual motion in the 4DCT (Fig.1B). Fig.1C demonstrates the robustness against potential minor asynchronies (≈5ms) between machine and motion logfiles. A workflow test during a pancreatic cancer IMPT treatment (Fig.2) revealed a data processing time of approximately 20min/fraction.
Conclusions: Due to satisfying accuracy and robustness for clinically aimed motion amplitudes (≤5mm), IMPT treatment of non-small cell lung cancer accompanied by daily 4D logfile-based dose monitoring will start in our institute within the first months of 2020.

  • Lecture (Conference) (Online presentation)
    PTCOG 2020 Online, 13.-14.09.2020, Prag, Tschechische Republik

Permalink: https://www.hzdr.de/publications/Publ-30015
Publ.-Id: 30015


Synthesis and Characterization of Tri- and Tetravalent Actinide Amidinates

Fichter, S.

Tri- and tetravalent actinide amidinates have been synthesized and characterized in solid state and in solution.

  • Lecture (others)
    FENABIUM Projekttreffen, 12.11.2019, Dresden, Deutschland
  • Invited lecture (Conferences)
    Jahrestagung der Fachgruppe Nuklearchemie 2022, 06.10.2022, Bergisch Gladbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30014
Publ.-Id: 30014


Some notes on eddy viscosity in wall-bounded turbulent bubbly flows

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

Recently, based on data from Direct Numerical Simulations (DNS), Ma et al. (Phys. Rev. Fluids 2, 034301, 2017) proposed a model for closing the bubble-induced turbulence (BIT) in a typical Euler-Euler two-equation model, which appears to yield improved performance for predicting $k$ and $\varepsilon$ over the previous models. The present study departures from this BIT model and purpose to use the same DNS data to investigate the behavior of the $C_\mu$ constant and standard eddy viscosity definition. It can be shown that $C_\mu$ constant computed using the DNS database has a very different behavior than that in single-phase flow. Checking closely, the deficiency originates from the description of the standard eddy viscosity that is intrinsic to this general hierarchy of Euler-Euler $k-\varepsilon$ type model, hence, cannot be overcome by a more complex correction function for $C_\mu$. Departing from this point, a modification to the definition of the eddy viscosity in bubbly flows is derived for the Euler-Euler two-equation models. The new expression is based on the bubble length-scale and its corresponding velocity scale. We focus on the intermediate region -- a region extended from the core region, where bubble-induced production and dissipation are nearly in balance, and find that the modified model can lead to significantly improved predictions for the mean liquid, when compared with DNS data.

  • Lecture (Conference)
    72nd Annual Meeting of the APS/DFD, 23.-26.11.2019, Seattle, USA

Permalink: https://www.hzdr.de/publications/Publ-30013
Publ.-Id: 30013


A Flow Pattern Adaptive Multi-field Two-fluid Concept for Turbulent Two-phase Flows

Schlegel, F.; Meller, R.; Lehnigk, R.; Hänsch, S.; Tekavčič, M.

Industrial applications feature a huge variety of different flow patterns, such as bubbly flow, slug flow or annular flow. Thereby a broad range of flow morphologies and different physical scales is involved. With the objective of reproduction of occurring phenomena with one single multi-fluid solver, we present an Euler-Euler-approach, which combines a number of different methods for treatment of the partial aspects. The implementation into OpenFOAM is always with focus on sustainable research, including a state-of-the-art IT concept. A segregated approach is used for treatment of the phase momentum equations, phase fraction equations and the pressure equation, featuring a consistent momentum interpolation scheme (Cubero et al., 2014). To fulfil the kinematic condition at resolved interfaces between different continuous phases, the latter may be coupled either by an isotropic (Strubelj and Tiselj, 2011) or by an anisotropic drag. In both cases, the immensely strong phase coupling requires an adapted numerical method. State and evolution of bubble size distribution in disperse phase context is solved with either class or moment methods.
The overall objective is to take interactions between the all different aspects, such as disperse phases, resolved interfaces and turbulence with effects on momentum and mass transfer into account.

  • Poster
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30012
Publ.-Id: 30012


On non drag interfacial force and thermal phase change modelling of reactingEulerFoam

Peltola, J.; Pättikangas, T.; Bainbridge, W.; Lehnigk, R.; Schlegel, F.

