Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41444 Publications

Data Science for Physicists Tutorial: Introduction to Deep Learning with a focus on Convolutional Neural Networks

Shah, K.

Data Science is playing an ever increasing role in physics. While some departments have offered courses, many of the examples are in the context of social science and other disciplines. In this tutorial, we will introduce data science in the physics context. We will start by introducing Jupyter notebooks and how to explore and visualize data. We will then introduce unsupervised learning techniques including clustering, random forests, etc. We will conclude with an introduction to neural networks and object tracking.
Graduate students, post-docs, and other scientists interested in learning how to apply data science to their research should attend this tutorial. The lectures will provide an introduction to data science and its applications in physics. We assume that participants will have some experience with Python, Numpy, and Matplotlib at the level of a software carpentry course and we will provide a link to learning materials before the tutorial.
Topics covered:
Data visualization and exploratory data analysis
Unsupervised learning
Convolutional neural networks

Keywords: Tutorial; Machine Learning; Deep Learning; Data Science

  • Open Access Logo Invited lecture (Conferences)
    March Meeting 2024, 03.-08.03.2024, Minneapolis, Minnesota, USA

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Permalink: https://www.hzdr.de/publications/Publ-38943


Data Publication: Positron emission tomography quantifies crystal surface reactivity during sorption reactions

Schöngart, J.; Kulenkampff, J.; Fischer, C.

This dataset contains time resolved positron emission tomography (pet) images of a transport study in artificial sediment, as well as ct images of the used sample.

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Permalink: https://www.hzdr.de/publications/Publ-38931


Collective out-of-plane magnetization reversal in tilted stripe domain systems via a single point of irreversibility

Heinig, P.; Salikhov, R.; Samad, F.; Fallarino, L.; Patel, G. I.; Kakay, A.; Kiselev, N. S.; Hellwig, O.

Periodic magnetic stripe domain patterns are a prominent feature of perpendicular anisotropy thin film systems. Here, we focus on the behavior of [Co(3.0 nm)/Pt(0.6 nm)]\textsubscript{$X$} multilayers within the transitional regime from preferred in-plane (IP), $X=6$, to out-of-plane (OOP), $X=22$, magnetization orientation, particularly, we examine a sample with $X=11$ repetitions, which exhibits a remanent state characterized by a significant presence of both OOP and IP magnetization components, here referred to as the "tilted" stripe domain state*. We investigate this specific sample with vibrating sample magnetometry, magnetic force microscopy and micromagnetic simulations, and find an unusual OOP field reversal behavior via a remanent parallel stripe domain state and a single point of irreversibility. Finally, we show that this characteristic reversal behavior is a rather general feature of transitional IP to OOP systems by comparing the Co/Pt multilayers with c-axis single Co thin films and Fe/Gd multilayers. \newline *[L. Fallarino et al., Phys. Rev. B 99, 024431 (2019)]

Keywords: tilted magnetization; single point of irreversibility; Co/Pt multilayer

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  • Poster
    87. Jahrestagung der DPG und DPG-Frühjahrstagung, 17.-22.03.2024, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38928


Understanding the collective out-of-plane magnetization reversal in tilted stripe domain systems via a single point of irreversibility

Heinig, P.; Salikhov, R.; Samad, F.; Fallarino, L.; Patel, G. I.; Kakay, A.; Kiselev, N. S.; Hellwig, O.

Perpendicular anisotropy thin film systems are well known for their periodic magnetic stripe domain structures. In this study, we focus on investigating the behavior of [Co(3.0 nm)/Pt(0.6 nm)]\textsubscript{$X$} multilayers within the transitional regime from preferred in-plane (IP) to out-of-plane (OOP) magnetization orientation, particularly, we examine the sample with $X=11$ repetitions, which exhibits a remanent state characterized by a significant presence of both OOP and IP magnetization components, here referred to as the "tilted" stripe domain state*. Using vibrating sample magnetometry, magnetic force microscopy and micromagnetic simulations we investigate this specific sample and find an unusual OOP field reversal behavior via a remanent parallel stripe domain state and a single point of irreversibility. While the reversal via distinct points of irreversibility is qualitatively similar to that of a nano-sized Stoner Wohlfarth particle or a vortex reversal in a micron-sized IP magnetized disk, our system is macroscopic. Finally, we show that this characteristic behavior is a rather general feature of transitional IP to OOP systems. \newline *[L. Fallarino et al., Phys. Rev. B 99, 024431 (2019)]

Keywords: tilted magnetization; single point of irreversibility; Co/Pt multilayer

Involved research facilities

Related publications

  • Lecture (Conference)
    87. Jahrestagung der DPG und DPG-Frühjahrstagung, 17.-22.03.2024, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38927


Evidence of free-bound transitions in warm dense matter

Dornheim, T.; Böhme, M.; Kraus, D.; Preston, T.; Döppner, T.; Moldabekov, Z.; Baczewski, A.; Fletcher, L.; Vorberger, J.

Warm dense matter (WDM) is now routinely created and probed in laboratories
around the world, providing unprecedented insights into conditions achieved in
stellar atmospheres, planetary interiors, and inertial confinement fusion
experiments. However, the interpretation of these experiments is often filtered
through models with systematic errors that are difficult to quantify. Due to the
simultaneous presence of quantum degeneracy and thermal excitation, processes in
which free electrons are de-excited into thermally unoccupied bound states
transferring momentum and energy to a scattered x-ray photon become viable [1].
Here we show that such free-bound transitions are a particular feature of WDM and
vanish in the limits of cold and hot temperatures. The inclusion of these processes
into the analysis of recent X-ray Thomson Scattering (XRTS) experiments on
WDM at the National Ignition Facility [2] (see the figure below) and the Linac
Coherent Light Source [3] significantly improves model fits, indicating that free-
bound transitions have been observed without previously being identified. This
interpretation is corroborated by agreement with a recently developed model-free
thermometry technique [4,5] and presents an important step for precisely
characterizing and understanding the complex WDM state of matter.

  • Poster
    Current challenges in the physics of white dwarf stars, 25.-29.03.2024, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-38925


Breaking the vicious cycle of warm dense matter diagnostics

Dornheim, T.

Matter at extreme densities and temperatures displays a complex quantum behavior that is characterized by Coulomb interactions, thermal excitations, and partial ionization. Such warm dense matter (WDM) is ubiquitous throughout the universe and occurs in a host of astrophysical objects such as giant planet interiors and white dwarf atmospheres. A particularly intriguing application is given by inertial confinement fusion, where both the fuel capsule and the ablator have to traverse the WDM regime in a controlled way to reach ignition.

In practice, rigorously understanding WDM is highly challenging both from experimental measurements and numerical simulations [1]. On the one hand, interpreting and diagnosing experiments with WDM requires a suitable theoretical description. One the other hand, there is no single method that is capable of accurately describing the full range of relevant densities and temperatures, and the interpretation of experiments is, therefore, usually based on a number of de-facto uncontrolled approximations. The result is the vicious cycle of WDM diagnostics: making sense of experimental observations requires theoretical modeling, whereas theoretical models must be benchmarked against experiments to verify their inherent assumptions.

In this work, we outline a strategy to break this vicious cycle by combining the X-ray Thomson scattering (XRTS) technique [2] with new ab initio path integral Monte Carlo (PIMC) capabilities [3,4,5]. As a first step, we have proposed to interpret XRTS experiments in the imaginary-time (Laplace) domain, which allows for the model-free diagnostics of the temperature [6] and normalization [7]. Moreover, by switching to the imaginary-time, we can directly compare our quasi-exact PIMC calculations with the experimental measurement [5]. This opens up novel ways to diagnose the experimental conditions, as we have recently demonstrated for the case of strongly compressed beryllium at the National Ignition Facility.

Our results open up new possibilities for improved XRTS set-ups that are specifically designed to be sensitive to particular parameters of interest [8]. Moreover, the presented PIMC capabilities are important in their own right and will allow for a gamut of applications, including equation-of-state calculations and the estimation of structural properties and linear response functions.

[1] T. Dornheim et al., Phys. Plasmas 30, 032705 (2023)
[2] S. Glenzer and R. Redmer, Rev. Mod. Phys. 81, 1625 (2009)
[3] T. Dornheim et al., J. Phys. Chem. Lett. 15, 1305-1313 (2024)
[4] T. Dornheim et al., arXiv:2403.01979
[5] T. Dornheim et al., arXiv:2402.19113
[6] T. Dornheim et al., Nature Commun. 13, 7911 (2022)
[7] T. Dornheim et al., arXiv:2305.15305
[8] Th. Gawne et al., arXiv:2403.02776

  • Lecture (others)
    Theory Seminar at Sandia National Laboratory, 20.03.2024, Albuquerque, USA

Permalink: https://www.hzdr.de/publications/Publ-38924


SE(3)-Transformers for predicting the electronic structure of hydrogen molecules

Brzoza, B.; Cangi, A.

In this work, we demonstrate the efficacy of a neural network model
implemented as the Materials Learning Algorithms (MALA) package
in predicting the electronic structure of a system of hydrogen molecules
under various pressure and temperature conditions across the molecular liquid-solid phase boundary, demonstrating the potential of our
methods for molecular systems. Additionally, we investigate the use
of SE(3)-Transformer Graph Neural Networks to improve the generalizability and extrapolation capabilities of our models. Our results
indicate that the MALA framework provides a powerful and efficient
tool for accelerating Kohn-Sham density functional theory calculations
in molecular systems. This work paves the way for future research in
developing advanced machine-learning algorithms for accelerating electronic structure calculations both accurately and efficiently.

Keywords: MALA; DFT; GNN; SE(3); Equivariant; Neural Networks; Electronic Structure

  • Lecture (Conference)
    DPG Spring Meeting, 18.-21.03.2024, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38901


Metalloid-doping in SMoSe Janus layers: first-principles study on efficient catalysts for the hydrogen evolution reaction

Vallinayagam, M.; Karthikeyan, J.; Posselt, M.; Devaraj, M.; Zschornak, M.

B, Si, and Ge dopants are inserted into SMoSe Janus layers (JLs) at Mo, S, and Se as well as at interstitial sites. Spin-polarized density functional theory calculations are employed to investigate the modified structural and electronic properties of the layers, the energetics of dopant incorporation, and the effect of doping on the interaction of the two-dimensional material with hydrogen. The detailed structural analysis exposes the influence of dopant atomic sizes on lattice distortion. The formation energy Ef of dopant X (X = B, Si, and Ge) at substitutional and interstitial sites is studied for two different chemical environments: (i) bulk X – or X-rich conditions, and (ii) dimer X2 – or X-poor conditions. It is found that under X-poor conditions, the stability of the dopants is always higher. Doping at the S site is energetically most favored, with EBf < ESif < EGef . The electron redistribution in the JLs due to the presence of dopants is explored using Bader analysis. Atomic sites with a number of electrons different from that on atoms in pristine SMoSe JLs may be potential hydrogen traps and are therefore interesting for the hydrogen evolution reaction (HER). Consequently, the interaction of H atoms with these sites is studied and the H adsorption energy is calculated. While pristine SMoSe JLs repel H, several attractive sites are found in the vicinity of the dopant atoms. In order to quantify the feasibility of the doped SMoSe JLs for use as a catalyst for the HER, the free adsorption energy is determined. The data show that all dopants may improve SMoSe for HER applications. The most favorable sites are B at S and Se, Si at Mo and S, and Ge at Mo and S. In particular, adsorption and desorption of H on B-doped (at S and Se sites) and on Ge doped (at an Mo site) JLs may be rapid. The present results demonstrate the potential of metalloid doped , SMoSe JLs as efficient HER catalysts.

Keywords: 2D materials; SMoSe Janus structures; metalloid doping; first-principle study; hydrogen evolution reaction

  • Open Access Logo Journal of Materials Chemistry A 12(2024), 7742-7753
    Online First (2024) DOI: 10.1039/d3ta07243f

Permalink: https://www.hzdr.de/publications/Publ-38900


Data publication: Ion-beam induced compositional and structural changes of Al-Cu-Co multilayer stacks

Černičková, I.; Noga, P.; Ďuriška, L.; Kusý, M.; Novaković, M.; Potočnik, J.; Ziegenrücker, R.; Halanda, J.; Janovec, J.

Measurement results, obtained with a CAMECA IMS 7f-auto, of an as-deposited sample and a sample after 500°C thermal treatment.

Keywords: Multilayer; Nanolayer; Heating; Ion-beam mixing; Electron microscopy; Ion irradiation

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Permalink: https://www.hzdr.de/publications/Publ-38898


Ion-beam induced compositional and structural changes of Al-Cu-Co multilayer stacks

Černičková, I.; Noga, P.; Ďuriška, L.; Kusý, M.; Novaković, M.; Potočnik, J.; Ziegenrücker, R.; Halanda, J.; Janovec, J.

The present work deals with the investigation of ion-beam assisted annealing/mixing effects on compositional and structural changes in Al-Cu-Co multilayers. 800 nm thick Al₆₄Cu₂₀Co₁₆ multilayers prepared by magnetron sputtering deposition, consisting of 28 successive single-metal Al-, Cu-, and Co-nanolayers were treated by thermal annealing at 300°C, 400°C, or 500°C as well as ion irradiation by 30 MeV Cu⁵⁺ ions at fluences of 1x10¹³ to 5x10¹⁴ with an average flux of 2.38×10¹⁰ at.cm⁻²s⁻¹. The samples were characterized with SEM, EDX, XRD, and TEM including HAADF. In contrast to the original multilayer, the treated samples were found to consist of two types of alternating nanolayers. A wider coarse-grained structurally and chemically homogeneous single-phase nanolayer formed by Al₂Cu, and a narrow fine-grained two-phase nanolayer, which has a heterogeneous composite structure in which the central Co sublayer (being a residue of the original single-metal Co nanolayer) is surrounded from both sides with Al-Co sublayers, consisting of Al₉Co₂. This Co sublayer is considered to be a diffusion blocker for Al and Cu as well as hindering the movement of borders between particular nanolayers. The formation of a ternary phase in the investigated samples was not confirmed in any of the samples.

Keywords: Multilayer; Nanolayer; Heating; Ion-beam mixing; Electron microscopy; Ion irradiation

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Permalink: https://www.hzdr.de/publications/Publ-38896


Cobalt-based Co3Mo3N/Co4N/Co Metallic Heterostructure as a Highly Active Electrocatalyst for Alkaline Overall Water Splitting

Liu, Y.; Wang, L.; Hübner, R.; Kresse, J.; Zhang, X.; Deconinick, M.; Vaynzof, Y.; Weidinger, I. M.; Eychmüller, A.

Alkaline water electrolysis holds promise for large-scale hydrogen production, yet it encounters challenges like high voltage and limited stability at higher current densities, primarily due to inefficient electron transport kinetics. Herein, a novel cobalt-based metallic heterostructure (Co3Mo3N/Co4N/Co) is designed for excellent water electrolysis. In operando Raman experiments reveal that the formation of the Co3Mo3N/Co4N heterointerface boosts the free water adsorption and dissociation, increasing the available protons for subsequent hydrogen production. Furthermore, the altered electronic structure of the Co3Mo3N/Co4N heterointerface optimizes ΔGH of the nitrogen atoms at the interface. This synergistic effect between interfacial nitrogen atoms and metal phase cobalt creates highly efficient active sites for the hydrogen evolution reaction (HER), thereby enhancing the overall HER performance. Additionally, the heterostructure exhibits a rapid OH- adsorption rate, coupled with great adsorption strength, leading to improved oxygen evolution reaction (OER) performance. Crucially, the metallic heterojunction accelerates electron transport, expediting the afore-mentioned reaction steps and enhancing water splitting efficiency. The Co3Mo3N/Co4N/Co electrocatalyst in the water electrolyzer delivers excellent performance, with a low 1.58 V cell voltage at 10 mAcm-2, and maintains 100% retention over 100 hours at 200 mAcm-2, surpassing the Pt/C // RuO2 electrolyzer.

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Permalink: https://www.hzdr.de/publications/Publ-38895


Data publication: Machine Learning-Driven Structure Prediction for Iron Hydrides

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

Here, we provide the training datasets and the resulting neural network potential for exploring the potential energy surfaces of the FeH system using the minima hopping method. Additionally, data for the minima structures identified in this work are included.

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Permalink: https://www.hzdr.de/publications/Publ-38894


Pressure-transferable neural network models for density-functional theory

Callow, T. J.; Fiedler, L.; Modine, N.; Cangi, A.

Density functional theory (DFT) is well-known as the workhorse of electronic structure calculations in materials science and quantum chemistry. However, its applications stretch beyond these traditionally-studied fields, such as to the warm-dense matter (WDM) regime. Under WDM conditions, there are different challenges to consider (compared to ambient conditions) when using DFT. Namely, the electronic structure problem must be solved (i) for large particle numbers, (ii) for a range of temperatures, and (iii) for a range of pressures. Promising solutions were demonstrated for problems (i) and (ii) [1,2] using a recently-developed workflow to machine-learn the local density of states (LDOS) [3]. In this talk, we discuss our progress in developing a solution for problem (iii). This problem presents additional challenges because the LDOS varies quite significantly with changes in the pressure, making it a difficult problem for neural network models.

[1] L Fiedler et al., npj Comput Mater 9, 115 (2023) [2] L Fiedler et al., Phys. Rev. B 108, 125146 (2023) [3] J. A. Ellis et al., Phys. Rev. B 104, 035120 (2021)

  • Lecture (Conference)
    87th Annual Conference of the DPG and DPG Spring Meeting, 17.-22.03.2024, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38892


Optimization of membraneless alkaline water electrolysis

Rox, H.; Gatter, J.; Frense, E.; Schoppmann, K.; Rüdiger, F.; Krause, L.; Yang, X.; Mutschke, G.; Fröhlich, J.; Eckert, K.

Objectives
Membraneless alkaline electrolyzer (MAEL) allow higher current densities compared to conventional designs [1] and provide very good access to the electrodes, making them ideal for research to better understand bubble formation and detachment.

