Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Approved and published publications
Only approved publications

41420 Publications

Comparison of 3D and 4D robustly optimized proton treatment plans for non-small cell lung cancer patients with tumour motion amplitudes larger than 5 mm

Spautz, S.; Haase, L.; Tschiche, M.; Makocki, S.; Richter, C.; Troost, E. G. C.; Stützer, K.

Background and purpose: There is no consensus about an ideal robust optimization (RO) strategy for proton therapy of targets with large intra-fractional motion. We investigated the plan robustness of different RO strategies regarding setup/range errors, interplay effects and interfractional anatomical changes.
Materials and methods: For eight non-small cell lung cancer patients with primary and/or nodal clinical target volume (CTVp/CTVn) with motion >5mm, different RO approaches were investigated: 3DRO considering the average CT (AvgCT) with a target density override, 4DRO considering three/all 4DCT phases, and 4DRO considering the AvgCT and three/all 4DCT phases. Realistic interplay scenarios were reconstructed based on patient breathing and machine logfile data for deliveries with/without layered rescanning. Robustness against setup/range errors, interplay effects and interfractional anatomical changes were analyzed for target coverage and OAR sparing.
Results: All nominal plans fulfilled the clinical requirements, while 4DRO without AvgCT generated the most conformal dose distributions. Robustness against setup/range errors was best for 4DRO with AvgCT. No RO strategy was sufficient in countervailing fraction-wise dose distortions caused by interplay effects. Irrespective of rescanning, target coverage was restored in all cases when accumulating four interplay scenarios. 4DRO with AvgCT showed higher CTVp robustness against interfractional changes, but plan adaptations are necessary for all RO strategies in case of relevant anatomical changes.
Conclusion: All RO strategies are clinically acceptable but exhibit equally low robustness against interplay effects. To ensure fraction-wise target coverage, additional motion mitigation is required for CTVs with large motion amplitudes and interfractional changes need to be monitored.

Keywords: Proton therapy; Treatment plannung; Non-small cell lung cancer; Robustness; Interplay effect

Permalink: https://www.hzdr.de/publications/Publ-36627
Publ.-Id: 36627


Three-dimensional dynamics of a single bubble rising near a vertical wall: paths and wakes

Yan, H.-J.; Zhang, H.-Y.; Zhang, H.-M.; Liao, Y.; Liu, L.

In order to clarify the migration mechanism and wake behavior of a single bubble rising near a vertical wall, three-dimensional direct numerical simulations are implemented based on the open-source software Basilisk and various types of migration paths like linear, zigzag and spiral are investigated. The volume of fluid (VOF) method is used to capture the bubble interface at a small scale, while the gas-liquid interface and high-velocity-gradient regions in the flow field are encrypted with the adaptive mesh refinement technology. The results show that the vertical wall has an obstructive effect on the diffusion of the vortex boundary layer on the surface of the bubble migrating in a straight line, and the resulting reaction force tends to push the bubbles away from the wall surface. For the zigzag or spiral movement of a bubble in the x-y plane, the perpendicular wall is an unstable factor, but on the contrary, the motion in
the z-y plane is stabilized.

Keywords: Bubble; Wall effect; Trajectory; Wake structure; VOF; Basilisk

Permalink: https://www.hzdr.de/publications/Publ-36626
Publ.-Id: 36626


Adversarial Attacks On Aerial Vehicle Policies; Poster 2022

Hanfeld, P.; Hönig, W.; Höhne, M. M.-C.; Bussmann, M.

Deep Neural Networks are widely applied for solving Computer Vision tasks for Unmanned Aerial Vehicles (UAVs). For some applications, the predictions of the neural networks (NNs) directly influence the motion planning or control of the UAVs. However, the neural networks are highly prone to adversarial attacks, which has a severe negative impact on the drone’s safe operation. With this work, we are planning to perform a physically realizable attack on a neural network analyzing camera images. The control of the UAV is directly influenced by the predictions of this NN. The generated adversarial attacks will be printed and attached as adversarial patches to an attacker UAV. By choosing which patch to present given the current relative poses of victim and attacker, the attacker will achieve full control over the victim UAV.

  • Open Access Logo Poster
    Big data analytical methods for complex systems, 06.-07.10.2022, Wrocław, Polska

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Permalink: https://www.hzdr.de/publications/Publ-36625
Publ.-Id: 36625


The p-center problem under locational uncertainty of demand points

Ataei, H.; Davoodi Monfared, M.

The p-center problem is finding the location of p facilities among a set of n demand points such that the maximum distance between any demand point and its nearest facility is minimized. In this paper, we study this problem in the context of uncertainty, that is, the location of the demand points may change in a region like a disk or a segment, or belong to a finite set of points. We introduce Max-p-center and Min-p-center problems which are the worst and the best possible solutions for the p-center problem under such locational uncertainty. We propose approximation and parameterized algorithms to solve these problems under the Euclidean metric. Further, we study the MinMax Regret 1-center problem under uncertainty and propose a linear-time algorithm to solve it under the Manhattan metric as well as an O(n4) time algorithm under the Euclidean metric.

Keywords: Facility location; p-center; Uncertainty; Regret; Robustness; Approximation algorithms

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Permalink: https://www.hzdr.de/publications/Publ-36624
Publ.-Id: 36624


LiFe-net: Data-driven Modelling of Time-dependent Temperatures and Charging Statistics Of Tesla’s LiFePo4 EV Battery

Rustamov, J.; Fennert, L.; Hoffmann, N.

Modelling the temperature of Electric Vehicle (EV) batteries is a fundamental task of EV manufacturing. Extreme temperatures in the battery packs can affect their longevity and power output. Although theoretical models exist for describing heat transfer in battery packs, they are computationally expensive to simulate. Furthermore, it is difficult to acquire data measurements from within the battery cell. In this work, we propose a data-driven surrogate model (LiFe-net) that uses readily accessible driving diagnostics for battery temperature estimation to overcome these limitations. This model incorporates Neural Operators with a traditional numerical integration scheme to estimate the temperature evolution. Moreover, we propose two further variations of the baseline model: LiFe-net trained with a regulariser and LiFe-net trained with time stability loss. We compared these models in terms of generalization error on test data. The results showed that LiFe-net trained with time stability loss outperforms the other two models and can estimate the temperature evolution on unseen data with a relative error of 2.77 % on average.

  • Open Access Logo Contribution to proceedings
    DLDE Workshop in the 36th Conference on Neural Information Processing Systems (NeurIPS 2022)., 21.10.2022, Virtual Workshop, Virtual Workshop

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Permalink: https://www.hzdr.de/publications/Publ-36623
Publ.-Id: 36623


Deep Spiking Quantum Neural Network for Noisy Image Classification

Konar, D.; Sarma, A. D.; Bhandary, S.; Cangi, A.

stochastic-based modelling, promising that the inherent uncertainty in quantum computing will prove to be a significant advantage, driving quantum and neuromorphic computing research
to new heights. Spiking Neural Networks (SNNs) are gaining popularity due to their inherent ability to process spatial and temporal data. However, it is a daunting task to train
the network weights of classical SNN due to the stochastic behaviour of neuron signals and the inherent non-differentiable spike events. This paper introduces a supervised Deep Spiking
Quantum Neural Network (DSQ-Net) using a hybrid classicalquantum framework having the merits of amplitude encoding in a dressed quantum layer. A novel attempt has been made
to obviate the challenges in training a classical SNN, assisted by a Variational Quantum Circuit (VQC) in the proposed hybrid classical-quantum framework. The proposed DSQ-Net
is rigorously validated and benchmarked on the ideal PennyLane Quantum Simulator with limited quantum hardware. The experiments have been conducted on unseen test images with imposed noise from the FashionMNIST, MNIST, KMNIST and CIFAR-10 datasets. Classification accuracy is reported to be 95.6% for the proposed DSQ-Net model and
it outperforms the classical counterpart (Deep Spiking Neural Networks), shallow Random Quantum Neural Networks (RQNN), ResNet-18 and AlexNet. The PyTorch implementation
of DSQ-Net is made available on Github0:https://anonymous.4open.science/r/DSQ-Net-037E.

Keywords: Quantum computing; Spiking neural networks; IBM quantum computer; qubit

  • Poster
    26th Quantum Information Processing Conference (QIP), 04.-10.02.2023, Ghent, Belgium

Permalink: https://www.hzdr.de/publications/Publ-36622
Publ.-Id: 36622


Reconstruction of SAXS Data using cINNs

Thiessenhusen, E.; Rödel, M.; Kluge, T.; Bussmann, M.; Cowan, T.; Hoffmann, N.

The understanding of laser-solid interactions is important to the development of future laser-driven particle and photon sources, e.g., for tumor therapy, astrophysics or fusion. Currently, these interactions can only be modeled by simulations which need verification in the real world. Consequently, in 2016, a
pump-probe experiment was conducted by Thomas Kluge to examine the laser-plasma interaction that occurs when an ultrahigh-intensity laser hits a solid density target. To handle the nanometer spatial and femtosecond temporal resolution of the laser-plasma interactions, Small-Angle X-Ray Scattering (SAXS) was used as a diagnostic to reconstruct the laser-driven target. However, the reconstruction of the target from the SAXS diffraction pattern is an inverse problem which are often ambiguous, due to the phase problem, and has no closed-form solution. We aim to simplify the process of reconstructing the target from SAXS images by employing Neural Networks, due to their speed and generalization capabilities. To be more specific, we use a conditional Invertible Neural Network (cINN), a type ofNormalizing Flows, to resolve the ambiguities of the target with a probability density distribution. The
target in this case is modelled by a simple grating function with three parameters. We chose this analytically well-defined and relatively simple target as a trial run for Neural Networks in this field to pave the way for more sophisticated targets and methods. Unfortunately, we don’t have enough and reliable experimental data that could be used as training. So, in consequence, the network is trained only on simulated diffraction patterns and their respective ground truth parameters. The cINN is able to accurately reconstruct simulated- as well as preshot data. The performance on main-shot data remains unclear due to the fact that the simulation might not be able to explain the governing processes.

  • Lecture (Conference)
    Helmholtz AI Conference, 02.-03.06.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36621
Publ.-Id: 36621


Reconstruction of Small-Angle X-ray Scattering data using Invertible Neural Networks

Thiessenhusen, E.; Rödel, M.; Kluge, T.; Bussmann, M.; Cowan, T.; Hoffmann, N.

The understanding of laser-solid interactions is important to the development of future laser-driven particle and photon sources, e.g., for tumor therapy, astrophysics or fusion. Currently, these interactions can only be modeled by simulations which need verification in the real world. Consequently, in 2016, a pump-probe experiment was conducted by Thomas Kluge to examine the laser-plasma interaction that occurs when an ultrahigh-intensity laser hits a solid density target. To handle the nanometer spatial and femtosecond temporal resolution of the laser-plasma interactions, Small-Angle X-Ray Scattering
(SAXS) was used as a diagnostic to reconstruct the laser-driven target. However, the reconstruction of the target from the SAXS diffraction pattern is an inverse problem which are often ambiguous, due to the phase problem, and has no closed-form solution. We aim to simplify the process of reconstructing the target from SAXS images by employing Neural Networks, due to their speed and generalization capabilities. To be more specific, we use a conditional Invertible Neural Network (cINN), a type of Normalizing Flows, to resolve the ambiguities of the target with a probability density distribution. The target in this case is modelled by a simple grating function with three parameters. We chose this analytically well-defined and relatively simple target as a trial run for Neural Networks in this field to pave the way for more sophisticated targets and methods. Unfortunately, we don’t have enough and reliable experimental data that could be used as training. So, in consequence, the network is trained only on simulated diffraction patterns and their respective ground truth parameters. The cINN is able to accurately reconstruct simulated- as well as preshot data. The performance on main-shot data remains unclear due to the fact that the simulation might not be able to explain the governing processes.

  • Lecture (Conference) (Online presentation)
    SEI Workshop, 21.-23.03.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36620
Publ.-Id: 36620


Reconstruction of SAXS data using Invertible Neural Networks

Thiessenhusen, E.; Rödel, M.; Kluge, T.; Bussmann, M.; Cowan, T.; Hoffmann, N.

The understanding of laser-solid interactions is important to the development of future laser-driven particle and photon sources, e.g., for tumor therapy, astrophysics or fusion. Currently, these interactions can only be modeled by simulations which need verification in the real world. Consequently, in 2016, a pump-probe experiment was conducted by Thomas Kluge to examine the laser-plasma interaction that occurs when an ultrahigh-intensity laser hits a solid density target. To handle the nanometer spatial and femtosecond temporal resolution of the laser-plasma interactions, Small-Angle X-Ray Scattering (SAXS) was used as a diagnostic to reconstruct the laser-driven target. However, the reconstruction of the target from the SAXS diffraction pattern is an inverse problem which are often ambiguous and has no closed-form solution. We aim to simplify the process of reconstructing the target from SAXS images by employing Neural Networks due to their speed and generalization capabilities. To be more specific, we use a conditional Invertible Neural Network (cINN) to resolve the ambiguities with a probability density distribution. In consequence, the cINN is trained on simulated diffraction patterns and their respective
ground truth parameters. The cINN is able to accurately reconstruct simulated- as well as preshot data.
The performance on main-shot data remains unclear due to the fact that the simulation might not be able
to explain the governing processes.

  • Lecture (Conference)
    SNI 2022, 05.-07.09.2022, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36619
Publ.-Id: 36619


Structure prediction of iron hydrides at high pressures with machine-learned interatomic potentials

Tahmasbi, H.; Ramakrishna, K.; Lokamani, M.; Bethkenhagen, M.; Cangi, A.

The structure and properties of iron hydrides under pressure have been of interest to geoscientists. At ambient conditions, there are no stable solid iron hydrides. Previous theoretical and experimental studies suggest that the double hcp phase of FeH is stable at low pressures with phase transitions to the hcp and fcc phases up to 80 and 140 GPa, respectively. Here, we present a theoretical investigation of the potential energy surfaces of FeH at high pressure. We construct a highly transferable machine-learned interatomic potential with a hierarchical approach using the PyFLAME code. Then, using this fast and accurate neural network potential, we systematically explore the potential energy surfaces of bulk structures of FeH by global sampling using the minima hopping method, to predict stable and metastable iron hydrides up to 200 GPa. We have carried out density functional theory calculations to refine the predicted structures and to evaluate the dynamical stability of selected structures as well. In an automated and systematic approach, we are going to show how a transferable machine-learned interatomic potential can be trained and validated using global optimization and analyze the phase diagram of the stoichiometric Fe-H system under pressure.

  • Poster
    DPG spring meetings, 27.03.2023, TU Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36618
Publ.-Id: 36618


Efficient calculations of equation-of-state data in the warm-dense matter regime

Callow, T. J.; Kraisler, E.; Cangi, A.

Equation-of-state (EoS) data — relating the pressure and internal energy to material density and temperature — is a key quantity in the warm dense matter regime, for example as input to hydrodynamics codes used to guide inertial confinement fusion experiments. The first-principles methods, density-functional theory and path-integral Monte–Carlo, are considered state-of-the-art approaches to calculate EoS data. However, both methods are computationally expensive, which motivates the development of low-cost approaches such as average-atom models. In the first part of this talk, we benchmark EoS results from an average-atom model against the extensive first-principles dataset from Militzer et al. (Phys. Rev. E 103, 013203). In the second part, we develop a neural-network surrogate model as a numerically feasible alternative to calculating EoS data. We train two neural networks to interpolate this dataset, with one being trained using average-atom outputs and the other without. We also compare the accuracy of the machine-learned and average-atom models using out-of-distribution data from other sources.

  • Lecture (Conference)
    APS March Meeting 2023, 05.-10.03.2023, Las Vegas, USA

Permalink: https://www.hzdr.de/publications/Publ-36617
Publ.-Id: 36617


Data publication: Modelling of non-uniform core deformations in SFRs by using DYN3D with coordinate transformation method in the framework of the ESFR-SMART project Task1.4.3

Nikitin, E.

The research data contains reactor core models, homogenized cross section data, calculation results and post-processing scripts for the verification and validation of the coordinate transformation method for non-uniform radial expansions of SFR cores.

Keywords: SFR; thermal expansion; core flowering; nodal diffusion; DYN3D

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Permalink: https://www.hzdr.de/publications/Publ-36616
Publ.-Id: 36616


Static modeling of core flowering scenarios in SFRs with nodal diffusion code DYN3D

Nikitin, E.; Fridman, E.

In recent years, the reactor core simulator DYN3D has become a frequently used tool for neutronic analyses of Sodium cooled Fast Reactors (SFRs) by the Reactor Safety Group of the Helmholtz-Zentrum Dresden-Rossendorf. The capabilities of the code are constantly expanding with new models, such as the various thermal expansion models relevant for SFR neutronic behavior. This study presents the extension of the radial expansion module for the modeling of non-uniform core expansions, i.e. core flowerings. Since DYN3D uses regular numerical meshes for its neutronic solvers, the implementation of the coordinate transformation method (CTM) was performed to cope with non-uniform core deformations. First, the implementation of the CTM was tested on a realistic SFR core for lifelike core flowering scenarios. The DYN3D results were compared against the Monte Carlo reference solutions. Second, DYN3D was validated against the core flowering experiment performed in the Phenix reactor. The measured reactivity effects of the static deformations were used to assess the DYN3D performance. At both stages, the obtained results show an acceptable agreement with the references, thus demonstrating the applicabilty of DYN3D for modeling various core flowering scenarios.

Keywords: SFR; thermal expansion; core flowering; nodal diffusion; DYN3D

Related publications

  • Contribution to proceedings
    2023 International Congress on Advances in Nuclear Power Plants (ICAPP 2023), 23.-27.04.2023, Gyeongju, Korea
  • Lecture (Conference)
    2023 International Congress on Advances in Nuclear Power Plants (ICAPP 2023), 23.-27.04.2023, Gyeongju, Korea

Permalink: https://www.hzdr.de/publications/Publ-36615
Publ.-Id: 36615


Assessment of anthropogenic actinide background levels on the ground of the new 1-MV compact AMS system HAMSTER

Fichter, S.; Wallner, A.; Hain, K.; Hotchkis, M.

