Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41396 Publications

Understanding warm dense matter: from ab initio simulations to experiments

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. Yet, the interpretation of these experiments requires a reliable diagnostics
based on accurate theoretical modeling, which is a notoriously difficult task [1].

In this work, I will give an overview of how we can use exact ab-initio path integral Monte Carlo
(PIMC) simulations [2] to get
new insights into the behavior of WDM. Moreover, I will show how switching to the imaginary-
time representation allows us to significantly improve the interpretation of X-ray Thomson
scattering (XRTS) experiments, which are a key diagnostic for WDM [3,4,5]. Specifically, I will show how new
PIMC capabilities will allow to give us novel insights into electronic correlations in warm dense
quantum plasmas, leading to unprecedented agreement between experiments [6] and theory.

[1] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[2] M. Böhme et al., Physical Review Letters 129, 066402 (2022)
[3] S. Glenzer and R. Redmer, Reviews of Modern Physics 81, 1625 (2009)
[4] T. Dornheim et al., Nature Communications 13, 7911 (2022)
[5] T. Dornheim et al., arXiv:2305.15305 (submitted)
[6] T. Döppner et al., Nature 618, 270-275 (2023)

  • Lecture (Conference)
    Big data and analytical methods for complex systems, 19.10.2023, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-37660
Publ.-Id: 37660


Forschung für den Rückbau von Kernkraftwerken: Das Projekt KOBEKA

Hampel, U.

Während der Beprobung der Betonstrukturen des Reaktorgebäudes im Kernkraftwerk Stade wurden tief eingedrungene Kontaminationen im unteren Teil des Reaktorsicherheitsbehälters, der so genannten Betonkalotte, vorgefunden. Diese waren durch Primärkreiswasser aus verschiedenen Systemen während des Anlagenbetriebes eingetragen worden. Das Durchdringen der wasserabweisenden Dekontaminationsbeschichtung und die weitere Ausbreitung entlang von Arbeitsfugen hatten zu großräumiger Kontamination in der Größenordnung des bis zu 100-fachen der Freigabewerte geführt. Durch fehlende Detailkenntnisse zur Kontaminationsverteilung gestaltete sich der Rückbau erheblich zeit- und kostenaufwändiger als ursprünglich veranschlagt. Es ist davon auszugehen, dass dieses Problem andere Kernkraftwerke in Deutschland und weltweit betrifft.
Die Beprobung des Betons mittels Kernbohrungen ist durch erschwerte Zugänglichkeit des Beprobungsortes, baustatische Randbedingungen und Kosten eingeschränkt. Eine Alternative zu Kernbohrungen sind Bohrungen ins Volle. Wegen der schlankeren Bohrlöcher können deutlich mehr Bohrungen gesetzt werden, ohne die strukturelle Integrität des Reaktorgebäudes in unannehmbarem Maße zu schwächen. Allerdings fehlt es dann an Bohrkernen für eine Analytik. Das Vorhaben KOBEKA (gefördert durch das BMBF im Rahmen des Förderkonzeptes „FORKA - Forschung für den Rückbau kerntechnischer Anlagen“) beschäftigt sich daher mit der Entwicklung innovativer Messtechnik zur Beprobung und in-situ Messung in solchen schlanken Bohrlöchern. Entwickelt werden Technologien zur Detektion von Kontaminationen und zur Bestimmung des Nuklidvektors. Weiterhin sollen Feuchte und Porosität der Betonmatrix sowie die Präsenz von Borverbindungen ermittelt werden. Die Kenntnis der Porosität dient der Bestimmung der Lage von Arbeitsfugen, die Kenntnis des Feuchte- und Borgehalts geben Evidenz über eingedrungenes Primärkreiswasser. Zusätzlich ist die hydraulische Permeabilität zwischen verschiedenen Bohrungen von Interesse, um mögliche Transportwege über Arbeitsfugen zu identifizieren und damit die Beprobungsplanung zu unterstützen. Ebenfalls werden Werkzeuge zur Kartierung und elektronischen Dokumentation der Befunde entwickelt.

Keywords: Rückbau von Kernkraftwerken

  • Lecture (Conference)
    55. Kraftwerkstechnisches Kolloquium, 10.-11.10.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37658
Publ.-Id: 37658


Ultrafast X-ray tomography and its application to studying particle flows

Hampel, U.; Barthel, F.; Baecke, A. M.; Bieberle, A.; Bieberle, M.; Lecrivain, G.; Papapetrou, T. N.; Windisch, D.

Ultrafast X-ray tomography is a key imaging technique for multiphase flows. In particular, it has been used with great success for studying particle flows. Here, we give an overview of recent developments in the scanner hardware and data processing, and demonstrate the use of this technique to the study of particle segregation in a rotating drum as an exemplary test case for analysing industrial particle mixing systems.

Keywords: Ultrafast X-ray tomography; Particle flow; Mixing and segregation

  • Contribution to proceedings
    11th World Congress on Industrial Process Tomography (WCIPT-11), 06.-08.09.2023, Mexico City, Mexico
  • Lecture (Conference)
    11th World Congress on Industrial Process Tomography (WCIPT-11), 06.-08.09.2023, Mexico City, Mexico

Permalink: https://www.hzdr.de/publications/Publ-37657
Publ.-Id: 37657


Entwicklung von Messtechnik zur Beprobung kontaminierter Betonstrukturen im Sicherheitsbehälter von Druckwasserreaktoren während des Kraftwerksrückbaus (KOBEKA)

Bertram, W.; Hampel, U.; Anthofer, A.; Dirk Döhler, D.; Herrmann, M.; Jansen, S.; Kahle, P.; Kormoll, T.; Kosowski, K.; Lösch, H.; Mechtcherine, V.; Nurjahan, T.; Rauf, A.; Reinecke, A.-M.; Schleicher, E.; Schröfl, C.; Werner, T.

Während der Beprobung der Betonstrukturen des Reaktorgebäudes im Kernkraftwerk Stade wurden tief eingedrungene Kontaminationen im unteren Teil des Reaktorsicherheitsbehälters, der so genannten Betonkalotte, vorgefunden. Diese waren durch Primärkreiswasser aus verschiedenen Systemen während des Anlagenbetriebes eingetragen worden. Das Durchdringen der wasserabweisenden Dekontaminationsbeschichtung und die weitere Ausbreitung entlang von Arbeitsfugen hatten zu großräumiger Kontamination in der Größenordnung des bis zu 100-fachen der Freigabewerte geführt. Durch fehlende Detailkenntnisse zur Kontaminationsverteilung gestaltete sich der Rückbau erheblich zeit- und kostenaufwändiger als ursprünglich veranschlagt. Es ist davon auszugehen, dass dieses Problem andere Kernkraftwerke in Deutschland und weltweit betrifft.
Die Beprobung des Betons mittels Kernbohrungen ist durch erschwerte Zugänglichkeit des Beprobungsortes, baustatische Randbedingungen und Kosten eingeschränkt. Eine Alternative zu Kernbohrungen sind Bohrungen ins Volle. Wegen der schlankeren Bohrlöcher können deutlich mehr Bohrungen gesetzt werden, ohne die strukturelle Integrität des Reaktorgebäudes in unannehmbarem Maße zu schwächen. Allerdings fehlt es dann an Bohrkernen für eine Analytik. Das Vorhaben KOBEKA (gefördert durch das BMBF im Rahmen des Förderkonzeptes „FORKA - Forschung für den Rückbau kerntechnischer Anlagen“) beschäftigt sich daher mit der Entwicklung innovativer Messtechnik zur Beprobung und in-situ Messung in solchen schlanken Bohrlöchern. Entwickelt werden Technologien zur Detektion von Kontaminationen und zur Bestimmung des Nuklidvektors. Weiterhin sollen Feuchte und Porosität der Betonmatrix sowie die Präsenz von Borverbindungen ermittelt werden. Die Kenntnis der Porosität dient der Bestimmung der Lage von Arbeitsfugen, die Kenntnis des Feuchte- und Borgehalts geben Evidenz über eingedrungenes Primärkreiswasser. Zusätzlich ist die hydraulische Permeabilität zwischen verschiedenen Bohrungen von Interesse, um mögliche Transportwege über Arbeitsfugen zu identifizieren und damit die Beprobungsplanung zu unterstützen. Ebenfalls werden Werkzeuge zur Kartierung und elektronischen Dokumentation der Befunde entwickelt.

Keywords: Rückbau von Kernkraftwerken

  • Contribution to proceedings
    KONTEC 2023: Internationales Symposium „Konditionierung radioaktiver Betriebs- und Stilllegungsabfälle“, 30.08.-01.09.2023, Dresden, Deutschland
  • Lecture (Conference)
    KONTEC 2023: Internationales Symposium „Konditionierung radioaktiver Betriebs- und Stilllegungsabfälle“, 30.08.-01.09.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37656
Publ.-Id: 37656


Efficient ultrafast field-driven spin current generation for spintronic terahertz frequency conversion (raw data in Origin project)

Ilyakov, I.; Brataas, A.; de Oliveira, T.; Ponomaryov, A.; Deinert, J.-C.; Hellwig, O.; Faßbender, J.; Lindner, J.; Salikhov, R.; Kovalev, S.

In this Origin project file (*.opju) we provide an access to the raw data which we obtained and analyzed. The result of our analysis are presented in the publication "Efficient ultrafast field-driven spin current generation for spintronic terahertz frequency conversion".

Keywords: spin current; spintronics; terahertz frequency conversion; high THz field

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Permalink: https://www.hzdr.de/publications/Publ-37655
Publ.-Id: 37655


High Field Suppression of Bremsstrahlung Emission in High-Intensity Laser-Plasma Interactions

Habibi, M.; Toncian, T.
Project Leader: Toncian, Toma

This dissertation investigates the effect of macroscopic electric and magnetic fields on bremsstrahlung emission in high-intensity laser-plasma interactions, specifically in the regime of relativistic-induced transparency. The Particle-in-Cell (PIC) EPOCH simulation code has been updated to incorporate a new suppression mechanism influenced by the presence of intense electric and magnetic fields. The study compared the bremsstrahlung emissions generated under relativistic transparency conditions using three distinct models: the original bremsstrahlung model in the EPOCH code, the model modified by the magnetic suppression (MS) effect, and the newly proposed suppression model by the electric and magnetic suppression (EMS) effect.
The results demonstrated that macroscopic electric and magnetic fields have a significant effect on the decrease of bremsstrahlung photons in laser-plasma interactions. In addition, differences in electron dynamics were observed between the EPOCH and EMS models, indicating that the suppression mechanism can influence the dynamics of electron acceleration. The study provides insight into bremsstrahlung emission under extreme conditions, where energetic electrons travel through a relativistically transparent plasma while being deflected by magnetic fields with MT-level strength.
On the basis of the results, it is suggested that the implementation of conventional bremsstrahlung in PIC codes be modified to account for the discussed suppression effect.

Keywords: EPOCH; PIC code; EMS model; Bremsstrahlung Suppression; Relativistic Transparency

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Permalink: https://www.hzdr.de/publications/Publ-37654
Publ.-Id: 37654


Monitoring Pancreatic α-Amylase of Postoperative Patients with Droplet-Based Microfluidics

Zhao, X.; Kolbinger, F. R.; Distler, M.; Weitz, J.; Makarov, D.; Bachmann, M.; Baraban, L.

This study presents a groundbreaking portable droplet-based microfluidic device capable of real-time detecting α-amylase activity in drainage fluids for postoperative patient monitoring. By implementing this strategy, the determination time for α-amylase levels is significantly reduced from several hours, the current clinical standard, to just three minutes.1 The device demonstrates a remarkable improvement in detection sensitivity, reaching a detection limit of 7 nmol/s·L, an order of magnitude enhancement compared to the recent state of the art.2 Moreover, a mere 10 μL of drain liquid and reagent are necessary for each measurement reducing material requirement and waste.3,4 Crucially, this real-time continuous detection strategy circumvents delays in diagnosis, ensuring prompt treatment of life-threatening complications. Figure 1A illustrates the schematic representation of real-time α-amylase detection in the microfluidic device. A minute volume of patient exudate is continuously gathered and enclosed with a starch reagent within 200 nL droplets. The emitted fluorescence intensity is monitored as a measure of α-amylase activity. Distinct fluorescence intensities were emitted when various concentrations of standard amylase solutions reacted with a fixed quantity of reagent, as shown in Figure 1B, by which the calibration curve is obtained (Figure 1C). A total of 32 patient samples were assessed, and the amylase concentration was determined using the established calibration curve. Evaluation of the results, as depicted in Figure 1D, reveals the dependable detection accuracy of the droplet-based microfluidic device compared to clinical gold-standard methods.

  • Open Access Logo Poster
    The 27th International Conference on Miniaturized Systems for Chemistry and Life Sciences (µTAS 2023), 15-19 October 2023 Katowice, Poland, 15.-19.10.2023, Katowice, Poland

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Permalink: https://www.hzdr.de/publications/Publ-37653
Publ.-Id: 37653


Towards Data-Driven Optimization of Experiments in Photon Science

Kelling, J.; Willmann, A.; Thiessenhusen, E.; Rustamov, J.; Aguilar, R. A.; Hänel, T.; Hoffmann, N.; Debus, A.; Juckeland, G.; Bachmann, M.

High-fidelity (computer-) experiments are very expensive to perform, hence
extracting as much information as possible from the collected data is vital.
We present methods to estimate experiment outcomes based on ingested past data,
to steer further sample acquisition both by suggesting paths for maximized
uncertainty reduction and highlighting sensitivities on inputs, with use-cases
from laser-light propagation and laser-plasma interactions to electron-bunch
kinetics.

Keywords: surrogate models; machine learning; digital twins; laser-plasma accelerators; free-electron laser

  • Open Access Logo Invited lecture (Conferences)
    9th Annual MT meeting, 09.-11.10.2023, Karlsruhe, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-37652
Publ.-Id: 37652


Defect Engineering of Ta3N5 Photoanodes: Enhancing Charge Transport and Photoconversion Efficiencies via Ti Doping

Wagner, L. I.; Sirotti, E.; Brune, O.; Grötzner, G.; Eichhorn, J.; Santra, S.; Munnik, F.; Olivi, L.; Pollastri, S.; Streibel, V.; Sharp, I. D.

Ta3N5 shows great potential as a semiconductor photoanode for solar water splitting. However, its performance is hindered by poor charge carrier transport and trapping due to a high density of defects that introduce electronic states deep within its bandgap. Here, we demonstrate that controlled Ti doping of Ta3N5 can dramatically reduce the concentration of deep-level defects and enhance its photoelectrochemical performance, yielding a sevenfold increase in photocurrent density and a 300 mV cathodic shift in photocurrent onset potential compared to undoped material. Comprehensive characterization reveals that Ti+4 ions substitute Ta+5 lattice sites, thereby introducing compensating acceptor states, reducing concentrations of nitrogen vacancies and reduced Ta+3 states, and thereby suppressing trapping and recombination. Importantly, Ti doping offers distinct advantages compared to Zr, an intensively investigated dopant of Ta3N5 in the same group of the periodic table. Specifically, Ti+4 and Ta+5 have more similar atomic radii, allowing for substitution without introducing lattice strain, and Ti exhibits a lower affinity for oxygen than Zr, enabling its incorporation without increasing the oxygen donor content. Consequently, we demonstrate that the electrical conductivity can be tuned by over seven orders of magnitude. Thus, Ti doping in Ta3N5 provides a powerful basis for precisely engineering the optoelectronic characteristics of Ta3N5 and to substantially improve its functional characteristics as an advanced photoelectrode for solar fuels applications.

Keywords: solar water splitting; tantalum nitride (Ta3N5); doping; defect engineering; charge carrier engineer

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Permalink: https://www.hzdr.de/publications/Publ-37651
Publ.-Id: 37651


FVV1455: CFD Simulation of Droplet Separators

Singh, D.; Boden, S.; Schlegel, F.
Producer: Schlottke, Jan; Producer: Weber, Andreas

For industrial applications, the two-fluid model is preferred due to its efficient modelling of small-scale interfaces. Whereas, a thin film model, based on a long wave approximation, is used for the unresolved interfaces to obtain the film features by solving the 2D Navier-Stokes equations for wall films. Within the project, the target is to develop an experimentally validated 3D-CFD model to investigate the separation efficiency of droplet separators for fuel cell systems. A hybrid model is developed, which couples the two-fluid model with a thin film model via mass transfer terms for droplet deposition, droplet entrainment and film separation. A two-way coupling between droplets and the thin film is established using mass and momentum source terms, derived analytical and from available experiments. The droplet separator is an essential component of an automotive fuel cell system that segregates a significant amount of liquid fractions from the air-water mixture. The flow dynamics inside a droplet separator consist of a dispersed gas and liquid with a wall adhered thin liquid film. The modelling is divided into the following stages due to the complex fluidic phenomenon inside a generic droplet separator:

  1. Droplet deposition model,
  2. Film separation model,
  3. Film transition model, and
  4. Population balance model.

The numerical simulations are validated and fine-tuned with experiments carried out at HZDR.

Keywords: Numerical Simulation; Droplets; Film Modeling; Multiphase Flow; Fuel Cell; Separation; Automotive

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Permalink: https://www.hzdr.de/publications/Publ-37650
Publ.-Id: 37650


Interfacial selective separation of fine particles for the recycling of PEM electrolyzer exploiting particle-fluid interactions in multiphase systems

Ahn, S.; Rudolph, M.