Methods
In the present study both elements of a MAEL, porous electrodes and cell geometry, are optimized individually. For the geometrical optimization, CFD and current simulations were performed to obtain an optimized cell geometry that ensures constant conditions for the water splitting reaction over the entire electrode area. A three-electrode cell was used to perform parametric studies of HER on porous electrodes [2] and functionalized surfaces [3]. Therefore, Particle Image Velocimetry and Shadowgraphy were used to systematically study the influence of the electrode surface and the electrolyte flow as driving force for an effective H2 and O2 separation in a MAEL.

Results & Conclusions
It is shown that below a critical Recrit the evolving bubbles are stuck on the porous electrodes and lead to a blockage of the electrochemical active sites and to an increase of the cell potential. At the optimal flow rate to current density ratio high gas purity and overall efficiency were observed. Importantly, this study presented an experimental framework that guides the electrode and cell design of MAELs and analyzes their performance limits.

Literature
[1] D.V. Esposito, Joule. 2017, 1, 651-658.
[2] H. Rox et al., Int. J. Hydrog. Energy. 2023, 48, 2892-2905.
[3] L. Krause et al., ACS Applied Materials & Interfaces. 2023, 15, 14, 18290-18299.

Keywords: Alkaline electrolysis; Membraneless electrolyzer; Bubble dynamics; Shadowgraphy; PIV

Involved research facilities

  • Data Center
  • Lecture (Conference)
    HydrogenDays 2024, 21.03.2024, Prague, Czech republic

Permalink: https://www.hzdr.de/publications/Publ-38888


Towards tailoring hydrophobic interaction with uranyl(VI) oxygen for C-H activation

Tsushima, S.; Kretzschmar, J.; Doi, H.; Okuwaki, K.; Kaneko, M.; Mochizuki, Y.; Takao, K.

Bovine serum albumin (BSA) has a uranyl(VI) binding hotspot where uranium is tightly bound by three carboxylates. Uranyl oxygen is “soaked” into the hydrophobic core of BSA. Isopropyl hydrogen of Val is trapped near UO22+ and upon photoexcitation, C–H bond cleavage is initiated. A unique hydrophobic contact with “yl”-oxygen, as observed here, can be used to induce C-H activation.

Permalink: https://www.hzdr.de/publications/Publ-38885


Optimization of Heat and Mass Transfer via Nano/Micro-Structured Surfaces: utilizing energy barriers between states and “semi-dimensional reduction”

Ding, W.; Zhang, J.; Zhao, P.; Reinecke, S.; Hampel, U.

Energy barriers inhibit the transition of a system from one state to another. This is evident in phenomena such as bubble nucleation during boiling, droplet expansion and contraction when it impacts a heated surface, and also cavitation. In this presentation, we will elucidate our insights and understanding of the exploitation of energy barriers post-state transition to augment heat and mass transfer in various processes. Specifically, in processes like bubble nucleation in boiling, the high energy required for nucleation (attributable to the energy barrier) triggers rapid bubble expansion and results in a semi-2D microlayer, just a few micrometers thin, on the surface. This can be viewed as a typical semi-dimensional reduction effect, transitioning a part of system from 3D to 2D. As a result, this thin liquid layer brings high efficiency on heat transfer. A similar phenomenon occurs when a droplet impacts a heated surface. Following impact, the droplet’s expansion and contraction on the surface incite capillary waves that propagate along the droplet interface, inducing a semi-1D, prickle-like jet along the droplet’s axis on the top side. This jet disrupts the vapor film beneath the droplet, expelling the vapor and delaying the Leidenfrost point. As a one more thing, cavitation, one of the most typical cases of ‘dimensional reduction’, utilizes a reduction from 3D to 0D and also the large energy barrier for bubble nucleation. Following bubble collapse, the local temperature and pressure reach 5000 K and ~ Mpa, respectively. Combined with O3, this effect facilitates a highly efficient oxidation process.

  • Invited lecture (Conferences)
    4th Conference on Micro FLow and Interfactial Phenomena (µFIP) 2024, 21.-24.06.2024, The Hong Kong Polytechnic University, HongKong, China

Permalink: https://www.hzdr.de/publications/Publ-38883


Applying an Explicit Temperature-dependent Generalized Gradient Approximation to Warm Dense Matter: Thermal PBE

Ramakrishna, K.; Lokamani, M.; Cangi, A.

Using the methodology of Kozlowski et al. [arXiv 2308.03319 (2023)] to extend the temperature dependence of the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation, we implement the thermal equivalent of the PBE functional (tPBE) in a plane wave code to study the equilibrium properties such as energies, pressures, and forces of warm dense matter using density functional theory and linear-response properties such as the electrical conductivity, dynamic structure factor using time-dependent density functional theory. In addition, we compare the effects with the thermal equivalent of LDA and the ground-state LDA and PBE functionals.

Keywords: Density functional theory; Matter under Extreme Conditions

  • Lecture (Conference)
    APS March Meeting 2024, 04.-08.03.2024, Minneapolis, USA

Permalink: https://www.hzdr.de/publications/Publ-38880


Structure prediction of iron hydrides across pressure range with transferable machine-learned interatomic potential

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

Recently, machine-learned interatomic potentials (ML-IAPs) have emerged as a solution to the computational limitations of density functional theory (DFT)-based approaches, enabling the modeling of large systems with hundreds or even thousands of atoms. Here, we demonstrate the efficacy of automated and systematic methods for training and validating transferable ML-IAPs through global optimization techniques.

We utilize the PyFLAME code [1] to construct a highly transferable neural network potential. With this accurate and fast potential, we systematically investigate the potential energy surfaces (PESs) of FeH through global sampling using the minima hopping method [2] over a wide range of pressures. This comprehensive exploration enables us to predict stable and metastable iron hydrides from 0 to 100 GPa.

Our analysis reveals the experimentally observed global minimum structures -the dhcp, hcp, and fcc phases- in agreement with previous studies. Furthermore, our exploration of the PESs of FeH at various pressures uncovers numerous interesting modifications and stacking faults of the aforementioned phases, including several remarkably low-enthalpy structures.

This investigation led to the discovery of a rich array of novel stoichiometric crystal phases of FeH across a wide pressure range, confirming the presence of coexisting regions containing known FeH structures. This finding demonstrates one of the benefits of using large-scale structure prediction techniques to uncover the PESs of materials.

[1] H. Mirhosseini, H. Tahmasbi, S. R. Kuchana, S. A. Ghasemi, and T. D. Kühne, Comput. Mater. Sci. 197, 110567 (2021).

[2] M. Amsler and S. Goedecker, J. Chem. Phys. 133, 224104 (2010).

  • Open Access Logo Lecture (Conference)
    APS MArch meeting 2024, 04.-08.03.2024, Minneapolis, US

Permalink: https://www.hzdr.de/publications/Publ-38878


Dynamics of particle attachment in a model stirred cell: A new technique to characterize and quantify particle floatability

Eftekhari, M.; Schwarzenberger, K.; Schlereth, P.; Eckert, K.

Floatability evaluation is critical to predicting flotation results and designing a flotation flowsheet. Laboratory-scale flotation cells are commonly used to study particle floatability, but differences in cell design and governing hydrodynamics make extrapolation to industrial scale operations difficult.
In this work, a new experimental approach based on particle attachment dynamics is proposed to evaluate particle floatability. This method allows precise control of hydrodynamic conditions, visualization of attachment processes, and direct observation of the bubble surfaces. It is therefore ideal for studying attachment dynamics as a function of collector concentration, particle size and concentration, and propeller speed. In addition, it opens the possibility for future studies of the packing density of the particles at the interface and their selective attachment. By evaluating the time-dependent surface coverage as a function of bubble residence time, we illustrate its ability to predict flotation kinetics within a flotation cell. This innovative technique provides a faster, more versatile means of studying particle floatability and attachment dynamics with practical implications for flotation cell optimization.

Keywords: Floatability; Stirred cell; Particle-bubble interactions; Dynamic surface coverage; Flotation kinetics

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Permalink: https://www.hzdr.de/publications/Publ-38871


Recent extensions to the NUSAR-RCS IT environment

Lehnigk, R.; Hänsch, S.; Schlegel, F.; Lucas, D.

Due to the growing importance of Computational Fluid Dynamics (CFD) for reactor safety research, there have been activities aimed at qualifying the associated methods for many years. This entails the development and validation of models on the basis of detailed experimental data, generated in comprehensive projects. There was and is a need for development, among other things, for multiphase flows, in particular for accident scenarios in the reactor coolant system. In order to be able to use the model developments and validation data generated throughout various publicly funded projects in the long term, these are carried out using the software provided by the OpenFOAM Foundation, which is thereby qualified for application. The project presented here is funded by the German Federal Ministry for Environment, Nature Conservation, Nuclear Safety and Consumer Protection (project number 1501658) and has the objective of gathering and maintaining addon software and simulation setups from partner institutions in a common repository, referred to as "Nuclear Safety Repository for OpenFOAM Foundation Software for Reactor Cooling System (NUSAR-RCS)". To this end, a GitLab-based IT environment has been developed that fosters collaborative developments and facilitates the maintenance of results from completed projects. The talk will highlight some recent additions to the environment. The first part is dedicated to a Python package, which, among other things, supplies functionality for bulk processing of simulation results, e.g. to extract global information on the agreement between simulation and experiment using statistical key figures. The second part will present efforts of making the NUSAR-RCS software more portable by means of containerization using Apptainer images.

  • Lecture (Conference)
    35th German CFD Network of Competence Meeting, 12.-13.03.2024, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38870


Repulsive Tomonaga-Luttinger liquid in the quasi-one-dimensional alternating spin-1/2 antiferromagnet NaVOPO4

Islam, S. S.; Mukharjee, P. K.; Biswas, P. K.; Telling, M.; Skourski, Y.; Ranjith, K. M.; Baenitz, M.; Inagaki, Y.; Furukawa, Y.; Tsirlin, A. A.; Nath, R.

We probe the magnetic field-induced Tomonaga-Luttinger liquid (TLL) state in the bond-alternating spin-1/2 antiferromagnetic (AFM) chain compound NaVOPO4 using thermodynamic as well as local μSR and 31P NMR probes down to mK temperatures in magnetic fields up to 14 T. The μSR and NMR relaxation rates in the gapless TLL regime decay slowly following characteristic power-law behavior, enabling us to directly determine the interaction parameter K as a function of the magnetic field. These estimates are crosschecked using magnetization and specific heat data. The field-dependent K lies in the range of 0.4 < K < 1 and indicates the repulsive nature of interactions between the spinless fermions, in line with the theoretical predictions. This renders NaVOPO4 the first experimental realization of TLL with repulsive fermionic interactions in hitherto studied S = 1/2 bond-alternating AFM-AFM chain compounds.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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Permalink: https://www.hzdr.de/publications/Publ-38863


Field-induced magnetic transitions in the highly anisotropic ferrimagnet ErFe5Al7 studied by high-field x-ray magnetic dichroism

Yamamoto, S.; Gorbunov, D.; Prokhnenko, O.; Weschke, E.; Miyata, A.; Diaz-Ortega, I. F.; Strohm, C.; Duc, F.; Henriques, M. S.; Gazizulina, A.; Uhlarz, M.; Mathon, O.; Andreev, A. V.; Nojiri, H.; Wosnitza, J.

We present a comprehensive study of the magnetic properties of the strongly anisotropic ferrimagnet ErFe5Al7 in pulsed magnetic fields up to 30 T applied along the hard magnetization axis within the basal plane of the tetragonal lattice around the compensation temperature (Tcomp). Macroscopic measurements showed two anomalies at about 8 T and 25 T in a small temperature range around Tcomp. High-field x-ray magnetic circular dichroism (XMCD) data at the Er M5- and the Fe L3-edge resonances provide insight into the element-selective magnetization processes, revealing a coherent rotation of Er 4f and Fe 3d moments, with stepwise jumps including an unexpected one from an easy to a hard magnetization axis. XMCD at the Er L3-edge resonance elucidates the role of Er 5d electrons in coupling the Er 4f and the Fe 3d moments. Finally, an in-plane anisotropy constant was evaluated from a simulation of the magnetization process at temperatures well below Tcomp using a two-sublattice model.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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  • Secondary publication expected from 05.03.2025

Permalink: https://www.hzdr.de/publications/Publ-38862


Pressure-tuned quantum criticality in the large-D antiferromagnet DTN

Povarov, K.; Graf, D. E.; Hauspurg, A.; Zherlitsyn, S.; Wosnitza, J.; Sakurai, T.; Ohta, H.; Kimura, S.; Nojiri, H.; Garlea, V. O.; Zheludev, A.; Paduan-Filho, A.; Nicklas, M.; Zvyagin, S.

Strongly correlated spin systems can be driven to quantum critical points via various routes. In particular, gapped quantum antiferromagnets can undergo phase transitions into a magnetically ordered state with applied pressure or magnetic field, acting as tuning parameters. These transitions are characterized by z = 1 or z = 2 dynamical critical exponents, determined by the linear and quadratic low-energy dispersion of spin excitations, respectively. Employing high-frequency susceptibility and ultrasound techniques,we demonstrate that the tetragonal easy-plane quantum antiferromagnet NiCl2 ⋅ 4SC(NH2)2 (aka DTN) undergoes a spin-gap closure transition at about 4.2 kbar, resulting in a pressure-induced magnetic ordering. The studies are complemented by high-pressure electron-spin-resonance measurements confirming the proposed scenario. Powder neutron diffraction measurements revealed that no lattice distortion occurs at this pressure and the high spin symmetry is preserved, establishing DTN as a perfect platform to investigate z = 1 quantum critical phenomena. The experimental observations are supported by DMRG calculations, allowing us to quantitatively describe the pressure-driven evolution of critical fields and spin-Hamiltonian parameters in DTN.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-38861


A guide to advanced MRI processing for clinical glioma research

Clement, P.; Beun, S.; Arzanforoosh, F.; Castellaro, M.; Debiasi, G.; Emblem, K. E.; Fuster-Garcia, E.; Grech-Sollars, M.; Kallehauge, J. F.; Lazen, P.; Nunes, R. G.; Ozturk-Isik, E.; Pinto, J.; Piskin, S.; Robinson, S. D.; Siugzdaite, R.; Sollmann, N.; Fløgstad Svensson, S.; Warnert, E. A. H.; Wiegers, E.; Petr, J.; Hangel, G.

Todate,multipleadvancedmagneticresonanceimaging(MRI)methodsbeyondconventionalqualitativestructuralimagingforthediagnosis,prognosis,andtreatmentfollow-upofgliomahavedemonstratedtheirutilityforclinicalstudies.However,thesemethodsoftenrelyoncomplexoff-scannerprocessingtoyieldthemostinformationandtoextractquantitativebiomarkers,limitingtheirpracticaluseforstudies,aswellastheirclinicaltranslation.Whilecommunity-drivensoftwaresolutionsexistfortheseadvancedMRImethods,manyaspiringclinicalresearchersfacechallengesinacquiringthenecessaryknowledgetoeffectivelyapplythesetools.Thisguide,aninitiativeoftheGliomaMRimaging2.0network(GliMR),aimstoprovideanoverviewofexistingsolutions,communities,andrepositorieswiththeultimategoalofenablingstandardization,openscience,andreproduciblequantitativeimagingstudiesofgliomas.Yet,mostofthereviewedtoolsandapproachestoimagedataanalysesmayalsobeusedinthecontextofstudiesondiseasesotherthanglioma.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-38856


NuScale SLB analysis with TrioCFD/ATHLET/DYN3D

Grahn, A.; Diaz Pescador, E.; Bilodid, Y.; Kliem, S.

The small modular reactor (SMR) NuScale has been modelled in the framework of the EURATOM McSAFER project. The main objective was to demonstrate the feasibility of a coupled approach using a thermal-hydraulic system code (ATHLET), a 3-D reactor dynamics code (DYN3D) and a CFD software (TrioCFD) to model the whole primary coolant loop and large parts of the secondary side of the plant, including the downcomer-integrated, helical-coiled steam generators (SG) and the decay heat removal system (DHRS). The 3-D neutronic calculation of the reactor core was performed with a cross-section library developed with Serpent, and the coolant flow in the downcomer and lower plenum of the pressure vessel was analyzed by CFD. A double-ended, non-isolatable steam line break sequence served as a test case for the code coupling. Simulation results at steady-state show agreement with the reference values from the Design certification Application (DCA) report. The transient simulation shows that the rapid depressurization and boil-off with high steam rates towards the break lead to enhanced primary-to-secondary heat removal. However, the symmetrical arrangement of SGs in the NuScale reactor limits the coolant temperature reduction at the core inlet to prevent a possible power excursion which highlights the inherent safety of this reactor design.

Keywords: small modular reactors; steam line break; thermal-hydraulics; reactor dynamics; system codes; computational fluid dynamics

  • Lecture (Conference)
    Workshop on Core and Plant Simulation with an Emphasis on Fuel Behaviour in Light Water Reactor based Small Modular Reactors, 27.-29.02.2024, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-38855


Developing blood-brain barrier arterial spin labelling as a non-invasive early biomarker of Alzheimer’s disease (DEBBIE-AD): a prospective observational multicohort study protocol

Padrela, B.; Mahroo, A.; Tee, M.; Sneve, M. H.; Moyaert, P.; Geier, O.; Kuijer, J. P. A.; Beun, S.; Nordhøy, W.; David Zhu, Y.; Buck, M. A.; Hoinkiss, D. C.; Konstandin, S.; Huber, J.; Wiersinga, J.; Rikken, R.; de Leeuw, D.; Grydeland, H.; Tippett, L.; Cawston, E. E.; Ozturk-Isik, E.; Linn, J.; Brandt, M.; Tijms, B. M.; van de Giessen, E. M.; Muller, M.; Fjell, A.; Walhovd, K.; Bjørnerud, A.; Pålhaugen, L.; Selnes, P.; Clement, P.; Achten, E.; Anazodo, U.; Barkhof, F.; Hilal, S.; Fladby, T.; Eickel, K.; Morgan, C.; Thomas, D. L.; Petr, J.; Günther, M.; Mutsaerts, H. J. M. M.

