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39109 Publications

Dataset for: Chemical absorption measurements in a lab scale bubble column

Kipping, R.; Hampel, U.

This data set contains gas phase hydrodynamic data obtained from ultrafast X-ray tomography measurements in a bubble column. Global and local gas holdups, as well as bubble size distributions are given for I) non reactive conditions with nitrogen (gas) and sodium hydroxide solution (liquid) and II) reactive conditions with carbon dioxide (gas) and sodium hydroxide solution (liquid). Additionally the data set contains the corresponding consumption rates obtained from wire-mesh sensor measurements.

Furhter details on the experiments are explained in the corresponding journal paper.

Keywords: bubble columns; wire-mesh sensor; UFXCT

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Permalink: https://www.hzdr.de/publications/Publ-32533
Publ.-Id: 32533


Isolation, identification and selection of bacteria with the proof-of-concept for bioaugmentation of whitewater from wood-free paper mills

Verdel, N.; Rijavec, T.; Rybkin, I.; Erzin, A.; Velišček, Ž.; Pintar, A.; Lapanje, A.

In the wood-free paper industry, whitewater is usually a mixture of additives for paper production. We are currently lacking an efficient, cost-effective purification technology for their removal. In closed whitewater cycles the additives accumulate, causing adverse production problems, such as the formation of slime and pitch. The aim of our study was to find an effective bio-based strategy for whitewater treatment using a selection of indigenous bacterial isolates. We first obtained a large collection of bacterial isolates and then tested them individually for their ability to degrade the papermaking additives, i.e., carbohydrates, resin acids, alkyl ketene dimers, polyvinyl alcohol, latex, and azo and fluorescent dyes. Of the 318 bacterial isolates, we selected a consortium of four strains (Xanthomonadales bacterium sp. CST37-CF, Sphingomonas sp. BLA14-CF, Cellulosimicrobium sp. AKD4-BF and Aeromonas sp. RES19-BTP) that degrade the entire spectrum of tested additives. A proof-of-concept study on a pilot scale was then performed by immobilizing the artificial consortium of the four strains and inserting them into a 33-litre, tubular flow-through reactor with a retention time of <15 h. The consortium caused an 88% reduction in the COD of the whitewater, even after 21 days.

Keywords: Aeromonas; azo dye; bioaugmentation; Cellulosimicrobium; PCA; water treatment

Permalink: https://www.hzdr.de/publications/Publ-32532
Publ.-Id: 32532


Advancing laser plasma accelerators by means of femto-scale diagnostics for a pilot study of high dose rate in-vivo irradiation

Schramm, U.

Talk on Advancing laser plasma accelerators by means of femto-scale diagnostics for a pilot study of high dose rate in-vivo irradiation

Keywords: laser proton acceleration; high dose rate radiobiology

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  • Invited lecture (Conferences) (Online presentation)
    4th international symposium on high power laser science and engineering, HPLSE, 12.-15.04.2021, Suzhou, China

Permalink: https://www.hzdr.de/publications/Publ-32531
Publ.-Id: 32531


Development of fluorinated and methoxylated benzothiazole derivatives as highly potent and selective cannabinoid CB2 receptor ligands

Aly, M. W.; Ludwig, F.-A.; Deuther-Conrad, W.; Brust, P.; Abadi, A. H.; Moldovan, R.-P.; Osman, N. A.

Numerous studies have indicated the upregulation of the cannabinoid type 2 receptors (CB2 receptors) in neuroinflammation and cancer, and that their visualization with PET (Positron emission tomography) could provide a valuable diagnostic and/or therapy-monitoring tool in such disorders. However, the availability of reliable CB2-selective imaging probes is still lacking in clinical practice. Encouraged by promising CB2 affinity results obtained for a benzothiazole lead compound, 6a, further structural optimizations led to the development of a series of fluorinated and methoxylated benzothiazole derivatives, endowed with extremely high CB2 binding affinity and an exclusive selectivity to the CB2 receptor, along with structural sites suitable for radiolabeling. Compounds 20, 21, 24, 25, 29, 32 and 33 displayed subnanomolar CB2 Ki values (ranging from 0.16 nM to 0.68 nM) while lacked affinity to the CB1 receptor subtype. The fluorinated analogs, 21 and 29, were evaluated for their in vitro metabolic stability in mouse and human liver microsomes (MLM and HLM). Both 21 and 29 displayed an exceptionally high stability (98% and 91% intact compounds, respectively) after 60 min incubation with MLM.
Contrastingly, compound 29 revealed an almost 2-fold greater metabolic stability after incubation with HLM for 60 min. Taken together, our data represent remarkably potent and selective CB2 ligands as credible leads that can be further exploited for 18F- or 11C-radiolabeling and utilization as PET tracers.

Keywords: Benzothiazole; Cannabinoid receptor type 2; CB2 ligands; Fluorine; Metabolic studies; PET

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Permalink: https://www.hzdr.de/publications/Publ-32530
Publ.-Id: 32530


Data for: Electron dose rate and oxygen depletion protect zebrafish embryos from radiation damage

Pawelke, J.; Brand, M.; Hans, S.; Hideghéty, K.; Karsch, L.; Leßmann, E.; Löck, S.; Schürer, M.; Szabo, E. R.; Beyreuther, E.

Primary data and data description to publication:

Electron dose rate and oxygen depletion protect zebrafish embryos from radiation damage

Abstract:

Background and purpose
In consequence of a previous study, where no protecting proton Flash effect was found for zebrafish embryos, potential reasons and requirements for inducing a Flash effect should be investigated with the beam pulse structure and the partial oxygen pressure (pO2) as relevant parameters.
Materials and methods
The experiments were performed at the research electron accelerator ELBE, whose variable pulse structure enables dose delivery as electron Flash and quasi-continuously (reference). Zebrafish embryos were irradiated with ~26 Gy either continuously with a dose rate of ~6.7 Gy/min or in one 111 µs long pulse with a pulse dose rate of 109 Gy/s and a mean dose rate of 105 Gy/s, respectively. Using the OxyLite system to measure the pO2 a low- (pO2 ≤ 5 mmHg) and a high-pO2 group were defined on basis of the oxygen depletion kinetics in sealed embryo samples.
Results
A protective Flash effect was seen for most endpoints ranging from 4 % less reduction in embryo length to about 20 – 25 % less embryos with spinal curvature and pericardial edema, relative to reference irradiation. The reduction of pO2 below atmospheric levels (148 mmHg) resulted in higher protection, which was however more pronounced in the low-pO2 group.
Conclusion
The Flash experiment at ELBE showed that the zebrafish embryo model is appropriate for studying the radiobiological response of high dose rate irradiation. Pulse dose and pulse dose rate as important beam parameters were confirmed as well as the pivotal role of pO2 during irradiation.

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Permalink: https://www.hzdr.de/publications/Publ-32529
Publ.-Id: 32529


A Robust PtNi Nanoframe/N-Doped Graphene Aerogel Electrocatalyst with Both High Activity and Stability

Yang, J.; Hübner, R.; Zhang, J.; Wan, H.; Zheng, Y.; Wang, H.; Qi, H.; He, L.; Li, Y.; Aregahegn Dubale, A.; Sun, Y.; Liu, Y.; Peng, D.; Meng, Y.; Zheng, Z.; Rossmeisl, J.; Liu, W.

Insufficient catalytic activity and stability and high cost are the barriers for Pt-based electrocatalysts in wide practical applications. Herein, a hierarchically porous PtNi nanoframe/N-doped graphene aerogel (PtNiNF-NGA) electrocatalyst with outstanding performance toward methanol oxidation reaction (MOR) in acid electrolyte has been developed via facile tert-butanol-assisted structure reconfiguration. The ensemble of high-alloying-degree-modulated electronic
structure and correspondingly the optimum MOR reaction pathway, the structure superiorities of hierarchical porosity, thin edges, Pt-rich corners, and the anchoring effect of the NGA, endow the PtNiNF-NGA with both prominent electrocatalytic activity and stability. The mass and specific activity (1647 mAmgPt -1, 3.8 mAcm-2) of the PtNiNF-NGA are 5.8 and 7.8 times higher than those of commercial Pt/C. It exhibits exceptional stability under a 5-hour chronoamperometry test and 2200-cycle cyclic voltammetry scanning.

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Permalink: https://www.hzdr.de/publications/Publ-32527
Publ.-Id: 32527


60Fe and 244Pu deposited on Earth constrain the r-process yields of recent nearby supernovae

Wallner, A.; Froehlich, M. B.; Hotchkis, M. A. C.; Kinoshita, N.; Paul, M.; Martschini, M.; Pavetich, S.; Tims, S. G.; Kivel, N.; Schumann, D.; Honda, M.; Matsuzaki, H.; Yamagata, T.

Half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). The sites and yields of this process are disputed, with candidates including some types of supernovae (SNe) and mergers of neutron stars. We search for two isotopic signatures in a sample of Pacific Ocean crust: 60Fe (half-life 2.6 million years, Myr), predominantly produced in massive stars and ejected in SN explosions; and 244Pu, (half-life 80.6 Myr) produced solely in r-process events. We detect two distinct influxes of 60Fe to Earth in the last 10 Myr and accompanying lower quantities of 244Pu. The 244Pu/60Fe influx ratios are similar for both events. The 244Pu influx is lower than expected if SNe dominate r-process nucleosynthesis, implying some contribution from other sources.

Keywords: r process; Supernova; interstellar medium; accelerator mass spectrometry; deep-sea archive; 60Fe; 244Pu

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-32525
Publ.-Id: 32525


Combining X-ray diffraction, X-ray absorption spectroscopy, and molecular dynamics simulations to probe metals in zeolites: the case of intergrown Cd2+-LEV/ERI.

Cametti, G.; Scheinost, A.; Churakov, S. V.

Despite cadmium being a toxic element for environmental and human health, it is widely used in industries for fabrication of nickel-cadmium batteries, as anticorrosive agent, color pigment, etc. The most common and effective techniques for Cd removal from wastewater include filtration, chemical precipitation, bio-remediation and ion exchange. Because of their microporous structure and extremely efficient cation exchange capacity, natural zeolites are good candidates for use as ionic filters. Moreover, heavy-metal exchanged zeolites show improved catalytic properties that can be exploited in post remediation processes. Therefore, the chemical reactivity and stability of heavy-metal enriched zeolite is of paramount importance. Additionally, the nature of the metal species and their interaction with the zeolite framework play a fundamental role. Nevertheless, the correct determination of the aforementioned aspects can be compromised by the high disorder of the extraframework species, making difficult an unequivocal interpretation of the coordination chemistry of the metal cations. In this respect, the combination of X-ray diffraction (XRD) based techniques together with X-ray absorption spectroscopy (XAS) represents a valid tool to probe the long and short-range order of the species of interest.
In this contribution, we used a complementary experimental and theoretical approach to investigate in detail the structure of two Cd2+ -exchanged zeolites, levyne (LEV) and erionite (ERI). These two minerals are classified as small-pore zeolites (pore size between 0.35 and 40 nm) and, due to their structural similarity, they are often found as intergrown phase in nature [4]. In this study, experimental data from single crystal XRD and XAFS were coupled with Molecular Dynamics (MD) simulations to determine the distribution and coordination chemistry of Cd2+ in the two framework types (LEV and ERI). Our results showed that in Cd-LEV, Cd2+ ions have a fairly ordered distribution, resembling that characteristic of the pristine material [5]. In contrast, a strong disorder of the extraframework species (Cd2+ and H2O) is detected in Cd-ERI pores, where the occupancy of the EF sites is lower than 20%. Such disorder was attributed to the presence of Cd+2(H2O)6 complexes, which are only partially coordinated to framework oxygen and, therefore, more mobile. To discriminate between the effect of thermal and structural disorder in the measured and theoretically calculated EXAFS spectra, we propose a theoretical approach based on a set of geometry optimizations performed starting from the uncorrelated atomic configuration of MD simulations. Moreover, based on EXAFS analysis, the formation of metallic Cd within the pores of both zeolites could be ruled out.
Finally, we present the effect of Cd2+ incorporation on the thermal stability of Cd-LEV. The structural changes were monitored in situ from 25 to 400°C by single crystal X-ray diffraction. Our results demonstrated that, even if Cd had little influence on the room temperature structure, the dehydration behaviour drastically changes compared to that of the pristine material (natural levyne-Ca). The most relevant differences can be summarized by: i) a stronger volume contraction of the unit-cell volume (8% and 5% for Cd-LEV and levyne-Ca, respectively) in the investigated temperature range, and ii) the lack, at high temperatures, of the phase transformation to levyne B’ topology, characteristic of natural levyne-Ca.

Keywords: zeolite; Cd; XRD; XAFS

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  • Lecture (Conference) (Online presentation)
    XXV General Assembly and Congress of the International Union of Crystallography - IUCr 2021, 14.-22.08.2021, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-32524
Publ.-Id: 32524


Metal-induced progressive alteration of conducting states in memristors for implementing an efficient analog memory: a DFT-supported experimental approach

Das, D.; Barman, A.; Sarkar, P. K.; Rajput, P.; Jha, S. N.; Hübner, R.; Kanjilal, D.; Johari, P.; Kanjilal, A.

Advancement of the memristor-based artificial synapse (AS) is urgently needed for rapid progress in neuromorphic devices. The precise structural and chemical engineering of metal oxide layers by metal dopants (Ni) is presented as an innovative way to set off a decent performance of the AS. An ON/OFF ratio of 103 as well as data retention and endurance capabilities of 104 s and 103 cycles, respectively, are achieved. With these properties, the symmetric alteration in conductance states, short-term plasticity (STP) and long-term plasticity (LTP) are realized within the same device, and compared with the reported values to establish its excellent cognitive behavioural ability. Our combined experimental and the DFT-based first-principles calculation results reveal that the rational designing of AS using metal cations (Ni) can promote an ultra-low-power of about 2.55 fJ per pulse (lower than human brain about 10 fJ per pulse) for STP, promising for next-generation smart memory devices. Here, Ni endorses strong electronic localization, which in turn familiarizes trap states within the forbidden energy gap and improves short-term memory loss. Further, it modifies the local electrostatic barriers to stimulate modulatory action (as commonly observed in the mammalian brain) for LTP. Overall, this work provides a novel pathway to overcome the technological bottleneck.

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Permalink: https://www.hzdr.de/publications/Publ-32523
Publ.-Id: 32523


Electric Quadrupolar Contributions in the Magnetic Phases of UNi4B

Yanagisawa, T.; Matsumori, H.; Saito, H.; Hidaka, H.; Amitsuka, H.; Nakamura, S.; Awaji, S.; Gorbunov, D.; Zherlitsyn, S.; Wosnitza, J.; Uhlirova, K.; Valiska, M.; Sechovsky, V.

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi4B. The transverse ultrasonic mode C66 shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to ∼0.33 K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that Γ6 (E2g) electric quadrupolar degrees of freedom in localized 5f2 (J = 4) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi4B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering.

Permalink: https://www.hzdr.de/publications/Publ-32522
Publ.-Id: 32522


Data for: Effective diffusivity prediction of radionuclides in clay formations using an integrated upscaling workflow

Yuan, T.; Fischer, C.

The effective diffusivity is a key parameter in the diffusive transport calculations, thus decisive for predicting the radionuclide migration in low-permeable clay-rich formations. Potential host rocks such as the Opalinus clay exhibit pore network heterogeneities, critically modified due to compositional variability in the sandy facies and owing to diagenetic minerals. Meaningful estimation of the effective diffusivity requires an understanding of transport mechanisms at the nanometer-scale as a starting point and a combination with upscaling strategies for considering compositional heterogeneities at the micrometer-scale.

In this study, we propose an upscaling workflow that integrates transport simulations at both the nanometer-scale and the micrometer-scale to predict the effective diffusivities of radionuclides in the sandy facies of the Opalinus clay. The respective synthetic digital rocks provide conceptually two types of materials at the pore scale, in which the pore space and pore network in the clay matrix at the nanometer scale and mineral complexity in shales at the micrometer scale are considered. The numerical approach using the introduced digital rocks is validated with published experimental data that confirm the general applicability of the models. Sensitivity studies reveal the increase of effective diffusivity of shales as a function of increased pore space, reduced tortuosity, and an increased sheet silicate concentration compared to other rock components. Thus, such spatial variabilities at the pore scale of more complex sedimentary rocks are now addressed in the proposed approach and available for studying heterogeneous diffusion patterns compared to commonly assumed homogeneous behavior. Finally, and as a starting point for further upscaling strategies, we investigate anisotropic diffusion by studying the effect of lamination of the shales towards enhanced predictability of radionuclide migration.

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Permalink: https://www.hzdr.de/publications/Publ-32519
Publ.-Id: 32519


Analysis of heterogeneity and anisotropy of diffusivity in the sandy facies of Opalinus Clay host rocks using multi-scale digital rock physics

Yuan, T.; Yang, Y.; Deissmann, G.; Fischer, C.

