Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41396 Publications

Micrometer thick Sm-Co films for applications on flexible systems

Tzanis, A.; Koutsokostas, N.; Helm, T.; Kollia, C.; Speliotis, T.

In the industry 4.0 eco-system, flexible electronic devices bear a huge potential for a broad range of applications due to their diverse properties, such as high stretchability, biocompatibility, portability, light weight, and low costs. In this work, Cobalt-samarium permanent magnetic thin films on flexible polyimide substrate are studied. The influence of the sputter deposition pressure on the structural, morphological, and magnetic properties is analyzed. A method for growing flexible magnetic films is proposed by achieving a maximum coercivity of 13.86 kOe and an energy product of 16.9 MGOe. These results lay the foundations for the design and fabrication of flexible magnetic devices.

Permalink: https://www.hzdr.de/publications/Publ-35479
Publ.-Id: 35479


Static magnetic and ESR spectroscopic properties of the dimer-chain antiferromagnet BiCoPO5

Iakovleva, M.; Petersen, T.; Alfonsov, A.; Skourski, Y.; Grafe, H.-J.; Vavilova, E.; Nath, R.; Hozoi, L.; Kataev, V.

We report a comprehensive study of the static susceptibility, high-field magnetization and highfrequency/high-magnetic field electron spin resonance (HF-ESR) spectroscopy of polycrystalline samples of the bismuth cobalt oxyphosphate BiCoPO5. This compound features a peculiar spin system that can be considered as antiferromagnetic (AFM) chains built of pairs of ferromagnetically coupled Co spins and interconnected in all three spatial directions. It was previously shown that BiCoPO5 orders antiferromagnetically at TN ≈ 10 K and this order can be continuously suppressed by magnetic field towards the critical value μ0Hc ≈ 15 T. In our experiments we find strongly enhanced magnetic moments and spectroscopic g factors as compared to the expected spin-only values, suggesting a strong contribution of orbital magnetism for the Co2+ ions. This is quantitatively confirmed by ab initio quantum chemical calculations.Within the AFM ordered phase, we observe a distinct field-induced magnetic phase transition. Its critical field rises to ∼6 T at T << TN. The HF-ESR spectra recorded at T << TN are very rich comprising up to six resonance modes possibly of the multimagnonic nature that soften towards the critical region around 6 T. Interestingly, we find that the Co moments are not yet fully polarized at Hc which supports a theoretical proposal identifying Hc as the quantum critical point for the transition of the spin system in BiCoPO5 to the quantum disordered state at stronger fields.

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Permalink: https://www.hzdr.de/publications/Publ-35478
Publ.-Id: 35478


Nanoscale magnetic bubbles in Nd2Fe14B at room temperature

He, Y.; Helm, T.; Soldatov, I.; Schneider, S.; Pohl, D.; Srivastava, A. K.; Sharma, A. K.; Kroder, J.; Schnelle, W.; Schaefer, R.; Rellinghaus, B.; Fecher, G. H.; Parkin, S. S. P.; Felser, C.

The increasing demand for computer data storage with a higher recording density can be addressed by using smaller magnetic objects, such as bubble domains. Small bubbles predominantly require a strong saturation magnetization combined with a large magnetocrystalline anisotropy to resist self-demagnetization. These conditions are well satisfied for highly anisotropic materials. Here, we study the domain structure of thin Nd2Fe14B lamellae. Magnetic bubbles with a minimum diameter of 74 nm were observed at room temperature, approaching even the range of magnetic skyrmions. The stripe domain width and the bubble size are both thickness dependent. Furthermore, a kind of bubble was observed below the spin-reorientation transition temperature that combine bubbles with opposite helicity. In this paper, we reveal Nd2Fe14B to be a good candidate for a high-density magnetic bubble-based memory.

Permalink: https://www.hzdr.de/publications/Publ-35477
Publ.-Id: 35477


Deformed spin-1/2 square lattice in antiferromagnetic NaZnVOPO4(HPO4)

Guchhait, S.; Ambika, D. V.; Ging, Q.-P.; Uhlarz, M.; Furukawa, Y.; Tsirlin, A. A.; Nath, R.

We report the structural and magnetic properties of a new spin-1/2 antiferromagnet NaZnVOPO4(HPO4) studied via x-ray diffraction, magnetic susceptibility, high-field magnetization, specific heat, and 31P nuclear magnetic resonance (NMR) measurements, as well as density-functional band-structure calculations. While thermodynamic properties of this compound are well described by the J1-J2 square-lattice model, ab initio calculations suggest a significant deformation of the spin lattice. From fits to the magnetic susceptibility we determine the averaged nearest-neighbor and second-neighbor exchange couplings of J1 ≃ −1.3 K and J2 ≃ 5.6 K, respectively, resulting in the effective frustration ratio α = J2/J1 ≃ −4.3 that implies columnar antiferromagnetic order as the ground state. Experimental saturation field of 15.3 T is consistent with these estimates if 20 % spatial anisotropy in J1 is taken into account. Specific heat data signal the onset of a magnetic long-range order at TN ≃ 2.1 K, which is further supported by a sharp peak in the NMR spin-lattice relaxation rate. The NMR spectra mark the superposition of two P lines due to two nonequivalent P sites where the broad line with the strong hyperfine coupling and short T1 is identified as the P(1) site located within the magnetic planes, while the narrow line with the weak hyperfine coupling and long T1 is designated as the P(2) site located between the planes.

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Permalink: https://www.hzdr.de/publications/Publ-35476
Publ.-Id: 35476


Ce and Dy substitutions in Nd2Fe14B: Site-specific magnetic anisotropy from first principles

Boust, J.; Aubert, A.; Fayyazi, B.; Skokov, K. P.; Skourski, Y.; Gutfleisch, O.; Pourovskii, L. V.

A first-principles approach combining density-functional and dynamical mean-field theories in conjunction with a quasiatomic approximation for the strongly localized 4 f shell is applied to Nd2Fe14B-based hard magnets to evaluate crystal-field and exchange-field parameters at rare-earth sites and their corresponding single-ion contribution to the magnetic anisotropy. In pure Nd2Fe14B, our calculations reproduce the easy-cone to easy-axis transition; theoretical magnetization curves agree quantitatively with experiment. Our study reveals that the rare-earth single-ion anisotropy in the 2-14-1 structure is strongly site dependent, with the g rare-earth site exhibiting a larger value. In particular, we predict that increased f- and g-site occupancy of R = Ce and Dy, respectively, leads to an increase of the magnetic anisotropy of the corresponding (Nd, R)2Fe14B-substituted
compounds.

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Permalink: https://www.hzdr.de/publications/Publ-35475
Publ.-Id: 35475


Martensitic fcc-hcp transformation pathway in solid krypton and xenon and its effect on their equations of state

Rosa, A. D.; Dewaele, A.; Garbarino, G.; Svitlyk, V.; Morard, G.; de Angelis, F.; Krstulovic, M.; Briggs, R.; Irifune, T.; Mathon, O.; Bouhifd, M. A.

The martensitic transformation is a fundamental physical phenomenon at the origin of important industrial applications. However, the underlying microscopic mechanism, which is of critical importance to explain the outstanding mechanical properties of martensitic materials, is still not fully understood. This is because for most martensitic materials the transformation is a fast process that makes in situ studies extremely challenging. Noble solids krypton and xenon undergo a progressive pressure-induced face-centered cubic (fcc) to hexagonal close-packed (hcp) martensitic transition with a very wide coexistence domain. Here, we took advantage of this unique feature to study the detailed transformation progress at the atomic level by employing in situ x-ray diffraction and absorption spectroscopy.We evidenced a four-stage pathway and suggest that the lattice mismatch between the fcc and hcp forms plays a key role in the generation of strain.We also determined precisely the effect of the transformation on the compression behavior of these materials.

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Permalink: https://www.hzdr.de/publications/Publ-35474
Publ.-Id: 35474


Deconvoluting Cr States in Cr-Doped UO2 Nuclear Fuels via Bulk and Single Crystal Spectroscopic Studies

Murphy, G. L.; Gericke, R.; Gilson, S.; Bazarkina, E.; Roßberg, A.; Kaden, P.; Thümmler, R.; Klinkenberg, M.; Henkes, M.; Kegler, P.; Svitlyk, V.; Marquardt, J.; Lender, T.; Hennig, C.; Kvashnina, K.; Huittinen, N. M.

Cr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U+4 in the fluorite lattice as Cr+3 with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr0) and oxide related Cr+2 and Cr+32O3 were identified and attributed to grain boundary species and precipitates, with concurrent (Cr+3xU+41-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.

Keywords: Cr-doped UO2; Nuclear Fuel; Uranium; EPR; HERFD-XANES; EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-35473
Publ.-Id: 35473


Vergleichende Untersuchungen zu Höhe und Aufbau der Zweiphasenschicht in Bodenkolonnen mittels Feldsensor und Lichtvorhang

Engel, F. S.; Wiedemann, P.; Schleicher, E.; Schubert, M.; Hampel, U.; Klein, H.; Rehfeldt, S.

Aufgrund des hohen Energiebedarfs thermischer Trennverfahren werden trennwirksame Einbauten in Kolonnen stetig weiterentwickelt und optimiert. In Bodenkolonnen kommen hierbei verstärkt Ventilböden mit Fixed Valves und Float Valves zum Einsatz, bei denen im Gegensatz zu den in der Literatur bereits ausführlich untersuchten Siebböden noch großes Forschungspotential besteht.

Eine essenzielle fluiddynamische Größe ist dabei die Zweiphasenschichthöhe, die einen großen Einfluss auf den Stoffaustausch auf dem Boden hat. Trotz ihrer großen Bedeutung wird diese Messgröße im Rahmen von fluiddynamischen Untersuchungen bisher hauptsächlich visuell abgeschätzt, was keine objektive Wiederholbarkeit gewährleistet und somit zu großen Unsicherheiten führt. Um verlässliche Aussagen zur Zweiphasenschichthöhe treffen zu können, ist daher die Aufzeichnung objektiver Messgrößen und Anwendung automatisierter Auswerteverfahren erforderlich.

Im Rahmen des AiF-Forschungsvorhabens Werkzeuge und Methoden zur verbesserten fluiddynamischen Auslegung von Querstromböden mit Hochleistungsventilen wurden zwei unabhängige Messmethoden eingesetzt, die im Rahmen dieses Beitrags vergleichend bewertet werden. Als erste Methode wurden Messungen mit dem Lichtvorhang Rapidoscan® durchgeführt, der mittels Infrarot-Strahlung die Zweiphasenschicht nicht-invasiv auf dem Boden detektieren kann. Als zweite Methode kam ein vom Helmholtz-Zentrum Dresden-Rossendorf (HZDR) entwickelter Feldsensor zum Einsatz, der mit 360 Elektrodenpaaren die Phasenverteilung in mehreren Ebenen über dem Boden vermisst. Hieraus lässt sich ein dreidimensionales Feld der Phasenverteilung rekonstruieren, das ebenfalls Rückschlüsse auf die Zweiphasenschichthöhe zulässt.

Die Messungen wurden an einem Gas/Flüssig-Kolonnenversuchsstand am Lehrstuhl für Anlagen- und Prozesstechnik der TU München durchgeführt, der einen Durchmesser von 1,2 m aufweist und mit dem Stoffsystem Luft/Wasser betrieben wurde. Vermessen wurden fünf verschiedene Bodenkonfigurationen von Sieb- und Fixed-Valve-Böden, die unter Berücksichtigung von relevanten in der Industrie eingesetzten Ventiltypen ausgewählt wurden.

Die Untersuchungen mit dem Feldsensor geben detaillierte Informationen zur Phasenverteilung der Zweiphasenschicht auf dem Boden bei verschiedenen
Belastungszuständen. Auf Grundlage der gewonnenen topographischen Daten können zudem Aussagen über die Höhe der Zweiphasenschicht getroffen und ein Vergleich der beiden Messmethoden vorgenommen werden. Abschließend werden daraus abgeleitete Erkenntnisse zur Gültigkeit und Anwendbarkeit von bekannten Zweiphasenschichtmodellen aus der Literatur vorgestellt.

  • Lecture (Conference)
    Jahrestreffen der DECHEMA-Fachgruppen Fluidverfahrenstechnik und Adsorption, 21.-23.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35471
Publ.-Id: 35471


Towards Real-Time Analysis of Gas-Liquid Pipe Flow: A Wire-Mesh Sensor for Industrial Applications

Wiedemann, P.; de Assis Dias, F.; Trepte, M.; Schleicher, E.; Hampel, U.

Real-time monitoring of gas-liquid pipe flow is highly demanded in industrial processes in the chemical and power engineering sector. Therefore, the present contribution describes the novel design of a robust wire-mesh sensor with integrated data processing unit. The developed device features a sensor body for industrial conditions of up to 400°C and 135 bar as well as real-time processing of measured data including phase fraction calculation, temperature compensation and flow pattern identification. Furthermore, user interfaces are included via a display and 4...20 mA connectivity for the integration into industrial process control systems. In the second part of the contribution we describe the experimental verification of the main functionalities of the developed system. Firstly, the calculation of cross-sectionally averaged phase fractions along with temperature compensation was tested. Considering temperature drifts of up to 55 K, an av-erage deviation of 3.9% across the full range of phase fraction was found by comparison against image references from camera recordings. Secondly, the automatic flow pattern identification was tested in an air-water two-phase flow loop. The results reveal reasonable agreement with well-established flow pattern maps for both horizontal and vertical pipe orientation. The present results indicate that all prerequisites for an application in industrial environments in near future are fulfilled.

Keywords: wire-mesh sensor; two-phase flow; flow pattern identification; online data processing

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Permalink: https://www.hzdr.de/publications/Publ-35470
Publ.-Id: 35470


Data publication: Variability of radionuclide sorption efficiency on muscovite cleavage planes

Schabernack, J.; Faria Oliveira, A.; Heine, T.; Fischer, C.

Dataset of outputs produced by DFT and KMC simulation described in the associated paper.

KMC data:

  • Adsorption distribution (Ad_mov_01.pdb to Ad_mov_10.pdb)
  • Surface nanotopography (surface_1.pdb)
  • Statistic files for dissolution and adsorption (Ad_num.txt, Ad_Sites_Stat.txt, sites_stat_1.txt, diss_num.txt)
  • Input files (testmusc9_KMC_Mica_1_6.inp, EuAdsorption_2_0.inp)
  • Excel files for adsorption evaluation (Adsorption_Results_File), input energy calculation (EnergyParameterCalc) and site sorting (Site-INDL-Sorting)

DFT data:

  • Excel file adsorption energy barriers (Adsorption_Energy_Barrier)
  • Site adsorption energies (.cvs files)
  • Site adsorption trajectories (.xyz files)

Excel file for the estimation of the desorption factor

Keywords: Radionuclide Sorption; Kinetic Monte Carlo; Density Functional Theory; Muscovite; Europium

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Permalink: https://www.hzdr.de/publications/Publ-35469
Publ.-Id: 35469


Variability of radionuclide sorption efficiency on muscovite cleavage planes

Schabernack, J.; Faria Oliveira, A.; Heine, T.; Fischer, C.

In deep geological repositories for nuclear waste, the surrounding rock formation serves as an important barrier against radionuclide migration. Multiple potential host rocks contain phyllosilicates, which have shown high efficiency in radionuclide sorption. Recent experimental studies reported a heterogeneous distribution of adsorbed radionuclides on nanotopographic mineral surfaces. In this study, we investigated the energetic differences of surface sorption sites available at nanotopographic structures such as steps, pits, and terraces. Eleven important surface sites were selected and the energies of ad- and desorption reactions were obtained from density functional theory calculations. The adsorption energies were then used for the parameterization of a kinetic Monte Carlo model simulating the distribution of adsorbed europium on a typical nanotopographic muscovite surface. On muscovite, silicon step sites are favorable for europium sorption and lead to an increased adsorption in regions with high step concentrations. Under identical chemical conditions, sorption on typical nanotopographic surfaces is increased by a factor of three compared to atomically flat surfaces. Desorption occurs preferentially at terrace sites, leading to an overall 2.5 times increased retention at nanotopographic structures. This study provides a mechanistic explanation for heterogeneous sorption on nanotopographic mineral surfaces due to the availability of energetically favorable sorption sites.

Keywords: Radionuclide Sorption; Kinetic Monte Carlo; Density Functional Theory; Muscovite; Europium

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Permalink: https://www.hzdr.de/publications/Publ-35468
Publ.-Id: 35468


Resolving surface chemical states of p-GaN:Cs photocathodes by XPS analysis

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

An x-ray photoelectron spectrometer (XPS) is used in the HZDR photocathode lab to understand the surface states of GaN photocathodes during its cleaning, cesium activation and degradation. The XPS probes the electronic structure of the p-doped GaN photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels and auger photoemission peaks of Ga, N, O, C and Cs are monitored.

Keywords: GaN photocathode; quantum efficiency; cesium activation; photocathode degradation; organic - cesium

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  • Open Access Logo Invited lecture (Conferences)
    EWPAA 2022: European workshop on photocathodes for particle accelerator applications, 20.-22.09.2022, Mailand, Italien

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Permalink: https://www.hzdr.de/publications/Publ-35467
Publ.-Id: 35467


Effect of Medium on Fundamental Interactions in Gravity and Condensed Matter

Zhuk, O.; Shulga, V.