Introduction Loss of blood-brain barrier (BBB) integrity is
hypothesised to be one of the earliest microvascular signs
of Alzheimer’s disease (AD). Existing BBB integrity imaging
methods involve contrast agents or ionising radiation, and
pose limitations in terms of cost and logistics. Arterial
spin labelling (ASL) perfusion MRI has been recently
adapted to map the BBB permeability non-invasively. The
DEveloping BBB-ASL as a non-Invasive Early biomarker
(DEBBIE) consortium aims to develop this modified
ASL-MRI technique for patient-specific and robust BBB
permeability assessments. This article outlines the study
design of the DEBBIE cohorts focused on investigating
the potential of BBB-ASL as an early biomarker for AD
(DEBBIE-AD).
Methods and analysis DEBBIE-AD consists of a
multicohort study enrolling participants with subjective
cognitive decline, mild cognitive impairment and AD, as
well as age-matched healthy controls, from 13 cohorts.
The precision and accuracy of BBB-ASL will be evaluated
in healthy participants. The clinical value of BBB-ASL will
be evaluated by comparing results with both established
and novel AD biomarkers. The DEBBIE-AD study aims to
provide evidence of the ability of BBB-ASL to measure BBB
permeability and demonstrate its utility in AD and ADrelated pathologies.
Ethics and dissemination Ethics approval was obtained
for 10 cohorts, and is pending for 3 cohorts. The results of
the main trial and each of the secondary endpoints will be
submitted for publication in a peer-reviewed journal.

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  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-38853


Experiences from first time RSE class at the Computer Science Faculty of TU Dresden

Juckeland, G.

For the first time, Introduction to Research Software Engineering was offered as a class in the Computer Science faculty of TU Dresden during this winter semester (2023/24) (https://tu-dresden.de/ing/informatik/smt/cgv/studium/lehrveranstaltungen/ws2324/RSE/index). This talk will briefly cover the content, feedback from students and own observations as well as ideas how to continue and extend the class in the future.

  • Open Access Logo Lecture (Conference)
    deRSE24 - Conference for Research Software Engineering in Germany, 05.-07.03.2024, Würzburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-38851


HELIPORT: An overarching Data Management System at HZDR

Müller, S.; Gruber, T.; Juckeland, G.; Kelling, J.; Knodel, O.; Lokamani, M.; Voigt, M.; Pape, D.

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf rely on a variety of systems and tools when it comes to administer their research data. Processes involving research data management include the project planning phase (proposal submission to the beamtime proposal management system, the creation of data management plans and data policies), the documentation during the experiment or simulation campaign (electronic laboratory notebooks, wiki pages), backup- and archival systems and the final journal and data publications (collaborative authoring tools, meta-data catalogs, software and data repositories, publication systems). In addition, modern research projects are often required to interact with a variety of software stacks and workflow management systems to allow reproducibility on the underlying IT infrastructure. The "HELmholtz ScIentific Project WORkflow PlaTform" (HELIPORT), which is currently developed by researchers at HZDR and their collaborators, tries to facilitate the management of research data and metadata by providing an overarching guidance system which combines all the information by interfacing the underlying processes and even includes a workflow engine which can be used to automate processes like data analysis or data retrieval.

Keywords: Data Management; HELIPORT; FAIR

Involved research facilities

  • Data Center
  • Lecture (Conference)
    DPG Spring Meeting 2024 (Section of Particle Physics), 04.-08.03.2024, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-38846


Directed transfer of liquid metal droplets between electrodes

Mutschke, G.; Weier, T.

Electric fields offer an easy means to manipulate liquid metal droplets. Now, directed droplet transfer between immersed electrodes is
achieved in an alkaline electrolyte without electrical short-circuit.

Keywords: electrocapillarity; oxide films; interfacial tension; liquid metal droplets; gallium; mercury; mercury beating heart; gallium beating heart

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  • Secondary publication expected from 02.04.2025

Permalink: https://www.hzdr.de/publications/Publ-38843


Sorption data: Enhancement of geochemical modeling by chemically evident surface speciation

Bok, F.; Zechel, S.; Miron, D.; Marinich, O.; Marques Fernandes, M.

Modeling geochemical scenarios for the safety analyses of disposal of hazardous radioactive and (chemo)toxic waste requires comprehensive and consistent thermodynamic data as well as sorption data for the surrounding host rocks. Whereas there are several projects running worldwide to develop at the comprehensive and consistent thermodynamic database for the aqueous phase and forming solids, the situation is much more complicated concerning the reactions on the mineral-water interface. For sorption data, there is currently no database providing quality assured thermodynamic surface complexation modeling (SCM) data. Even though spectroscopic methods to determine the actual surface species have made great progress in recent years, the SCM data still contain questionable to assuredly non-existent species. This leads to hardly comparable results in geochemical modeling.
To address this problem, publicly available SCM (protolysis and sorption) data are currently being reevaluated and new reaction data are generated building on spectroscopically evidenced surface complexes. Critical data gaps shall be closed by the use of analogies (for both radionuclides’ chemistry as well as the mineral phases) or established estimation methods (e.g. linear free energy relationship). The RES³T sorption database¹, the PSI Chemical Thermodynamic Database² as well as the LLNL’s sorption raw data compilation³ provide the solid basis for this work. In combination with surface site density data from crystallographic calculations, this approach yields realistic and robust models that significantly improve sorption in geochemical calculations e.g. through so-called smart Kd values⁴. The results of this work will be published within the THEREDA framework⁵ including ready-to-use parameter files for common geochemical codes (e.g. GEMS, Geochemist’s Workbench, PHREEQC).
This work is funded by BGE – the federal company for radioactive waste disposal in Germany, with the contract number TEKFuE-21-03-js.
References:
1) RES³T – Rossendorf Expert System for Surface and Sorption Thermodynamics, Helmholtz-Zentrum Dresden-Rossendorf, (https://www.hzdr.de/res3t)
2) PSI Chemical Thermodynamic Database (https://www.psi.ch/de/les/thermodynamic-databases).
3) Smart-Kd concept (https://www.smartkd-concept.de/)
4) Zavarin M. et al. (2022): Community Based Data of Uranium Adsorption onto Quartz, ESS-DIVE repository, DOI: 10.15485/1880687.
5) THEREDA – Thermodynamic Reference Database (https://www.thereda.de)

Keywords: Sorption Reference Database; SOREDA; Sorption; SCM; Surface Complexation Modelling; Thermodynamic

  • Lecture (Conference)
    American Chemical Society Spring Meeting 2024, 17.-21.03.2024, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-38840


Data publication: X-ray Thomson scattering absolute intensity from the f-sum rule in the imaginary-time domain

Dornheim, T.

This repository contains the raw data for the relevant figures of the article "X-ray Thomson scattering absolute intensity from the f-sum rule in the imaginary-time domain". All data are standard gnuplot output.

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Permalink: https://www.hzdr.de/publications/Publ-38839


Documenting ML Experiments in HELIPORT

Pape, D.; Knodel, O.; Starke, S.

HELIPORT is a data management guidance system that aims at making the components and steps of the entire research experiment’s life cycle findable, accessible, interoperable and reusable according to the FAIR principles. It integrates documentation, computational workflows, data sets, the final publication of the research results, and many more resources. This is achieved by gathering metadata from established tools and platforms and passing along relevant information to the next step in the experiment's life cycle. HELIPORT's high-level overview of the project allows researchers to keep all aspects of their experiment in mind.

A particularly interesting use case are machine learning projects. They are often prototypical in nature and driven by iterative development, so reproducibility and tranparency are a great concern. It is essential to keep track of the relationship between input data, choices in model parameters, the code version in use, and performance measures and generated outputs at all times. This requires a data management platform that automatically records the changes made and their effects. Existing MLOps tools (such as Weights and Biases, MLFlow) live entirely in the ML domain and start their workflow with the assumption that data is available. HELIPORT, on the other hand, takes care of the data lifecycle as well. Our envisioned platform interoperates with the domain specific tools already used by the scientists, and is able to extract relevant metadata (e.g. provenance). It can also make persistent any additional information such as papers the work was based on, documentation of software components, workflows, or failure cases. Moreover, it should be possible to publish these metadata in machine-readable formats.

The challenge arising from these aspects consists in integrating ML workflows into HELIPORT in such a way that they work on the provided data and metadata. The goal is also to enable the comprehensible development of ML models alongside the experiment documented in HELIPORT. This allows different teams (e.g. experimentalists and AI specialists) to work together on the same project in a seamless manner, and help generate FAIRer outcomes. In the long term we hope to aide in establishing digital twins of facilities, and making their maintenance a part of the data management proces.

Keywords: data management; research software engineering; machine learning; metadata; ontologies

  • Open Access Logo Lecture (Conference)
    deRSE24 - 4th Conference for Research Software Engineering in Germany, 05.-07.03.2024, Würzburg, Deutschland
    DOI: 10.5281/zenodo.10807608

Permalink: https://www.hzdr.de/publications/Publ-38838


HZDR Software Policy

Konrad, U.; Bieberle, A.; Bussmann, M.; Grzeganek, M.; Hüser, C.; Huste, T.; Juckeland, G.; Kaever, P.; Moravcikova, M.; Schlegel, F.; Wagner, N.; Wolf, B.

Software is a central component of academic research and the scientific infrastructure and is devel-oped and used in all HZDR institutes. In this regulation, software refers to all forms of program code (e.g. source code together with associated documentation) and executable programs generated from it, which are developed, made available and passed on within the scope of activities at the HZDR. The development of software is an integral part of modern publication contexts consisting of written publica-tions, data sets and software. 

The policy covers the software life cycle, from software development and documentation to the transfer and maintenance of the software. The regulation is intended to support the establishment of modern software engineering methods at the HZDR, which enable high standards in software de-velopment, software quality and management. This professionalization will achieve greater sustain-ability and promote good scientific practice in terms of the verifiability and reproducibility of research results.

Keywords: Research Software Engineering; Software Development; Software Policy; HIFIS; Helmholtz

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Permalink: https://www.hzdr.de/publications/Publ-38813


Connecting Processes to Data via Meta-Data

Knodel, O.

The presentation explores the intricate relationship between data management, computational processes and metadata descriptions. It delves into how metadata serves as a crucial bridge, facilitating the seamless connection between various data processes, RAW and derived data. The importance of the research institute's infrastructure facilities in preparing data and metadata and supporting systems such as Heliport to improve the understanding, accessibility and interoperability of data in different systems was highlighted. This research highlights the central role of metadata in optimising data-driven workflows and promoting efficient data use strategies.

Keywords: Data management; workflows; Machine Learning (ML); Heliport; Thrill

  • Open Access Logo Invited lecture (Conferences)
    Thrill WP5 ML Workshop, 27.-28.02.2024, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-38811


Contribution of black carbon and desert dust to aerosol absorption in the atmosphere of the Eastern Arabian Peninsula

Mahfouz, M. M. K.; Skok, G.; Sciare, J.; Pikridas, M.; Rami Alfarra, M.; Moosakutty, S.; Alfoldy, B.; Ivančič, M.; Rigler, M.; Gregorič, A.; Podlipec, R.; Lohmann, S.; Hlawacek, G.; Heller, R.; Tutsak, E.; Močnik, G.

Discriminating the absorption coefficients of aerosol mineral dust and black carbon (BC) in different aerosol size fractions is a challenge because of BC's large mass absorption cross-section compared to dust. Ambient aerosol wavelength dependent absorption coefficients in supermicron and submicron size fractions were determined with a high time resolution. The measurements were performed simultaneously using identical systems at an urban and a regional background site in Qatar. At each site, measurements were taken by co-located Aethalometers, one with a virtual impactor (VI) and the other with a PM1 cyclone to respectively collect super-micron-enhanced and submicron fractions. The combined measurement of aerosol absorption and scattering coefficients enabled the particles to be classified based on their optical properties' wavelength dependence. The classification reveals the presence of BC internally/externally mixed with different aerosols. Helium ion microscopy images provided information concerning the extent of mineral dust in the submicron fraction. The determination of absorption coefficients during dust storms and non-dust periods was used to establish the absorption Ångström exponent for dust and BC. Non-parametric wind regression, potential source contribution function and back-trajectory analysis reveal major regional sources of desert dust associated with north-westerly winds and a minor local dust contribution. In contrast, major BC sources found locally were associated with south-westerly winds with a smaller contribution made by offshore emissions transported by north-easterly and easterly winds. The use of a pair of Aethalometers with VI and PM1 inlets separates contributions of BC and dust to the aerosol absorption coefficient.

Keywords: helium ion microscopy; him

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Permalink: https://www.hzdr.de/publications/Publ-38810


Nonperturbative Floquet engineering of the toric-code Hamiltonian and its ground state

Petiziol, F.; Wimberger, S.; Eckardt, A.; Mintert, F.

We theoretically propose a quantum simulation scheme for the toric-code Hamiltonian, the paradigmatic model of a quantum spin liquid, based on time-periodic driving. We develop a hybrid continuous-digital strategy that exploits the commutativity of different terms in the target Hamiltonian. It allows one to realize the required four-body interactions in a nonperturbative way, attaining strong coupling and the suppression of undesired processes. In addition, we design an optimal protocol for preparing the topologically ordered ground states with high fidelity. A proof-of-principle implementation of a topological device and its use to simulate the topological phase transition are also discussed. The proposed scheme finds natural implementation in architectures of superconducting qubits with tunable couplings.

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Permalink: https://www.hzdr.de/publications/Publ-38801


Bubble paths in two-phase flows through open-porous foams: Imaging measurements by X-ray and neutron radiography

Lappan, T.; Jiao, G.; Heinrich, J.; Trtik, P.; Michak, R. L.; Shevchenko, N.; Eckert, K.; Eckert, S.

In water electrolysis, the porous transport layer (PTL) is an essential component of both proton (PEM) as well as anion exchange membrane (AEM) electrolysers. Besides establishing an electrical contact, the PTL enables the electrolyte to be transported to the anode. In the opposite direction, the oxygen (O2) formed at the anode must be transported away, resulting in a complex counterflow of liquid and gas through the PTL, thus limiting the mass transport and, consequently, the conversion of electrical energy. The further development of electrolysers faces so far unexplored operating conditions, in particular by increasing the electric current density. This, in turn, affects the formation and transport of gas bubbles in the PTL, which is not yet sufficiently understood.

As the gas-liquid two-phase flow in the PTL is inaccessible for flow measurement by optical methods, we employed time-resolved X-ray and neutron radiography. Using the model experiment sketched in Fig. 1, we aimed for imaging measurements of the gas transport through open-porous foam by mapping the gas fraction distribution over time. In previous experimental studies, we have used X-ray and neutron radiography for flow visualisation in optically opaque fluids such as liquid metal [1] and aqueous foam [2]. Similar to the approach of radiographic measurements of the liquid fraction in aqueous foam [3], this conference contribution showcases the detection and tracking of bubbles based on their gas fraction in X-ray or neutron images. As exemplarily illustrated in Fig. 2, we observed preferred paths of the bubbles moving upwards through the open-porous foam samples. Moreover, we found that bubbles smaller than the pore size are significantly slowed down, even in the case of a hydrophilic surface character of the foam. In summary, the measurement results and conclusions from our experimental parameter study are available for comparison with computational fluid dynamics.

  • Poster
    Gemeinsames Jahrestreffen der DECHEMEA / VDI Fachgruppen MPH & CFD & AT, 20.-21.03.2024, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38799


Synthesis and Twin Polymerization of Si(OCH2py)4 for Nitrogen-containing Carbon Materials

Scharf, S.; Notz, S.; Pfefferkorn, K.; Rüffer, T.; Formánek, P.; Hübner, R.; Selyshchev, O.; Madeira, T. I.; Zahn, D. R. T.; Lang, H.

The synthesis and twin polymerization (TP) of Si(OCH2py)4 (3a, py=2-cC5H4N; 3b, py=3-cC5H4N; 3c, py=4-cC5H4N) is discussed. The solid state structures of 3b, c were confirmed by single-crystal X-ray crystallography showing non-conventional H-bonding, forming 2D chains (3b) or 3D networks (3c). Thermally induced TP of 3a–c and their simultaneous polymerization with 2,2‘-spiro-bi[4H-1,3,2-benzodioxasiline] (4) is described. The resulting hybrid materials were characterized by 1H, 13C{1H}, and 29Si{1H} CP MAS NMR spectroscopy confirming the transformation of the SiOCH2 moieties into CH2 groups enabling the formation of the respective polymers. These results were supported by HAADF-STEM studies, displaying micro-structuring. Nitrogen-containing porous carbon materials C_1–C_3 show surface areas of 1300 and 1700 m2g-1, large pore volumes between 0.6–1.2 cm3g-1, and nitrogen contents of up to 3.1 at-%. X-ray photoemission spectroscopy reveal that pyrrolic, pyridine, and pyridone nitrogen atoms are present. If equimolar amounts of 3a–c and 4 are simultaneously polymerized in the presence of [Pd(OAc)2] (5), then the Pd nanoparticle-decorated material Pd@C_3 (900 m2g-1) was obtained, which showed k values of -0.083 and -0.066 min-1 in the reduction of methylene blue and methyl orange, proving the accessibility of the Pd NPs.

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Permalink: https://www.hzdr.de/publications/Publ-38798


Reproducibility of Arterial Spin Labeling Cerebral Blood Flow image processing: A Report of The ISMRM Open Science Initiative for Perfusion Imaging and the ASL MRI Challenge

Paschoal, A. M.; Woods, J. G.; Pinto, J.; Bron, E. E.; Petr, J.; Kennedy McConnell, F. A.; Bell, L.; Dounavi, M.-E.; van Praag, C. G.; Mutsaerts, H.-J.; Oliver Taylor, A.; Zhao, M. Y.; Brumer, I.; Siang Marcus Chan, W.; Toner, J.; Hu, J.; Zhang, L. X.; Domingos, C.; Monteiro, S. P.; Figueiredo, P.; Harms, A. G. J.; Padrela, B.; Tham, C.; Abdalle, A.; Croal, P. L.; Anazodo, U.