The effective diffusivity is a key parameter in numerical tools required for the simulation of radionuclide migration in low-permeable rocks. Potential host rocks for deep geological repositories for nuclear waste such as the Opalinus Clay (OPA) exhibit pore network heterogeneities at the nanometer to micrometer scale. In the sandy facies of OPA, this pore network is critically modified due to compositional variability and owing to diagenetic reaction products, e.g., carbonate minerals. Such spatial variability is responsible for heterogeneous and anisotropic diffusion patterns contrary to the commonly assumed homogeneous conditions in the shaly facies. At the continuum scale, the representative elementary volume (REV) is a fundamental parameter for the quantification of the effective diffusivity. Therefore, meaningful modeling of heterogeneous and anisotropic diffusion in the sandy facies of OPA at the continuum scale requires an accurate estimation of the REV.
Here, we first utilize digital rock physics and propose an upscaling workflow that integrates transport simulations at both the nanometer-scale and the micrometer-scale to estimate the effective diffusivity of radionuclides in the sandy facies of OPA. In the proposed upscaling workflow, the lattice Boltzmann method (LBM) is used to solve the Poisson-Nernst-Planck (PNP) equation at the nanometer-scale [1]. The nanometer-scale results are then used as input parameters in the micrometer-scale model for diffusive transport calculations. At the micrometer-scale, the three-dimensional (3D) diffusion-sorption equation is numerically solved by a previously developed numerical simulator [2]. The diffusivity is calculated using the proposed upscaling approach, which is validated with published experimental data that confirm the general applicability of the models. Next, we determine the REV for diffusivity by analyzing the calculated diffusivity of the selected regions of interest (ROIs) as a function of the length scale [3]. The determined REV provides critical insight into the heterogeneity and anisotropy of the diffusivity in the sandy facies of OPA, which contributes to enhanced predictability of radionuclide migration.

  • Lecture (Conference) (Online presentation)
    Goldschmidt 2021, 04.-09.07.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-32518
Publ.-Id: 32518


Range verification in proton therapy: Feasibility of CNN-based detection and classification of treatment deviations from realistic prompt-gamma-imaging data

Pietsch, J.; Khamfongkhruea, C.; Berthold, J.; Janssens, G.; Stützer, K.; Löck, S.; Richter, C.

Introduction
Within a clinical study, we investigate the potential benefit of prompt-gamma-imaging (PGI) based range verification in proton therapy. As the manual interpretation of detected spot-wise range-shift information is time-consuming and complex, we aim to automatically detect and classify treatment deviations from realistic PGI data using convolutional neural networks (CNNs).

Materials & Methods
For 12 head-and-neck cancer patients and an anthropomorphic head phantom, monitoring of single fields from pencil-beam-scanning plans with the IBA slit camera was considered. In total, 386 treatment deviations were simulated on planning and control CTs and manually classified into 7 classes: non-relevant changes (NRC) and relevant changes triggering treatment intervention due to range-prediction errors (±RPE), setup errors in beam direction (±SE), anatomical changes (AC), or a combination of such errors (CE). The spatial maps of filtered PGI-determined range deviations were converted to 16x16x16 voxel grids. Three complexity levels were investigated using 3D-CNNs [training cohort (n=9), test cohort (n=4), Fig.1]: (A) optimal PGI data, (B) realistic PGI data with simulated Poisson noise based on the locally delivered proton number, (C) realistic PGI data with additional positioning uncertainty of the slit camera.

Results
During validation on the independent test data, the 3D-CNNs achieved multi-class accuracies of 81%, 77%, 76% and binary accuracies of 97%, 95%, 93% for the respective complexity levels (A,B,C) (Fig.2). In the most realistic scenario (C), relevant treatment deviations were detected with 97% sensitivity and 82% specificity. Misclassifications of the AC class were caused by similar PGI characteristics of the CE class.

Conclusion
CNNs can reliably detect and classify relevant treatment deviations from realistically simulated PGI data. While validation on measured patient data is needed, our study highlights the potential of automated PGI interpretation, which is desired for broad clinical application and a prerequisite for including PGI in an automated feedback loop for online adaptation.

Keywords: range verification; prompt gamma imaging; proton therapy; artificial intelligence; machine learning

  • Lecture (Conference) (Online presentation)
    Dreiländertagung der Medizinischen Physik 2021, 19.-21.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32517
Publ.-Id: 32517


Prompt-gamma-based verification in proton therapy: CNN-based classification of treatment deviations

Pietsch, J.; Khamfongkhruea, C.; Berthold, J.; Janssens, G.; Stützer, K.; Löck, S.; Richter, C.

Purpose & Objective
Prompt-gamma imaging (PGI) based range verification has been utilized in first pencil-beam scanning (PBS) proton therapy treatments and is under systematic investigation concerning its potential benefit in a clinical study at our institution. Manual interpretation of the detected spot-wise range shift information is time-consuming, highly complex, and therefore not feasible in a broad routine application. Here, we present an approach to automatically detect and classify treatment deviations in realistically simulated PGI data for head and neck cancer treatments using convolutional neural networks (CNNs).

Materials & Methods
For 12 patients and an anthropomorphic head phantom, PBS treatment plans were generated and one field per plan was assumed to be monitored with the IBA slit camera. In total, 386 scenarios resembling different relevant or non-relevant treatment deviations were simulated on planning and control CTs and manually classified into 7 classes: non-relevant changes (NRC) and relevant changes triggering treatment intervention due to range prediction errors (±RPE), setup errors in beam direction (±SE), anatomical changes (AC), or a combination of such errors (CE). After filtering of PBS spots with reliable PGI information, the 3D spatial maps of PGI-determined range deviations (reference vs. change scenario) were converted to 16x16x16 voxel grids. Three complexity levels of simulated PGI data were investigated: (A) optimal PGI data, (B) realistic PGI data with simulated Poisson noise based on the locally delivered proton number, (C) realistic PGI data with an additional positioning uncertainty of the slit camera following an experimentally determined distribution.
For each complexity level, 3D-CNNs (6 convolutional & 2 downsampling layers) were trained on a subset of 8 patients and the phantom dataset using patient-specific leave-one-out cross-validation and tested on an independent test cohort of 4 patients.

Results
On the test data, the CNN ensemble achieved an accuracy of 0.81, 0.77, and 0.76 for the complexity levels (A), (B), and (C), respectively. Similarly, for the task to solely differentiate relevant from non-relevant changes, the binary accuracy was 0.97, 0.95, and 0.93. The trained ensemble provided fast (<1 s) predictions and detected treatment deviations in the most realistic scenario (C) with a sensitivity of 0.97 and a specificity of 0.82. Misclassifications of the AC class were likely due to similar PGI characteristics to the CE class.

Conclusion
This study demonstrates that CNNs can reliably detect relevant changes in realistically simulated PGI data and classify most of the underlying sources of treatment deviations. While validation on measured patient data is needed, our study highlights the potential of a reliable, automatic interpretation of PGI data, which is highly desired for broad clinical application and a prerequisite for the inclusion of PGI in an automated feedback loop for online adaptation.

Keywords: range verification; prompt gamma imaging; proton therapy; artificial intelligence; machine learning

  • Lecture (Conference)
    ESTRO 2021, 27.-31.08.2021, Madrid, Spanien
  • Abstract in refereed journal
    Radiotherapy and Oncology 161(2021)Supplement, 134-136
    DOI: 10.1016/S0167-8140(21)06819-5

Permalink: https://www.hzdr.de/publications/Publ-32516
Publ.-Id: 32516


Synthesis of novel fluorinated xanthine derivatives with high adenosine A2B receptor binding affinity

Lindemann, M.; Dukic-Stefanovic, S.; Hinz, S.; Deuther-Conrad, W.; Teodoro, R.; Juhl, C.; Steinbach, J.; Brust, P.; Müller, C. E.; Wenzel, B.

The G protein-coupled adenosine A2B receptor is suggested to be involved in various patholog-ical processes accompanied by increased levels of adenosine as found in inflammation, hypoxia, and cancer. Therefore, the adenosine A2B receptor is currently in the focus as a novel target for cancer therapy as well as for noninvasive molecular imaging via positron emission tomography (PET). Aiming at the development of a radiotracer labeled with the PET radionuclide fluorine-18 for imaging the adenosine A2B receptor in brain tumors, one of the most potent and selective an-tagonists, the xanthine derivative PSB-603, was selected as a lead compound. As initial biodis-tribution studies in mice revealed a negligible brain uptake of [3H]PSB-603 (SUV3min: 0.2), struc-tural modifications were performed to optimize the physicochemical properties regarding blood-brain barrier penetration. Two novel fluorinated derivatives bearing a 2-fluoropyridine (7) and a 4-fluoropiperidine (8) moiety have been synthesized, and their affinities for the four adenosine receptor subtypes were determined in competition binding assays. Both compounds showed high affinity towards the adenosine A2B receptor (Ki (7) = 9.97 ± 0.86 nM; Ki (8) = 12.3 ± 3.6 nM) with moderate selectivities versus the other adenosine receptor subtypes.

Keywords: xanthine; adenosine A2B receptor; adenosine; PSB-603

Permalink: https://www.hzdr.de/publications/Publ-32515
Publ.-Id: 32515


Precise measurement of gas parameters in a realistic RPC configuration: the currently used R134a gas and a potential alternative eco-gas

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

In this work, we present a comprehensive method to measure the gas parameters, such as the effective Townsend coefficient and electron drift velocity in homogeneous high electric fields (up to 100 kV/cm}) at atmospheric pressure and room temperature. A pulsed laser facility with micro-meter spatial accuracy and picosecond pulse duration is used to ignite primary ionizations at specific positions in the gas gap of a Resistive Plate Chamber (RPC) detector prototype. The gas parameters are determined solely by the RPC signals. The main component of the current standard gas for RPC is Tetrafluoroethane (R134a) which has a high Global Warming Potential. Therefore, using Tetrafluoropropene (HFO-1234ze) is under research as an eco-friendly substance. We measure the parameters of these two types of working gases.It is the first direct measurement of the gas parameters of timing RPCs under working conditions. By comparison with existing data from other investigation points, we observe a dependence of gas parameters on the pressure.

Keywords: Resistive Plate Chambers; Townsend coefficient; Electron drift velocity; HFO

Permalink: https://www.hzdr.de/publications/Publ-32514
Publ.-Id: 32514


Multi-channel detector module for multi-energy computed gamma ray tomography

Bieberle, A.; Berger, R.; Stave, P.; Hampel, U.

In this paper an enhanced signal processing electronics for an existing multi-channel detector module for gamma ray computed tomography is presented. The detector electronics is able to evaluate gamma photon energies by measuring pulse duration times, which makes it perfectly suitable for attenuation measurements with multi-energy and/or multiple isotopic sources.
The duration time of each voltage pulse generated by a gamma photon within the radiation detector is measured using a complex programmable logic device (CPLD). A sophisticated logic circuit for eight detector channels is designed to acquire the pulse duration time spectra in a total of 256 channels per detector channel. This paper introduces the basic concept, describes the general and the specific CPLD design, provides an analysis of the accuracy and presents measured pulse duration time spectra.

Keywords: gamma ray computed tomography; radiation detection; complex programmable logic device

Permalink: https://www.hzdr.de/publications/Publ-32513
Publ.-Id: 32513


Critical role of electrical resistivity in magnetoionics

de Rojas, J.; Salguero, J.; Quintana, A.; Lopeandia, A.; Liedke, M. O.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.; Abad, L.; Costa-Krämer, J. L.; Sort, J.; Menéndez, E.

The critical role of electrical resistivity in governing ion motion in magneto-ionic thin-film systems is demonstrated. A series of highly nanocrystalline cobalt-nitride (Co-N) thin films (85 nm thick) with similar composition but a broad range of electrical properties exhibit markedly different magneto-ionic behavior. Semiconducting, near stoichiometric films show the best performance, better than their metallic- and insulating- counterparts. Resistivity reflects the interplay between atomic bonding, carrier localization and structural defects, which in turn determines the strength and distribution of applied electric fields inside the actuated films. This fact, generally overlooked, reveals that resistivity is a good indicator of the potential of a system to exhibit optimal magneto-ionic effects, while also opening interesting challenges.

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Permalink: https://www.hzdr.de/publications/Publ-32512
Publ.-Id: 32512


Boundary conditions for the Neel order parameter in a chiral antiferromagnetic slab

Pylypovskyi, O.; Tomilo, A.; Sheka, D.; Faßbender, J.; Makarov, D.

Understanding of the interaction of antiferromagnetic solitons including domain walls and skyrmions with boundaries of chiral antiferromagnetic slabs is important for the design of prospective antiferromagnetic spintronic devices. Here, we derive the transition from spin lattice to micromagnetic nonlinear σ model with the corresponding boundary conditions for a chiral cubic G-type antiferromagnet and analyze the impact of the slab boundaries and antisymmetric exchange (Dzyaloshinskii-Moriya interaction) on the vector order parameter. We apply this model to evaluate modifications of antiferromagnetic domain walls and skyrmions upon interaction with boundaries for different strengths of the antisymmetric exchange. Due to the presence of the antisymmetric exchange, both types of antiferromagnetic solitons become broader when approaching the boundary and transform to a mixed Bloch-Néel structure. Both textures feel the boundary at the distance of about five magnetic lengths. In this respect, our model provides design rules for antiferromagnetic racetracks, which can support bulklike properties of solitons.

Keywords: antiferromagnetism; slab; Dzyaloshinskii-Moriya interaction; domain wall; skyrmion

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Permalink: https://www.hzdr.de/publications/Publ-32511
Publ.-Id: 32511


Effects of geometry on curvilinear antiferromagnetic spin chains

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

Antiferromagnets are technologically promising materials for spintronic and spinorbirtonic devices [1]. An efficient manipulation of antiferromagnetic textures requires the presence of the Dzyaloshinskii-Moriya interaction (DMI), which is present in crystals of special symmetry, and thus limits the number of available materials. In contrast to antiferromagnets, it is already established that in ferromagnetic thin films and nanowires chiral responses can be tailored relying on curvilinear geometries [2]. Here, we explore geometry-induced effects in curvilinear antiferromagnets. We demonstrate theoretically that intrinsically achiral curvilinear antiferromagnetic spin chains behave as a biaxial chiral helimagnet with a curvature-tunable anisotropy and DMI [3]. The geometry-driven easy axis anisotropy determines the homogeneous antiferromagnetic state at low curvatures and the gap for spin waves. The geometry-driven DMI determines the helimagnetic phase transition and leads to the appearance of the region with the negative group velocity at the dispersion curve.

[1] V. Baltz et al., Rev. Mod. Phys. 90, 015005 (2018).
[2] R. Streubel et al., J. Phys. D.: Appl. Phys. 49, 363001 (2016).
[3] O. V. Pylypovskyi et al., Nano Lett. (2020) DOI: 10.1021/acs.nanolett.0c03246.

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

  • Lecture (Conference) (Online presentation)
    APS March Meeting 2021, 15.-19.03.2021, Online, USA

Permalink: https://www.hzdr.de/publications/Publ-32510
Publ.-Id: 32510


Proton PBS delivery within the treatment volume of an in-beam MR scanner

Sepúlveda, C.; Gebauer, B.; Schneider, S.; Hoffmann, A. L.; Lühr, A.; Burigo, L.

Introduction: The magnetic fringe field of an in-beam MR scanner integrated with a proton pencil beam scanning (PBS) beamline needs to be taken into account for accurate dose delivery of IMPT plans. This work investigates corrections to proton pencil beams when delivered in the treatment volume of an in-beam MR imager.
Materials and Methods: Monte Carlo (MC) simulations using TOPAS version 3.5 were applied to model the PBS dose delivery to the treatment volume of an in-beam MR imager at the PBS beamline at OncoRay. A 3D map of the full magnetic fringe field of the 0.33 T (vertical field) open MR imager was mapped out and incorporated in the MC simulations. To estimate the distortion of the beam profile in the treatment volume, the delivery of a 10x10 cm2 spot pattern for beam energies of 100, 150 and 200 MeV was simulated in air at the MR isocenter positioned 57 cm downstream of the beam isocenter. The energy-dependent mean lateral deflection was used to correct the beam delivery by a rigid shift of the field.
Results: Lateral deflections of 32.2 mm (100 MeV), 25.6 mm (150 MeV) and 22.2 mm (200 MeV) were observed for all spots. When correcting for these deflections, the mean error in the spot positions were 0.9  0.2 mm (100 MeV), 0.5  0.6 mm (150 MeV) and 0.7  0.1 mm (200 MeV), with maximum differences of 2.0, 2.3 and 0.9 mm, respectively. No distortion of the spot pattern was found.
Conclusions: A submillimeter error in the spot position at the isocenter of the in-beam MR scanner can be achieved for a 10x10 cm2 field when applying energy-dependent corrections in the delivery of the spots. Ongoing research will consider larger fields sizes and corrections needed to account for the beam stopping in water.

Keywords: MRiPT

  • Lecture (Conference) (Online presentation)
    Joint Conference of the ÖGMP, DGMP and SGSMP Dreiländertagung der Medizinischen Physik, 19.-22.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32509
Publ.-Id: 32509


First steps towards dosimetric commissioning of an in-beam MR system for proton pencil beam scanning

Gebauer, B.; Sepúlveda, C.; Burigo, L.; Pawelke, J.; Bodenstein, E.; Schneider, S.; Hoffmann, A. L.; Lühr, A.

Introduction: A prototype system for MR‐integrated proton therapy (MRiPT) with an in-beam MR scanner is currently under investigation at our facility. The commissioning thereof requires an accurate beam model, a 3D map of the full static magnetic field (MF) of the MR scanner and consideration of their interaction. This work describes measurements of the proton beam, the MF and beam modeling performed to set up a proton beam model for the MRiPT prototype system.