The reactingEulerFoam framework included in OpenFOAM releases since 3.0.0 provides a highly flexible platform for the modelling of multiphase flows. Extensive selection of interfacial force models is provided along with alternate turbulence models. The thermal phase change capability [1,2] was first introduced in OpenFOAM 3.0.1 [3] and has since been extended and refined in subsequent releases.
The current OpenFOAM 7 release features include support for non-equilibrium wall boiling, n-phase thermal phase change and for bubble diameter modelling algebraic, IATE and inhomogeneous class method models are supported.The present simulations have been carried out with the OpenFOAM Foundation development release [4]. The goal is to aid those that intend to use the publicly available reactingEulerFoam by providing a summary of the models and demonstrations of a few modelling details by expanding upon tutorials recently added to the OpenFOAM Foundation development line.
DEDALE experiments [5] are used as a reference for the non-drag interfacial force modelling.
Subcooled nucleate boiling simulation results with different models combinations are compared to the DEBORA experiments [6,7]. Finally, a more complex direct contact condensation simulation of SEF-POOL test facility [8] is presented and results are compared to the experiment.

References

[1] Peltola, J., & Pättikangas, T.J.H. Development and validation of a boiling model for OpenFOAM multiphase solver. CFD4NRS-4 Conference Proceedings, Daejeon, Korea, paper 59, (2012).
[2] Peltola, J., Pättikangas, T., Bainbridge, W., Lehnigk, R., Schlegel, F., On development and validation of subcooled nucleate boiling models for OpenFOAM Foundation release. NURETH-18 Conference Proceedings, Portland, Oregon, United States (2019).
[3] OpenFOAM Foundation, “OpenFOAM 3.0.1,” http://openfoam.org/version/3.0.1/ (2015).
[4] OpenFOAM Foundation, “OpenFOAM-dev,” https://openfoam.org/version/dev/ (2014-2019).
[5] Grossetete, C., Experimental investigation and numerical simulations of void profile development in a vertical cylindrical pipe (No. EDF--96-NB-00120). Electricite de France (EDF), (1995).
[6] E. Manon, Contribution à l’anayse et à la modélisation locale des écoulements boillants sous-saturésdans les conditions des Réacteurs à Eau sous Pression, PhD thesis, Ecole Centrale Paris (2000).
[7] J. Garnier, E. Manon, G. Cubizolles, “Local measurements on flow boiling of refrigerant 12 in avertical tube”, Multiphase Science and Technology, pp. 1-111 (2001).
[8] M. Puustinen, J. Laine, A. Räsänen, E. Kotro, and K. Tielinen, “Characterizing tests in SEF-POOLfacility,” Technical Report, Lappeenranta University of Technology, Nuclear Engineering, INSTAB3/2017 (2017).

  • Lecture (Conference)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30011
Publ.-Id: 30011


Flexible development framework for the Euler Euler approach

Schlegel, F.; Greenshields, C.

The presentation gives a detailed insight into the OpenFOAM Developments for Euler-Euler simulations at HZDR, i.p. the multi-field two-fluid model approach, LES simulations, stratified flow simulations, entrainment modelling and more. Furthermore, the successfull development strategy and co-working with the OpenFOAM Foundation is explained.

Keywords: Euler-Euler; OpenFOAM; Numerical Simulation; Entrainment; Gentop; Stratified Flow

  • Invited lecture (Conferences)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30010
Publ.-Id: 30010


X2 benchmark specification dataset

Bilodid, Y.

The X2 VVER-1000 benchmark specification dataset.
 - version 1.0: original dataset
 - version 1.1: added results template for the Control Cor Ejection exercise.

Keywords: VVER-1000; X2 benchmark

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Permalink: https://www.hzdr.de/publications/Publ-30009
Publ.-Id: 30009


AER working group D meeting on VVER safety analysis - report of the 2019 meeting

Kliem, S.

The AER Working Group D on VVER reactor safety analysis held its 28th meeting in Garching, Germany, during the period 26-27 June, 2019. The meeting was hosted by GRS Garching and was held in conjunction with the second workshop on multi-physics MPMV-2 and the first workshop on the ROSTOV-2 benchmark. Altogether 20 participants from eleven AER member organizations and seven guests attended the meeting of the working group D. The co-ordinator of the working group, Mr. S. Kliem, served as the chairperson of the meeting.

The meeting started with a general information exchange about the recent activities in the participating organizations.

The given 12 presentations and the discussions can be attributed to the following topics:

  • Safety analyses methods and results
  • Code development and benchmarking
  • Future activities

A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairperson.

  • Contribution to proceedings
    29th Symposium of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2019, Mochovce, Slovakia
    Proceedings of the 29th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: Kiadja az EK, 9789637351327, 325-330

Permalink: https://www.hzdr.de/publications/Publ-30008
Publ.-Id: 30008


Microstructural evolution and thermal stability of AlCr(Si)N hard coatings revealed by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction

Jäger, N.; Meindlhumer, M.; Spor, S.; Hruby, H.; Julin, J.; Stark, A.; Nahif, F.; Keckes, J.; Mitterer, C.; Daniel, R.