Purpose: Arterial Spin Labeling (ASL) is widely used in clinical research as a contrast-free MRI method for
assessment of cerebral blood flow (CBF). While the recommended guideline for ASL acquisition is
generally adopted to standardize quantification of CBF, ASL analysis still produces wide variability in CBF
estimates, limiting research and clinical interpretation of ASL results. This study explored the extent of
variability in ASL CBF quantification through the ISMRM OSIPI ASL MRI Challenge. The goal of the challenge
was to minimize sources of variability in ASL analysis by establishing best practice in ASL data processing
to make ASL analysis more reproducible and clinically meaningful.
Methods: Eight international teams analyzed the challenge data consisting of a high-resolution T1-
weighted anatomical image and ten pseudo-continuous ASL (PCASL) datasets. The datasets were
simulated using an ASL digital reference object to produce ground-truth CBF values in normal and
pathological states. The accuracy of CBF quantification from each team’s analysis was compared to
ground-truth values across all voxels and within pre-defined brain regions. Reproducibility of CBF
estimates across analysis pipelines was assessed using intra-class correlation coefficient (ICC), the limits
of agreement (LOA) and the replicability of generating similar CBF estimates from the image processing
approaches as documented.
Results: The absolute errors in CBF estimates compared to the ground-truth synthetic data ranged from
18.36 to 48.12 ml/100g/min. Realistic motion incorporated in three of the ten synthetic data produced
the largest absolute CBF error, largest variability between teams, and the least agreement (ICC and LOA)
with ground truth results. Fifty percent (4/8) of the teams’ methods were replicated, and one method
produced three times larger CBF errors (46.59 ml/100g/min) compared to submitted results.
Conclusions: The apparent variability in CBF measurements, influenced by differences in image processing
strategies, particularly in compensating for motion, demonstrates the significance for standardization of
ASL image analysis workflow. Therefore, we provide a recommendation for ASL image processing based
on top performing approaches as a step towards standardization of ASL imaging for clinical use.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-38797


Application of solvent extraction process for zinc recovery from old silver mine “Davidschachthalde” tailings

Kelly, N.; Aamir, M. H.; Helbig, T.; Werner, A.; Patil, A. B.

The historic mining activities have produced a vast amount of mine tailings covering a huge landscape and containing hazardous substances that are harmful to the environment. In addition, the mine tailings also contain valuable materials that become economical after a certain period depending on the criticality of the commodity. Likewise, the old silver mine tailings “Davidschachthalde” near Freiberg, Germany, bears hazardous substances such as As, Cd and valuable elements such as Zn, In, and Cu. Thus, an innovative flowsheet is developed to recover Zn from mine tailings. Firstly, the Fe and Al are removed using the precipitation method which also removes As. Then, the solution is passed through the cementation steps for Cu and Cd removal. In order to purify and enrich Zn(II) in the aqueous solution before electrowinning the conceptional flowsheet consists of a solvent extraction process.
The filtrate from precipitation steps with the composition of 1120 mg/L Zn(II), 4 mg/L Cu(II), 10 mg/L Al(III), 243 mg/L Ca(II), 21 mg/L Cd(II) and pHini 4.7 is subjected to solvent extraction unit with 3 extraction and 2 stripping stages in MEAB lab scale Mixer Settler. Figure 1 depicts the results for the extraction step which is carried out with 0.5 M Cyanex® 272 in kerosene as the organic phase, A/O ratio of 1:1, a contact time of 10 min with a 1-hour sampling interval. Under the chosen conditions Zn(II) extraction is 89% after reaching equilibrium and shows a high selectivity related to low concentrated impurities Cu(II), Cd(II) and Al(III). However, a Ca(II) co-extraction of up to 22% is observed during the process which would affect the following stripping and electrowinning processes in a negative way. Therefore, a high selectivity between Zn(II) and Ca(II) needs to be achieved in the extraction step.
Here, we report the development of the highly selective solvent extraction process for the Zn(II) containing solutions generated during the previous precipitation and cementation steps. Effects of crucial parameters such as pH control and A/O ratio as well as the composition of the stripping agent on extraction yields, up-concentration and selectivity are discussed in detail.

Keywords: ReminingPlus; Davidschachthalde; Mine tailings; Selective Solvent Extraction; Cyanex 272

Involved research facilities

  • Metallurgy Technical Centre
  • Lecture (Conference)
    Annual Meeting of DECHEMA/VDI Group Extraction, 14.-15.02.2024, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38794


Pulsating dissolution of crystalline matter: A surface-controlled process

Schabernack, J.; Fischer, C.

Rate maps quantify the variability of surface rates during the dissolution of crystalline matter. Recently, highly spatially resolved rate maps revealed the existence of rhythmic pulses of the material flux from the crystal surface. The mechanism underpinning this behavior is not yet understood but the two potential influencing factors are surface-controlled or transport-controlled conditions that may govern the resulting pulsating reaction kinetics in the system. In this study, we apply two numerical methods to identify the dominating mechanism of pulsating dissolution. First, the influence of solute transport is simulated using a reactive transport model, which yields dissolution rates and concentration distribution due to the flow field, i.e., extrinsic reactivity. Second, the influence of intrinsic surface reactivity inherent to the material is simulated using kinetic Monte Carlo (KMC) simulations, where the distribution of reactive sites over time is observed on an atomic scale. Local dissolution rates can be reproduced with the reactive transport model, but no kinetically effective periodic changes of the concentration gradients can be observed and no new dissolution pulses are generated. Control via periodic changes in extrinsic reactivity is thus ruled out as a governing mechanism. In contrast, pulsating dissolution is clearly observed in the KMC simulation, leading to the conclusion that the self-assembly of varying reactive surface building blocks causes the pulsating dissolution. The simulation results suggest that etch pits generate regions with a high number of steps of single crystal layers and, consequently, with sites of increased reactivity at periodic intervals. These steps move over the crystal surface outward from the pit center and are followed by a region with a low number of surface steps. Only when the steps reach a certain spacing to the center new steps are generated at the transition between the hollow core and the etch pit. This self-assembly is observed as a fundamental behavior of crystalline dissolution in KMC models, without any additional parametrization. It thus represents a fundamental mechanism in crystal dissolution and should be considered for an accurate atomic understanding of crystal dissolution.

Keywords: Surface reactivity; Pulsating dissolution; Kinetic Monte Carlo; Reactive transport; Calcite

Permalink: https://www.hzdr.de/publications/Publ-38793


The effects of fracture cross-scale surface roughness in crystalline host rocks on hydrodynamics studied by 3D modeling

Zhou, W.; Kulenkampff, J.; Heredia, D. J.; Schäfer, T.; Fischer, C.

This data provides the original inputs and COMOSL scripts for the paper 'The effects of fracture cross-scale surface roughness in crystalline host rocks on hydrodynamics studied by 3D modeling'. 

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Permalink: https://www.hzdr.de/publications/Publ-38787


Value of [18F] FDG PET/CT parameters of the primary tumor in assessing overall survival in NSCLC patients with cN1-cN3 lymph nodes involvement

Cegla, P.; Hofheinz, F.; Czepczyński, R.; Witkowska, K.; van den Hoff, J.; Trojanowski, M.; Bos-Liedke, A.; Cholewinski, W.

Background: The aim of this retrospective study was to assess the value of 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ([18F]FDG PET/CT parameters in cN1-cN3 non-small cell lung cancer (NSCLC) patients.

Materials and methods: 59 consecutive patients (35 M, 24 F) with NSCLC who underwent pretreatment [18F]FDG PET/CT were enrolled to this study. Several primary tumor PET parameters, including the maximum and mean standardized uptake value (SUVmax and SUVmean), the metabolic active tumor volume (MTV) and the total lesion glycolysis (TLG = MTVxSUVmean), were extracted and analysed. Overall survival was defined as time from primary diagnosis to death or the last info.

Results: In the whole analysed group 44 patients underwent curative treatment, while 15, because of the severity of the disease, were classified for palliative treatment. Univariate Cox analysis of clinical and metric PET parameters revealed that MTV was a significant prognostic factor for OS (p = 0.024), while TLG and curative treatment showed a trend for significance (p < 0.1). In multivariate Cox regression (MTV and curative treatment) MTV remained a significant factor (p = 0.047).

Conclusions: Metabolic tumor volume of the primary tumor was the only independent prognostic factor for cN1–cN3 NSCLC patients.

Keywords: positron emission tomography/computed tomography; NSCLC; overall survival

Involved research facilities

  • PET-Center
  • Reports of Practical Oncology and Radiotherapy (2024)
    Online First (2024) DOI: 10.5603/rpor.99360

Permalink: https://www.hzdr.de/publications/Publ-38786


Pioneering Digital Research Landscapes: Innovations at HZDR

Knodel, O.

Digital infrastructures have become indispensable in the field of modern research and science. These technological frameworks play a crucial role for the entire research cycle, supporting literature searches, aiding in data collection and analysis, facilitating the creation and publication of scholarly works, and ensuring the thorough documentation and long-term storage of research findings. Additionally, these infrastructures serve as a vital means for networking and communication among peers, creating the essential foundation of an open and transparent science and research ecosystem.
In this lecture, the entire digital research landscape at the HZDR will be presented and illustrated using a representative experiment.

Keywords: Data management; Heliport; FAIR; Data provenance; metadata; workflows

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Helmholtz Open Science Forum: Towards Open Digital Research Ecosystems – Interconnecting Infrastructures, 14.02.2024, online, online

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Permalink: https://www.hzdr.de/publications/Publ-38785


A comparative compositional study of Egyptian glass from Amarna with regard to cobalt sources and other colourants

Hodgkinson, A. K.; Lemasson, Q.; Mäder, M.; Munnik, F.; Pichon, L.; Röhrs, S.; Reiche, I.

A selection of Late Bronze Age glass objects from the site of Amarna (Egypt) was analysed for their overall chemical composition, colourants and transition metals associated with the sources of cobalt ore. The objects were analysed by means of Particle Induced X-Ray and Gamma-ray Emission and Rutherford Backscattering Spectrometry at the IBC, HZDR, Dresden and the New AGLAE facility, C2RMF, Paris. The data was subsequently compared with further measurements obtained by portable X-Ray Fluorescence (and by Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry) in order to sound the potential of these non-destructive methods to obtain new insights into the production process of glass from Amarna and its provenancing.

Keywords: Glass; Amarna; Egypt; PIXE; PIGE; RBS; microPIXE-imaging; Trace elements; Cobalt sources; Colourants

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Permalink: https://www.hzdr.de/publications/Publ-38780


Assessment of anthropogenic actinide background levels on HZDR’s research campus

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

The new multi-purpose 1-MV AMS facility HAMSTER (Helmholtz Accelerator Mass Spectrometer for Tracing Environmental Radionuclides) in Dresden-Rossendorf will get in operation in 2024. The new machine is dedicated to the analysis of ultra-trace levels of actinides in environmental samples. Thus, the aim of this study is to assess the actinide background on HZDR’s research campus to rule out any potential contamination caused by the former research reactor onsite. Hence, several soil samples close to the construction site of the new accelerator building and former radioisotope production facilities
have been analyzed. The samples have been processed in the existing chemistry labs of HZDR’s 6-MV DREAMS facility and the newly established
HAMSTER labs showing comparable low background levels. The measured Pu concentrations and isotopic ratios are in agreement with global fallout signature. 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 sample analysis will be performed with HAMSTER in 2024.

  • Lecture (Conference)
    DPG Frühjahrstagung, 13.03.2024, Freiburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38777


Development and improvement of radiochemical separation schemes for actinide determination using AMS

Wolf, J.; Koll, D.; Zwickel, S.; Fichter, S.; Hotchkis, M.; Wallner, A.

The determination of minute amounts of actinides in a huge variety of sample matrices is a challenging task. The current capabilities of state-of-the-art accelerator mass spectrometers enable detection limits close to a few hundred atoms per sample. However, proper sample preparation is inevitable to separate the element of interest from the overwhelming majority of the sample mass. Here, we present some of our current activities regarding the optimization of work-up procedures for different actinides (i.e. Pa, Np, Pu, Am, Cm) from environmental samples like water, soil, deep sea ferromanganese crusts and lunar
regolith.

  • Poster
    DPG Frühjahrstagung, 12.03.2024, Freiburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38776


Case studies of three geological archives for rare radionuclide measurements using Accelerator Mass Spectrometry

Fichter, S.; Koll, D.; Rolofs, A. V.; Wallner, A.

Long-lived radionuclides in our environment provide important information on natural and anthropogenic processes. Their
presence and concentration reflect the balance of production and decay. Geological archives store such information and the nuclides
can be chemically extracted from the bulk sample. Accelerator mass spectrometry (AMS) represents a sensitive method to quantify
those nuclides at natural levels. Three different terrestrial archives are discussed here as examples for radionuclide extraction
using various chemical separation methods for subsequent AMS measurements. We focus on sample preparation for the cosmogenic
radionuclides Be-10 and Al-26, various anthropogenic actinide isotopes such as U, Pu and Am as well as the astrophysically
interesting nuclides Ca-41, Mn-53 and Fe-60. The processed materials cover samples with masses between a few mg and up to a
few hundred kg and protocols are presented for the quantitative extraction of some 10,000 atoms of cosmogenic or interstellar
origin per sample and even as low as a few hundred actinide atoms.

Keywords: Accelerator Mass Spectrometry; Radionuclides; Environment; Chemical Purification; Astrophysics

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Permalink: https://www.hzdr.de/publications/Publ-38775


Search for r-process Pu-244 in the K-Pg boundary layer

Koeberl, C.; Fichter, S.; Hotchkis, M. A. C.; Child, D.; Froehlich, M.; Hartnet, M.; Koll, D.; Merchel, S.; Wallner, A.

The K-Pg (Cretaceous–Paleogene) boundary at 66 Ma marks one of five major mass extinctions in Earth’s fossil history. Based on strong enrichments of the platinum-group elements in the boundary layer, Alvarez et al. [1], in 1980, suggested that the impact of a large asteroid was responsible for the K/Pg event.
Earlier, other possible causes for the mass extinction, e.g., a nearby supernova(SN)-explosion, were also discussed, and indeed also Alvarez et al. initially considered this option to explain the high Ir concentration. However, to explain the observed Ir content, the distance for a SN would have to be less than one light-year. To exclude the SN option for the K-Pg event, they searched for a specific long-lived radionuclide, 244Pu, which has a half-life of 81 Myr and does not exist naturally on Earth. Assuming that this radionuclide is predominantly produced and ejected in SNe, its presence could indicate a nearby SN. No 244Pu at required levels was detected, leaving an impact as the most plausible cause (which was later confirmed by the discovery of shocked minerals and also a source crater, Chicxulub). However, since 1980, strong evidence evolved that the heavy r-process elements, e.g., actinides such as 244Pu, are produced in rare explosive events (ca. 1000 times less frequent than common type II core-collapse SNe in the galaxy) [2]. Neutron star mergers are potential candidates or rare subsets of SNe. Thus, the common core-collapse SNe might not have contributed significantly to actinide nucleosynthesis for the past few 100 Myr. This assumption agrees also with recent observations following the gravitational-wave event GW170817 [3]. Furthermore, by searching deep-sea archives for interstellar signatures we confirmed recently that nucleosynthesis yields of 244Pu are much lower (possibly a factor of 100) than expected if SNe dominate heavy isotope r-process nucleosynthesis [4-6]. However, the detection of a significant 244Pu influx above background into these terrestrial archives suggests the possibility of a nearby explosive event within the past few hundred millions years, possibly from a rare event. Thus, a small r-process contribution to actinide production from SNe is still a possibility. In general, site and frequency of r-process events are still strongly debated [2]. Thus, in contrast to the assumption of Alvarez et al. [1], it is not clear that non-detection of 244Pu excludes a nearby supernova explosion at 66 Ma. Despite the overwhelming evidence for an asteroid impact, a new method for direct atom counting has emerged with superior detection efficiency for 244Pu: since the original work by Alvarez et al. in 1980, the 244Pu detection-sensitivity has improved by more than a factor of a million by applying the method of Accelerator Mass Spectrometry (AMS) [5,7,8]. This enormous gain in abundance sensitivity prompted us to reinvestigate the 244Pu concentration in the K-Pg boundary layers. Here we present first results for a set of samples covering this transition period from the Cretaceous to the Paleogene.

  • Poster
    55th Lunar and Planetary Science Conference, 12.03.2024, The Woodlands, USA

Permalink: https://www.hzdr.de/publications/Publ-38774


Tumour response to hypoxia: understanding the hypoxic tumour microenvironment to improve treatment outcome in solid tumours

Bigos, K.; Quiles, C.; Lunj, S.; Smith, D.; Krause, M.; Troost, E. G. C.; West, C.; Hoskin, P.; Choudhury, A.

Hypoxia is a common feature of solid tumours affecting their biology and response
to therapy. One of the main transcription factors activated by hypoxia is hypoxia-
inducible factor (HIF), which regulates the expression of genes involved in various
aspects of tumourigenesis including proliferative capacity, angiogenesis, immune
evasion, metabolic reprogramming, extracellular matrix (ECM) remodelling, and
cell migration. This can negatively impact patient outcomes by inducing
therapeutic resistance. The importance of hypoxia is clearly demonstrated by
continued research into finding clinically relevant hypoxia biomarkers, and
hypoxia-targeting therapies. One of the problems is the lack of clinically
applicable methods of hypoxia detection, and lack of standardisation.
Additionally, a lot of the methods of detecting hypoxia do not take into
consideration the complexity of the hypoxic tumour microenvironment (TME).
Therefore, this needs further elucidation as approximately 50% of solid tumours are
hypoxic. The ECM is important component of the hypoxic TME, and is developed
by both cancer associated fibroblasts (CAFs) and tumour cells. However, it is
important to distinguish the different roles to develop both biomarkers and novel
compounds. Fibronectin (FN), collagen (COL) and hyaluronic acid (HA) are
important components of the ECM that create ECM fibres. These fibres are
crosslinked by specific enzymes including lysyl oxidase (LOX) which regulates
the stiffness of tumours and induces fibrosis. This is partially regulated by HIFs.
The review highlights the importance of understanding the role of matrix
stiffness in different solid tumours as current data shows contradictory results
on the impact on therapeutic resistance. The review also indicates that further
research is needed into identifying different CAF subtypes and their exact roles;
with some showing pro-tumorigenic capacity and others having anti-
tumorigenic roles. This has made it difficult to fully elucidate the role of
CAFs within the TME. However, it is clear that this is an important area of
research that requires unravelling as current strategies to target CAFs have
resulted in worsened prognosis. The role of immune cells within the tumour
microenvironment is also discussed as hypoxia has been associated with
modulating immune cells to create an anti-tumorigenic environment. Which
has led to the development of immunotherapies including PD-L1. These
hypoxia-induced changes can confer resistance to conventional therapies,
such as chemotherapy, radiotherapy, and immunotherapy. This review
summarizes the current knowledge on the impact of hypoxia on the TME
and its implications for therapy resistance. It also discusses the potential of
hypoxia biomarkers as prognostic and predictive indictors of treatment
response, as well as the challenges and opportunities of targeting hypoxia in
clinical trials.