For large-scale of green hydrogen production via water electrolysis, catalysts containing critical materials in a submicron down to nanometer scale have advantages as active materials in the application. The circularity of critical raw materials such as PGM after the utilization phase becomes and thus recycling processes for end-of-life water electrolyzers need to be developed.
In the range of ultra-fine particle systems (0.1 to 10 µm), established techniques like flotation have challenges for their efficient separation. Liquid-liquid phase transfer is one possible alternative approach for the selective separation of such fine particles. In this phase transfer process, the interactions between particles and oil droplets are greater than those between particles and air bubbles in classic flotation. Hence, particles can be enriched much more efficiently at the oil-water interfaces.
In this study, titanium oxide TiO2 and carbon black are separated representing anode and cathode material in polymer electrolyte membrane (PEM) water electrolyzer respectively. Wettability characterization studies revealed their significant contrast in hydrophobicity. TiO2 exhibits a rather hydrophilic surface while carbon black shows hydrophobic characteristic, however there are still many unknown properties of the surface characteristics of various carbon black variants.
By using the analytic particle solvent extraction (APSE) method, particle mixtures can be transferred into organic and aqueous phases respectively, and selectively separated with high recovery. This approach provides a contribution to scale-up the recycling processes of PEM water electrolyzers.

Keywords: Fine particles; Recycling; Particle separation; PEM water electrolyzer; Wettability

  • Lecture (Conference)
    Jahrestreffen der DECHEMA-Fachgruppen Kristallisation, Grenzflächenbestimmte Systeme und Prozesse sowie Mechanische Flüssigkeitsabtrennung, 09.-10.03.2023, Frankfurt am Main, Germany

Permalink: https://www.hzdr.de/publications/Publ-37649
Publ.-Id: 37649


Application of particle-fluid interactions for selective separation of fine particles for the recycling of HTEL electrolyzer

Ahn, S.; Rudolph, M.

For efficient renewable energy circulation, hydrogen production via water electrolysis technology has been developed over past decades. Amongst three technologies, high temperature water electrolysis (HTEL) is considered as a promising technology because of its high efficiency. Rare earth elements are the best candidates to make the cell more promising. However, reaching a long-term operation is an unsolved challenge because the durability of used ceramic materials is still an issue. Hence, development of the recycling processes for these critical raw materials is an important topic.
Ceramic materials used in HTEL cell have a similar surface property in terms of wettability. For this reason, fine particles cannot be separated without help from surfactants. In this study, representative materials such as Nickel oxide (NiO), Lanthanum strontium manganite (LSM), Yttria stabilized zirconia (YSZ), and Zirconium (ZrO2) oxide are used and their surface charge are investigated. Depending on the pH value, materials show change of their surface charge. Considering their electric charge, different surfactants applied to drive the particle surface hydrophobic. Since NiO and LSM have positive surface charge in base dispersion, particles may be hydrophobized with anion surfactant. Wettability of the YSZ and ZrO2, materials with opposite surface charge, changed by addition of cation surfactant. Their changed wettability can be described by using particle attachment on single air bubbles. Additional approach by using liquid-liquid phase transfer explain their behavior at the oil-water interfaces. This approach provides a contribution to scale-up the recycling processes of HTEL cells.

Keywords: Fine particles; Recycling; Particle separation; Interfaces; high temperature electrolyzer

  • Lecture (Conference)
    14th European Congress of Chemical Engineering and 7th European Congress of Applied Biotechnology, 17.-21.09.2023, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-37648
Publ.-Id: 37648


Application of novel hydrophobic binders for the selective agglomeration of fine particles for the recycling of PEM water electrolyzers

Ahn, S.; Rudolph, M.

With the tremendous increase of hydrogen production via water electrolysis technology, the development of a recycling process for valuable raw materials is emerging as an important issue for a functional circular economy. Especially, platinum group metals such as Iridium oxide and platinum particles on carbon black are used as active materials in the polymer electrolyte membrane (PEM) water electrolyzer. Since the size range of those particles is well below 100 µm, the development of mechanical separation technologies has not been well established. Conventional mechanical separation processes, such as flotation, are not effective for particles in the submicron scale.
According to previous investigations, each material on both electrodes shows a contrast in surface properties in terms of (de)wett(ing)ability. Cathode materials such as carbon black exhibit a hydrophobic character, while anode materials like Iridium oxide show a rather good affinity for water. For this study, pure particle fractions of carbon black and titanium oxide are used as representative materials.
Oil agglomeration is one of the widespread technologies to recover hydrophobic particles. As reported by Kim Van Netten in 2017, the separation of fine coal particles from a suspension was achieved by using a new type of hydrophobic binder comprising only 5 % of organic liquid. In this study, this novel organic emulsion system is applied to separate ultra-fine carbon black particles selectively and to assess the functionality of the emulsion to develop a process for PEM recycling. Those water-in-oil-in-water emulsion droplets enable to reach the agglomeration of carbon black particles in a few seconds which is a promising pre-treatment result for subsequent enrichment.

Keywords: Fine particles; Wettability; Recycling; PEM water electrolyzer

  • Poster
    PARTEC 2023, International Congress on Particle Technology, 26.-28.09.2023, Nürnberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-37647
Publ.-Id: 37647


Development of Fine Particle Mechanical Separation Processes with Representative Catalyst Materials for Recycling PEM Water Electrolyzers Exploiting their Wetting Characteristics

Ahn, S.; Rudolph, M.

Demand for technologies using water electrolysis to produce green hydrogen is increasing, although recycling research on membrane electrode assemblies, which contain various precious and highly critical metals, is still limited. This study therefore aims at exploiting the feasibility of fine particle separation processes based on the difference in hydrophobicity of the ultrafine materials used as catalysts in polymer electrolyte membrane electrolyzers and at providing a fundamental study with representative materials of carbon black and TiO2. Since the cathode materials including carbon black are hydrophobic and the anode materials as well as TiO2 are hydrophilic, the characterizations of their various surface properties such as zeta potentials, dispersion characteristics, and bubble coverage angle tests have been investigated. In addition, using liquid-liquid particle extraction in a mixture model, 99 % of carbon black is recovered in the organic phase and 97 % of TiO2 is selectively separated in the aqueous phase with the help of the dispersant, sodium hexametaphosphate.

Keywords: Fine particles; Interfaces; PEM water electrolyzer; Surface chemistry; Wettability

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Permalink: https://www.hzdr.de/publications/Publ-37646
Publ.-Id: 37646


Magnetic State Control of Non-van der Waals 2D Materials by Hydrogenation

Barnowsky, T.; Curtarolo, S.; Krasheninnikov, A. V.; Heine, T.; Friedrich, R.

Controlling the magnetic state of two-dimensional (2D) materials is crucial for spintronic applications.
By employing data-mining and autonomous density functional theory calculations, we
demonstrate the switching of magnetic properties of 2D non-van der Waals materials upon hydrogen
passivation. The magnetic configurations are tuned to states with flipped and enhanced moments.
For 2D CdTiO3 - a nonmagnetic compound in the pristine case - we observe an onset of ferromagnetism
upon hydrogenation. Further investigation of the magnetization density of the pristine
and passivated systems provides a detailed analysis of modified local spin symmetries and the emergence
of ferromagnetism. Our results indicate that selective surface passivation is a powerful tool
for tailoring magnetic properties of nanomaterials such as non-vdW 2D compounds.

Keywords: 2D materials; non-van der Waals compounds; passivation; magnetism; data-driven research; computational materials science; high-throughput computing

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  • Open Access Logo Nano Letters (2024)

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Permalink: https://www.hzdr.de/publications/Publ-37645
Publ.-Id: 37645


Preparation of 18F-Labeled Tracers Targeting Fibroblast Activation Protein via Sulfur [18F]Fluoride Exchange Reaction

Craig, A.; Kogler, J.; Laube, M.; Ullrich, M.; Donat, C.; Wodtke, R.; Kopka, K.; Stadlbauer, S.

Early detection and treatment of cancers can significantly increase patient prognosis and enhance the quality of life of affected patients. The emerging significance of the tumor microenvironment (TME) as a new frontier for cancer diagnosis and therapy may be exploited by radiolabeled tracers for diagnostic imaging techniques such as positron emission tomography (PET). Cancer-associated fibroblasts (CAFs) within the TME are identified by biomarkers such as fibroblast activation protein alpha (FAPα), which are expressed on their surfaces. Targeting FAPα using small molecule 18F-labeled inhibitors (FAPIs) have recently garnered significant attention for non-invasive tumor visualization using PET. Currently, the predominant 18F-fluorination method for radiolabeling FAPIs involves chelation-based radiofluorination strategies using aluminum [18F]fluoride ([18F]AlF). Herein, a powerful radiofluorination protocol for the preparation of two 18F-labeled FAPIs via the sulfur [18F]fluoride exchange ([18F]SuFEx) reaction and preliminary biological evaluation is disclosed.

Keywords: Automation; cancer-associated fibroblast; FAPI; 18F-fluorination; positron emission tomography (PET); [18F]SuFEx

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Permalink: https://www.hzdr.de/publications/Publ-37644
Publ.-Id: 37644


Data publication: Influence of oxidic and metallic interfaces on the magnetic damping of Permalloy thin films

Ney, V.; Salikhov, R.; Lenz, K.; Hellwig, O.; Lindner, J.; Ney, A.

FMR Rohdaten und Auswertungen.

Keywords: Thin films; ferromagnetism; ferromagnetic resonance; anisotropy; linewidth

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Permalink: https://www.hzdr.de/publications/Publ-37643
Publ.-Id: 37643


Data publication: Magnetic State Control of Non-van der Waals 2D Materials by Hydrogenation

Barnowsky, T.; Curtarolo, S.; Krasheninnikov, A.; Heine, T.; Friedrich, R.

This dataset includes the primary research data for the publication "Magnetic State Control of Non-van der Waals 2D Materials by Hydrogenation".

Keywords: 2D materials; magnetism; non-van der Waals compounds; passivation; data-driven research; computational materials science; high-throughput computing

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Permalink: https://www.hzdr.de/publications/Publ-37642
Publ.-Id: 37642


A Monte Carlo photonic model to simulate the UV inactivation of airborne microorganisms

Cavagnola, M. A.; Hampel, U.; Lecrivain, G.

A model based on a photonic approach is developed, that allows us to track each of the flowing airborne microorganisms and predict, by using a kinetic Monte Carlo algorithm, whether it is active or not.

  • Poster
    HZDR - PhD seminar, 17.-19.10.2023, Rittergut Schilbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37641
Publ.-Id: 37641


Data publication: Control of Four-Magnon Scattering by Pure Spin Current in a Magnonic Waveguide

Hache, T.; Körber, L.; Hula, T.; Lenz, K.; Kakay, A.; Hellwig, O.; Lindner, J.; Faßbender, J.; Schultheiß, H.

This dataset contains the numerical and experimental data (both raw and evaluated), labbooks associated with the measurements for our paper published in Physical Review Applied.

Keywords: spin waves; magnetism; BLS; four-magnon scattering; spin current; spintronics; magnonics

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Permalink: https://www.hzdr.de/publications/Publ-37640
Publ.-Id: 37640


Investigations on the Eu(III) translocation in hydroponically grown plants

Klotzsche, M.; Steudtner, R.; Vogel, M.; Drobot, B.; Schymura, S.; Raff, J.

Lanthanides (Ln) have become indispensable for science, technology and everyday objects. The intense
exploitation of Ln-bearing ores, their further processing as well as the improper disposal of high-tech
products lead to anthropogenic increased levels of these metals in the environment. Knowledge about their
fate in the plant biosphere is crucial to maintain food safety and to develop feasible phytoremediation
strategies.
In our research, we aim to follow Eu(III) on its journey through hydroponically grown sand oat (Avena
strigosa) – a potential candidate for phytoremediation – from initial exposure and cellular uptake over
localization in root tissue followed by translocation via plant sap into aboveground parts and the metal’s
distribution in leaves. Therefore, we apply a set of spectroscopic (TRLFS, ICP-MS), microscopic (chemical
microscopy), chromatographic (HPLC) and photographic (autoradiography) analysis techniques. In short,
following an exposure time of 96 h with 200 μM Eu(III), chemical microscopy reveals roots hairs and root
tips a s well as epidermis cells to be one uptake pathway for the Ln. Quantification of the metal content in
roots and shoots by ashing and subsequent acid digestion unveils that the majority of Eu(III) accumulates
in the roots (≈14242 μg/gdry weight) whereas only 35 μg/gdry weight) is translocated into the green plant parts.
The upwards transport of Eu(III) takes place via the xylem sap, in which organic acids are probably
responsible for Eu(III) translocation in measurable quantity. In order to visualize not solely the microscopic
distribution of Eu(III) in roots, but also account for the shoots, experiments with the radioactive isotope
Eu-152 were conducted and the dried plant was scrutinized by autoradiography (Fig. 1).
These studies contributed to a comprehensive understanding of the fate of Ln(III) in plants. Investigations
regarding the uptake and distribution of Cm(III) are currently under way.

Keywords: bioassociation; europium; lanthanide; plant; chemical microscopy

  • Lecture (Conference)
    21st Jena Remediation Symposium, 05.-06.10.2023, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37639
Publ.-Id: 37639


Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2

Tschirner, T.; Keßler, P.; Gonzalez Betancourt, R. D.; Kotte, T.; Kriegner, D.; Büchner, B.; Dufouleur, J.; Kamp, M.; Jovic, V.; Smejkal, L.; Sinova, J.; Claessen, R.; Jungwirth, T.; Moser, S.; Reichlova, H.; Veyrat, L.

Observations of the anomalous Hall effect in RuO2 and MnTe have demonstrated unconventional time-reversal symmetry breaking in the electronic structure of a recently identified new class of compensated collinear magnets, dubbed altermagnets. While in MnTe, the unconventional anomalous Hall signal accompanied by a vanishing magnetization is observable at remanence, the anomalous Hall effect in RuO2 is excluded by symmetry for the Néel vector pointing along the zero-field [001] easy-axis. Guided by a symmetry analysis and ab initio calculations, a field-induced reorientation of the Néel vector from the easy-axis toward the [110] hard-axis was used to demonstrate the anomalous Hall signal in this altermagnet. We confirm the existence of an anomalous Hall effect in our RuO2 thin-film samples, whose set of magnetic and magneto-transport characteristics is consistent with the earlier report. By performing our measurements at extreme magnetic fields up to 68 T, we reach saturation of the anomalous Hall signal at a field Hc ≃ 55 T that was inaccessible in earlier studies but is consistent with the expected Néel-vector reorientation field.

Permalink: https://www.hzdr.de/publications/Publ-37638
Publ.-Id: 37638


Composition-dependent absorption of radiation in semiconducting MSi2Z4 Monolayers

Muhammad, S. R.; Tomasz, W.; Kuc, A. B.; Caterina, C.

The recent synthesis of MoSi2N4 material, along with theoretical predictions encompassing the entire family of chemical analogs, has opened up a new array of low-dimensional materials for a diverse range of optoelectronics and photovoltaics applications. In this study, we conducted state-of-the-art many-body first-principles calculations to analyze the quasi-particle electronic structure of the material class MSi2Z4 (where M = Mo, W, and Z = N, P, As, Sb). All monolayers display a direct band gap at the K point, with the exception of MoSi2N4. In tungsten-based compounds, the fundamental-gap can be adjusted over a significantly broader energy range compared to their molybdenum-based counterparts. Additionally, increasing atomic weight of the Z, both the band gap and exciton binding energies decrease. A noteworthy feature is the absence of a lateral valley (Λ or Q) near the conduction band minimum, indicating potential higher photoluminescence efficiencies compared to conventional transition-metal dichalcogenide monolayers. The optical spectra of these materials are predominantly characterized by tightly bound excitons, leading to an absorption onset in the visible range (for N-based) and in the infrared region (for others). This diversity offers promising opportunities to incorporate these materials and their heterostructures into optoelectronic devices, with tandem solar cells being particularly promising.

Permalink: https://www.hzdr.de/publications/Publ-37637
Publ.-Id: 37637


Understanding warm dense matter: from ab initio simulations to experiments

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. Yet, the interpretation of these experiments requires a reliable diagnostics
based on accurate theoretical modeling, which is a notoriously difficult task [1].

In this work, I will give an overview of how we can use exact ab-initio path integral Monte Carlo
(PIMC) simulations [2] to get
new insights into the behavior of WDM. Moreover, I will show how switching to the imaginary-
time representation allows us to significantly improve the interpretation of X-ray Thomson
scattering (XRTS) experiments, which are a key diagnostic for WDM [3]. Specifically, I will
present a model-free temperature diagnostic [4] based on the well-known principle of detailed
balance, but available for all wave numbers, and a new idea to directly extract the electron—
electron static structure factor from an XRTS measurement [5]. As an outlook, I will show how new
PIMC capabilities will allow to give us novel insights into electronic correlations in warm dense
quantum plasmas, leading to unprecedented agreement between experiments [6] and theory.