Materials & Methods: Measurements of central proton beam spot sizes in air at 10 distances from the beam isocenter (between -15 and 54 cm) and integral depth-dose profiles (100 to 226.7 MeV) in water were obtained without MF using a scintillation detector and a water phantom with a Bragg peak chamber, respectively. A beam model was fitted to these measurements by utilizing an automated regularization-based optimization process. A 3D magnetic field map of the 0.33 T open MR scanner was acquired using spatially resolved Hall probe measurements.

Results: In the absence of the MF, the optimized beam model reproduced the measured beam spot sizes in air with an error <0.5 mm for 100 – 226.7 MeV and depth dose curves in water with an error <0.1 g/cm² for 100 – 226.7 MeV. The magnetic field measuring approach delivers reproducible results with high accuracy and an uncertainty <±5 mT.

Summary: A proton beam model for the MRiPT prototype system without MF was established and a high-precision method for mapping the 3D MF of the MR scanner was developed. The MF map and the beam model will be used to establish an experimental treatment planning system providing a correction algorithm accounting for the influence of the MF of the MR scanner on proton beams. Further investigations are necessary to validate the beam model in the presence of the MF.

Keywords: MRiPT

  • Lecture (Conference) (Online presentation)
    Joint Conference of the ÖGMP, DGMP and SGSMP Dreiländertagung der Medizinischen Physik, 19.-22.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-32508
Publ.-Id: 32508


Data for: Bubble formation from a microscale submerged orifice- A numerical approach

Mohseni, E.

We developed a mechanistic model for calculation of bubble volume from orifices in the range from 0.03 mm to 0.193 mm under the constant gas flow conditions in a quiescent liquid. It is known that for such small orifices, the mechanism of bubble formation is highly dependent on the gas momentum force and the liquid inertia force. Accordingly, the model incorporates these forces to calculate the bubble volume in three consecutive stages. Moreover, the model includes the influence of the bubble base expansion and bubble rising induced liquid velocity on the formation of bubbles. Eventually the model is validated with own experimental data using air and deionized water. Experimental validation of the model confirms that the maximum deviation of the model is less than 10%.

Keywords: Bubble formation; Micro-scale orifice; Mechanistic model; Stainless steel orifice; Force balance

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Permalink: https://www.hzdr.de/publications/Publ-32507
Publ.-Id: 32507


Highly sensitive ²⁶Al measurements by Ion-Laser-InterAction Mass Spectrometry

Lachner, J.; Martschini, M.; Kalb, A.; Kern, M.; Marchhart, O.; Plasser, F.; Priller, A.; Steier, P.; Wieser, A.; Golser, R.

The method of Ion-Laser InterAction Mass Spectrometry (ILIAMS) offers new options for the determination of ²⁶Al by Accelerator Mass Spectrometry (AMS) and improves the sensitivity and efficiency for the detection of this isotope in artificial and environmental samples. In ILIAMS, a laser is overlapped with the ion beam during its passage through a radiofrequency quadrupole ion cooler. Those ions with electron affinity lower than the energy of the photons are selectively neutralized in a photodetachment process. Because the electron affinity of MgO is lower than that of AlO, ILIAMS can suppress the isobar ²⁶Mg by 14 orders of magnitude. No further isobar suppression on the high-energy side of the spectrometer is necessary, so that the more prolific AlO⁻ beam can now also be used at facilities with terminal voltages < 5 MV. At the 3 MV Vienna Environmental Research Accelerator (VERA) routine ²⁶Al AMS measurements assisted by ILIAMS are performed utilizing AlO⁻ extracted from the ion source and charge states 2+ and 3+ for the Al ions after the accelerator on the high-energy side of the spectrometer. The most efficient generation of AlO- currents (in the range of several mA) is realized when mixing the Al₂O₃ sample material with Fe powder. Blank materials are measured down to ²⁶Al/²⁷Al ratios of 5*10⁻¹⁶. The efficiency relative to the use of Al⁻ extraction is improved typically by a factor 3-5 and thus the new method is useful for measurements with highest sensitivity and down to very low ²⁶Al/²⁷Al ratios.

Permalink: https://www.hzdr.de/publications/Publ-32506
Publ.-Id: 32506


Cisplatin - A more Efficient Drug in Combination with Radionuclides?

Reissig, F.; Runge, R.; Naumann, A.; Kotzerke, J.

The combination of conventional chemotherapeutic drugs with radionuclides or external radiation is discussed for a long period of time. The major advantage of a successful combination therapy is the reduction of severe side effects by decreasing the needed dose and simultaneously increasing therapeutic efficiency. In this study, pUC19 plasmid DNA was incubated with the cytostatic drug cisplatin and additionally irradiated with 99mTc, 188Re and 223Ra. DNA damages, such as single- and double strand breaks were determined by agarose gel electrophoresis. The threshold concentration value of cisplatin, which was tolerated by pUC19 plasmid DNA was determined to be 18-24 nM. Nevertheless, even at higher dose values (>100 Gy) and simultaneous incubation of cisplatin to 200 ng plasmid DNA, no significant increase in the number of induced single- and double-strand breaks was obtained, compared to the damage solely caused by the radionuclides. We thereby conclude that there is no direct dependence of the mechanism of strand break induction to the absence or presence of platinum atoms attached to the DNA. Reported increasing DNA damages in therapy approaches on a cellular level strongly depend on the study design and are mainly influenced by repair mechanisms in living cells. Nevertheless, the use of radioactive cisplatin, containing the Auger electron emitter 191Pt, 193mPt or 195mPt, is a bright prospect for future therapy by killing tumor cells combining two operating principles: a cytostatic drug and a radiopharmaceutical at the same time.

Keywords: Auger Therapy; Cisplatin; Chemotherapy; Radiotherapy

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  • Secondary publication expected from 06.04.2023

Permalink: https://www.hzdr.de/publications/Publ-32504
Publ.-Id: 32504


A critical analysis of drag force modelling for disperse gas-liquid flow in a pipe with an obstacle

Tas-Köhler, S.; Liao, Y.; Hampel, U.

The accuracy of gas-liquid flow modelling strongly depends on an appropriate modelling of interfacial forces. Among those, the drag is dominating. Most drag models reported in the literature have been derived and validated for laminar or low-turbulence flow conditions only. In this study, we evaluated different drag models from the literature for a highly turbulent gas-liquid flow around an obstacle in a pipe that produces a pronounced vortex region. We compared void fraction, as well as gas and liquid velocity profiles with experimental data obtained by means of Ultrafast X-ray Computed Tomography. We found that all the models except Bakker and Feng, predict the void fraction well compared to experimental data upstream of the obstacle, that is, for a developed two-phase pipe flow with axial symmetry. However, the void fraction downstream is grossly overestimated by all of the models. Based on the results, a hybrid drag model is proposed, which improves void fraction predictions considerably.

Keywords: CFD; bubbly flow; drag force coefficient; turbulence; vortex; hybrid drag model

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Permalink: https://www.hzdr.de/publications/Publ-32503
Publ.-Id: 32503


Multidisciplinary Characterization of Mine Water from a Former Uranium Mine for Bioremediation Purposes

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

In Saxony and Thuringia (Germany), an intensive uranium mining took place for decades until 1990. After the stop of the mining activities, the mines have been flooded for remediation purposes, which continues in many mines to this day. The resulting release of the soluble U into the mine water represents a major health risk. Remediation approaches using indigenous microbial communities are an efficient strategy1,2. In this study, we have characterized the microbial diversity and geochemistry of water from two German former uranium mines (Schlema-Alberoda and Pöhla) to design a bioremediation approach.
ICP-MS and Ion-Chromatography studies showed that the mine waters exhibited a higher concentration of U, sulfate, iron and manganese in Schlema-Alberoda compared to that of Pöhla (U: 1.01 and 0.11mg/L, sulfate: 335 and 0.26mg/L, iron: 0.99 and 0.13mg/L and manganese: 1.44 and 0.16mg/L, respectively). The 16S rRNA gene and the ITS1 rRNA analyses of both mine waters revealed a high microbial diversity. The total bacterial community composition combining both mine waters indicated an average relative abundance of sulfate-reducing-bacteria (e.g., Sulfuricuvum 9.5%, Sulfurimonas 4.5% and Sulfurovum 6.5%) and iron-oxidizing-bacteria (e.g., Gallionella 3%, Sideroxydans 3%). These bacterial groups are reported to be involved in U(VI) reduction as a key process in the bioremediation of anoxic U contaminated sites2. Therefore, to design bioremediation strategies for these U-contaminated waters, the Schlema-Alberoda water was used as a reference for setting anoxic-microcosms. Concretely, U-reducing-bacteria were biostimulated by supplementing with glycerol (10mM) as electron donor. ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease of U (≈89%), sulfate (≈99%), iron (≈86%) and manganese (≈88%). In addition, a drop of Eh and pH of the system was detected. A thermodynamical Eh-pH predominance diagram was calculated by Geochemist´s Workbench, indicating the formation of U(IV) precipitates, probably uraninite, after 3 months at the latest.
These results show that the U enzymatic reduction of soluble U(VI) to insoluble U(IV), as uraninite, is favored by the addition of an electron donor (such as glycerol) in low concentrated U-contaminated mine waters. Therefore, this strategy might be an efficient bioremediation approach relevant for U-contaminated waters, by biostimulating their native microbial community.

Keywords: uranium; reduction; bioremediation; 16S rRNA; ITS1 rRNA; bacteria

  • Lecture (Conference) (Online presentation)
    Goldschmidt Conference 2021, 04.-09.07.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-32502
Publ.-Id: 32502


Design of U mine water bioremediation strategy through U(VI) bioreduction process: Multidisciplinary characterization

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

The present study describes a U(VI) bioremediation strategy of a U mine water through the stimulation of the growth of U(VI) reducing bacteria (e.g. sulfate reducing bacteria). Thus, anoxic-microcosms of mine water amended with glycerol, as electron donor, were elaborated and incubated for 3 months. The original U mine water exhibit relatively high concentration of sulfate and iron. Furthermore, 16S and ITS1 rRNA gene analyses indicated a relative abundance of natural microbial groups with U(VI)-reduction ability. After 3 months, ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease around the 90% of U, sulfate, iron and manganese. A thermodynamical Eh-pH predominance diagram was calculated by Geochemist´s Workbench, showing the solid U ore (uraninite) after 3 months.
The results obtained revealed the U-enzymatic-reduction of U(VI) to U(IV), as uraninite, by the addition of an electron-donor in low concentrated U-contaminated-mine-waters. Thus, this strategy might be an efficient bioremediation approach for U-contaminated-mine-waters, by biostimulating their native microbial community.

Keywords: uranium; bioremediation; reduction; bacteria; 16S rRNA; ITS1 rRNA

  • Lecture (Conference) (Online presentation)
    10th International Symposium on Biomining (Biomining '21), 07.-09.06.2021, Falmouth, Cornwall, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-32501
Publ.-Id: 32501


Investigation of an opposed-contact GaAs photoconductive semiconductor switch at 1-kHz excitation

Xu, M.; Dong, H.; Liu, C.; Wang, Y.; Hu, L.; Lan, C.; Luo, W.; Schneider, H.

The transient performance of gallium arsenide (GaAs) photoconductive semiconductor switches (PCSSs) triggered by laser diodes (LDs) at nano-joules (nJ) energy is of great significance for the potential high-power applications at high repetition rates. An opposed-contact GaAs PCSS with Ni/AuGe/WTi/Au electrodes is presented at single-shot and 1-kHz excitation. The influences of bias electric field up to 80 kV/cm on nonlinear characteristics are investigated quantitatively with a carriers' avalanche multiplication factor as high as 0.8 x 10⁴. The effect of electric field on the carriers' dynamic process and thermal accumulation in repetitive operation is analyzed. The transient electric field distribution is demonstrated by an ensemble Monte Carlo simulation.

Keywords: Avalanche multiplication; gallium arsenide GaAs; photoconductive semiconductor switch PCSS

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Permalink: https://www.hzdr.de/publications/Publ-32500
Publ.-Id: 32500


Review mr image changes of normal-appearing brain tissue after radiotherapy

Witzmann, K.; Raschke, F.; Troost, E. G. C.

Radiotherapy is part of the standard treatment of most primary brain tumors. Large clinical target volumes and physical characteristics of photon beams inevitably lead to irradiation of surrounding normal brain tissue. This can cause radiation-induced brain injury. In particular, late brain injury, such as cognitive dysfunction, is often irreversible and progressive over time, resulting in a significant reduction in quality of life. Since 50% of patients have survival times greater than six months, radiation-induced side effects become more relevant and need to be balanced against radiation treatment given with curative intent. To develop adequate treatment and prevention strategies, the underlying cause of radiation-induced side-effects needs to be understood. This paper provides an overview of radiation-induced changes observed in normal-appearing brains measured with conventional and advanced MRI techniques and summarizes the current findings and conclusions. Brain atrophy was observed with anatomical MRI. Changes in tissue microstructure were seen on diffusion imaging. Vascular changes were examined with perfusion-weighted imaging and susceptibility-weighted imaging. MR spectroscopy revealed decreasing N-acetyl aspartate, indicating decreased neuronal health or neuronal loss. Based on these findings, multicenter prospective studies incorporating advanced MR techniques as well as neurocognitive function tests should be designed in order to gain more evidence on radiation-induced sequelae.

Keywords: radiotherapy; radiation-induced brain injuries; normal-appearing brain tissue; functional MRI; anatomical MRI; perfusion; diffusion; spectroscopy; atrophy

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Permalink: https://www.hzdr.de/publications/Publ-32499
Publ.-Id: 32499


Proton beam quality enhancement by spectral phase control of a PW-class laser system

Ziegler, T.; Albach, D.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Dover, N. P.; Garten, M.; Gaus, L.; Gebhardt, R.; Goethel, I.; Helbig, U.; Irman, A.; Kiriyama, H.; Kluge, T.; Kon, A.; Kraft, S.; Kroll, F.; Löser, M.; Metzkes-Ng, J.; Nishiuchi, M.; Obst-Hübl, L.; Püschel, T.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

We report on experimental investigations of proton acceleration from solid foils irradiated with PW‑class laser‑pulses, where highest proton cut‑off energies were achieved for temporal pulse parameters that varied significantly from those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto‑optic programmable dispersive filter enabled us to manipulate the temporal shape of the last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that applying positive third order dispersion values to short pulses is favourable for proton acceleration and can lead to maximum energies of 70 MeV in target normal direction at 18 J laser energy for thin plastic foils, significantly enhancing the maximum energy compared to ideally compressed FTL pulses. The paper further proves the robustness and applicability of this enhancement effect for the use of different target materials and thicknesses as well as laser energy and temporal intensity contrast settings. We demonstrate that application relevant proton beam quality was reliably achieved over many months of operation with appropriate control of spectral phase and temporal contrast conditions using a state‑of‑the‑art high‑repetition rate PW laser system.

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Permalink: https://www.hzdr.de/publications/Publ-32498
Publ.-Id: 32498


Experimental and numerical study of particles resuspension

Banari, A.; Eidt, R.; Lecrivain, G.; Hampel, U.

One of the first fundamental investigations on the resuspension of micron-sized particles in shear flows probably dates back to the 1930s, when Shields reported the existence of a threshold wall shear, beyond which particle re-entrainment into the flow occurs. Improvements have since been made, yet they do not provide all ingredients for a complete description of all mechanisms occurring at the particle scale. In this work, we experimentally discover, that the inter-particle collisions are key to the resuspension of a mono-layer bed of 40 micrometer glass beads in a gas flow. Our experimental findings, supported by simulations, stress the need to account for the role of inter-particle collisions, that all models have so far neglected.

Keywords: paticle resuspension; Inter-particle collisions; experimental test

  • Lecture (Conference) (Online presentation)
    Jahrestreffen der ProcessNet-Fachgruppen Mehrphasenströmungen und Computational Fluid Dynamics, 09.-10.04.2021, Online Conference, Germany

Permalink: https://www.hzdr.de/publications/Publ-32497
Publ.-Id: 32497


Dynamics of non-spherical particles at fluidic interface

Lecvrivain, G.

During this talk, I will report about my experimental and numerical results on the attachement of non-spherical particles on and off fluidic interfaces. The results apply to the field of mineral flotation, where hydrophobic particles are separated from water by rising gas bubbles.

  • Invited lecture (Conferences)
    Seminar at the Institute for Nano- and Microfluidics, Center of Smart, Interfaces, TU Darmstadt, 25.04.2019, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-32496
Publ.-Id: 32496


Recovery of non-spherical solid particles by rising bubbles

Lecrivain, G.

During this invited lecture, I will discuss the dynamics of glass particles settling on the gas-liquid interface of an immersed gas bubbles.

  • Invited lecture (Conferences)
    Seminar über Nichtlinearität und Unordnung in komplexen Systemen, 02.07.2018, Magdeburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-32495
Publ.-Id: 32495


MHT-X: Offline Multiple Hypothesis Tracking with Algorithm X

Zvejnieks, P.; Birjukovs, M.; Klevs, M.; Akashi, M.; Eckert, S.; Jakovics, A.

An efficient and versatile implementation of offline multiple hypothesis tracking with Algorithm X for optimal association search was developed using Python. The code is intended for scientific applications that do not require online processing. Directed graph framework is used and multiple scans with progressively increasing time window width are used for edge construction for maximum likelihood trajectories. The current version of the code was developed for applications in multi-phase hydrodynamics, e.g. bubble and particle
tracking, and is capable of resolving object motion, merges and splits. Feasible object associations and trajectory graph edge likelihoods are determined using weak mass and momentum conservation laws translated to statistical functions for object properties. The code is compatible with n-dimensional motion with arbitrarily many tracked object properties. This framework is easily extendable beyond the present application by replacing the currently used heuristics with ones more appropriate for the problem at hand. The code is open-source and will be continuously developed further.