The new multi-purpose 1-MV AMS facility HAMSTER (Helmholtz
Accelerator Mass Spectrometer for Tracing Environmental Radionuclides)
is built within the HZDR research campus in Dresden-
Rossendorf starting in 2022. The new machine is especially dedicated
to the analysis of ultra-trace levels of actinides in environmental
samples. Therefore, eventual contamination of the site where the
new accelerator building is being constructed should be avoided and
clarified. Hence, several soil samples close to the construction site of
the new accelerator building have been analyzed to assess the content
and isotopic ratios of the actinides U, Np and Pu. The samples
have been processed in the existing chemistry labs of HZDR’s 6-MV
DREAMS facility showing low background levels. Overall, the samples
show expected signatures of global fallout in Pu concentrations
and APu/239Pu ratios. However, in some samples increased 236U
concentrations and relatively low 233U/236U atomic ratios have been
detected pointing to an additional source of 236U. Additional analysis
is currently ongoing.

  • Poster
    DPG-Frühjahrstagung, 09.03.2023, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36614
Publ.-Id: 36614


Concepts in Strong-field QED

Hernandez Acosta, U.

Usually, quantum electrodynamics is the prime example, when it comes to a well-understood and outstandingly precise description of elementary particle processes. However, modern laser facilities provide highly intense light with a non-trivial temporal structure, where an arbitrary number of ‘photons’ from the light source may interact with the colliding particles. In this case, the standard perturbative treatment, e.g. known from quantum electrodynamics, becomes very cumbersome and impractical. Accordingly, there are, among others, wide theoretical investigations w.r.t. scattering processes of particles impinging these extreme light sources. This has been done by applying strong-field quantum electrodynamics, which is a theory of electromagnetic interactions within coherent highly intense light treated as a classical background field. Here, the distinction between a classical background field and a quantised photon field revealed a vast amount of novel non-linear structures and non-perturbative phenomena. In this seminar, we introduce the basic concepts of strong-field QED and derive the Feynman rules for the theory. Then we apply those rules to the Breit-Wheeler process, i.e. the electron-positron pair production in the collision of a laser field and a highly energetic photon

  • Invited lecture (Conferences)
    IKTP - Institutsseminar, 12.01.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36613
Publ.-Id: 36613


Strong-field physics prospects at 50 keV at EuXFEL

Hernandez Acosta, U.; Steiniger, K.; Bussmann, M.; Cowan, T.

Some studies of applying a 50 keV XFEL for strong-field physics, modelled by the interaction with an electron beam, were presented. The process of electron-positron pair production in strong fields deviates from the well-known perturbative result in weak field backgrounds. In a strong field background, an electron can directly emit a photon, generating a pair via the trident process. Using 50 keV photons, only about 5 MeV kinetic electron energy is required to reach the trident threshold, which is available by electron guns or laser acceleration (in solids, or wakefield). The trident process can also be used to test models for dark matter candidates. Using the proposed massive “dark photon”, the assumed mass and coupling to ordinary could be determined more precisely than with hadron experiments. Certain exclusion regions can be scanned, but the trident experiment could also be used to detect dark matter (instead of excluding certain mass/coupling ranges) because there is full control over the QED background. A second scheme is the interaction of hard x-rays with electrons in the presence of an intense, infrared few-cycle laser light field. It allows to study of laser-assisted Compton scattering, Breit Wheeler pair production and trident, where during the peaks of the few-cycle IR laser field, spectral features are introduced. A (quasi-) continuous X-ray beam (as in a synchrotron) is not sufficient for strong-field studies as high intensity is required. A user community, similar to established synchrotron or XFEL users, may not exist yet. Many colleagues work on theoretical models, but more experimentalists will emerge with upcoming experimental capabilities at XFELs. The LUXE experiment at DESY, and the detection of QED vacuum birefringence at HED/HIBEF, EuXFEL, are examples of such developments.

  • Invited lecture (Conferences)
    Scientific Opportunities with very Hard XFEL Radiation, 18.-20.01.2023, Desy, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-36612
Publ.-Id: 36612


QED.jl - First-Principal Description of QED-Processes in x-ray laser fields

Hernandez Acosta, U.; Steiniger, K.; Jungnickel, T.; Bussmann, M.

We present a novel approach for an event generator inherently using exact QED descriptions to predict the results of high-energy electron-photon scattering experiments that can be performed at modern X-ray free-electron laser facilities. Future experiments taking place at HIBEF, LCLS, and other facilities targeting this regime, will encounter processes in x-ray scattering from (laser-driven) relativistic plasmas, where the effects of the energy spectrum of the laser field as well as multi-photon interactions can not be neglected anymore. In contrast to the application window of existing QED-PIC codes, our event generator makes use of the fact, that the classical nonlinearity parameter barely approaches unity in high-frequency regimes, which allows taking the finite bandwidth of the x-ray laser into account in the description of the QED-like multi-photon interaction. Consequently, we exploit these effects in Compton scattering, Breit-Wheeler pair-production and trident pair-production in x-ray laser fields as one of the driving forces of electromagnetic cascades and plasma formation.

Keywords: Strong-field QED; Simulation; Monte-Carlo methods

  • Lecture (Conference)
    43rd International Workshop on High-Energy-Density Physics with Intense Ion and Laser Beams, 30.01.-03.02.2023, Hirschegg, Austria

Permalink: https://www.hzdr.de/publications/Publ-36611
Publ.-Id: 36611


Potential margin reduction in prostate cancer proton therapy when using prompt gamma imaging for online treatment verification

Bertschi, S.; Stützer, K.; Berthold, J.; Pietsch, J.; Smeets, J.; Janssens, G.; Richter, C.

An estimation for the potential reduction of clinical margins when using prompt gamma imaging for online treatment verification in proton therapy of prostate cancer is provided. For two adaptive scenarios a potential reduction relative to the clinical practice was evaluated. Using the current trolley-mounted PGI system for online treatment verification to trigger an adaptation, the current range uncertainty margins used at our institute could be reduced by 57%. Additional volumetric imaging at isocenter before irradiation could also reduce the setup uncertainty margins by 66%. A case example illustrates the corresponding dose sparing.

Keywords: proton therapy; range verification; prompt gamma imaging; margin reduction; prostate cancer

Permalink: https://www.hzdr.de/publications/Publ-36610
Publ.-Id: 36610


Data publication: ESFR-SMART T1.2.4

Nikitin, E.

Coupled Neutronic/Thermal-Hydraulic calculations of the European Sodium cooled Fast Reactor core with reactor simulator DYN3D in the framework of the H2020 ESFR-SMART project, Task 1.2.4.

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Permalink: https://www.hzdr.de/publications/Publ-36609
Publ.-Id: 36609


Impact of Thermal-Hydraulic Feedback and Differential Thermal Expansion on European SFR Core Power Distribution

Lindley, B.; Álvarez Velarde, F.; Baker, U.; Bodi, J.; Cosgrove, P.; Charles, A.; Fiorina, C.; Fridman, E.; Krepel, J.; Lavarenne, J.; Mikityuk, K.; Nikitin, E.; Ponomarev, A.; Radman, S.; Shwageraus, E.; Tollit, B.

The objective of this paper is to quantify the coupling effect on the power distribution of sodium-cooled
fast reactors (SFRs), specifically the European SFR. Calculations are performed with several state-of-the-art
reactor physics and Multiphysics codes (TRACE/PARCS, DYN3D, WIMS, COUNTHER and GeN-Foam) to build
confidence in the methodologies and validity of results. Standalone neutronics calculations were generally
in excellent agreement with a reference Monte Carlo-calculated power distribution (from Serpent). Next,
the impact of coolant density and fuel temperature Doppler feedback was calculated. Reactivity
coefficients for perturbations in the inlet temperature, coolant heat up and core power were shown to be
negative with values of around -0.5 pcm/°C, -0.3 pcm/°C and -3.5 pcm/% respectively. Fuel temperature
and coolant density feedback was found to introduce a roughly -1%/+1% in/out power tilt across the core.
Calculations were then extended to axial expansion for cases where fuel is linked and unlinked to the clad.
Core calculations are in good agreement with each other. The impact of differential fuel expansion is found
to be larger for fuel both linked and unlinked to the clad, with the in/out power tilt increasing to around -
4%/+2%. Thus, while broadly confirming the known result that standalone physics calculations give good
results, the expansion coupling effect is perhaps more than anticipated a priori. These results provide a
useful benchmark for the further development of Multiphysics codes and methodologies in support of
advanced reactor calculations.

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Permalink: https://www.hzdr.de/publications/Publ-36608
Publ.-Id: 36608


Coupled Neutronic-Thermal-Hydraulic Simulations of the European SFR Core

Lindley, B.; Álvarez, V. F.; Bodi, J.; Charles, A.; Di Nora, V. A.; Fridman, E.; Krepel, J.; Lavarenne, J.; Mikityuk, K.; Nikitin, E.; Ponomarev, A.; Tollit, B.

Within the European SFR – Safety Measures Assessment and Research Tools (ESFR-SMART) project, steady-state coupled simulation of the ESFR core has been performed using several core analysis packages, with the objective of quantifying the coupling effect. Focus is on the fuel Doppler effect and coolant expansion effect. Standalone neutronics calculations in TRACE/PARCS (PSI), DYN3D (HZDR) and WIMS (Jacobs) showed superb agreement with the reference Serpent power distribution (root mean square (rms) discrepancies of 1.3%, 1.5% and 0.7% respectively). Results for COUNTHER (CIEMAT) were also in reasonable agreement, but with a somewhat higher discrepancy of 3.7%. Temperature distributions from thermal-hydraulic calculations were also compared and are found to be in good agreement. The effect of Doppler and coolant density feedback on core power distribution was predicted by TRACE/PARCS, DYN3D and WIMS to be between 0.4% and 0.8% rms difference in assembly powers. Reactivity coefficients for perturbations in the inlet temperature, flow rate and core power were shown to be negative for these three codes, with values of roughly -0.5 pcm/°C, -0.3 pcm/°C and -3.5 pcm/% respectively. A preliminary investigation of differential thermal expansion effects indicates that this may have a significant effect on core power distribution of a few %, greater than anticipated a priori and may warrant inclusion in coupled core analysis to ensure the accurate calculation of power distributions.

Keywords: ESFR-SMART; coupled calculations; sodium-cooled fast reactors

Related publications

  • Contribution to proceedings
    PHYSOR 2022: Making Virtual a Reality - Advancements in Reactor Physics To Leap Forward Reactor Operation and Deployment, 15.-20.05.2022, Pittsburg, USA

Permalink: https://www.hzdr.de/publications/Publ-36607
Publ.-Id: 36607


Data to Impact on various cleaning procedures on p-GaN surfaces

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

This folder "XPS data" contains original and evaluated XPS data (.vms) on a p-GaN sample which was treated at various temperatures and underwent Ar+ irradiation.

Furthermore, the folder "REM Images" contains REM images (.tif) and EDX data (.xlsx) on the used excessively treated sample.

All images that are published in the main manuscript are collected as .tif files in the folder "images".

Keywords: damage effects; sputtering damage; surface cleaning; p-GaN; photocathode

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Permalink: https://www.hzdr.de/publications/Publ-36606
Publ.-Id: 36606


HIFIS - Building a Workshop Portfolio from 0

Erxleben, F.

Presentation for the deRSE23 conference, outlining which steps were taken by the HIFIS incubator platform to establish their workshop portfolio, with details on challenges encountered and current state as of February 2023.

Keywords: HIFIS; deRSE23; Education; Indico; GitLab; Hedgedoc

Permalink: https://www.hzdr.de/publications/Publ-36605
Publ.-Id: 36605


From source code to software as a service, how to make software more accessible?

Konrad, U.; Huste, T.; Schnicke, T.; Schäfer, D.; Jandt, U.

In the development of software - for products, projects and platforms - different approaches are pursued. For the life cycle of the software, it is important to determine the appropriate approach as early as possible in order to set the framework conditions for software engineering.

Increasingly, scientific software applications are developing into services that are embedded in and used via community platforms. The goal in developing and operating a software platform is to create a sustainable and scalable set of services for a defined target group. Added value compared to local software solutions arises, among other things, from the fact that data storage, computing capacities and communication options are offered in addition to core functions such as modeling, data analysis, project management or software development. The need for continuous operation and development as well as flexible scalability requires special software development methods such as DevOps and CI/CD. The sustainability approach also requires the embedding into scientific communities as well as continuous funding or a viable business model.

Specifics and experiences of this approach will be discussed on the basis of applications from the Helmholtz platform hifis.net.

Keywords: Software; HIFIS; Research Software Engineering; Micro Services; Software Platform

Related publications

  • Open Access Logo Lecture (Conference)
    deRSE23 - Conference for Research Software Engineering in Germany, 20.-22.02.2023, Paderborn, Deutschland
    DOI: 10.5281/zenodo.7653477

Permalink: https://www.hzdr.de/publications/Publ-36604
Publ.-Id: 36604


HIFIS - Boosting Research Software Engineering at Helmholtz

Huste, T.

HIFIS, the Helmholtz Federated IT Services, is a Helmholtz-wide platform that supports scientific projects with IT resources, services, consulting and expertise from the collection, storage, linking and analysis of research data to the publication of the results. In addition to offering federated cloud and backbone services, a particular focus is on research software engineering. In recent years, extensive support services have been developed around this topic. The areas of consulting, education, community and technology offerings are covered and help scientists across all of Helmholtz to boost their software engineering practice. The poster will take a look at those offerings, outline the extensive reuse opportunities, and will provide a way to see how such offerings could be transferred to other institutions.

Keywords: HIFIS; Software; RSE; Reproducibility

  • Open Access Logo Poster
    deRSE23 - Conference for Research Software Engineering in Germany, 20.-22.02.2023, Paderborn, Deutschland
    DOI: 10.5281/zenodo.7638538

Permalink: https://www.hzdr.de/publications/Publ-36603
Publ.-Id: 36603


A simulation framework for electrochemical processes with electrolyte flow

Huang, M.; Weber, N.; Mutschke, G.

Software tools for simulating electrochemical processes (e.g. COMSOL Multi-physics, ELSYCA) are mostly of commercial type. Besides, three-dimensional simulations in complex cell geometries are known to become resource-expensive, as typically thin concentration boundary layers need to be resolved. The present work presents a simulation framework for electrochemical processes based on the open source platform OpenFOAM. The finite volume method used and combined with domain decomposition is able to efficiently benefit from multicore computer architectures. Our framework takes into account electrolyte flow, which is well known to affect mass transfer, and allows to consider multi-species electrolytes and forcing of the electrolyte. The stability and fast convergence of the method presented is found to rely on the linearization of the Butler-Volmer condi-
tion in the iterative solver. The framework is validated against an analytical solution valid for simplified conditions and an electrodeposition process at a conically shaped electrode in an external magnetic field. The latter exhibits transient departure of the concentration boundary layer from the cathode, and excellent agreement with COMSOL simulation results is found.

Keywords: metal electrodeposition; magnetic field; surface-structured electrode; Lorentz force; Finite Volume Method; Butler-Volmer equation; OpenFOAM

Permalink: https://www.hzdr.de/publications/Publ-36602
Publ.-Id: 36602


Data publication: The evolutionary stability of antagonistic plant facilitation across environmental gradients

Maciel, G. A.; Cabal, C.; Martinez Garcia, R.

Set of Python scripts used to produce paper results

Keywords: Ecosystem engineers; Facilitation; Primary sucession; Stress gradient hypothesis; Soil amelioration

Related publications

  • Software in external data repository
    Publication year 2023
    Programming language: Python
    System requirements: The code can be run in any system with Python3
    License: GitHub
    Hosted on GitHub: Link to location
    DOI: 10.5281/zenodo.7634036

Permalink: https://www.hzdr.de/publications/Publ-36601
Publ.-Id: 36601


Metastatic pheochromocytoma and paraganglioma: somatostatin receptor 2 expression, genetics and therapeutic responses

Fischer, A.; Kloos, S.; Maccio, U.; Friemel, J.; Remde, H.; Fassnacht, M.; Pamporaki, C.; Eisenhofer, G.; Timmers, H. J. L. M.; Robledo, M.; Fliedner, S. M. J.; Wang, K.; Maurer, J.; Reul, A.; Zitzmann, K.; Bechmann, N.; Žygienė, G.; Richter, S.; Hantel, C.; Vetter, D.; Lehmann, K.; Mohr, H.; Pellegata, N. S.; Ullrich, M.; Pietzsch, J.; Ziegler, C. G.; Bornstein, S. R.; Kroiss, M.; Reincke, M.; Pacak, K.; Grossman, A. B.; Beuschlein, F.; Nölting, S.

Context
Pheochromocytomas/paragangliomas (PPGLs) with pathogenic mutations in the succinate dehydrogenase subunit B (SDHB) are associated with a high metastatic risk. Somatostatin receptor 2 (SSTR2)-dependent imaging is the most sensitive imaging modality for SDHB-related PPGLs, suggesting that SSTR2 expression is a significant cell surface therapeutic biomarker of such tumors.
Objective
Exploration of the relationship between SSTR2 immunoreactivity and SDHB immunoreactivity, mutational status, and clinical behavior of PPGLs. Evaluation of SSTR-based therapies in metastatic PPGLs.
Design
Retrospective analysis of a multicenter cohort of PPGLs.
Setting
Six specialized Endocrine Tumor Centers in Germany, the Netherlands and Switzerland.
Patients
Patients with PPGLs participating in the ENSAT registry.
Methods
Clinical data were extracted from medical records and immunohistochemistry (IHC) for SDHB and SSTR2 was performed in patients with available tumor tissue. Immunoreactivity of SSTR2 was investigated using Volante scores.
Main outcome measure
Association of SSTR2 IHC positivity with genetic and clinic-pathological features of PPGLs.
Results
Of 202 patients with PPGLs, 50% were SSTR2 positive. SSTR2 positivity was significantly associated with SDHB- and SDHx-related PPGLs, with the strongest SSTR2 staining intensity in SDHB-related PPGLs (p=0.01). Moreover, SSTR2 expression was significantly associated with metastatic disease independent of SDHB/SDHx mutation status (p<0.001).
In metastatic PPGLs, the disease control rate with first-line SSTR-based radionuclide therapy was 67% (n=22, n=11 SDHx), and with first-line “cold” somatostatin analogs 100% (n=6, n=3 SDHx).
Conclusions
SSTR2 expression was independently associated with SDHB/SDHx mutations and metastatic disease. We confirm a high disease control rate of somatostatin receptor-based therapies in metastatic PPGLs.