An extensive understanding about the microstructural evolution and thermal stability of the metastable AlCr(Si)N coating system is of considerable importance for applications facing high temperatures, but it is also a challenging task since several superimposed processes simultaneously occur at elevated temperatures. In this work, three AlCr(Si)N coatings with 0 at.%, 2.5 at.% and 5 at.% Si were investigated by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction (HT-HE-GIT-XRD) and complementary differential scanning calorimetry and thermogravimetric analysis measurements combined with conventional ex-situ X-ray diffraction. The results revealed (i) a change in the microstructure from columnar to a fine-grained nano-composite, (ii) a reduced decomposition rate of CrN to Cr₂N, also shifted to higher onset temperatures from ∼ 1000 ℃ to above 1100 ℃ and (iii) an increase of lattice defects and micro strains resulting in a significant increase of compressive residual strain with increasing Si content. While the Si-containing coatings in the as-deposited state show a lower hardness of 28 GPa compared to AlCrN with 32 GPa, vacuum annealing at 1100℃ led to an increase in hardness to 29 GPa for the coatings containing Si and a decrease in hardness to 26 GPa for AlCrN. Furthermore, the in-situ HT-HE-GIT-XRD method allowed for simultaneously accessing temperature-dependent variations of the coating microstructure (defect density, grain size), residual strain state and phase stability up to 1100℃. Finally, the results established a deeper understanding about the relationships between the elemental composition of the materials, the resulting microstructure including crystallographic phases and residual strain state, and the coating properties from room temperature up to 1100℃.

Keywords: AlCrSiN; nano-composite; cathodic arc; thermal stability

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Permalink: https://www.hzdr.de/publications/Publ-30007
Publ.-Id: 30007


Multi-centric study to harmonize LET-calculations in proton therapy

Hahn, C.; Vestergaard, A.; Sokol, O.; Bourhaleb, F.; Leite, A.; Rose, C.; Dasu, A.; Grzanka, L.; Lühr, A.

Purpose
Emerging clinical evidence for a varying relative biological effectiveness (RBE) in proton therapy poses the urgent need to consider RBE-driving physical parameters such as the linear energy transfer (LET). However, no harmonized concept exists on how to calculate the LET in clinical practice. Therefore, a multi-centric study was set up with the objective to standardize LET-calculations in Europe.

Materials and Methods
Eight European proton therapy institutions generated non-robust single-field-uniform-dose PBS treatment plans using common strict dose objectives. Multiple treatment field arrangements (single-field SOBP, perpendicular fields, opposing fields) were employed to cover a target cube in a water phantom. The institutions provided their dose and corresponding LET distributions. Here, four different LET-calculation methods (including analytical codes, dedicated LET scripts, Monte Carlo engines) were analyzed.

Results
Single-field SOBP ranges (distal R80) and average dose (range: D99 to D1) in the target volume agreed within 2% (Fig.1). In contrast, the corresponding near minimum LET values (LET99), average LET and near maximum LET (LET1) in the target volume differed up to 30%, 19% and 5%, respectively. In the volume 1 cm distal to the target, absolute (relative) LET1 values differed by up to 1.63 keV/µm (17%) in voxels with average physical dose above 40 Gy. Individual institutions included different ions in their LET-calculations partially explaining the observed differences in LET-values and LET-distributions (Fig.2).

Conclusion
Despite comparable dose distributions, substantial LET-differences occurred among the participating institutions. They hamper the consistent analyses of clinical follow-up data and might lead to discrepancies in predicting variable RBE. Therefore, standardized clinical LET-calculations are recommended.

  • Open Access Logo Lecture (Conference) (Online presentation)
    59th Annual Conference of the Particle Therapy Co-Operative Group - PTCOG, 09.-14.05.2020, Taipei, Taiwan

Permalink: https://www.hzdr.de/publications/Publ-30006
Publ.-Id: 30006


Analysis of studies and research projects regarding the detection of nanomaterials in different environmental compartments and deduction of need for action regarding method development

Hildebrand, H.; Schymura, S.; Franke, K.; Fischer, C.