Recently, it was shown that the gravitational field undergoes exponential cutoff at large cosmological scales due to the presence of background matter. In this article, we demonstrate that there is a close mathematical analogy between this effect and the behavior of the magnetic field induced by a solenoid placed in a superconductor.

Permalink: https://www.hzdr.de/publications/Publ-35466
Publ.-Id: 35466


Resolving surface chemical states of p-GaN:Cs photocathodes by XPS analysis

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

An x-ray photoelectron spectrometer (XPS) is used in the HZDR photocathode lab to understand the surface states of GaN photocathodes during its cleaning, cesium activation and degradation. The XPS probes the electronic structure of the p-doped GaN photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels and auger photoemission peaks of Ga, N, O, C and Cs are monitored.
In our experiments, p-GaN on sapphire samples were cleaned with 99 % ethanol in an ultrasonic bath, followed by a thermal cleaning in a vacuum with the intention to remove carbon and oxygen contaminations on the p-GaN surface. Although still some carbon remained on the surface, the p-GaN was successfully activated by the deposition of a thin layer of cesium. Quantum efficiencies (QE) of
3 - 9 % were achieved. XPS photoemission spectra show a shift towards higher binding energies for the photoemission peaks, which is caused by a new component, so-called organic – cesium.
During the storage under ultra – high vacuum, the GaN:Cs photocathodes were measured from time to time in the photocurrent and by XPS. We found a shift of 0.35 eV towards lower binding energies, which is related to the formation of the organic – cesium islands. This island growth is assumed to be in close correlation to the photocathode degradation.
The p-GaN:Cs photocathodes showed a big QE loss after XPS analysis and therefore we investigated the potential damage from x-ray irradiation. The long-time irradiation experiments show that the x-ray damage has a high influence on the cesium component and the degradation of the p-GaN:Cs photocathode.

Keywords: GaN photocathode; photocathode degradation; cesium deposition

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  • Open Access Logo Poster
    International Workshop on Nitride Semiconductors (IWN), 09.-14.10.2022, Berlin, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-35465
Publ.-Id: 35465


DGN-Handlungsempfehlung (S1-Leitlinie) PSMA-Liganden-PET/CT in der Diagnostik des Prostatakarzinoms Stand: 01/2022 AWMF-Registernummer: 031-055

Afshar-Oromieh, A.; Eiber, M.; Fendler, W.; Schmidt, M.; Rahbar, K.; Ahmadzadehfar, H.; Umutlu, L.; Hadaschik, B.; Hakenberg, O.; Fornara, P.; Kurth, J.; Neels, O.; Wester, H.-J.; Schwaiger, M.; Kopka, K.; Haberkorn, U.; Herrmann, K.; Krause, B.

PSMA-PET/CT for imaging prostate cancer (PC) has spread worldwide since its clinical introduction in 2011. The majority of experiences have been collected for PSMA-PET-imaging of recurrent PC. Data for primary staging of high-risk PC are highly promising. Meanwhile, a plethora of PSMA-ligands are available for clinical use (e.g. 68Ga-PSMA-11, 68GaPSMA-I&T, 68Ga-PSMA-617, 18F-DCFBC, 18F-DCFPyL, 18F-PSMA-1007, 18F-rhPSMA-7 and 18F-JK-PSMA-7). However, an official approval is available only for 68Ga-PSMA-11 (approved by the US FDA in 2020) and 18F-DCFPyL (approved by the US FDA in 2021).
Recommendations for acquisition times vary from 1-2h p.i. It has been shown that for the majority of tumour lesions, the contrast in PSMAPET/CT increases with time. Therefore, additional late imaging can help to clarify unclear findings. PSMA-PET/CT should be performed prior to commencing an androgen deprivation therapy (ADT) since (long term) ADT reduces the visibility of PC lesions.
Following injection of PSMA-ligands, hydration and forced diuresis are recommended for PSMA-ligands with primarily excretion via the kidneys in order to increase the visibility of tumour lesions adjacent to the urinary bladder.
PSMA-ligands are physiologically taken up in multiple normal organs. For some 18F-labelled PSMA-ligands, presence of unspecific focal bone uptake has been reported. When using these tracers, focal bone uptake
without CT-correlate should be interpreted with great caution. Besides prostate cancer, practically all solid tumors express PSMA in their neovasculature thereby taking up PSMA-ligands, although usually at a lower extent compared to PC. Also multiple benign lesions and inflammatory processes (e.g. lymph nodes) take up PSMA-ligands, also
usually at lower extent compared to PC.

Keywords: PSMA; PET/CT; Prostate Cancer; Guideline; Positron Emission Tomography; Prostate Specific Membrane Antigen

Permalink: https://www.hzdr.de/publications/Publ-35464
Publ.-Id: 35464


Cleaning influence on p-GaN surfaces for photocathodes with negative electron affinity

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

Achieving an atomically clean surface is an important step to improving the quality of semiconductor photocathodes, but it is a challenging requirement for surface treatment [1]. In order to understand the surface during the cleaning, the cesium deposition, and the storage of the photocathode, the use of an x-ray photoelectron spectrometer (XPS) is needed. The XPS probes the electronic structure of the p-doped gallium nitride (GaN) photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels of Ga, N, O, C and Cs are monitored.

Keywords: GaN photocathode; cesium deposition; quantum efficiency; photocathode degradation

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  • Open Access Logo Poster
    ECASIA 2022-European Conference on Applications of Surface and Interface Analysis, 30.05.-03.06.2022, Limerick, Irland

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Permalink: https://www.hzdr.de/publications/Publ-35463
Publ.-Id: 35463


New Perspectives for Warm Dense Matter Theory: from Quantum Monte Carlo to Temperature Diagnostics

Dornheim, T.

Warm dense matter (WDM) an extreme state that is characterized by extreme densities and temperatures has emerged as
one of the most active frontiers in plasma physics and material science. In nature, WDM occurs in astrophysical objects
such as giant planet interiors and brown dwarfs. In addition, WDM is highly important for cutting-edge technological
applications such as inertial confinement fusion and the discovery of novel materials.
In the laboratory, WDM is studied experimentally in large facilities around the globe, and new techniques have facilitated
unprecedented insights into exciting phenomena like the formation of nanodiamonds at planetary interior conditions [1].
Yet, the interpretation of these experiments requires a reliable diagnostics based on accurate theoretical modeling, which is
a notoriously difficult task [2].
In this talk, I give an overview of recent developments in this field [3,4,5], which will allow for a rigorous treatment of the
intricate interplay of Coulomb coupling with thermal excitations and quantum degeneracy effects based on approximation-
free quantum Monte Carlo (QMC) simulations. Finally, I will present a new idea to extract the exact temperature [6] and
other material properties [7] from an X-ray Thomson scattering experiment without any models or simulations.
[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017)
[2] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[3] T. Dornheim et al., Physics Reports 744, 1-86 (2018)
[4] T. Dornheim et al., Physical Review Letters 121, 255001 (2018)
[5] M. Böhme et al., Physical Review Letters 129, 066402 (2022)
[6] T. Dornheim et al., arXiv:2206.12805
[7] T. Dornheim et al., arXiv:2209.02254

  • Lecture (others)
    Physikseminar der Universität Rostock, 15.11.2022, Rostock, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35462
Publ.-Id: 35462


Crystal Structures of Ce(IV) Nitrates with Bis(2-pyrrolidone) Linker Molecules Deposited from Aqueous Solutions with Different HNO3 Concentrations

Ono, R.; Kazama, H.; März, J.; Tsushima, S.; Takao, K.

Previously, we found that tetravalent actinides (An4+, An = Th, U, Np) in HNO3(aq) commonly afford sparingly soluble salts of [An(NO3)6]- with anhydrous H+ countercations stabilized by hydrogenbonding with bis(2-pyrrolidone) linker molecules selected appropriately. In contrast, this is not the case for Zr4+ in Group IV probably due to difference in the ionic radius. This fact motivated us to know how Ce(IV) behaves under the same condition. As a result, we have found that, after loading bis(2-pyrrolidone) linker molecule having trans-1,4-cyclohexyl bridging moiety (L), Ce(IV) in HNO3(aq) exclusively provides one of different crystalline phases, (HL)2[Ce(NO3)6] or [Ce2(mu-O)(NO3)6(L)2]n 2D MOF, depending on [HNO3]. The former has been obtained at [HNO3] = 4.70-9.00 M, and is isomorphous with the analogous (HL)2[An(NO3)6] we reported previously. In contrast, deposition of the latter phase at the lower [HNO3] conditions (1.00-4.30 M) demonstrates that hydrolysis and oxolation of Ce4+ proceeds even below pH 0 to provide a [Ce-O-Ce]6+ unit included in this compound. These different Ce(IV) phases are exchangeable each other under soaking in HNO3(aq), implying those chemical equilibria of dissolution/deposition of these crystalline phases, hydrolysis and oxolation of Ce4+, and its complexation with NO3- occur in parallel. Indeed, such coordination chemistry of Ce(IV) in HNO3(aq) was well corroborated by 17O NMR, Raman, and IR spectroscopy.

Permalink: https://www.hzdr.de/publications/Publ-35459
Publ.-Id: 35459


Data publication: One chelator for imaging and therapy with lutetium-177 and actinium-225

Cieslik, P.; Kubeil, M.; Zarschler, K.; Ullrich, M.; Brandt, F.; Anger, K.; Wadepohl, H.; Kopka, K.; Bachmann, M.; Pietzsch, J.; Stephan, H.; Comba, P.

Bei diesem Datensatz handelt es sich um analytische Charakterisierungen (ESI-MS, HR-MS, MALDI-TOF-MS) und Radiomarkierungsuntersuchungen zum nonadentaten Bispidin-Chelator bzw. Bispidin-TATE Konjugat mit Lutetium-177, Indium-111 und/oder Actinium-225.

1H, 13 C NMR and crystallographic data stored by collaboration partner (Heidelberg University)

Keywords: bispidine; trivalent metal ions; radionuclide theranostics; somatostatin analogue; actinium; lutetium

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Permalink: https://www.hzdr.de/publications/Publ-35458
Publ.-Id: 35458


Effects of static magnetic fields in antiferromagnetic ring-shaped spin chains

Borysenko, Y.; Sheka, D.; Faßbender, J.; van den Brink, J.; Makarov, D.; Pylypovskyi, O.

While antiferromagnets with the easy axis of anisotropy are considered to be robust against external magnetic fields of a moderate strength, strong-field-driven spin reorientations provide an insight into subtle properties of the material usually hidden by the high symmetry of the ground state. Here, we address theoretically the effects of curvature in the curvilinear antiferromagnetic achiral anisotropic ring-shaped spin chains in strong magnetic fields. We identify the geometry-driven helimagnetic phase transition above the spin-flop field between the vortex and onion states. The spin-flop transition is of the first- or second-order depending on the ring curvature, which is influenced by the geometry-induced Dzyaloshinskii–Moriya interaction. Inhomogeneity of the Néel vector distribution in spin-flop phase generates weakly ferromagnetic response, which lies in the plane perpendicular to the applied magnetic field. Our findings provide an understanding of complex responses of curvilinear antiferromagnets on magnetic fields and allow further experimental study of geometrical effects relying on spin-chain-based nanomagnets.

Keywords: antiferromagnetism; spin chains; ring

  • Lecture (Conference)
    DPG Meeting of the Condensed Matter Section: Magnetism Division, 04.-09.09.2022, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35457
Publ.-Id: 35457


Uncertainty quantification for neural network models

Schmerler, S.

Uncertainty quantification for neural network models

Keywords: machine learning; uncertainty

  • Open Access Logo Lecture (others) (Online presentation)
    ML at HZDR symposium, 06.12.2021, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35456
Publ.-Id: 35456


Uncertainty quantification in machine learning applications

Schmerler, S.; Starke, S.; Steinbach, P.; M. K. Siddiqui, Q.; Fiedler, L.; Cangi, A.; Kulkarni, S. H.

We strive to popularize the usage of uncertainty quantification methods in machine learning through publications and application in various projects covering diverse fields from regression and classification to instance segmentation. In addition, we employ domain shift detection techniques to tackle population-level out-of-distribution scenarios. In all cases, the goal is to assess model prediction validity given unseen test data.

Keywords: machine learning; uncertainty

  • Open Access Logo Poster
    Helmholtz AI Evaluation 2022, 05.-07.10.2022, München, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35454
Publ.-Id: 35454


Aqueous vs. high-temperature syntheses of crystalline zirconia (ZrO2) containing Cm3+

Huittinen, N. M.; Opitz, L.; Eibl, M.

The zirconia (ZrO2) crystal structure can incorporate a variety of metal cations with differing oxidation states up to high dopant loadings, which is why the material has been considered as a potential host phase for the immobilization of especially actinide elements present in specific high-level waste streams. Furthermore, zirconia is the main corrosion product of the Zircaloy cladding material surrounding nuclear fuel rods. The corrosion of Zircaloy and subsequent formation of zirconia already occurs during reactor operation and is expected to proceed during long-term disposal of the spent nuclear fuel (SNF) assemblies. Thus, during final storage, zirconia may play an important role as the first retention barrier for released radionuclides. ZrO2 is monoclinic phase at ambient conditions, and transforms into tetragonal and cubic phases at high temperatures of around 1200 °C and 2370 °C, respectively. However, particle size effects, the incorporation of foreign ions such as the actinides, as well as high radiation fields are known to also influence the stability fields of the polymorphs.
In the present work, the incorporation of the trivalent actinide curium in the pristine, monoclinic ZrO2 structure has been investigated following synthesis (i) in aqueous solution at 80°C for several weeks [1], and (ii) at high temperatures (1000°C, 5h) [2]. The evolution of the ZrO2 crystal structure during synthesis was analyzed with powder x-ray diffraction, while the Cm-environment was studied via luminescence spectroscopy. For the syntheses, a hydrous zirconia phase was precipitated in the presence of Cm from alkaline NaCl solutions at pH 12. The precipitate was thereafter either re-suspended in 0.5 M NaCl at pH 5 or pH 12 and hydrothermally treated at 80°C for up to 117 days, or calcined at 1000°C for 5 hours. The hydrothermal samples at pH 12, show crystallization of the amorphous ZrO(OH)2 phase to a mixture of monoclinic and tetragonal ZrO2 after 16 d at 80°C. In contrast, the samples at pH 5 show no crystallinity even after 32 days. Luminescence emission spectra indicate the presence of two Cm-environments in the amorphous precipitate. With increasing crystallinity, a bathochromic shift and a narrowing of the emission spectra can be seen. The shift is untypically large, resulting in emission peak maxima at around 650 nm for crystalline ZrO2. A similar, equally pronounced shift is obtained for Cm incorporated into the monoclinic ZrO2 structure following calcination. Therefore, the actinide speciation seems to be identical in the solid phases obtained with the two different synthesis methods, at least for the fully crystalline solids. These combined results imply that actinides are incorporated into the crystal structure of ZrO2, even at low concentrations where no structural transformations take place, which in turn speaks for zirconia as a good retention barrier for released trivalent actinides from the SNF matrix.

  • Lecture (Conference)
    Jahrestagung der Fachgruppe Nuklearchemie 2022, 04.-06.10.2022, Bergisch Gladbach, Germany

Permalink: https://www.hzdr.de/publications/Publ-35453
Publ.-Id: 35453


Editorial for "Decreased cerebral blood flow in non-hospitalized adults who self-isolated due to COVID-19"

Petr, J.; Keil, V. C.

Neurological manifestations are well-recognized in patients with COVID-19, with inflammation and damage to the brain vasculature being the common neuroimaging findings (1). A considerable number of individuals continue to experience – or even develop secondarily – neurological symptoms such as cognitive impairment (2.2% of individuals after SARS-CoV-2 infection) and fatigue or mood swings (3.2%) lasting up to several months after the recovery from COVID-19 (2). This condition is commonly referred to as “long COVID” or “post-COVID condition,” and it creates a substantial burden for social networks, health care, and economics beyond the personal suffering of the patient (3). Understanding the pathophysiological mechanisms of the condition plays a pivotal role in the quest for treatment approaches. Neuroimaging is a key diagnostic technique in this process.

An interesting neuroimaging method potentially sensitive to the long-term effects of COVID-19 is MRI perfusion measurement with arterial spin labeling (ASL). Previously, ASL was employed in applications assessing cognitive decline related to microvascular damage and neuroinflammation in the context of cancer therapy or dementia. In these cases, ASL was able to document longitudinal perfusion decrease following radiochemotherapy (4) or to help to detect changes in severe Alzheimer’s disease and even in the prodromal stage (5).

The use of ASL perfusion MRI to measure acute and chronic effects of COVID-19 remains limited. ASL was used to demonstrate that a post-COVID olfactory dysfunction was associated with lower tissue perfusion in the orbital and medial frontal regions (6). ASL also showed decreased perfusion in hospitalized subjects with the severe disease three months after discharge (7). However, perfusion still needs to be systematically studied in the largest group of individuals that underwent COVID-19 but did not require hospitalization.

In this issue of JMRI, an article by [AuthorName] et al. provides new results in a cross-sectional ASL study of 39 subjects who self-isolated at home due to COVID-19 and were scanned on average four months after the positive test (10). Typically, CBF measured with ASL have a relatively large intra-subject variability due to instrumental issues and physiological confounders. In theory, CBF could be influenced by various physiological and psychological factors related to contracting an infectious disease other than COVID-19. To address this, the authors have included a control group of eleven subjects who experienced flu-like symptoms but tested negative for COVID-19. Decreased perfusion in the COVID-19 group relative to the control group was found in several brain regions, including the basal ganglia, thalami, and orbitofrontal gyri. Further differences were discovered between COVID-19 subgroups with and without fatigue.