Keywords: Metastatic pheochromocytoma/paraganglioma; SDHB mutation; SDHx mutation; somatostatin receptor 2; somatostatin receptor-based therapies

Permalink: https://www.hzdr.de/publications/Publ-36600
Publ.-Id: 36600


Linear-response time-dependent density functional theory approach to warm dense matter with adiabatic exchange--correlation kernels

Moldabekov, Z.; Pavanello, M.; Boehme, M. P.; Vorberger, J.; Dornheim, T.

We present a new methodology for the linear-response time-dependent density functional theory (LR-TDDFT) calculation of the dynamic density response function of warm dense matter in an adiabatic approximation that can be used with any available exchange-correlation (XC) functional across Jacob's Ladder and across temperature regimes. The main novelty of the presented approach is that it can go beyond the adiabatic local density approximation (ALDA) and generalized LDA (AGGA) while preserving the self-consistence between the Kohn-Sham (KS) response function and adiabatic XC kernel for extended systems. The key ingredient for the presented method is the combination of the adiabatic XC kernel from the direct perturbation approach with the macroscopic dynamic KS response from the standard LR-TDDFT method using KS orbitals. We demonstrate the application of the method for the example of warm dense hydrogen, for which we perform a detailed analysis of the KS density response function, the RPA result, the total density response function and of the adiabatic XC kernel. The analysis is performed using LDA, GGA, and meta-GGA level approximations for the XC effects. The presented method is directly applicable to disordered systems such as liquid metals, warm dense matter, and dense plasmas.

Keywords: linear-response time-dependent density functional theory; warm dense matter; warm dense hydrogen

Permalink: https://www.hzdr.de/publications/Publ-36599
Publ.-Id: 36599


Utility of redox-active ligands for reversible multi-electron transfer in uranyl(VI) complexes

Takeyama, T.; Tsushima, S.; Takao, K.

In most cases, redox activity of a UO22+ complex is regarded as metal-centered phenomena, because uranium has small energy gaps amongst 5f/6d/7s subshells thereby exhibiting a wide range of oxidation states commonly from +III to +VI or in some instances even +I or +II. While a wide variety of redox-active ligands are known for transition metal complexes including multi-electron reduction that could facilitate inert bond or small molecule activation, only few such examples are known for UO22+. In this study, three UO22+ complexes bearing alpha-diimine-, o-quinonediimine- and 2,6-diiminopyridinebased
ligands were synthesized which exhibited two redox couples in the range from −0.79 V to −2.02 V vs. Fc+/0 to stepwise afford singly- and doubly-reduced complexes. Unique electronic transitions of UO22+ complexes with a manifold of low-lying excited states helped us to complementarily combine spectroelectrochemistry and time-dependent density functional theory (TD-DFT) calculations to assign the redox-active site in these UO22+ complexes, i.e., whether or not a ligand of interest becomes redox-active. During the whole redox processes observed here, the ligands employed are found to be exclusively redox-active, i.e., non-innocent, while the centered UO22+ is just spectating and remains unchanged, i.e., innocent. Whereas double reduction of UO22+ complexes usually involves breakening of strong U≡O bonds, this is not required in the present examples and therefore may find the basis for the synthesis of new types of uranium molecular catalysts and magnetic materials.

Permalink: https://www.hzdr.de/publications/Publ-36598
Publ.-Id: 36598


Fragment molecular orbital (FMO) method for studying actinide-protein interaction

Tsushima, S.

In this talk, I will present progress in the research on the use of fragment molecular orbital calculations to the system containing lanthanide and actinide.

  • Invited lecture (Conferences)
    Theory Frontiers in Actinide Science: Chemistry and Materials, 26.02.-01.03.2023, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-36597
Publ.-Id: 36597


The evolutionary stability of antagonistic plant facilitation across environmental gradients

Cabal, C.; Maciel, G. A.; Martinez Garcia, R.

Plant interactions, understood as the net effect of an individual on the fitness of a neighbor, vary in strength and can shift from negative interference to positive facilitation as the environmental conditions change in time and space. However, the biophysical mechanisms underlying these changes are not well understood. Additionally, evolutionary theory questions the stability of antagonistic facilitation. Using a mechanistic model for belowground resource competition between individual plants, we find that, under stress conditions, antagonistic facilitation is evolutionarily stable even when both interacting plants compete for resources. This supports the theory of ecosystem engineers in primary succession and nurse plants in the stress gradient hypothesis. Furthermore, we find that the proportion of the limiting resource that spontaneously becomes available to any plant is the key environmental parameter determining the evolutionary stability of facilitation. This represents a challenge and a potential confusion factor for empirical studies.

Keywords: Ecosystem engineers; Facilitation; Primary sucession; Stress gradient hypothesis; Soil amelioration

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36595
Publ.-Id: 36595


Nonlinear and higher order terms in warm dense matter

Vorberger, J.

Higher order correlations influence the physics of the system on many levels. They may be summarized by local field corrections or appear explicitly as non-linear contributions in the density response or in other properties like the stopping power. We present the latest results for nonlinear properties of the electron gas as they have been obtained using real time Green's functions, path integral Monte Carlo, and density functional theory. We show how nonlinear properties can be extracted from simulations with and without external perturbations.

Keywords: warm dense matter; nonlinear response; higher order correlation functions; higher harmonics; x-ray scattering

  • Lecture (Conference)
    43 rd International Workshop on High Energy Density Physics with Intense Ion and Laser Beams, 30.01.-03.02.2023, Hirschegg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36594
Publ.-Id: 36594


A Lagrangian model for drifting ecosystems reveals heterogeneity-driven enhancement of marine plankton blooms

Ser-Giacomi, E.; Martinez Garcia, R.; Dutkiewicz, S.; Follows, M. J.

Marine plankton play a crucial role in carbon storage, oxygen production, global climate, and ecosystem function. Planktonic ecosystems are embedded in a Lagrangian patches of water that are continuously moving, stretching, and diluting. These processes drive inhomegeneities on a range of scales, with implications for the integrated ecosystem properties, but are hard to characterize. We present a theoretical framework which accounts for all these aspects; tracking the water patch hosting a drifting ecosystem along with its physical, environmental, and biochemical features. The model resolves patch dilution and internal physical mixing as a function of oceanic strain and diffusion. Ecological dynamics are parameterized by an idealized nutrient and phytoplankton population and we specifically capture the propagation of the biochemical spatial variances to represent within-patch heterogeneity. We find that, depending only on the physical processes to which the water patch is subjected, the plankton biomass response to a resource perturbation can vary several fold. This work indicates that we must account for these processes when interpreting and modeling marine ecosystems and provides a framework with which to do so.

Permalink: https://www.hzdr.de/publications/Publ-36593
Publ.-Id: 36593


Revealing Non-equilibrium and Relaxation in Laser Heated Matter

Vorberger, J.; Preston, T. R.; Medvedev, N.; Böhme, M.; Moldabekov, Z.; Kraus, D.; Dornheim, T.

Experiments creating extreme states of matter almost invariably create non-equilibrium states.
These are very interesting in their own right but need to be understood even if the ultimate goal
is to probe high pressure or high temperature equilibrium properties like the equation of state.
Here, we report on the capabilities of the newly developed imaginary time correlation function
(ITCF) technique [1] to detect and quantify non-equilibrium in pump-probe experiments fielding
time resolved x-ray scattering diagnostics. We find a high sensitivity of the ITCF even to a small
fraction of non-equilibrium electrons in the Wigner distribution. The behavior of the ITCF technique is such that modern lasers and detectors should be able to trace the non-equilibrium relaxation from tens of femto-seconds to several 10s of picoseconds without the need for a model.

Keywords: plasma; warm dense matter; x-ray scattering; non-equilibrium; dynamic structure; imaginary time correlation function; detailed balance

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36592
Publ.-Id: 36592


Dataset to publication: Influence of surface carbon on the performance of cesiated p-GaN photocathodes with high quantum efficiency

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

This data repository contains analyzed data files of the shown figures.

Please see the info.txt files in the individual directories and the original manuscript for guidance. Manuscript title: Influence of surface carbon on the performance of cesiated p-GaN photocathodes with high quantum efficiency

Original datasets of the surface study of p-GaN: after wet chemical cleaning, after Cs deposition, during the degradation, and the influence of X-rays on p-GaN:Cs photocathodes. The folder contains datasets from origin, excel and XPS files (.vms) The XPS data were evaluated by using CasaXPS.

Keywords: p-GaN; negative electron affinity surface; XPS; surface cleaning; cesium carbide; quantum efficiency

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-36591
Publ.-Id: 36591


Highlight selection of radiochemistry and radiopharmacy developments by editorial board

Kiß, O.; Scott, P.; Behe, M.; Penuelas, I.; Passchier, J.; Rey, A.; Patt, M.; Aime, S.; Jalilian, A.; Laverman, P.; Cheng, Z.; Faivre Chauvet, A.; Engle, J.; Cleeren, F.; Zhu, H.; Vercouille, J.; van Dam, M.; Zhang, M.-R.; Perk, L.; Guillet, B.; Alves, F.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biannual highlight commentary to update the readership on trends in the field of radiopharmaceutical development.
Main Body: This selection of highlights provides commentary on 21 different topics selected by each coauthoring Editorial Board member addressing a variety of aspects ranging from novel radiochemistry to first-in-human application of novel radiopharmaceuticals.
Conclusion: Trends in radiochemistry and radiopharmacy are highlighted. Hot topics cover the entire scope of EJNMMI Radiopharmacy and Chemistry, demonstrating the progress in the research field, and include new PET-labelling methods for 11C and 18F, the importance of choosing the proper chelator for a given radioactive metal ion, implications of total body PET on use of radiopharmaceuticals, legislation issues and radionuclide therapy including the emerging role of 161Tb.

Permalink: https://www.hzdr.de/publications/Publ-36590
Publ.-Id: 36590


Large scale energy storage systems based on SNG and subsurface carbon dioxide storage

Fogel, S.; Unger, S.; Hampel, U.

Large-scale energy storage plants based on power-to-gas-to-power (PtG-GtP) technologies incorporating high temperature electrolysis, catalytic methanation for the provision of synthetic natural gas (SNG) and novel, highly efficient SNG-fired Allam reconversion cycles allow for a confined and circular use of CO2/CH4 and thus an emission-free storage of intermittent renewable energy. This study features a thorough technology assessment for large-scale PtG-GtP storage plants based on highly efficient sCO2 power cycles combined with subsurface CO2 storage. The Allam cycle employs supercritical CO2 as working fluid as well as an oxy-combustion process to reach high efficiencies of up to 66 %. The entire PtG-GtP process chain assessed in this study is expected to reach maximum roundtrip efficiencies of 54.2 % (with dedicated and sufficient O2 storage) or 49.0 % (with a dedicated air separation unit). The implementation of said energy storage systems into existing national energy grids will pose a major challenge, since they will require far-reaching infrastructural changes to the respective systems itself, such as extensive installations of renewable generation and electrolysis capacities as well as sufficient subsurface storage capacities for both CO2 and CH4. Therefore, this study incorporates an assessment of the present subsurface storage potential for CO2 and CH4 in Germany. Furthermore, a basic forecast study for the German energy system with an assumed mass deployment of the proposed SNG-based PtG-GtP energy storage system for the year 2050 is conducted. In case of a fully circular use of CO2/CH4, when electricity is solely generated by renewable energy sources, 736 GW of renewables, 234 GW of electrolysis and 62 GW of gas-to-power capacities are required in the best case scenario in 2050. The total storage volume on the national scale of Germany for both CO2 and CH4 was determined to be 7.8 billion Nm3, respectively, leading to a CH4 storage capacity of 54.5 TWh. The presented investigations illustrate the feasibility of large-scale energy storage systems for renewable electricity based on high temperature electrolysis, catalytic methanation and Allam power cycles paired with large subsurface storages for CO2 and CH4.

Keywords: CCUS; CCU; methanation; SOEC; subsurface CO2 storage; sCO2 power cycles; carbon loop; hydrogen storage

  • Poster
    Helmholtz Energy Conference, 12.-13.06.2023, Koblenz, Germany

Permalink: https://www.hzdr.de/publications/Publ-36589
Publ.-Id: 36589


DFTB Parameters for the Periodic Table: Part III, Spin-Orbit Coupling

Jha, G.; Heine, T.

Spin-orbit coupling (SOC) is crucially important for the correct description of the electronic structure and transport properties of inorganic semiconductors, and for assessing topological properties as in topological insulators. We present a consistent set of SOC parameters for the density-functional based tight-binding (DFTB) method covering the elements throughout the periodic table. The parameters are based on atomic SOC data calculated at the level of density-functional theory (DFT). We tested these parameters for representative systems with significant SOC, including transition metal dichalcogenide two-dimensional crystals, III-V bulk semiconductors, and topological insulators. Our parameterization opens the door for DFTB-based electronic structure and transport calculations of very large systems, such as twisted van der Waals heterostructures.

Downloads

Permalink: https://www.hzdr.de/publications/Publ-36588
Publ.-Id: 36588


Data files for determination of inhibitory potency of the published compounds at cathepsins B, L , S and K by fluorimetric activity assay

Löser, R.; Behring, L.

archived files (GraphPad prism) containing raw data (time-resolved fluoresence intensities) and associated data analysis for determination of inhibitory potencies

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-36587
Publ.-Id: 36587


Eu(III) and Cm(III) complexation by nitrilotriacetic acid to further evaluate its impact on the radionuclide retention by cementitious phases

Sieber, C.; Kretzschmar, J.; Drobot, B.; Tsushima, S.; Schmeide, K.; Stumpf, T.

Aminopolycarboxylates (APCs) show great complexation potential towards (lanthanide and actinide) metal ions. As such they are often used as decontamination or decorporation agents. Especially trivalent actinides are of great interest, due to their prevalence in spent nuclear fuel. Accurate thermodynamic data on this complexation behavior is key for safety assessments of nuclear waste repositories. In a worst-case scenario – a groundwater intrusion into the repository a (re-)mobilization of radionuclides (RNs) is to be avoided. Low molecular weight organic ligands may however alter the retention potential of the repository relevant solid phases towards the RNs. A ligand of interest is nitrilotriacetic acid (NTA), which is a typical representative of the APCs. It has been previously shown that it forms complexes with trivalent RNs such as Eu(III)[1] and Am(III)[2] and is used as a decontaminating agent. This work focuses on Eu(III) as a nonradioactive analog to some trivalent actinides with outstanding luminescence properties which make it a great probe for time-resolved laser-induced fluorescence spectroscopy (TRLFS) study.
This work utilizes a multi-method approach with nuclear magnetic resonance (NMR) spectroscopy, TRLFS and isothermal titration calorimetry (ITC) to gain accurate and reliable thermodynamic and spectroscopic data on the Eu(III)-NTA system. NMR spectroscopic experiments showed three distinct complexes, which could be attributed to a 1:1, a 1:2 and a 2:2 Eu(III)-NTA complex, the latter of which existing only at increased concentrations. This observation could be confirmed by TRLFS[3]. Complex formation constants were determined from pH and concentration series applying TRLFS. TRLFS data were evaluated using parallel factor analysis as described elsewhere[4]. Verification of those log β values as well as information about the reaction enthalpy ΔH, the reaction entropy ΔS and the Gibbs free energy ΔG were obtained via ITC measurements.
To confirm the proposed similarities in thermodynamic data for complex formation, similar experiments have been conducted with Cm(III). The formation of the 1:1 and the 1:2 complex could be confirmed with log β values similar to Eu(III).
The retention of Eu(III) on calcium aluminum silicate hydrate (C-A-S-H) phases was observed using batch experiments. Preliminary results have shown little to no impact of NTA on the Eu(III) retention. This may be explained by the high concentration of Al(III) and Ca(II) ions in the supernatants of the samples, as NTA readily complexes these ions as well.
Acknowledgement: The German Federal Ministry for Economic Affairs and Energy (BMWi) is thanked for financial support within the GRaZ II project, no. 02E11860B.

[1] Choppin, G. R. et al. (1977). The complexation of lanthanides by aminopolycarboxylate ligands - II. J. Inorg. Nucl. Chem. 39: 2025-2030
[2] Akram, N. and Bourbon, X. (1995). Analyse critique de donnees thermodynamiques: pouvoir complexant de l'EDTA, du NTA, du citrate et de l'oxalate vis a vis de cations metalliques. Etudes Experimentations Calculs. Andra.
[3] Sieber, C. et al. (2023). Eu(III) and Cm(III) complexation of NTA, EDTA, and EGTA studied by means of NMR, TRLFS, and ITC – an improved approach to more robust thermodynamics. in preparation
[4] Drobot, B. et al. (2015). Combining luminescence spectroscopy, parallel factor analysis and quantum chemistry to reveal metal speciation–a case study of uranyl (VI) hydrolysis. Chem. Sci. 6: 964-972

Keywords: aminopolycarboxylates; nitrilotriacetic acid; europium; curium

  • Poster
    Migration 2023, 24.-29.09.2023, Nantes, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36584
Publ.-Id: 36584


Scientific Metadata: From Filesystem to Metadata Catalog

Pape, D.

A common problem across scientific domains concerns metadata: Important information about experiments can only be found in file names and directory structures scattered around the filesystem. Fully manual or semi-automated naming of the files, or retrospective changes in the templated structure can worsen the situation by introducing inconsistencies and ambiguities. Not only can this impede scientists in their daily work, but it also prevents reuse or automated post-processing of the data. This talk will present an approach to (i) extracting the metadata from a large collection of real-world datasets suffering from these issues and (ii) improving their (machine-)actionability by ingesting the results into a dedicated metadata catalog.