[1] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[2] M. Böhme et al., Physical Review Letters 129, 066402 (2022)
[3] S. Glenzer and R. Redmer, Reviews of Modern Physics 81, 1625 (2009)
[4] T. Dornheim et al., Nature Communications 13, 7911 (2022)
[5] T. Dornheim et al., arXiv:2305.15305 (submitted)
[6] T. Döppner et al., Nature 618, 270-275 (2023)

  • Lecture (Conference)
    The 9th annual meeting of the programme "Matter and Technologies", 09.-11.10.2023, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37636
Publ.-Id: 37636


Implementing code review in the scientific workflow: Insights from ecology and evolutionary biology

Ivimey-Cook, E. R.; Pick, J. L.; Bairos-Novak, K. R.; Culina, A.; Gould, E.; Grainger, M.; Marshall, B. M.; Moreau, D.; Paquet, M.; Royauté, R.; Sánchez-Tójar, A.; Simoes Silva, I. M.; Windecker, S. M.

Code review increases reliability and improves reproducibility of research. As such, code review is an inevitable step in software development and is common in fields such as computer science. However, despite its importance, code review is noticeably lacking in ecology and evolutionary biology. This is problematic as it facilitates the propagation of coding errors and a reduction in reproducibility and reliability of published results. To address this, we provide a detailed commentary on how to effectively review code, how to set up your project to enable this form of review and detail its possible implementation at several stages throughout the research process. This guide serves as a primer for code review, and adoption of the principles and advice here will go a long way in promoting more open, reliable, and transparent ecology and evolutionary biology.

Keywords: ecology; evolutionary biology; open science; reliability; reproducibility; research process; software development; coding errors

Permalink: https://www.hzdr.de/publications/Publ-37635
Publ.-Id: 37635


Numerical modelling and simulation of electric heater for thermal energy storage system

Bouldorie, J.; Bangalore Mohankumar, M.

As a part of my graduation in engineering school in France and master’s degree, I am doing
my 6-month internship/master thesis in the Helmholtz-Zentrum Dresden-Rossendorf in the Institute
of Fluid Dynamics. The team comprised of my supervisor and PhD student, Mrs. Malini Bangalore
Mohankumar, Dr. Sebastian Unger, PhD student Alexandre Guille Bourdas, and I, is working on a
project of Thermal Energy Storage (TES). This system would store the surplus of electricity when
the production is higher than the demand. The electricity is used in order to heat a storage material.
Indeed, an electrical heater heats a CO2 flow, which will through a tank heating the storage material.
The electrical heater is the subject of my work and thesis.
The choice of the fluid was already determined: the CO2 at atmospheric pressure, as it is non
toxic, non inflammable, low corrosive and has advantageous thermodynamic properties.
Nevertheless, other fluids will be studied in the future. Furthermore, the mass flow rate and the
temperatures are fixed by the process of the other systems, such as the thermal storage cycle and the
power cycle. The mass flow rate is 5 kg/s and the inlet/outlet temperatures are 400°C/1000°C. These
are the only constraints for designing the heater. Then different sizes, geometries of the heater will
be studied in order to determine the configuration of the heater.
In this aim, a review of heaters and heat transfer in the shell part of shell-and-tube heat
exchangers is developed. In fact, few articles are available on the operation of electrical heaters at
high temperature. Moreover, shell-and-tube heat exchangers work in the same way as the heater.
However, the range of temperatures differs, so some work has to be done in order to model the heat
transfer in the heater.
With this in mind, an analytical work is developed, in order to have an order of magnitude of
the heat transfer. In this part, different models and correlations are used, to have a first estimation of
the heater length.
Then, a simulation approach applying numerical methods, such as Computational Fluid
Dynamics (CFD) is done. This approach, allows to determine more accurate results, which include
radiation. However, a focus is necessary on the validity of the model of resolution/radiation on the
software.
Finally, to optimize the heat transfer performance in the heater, the results of different designs
are compared,

Keywords: Thermal energy storage; Supercritical CO2; electrical heater

  • Master thesis
    University of Poitiers, France, 2023
    Mentor: Malini Bangalore Mohankumar
    102 Seiten

Permalink: https://www.hzdr.de/publications/Publ-37634
Publ.-Id: 37634


Metal Deportment in Complex Secondary Raw Materials: The Case of Vanadium in Basic Oxygen Furnace Slags

Renno, A.; Möckel, R.; Frenzel, M.; Ebert, D.; Bachmann, K.; Krause, J.; Gutzmer, J.

With the increasing demand for metalliferous and mineral raw materials and the consequent depletion of the global natural resource base, the possible utilization of secondary raw material sources is receiving more and more attention. In the present study, we present results from a detailed vanadium deportment study of three basic oxygen furnace slag (BOS) samples known to containing elevated bulk concentrations of vanadium. Complementary analytical methods that were used to quantify the abundance and composition of V-containing phases include SEM-based automated mineralogy, X-ray fluorescence analysis, and X-ray powder diffraction as well as electron probe microanalysis. The vanadium deportment was quantified using Monte-Carlo simulations of the data obtained from automated mineralogy and electron microprobe analysis. The total V concentrations identified by XRF are between 1.7 and 2.2 wt.% V. The most important hosts of vanadium are larnite-, brownmillerite- and portlandite-solid solutions. In two samples Ca carbonates also significantly contribute to the V deportment, while wuestite, lime, and native iron do not contribute significantly to the vanadium deportment. A thorough consistency
check identifies considerable uncertainties in the density of the V-bearing phases as the most likely reason to explain
remaining discrepancies between measured and calculated V values

Keywords: Steel slag; Basic oxygen furnace slag; Vanadium-bearing slag; Vanadium; Vanadium deportment

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Permalink: https://www.hzdr.de/publications/Publ-37633
Publ.-Id: 37633


Photonic model for airborne microorganisms inactivation by UV radiation

Cavagnola, M. A.; Eßlinger, F.; Hampel, U.; Ebert, G.; Lecrivain, G.

Since the coming of the COVID-19 pandemic in 2019, virus spreading in confined spaces has been in the spotlight. Ultraviolet germicidal irradiation has proven to be an efficient method of rendering airborne microorganisms inactive. In the present study, a novel model for airborne virus/bacteria inactivation using UV-light is presented. A particle-to-particle photonic approach that takes into account each of the interactions between the microorganism particles and UV-light photons is obtained. The main advantage of the presented model is its faithfulness to the physical reality of the inactivation process, i.e. that the ultraviolet inactivation effect is a stochastic process not a deterministic one. This characteristic allows the model to track and calculate the inactivation success for each of the single particles conforming a particle cloud. The model is validated against published data of inactivation of aerolized Escherichia coli bacteria in a UV-reactor and will be validated experimentally using a seasonal coronavirus in a Potential Aerosol Mass Oxidation Flow Reactor at the Helmholtz-Zentrum in Munich.

  • Poster
    European Aerosol Conference, 04.-08.09.2023, Malaga, Spanien

Permalink: https://www.hzdr.de/publications/Publ-37632
Publ.-Id: 37632


PSMA: Aktuelle und zukünftige Entwicklungen

Kiß, O.

PSMA: Aktuelle und zukünftige Entwicklungen

  • Invited lecture (Conferences)
    29. Jahrestagung der Berlin-Brandenburgischen Gesellschaft für Nuklearmedizin, 10.-11.11.2023, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37631
Publ.-Id: 37631


RIVERSAND: A new tool for efficient computation of catchmentwide erosion rates

Stübner, K.; Balco, G.; Schmeißer, N.

In-situ cosmogenic 10Be (and 26Al) concentrations in alluvial sediments provide a spatially averaged signal of the erosion rate of the catchment area. Catchmentwide erosion rates reflect the production rate of the entire basin, and their calculation requires knowledge of the complete production rate model. Available calculators determine production rates on a pixel-based approach and achieve computational efficiency by relying on a scaling method that ignores geomagnetic field strength variations. Here we introduce a new python-based tool that determines erosion rates based on the hypsometry of the catchment. The method relies on the fact that production rates are much more sensitive to changes in elevation than latitude. Our tool has two main advantages: (1) computation time is short (<30 seconds) and independent of the scaling method; there is no need to neglect magnetic field variations, and (2) because production rate scaling is performed by a widely used online calculator, the results are fully comparable to exposure ages or point-based erosion rates determined with the same calculator; future updates to production rate scaling are immediately effective for catchmentwide erosion rate calculation. We demonstrate in two case studies that (1) for similar scaling methods, our calculator reproduces pixel-based results within a few percent, and (2) erosion rates determined with different scaling methods may differ by >20%, differences can vary systematically with erosion rate, and using a time-constant scaling method may result in a bias in the interpretation of catchmentwide erosion rates.

Keywords: AMS; AMS dating; denudation; erosion; landscape evolution

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Permalink: https://www.hzdr.de/publications/Publ-37630
Publ.-Id: 37630


Photonic model for airborne microorganisms inactivation by UV radiation

Cavagnola, M. A.; Eßlinger, F.; Hampel, U.; Ebert, G.; Lecrivain, G.

Since the coming of the COVID-19 pandemic in 2019, virus spreading in confined spaces has been in the spotlight. Ultraviolet germicidal irradiation (UVGI) has proven to be an efficient method of rendering airborne microorganisms inactive. In the present study, a novel model for airborne microorganisms inactivation using UV-light is presented. A particle-to-particle photonic approach that takes into account each of the interactions between microorganisms and UV-light photons is obtained. The main advantage of the presented model is its faithfulness to to the physical reality of the inactivation process, i.e. that ultraviolet inactivation is a stochastic process not a deterministic one. This characteristic allows the model to track and calculate the inactivation success for each of the single particles conforming a particle cloud. The model is validated against experimental data of SARS Corona-virus 2 inactivation in a UV-reactor and against published data of of aerolized Escherichia coli and Pseudomonas aeruginosa bacteria inactivation.

  • Poster
    CORAERO spring PhD School, 09.05.2023, DLR Göttingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37629
Publ.-Id: 37629


Three Pleistocene glacial advances and a warm episode during MIS-3: Towards a more complete glacial history of the Pamir Mountains

Stübner, K.; Gadoev, M.; Rugel, G.; Lachner, J.; Bookhagen, B.

Understanding the spatial and temporal variations of Pleistocene glaciations is key to understanding present-day climate-driven glacier changes. Glacial chronologies of high-mountain Asia, which are mostly based on cosmogenic 10Be exposure dating of moraine boulders, remain scarce and often inaccurate due to geologically induced age scatter. We present 53 new 10Be exposure ages from rockslides, glacial sediment deposits and glacial erosion surfaces in the southwestern Pamir. In conjunction with previously published 10Be data, we constrain the timing and extent of three major glacial stages in the Pamir. During the Middle Pleistocene, a continuous ice sheet covered most of the Pamir. This stage is older than 200 ka and may have occurred during Marine Isotope Stages (MIS) 8, 10, or 12. The deep valleys of the western Pamir, which constrast with the east Pamir plateau, are partly attributed to Middle Pleistocene glacial erosion. Successively less extensive glacial advances occurred during MIS-4/5 (between 60 and 100 ka ago) and during MIS-2 (at 18-22 ka). The last glacial maximum was synchronous in most of the Pamir, except for prolonged glaciation of the Muztagh Ata ice cap until 14 ka ago. Similar to today, Late Pleistocene glaciers were precipitation-limited with moisture supplied mostly by westerly winds. An episode of increased mass wasting (e.g. Zuvor rockslide: 34 ± 1 ka) and glacier surging correlates with a peak in δ 18 O values in the Guliya ice core and is attributed to a warmer climate.

Keywords: Central Asia; glacial chronology; cosmogenic nuclide; exposure age; moraine; rockslide

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Permalink: https://www.hzdr.de/publications/Publ-37628
Publ.-Id: 37628


Influence of oxidic and metallic interfaces on the magnetic damping of Permalloy thin films

Ney, V.; Salikhov, R.; Lenz, K.; Hellwig, O.; Lindner, J.; Ney, A.

Magnetic damping within Permalloy (Py) thin films is studied via temperature- and frequencydependent ferromagnetic resonance (FMR) experiments. While the Py thickness is kept constant at 20 nm, the environment at the film interfaces was systematically varied by fabricating a set of Py thin films grown on widely used substrates and capped with common layers, which are assumed to be suitable to prevent oxidation. The resulting frequency- and temperature-dependence of the FMR linewidth significantly deviates from the expected Gilbert-like behavior and especially for oxidic interfaces unwanted non-Gilbert-like contributions to the magnetic damping appear, in particular at low temperatures. It turns out that Py sandwiched in-between metallic capping and buffer layers
of Al exhibits the smallest magnetic damping of purely Gilbert-like nature.

Keywords: Thin films; ferromagnetism; ferromagnetic resonance; anisotropy; linewidth

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  • Secondary publication expected from 11.12.2024

Permalink: https://www.hzdr.de/publications/Publ-37626
Publ.-Id: 37626


Terahertz Twistoptics–Engineering Canalized Phonon Polaritons

Obst, M.; Nörenberg, T.; Álvarez-Pérez, G.; de Oliveira, T.; Taboada-Gutiérrez, J.; Feres, F. H.; Kaps, F. G.; Hatem, O.; Luferau, A.; Nikitin, A. Y.; Klopf, J. M.; Alonso-González, P.; Kehr, S. C.; Eng, L. M.

The terahertz (THz) frequency range is key to studying collective excitations in many crystals and organic molecules. However, due to the large wavelength of THz radiation, the local probing of these excitations in smaller crystalline structures or few-molecule arrangements requires sophisticated methods to confine THz light down to the nanometer length scale, as well as to manipulate such a confined radiation. For this purpose, in recent years, taking advantage of hyperbolic phonon polaritons (HPhPs) in highly anisotropic van der Waals (vdW) materials has emerged as a promising approach, offering a multitude of manipulation options, such as control over the wavefront shape and propagation direction. Here, we demonstrate the THz application of twist-angle-induced HPhP manipulation, designing the propagation of confined THz radiation between 8.39 and 8.98 THz in the vdW material α-molybdenum trioxide (α-MoO3), hence extending twistoptics to this intriguing frequency range. Our images, recorded by near-field optical microscopy, show the frequency- and twist-angle-dependent changes between hyperbolic and elliptic polariton propagation, revealing a polaritonic transition at THz frequencies. As a result, we are able to allocate canalization (highly collimated propagation) of confined THz radiation by carefully adjusting these two parameters, i.e. frequency and twist angle. Specifically, we report polariton canalization in α-MoO3 at 8.67 THz for a twist angle of 50°. Our results demonstrate the precise control and manipulation of confined collective excitations at THz frequencies, particularly offering possibilities for nanophotonic applications.

Keywords: s-SNOM; FEL; FELBE; THz; IR; nearfield spectroscopy; phonon polariton; twisted bilayer

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Permalink: https://www.hzdr.de/publications/Publ-37625
Publ.-Id: 37625


Data publication: Estimation of the yield strength from small punch testing

Altstadt, E.

Finite element simulations of the small punch test are performed.Generic elastic-plastic material properties are used. A systematic variation of the yield stress, ultimate tensile stress and uniform elongation is performed to investigate the effects of these parameters of the uniaxial stress-strain curve on the characteristics of small punch force-deflection curves. Moreover, the effect of sample thickness is studied. It is shown that the currently used elastic-plastic transition force – obtained by bi-linear fitting – does not only depend on the yield strength but also on the work hardening behavior of the material. An alternative definition of the elastic-plastic transition force is proposed, which significantly less depends on the work hardening of the material. The approach is based on the deviation of the force-deflection curve from the analytical elastic slope derived by Reissner's plate theory. The new definition of the transition force leads to significantly reduced dependence of the correlation factor on the geometry of the small punch set-up.

Keywords: small punch test; yield strength; empirical correlation; finite element simulation; plate theory

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Permalink: https://www.hzdr.de/publications/Publ-37624
Publ.-Id: 37624


Challenges for the CFD-Modelling in the Multi-Fluid Framework

Lucas, D.

The need to optimise processes, e.g. in terms of energy consumption and product properties, is leading to an increasing demand from industry to be able to reliably predict multiphase flows or even to simulate them as a digital twin in parallel with industrial processes. Because of the large range of scales to be considered, the Euler-Euler approach is often the only feasible framework for medium and large industrial scales. Improving closure models and bringing together different modelling approaches for different scales of phase interfaces are important tasks to achieve a better reliability. For the latter, a flexible hybrid framework for OpenFOAM was developed at the HZDR, which is presented in the talk. Improving closure models requires a better understanding of local phenomena that influence the interactions between phases. Enhanced possibilities for measurements (e.g. with high-speed cameras and ultra-fast X-ray tomography), growing feasibility of DNS for multiphase flows and the use of artificial intelligence open up new possibilities here. Some recent developments and requirements for future activities are discussed.

Keywords: CFD; multiphase; multiscale

  • Invited lecture (Conferences)
    50 years of International Journal of Multiphase Flows, 30.08.-01.09.2023, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-37623
Publ.-Id: 37623


Data publication: Impact of electronic correlations on high-pressure iron: insights from time-dependent density functional theory

Ramakrishna, K.; Lokamani, M.; Baczewski, A.; Vorberger, J.; Cangi, A.

Simulation and literature data on the electrical and thermal conductivity of high-pressure iron. The raw simulation data was generated from time-dependent density functional theory calculations. Post-processing was applied to obtain the transport properties (conductivities) as described in the associated journal publication. The literature data was compiled from available publication data as referenced in the associated journal publication.

Keywords: Time-dpenedent density functional theory; Electronic structure; Electrical conductivity

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Permalink: https://www.hzdr.de/publications/Publ-37622
Publ.-Id: 37622


Impact of electronic correlations on high-pressure iron: insights from time-dependent density functional theory

Ramakrishna, K.; Lokamani, M.; Baczewski, A.; Vorberger, J.; Cangi, A.