Despite the smaller size of this study, it backs findings from the UK Biobank study, which have demonstrated gray matter tissue loss in the orbitofrontal cortex and whole brain and higher cognitive decline longitudinally in participants infected with SARS-CoV-2 (8). Further population studies are currently being conducted (9), and the presented study by [AuthorName] et al. indicated the value ASL could have to provide quantifiable perfusion information.

Limitations of the study are a lack of pre-COVID baseline measurements and long-term outcomes of the post-COVID symptoms. In addition, the limited sample size did not allow more detailed subgroup analyses. However, showing a correlation between severity and worsened perfusion compared with patients recovering from a non-COVID flu-like respiratory illness is a step in the right direction in shedding light on the long-term effects of COVID-19 on brain perfusion.

  • Open Access Logo Abstract in refereed journal
    Journal of Magnetic Resonance Imaging 58(2023)2, 603-604
    Online First (2022) DOI: 10.1002/jmri.28556

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Permalink: https://www.hzdr.de/publications/Publ-35452
Publ.-Id: 35452


Physics-informed and data-driven modeling of matter under extreme conditions

Cangi, A.; Fiedler, L.; Shah, K.; Callow, T. J.; Ramakrishna, K.; Kotik, D.; Schmerler, S.

Understanding the properties of matter under extreme conditions is essential for advancing our fundamental understanding of astrophysical objects and guides the search for exoplanets, it propels the discovery of materials exhibiting novel properties that emerge under high temperatures and pressure, it enables novel technologies such as nuclear fusion, and supports diagnostics of experiments at large-scale brilliant photon sources. While modeling in this challenging research domain has so far relied on first-principles methods [1,2], these turn out to be computationally too expensive for simulations at the required time and length scales. Reduced models, such as average-atom models [3], come at a reduced computational and are useful by connecting atomistic details with hydrodynamics simulations, but they provide less accuracy. Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [4]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations with deep neural networks in terms of our Materials Learning Algorithms framework [5,6] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [7].

[1] T. Dornheim, A. Cangi, K. Ramakrishna, M. Böhme, S. Tanaka, J. Vorberger, Phys. Rev. Lett. 125, 235001 (2020).
[2] K. Ramakrishna, A. Cangi, T. Dornheim, J. Vorberger, Phys. Rev. B 103, 125118 (2021).
[3] T. J. Callow, E. Kraisler, S. B. Hansen, A. Cangi, Phys. Rev. Research 4, 023055 (2022).
[4] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301 (2022).
[5] A. Cangi et al., MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[6] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022).

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

  • Lecture (Conference)
    Big data analytical methods for complex systems, 06.-07.10.2022, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-35451
Publ.-Id: 35451


Accelerating Kohn-Sham Density Functional Theory with Neural Networks

Cangi, A.

Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [1]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations at finite temperatures with deep neural networks in terms of our Materials Learning Algorithms framework [2,3] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [4]. Finally, I will conclude with a preview of our most recent result that enables neural-network-driven electronic structure calculations for systems containing more than 100,000 atoms.

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, Phys. Rev. B 104, 035120 (2021).
[4] o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022).

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

  • Invited lecture (Conferences)
    Multiscale Modeling of Matter under Extreme Conditions, 11.-16.09.2022, Görlitz, Germany
  • Invited lecture (Conferences) (Online presentation)
    NHR-Atomistic Simulation Symposium 2022, 28.-29.11.2022, Online, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-35450
Publ.-Id: 35450


Accelerating Kohn-Sham Density Functional Theory at Finite Temperature with Deep Neural Networks

Cangi, A.

Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [1]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations at finite temperature with deep neural networks in terms of our Materials Learning Algorithms framework [2,3] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [4]. Finally, I will conclude with a preview on our most recent result that enables neural-network-driven electronic structure calculations for systems containing more than 100,000 atoms.

[1] L. Fiedler, K. Shah, M. Bussmann, and A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi et al., MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, and S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022). (2022).

Keywords: Electronic structure theory; Density functional theory; Machine learning; Neural networks; Hyperparameter optimization

  • Lecture (Conference)
    Psi-k Conference 2022, 22.-25.08.2022, Lausanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-35449
Publ.-Id: 35449


Data-Driven and Physics-Informed Modeling of Matter under Extreme Conditions

Cangi, A.

The successful characterization of high energy density (HED) phenomena in laboratories using photon sources or pulsed power facilities is possible only with numerical modeling for design, diagnostic development, and data interpretation. The persistence of electron correlation is one of the greatest challenges for accurate numerical modeling and has hitherto impeded our ability to model HED phenomena across multiple length and time scales at sufficient accuracy. Standard methods from electronic structure theory capture electron correlation at high accuracy, but are limited to small scales due to their high computational cost.
Artificial intelligence (AI) has emerged as a powerful tool for analyzing complex datasets. It has the potential to accelerate electronic structure calculations to hitherto unattainable scales [1].
In this talk, I will present our recent efforts on devising a data-driven and physics-informed machine-learning workflow to tackle this challenge. Based on first-principles data we generate machine-learning surrogate models that replace traditional density functional theory calculations. Our Materials Learning Algorithms framework [2] predicts the electronic structure and related properties of matter under extreme conditions highly efficiently while maintaining the accuracy of traditional methods [3]. Our most recent results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural network models and set the stage for large-scale investigations based on AI-driven methods [4].

References:

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA (Version 0.2.0), https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, arXiv:2202.09186 (2022).

  • Invited lecture (Conferences)
    Helmholtz AI Conference 2022, 02.-03.06.2022, Dresden, Germany
  • Invited lecture (Conferences)
    UWr – CASUS – HZDR International Conference on Advanced Systems Research, 11.-15.07.2022, Wroclaw, Poland
  • Lecture (Conference)
    Strongly Coupled Coulomb Systems 2022, 24.-29.07.2022, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-35448
Publ.-Id: 35448


Machine-Learning Surrogate Models for Predicting Electronic Structures

Cangi, A.

The successful characterization of high energy density (HED) phenomena in laboratories using photon sources or pulsed power facilities is possible only with numerical modeling for design, diagnostic development, and data interpretation. The persistence of electron correlation is one of the greatest challenges for accurate numerical modeling and has hitherto impeded our ability to model HED phenomena across multiple length and time scales at sufficient accuracy. Standard methods from electronic structure theory capture electron correlation at high accuracy, but are limited to small scales due to their high computational cost.
Artificial intelligence (AI) has emerged as a powerful tool for analyzing complex datasets. It has the potential to accelerate electronic structure calculations to hitherto unattainable scales [1].
In this talk, I will present our recent efforts on devising a data-driven and physics-informed machine-learning workflow to tackle this challenge. Based on first-principles data we generate machine-learning surrogate models that replace traditional density functional theory calculations. Our Materials Learning Algorithms framework [2] predicts the electronic structure and related properties of matter under extreme conditions highly efficiently while maintaining the accuracy of traditional methods [3]. Our most recent results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural network models and set the stage for large-scale investigations based on AI-driven methods [4].

References:

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA (Version 0.2.0), https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, arXiv:2202.09186 (2022).

Keywords: Quantum mechanics; Electronic structure theory; Density functional theory; Machine learning; Neural networks

  • Poster
    Advancing Quantum Mechanics with Mathematics and Statistics, Workshop IV: Monte Carlo and Machine Learning Approaches in Quantum Mechanics, 23.-27.05.2022, University of California, Los Angeles, United States
  • Lecture (others)
    Invitation to the Department of Chemistry, University of California, Irvine, 19.05.2022, Irvine, CA, United States

Permalink: https://www.hzdr.de/publications/Publ-35447
Publ.-Id: 35447


KLOE data and prospects with 1.7 fb −1 for a_\mu^HLO

Müller, S.

Invited Presentation at "Workshop on Muon Precision Physics" in Liverpool

Keywords: a_mu; g-2; muon; KLOE

  • Invited lecture (Conferences)
    Workshop on Muon Precision Physics, 07.-10.11.2022, Liverpool, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35446
Publ.-Id: 35446


Effect of medium on fundamental interaction

Zhuk, O.

We show that the gravitational field undergoes exponential cutoff at large cosmological scales due to the presence of background matter. This reflects the nonlinear nature of the gravitational interaction. This effect is illustrated by the example of different types of background matter, which confirms its universality. We also demonstrate that there is a close mathematical analogy between this effect and the behavior of the magnetic field induced by a solenoid placed in a superconductor.

  • Invited lecture (Conferences) (Online presentation)
    2022 International Conference on the Cooperation and Integration of Industry, Education, Research and Application, 25.10.2022, Changchun City, China

Permalink: https://www.hzdr.de/publications/Publ-35445
Publ.-Id: 35445


A fascinating story of the discovery of a non-stationary Universe: from a great "blunder" to experimental confirmation

Zhuk, O.

Today it is well known that our universe is expanding. However, even 100 years ago, the notion of a static universe was considered correct. In my talk, I will tell a fascinating story about how a few great men have changed our mind.

  • Invited lecture (Conferences) (Online presentation)
    22nd Gamow Conference : “ASTRONOMY AND BEYOND: ASTROPHYSICS, COSMOLOGY AND GRAVITATION, ASTROPARTICLE PHYSICS, RADIOASTRONOMY AND ASTROBIOLOGY, 22.-26.08.2022, Odessa, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-35443
Publ.-Id: 35443


Effect of peculiar velocities of inhomogeneities on the shape of gravitational potential in spatially curved universe

Canay, E.; Eingorn, M.; McLaughlin, I. A.; Arapoglu, A. S.; Zhuk, O.

We investigate the effect of peculiar velocities of inhomogeneities and the spatial curvature of the universe on the shape of the gravitating potential. To this end, we consider scalar perturbations of the FLRW metric. The gravitational potential satisfies a Helmholtz-type equation which follows from the system of linearized Einstein equations. We obtain analytical solutions of this equation in the cases of open and closed universes, filled with cold dark matter in presence of the cosmological constant. We demonstrate that, first, peculiar velocities significantly affect the screening length of the gravitational interaction and, second, the form of the gravitational potential depends on the sign of the spatial curvature.

Keywords: Scalar perturbations Peculiar velocities Gravitational potential

Permalink: https://www.hzdr.de/publications/Publ-35442
Publ.-Id: 35442


Relativistic approach to the large-scale structure formation: cosmic screening vs. gevolution

Zhuk, O.

Due to the modern telescopes, we found that the Universe is filled with a cosmic web which is composed of interconnected filaments of galaxies separated by giant voids. The emergence of this large-scale structure is one of the major challenges of modern cosmology. We study this phenomenon with the help of relativistic N-body cosmological simulation based on General Relativity. It is well known that gravity is the main force responsible for the structure formation in the Universe. In the first part of my talk, I demonstrate that in the cosmological setting gravitational interaction undergoes an exponential cutoff at large cosmological scales.
This effect is called cosmic screening. It arises due to the interaction of the gravitational field with the background matter. Then, I compare two competing relativistic approaches to the N-body simulation of the Universe large-scale structure: “gevolution” vs. “screening”.
To this end, employing the corresponding alternative computer codes, I demonstrate that
the corresponding power spectra are in very good agreement between the compared schemes.
However, since the perturbed Einstein equations have much simpler form in the “screening” approach, the simulation with this code consumes less computational time, saving almost 40% of CPU (central processing unit) hours.

  • Lecture (others)
    The Central European Institute for Cosmology and Fundamental Physics (CEICO), Institute of Physics of the Czech Academy of Sciences, 16.06.2022, Prag, Czech Republic
  • Lecture (others)
    Ludwig-Maximilians-Universität, 28.06.2022, München, Deutschland
  • Lecture (others)
    Universität Oldenburg, Fakultät V, Institut für Physik, 12.07.2022, Oldenburg, Germany
  • Lecture (others)
    CERN, the European Organization for Nuclear Research, Department of Theoretical Physics, 21.09.2022, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-35441
Publ.-Id: 35441


In vitro assessment of [¹⁸F]JHU94620-d8 to determine the expression of cannabinoid receptor 2 – a prognostic biomarker in breast cancer

Heerklotz, A.; Moldovan, R.-P.; Bormans, G.; Pietzsch, J.; Belter, B.; Kopka, K.; Gündel, D.

The cannabinoid receptor 2 (CB2R) is involved in inflammatory processes [1], whereby an increased expression correlates with malignancy in various cancer types like human epidermal growth receptor 2 positive (HER2+) or triple negative breast cancer (TNBC) [2]. Hence, the CB2R is suggested as a pharmacological target, as well as a prognostic biomarker for the stratification and staging of patients [3]. In this study, we evaluated the potential of our novel CB2R-specific radioligand [¹ ⁸F]JHU94620-d8 for the assessment of the CB2R expression in HER2+ breast cancer and TNBC models in vitro.
The KD value of [¹ ⁸F]JHU94620-d8 was determined by autoradiography on cryosections of rat and mouse spleen, as well as on rat brains harbouring a local overexpression of the hCB2R (AAV-hCB2R) [4]. The CB2R status was investigated by competitive radioligand binding assays (CRBA) in cell membranes of CHO cells overexpressing the human CB2R (CHOhCB2R), human breast cancer cell lines HCC1954 (HER2+) and MDA-MB-231 (TNBC) with 3.1±0.4 nM [³H]WIN55,212-2 using 10 µM of WIN55,212-2, GW405833 and JHU94620-d8 (each n=3) as agonistic competitors. CB2R expression was validated by immunofluorescence microscopy (IFM). On cryosections of 4T1 tumors the CB2R specific binding of [¹ ⁸F]JHU94620-d8 was investigated by CRBA and the colocalisation of CB2R with Iba1 (macrophages) and CD31 (blood vessels) by IFM.
We determined KD values for [¹ ⁸F]JHU94620-d8 of 30 nM in mouse spleen, of 1.0 nM in rat spleen, and of 42 nM in AAV-hCB2R. The cell membrane binding of [³H]WIN55,212-2 was comparable in all used cell lines between 20 ± 1 and 30 ± 11 fmol/106 cells. Competition by JHU94620-d8 decreased the total binding by 57 % (p<0.01) only in CHOhCB2R cells, WIN55,212-2 by 37 % (p=0.01) and 77 % (p<0.01) and GW405833 by 42 % (p<0.01) and 75 % (p<0.01) in HCC1954 and CHOhCB2R cells, respectively, however in MDA MB 231 cells binding was not affected by these compounds (Fig. 1A). The expression of CB2R was confirmed by IFM (Fig. 1B). IFM analysis of murine 4T1 tumours revealed a high correlation between the heterogeneously distributed CB2R and Iba1 (Pearson´s coefficient r=0.69±0.03), and a weak correlation between CB2R and CD31 (r=0.35±0.09), however autoradiography studies revealed a non-displaceable binding of [¹ ⁸F]JHU94620-d8 (Fig. 2).
The potential of [¹ ⁸F]JHU94620-d8 as radioindicator to assess the CB2R status of tumours as a prognostic imaging biomarker should be investigated in vivo in PET studies. As shown in this study, the apparently species depended CB2R binding affinity and cell type specific (tumour cells and tumour associated macrophages) CB2R expression should be considered.

References
1. Turcotte, C.; Blanchet, M.-R.; Laviolette, M.; Flamand, N. The CB2 Receptor and its Role as a Regulator of Inflammation. Cell. Mol. Life Sci. 2016, 73, 4449–4470, doi:10.1007/s00018-016-2300-4.
2. Ladin, D.A.; Soliman, E.; Griffin, L.; van Dross, R. Preclinical and Clinical Assessment of Cannabinoids as Anti-Cancer Agents. Front. Pharmacol. 2016, 7, 361, doi:10.3389/fphar.2016.00361.
3. Pérez-Gómez, E.; Andradas, C.; Blasco-Benito, S.; Caffarel, M.M.; García-Taboada, E.; Villa-Morales, M.; Moreno, E.; Hamann, S.; Martín-Villar, E.; Flores, J.M.; et al. Role of Cannabinoid Receptor CB2 in HER2 Pro-Oncogenic Signaling in Breast Cancer. J. Natl. Cancer Inst. 2015, 107, djv077, doi:10.1093/jnci/djv077.
4. Teodoro, R.; Gündel, D.; Deuther-Conrad, W.; Ueberham, L.; Toussaint, M.; Bormans, G.; Brust, P.; Moldovan, R.-P. Development of 18FLU14 for PET Imaging of Cannabinoid Receptor Type 2 in the Brain. IJMS 2021, 22, 8051, doi:10.3390/ijms22158051.

Acknowledgement
The human mammary cell lines were provided by Dr. Joan Massagué (MSKCC, NY, USA).
This research was funded by the Deutsche Forschungsgemeinschaft (DFG), grant number MO2677/4-1.

Keywords: Imaging biomarker; Cannabinoid receptor 2; CB2 tracer/radioindicator; Breast cancer

  • Poster
    EMIM 2023 - European Molecular Imaging Meeting, 14.-17.03.2023, Salzburg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-35439
Publ.-Id: 35439


An experimental study of boiling two-phase flow in a vertical rod bundle with a spacer grid. Part 1: Effects of mass flux and heat flux

Tas-Köhler, S.; Boden, S.; Franz, R.; Liao, Y.; Hampel, U.