Keywords: Metadata; Scientific Metadata; Metadata Catalog; Data Managment; FAIR

  • Open Access Logo Lecture (Conference)
    deRSE23 - Conference for Research Software Engineering in Germany, 20.02.2023, Paderborn, Deutschland
    DOI: 10.5281/zenodo.7662462

Permalink: https://www.hzdr.de/publications/Publ-36583
Publ.-Id: 36583


The bio-factor – implications for nuclear waste repository and other key challenges

Raff, J.; Drobot, B.; Steudtner, R.; Cherkouk, A.; Sachs, S.

The energy transition in Germany is one of the greatest challenges for the coming decades. An important part of this is the phase-out of nuclear power generation and the safe long-term storage of highly radioactive waste in a future deep geological repository. When considering safety aspects of a potential repository, the influence of biological processes on the integrity of a potential repository is increasingly taken into account in addition to the necessary (physical-) chemical data basis. The effects of the bio-factor are manifold. Our research shows that the interaction of radionuclides with whole (micro)organisms or organic substances produced by them form complexes that alter the migration behavior of radionuclides. In addition, the mineral phases of the host rock are altered by bio-degradation and biomineralization processes. Another important aspect is that microbial induced electron transfer processes cause corrosion that reduces the integrity of potential containers. Last but not least, metabolic processes, especially under anaerobic conditions, lead to gas production that directly alters physical parameters such as pressure. However, the knowledge gained will not only be incorporated into state-of-the-art algorithms for modeling hydrogeological and ecological systems, but will also be important far beyond repository research.
Studying the interaction of radionuclides with bacteria, for example, has provided new insights that have led to the development of an innovative process for plastic electroplating. The novel process allows the coating of highly complex polymer parts with functional metal surfaces while at the same time substituting highly toxic chemicals and saving resources. The investigation and comparison of different mine waters from former uranium ore mining has also led to the development of a new concept for the cost-effective, biotechnological purification of contaminated mine waters. The process and the potential of the procedure are currently being investigated in more detail as part of a project. In addition, thermodynamic studies of biopolymers identified as cellular radionuclide binding sites have demonstrated their potential for separation processes. Due to the chemical similarity of actinides and lanthanides, these findings are being applied to the field of circular economy, rare earth extraction and recycling.
The examples mentioned clearly show how repository and radioecological research can also make an important contribution to a sustainable and successful energy transition beyond the actual research topic.

Keywords: repository; radionuclides; biosphere; remediation; recycling

Related publications

  • Poster
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36580
Publ.-Id: 36580


Synchronization transitions on connectome graphs with external force

Ódor, G.; Papp, I.; Deng, S.; Kelling, J.

We investigate the synchronization transition of the Shinomoto-Kuramoto model Q21
on networks of the fruit-fly and two large human connectomes. This model
contains a force term, thus is capable of describing critical behavior in the
presence of external excitation. By numerical solution we determine the
crackling noise durations with and without thermal noise and show extended
non-universal scaling tails characterized by 2 < τt < 2.8, in contrast with the Hopf
transition of the Kuramoto model, without the force τt = 3.1 (1). Comparing the
phase and frequency order parameters we find different transition points and
fluctuations peaks as in case of the Kuramoto model. Using the local order
parameter values we also determine the Hurst (phase) and β (frequency)
exponents and compare them with recent experimental results obtained by
fMRI. We show that these exponents, characterizing the auto-correlations are
smaller in the excited system than in the resting state and exhibit module
dependence.

Keywords: Shinomoto-Kuramoto model; synchronisation; human connectome; fruit-fly; network

Permalink: https://www.hzdr.de/publications/Publ-36579
Publ.-Id: 36579


Fundamental understanding of technetium interactions in the environment of nuclear waste repositories

Mayordomo, N.; Rodríguez, D. M.; Brendler, V.; Roßberg, A.; Schild, D.; Müller, K.

Technetium (Tc) is an element of concern for the environment and living organisms. In particular, 99Tc a beta emitter with a long half-life (t1/2 = 2∙105 years) is the most abundant isotope of Tc. Besides its generation by medical applications, it is a fission product in nuclear reactors during energy production and must be considered in the safety assessment of nuclear waste repositories. Tc is known to be very mobile in water fluxes under aerobic condition, when mainly TcVII is present. TcVII barely interacts with minerals or microorganisms that could restrict its migration. Thus, the strategy to immobilize TcVII employs the reduction of TcVII to TcIV, since the main species of TcIV is a low soluble oxide (TcIVO2), limiting Tc migration through aquifers. The change in redox state is triggered by reducing agents, such as Fe2+, sulfide or by microbiological redox cascades. Thus, it is necessary to evaluate the interaction of Tc with different materials present in engineered or natural environments also under more complex experimental conditions. We use a broad variety of advanced techniques along a value chain that starts with determination of thermodynamic data (i.e. complex formation constants, solubility constants of minerals, redox potentials and Tc distribution coefficients) it is followed by structural verification by micro-spectroscopy approaches up to establishment in thermodynamic databases. Our particular interest is the in situ monitoring of molecular sorption and redox processes at biogeochemical interfaces and in solutions. As a result, a deep chemical understanding of environmental behavior of technetium will allow the development of sound risk assessments and remediation strategies. This is only feasible by a multidisciplinary approach, including chemistry, geosciences and microbiology.
Some of the work presented here is part of the BMBF funded young investigator group TecRad (Ref 02NUK072, further details can be found at https://www.hzdr.de/db/Cms?pNid=1375).

Related publications

  • Lecture (Conference)
    Helmholtz Energy Conference, 12.-13.06.2023, Koblenz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36576
Publ.-Id: 36576


Advances in radiative capture studies at LUNA with a segmented BGO detector

Skowronski, J.; Gesuè, R. M.; Boeltzig, A.; Ciani, G. F.; Piatti, D.; Rapagnani, D.; Aliotta, M.; Ananna, C.; Barile, F.; Bemmerer, D.; Best, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Campostrini, M.; Cavanna, F.; Colombetti, P.; Compagnucci, A.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fulop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyurky, G.; Imbriani, G.; Junker, M.; Lugaro, M.; Marigo, P.; Masha, E.; Menegazzo, R.; Paticchio, V.; Perrino, R.; Prati, P.; Rigato, V.; Schiavulli, L.; Sidhu, R. S.; Straniero, O.; Szücs, T.; Zavatarelli, S.

Studies of charged-particle reactions for low-energy nuclear astrophysics require high sensitivity, which can be achieved by means of detection setups with high efficiency and low backgrounds, to obtain precise measurements in the energy region of interest for stellar scenarios. High-efficiency total absorption spectroscopy is an established and powerful tool for studying radiative capture reactions, particularly if combined with the cosmic background reduction by several orders of magnitude obtained at the Laboratory for Underground Nuclear Astrophysics (LUNA). We present recent improvements in the detection setup with the Bismuth Germanium Oxide (BGO) detector at LUNA, aiming to reduce high-energy backgrounds and to increase the summing detection efficiency. The new design results in enhanced sensitivity of the BGO setup, as we demonstrate and discuss in the context of the first direct measurement of the 65 keV resonance (Ex = 5672 keV) of the 17O(p,gamma)18F reaction. Moreover, we show two applications of the BGO detector, which exploit its segmentation. In case of complex gamma-ray cascades, e.g. the de-excitation of Ex = 5672 keV in 18F, the BGO segmentation allows to identify and suppress the beam-induced background signals that mimic the sum peak of interest. We demonstrate another new application for such a detector in form of in-site activation measurements of a reaction with beta+ unstable product nuclei, e.g., the 14N(p,gamma)15O reaction.

Permalink: https://www.hzdr.de/publications/Publ-36575
Publ.-Id: 36575


Insight into ThO2 electronic structure through the O K edge XANES

Amidani, L.; Kvashnina, K.

Ligand K-edge XANES is an effective mean to probe the electronic structure of actinides in molecular complexes and solid-state compounds. The hybridization of actinide 5f and 6d states with ligand p-orbitals makes the metal contribution visible in the K-edge XANES, offering a different point of view to observe the electronic structure of the system.

In this contribution, we will report our recent analysis of the O K-edge XANES of ThO2 and compare it with that of CeO2 [1]. We found that despite the similarity of the spectra, the interpretation of the main spectral features is different and reflects the different roles of f- and d- orbitals in shaping the electronic structure of the two compounds.
The stronger localization of Ce 4f over Th 5f emerges from the sharpness of the corresponding spectral features. The splitting of the 5d/6d orbitals in two bands, i.e., eg and t2g, is observed and reproduced by DFT-bases calculations. The Ce 4f orbitals are found below the 5d bands, while for ThO2 the 5f band is between the 6d-eg and 6d-t2g bands. Figure 1 summarizes these findings.

  • Lecture (Conference)
    52nd Journée des Actinides, 17.-21.04.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36573
Publ.-Id: 36573


Supercritical CO2 cycle for sensible thermal energy storage and power generation applications

Unger, S.; Fogel, S.; Bangalore Mohankumar, M.; Guille-Bourdas, A. F.; Schütz, P.; Hampel, U.

The necessity of energy independency, political and climatic concerns is driving the global attention towards sustainable energy sources. The European commission targets carbon-neutrality with net zero greenhouse gas emission by 2050 [1], which results in a decarbonization of the energy sector by renewable energy sources. Nevertheless, a significant challenge arises from the fluctuating power infeed of wind and solar based plants, which may result in grid instability, overstrain and mismatch in supply-demand. Thus, energy storage systems (ESS) are required to decouple electricity generation from the demand and to enhance the reliability of the energy system. Furthermore, a successful implementation of such a storage technology on a large scale requires cost-effective cycles for energy storage and reconversion.
Therefore, a Power-to-Heat-to-Power system is proposed, based on electrical charged high temperature ceramics and a supercritical CO2 (sCO2) power cycle for discharge. The high temperature sensible thermal energy storage is manufactured from waste material of the aluminum production, which is a low-cost storage solution. As a result, such a thermal storage combines an important contribution to the circular economy with an economic solution for large scale, location-independent energy storage. CO2 becomes supercritical when temperature and pressure are higher than 31 °C and 74 bar. In this phase the viscosity is low and the density as well as the heat capacity are high. Hence, the installed components, in particular the turbomachinery of the sCO2 power cycle are highly compact, which results in low investment costs and low thermal losses. Furthermore, high temperatures up to 600 °C can be utilized to generate electricity at high thermal efficiency.
An inhouse code was used to study various heat transfer fluids, materials and designs for the thermal storage vessel during the charge and discharge cycle. Furthermore, the heat exchanger transferring the heat from the thermal storage cycle to the sCO2 power cycle was numerically investigated, to optimize compactness and thermal efficiency. Finally, the experimental facility CARBOSOLA was designed in cooperation with the Siemens Energy AG, the TU Dresden and the DLR, to investigate the involved components of the power cycle as well as the cycle performance. Various questions will be addressed, such as material resistance at temperatures up to 650 °C, optimal heat exchanger designs, part load operation of the facility, cost effective volume flow measurement, compression and expansion processes and the favorable integration of the thermal storage cycle. Furthermore, the mentioned partners perform techno-economical-analysis of the described systems and the facility will be used to validate these models.
References
[1] G. Subbaraman et al., “ZEPS TM Plant Model: A High Efficiency Power Cycle with Pressurized Fluidized Bed Combustion Process,” 2nd Oxyfuel Combust. Conf., pp. 2–5, 2011.

Keywords: supercritical carbon dioxide; thermal energy storage; CARBOSOLA; power cycle

  • Contribution to proceedings
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland
    Proceedings of the Helmholtz Energy Conference 2023
  • Lecture (Conference)
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36572
Publ.-Id: 36572


Simulating the shredding process of multi-material structures for recyclability assessment

Heibeck, M.; Richter, J.; Hornig, A.; Mütze, T.; Rudolph, M.; Reuter, M.; Modler, N.; Filippatos, A.

A sustainable future requires products to be recyclable. An important process in recycling is shredding where materials joined in multi-material structures are liberated or detached. Until now, no physics-based models exist to describe shredding processes adequately. The proposed approach uses finite element simulations to model the shredding of a multi-material structure (steel and fiber-reinforced polymers with an adhesion joint) in a rotary shredder based on previous experimental investigations. Simulations successfully replicate the shredding phenomena, but the stochastic nature of the process results in different load cases making a strict quantitative comparison between simulations and experiments challenging. Comparing similar load cases of two experiments and the corresponding simulations, the estimated liberation degree ranges from 56 % to 100 % (63 % to 99 % in experiments). The estimated energy consumption varies from 1.4 kWh/t to 1.7 kWh/t (1.0 kWh/t to 1.4 kWh/t in experiments), marking a significant step in achieving a reasonable physics-based estimation of required energy. However, the number of fiber-reinforced polymer fragments is underestimated, ranging from 22 to 50 fragments (50 to 78 in experiments). The presented method is a novel contribution to recyclability assessment and recycling-oriented design.

Keywords: Recycling; Finite element analysis (FEA); Fragmentation; Joints/Joining; Shredding

Permalink: https://www.hzdr.de/publications/Publ-36571
Publ.-Id: 36571


Physics-Informed Machine Learning for Density Functional Theory

Cangi, A.

In this talk, I will present our recent advancements in utilizing Artificial Intelligence (AI) to significantly enhance the efficiency of electronic structure calculations [1]. In particular, I will focus on our efforts to accelerate Kohn-Sham density functional theory calculations atfinite temperatures by incorporating deep neural networks within the Materials Learning Algorithms framework [2,3]. Our results demonstrate substantial gains in calculation speed for metals across their melting point. Furthermore, our implementation of automated machine learning hasresulted in significant savings in computational resources when identifying optimal neural network architectures, thereby laying the foundation forlarge-scale AI-driven investigations [4]. I will also showcase our most recent breakthrough, which enables neural-network-driven electronic structure calculations for systems containing over 100,000 atoms [5]. Finally, I will provide an outlook on the potential of physics-informed neural networks for solving time-dependent Kohn-Sham equations, which describe electron dynamics in response to incident electromagnetic waves [6]. [1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301, (2022). [2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA, https://doi.org/10.5281/zenodo.5557254 (2021). [3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, Phys. Rev. B 104, 035120 (2021). [4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022). [5] L. Fiedler, N. A. Modine, S. Schmerler, D. J. Vogel, G. A. Popoola, A. P. Thompson, S. Rajamanickam, A. Cangi, arXiv:2210.11343 (2022). [6] K. Shah, P. Stiller, N. Hoffmann, A. Cangi, Physics-Informed Neural Networks as Solvers for the Time-Dependent Schrödinger Equation, NeurIPS Machine Learning and the Physical Sciences, arXiv:2210.12522 (2022).

Keywords: Machine learning; Neural networks; Density functional theory; Materials science; Electronic structure theory

  • Invited lecture (Conferences)
    Joint Theory Seminar of European XFEL, CFEL, and University of Hamburg, 16.02.2023, Hamburg, Germany
  • Invited lecture (Conferences) (Online presentation)
    Forschungs-Seminar Vielteilchen-Theorie, Christian-Albrechts-Universität, Kiel, 31.01.2023, Kiel, Germany
  • Invited lecture (Conferences)
    Seminar, Arbeitsgruppe für Theoretische Chemie, 07.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36570
Publ.-Id: 36570


Physics-Informed Neural Network Models for Predicting the Electronic Structure of Matter

Cangi, A.

Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [1]. I will present our recent efforts accomplishing speeding up Kohn-Sham density functional theory calculations at finite temperatures with deep neural networks in terms of our Materials Learning Algorithms framework [2,3] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [4]. Finally, I will conclude with a preview of our most recent result that enables neural-network-driven electronic structure calculations for systems containing more than 100,000 atoms.
[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, Phys. Rev. B 104, 035120 (2021).
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022).

Keywords: Machine learning; Neural networks; Density functional theory; Materials science

  • Invited lecture (Conferences)
    Institute Seminar, 13.01.2023, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-36569
Publ.-Id: 36569


Near IR bandgap semiconducting 2D conjugated metal-organic framework with rhombic lattice and high mobility

Sporrer, L.; Zhou, G.; Wang, M.; Balos, V.; Revuelta, S.; Jastrzembski, K.; Löffler, M.; Petkov, P.; Heine, T.; Kuc, A. B.; Cánovas, E.; Huang, Z.; Feng, X.; Dong, R.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are emerging as a unique class of electronic materials. However, 2D c-MOFs with band gaps in the Vis-NIR and high charge carrier mobility are rare. Most of the reported semiconducting 2D c-MOFs are metallic (i.e. gapless), which largely limits their use in logic devices. Herein, we design a phenanthrotriphenylene-based, D2h-symmetric π-extended ligand (OHPTP), and synthesize the first rhombic 2D c-MOF single crystals (Cu2(OHPTP)). The continuous rotation electron diffraction (cRED) analysis unveils the orthorhombic crystal structure at the atomic level with a unique AB layer stacking. The Cu2(OHPTP) is a p-type semiconductor with an indirect band gap of ~0.50 eV and exhibits high electrical conductivity of 0.10 S cm-1 and high charge carrier mobility of ~10.0 cm2 V-1 s-1. Theoretical calculations underline the predominant role of the out-of-plane charge transport in this semiquinone-based 2D c-MOF.

Permalink: https://www.hzdr.de/publications/Publ-36568
Publ.-Id: 36568


Towards an integral clinical proton dose prediction uncertainty by considering delineation variation

Peters, N.; Muren, L. P.

Permalink: https://www.hzdr.de/publications/Publ-36567
Publ.-Id: 36567


Analyses of molecular subtypes and their association to mechanisms of radioresistance in patients with HPV-negative HNSCC treated by postoperative radiochemotherapy

Patil, S.; Tawk, B.; Grosser, M.; Lohaus, F.; Gudziol, V.; Kemper, M.; Nowak, A.; Haim, D.; Tinhofer, I.; Budach, V.; Guberina, M.; Stuschke, M.; Balermpas, P.; Rödel, C.; Schäfer, H.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Ganswindt, U.; Belka, C.; Pigorsch, S.; Combs, S. E.; Boeke, S.; Zips, D.; Baretton, G. B.; Baumann, M.; Krause, M.; Löck, S.; Linge, A.