Keywords: hypoxia; tumour microenvironment; extracellular matrix; immune cells; cancer associated fibroblasts

  • Open Access Logo Frontiers in Oncology 14(2024), 1331355

Permalink: https://www.hzdr.de/publications/Publ-38768


20 years of experience with CW-SRF operation at ELBE

Arnold, A.

ELBE is a compact, accelerator-driven photon and particle source. The variety of secondary radiation being offered extends from high-energy gamma rays to infrared and THz radiation as well as from neutrons to positrons and electrons. Since 2001 ELBE is operated as a user facility, providing more than 5500 hours of beamtime with an efficiency of more than 90% each year. The electron accelerator is based on four superconducting 9-cell TESLA cavities that are driven in CW operation to accelerate an average current of 1 mA up to beam energies of 40 MeV. In addition an upgraded version of a superconducting radio-frequency (SRF) photoinjector was brought into operation in 2014. After a period of commissioning, a gradual transfer to routine operation took place in 2017, so that now more than 1800h of user beam are generated by this unique CW electron source every year.

The talk will summarize our experiences of operating all our SRF cavities over two decades in CW. In detail, this includes the cavity performance and attempts to improve it, as well as investigations on their limitations. Additionally, we will discuss several issues that are related to the high average RF as well as beam power and we will present appropriate measures to protect the machine. In this regard we will also introduce a resonant ring for RF component tests at CW power levels up to 100 kW. Regarding the SRF gun, the main emphasis lies in seamlessly integrating a normal-conducting photocathode into the SRF cavity, alongside addressing associated intricacies like dark current, multipacting, and contamination of the resonator.

Keywords: ELBE; CW SRF; TESLA cavity; SRF gun; photo cathode; electron source; injector

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  • Lecture (others)
    MAMI Seminar - Seminar über spezielle Probleme der Beschleunigerphysik, 08.02.2024, Mainz, Deutschland
    PURL: https://www.kernphysik.uni-mainz.de/beschleuniger/mami-seminar/

Permalink: https://www.hzdr.de/publications/Publ-38759


Data publication: Analysis of loss of flow without scram test in the FFTF reactor – Thermal hydraulics data

Ponomarev, A.; Nikitin, E.; Fridman, E.

Thermal hydraulic system models of the FFTF with the Cycle 8C core for LOFWOS Test #13, created using the ATHLET code, along with the benchmark results (point kinetics and spatial kinetics), sensitivity analyses, cross section data and DYN3D models for coupled DYN/ATHLET calculations.

Keywords: ATHLET; FFTF; Gas Expansion Module; loss of flow; point kinetics; SFR; unprotected transient; spatial kinetics; coupled calculations; DYN3D

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Permalink: https://www.hzdr.de/publications/Publ-38758


Solutal Marangoni force controls lateral motion of electrolytic gas bubbles

Zhang, H.; Ma, Y.; Huang, M.; Mutschke, G.; Zhang, X.

Electrochemical gas-evolving reactions have been widely used for industrial energy conversion and storage processes. Gas bubbles form frequently at the electrode surface due to a small gas solubility, thereby reducing the effective reaction area and increasing the over-potential and ohmic resistance. However, the growth and motion mechanisms for tiny gas bubbles on the electrode remains elusive. Combining molecular dynamics (MD) and fluid dynamics simulations (CFD), we show that there exists a lateral solutal Marangoni force originating from an asymmetric distribution of dissolved gas near the bubble. Both MD and CFD simulations deliver a similar magnitude of the Marangoni force of B~0.01 nN acting on the bubble. We demonstrate that this force may lead to lateral bubble oscillations and analyze the phenomenon of dynamic self-pinning of bubbles at the electrode boundary.

Permalink: https://www.hzdr.de/publications/Publ-38757


Data publication: Ultralong-term high-density data storage with atomic defects in SiC

Hollenbach, M.; Kasper, C.; Erb, D.; Bischoff, L.; Hlawacek, G.; Kraus, H.; Kada, W.; Ohshima, T.; Helm, M.; Facsko, S.; Dyakonov, V.; Astakhov, G.

Experimental data in OriginPro

Keywords: data storage; silicon carbide; color centers; focused ion beams; cathodoluminescence

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Permalink: https://www.hzdr.de/publications/Publ-38751


Ultralong-term high-density data storage with atomic defects in SiC

Hollenbach, M.; Kasper, C.; Erb, D.; Bischoff, L.; Hlawacek, G.; Kraus, H.; Kada, W.; Ohshima, T.; Helm, M.; Facsko, S.; Dyakonov, V.; Astakhov, G.

There is an urgent need to increase the global data storage capacity, as current approaches lag behind the exponential growth of data generation driven by the Internet, social media and cloud technologies. In addition to increasing storage density, new solutions should provide long-term data archiving that goes far beyond traditional magnetic memory, optical disks and solid-state drives. Here, we propose a concept of energy-efficient, ultralong, high-density data archiving based on optically active atomic-size defects in a radiation resistance material, silicon carbide (SiC). The information is written in these defects by focused ion beams and read using photoluminescence or cathodoluminescence. The temperature-dependent deactivation of these defects suggests a retention time minimum over a few generations under ambient conditions. With near-infrared laser excitation, grayscale encoding and multi-layer data storage, the areal density corresponds to that of Blu-ray discs. Furthermore, we demonstrate that the areal density limitation of conventional optical data storage media due to the light diffraction can be overcome by focused electron-beam excitation.

Keywords: data storage; silicon carbide; color centers; focused ion beams; cathodoluminescence

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Permalink: https://www.hzdr.de/publications/Publ-38750


Improved automated one-pot two-step radiosynthesis of (S)-[18F]FETrp, a radiotracer for PET imaging of indoleamine 2,3-dioxygenase 1 (IDO1)

Maisonial-Besset, A.; Kryza, D.; Kopka, K.; Levesque, S.; Moreau, E.; Wenzel, B.; Chezal, J.-M.

Background: (S)-[18F]FETrp is a promising PET radiotracer for imaging IDO1 activity, one of the main enzymes involved in the tryptophan metabolism that plays a key role in several diseases including cancers. To date, the radiosynthesis of this tryptophan analogue remains highly challenging due to partial racemization occurring during the nucleophilic radiofluorination step. This work aims to develop a short, epimerization-free and efficient automated procedure of (S)-[18F]FETrp from a corresponding enantiopure tosylate precursor.
Results: Enantiomerically pure (S)- and (R)-FETrp references as well as tosylate precursors (S)- and (R)-3 were obtained from corresponding N-Boc-(L and D)-tryptophan in 2 and 4 steps, respectively. Manual optimisation of the radiolabelling conditions resulted in >90% radiochemical conversion with more than 99% enantiomeric purity. Based on these results, the (S)-[18F]FETrp radiosynthesis was fully automated on a SynChrom R&D EVOI module to produce the radiotracer in 55.2 ± 7.5% radiochemical yield, 99.9% radiochemical purity, 99.1 ± 0.5% enantiomeric excess, and molar activity of 53.2 ± 9.3 GBq/mol (n = 3).
Conclusions: To avoid racemisation and complicated purification processes, currently encountered for the radiosynthesis of (S)-[18F]FETrp, we report herein significant improvements, including a versatile synthesis of enantiomerically pure tosylate precursor and reference compound and a convenient one-pot two-step automated procedure for the radiosynthesis of (S)-[18F]FETrp. This optimised and robust production method could facilitate further investigations of this relevant PET radiotracer for imaging IDO1 activity.

Keywords: [18F]FETrp; IDO1; Fluorine-18; Radiochemistry; Radiofluorination; Automation; Racemization-free radiolabelling; Circular dichroism detection

Permalink: https://www.hzdr.de/publications/Publ-38748


Anatomy of localized edge modes in laterally coupled waveguides

Iurchuk, V.; Stienen, S.; Lindner, J.; Kakay, A.

We present a systematic micromagnetic study of standing spin-wave modes in infinitely long Permalloy strips with rectangular cross-section. Using a finite-element dynamic-matrix method, we first calculate the eigenfrequencies and the corresponding eigenvectors (mode profiles), as a function of the in-plane magnetic field applied across the strip. The ferromagnetic resonance spectra is computed from the mode profiles, assuming a homogeneous radio-frequency excitation, equivalently to an experimental ferromagnetic resonance measurement. The investigation of the field-dependent mode profiles enables for the classification of the observed resonances, here focusing mostly on the \textit{true edge mode} localized at the vicinity of strip edges. Furthermore, we study the mode localization in pairs of 50-nm-thick Permalloy strips as a function of the strip width and their lateral separation. For closely spaced strips, the spatial profile of the quasi-uniform mode is substantially modified due to a significant hybridization with the edge-localized standing spin-wave modes of the neighbouring strip. We show that a wide-range-tunability of the localized edge-mode resonances can be achieved with a precise control of the magnetostatic coupling between the strips. Extreme sensitivity of the edge mode frequency on the bias field demonstrates a potential of the edge resonances for field sensing. Furthermore, for narrow strips ($\approx$100~nm in width), due to the reduced number of the allowed confined modes, a field-controllable switching between the resonances localized either in the strip center or at the edges of the strips can be achieved.

Keywords: Spin waves; Edge modes; Ferromagnetic resonance; Micromagnetic modeling; Magnetostatic coupling

Permalink: https://www.hzdr.de/publications/Publ-38747


Surface-symmetry-driven phenomena in magnetoelectric Cr2O3

Pylypovskyi, O.; Weber, S.; Makushko, P.; Veremchuk, I.; Spaldin, N.; Makarov, D.

Antiferromagnetic (AFM) Cr$_2$O$_3$ is a unique collinear magnetoelectric material at room temperature. The bulk properties stemming from its magnetic symmetry render chromia of high interest for fundamentals and applications [1]. Features of the chromia surface remain much less explored. Here, we consider nominally compensated surfaces ($m$~and $a$~planes) of Cr$_2$O$_3$ [2]. We show that they provide a sizeable Dzyaloshinskii--Moriya interaction (DMI) determined by the surface magnetic symmetry point group and quantify it to be about 1\,mJ/m$^2$ by means of \textit{ab initio} and micromagnetic approaches. The DMI leads to the development of nonzero surface magnetization $\vec{M}$ whose sign is uniquely determined by the AFM state. The $m$ and $a$ planes of Cr$_2$O$_3$ behave as the canted ferrimagnet and canted 4-sublattice antiferromagnet, respectively. The coupling of $\vec{M}$ to the direction of the N\'{e}el vector is shown by magnetotransport measurements.

[1] P. Makushko et al., Nat. Comm. 13, 6745 (2022). [2] O.V. Pylypovskyi, S. F. Weber et al., ArXiv:2310.13438 (2023).

Keywords: Cr2O3; antiferromagnetism; single crystal; symmetry

  • Lecture (Conference)
    DPG Spring Meeting, 17.-22.03.2024, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-38738


A didactical dataset to learn supervised classification with candy

Sinichenko, V. A.; Bähr, M.; Maximilian, M.; Philip, N.; Gabriele, N.; Ihor, T.; Jessica, A.; Florian, L. C.; Martina, R.; Franziska, B.; Yashkumar, P. F.; Anna, S.; Satyam, S. G.; Dora, H.; Asma, W.; Nico, B.; Tim, Q.; Muhammad, H. K.; Benjamin, B.; Roland, N.; Laura, M.; Marius, P.; Siddhartha, J.; Tom, G.; Yaqian, Z.; Yan, A.; Lena, S.; Hamdaan, A. F.; Florens, K.; Shayan, P.; Lukas, P.; Steinbach, P.

A didactical dataset to learn supervised classification

It was obtained from university level students measuring candy that was mixed and distributed in bowls to them. The goal of this dataset creation was to expose the students to the data taking process. Further, the dataset is meant for classificatio

Keywords: Data Science; machine learning

Permalink: https://www.hzdr.de/publications/Publ-38732


Inverting the Kohn-Sham equations with physics-informed machine learning

Martinetto, V.; Shah, K.; Cangi, A.; Pribram-Jones, A.

This data repository contains the datasets used in the paper "Inverting the Kohn-Sham equations with physics-informed machine learning". 

It contains the data generation scripts, datasets for the systems used in the paper (Single Well - 1D atom, Double Well - 1D diatomic molecule) and output potentials generated by the physics-informed machine learning models (physics-informed neural networks and Fourier neural operators).

Keywords: density functional theory; machine learning

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  • Data Center

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Permalink: https://www.hzdr.de/publications/Publ-38725


Retrained Models and Scripts for Aluminum at 298K and 933K

Fiedler, L.; Cangi, A.

Retrained Models and Scripts for Aluminum at 298K and 933K

Authors

- Fiedler, Lenz (HZDR/CASUS)
- Cangi, Attila (HZDR/CASUS)

Affiliations:

HZDR - Helmholtz-Zentrum Dresden-Rossendorf
CASUS - Center for Advanced Systems Understanding

Data set description

This data sets contains models, scripts and inference results for aluminum at room temperature and the melting point. Training data, hyperparameters and general methodology follow Ref. [1]. The models here are retrained versions of the ones discussed in this publication, and therefore retrained versions of the models contained in Ref. [2]. As such, data from Ref. [2] has been used. Only a subset of models contained in Ref. [1] have been retrained, namely the room temperature model, one liquid and one solid melting point model with four training snapshot each, and the final melting point hybrid model (six training snapshots per phase). Furthermore, for both the hybrid melting temperature model and the room temperature model, multiple models with different initializations were trained.

All models were trained with the MALA code [3] version 1.2.1. They show better accuracy than their original counterparts, as they were trained using the inter-snapshot shuffling algorithm first discussed for the MALA code in Ref. [4].

[1] - "Accelerating finite-temperature Kohn-Sham density functional theory with deep neural networks", Physical Review B, doi.org/10.1103/PhysRevB.104.035120
[2] - "RODARE", doi.org/10.14278/rodare.2485 (v1.0.0)
[3] - "MALA", Zenodo, doi.org/10.5281/zenodo.5557254
[4] - "Machine learning the electronic structure of matter across temperatures", Physical Review B, doi.org/10.1103/PhysRevB.108.125146

Contents

- The models themselves, labeled as either Al298K or Al933K, given as one .zip file per model
    - For 933K, additionally "liquid", "solid" and "hybrid" denotes the training data set
    - For ensembles, a running index denotes the number in the ensemble
- Inference results, given as a single .zip file
    - For all models, band energy and total free energy results are given in the .csv format
        - The columns in these files correspond to "Calculated via DFT LDOS", "Calculated via ML-DFT LDOS", "Calculated via Kohn-Sham system", respectively
    - For some models, additionally the predicted electronic density and density of states on select snapshots is given
- Shuffling, training and testing scripts, given as a single .zip file
    - Scripts are ready-to-use with suitable MALA installation, however, correct data paths have to be filled in
    
   

Keywords: Data set; DFT

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Permalink: https://www.hzdr.de/publications/Publ-38719


High-field magnetization of KEr(MoO4)2

Kutko, K.; Bernáth, B.; Khrustalyov, V.; Young, O.; Engelkamp, H.; Christianen, P. C. M.; Prodan, L.; Skourski, Y.; Pourovskii, L. V.; Khmelevskyi, S.; Kamenskyi, D.

We report a magnetization study of the rare-earth-based paramagnet KEr(MoO4)2 in a magnetic field up to 50 T. A recent observation of massive magnetostriction and rotational magnetocaloric effects in this compound triggered interest in the microscopic mechanism behind these phenomena. We combine several experimental techniques to investigate the magnetization behavior up to its saturation along three main crystallographic directions. The synergy of magnetic torque measurements and vibrating sample magnetometry allowed us to reconstruct parallel and perpendicular components of the magnetization vector, enabling us to trace its evolution up to 30 T. Our experiments reveal the magnetization saturation along all principle axes well below the value, expected from crystal electric field calculations. We argue that an externally applied magnetic field induces a distortion of the local environment of Er3+ ions and affects its crystal electric field splitting.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-38714


Templates of expected measurement uncertainties for neutron-induced capture and charged-particle production cross section observables

Lewis, A. M.; Neudecker, D.; Carlson, A. D.; Smith, D. L.; Thompson, I.; Wallner, A.; Barry, D. P.; Bernstein, L. A.; Block, R. C.; Stephen Croft, Y. D.; Drosg, M.; Haight, R. C.; Herman, M. W.; Young Lee, H.; Otuka, N.; Sjöstrand, H.; Sobes, V.

This paper provides a template of expected uncertainties and correlations for measurements
of neutron-induced capture and charged-particle production cross sections. Measurements performed in-
beam include total absorption spectroscopy, total energy detection, gamma-ray spectroscopy, and direct charged-
particle detection. Offine measurements include activation analysis and accelerator mass spectrometry. The
information needed for proper use of the datasets in resonance region and high energy region evaluations is
described, and recommended uncertainties are provided when specific values are not available for a dataset.

Permalink: https://www.hzdr.de/publications/Publ-38712


Templates of expected measurement uncertainties

Neudecker, D.; Lewis, A. M.; Matthews, E. F.; Vanhoy, J.; Haight, R. C.; Smith, D. L.; Talou, P.; Croft, S.; Carlson, A. D.; Pierson, B.; Wallner, A.; Al-Adili, A.; Bernstein, L.; Capote, R.; Devlin, M.; Drosg, M.; Duke, D. L.; Finch, S.; Herman, M. W.; Kelly, K. J.; Koning, A.; Lovell, A. E.; Marini, P.; Montoya, K.; Nobre, G. P. A.; Paris, M.; Pritychenko, B.; Sjöstrand, H.; Snyder, L.; Sobes, V.; Solders, A.; Taieb, J.