We present a comprehensive investigation of the electrical and thermal conductivity of iron under high pressures at ambient temperature, employing the real-time formulation of time-dependent density functional theory (RT-TDDFT). Specifically, we examine the influence of a Hubbard correction (+U) to account for strong electron correlations. Our calculations based on RT-TDDFT demonstrate that the evaluated electrical conductivity for both high-pressure body-centered cubic (BCC) and hexagonal close-packed (HCP) iron phases agrees well with experimental data. Furthermore, we explore the anisotropy in the thermal conductivity of HCP iron under high pressure, and our findings are consistent with experimental observations. Interestingly, we find that the incorporation of the +U correction significantly impacts the ground state and linear response properties of iron at pressures below 50 GPa, with its influence diminishing as pressure increases. This study offers valuable insights into the influence of electronic correlations on the electronic transport properties of iron under extreme conditions.

Keywords: electrical conductivity; time-dependent density functional theory; transition metals

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Permalink: https://www.hzdr.de/publications/Publ-37621
Publ.-Id: 37621


Density driven granular mixing and segregation in a rotating drum

Papapetrou, T. N.; Lecrivain, G.; Bieberle, M.; Hampel, U.

The shearing of a particle bed composed of two or more species results in spontaneous segregation. This poses problems in many industries, where the mixing of granules and powders is a common process and a homogeneous product is desired. In this work, the segregation dynamics occurring in a horizontal rotating drum filled with two granular species that only differ in density is investigated. In this system, radial segregation is relatively fast and occurs over the course of a few drum rotations. State-of-the art techniques allow the study of segregation dynamics at the end walls of a drum, as well as the observation of slow axial dynamics and the steady state of radial mixing inside the drum bulk. They do not allow, however, continuous observation of the transient radial mixing in the bulk. Using the ultrafast X-ray computer tomography it is possible to take cross-sectional images through the opaque granular systems at 1000 frames per second. The high-speed image sequences from intermediate planes of the drum can reveal the segregation dynamics in the bulk. Here we present experimental results from the transient state of radial mixing for a binary granular system with density difference (density ratio 2.8) and equal size (4 mm) spherical beads in a half-filled drum. Using a dimensionless mixing index (M), we compare the dynamics of radial mixing and segregation in transverse planes in the bulk of the drum, captured with UFXCT, with the dynamics from the circular end caps to highlight wall effects. We also compare two dynamic models for radial mixing and consider the effect of flow on mixing dynamics. We find that second-order dynamics fit better the data than the commonly used first-order, since it accounts for the overshooting mixing dynamics occurring at higher drum speeds. We also find that, compared to the end cap, the dense particle segregation core is larger in the bulk plane and the overshooting in the mixing index is smaller, suggesting a correlation between mixing and flow characteristics, such as the dynamic angle of repose. Our results, because of better describing overmixing, are highly relevant to the pharmaceutical, food and cement industries.

Keywords: Ultrafast X-ray computed tomography; Rotating drum; Granular mixing

  • Lecture (others)
    Presentation in Prof. Stannarius' group, 12.09.2023, Magdeburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37620
Publ.-Id: 37620


Comparison of straight and zig-zag channel designs for a CO2-sCO2 PCHE in a Thermal Energy Storage

Guille-Bourdas, A. F.

Renewable energy sources are the key for long-term decarbonisation of the energy system. However, the intermittent nature of renewables, such as solar energy or wind energy, does not always meet the energy demand in the electrical grid. Considering the fact that both electricity production and consumption vary independently, balancing the grid is a major challenge for the development of an energy system based on renewable energies. Within this framework, Thermal Energy Storage systems (TES) coupled with a power cycle have gained popularity since they can store energy from renewable sources during the periods of high production and release it when necessary.
To convert thermal energy into electricity, a power cycle is required. Given the relative high temperature range (600 - 1000 °C), supercritical CO2 (sCO2) is the most promising material as working fluid for the power cycle, from efficiency and safety considerations. Thus, the Primary Heat Exchanger (PHX) must be carefully designed as the fluid pressures in the TES and the power cycle are namely 1 - 10 bar and 200 - 250 bar.
A Printed Circuit Heat Exchanger (PCHE) with straight or zigzag channels is numerically studied. A 1D model were developped and Computational Fluid Dynamics (CFD) simulations were conducted to design and to optimize the PCHE.

Keywords: Thermal Energy Storage; Primary Heat Exchanger; Printed Circuit Heat Exchanger; Atmospheric pressured gas; Supercritical fluid; Computational Fluid Dynamics; Nodal 1D model; Opitmization

  • Lecture (Conference)
    ESD – MTET PhD Workshop, 26.-27.09.2023, Friendly Cityhotel Oktopus, Siegburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37619
Publ.-Id: 37619


Pd–Si complexes of the type ClPd(μ²-pyO)₄SiR (R = Me, Ph, Bn, Allyl, κO-(pyO)PdCl(η³-allyl); pyO = pyridine-2-olate): The influence of substituent R on the Pd–Si bond

Wagler, J.; Gericke, R.

The reactions of organosiliconpyridine-2-olates (pyridyl-2-oxysilanes) RSi(pyO)₃ (pyO = pyridine-2-olate, R = Me (1a), Ph (1b), Bn (1c) and Allyl (1d)) and [PdCl₂(NCMe)₂] in chloroform afforded the hexacoordinate silicon complexes RSi(μ²-pyO)₄PdCl (R = Me (2a), Ph (2b), Bn (2c) and Allyl (2d), respectively), which feature a Pd–Si bond, in which the Pd atom is the formal lone pair donor toward Si. The new compounds 2b, 2c, 2d were characterized with multi-nuclear NMR spectroscopy and elemental analysis. The effect of the Si-bound substituent R on the trans-disposed Pd–Si bond was studied by single-crystal X-ray diffraction and computational analyses (e.g., Natural Localized Molecular Orbitals, NLMO; topological analyses of the electron density at the bond critical point with Quantum Theory of Atoms-In-Molecules, QTAIM). A structurally related byproduct, (η³-allyl) ClPd(pyO)Si(μ²-pyO)₄PdCl 2d’, which formed along with target product 2d and features an Si–O bond trans to Pd–Si, was included in this systematic study. Another byproduct from the synthesis of 2d, the pentanuclear complex ClPd(μ²-pyO)₂Si(μ²-pyO)₂Pd(μ²-pyO)₂Si(μ²-pyO)₂PdCl (compound 3) was characterized crystallographically. This compound features pentacoordinate Si atoms within trigonal–bipyramidal Si(O₄Pd) coordination spheres with equatorial Pd–Si bonds to the terminal Pd atoms. The Pd–Si bond situation in this compound was elucidated with the aid of computational analyses. QTAIM analyses of 3 in conjunction with a model compound PdSi4, which features two silyl groups and two silylene ligands, indicate topological properties of the electron density at the Pd–Si bond critical point which are similar to Pd–Si bonds of silyl and silylene compounds. The latter exhibit greater similarity, which indicates features of a Pd←Si bond. In contrast, NLMO analyses of 3 identify a polar covalent Pd–Si bond with predominant Pd contribution (formal Pd→Si donation).

Keywords: Ambidentate ligands; Hypercoordination; NMR spectroscopy; Palladium; Silicon; Single-crystal X-ray diffraction; Topological analysis

Permalink: https://www.hzdr.de/publications/Publ-37618
Publ.-Id: 37618


The revision of the pharmaceutical legislation – it is time to act for nuclear medicine in Europe

Patt, M.; Decristoforo, C.; de Martini, A.; Koole, M.; Oyen, W.; Kiß, O.

The revision of the pharmaceutical legislation – it is time to act for nuclear medicine in Europe

Permalink: https://www.hzdr.de/publications/Publ-37617
Publ.-Id: 37617


Ion-induced telecom single-photon emitters in silicon

Astakhov, G.; Hollenbach, M.; Klingner, N.; Jagtap, N.; Bischoff, L.; Fowley, C.; Kentsch, U.; Hlawacek, G.; Erbe, A.; Abrosimov, N. V.; Berencen, Y.; Helm, M.

Single-photon emitters (SPEs) are one of the elementary building blocks for photonic quantum information and optical quantum computing. One of the upcoming challenges is the monolithic photonic integration and coupling of single-photon emission, reconfigurable photonic elements, and single-photon detection on a sili- con chip in a controllable manner. Particularly, fully integrated SPEs on-demand are required for enabling a smart integration of advanced functionalities in on-chip quantum photonic circuits. The major challenge in realizing a fully monolithic, photonic integrated circuitry lies in the development of a quantum light source in silicon since the indirect nature of the small energy bandgap does not allow for efficient PL emission. Nev- ertheless, below-bandgap light emission can be used for good advantage by exploiting extrinsic and intrinsic point defects acting as SPEs. Indeed, the isolation of SPEs, such as G-, W-, and T-centers, in the optical telecom- munication O-band has been recently realized in silicon [1-4]. In all these cases, however, SPEs were created uncontrollably in random locations, preventing their scalability.
We present mask-free nanofabrication involving a quasi-deterministic creation of single G- and W-centers in silicon wafers using focused-ion beam (FIB) writing. We also implement a scalable, broad-beam implan- tation protocol compatible with the complementary-metal-oxide-semiconductor (CMOS) technology to fabri- cate telecom SPEs at desired positions on the nanoscale [5].
[1] M. Hollenbach et al., Optics Express 28, 26111 (2020) [2] W. Redjem et al., Nature Electronics 3, 738 (2020)
[3] Y. Baron et al., ACS Photonics 9, 2337 (2022)
[4] D. B. Higginbottom et al., Nature 607, 266 (2022)
[5] M. Hollenbach et al., Nat. Commun. 13, 7683 (2022)

Keywords: Quantum technology; Single photon emitters; Silicon; Implantation

Related publications

  • Invited lecture (Conferences)
    4th Science Workshop of the Program MML, 27.-29.09.2023, Jena, Germany

Permalink: https://www.hzdr.de/publications/Publ-37614
Publ.-Id: 37614


Temperature-dependent Generalized Gradient Approximation for Warm Dense Matter

Ramakrishna, K.

Warm dense matter, density functional theory

  • Open Access Logo Invited lecture (Conferences)
    11th Workshop on High Pressure, Planetary and Plasma Physics (HP4), 25.09.2023, Rostock, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-37613
Publ.-Id: 37613


PREFACE Strongly Coupled Coulomb Systems

Cangi, A.; Moldabekov, Z.; Neilson, D.

This special issue compiles papers presented at the International Conference on Strongly Coupled Coulomb Systems (SCCS) held in July 2022. Organized by The Center for Advanced Systems Understanding at the Helmholtz-Zentrum Dresden-Rossendorf, this conference brought together researchers from diverse disciplines to explore plasma-liquid and condensed-matter systems dominated by strong Coulomb interactions. The conference series, initiated in 1977, has evolved to encompass a wide range of topics in theory, simulation, and experiment, including astrophysical plasmas, dense hydrogen, laser-generated plasmas, and more. This fifteenth edition also featured discussions on the intersection of Coulombic systems with machine-learning methods. These proceedings present a comprehensive overview of research in Strongly Coupled Coulomb Systems and offer insights into this dynamic field.

Keywords: Coulomb systems; Astrophysical plasmas; Dusty plasmas; Electron-hole plasmas; Ultra-cold plasmas; Quark-gluon plasmas; Statistical and kinetic theories; Machine learning; Condensed matter

  • Open Access Logo Contribution to proceedings
    Strongly Coupled Coulomb Systems, 24.-29.07.2022, Görlitz, Deutschland
    Strongly Coupled Coulomb Systems (2022): Wiley-VCH GmbH, e202300110
    DOI: 10.1002/ctpp.202300110

Permalink: https://www.hzdr.de/publications/Publ-37612
Publ.-Id: 37612


Wege zum effizienten Rückbau von Reaktorkomponenten und Betonabschirmung: Berechnung des Aktivitätsinventars und deren Validierung an Bohrkernen sowie Mobilitätsuntersuchungen von Radionukliden“ – WERREBA

Konheiser, J.; Barkleit, A.; Pönitz, E.

Das Ziel des Vorhabens war es, genaue Kenntnisse über die entstandenen radioaktiven Nuk-lide während des Leistungsbetriebs eines Kernkraftwerkes, die zeitliche Veränderung der Ak-tivität und die daraus resultierende Verteilung der Aktivität in den einzelnen Phasen des Rück-baus zu erhalten. Die Aktivitätsverteilungen sollten dabei anlagenspezifisch für den Reaktor-druckbehälter (RDB), dessen Einbauten, den Reaktordeckel und die erste Betonabschirmung (biologisches Schild) bestimmt werden. Dabei lag der Schwerpunkt besonders auf der expe-rimentellen Bestimmung der Nuklidzusammensetzung sowie deren Aktivität und chemischen Bindung im Material. Die Untersuchungen wurden an Originalmaterial sowohl aus dem RDB als auch aus dem Beton durchgeführt und dienen der Validierung und Verifizierung der durchgeführten Rechnungen.
Im Fall der stark aktivierten Reaktorkomponenten könnten den Behörden und Betreibern In-formationen bereitgestellt werden, ob neben der direkten Zerlegung die Methode der Abkling-lagerung als eine ökologische und wirtschaftliche Alternative in Betracht kommt. Mit einer möglichen Zwischenlagerung könnten sowohl die endzulagernde aktive Abfallmenge reduziert als auch wertvolle Metalle wieder recycelt werden. Zusätzlich wird die Strahlenbelastung für das Rückbaupersonal verringert.
Im Fall der Betonabschirmung wurden Aussagen zur möglichen chemischen Mobilität der Radionuklide getroffen, welche direkten Einfluss auf die Rückbaustrategie und die Endlage-rung hat. Denn für beides ist nicht nur die absolute Menge, sondern auch die strukturelle Ein-bindung der Radionuklide im Beton wichtig. Diese ist entscheidend für die Stabilität der Bin-dung der Radionuklide im Beton und damit für den Umfang und die Kinetik möglicher Auflö-sungen mit Übergang in die wässrige Phase während des Rückbaus und im Endlager.

Keywords: Rückbau von KKW; Neutronenfluenzrechnungen; Betonaktivierung; Nuklidbestimmung

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-127 2023
    ISSN: 2191-8708, eISSN: 2191-8716
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-37611
Publ.-Id: 37611


Mixing and Agglomeration of Shredder Fines and Flue Dust

Baecke, A. M.; Renno, A.; Hampel, U.; Lecrivain, G.

Industrial processes are inevitably associated with generating fine-grained particulate matter. Such fine-grained residues rarely find re-entry into industrial value chains; typically they are disposed and become an environmental burden. Prominent examples are dusts from mineral processing, degraded end-of-life fibers, or micro plastic entering the natural environment. The project FINEST will process different residues in an optimized manner to generate value and to minimize hazards. FINEST will design high-value products and inert residues. Material assay, beneficial material mixing and logistic concepts will provide ideal opportunities to transform hazardous end of life products to inert residues and to products generating economic value.
Economic and ecological assessment of waste management concepts will provide op-opportunities to create value by decreased disposal costs. The project assembles a well-tailored network of industry associations, industry companies, SMEs, governmental and non-governmental institutions. Associated institutions will provide the capability to transfer FINEST results to the relevant industrial sectors and potential consumers. The appendant Research School will educate a next generation of experts for leadership positions in industry and academia. A transfer design will consider the transfer of knowledge through careers. Young postgraduate colleagues will accordingly receive tailored education in establishing technology transfer concepts and are expected to conduct internships in the course of their doctoral studentship. A central transfer desk will provide organized knowledge transfer to industry clusters and associations in order to promote joint position papers and to suggest market-shaping policies. Individual TTOs have stated their full support for the screening and exploitation of evolving IP within the sub-projects. FINEST represents an ideal combination of scientific excellence and tailored networking with an application-oriented education of the next generation of leadership personnel for the industry and academia. The project offers a well-structured approach to reduce uncertainties for an actual application of developed technologies and is ready to increase the degree of circularity in the economy by transferring its research, and to contribute to more sustainable value chains.
Fine-grained solid particles from various industrial sources, which would otherwise be discarded, should ideally be processed to valuable products or inert residues. Among others, a) shredder fines from electronics and end-of-life vehicles, and b) flue dusts from non-ferrous metallurgical processes are of timely interest. They contain valuable residuals, such as metals, that can be returned to the industrial cycle instead of being landfilled. This is one aim of the Helmholtz project FINEST in which this work is embedded. In this work, mixing and agglomeration of such particles with a size below 1 mm are investigated for further use in the metallurgical industry. Different particle sizes, shapes and densities are considered, as well as varying moisture content. Most relevant product parameters are the mixture’s homogeneity, agglomerate size and porosity. A strong focus is on the rheological behavior of the bulk goods. A continuum model will be used to simulate mixing and prospectively granulation in a cylindrical bladed mixer. The three phases, namely shredder fines, flue dust and interparticle liquid will be modelled using Computational Fluid Dynamics, adding in a Convection-Dispersion-Segregation-Model for microprocesses of mixing. The latter will introduce a Segregation-Term specifically for density differences among component. We present an experimental setup and methods for the aforementioned investigations. The process is observed experimentally using camera imaging technique and µCT. From the µCT images a mixing index is acquired. Using rapid prototyping mixing and agglomeration equipment can be adapted easily and varied for parameter studies. The results will contribute to improved mixing and agglomeration processes for efficient recycling of fine particles as well as improved understanding of mixing in many other fields, such as pharmaceuticals, construction material and food industry.