Purpose

To assess the relation of the previously reported classification of molecular subtypes to the outcome of patients with HNSCC treated with postoperative radio(chemo)therapy (PORT-C), and to assess the association of these subtypes with gene expressions reflecting known mechanisms of radioresistance.
Material and methods

Gene expression analyses were performed using the GeneChip Human Transcriptome Array 2.0 on a multicentre retrospective patient cohort (N = 128) of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG) with locally advanced HNSCC treated with PORT-C. Tumours were assigned to four molecular subtypes, and correlation analyses between subtypes and clinical risk factors were performed. In addition, the classifications of eight genes or gene signatures related to mechanisms of radioresistance, which have previously shown an association with outcome of patients with HNSCC, were compared between the molecular subtypes. The endpoints loco-regional control (LRC) and overall survival (OS) were evaluated by log-rank tests and Cox regression.
Results

Tumours were classified into the four subtypes basal (19.5%), mesenchymal (18.8%), atypical (15.6%) and classical (14.1%). The remaining tumours could not be classified (32.0%). Tumours of the mesenchymal subtype showed a lower LRC compared to the other subtypes (p = 0.012). These tumours were associated with increased epithelial-mesenchymal transition (EMT) and overexpression of a gene signature enriched in DNA repair genes. The majority of the eight considered gene classifiers were significantly associated to LRC or OS in the whole cohort.
Conclusion

Molecular subtypes, previously identified on HNSCC patients treated with primary radio(chemo)therapy or surgery, were related to LRC for patients treated with PORT-C, where mesenchymal tumours presented with worse prognosis. After prospective validation, subtype-based patient stratification, potentially in combination with other molecular classifiers, may be considered in future interventional studies in the context of personalised radiotherapy and may guide the development of combined treatment approaches.

Keywords: Head and neck squamous cell carcinoma Primary radiotherapy Postoperative radiotherapy Hypoxia Cancer

Permalink: https://www.hzdr.de/publications/Publ-36566
Publ.-Id: 36566


A novel multi-shot target platform for laser-driven laboratory astrophysics experiments

Perez-Martin, P.; Prencipe, I.; Sobiella, M.; Donat, F.; Kang, N.; He, Z.; Liu, H.; Ren, L.; Xie, Z.; Xiong, J.; Zhang, Y.; Brack, F.-E.; Cervenak, M.; Gajdos, P.; Hronova, L.; Kaniz, K.; Kozlová, M.; Kroll, F.; Pan, X.; Schaumann, G.; Singh, S.; Smid, M.; Suzuki-Vidal, F.; Zhang, P.; Sun, J.; Zhu, J.; Krus, M.; Falk, K.

Anewapproach to target development for laboratory astrophysics experiments at high power laser facilities is presented. With the dawnofhighpowerlasers, laboratory astrophysics emerged as a field, bringing insight into physical processes in astrophysical objects, such as formation of stars. An important factor for success on these experiments is targetry. To date, targets have mainly relied on expensive and challenging microfabrication methods. The design presented incorporates replaceable machined parts which assemble into a structure that defines the experimental geometry. This can make targets cheaper and faster to manufacture, while maintaining robustness and reproducibility. The platform is intended for experiments on plasma flows, but it is flexible and may be adapted to the constraints of other experimental setups. Examples of targets used in experimental campaigns are shown, including a design for insertion in a high magnetic field coil. Experimental results are included demonstrating the performance of the targets.

Keywords: Target design; laboratory astrophysics; laser-plasma interaction; high magnetic fields; magnetized plasmas

Permalink: https://www.hzdr.de/publications/Publ-36565
Publ.-Id: 36565


Energy Flexibility Potential and Costs of the Materials- and Recycling Industry

Parvez, A. M.; van den Boogaart, K. G.; Sajjad, M.

Renewable Electricity production will strongly vary over time in the
Energy System of 2045. Simultaneously the raw materials industry
needs to have its own transition towards a more local circular economy
and from fossil carbon based energy sources to renewables. As a major
and increasingly important energy consumer, this industry might need
to adapt energy consumption to current energy availability.

In this contribution we discuss four major technical possibilities on
different time scales (Inner Energy variation, throughput variation,
scheduled production pauses, and dual power options) for power
flexibility in this sector, their characteristics with regard to grid
service and power market, and with respect to economic and
environmental impacts generated by providing and by using these
flexibility options. The contribution provides generic formulas to
compute such impacts from LCA and LCC results for stationary operation
conditions plus direct impacts of certain actions, and shows how they
depend on market conditions. It also discusses the need for energy
system models to provide predictions of flexibility requirements early
on, to allow the industry to take the right investment decisions with
respect to flexibility.

The contribution shows that while technically major flexibility
potentials exist, considerable investment is required to make them
practically available for the future energy system. It also shows that
Germany needs a considerable local hydrogen infrastructure
(production, distribution and storage) in order to sustain such
industry.

Keywords: Energy Transition; Recycling; Flexibility; LCA

  • Lecture (Conference)
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36564
Publ.-Id: 36564


Transfer printing of GMR sensing elements for curved electronics

Bezsmertna, O.; Xu, R.; Oliveros Mata, E. S.; Voigt, C.; Mosch, S.; Faßbender, J.; Vinnichenko, M.; Makarov, D.

In the post-covid era, touchless interaction between human beings and environments is attracting more and more attentions. Sensors based on giant magnetoresistance (GMR) effect are widely considered as a workhorse to address this demand. However, the fabrication of GMR
multi-layer elements face many limitations (e.g., inappropriate to substrates with curved and/or rough surfaces) due to the layer thickness
dependence of performance. Here, we propose a transfer technique to overcome the aforementioned limitations. With the assistance of two
sacrificial layers, a large scale and wrinkle-free coverage is realized on
various substrates (of different materials, roughness, and curvatures) with little loss of GMR performance. Notably, such technique is easy
processing, without the need of any substrate deformation, temporary carriers or high-temperature processing. The transferred sensors are
integrated into skin-mountable electronics, successfully functioning as a human-machine interface.

  • Lecture (Conference)
    DPG Spring Meeting 2023, 26.-31.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36563
Publ.-Id: 36563


Supervised folding of magnetic origami actuators using highly compliant magnetic field sensors

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

Soft actuators are mechanically active functional systems. Magnetic polymeric composites have been used as grippers, rollers, and walkers responding to applied magnetic fields. Flexible, light and conformal sensory systems are still under research to have on-board control of actuation of soft systems. We show electronic skins with magnetic field sensors that provides awareness of the folding state to origami-like magnetic foils.
[1] M. Ha, et al. Adv. Mater. 33, 2008751 (2021)

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie 2023, 26.-31.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36562
Publ.-Id: 36562


Printed magnetic field sensors based on bismuth showing large non-saturating magnetoresistance

Oliveros Mata, E. S.; Voigt, C.; Cañón Bermúdez, G. S.; Zabila, Y.; Illing, R.; Fritsch, M.; Mosch, S.; Kusnezoff, M.; Faßbender, J.; Vinnichenko, M.; Makarov, D.

The development of functional inks allows to create novel printed electronics with unconventional form factors. Here, we show the fabrication of printed magnetic field sensors based on bismuth microparticles. Sensors showed non-saturating large magnetoresistance (146%, 5T, at room temperature), and resilience to mechanical bending (2000 cycles). We demonstrated large area magnetically sensitive interfaces as smart lock and interactive wallpapers.[1]
[1] E.S. Oliveros-Mata, C. Voigt, et al. Adv. Mater. Technol.2200227 (2022)

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie 2023, 23.-31.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36561
Publ.-Id: 36561


The morphology adaptive multifield solver OpenFOAM-Hybrid and its application to multiphase flow problems in nuclear safety

Krull, B.; Lucas, D.; Meller, R.; Schlegel, F.; Tekavcic, M.

A typical feature of nuclear safety facilities are multiphase flows with coexisting morphologies, i.e. with phases which occur both in a continuous form (such as in a stratified flow) and in a disperse form (bubbles or droplets). Established simulation methods are usually suitable for either resolved structures (e.g., Volume-of-Fluid) or dispersed structures (e.g., Euler-Euler). We propose a morphology adaptive multifield two-fluid model, which is able to handle both disperse and resolved interfacial structures coexisting in a common computational domain, covered by a unified set of equations. This requires (A) a careful selection of closure models. On the continuous side, the interfacial drag formulation of Štrubelj and Tiselj (Int J Numer Methods Eng, 2011, 85, 575-590) is used to describe large interfacial structures in a volume-of-fluid-like manner. For the dispersed structures, the HZDR baseline model is applied. Meller et al. (Int J for Numer Method Fluid, 2021, 93, 748-773) and Tekavčič et al. (Nucl Eng Des, 379, 111223) presented several test cases to prove that the numerical consistent coexistence of different morphologies is ensured. The interaction of the morphologies is only controlled by the aforementioned closure models without being disturbed by numerical effects. A second requirement is (B) a reliable transition between continuous and disperse states, depending on the size of the structures and the degree of spatial resolution. This is subject of the current work. A prerequisite for reliable transitions is the stable coverage of intermediate situations, where bubbles are either over- or under-resolved for Euler-Euler or Volume-of-Fluid (Fig. 1). An adaptive interfacial drag model and a filtering technique are applied for stable and robust handling of the transition regions. Two morphology transfer models are established, allowing large resolved structures to disintegrate into small unresolved fluid particles and, vice versa, the accumulation of disperse fluid particles to continuous large-scale structures. This is applied to generic verification and validation test cases, representing typical sub-problems relevant in safety facilities. The model is applied to a cyclic separator (Fig. 2), which can only be simulated with methods allowing the transition from a disperse to a continuous morphology. This is particularly challenging because the gas core must exhibit a stable behavior in the highly rotating flow while gas and liquid are moving in opposite directions along the rotational axis.

Related publications

  • Contribution to proceedings
    Workshop on Experimental Validation and Application of CFD and CMFD codes to Nuclear Reactor Safety Issues (CFD4NRS-9), 20.-22.02.2023, College Station, USA
    Proceedings of the CFD4NRS-9
  • Lecture (Conference)
    Workshop on Experimental Validation and Application of CFD and CMFD codes to Nuclear Reactor Safety Issues (CFD4NRS-9), 20.-22.02.2023, College Station, USA

Permalink: https://www.hzdr.de/publications/Publ-36560
Publ.-Id: 36560


Realisierung von neuronalen Netzwerken mit hls4ml auf einer Alveo Accelerator Card

Ufer, R.

Für die Lösung von komplexen Problemen können neben Algorithmen auch künstliche neuronale Netzwerke verwendet werden. Mit maschinellem Lernen werden diese Netzwerke standardmäßig auf CPU und GPU erstellt und ausgeführt. Zur Verwendung von trainierten Netzwerken auf FPGAs gibt es jedoch keine direkte Umsetzung innerhalb der bekannten Machine Learning Frameworks. Um dieses Problem zu beheben wurde für Xilinx und Intel FPGA die Portierungs-Software hls4ml entwickelt. Diese Open-Source Software ermöglicht eine Übersetzung von trainierten Netzwerken die mit etablierten Machine Learning Frameworks erstellt wurden in eine High-Level Synthese Sprache.

Innerhalb dieses Projekts erfolgt die Implementierung eines neuronalen Netzwerks für die MNIST-Datensatz Klassifikation, welches anschließend mit hls4ml für die Xilinx Alveo U200 Data Center Accelerator Card portiert wird. Die Portierung erfolgt mit verschiedenen Konfigurationen, um unterschiedlich optimierte Implementierungen zu generieren. Der gesamte Prozess vom Erstellen des Netzwerks bis zur Ausführung der Implementierung und Auswertung der Ergebnisse wird mithilfe von Continous Integration automatisiert.

Die Evaluation zeigt, dass eine Portierung des Netzwerks auf die Xilinx Alveo U200 Data Center Accelerator Card möglich ist. Es sollte jedoch dabei beachtet werden das nicht mit allen Konfigurationen eine ausführbare Implementierung erstellt werden kann.

Keywords: FPGA; hls4ml; MNIST; ML; CI

  • Other
    TU Dresden, 2023
    Mentor: Seniorprofessor Dr.-Ing. habil. Rainer G. Spallek, Dr.-Ing. Oliver Knodel
    27 Seiten

Permalink: https://www.hzdr.de/publications/Publ-36559
Publ.-Id: 36559


Reproducibility in Data Science and Machine Learning: How far should we go to enable products?

Steinbach, P.

Machine Learning is becoming ubiquitous in many scientific domains. However, practitioners struggle to apply every new addition to the Machine Learning market on their data with comparable effects than published. In this talk, I'd like to present recent observations on reproducibility of Machine Learning results and how the community strives to tackle related challenges.

Keywords: machine learning; reproducibility; replication; generalisation

Permalink: https://www.hzdr.de/publications/Publ-36556
Publ.-Id: 36556


Data publication: Impedimetric Nanobiosensor for the Detection of SARS-CoV-2 Antigens and Antibodies

Sandoval Bojorquez, D. I.; Janićijević, Ž.; Palestina Romero, B.; Oliveros Mata, E. S.; Laube, M.; Feldmann, A.; Kegler, A.; Drewitz, L.; Fowley, C.; Pietzsch, J.; Faßbender, J.; Tonn, T.; Bachmann, M.; Baraban, L.

This publication includes datasets of electrical impedance spectroscopy measurements of the response of functionalized gold nanowires when interacting with antigens and antibodies related to SARS-CoV-2 in physiological conditions and in human plasma samples.

Keywords: impedimetric sensing; point-of-care testing; SARS-CoV-2; gold nanowires; impedance model; reliability; electrochemical impedance spectroscopy (EIS); surface plasmon resonance (SPR)

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Permalink: https://www.hzdr.de/publications/Publ-36555
Publ.-Id: 36555


Energy response and spatial alignment of the perturbed electron gas

Dornheim, T.; Tolias, P.; Moldabekov, Z.; Vorberger, J.

We present extensive new \emph{ab initio} path integral Monte Carlo (PIMC) simulations of the harmonically perturbed uniform electron gas (UEG) for different densities and temperatures. This allows us to study the linear response of the UEG with respect to different contributions to the total energy for different wave numbers. We find that the induced change in the interaction energy exhibits a non-monotonic behaviour, and becomes negative for intermediate wave numbers. This effect is strongly dependent on the coupling strength and can be traced back to the spatial alignment of electrons introduced in earlier works [T.~Dornheim \emph{et al.}, Communications Physics \textbf{5}, 304 (2022)]. The observed quadratic dependence on the perturbation amplitude in the limit of weak perturbations and the quartic dependence of the perturbation amplitude corrections are consistent with linear and non-linear versions of the density stifness theorem. All PIMC simulation results are freely available online and can be used to benchmark new methods, or as input for other calculations.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36554
Publ.-Id: 36554


Impedimetric Nanobiosensor for the Detection of SARS-CoV-2 Antigens and Antibodies

Sandoval Bojorquez, D. I.; Janićijević, Ž.; Palestina Romero, B.; Oliveros Mata, E. S.; Laube, M.; Feldmann, A.; Kegler, A.; Drewitz, L.; Fowley, C.; Pietzsch, J.; Faßbender, J.; Tonn, T.; Bachmann, M.; Baraban, L.

Detection of antigens and antibodies (Abs) is of great importance in determining the infection and immunity status of the population, as they are key parameters guiding the handling of pandemics. Current point-of-care (POC) devices are a convenient option for rapid screening; however, their sensitivity requires further improvement. We present an interdigitated gold nanowire-based impedance nanobiosensor to detect COVID-19-associated antigens (receptor-binding domain of S1 protein of the SARS-CoV-2 virus) and respective Abs appearing during and after infection. The electrochemical impedance spectroscopy technique was used to assess the changes in measured impedance resulting from the binding of respective analytes to the surface of the chip. After 20 min of incubation, the sensor devices demonstrate a high sensitivity of about 57 pS·sn per concentration decade and a limit of detection (LOD) of 0.99 pg/mL for anti-SARS-CoV-2 Abs and a sensitivity of around 21 pS·sn per concentration decade and an LOD of 0.14 pg/mL for the virus antigen detection. Finally, the analysis of clinical plasma samples demonstrates the applicability of the developed platform to assist clinicians and authorities in determining the infection or immunity status of the patients.

Keywords: impedimetric sensing; point-of-care testing; SARS-CoV-2; gold nanowires; impedance model; reliability; electrochemical impedance spectroscopy (EIS); surface plasmon resonance (SPR)

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36553
Publ.-Id: 36553


A thermodynamic database for the solution chemistry and solubility of europium(III) inorganic species: recent developments

Jordan, N.; Thoenen, T.; Starke, S.; Spahiu, K.; Brendler, V.

Performance assessments of geological repositories for the underground disposal of high-level radioactive waste require a deep understanding of the phenomena influencing the mobility of radionuclides, e.g. sorption, redox immobilization, surface precipitation, incorporation, etc. Reliable thermodynamic databases (TDB) are essential in order to generate speciation calculations, surface complexation and reactive transport models to predict the aforementioned mechanisms. In this work, the focus was set on europium (Eu), a lanthanide used for decades as a chemical analogue of trivalent actinides (Pu, Am). However, a consolidated and internationally recognized Eu TDB does currently not exist.

Several reviews and reports [1-4] on the aqueous chemistry/geochemistry of europium were published, but had various drawbacks, for example:

→ Insufficient transparency about the selection procedure,

→ Lack of systematic screening to gather primary literature sources,

→ No original data but rather analogue values from other REE or compilations from secondary references,

→ Postulation of species not independently evidenced by means of advanced spectroscopic techniques,

→ Too high reliance on the analogy with trivalent actinides,

→ For weak complexes such as chloride and nitrate, changes in the activity coefficients due to the replacement of up to 100 % of the background electrolyte anion by Cl⁻ or NO₃⁻ was either completely overlooked or, if recognized, not handled properly,

→ Too high reliance on the charge analogy for the estimation of missing ion interaction coefficients when the Specific ion Interaction theory was applied.

This study aims at significantly improving the situation by carefully addressing all aforementioned issues in order to provide a reliable, robust, and internally consistent TDB for europium. For this, an extensive data survey of more than 350 peer-reviewed publications from around 1900 until June 2021 was performed. Furthermore, technical reports, scientific books, collected editions as well as various thermodynamic databases (Nagra/PSI [2], Thermochimie [5], etc.) were surveyed to identify their original Eu(III) data sources and references used therein. Data up to 90 °C and 5 M ionic strength were selected for screening, but all data dealing with hydrothermal conditions were out of the scope of this review. Thermodynamic data determined in non-aqueous solvents were explicitly not considered either. For the three ligands (SO₄²⁻, Cl⁻, PO₄³⁻) to which our attention was focused on in a first step, the result of the screening together with the number of selected data for aqueous complexation constants is shown in Table 1.