Keywords: Algorithm X; two-phase flow; bubble dynamics; liquid metal; X-ray radiography; neutron imaging; image processing

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Permalink: https://www.hzdr.de/publications/Publ-32494
Publ.-Id: 32494


Ion beam joining of ceramic and carbon-based nanostructures

Das, P.; Möller, W.; Elliman, R. G.; Chatterjee, S.

Ion beam assisted joining of nanostructured materials is a relatively new field. In particular, ion beam technique
has been proven to be worthwhile for joining ceramic nanostructures. However, a large scope is still remaining to
study heterojunctions between two dissimilar materials as the process of formation of bonds between two dis
similar
materials is still to be understood. In this work we pick up a ceramic oxide and carbon based material to
study ion beam joining. Specifically, we for the first time show heterojunction formation between hydrogen
titanate nanowire (HTNW) and carbon nanotube (CNT) by the low energy ion beam. In order to understand the
mechanism, we have invoked density functional theory and three-dimensional ion–solid interaction simulations.
Experimental results are supported by predictions of simulations and suggest that the joining is established
through ion beam mixing, surface defects and sputter redeposition at the junction points. The current study
enlightens how the defects and sputtered out atoms are involved in the joining process. The chemical bonds
between HTNW and CNT are formed only when C vacancy and simultaneously non-lattice O and C were pro
duced
during irradiation. The effect of joining on electrical conductivity and surface wetting has also been
studied experimentally in this work, which is supported by simulations.

Keywords: Ion irradiation; Heterojunction; TRI3DYN; Density functional theory; Transport property; Wetting

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Permalink: https://www.hzdr.de/publications/Publ-32493
Publ.-Id: 32493


Data for: High-bias-field operation of GaAs photoconductive terahertz emitters

Welsch, M.; Singh, A.; Winnerl, S.; Pashkin, O.; Xu, M.; Li, M.; Helm, M.; Schneider, H.

Data file names start with the corresponding figure in the manuscript. For example- file "F1cd_velocity vs E_hs_Jan8.opju" means this data set is used to plot Fig. 1c and 1d (So, name start with F1cd_). 

Keywords: Terahertz emitter; Photoconductive; Terahertz

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Permalink: https://www.hzdr.de/publications/Publ-32492
Publ.-Id: 32492


Data for: Influence of Muscovite (001) Surface Nanotopography on Radionuclide Adsorption studied by kinetic Monte Carlo Simulations

Schabernack, J.; Kurganskaya, I.; Fischer, C.; Luttge, A.

Raw Data for the Publication: Influence of Muscovite (001) Surface Nanotopography on Europium Adsorption studied by kinetic Monte Carlo Simulations

Kinetic Monte Carlo (KMC) simulations were performed on the (001) muscovite face.
KMC simulations were divided in two parts: (1) surface dissolution (2) europium (Eu3+) adsorption to resulting surface

Simulation Settings:
    - Surface Size [unit cells]: 700 in a, 300 in b, 8 in c
    - Dissolved Atoms: 2,000,000
    - Adsorbed Atoms: 300,000

KMC Simulations:
    - Case(I)  [1PitDepth6]  : One single etch pit with a depth of 6 unit cells or ~12 nm / 10 Simulation Runs
    - Case(II) [6PitsDepth1] : Six inital etch pits with depths of 1 uni cell or ~2 nm / 10 Simulation Runs
    - Study of etch pit depth vs. number of octahedral surface atoms [OctahedralSitesDepth]: Six simulations with pit depths from 1 to 6 unit cells / 1 Simulation Run each

Produced Output Data from KMC Simulations. Each Run contains:
    - Number of Adsorbed Atoms and Time (Ad_Num.txt)
    - Number of Adsorbed Atoms by Position and Time (Ad_Site_Stat.txt)
    - Number of Dissolved Atoms and Time (diss_num_1.txt)
    - Number of Dissolved Atoms by Position and Time (site_stats_1.txt)
    - Four Files for Adsorption Visualization (Ad_mov_01 to _04.pdb)
    - Four Files for Dissolution Visualization (m_mov_001_1 to _4.pdb)

    .pdb files can be opened and viewed by using the Visual Molecular Dynamics (VMD) viewer (https://www.ks.uiuc.edu/Research/vmd/)
        Humphrey, W., Dalke, A. and Schulten, K., "VMD - Visual Molecular Dynamics", J. Molec. Graphics, 1996, vol. 14, pp. 33-38.

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Permalink: https://www.hzdr.de/publications/Publ-32491
Publ.-Id: 32491


Heterogeneous sorption of radionuclides predicted by crystal surface nanoroughness

Yuan, T.; Schymura, S.; Bollermann, T.; Molodtsov, K.; Chekhonin, P.; Schmidt, M.; Stumpf, T.; Fischer, C.

Reactive transport modeling (RTM) is an essential tool for the prediction of contaminants’ behavior in the bio- and geosphere. However, RTM of sorption reactions is constrained by the reactive surface site assessment. The reactive site density variability of the crystal surface nanotopography provides an “energetic landscape”, responsible for heterogeneous sorption efficiency, not covered in current RTM approaches. Here, we study the spatially heterogeneous sorption behavior of Eu(III), as an analogue to trivalent actinides, on a polycrystalline nanotopographic calcite surface and quantify the sorption efficiency as a function of surface nanoroughness. Based on experimental data from micro-focus time-resolved laser-induced luminescence spectroscopy (μTRLFS), vertical scanning interferometry, and electron back-scattering diffraction (EBSD), we parameterize a surface complexation model (SCM) using surface nanotopography data. The validation of the quantitatively predicted spatial sorption heterogeneity suggests that retention reactions can be considerably influenced by nanotopographic surface features. Our study presents a way to implement heterogeneous surface reactivity into a SCM for enhanced prediction of radionuclide retention.

Keywords: Sorption reactions; Crystal surface reactivity; µTRLFS; Surface complexation modeling; Radionuclide migration

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Permalink: https://www.hzdr.de/publications/Publ-32490
Publ.-Id: 32490


Effective diffusivity prediction of radionuclides in clay formations using an integrated upscaling workflow

Yuan, T.; Fischer, C.

The effective diffusivity is a key parameter in the diffusive transport calculations, thus decisive for predicting the radionuclide migration in low-permeable clay-rich formations. Potential host rocks such as the Opalinus clay exhibit pore network heterogeneities, critically modified due to compositional variability in the sandy facies and owing to diagenetic minerals. Meaningful estimation of the effective diffusivity requires an understanding of transport mechanisms at the nanometer-scale as a starting point and a combination with upscaling strategies for considering compositional heterogeneities at the micrometer-scale.
In this study, we propose an upscaling workflow that integrates transport simulations at both the nanometer-scale and the micrometer-scale to predict the effective diffusivities of radionuclides in the sandy facies of the Opalinus clay. The respective synthetic digital rocks provide conceptually two types of materials at the pore scale, in which the pore space and pore network in the clay matrix at the nanometer scale and mineral complexity in shales at the micrometer scale are considered. The numerical approach using the introduced digital rocks is validated with published experimental data that confirm the general applicability of the models. Sensitivity studies reveal the increase of effective diffusivity of shales as a function of increased pore space, reduced tortuosity, and an increased sheet silicate concentration compared to other rock components. Thus, such spatial variabilities at the pore scale of more complex sedimentary rocks are now addressed in the proposed approach and available for studying heterogeneous diffusion patterns compared to commonly assumed homogeneous behavior. Finally, and as a starting point for further upscaling strategies, we investigate anisotropic diffusion by studying the effect of lamination of the shales towards enhanced predictability of radionuclide migration.

Keywords: Radionuclide migration; Diffusive transport modeling and Upscaling; Digital rock; Opalinus Clay; Nuclear waste disposal; Clay rock formations

Permalink: https://www.hzdr.de/publications/Publ-32489
Publ.-Id: 32489


A combined experimental and theoretical study of 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene adsorption on Au(111)

Lokamani, M.; Kelling, J.; Ohmann, R.; Meyer, J.; Kühne, T.; Cuniberti, G.; Wolf, J.; Huhn, T.; Zahn, P.; Moresco, F.; Gemming, S.

The electronic and geometrical structure of 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene
(PEEB) molecules adsorbed on a Au(111) surface is investigated by low temperature scanning tun-
neling microscopy (STM) and scanning tunneling spectroscopy (STS) in conjunction with density-
functional-based tight-binding (DFTB) simulations of the density of states and the interaction with
the substrate. Our density functional theory calculations indicate that the PEEB molecule is ph-
ysisorbed on the Au(111) substrate, with negligible distortion of the molecular geometry and charge
transfer between molecule and substrate.

Keywords: 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene; DFT; STM; Au(111)

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Permalink: https://www.hzdr.de/publications/Publ-32488
Publ.-Id: 32488


Data for: Entrance effects in a radial Hele-Shaw cell: numerical and experimental study

Stergiou, G.; Eckert, K.; Schwarzenberger, K.

Hele-Shaw cells are a frequently used tool in various fields of chemical technology, and in environmental and biomedical engineering. The flow conditions near the inlet of a radial Hele-Shaw cell significantly affect the outcome of its technological applications. The present work combines Computational Fluid Dynamics (CFD) and micro-Particle Image Velocimetry (μPIV) to explain the entrance phenomena, i.e. flow detachment and vortex generation, in radial Hele-Shaw cells. The experiments show that the flow detachment is determined by the inlet flow Reynolds number, Re. Two-dimensional numerical simulations were employed to further investigate the role of the gap width, w to inlet diameter, D aspect ratio, w/D. The resulting flow regime map is divided by a transitional Re number, Ret, that depends on the aspect ratio. A further parametric study examining how Re and the aspect ratio affect the reattachment length yields an empirical correlation in power-law form. Finally, the impact of the inlet's geometrical features is briefly examined. The current work can be used as a design guide for future radial HS engineering applications.

Keywords: Hele-Shaw cell; flow separation; laminar flow; reattachment length; CFD; μPIV

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Permalink: https://www.hzdr.de/publications/Publ-32487
Publ.-Id: 32487


Linear, spatio-temporally resolved ultrasound measurement of the liquid fraction distribution in froth

Emmerich, H.; Schaller, L.; Nauber, R.; Knüpfer, L.; Heitkam, S.; Czarske, J.; Büttner, L.

Froth flotation is an important process for separating metal particles from gangue. A single flotation circuit for copper uses approx. 44 billion litres water a year. In situ process monitoring of the foam’s parameters and closed-loop control can reduce the resource use. However, no measurement technique is broadly employed that yields the liquid fraction distribution in the froth. Optical measurement are prevented by the bulk foam’s opacity. Though, ultrasound in the low frequency range is able to penetrate froth. In this paper we investigate the application of ultrasound to measure the local liquid content of aqueous foam in the axis of the ultrasound beam. Assuming a dependency of the reflection coefficient 𝑟 on the foam’s liquid fraction 𝜑, we developed a model to calculate 𝑟 from the reflected signal. Local reflection coefficients 𝑟_𝑛 can be determined for timegated windows and show a monotonic dependency on the foam’s liquid fraction 𝜑 (for 𝜑< 0.8 %). The uncertainty of the liquid fraction determined by means of a electrical reference measurement is 𝜎_𝜑= 0.079%. We demonstrated the capability of spatio-temporally resolved measurements with a frame rate of 3 s and an axial resolution of 0.79 mm in an experiment with a time-varying, inhomogeneous liquid fraction. This research work is contributing to a determination of in situ information of the foam’s parameter in a flotation process.

Keywords: foam; ultrasound

Permalink: https://www.hzdr.de/publications/Publ-32486
Publ.-Id: 32486


Design, radiosynthesis and preliminary biological evaluation in mice of a brain-penetrant 18F-labelled σ2 receptor ligand

Moldovan, R.-P.; Gündel, D.; Teodoro, R.; Ludwig, F.-A.; Fischer, S.; Toussaint, M.; Schepmann, D.; Wünsch, B.; Brust, P.; Deuther-Conrad, W.

The σ2 receptor (transmembrane protein 97), which is involved in cholesterol homeostasis, is of high relevance for neoplastic processes. The upregulated expression of σ2 receptors in cancer cells and tissue in combination with the antiproliferative potency of σ2 receptor ligands motivates the research in the field of 2 receptors for the diagnosis and therapy of different types of cancer. Starting from the well described 2-(4-(1H-indol-1-yl)butyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline class of compounds, we synthesized a novel series of fluorinated derivatives, bearing the F-atom at the aromatic indole/azaindole subunit. RM273 (2-[4-(6-fluoro-1H-pyrrolo[2,3-b]pyridin-1-yl)butyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) was selected for labelling with 18F and evaluation regarding detection of σ2 receptors in the brain by positron emission tomography. Initial metabolism and biodistribution studies of [18F]RM273 in healthy mice revealed promising penetration of the radioligand into the brain. Preliminary in vitro autoradiography on brain cryosections of an orthotopic rat glioblastoma model proved the potential of the radioligand to detect the upregulation of σ2 receptor in glioblastoma cells compared to healthy brain. The results indicate that the herein developed σ2 receptor ligand [18F]RM273 has potential to assess by non-invasive molecular imaging the correlation between the availability of σ2 receptors with properties of brain tumors such as tumor proliferation or resistance towards particular therapies

Keywords: σ2 receptor; transmembrane protein 97; azaindoles; binding affinity; radiochemistry; fluorine-18 labeling; positron emission tomography (PET); brain-penetration; glioblastoma; orthotopic

Permalink: https://www.hzdr.de/publications/Publ-32485
Publ.-Id: 32485


Status of LISEL@DREAMS

Forstner, O.; Weber, T.; Wendt, K.; Gadelshin, V.; Merchel, S.; Rugel, G.

Accelerator Mass Spectrometry (AMS) is a highly versatile tool to detect radionuclides on the ultra-trace level. LISEL@DREAMS aims for improving the AMS method by reducing the amount of stable isobars limiting its applicability especially in the mass region 50

Keywords: Accelerator Mass Spectrometry; Low-energy Isobar SEparation by Lasers; LISEL; AMS; radionuclide

Related publications

  • Poster (Online presentation)
    Ion beam workshop 2021 - virtual meeting, 24.-25.03.2021, Online, World-wide

Permalink: https://www.hzdr.de/publications/Publ-32484
Publ.-Id: 32484


Influence of Muscovite (001) Surface Nanotopography on Radionuclide Adsorption Studied by Kinetic Monte Carlo Simulations

Schabernack, J.; Kurganskaya, I.; Fischer, C.; Luttge, A.

Mechanistic understanding and prediction of solute adsorption from fluids onto mineral surfaces is relevant for many natural and technical processes. Mineral surfaces in natural systems are often exposed to fluids at non-equilibrium conditions resulting in surface dissolution reactions. Such reactions cause the formation of surface nanotopography and, consequently, the exposure of different types of surface atoms. The quantitative effect of nanotopography on the efficiency of adsorption reactions at crystal surfaces is not known. Using kinetic Monte Carlo simulations, we combine a model of muscovite (001) face dissolution with a consequent model of europium adsorption on the rough mineral surface. The model considers three different adsorption sites based on the muscovite surface cations: silicon, tetrahedral and octahedral aluminum. Two different surface nanotopography configurations are investigated, both showing similar adsorption behavior. Octahedral aluminum surface atoms defined by having the highest reactivity towards adsorption are exposed solely on steps and pits on the muscovite (001) face. Thus, their availability directly depends on the surface nanotopography. The model results show the need for a more precise parameterization of surface site-specific adsorption, taking into account the coordination of the involved surface cation such as kink, step or terrace sites.

Keywords: kinetic Monte Carlo simulation; adsorption; dissolution; radionuclides; muscovite

Permalink: https://www.hzdr.de/publications/Publ-32483
Publ.-Id: 32483


MHD driven localized short circuits in liquid metal batteries

Benard, S.; Landgraf, S.; Weber, N.; Weier, T.

Liquid metal batteries (LMBs) are electrochemical devices, which operate as simple concentration cells at elevated temperature. Abundant raw materials and the totally liquid interior promise a very long life time, extreme current densities and a very competitive price of these storage devices. For this reason, LMBs are discussed as an ideal candidate for grid-scale energy storage.
The cathode of the cells (e.g. molten Bi, at the bottom) is typically contained in a metal vessel, while the anode (e.g. molten Li, at the top) is soaked into a FeNi-foam. Both electrodes are separated by a molten salt electrolyte. When discharging the cell, Li is oxidised, crosses the electrolyte layer and alloys into Bi; upon charge, the process is reversed. Due to corrosion or electrochemical reactions of the molten salt layer with the FeNi-foam, the Li-wetting of the foam might decrease during operation. In case of insufficient wetting of this current collector, it might happen that the Li does not penetrate the foam any more, when the cell is charged. Consequently, small Li-droplets will appear below of the foam, and will grow into the electrolyte layer, when charging the battery. As the conductivity of the electrolyte is four orders of magnitude smaller than that of the metals, the current will take the shortest way through the electrolyte, i.e. a large current will flow through the Li-droplets. This current might pinch the droplet locally, possibly deforming, or even cutting it off. Hence, small Li-spheres might be transferred into the electrolyte. This might lead to unwanted self-discharge, if Li reaches the Bi-layer.
In the presentation, the appearance and significance of such localised droplet-transfer and short-circuits will be discussed first. Then, some experimental evidence of similar effects will be presented. Finally, numerical simulations of the transfer of a single droplet will be shown. Moreover, the relevance of the results for practical applications and real cells will be explained.