Keywords: Mixing; Granulation; Bulk Goods; Computed Tomography; Metallurgical Recycling; Bladed Mixer

  • Poster
    PARTEC, 26.-28.09.2023, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37609
Publ.-Id: 37609


Potential of the Julia programming language for high energy physics computing

Eschle, J.; Gal, T.; Giordano, M.; Gras, P.; Hegner, B.; Heinrich, L.; Hernandez Acosta, U.; Kluth, S.; Ling, J.; Mato, P.; Mikhasenko, M.; Moreno Briceño, A.; Pivarski, J.; Samaras-Tsakiris, K.; Schulz, O.; Stewart, G. . . A.; Strube, J.; Vassilev, V.

Research in high energy physics (HEP) requires huge amounts of computing and storage, putting strong constraints on the code speed and resource usage. To meet these requirements, a compiled high-performance language is typically used; while for physicists, who focus on the application when developing the code, better research productivity pleads for a high-level programming language. A popular approach consists of combining Python, used for the high-level interface, and C++, used for the computing-intensive part of the code. A more convenient and efficient approach would be to use a language that provides both high-level programming and high performance. The Julia programming language, developed at MIT especially to allow the use of a single language in research activities, has followed this path. In this paper the applicability of using the Julia language for HEP research is explored, covering the different aspects that are important for HEP code development: runtime performance, handling of large projects, interface with legacy code, distributed computing, training, and ease of programming. The study shows that the HEP community would benefit from a large-scale adoption of this programming language. The HEP-specific foundation libraries that would need to be consolidated are identified

Keywords: Julia programming language; High energy physics; phenomenology

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Permalink: https://www.hzdr.de/publications/Publ-37608
Publ.-Id: 37608


Monte-Carlo event generation for the interaction of x-ray laser fields and hot electrons

Hernandez Acosta, U.

We present a novel approach for an event generator inherently using exact QED descriptions to predict the results of high-energy electron-photon scattering experiments that can be performed at modern x-ray laser facilities.
With the advent of advanced laser systems producing high-frequency x-ray beams, e.g. the EuropeanXFEL as a prominent example, a regime of laser-plasma interaction is reached, where all-optical methods are no longer applicable. Instead, the interaction of hot electrons and the x-ray laser pulse needs to be modeled with a QED-driven approach. Future experiments taking place at HED-HIBEF, LCLS, and other facilities targeting this regime, will encounter processes in x-ray scattering from (laser-driven) relativistic electrons, where the effects of the energy spectrum of the laser field as well as multi-photon interactions can not be neglected anymore.
In contrast to the application window of existing QED-PIC codes, our event generator makes use of the fact, that the classical nonlinearity parameter barely approaches unity in high-frequency regimes. Therefore, based on a momentum-space Furry-picture formulation of strong-field QED, this allows taking the finite bandwidth of the x-ray laser into account in the description of the QED-like multi-photon interaction. Consequently, we exploit these effects in Compton scattering, Breit-Wheeler pair production, and trident pair production in x-ray laser fields.

Keywords: Monte-Carlo event generation; Strong-field QED; X-ray interactions

  • Lecture (Conference)
    5th Conference on Extremely High Intensity Laser Physics (ExHILP 2023), 12.09.2023, Gwangju, South Korea

Permalink: https://www.hzdr.de/publications/Publ-37607
Publ.-Id: 37607


Influence of Dielectric Capping on the Optical Properties of Two-Dimensional Transition Metal Dichalcogenides: Implications for nano optoelectronics

Li, Y.; Steuer, O.; Lin, K.; Samad, F.; Sokolova, D.; Erbe, A.; Helm, M.; Zhou, S.; Prucnal, S.

The properties of transition metal dichalcogenides (TMDCs) are highly sensitive to doping and surface-state defects, making it crucial to fabricate high-performance nanoelectronic devices from defect-free materials and gate dielectrics that have a low interface-state density. In this work, the optical and structural properties of mechanically exfoliated mono-, bi- and trilayer thick TMDCs with Al2O3, Si3N4 or SiO2 as a potential gate dielectric layer are investigated. The photoluminescence (PL) and micro-Raman results indicate that all the dielectrics investigated increase the doping of the TMDCs monolayers, quench the emission of neutral excitons and enhance the trion emission. Plasma enhanced chemical vapour deposition was found to generate more defects in the monolayer TMDCs than atomic layer deposition. We establish the relationship between the dielectric deposition process and the optical properties of TMDCs, which could be of interest for future nanoelectronics based on 2D materials.

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Permalink: https://www.hzdr.de/publications/Publ-37605
Publ.-Id: 37605


What governs the atomic structure of the interface between 2D transition metal dichalcogenides in lateral heterostructures?

Davies, F.; Mehlich, K.; Busse, C.; Krasheninnikov, A.

The development of lateral heterostructures (LHs) based on two- dimensional (2D) materials with similar atomic structure but distinct electronic properties, such as transition metal dichalcogenides (TMDCs), opened a new route towards realisation of optoelectronic devices with unique characteristics. In contrast to van der Waals vertical heterostructures, the covalent bonding at the interface between subsystems in LHs is strong, so that the morphology of the interface, which can be coherent or contain dislocations, strongly a↵ects the properties of the LH. We predict the atomic structure of the interface with account for the mismatch between the primitive cell sizes of the components, and more important, the widths of the joined materials using parameters derived from first-principles calculations. We apply this approach to a variety of TMDCs and set a theoretical limit on when the transition of the interface from coherent to dislocation-type should occur. We validate our theoretical results by comparison with the initial stage of two-dimensional heteropitaxial growth of junctions between MoS2 and TaS2 on Au(111).

Keywords: Transition metal dichalcogenides; ab initio calculations; lateral heterostructures; 2D materials

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Permalink: https://www.hzdr.de/publications/Publ-37604
Publ.-Id: 37604


Machine Learning Meets Quantum Mechanics for Materials

Cangi, A.

This talk will present our research on merging machine learning with quantum mechanics. Electron-nuclear interactions determine all materials' properties, and accurate simulations of electronic structure are essential to address critical scientific questions related to renewable energy, sustainable materials, and semiconductor devices. However, electronic structure simulations face an accuracy-size tradeoff.
I will first present our ongoing efforts on developing the Materials Learning Algorithms (MALA) package to solve the electronic structure problem faster. MALA leverages a combination of neural networks, physically constrained optimization algorithms, and efficient post-processing routines. Next, I will present our work on using physics-informed neural networks to solve the time-dependent Kohn-Sham equations, which describe electron dynamics in response to incident electromagnetic waves.

Keywords: Machine learning; Quantum; Materials science; Neural Networks

  • Invited lecture (Conferences)
    Big data analytical methods for complex systems, 19.10.2023, University of Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-37603
Publ.-Id: 37603


Transferable and scalable electronic structure simulations with the Materials Learning Algorithms package

Cangi, A.

Interactions between electrons and nuclei in matter determine all materials' properties. Understanding and modeling these interactions is of paramount importance, particularly in addressing critical scientific questions related to renewable energy solutions, sustainable materials, and semiconductor device modeling. However, simulations of the electronic structure face a common constraint—an accuracy-size tradeoff. While it is possible to simulate materials at the quantum level of accuracy, this is typically limited to a few thousand atoms, even with advanced tools like density functional theory (DFT). On the other hand, large-scale simulations often sacrifice predictive power due to necessary approximations.
The Materials Learning Algorithms (MALA) [1] package addresses these challenges by leveraging a combination of neural networks, physically constrained optimization algorithms [2], and efficient post-processing routines. Unlike existing approaches, MALA replaces DFT entirely, providing access to both scalar quantities of interest, such as energies, and volumetric information about the electronic structure, such as the electronic density. Our research has demonstrated that MALA can be applied to systems with arbitrary numbers of atoms (successfully testing up to 100,000 atoms) [3], across various temperature and pressure ranges [4]. We anticipate that MALA will have a significant impact, enabling unprecedented modeling capabilities in the fields of materials science and semiconductor device modeling.

[1] L. Fiedler, Z. A. Moldabekov, X. Shao, K. Jiang, T. Dornheim, M. Pavanello, A. Cangi, Phys. Rev. Res. 4, 043033 (2022).
[2] 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).
[3] L. Fiedler, N. A. Modine, S. Schmerler, D. J. Vogel, G. A. Popoola, A. P. Thompson, S. Rajamanickam, A. Cangi, Npj Comput. Mater. 9, 115 (2023).
[4] L. Fiedler, N. A. Modine, K. D. Miller, A. Cangi, arXiv:2306.06032 (2023).

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

  • Lecture (Conference) (Online presentation)
    9th annual meeting of the program "Matter and Technologies", 09.-11.10.2023, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-37602
Publ.-Id: 37602


Machine-Learning for Static and Dynamic Electronic Structure Theory

Fiedler, L.; Shah, K.; Cangi, A.

Machine learning has emerged as a powerful technique for processing large and complex datasets. Recently it has been utilized for both improving the accuracy and accelerating the computational speed of electronic structure theory. In this chapter, we provide the theoretical background of both density functional theory, the most widely used electronic structure method, and machine learning on a generally accessible level. We provide a brief overview of the most impactful results in recent times. We, further, showcase how machine learning is used to advance static and dynamic electronic structure calculations with concrete examples. This chapter highlights that fusing concepts of machine learning and density functional theory holds the promise to greatly advance electronic structure calculations enabling unprecedented applications for in-silico materials discovery and the search for novel chemical reaction pathways.

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

  • Book chapter
    C. Qu, J. Liu: Machine Learning in Molecular Sciences, Challenges and Advances in Computational Chemistry and Physics, Vol. 36, Cham: Springer, 2023, 978-3-031-37196-7, 113-160
    DOI: 10.1007/978-3-031-37196-7_5

Permalink: https://www.hzdr.de/publications/Publ-37601
Publ.-Id: 37601


Primordial nuclides and low-level counting at Felsenkeller

Turkat, S.

Within cosmology, there are two entirely independent pillars which can jointly drive this field towards precision: Astronomical observations of primordial element abundances and the detailed surveying of the cosmic microwave background. However, the comparatively large uncertainty stemming from the nuclear physics input is currently still hindering this effort, i.e. stemming from the 2H(p,γ)3He reaction. An accurate understanding of this reaction is required for precision data on primordial nucleosynthesis and an independent determination of the cosmological baryon density.
Elsewhere, our Sun is an exceptional object to study stellar physics in general. While we are now able to measure solar neutrinos live on earth, there is a lack of knowledge regarding theoretical predictions of solar neutrino fluxes due to the limited precision (again) stemming from nuclear reactions, i.e. from the 3He(α,γ)7Be reaction. This thesis sheds light on these two nuclear reactions, which both limit our understanding of the universe. While the investigation of the 2H(p,γ)3He reaction will focus on the determination of its cross- section in the vicinity of the Gamow window for the Big Bang nucleosynthesis, the main aim for the 3He(α,γ)7Be reaction will be a measurement of its γ-ray angular distribution at astrophysically relevant energies.
In addition, the installation of an ultra-low background counting setup will be reported which further enables the investigation of the physics of rare events. This is essential for modern nuclear astrophysics, but also relevant for double beta decay physics and the search for dark matter. The presented setup is now the most sensitive in Germany and among the most sensitive ones worldwide.

Keywords: Nuclear astrophysics; Big Bang Nucleosynthesis; Solar neutrinos; Low-level counting; underground physics

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-126 2023
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-37600
Publ.-Id: 37600


Complex workflows in modern computational science using AiiDA and HELIPORT

Lokamani, M.; Kelling, J.; Pape, D.; Knodel, O.; Juckeland, G.

AiiDA is an open-source Python infrastructure for devising complex workflows associated with modern computational science and streamlining the four core pillars of the ADES model: Automation, Data, Environment, and Sharing. In this contribution, we showcase features of AiiDA like workflow-forging, high-throughput capability and data provenance as implemented in the AiiDA-FLEUR plugin. Finally, we address the possibility of managing AiiDA-projects through HELIPORT.

  • Open Access Logo Lecture (Conference)
    IT4Science-Days 2023, 26.-28.09.2023, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37599
Publ.-Id: 37599


Two-Dimensional Non-van der Waals Materials by Design

Friedrich, R.; Barnowsky, T.; Ghorbani-Asl, M.; Curtarolo, S.; Krasheninnikov, A. V.

Two-dimensional (2D) materials are traditionally derived from bulk layered compounds bonded by weak
van der Waals (vdW) forces. In this context, the recent surprising experimental realization of non-vdW
2D compounds obtained from non-layered crystals [1,2] foreshadows a new direction in 2D systems
research. These materials are distinct from traditional 2D sheets as their surface was revealed to be
terminated by cations rather than anions.
Here, we present several dozens of candidates of this novel materials class derived from applying data-driven
research methodologies in conjunction with autonomous ab initio calculations and also outline
how to tune their properties [3,4]. We find that the oxidation state of the surface cations of the
2D sheets is an enabling descriptor regarding the manufacturing of these systems as it determines their
exfoliation energy: small oxidation states promote easy peel off [3]. When extending the set from oxides
to sulfides and chlorides, the exfoliation energy becomes ultra low due to strong surface relaxations [4].
The materials also pass several tests validating their vibrational and dynamic stability. The candidates
exhibit a wide range of appealing electronic, optical and magnetic properties which can be tuned by proper
chemical functionalization of the 2D sheets making these systems an attractive platform for fundamental
and applied nanoscience.
References
[1] A. Puthirath Balan et al., Nat. Nanotechnol. 13, 602 (2018).
[2] A. Puthirath Balan et al., Chem. Mater. 30, 5923 (2018).
[3] R. Friedrich et al., Nano Lett. 22, 989 (2022).
[4] T. Barnowsky et al., Adv. Electron. Mater. 2201112 (2023).

Related publications

  • Lecture (Conference)
    Flatlands beyond graphene 2023, 25.-29.09.2023, Prag, Tschechien

Permalink: https://www.hzdr.de/publications/Publ-37598
Publ.-Id: 37598


Targeting colorectal cancer cells using AND-gated Adaptor RevCAR T-cells

González Soto, K. E.; Rodrigues Loureiro, L. R.; Bartsch, T.; Arndt, C.; Kegler, A.; Mitwasi, N.; Drewitz, L.; Hoffmann, L.; Abdelfatah Saleh Hassan, H. A.; Crespo, E.; Mehnert, M.; Daglar, C.; Abken, H.; Momburg, F.; Bachmann, M.; Feldmann, A.

Despite the success of chimeric antigen receptor (CAR) T-cells especially for treating hematological malignancies, critical drawbacks, such as “on-target, off-tumor” toxicities, need to be addressed to improve safety in translating to clinical application. This is especially true, when targeting tumor-associated antigens (TAAs) that are not exclusively expressed by solid tumors but also on healthy tissues. To improve the safety profile, we developed switchable adaptor CAR systems including the RevCAR system. RevCAR T-cells are activated by cross-linking of bifunctional adaptor molecules termed target modules (RevTM). In a further development, we established a Dual-RevCAR system for an AND-gated combinatorial targeting by splitting the stimulatory and co-stimulatory signals of the RevCAR T-cells on two individual CARs. Examples of common markers for colorectal cancer (CRC) are the carcinoembryonic antigen (CEA) and the epithelial cell adhesion molecule (EpCAM), while these antigens are also expressed by healthy cells. Here we describe four novel structurally different RevTMs for targeting of CEA and EpCAM. All anti-CEA and anti-EpCAM RevTMs were validated and the simultaneous targeting of CEA+ and EpCAM+ cancer cells redirected specific in vitro and in vivo killing by Dual-RevCAR T-cells. In summary, we describe the development of CEA and EpCAM specific adaptor RevTMs for monospecific and AND-gated targeting of CRC cells via the RevCAR platform as an improved approach to increase tumor specificity and safety of CAR T-cell therapies.

Keywords: colorectal cancer; CAR T-cells; AND-gate targeting; CEA; EpCAM

Permalink: https://www.hzdr.de/publications/Publ-37596
Publ.-Id: 37596


Ni-doping assisted modification of the non-collinear antiferromagnetic ordering in Mn5Si3 alloy

Adhikari, S. K.; Roy, R.; Das, S. C.; Sannigrahi, J.; Pramanick, S.; Chattopadhyay, S.; Ritter, C.; Adroja, D. T.; Chatterjee, S.

Ni-doped Mn5Si3 alloys of nominal compositions Mn5-xNixSi3 (for x = 0.05, 0.1, and 0.2) have been investigated through detailed neutron powder diffraction (NPD) studies in zero magnetic field and ambient pressure. At room temperature, all three Ni-doped alloys crystallize with D88 type hexagonal structure having P63∕mcm space group. These alloys undergo paramagnetic → collinear antiferromagnetic → non-collinear antiferromagnetic transitions on cooling from room temperature. A significant decrease in collinear to non-collinear antiferromagnetic transition temperature has been observed with increasing Ni concentration. The magnetic structure of both antiferromagnetic phases can be described by the magnetic propagation vector k = (0,1,0). However, the moment size and the orientation in the non-collinear antiferromagnetic phase are found to be notably affected by the Ni-doping. Approaching near-parallel arrangement of Mn-moments with increasing Ni-doping is found to be responsible for the gradual disappearance of unusual magnetic properties (inverted hysteresis loop, thermomagnetic irreversibility, etc.) observed in Mn5Si3 alloy.