Table 1. Summary of the aqueous inorganic Eu complexation data records
System #total #selected
Eu – sulphate 244 34
Eu – chloride 186 0
Eu – phosphate 40 8

The complexation of Eu(III) with sulphate was investigated by ion exchange, solvent extraction, spectrophotometry, electrophoresis, and time resolved laser-induced fluorescence spectroscopy [6]. Despite the broad variety of methods used for the determination of the conditional complexation constants of the Eu(III) sulphate species in the literature, a consistent set of data was obtained for both EuSO₄⁺ and Eu(SO₄)₂⁻ aqueous complexes at 25 °C.
Chloride complexes with Eu(III) are very weak, and high chloride concentrations are required to form them. Related experiments (up to 4 mol∙L⁻¹ Cl⁻ at 25 °C) need to be considered with extra care because the perchlorate ion was systematically substituted by the chloride ion by more than 10 %, and in some cases even completely. However, the resulting changes in the activity coefficients due to such large compositional modifications of the background electrolyte were simply ignored. All our recalculations [7] based on the exclusive consideration of changes in activity coefficients without considering the formation of Eu-chloro complexes as proposed in the original studies, are able to describe the experimental data of the literature [6]. This means that the formation of Eu(III)-chloro complexes postulated in the literature was an artefact [6].
Unfortunately, very little is known concerning the complexation of Eu(III) with phosphate ions. The only experimental study was performed recently [8], by means of laser-induced luminescence spectroscopy at 25 °C and at different ionic strengths (0.6 – 3.1 mol∙L⁻¹) imposed by NaClO₄. The impact of temperature up to 80 °C on the formation of the EuH₂PO₄²⁺ complex was also investigated [8].

Recently, results of our critical evaluation for the chloride, sulphate, and phosphate ligands were published [6]. The recommended complexation constants and solubility products for further inorganic ligands, e.g. hydroxide and carbonate, will also be presented [9].

[1] Brown, P.L. and Ekberg, C. (2016) Hydrolysis of Metal Ions. Vol. 1, Wiley-VCH, Weinheim.
[2] Hummel, W. et al. (2002) Nagra/PSI Chemical Thermodynamic Data Base 01/01, Technical Report 02-16.
[3] Rard, J.A. (1985). Chemistry and thermodynamics of europium and some of its simpler inorganic compounds and aqueous species. Chem. Rev. 85(6): 555-582.
[4] Spahiu, K. and Bruno, J. (1995) A selected thermodynamic database for REE to be used in HLNW performance assessment exercises, SKB Technical Report.
[5] Giffaut, E, et al. (2014). Andra thermodynamic database for performance assessment: ThermoChimie. Appl. Geochem. 49: 225–236.
[6] Jordan, N. et al. (2022). A critical review of the solution chemistry, solubility, and thermodynamics of europium: recent advances on the Eu3+ aqua ion and the Eu(III) aqueous complexes and solid phases with the sulphate, chloride, and phosphate inorganic ligands. Coord. Chem. Rev. 473, 214608.
[7] Spahiu, K. and Puigdomènech, I. (1998). On weak complex formation: re-interpretation of literature data on the Np and Pu nitrate complexation. Radiochim. Acta 82: 413-419.
[8] Jordan, N. et al. (2018). Complexation of trivalent lanthanides (Eu) and actinides (Cm) with aqueous phosphates at elevated temperatures. Inorg. Chem. 57(12): 7015-7024.
[9] Jordan, N. et al. (2023). Coord. Chem. Rev. (in preparation).

Keywords: thermodynamic database; europium

  • Contribution to proceedings
    Migration 2023, 24.-29.09.2023, Nantes, France
  • Poster
    Migration 2023, 24.-29.09.2023, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-36552
Publ.-Id: 36552


Data publication: A shallow hybrid classical-quantum spiking feedforward neural network for noise-robust image classification

Konar, D.; Sarma, A. D.; Bhandary, S.; Bhattacharyya, S.; Cangi, A.; Aggarwal, V.

The PyTorch implementation of SQNN is available on Github at https://github.com/darthsimpus/ASOC

Keywords: Quantum machine learning; Spiking neural networks; Variational quantum circuit; Hybrid classical-quantum neural networks

Related publications

  • Reseach data in external data repository
    Publication year 2023
    License: Common
    Hosted on Github: Link to location

Permalink: https://www.hzdr.de/publications/Publ-36551
Publ.-Id: 36551


Establishment of a thermodynamic database for the solution chemistry and solubility of Eu(III) inorganic species

Jordan, N.; Thoenen, T.; Starke, S.; Spahiu, K.; Brendler, V.

Performance assessments of geological repositories for the underground disposal of high-level radioactive waste require a deep understanding of the phenomena influencing the mobility of radionuclides, e.g. sorption, redox immobilization, surface precipitation, incorporation, etc. Reliable thermodynamic databases (TDB) are required in order to generate speciation calculations, surface complexation and reactive transport models to predict the aforementioned mechanisms. In this work, the focus was set on europium (Eu), a lanthanide used for decades as a chemical analogue of trivalent actinides (Pu, Am). Indeed, a consolidated and internationally recognized Eu TDB does currently not exist.

Several reviews and reports [1-4] on the aqueous chemistry/geochemistry of europium were published, but had several drawbacks, for example:

→ Insufficient transparency about the selection procedure,

→ Lack of systematic screening to gather primary literature sources,

→ Too high reliance on the analogy with trivalent actinides,

→ For weak complexes such as chloride and nitrate, changes in the activity coefficients due to the replacement of up to 100 % of the background electrolyte anion by Cl⁻ or NO₃⁻ was either completely overlooked or, if recognized, not handled properly,

→ Too high reliance on the charge analogy for the estimation of missing ion interaction coefficients when the Specific ion Interaction theory was applied.

This study aims at significantly improving the situation by carefully addressing all aforementioned issues in order to provide a reliable, robust, and internally consistent TDB for europium. Recently, results of our critical evaluation for the chloride, sulphate, and phosphate ligands were published. The recommended complexation constants and solubility products for further inorganic ligands, e.g. hydroxide and carbonate, will also be presented [6].

[1] P.L. Brown, C. Ekberg, Hydrolysis of Metal Ions. Vol. 1, Wiley-VCH, Weinheim, 2016.
[2] W. Hummel, et al., Nagra/PSI Chemical Thermodynamic Data Base 01/01, Technical Report 02-16, 2002.
[3] J.A. Rard, Chemical Reviews, 85(6) (1985) 555-582.
[4] K. Spahiu, J. Bruno, A selected thermodynamic database for REE to be used in HLNW performance assessment exercises, SKB Technical Report, 1995.
[5] N. Jordan et al., Coordination Chemistry Reviews, 473, 214608 (2022).
[6] N. Jordan et al., Coordination Chemistry Reviews, (2023) (in preparation).

Keywords: thermodynamic database; europium; SIT

  • Contribution to proceedings
    Goldschmidt2023, 09.-14.07.2023, Lyon, France
  • Poster
    Goldschmidt2023, 09.-14.07.2023, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-36550
Publ.-Id: 36550


Reliable europium thermodynamic database: uses and needs in the energy field

Jordan, N.; Thoenen, T.; Starke, S.; Spahiu, K.; Brendler, V.

For hydrometallurgy, mining and ore processing, disposal of chemotoxic and radioactive waste as well as for remediation of polluted areas, scientists and engineers from various disciplines need reliable thermodynamic data. Researchers from HZDR, together with colleagues from Sweden and Switzerland, developed a respective database for europium, one of the most important rare earth elements (REE). The result is the first comprehensive, self-consistent, transparent, and openly accessible database of chemical and thermodynamic aspects of that element. Basis is a state-of-the-art critical, internally consistent, and thorough evaluation of all data previously published for europium worldwide. This new compilation of high-quality data will now render extraction, separation, and recycling processes more efficient for europium as well as other rare earth elements. An increased recycling rate of REE, currently lower than 5 %, could decrease the need for exploitation of new primary deposits, reduce environmental impacts, and minimize the overall energy consumption. Further fields of application concern fundamental geological aspects, e.g. relevant for chemical evolutions and alterations of sedimentary rocks and deposits. Eventually, it will also significantly improve mobility predictions of trivalent actinides in nuclear waste disposals where europium serves as a chemical analogue. Thus, the new data will serve both industrial and ecological applications in Germany and many other countries depending on high-technology metals such as europium.

Keywords: europium; thermodynamic database

  • Poster
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Germany

Permalink: https://www.hzdr.de/publications/Publ-36549
Publ.-Id: 36549


Data publication: Assessing the accuracy of hybrid exchange-correlation functionals for the density response of warm dense electrons

Moldabekov, Z.; Lokamani, M.; Vorberger, J.; Cangi, A.; Dornheim, T.

This repository contains the DFT simulation results presented in the article "Assessing the accuracy of hybrid exchange-correlation functionals for the density response of warm dense electrons". The minimal dataset that would be necessary to interpret, replicate and build upon the findings reported in the article.

Keywords: warm dense matter; hybrid functionals; Hartree-Fock

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Downloads

Permalink: https://www.hzdr.de/publications/Publ-36547
Publ.-Id: 36547


A shallow hybrid classical-quantum spiking feedforward neural network for noise-robust image classification

Konar, D.; Sarma, A. D.; Bhandary, S.; Bhattacharyya, S.; Cangi, A.; Aggarwal, V.

Deep Convolutional Neural Network (CNN)-based image classification systems are often susceptible to noise interruption, i.e., minor image noise may significantly impact the outcome. On the contrary, classical Spiking Neural Network (SNN) is known for handling noisy data due to the stochastic and temporal behaviour of the spiking neuron signals. However, it is not always feasible to train the weights of the classical SNN due to stochastic and non-differentiable spiking signals. Recent applications of quantum machine learning to stochastic modelling have predicted that quantum computing would prove to be a significant advantage, hence catapulting the study of quantum and neuromorphic computing to a new level of development. Motivated by these observations, this paper introduces a shallow hybrid classical-quantum spiking feedforward neural network referred to as Spiking Quantum Neural Network (SQNN) for dealing with a robust image classification task in the presence of noise and adversarial attacks. The proposed SQNN offers the inherent capabilities of processing unforeseen noisy test images due to its spatial and temporal information. An efficient variational quantum circuit training with the help of a standard back-propagation algorithm obviates the classical Spiking Time-Dependent Plasticity (STDP) and Spike-Prop algorithms, which are often found inefficient in training the feedforward SNN. The proposed SQNN is extensively tested and benchmarked on the PennyLane Quantum Simulator. Experimental results show that the proposed SQNN model supersedes the feedforward SNN (SFNN), Random Quantum Neural Networks (RQNN), AlexNet and ResNet-18 on unseen test images with added noise from the FashionMNIST, MNIST, KMNIST, CIFAR10, and ImageNet datasets.

Keywords: Quantum machine learning; Spiking neural networks; Variational quantum circuit; Hybrid classical-quantum neural networks

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Permalink: https://www.hzdr.de/publications/Publ-36546
Publ.-Id: 36546


The Effect of Macroscopic Particle Features on Mineral Dissolution

Winardhi, C. W.; Da Assuncao Godinho, J. R.; Gutzmer, J.

Mineral dissolution is a dynamic process in which kinetics depend on the reactive surface area, orientation, and geometry of the dissolving mineral grain. Dissolution rate is, thus, not represented by a single value, but rather, by a spectrum that is affected by the reactivity of different types of surface features. Such dissolution rate spectra are usually obtained by very detailed studies of perfectly cleaved surfaces by atomic force microscopy or in situ studies, such as flow-through experiments. This study visualizes dissolution progress by repeated X-ray computed tomography scans of a single particle. This allows studying the influence of larger particle features, such as corners and edges, at the interception of macroscopic faces of particles, as well as the influence of those macroscopic features on the dissolution rate spectra. As a suitable case study, the dissolution of a monomineralic galena (PbS) particle in ethaline is studied. The observed changes in particle geometry are evaluated using a newly developed empirical model in order to break down the rate spectra as a function of the particle geometry. Results illustrate that dissolution rates are exponentially correlated with the distance to crystal corners and edges. The reactivity map generated from these exponential relations shows a linear trendline with the dissolution rates over the entire surface of the studied galena particle. The empirical reactivity map developed here opens the possibility of predicting the dissolution rate of particulate materials based on computed tomography and the optimal geometrical properties of the particles that maximize the dissolution, e.g., size and shape.

Keywords: computed tomography (CT); corners and edges; dissolution; dissolution rate spectra; reactivity map

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36545
Publ.-Id: 36545


Herausforderungen in der Radiopharmazie aus europäischer Sicht

Kiß, O.

6th Life Sciences Forum Sachsen

  • Invited lecture (Conferences)
    6th Life Sciences Forum Sachsen, 01.12.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36543
Publ.-Id: 36543


EANM perspective on Health/Pharmaceutical Regulations

Kiß, O.; Patt, M.

Technical Meeting

  • Invited lecture (Conferences)
    Technical Meeting on Health/Pharmaceutical Regulations for Radiopharmaceuticals, 06.-10.03.2023, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36542
Publ.-Id: 36542


A short history of the Heidelberg PSMA compounds – what will tomorrow bring?

Kiß, O.

New Horizons in Imaging and Therapy

  • Invited lecture (Conferences)
    2nd 180°N Conference, 25.-27.04.2023, Bergen, Norwegen

Permalink: https://www.hzdr.de/publications/Publ-36541
Publ.-Id: 36541


Planungsschritte und Antragsstellung im Rahmen von prospektiven Studien

Kiß, O.

Young DGN Fortbildung

  • Invited lecture (Conferences)
    NuklearMedizin 2023, 19.-22.04.2023, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36540
Publ.-Id: 36540


Data publication: 3D gas distribution in lab-scale zero-gap water electrolysers measured by 3D X-ray computed microtomography

Dung, O.-Y.; Boden, S.

Postprocessed 3D raw attenuation data of lab-scale zero-gap water electrolysers at different operating conditions.

Keywords: X-ray computed tomography; Microtomography; Zero-gap electrolyser; Fluid Dynamics

Downloads

Permalink: https://www.hzdr.de/publications/Publ-36539
Publ.-Id: 36539


Modelling water circulation and solute transport at a former french uranium mining site

Katz, A.; Veilly, E.; Lévrier, L.; Pérez-Sànchez, D.; Arnold, T.; Bok, F.; Montavon, G.; Bertin, C.; Urso, L.; Chardon, P.; Sarramia, D.; Vaudelet, P.; Mallet, C.

Within the frame of the RadoNorm project (https://www.radonorm.eu/), the goal is to better understand the importance of hydrogeochemical and chemical processes for radionuclides’ transfer in the environment with a focus on Naturally Occurring Radioactive Material (NORM). In that context, a wetland in a downstream area of a former uranium mine tailing, i. e. the Rophin site, has been selected and the following water flows and solute transport models, in 1, 2 or 3 D could be used: HYTEC [1], HYDRUS [2], CIEMAT model [3], and MELODIE [4]. This application should allow to understand the fate of uranium and radium observed in the wetland area, the link between radionuclides’ concentration in the wetland and in the crossing stream and also to highlight a possible transfer of radionuclides to the groundwater.
The Rophin site located in the department of Puy-de-Dôme of the region Auvergne-Rhone-Alpes (France) where measured dose rates are 20 to 30 times higher than the background along the Gourgeat stream and in a so-called “wetland area”. A source of contamination is present due to successive discharges from settling ponds during the operational phase of the mine and located in the whitish layer of the wetland, where three different soil horizons are identified (an organic-rich surface layer, a whitish layer, and a paleosol layer).
The watershed has been equipped since 2019 with piezometers and surface sensors to monitor the water (electrical conductivity, temperature and water flow). Metereological data is available to identify patterns for precipitation regimes for the wet and dry seasons. First results from measuring campaigns in 2021 and 2022 confirm the presence of a groundwater table in the wetland, which is rather close to the surface and varies depending on meterological conditions. To characterise the different horizons in the wetland, a field study was carried out in October 2022 which provides information about geophysical parameters. In parallel, parameters such as soil permeability, soil porosity, diffusion coefficients and dispersivity are going to be obtained by laboratory measurements in spring 2023. Surface mapping data (dose rates and gamma-ray spectroscopy analysis) and Light Detection and Ranging (LiDaR) data are available as well as information about water chemical composition and soil/sediment mineralogy both in the wetland and in the Gourgeat stream. To evaluate radionuclides sorption onto the various soil layers and partition of radionuclides between solid and liquid phases, distribution coefficients are determined either experimentally (Kd) or modelled with the mechanistic "Smart Kd" approach [5].
A description of water flows and soil layers to be modelled is presented. In a first approach assuming a saturated zone, modelling of the three layers system will be performed in 1D and 2D. Two types of simulation are considered, one with a low flux regime when the stream and the wetland seems to be disconnected and the other with a high flux regime when the stream and the wetland should be hydraulically connected. The aim is to evaluate the evolution of uranium and radium concentration within the layers of the wetland and also to quantify the concentrations of those radionuclides released into the environment, i.e. groundwater and Gourgeat stream.

References
[1] Van Der Lee, J., De Windt, L., Lagneau, V., & Goblet, P. (2003). Module-oriented modeling of reactive transport with HYTEC. Computers & Geosciences, 29(3), 265-275.
[2] Simunek, J., Jacques, D., van Genuchten, M. T., & Mallants, D. (2006). Multicomponent geochemical transport modeling using HYDRUS-1 D and HP 1. Journal of the American water resources Association, 42(6), 1537-1547.
[3] Pérez-Sánchez, D., & Thorne, M. C. (2014). Modelling the behaviour of uranium-series radionuclides in soils and plants taking into account seasonal variations in soil hydrology. Journal of environmental radioactivity, 131, 19-30.
[4] Mathieu, G., Dymitrowska, M., & Bourgeois, M. (2008). Modeling of radionuclide transport through repository components using finite volume finite element and multidomain methods. Physics and Chemistry of the Earth, Parts A/B/C, 33, S216-S224.
[5] Stockmann, M. & Schikora, J. & Becker, D.-A. & Flügge, J. & Noseck, U. & Brendler, V. (2017). Smart Kd-values, their uncertainties and sensitivities - Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems. Chemosphere. 187. 10.1016/j.chemosphere.2017.08.115.
Acknowledgments

The RadoNorm project has received funding from the Euratom research and training programme 2019-2020 under grant agreement No 900009.