  • Lecture (Conference)
    Fourth Russian Conference on Magnetohydrodynamics, 20.09.2021, Perm, Russland

Permalink: https://www.hzdr.de/publications/Publ-32482
Publ.-Id: 32482


Teaching Machine Learning in 2020

Steinbach, P.; Seibold, H.; Guhr, O.

Faced by the abundant use of machine learning in industry and academia, the effective and efficient teaching of core concepts in this field becomes of high importance. For this, we organized a workshop on teaching methods in the field of machine learning. In this document, we summarize the current standing of the community as by our workshop and their methods. We touch on existing working concepts in machine learning didactics, what methods present initiatives use and cover open teaching resources available to date. With this, we hope to provide a starting point for future collaborations on this central topic given the expanding use of machine learning in science, industry and our daily lives.

Keywords: Machine Learning; Deep Learning; Data Science; Teaching; Didactics

  • Open Access Logo Contribution to proceedings
    Proceedings of the first Teaching Machine Learning and Artificial Intelligence Workshop at ECML-PKDD 2020, 14.09.2020, virtuell, virtuell
    Volume 141: European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases, http://proceedings.mlr.press/v141/

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Permalink: https://www.hzdr.de/publications/Publ-32481
Publ.-Id: 32481


Investigating the interplay of heat and mass transport in a three-layer liquid metal battery model

Klopper, T. S.

Thermal and solutal convection effects have been proven to have a significant impact in liquid metal batteries (LMBs) with potentially beneficial but eventually detrimental effects on their operation. LMBs are likely to be good candidates for solving the 21st century challenge of storing electrical energy on a large scale in order to ensure the stability of electrical grids in the future, which will consist of an increasing amount of renewable energies. With their fully liquid interior, they feature numerous phenomena of fluid dynamics, which are studied in order to adjust the battery’s design. Among them are convective phenomena, which play a role when density gradients form due to heating or compositional variations. The typical LMB consists of three segregated layers featuring different characteristics. Thermal convection typically occurs in the negative electrode and the electrolyte, while solutal convection is unique in the positive electrode, where it occurs during charge of the battery. Previous numerical studies observed that thermal convection is dominant either in the negative electrode or in the electrolyte, which depends strongly on the layers’ thicknesses. Coupling between the interfaces has been observed, but was not yet studied in-depth. Effects of solutal convection have been studied on the isolated positive electrode only and could be associated with substantial flow.
We performed numerical studies to examine the interfacial coupling of the two types of convection in a three-layer model. Therefore we made use of an OpenFOAM solver specifically developed for this problem. The solver was first validated by performing a grid independence study and comparing the results to previous solutions. A configuration was then studied, where significant flow evolves due to both thermal and solutal convection in all three regions. We observed chaotic flow patterns, which were strongly affected by the interfacial coupling. As a result, the flow phenomena in the electrolyte are highly irregular, as it is affected from the other layers both at its top and bottom interfaces. We suspect the behaviour to be highly dependent on the exact configuration of the battery and therefore suggest that these phenomena are studied more extensively in the future.

  • Master thesis
    Carl von Ossietzky Universität Oldenburg, 2021

Permalink: https://www.hzdr.de/publications/Publ-32480
Publ.-Id: 32480


Entrance effects in a radial Hele-Shaw cell: numerical and experimental study

Stergiou, G.; Eckert, K.; Schwarzenberger, K.

Hele-Shaw cells are a frequently used tool in various fields of chemical technology, and in environmental and biomedical engineering. The flow conditions near the inlet of a radial Hele-Shaw cell significantly affect the outcome of its technological applications. The present work combines Computational Fluid Dynamics (CFD) and micro-Particle Image Velocimetry (μPIV) to explain the entrance phenomena, i.e. flow detachment and vortex generation, in radial Hele-Shaw cells. The experiments show that the flow detachment is determined by the inlet flow Reynolds number, Re. Two-dimensional numerical simulations were employed to further investigate the role of the gap width, w to inlet diameter, D aspect ratio, w/D. The resulting flow regime map is divided by a transitional Re number, Ret, that depends on the aspect ratio. A further parametric study examining how Re and the aspect ratio affect the reattachment length yields an empirical correlation in power-law form. Finally, the impact of the inlet's geometrical features is briefly examined. The current work can be used as a design guide for future radial HS engineering applications.

Keywords: Hele-Shaw cell; flow separation; laminar flow; reattachment length; CFD; μPIV

Permalink: https://www.hzdr.de/publications/Publ-32479
Publ.-Id: 32479


Post-implantation defects in heavy ion implanted monocrystalline ZnO

Werner, Z.; Barlak, M.; Ratajczak, R.; Akhmadaliev, S.; Heller, R.; Staszkiewicz, B.; Zagórski, J.

Monocrystalline ZnO samples were implanted with Co (transition metal) and with Ar and Kr noble gas ions, with energies and doses leading to comparable damage in the host lattice as regards its extension and magnitude. Structural properties of the implantedZnOwere investigated by channeled Rutherford Backscattering Spectrometry (cRBS), aided with calculations using McChasy code. It was shown that the damage produced by implantation does not reach an amorphization level in all cases and is produced deeper in the crystal in comparison with theoretical predictions. The range and magnitude of damaged region are comparable in all cases of ion implantation.

Keywords: ZnO; heavy ion implantation; cRBS measurements; damage simulation

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Permalink: https://www.hzdr.de/publications/Publ-32478
Publ.-Id: 32478


Oscillatory Copper Deposition on Conical Iron Electrodes in a Nonuniform Magnetic Field

Marinaro, G.; Huang, M.; Mutschke, G.; Yang, X.; Eckert, K.

We report the effect of a magnetic field on the deposition of copper ions on a conically shaped iron probe. In our setup, the magnetic forces and buoyancy are the key factors influencing the electrolyte flow and the mass transfer. Without external current, a spontaneous reduction of copper on the iron cone occurs, known as electroless deposition. Mach–Zehnder and differential interferometry indicate a variation in the concentration of copper ions near the cone. After an initial transient of about 60 s, temporal oscillations in the copper concentration are found under the effect of a magnetic field. In galvanostatic conditions, a similar oscillatory behavior of the concentration of the electrolyte is observed. Numerical simulations show that the oscillations are caused by the magnetic gradient, Lorentz force, and buoyancy force counteracting one an-other, and the oscillation frequency is estimated analytically based on this mechanism. Fur-thermore, we present a study on the oscillation frequency for both electroless and galvanostatic conditions with different current densities. The results of this study may stimulate future re-search aimed at the local control of the deposition rate and the realization of miniaturized, reg-ularly structured deposits using magnetic fields.

Keywords: Electrodeposition; magnetic field; mass transport; variation of ion concentration; Mach-Zehnder Interferometry

Permalink: https://www.hzdr.de/publications/Publ-32477
Publ.-Id: 32477


Numerical and experimental data set obtained from paraffin phantom measurements based on the capacitance wire-mesh sensor.

de Assis Dias, F.; Wiedemann, P.; Da Silva, M. J.; Schleicher, E.; Hampel, U.

This data set contains experimental and numerical data from a 12x12 wire-mesh sensor. A 12x12 WMS was used to measure paraffin phantoms created to mimic three flow patterns: slug, annular and bubble flow. The sensor was assembled with flanges and filled with tap water. Two models based on finite element model were used to generate the synthetic data. The first one is a basic FEM model, which was designed based on other models reported in the literature (i.e. the output signal is obtained by integrating the current density over the surface of a receiver wire). In the second model (FEM+EC), the electric potential is solved as the basic one, however, external circuits (macromodels) were coupled to the 3D geometry of the sensor to emulate the excitation and amplification systems of a real WMS.A mapping containing the coordinates and electrical properties of the paraffin phantoms was created through image processing and imported into the software COMSOL v.5.6. Thus, both basic FEM and FEM+EC models were used to generate synthetic data that can be direct compared to the experimental data.

Keywords: capacitance wire-mesh sensor; data set; phantom measurement; multiphase flow; finite element method

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Permalink: https://www.hzdr.de/publications/Publ-32476
Publ.-Id: 32476


Correlative light and Helium Ion Microscopy to identify lung response to metal oxide and carbon nanomaterials done on model lung epithelium

Podlipec, R.; Kriselj, A.; Vogel Mikus, K.; Klingner, N.; Hlawacek, G.; Strancar, J.

Comprehensive understanding of molecular events governing lung epithelium response to inhaled nanoparticles is still lacking. These repeating events in lungs could eventually lead to persistent inflammation and further cardiovascular diseases [1,2]. To better understand how it all start on a molecular, nanoscale level one urgently needs an appropriate model system and an advanced imaging technique(s) capable of unravelling key information on a nanoscale. Many studies addressing such complex biological problems have been lately tackled by correlative microscopy (CM) approach using an optimal combination of complementary and advanced techniques [3].
Our approach was thus to apply live cell epithelium model imaging using an advanced high-resolution fluorescence microscopy followed by helium ion microscopy (HIM) to visualize structures and morphology further down at nano-scale. One of the HIM advantages to other high-resolution, high-vacuum imaging techniques is large depth of focus, sub-nm resolution, nm surface sensitivity, and especially no need for sample coating that changes the nanostructure morphology on the surface. To gather any further structure-function information of the investigated biological system using such diametrical techniques, an appropriate sample preparation needed to be developed. Once done, we could study sub-micron to nanometer changes that govern model lung epithelium interaction with various nanoparticles. Exposure of metal oxide (TiO2) nanotubes has revealed active passivation of nanomaterial-biological matter composites on the cell surface with lipo-proteins present, identified both with optical and ion beam technique (Figure, below). Findings of CM studies have contributed to better understand chronic inflammation prediction in lung diseases [4]. On the other hand, exposed carbon nanoparticles have shown completely different cell response and will be discussed.

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. Ando, T. The 2018 correlative microscopy techniques roadmap, J. Phys. D: Appl. Phys. 51, (2018).
4. Kokot, H., et. al, Prediction of Chronic Inflammation for Inhaled Particles: the Impact of Material Cycling and Quarantining in the Lung Epithelium, Advanced Materials 32, 2003913 (2020)

Related publications

  • Lecture (Conference)
    Focus on Microscopy, 2021, 28.-31.03.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-32475
Publ.-Id: 32475


Aktuelle radiopharmazeutische Entwicklungen für die theranostische Anwendung

Neels, O.; Kratochwil, C.; Patt, M.

Im vorliegenden CME-Beitrag sollen die Grundlagen des Theranostik-Prinzips beginnend bei den Eigenschaften der Radionuklide sowie deren Verfügbarkeit erläutert werden. Anhand von medizinischen und chemischen Beispielen aus den prominentesten Anwendungsgebieten der Theranostik (Prostatakarzinom/PSMA, neuroendokrine Tumoren und Fibroblasten-Aktivierungsprotein Inhibitoren) werden die unterschiedlichen Arten von theranostischen Radionuklid- und Radioliganden-Paaren beschrieben. Abgerundet wird der Artikel durch Ausführungen zu den regulatorischen Randbedingungen wie Verfügbarkeit und Verkehrsfähigkeit von Radionuklidvorstufen und radioaktiven Arzneimitteln sowie zu deren Eigenherstellung.

Keywords: Theranostik; Radiopharmazie; PET; SPECT; Gesetzgebung; AMG; erlaubnisfreie Herstellung; AMRadV

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Permalink: https://www.hzdr.de/publications/Publ-32474
Publ.-Id: 32474


Predicting the Risk of Metastases by PSMA-PET/CT—Evaluation of 335 Men with Treatment-Naïve Prostate Carcinoma.

Koerber, S.; Boesch, J.; Kratochwil, C.; Schlampp, I.; Ristau, J.; Winter, E.; Zschaebitz, S.; Hofer, L.; Herfarth, K.; Kopka, K.; Holland-Letz, T.; Jaeger, D.; Hohenfellner, M.; Haberkorn, U.; Debus, J.; Giesel, F.

Men diagnosed with aggressive prostate cancer are at high risk of local relapse or systemic
progression after definitive treatment. Treatment intensification is highly needed for that patient
cohort; however, no relevant stratification tool has been implemented into the clinical work routine
so far. Therefore, the aim of the current study was to analyze the role of initial PSMA-PET/CT as a prediction tool for metastases. In total, 335 men with biopsy-proven prostate carcinoma and PSMA-PET/CT for primary staging were enrolled in the present, retrospective study. The number
and site of metastases were analyzed and correlated with the maximum standardized uptake value (SUVmax) of the intraprostatic, malignant lesion. Receiver operating characteristic (ROC) curves were used to determine sensitivity and specificity and a model was created using multiple logistic regression. PSMA-PET/CT detected 171 metastases with PSMA-uptake in 82 patients. A statistically significant higher SUVmax was found for men with metastatic disease than for the cohort without distant metastases (median 16.1 vs. 11.2; p < 0.001). The area under the curve (AUC) in regard to predicting the presence of any metastases was 0.65. Choosing a cut-off value of 11.9 for SUVmax, a sensitivity and specificity (factor 1:1) of 76.0% and 58.4% was obtained. The current study confirms, that initial PSMA-PET/CT is able to detect a relatively high number of treatment-naïve men with metastatic prostate carcinoma. Intraprostatic SUVmax seems to be a promising parameter for the prediction of distant disease and could be used for treatment stratification—aspects which should be verified within prospective trials.

Keywords: prostate cancer; PSMA; PET; metastases; intraprostatic SUV

Permalink: https://www.hzdr.de/publications/Publ-32473
Publ.-Id: 32473


Chlorine doping of MoSe2 flakes by ion implantation

Prucnal, S.; Hashemi, A.; Ghorbani Asl, M.; Hübner, R.; Duan, J.; Wei, Y.; Sharma, D.; Zahn, D. R. T.; Ziegenrücker, R.; Kentsch, U.; Krasheninnikov, A.; Helm, M.; Zhou, S.

The efficient integration of transition metal dichalcogenides (TMDs) into the current electronic device technology requires mastering the techniques of effective tuning of their optoelectronic properties. Specifically, controllable doping is essential. For conventional bulk semiconductors, ion implantation is the most developed method offering stable and tunable doping. In this work, we demonstrate n-type doping in MoSe2 flakes realized by low-energy ion implantation of Cl+ ions followed by millisecond-range flash lamp annealing (FLA). We further show that FLA for 3 ms with a peak temperature of about 1000 °C is enough to recrystallize implanted MoSe2. The Cl distribution in few-layer-thick MoSe2 is measured by secondary ion mass spectrometry. An increase in the electron concentration with increasing Cl fluence is determined from the softening and red shift of the Raman-active A1g phonon mode due to the Fano effect. The electrical measurements confirm the n-type doping of Cl-implanted MoSe2. A comparison of the results of our density functional theory calculations and experimental temperature-dependent micro-Raman spectroscopy data indicates that Cl atoms are incorporated into the atomic network of MoSe2 as substitutional donor impurities.

Keywords: MoSe2; ion implantation; Flash Lamp Annealing; doping; 2D materials; DFT; Raman

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Permalink: https://www.hzdr.de/publications/Publ-32472
Publ.-Id: 32472


Flow morphologies in straight and bent horizontal pipes

Döß, A.; Schubert, M.; Wiedemann, P.; Junge, P.; Hampel, U.; Schleicher, E.; Mehringer, C.; Geipel, C.

Two-phase flows in pipes develop characteristic patterns or flow morphologies. Their transport between process units and plant components often involves short pipes, large pipe diameters as well as bends and curvatures. The prediction of the predominantly undeveloped flow morphologies in such systems is challenging and subject to high uncertainties due to lacking experimental data and universal engineering models. In this work comprehensive experimental studies were conducted in horizontal straight and bent pipes of 50 mm and 200 mm diameter. Wire-mesh sensors were applied at characteristic positions to obtain the gas-liquid distributions with high spatiotemporal resolution. Subsequently, a fuzzy classification method is applied to assign a flow pattern to characterize the flow conditions. As this assignment is fuzzy, we introduce an advanced concept of a color-coded flow map visualization for further analyses. As a result, we analyze the effect of pipe curvatures on the flow morphology and its downstream recovery.

Keywords: Developing two-phase flow; horizontal pipe flow; wire-mesh sensor; fuzzy flow pattern identification; flow morphology

Permalink: https://www.hzdr.de/publications/Publ-32471
Publ.-Id: 32471


Combined Finite Element and Electronic Circuit Model of a Wire-Mesh Sensor

de Assis Dias, F.; Wiedemann, P.; Da Silva, M. J.; Schleicher, E.; Hampel, U.

A new wire-mesh sensor model based on electric field and circuit simulations is presented. In our approach, the excitation and amplification stages of the capacitance WMS are created as macromodels and coupled to the electrodes of a 3D geometry of the sensor. Thus, the effects caused by nonideal characteristics of the amplifiers are considered (e.g. finite open-loop gain and bandwidth). In order to evaluate the performance of the model, a static validation based on phantom measurement was performed. The phantoms were created with paraffin to emulate typical flow regimes, i.e. annular, slug and bubble flow. A mapping containing the position and the electrical properties of the patterns was obtained by image processing and incorporated to the field simulation. Hence the numerical simulations could be directly compared to the experimental data. The results show that coupling the external circuits to the capacitance WMS model is crucial to provide reliable synthetic data.