Permalink: https://www.hzdr.de/publications/Publ-37591
Publ.-Id: 37591


Robust intralayer antiferromagnetism and tricriticality in the van der Waals compound VBr3

Hovancik, D.; Kratochvilova, M.; Haidamak, T.; Dolezal, P.; Carva, K.; Bendova, A.; Prokleska, J.; Proschek, P.; Misek, M.; Gorbunov, D.; Kotek, J.; Sechovsky, V.; Pospisil, J.

We studied magnetic states and phase transitions in the van der Waals antiferromagnet VBr3 experimentally by specific heat and magnetization measurements of single crystals in high magnetic fields and theoretically by the density functional theory calculations focused on exchange interactions. The magnetization behavior mimics Ising antiferromagnets with magnetic moments pointing out-of-plane due to strong uniaxial magnetocrystalline anisotropy. The out-of-plane magnetic field induces a spin-flip metamagnetic transition of first-order type at low temperatures, while at higher temperatures, the transition becomes continuous. The first-order and continuous transition segments in the field-temperature phase diagram meet at a tricritical point. The magnetization response to the in-plane field manifests a continuous spin canting which is completed at the anisotropy field μ0HMA ≈ 27 T. At higher fields, the two magnetization curves above saturate at the same value of magnetic moment μsat ≈ 1.2 μB/f.u., which is much smaller than the spin-only (S = 1) moment of the V3+ ion. The reduced moment can be explained by the existence of an unquenched orbital magnetic moment antiparallel to the spin. The orbital moment is a key ingredient of a mechanism responsible for the observed large anisotropy. The exact energy evaluation of possible magnetic structures shows that the intralayer zigzag antiferromagnetic (AFM) order is preferred, which renders the AFM ground state significantly more stable against the spin-flip transition than the other options. The calculations also predict that a minimal distortion of the Br ion sublattice causes a radical change of the orbital occupation in the ground state, connected with the formation of the orbital moment and the stability of magnetic order.

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Permalink: https://www.hzdr.de/publications/Publ-37590
Publ.-Id: 37590


Electronic ground-state hysteresis under magnetic field in GdMn2O5

Balédent, V.; Vaunat, A.; Petit, S.; Nataf, L.; Chattopadhyay, S.; Raymond, S.; Foury-Leylekian, P.

In this paper, we investigate the physical properties of the type-II multiferroic GdMn2O5 material by means of neutron scattering, electric polarization, and magnetization measurements. A complex (T,H) phase diagram shows up, with especially a field-induced magnetic transition around 11 T at low temperature. The high-field phase is accompanied by an additional electric polarization along both the a and b directions, as authorized by symmetry, but never observed experimentally up to now. While the magnetic properties recover their initial states after driving the field back to zero, the polarization along a shows a significant increase. This behavior is observed for all directions of the magnetic field. It constitutes a novel and striking manifestation of the magnetoelectric coupling, resulting in the establishment of a new ground state at zero magnetic field.

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Permalink: https://www.hzdr.de/publications/Publ-37589
Publ.-Id: 37589


Data publication: Bispidine Chelators for Radiopharmaceutical Applications with Lanthanide, Actinide and Main Group Metal Ions

Kopp, I.; Cieslik, P.; Anger, K.; Josephy, T.; Neupert, L.; Velmurugan, G.; Gast, M.; Wadepohl, H.; Brühlmann, S. A.; Walther, M.; Kopka, K.; Bachmann, M.; Stephan, H.; Kubeil, M.; Comba, P.

UV/Vis of natural Bi(III)- and Pb(II)-L2 and Bi(III)- and Pb(II)-L3; radio-SEC of 133La-L2; radiolabeling kinetics

Keywords: bispidine; bismuth; lead; chelator; kinetics

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Permalink: https://www.hzdr.de/publications/Publ-37587
Publ.-Id: 37587


Magnetic particle tracking enabled by planar Hall effect sensors

Schmidtpeter, J.; Zabila, Y.; Sieger, M.; Gundrum, T.; Schubert, C.; Wondrak, T.; Makarov, D.; Eckert, S.

Foam processes are essential in many industrial applications e.g., in froth flotation for material
separation. A detailed understanding of foam flows is vital for improvements in process efficiency. X-
Ray and Neutron imaging can measure flow fields in foam, but require a complex setup and cannot be
performed in-situ. Magnetic particle tracking (MPT) is an alternative approach, that measures the
trajectory of a small magnetic tracer particle inside the foam as a representation of its movement.
Different magnetic field sensors can be applied to detect the magnetic tracer particle. We chose thin film
sensors based on the planar Hall effect (PHE) due to their small size, high sensitivity, high signal-to-
noise ratio and low cost. Our sensors have a size of only 2 mm x 2 mm and are capable of measuring
magnetic fields as low as 10 nT at a sampling frequency of 1 Hz. A sensitivity of 20 V/T at a driving
current of 1 mA was achieved by means of sensor bridging. Our PHE-sensors are almost as precise as
currently used Fluxgate probes, but offer several advantages due to their reduced size. This includes
being installed closer to the area to be measured, enabling finer grids of sensors and decreasing the
detection volume, which increases the precision of the MPT as well as other tomographic methods.

Keywords: planar Hall effect; magnetic field sensors; magnetic particle tracking

  • Lecture (Conference)
    11th World Congress on INDUSTRIAL PROCESS TOMOGRAPHY, 06.-08.09.2023, Ciudad de México, México

Permalink: https://www.hzdr.de/publications/Publ-37586
Publ.-Id: 37586


Three-dimensional flow structures in turbulent Rayleigh-Bénard convection at low Prandtl number Pr = 0.03

Wondrak, T.; Sieger, M.; Mitra, R.; Schindler, F.; Stefani, F.; Vogt, T.; Eckert, S.

In this paper we report on an experimental study focusing on the manifestation and dynamics of the large-scale circulation (LSC) in turbulent liquid metal convection. The experiments are performed inside a cylinder of aspect ratio Γ = 0.5 filled with the ternary alloy GaInSn, which has a Prandtl number of Pr = 0.03. The large-scale flow structures are classified and characterized at Rayleigh numbers of Ra = 9.33×10⁶ , 5.31×10₇ and 6.02×10₈ by means of the contactless inductive flow tomography (CIFT) which enables the full reconstruction of the three-dimensional flow structures in the entire convection cell. This is complemented with the multi-thermal-probe method for capturing the azimuthal temperature variation induced by the LSC at the sidewall. We use proper orthogonal decomposition (POD) to identify the dominating modes of the turbulent convection. The analysis reveals that a single-roll structure (SRS) of the LSC alternates in short succession with double-roll structures (DRS) or a three-roll structure (TRS). This is accompanied by dramatic fluctuations of the Reynolds number, whose instantaneous values can deviate by more than 50% from the time-average value. No coherent oscillations are observed, whereas a correlation analysis indicates a residual contribution of the torsion and sloshing modes. Results of the POD analysis suggest a stabilisation of the single-roll LSC with increasing Ra at the expense of flow structures with multiple rolls. Moreover, the relative lifetime of all identified flow states, measured in units of free-fall times, increases with rising Ra.

Keywords: Rayleigh-Bénard convection; thermal turbulence; heat transport; large-scale circulation; liquid metal; low Prandtl number; contactless inductive flow tomography

Permalink: https://www.hzdr.de/publications/Publ-37585
Publ.-Id: 37585


High-quality reconstruction of real space structures from X-ray holography by a conditional Wavelet Flow

Zhang, Y.

Digital holographic reconstruction has been a challenging task for many years due to its strict
requirements of prior knowledge of experimental setups as well as additional filtering algorithms
to suppress the zeroth-order light and twin image problems. Inspired by the data-driven
deep learning method, which is directly able to learn the non-linearity mapping between two
variables, a variety of research has been done in this area by pioneers. However, previous
methods are mainly constrained to discriminative models and they ignore the ill-posed nature
of holographic reconstruction. To address this problem, in this work, we define a novel variant
of normalizing flow, named conditional Wavelet Flow (cWavelet Flow), to reconstruct original
real space structures from digital X-ray holograms with a high degree of generative diversity
and quality. To pave the ground for the construction of cWavelet Flow, we first reproduce the
architecture and part of the experimental results of Wavelet Flow [2] based on PyTorch and
then extend it as cWavelet Flow by attaching an additional conditioning network on top of it.
The conditioning network, which consists of an optional pre-trained backbone network and a
head network, is constructed as an exceptionally lightweight yet performant structure. Such an
architectural design allows cWavelet Flow to directly model the conditional data distribution
of high resolution up to 1024 × 1024, which is almost impossible with the flow-based models
developed previously. Furthermore, another appealing point of cWavelet Flow is its highly
efficient training process. In comparison to other state-of-the-art baseline models like cINN
and U-Net, an improvement of up to 11.5× and 126.2× fewer FLOPs are achieved, respectively,
while maintaining reconstruction quality comparable to these baseline models.

  • Diploma thesis
    TU Dresden, 2023

Permalink: https://www.hzdr.de/publications/Publ-37584
Publ.-Id: 37584


Efficiency-Optimized Setup for Low Grade Waste Heat Harvesting with Shape Memory Alloys

Neumann, B.; Fähler, S.

More than half of all energy converted by humankind is lost in the form of waste heat. Not only
does that strongly contribute to the acceleration of global warming [1], it also leaves an enormous
economic potential untouched. However, suitable technologies are limited [2], since most
of this heat is of low temperature (< 100 °C) [3] and low grade. In the last years, materials and
technologies for thermoelectric harvesting and thermomagnetic harvesting have been explored,
but reaching a high efficiency of those systems remains a challenge. With our work, we present
a thermoelastic harvesting approach for converting the waste heat of a fluid into electricity,
utilizing Nickel-Titanium wires. The inherent advantage of a higher material efficiency than
thermoelectrics [4,5], together with the possibility to adapt the wires to the desired temperature
range via alloying and prestrain, and the commercial availability of the material makes NiTi a
solid candidate for a waste heat harvesting system. The core structure of our harvesting system
is a newly developed design for a fluid chamber. With the use of coupled FEM-Simulations we
optimized the heat exchange process between a thermal fluid and the wire and therefore maximized
the thermodynamic efficiency of the thermal energy to mechanical energy conversion
(32 % of Carnot). In this work, we show our approach in optimizing the heat exchange between
the fluid and the wire and the influence of parameters, like preload and waste heat temperature,
on the efficiency of the system.

  • Invited lecture (Conferences)
    Bochumer Kolloquium für Martensitische Transformationen, 28.-29.09.2023, Bochum, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37583
Publ.-Id: 37583


A strain-controlled magnetostrictive pseudo spin valve

Iurchuk, V.; Bran, J.; Acosta, M.; Kundys, B.

Electric-field control of magnetism via an inverse magnetostrictive effect is an alternative path toward improving energy-efficient storage and sensing devices based on a giant magnetoresistance effect. In this Letter, we report on lateral electric-field driven strain-mediated modulation of magnetotransport properties in a Co/Cu/Py pseudo spin valve grown on a ferroelectric 0.7Pb[Mg1/3Nb2/3]O3–0.3PbTiO3 substrate. We show a decrease in the giant magnetoresistance ratio of the pseudo spin valve with the increase in the electric field, which is attributed to the deviation of the Co layer magnetization from the initial direction due to strain-induced magnetoelastic anisotropy contribution. Additionally, we demonstrate that strain-induced magnetic anisotropy effectively shifts the switching field of the magnetostrictive Co layer, while keeping the switching field of the nearly zero-magnetostrictive Py layer unaffected due to its negligible magnetostriction. We argue that magnetostrictively optimized magnetic films in properly engineered multilayered structures can offer a path to enhancing the selective magnetic switching in spintronic devices.

Keywords: Inverse magnetostrictive effect; Magnetoresistance; Ferroelectric materials; Magnetic anisotropy; Pseudo spin valve; Spintronics

Permalink: https://www.hzdr.de/publications/Publ-37582
Publ.-Id: 37582


Kidnapping Deep Learning-based Multirotors using Optimized Flying Adversarial Patches

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

Autonomous flying robots, such as multirotors, often rely on deep learning models that makes predictions based on a camera image, e.g. for pose estimation. These models can predict surprising results if applied to input images outside the training domain. This fault can be exploited by adversarial attacks, for example, by computing small images, so-called adversarial patches, that can be placed in the environment to manipulate the neural network's prediction. We introduce flying adversarial patches, where multiple images are mounted on at least one other flying robot and therefore can be placed anywhere in the field of view of a victim multirotor. By introducing the attacker robots, the system is extended to an adversarial multi-robot system. For an effective attack, we compare three methods that simultaneously optimize multiple adversarial patches and their position in the input image. We show that our methods scale well with the number of adversarial patches. Moreover, we demonstrate physical flights with two robots, where we employ a novel attack policy that uses the computed adversarial patches to kidnap a robot that was supposed to follow a human.

Keywords: Multi-Robot Systems; Deep Learning; Adversarial Attacks; Security

  • Open Access Logo Contribution to proceedings
    International Symposium on Multi-Robot & Multi-Agent Systems (MRS), 04.-05.12.2023, Boston, United States of America
    2023 International Symposium on Multi-Robot and Multi-Agent Systems (MRS), Boston, MA, USA: IEEE, 979-8-3503-7076-8, 78-84
    DOI: 10.1109/MRS60187.2023.10416782

Permalink: https://www.hzdr.de/publications/Publ-37581
Publ.-Id: 37581


Methods gold standard in clinic millifluidics multiplexed extended gate field-effect transistor biosensor with gold nanoantennae as signal amplifiers

Janićijević, Ž.; Nguyen Le, T. A.; Alsadig, A.; Cela, I.; Zilenaite, R.; Tonmoy, T. H.; Kubeil, M.; Bachmann, M.; Baraban, L.

We present a portable multiplexed biosensor platform based on the extended gate field-effect transistor and demonstrate its amplified response thanks to gold nanoparticle-based bioconjugates introduced as a part of the immunoassay. The platform comprises a disposable chip hosting an array of 32 extended gate electrodes, a readout module based on a single transistor operating in constant charge mode, and a multiplexer to scan sensing electrodes one-by-one. Although employing only off-the-shelf electronic components, our platform achieves sensitivities comparable to fully customized nanofabricated potentiometric sensors. In particular, it reaches a detection limit of 0.2 fM for the pure molecular assay when sensing horseradish peroxidase-linked secondary antibody (∼0.4 nM reached by standard microplate methods). Furthermore, with the gold nanoparticle bioconjugation format, we demonstrate ca. 5-fold amplification of the potentiometric response compared to a pure molecular assay, at the detection limit of 13.3 fM. Finally, we elaborate on the mechanism of this amplification and propose that nanoparticle-mediated disruption of the diffusion barrier layer is the main contributor to the potentiometric signal enhancement. These results show the great potential of our portable, sensitive, and cost-efficient biosensor for multidimensional diagnostics in the clinical and laboratory settings, including e.g., serological tests or pathogen screening.

Keywords: Extended gate field-effect transistor; Multiplexing; Immunosensor; Gold nanoparticle bioconjugates; Potentiometric response; Electrochemical impedance spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-37580
Publ.-Id: 37580


SPP2045 - Multidimensional separation of ultrafine particles using a mechanical flotation cell combined with froth fractionation - MultiDimFlot

Sygusch, J.; Rudolph, M.

Froth flotation is one of the most important techniques in the mining industry to efficiently separate particles with sizes between 10 μm and 200 μm. The particles are separated according to their difference in wettability, as hydrophobic particles attach to gas bubbles and are recovered in a froth, whereas hydrophilic particles tend to stay in the pulp. Although, the wettability is the most prominent separation feature, other particle properties, such as size, morphology, surface energy or the dispersion state also affect the separation process since it includes a number of complex micro processes with specific particle-bubble interactions that occur in the pulp and in the froth phase. Low ore grades and very fine composite particles in electronic devices are forcing the industry to adapt and improve existing flotation techniques to the processing of ultrafine particles (< 10 μm), as the material needs to be milled down to finer size fractions to obtain sufficient liberation of the valuable minerals. For that reason, the project “MultiDimFlot”, which is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart”, investigates the separation of ultrafine particles (< 10 μm) based on multiple particle properties. A novel separation apparatus is used that combines the advantages of a mechanical flotation cell that comes with a high particle-bubble collision rate (thus a high recovery) with those from a flotation column with a fractionating effect due to its deep froth (thus a high grade). A well-characterised model particle system, consisting of glass spheres and glass fragments as the floatable fraction and magnetite as the non-floatable fraction is used for the separation tests. These investigations will help to further understand the behaviour of ultrafine particles during flotation and how certain particle properties affect the separation process. Furthermore, the possibilities and limitations of different analysis techniques, e.g. coupled SEM-EDX, flow cytometry or inverse gas chromatography are investigated for their use in ultrafine particle characterization.

Keywords: Ultrafine particles; Multidimensional separation; Flotation; Partition Curves

  • Poster
    PARTEC 2023: International Congress on Particle Technology, 26.-28.09.2023, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37579
Publ.-Id: 37579


The influence of the particle properties of size, shape and surface energy on the separation of ultrafine particles via froth flotation using multidimensional tromp maps for evaluation

Sygusch, J.; Rudolph, M.