The covariance committee of CSEWG (Cross Section Evaluation Working Group) estab-
lished templates of expected measurement uncertainties for neutron-induced total, (n,γ), neutron-induced
charged-particle, and (n,xn) reaction cross sections as well as prompt fission neutron spectra, average
prompt and total fission neutron multiplicities, and fission yields. Templates provide a list of what uncer-
tainty sources are expected for each measurement type and observable, and suggest typical ranges of these
uncertainties and correlations based on a survey of experimental data, associated literature, and feedback
from experimenters. Information needed to faithfully include the experimental data in the nuclear-data
evaluation process is also provided. These templates could assist (a) experimenters and EXFOR compilers
in delivering more complete uncertainties and measurement information relevant for evaluations of new
experimental data, and (b) evaluators in achieving a more comprehensive uncertainty quantification for
evaluation purposes. This effort might ultimately lead to more realistic evaluated covariances for nuclear-
data applications. In this topical issue, we cover the templates coming out of this CSEWG effort–typically,
one observable per paper. This paper here prefaces this topical issue by introducing the concept and
mathematical framework of templates, discussing potential use cases, and giving an example of how they
can be applied (estimating missing experimental uncertainties of 235U(n,f) average prompt fission neutron
multiplicities), and their impact on nuclear-data evaluations.

Permalink: https://www.hzdr.de/publications/Publ-38711


Time-resolved nanospectroscopy on Si-doped GaAs-InGaAs core-shell nanowires

Luferau, A.; Obst, M.; Kehr, S.; Eng, L.; Winnerl, S.; Pashkin, O.; Dimakis, E.; Helm, M.

High-quality epitaxial nanowires (NWs) based on III-V semiconductors offer the possibility to fabricate ultrafast optical devices due to their direct bandgap and the high electron mobility. Contactless investigation of photoexcited carriers within single NWs is enabled by optical-pump THz-probe scanning near-filed optical microscopy (SNOM) experiment. Here we report on first THz-pump MIR-probe SNOM studies on Si-doped GaAs-InGaAs core-shell NWs utilizing THz radiation from the free-electron laser FELBE. The experiment was carried out with SNOM setup from Neaspec equipped with nanoFTIR module, where a broadband MIR source (5-15μm) serves as a probe. Upon intraband THz-pump (25μm) we observed a red shift of amplitude and phase of the NW plasma resonance, while control interband optical pumping (780nm) induced a blue shift of the resonance, and in both cases an exponential decay with a time constant of 4-5ps is seen. We attribute the blue shift to the contribution of photogenerated carriers. The red shift is assigned to the heating of the electrons in the conduction band and the subsequent increase of the effective mass in the nonparabolic Γ-valley due to high peak electric fields of THz pulses.

Keywords: s-SNOM; nanowires; nanospectroscopy

Involved research facilities

  • F-ELBE
  • Contribution to proceedings
    DPG Spring Meeting of the Condensed Matter Section 2023, 26.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38710


THz-pump / MIR-probe nanospectroscopy on Si-doped GaAs-InGaAs core-shell nanowires

Luferau, A.; Obst, M.; Winnerl, S.; Kehr, S. C.; Dimakis, E.; Pashkin, O.; Kaps, F.; Eng, L. M.; Helm, M.

We report on first THz-pump / MIR-probe SNOM studies on Si-doped GaAs-InGaAs core-shell NWs utilizing THz radiation from the free-electron laser FELBE. Upon intraband THz-pump we observe a red shift of the NW plasma resonance in both amplitude and phase spectra, while a controlled interband optical pumping induces a blue shift of the resonance. In both cases, the signal exponentially decays with a time constant of 4-5 ps. We attribute the blue shift to the contribution of photogenerated charge carriers, while the red shift is assigned to the heating of electrons in the conduction band accelerated by the THz electric field of the pump pulses and the subsequent increase of their effective mass due to the nonparabolic Γ-valley dispersion.

Keywords: s-SNOM; nanowires; nanospectroscopy; FEL

Involved research facilities

  • F-ELBE
  • Contribution to proceedings
    2023 48th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 17.09.-31.10.2023, Montreal, Canada

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Permalink: https://www.hzdr.de/publications/Publ-38709


Data publication: Significant Resistance Reduction in Modulation-Doped Silicon Nanowires via Aluminum-Induced Acceptor States in SiO2

Ratschinski, I.; Nagarajan, S.; Trommer, J.; Luferau, A.; Khan, M. B.; Erbe, A.; Georgiev, Y.; Mikolajick, T.; Smith, S. C.; König, D.; Hiller, D.

Measured resistance as a function of nanowire (NW) width for different modulation doped Si NWs.

Keywords: electrical properties; modulation doping; resistance; silicon nanowires

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Permalink: https://www.hzdr.de/publications/Publ-38708


Significant Resistance Reduction in Modulation-Doped Silicon Nanowires via Aluminum-Induced Acceptor States in SiO2

Ratschinski, I.; Nagarajan, S.; Trommer, J.; Luferau, A.; Khan, M. B.; Erbe, A.; Georgiev, Y.; Mikolajick, T.; Smith, S. C.; König, D.; Hiller, D.

Silicon nanowires (Si NWs) like structures in the form of nanosheets are the building blocks for future transistors in the most advanced complementary metal–oxide–semiconductor technologies. However, Si NWs with few nanometers in diameter suffer from severe difficulties with respect to efficient impurity doping. These difficulties can be overcome by a novel doping concept for Si NWs comparable to the modulation doping approach known from III–V semiconductors. Modulation doping means that the parent dopant atoms are spatially separated from the volume that is to be doped by embedding them into an adjacent material with a higher bandgap. Herein, Al-doped SiO2 shells around the Si NWs are used for the experimental realization of modulation doping. In two independent experiments, a significant reduction of the electrical resistance of Si NWs by several orders of magnitude is measured, when compared to the resistance of Si NWs with undoped SiO2 shells. The results are discussed in the context of modulation doping by the surface functionalization with SiO2:Al shells.

Keywords: electrical properties; modulation doping; resistance; silicon nanowires

Related publications

Permalink: https://www.hzdr.de/publications/Publ-38707


Data publication: A quantitative analysis of the effect of box size in N-body simulations of the matter power spectrum

Eingorn, M.; Yilmaz, E.; Yukselci, A. E.; Zhuk, O.

The dataset consists of the matter power spectra at four redshifts (z=80,50,15,0) generated by simulating Lambda-Cold Dark Matter cosmology within the cosmic screening approach as described in the associated paper. Outputs of six distinct runs are available for boxes with L= 280, 560, 1680, 4480, 5120, 5632 Mpc/h comoving sizes, each with 2 Mpc/h resolution.

Keywords: inhomogeneous Universe; large-scale structure; cosmic screening; cosmological perturbations; N-body simulations; power spectrum

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Permalink: https://www.hzdr.de/publications/Publ-38704


Analyse, Planung und Umsetzung einer verteilten Informationsarchitektur für ein New Work Konzept am HZDR

Schwabe, J.

Im Zuge der zunehmenden Digitalisierung bleibt auch die Arbeitswelt von Veränderungen auf diesem Gebiet nicht unberührt.
Wechselnde Arbeitszeitmodelle und flexible sowie hybride Arbeitsplätze stellen eine Herausforderung für das klassische Flächenmanagement und die Erreichbarkeit von Mitarbeitenden dar.
Um eine veränderliche Belegung von Büroräumen für Beschäftigte zu vereinfachen, werden zunehmend verschiedene Smart Office Solutions entwickelt.
Dazu zählt auch eine flexible Informationsanzeige, um Mitarbeitende auch bei zeitlich und räumlich wechselnden Arbeitsplätzen auffinden zu können.
Am Beispiel eines am Helmholtz-Zentrum Dresden - Rossendorf (HZDR) neu entstehenden Bürogebäudes wird im Rahmen dieser Arbeit ein verteiltes Informationssytem konzipiert und ein Prototyp dessen mit den Basis-Funktionalitäten implementiert.
Dabei kommuniziert ein digitales, kabelloses Türschild in einem drahtlosen Netzwerk mit einem zentralen Server, welcher Informationen aus bestehenden Datenbanken zu aktuellen Raumbelegungen ausliest.
Diese Informationen werden automatisiert auf dem ePaper-Display des Türschildes angezeigt.
Im Vordergrund steht dabei ein möglichst geringer Energiebedarf der über eine mobile Spannungsquelle mit Strom zu versorgenden Türschilder.

Keywords: Data Science; Data Management; Electronic Door Sign; E-Paper; New Work; Smart Office; Python; Arduino; ESP8266

Related publications

  • Bachelor thesis
    Berufsakademie Sachsen, Staatliche Studienakademie Dresden, 2023
    Mentor: Dr.-Ing. Oliver Knodel, Dr. rer. nat. Dietbert Gütter

Permalink: https://www.hzdr.de/publications/Publ-38703


Evaluating the quality of pure mineral extraction during luminescence sample preparation

Melo Girón, A. M.; Fuchs, M.; Gloaguen, R.; Dornich, K.; Heitmann, J.

Through the last 50 years, Optically Stimulated Luminescence (OSL) dating has been applied to get absolute age estimates for the last exposure of minerals like quartz or feldspar to light or heat. The method provides manifold applications for unraveling the geochronological scale of surface processes and related sediment archives. Over time, technology and techniques improved creating new ways to get a more accurate age. However, ensuring the quality of dating results commenceswith sample preparation and accurate extraction of the dosimeter (quartz or feldspar). Standard separation procedures for quartz-based OSL dating involve a series of steps to enrich the quartz. Due different wettability of feldspar and quartz is possible
to separate them through froth flotation. Our goal is to determine the quality of quartz separation of one poly-mineral sample of fluvial sediments from Pamir applying feldspar flotation. This froth-type method showed in past experiments quartz concentrations of 95-100 %. Using X-ray diffraction analysis, we trace the chemical composition of each step of the process to illustrate the advantage of this froth method in getting high-purity quartz extracts.

Keywords: Luminescence

Permalink: https://www.hzdr.de/publications/Publ-38701


Luminescence dating of active faults in New Zealand: first insights from pIRIR225

Melo Girón, A. M.; Tsukamoto, S.; Fuchs, M.; Tanner, D.; Brandes, C.; Kroner, U.; Gloaguen, R.

We aim to test the potential of luminescence dating to determine the relative activity of three active faults in New Zealand. To this end, we collected four dark-gray, fine to very fine grain-size samples classified as cataclasite and gouge from outcrops situated along the fault traces of the Alpine Fault, Hope Fault, and Hundalee Fault. Through sample processing, we obtained polymineral fine grains, ranging from 4 to 11 µm, to conduct post-infrared infrared stimulated luminescence (pIRIR225) dating. In this work, we show the first insights into the Luminescence properties, in the first attend to record ages in active faults in New Zealand using direct dating on gouge and cataclasites.

Keywords: Earthquakes

Permalink: https://www.hzdr.de/publications/Publ-38700


Data publication: Microstructure-informed prediction of hardening in ion-irradiated reactor pressure vessel steels

Lai, L.; Brandenburg, J.-E.; Chekhonin, P.; Duplessi, A.; Cuvilly, F.; Etienne, A.; Radiguet, B.; Rafaja, D.; Bergner, F.

Mainly the original data for model establishment.

Keywords: reactor pressure vessel steels; ion irradiation; microstructure characterization; transmission electron microscopy; atom probe tomography; nanoindentation; hardening

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-38698


Microstructure-informed prediction of hardening in ion-irradiated reactor pressure vessel steels

Lai, L.; Brandenburg, J.-E.; Chekhonin, P.; Duplessi, A.; Cuvilly, F.; Etienne, A.; Radiguet, B.; Rafaja, D.; Bergner, F.

Ion irradiation combined with nanoindentation is a promising tool to study irradiation-induced hardening of nuclear materials including reactor pressure vessel (RPV) steels. For RPV steels, the major sources of hardening are nm-sized irradiation-induced dislocation loops and solute atom clusters, both representing barriers for dislocation glide. The dispersed barrier hardening (DBH) model provides a link between the irradiation-induced nanofeatures and hardening. However, a number of details of the DBH model still require consideration. These include the role of the unirradiated microstructure, the proper treatment of the indentation size effect (ISE), and the appropriate superposition rule of individual hardening contributions. In the present study, two well characterized RPV steels, each ion-irradiated up to two different levels of displacement damage, were investigated. Dislocation loops and solute atom clusters were characterized by transmission electron microscopy and atom probe tomography, respectively. Nanoindentation with a Berkovich indenter was used to measure indentation hardness as a function of the contact depth. In the present paper, the measured hardening profiles are compared with predictions based on different DBH models. Conclusions about the appropriate superposition rule and the consideration of the ISE (in terms of geometrically necessary dislocations) are drawn.

Keywords: reactor pressure vessel steels; ion irradiation; microstructure characterization; transmission electron microscopy; atom probe tomography; nanoindentation; hardening

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-38696


In operando visualization of mass transfer in a sodium-zinc molten salt battery with liquid electrolyte

Sarma, M.; Nash, W.; Weber, N.; Weier, T.

To bring the novel Na-Zn molten salt battery to market, many unresolved issues – such as self-discharge, migration of Na away from the current collector, and electrolyte “creeping” – must be resolved. Within the framework of the Horizon 2020 project SOLSTICE, a working battery prototype must be delivered. To support this objective, a small-scale experimental cell that can be used for fundamental research has been built. The cell has been designed to permit in situ radiographic imaging of its interior. The aim is to charge and discharge this cell in a neutron beamline and an X-ray source, to observe mass transfer of electroactive species and any flow that occurs during cycling. Of most interest are how these phenomena depend on the geometry and chemical composition of the different cell components, e.g. the positive and negative current collectors.
With a completely liquid interior, all the cell’s components must retain their performance characteristics at its 600oC operating temperature. Besides thermal stress, the cell’s walls and current collectors must resist corrosion by liquid Zn, Na, and the molten salt electrolyte (as well as their vapors). Maintenance of this high internal temperature also requires sufficient thermal insulation, and – in an isolated test cell – an external heating system, and neither of these should interfere with the imaging techniques.
Preliminary attempts to cycle the cell for an extended period of time (>4 weeks) have been successful. Pilot imaging tests using neutron and X-ray radiography have confirmed that the different layers (the electrodes and electrolyte) can be distinguished from one another, and spatial variations in the chemical composition of the electrolyte can be resolved. However, corrosion remains a limitation for long-term structural stability, so optimization of the cell’s components is ongoing. Long-term cycling data and X-ray/neutron images will be presented in this talk, and their implications for improvements to the cell design will be discussed.

  • Lecture (Conference)
    4th International Sodium Battery Symposium (SBS4), 04.09.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38694


Mass transport and solutal convection in a sodium-zinc molten salt battery with liquid electrolyte: comparison of modelling and experiments

Sarma, M.; Duczek, C.; Nash, W.; Weber, N.; Weier, T.

Within the Horizon 2020 project SOLSTICE, a molten salt battery has been developed. The battery employs sodium and zinc as anode and cathode respectively and operates at around 600 oC with a completely liquid interior. The primary advantage of this design is its low materials’ cost. However, multiple challenges must be overcome if it is to become commercially viable. These include corrosion of metallic components by the molten salt electrolyte, and self-discharge promoted by transport of cathode materials (Zn2+ ions) to the anode. Efforts to suppress the latter especially benefit from modelling, as the rate of self-discharge is primarily determined by mass transport processes in the electrolyte. Such models require experimental validation, thus, a small-scale experimental cell has been constructed for this purpose. It has been designed specifically for operation during analysis by radiographic methods (neutron beam and X-ray imaging). The distribution of the active materials can be observed at different stages of the charging-discharging cycle. This presentation will provide an overview of current modelling activities at HZDR related to the sodium-zinc battery, together with first (preliminary) experimental results and the most recent progress towards designing a “transparent” cell.

  • Lecture (Conference)
    9th International Scientific Colloquium "Modelling for Materials Processing" 2023, 18.09.2023, Riga, Latvija

Permalink: https://www.hzdr.de/publications/Publ-38693


Magnetocaloric effect in the Laves phases RCo2 (R = Er, Ho, Dy, and Tb) in high magnetic fields

Bykov, E.; Karpenkov, A.; Liu, W.; Straßheim, M.; Niehoff, T.; Skokov, K.; Scheibel, F.; Gutfleisch, O.; Salazar Mejia, C.; Wosnitza, J.; Gottschall, T.

The heavy rare-earth-based Laves phases are well-studied intermetallic materials that stand out for their remarkably high magnetocaloric effects, particularly at cryogenic temperatures. In this study, we present the findings of our comprehensive investigation of cobalt Laves phases RCo2 with R standing for erbium, holmium, dysprosium, and terbium. This includes the determination of the magnetocaloric effect by indirect methods using calorimetric and magnetization data. Furthermore, for the first time in these materials, we directly measured the adiabatic temperature change at high magnetic fields up to 20 T. The largest ΔTad value of 17 K, we obtained for ErCo2. Because the order of the transition significantly impacts the efficiency of thermodynamic cycles, we have also focused on determining the transition order in these materials. This was done through the application of established methods and a recently proposed quantitative criterion including the value of the local exponent n. Further, we compare our results with other materials using a straightforward material-based figure of merit - the temperature-averaged entropy change (TEC). Our results demonstrate the great potential of these materials for applications such as for magnetic hydrogen liquefaction.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-38692


Data publication: How to verify the precision of density-functional-theory implementations via reproducible and universal workflows

Bosoni, E.; Beal, L.; Bercx, M.; Blaha, P.; Blugel, S.; Broder, J.; Callsen, M.; Cottenier, S.; Degomme, A.; Dikan, V.; Eimre, K.; Flage-Larsen, E.; Fornari, M.; Garcia, A.; Genovese, L.; Giantomassi, M.; Huber, S. P.; Janssen, H.; Kastlunger, G.; Krack, M.; Kresse, G.; Kühne, T. D.-S.; Lejaeghere, K.; Madsen, G. K. H.; Marsman, M.; Marzari, N.; Michalicek, G.; Mirhosseini, H.; Muller, T. M. A.; Petretto, G.; Pickard, C. J.; Ponce, S.; Rignanese, G.-M.; Rubel, O.; Ruh, T.; Sluydts, M.; Vanpoucke, D. E. P.; Vijay, S.; Wolloch, M.; Wortmann, D.; Yakutovich, A. V.; Yu, J.; Zadoks, A.; Zhu, B.; Pizzi, G.