We conducted boiling flow experiments and measured the void fraction in a 3 x 3 rod bundle with a spacer grid using high resolution X-ray computed tomography. We focused on the effects of mass and heat flux on the void fraction downstream of the spacer. We found that the void fraction increases as the
flow passes through the vanes and then decreases downstream until 𝑍 ≈ 4𝐷ℎ , and then increases again. In addition, we found that the mixing vanes cause a local increase in void fraction even at low heat flux or high mass flux, and that the arrangement of the vanes influences the size and location of the high and low void content regions. We also found that the effect of heat flux on the relative void fraction is more noticeable at high mass flux than at low mass flux. Furthermore, the experimental database obtained in this study can be used to validate CFD simulations.

Keywords: X-ray computed tomography; experimental database; boiling flow; rod bundle; void fraction

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  • Secondary publication expected from 21.03.2024

Permalink: https://www.hzdr.de/publications/Publ-35438
Publ.-Id: 35438


c2st: Classifier Two-Sample Testing for comparing high-dimensional point sets

Schmerler, S.; Steinbach, P.

Test whether two sets of points are samples from the same D-dimensional probability distribution without
having access to the PDF.

Keywords: c2st; two-sample testing

  • Open Access Logo Poster
    Helmholtz AI conference, 02.-03.06.2022, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35437
Publ.-Id: 35437


Long term operation of Cs2Te in SRF-gun for TELBE user facility

Xiang, R.

We share the status of long term operation of Cs2Te in SRF-gun for CW mode facility, which is intested for the ERL society.

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  • Invited lecture (Conferences)
    66th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs (ERL 2022), 03.-06.10.2022, Ithaca, USA

Permalink: https://www.hzdr.de/publications/Publ-35436
Publ.-Id: 35436


Operation of Cs2Te in SRF gun for ELBE

Xiang, R.

we share the experience of Cs2Te operation in SRF gun for ELBE user facility.

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  • Open Access Logo Invited lecture (Conferences)
    European Workshop on Photocathodes for Particle Accelerator Applications (EWPAA 2022), 20.-22.09.2022, Milano, Italy

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Permalink: https://www.hzdr.de/publications/Publ-35435
Publ.-Id: 35435


Study on Cs2Te photocathode degradation in SRF gun-II during user operation

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

The quality of the photocathodes is critical for the stable operation of the photoinjector. Thanks to the robust Cs2Te photocathodes, SRF gun at HZDR has been proven to be a type of successful CW e- source. In this contribution, we will present the operation experience of Cs2Te photocathodes in SRF gun, especially the QE evolution of Cs2Te photocathode during user operation. The possible reason for QE degradation will be discussed.

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  • Poster
    The 31st Linear Accelerator Conference (LINAC2022), 28.08.-02.09.2022, Liverpool, UK

Permalink: https://www.hzdr.de/publications/Publ-35434
Publ.-Id: 35434


A Quarter Wave Resonator based SRF Gun for the LCLS II High Energy project

Xiang, R.

A Quarter Wave Resonator based SRF Gun for the LCLS II High Energy project

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  • Open Access Logo Invited lecture (Conferences)
    The 8th annual meeting of the programme "Matter and Technologies", 26.-27.09.2022, Hamburg, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35433
Publ.-Id: 35433


Cs2Te photocathodes for SRF gun-II at ELBE

Xiang, R.

Status report of Cs2Te photocathodes for SRF gun-II at ELBE

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  • Open Access Logo Invited lecture (Conferences)
    PITZ collaboration meeting (DESY), 06.-07.06.2022, Zeuthen, Germany

Permalink: https://www.hzdr.de/publications/Publ-35432
Publ.-Id: 35432


Wash water addition on protein foam for removal of soluble impurities in foam fractionation process

Keshavarzi, B.; Krause, T.; Schwarzenberger, K.; Eckert, K.; Ansorge-Schumacher, M. B.; Heitkam, S.

This work evaluates the addition of wash water to a foam fractionation cell in order to remove the soluble impurities from a protein foam. Due to the irreversible adsorption of the proteins at the air interface, the addition of wash water to the foam can displace the entrained substances downward together with the liquid, while the adsorbed proteins are not desorbed from the foam surface. Here, we performed experiments on bovine serum albumin (BSA), as a model protein and NaCl salt, as a model of soluble impurities. The experiments were conducted in a glass foam fractionation cell, where the liquid level was kept constant. The wash water was added on the foam top with different flow rates and BSA and NaCl concentrations were measured at the outlets for further analysis. The influence of initial bubble size and the wash water rate on purification efficiency were investigated. The results show that wash water displaces the entrained liquid in foam and reduces the salt content of the foam. The process shows higher salt removal for higher wash water rates as well as for foams with larger bubble sizes, where up to 93 % of the salt was removed from the main solution. A lower air flow rate can further enhance the washing efficiency. However, it intensifies the foam collapse and hence diminishes the foam outflow.

Keywords: Protein purification; Foam fractionation; Flotation; Wash water; Separation; BSA

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-35430
Publ.-Id: 35430


Thermal-hydraulic and particle deposition analysis of supercritical CO2 in different tubes

Mao, S.; Zhou, T.; Liao, Y.; Tang, J.; Liu, X.

To compare the thermo-hydraulic and particle deposition characteristics of supercritical CO2 (SCO2) in different tubes, the SCO2 thermal-hydraulic performance and particle deposition characteristics were numerically investigated. Three different tube types, including circular tubes, semi-circular tubes and square tubes, were created. The effects of cross sections on heat transfer and particle type, mass flux and heat flux on particle deposition were investigated and discussed. The results indicated that the heat transfer coefficients (h) reach the peaks when the bulk temperature (Tb) is just below pseudo-critical temperature (Tpc) among three tubes. The h peaks are 4.8 kW/(m2·K), 8.4 kW/(m2·K) and 7.9 kW/(m2·K) for circular, semi-circular and square tubes, respectively. The semi-circular tube has the best heat transfer performance and it could alleviate the buoyancy effect efficiently. Moreover, the corners of the semicircular and square tubes should be further optimized to avoid excessive temperatures. The particle deposition efficiency (η) is 79.6%, 76.1% and 84.4% for circular, semicircular and square tubes, respectively, at dp=1 μm. Therefore, the semi-circular tube has a certain anti-deposition. The η for steel and graphite overlaps at dp<1 μm and steel is obvious higher than graphite at dp≥1 μm. Furthermore, small particles are impacted by mass and heat fluxes, whereas large particles are hardly affected. The η of small particles (dp<10 μm) increase with increasing mass flux. However, the η of small particles (dp<1 μm) decrease with increasing heat flux. It would be desirable that the flow channels can be further optimized to obtain the high thermal performance and anti-deposition for heat exchangers using SCO2 as working fluid.

Keywords: Supercritical carbon dioxide (SCO2); Thermal-hydraulic performance; Particle deposition; Different channels

Permalink: https://www.hzdr.de/publications/Publ-35429
Publ.-Id: 35429


Software publication: Estimating cross-border mobility from the difference in peak-timing: A case study in Poland-Germany border regions

Senapati, A.; Mertel, A.; Schlechte-Welnicz, W.; Calabrese, J.

Codes for reproducing the results in the research article "Estimating cross-border mobility from the difference in peak-timing: A case study in Poland-Germany border regions"

Keywords: Coupling strength; Disease outbreak; Spatio-temporal model; Stochastic simulation; Maximum likelihood estimation

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Permalink: https://www.hzdr.de/publications/Publ-35428
Publ.-Id: 35428


Estimating cross-border mobility from the difference in peak-timing: A case study in Poland-Germany border regions

Senapati, A.; Mertel, A.; Schlechte-Welnicz, W.; Calabrese, J.

Human mobility contributes to the fast spatio-temporal propagation of infectious diseases. During an outbreak, monitoring the infection situation on either side of an international border is very crucial as there is always a higher risk of disease importation associated with cross-border migration. Mechanistic models are effective tools to investigate the consequences of cross-border mobility on disease dynamics and help in designing effective control strategies. However, in practice, due to the unavailability of cross-border mobility data, it becomes difficult to propose reliable, model-based strategies. In this study, we propose a method for estimating cross-border mobility flux between any pair of regions that share an international border from the observed difference in the timing of the infection peak in each region. Assuming the underlying disease dynamics is governed by a Susceptible-Infected-Recovered (SIR) model, we employ stochastic simulations to obtain the maximum likelihood cross-border mobility estimate for any pair of regions where the difference in peak time can be measured. We then investigate how the estimate of cross-border mobility flux varies depending on the disease transmission rate, which is a key epidemiological parameter. We further show that the uncertainty in mobility flux estimates decreases for higher disease transmission rates and larger observed differences in peak timing. Finally, as a case study, we apply the method to some selected regions along the Poland-Germany border which are directly connected through multiple modes of transportation and quantify the cross-border fluxes from the COVID-19 cases data during the period $20^{\rm th}$ February $2021$ to $20^{\rm th}$ June $2021$.

Keywords: Coupling strength; Disease outbreak; Spatio-temporal model; Stochastic simulation; Maximum likelihood estimation

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Permalink: https://www.hzdr.de/publications/Publ-35427
Publ.-Id: 35427


Progress in the Evaluation and Validation of n+56,57Fe Cross Sections

Trkov, A.; Capote, R.; Bernard, D.; Beyer, R.; Danon, Y.; Daskalakis, A.; Junghans, A.; Kostal, M.; Leconte, P.; Schulc, M.; Simakov, S.

There has been a continued effort since 2019 within the IAEA INDEN collaboration to improve the evaluation of neutron induced reactions on iron isotopes. The reason for the 30% underestimation of the neutron leakage spectrum from a thick iron sphere was found primarily to be due to the overestimation of the inelastic cross sections in the 56Fe evaluated data file produced within the CIELO project of the OECD/NEA Data Bank. The over-estimation of the neutron flux between the resonances near 300 keV was traced to neglecting the fluctuating nature of the total cross section of 57Fe in the fast neutron energy range, since the evaluated resolved resonance range of 57Fe extended only up to 190 keV. The added 1=v background in the "iron window" below 28 keV is in excellent agreement with the independently evaluated one in the JENDL-5.0 library that included the direct capture component in the evaluation. Performance of the updated 56;57Fe evaluations was tested on a set of criticality benchmarks from the ICSBEP Handbook, including the dependence on reflector thickness and on new deep penetration shielding benchmark using a 252Cf(sf) neutron source undertaken at Rez, Czech
Republic. Neutron leakage for 43 MeV incident neutrons was also validated.

Keywords: nuclear data evaluation; iron-56; INDEN; nELBE

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Permalink: https://www.hzdr.de/publications/Publ-35426
Publ.-Id: 35426


Challenges and opportunities integrating LLAMA into AdePT

Gruber, B. M.; Amadio, G.; Hageböck, S.

Particle transport simulations are a cornerstone of high-energy physics (HEP), constituting almost half of the entire computing workload performed in HEP. To boost the simulation throughput and energy efficiency, GPUs as accelerators have been explored in recent years, further driven by the increasing use of GPUs on HPCs. The Accelerated demonstrator of electromagnetic Particle Transport (AdePT) is an advanced prototype for offloading the simulation of electromagnetic showers in Geant4 to GPUs, and still undergoes continuous development and optimization. Improving memory layout and data access is vital to use modern, massively parallel GPU hardware efficiently, contributing to the challenge of migrating traditional CPU based data structures to GPUs in AdePT. The low-level abstraction of memory access (LLAMA) is a C++ library that provides a zero-runtime-overhead data structure abstraction layer, focusing on multidimensional arrays of nested, structured data. It provides a framework for defining and switching custom memory mappings at compile time to define data layouts and instrument data access, making LLAMA an ideal tool to tackle the memory-related optimization challenges in AdePT. Our contribution shares insights gained with LLAMA when instrumenting data access inside AdePT, complementing traditional GPU profiler outputs. We demonstrate traces of read/write counts to data structure elements as well as memory heatmaps. The acquired knowledge allowed for subsequent data layout optimizations.

Keywords: AdePT; LLAMA; particle transport simulation; GPU

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Permalink: https://www.hzdr.de/publications/Publ-35425
Publ.-Id: 35425


Updates on the Low-Level Abstraction of Memory Access

Gruber, B. M.

Choosing the best memory layout for each hardware architecture is increasingly important as more and more programs become memory bound. For portable codes that run across heterogeneous hardware architectures, the choice of the memory layout for data structures is ideally decoupled from the rest of a program.
The low-level abstraction of memory access (LLAMA) is a C++ library that provides a zero-runtime-overhead abstraction layer, underneath which memory layouts can be freely exchanged, focusing on multidimensional arrays of nested, structured data.
It provides a framework for defining and switching custom memory mappings at compile time to define data layouts, data access and access instrumentation, making LLAMA an ideal tool to tackle memory-related optimization challenges in heterogeneous computing.
After its scientific debut, several improvements and extensions have been added to LLAMA. This includes compile-time array extents for zero memory overhead, support for computations during memory access, new mappings (e.g. int/float bit-packing or byte-swapping) and more. This contribution provides an overview of the LLAMA library, its recent development and an outlook of future activities.

Keywords: memory layout; struct of arrays; performance portability

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Permalink: https://www.hzdr.de/publications/Publ-35424
Publ.-Id: 35424


A novel, scenario-based approach to comparing non-pharmaceutical intervention strategies across nations

Fu, X.; Calabrese, J.; Schüler, L.; Attinger, S.

Comparing the non-pharmaceutical intervention (NPI) strategies different nations employed to combat COVID-19 is a key step in preparing for future pandemics. Conventional approaches to this problem focus on identifying and ranking individual NPI effects. These efforts are complicated by vastly different political, economic, and social conditions among nations, which we refer to collectively as national framework conditions (NFCs). Furthermore, NPIs are typically applied as packages of interventions, which makes identifying their independent effects challenging. In addition, conventional approaches to studying NPI effects frequently neglect the economic and social consequences of these measures. Here, we introduce a novel, scenario-based approach to understanding NPI effects across nations. Our method couples simple epidemiological, behavioral, and economic models, and allows us to transfer NPI strategies from a reference nation to a focal nation while preserving the packaged nature of NPIs and controlling for NFCs. We conclude by considering future extensions to our framework and discussing its potential to facilitate NPI inter-comparisons worldwide.

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

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Permalink: https://www.hzdr.de/publications/Publ-35423
Publ.-Id: 35423


Software publication: Optimal workplace occupancy strategies during the COVID-19 pandemic

Davoodi Monfared, M.; Senapati, A.; Mertel, A.; Schlechte-Welnicz, W.; Calabrese, J.

Codes for "Optimal workplace occupancy strategies during the COVID-19 pandemic"

Keywords: COVID-19; Pandemic; Optimal Presence Strategy; Productivity\sep Infection

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Permalink: https://www.hzdr.de/publications/Publ-35422
Publ.-Id: 35422


Data publication: Learning-based systems for assessing hazard places of contagious diseases and diagnosing patient possibility

Davoodi Monfared, M.; Ghaffari, M.

The codes and data for the paper "Learning-based systems for assessing hazard places of contagious diseases and diagnosing patient possibility"

Keywords: Machine learning; Trajectory tracking; Patient prediction; Hidden Markov model; Covid-19; Trajectory clustering

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Permalink: https://www.hzdr.de/publications/Publ-35419
Publ.-Id: 35419


Predicting electronic structures at any length scale with machine learning

Fiedler, L.; Modine, N.; Schmerler, S.; Vogel, D. J.; Popoola, G. A.; Thompson, A.; Rajamanickam, S.; Cangi, A.

The properties of electrons in matter are of fundamental importance. They give rise to virtually all molecular and material properties and determine the physics at play in objects ranging from semiconductor devices to the interior of giant gas planets. Modeling and simulation of such diverse applications rely primarily on density functional theory (DFT), which has become the principal method for predicting the electronic structure of matter. While DFT calculations have proven to be very useful to the point of being recognized with a Nobel prize in 1998, their computational scaling limits them to small systems. We have developed a machine learning framework for predicting the electronic structure on any length scale. It shows up to three orders of magnitude speedup on systems where DFT is tractable and, more importantly, enables predictions on scales where DFT calculations are infeasible. Our work demonstrates how machine learning circumvents a long-standing computational bottleneck and advances science to frontiers intractable with any current solutions. This unprecedented modeling capability opens up an inexhaustible range of applications in astrophysics, novel materials discovery, and energy solutions for a sustainable future.

Keywords: Machine learning; density functional theory; Surrogate Model

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Permalink: https://www.hzdr.de/publications/Publ-35418
Publ.-Id: 35418


Study on QE Evolution of Cs2Te photocathodes in ELBE SRF GUN-II

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

The quality of the photocathodes is critical for the stability and reliability of the photoinjector’s operation. Thanks
to the robust magnesium and Cs2Te photocathodes, SRFgun-II at HZDR has been proven to be a successful example
in CW mode for high current user operation.
In this contribution, we will present our observation of the QE evolution of Cs2Te photocathodes during SRF gun
operation. The variables including substrate surface, film thickness, Cs/Te stoichiometric, multipacting, RF loading
and charge extract are considered in the analysis.

Keywords: SRF gun; photocathode; QE Evolution

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Permalink: https://www.hzdr.de/publications/Publ-35417
Publ.-Id: 35417


Joint recovery of graphite and lithium metal oxides from spent lithium-ion batteries using froth flotation and investigation on process water re-use

Salces, A. M.; Bremerstein, I.; Rudolph, M.; Vanderbruggen, A.