Froth flotation is one of the most important beneficiation techniques in the mining industry. For particles with sizes ranging from 10 μm to 200 μm it efficiently separates the valuable minerals from unwanted gangue according to their differences in the particle wettabilities. For an efficient flotation separation of ultrafine particles (< 10 μm) existing techniques need to be adapted and improved in order to maintain an efficient separation. Furthermore, there is a potential in separating particles not only by wettability (surface energy) and size but also by their morphology. To investigate this is the aim of this project, which is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart”. A well-characterised model particle system consisting of ultrafine size fractions of glass particles as the floatable and magnetite as the non-floatable fraction is used for this study. The wettability of the glass particles is modified via an esterification reaction using alcohols with differing chain length and the resulting wettability states are analysed using inverse gas chromatography as well as analytic particle solvent extraction. Information on the particle size and shape are obtained via a combination of laser diffraction and microscopic analysis. All separation tests are carried out in batch mode using a novel separation apparatus, specifically designed for the flotation of ultrafine particles by combining advantages from machine-type froth flotation and column flotation and the separation process is evaluated using multidimensional tromp maps. This investigation will help to further understand the recovery of particles with variable properties in flotation, as well as other separation processes. In this way, the separation of ultrafine particles will become more efficient, which will play an important role in the recycling of secondary materials and in the processing of ultrafine particles in the chemical industry.

Keywords: Ultrafine particles; Multidimensional separation; Flotation; Particle Characterization; Partition curves

  • Lecture (Conference)
    PARTEC 2023: International Congress on Particle Technology, 26.-28.09.2023, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37578
Publ.-Id: 37578


Recycling of spheroidized graphite from spent lithium ion batteries

Sygusch, J.; Vanderbruggen, A.; Rudolph, M.

Presentation on the recycling of graphite from spent lithium ion batteries, including the characterization of surface properties that are important for the separation process of flotation, by which the graphite is separated effectively from the remaining metal oxides.

Keywords: Lithium ion battery; Recycling; Graphite; Cathode active materials; Wettability

  • Lecture (Conference)
    NanoCarbon Annual Conference 2023, 14.03.2023, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37577
Publ.-Id: 37577


Battery Electrode Active Materials Characterization

Sygusch, J.; Vanderbruggen, A.; Rudolph, M.

Presentation about Li-ion battery characterization with a focus on the characterization of the anode and cathode active materials using different techniques such as inverse gas chromatography, dynamic vapour sorption, contact angle measurement.

Keywords: Battery materials; Characterization; Inverse gas chromatography; Wettability; Graphite; Cathode active materials

  • Lecture (others) (Online presentation)
    Online Webinar, 09.02.2023, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-37576
Publ.-Id: 37576


Immunotheranostic target modules for imaging and navigation of UniCAR T-cells to strike FAP-expressing cells and the tumor microenvironment

Rodrigues Loureiro, L. R.; Hoffmann, L.; Neuber, C.; Rupp, L.; Arndt, C.; Kegler, A.; Kubeil, M.; Hagemeyer, C. E.; Stephan, H.; Schmitz, M.; Feldmann, A.; Bachmann, M.

Background: Chimeric antigen receptor (CAR) T-cells are a promising approach in cancer immunotherapy, particularly for treating hematologic malignancies. Yet, their effectiveness is limited when tackling solid tumors, where immune cell infiltration and immunosuppressive tumor microenvironments (TME) are major hurdles. Fibroblast activation protein (FAP) is highly expressed on cancer-associated fibroblasts (CAFs) and various tumor cells, playing an important role in tumor growth and immunosuppression. Aiming to modulate the TME with increased clinical safety and effectiveness, we developed novel small and size-extended immunotheranostic UniCAR target modules (TMs) targeting FAP.
Methods: The specific binding and functionality of the anti-FAP-scFv TM and the size extended anti-FAP-IgG4 TM were assessed using 2D and 3D in vitro models as well as in vivo. Their specific tumor accumulation and diagnostic potential was evaluated using PET studies after functionalization with a chelator and suitable radionuclide.
Results: The anti-FAP-scFv and -IgG4 TMs effectively and specifically redirected UniCAR T-cells using 2D, 3D, and in vivo models. Moreover, a remarkably high and specific accumulation of radiolabeled FAP-targeting TMs at the tumor site of xenograft mouse models was observed.
Conclusions: These findings demonstrate that the novel anti-FAP TMs are promising immunotheranostic tools to foster cancer imaging and treatment, paving the way for a more convenient, individualized, and safer treatment of cancer patients.

Keywords: Cancer Immunotherapy; UniCAR T-cells; Fibroblast Activation Protein (FAP); Tumor Microenvironment (TME); 3D in vitro Models; Immunotheranostic Target Modules (TMs)

Permalink: https://www.hzdr.de/publications/Publ-37575
Publ.-Id: 37575


Examining the Nonlinear Response of Quantum Electrons with the Assistance of Wigner Distribution Function

Moldabekov, Z.

Examining the Nonlinear Response of Quantum Electrons with the Assistance of Wigner Distribution Function

Zhandos Moldabekov

z.moldabekov@hzdr.de

Center of Advanced Systems Understanding at Helmholtz-Zentrum Dresden-Rossendorf, Germany

A linear response of quantum electrons is well studied and for that well developed theoretical and computational methods computing the linear response properties are available. However, recent introduction of THz lasers and the novel seeding technique to reach high intensities [1] allow us to generate nonlinear response of quantum electrons in extended systems. Therefore, in this talk the results will be presented for the non-linear density response of quantum electrons and the applicability of various approximations and methods for extended systems will be discussed [3-5]. The utility of the quantum Wigner distribution function for the analytic solution of the non-linear response problem of arbitrary order will be presented [5].

[1] B.K. Ofori-Okai, et al., J. Inst13, P06014 (2018).
[2] T Kluge, et al., Phys. Rev. X 8, 031068 (2018).
[3] Z. Moldabekov, Jan Vorberger, and Tobias Dornheim, Journal of Chemical Theory and Computation 18, 2900–2912 (2022).
[4] T.Dornheim, M. Boehme, Z. Moldabekov, J. Vorberger, and M. Bonitz, Phys. Rev. Research 3, 033231 (2021).
[5] P. Tolias, T. Dornheim, Z. Moldabekov, and J. Vorberger, EPL 142 , 44001 (2023).

Keywords: linear-response time-dependent density functional theory; non-linear density response; quantum Wigner distribution

  • Open Access Logo Invited lecture (Conferences)
    Wigner 121 Scientific Symposium, 18.-20.09.2023, Budapest, Hungary

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Permalink: https://www.hzdr.de/publications/Publ-37573
Publ.-Id: 37573


Lossless and Lossy Compression for Photon Science

Felicita, G.; Steinbach, P.

High bandwidth instruments (data production rates of GB/s) have proliferated in photon science experimental facilities in the last years across the globe. Some of them are planned to be operated 24/7. Data volumes thus produced exceed both the budget of storage facilities and sometimes even the ingest capacities of hardware. In this talk, I'd like to highlight key challenges when considering both lossless and lossy compression in photon science. I will highlight data science approaches to characterize or preprocess data. The talk will also showcase advances in finding optimal encoding parameters to achieve high data ingest bandwidths at high compression ratios. In addition, I'd like to introduce challenges for lossy compression with respect to good scientific practice and our advances to mitigate them without regressing to data quality metrics.

The presentation was given at the 2023 European HDF User Group (HUG) plugins and data compression summit. For more information on the event, see https://indico.desy.de/event/39343/

Keywords: lossy; lossless; compression; machine learning; photon science

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    2023 European HDF User Group (HUG) plugins and data compression summit, 19.-21.09.2023, Hamburg, Germany
    DOI: 10.6084/m9.figshare.24173937.v1

Permalink: https://www.hzdr.de/publications/Publ-37572
Publ.-Id: 37572


Ab initio insights on the ultrafast strong-field dynamics of anatase TiO2

Suma Balakrishnan, S. L.; Lokamani, M.; Ramakrishna, K.; Cangi, A.; Murali, D.; Posselt, M.; Assa Aravindh, S.

Electron dynamics of anatase TiO2 under the influence of ultrashort and intense laser field is studied using the real-time time-dependent density functional theory (TDDFT). Our findings demonstrate the effectiveness of TDDFT calculations in modeling the electron dynamics of solids during ultrashort laser excitation, providing valuable insights for designing and optimizing nonlinear photonic devices. We analyze the perturbative and non-perturbative responses of TiO2 to 30 fs laser pulses at 400 and 800 nm wavelengths, elucidating the underlying mechanisms. At 400 nm, ionization via single photon absorption dominates, even at very low intensities. At 800 nm, we observe ionization through two-photon absorption within the intensity range of 1×1010 to 9×1012 W/cm2, with a transition from multiphoton to tunneling ionization occurring at 9×1012 W/cm2. We observe a sudden increase in energy and the number of excited electrons beyond 1×1013 W/cm2, leading to their saturation and subsequent laser-induced damage. We estimate the damage threshold of TiO2 for 800 nm to be 0.1 J/cm2. In the perturbative regime, induced currents exhibit a phase shift proportional to the peak intensity of the laser pulse. This phase shift is attributed to the intensity-dependent changes in the number of free carriers, indicative of the optical Kerr effect. Leveraging the linear dependence of phase shift on peak intensities, we estimate the nonlinear refractive index (n2) of TiO2 to be 3.54×10−11 cm2/W.

Keywords: Density functional theory; Electron dynamics; Quantum systems; Thin films

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Permalink: https://www.hzdr.de/publications/Publ-37571
Publ.-Id: 37571


Principles of ASL: Research and Clinical Applications

Petr, J.

Practical 30min guide into ASL basics and its use in clinics and clinical research with focus given on the most important guidelines for practical use.

  • Invited lecture (Conferences) (Online presentation)
    First ISMRM African Chapter Conference, 20.09.2023, Accra, Ghana

Permalink: https://www.hzdr.de/publications/Publ-37570
Publ.-Id: 37570


Bacterial filamentation mediates cross-protection against β-lactam antibiotics in droplet microreactors

Zhao, X.; Ruelens, P.; Farr, A. D.; de Visser, J. A. G. M.; Baraban, L.

Bacterial strains that are resistant to antibiotics may protect not only themselves, but also sensitive bacteria nearby if resistance involves antibiotic degradation. Such cross-protection poses a challenge to effective antibiotic therapy by enhancing the long-term survival of bacterial infections. In this study, we utilize an automated nanoliter droplet analyzer to study the interactions between Escherichia coli strains expressing a β-lactamase (resistant) and those not expressing it (sensitive) when exposed to the β-lactam antibiotic cefotaxime (CTX), with the aim to define criteria contributing to cross-protection. We observed a cross-protection window of CTX concentrations for the sensitive strain, extending up to approximately 100 times its minimal inhibitory concentration (MIC). Through both microscopy and enzyme activity analyses, we demonstrate that filamentation of bacterial cells, triggered by antibiotic stress contributes to cross-protection through increased extracellular β-lactamase activity, resulting from cell lysis and/or β-lactamase leakage due to greater cell wall permeability. The antibiotic concentration window for cross-protection depends on the difference in β-lactamase activity between co-cultured strains: larger differences shift the ‘cross-protection window’ towards higher CTX concentrations. Our findings highlight the crucial role of bacterial filamentation in community-wide antibiotic resistance and emphasize the need for intervention therapies that consider -and potentially suppress- filamentation

Keywords: Droplet-based microreactors; Bacterial cross-protection; β-lactam antibiotics; Antibiotic resistance

Permalink: https://www.hzdr.de/publications/Publ-37569
Publ.-Id: 37569


Data publication: Unravelling the water adsorption mechanism in hierarchical MOFs: insights from in situ positron annihilation lifetime studies

Attallah, A. G.; Bon, V.; Maity, K.; Hirschmann, E.; Butterling, M.; Wagner, A.; Kaskel, S.

Positron lifetime data for in situ humidity measurements

Keywords: MOFs; DUT-67; positron annihilation lifetime spectroscopy; sorption mechanism; water harvesting

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Permalink: https://www.hzdr.de/publications/Publ-37568
Publ.-Id: 37568


Unravelling the water adsorption mechanism in hierarchical MOFs: insights from in situ positron annihilation lifetime studies

Attallah, A. G.; Bon, V.; Maity, K.; Hirschmann, E.; Butterling, M.; Wagner, A.; Kaskel, S.

Atmospheric water harvesting with metal-organic frameworks (MOFs) is a new technology
providing clean, long-term water supply in arid areas. In situ positron annihilation lifetime
spectroscopy (PALS) is proposed as a valid methodology for mechanistic understanding of water
sorption in MOFs and the selection of prospective candidates for desired applications. DUT-67-Zr
and DUT-67-Hf frameworks are used as model systems for method validation because of their
hierarchical pore structure, high adsorption capacity and chemical stability. Both frameworks are
characterized using complementary techniques such as nitrogen (77 K) and water vapour (298 K)
physisorption, SEM, and PXRD. DUT-67-Zr and DUT-67-Hf are investigated by PALS upon
exposure to humidity for the first time, demonstrating the stepwise pore filling mechanism by
water molecules for both MOFs. In addition to exploring the potential of PALS as a tool for
probing MOFs during in situ water loading, this work offers perspectives on the design and use of
MOFs for water harvesting.

Keywords: MOFs; DUT-67; positron annihilation lifetime spectroscopy; sorption mechanism; water harvesting

Related publications

Permalink: https://www.hzdr.de/publications/Publ-37567
Publ.-Id: 37567


The influence of adjustable parameters based on VOF method on the computational accuracy and cost of bubble coalescence process

Zhou, P.; Jiang, Y.; Liao, Y.; Li, J.

Bubble coalescence affects the interphase heat and mass transfer by changing the interfacial area of gas and liquid phases. The coalescence time and liquid film thickness are important physical parameters to describe the bubble coalescence process. When simulating the bubble coalescence with volume of fluid(VOF) method, reasonable settings of adjustable parameters(such as mesh size, maximum Courant number and equation cycle
times, etc.) can improve the convergence of the solution and save the computational time. The aim of this paper is to investigate the coalescence process of two coaxial bubbles combining the VOF method with the adaptive mesh refinement technology based on OpenFOAM. The influence of the maximum Courant number Comax, the cycle times of phase equation nα and the cycle times of governing equation npimple on the computational efficiency and accuracy of numerical simulation of bubble coalescence process was explored. Meanwhile, the time evolution of the liquid film thickness among bubbles was obtained for different adjustable parameters. The results show that the thinning speed of the liquid film between two bubbles is proportional to nα and npimple, while is inversely proportional to Comax. This is because the computational accuracy is promoted by the decrease of Comax and the increase of nα and npimple. The transport lag of the fluid on the grid element is therefore improved, and the bubble coalescence and liquid film thinning is accelerated. Considering the computational accuracy and cost, a set of better adjustable parameters for simulating bubble coalescence with VOF method is obtained, i. e., (Comax, nα,npimple)=(0.05, 3, 8).

Keywords: OpenFOAM; Bubble coalescence; VOF method; Adaptive mesh refinement; Adjustable parameters; Computational accuracy; Computational cost

Permalink: https://www.hzdr.de/publications/Publ-37566
Publ.-Id: 37566


Combination of tumor asphericity and an extracellular matrix-related prognostic gene signature in non-small cell lung cancer patients

Zschaeck, S.; Klinger, B.; van den Hoff, J.; Cegla, P.; Apostolova, I.; Kreissl, M.; Cholewiński, W.; Kukuk, E.; Strobel, H.; Amthauer, H.; Blüthgen, N.; Zips, D.; Hofheinz, F.

The aim of this retrospective multicenter study was an independent validation of a gene expression signature ECM-related prognostic and predictive indicator (EPPI) and the novel positron emission tomography (PET) parameter tumor asphericity (ASP) in non-small cell lung cancer (NSCLC) patients. The whole cohort comprised 253 NSCLC patients, all treated with surgery. Clinical and PET parameters were available for all patients, additional gene expression data for 120 patients. Univariate and multivariate Cox regression and Kaplan-Meier analyses were calculated for progression-free survival (PFS).
A significant association with PFS was observed for ASP (p < 0.001) and EPPI (p = 0.012). Upon multivariate testing, ASP was significantly associated with PFS (p = 0.012), and EPPI (p = 0.018) in patients with additional gene data. In stage II patients, ASP was significantly associated with PFS (p = 0.009) and a previously published cutoff value for ASP (19.5%) was successfully validated (p = 0.008). EPPI showed a significant association with PFS in stage II patients, too (p = 0.033). Exploratory combination of ASP and EPPI showed potentially improved stratification.
We report the first successful validation of EPPI and ASP in stage II NSCLC patients, combination of both parameters seems encouraging.

Keywords: Non small cell lung cancer; fluorodeoxyglucose positron emission tomography; tumor asphericity; extracellular matrix-related prognostic gene signature; gene expression; quantitative PET data

Permalink: https://www.hzdr.de/publications/Publ-37565
Publ.-Id: 37565


A Pion-Production Target for Mu2e-II: Design and Prototype

Neuffer, D.; Fang, I.; Liu, A.; Lynch, K.; Müller, S.; Pronskikh, V.; Popp, J.; Pushka, D.