The aim of the present report was to obtain an overview of current strategies and methods for the detection of (manufactured) nanomaterials (NMs) in the environmental compartments surface water, soil, sediment, air, biota and sewage sludge. Based on this several recommendations for future needs of action in the short to long term are derived in order to establish a standardized detection of NMs in the environment that is necessary in order to check the pollution in the environment, to check whether or not potential risk management measures take the intended effect and to validate NM release models with real data.
A literature review was performed using predominantly “Web of Science” and screening for literature, such as review articles summarising the state of the art of NM detection techniques for environmental samples. More than 160 scientific publications were evaluated concerning NM detection methods. Results of the literature survey clearly show that a combination of detection techniques is necessary in order to detect and identify NMs, and to differentiate between natural NMs and manufactured NMs. The crucial step is accurate sample preparation for the selected detection method which means in most cases complete removal of the (disturbing) matrix and transfer of the NM in appropriate media for measurement. So far field studies in terms of detection of unknown amounts of unspecific engineered NMs in natural samples are rare and only existing for a few compartments, mainly surface waters.
Hence, it is concluded that the need of action is focused on the development, standardization and validation of existing methods in a combinatory approach.

Keywords: technische Nanomaterialien; manufactured nanomaterials Detektion; detection; Umwelt; Environment

  • Open Access Logo Other report
    Desssau-Roßlau: Umweltbundesamt, 2019
    63 Seiten

Permalink: https://www.hzdr.de/publications/Publ-30005
Publ.-Id: 30005


Soft hydrothermal synthesis of hafnon, HfSiO4

Estevenon, P.; Kaczmarek, T.; Rafiuddin, M. R.; Welcomme, E.; Szenknect, S.; Mesbah, A.; Moisy, P.; Poinssot, C.; Dacheux, N.

Despite being a member of the zircon type silicate family, the conditions allowing the hydrothermal synthesis of HfSiO4 were not well constrained. A multiparametric study was performed in order to follow the synthesis of this phase under soft hydro-thermal conditions and thus to determine the most efficient conditions to form single phase samples. Among the experi-mental parameters investigated, concentration of reactants, pH of the reactive media, temperature and duration of the hydrothermal treatment impacted significantly the formation rate of hafnon and its crystallization state. Pure HfSiO4 was obtained in acid reactive media with an acidity ranging from CHCl = 1.5 M to pH = 1.0 and for CSi ≈ CHf ≥ 0.21 mol·L 1. The silicate phase was prepared after a 24-hours treatment at temperatures ranging from 150°C to 250°C. However, rise of tem-perature and extension of the duration of the hydrothermal treatment favored the crystallization state of the final HfSiO4 samples.

Keywords: hafnium silicate; hafnon; wet chemistry route; hydrothermal synthesis; zircon structure type

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Permalink: https://www.hzdr.de/publications/Publ-30004
Publ.-Id: 30004


Thermal and flow performance of tilted oval tubes with novel fin designs

Unger, S.; Beyer, M.; Szalinski, L.; Hampel, U.

These are the raw data and the processed data of the journal paper "Thermal and flow performance of tilted oval tubes with novel fin designs".

The raw data contains the measured values on the experimental setup and the processed data contains the data of the data used in the corresponding journal publication.

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Permalink: https://www.hzdr.de/publications/Publ-30003
Publ.-Id: 30003


Solutal buoyancy and electrovortex flow in liquid metal batteries

Herreman, W.; Benard, S.; Nore, C.; Personnettaz, P.; Cappanera, L.; Guermond, J.-L.

Solutal buoyancy has a large impact on the flow of the alloy phase composing the positive electrode in liquid metal batteries. During discharge solutal buoyancy creates a stabilizing stratification, during charge it creates a vigorous solutal convection. In this article we provide new physical understandings of the role of solutal buoyancy during both charge and discharge. In particular we find that during discharge the electrovortex mechanism is in general not strong enough to counter the stabilizing effect of solutal buoyancy, and therefore this mechanism cannot be used to mix the alloy as is sometimes suggested in the literature. We show that the mixing capability of a generic flow in the alloy phase can be estimated by comparing the typical flow magnitude U to two velocity scales: Up and Um. Below Up the flow cannot mix the alloy, and above Um the flow significantly opposes solutal buoyancy. Although we focus on Li||Pb-based batteries, these simple mixing criteria can be used during the discharging phase in other types of liquid batteries. We also present new, fully three-dimensional simulations of solutal convection during the charging cycle. These simulations suggest scaling laws for the magnitude of the convective flow, the time for the onset of solutal convection, and the typical inhomogeneity level in the alloy during charge. We propose physical arguments to explain these scaling laws.

Keywords: mass transport; electro-vortex flow; liquid metal batteries; liquid metal electrode

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Permalink: https://www.hzdr.de/publications/Publ-30001
Publ.-Id: 30001


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