Spent lithium-ion batteries (LIBs) contain critical raw materials that need to be recovered and recirculated into the battery
supply chain. This work proposes the joint recovery of graphite and lithium metal oxides (LMOs) from pyrolyzed black mass
of spent LIBs using froth flotation. Since flotation is a water-intensive process, the quality of the aqueous phase directly
impacts its performance. In pursuit of an improved water-management strategy, the effect of process water recirculation on
black mass flotation is also investigated. The fine fraction (<90 μm) of the black mass from pyrolyzed and crushed spent
LIBs was used. After flotation, 85% of the graphite in the overflow product and 80% of the LMOs in the underflow product
were recovered. After flotation with 8 wt% solids, the process water contained about 1,000 mg/L Li and accumulated up to
2,600 mg/L Li after three cycles. The flotation with process water showed no significant impact on the recovery and grade of
flotation products, suggesting the feasibility of water recirculation in black mass flotation.

Keywords: Black mass; Froth flotation; Lithium metal oxide; Lithium-ion batteries; Recycling; Spheroidized graphite; Water recirculation

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Permalink: https://www.hzdr.de/publications/Publ-35416
Publ.-Id: 35416


Head-to-Head Comparison of PET and ASL-MRI BBB Permeability measurements for Dementia Imaging: Study Protocol

Moyaert, P.; Oyeniran, O.; Dassanayake, P.; Liu, L.; Petr, J.; Achten, E.; Mutsaerts, H.; Hicks, J.; Guenther, M.; Anazodo, U.

Aim/Introduction: Blood-brain barrier (BBB) breakdown has been suggested to be an early biomarker of cognitive dysfunction. Currently, PET using [15O]-water and [11C]-Butanol is the standard for measuring BBB permeability. Arterial Spin Labeling (ASL) MRI is a promising alternative as no exogenous contrast is used. This study will validate BBB-ASL MRI by comparing it with PET and assess if BBB-ASL indeed robustly quantifes BBB permeability. Here we present our protocol and preliminary results using image-derived input function (IDIF) to quantify BBB-PET, noninvasively. Materials and Methods: Integrated PET/MR imaging provides a unique opportunity to assess - for the frst time - the ability of ASL to noninvasively image BBB permeability by comparing it to PET in the same subjects and under the same conditions. First, the BBBASL (1) sensitivity in pigs will be investigated by mimicking BBB dysfunction using an Aquaporin-4 inhibitor that will block the fow of water (2). Absolute BBB measurements (as obtained by arterial sampling) will be compared to BBB-ASL measurements. Second, to determine whether any changes in BBB permeability measured by MRI translate to humans, permeability measured by PET and MRI in 10 ischemic stroke patients will be compared. Third, the accuracy of BBB-ASL will be assessed in humans with subtle BBB dysfunction in 12 patients with Alzheimer’s disease, 12 with mild cognitive impairment and 12 age-matched controls. Results: While the preclinical validation studies are underway, we evaluated our PET/MRI IDIF approach (3) for absolute PET quantifcation to eliminate the need for arterial sampling in the two clinical studies. In three pigs, the [15O]-water PET/MR IDIFs were similar to arterial-sampled input functions with area-under-the-curve ratio (IDIF/AIF) of 1.03 - 1.1, demonstrating the potential of IDIF for BBB permeability estimates. Conclusion: The goal of this work is twofold. On one hand, it will demonstrate the potential of ASL measurements as a reliable imaging approach for assessing BBB permeability changes, particularly for early dysfunction detection in otherwise healthy individuals. On the other hand, it will optimize PET for clinical use by integrating IDIF for quantifcation, thereby representing a clinically viable alternative to arterial blood sampling.

  • Contribution to proceedings
    Annual Congress of the European Association of Nuclear Medicine, 15.09.2022, Barcelona, Spain, 550-550
    DOI: 10.1007/s00259-022-05924-4
  • Poster
    Annual Congress of the European Association of Nuclear Medicine, 15.09.2022, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-35415
Publ.-Id: 35415


Synthese neuer Chelatliganden für Radium-223/-224 und Barium-131

Höffmann, L.

Ziel dieser Masterarbeit ist es, neue Chelatliganden für die Alphastrahler Radium-223/-224 als zweiwertige Kationen und deren diagnostischem Pendant Barium-131 zu synthetisieren. Als Ausgangsverbindung für weitere Funktionalisierungen soll ein durch Lehn beschriebener Kryptand dienen.
Dieser wird über sechs Syntheseschritte hergestellt und besitzt neun Koordinationsstellen, welche durch die Funktionalisierung der sekundären Aminofunktionen mit Seitenketten modifiziert werden sollen. Durch die Verwendung von Carbonsäurederivaten können auf diesem Weg auch Bindungsstellen für ein späteres Trägermolekül eingeführt werden. Während dieser Arbeit sollen vier verschiedene Funktionalisierungen auf Basis von armoatischen Carbonsäurefunktionen (Picolinsäure, Pyrimidincarbonsäure und Bipyridylcarbonsäure) untersucht werden.
Die entstandenen Verbindungen sollen charakterisiert und mittels NMR-Spektroskopie auf ihr Komplexbildungsverhalten mit unterschiedlichen in der Radiopharmazie verwendeten Metallionen wie Barium, Scandium, Blei, Lanthan, Lutetium und Indium untersucht werden. Dazu sollen NMR-Titrationen mit den oben genannten Metallen durchgeführt werden, auf deren Grundlage es möglich ist, die Komplexbildungskonstanten zu berechnen. Zusätzlich sollen die finalen Verbindungen mit Barium-131 und Actinium-225 radiomarkiert und mit dem Bindungsverhalten von macropa verglichen werden.

Keywords: Theranostics; Barium-131; Kryptand; Radium-123

  • Master thesis
    TU Dresden, 2022
    Mentor: PD Dr. habil. Constantin Mamat
    98 Seiten

Permalink: https://www.hzdr.de/publications/Publ-35414
Publ.-Id: 35414


Temporal and spatial evolution of enzymatic degradation of amorphous PET plastics

Lippold, H.; Kahle, L.; Sonnendecker, C.; Matysik, J.; Fischer, C.

Biocatalytic degradation is an emerging strategy aiming for an energy-efficient recycling of poly(ethylene terephthalate) (PET), the most commonly used thermoplastic polyester. Besides material composition and physico-chemical parameters, the degradation kinetics is co-determined by the evolving nanotopography. In this study, the 3-dimensional development of the surface characteristics of an amorphous PET film, reacted with a highly effective hydrolase enzyme for up to 24 hours, was explored by vertical scanning interferometry and confocal microscopy. The spatio-temporal analysis unveiled that the degradation process is not uniform with respect to reaction time and spatial reactivity distribution. An early phase of an unspecific roughness evolution is followed by an advanced phase characterized by a circular degradation pattern, consisting of shallow pits that are steadily renewed over time. The data suggest a hindrance of degradation during the initial roughening process, demonstrating the potential role of targeted surface modification in the large-scale treatment of plastic waste.

Permalink: https://www.hzdr.de/publications/Publ-35413
Publ.-Id: 35413


Momentum exchange modelling for coarsely resolved interfaces in a multifield two-fluid model

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

Morphology-adaptive multiphase models are becoming more established for the numerical description of complex gas-liquid flows adapting dynamically to the local flow morphology. In the present study two different numerical methods originally designed for distinct flow morphologies are combined, namely the Volume-Of-Fluid and the Euler-Euler method. Both edge cases have been proven to be capable of delivering reliable predictions in the respective use cases. The long-term goal is to improve the prediction of gas-liquid flows, regardless of the flow regime in a specific application. To capture the system dynamics with a given grid resolution, the flow fields need to be predicted as precise as possible, while the shape of structures such as gas bubbles need to be recovered adequately in topology and shape. The goal is to obtain reliable predictions on intermediate mesh resolutions rather than relying on fine meshes requiring more computational resources. Therefore, a procedure is proposed to locally measure the degree of resolution. With this information, the hydrodynamics in the interface region can be controlled by means of a dedicated interfacial drag formulation in order to improve simulation results across several levels of spatial resolution. A modified formulation of buoyancy is proposed to prevent unphysical oscillations of vertical velocity near a horizontal interface. The functionality is demonstrated in a three-dimensional case of a gas bubble rising in stagnant liquid and in a co-current stratified air-water channel flow in two-dimensional space. The choice of these different applications demonstrates the general applicability of the proposed model framework.

Keywords: Finite volume; Multi-phase flows; Validation; Euler; Adaptivity; Bubbles; Eulerian; Free surface; Hydrodynamics; Two-phase flow

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Permalink: https://www.hzdr.de/publications/Publ-35412
Publ.-Id: 35412


Reactivity Map Code

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

Matlab code to generate reactivity map of the galena particle

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Permalink: https://www.hzdr.de/publications/Publ-35411
Publ.-Id: 35411


Segmented Galena Dissolution Data

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

Raw CT data which are used to calculate the dissolution rates spectra and to generate reactivity map.

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Permalink: https://www.hzdr.de/publications/Publ-35410
Publ.-Id: 35410


Understanding of the evolution of mechanical properties of steels under irradiation: micromechanics and microstructure

Pareige, C.; Gupta, J.; Vrellou, M.; Kaden, C.; Moldovan, S.; Nomoto, A.; Pareige, P.; Radiguet, B.

Steels are the main structural materials in current and future nuclear power plants. Radiation induced segregation/precipitation and radiation enhanced precipitation at the nanoscale impact significantly their mechanical properties. Under ion irradiation, the small thickness of the irradiated layer imposes micro-mechanical testing methods to be used such as nanoindentation and micropillar compression. The objective is to make the link between microstructural evolution and hardening owing to the combination of: atom probe tomography, transmission electron microscopy,
SEM/FIB/EBSD on one hand and nanoindentation and micropillar compression on the other hand. This correlative approach can also be used on the same materials irradiated with neutrons allowing the comparison between ion and neutron irradiation.

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  • Lecture (Conference)
    26th International Conference on the Application of Accelerators in Research & Industry (CAARI-SNEAP 2022), 30.10.-03.11.2022, Denton, Texas, USA

Permalink: https://www.hzdr.de/publications/Publ-35408
Publ.-Id: 35408


Comparing Wire-Mesh sensor with neutron radiography for measurement of liquid fraction in foam

Ziauddin, M.; Schleicher, E.; Trtik, P.; Knüpfer, L.; Skrypnik, A.; Lappan, T.; Eckert, K.; Heitkam, S.

The liquid fraction of foam is an important quantity in engineering process control and essential to interpret foam rheology.
Established measurement tools for the liquid fraction of foam, such as optical measurement or radiography techniques
as well as weighing the foam, are mostly laboratory-based, whereas conductivity-based measurements are limited to the
global measurement without detailed spatial information of liquid fraction. In this work, which combines both types of
measurement techniques, the conductivity-based wire-mesh sensor is compared with neutron radiography. We found a
linear dependency between the liquid fraction of the foam and the wire-mesh readings with a statistical deviation less than
15%. However, the wire-mesh sensor systematically overestimates the liquid fraction which we attribute to liquid bridge
formation between the wires.

Keywords: foam; Wire-mesh-sensor; Neutron radiography

Permalink: https://www.hzdr.de/publications/Publ-35407
Publ.-Id: 35407


Data publication: Discovery, nuclear properties, synthesis and applications of technetium-101

Johnstone, E. V.; Mayordomo, N.; Mausolf, E. J.
ContactPerson: Johnstone, Erik V.; ContactPerson: Mausolf, Edward J.; ContactPerson: Mayordomo, Natalia

This article is a review paper, it is not based in experimental data

Keywords: Tc-101; Synthesis; Discovery; Properties; Applications

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Permalink: https://www.hzdr.de/publications/Publ-35406
Publ.-Id: 35406


Discovery, nuclear properties, synthesis and applications of technetium-101

Johnstone, E. V.; Mayordomo, N.; Mausolf, E. J.

Technetium-101 ( 101 Tc) has been poorly studied in comparison with other Tc isotopes, although it was first identified over ~80 years ago shortly after the discovery of the element Tc itself. Its workable half-life and array of production modes, i.e., light/heavy particle reactions, fission, fusion-evaporation, etc., allow it to be produced and isolated using an equally diverse selection of chemical separation pathways. The inherent nuclear properties of 101 Tc make it important for research and applications related to radioanalytical tracer studies, as a fission signature, fusion materials, fission reactor fuels, and potentially as a radioisotope for nuclear medicine. In this review, an aggregation of the known literature concerning the chemical, nuclear, and physical properties of 101 Tc and some its applications are presented. This work aims at providing an up-to-date and first-of-its-kind overview of 101 Tc that could be of importance for further development of the fundamental and applied nuclear and radiochemistry of 101 Tc.

Keywords: Tc-101; Synthesis; Discovery; Properties; Applications

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Permalink: https://www.hzdr.de/publications/Publ-35405
Publ.-Id: 35405


Tc(VII) reductive immobilization by Sn(II) pre-sorbed on alumina nanoparticles

Mayordomo, N.; Roßberg, A.; Prieur, D.; Scheinost, A.; Kvashnina, K.; Müller, K.

The interaction of highly mobile radioactive elements in the spent fuel with the different technical and geological barriers of a nuclear waste repository needs quantification and mechanistic understanding to allow a reliable safety assessment.
One of the most concerning mobile fission products is Tc-99. It is a long-lived radionuclide (half-life of 0.213 million years) that is expected to occur as Tc(VII) under oxidizing conditions and as Tc(IV) under reducing conditions. The anion pertechnetate (TcO4) is the main species of Tc(VII) and it is known to be a highly mobile species since it barely interacts with mineral surfaces. On the contrary, TcO2 is the main species of Tc(IV) and it is a hardly soluble solid. Therefore, the reduction of Tc(VII) to Tc(IV) limits the mobility of Tc in water and is triggered by reducing agents such as Fe(II) or Sn(II). [1] In a previous work, we have observed that pre-sorption of Fe(II) on alumina enabled the Tc(VII) reduction at the interface, even at low pH values when Tc(VII) reduction by Fe(II) was expected to be limited due to the low sorption of Fe(II) on alumina. [2] In this study we focus on the impact of Sn(II).
We have performed sorption experiments following a stepwise strategy to ensure that Tc(VII) reduction by Sn(II) occurred at the interface (heteroreduction). i) Sn(II) was sorbed on alumina, ii) the Sn(II) pre-sorbed on alumina solid was isolated and dried, iii) a solution of Tc(VII) was added to this modified alumina, and iv) the yield of Tc removal by Sn(II) pre-sorbed on alumina was analyzed. The resulting Tc-containing solid was analyzed by X-ray absorption spectroscopy (XAS) at the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility in Grenoble (France). Bothe Tc K-Edge and Sn K-Edge were recorded at 15 K.
Re-oxidation experiments were performed in samples where Tc(VII) reduction by Sn(II) was obtained by different pathways: i) Tc(VII) direct reduction by dissolved Sn(II) (homoreduction) and ii) Tc(VII) reduction by Sn(II) pre-sorbed on alumina (heteroreduction).
The results show that Tc is removed from solution with a high yield (85-100% removal from solution), being maximum at pH values between 3.5 and 9.5, and minimum at pH 10. Re-oxidation studies show that Tc(IV) obtained by heteroreduction presents lower oxidation kinetics than Tc(IV) obtained by homoreduction. These results support that the presence of alumina plays an important role by preventing Tc(IV) re-oxidation.
Figure 1 shows that the spectrum of TcO2 differs from those preliminar X-ray absorption fine structure (EXAFS) fits for the Tc-loaded samples. This indicates that Al or Sn might also interact with the resulting Tc(IV) species. Further analysis are needed to determine the exact molecular structure of Tc(IV) in the interaction.

Keywords: Technetium; Heteroreduction; Oxidation; EXAFS; Tin

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  • Lecture (Conference)
    ATAS-AnXAS 2022 - Joint Workshop, 17.-21.10.2022, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-35404
Publ.-Id: 35404


Selective a3b4 nicotinic acetylcholine receptor ligand as a potential tracer for drug addiction

Kanasuwan, A.; Deuther-Conrad, W.; Sarasamkan, J.; Chotipanich, C.; Vajragupta, O.; Arunrungvichian, K.

34 Nicotinic acetylcholine receptor (nAChR), a receptor involved in drug-seeking behavior, has been recognized as the emerging biomarker for early detection of the drug addiction. Herein, 34 nAChR ligands were designed and synthesized to improve binding affinity and selectivity of two lead compounds, (S)-QND8 and (S)-T2 for the development of an 34 nAChR tracer. Structural modification was achieved by retaining the key features and expanding the molecular structure with a benzyloxy group to increase the lipophilicity for blood brain barrier penetration and to extend the ligand-receptor interaction. The preserved key features are a fluorine atom for a radiotracer development and a p-hydroxyl motif for ligand-receptor binding affinity. Four (R)- and (S)-quinuclidine-triazole (AK1-AK4) were synthesized and the binding affinity together with selectivity to 34 nAChR subtype were determined by competitive radioligand binding assay using [3H]epibatidine as a radioligand. Among all modified compounds, AK3 showed highest binding affinity and selectivity to 34 nAChR with a Ki value of 3.17 nM, comparable to (S)-QND8 and (S)-T2 and 3109-fold higher affinity to 34 nAChR in comparison to 7 nAChR. The 34 nAChR selectivity of AK3 was tremendously higher than those of (S)-QND8 (11.8-fold) and (S)-T2 (294-fold). AK3 is the promising 34 nAChR tracer for further development as a radiotracer for drug addiction.