Keywords: RadoNorm; Modelling; Smart Kd; Naturally Occurring Radioactive Material

  • Lecture (Conference)
    Migration, 24.-29.09.2023, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-36538
Publ.-Id: 36538


Quantum version of the integral equation theory based dielectric scheme for strongly coupled electron liquids

Tolias, P.; Lucco Castello, F.; Dornheim, T.

A novel dielectric scheme is proposed for strongly coupled electron liquids that handles quantum mechanical effects beyond the random phase approximation level and treats electronic correlations within the integral equation theory of classical liquids. The self-consistent scheme features a complicated dynamic local field correction functional and its formulation is guided by ab initio path integral Monte Carlo simulations. Remarkably, our scheme is capable to provide unprecedently accurate results for the static structure factor with the exception of the Wigner crystallization vicinity, despite the absence of adjustable or empirical parameters.

Permalink: https://www.hzdr.de/publications/Publ-36537
Publ.-Id: 36537


Impact of various cleaning procedures on p-GaN surfaces

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

This work discusses the influence of different cleaning procedures on p-GaN grown on sap-phire by metal-organic chemical vapor deposition. The cleaned p-GaN surface was trans-ferred into an ultra-high vacuum chamber and studied by an X-ray photoelectron spectrome-ter, revealing that a cleaning with a so-called „piranha“ procedure results in low carbon and oxygen concentrations on the p-GaN surface. Contrary, a cleaning that solely uses ethanol represents a simple cleaning, but leads to an increase of carbon and oxygen contaminations on the surface. Afterward, the cleaned p-GaN samples underwent a subsequential vacuum thermal cleaning at various temperatures to achieve an atomically clean surface. XPS meas-urements revealed residual oxygen and carbon on the p-GaN surface. Thus, a thermal treat-ment under a vacuum did not entirely remove these organic contaminations, although the thermal cleaning reduced their peak intensities. The complete removal of carbon and oxygen contaminants was only achieved by argon ion sputtering, which is accompanied by a strong depletion of the nitrogen on the p-GaN surface. The treatments cause a large number of sur-face defects preventing the formation of a negative electron surface when the p-GaN is acti-vated with a thin layer of cesium.

Keywords: p-GaN; photocathode; sputtering damage; surface cleaning; damage effects

Related publications

  • Open Access Logo Surface and Interface Analysis 55(2023), 507-514
    Online First (2023) DOI: 10.1002/sia.7207

Permalink: https://www.hzdr.de/publications/Publ-36534
Publ.-Id: 36534


Boosting complex Systems Research through RSE Collaboration

Kelling, J.; Tripathi, R.; Calabrese, J.

Stochastic simulations of complex systems from domains including physics, biology, ecology or economics often require large system sizes, long time scales, and numerous replications
to fully explore model behavior. The simple rules defining many models can lead researchers
to prefer familiar but inefficient programming techniques, which severely hinder progress
by creating computational bottlenecks. While such studies often benefit from combined
domain-specific, statistical, and programming knowledge, few individual researchers span
the full range of necessary skills. Here, we present a collaboration on the neutral model
of biodiversity in dendritic river networks, where the goal is to analyze biodiversity data
across the world’s major river systems. We show how we achieved large performance gains
by engaging the problem at its foundations and thereby enabled research at a new scale.

Keywords: performance; GPU; complex systems; computational science

Permalink: https://www.hzdr.de/publications/Publ-36533
Publ.-Id: 36533


The self-assembly process of helical molecules

Thi, N. H. N.; Günther, F.; Preis, K.; Kelling, J.; Tegenkamp, C.; Gemming, S.

Helical polyalanine (PA) molecules gathered a lot of interest as the propagation of electrons along the helical backbone structure comes along with spin polarization. Via liquid and solid scanning tunneling microscopy (STM) we studied the ordering of physisorbed and chemisorbed PA molecules on HOPG and Au surfaces. While enantiopure PA molecules adsorb in a hexagonally close-packed structure, we found heterochiral dimers with a rectangular unit cell for DL-PA. Despite the steric hindrance, the packing density of the DL-PA heterophase is increased by 25% compared to the enantiopure PA structure. Apparently, this is achieved by shifting D- and L-PA along their helical axis. Moreover, the alpha-helix structure of the PA molecules seems to be preserved; thus, electrostatic forces indeed play an important role for the formation and stabilization of the helical structure. In parallel, the interactions between PA homo- and heterochiral pairs were analyzed by van-der-Waals-corrected DFT-based tight binding calculations. Denser packing geometries can be reached by heterochiral PA pairs. Second, coarse-grained classical potentials were derived from the DFTB data, and the different PA phases seen in STM were also successfully obtained from Monte-Carlo simulations.

Keywords: self-assembled monolayer; chiral organic molecules; scanning tunneling microscopy

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 26.-31.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36532
Publ.-Id: 36532


Efficient integration of short-range models on complex networks

Kelling, J.; Ódor, G.; Barancsuk, L.; Deng, S.; Hartmann, B.; Gemming, S.

Complex, hierarchical or random network topolgies can give rise to unique behavior in many physical models. We study dynamical synchronization behavior in Kuramoto models on power grids and brain connectomes with millons of connections and O(100k) nodes. At these scales it is crucial to use the sparsity when computing derivatives, which, due to the random network structure, makes employing modern parallel hardware tricky. Here, we present our approach to numerically solving large systems ordinary differential equations on random directed graphs, where we focus on the computationally expensive task of computing derivatives and leave the common integration step to the boost::odeint library. Our application can utilize both parallel CPUs and GPUs. We also provide an overview of our results on human and fly brain connectomes as well as failure cascades in power grids and provide a measure of the advantage gained from our computational optimization efforts.

Keywords: synchronization; networks; brain; power grids; GPU

Permalink: https://www.hzdr.de/publications/Publ-36531
Publ.-Id: 36531


Simulating neutral biodiversity in large-scale networks

Kelling, J.; Tripathi, R.; Calabrese, J.

The neutral model of biodiversity describes a Markov process of death and replacement of neutral individuals constituting the species occupying an ecosystem. It predicts a number macroscopic ecosystem observables, including local and global abundances, and can serve as advanced null-hypothesis for more complex models. We present a massively parallel approach to simulating the neutral model which both enables simulations on large networks, to, e.g., capture fine details of real river networks, and efficiently produces averages results to enable comparisons with empirical data or other models at high statistical significance or accurately compute correlations or responses.

Keywords: biodiversity; GPU; research software engineering; networks

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 26.-31.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36530
Publ.-Id: 36530


U(VI) retention on bentonite and cementitious materials: Effect of increased ionic strengths and presence of organics

Schmeide, K.; Philipp, T.; Huittinen, N. M.; Shams Aldin Azzam, S.; Kretzschmar, J.

The safe disposal of radioactive waste from operation and decommissioning of nuclear power plants in geological repositories requires the application of multiple barriers to isolate the waste from the biosphere. Most disposal concepts consider the extensive use of bentonite and cementitious materials in the geoengineered barrier as buffer and borehole sealing material as well as to enforce mechanical stability of disposal facilities. To evaluate the radionuclide retention potential of these barrier materials, it is necessary to examine the effects of various repository-relevant conditions that are expected to develop over time, such as altered pH, increased ionic strengths or temperatures, or the release of organic constituents.
Pore waters of the North German clay deposits are characterized by high ionic strengths up to 4 M [1,2]. The contact of such saline formation waters with concrete will result in an enhanced corrosion of concrete and to the evolution of highly alkaline cement pore waters (10 < pH < 13), which in turn, can react with the bentonite buffer as well as with the clay host rock, changing their retention potential towards radionuclides. Moreover, the role of organics (as admixtures in cement-based materials or waste constituents [3]) on actinide retention has to be studied.
The U(VI) retention on Ca-bentonite in mixed electrolyte solutions (‘diluted Gipshut solution’, I = 2.6 M) was found to be very effective at pH>10, even in the presence of carbonate and despite the prevalence of anionic aqueous uranyl species [4]. By means of luminescence and X-ray absorption spectroscopy, two dominating U(VI) surface species at hyperalkaline conditions were identified: (i) a ternary U(VI) complex, where U(VI) is bound to the surface via bridging Ca cations with the configuration surface ≡Ca–OH–U(VI) and, (ii) U(VI) sorption into the interlayer space of calcium (aluminum) silicate hydrates (C-(A-)S-H), which form as secondary phases in the presence of Ca due to partial dissolution of alumosilicates at hyperalkaline conditions (Figs. 1 and 2) [5]. Citrate and 2 phosphonobutane-1,2,4,-tricarboxylate (PBTC) were found to reduce U(VI) retention only when present at high concentrations.
The U(VI) retention by C-A-S-H, formed due to Al-rich additives in cement formulations, was studied applying samples with Ca/Si molar ratios of 0.8, 1.2 and 1.6, representing different alteration stages of concrete, and with increasing Al/Si molar ratios of 0, 0.06 and 0.18 in each series. Furthermore, the impact of temperature (25°C, 100°C, 200°C) on both the C-A-S-H structure and the U(VI) retention mechanism was studied. Solid-state 27Al and 29Si NMR spectroscopy along with XRD revealed that enhanced temperatures increase the crystallinity of the material with the appearance of neoformed crystalline phases. Surface-sorbed and interlayer-sorbed U(VI) species were detected by luminescence spectroscopy. U(VI) mobilization due to high ionic strengths or presence of organics (gluconate or PBTC) was very low [6,7].
The results show that both bentonite and cementitious material constitute an important geoengineered retention barrier for U(VI) under hyperalkaline conditions at increased ionic strengths and in presence of organics. Thus, both bentonite and cementitious material strongly contribute to the safe confinement of radionuclides in a repository to isolate radiotoxic contaminants from the hydrosphere and biosphere.

Keywords: uranium; bentonite; cement; organics; ionic strength; retention; geotechnical barrier

Related publications

  • Lecture (Conference)
    18th International Conference on Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 2023, 24.-29.09.2023, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-36529
Publ.-Id: 36529


Cement-based materials in the multi-barrier system of nuclear waste repositories – impact on radionuclide retention

Gaona, X.; Ait Mouheb, N.; Altmaier, M.; Bosbach, D.; Deissmann, G.; Geckeis, H.; Kretzschmar, J.; Schmeide, K.; Stumpf, T.

The safe disposal of long-lived nuclear waste is a grand societal challenge and part of the current energy transition in Germany. Safety concepts regarding nuclear waste disposal in underground repositories generally rely on a combination of engineered and geological barriers, which minimize the potential release of radionuclides out of the containment providing rock zone or even the transport into the biosphere. Cementitious materials are very important in this context. They are used for conditioning of certain nuclear waste types, as components of waste containers and overpacks as well as constituents of structural materials at the interface between backfill and host-rocks in some repository concepts. In order to assess the potential impact of cement-based materials on the (geo)chemical behaviour of radionuclides in a repository system, targeted studies on the interaction of radionuclides with cementitious materials are required.
In the event of water interacting with cementitious materials, pore water solutions characterized by (highly) alkaline pH conditions will form. These boundary conditions define the chemical response of the radionuclides, but also influence the behaviour of neighbouring components of the multi-barrier system, e.g. bentonitic or argillaceous backfill and host-rocks, respectively. Hardened cement pastes are considered to be the main sorbing materials present in the near field of repositories for low and intermediate level waste. Hence, interactions of radionuclides with cementitious materials represent a very important mechanism retarding their mobility and potential migration from the near field. In addition to a robust quantitative description of the sorption processes (usually in terms of sorption coefficients, i.e. Kd values), the detailed mechanistic analysis and understanding of sorption phenomena provide additional scientific arguments and important process understanding and thus enhance both the quality of safety arguments and the overall confidence in the safety assessment process.
The NUSAFE partners KIT, HZDR and FZJ have contributed to a significantly improved understanding on various processes related to the retention of radionuclides on cement-based materials. Within the framework of the EU project EURAD (https://www.ejp-eurad.eu/), NUSAFE partners are contributing to and coordinating the workpackage (WP) Cement Organic Radionuclide Interactions - CORI, providing new insights into the role of organic molecules with respect to radionuclide mobility. With a focus on the elevated ionic strength conditions expected for the north German clay formations, NUSAFE partners likewise collaborate within the GRAZ II project, funded by the Federal Ministry for the Environment, Nature Conservation, Nuclear Safety, and Consumer Protection (BMUV). Further work is performed within bilateral international contracts or cooperations. Apart from the frequently studied actinide elements, long-lived fission and activation products receive specific attention. The combination of classical experimental (wet-chemistry) methods, advanced spectroscopic techniques, and theoretical calculations provides both an accurate quantitative evaluation and a fundamental understanding of the sorption processes. The present state-of-knowledge as well as main remaining uncertainties affecting the retention processes of radionuclides in cementitious environments under different conditions will be critically discussed.

Keywords: cement; concrete; actinide; organic ligands; ionic strength; geotechnical barrier; nuclear waste management

  • Lecture (Conference)
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Germany

Permalink: https://www.hzdr.de/publications/Publ-36528
Publ.-Id: 36528


Regulating oxygen ion transport at the nanoscale to enable highly cyclable magneto-ionic control of magnetism

Tan, Z.; Ma, Z.; Fuentes-Rodriguez, L.; Liedke, M. O.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.; Abad, L.; Casañ-Pastor, N.; Lopeandia, A.; Menéndez, E.; Sort, J.

Magneto-ionics refers to the control of magnetic properties of materials through voltage-driven ion motion. To generate effective electric fields, either solid or liquid electrolytes are utilized,
which also serve as ion reservoirs. Thin solid electrolytes have difficulties to (i) withstand high electric fields without electric pinholes and (ii) maintain stable ion transport during long-term
actuation. In turn, the use of liquid electrolytes can result in poor cyclability, thus limiting their applicability. Here we propose a nanoscale-engineered magneto-ionic architecture (comprising a thin solid electrolyte in contact with a liquid electrolyte), that drastically enhances cyclability while preserving sufficiently high electric fields to trigger ion motion. Specifically, we show that the insertion of a highly nanostructured (amorphous-like) Ta layer (with suitable thickness and electric resistivity) between a magneto-ionic target material (i.e., Co3O4) and the liquid electrolyte, increases magneto-ionic cyclability from < 30 cycles (when no Ta is inserted) to more than 800 cycles. Transmission electron microscopy together with variable energy positron annihilation spectroscopy reveal the crucial role of the generated TaOx interlayer as a solid-electrolyte (i.e., ionic conductor) that improves magneto-ionic endurance by proper tuning of the types of voltage driven structural defects. The Ta layer is very effective in trapping oxygen and hindering O2– ions from moving into the liquid electrolyte, thus keeping O2– motion mainly restricted between Co3O4 and Ta when voltage of alternating polarity is applied. We demonstrate that this approach provides a suitable strategy to boost magneto-ionics by combining the benefits of solid and liquid electrolytes in a synergetic manner.

Keywords: magnetoelectricity; voltage control of magnetism; magneto-ionics; transition metal oxide; ion diffusion; positron annihilation spectroscopy; defects

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36527
Publ.-Id: 36527


Effect of citric acid and malic acid on the uranium uptake into Brassica napus plants in hydroponic culture

John, W. A.; Jessat, J.; Steudtner, R.; Hübner, R.; Sachs, S.

The transport and transfer of radionuclides in the environment is an important aspect with regard to the health risk assessment of sites contaminated with naturally occurring radionuclides. In addition, this knowledge is highly relevant for the long-term safety assessment of future nuclear waste repositories. Radionuclides such as uranium are non-essential elements for plants. However, when present in contaminated soil, they can be taken up by plants and thus enter the food chain, posing a health risk to humans. Plants exude organic acids such as citric acid, malic acid, and/or oxalic acid into the rhizosphere. Under deficiency conditions, this can induce the dissolution of previously unavailable insoluble compounds, e.g., iron and phosphate minerals [1]. However, these processes can lead to the acquisition not only of essential nutrients, but also of non-essential ones, such as uranium. Therefore, plants may influence the mobility and bioavailability of radionuclides in the environment.
In the present work, we investigated the effect of citric acid and malic acid, both characteristic plant exudates, on the solubility of uranium in hydroponic plant culture medium as well as on the uranium uptake by Brassica napus (canola) plants in hydroponic culture. Prior to plant exposure, the solubility and speciation of 20 µM uranium(VI) in a phosphate reduced hydroponic solution (HRred, [2]) in the absence and presence of citric acid or malic acid was studied. After 24 h equilibration of uranium(VI) in HRred solution in the absence of citric acid or malic acid, a part of the uranium (~50%) precipitated, most probably in form of a uranyl(VI) phosphate. The control samples without organic acids stayed at the minimum concentration of dissolved uranium for 72 h, whereas those with citric acid or malic acid showed a re-solubilisation to the maximum uranium concentration of 20 µM within the first 24 h after addition of the respective organic acid. Following the uranium speciation in the hydroponic solutions during the exposure period by time-resolved laser-induced fluorescence spectroscopy (TRLFS) indicated the formation of uranium(VI) citrate and malate complexes, whereas in the organic-acid-free solution, the UO2(CO3)34- complex predominated.
B. napus plants were cultivated according to Jessat et al. [2]. To study the influence of the two organic acids on uranium exposure to B. napus, 20 µM U(VI) were added to HRred solution and allowed to equilibrate for 24 h in a plant growth chamber. After pre-equilibration, citric acid or malic acid (100 and 1000 µM) were added to the solutions. Immediately after that, the plants were inserted for exposure to uranium. For comparison, control samples were studied under the same conditions, however, without addition of citric acid or malic acid. The uranium concentration of the solutions was regularly determined by inductively coupled mass spectrometry (ICP-MS) within 72 h. After 72 h, the uranium content in the roots, stems, and leaves was analyzed by ICP-MS after drying and incineration. Furthermore, scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray spectroscopy (EDX) was used to qualitatively confirm the presence of uranium in the roots.
The time-dependent bioassociation experiments showed a strong immobilization of uranium by the B. napus plants either in the absence or in the presence of organic acids. However, in the presence of citric acid and malic acid, this process seems to be retarded due to the re-dissolution of the uranium precipitate by the organic acids. Using TRLFS, uranium(VI) citrate and malate complexes were identified in the hydroponic solutions in the presence of the plants at the beginning of exposure. After longer exposure times, however, their contribution decreased and the UO2(CO3)34- complex dominated the speciation. For all conditions, STEM/EDX results verified the uptake of uranium into the whole root tissue. After 72 h of uranium exposure in the presence of citric acid or malic acid, more uranium was found in the leaves of B. napus compared to the control samples, indicating a stronger translocation of uranium in the plants. Despite that, in the presence of 1000 µM malic acid, a significantly lower amount of uranium was observed in the roots. These results demonstrate the ability of plant metabolites to dissolve hardly soluble uranium precipitates and shed more light on the speciation dependent uranium uptake into and translocation in canola plants.
The results of this study may contribute to a more pronounced process understanding on the uranium uptake into plants and their impact on the uranium mobility in the environment. This knowledge is required for the improvement of radioecological models to assess the migration and transfer of radionuclides in the environment, to develop efficient and cost-effective remediation technologies for contaminated sites, and to perform reliable dose predictions for humans and environment.