Keywords: complex impedance; multiphase flow; flow visualization; finite-element method; wire-mesh sensor

Permalink: https://www.hzdr.de/publications/Publ-32470
Publ.-Id: 32470


Conductive hydrogels with dynamic reversible networks for biomedical applications

Xu, Y.; Patino Gaillez, M.; Rothe, R.; Hauser, S.; Voigt, D.; Pietzsch, J.; Zhang, Y.

Conductive hydrogels (CHs) are emerging as a promising and well-utilized platform for three-dimensional (3D) cell culture and tissue engineering to incorporate electron signals as biorelevant physical cues. In conventional covalently crosslinked conductive hydrogels, the network dynamics (e.g., stress relaxation, shear shining, and self-healing) required for complex cellular functions and many biomedical utilities (e.g., injection) cannot be easily realized. In contrast, dynamic conductive hydrogels (DCHs) are fabricated by dynamic and reversible crosslinks. By allowing for the breaking and reforming of the reversible linkages, DCHs can provide dynamic environments for cellular functions while maintaining matrix integrity. These dynamic materials can mimic some properties of native tissues, making them well suited for several biotechnological and medical applications. An overview of the design, synthesis, and engineering of DCHs is presented in this review, focusing on the different dynamic crosslinking mechanisms of DCHs and their biomedical applications.

Permalink: https://www.hzdr.de/publications/Publ-32469
Publ.-Id: 32469


High Bias Field Operation of GaAs Photoconductive Terahertz Emitter

Welsch, M.; Singh, A.; Winnerl, S.; Pashkin, O.; Xu, M.; Li, M.; Helm, M.; Schneider, H.

We demonstrate experimentally the increase of optical-to-terahertz conversion efficiency for GaAs-based photoconductive terahertz emitters. This increase is achieved by preventing device breakdown through series resistors, which act as a current limiter. Pulsed photoexcitation and potential current fluctuations result in heat dissipation leading to local heating, which further increases the current and may lead to device breakdown. We manage to increase the maximum bias field before device breakdown by a factor of 3 under illuminated conditions. For a laser system with 250 kHz repetition rate, the terahertz emission amplitude increases linearly with applied bias field up to 120 kV/cm bias field, which results in 3 times higher signal as compared to the standard device. Furthermore, we have also achieved this expanded breakdown prevention at 78 MHz repetition rate, where an integrated on-chip resistance leads to an enhancement of the terahertz field amplitude by 70%. This simple technique can increase the performance of almost all photoconductive terahertz emitters by using appropriate resistances according to the emitter capacitance and laser repetition rate.

Keywords: Terahertz emitter; Terahertz; Photoconductive emitter

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Permalink: https://www.hzdr.de/publications/Publ-32468
Publ.-Id: 32468


Two Be or Not Two Be: The Nuclear Autoantigen La/SS-B Is able to form Dimers and Oligomers in a Redox Dependent Manner

Berndt, N.; Bippes, C. C.; Michalk, I.; Bachmann, D.; Bachmann, J.; Puentes-Cala, E.; Bartsch, T.; Rodrigues Loureiro, L. R.; Kegler, A.; Bergmann, R.; Gross, J. K.; Gross, T.; Kurien, B. T.; Scofield, R. H.; Farris, A. D.; James, J. A.; Schmitz, M.; Fahmy, K.; Feldmann, A.; Arndt, C.; Bachmann, M.

According to the literature, the autoantigen La is involved in Cap-independent translation. It was proposed that one prerequisite for this function is the formation of a protein dimer. However, structural analyses argue against La protein dimers. Noteworthy to mention, these structural analyses were performed under reducing conditions. Here we describe that La protein can undergo redox-dependent structural changes. The oxidized form of La protein can form dimers, oligomers and even polymers stabilized by disulfide bridges. The primary sequence of La protein contains three cysteine residues. Only after mutation of all three cysteine residues to alanine La protein becomes insensitive to oxidation, indicating that all three cysteines are involved in redox-dependent structural changes. Biophysical analyses of the secondary structure of La protein support the redox-dependent conformational changes. Moreover, we identified monoclonal anti-La antibodies (anti-La mAbs) that react with either the reduced or oxidized form of La protein. Differential reactivities to the reduced and oxidized form of La protein were also found in anti-La sera of autoimmune patients.

Keywords: anti-La/SS-B antibodies; autoimmunity; La/SS-B autoantigen; systemic lupus erythematosus; primary Sjögren’s syndrome

Permalink: https://www.hzdr.de/publications/Publ-32466
Publ.-Id: 32466


LWFA PIConGPU setup for minimizing transverse phase space effects paper

Pausch, R.; Köhler, A.; Bastrakov, S.; Bussmann, M.; Couperus Cabadağ, J. P.; Irman, A.; Steiniger, K.; Widera, R.; Debus, A.

This repository contains the PIConGPU source code and setup files used for the "Minimizing transverse phase space effects on beam-loaded laser-wakefield accelerated electron beams" paper.

Keywords: PIConGPU; HPC; LWFA

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Permalink: https://www.hzdr.de/publications/Publ-32465
Publ.-Id: 32465


Overestimation of grey matter atrophy in glioblastoma patients following radio(chemo)therapy

Gommlich, A.; Raschke, F.; Petr, J.; Seidlitz, A.; Jentsch, C.; Platzek, I.; van den Hoff, J.; Kotzerke, J.; Beuthien-Baumann, B.; Baumann, M.; Krause, M.; Troost, E. G. C.

Objective
Brain atrophy has the potential to become a biomarker for severity of radiation-induced side-effects. Particularly brain tumour patients can show great MRI signal changes over time caused by e.g. oedema, tumour progress or necrosis. The goal of this study was to investigate if such changes affect the segmentation accuracy of normal appearing brain and thus influence longitudinal volumetric measurements.
Materials and Methods
T1-weighted MR images of 52 glioblastoma patients with unilateral tumours acquired before and three months after the end of radio(chemo)therapy were analysed. GM and WM volumes in the contralateral hemisphere were compared between segmenting the whole brain (full) and the contralateral hemisphere only (cl) with SPM and FSL. Relative GM and WM volumes were compared using paired t-tests and correlated with the corresponding mean dose in GM and WM, respectively.
Results
Mean GM atrophy was significantly higher for full segmentation compared to cl segmentation when using SPM (mean ± std: ΔVGM,full = -3.1% ± 3.7%, ΔVGM,cl = -1.6% ± 2.7%; p < 0.001 , d = 0.62). GM atrophy was significantly correlated with the mean GM dose with the SPM cl segmentation (r = -0.4, p = 0.004), FSL full segmentation (r = -0.4, p = 0.004) and FSL cl segmentation (r = -0.35, p = 0.012) but not with the SPM full segmentation (r = -0.23, p = 0.1).
Conclusions
For accurate normal tissue volume measurements in brain tumour patients using SPM, abnormal tissue needs to be masked prior to segmentation, however, this is not necessary when using FSL.

Keywords: radiotherapy; tissue segmentation; SPM; atrophy; glioblastoma; proton

Permalink: https://www.hzdr.de/publications/Publ-32464
Publ.-Id: 32464


Efficient and low-voltage vertical organic permeable base light-emitting transistors

Wu, Z.; Liu, Y.; Guo, E.; Darbandy, G.; Wang, S.-J.; Hübner, R.; Kloes, A.; Kleemann, H.; Leo, K.

Organic light-emitting transistors, three-terminal devices combining a thin-film transistor with a light-emitting diode, have generated increasing interest in organic electronics. However, increasing their efficiency while keeping the operating voltage low still remains a key challenge. Here, we demonstrate organic permeable base light-emitting transistors; these three-terminal vertical optoelectronic devices operate at driving voltages below 5.0 V; emit in the red, green and blue ranges; and reach, respectively, peak external quantum efficiencies of 19.6%, 24.6% and 11.8%, current efficiencies of 20.6 cd A–1, 90.1 cd A–1 and 27.1 cd A–1 and maximum luminance values of 9,833 cd m–2, 12,513 cd m–2 and 4,753 cd m–2. Our simulations demonstrate that the nano-pore permeable base electrode located at the centre of the device, which forms a distinctive optical microcavity and regulates charge carrier injection and transport, is the key to the good performance obtained. Our work paves the way towards efficient and low-voltage organic light-emitting transistors, useful for power-efficient active matrix displays and solid-state lighting.

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Permalink: https://www.hzdr.de/publications/Publ-32463
Publ.-Id: 32463


Reconfigurable magnetic origami actuators with on-board sensing for guided assembly

Ha, M.; Canon Bermudez, G. S.; Liu, J. A.-C.; Oliveros Mata, E. S.; Evans, B. A.; Tracy, J. B.; Makarov, D.

Origami utilizes orchestrated transformation of soft two-dimensional structures into complex three-dimensional architectures, mimicking shapes and functions found in nature. In contrast to origami in nature, synthetic origami lacks the ability to monitor the environment and correspondingly adjust its behavior. Here, we design, fabricate, and demonstrate magnetic origami actuators with capabilities to sense their orientation and displacement and detect their own magnetization state and readiness for supervised folding. These origami actuators integrate photothermal heating and magnetic actuation by using composite thin films (~60 µm thick) of shape-memory polymers with embedded magnetic NdFeB microparticles. Mechanically compliant magnetic field sensors, known as magnetosensitive electronic skins, are laminated on the surface of the soft actuators. These ultrathin actuators accomplish sequential folding and recovery, with hinge locations programmed on the fly. Endowing mechanically active smart materials with cognition is an important step toward realizing intelligent, stimuli-responsive structures.

Keywords: magnetic; origami; reconfigurable; actuation; sensor

Permalink: https://www.hzdr.de/publications/Publ-32462
Publ.-Id: 32462


Complexation and longer-term dynamics of the coordination of Cm(III) and Eu(III) in Human serum Transferrin

Taylor, C. J.

Conference presentation, International Workshop on Theory Frontiers in Actinide Sciences: Chemistry and Materials, 2nd-5th of Feb, Hilton Santa Fe, Santa Fe, New Mexico, USA

  • Lecture (Conference)
    International Workshop on Theory Frontiers in Actinide Sciences: Chemistry and Materials, 02.-05.02.2020, Santa Fe, NM, USA

Permalink: https://www.hzdr.de/publications/Publ-32461
Publ.-Id: 32461


Porosity characterisation of intact concrete specimens.

Roode-Gutzmer, Q. I.; Kulenkampff, J.; Barkleit, A.; Stumpf, T.

The chemical durability of concrete is largely dependent on the chemical reactivity of the silicate aggregates to alkaline pore water. Concrete irradiated at sufficient neutron fluences results in the breakdown of the Si-tetrahedron connected to 4 Si-atoms (Q⁴) to produce Q³ species, which is significantly more soluble in aqueous media. This leads to the alkali silica reaction (ASR), which is the most important degradation process in radiation-damaged concrete. For biological shielding concrete the occurrence of ASR has two ramifications: loss of mechanical strength (which shortens service life), and changes to the pore structure and reactive surface that play a role in the sorption characteristics and transport of radionuclides (neutron activated species or fission products from leaked reactor cooling water). Most investigations on the porosity of materials are conducted on pulverized specimens. We employ intact specimens. In order to achieve the highest possible resolution via μ-computed tomography (μ-CT), small cylindrical cores (0.15±0.01 g) were examined. The connected porosity of these specimens is examined using mercury intrusion porosimetry.

Keywords: concrete; intact specimens; porosity; mercury intrusion porosimetry; micro computed tomography

  • Open Access Logo Poster (Online presentation)
    3rd ICCCM International Conference on the Chemistry of Construction Materials, 15.-17.03.2021, Karlsruhe / Online, Germany

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Permalink: https://www.hzdr.de/publications/Publ-32460
Publ.-Id: 32460


Sub-diffractional cavity modes of terahertz hyperbolic phonon polaritons in tin oxide

Feres, F. H.; Mayer, R. A.; Wehmeier, L.; Maia, F. C. B.; Viana, E. R.; Malachias, A.; Bechtel, H. A.; Klopf, J. M.; Eng, L. M.; Kehr, S. C.; González, J. C.; Freitas, R. O.; Barcelos, I. D.

Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes. Here we introduce tin oxide (SnO2) nanobelts as a photonic platform for the transport of surface and volume phonon polaritons in the mid- to far-infrared frequency range. This report brings a comprehensive description of the polaritonic properties of SnO2 as a nanometer-sized dielectric and also as an engineered material in the form of a waveguide. By combining accelerator-based IR-THz sources (synchrotron and free-electron laser) with s-SNOM, we employed nanoscale far-infrared hyperspectral-imaging to uncover a Fabry–Perot cavity mechanism in SnO2 nanobelts via direct detection of phonon-polariton standing waves. Our experimental findings are accurately supported by notable convergence between theory and numerical simulations. Thus, the SnO2 is confirmed as a natural hyperbolic material with unique photonic properties essential for future applications involving subdiffractional light traffic and detection in the farinfrared range.

Keywords: s-SNOM; near-field; THz; phonon polariton

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Permalink: https://www.hzdr.de/publications/Publ-32459
Publ.-Id: 32459


Enhanced thermoelectric performance in Mg3+xSb1.5Bi0.49Te0.01 via engineering microstructure through melt-centrifugation

Ozen, M.; Yahyaoglu, M.; Candolfi, C.; Veremchuk, I.; Kaiser, F.; Burkhardt, U.; Snyder, G. J.; Grin, Y.; Aydemir, U.

N-type Zintl phases with earth-abundant and non-toxic constituent elements have attracted intense research interest thanks to their high thermoelectric efficiencies in the mid-temperature range, exemplified by the recently discovered Mg3Sb2 material. In this study, the liquid phase is expelled from the microstructure of the optimized n-type phase Mg3+xSb1.5Bi0.49Te0.01 by applying a melt-centrifugation technique leading to the formation of lattice dislocations, grain boundary dislocations and increasing porosity. Additional phonon scattering mechanisms were introduced in the microstructure through this manufacturing method, resulting in a significant 50% reduction in the total thermal conductivity from ∼1 W m−1 K−1 to ∼0.5 W m−1 K−1 at 723 K. Combined with high power factors, this reduced heat transport leads to a dimensionless thermoelectric figure of merit, zT, value of ∼1.64 at 723 K, 43% higher than the value obtained in untreated Mg3+xSb1.5Bi0.49Te0.01 (zT ∼ 1.14 at 723 K). This peak zT value yields a predicted device ZT of 0.95, and a promising theoretical thermoelectric efficiency of about 12%. These results further underline the great potential of the lightweight Mg3Sb2 material for mid-temperature energy harvesting via thermoelectric effects.

Permalink: https://www.hzdr.de/publications/Publ-32458
Publ.-Id: 32458


FIT4NANO---Focused Ion Technology for functional nanomaterials

Hlawacek, G.; Popovic, M.; Wirtz, T.; Hobler, G.; Höflich, K.; Rius, G.; Gandy, A.

FIT4NANO[1] is a European COST[2] network of researchers with the aim to further
develop focused ion beam (FIB) technology for the fabrication and characterization of
functional nanomaterials. This will help to further strengthen Europe’s leading role in
the evolution of this enabling technology. FIBs are enabling research in numerous
fields including semiconductor technology, quantum sensing and communication,
development of devices based on 2D materials, photonic and phononic crystals,
health and biology as well as raw materials, structural materials and space
applications.
The Action comprises three groups of academic and industrial researchers. First,
there is the group of developers of new focused ion beam sources, optics, detectors
and spectrometers as well as add-ons for in-situ and in-operando experiments. The
second and biggest group is applying FIBs to materials science, health and other
research challenges, utilizing bleeding edge developments provided by group one.
Both groups are supported by the third group that provides the software tools to
understand and predict ion solid interaction effects at the nanoscale.
The instruments and methods developed by the Action are shared with stakeholders
around the globe and a new FIB road-map will showcase current and future develop-
ments of this enabling technology for materials characterization and fabrication.
[1] https://www.fit4nano.eu.
[2] https:/www.cost.eu/actions/CA19140

Keywords: Focused ion beam; nanomaterials; functional nanomaterials

Related publications

  • Poster (Online presentation)
    Euro Nano Forum 2021, 05.-06.05.2021, Braga, Portugal

Permalink: https://www.hzdr.de/publications/Publ-32457
Publ.-Id: 32457


Effect of silver ion implantation on antibacterial ability of polyethylene food packing films

Lu, N.; Chen, Z.; Zhang, W.; Yang, G.; Liu, Q.; Böttger, R.; Zhou, S.; Liu, Y.

Bacterial adhesion on medical instruments’ and food packages’ surfaces causes implanted infections, food spoilage and human disease, therefore attracts a lot of attention in the field of medical and food applications. Containing the initial adhesion of bacteria on the surface of the material plays an important role in reducing potential safety hazards. In this work, we investigate the influence of silver ion implantation with different doses on the antibacterial performance of the polyethylene (PE) films. It is found out that silver ion implantation will not color the PE films but can improve their surface hydrophilicity. The silver-implanted PE films show the ability to inhibit bacterial adhesion and have the bactericidal effect, both of which can be improved with increasing silver implantation dose. This method also proves relatively safe, because the silver ions are relatively stable. The results will introduce potential applications for ion implantation in the food packing and food accessible materials.