Keywords: α3β4 Nicotinic acetylcholine receptor; quinuclidine; triazole; drug-seeking behavior monitoring; drug addition

Permalink: https://www.hzdr.de/publications/Publ-35403
Publ.-Id: 35403


Data publication: Path integral Monte Carlo results for electrons in 2D and 3D quantum dots

Dornheim, T.

This repository contains a collection of raw path integral Monte Carlo simulation results for various properties of electrons in 2D and 3D quantum dots published in Ref. [1].

[1] http://iopscience.iop.org/article/10.1088/1367-2630/ac9f29

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Permalink: https://www.hzdr.de/publications/Publ-35402
Publ.-Id: 35402


Tutorial: Thermal processes in short time annealing: application examples and current trends

Rebohle, L.

The tutorial gives an introduction to the technology of flash lamp annealing, discusses process-relevant issues like temperature profile, homogeneity and stress distribution, and presents a couple of examples in which thermal treatments of materials on short time scale is beneficial.

Keywords: flash lamp annealing; crystallization

Related publications

  • Invited lecture (Conferences)
    18th International Conference on Plasma Surface Engineering, 12.-15.09.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35401
Publ.-Id: 35401


177Lu(III) - and 225Ac(III) -labelled bispidine conjugates targeting neuroendocrine tumours

Kopp, I.; Kubeil, M.; Cieslik, P.; Brandt, F.; Zarschler, K.; Ullrich, M.; Pietzsch, J.; Bachmann, M.; Kopka, K.; Stephan, H.; Comba, P.

Bispidines (3,7-diazabicyclo[3.3.1]nonane) and their derivatives act as bifunctional
chelators (BFC), combining the advantages of multidentate macrocyclic and acyclic
ligands (e.g., high kinetic inertness, rapid radiolabelling under mild conditions) [1]. This
bicyclic chelator system shows a great diversity in terms of its denticity and type of
functional groups, yielding a wide range of multidentate ligands that can bind a variety of
different metal ions [1-3]. In addition, they allow a facile functionalisation of targeting
molecules such as peptides, peptidomimetics, and bispecific antibodies which can also
be used as target modules for adapter CAR T-cell cross-linkage [1, 4]. Herein, we present
a nonadentate bispidine ligand labelled with [177Lu]Lu3+ and [225Ac]Ac3+ at mild
conditions. The radiometal complexes have been obtained with high radiochemical yields
(99%) and are stable in human serum [3]. This is unique so far, as many chelators are
not able to bind both LuIII and AcIII under mild conditions (physiological pH, T<40°C) with
fast complexation kinetics and high molar activities (>100 MBq/nmol for [177Lu]Lu3+ and
~0.2 MBq/nmol for [225Ac]Ac3+). For targeting, the chelator was functionalised with a
peptidic somatostatin analogue (Tyr3
-octreotate), which addresses the somatostatin
subtype receptor 2 in neuroendocrine tumours. Both 177Lu(III)- and 225Ac(III)-labelled
conjugates were investigated towards their binding affinity and internalization in a murine
pheochromocytoma (MPC) and human pancreatic carcinoid (BON1) tumour cell line and
were compared with [177Lu]Lu(III)- and [
225Ac]Ac(III)-DOTA-TATE. The presented
177Lu(III)- and 225Ac(III)-labelled bispidine-conjugates show favourable labelling kinetics
and high radiostabilities in human serum. The radioconjugates exhibited dissociation
constants in the lower nanomolar range (<10 nM) and high internalisation rates (>95 %)
in both cell lines. In comparison to the corresponding DOTA-radioconjugates, milder
radiolabelling conditions might facilitate the labelling of heat-sensitive biomolecules.
Thus, this bispidine chelator shows promising characteristics for future nuclear medicine
applications.

References:

[1] P. Comba et al., Dalton Trans. 2018, 47, 9202. [2] L. Abad‐Galán et al., Chem. Eur.
J. 2021, 27, 10303. [3] P. Cieslik et al., Bispidine derivatives and the use thereof.
EP20216739, 2020. [4] G. Singh et al., Chem. Eur. J. 2020, 26, 1989.

Keywords: bispidine; neuroendocrine tumors; lutetium; actinium; CAR-T; bifunctional chelators; endoradiotherapy; chelator development; somatostatin

  • Lecture (Conference)
    Jahrestagung FG Nuklearchemie, 04.-06.10.2022, Bergisch Gladbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35400
Publ.-Id: 35400


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

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

Background and Purpose:

Motion mitigation is of crucial importance in particle therapy (PT) of patients with abdominal tumors to ensure high-precision irradiation. Magnetic resonance imaging (MRI) is an excellent modality for target volume delineation and motion estimation of mobile soft-tissue tumors. Thus, the aims of this study were to develop an MRI- and PT-compatible abdominal compression device, to investigate its effect on pancreas motion reduction, and to evaluate patient tolerability and acceptance.
Materials and Methods:
In a prospective clinical study, 16 patients with abdominal tumors received an individualized polyethylene-based abdominal corset. Pancreas motion was analyzed using time- and phase resolved MRI scans (orthogonal 2D-cine and 4D MRI) with and without compression by the corset. The pancreas was manually segmented in each MRI data set and the population-averaged center-of-mass motion in inferior-superior (IS), anterior-posterior (AP) and left-right (LR) directions was determined. A questionnaire was developed to investigate the level of patient acceptance of the corset, which the patients completed after acquisition of the planning computed tomography (CT) and MRI scans.
Results:
The corset was found to reduce pancreas motion predominantly in IS direction by on average 47 % - 51 % as found in the 2D-cine and 4D MRI data, respectively, while motion in the AP and LR direction was not significantly reduced. Most patients reported no discomfort when wearing the corset.
Conclusion:
An MRI- and PT-compatible individualized abdominal corset was presented, which substantially reduced breathing-induced pancreas motion and can be safely applied with no additional discomfort for the patients. The corset has been successfully integrated into our in-house clinical workflow for PT of tumors of the upper abdomen.

Keywords: MR guided proton therapy; image guidance; tumor motion; abdominal compression

Permalink: https://www.hzdr.de/publications/Publ-35399
Publ.-Id: 35399


Hybridised production of technetium-99m and technetium-101 with fluorine-18 on a low-energy biomedical cyclotron

Johnstone, E. V.; Mayordomo, N.; Mausolf, E. J.

New modes of production and supply of short-lived radioisotopes using accelerators
are becoming attractive alternatives to the use of nuclear reactors. In this study, the
use of a compact accelerator neutron source (CANS) was implemented to explore the
production of 99mTc and 101Tc. Irradiations were performed with neutrons generated
from a 16.5 MeV cyclotron utilising the 18O(p, n)18F reaction during routine 18F[FDG]
production in a commercial radiopharmacy. Natural molybdenum targets in metal form
were employed for the production of Tc isotopes of interest via (n, ) reactions on 98Mo
and 100Mo. The production of 99mTc and 101Tc under these conditions is considered
and discussed.

Keywords: Tc-99m; Tc-101; F-18; CANS; Compact accelerator neutron source

Permalink: https://www.hzdr.de/publications/Publ-35398
Publ.-Id: 35398


A brief summary about technetium: Origin, medical applications, and environmental immobilization strategies

Mayordomo, N.

This lecture will be given in the frame of the "Week science" at Universidad de Alcalá (Spain). I will give an overview about technetium origins, applications, and environmental remediation.

Keywords: Techenetium; Lecture; Environment; Applications

  • Invited lecture (Conferences) (Online presentation)
    Week of science at Universidad de Alcalá, 23.11.2022, Alcalá de Henares, Spain

Permalink: https://www.hzdr.de/publications/Publ-35397
Publ.-Id: 35397


177Lu-, 225Ac- and 111In-labelled nonadentate bispidine ligands synthesis, radiolabelling experiments and stability assays

Kopp, I.; Cieslik, P.; Kopka, K.; Bachmann, M.; Stephan, H.; Comba, P.; Kubeil, M.

Objectives
Bispidines (3,7-diazabicyclo[3.3.1]nonanes) are of great interest for the use in radiopharmaceutical applications. Combining the advantages of highly preorganised rigid macrocyclic ligands and the flexibility of open-chain ligands, they are able to form highly stable complexes at mild reaction conditions with a broad range of di- and trivalent metal ions.1,2 Here, we present a nonadentate bispidine ligand (Fig. 1) labelled with [177Lu]LuCl3, [225Ac]AcCl3 and [111In]InCl3 at mild conditions and report their stability and inertness in aqueous solution and human serum.3 The results in terms of radiolabelling conditions and serum stabilities are compared with the “gold standard” DOTA, which requires harsh radiolabelling conditions, and the octadentate bispidine ligand H2bispa.2,4

Methods
The bispidine ligand was synthesised according to literature on a multigram scale, with an overall yield of 5% over 9 steps.2

Radiolabelling experiments of the nonadentate bispidine ligand with [177Lu]Lu3+ and [225Ac]Ac3+ were carried out at 40 °C using 150 mM NH4OAc buffer (pH 6). Radiolabelling with [111In]In3+ was performed in the same buffer at room temperature. For comparison, the DOTA and the octadentate bispidine ligand H2bispa2 were labelled with the trivalent radiometals as well. The radiochemical yields and purities were monitored via radio-TLC and radio-HPLC for different ligand concentrations after 5 min, 30 min and 60 min. Radiostabilities in human serum were studied by radio-TLC and radio-SEC after 1 h, 1 d, 3 d and 7 d.

Results
Radiolabelling experiments gave quantitative yields for the formation of both 177Lu- and 225Ac‑complexes at 40 °C after 5 minutes for ligand concentrations of 10-6 mol/L. With [111In]In3+ a quantitative conversion was obtained even at room temperature after 60 minutes with a ligand concentration of 5·10-6 mol/L. For [177Lu]Lu3+, a molar activity of >100 MBq/nmol, for [225Ac]Ac3+ 0.2 MBq/nmol and for [111In]In3+ >20 MBq/nmol was found at the end of synthesis. Furthermore, the radiolabelled bispidine complexes showed high stability in human serum after 7 d ([225Ac]Ac‑bispidine: 80±2%; n=3, [177Lu]Lu-bispidine: 94%; n=2,), whereas only moderate stability was achieved for [111In]In-bispidine (74%; n=2 ) after 3 d.

Conclusions
The presented 177Lu- and 225Ac-labelled bispidine complexes showed favourable labelling kinetics and radiostabilities in human serum. The 111In-labelled bispidine gave moderate molar activities and stabilities in human serum. In comparison to DOTA, milder conditions for bispidine ligands allow the radiolabelling of heat-sensitive biomolecules.

References

[1] Comba, P.; Kerscher, M.; Rück, K.; Starke, M. Bispidines for Radiopharmaceuticals. Dalton Trans. 2018, 47, 9202–9220.

[2] Abad‐Galán, L.; Cieslik, P.; Comba, P.; Gast, M.; Maury, O.; Neupert, L.; Roux, A.; Wadepohl, H. Excited State Properties of Lanthanide(III) Complexes with a Nonadentate Bispidine Ligand. Chem. – Eur. J. 2021, 27, 10303–10312.

[3] Cieslik, P.; Kubeil, M.; Stephan, H.; Comba, P. Bispidine derivatives and the use thereof. EP20216739, 2020.

[4] Comba, P; Jermilova, U.; Orvig, C.; Patrick, B. O.; Ramogida, C.; Rueck, K.; Schneider, C.; Starke, M. Inorg. Chem. 2017, 23, 15945 – 15956.

Keywords: radiopharmacy; theranostics; bispidines; trivalent metals; actinium; lutetium; indium; ligand development

  • Lecture (Conference)
    Terachem, 14.-17.09.2022, Brixen, Italien

Permalink: https://www.hzdr.de/publications/Publ-35396
Publ.-Id: 35396


A novel bispidine-based chelator for radiopharmaceutical applications

Kubeil, M.; Ullrich, M.; Zarschler, K.; Pietzsch, J.; Kopka, K.; Bachmann, M.; Stephan, H.

Bispidines (3,7-diazabicyclo[3.3.1]nonane) and their derivatives act as bifunctional chelating agents (BFCAs). Combining the advantages of highly preorganised rigid macrocyclic ligands and the flexibility of open-chain ligands, bispidines are able to form highly stable complexes at mild reaction conditions with a broad range of di- and trivalent metal ions. Of particular interest, they allow the coupling to biological targeting vectors such as peptides, peptidomimetics, T cell receptor derivatives as well as any kind of natural and recombinant antibody derivatives to construct effective radiopharmaceuticals for diagnostic and therapeutic purposes. Here, we present a nonadentate bispidine ligand (Figure 1), which forms stable and inert complexes with [177Lu]LuCl3, [225Ac]AcCl3 and [111In]InCl3 at mild conditions. This is unique so far, as few chelators are able to tightly bind both Lu(III) and Ac(III) under mild conditions
(physiological pH, T<40°C) with fast complexation kinetics. We investigated the thermodynamic and kinetic properties of the radio-complexes. For targeting, the chelator was functionalised with a peptidic somatostatin analogue (Tyr3-octreotate, TATE), which addresses the somatostatin subtype receptor 2 in neuroendocrine tumors. The bispidine-TATE conjugate was labelled with 177Lu(III) and 225Ac(III) and investigated in SSTR2-positive mouse pheochromocytoma (MPC) and human pancreatic carcinoid tumour (BON-SSTR2) cell lines. Moreover, quantitative small animal SPECT imaging showed specific uptake of the [177Lu]Lu-conjugate in vivo in naturally SSTR2-positve MPC tumour allografts. Some structural optimisation will be required to further reduce off-target accumulation. However, the bispidine chelator shows a promising potential for a broad application in nuclear medicine, both in imaging and radionuclide therapy.

  • Lecture (Conference)
    Australian Society of Molecular Imaging (ASMI) 2022, 06.-07.10.2022, Melbourne, Australia

Permalink: https://www.hzdr.de/publications/Publ-35395
Publ.-Id: 35395


Towards personalized medicine: one chelator for imaging and therapy with lutetium-177 and actinium-225

Cieslik, P.; Kubeil, M.; Zarschler, K.; Ullrich, M.; Brandt, F.; Anger, K.; Wadepohl, H.; Kopka, K.; Bachmann, M.; Pietzsch, J.; Stephan, H.; Comba, P.

We report a nonadentate bispidine (3,7-diazabicyclo[3.3.1]nonane) that unveils the potential to bind theranostically relevant radionuclides, including indium-111, lutetium-177 and actinium-225 at mild labeling conditions. This radiopharmaceutical candidate allows the simultaneous application of imaging and treatment (radionuclide theranostics) without changing the type of bioconjugate, i.e. it allows the strong binding to an imaging and a therapeutic radionuclide by the same chelator. Since sophisticated coordination chemistry is required to achieve high thermodynamic and kinetic stability, it is not surprising that only a few chelators have been reported that are able to strongly bind several radionuclides to a satisfactory extent. Bispidine-derived ligands have proven to be ideal for di- and trivalent metal ions with generally fast complexation kinetics and high in vitro and in vivo stabilities. The presented (radio)complexes are formed under mild conditions (pH 6, <40°C) and exhibit thermodynamic stability and inertness in human serum comparable to the corresponding DOTA complexes. The bispidine-based complexing agent was conjugated to a peptide, targeting somatostatin type 2 receptors (SSTR2), overexpressed on neuroendocrine tumors. The 177Lu- and 225Ac-labeled conjugates were investigated, considering their binding to two different SSTR2 positive cell lines, including the human pancreatic carcinoid tumor (BON-SSTR2+) and the murine pheochromocytoma cell line (MPC). The biodistribution and accumulation pattern in MPC tumor-bearing mice was also evaluated. The LuIII and AcIII complexes studied show how ligand structures can be optimized in general by extending the denticity and varying the donor set in order to allow for fast complex formation and medically relevant inertness.

Keywords: bispidine; trivalent metal ions; radionuclide theranostics; somatostatin analogue; actinium; lutetium

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Permalink: https://www.hzdr.de/publications/Publ-35394
Publ.-Id: 35394


Rare radioisotopes at the ready

Kvashnina, K.

The study of rare isotopes, including many in the f-block, is a key step to advancing our fundamental understanding of these elements but their scarcity poses challenges. Now, minute amounts of such materials have been isolated and characterized through complexation with polyoxometalate clusters.

Permalink: https://www.hzdr.de/publications/Publ-35393
Publ.-Id: 35393


Radiolabelling of nanoparticles for colloid tracing A versatile tool in nanosafety research

Schymura, S.; Mansel, A.; Kulenkampff, J.; Franke, K.

Many studies in the field of nanosafety research „do not offer any kind of clear statement on the safety of nanomaterials“, as methodological problems considerably hinder the reliable detection of nanoparticles (NPs) at the predicted low environmentally relevant concentrations.
The radiolabeling of nanoparticles has the potential for detecting nanoparticles at minimal concentrations in complex matrices, even against a same-element background, with unprecedented experimental ease, making it a versatile tool for NP release, transport, and uptake studies.

Keywords: Radiolabelling; Nanoparticles

  • Poster
    Week of Microbial Technologies, 07.-11.11.2022, Ljubljana, Slowenien

Permalink: https://www.hzdr.de/publications/Publ-35392
Publ.-Id: 35392


Ca-Caseinat-unterstützte Remineralisierung von Zähnen

Schymura, S.; Schneider, E.; Messerschmidt, J.; Lechner, B.-D.