In this Expert Recommendation, we list a set of guiding principles to perform new verification studies of DFT calculations, and we illustrate examples of verification by using a curated reference set of highly converged results for the EOS of 960 crystals, with two independent state-of-the-art all-electron (AE) DFT codes (FLEUR and WIEN2k).

Keywords: Density-functional theory; Verification; pseudopotential codes

Related publications

  • Reseach data in external data repository
    Publication year 2023
    License: CC-BY-4.0
    Hosted on materials cloud: Link to location

Permalink: https://www.hzdr.de/publications/Publ-38691


Laterally resolved polymorph conversion in Ga2O3 using FIBs

Bektas, U.; Klingner, N.; Hübner, R.; Chekhonin, P.; Liedke, M. O.; Hlawacek, G.

Laterally resolved polymoprh conversion in Galliumoxide
using Focused Ion Beams

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (Conference) (Online presentation)
    Defect Engineering in SiC and Other Wide Bandgap Semiconductor, 22.-24.10.2023, Erlangen, Shenzen, Deutschaldn, China

Permalink: https://www.hzdr.de/publications/Publ-38690


Materials Science with Fibs across Applications and Fluencies at the HZDR Ion Beam Center.

Hlawacek, G.

Materials Science with Fibs across Applications and Fluencies at the HZDR Ion Beam Center.

Keywords: FIB

Involved research facilities

Related publications

  • Invited lecture (Conferences)
    CINT User meeting, 19.-20.09.2023, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-38689


Applications of unconventional focused ion beams in quantum and semiconductor technology

Hlawacek, G.

Applications of unconventional focused ion beams in
quantum and semiconductor technology

Keywords: FIB

Involved research facilities

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  • Lecture (others)
    Institutsseminar, 10.05.2023, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38688


Application of gas field ion source and liquid metal alloy ion source based focused ion beams

Hlawacek, G.

I will present recent results obtained in our group using gas field ion sources (GFIS)1 and liquid metal alloy ion
source (LMAIS)2 based focused ion beams (FIB). I will briefly explain the source technology and our efforts
in developing new and unconventional ion sources for their application in FIB instruments. A few selected
examples will include the LMAIS based fabrication of single photon emitters (SPE) which are fundamental
building blocks for future quantum technology applications. I will present a method to fabricate at will placed
single or few SPEs emitting in the telecom O-band in Silicon3 . The successful integration of these telecom
quantum emitters into photonic structures such as micro-resonators, nanopillars and photonic crystals with
sub-micrometer precision paves the way toward a monolithic, all-silicon-based semiconductor-superconductor
quantum circuit for which this work lays the foundations. To achieve our goal we employ home built AuSi
and a unique CeC LMAIS both operated in an Orsay Physics CANION M31Z+ FIB. Silicon-on-insulator
substrates from different fabrication methods have been irradiated with a spot pattern. The achieved lateral
SPE placement accuracy is below 100 nm in both cases and the success rate of SPE formation is more than
50%. In addition I will present recent results obtained on the helium ion microscope using FIB and He ion
extracted from a GFIS source. These examples will include the epitaxial over growth of Sn spheres during He
ion beam irradiation. This more fundamental experiment show cases the importance of the ion beam driven
generation of interstitials and their diffusion during the ion beam irradiation4 . Finally, I’d like to demonstrate
how GFIS based HIM can be used to generate electrically controlled magnetic landscapes in spin orbit torque
(SOT) materials. Here, we use in-situ controlled irradiation to identify the best irradiation conditions for the
preparation of µm sized areas which will switch magnetization direction at different SOT currents5 .
Financial support by the COST Action CA19140 is acknowledged. http://www.fit4nano.eu/

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (others)
    Department Seminar, 13.04.2023, Pasadena, USA

Permalink: https://www.hzdr.de/publications/Publ-38687


High fluence He irradiation of materials using Helium Ion Microscopy

Hlawacek, G.; Klingner, N.; Lohmann, S.; Hübner, R.; Gandy, A.

I will present some recent results on the high fluence irradiation of metals using gas field ion source (GFIS) based
helium ion microscope (HIM)1 .
High entropy alloys (HEAs) are a relatively new class of metal alloys composed of several principal elements, usually
at (near) equiatomic ratios. Here, our goal is to understand how such a multicomponent alloy behaves under irradiation.
The FeCoCrNiV HEA exhibits both a face-centred cubic (fcc) and a body-centred tetragonal (bct) phase, thus allowing
us to specifically study the influence of crystalline structure at very similar chemical composition. We irradiated both
phases with a focussed He beam provided by a HIM at temperatures between room temperature and 500 ∘ C. The
irradiation fluence was varied between 6 × 1017 ions cm−2 to 1 × 1020 ions cm−2 . High-resolution images of the irradiated
areas were taken with the same HIM. Selected irradiated areas were additionally studied by transmission electron
microscopy (TEM) in combination with energy dispersive X-ray spectroscopy (EDXS). Under irradiation, pores start
to be generated in the material with pore sizes differing significantly between the two phases. At higher fluences and
above a critical temperature, a tendril structure forms in both phases. We found that the critical temperature depends
on the phase and is lower for fcc. TEM images reveal that the tendrils span the whole depth of the irradiated area, and
are accompanied by bubbles of various sizes. Scanning TEM-based EDXS of these structures indicates a He-induced
change in composition.
In the second part I want to present an intriguing observation shedding light on the fundamental processes related
to interstitial diffusion during irradiation. I will show how epitaxial growth of tin extrusions on tin-oxide-covered tin
spheres can be induced and simultaneously observed by implanting helium using a HIM2 . Calculations of collision
cascades based on the binary collision approximation (BCA) and 3D-lattice-kinetic Monte Carlo (3D-lkMC) simulations
show that the implanted helium will occupy vacancy sites, leading to a tin interstitial excess. Sputtering and phase
separation of the tin oxide skin, which is impermeable for tin atoms, create holes and will allow the epitaxial overgrowth
to start. Simultaneously, helium accumulates inside the irradiated spheres. Fitting the simulations to the experimentally
observed morphology allows us to estimate the tin to tin-oxide interface energy to be 1.98 J m−2 .
Both approach have in common that they employ spatially resolved irradiation and in-situ observation of defect
diffusion-driven effects to improve the understanding of the formation mechanism of ion induced structures.
Financial support by the COST Action CA19140 is acknowledged. http://www.fit4nano.eu/

Keywords: FIB

Involved research facilities

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  • Lecture (others)
    Department Seminar, 11.04.2023, Berkeley, USA

Permalink: https://www.hzdr.de/publications/Publ-38686


Gallium Oxide Fabrication with Ion Beams

Hlawacek, G.; Klingner, N.; Bektas, U.; Chekhonin, P.; Erb, D.; Kuznetsov, A.; Azarov, A.; García Fernández, J.; Zhao, J.; Djurabekova, F.

Gallium oxide is a novel ultra-wide band gap material, and the rationale for the current research project
is that its thin film fabrication technology is immature. In particular, the metastability conditions are
difficult to control during sequential deposition of different polymorphs with existing techniques. However, the
polymorphism may turn into a significant advantage if one can gain control over the polymorph multilayer
and nanostructure design. Our objective is to develop a method for the controllable solid state polymorph
conversion of gallium oxide assisted by ion irradiation. This fabrication method may pave the way for several
potential applications (e.g. in power electronics, optoelectronics, thermoelectricity batteries) and we will test
the corresponding functionalities during the project. Thus, we envisage multiple positive impacts and potential
benefits across a wide range of stakeholders.
I will introduce the aims and objectives of project paying specific attention to the planned methodology to
gain spatial control over the polymorph conversion. In the second half I will present the first results obtained
in the last 5 month. This includes broad beam irradiation which confirms the successful polymorph conversion
independent of primary ion species and the related exceptional radiation tolerance of the formed g-Ga2 O3 layer.
Further I will report the first spatially resolved focused ion beam (FIB) induced b- to g-Ga2 O3 polymorph
conversion. For this result different FIBs—available at the Ion Beam Center—have been used. These are in
particular the Helium Ion Microscope (HIM) using Neon ions, a conventional Gallium liquid metal ion source
(LMIS) based FIB as well as a liquid metal alloy ion source (LMAIS) FIB using Co ions. The confirmation of
the latter result also required the test and optimization of an electron backscatter diffraction (EBSD) based
analysis method.
I will end with an outlook on experiments foreseen for the rest of the project duration.
Support by the State of Saxony via Project 100629936 GoFIB—Gallium Oxide Fabrication with Ion Beams
and the COST Action 19140 FIT4NANO is acknowledged.

Keywords: FIB

Involved research facilities

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  • Lecture (others)
    Infineon InnoTalk, 05.04.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38685


PCB-Vision: A Multiscene RGB-Hyperspectral Benchmark Dataset of Printed Circuit Boards

Arbash, E.; Fuchs, M.; Rasti, B.; Lorenz, S.; Ghamisi, P.; Gloaguen, R.

PCB-Vision Dataset

Description:

The PCB-Vision dataset is a multiscene RGB-Hyperspectral benchmark dataset comprising 53 Printed Circuit Boards (PCBs). The RGB images are collected using a Teledyne Dalsa C4020 camera on a conveyor belt, while hyperspectral images (HSI) are acquired with a Specim FX10 spectrometer. The HSI data contains 224 bands in the VNIR range [400 - 1000]nm.

Data Format

  • RGB Images: .png files
  • PCB Masks: .jpg files
  • HSI Data: Each hyperspectral data cube is accompanied by a data file and a .hdr file.

Folder Organization

  • PCBVision
    • HSI/
      • 53 subfolders (one for each PCB)
      • 'General_masks' folder for 'General' segmentation ground truth
      • 'Monoseg_masks' folder for 'Monoseg' segmentation ground truth
      • 'PCB_Masks' folder for masks of the 53 PCBs in the hyperspectral cube
    • RGB/
      • 53 .jpg images
      • 'General' folder for RGB images 'General' segmentation ground truth
      • 'Monoseg_masks' folder for RGB images 'Monoseg' segmentation ground truth

Data Classes in Masks

  • Masks (both 'General' and 'Monoseg') contain 1 to 4 segmentation classes:
    • 0: "Others"
    • 1: "IC"
    • 2: "Capacitors"
    • 3: "Connectors"

Code Repository

To facilitate reading and working with the data, Python codes are available on the GitHub repository:

https://github.com/hifexplo/PCBVision

Citation

If you use this dataset, please cite the following article:

Word:

Arbash, Elias, Fuchs, Margret, Rasti, Behnood, Lorenz, Sandra, Ghamisi, Pedram, & Gloaguen, Richard. (2024). PCB-Vision: A Multiscene RGB-Hyperspectral Benchmark Dataset of Printed Circuit Boards (Version 1) [Data set]. Rodare. http://doi.org/10.14278/rodare.2704

Latex:

@article{arbash2024pcb, title={PCB-Vision: A Multiscene RGB-Hyperspectral Benchmark Dataset of Printed Circuit Boards}, author={Arbash, Elias and Fuchs, Margret and Rasti, Behnood and Lorenz, Sandra and Ghamisi, Pedram and Gloaguen, Richard}, journal={arXiv preprint arXiv:2401.06528}, year={2024} }

Contact

For further information or inquiries, please visit our website:

https://www.iexplo.space/

Contact Email: e.arbash@hzdr.de

Keywords: circular economy; automated data processing; optical sensors; recycling; e-waste; printed circuit board; hyperspectral; dataset; RGB; conveyor belt; sensors; machine learning; deep learning; PCBVision; open-source data; digitalization

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Permalink: https://www.hzdr.de/publications/Publ-38684


Spatially Resolved Polymorph Conversion in Ga2O3

Bektas, U.; Chekhonin, P.; Heller, R.; Hübner, R.; Liedke, M. O.; Klingner, N.; Hlawacek, G.

Monoclinic galliumoxide (β-Ga2O3) is a promising wideband gap
semiconductor with a bandgap of 4.7 eV and a high breakdown voltage.
However, the existence of several metastable polymorphs and the
immature fabrication technology limits its applications. The research is
based on the recent observation that β-Ga2O3 can reliable be converted
into γ-Ga2O3 using high energy ion beams [1,2]. It could also be shown that
the resulting γ-Ga2O3 layer exhibits an exceptional tolerance towards high
fluence ion beam irradiation [3].
Here, we use focused ion beam (FIB) induced processing to convert β-Ga2O3
into γ-Ga2O3 in a spatially controlled way. We employ focused Ne ions from
a helium ion microscope (HIM) and liquid metal alloy ion sources (LMAIS)
based FIB with Co, Si, and In to induce the polymorph conversion. Electron
backscatter diffraction (EBSD), transmission electron microscopy (TEM) and
atomic force microscopy (AFM) are used to confirm, in a spatially resolved
way, the successful polymorph conversion. From the obtained EBSD data
the orientation relationship between the irradiated and unirradiated
material is resolved. Broadbeam irradiated reference samples have been
used to corroborate these results with channeling Rutherford
backscattering spectrometry (c-RBS), X-ray diffraction (XRD) and Doppler
broadening variable energy positron annihilation spectroscopy (DB-VEPAS)
results. The obtained crystal structure and defect distribution data supports
the model suggested for the conversion mechanism [3].
This research is supported by the tax funds on the basis of the budget
passed by the Saxonian state parliament in Germany and the COST Action
CA19140 FIT4NANO https://www.fit4nano.eu/.
[1] A. Azarov, C. Bazioti, Disorder-Induced Ordering in Gallium Oxide
Polymorphs, Phys. Rev. Lett. 128 (2022), 015704.
[2] J. Garcia-Fernandez, S.B. KJeldby, Formation of γ-Ga2O3 by ion
implantation: Polymorphic phase transformation of β- Ga2O3, Appl. Phys.
Lett. 121 (2022), 191601.
[3] A. Azarov, J. G. Fernández, J. Zhao, F. Djurabekova, H. He, R. He, Ø. Prytz,
L. Vines, U. Bektas, P. Chekhonin, N. Klingner, G. Hlawacek, A. Kuznetsov,
Universal radiation tolerant semiconductor (2023),
doi:10.48550/ARXIV.2303.13114.

Keywords: FIB

Involved research facilities

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  • Lecture (Conference)
    AVS 69, 05.-10.11.2023, Portland, OR, USA

Permalink: https://www.hzdr.de/publications/Publ-38683


Influence of crystal structure on helium-induced tendril formation in an FeCoCrNiV high-entropy alloy

Lohmann, S.; Goodall, R.; Hlawacek, G.; Hübner, R.; Ma, L.; Gandy, A. S.

High-entropy alloys (HEAs) are a relatively new class of metal alloys
composed of several principal elements, usually at (near) equiatomic
ratios. Our goal is to understand how such a multicomponent alloy
behaves under irradiation. The FeCoCrNiV HEA exhibits both a face-
centred cubic (fcc) and a body-centred tetragonal (bct) phase, thus
allowing us to specifically study the influence of crystalline structure
at very similar chemical composition. We irradiated both phases with
a focussed He beam provided by a helium ion microscope (HIM) at
temperatures between room temperature and 500∘ C. The irradiation
fluence was varied between 6 × 1017 ions/cm2 and 1 × 1020 ions/cm2 .
High-resolution images of the irradiated areas were taken with the same
HIM. Selected irradiated areas were additionally studied by TEM in
combination with EDXS. Under irradiation, pores start to be generated
in the material with pore sizes differing significantly between the two
phases. At higher fluences and above a critical temperature, a tendril
structure forms in both phases. We found that the critical tempera-
ture depends on the phase and is lower for fcc. TEM images reveal
that the tendrils span the whole depth of the irradiated area, and are
accompanied by bubbles of various sizes. Scanning TEM-based EDXS
of these structures indicates a He-induced change in composition.

Keywords: FIB

Involved research facilities

Related publications

  • Lecture (Conference)
    DPG, 20.-24.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38682


Influence of Crystal Structure on Helium-induced Nano-tendril Formation in a Multiphase, Multicomponent Alloy

Gandy, A.; Lohmann, S.; Hlawacek, G.; Hübner, R.; Ma, L.; Goodall, R.

Plasma-facing materials (PFMs) for magnetic fusion will experience a unique set of challenges, including plasma-surface interactions. In tungsten, helium ions diffuse through the surface resulting in the formation of nano-tendrils which may contaminate the fusion plasma. Multicomponent alloys are being considered as alternative PFMs though little is known about how they will behave in a plasma environment. Using a focused helium beam provided by a helium ion microscope (HIM), we irradiated equiatomic FeCoCrNiV, which comprises FCC and BCT crystal structures with similar compositions, enabling us to determine the influence of crystal structure on the formation of nano-tendrils. Irradiations were performed up to 500°C, and fluences between 6x1017 and 1x1020 He ions/cm2. Here, we present HIM images from the irradiated regions, and cross-sectional TEM/EDX images on selected samples. The data reveals a critical temperature for tendril formation dependant on crystal structure, helium bubbles, and helium-induced changes in composition.

Keywords: FIB

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  • Lecture (Conference)
    TMS 2023 - 152nd Annual Meeting & Exhibition, 19.-23.03.2023, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-38680


Creep strength boosted by a high-density of stable nanoprecipitates in high-chromium steels

Vivas, J.; De-Castro, D.; Poplawsky, J. D.; Altstadt, E.; Houska, M.; Urones-Garrote, E.; San Martín, D.; Caballero, F. G.; Serrano, M.; Capdevila, C.

there is a need worldwide to develop materials for advanced power plants with steam temperatures of 700°c and above that will achieve long-term creep-rupture strength and low cO2 emissions. the creep resistance of actual 9-12cr steels is not enough to fulfil the engineering requirements above 600°c. in this paper, the authors report their advances in the improvement of creep properties of this type of steels by the microstructural optimization through nano-precipitation using two methodologies. 1) Applying a high temperature austenitization cycle followed by an ausforming step (thermomechanical treatment, tMt ) to G91 steel, to increase the martensite dislocation density and, thus, the number density of MX precipitates (M = v,Nb; X = c,N) but at the expense of deteriorating the ductility. 2) compositional adjustments, guided by computational thermodynamics, combined with a conventional heat treatment (no tMt ), to design novel steels with a good ductility while still possessing a high number density of MX precipitates, similar to the one obtained after the tMt in G91. the microstructures have been characterized by optical, scanning and transmission electron microscopy, eBSD and atom probe tomog- raphy. the creep behaviour at 700°c has been eval- uated under a load of 200 N using small punch creep tests.