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Permalink: https://www.hzdr.de/publications/Publ-32456
Publ.-Id: 32456


An Internet of Things Approach for Water Efficiency: A Case Study of the Beverage Factory

Jagtap, S.; Skouteris, G.; Choudhari, V.; Rahimifard, S.; Nguyen Khanh Duong, L.

There is a lack of knowledge among food manufacturers about adopting the Internet of Things (IoT)-based water monitoring system and its ability to support water minimisation activities. It is therefore necessary to investigate the applicability of IoT-based real-time water monitoring systems in a real food manufacturing environment to pursue water-saving opportunities accordingly. This article aims to propose an architecture of an IoT-based water-monitoring system needed for real-time monitoring of water usage, and address any water inefficiencies within food manufacturing. This article looks at a study conducted in a food beverage factory where an IoT-based real-time water monitoring system is implemented to analyse the complete water usage in order to devise solutions and address water overconsumption/wastage during the manufacturing process. The successful implementation of an IoT-based real-time water monitoring system offered the beverage factory a detailed analysis of the water consumption and insights into the water hotspots that needed attention. This action initiated several water-saving project opportunities, which contributed to the improvement of water sustainability and led to an 11% reduction in the beverage factory’s daily water usage.

Keywords: Internet of Things; Water Monitoring System; Food Beverage Industry; Water Sustainability

Permalink: https://www.hzdr.de/publications/Publ-32455
Publ.-Id: 32455


Reductive immobilization of 99Tc(VII) by FeS2: the effect of marcasite

Rodriguez Hernandez, D. M.; Mayordomo, N.; Schild, D.; Shams Aldin Azzam, S.; Brendler, V.; Müller, K.; Stumpf, T.

Reductive immobilization of 99Tc by a synthetic FeS2 mixture, i.e. marcasite-pyrite 60:40, was studied by a combined approach of batch experiments and powder X-ray diffraction, X-ray photoelectron spectroscopy as well as Raman microscopy. It was found that the FeS2 mixture removes 100% of Tc from the suspension after 7 days in contact at 6.0 < pH ≤ 9.0. The retention outside that pH range was slower and incomplete. Spectroscopic analysis showed that the redox active species at pH 6.0 is Fe2+ as expected from previous works with pyrite. However, at pH 10.0 the surprising oxidation of S2- to SO42- was found responsible for Tc immobilization. This was explained by the high reactivity of marcasite that is easily oxidized to produce H2SO4. Our work provides new molecular insights into the reductive mobilization of Tc(VII) by oxidative formation of sulfate. The assigned molecular reactions may also be relevant for the assessment of other redox reactive contaminants. Technetium re-oxidation essays showed that the fast oxidation of marcasite is associated to the reduction of the remaining Tc(VII) in solution, which gives marcasite the potential of Tc natural remediation since it delays the re-oxidation of Tc(IV).

Keywords: Technetium removal; iron sulfide; iron sulfate; pyrite; remediation

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Permalink: https://www.hzdr.de/publications/Publ-32454
Publ.-Id: 32454


Ekman boundary layers in a fluid filled precessing cylinder

Pizzi, F.; Giesecke, A.; Stefani, F.

The fluid flow in a precessing cylinder is investigated numerically with focus on the Ekman boundary layers in the strongly forced regime. Not surprisingly, in that regime, we find deviations from the linear theory due to significant modifications of the base flow in terms of an axisymmetric geostrophic mode whose rotation is opposite to that of the container. The transition of the bulk flow from a three-dimensional non-axisymmetric base flow to a geostrophic axisymmetric pattern is reflected in the scaling of both the sidewall boundary layers and the Ekman boundary layers on top and bottom of the cylinder. In our simulations, the Ekman layers surpass the threshold of the first instability (class A) and show an increase in the thickness together with a marked vertical flow advection inside the boundary layer in a limited range of the forcing magnitude. However, due to numerical restrictions in our simulations, which limit the range of achievable Ekman numbers, no developed boundary layer turbulence is found. An estimation by extrapolation shows that, for this purpose, Ekman numbers smaller by a factor of two have to be achieved.

Permalink: https://www.hzdr.de/publications/Publ-32453
Publ.-Id: 32453


Overview of the Rossendorf Data Repository (RODARE) at HZDR

Knodel, O.; Fiedler, M.; Gruber, T.

The lecture gives a short introduction of the Rossendorf Data Repository RODARE. Features are highlighted, the typical usage is demonstrated and best practices are provided.

Keywords: Rodare; Data Management

  • Invited lecture (Conferences) (Online presentation)
    RADIATE Data Management and Standards Workshop, 17.03.2021, Lisboa, Portugal

Permalink: https://www.hzdr.de/publications/Publ-32452
Publ.-Id: 32452


Stress-induced modification of gyration dynamics in stacked double-vortex structures studied by micromagnetic simulations

Iurchuk, V.; Kakay, A.; Deac, A. M.

In this paper, using micromagnetic simulations, we investigate the stress-induced frequency tunability of double-vortex nano-oscillators comprising magnetostrictive and non-magnetostrictive ferromagnetic layers separated vertically by a non-magnetic spacer. We show that the the relative orientations of the vortex core polarities p₁ and p₂ have a strong impact on the eigen-frequencies of the dynamic modes. When the two vortices with antiparallel polarities have different eigen-frequencies and the magnetostatic coupling between them is sufficiently strong, the stress-induced magnetoelastic anisotropy can lead to the single-frequency gyration mode of the two vortex cores. Additionally, for the case of parallel polarities, we demonstrate that for sufficiently strong magnetostatic coupling, the magnetoelastic anisotropy leads to the coupled vortex gyration in the stochastic regime and to the lateral separation of the vortex core trajectories. These findings offer a fine control over gyration frequencies and trajectories in vortex-based oscillators via adjustable elastic stress, which can be easily generated and tuned electrically, mechanically or optically.

Keywords: Magnetic vortex; Magnetization dynamics; Magnetoelastic anisotropy; Micromagnetic modelling

Permalink: https://www.hzdr.de/publications/Publ-32451
Publ.-Id: 32451


An Approach to Self-Supervised Object Localisation through Deep Learning Based Classification

Politov, A.

Deep learning has become ubiquitous in science and industry for classifying images or identifying patterns in data. The most widely used approach to training convolutional neural networks is supervised learning, which requires a large set of annotated data. To elude the high cost of collecting and annotating datasets, self-supervised learning methods represent a promising way to learn the common functions of images and videos from large-scale unlabeled data without using human-annotated labels. This thesis provides the results of using self-supervised learning and explainable AI to localise objects in images from electron microscopes. The work used a synthetic geometric dataset and a synthetic pollen dataset. The classifica-tion was used as a pretext task. Different methods of explainable AI were applied: Grad-CAM and backpropagation-based approaches showed the lack of prospects; at the same time, the Extremal Perturbation function has shown efficiency. As a result of the downstream localisation task, the objects of interest were detected with competitive accuracy for one-class images. The advantages and limitations of the approach have been analysed. Directions for further work are proposed.

Keywords: deep learning; self-supervised learning; diamonds; scanning electron microscope; localisation

  • Open Access Logo Master thesis
    TU Dresden, 2021
    Mentor: Peter Steinbach
    76 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-32450
Publ.-Id: 32450


Determination of the froth height as a prerequisite of a model-based flotation control

Rau, F.; Buchmann, M.; Hoang, D. H.; Rudolph, M.; van den Boogaart, K. G.

Flotation represents one of the most important separation processes in the mineral processing industry. By exploiting differences of the surface properties, it enables an effective way for the separation of valuable from gangue material. Through the addition of air to the material pulp it is possible to selectively attach hydrophobic particles to air bubbles and to transport them to the upper end of a flotation cell. The froth phase on top of the pulp is crucial for the generation of a high quality concentrate, as it serves as a cleaning region to remove unselectively entrained particles from the product stream. Therefore, the detailed monitoring and control of this froth phase is a crucial requirement for an efficient and stable process. Flotation represents a complex process, where multiple input variables influence several sub-processes and output parameters. Such a multi-input multi-output problem cannot be efficiently controlled by conventional PIDs.
A model-based predictive controller (MPC) is required to reproduce the complex relations between the various in- and outputs to calculate an optimum set of parameters. For the successful implementation of MPCs the calculation time represents a critical factor. The required complexity of the model and therefore the calculation time can be reduced by measuring relevant process parameters. Such characteristic variables are the density of the pulp, the froth and the pulp height. Nevertheless these information need to be available at all time and as accurate as possible, so the complexity of the MPC is reduced permanently since no further failsafe methods are required.
This contribution focuses on a combination of a radar level meter and a hydrostatic pressure sensor to form a measurement system, being capable of measuring the three mentioned values at once. It is implemented into a pilot flotation plant to investigate its applicability for the concept of a “reduced” MPC. One scope of the investigations is the response of the radar signal to the typical flotation fluid, forming a three-phase systems (solid, liquid, gaseous), and consequently the robustness to disturbances and the reasonable sample rate of the sensor system. Additionally, the pilot plant is equipped with optical sensors to assess the accuracy.

Keywords: Flotation; control; sensor; froth height

  • Lecture (Conference) (Online presentation)
    13th European Congress of Chemical Engineering, 20.-23.09.2021, Frankfurt am Main, Germany

Permalink: https://www.hzdr.de/publications/Publ-32449
Publ.-Id: 32449


Agility of spin Hall nano-oscillators

Trindade Goncalves, F. J.; Hache, T.; Bejarano, M.; Hula, T.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

We investigate the temporal response of constriction-based spin Hall nano-oscillators driven by pulsed stimuli using time-resolved Brillouin light scattering microscopy. The growth rate of the magnetization auto-oscillations, enabled by spin Hall effect and spin orbit torque, is found to vary with the amplitude of the input voltage pulses, as well as the synchronization frequency set by an external microwave input. The combination of voltage and microwave pulses allows to generate auto-oscillation signals with multi-level amplitude and frequency in the time-domain. Our findings suggest that the lead time of processes such as synchronization and logic using spin Hall nano-oscillators can be reduced to the nanosecond time-scale.

Keywords: Spintronics; Magnons; Spin waves; Brillouin scattering & spectroscopy; Microwave techniques

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Permalink: https://www.hzdr.de/publications/Publ-32448
Publ.-Id: 32448


FFTF startup tests - joint publication raw data

Nikitin, E.

Models and results with DYN3D and Serpent (HZDR), and results of PARCS (PSI) and GenFoam (EPFL).

Keywords: SFR; DYN3D; PARCS; GeN-Foam; diffusion solver

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Permalink: https://www.hzdr.de/publications/Publ-32446
Publ.-Id: 32446


Neutronic Modelling of the FFTF Control Rod Worth Measurements with Diffusion Codes

Nikitin, E.; Fridman, E.; Mikityuk, K.; Radman, S.; Fiorina, C.

This paper presents an assessment of three deterministic core simulators with the focus on the neutronic performance in steady-state calculations of small Sodium cooled Fast Reactor cores. The selected codes are DYN3D, PARCS and the novel multi-physics solver GeN-Foam. By using these codes, the multi-group diffusion solutions are obtained for the selected twenty control rod worth measurements performed during the isothermal physics tests of the Fast Flux Test Facility (FFTF). The identical set of homogenized few-group cross sections applied in the calculations is generated with the Serpent Monte Carlo code. The numerical results are compared with each other as well as with the measured values. The obtained numerical results, such as the multiplication factors and control rod worth values, are in good agreement as compared to the experimental data. Furthermore, a comparison of the radial power distributions is presented between DYN3D, PARCS and GeN-Foam. Ultimately, the power distributions are compared to the full core Serpent solution, demonstrating an adequate performance of the selected deterministic tools. In overall, this study presents a verification and validation of the neutronic solvers applied by DYN3D, PARCS and GeN-Foam to steady-state calculations of SFR cores.

Keywords: SFR; DYN3D; PARCS; GeN-Foam; diffusion solver

Permalink: https://www.hzdr.de/publications/Publ-32445
Publ.-Id: 32445


Identification and characterization of gallium-binding peptides

Schönberger, N.

The present work demonstrates how a peptide-based material can be obtained for the biosorptive recovery of metals from contaminated industrial wastewater. Starting with Phage surface display for the initial identification and optimization of gallium-binding peptides, all the following application-focussed experiments are based on chemically synthesized peptides.
Two chromatography-based biopanning methods for the identification of gallium-binding peptides from a commercial phage display library were developed. Five gallium-binding peptide sequences were identified and evaluated to show good gallium-binding properties.
Furthermore, the biosorption of free gallium and arsenic by gallium-binding bacteriophage clones was investigated. A large influence of the pH-value on the respective interactions was demonstrated.
Mutagenesis experiments were also carried out for a bacteriophage clone expressed peptide, in which a cysteine pair systematically replaced amino acids. Biosorption experiments with the resulting seven different bacteriophage mutants suggested a relationship between the rigidity of the peptide structure and the gallium-binding properties.
In isothermal titration experiments, the thermodynamics of the interaction between gallium and the peptides as chemically synthesized derivatives were characterized, independent of the bacteriophage. The peptides differed strongly in their interaction with gallium, and in some cases, the complex formation with gallium depended strongly on the surrounding buffer conditions.
The peptide with the amino acid sequence NYLPHQSSSPSR has particularly promising gallium-binding properties. Computer modeling suggests the probable structure of the peptide in aqueous solution and postulates a possible binding site for gallium.
The side-selective and covalent immobilization of the peptides on a polystyrene matrix led to the creation of a biocomposite for the biosorptive recovery of gallium. The sorption performance and desorbability of the peptide-based biosorption materials were determined in studies with model solutions and real waters from the semiconductor industry.

Keywords: Phage Surface Display; Gallium; Wastewater treatment; Peptides

  • Doctoral thesis
    TUBAF, 2021
    Mentor: Dr. Katrin Pollmann
    0112 Seiten

Permalink: https://www.hzdr.de/publications/Publ-32444
Publ.-Id: 32444


DNA-Mediated Stack Formation of Nanodiscs

Subramanian, M.; Kielar, C.; Tsushima, S.; Fahmy, K.; Oertel, J.

Membrane-scaffolding proteins (MSPs) derived from apolipoprotein A-1 have become a versatile tool in generating nano-sized discoidal membrane mimetics (nanodiscs) for membrane protein research. Recent efforts have aimed at exploiting their controlled lipid protein ratio and size distribution to arrange membrane proteins in regular supramolecular structures for diffraction studies. Thereby, direct membrane protein crystallization, which has remained the limiting factor in structure determination of membrane proteins, would be circumvented. We describe here the formation of multimers of membrane-scaffolding protein MSP1D1-bounded nanodiscs using the thiol reactivity of engineered cysteines. The mutated positions N42 and K163 in MSP1D1 were chosen to support chemical modification as evidenced by fluorescent labeling with pyrene. Minimal interference with the nanodisc formation and structure was demonstrated by circular dichroism spectroscopy, differential light scattering and size exclusion chromatography. The direct disulphide bond formation of nanodiscs formed by the MSP1D1_N42C variant led to dimers and trimers with low yield. In contrast, transmission electron microscopy revealed that the attachment of oligonucleotides to the engineered cysteines of MSP1D1 allowed the growth of submicron-sized tracts of stacked nanodiscs through the hybridization of nanodisc populations carrying complementary strands and a flexible spacer.

Keywords: membrane-scaffolding protein; nanodisc; membrane protein; lipid bilayer; lipid protein interaction; multimerization; self-assembly; bionanotechnology

Permalink: https://www.hzdr.de/publications/Publ-32443
Publ.-Id: 32443


Influence of interstitial and substitutional atoms on magnetocaloric effects in RNi compounds

Chzhan, V. B.; Kurganskaya, A. A.; Tereshina, I. S.; Karpenkov, A. Y.; Ovchenkova, I. A.; Tereshina-Chitrova, E. A.; Andreev, A. V.; Gorbunov, D.; Lushnikov, S. A.; Verbetsky, V. N.

The effects of substitutional and interstitial atoms on the magnetic and magnetocaloric properties are investigated for RNi (R is rare earth) compounds attractive for magnetic solid-state cooling at cryogenic temperatures. We focused on combining weakly and highly anisotropic rare earth compounds and obtained GdxDy1-xNi (x = 0.1 and 0.9) compounds and their GdxDy1-xNiH3 hydrides. We observed a considerable decrease in Curie temperatures (TC) in the hydrides GdxDy1-xNiH3 compared to their parent alloys. The magnetocaloric effect (MCE) values of GdxDy1-xNiHy (y = 0 and 3) in the vicinity of TC were obtained and compared with literature data for the final GdNi and DyNi compounds. The maximum specific isothermal entropy changes –ΔsT at μ0ΔH = 5 T were 14.5, 17, and 17.5 J kg−1K−1 for GdNi, Gd0.9Dy0.1Ni, and Gd0.9Dy0.1NiH3, respectively. For DyNi, Gd0.1Dy0.9Ni, and Gd0.1Dy0.9NiH3, they were –ΔsT = 18, 15.5, and 12.5 J kg−1K−1 at μ0ΔH = 5 T, respectively. –ΔsT(H) in Gd0.9Dy0.1NiH3 at T = TC linearly increased in fields up to 7 T, while Gd0.1Dy0.9NiH3 at T ≥ TC showed a plateau-like magnetocaloric effect at μ0ΔH = 5 and 7 T. The observed effects were explained based on altered exchange and magnetocrystalline interactions in the modified compounds.