Menschliche Zähne sind täglich chemischen Erosionsprozessen ausgesetzt, die zu einer Verschlechterung der Zahnsubstanz führen können. Verantwortlich hierfür sind in erster Line das Konsumieren von Säurehaltigen Getränken und Speisen. Niedriger pH, sowie Komplexierende Stoffe führen zu einer Demineralisierung des Zahn Hydroxylapatits {Ca5(PO4)3OH}2) (HAP). Es wird geschätzt dass weltweit 30-50% der Milchzähne und 20-45% der permanenten Zähne von Zahnerosion betroffen sind. Folgen von Zahnerosion können ein erhöhtes Kariesrisiko, Zahnsensibilität, Zahnverfärbung und im schlimmsten Fall Zahnverlust sein.
Eine potentielle Maßnahme um Zahnerosion entgegenzuwirken stellt die Förderung der Remineralisierung dar, indem die Calcium und Phosphat-Konzentration im Speichel erhöht wird, z. B. durch die Gabe von Casein, einem Milchprotein. Die im Casein enthaltenen Ca9(PO4)6 Nanocluster können in die erodierte Zahnsubstanz eingebaut werden und die Schäden rückgängig machen. Unter Verwendung der Weißlichtinterferometrie zur Rauheitsanalyse zeigen wir die Dynamik der DEM/REM Prozesse in-Vitro und zeigen in Fallstudien die Anwendung von Ca Kaseinat als wenig intrusive Behandlungsmethode mit REM Potential in-Vivo.

Keywords: Zahnremineralisation; Apatit; Ca-Caseinat

  • Poster
    15. Thüringer Zahnärztetag, 25.-26.11.2022, Erfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35391
Publ.-Id: 35391


Ca-Caseinate-enhanced remineralisation of dental apatite

Schymura, S.; Schneider, E.; Messerschmidt, J.; Lechner, B.-D.

Human teeth are subject to chemical erosion processes that can lead to a loss of tooth hard substance. Low pH and complexing agents in food and drink can demineralize the dental hydroxyapatite. It is estimated that 20-45 % of permant teeth worldwide are affected by tooth errosion. This can lead to increased caries risk, tooth sensitivity, tooth colouration and in the worst case tooth loss. One potential treatment of tooth errosion is the promotion of naturally ocurring remineralisation processes, e.g. by application of caseine milk protein. The Ca9(PO4)6 nanoclusters have the potential to cure damaged tooth material. Using vertical scanning interferometry we show the dynamics of de- and remineralisation tooth samples by analysis of the surface roughness development.

Keywords: Remineralisation; apatite; dental material; Ca-Caseinate

  • Invited lecture (Conferences)
    Week of Microbial Technologies, 07.-11.11.2022, Ljubljana, Slowenien

Permalink: https://www.hzdr.de/publications/Publ-35390
Publ.-Id: 35390


Wastewater-based epidemiology dashboard for research of COVID-19 in Saxony

Mertel, A.; Schüler, L.; Abdussalam, W.; Schlechte-Welnicz, W.; Calabrese, J.

The COVID-19 pandemic has had unprecedented health and economic impacts worldwide. Various fields of science
approached this topic to better understand the pandemic’s spread characteristics and provide a factual base for nonpharmaceutical interventions. One of the interesting non-invasive methodologies, wastewater epidemiology, looks for
the correlation between the outcomes of the wastewater-based PCR analysis and the epidemiological situation in their
catchment (e.g., Bogler et al., 2020; Farkas et al., 2020). This approach may efficiently predict the outbreak in the
endemic phase when the conventional testing is usually underrated. Therefore a visual analytical tool may be beneficial
for observing the spatiotemporal correlations of the wastewater indicators and the focal incidence levels. However,
based on the analysis of existing tools (Naughton et al., 2021), most dashboards integrating wastewater indicators do
not use information about geographical space at all, or the functionality of the map component is limited to the
identification of the particular wastewater plant.
In the where2test project (www.where2test.de), we established a scalable operational data store (ODS) to automatically
collect, store and integrate heterogeneous epidemiology-related data for various administrative levels of several
European countries, focusing primarily on the region of Saxony. The project includes various activities, including
spatiotemporal analyses (Mertel et al., 2022), epidemiological models and applications (Davoodi et al., 2022), and
forecasts. In this paper, we present a prototype of an interactive dashboard to explore the correlation between the local
incidence as estimated by conventional testing and the wastewater-based PCR indicators (cT values) in Saxony.
Another goal of this application is to focus on the geospatial aspect of these data.
The top part of the dashboard features an interactive timeline linked to a multidimensional heatmap. Here, the user can
navigate in time and explore the correlation between the epidemiological situation of the neighborhood of the
wastewater plants (defined by the temporal distance) and the cT indicators in time. For the week selected in the
timeline, the user can observe the spatial context within the Saxonian municipalities on the map below. The map allows
interaction with the single municipalities and all the wastewater plants integrated with our ODS to access detailed
information and additional charts. In the future, we plan to integrate more metrics and parameters that may be beneficial
for exploring spatiotemporal inference. Our scalable infrastructure also easily allows the integration of more wastewater
plants. The application is available on www.where2test.de/wastewater from August 2022.

Keywords: Waste water; Covid-19; Epidemiology

  • Open Access Logo Contribution to proceedings
    European Cartographic Conference – EuroCarto 2022, 19.-21.09.2022, Vienna, Austria
    Abstracts of the International Cartographic Association 5, 131
    DOI: 10.5194/ica-abs-5-131-2022

Permalink: https://www.hzdr.de/publications/Publ-35389
Publ.-Id: 35389


A scalable pipeline for COVID-19

Abdussalam, W.

Throughout the coronavirus disease 2019 (COVID-19) pandemic, decision makers have relied on forecasting models to determine and implement non-pharmaceutical interventions (NPI). In building the forecasting models, continuously updated datasets from various stakeholders including developers, analysts, and testers are required to provide precise predictions. Here we report the design of a scalable pipeline which serves as a data synchronization to support inter-country top-down spatiotemporal observations and forecasting models of COVID-19, named the where2test, for Germany, Czechia and Poland. We have built an operational data store (ODS) using PostgreSQL to continuously consolidate datasets from multiple data sources, perform collaborative work, facilitate high performance data analysis, and trace changes. The ODS has been built not only to store the COVID-19 data from Germany, Czechia, and Poland but also other areas. Employing the dimensional fact model, a schema of metadata is capable of synchronizing the various structures of data from those regions, and is scalable to the entire world. Next, the ODS is populated using batch Extract, Transfer, and Load (ETL) jobs. The SQL queries are subsequently created to reduce the need for pre-processing data for users. The data can then support not only forecasting using a version-controlled Arima-Holt model and other analyses to support decision making, but also risk calculator and optimisation apps. The data synchronization runs at a daily interval, which is displayed at this https URL.

  • Open Access Logo Lecture (Conference)
    Data Ecosystems in conjunction with very large databases 2022, 05.-09.09.2022, Sydney, Australia

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Permalink: https://www.hzdr.de/publications/Publ-35388
Publ.-Id: 35388


Molecular Structures of the Silicon Pyridine-2-(thi)olates Me3Si(pyX), Me2Si(pyX)2 and Ph2Si(pyX)2 (py = 2-Pyridyl, X = O, S), and Their Intra- and Intermolecular Ligand Exchange in Solution

Seidel, A.; Weigel, M.; Ehrlich, L.; Gericke, R.; Brendler, E.; Wagler, J.

A series of pyridine-2-olates (pyO) and pyridine-2-thiolates (pyS) of silicon was studied in solid state and in solution. The crystal structures of Me3Si(pyO) (1a), Me3Si(pyS) (1b), Me2Si(pyO)2 (2a), Me2Si(pyS)2 (2b), Ph2Si(pyO)2 (3a) and Ph2Si(pyS)2 (3b) were determined by X-ray diffraction. For that purpose, crystals of the (at room temperature) liquid compounds 1a and 1b were grown in a capillary on the diffractometer. Compounds 1a, 1b, 2a, 2b and 3a feature tetracoordinate silicon atoms in the solid state, whereas 3b gave rise to a series of four crystal structures in which the Si atoms of this compound are hexacoordinate. Two isomers (3b1 with all-cis arrangement of the C2N2S2 donor atoms in P-1, and 3b2 with trans S-Si-S axis in P21/n) formed individual crystal batches, which allowed for their individual 29Si NMR spectroscopic study in the solid state (the determination of their chemical shift anisotropy tensors). Furthermore, the structures of a less stable modification of 3b2 (in C2/c) as well as a toluene solvate 3b2 (toluene) (in P-1) were determined. In CDCl3, the equimolar solutions of the corresponding pairs of pyO and pyS compounds (2a/2b and 3a/3b) showed substituent scrambling with the formation of the products Me2Si(pyO)(pyS) (2c) and Ph2Si(pyO)(pyS) (3c), respectively, as minor components in the respective substituent exchange equilibrium.

Keywords: chemical shift anisotropy; 2-hydroxypyridine; hypercoordination; 2-mercaptopyridine; organosilanes; quantum chemical calculation

Permalink: https://www.hzdr.de/publications/Publ-35387
Publ.-Id: 35387


Bonding Trends in Tetravalent Actinide (Th - Pu) Complex Series

Gericke, R.; März, J.; Kaden, P.; Patzschke, M.; Radoske, T.; Fichter, S.; Blei, M. K.; Schmidt, M.; Stumpf, T.

Actinides play an important role in chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories.1 One of the major tools to obtain a profound knowledge about actinide (An) binding is their coordination chemistry. However, the understanding of complexation properties of the actinides is lacking behind those of the d- or 4f-elements. Characteristic of the actinides is their huge variety of possible oxidation states, typically ranging from +II to +VII for early An. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series of isostructural An compounds in which the An is in the same oxidation state.2 Therefore our investigations are directed towards the synthesis of actinide complexes with the f-element in the oxidation state IV, the dominant oxidation state particularly under anoxic environmental conditions. Observed changes in e.g., the binding situation or magnetic effects along such a series may deliver insight into the elements’ unique electronic properties mainly originating from the f-electrons. One important question in the field of An chemistry is the degree of “covalency” in compounds across the An series,3 which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
In these studies, we investigate the coordination chemistry of tetravalent actinides (An(IV)), using organic mono- or dianionic ligands with O- and mixed O/N-donor atoms of the acetylacetonate and salen-type.4 The An complexes are typically synthesized via salt metathesis reactions under strict exclusion of moisture and air. Single crystal X-ray diffraction analysis provides insight into isostructural complex series, which were achieved in each case. The resulting compounds were further analysed by NMR, IR, UV-vis-NIR, and EPR spectroscopy and cyclic voltammetry. These results are used as a basis to further analyse bonding trends along the actinide series by means of quantum chemical calculations.
From the results, trendlines along the actinides An = Th, U, Np and Pu in various complex series were obtained, which shed some light in the ongoing debate of covalency in actinide bonding.

References
[1] L. S. Natrajan, A. N. Swineburn, M. B. Andrews, S. Randall, S. L. Heath, Coord. Chem. Rev. 2014, 266-267, 171-193.
[2] M. B. Jones, A. J. Gaunt, J. C. Gordon, N. Kaltsoyannis, Chem. Sci. 2013, 4, 1189-1203.
[3] M. P. Kelley, J. Su, M. Urban, M. Luckey, E. R. Batista, P. Yang, J. C. Shafer, J. Am. Chem. Soc. 2017, 139, 9901-9908.
[4] T. Radoske, J. März, M. Patzschke, P. Kaden, O. Walter, M. Schmidt, T. Stumpf, Chem. Eur. J. 2020, 26, 16853-16859.

Acknowledgement
This study was supported by the German Federal Ministry of Education and Research (BMBF) funding under the project No. 02NUK046B (FENABIUM).

Keywords: actinides; NMR; EPR; single crystal X-ray diffaction; quantum chemical calculations

Related publications

  • Invited lecture (Conferences)
    Terrae Rarae - Tage der Seltenen Erden, 27.-29.09.2022, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-35386
Publ.-Id: 35386


[An(acac)4] - complexes revisited

Gericke, R.; Kaden, P.

Actinides (An) play an important role in chemical research and environmental science related to the nuclear industry or nuclear waste repositories.1 Investigating their coordination chemistry can function as a tool to obtain fundamental understanding of actinide binding. Due to the radiotoxicity of actinide complexes, special care in handling those material need to be employed in form of working in a controlled area lab. Therefore, the understanding of complexation properties of the actinides, in particular the transuranium (TRU) elements, is lacking behind those of the d- or 4f-elements, which can be handeled in ordinary laboratories.
For the early actinides possible oxidation states are typically ranging from +II to +VII. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series of isostructural An compounds in which the An is in the same oxidation state.2 Therefore our investigations are directed towards the synthesis of actinide complexes (An = Th, U, Np and Pu) with the f-element in the oxidation state IV, the dominant oxidation state particularly under anoxic environmental conditions. Observed changes in e.g., the binding situation or magnetic effects along such a series deliver insight into the elements’ unique electronic properties mainly originating from the f-electrons. One important question in the field of An chemistry is the degree of “covalency” in compounds across the An series,3 which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
An-complexes using pure O-donor ligand systems can act as molecular mimic for related An-O-systems, e.g. UO2 used as fuel in nuclear reactors. In these studies, we investigate the coordination chemistry of tetravalent actinides (An(IV)), using an organic monoanionic ligand with O-donor atoms of the acetylacetonate (acac) type. Since 1958, actinide complexes of the type [An(acac)4] have structurally been caracterized at ambient temperature.4-8 However, spectroscopic data is limited to vibrational spectroscopy especially for the transuranium complexes, leaving open questions of the actinide bonding. The [An(acac)4] complexes are typically synthesized via salt metathesis reactions under strict exclusion of moisture and air. Single crystal X-ray diffraction analysis at 100 K provides insight into isostructural complex series, which were achieved in each case. In order to obtain further insight into the electronic structure of these complexes, the compounds were further analysed by NMR, IR, UV-vis-NIR, and EPR spectroscopy. The redox chemistry of the series of [An(acac)4] complexes in NCMe was further investigated with cyclic voltammetry. These results are used as a basis to further analyse bonding trends along the actinide series by means of quantum chemical calculations.
From the results, trendlines along the actinides An = Th, U, Np and Pu in this complex series were obtained, which shed some light in the ongoing debate of covalency in actinide bonding.

References
1. L. S. Natrajan, A. N. Swineburn, M. B. Andrews, S. Randall, S. L. Heath, Coord. Chem. Rev. 2014, 266-267, 171-193.
2. M. B. Jones, A. J. Gaunt, J. C. Gordon, N. Kaltsoyannis, Chem. Sci. 2013, 4, 1189-1203.
3. M. P. Kelley, J. Su, M. Urban, M. Luckey, E. R. Batista, P. Yang, J. C. Shafer, J. Am. Chem. Soc. 2017, 139, 9901-9908.
4. D. Grdenić, B. Matković, Nature 1958, 182, 465-466.
5. D. Grdenić, B. Matković, Acta Cryst. 1959, 12, 817-817.
6. B. Allard, Acta Chem. Scand. 1972, 26, 3492-3504.
7. D. Brown, B. Whittaker, J. Tacon, J. Chem. Soc., Dalton Trans. 1975, 1, 34-39.
8. B. Allard, J. Inorg. Nucl. Chem. 1976, 38, 2109-2115.

Keywords: actinides; NMR; EPR; single crystal X-ray diffraction; quantum chemical calculations

  • Lecture (Conference)
    Actinides revisited 2022, 21.-23.09.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-35385
Publ.-Id: 35385


Intelligent Materials and Systems

Makarov, D.

In this presentation, we review current research activities at the FWID.

Keywords: curvature effects in magnetism; antiferromagnetic spintronics; magnetic soft robots

Related publications

  • Lecture (others)
    seminar at the Central European Institute of Technology (CEITEC), 03.11.2022, Brno, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-35384
Publ.-Id: 35384


Feasibility of MR phase-contrast imaging for proton beam visualisation in liquid water phantoms

Peter, J.; Gantz, S.; Hoffmann, A. L.; Pawelke, J.

Proton beam-induced convection in water triggered local MRI magnitude signal loss in combined
imaging and irradiation experiments performed on a new research prototype in-beam low-field MRI
proton radiotherapy device. In this study, the influence of convection on the MRI phase signal was
tested. Both mechanical and thermal inhibition of convection in dedicated water phantoms resulted in
the absence of MRI phase signatures, which were clearly visible under conditions were convection
could develop. Moreover, a change in either convection velocity or Venc sequence motion sensitivity
changed the observed phase contrast, confirming the convection-driven phase contrast mechanism.

  • Contribution to proceedings
    2023 ISMRM & ISMRT Annual Meeting & Exhibition, 03.-08.06.2023, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-35383
Publ.-Id: 35383


Coupling of terahertz light with nanometre-wavelength magnon modes via spin–orbit torque

Salikhov, R.; Ilyakov, I.; Körber, L.; Kakay, A.; Gallardo, R. A.; Ponomaryov, O.; Deinert, J.-C.; de Oliveira, T.; Lenz, K.; Faßbender, J.; Bonetti, S.; Hellwig, O.; Lindner, J.; Kovalev, S.