Keywords: creep resistant steels; thermomechanical treatment; creep fracture behaviour; microstructural degradation; small punch creep tests; ausforming

Permalink: https://www.hzdr.de/publications/Publ-38678


Nanoparticle depressants - The effect of colloidal silica in the froth flotation of calcium minerals

Ben Said, B.; Pereira, L.; Rudolph, M.

Colloidal silica is investigated as a potential selective nanoparticle depressant in the flotation process of calcium minerals. The micro particle separation of calcium minerals by selective froth flotation is a challenging task. The difficulty arises from the similar surface properties of the minerals and thus similar responses to different known families of flotation collectors (selectively adsorbing surfactants). The effect of colloidal silica and its interactions with the reagent system were investigated by varying its modification and specific surface area/particle size. Microflotation of scheelite (calcium tungstate), fluorite (calcium fluoride), calcite (calcium carbonate) and apatite (calcium fluorophosphate) was used to investigate whether colloidal silica has an effect on the minerals. Initial results show that colloidal silica prevents calcite from floating, while scheelite, fluorite and apatite are not affected by the presence of the reagent, regardless of the dosage. Moreover, batch flotation tests have shown significant differences between the three modifications (Sodium stabilized colloidal silica, sodium stabilized modified with aluminate and sodium stabilized modified with silane) in terms of the significant effect on the selectivity. Fundamental investigations have been carried out to figure out how the different modifications perform and at which phase of the flotation process. The upscaling of the technology was then investigated on a pilot and industrial scale.

Keywords: Froth Flotation; Nanoparticles; Adsorption; Bubble Attachment; Particle Interactions

  • Poster
    Flotation23, 05.-09.11.2023, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-38675


Data publication: MRF timing system characterization and 1-wire sensor calibration using a climate chamber

Zenker, K.; Kuntzsch, M.

This data was taken at DSEY (04-08.12.2023) using a climate chamber.

Multiple temperature and humidity sensors were put into the climate chamber.

Due to problems with the ChimeraTK server not all data was collected by a single ChimeraTK server,

but the sensors were grouped and read by different 1-wire servers (`1-wire_1`, `1-wire_2`, `1-wire_3`, `1-wire_4`, `1-wire_5`). Each sensor identification is listed in the owfs.xlmap file. First sensor in owfs.xlmap corresponds e.g. to DS18B20/0. Data is available as HDF5 and ROOT file.

In addition the MRF timing system was running. Two EVRs (EVR2, EVR3) were connected via long fibers (100m) to the EVM. The fibers routed through the climate chamber, such that most of the fiber was inside the chamber. A Rhode&Schwartz oscilloscope was used to measure the delay of the timing output signals with respect to a third EVR (EVR1), that was connected via a short cable outside the climate chamber. That data is included in timing-data.root, which includes:

  • Delay of EVR2 with respect to EVR1 -> Delay_C1C2
  • Delay of EVR3 with respect to EVR1 -> Delay_C1C3
  • Delay compensation (actual, correction) for each EVR

The intended measurement, was to use active delay compensation for EVR2 and deactivated delay compensation for EVR3. However, the measurement was spoiled by periodic delay shifts in case of EVR2. On 07.12. 10:20 the delay compensation was also activated for EVR3.

For technical reasons not all timing related data is included in rs-data.root. The delay compensation data (actual, correction) should be taken from the aggregated raw data. It includes basically all data (temperature, humidity, oscilloscope data), but in the beginning the actual delay measurement was missing (which should be taken from timing-data.root).

Selected data periods are listed in the file data.ods.

Some analysis results are already included here for convenience:

  • Plots includes:
    • Temperature calibration
    • Humidity calibration
    • Delay measurements
  • Calibration.root includes calibration constants for humidity/temperature calibration and graphs/plots

Keywords: ELBE; Timing System

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Permalink: https://www.hzdr.de/publications/Publ-38668


How to verify the precision of density-functional-theory implementations via reproducible and universal workflows

Bosoni, E.; Beal, L.; Bercx, M.; Blaha, P.; Blugel, S.; Broder, J.; Callsen, M.; Cottenier, S.; Degomme, A.; Dikan, V.; Eimre, K.; Flage-Larsen, E.; Fornari, M.; Garcia, A.; Genovese, L.; Giantomassi, M.; Huber, S. P.; Janssen, H.; Kastlunger, G.; Krack, M.; Kresse, G.; Kühne, T. D.-S.; Lejaeghere, K.; Madsen, G. K. H.; Marsman, M.; Marzari, N.; Michalicek, G.; Mirhosseini, H.; Muller, T. M. A.; Petretto, G.; Pickard, C. J.; Ponce, S.; Rignanese, G.-M.; Rubel, O.; Ruh, T.; Sluydts, M.; Vanpoucke, D. E. P.; Vijay, S.; Wolloch, M.; Wortmann, D.; Yakutovich, A. V.; Yu, J.; Zadoks, A.; Zhu, B.; Pizzi, G.

Density-functional theory methods and codes adopting periodic boundary conditions are extensively used in condensed matter physics and materials science research. In 2016, their precision (how well properties computed with different codes agree among each other) was systematically assessed on elemental crystals: a first crucial step to evaluate the reliability of such computations. In this Expert Recommendation, we discuss recommendations for verification studies aiming at further testing precision and transferability of density-functional-theory computational approaches and codes. We illustrate such recommendations using a greatly expanded protocol covering the whole periodic table from Z = 1 to 96 and characterizing 10 prototypical cubic compounds for each element: four unaries and six oxides, spanning a wide range of coordination numbers and oxidation states. The primary outcome is a reference dataset of 960 equations of state cross-checked between two all-electron codes, then used to verify and improve nine pseudopotential-based approaches. Finally, we discuss the extent to which the current results for total energies can be reused for different goals.

Keywords: Density-functional theory; Verification; pseudopotential codes

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Permalink: https://www.hzdr.de/publications/Publ-38667


Triply Bonded Pancake π-Dimers Stabilized by Tetravalent Actinides

Barluzzi, L.; Ogilvie, S. P.; Dalton, A. B.; Kaden, P.; Gericke, R.; Mansikkamäki, A.; Giblin, S. R.; Layfield, R. A.

Aromatic π-stacking is a weakly attractive, non-covalent interaction often found in biological macromolecules and synthetic supramolecular chemistry. The weak non-directional nature of π-stacking can present challenges in the design of materials owing to their weak, non-directional nature. However, when aromatic π-systems contain an unpaired electron, stronger attraction involving face-to-face π-orbital overlap is possible, resulting in covalent so-called ‘pancake’ bonds. Two-electron, multicentre single pancake bonds are well-known whereas four-electron double pancake bonds are rare. Higherorder
pancake bonds have been predicted, but experimental systems are unknown. Here, we show that six-electron triple pancake bonds can be synthesized by threefold reduction of hexaazatrinaphthylene (HAN) and subsequent stacking of the [HAN]³‾ tri-radicals. Our analysis reveals a multicentre covalent triple pancake bond consisting of a π-orbital and two equivalent π-orbitals. An electrostatic stabilizing role is established for tetravalent thorium and uranium ions in these systems. We also show that the electronic absorption spectrum of the triple pancake bonds closely matches computational predictions, providing experimental verification of these unique interactions. The discovery of conductivity in thin films of the triply bonded π-dimers presents new opportunities for the discovery of single-component molecular conductors and other spinbased molecular materials.

Keywords: actinides; triply bonded pancake; stabilization; magnetism; EPR; quantum chemistry

  • Open Access Logo Journal of the American Chemical Society 146(2024)6, 4234-4241
    Online First (2024) DOI: 10.1021/jacs.3c13914

Permalink: https://www.hzdr.de/publications/Publ-38655


Impact of Viscosity on Human Hepatoma Spheroids in Soft Core-Shell Microcapsules

Peng, X.; Janićijević, Ž.; Lemm, S.; Hauser, S.; Knobel, M.; Pietzsch, J.; Bachmann, M.; Baraban, L.

The extracellular environment regulates the structures and functions of cells, from the molecular to the tissue level. However, the underlying mechanisms influencing the organization and adaptation of cancer in three-dimensional (3D) environments are not yet fully understood. In this study, the influence of the viscosity of the environment is investigated on the mechanical adaptability of human hepatoma cell (HepG2) spheroids in vitro, using 3D microcapsule reactors formed with droplet-based microfluidics. To mimic the environment with different mechanical properties, HepG2 cells are encapsulated in alginate core–shell reservoirs (i.e., microcapsules) with different core viscosities tuned by incorporating carboxymethylcellulose. The significant changes in cell and spheroid distribution, proliferation, and cytoskeleton are observed and quantified. Importantly, changes in the expression and distribution of F-actin and keratin 8 indicate the relation between spheroid stiffness and viscosity of the surrounding medium. The increase of F-actin levels in the viscous medium can indicate an enhanced ability of tumor cells to traverse dense tissue. These results demonstrate the ability of cancer cells to dynamically adapt to the changes in extracellular viscosity, which is an important physical cue regulating tumor development, and thus of relevance in cancer biology.

Keywords: hepatoma spheroids; cell adaptation; cytoskeleton; tumor microenvironment; hydrogel microcapsule

Permalink: https://www.hzdr.de/publications/Publ-38654


Data publication: AFLOW-CCE for the thermodynamics of ionic materials

Friedrich, R.; Curtarolo, S.

The data set contains the calculated results from which the formation enthalpies have been calculated.

Involved research facilities

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  • Reseach data in external data repository
    Publication year 2024
    License: CC BY; Creative Commons Attribution 4.0 International
    Hosted on aflow.org: Link to location
    DOI: 10.1063/5.0184917

Permalink: https://www.hzdr.de/publications/Publ-38653


AFLOW-CCE for the thermodynamics of ionic materials

Friedrich, R.; Curtarolo, S.

Accurate thermodynamic stability predictions enable data-driven computational materials design. Standard density functional theory
(DFT) approximations have limited accuracy with average errors of a few hundred meV/atom for ionic materials, such as oxides
and nitrides. Thus, insightful correction schemes as given by the coordination corrected enthalpies (CCE) method, based on an intuitive
parametrization of DFT errors with respect to coordination numbers and cation oxidation states, present a simple, yet accurate
solution to enable materials stability assessments. Here, we illustrate the computational capabilities of our AFLOW-CCE software by
utilizing our previous results for oxides and introducing new results for nitrides. The implementation reduces the deviations between
theory and experiment to the order of the room temperature thermal energy scale, i.e., ∼25 meV/atom. The automated corrections
for both materials classes are freely available within the AFLOW ecosystem via the AFLOW-CCE module, requiring only structural
inputs.

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-38652


Predicting the electronic structure of matter at scale with machine learning

Cangi, A.

In this talk, I will present our recent advancements in utilizing machine learning 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 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 has resulted in significant savings in computational resources when identifying optimal neural network architectures, thereby laying the foundation for large-scale 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].

References
[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, Phys. Rev. B 104, 035120 (2021). [3] J. Ellis, L. Fiedler, G. Popoola, N. Modine, J. Stephens, A. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B, 104, 035120 (2021)
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. Popoola, T. Yovell, V. Oles, J. Austin Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol., 3, 045008 (2022)
[5] L. Fiedler, N. Modine, S. Schmerler, D. Vogel, G. Popoola, A. Thompson, S. Rajamanickam, A. Cangi, npj. Comput. Mater., 9, 115 (2023)

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

  • Invited lecture (Conferences)
    APS March Meeting 2024, 04.-08.03.2024, Minneapolis, United States

Permalink: https://www.hzdr.de/publications/Publ-38651


Scalable Machine Learning for Predicting the Electronic Structure of Matter

Cangi, A.

I will present our recent progress in significantly scaling up density functional theory calculations with machine learning [1], for which we have developed the Materials Learning Algorithms (MALA) framework [2]. We have demonstrated the transferability of our machine learning model across phase boundaries, such as metals at their melting point [3] and electronic temperature [4]. In addition, our use of automated machine learning has led to a significant reduction in the computational resources required to identify optimal neural network architectures [5]. Most importantly, I will present our recent breakthrough in enabling fast neural-network driven electronic structure calculations for ultra-large systems unattainable by conventional density functional theory calculations [6]. I will mention in passing our other efforts in solving the Kohn-Sham equations of time-dependent density functional theory in terms of physics-informed neural networks [7], and in developing a robust framework for inverting the Kohn-Sham equations in terms of Fourier neural operators [8].

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials, 6, 040301 (2022).
[2] A. Cangi, S. Rajamanickam, B. Brzoza, T. J. Callow, J. A. Ellis, O. Faruk, L. Fiedler, J. Fox, N. Hoffmann, K. D. Miller, D. Kotik, S. Kulkarni, N. Modine, P. Mohammed, V. Oles, G. A. Popoola, F. Pöschel, J. Romero, S. Schmerler, J. A. Stephens, H. Tahmasbi, A. P. Thompson, S. Verma, D. J. Vogel, Materials Learning Algorithms (MALA), doi.org/10.5281/zenodo.5557254, (2023).
[3] J. Ellis, L. Fiedler, G. Popoola, N. Modine, J. Stephens, A. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B, 104, 035120 (2021).
[4] L. Fiedler, N. A. Modine, K. D. Miller, A. Cangi, Phys. Rev. B 108, 125146 (2023).
[5] L. Fiedler, N. Hoffmann, P. Mohammed, G. Popoola, T. Yovell, V. Oles, J. Austin Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol., 3, 045008 (2022).
[6] L. Fiedler, N. Modine, S. Schmerler, D. Vogel, G. Popoola, A. Thompson, S. Rajamanickam, A. Cangi, npj. Comput. Mater., 9, 115 (2023).
[7] K. Shah, P. Stiller, N. Hoffmann, A. Cangi, Physics-Informed Neural Networks as Solvers for the Time-Dependent Schrödinger Equation, NeurIPS Workshop Machine Learning and the Physical Sciences, arXiv:2210.12522 (2022).
[8] V. Martinetto, K. Shah, A. Cangi, A. Pribram-Jones, Inverting the Kohn-Sham equations with physics-informed machine learning, arXiv:2312.15301 (2023).

Keywords: Electronic structure theory; Density functional theory; Artificial intelligence; Machine learning; Neural networks; Materials science; Condensed-matter physics

  • Invited lecture (Conferences)
    Machine Learning in Electronic-Structure Theory, 25.-29.03.2024, 1155 E. 60th Street, Chicago, IL 60637, United States
  • Lecture (Conference)
    Jahrestagung/Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 17.-22.03.2024, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38650


A survey of practice patterns for real-time intrafractional motion-management in particle therapy

Zhang, Y.; Trnkova, P.; Toshito, T.; Heijmen, B.; Richter, C.; Aznar, M.; Albertini, F.; Bolsi, A.; Daartz, J.; Bertholet, J.; Knopf, A.

Background and purpose: Organ motion compromises accurate particle therapy delivery. This study reports on the practice patterns for real-time intrafractional motion-management in particle therapy to evaluate current clinical practice and wishes and barriers to implementation.
Materials and methods: An institutional questionnaire was distributed to particle therapy centres worldwide (7/ 2020–6/2021) asking which type(s) of real-time respiratory motion management (RRMM) methods were used, for which treatment sites, and what were the wishes and barriers to implementation. This was followed by a three-round DELPHI consensus analysis (10/2022) to define recommendations on required actions and future vision. With 70 responses from 17 countries, response rate was 100% for Europe (23/23 centres), 96% for Japan (22/23) and 53% for USA (20/38).
Results: Of the 68 clinically operational centres, 85% used RRMM, with 41% using both rescanning and active methods. Sixty-four percent used active-RRMM for at least one treatment site, mostly with gating guided by an external marker. Forty-eight percent of active-RRMM users wished to expand or change their RRMM technique. The main barriers were technical limitations and limited resources. From the DELPHI analysis, optimisation of rescanning parameters, improvement of motion models, and pre-treatment 4D evaluation were unanimously
considered clinically important future focus. 4D dose calculation was identified as the top requirement for future commercial treatment planning software.
Conclusion: A majority of particle therapy centres have implemented RRMM. Still, further development and clinical integration were desired by most centres. Joint industry, clinical and research efforts are needed to translate innovation into efficient workflows for broad-scale implementation.

Keywords: Particle/proton therapy; Intrafraction motion; Real-time respiratory motion management; Image-guided particle therapy; Rescanning

Involved research facilities

  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-38649


A survey of practice patterns for adaptive particle therapy for interfractional changes

Trnkova, P.; Zhang, Y.; Toshito, T.; Heijmen, B.; Richter, C.; Aznar, M. C.; Albertini, F.; Bolsi, A.; Daartz, J.; Knopf, A. C.; Bertholet, J.

Background and purpose: Anatomical changes may compromise the planned target coverage and organs-at-risk dose in particle therapy. This study reports on the practice patterns for adaptive particle therapy (APT) to evaluate current clinical practice and wishes and barriers to further implementation. Materials and methods: An institutional questionnaire was distributed to PT centres worldwide (7/2020–6/2021) asking which type of APT was used, details of the workflow, and what the wishes and barriers to implementation were. Seventy centres from 17 countries participated. A three-round Delphi consensus analysis (10/2022) among the authors followed to define recommendations on required actions and future vision.
Results: Out of the 68 clinically operational centres, 84% were users of APT for at least one treatment site with head and neck being most common. APT was mostly performed offline with only two online APT users (plan-library). No centre used online daily re-planning. Daily 3D imaging was used for APT by 19% of users. Sixty-eight percent of users had plans to increase their use or change their technique for APT. The main barrier was “lack of integrated and efficient workflows”. Automation and speed, reliable dose deformation for dose accumulation and
higher quality of in-room volumetric imaging were identified as the most urgent task for clinical implementation of online daily APT.
Conclusion: Offline APT was implemented by the majority of PT centres. Joint efforts between industry research and clinics are needed to translate innovations into efficient and clinically feasible workflows for broad-scale implementation of online APT.

Keywords: Particle/proton therapy; Adaptive radiotherapy (ART); Interfraction anatomical variation; Image guided particle therapy; Adaptive treatment planning

Permalink: https://www.hzdr.de/publications/Publ-38648


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