Permalink: https://www.hzdr.de/publications/Publ-32442
Publ.-Id: 32442


Compensating for artifacts in scanning near-field optical microscopy due to electrostatics

Nörenberg, T.; Wehmeier, L.; Lang, D.; Kehr, S. C.; Eng, L. M.

Nanotechnology and modern materials science demand reliable local probing techniques on the nanoscopic length scale. Most commonly, scanning probe microscopy methods are applied in numerous variants and shades, for probing the different sample properties. Scattering scanning near-field optical microscopy (s-SNOM), in particular, is sensitive to the local optical response of a sample, by scattering light off an atomic force microscopy (AFM) tip, yielding a wavelength-independent lateral resolution in the order of ∼10 nm. However, local electric potential variations on the sample surface may severely affect the probe-sample interaction, thereby introducing artifacts into both the optical near-field signal and the AFM topography. On the other hand, Kelvin-probe force microscopy (KPFM) is capable of both probing and compensating such local electric potentials by applying a combination of ac and dc-voltages to the AFM tip. Here, we propose to combine s-SNOM with KPFM in order to compensate for undesirable electrostatic interaction, enabling the in situ probing of local electric potentials along with pristine optical responses and topography of sample surfaces. We demonstrate the suitability of this method for different types of materials, namely, metals (Au), semiconductors (Si), dielectrics (SiO2), and ferroelectrics (BaTiO3), by exploring the influence of charges in the systems as well as the capability of KPFM to compensate for the resulting electric force interactions.

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Permalink: https://www.hzdr.de/publications/Publ-32441
Publ.-Id: 32441


Experimental assessment of inter-centre variation in stopping-power and range prediction in particle therapy

Peters, N.; Wohlfahrt, P.; Dahlgren, C. V.; de Marzi, L.; Ellerbrock, M.; Fracchiolla, F.; Free, J.; Goma, C.; Gora, J.; Jensen, M. F.; Kajdrowicz, T.; Mackay, R.; Molinelli, S.; Rinaldi, I.; Rompokos, V.; Siewert, D.; van der Tol, P.; Vermeren, X.; Nyström, H.; Lomax, T.; Richter, C.

Purpose: Experimental assessment of inter-centre variation and absolute accuracy of stopping-power ratio (SPR) prediction within 17 particle therapy centres of the European Particle Therapy Network.
Material and Methods: A head and body phantom with seventeen tissue-equivalent materials were scanned consecutively at the participating centres using their individual clinical CT scan protocol and translated into SPR with their in-house CT-number-to-SPR conversion. Inter-centre variation and absolute accuracy in SPR prediction were quantified for three tissue groups: lung, soft tissues and bones. The integral effect on range prediction for typical clinical beams traversing different tissues was determined for representative beam paths for the treatment of primary brain tumours as well as lung and prostate cancer.
Results: An inter-centre variation in SPR prediction (2σ) of 8.7%, 6.3% and 1.5% relative to water was determined for bone, lung and soft-tissue surrogates in the head setup, respectively. Slightly smaller variations were observed in the body phantom (6.2%, 3.1%, 1.3%). This translated into inter-centre variation of integral range prediction (2σ) of 2.9%, 2.6% and 1.3% for typical beam paths of prostate-, lung- and primary brain-tumour treatments, respectively. The absolute error in range exceeded 2% in every fourth participating centre. The consideration of beam hardening and the execution of an independent HLUT validation had a positive effect, on average.
Conclusion: The large inter-centre variations in SPR and range prediction justify the currently clinically used margins accounting for range uncertainty, which are of the same magnitude as the inter-centre variation. This study underlines the necessity of higher standardisation in CT-number-to-SPR conversion.

Permalink: https://www.hzdr.de/publications/Publ-32440
Publ.-Id: 32440


Broadband frequency filters with quantum dot chains

Ehrlich, T.; Schaller, G.

Two-terminal electronic transport systems with a rectangular transmission can violate standard thermodynamic uncertainty relations. This is possible beyond the linear response regime and for parameters that are not accessible with rate equations obeying detailed-balance. Looser bounds originating from fluctuation theorem symmetries alone remain respected. We demonstrate that optimal finite-sized quantum dot chains can implement rectangular transmission functions with high accuracy and discuss the resulting violations of standard thermodynamic uncertainty relations as well as heat engine performance.

Keywords: fluctuation theorems; thermodynamic uncertainty relation; Levitov-Lesovik formula; transmission; reaction-coordinate mapping

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Permalink: https://www.hzdr.de/publications/Publ-32439
Publ.-Id: 32439


Imaging and milling resolution of light ion beams in modern FIBs

Mazarov, P.; Pilz, W.; Meyer, F.; Richter, T.; Klingner, N.; Bischoff, L.; Hlawacek, G.

Light ions are of increasing interest by application of focused ion beam (FIB) techniques due to the available high beam resolution in the nanometer range and their special chemical and physical behavior in the substrate [1, 2]. We compare helium and neon ion beams from a helium ion microscope with ion beams such as lithium, boron, and silicon, obtained from a mass-separated FIB using a liquid metal alloy ion source (LMAIS) with respect to the imaging and milling resolution, as well as the current stability [3]. While He+ offers, experimentally and in simulations, the smallest minimum trench width, light ion species such as Li+ from a LMAIS [4] offer higher milling rates and ion currents while outperforming the milling resolution of Ne+ from a gas field ion source. The comparison allows one to select the best possible ion species for the specific demands in terms of resolution, beam current, and volume and time for milling.

References
[1] L. Bischoff et al., Appl. Phys. Rev. 3 021101 (2016).
[2] P. Mazarov et al., Phys. Usp. 63 1219–1255 (2020).
[3] N. Klingner et al., Beilstein J. Nanotechnol. 11 1742–1749 (2020).
[4] W. Pilz et al., JVSTB 37 021802 (2019).

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  • Lecture (Conference) (Online presentation)
    Virtual 13th Annual FIB SEM Meeting, 29.04.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-32438
Publ.-Id: 32438


The Mu2e experiment at Fermilab

Müller, S.; Ferrari, A.; Knodel, O.; Rachamin, R.

Presentation in parallel session "Detector Systems (T19.1)" at 2021 spring meeting of German Physical Society (DPG), section "Particle Physics"

Keywords: Mu2e; DPG; Charged Lepton Flavor Violation

  • Lecture (Conference) (Online presentation)
    2021 spring meeting of German Physical Society (DPG), section "Particle Physics", 15.-19.03.2021, Dortmund (virtual), Germany

Permalink: https://www.hzdr.de/publications/Publ-32437
Publ.-Id: 32437


Demonstration of a laser-driven, narrow spectral bandwidth x-ray source for collective x-ray scattering experiments

Macdonald, M. J.; Saunders, A. M.; Bachmann, B.; Bethkenhagen, M.; Divol, L.; Doyle, M. D.; Fletcher, L. B.; Glenzer, S. H.; Kraus, D.; Landen, O. L.; Lefevre, H. J.; Klein, S. R.; Neumayer, P.; Redmer, R.; Schörner, M.; Whiting, N.; Falcone, R. W.; Döppner, T.

X-ray Thomson scattering (XRTS) is a powerful diagnostic technique that involves an x-ray source interacting with a dense plasma sample,
resulting in a spectrum of elastically and inelastically scattered x-rays. Depending on the plasma conditions, one can measure a range of
parameters from the resulting spectrum, including plasma temperature, electron density, and ionization state. To achieve sensitivity to collective
electron oscillations, XRTS measurements require limited momentum transfer where the spectral separation of elastic and inelastic scattering
is small. Such measurements require an x-ray probe source with a narrow bandwidth in order to reduce the spectral overlap between
scattering contributions, allowing for the different features to be more precisely deconvolved. In this investigation, we discuss the theory
behind how the bandwidth for a common XRTS probe, Zn He-a emission at 9 keV, can be reduced using a Cu K-edge filter. Proof-of-principle
experiments conducted at the OMEGA laser facility confirm that this is an effective method for attenuating the higher energy He-a peak in
the Zn emission spectrum. Calibration measurements at the National Ignition Facility show a reduction in spectral bandwidth from 87 eV to
48 eV when using the Cu filter, which will be important to improve the spectral resolution of future XRTS measurements that will probe plasmon
oscillations in strongly compressed plasmas of low-Z materials at densities of tens of g/cm3.

Permalink: https://www.hzdr.de/publications/Publ-32436
Publ.-Id: 32436


DFT/DFT-MD IPD Publication Data

Böhme, M.
Supervisor: Vorberger, Jan; Supervisor: Militzer, Burkhard; Researcher: Massacrier, Gerard; Researcher: Soubiran, Francois

Average atom (AA) models allow one to efficiently compute electronic and optical properties of materials over a wide range of conditions and are often employed to interpret experimental data. However, at high pressure, predictions from AA models have been shown to disagree with results from ab initio computer simulations. We represent a new innovative AA model, AvIon, that computes the electronic eigenstates with novel boundary conditions within the ion sphere. Bound and free states are derived consistently. We drop the common AA assumption that the free-particle spectrum starts at the potential threshold, which we found to be incompatible with ab initio calculations. We perform ab initio simulations of crystalline and liquid carbon and aluminum over a wide range of densities and show that the computed band structure is in very good agreement with predictions from AvIon.

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Permalink: https://www.hzdr.de/publications/Publ-32435
Publ.-Id: 32435


Implicit reduced Vlasov–Fokker–Planck–Maxwell model based on high-order mixed elements

Nikl, J.; Göthel, I.; Kuchařík, M.; Weber, S.; Bussmann, M.

etailed description of the transport processes in plasma is crucial for many disciplines. When the mean-free-path of the electrons is comparable or exceeds a characteristic length scale of the plasma profile, non-local behavior can be observed. Predictions of the diffusion theory are not valid and non-local electric and magnetic fields are generated. Kinetic modeling of these phenomena on time scales several orders of magnitude longer than the electron–electron collision time has proven to be cumbersome due to prohibitive requirements on the time step and violation of the conservation laws in the classical explicit Vlasov–Fokker–Planck methods. Therefore, a multi-dimensional conservative implicit Vlasov–Fokker–Planck–Maxwell method is proposed, where the distribution function is approximated by a truncated Cartesian tensor expansion. The electric and magnetic fields are modeled self-consistently, describing the generation process and emergence of non-locality in detail. Mixed finite elements are employed in space and the velocity dimension is discretized by staggered finite differences. Conservation properties are proved theoretically and the overall features are benchmarked on a series of physically representative problems. The second order convergence in velocity and the spatial order proportional to the polynomial order of the finite elements is shown. Further possible extensions of the method are discussed.

Keywords: plasma; simulation; vlasov; focker-planck; numerical methods; implicit; collisions

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Permalink: https://www.hzdr.de/publications/Publ-32434
Publ.-Id: 32434


SPX Benchmark Part I: Results of Static neutronics -- HZDR results

Nikitin, E.; Fridman, E.

DYN3D and Serpent calculations (inputs and results) of the SPX Benchmark Part I: Results of Static neutronics.

Keywords: DYN3D; Serpent; Superphénix; Neutronics

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Permalink: https://www.hzdr.de/publications/Publ-32433
Publ.-Id: 32433


ESFR-SMART WP1.2.2 dataset - DecayHeat

Fridman, E.

I/O for ESFR-SMART WP1.2.2  (DecayHeat)

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Permalink: https://www.hzdr.de/publications/Publ-32432
Publ.-Id: 32432


Static Density Response of the Warm Dense Electron Gas beyond Linear Response Theory: Excitation of Harmonics

Böhme, M.; Dornheim, T.; Moldabekov, Z.; Vorberger, J.; Bonitz, M.

Experimental diagnostics as well as theoretical modeling of warm
dense matter (WDM) heavily rely on linear response theory.
However, Dornheim et. al. [Phys. Rev. Lett.125, 085001 (2020)]
showed that assuming the linear regime may not always be
justified in experiments studying WDM. In addition, the
intentional driving of non-linear effects should make new insight
into many-particle effects possible. We use ab initio Path-Integral
Monte-Carlo (PIMC) to obtain exact results for a harmonically
perturbed homogeneous electron gas. A thorough analysis for
different perturbation amplitudes is carried out. The
corresponding density response reveals resonances at the higher
harmonics of the perturbation wave vector. Analyzing the induced
density response as a function of the perturbation amplitude
shows the importance of the cubic response at the first harmonic
and of the quadratic response at the second harmonic.

Keywords: Warm Dense Matter; Path-Intergral Monte-Carlo

  • Poster (Online presentation)
    APS March Meeting, 15.-19.03.2021, Washington DC, USA
  • Open Access Logo Lecture (Conference)
    Division of Plasma Physics Meeting 2021, 08.-12.11.2021, Pittsburgh, PA, USA
  • Open Access Logo Poster (Online presentation)
    MML - "From Matter to Materials and Life", 22.-24.11.2021, Online, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-32431
Publ.-Id: 32431


SPX-StartUp-ATHLET-StandAlone

Di Nora, V. A.

SPX StartUp tests: ATHLET-StandAlone models

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Permalink: https://www.hzdr.de/publications/Publ-32430
Publ.-Id: 32430


Evaluation of the ESFR End of Equilibrium Cycle State: Spatial Distributions of Reactivity Coefficients

Baker, U.; Margulis, M.; Shwageraus, E.; Fridman, E.; Jiménez-Carrascosa, A.; García-Herranz, N.; Cabellos, O.; Gregg, R.; Krepel, J.

The Horizon 2020 ESFR-SMART project investigates the behaviour of the commercial-size European Sodium-cooled Fast Reactor (ESFR) throughout its lifetime. This paper reports work focused on the End of Equilibrium Cycle (EOEC) loading of the ESFR, including neutronic analysis, core- and zone-wise reactivity coefficients, and more detailed local mapping of important safety-relevant parameters. Sensitivity and uncertainty analysis on these parameters have also been performed and a detailed investigation into decay heat mapping carried out.
Due to the scope of this work the results have been split into three papers. The nominal operating conditions and both zone-wise and local mapping of reactivity coefficients are considered in this paper; the sensitivity and uncertainty analysis are detailed in Margulis et al. and the decay heat mapping calculations are reported in Jimenez-Carrascosa et al. The work was performed across four institutions using both continuous-energy Monte Carlo and deterministic reactor physics codes. A good agreement is observed between the methods, verifying
the suitability of these codes for simulation of large, complicated reactor configurations; and giving confidence in the results for the most limiting ESFR EOEC core state for safety analysis. The results from this work will inform the transient calculations planned for the next stage of work on the ESFR, allowing for more in-depth studies to be performed on the multiphysics behaviour of the reactor.

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Permalink: https://www.hzdr.de/publications/Publ-32429
Publ.-Id: 32429


Superphénix Benchmark Part II: Transient Results

Ponomarev, A.; Mikityuk, K.; Fridman, E.; Di Nora, V. A.; Bubelis, E.; Schikorr, M.

The paper presents a transient simulation phase of the new benchmark on a large sodium fast reactor core. This phase of the benchmark was devoted to the modelling of selected operational transients performed during start-up tests of French SFR Superphénix in order to evaluate its reactivity characteristics and core response to certain perturbations. Six operational transients were selected for the analysis. The specification of a simplified thermal hydraulic model equipped with point kinetics reactivity data and boundary conditions for the selected transients are given in the paper and the results of simulations with several system codes are reported. The study uses the results of the reference Serpent 2 Monte Carlo solution obtained during the first phase of the benchmark related to static neutronic characterization of the core. The developed model contains necessary thermal hydraulic description of primary system components and assumptions to account for thermal expansion reactivity feedbacks from in-reactor structures, neutron kinetics parameters, power distribution and reactivity coefficients. Thus the transient benchmark appears as an effective tool for validation and cross comparisons of system codes including approbation and comparison of different modelling features for thermal expansion of the in-reactor structures, giving a reference core behaviour with use of relatively simple models. The results of the modelling demonstrate a reasonable agreement between all solutions and with the experimentally measured evolution of the core parameters. Particular discrepancies with experimental data could not be resolved using the simplified benchmark model and available experimental data reconstructed from the published analysis of start-up tests. Because of that, the future steps for achieving the improved agreement between the simulated results and the experimental data were proposed.

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Permalink: https://www.hzdr.de/publications/Publ-32428
Publ.-Id: 32428


Decay heat characterization for the European Sodium Fast Reactor

Jiménez-Carrascosa, A.; García-Herranz, N.; Krepel, J.; Margulis, M.; Davies, U.; Shwageraus, E.; Fridman, E.; Gregg, R.

In this work a detailed assessment of the decay heat power for the commercial-size European Sodium-cooled Fast Reactor (ESFR) at the end of its equilibrium cycle has been performed. The summation method has been used to compute very accurate spatial- and time-dependent decay heat by employing state-of-the-art coupled transport-depletion computational codes and nuclear data. This detailed map provides basic information for subsequent transient calculations of the ESFR. A comprehensive analysis of the decay heat has been carried out and interdependencies among decay heat and different parameters characterizing the core state prior to shutdown, such as discharge burnup or type of fuel material, have been identified. That analysis has served as a basis to develop analytic functions to reconstruct the spatial-dependent decay heat power for the ESFR for cooling times within the first day after shutdown.

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Permalink: https://www.hzdr.de/publications/Publ-32427
Publ.-Id: 32427


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