Spin-based technologies can operate at terahertz frequencies but require manipulation techniques that work at ultrafast timescales to become practical. For instance, devices based on spin waves, also known as magnons, require efficient generation of high-energy exchange spin waves at nanometre wavelengths. To achieve this, a substantial coupling is needed between the magnon modes and an electro-magnetic stimulus such as a coherent terahertz field pulse. However, it has been difficult to excite non-uniform spin waves efficiently using terahertz light because of the large momentum mismatch between the submillimetre-wave radiation and the nanometre-sized spin waves. Here we improve the light–matter interaction by engineering thin films to exploit relativistic spin–orbit torques that are confined to the interfaces of heavy metal/ferromagnet heterostructures. We are able to excite spin-wave modes with frequencies of up to 0.6 THz and wavelengths as short as 6 nm using broadband terahertz radiation. Numerical simulations demonstrate that the coupling of terahertz light to exchange-dominated magnons originates solely from interfacial spin–orbit torques. Our results are of general applicability to other magnetic multilayered structures, and offer the prospect of nanoscale control of high-frequency signals.

Keywords: Magnonics; Spintronics; Terahertz; Magnetism

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Permalink: https://www.hzdr.de/publications/Publ-35382
Publ.-Id: 35382


Learning-based systems for assessing hazard places of contagious diseases and diagnosing patient possibility

Davoodi Monfared, M.; Ghaffari, M.

To manage the propagation of infectious diseases, particularly fast-spreading pandemics, it is necessary to provide information about possible infected places and individuals, however, it needs diagnostic tests and is time-consuming and expensive. To smooth these issues, and motivated by the current Coronavirus disease (COVID-19) pandemic, in this paper, we propose a learning-based system and a hidden Markov model (i) to assess hazardous places of a contagious disease, and (ii) to predict the probability of individuals’ infection. To this end, we track the trajectories of individuals in an environment. For evaluating the models and the approaches, we use the Covid-19 outbreak in an urban environment as a case study. Individuals in a closed population are explicitly represented by their movement trajectories over a period of time. The simulation results demonstrate that by adjusting the communicable disease parameters, the detector system and the predictor system are able to correctly assess the hazardous places and determine the infection possibility of individuals and cluster them accurately with high probability, i.e., on average more than 96%. In general, the proposed approaches to assessing hazardous places and predicting the infection possibility of individuals can be applied to contagious diseases by tailoring them to the influential features of the disease.

Keywords: Machine learning; Trajectory tracking; Patient prediction; Hidden Markov model; Covid-19; Trajectory clustering

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Permalink: https://www.hzdr.de/publications/Publ-35381
Publ.-Id: 35381


Microstructural characterisation of brittle fracture initiation sites in reactor pressure vessel steels

Chekhonin, P.; Das, A.; Bergner, F.; Altstadt, E.

Neutron embrittlement of reactor pressure vessel (RPV) steels limits the safe operational time of nuclear reactors. Microcracks in RPV steels are known to originate from cleaved precipitates, inclusions or grain boundaries, which eventually lead to brittle fracture. In most cases, these precipitates are reported as carbides. Latest research indicates the critical fracture event to be the crossing of grain boundary instead of the particle-matrix interface by the microcrack. Very few works have performed detailed fractography, which revealed the size and type of the feature found in the crack nucleation centre, together with metallographic bulk investigations. Additionally, the effect of neutron irradiation on microcrack nucleation is unknown. In the present work, detailed fractography and metallography is performed on a RPV steel in both its unirradiated as well as neutron irradiated state. While no particles were involved in more than 1/3 of all samples, a particle in the centre of the initiation site has been identified in a majority of the cases. Those particles are either Mo-rich carbides or Al-rich inclusions. In comparison, the metallographic analysis of the bulk steel reveals Mo-rich and Mn-rich carbides. Mn-rich carbides constitute the majority of all carbides in the steel but are never found to be responsible for brittle fracture initiation. Only a small fraction of observable carbides is Mo-rich which are responsible for fracture. Thus, the present work demonstrates a discrepancy between particles found in brittle fracture initiation sites and particles that are directly observable in bulk steel. Some of the initiating particles are extremely rare in the bulk. Furthermore, it is revealed that the local fracture stress does not depend on the type or size of particle or grain involved at the initiation site. In conclusion, the fracture stress strongly depends on the type of the grain boundary, rather than on a stress based upon a Griffith criterion, which considers particle or grain size alone. The brittle fracture mechanism was found to be unaffected by neutron irradiation. These findings could help refine modelling of the critical brittle fracture stress and fracture toughness using microstructural parameters as input.

Keywords: reactor pressure vessel steel; brittle fracture; brittle fracture initiation; initiation particles

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35378
Publ.-Id: 35378


Superconductivity in the amorphous phase of the half-Heusler TiNiSn alloy

Barzola-Quiquia, J.; Osmic, E.; Bercoff, P. G.; Venosta, L.; Häussler, P.

Amorphous TiNiSn films were prepared at 𝑇 ≈ 4.2 K and resistance 𝑅(𝑇 ) and thermopower 𝑆(𝑇 ) have been investigated. 𝑅(𝑇 ) shows that the sample is superconducting and the transition temperature 𝑇𝑐 increases with increasing annealing temperature, being the maximum 𝑇𝑐3 = 4.19 K. The electron–phonon coupling estimated from 𝑆(𝑇 ) results is very close to the value calculated using McMillan equation for the superconducting transition 𝑇𝑐 , indicating that amorphous TiNiSn is an intermediate electron–phonon coupled superconductor. After annealing up to 𝑇 = 850 K, the amorphous sample crystallizes at 𝑇𝐾 ≈ 785 K. The atomic structure and high stability of the amorphous phase can be explained in the framework of electronically stabilized Hume–Rothery phases, where hybridization from Ti-𝑑 and Ni-𝑑 electrons plays an important role. The crystallized sample shows a well-ordered half-Heusler crystalline phase, space group 𝐹43𝑚, with a TiNiSn atomic order in the unit cell instead of the common NiTiSn type.

Permalink: https://www.hzdr.de/publications/Publ-35376
Publ.-Id: 35376


Dimensional reduction and incommensurate dynamic correlations in the S = 1/2 triangularlattice antiferromagnet Ca3ReO5Cl2

Zvyagin, S. A.; Ponomaryov, A. N.; Wosnitza, J.; Hirai, D.; Hiroi, Z.; Gen, M.; Kohama, Y.; Matsuo, A.; Matsuda, Y. H.; Kindo, K.

The observation of spinon excitations in the S = 1/2 triangular antiferromagnet Ca3ReO5Cl2 reveals a quasi-one-dimensional (1D) nature of magnetic correlations, in spite of the nominally 2D magnetic structure. This phenomenon is known as frustration-induced dimensional reduction. Here, we present high-field electron spin resonance spectroscopy and magnetization studies of Ca3ReO5Cl2, allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics. We argue that the presence of the uniform Dzyaloshinskii-Moriya interaction (DMI) shifts the spinon continuum in momentum space and, as a result, opens a zero-field gap at the Γ point.We observed this gap directly. The shift is found to be consistent with the structural modulation in the ordered state, suggesting this material as a perfectmodel triangular-lattice ystem,where a pure DMI-spiral ground state can be realized.

Permalink: https://www.hzdr.de/publications/Publ-35375
Publ.-Id: 35375


Molecular engineering of naphthalene spacers in low-dimensional perovskites

Mitrofanov, A.; Berencén, Y.; Sadrollahi, E.; Boldt, R.; Bodesheim, D.; Weiske, H.; Paulus, F.; Geck, J.; Cuniberti, G.; Kuc, A. B.; Voit, B.

Hybrid organic-inorganic lead halide perovskites have drawn much interest due to their optical and electronic properties. The ability to fine-tune the structure by the organic component allows for obtaining a wide range of materials with various dimensionalities. Here, we combine experimental and theoretical work to investigate the structures and properties of a series of low- dimensional hybrid organic-inorganic perovskites, based on naphthalene ammonium cations (2,6-diaminonaphthalene (2,6-DAN), 1-aminonaphthalene (1-AN) and 2-aminonaphthalene (2-AN)). All materials exhibit edge- or face-sharing 1D chain structures. Compared to the 2D counterpart containing isomeric 1,5-diaminonaphthalene (1,5-DAN), 1D hybrid materials exhibit broadband light emission arising from the self-trapped excitons (STEs) owing to their highly distorted structure. This work expands the library of low-dimensional hybrid perovskites and opens new possibilities for obtaining broadband-light-emitting materials.

Permalink: https://www.hzdr.de/publications/Publ-35374
Publ.-Id: 35374


Direct numerical simulation of particles, rigid and flexible fibers interacting with a drop

Lecrivain, G.; Hampel, U.; Yamamoto, R.; Taniguchi, T.

The present work results from a three-year collaboration between the Helmholtz-Zentrum Dresden-Rossendorf (Germany) and the University of Kyoto (Japan), which took place within the frame of International Marie Curie Fellowship. The dynamics of colloidal particles and fibers at a fluidic interface is of significant importance in various processes, one of which is the flotation process. It is widely used in the mineral industry for the selective separation of particles based on their affinity to rising gas bubbles. It is also one of the most common de-inking processes used to recover the paper fibers. In an attempt to develop numerical tools, which will find future applications in the flotation process, direct numerical simulations of particles, rigid and flexible fibers interacting with a drop were performed.

Keywords: Flotation; Fibers; Three phase flow

  • Lecture (Conference)
    4th International Symposium on Multiscale Multiphase Process Engineering (MMPE), 25.-28.09.2022, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-35373
Publ.-Id: 35373


A phase-field model to simulate foams flowing in an obstructed channel

Lecrivain, G.; Heitkam, S.; Hampel, U.

Numerical simulations are a valid alternative for the investigation of flowing foams in two- and three-dimensional domains. Large advances in this field have for instance been achieved with the Surface Evolver [Brakke, 1992; Cox, 2006], which discretizes the air-liquid interfaces of the foam with a triangle mesh. A numerical model derived from the phase field theory is here suggested to simulate flowing foams with gas concentration (ε) ranging from 40 to 99%.

Keywords: Foam; Phase field model

  • Poster
    EUFOAM 2022, 03.-06.07.2022, Kraków, Poland

Permalink: https://www.hzdr.de/publications/Publ-35372
Publ.-Id: 35372


Covalent Organic Framework Thin-film Photodetectors from Solution Processable Porous Nanospheres

Bag, S.; Sekhar Sasmal, H.; Pratap Chaudhary, S.; Dey, K.; Blätte, D.; Guntermann, R.; Zhang, Y.; Položij, M.; Kuc, A. B.; Shelke, A.; Vijayaraghavan, R. K.; Ajithkumar, T. G.; Bhattacharyya, S.; Heine, T.; Bein, T.; Banerjee, R.

The synthesis of homogeneous covalent organic framework (COF) thin films on the desired substrate with decent crystallinity, porosity, and uniform thickness has great potential for optoelectronic applications. We have used a solution- processable sphere transmutation process to synthesize 300±20 nm uniform COF thin films on a 2×2 cm2 TiO2-coated FTO surface. This process controls the nucleation of COF crystallites and molecular morphology that helps the nanospheres to arrange periodically to form homogeneous COF thin films. We have synthesized four COF thin films (TpDPP, TpEtBt, TpTab, and TpTta) with different functional backbones. In a close agreement between the experiment and density functional theory, the TpEtBr COF film showed the lowest optical bandgap (2.26 eV) and highest excited-state lifetime (8.52 ns) among all four COF films. Hence, the TpEtBr COF film can participate in efficient charge generation and separation. We constructed optoelectronic devices having a glass/FTO/TiO2/COF-film/Au architecture, which serves as a model system to study the optoelectronic charge transport properties of COF thin films under dark and illuminated conditions. The visible light with a calibrated intensity of 100 mW cm-2 was used for the excitation of COF thin films. All the COF thin films exhibit significant photocurrent after illumination with visible light in comparison to the dark. Hence, all the COF films behave as good photoactive substrates with minimal pin hole defects. The fabricated out-of-plane photodetector device based on the TpEtBr COF thin film exhibits high photocurrent density (2.65 ± 0.24 mA cm-2 at 0.5 V) and hole mobility (8.15±0.64 ×10-3 cm2 V-1 S- 1) compared to other as-synthesized films, indicating the best photoactive characteristics.

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Permalink: https://www.hzdr.de/publications/Publ-35371
Publ.-Id: 35371


Software publication: Structure-imposed electronic topology in cove-edged graphene nanoribbons

Arnold, F. M.; Liu, T.-J.; Kuc, A. B.; Heine, T.

The repository contains the inputs and outputs of tight-binding (TB) calculations of ZGNR-C based on PythTB. For each analysed structure one subdirectory is created, labelled as "N-ZGNR-C_a_b_inv_cellα_termination". This corresponds to a N-ZGNR-C(a,b) with inversion center at the unit cell boundary S or L ("inv"), unit cell angle α
("cellα": 60°, 90°, or 120°) and a given unit cell termination (armchair, zigzag or bearded). Each directory contains the atomic structure in xsf and cif format, the PythTB input file, the output as a json file, and the calculated band structure as image file. The json file contains the band structure information (path and eigenvalues), the raw Zak phase in units of π without modulo 2, and the final ℤ2 invariant.

Related publications

  • Software in external data repository
    Publication year 2022
    Programming language: python
    System requirements: linux
    License: Creative Commons Attribution 4.0 International
    Hosted on ZENODO: Link to location
    DOI: 10.5281/zenodo.7254202

Permalink: https://www.hzdr.de/publications/Publ-35370
Publ.-Id: 35370


Sustainable development of simulation setups and addons for OpenFOAM for nuclear reactor safety research

Lehnigk, R.; Bruschewski, M.; Huste, T.; Lucas, D.; Rehm, M.; Schlegel, F.

Open-source environments such as the Computational Fluid Dynamics software OpenFOAM are very appealing for research groups since they allow for an efficient prototyping of new models or concepts. However, for downstream developments to be sustainable, i.e. reproduci-ble and reusable in the long term, a significant amount of maintenance work must be account-ed for. To allow for growth and extensibility, the maintenance work should be underpinned by a high degree of automation for repetitive tasks such as build tests, code deployment and validation runs, in order to keep the focus on scientific work. Here, an information technology environment referred to as OpenFOAM_RCS is presented that aids the centralized mainte-nance of simulation code and setup files for OpenFOAM developments concerned with reac-tor coolant system safety research. It fosters collaborative developments and review processes. State-of-the-art tools for managing software developments are adapted to meet the require-ments of OpenFOAM. A flexible approach for upgrading the underlying installation is pro-posed, based on snapshots of the OpenFOAM development line rather than yearly version releases, to make new functionality available when needed by associated research projects. The process of upgrading within so-called sprint cycles is accompanied by several checks to ensure compatibility of downstream code and simulation setups. Furthermore, the foundation for building a validation data base from contributed simulation setups is laid, creating a basis for continuous quality assurance.

The content of this article was initially presented at the 33rd German CFD Network of Com-petence Meeting, held on March 22-23 2022 at GRS in Garching, Germany.

Permalink: https://www.hzdr.de/publications/Publ-35366
Publ.-Id: 35366


Effect of Coulomb impurities on the electronic structure of magic angle twisted bilayer graphene

Ramzan, M. S.; Goodwin, Z. A. H.; Mostofi, A. A.; Kuc, A. B.; Lischner, J.

In graphene, charged defects break the electron-hole symmetry and can even give rise to exotic collapse states when the defect charge exceeds a critical value which is proportional to the Fermi velocity. In this work, we investigate the electronic properties of twisted bilayer graphene (tBLG) with charged defects using tight-binding calculations. Like monolayer graphene, tBLG exhibits linear bands near the Fermi level but with a dramatically reduced Fermi velocity near the magic angle (approximately 1.1°). This suggests that the critical value of the defect charge in magic-angle tBLG should also be very small. We find that charged defects give rise to significant changes in the low-energy electronic structure of tBLG. Depending on the defect position in the moiré unit cell, it is possible to open a band gap or to induce an additional flattening of the low-energy valence and conduction bands. Our calculations suggest that the collapse states of the two monolayers hybridize in the twisted bilayer. However, their in-plane localization remains largely unaffected by the presence of the additional twisted layer because of the different length scales of the moiré lattice and the monolayer collapse state wavefunctions. These predictions can be tested in scanning tunnelling spectroscopy experiments.

Permalink: https://www.hzdr.de/publications/Publ-35364
Publ.-Id: 35364


Analysing the dynamic structure of warm dense matter in the imaginary-time domain: theoretical models and simulations

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

The rigorous diagnostics of experiments with warm dense matter (WDM) is notoriously difficult. A key method is given by X-ray Thomson scattering (XRTS), but the interpretation of XRTS measurements is usually based on theoretical models that entail various approximations. Recently, Dornheim et al. [arXiv:2206.12805] have introduced a new framework for temperature diagnostics of XRTS experiments that is based on imaginary-time correlation functions (ITCF). On the one hand, switching from the frequency- to the imaginary-time domain gives one direct access to a number of physical properties, which facilitates the extraction of the temperature of arbitrarily complex materials without any models or approximations. On the other hand, the bulk of theoretical works in dynamic quantum many-body theory is devoted to the frequency-domain, and, to our knowledge, the manifestation of physics properties within the ITCF remains poorly understood. In the present work, we aim to change this unsatisfactory situation by introducing a simple, semi-analytical model for the imaginary-time dependence of two-body correlations within the framework of imaginary-time path integrals. As a practical example, we compare our new model to extensive ab initio path integral Monte Carlo results for the ITCF of a uniform electron gas, and find excellent agreement over a broad range of wave numbers, densities, and temperatures.

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