Acknowledgement
This work was performed within the RadoNorm project. This project has received funding from the Euratom research and training programme 2019-2020 under grant agreement No. 900009.

References
[1] Jones, D. L. (1998). Organic acids in the rhizosphere - a critical review. Plant and Soil 205: 25-44.
[2] Jessat, J., John, W.A., Moll, H., Vogel, M., Steudtner, R., Drobot, B., Hübner, R., Stumpf, T., Sachs, S. (2023), Ecotox. Environ. Saf., under review.

Keywords: Radioecology; Naturally occurring radionuclides; NORM; Uranium; Plants; Transport; Transfer; Environment; Speciation; Localization; Organic acids

  • Poster
    18th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 2023, 24.-29.09.2023, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-36526
Publ.-Id: 36526


Strahlenschutzmaßnahmen bei der Anwendung von PET-Nukliden in der Krebsforschung

Wendler, M.; Kowe, S.

Der Strahlenschutz bei der Erzeugung, Verarbeitung und Forschung an PET-Nukliden wird betrachtet. Es werden die verschiedenen Abläufe im Herstellungsprozess - vom Zyklotron bis zur Auslieferung - betrachtet. Darüber hinaus wird auch auf die speziellen Berührungspunkte und Kompromissfindung mit z. B. dem Tierschutz verwiesen und an einem Beispiel die Lösung eines konkreten Problems geschildert.

Keywords: Strahlenschutz; Radiation Protection; Betrieblicher Strahlenschutz; PET

  • Strahlenschutz-Praxis 2(2023), 27-29
    ISSN: 0947-434 X

Downloads

  • Secondary publication expected from 26.05.2024

Permalink: https://www.hzdr.de/publications/Publ-36525
Publ.-Id: 36525


Element Distributions in Bimetallic Aerogels

Wang, C.; Herranz, J.; Hübner, R.; Schmidt, T. J.; Eychmüller, A.

Metal aerogels assembled from nanoparticles have captured grand attention because they combine the virtues of metals and aerogels and are regarded as ideal materials to address current environmental and energy issues. Among these aerogels, those composed of two metals not only display combinations (superpositions) of the properties of their individual metal components but also feature novel properties distinctly different from those of their monometallic relatives. Therefore, quite some effort has been invested in refining the synthetic methods, compositions, and structures of such bimetallic aerogels as to boost their performance for the envisaged application(s). One such use would be in the field of electrocatalysis, whereby it is also of utmost interest to unravel the element distributions of the (multi)metallic catalysts to achieve a ratio of their bottom-to-up design. Regarding the element distributions in bimetallic aerogels, advanced characterization techniques have identified alloys, core-shells, and structures in which the two metal particles are segregated (i.e., adjacent but without alloy or core-shell structure formation). While an almost infinite number of metal combinations to form bimetallic aerogels can be envisaged, the knowledge of their formation mechanisms and the corresponding element distributions is still in its infancy. The evolution of the observed musters is all but well understood, not to mention the positional changes of the elements observed in operando or in beginning- vs end-of-life comparisons (e.g., in fuel cell applications).
With this motivation, in this Account we summarize the endeavors made in element distribution monitoring in bimetallic aerogels in terms of synthetic methods, expected structures, and their evolution during electrocatalysis. After an introductory chapter, we first describe briefly the two most important characterization techniques used for this, namely, scanning transmission electron microscopy (STEM) combined with element mapping (e.g., energy-dispersive X-ray spectroscopy (EDXS)) and X-ray absorption spectroscopy (XAS). We then explain the universal methods used to prepare bimetallic aerogels with different compositions. Those are divided into one-step methods in which gels formed from mixtures of the respective metal salts are coreduced and two-step approaches in which monometallic nanoparticles are mixed and gelated. Subsequently, we summarize the current state-of-knowledge on the element distributions unraveled using diverse characterization methods. This is extended to investigations of the element distributions being altered during electrochemical cycling or other loads. So far, a theoretical understanding of these processes is sparse, not to mention predictions of element distributions. The Account concludes with a series of remarks on current challenges in the field and an outlook on the gains that the field would earn from a solid understanding of the underlying processes and a predictive theoretical backing.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36524
Publ.-Id: 36524


Terahertz harmonic generation from graphite pencil drawings

Arshad, A.; Koyun, H. N.; Salikhov, R.; Gensch, M.; Ilyakov, I.; Ponomaryov, O.; Prajapati, G. L.; Mavridou, K.; Lindner, J.; Deinert, J.-C.; Ünlü, C.; de Oliveira, T.; Kovalev, S.

We study the third harmonic generation (THG) of graphite layers on paper substrate upon excitation with intense (up to 100 kV/cm) narrowband terahertz (THz) pulses. Highest THG efficiencies are comparable with those of CVD-grown single-layer graphene. Samples were hand-drawn, using commercially available pencils. The THG response showed a high sensitivity regarding the hatching direction relative to the THz polarization orientation. Using Raman spectroscopy, we confirmed the occurrence of graphene-like structures in the samples. Our findings demonstrate the feasibility of virtually no cost and easy to fabricate materials for THz nonlinear optics.

Keywords: Graphite; terahertz harmonic generation; Dirac materials; nonlinear terahertz optics; Raman Spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-36523
Publ.-Id: 36523


Biomedical research with laser-driven ion sources

Metzkes-Ng, J.

Biomedical research with laser-driven ion sources

  • Invited lecture (Conferences)
    Special Laser Symposium "The path from chirped pulse amplification to applications of laser plasma accelerators and x-ray probing of extreme states of matter”, 06.-07.02.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36522
Publ.-Id: 36522


High energy proton acceleration at DRACO-PW and radiobiological applications

Metzkes-Ng, J.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser driven compact plasma accelerators can generate short, high-intensity pulses of high energy ions with special beam properties. By that they may expand the portfolio of conventional machines in many application areas. The maturating of laser-driven ion accelerators from physics experiments to turn-key sources for these applications will rely on breakthroughs in both, generated beam parameters (kinetic energy, flux), as well as increased reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production of polychromatic proton beams with unprecedented stability [1]. This allowed the first in vivo radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to achieve energies beyond the 100 MeV frontier is matter of ongoing research, mainly addressed by exploring advanced acceleration schemes like the relativistically induced transparency (RIT) regime.
In this talk, we report on experimental proton acceleration studies at the onset of relativistic transparency using pre-expanded plastic foils. Combined hydrodynamic and 3D particle-in-cell (PIC) simulations helped to identify the most promising target parameter range matched to the prevailing laser contrast conditions carefully mapped out in great detail beforehand. A complex suite of particle and optical diagnostics allowed characterization of spatial and spectral proton beam parameters and the stability of the regime of best acceleration performance, yielding cut-off energies larger than 100 MeV in the best shots.
The reported progress for proton acceleration directly feeds into our program on ultra-high dose rate radiobiology. We operate a fully-equipped beamline including beam monitoring and dosimetry adapted to ultra-high dose rate proton pulses at DRACO-PW with the future perspective of a dedicated beamline at our high-power laser facility PENELOPE within the ATHENA project.

References
[1] Ziegler, T. et al. Proton beam quality enhancement by spectral phase control of a PW-class laser system. Sci Rep 11, 7338 (2021)
[2] Kroll, F. et al. Tumour irradiation in mice with a laser-accelerated proton beam. Nat. Phys. 18, 316–322 (2022)

  • Invited lecture (Conferences)
    43rd Workshop on High-Energy-Density Physics with laser and Ion beams, 26.02.-03.03.2023, Hirschegg, Österreich
  • Invited lecture (Conferences)
    6th European Advanced Accelerator Concepts workshop, 17.09.-22.10.2023, La Biodola, Elba, Italien
  • Invited lecture (Conferences)
    ELI-NP 10 YEAR ANNIVERSARY SYMPOSIUM, 24.-25.10.2023, Magurele, Rumänien

Permalink: https://www.hzdr.de/publications/Publ-36521
Publ.-Id: 36521


High energy proton acceleration at DRACO-PW and radiobiological applications

Metzkes-Ng, J.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser driven compact plasma accelerators can generate short, high-intensity pulses of high energy ions with special beam properties. By that they may expand the portfolio of conventional machines in many application areas. The maturating of laser-driven ion accelerators from physics experiments to turn-key sources for these applications will rely on breakthroughs in both, generated beam parameters (kinetic energy, flux), as well as increased reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production of polychromatic proton beams with unprecedented stability [1]. This allowed the first in vivo radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to achieve energies beyond the 100 MeV frontier is matter of ongoing research, mainly addressed by exploring advanced acceleration schemes like the relativistically induced transparency (RIT) regime.
In this talk, we report on experimental proton acceleration studies at the onset of relativistic transparency using pre-expanded plastic foils. Combined hydrodynamic and 3D particle-in-cell (PIC) simulations helped to identify the most promising target parameter range matched to the prevailing laser contrast conditions carefully mapped out in great detail beforehand. A complex suite of particle and optical diagnostics allowed characterization of spatial and spectral proton beam parameters and the stability of the regime of best acceleration performance, yielding cut-off energies larger than 100 MeV in the best shots.
The reported progress for proton acceleration directly feeds into our program on ultra-high dose rate radiobiology. We operate a fully-equipped beamline including beam monitoring and dosimetry adapted to ultra-high dose rate proton pulses at DRACO-PW with the future perspective of a dedicated beamline at our high-power laser facility PENELOPE within the ATHENA project.

References
[1] Ziegler, T. et al. Proton beam quality enhancement by spectral phase control of a PW-class laser system. Sci Rep 11, 7338 (2021)
[2] Kroll, F. et al. Tumour irradiation in mice with a laser-accelerated proton beam. Nat. Phys. 18, 316–322 (2022)

  • Invited lecture (Conferences)
    43rd International Workshop on High- Energy-Density Physics with Intense Ion and Laser Beams, 29.01.-03.02.2023, Hirschegg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36520
Publ.-Id: 36520


Electron-Beam- and Thermal-Annealing-Induced Structural Transformations in Few-Layer MnPS₃

Storm, A.; Köster, J.; Ghorbani Asl, M.; Kretschmer, S.; Gorelik, T. E.; Kinyanjui, M. K.; Krasheninnikov, A.; Kaiser, U.

Quasi-two-dimensional (2D) manganese phosphorus trisulfide, MnPS₃, which exhibits antiferromagnetic ordering, is a particularly interesting material in the context of magnetism in a system with reduced dimensionality and its potential technological applications. Here, we present an experimental and theoretical study on modifying the properties of freestanding MnPS₃ by local structural transformations via electron irradiation in a transmission electron microscope and thermal annealing in vacuum. In both cases we find that phases with the net formula MnS₁₋ₓPₓ in the α- or γ-MnS crystal structure can be formed. The phase transformations can be locally and precisely controlled by the total applied electron dose and explored at the atomic scale. For the MnS structures generated in this process, our ab-initio calculations indicate that their electronic and magnetic properties strongly depend on both in-plane crystallite orientation and thickness. Moreover, the electronic properties of the MnS phases can be further tuned by alloying with phosphorus, suggesting a novel route toward the design of lateral heterostructures. Therefore, our results may enable pathways for the controlled growth of new phases with distinct properties embedded in freestanding quasi-2D MnPS₃.

Keywords: Structural transformations; MnPS3; α-MnS; γ-MnS; 3D electron diffraction; thermal annealing; modification

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36519
Publ.-Id: 36519


A new ultra low-level HPGe activity counting setup in the Felsenkeller shallow-underground laboratory

Turkat, S.; Bemmerer, D.; Boeltzig, A.; Domula, A. R.; Koch, J.; Lossin, T.; Osswald, M.; Schmidt, K.; Zuber, K.

A new ultra low-level counting setup has been installed in the shallow-underground laboratory Felsenkeller in Dresden, Germany. It includes a high-purity germanium detector (HPGe) of 163\% relative efficiency within passive and active shields. The passive shield consists of 45m rock overburden (140 meters water equivalent), 40 cm of low-activity concrete, and a lead and copper castle enclosed by an anti-radon box. The passive shielding alone is found to reduce the background rate to rates comparable to other shallow-underground laboratories. An additional active veto is given by five large plastic scintillation panels surrounding the setup. It further reduces the background rate by more than one order of magnitude down to 116±1 kg−1 d−1 in an energy interval of 40-2700 keV. This low background rate is unprecedented for shallow-underground laboratories and close to deep underground laboratories.

Keywords: Nuclear astrophysics; Low-background physics; Underground physics; Radioactivity Measurements

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Permalink: https://www.hzdr.de/publications/Publ-36518
Publ.-Id: 36518


Data publication: Bottom-up Fabrication of FeSb₂ Nanowires on Crystalline GaAs Substrates with Ion-induced Pre-patterning

Weinert, T.; Erb, D.; Hübner, R.; Facsko, S.

Bei dem Datensatz handelt es sich um die Daten für die Abscheidung von FeSb₂ Nanodrähten auf GaAs-Substraten mit ioneninduzierter Vorstruckturierung. Der Datensatz beinhaltet die AFM-Aufnahme der verwendeten Substratoberfläche und die TEM-Aufnahmen mit den EDXS- udn FFT-Ergebnisse.

Keywords: bottom-up nanofabrication; ion-induced nanopatterning; physical vapor deposition; transmission electron microscopy; energy-dispersive X-ray spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-36517
Publ.-Id: 36517


Curvilinear magnetism: from fundamentals to applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films and nanowires [2,3]. In this talk, we will address fundamentals of curvature-induced effects in magnetism and review current application scenarios. In particular, we will demonstrate that curvature allows tailoring fundamental anisotropic and chiral magnetic interactions [4] and enables fundamentally new non-local chiral symmetry breaking effect [5]. Application potential of geometrically curved magnetic architectures is currently being explored as mechanically reshapeable magnetic field sensors for automotive applications, memory, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics relying on thin films [6,7] as well as printed magnetic composites [8,9].

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
[2] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
[3] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications (Springer, Zurich, 2022).
[4] O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Physical Review Letters 123, 077201 (2019).
[5] D. D. Sheka et al., Nonlocal chiral symmetry breaking in curvilinear magnetic shells. Communications Physics 3, 128 (2020).
[6] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[7] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[8] M. Ha et al., Printable and Stretchable Giant Magnetoresistive Sensors for Highly Compliant and Skin-Conformal Electronics. Advanced Materials 33, 2005521 (2021).
[9] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).

Keywords: curvature effects in magnetism; curvilinear magnetism; magnetic field sensing

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    Colloquia in the frame of the CRC/TRR 270 - Hysteresis design of magnetic materials for efficient energy conversion, 14.02.2023, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-36515
Publ.-Id: 36515


Magnetic soft robots from macro- to nanoscale

Pylypovskyi, O.

The talk will be about theoretical description of magnetic soft robots at different scales starting from the macroscopic actuators based on polymer membranes to properties of nanoscaled mechanically soft exchange-coupled systems.

Keywords: soft robots

  • Invited lecture (Conferences)
    Bio Meets Magnetism, 10.02.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36514
Publ.-Id: 36514


Tailoring of thermomagnetic properties in Ni-Mn-Ga films through Cu addition

Fink, L.; Nielsch, K.; Fähler, S.

Thermomagnetic generators enable the conversion of low-grade waste heat into electric energy. The performance of a generator is intimately connected with the active thermomagnetic material used. Heusler alloys had been proposed as ideal systems for thermomagnetic microsystems, as they comprise a tuneable transition temperature just above room temperature, a steep change of magnetization within a narrow temperature change, a low heat capacity, and are easily processable by common deposition techniques.
In this work, we present a path to optimize Heusler films for thermomagnetic applications, which need different properties compared to magnetocaloric applications. We focus on the key thermomagnetic properties like 1) the thermomagnetic working temperature T* and 2) the change of magnetization with the change of temperature ∆M/∆T and correlate them with common properties like 3) crystal structure, 4) martensitic transition temperature, 5) Curie temperature and 6) spontaneous magnetization M0073. We systematically examine all these properties on polycrystalline Ni-Mn-Ga-Cu films prepared by combinatorial sputter deposition and subjected to a heat treatment. Our analysis allows disentangling the effects in changing the number of valence electrons trough the addition of Cu and the alteration of chemical order before and after heat treatment.

Keywords: Heusler alloys; Curie temperature; Magnetic films; Thermomagnetic material; Energy harvesting

Permalink: https://www.hzdr.de/publications/Publ-36512
Publ.-Id: 36512


Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.] [329.] [330.] [331.] [332.] [333.] [334.] [335.] [336.] [337.] [338.] [339.] [340.] [341.] [342.] [343.] [344.] [345.] [346.] [347.] [348.] [349.]