The higher beam intensity available for Mu2e-II will require a substantially different target design. This paper discusses our recent advances in conceptual R&D for a Mu2e-II target station. The design is based on energy deposition and radiation damage simulations, as well as thermal and mechanical analyses, to estimate the survivability of the system. We considered rotated targets, fixed granular targets and a novel conveyor target with tungsten or carbon spherical elements that are circulated through the beam path. The motion of the spheres can be generated either mechanically or both mechanically and by a He gas flow. The simulations identified the conveyor target as the preferred approach, and that approach has been developed into a prototype. We describe this first prototype for the Mu2e-II target and report on its mechanical tests performed at Fermilab, which indicate the feasibility of the design, and discuss its challenges as well as suggest directions for further improvement.

Keywords: muons; production target; lepton flavor violation; Mu2e-II

  • Open Access Logo Contribution to proceedings
    23rd International Workshop on Neutrinos from Accelerators, 30.-31.07.2022, Salt Lake City, UT, USA
    A Pion-Production Target for Mu2e-II: Design and Prototype
    DOI: 10.3390/psf2023008059

Permalink: https://www.hzdr.de/publications/Publ-37564
Publ.-Id: 37564


Time-resolved THz spectroscopy of single nanowires

Luferau, A.; Dimakis, E.; Pashkin, O.; Winnerl, S.; Helm, M.

We present two types of pump-probe spectroscopy on single core-shell III-V nanowires: while the pump is either interband or intraband, a broad-band mid-infrared beam is used as probe. This provides interesting insight into carrier heating and relaxation.

Keywords: nanowires; terahertz; free electron laser; microscopy; SNOM

Related publications

  • Invited lecture (Conferences)
    10th International Symposium on Terahertz-Related Devices and Technologies (TeraTech 2023), 04.-08.09.2023, Aizu-Wakamatsu, Japan

Permalink: https://www.hzdr.de/publications/Publ-37563
Publ.-Id: 37563


A regional assessment of the deglaciation history of the Swiss Plateau based on newly obtained and re-evaluated Be-10 cosmic-ray exposure ages

Martin Hofmann, F.; Groos, A. R.; Garcia Morabito, E.; Struck, J.; Gnägi, C.; Scharf, A.; Rugel, G.; Merchel, S.; Zech, R.

During marine oxygen isotope stage (MIS) 2, the Swiss Plateau temporarily hosted large piedmont lobe glaciers that retreated after their maximum advance back to the fringe of the Alps. The presence of moraines in this region indicates that overall glacier recession was punctuated by repeated phases of ice-marginal stability and re-advances. The timing of these events in the region formerly covered by the eastern lobe of the Rhône (or Valais) glacier has been controversial but remains poorly constrained due to the lack of chronological data. To fill this gap, 10Be cosmic-ray exposure (CRE) dating was applied to erratic boulders inside the assumed MIS 2 maximum extent of this piedmont lobe. Erratic boulders close to the suspected MIS 2 maximum extent gave unrealistically young CRE ages. Erratic boulders at a presumably younger ice-marginal position (Brästenberg position) yielded an average age of ~19 ka, consistent with recalibrated basal radiocarbon ages from lakes and recomputed radiocarbon ages from large Late Pleistocene mammals buried in glacio-fluvial deposits. However, several erratic boulders beyond the Brästenberg position gave internally consistent, but stratigraphically too young ages of ~17 ka. We cannot rule out that glacier recession from the Brästenberg position began no later than ~17 ka. CRE dating of a moraine of a presumably younger ice-marginal position (Solothurn position) gave unrealistically old ages and an incredibly young age (86 ka, 41 ka, and 4 ka). 14C CRE dating should be applied to check whether the boulders associated with the Solothurn and Brästenberg positions were previously exposed to cosmicradiation. Nevertheless, despite outlying ages, the presented chronological data contribute to an overall consistent and increasingly refined chronology of the last deglaciation of the Swiss Plateau when compared with 59 previously published CRE ages.

Keywords: terrestrial in situ cosmogenic nuclides; exposure dating; moraine; erratic boulder; Swiss Plateau; deglaciation; glacier reconstruction

Related publications

Permalink: https://www.hzdr.de/publications/Publ-37562
Publ.-Id: 37562


Dynamic system modeling and simulation of a power-to-methanol process based on proton-conducting tubular solid oxide cells

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

The importance of methanol as a basic building block of the chemical industry and as a means of chemical energy storage of renewable energy sources (e.g. wind & PV) will steadily increase in the upcoming years. Based on renewable electricity and through the coupling of a proton-conducting steam electrolyzer for the generation of pure H2 with a heterogeneously catalyzed direct synthesis of methanol from anthropogenic CO2, an attractive method for the production of methanol can be provided. To enable an efficient and economic application of these so-called power-to-methanol processes, high system efficiencies as well as suitable concepts for system control as well as system and heat integration for alternating operating conditions are of particular importance. In this work, a transient and real-time capable system model of a power-to-methanol process based on tubular proton-conducting high temperature electrolyzers is presented. The obtained stationary simulation results reveal beneficial operational windows and system efficiencies (0.488 to 0.617) with respect to the chosen process design and heat integration concept. The power-to-methanol process model also incorporates a multitude of feedback control loops or controllers, to manipulate relevant operating parameters of all employed sub-processes in case of fluctuating power inputs. The presented studies assess the transient responses of the modeled power-to-methanol system to defined step changes of the apparent cell voltage under negative feedback control of crucial operational parameters.

Keywords: Dynamic model; Power-to-methanol; SOEC; Renewable methanol; Energy storage; System control

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  • Secondary publication expected from 14.12.2024

Permalink: https://www.hzdr.de/publications/Publ-37561
Publ.-Id: 37561


DEveloping BBB-ASL as non-Invasive Early biomarker of Alzheimer’s Disease (DEBBIE-AD): Study design

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

Introduction: Loss of blood-brain barrier (BBB) integrity is hypothesized to be one of the earliest microvascular signs of Alzheimer’s disease (AD). Arterial spin labeling (ASL) perfusion MRI has recently been adapted to map the BBB permeability non-invasively. This article outlines the study design of the DEveloping BBB-ASL as a non-Invasive Early biomarker (DEBBIE) consortium, focused on investigating the potential of BBB-ASL as an early biomarker for AD (DEBBIE-AD).
Methods: DEBBIE-AD consists of 13 cohorts enrolling participants from subjective cognitive decline to AD, as well as healthy controls across the lifespan. The reproducibility and accuracy of BBB-ASL will be evaluated in healthy participants, and its clinical value will be evaluated with both established and novel AD biomarkers.
Expected endpoints: DEBBIE-AD aims to provide evidence on the ability of BBB-ASL to measure BBB permeability and demonstrate its utility in AD-related pathologies, which may provide new targets for treatment.

  • Poster
    VasCog 2023 - The 14th International Conference of The International Society of Vascular Behavioural and Congnitive Disorders, 13.09.2023, Goteborg, Sweden

Permalink: https://www.hzdr.de/publications/Publ-37560
Publ.-Id: 37560


Scalable Atomic Arrays for Spin-Based Quantum Computers in Silicon

Jakob, A. M.; Robson, S. G.; Firgau, H. R.; Mourik, V.; Schmitt, V.; Holmes, D.; Posselt, M.; Mayes, E. L. H.; Speemann, D.; Morello, A.; Jamieson, D. N.

Semiconductor spin qubits combine excellent quantum performance with the prospect of manufacturing quantum devices using industry-standard metal-oxide-semiconductor (MOS) processes. This applies also to ion-implanted donor spins, which further afford exceptional coherence times and large Hilbert space dimension in their nuclear spin. Here we demonstrate and integrate multiple strategies to manufacture scale-up donor-based quantum computers. We use 31PF2 molecule implants to triple the placement certainty compared to 31P ions, while attaining 99.99% confidence in detecting the implant. Similar confidence is retained by implanting heavier atoms such as 123Sb and 209Bi, which represent high-dimensional qudits for quantum information processing, while Sb2 molecules enable deterministic formation of closely-spaced qudits. We demonstrate the deterministic formation of regular arrays of donor atoms with 300 nm spacing, using step-and-repeat implantation through a nano aperture. These methods cover the full gamut of technological requirements for the construction of donor-based quantum computers in silicon.

Keywords: spin qubits in Si; atomic arrays; single ion implantation; high confidence in detecting the implant; Sb Bi PF2 implants

Permalink: https://www.hzdr.de/publications/Publ-37559
Publ.-Id: 37559


EOSC Task Force on Infrastructure for Quality Research Software: Research Software Lifecycle

Konrad, U.; Courbebaisse, G.; Flemisch, B.; Graf, K.; Maassen, J.; Ritz, R.

Software developed in the process of doing research is receiving increased attention. It is now more and more often considered a genuine research output next to scientific articles and research data publications. Based on representative user stories we identify and characterize the different phases and stages that the research software development process can go through thereby defining the “Research Software Lifecycle”. Different approaches to software development such as product-, project- or platform-orientation are also outlined. We close with recommendations on EOSC infrastructure components needed to support the identified processes and platforms.

Keywords: Software; EOSC; European Open Science Cloud; Research; Quality; Development

Permalink: https://www.hzdr.de/publications/Publ-37558
Publ.-Id: 37558


EOSC Task Force on Infrastructure for Quality Research Software: Research Software Lifecycle

Konrad, U.; Courbebaisse, G.; Flemisch, B.; Graf, K.; Maassen, J.; Ritz, R.

Software developed in the process of doing research is receiving increased attention. It is now more and more often considered a genuine research output next to scientific articles and research data publications. Based on representative user stories we identify and characterize the different phases and stages that the research software development process can go through thereby defining the “Research Software Lifecycle”. Different approaches to software development such as product-, project- or platform-orientation are also outlined. We close with recommendations on EOSC infrastructure components needed to support the identified processes and platforms.

Keywords: Software; EOSC; European Open Science Cloud; Research; Quality; Development

Permalink: https://www.hzdr.de/publications/Publ-37557
Publ.-Id: 37557


Multi-objective optimization of fractal-tree microchannels in a rectangular heat sink by a distributed-adaptive genetic algorithm

Yu, F.; Ding, W.; Luo, X.; He, B.; Hampel, U.

Recently, an innovative heat dissipation technique of fractal-tree structures has attracted attention due to its excellent high heat transfer efficiency and low pumping power. Though the impact of geometrical parameters such as branching level and dimension ratios of successive branches on the heat transfer efficiency and pumping power are considered to be critical, the impact mechanisms are still not well studied and formulated. Hence, there is still no clear method to optimally arrange the fractal-tree microchannels (FTMCs) in a rectangular heat sink to achieve better thermal and hydraulic performance. Therefore, we developed a multi-objective optimization algorithm (distributed-adaptive genetic algorithm, DAGA) to optimize the different types of novel FTMCs concerning achieving an optimal COP (coefficient of performance, heat transfer/ pumping power). The developed DAGA can improve the computational efficiency and the quality of solutions by around 87.63% and 12.48% respectively in present work. Then, taking conventional rectangular parallel microchannels (RPMCs) as a reference, the COP of the optimized FTMCs in the same heat sink shows an enhancement of around 0.09 ~ 0.57. The highest COP is achieved by the three-level branching FTMC. Furthermore, the optimized results reveal that branching level, bifurcation number, and microchannel width at the first branching level are sensible, while dimension ratio factors and microchannel length at the first branching level show low sensibility to the COP of FTMCs.

Keywords: Fractal-Tree Microchannel; Multi-Objective Optimization; Coefficient of Performance; Distributed-Adaptive Genetic Algorithm

Permalink: https://www.hzdr.de/publications/Publ-37556
Publ.-Id: 37556


Model code for: A novel, scenario-based approach to comparing non-pharmaceutical intervention strategies across nations

Schüler, L.; Wolf, G.; Fu, X.

This model code includes all scripts necessary  to reproduce the results of the publication "A novel, scenario-based approach to comparing non-pharmaceutical intervention strategies across nations".

Keywords: COVID-19; NPI; modelling; epidemiological; behavioural; macroeconomic

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Permalink: https://www.hzdr.de/publications/Publ-37554
Publ.-Id: 37554


Position Paper to facilitate patient access to radiopharmaceuticals - considerations for a suitable pharmaceutical regulatory framework

Korde, A.; Patt, M.; Selivanova, S.; Scott, A.; Hesselmann, R.; Kiß, O.; Ramamoorthy, N.; Todde, S.; Rubow, S.; Gwaza, L.; Lyashchenko, S.; Andersson, J.; Hockley, B.; Kaslival, R.; Decristoforo, C.

Nuclear medicine has made enormous progress in the past decades. However, there are still significant inequalities in patient access among different countries, which could be mitigated by a suitable pharmaceutical regulatory framework and associated guidelines. This paper summarizes major considerations for a suitable pharmaceutical regulatory framework to facilitate patient access to radiopharmaceuticals. These include the distinct characteristics of radiopharmaceuticals advocating dedicated regulations, the impact of variable complexity of radiopharmaceutical preparation, personnel requirements, manufacturing practices and quality assurance, regulatory authorities interfaces, communication and training, as well as marketing authorization procedures to ensure availability of radiopharmaceuticals. Finally domestic and regional supply to ensure patient access via alternative regulatory pathways, including in-house production of radiopharmaceuticals, is described and an outlook on regulatory challenges faced by new developments, such as the use of alpha emitters, is provided. All these considerations are an outcome of a dedicated Technical Meeting organized by the IAEA in 2023.

Keywords: Radiopharmaceutical; Regulations; Legislation; Regulatory framework; GMP; Marketing authorization

Permalink: https://www.hzdr.de/publications/Publ-37553
Publ.-Id: 37553


Establishment and Molecular Characterization of an In Vitro Model for PARPi-Resistant Ovarian Cancer.

Klotz, D. M.; Schwarz, F.; Dubrovska, A.; Schuster, K.; Theis, M.; Krüger, A.; Kutz, O.; Link, T.; Wimberger, P.; Drukewitz, S.; Buchholz, F.; Thomale, J.; Kuhlmann, J. D.

Overcoming PARPi resistance is a high clinical priority. We established and characterized comparative in vitro models of acquired PARPi resistance, derived from either a BRCA1-proficient or BRCA1-deficient isogenic background by long-term exposure to olaparib. While parental cell lines already exhibited a certain level of intrinsic activity of multidrug resistance (MDR) proteins, resulting PARPi-resistant cells from both models further converted toward MDR. In both models, the PARPi-resistant phenotype was shaped by (i) cross-resistance to other PARPis (ii) impaired susceptibility toward the formation of DNA-platinum adducts upon exposure to cisplatin, which could be reverted by the drug efflux inhibitors verapamil or diphenhydramine, and (iii) reduced PARP-trapping activity. However, the signature and activity of ABC-transporter expression and the cross-resistance spectra to other chemotherapeutic drugs considerably diverged between the BRCA1-proficient vs. BRCA1-deficient models. Using dual-fluorescence co-culture experiments, we observed that PARPi-resistant cells had a competitive disadvantage over PARPi-sensitive cells in a drug-free medium. However, they rapidly gained clonal dominance under olaparib selection pressure, which could be mitigated by the MRP1 inhibitor MK-751. Conclusively, we present a well-characterized in vitro model, which could be instrumental in dissecting mechanisms of PARPi resistance from HR-proficient vs. HR-deficient background and in studying clonal dynamics of PARPi-resistant cells in response to experimental drugs, such as novel olaparib-sensitizers.

Keywords: PARPi resistance; cisplatin; ovarian cancer

Permalink: https://www.hzdr.de/publications/Publ-37552
Publ.-Id: 37552


Ion-induced telecom single photon emitters in silicon

Astakhov, G.; Hollenbach, M.; Klingner, N.; Jagtap, N.; Bischoff, L.; Fowley, C.; Kentsch, U.; Hlawacek, G.; Erbe, A.; Abrosimov, N. V.; Helm, M.; Berencen, Y.

A review of single photon emitters in silicon based on ion-induced defects is provided. Fabrication methods and current state of the art are discussed.

Keywords: Telecom-wavelength single-photon sources; Color centers in silicon; Focused ion beam

Related publications

  • Invited lecture (Conferences)
    Workshop on Spin-Photon Interfaces for Quantum Communication, 01.09.2023, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-37551
Publ.-Id: 37551


Superstructure-dependent stability of DNA origami nanostructures in the presence of chaotropic denaturants

Hanke, M.; Dornbusch, D.; Tomm, E.; Grundmeier, G.; Fahmy, K.; Keller, A.

The structural stability of DNA origami nanostructures in various chemical environments is an important factor in numerous applications, ranging from biomedicine and biophysics to analytical chemistry and materials synthesis. In this work, the stability of six different 2D and 3D DNA origami nanostructures is assessed in the presence of three different chatropic salts, i.e., guanidinium sulfate (Gdm2SO4), guanidinium chloride (GdmCl), and tetrapropylammonium chloride (TPACl), which are widely employed denaturants. Using atomic force microscopy (AFM) to quantify nanostructural integrity, Gdm2SO4 is found to be the weakest and TPACl the strongest DNA origami denaturant, respectively. Despite different mechanisms of actions of the selected salts, DNA origami stability in each environment is observed to depend on DNA origami superstructure. This is especially pronounced for 3D DNA origami nanostructures, where mechanically more flexible designs show higher stability in both GdmCl and TPACl than more rigid ones. This is particularly remarkable as this general dependence has previously been observed under Mg2+-free conditions and may provide the possibility to optimize DNA origami design toward maximum stability in diverse chemical environments. Finally, it is demonstrated that melting temperature measurements may overestimate the stability of certain DNA origami nanostructures in certain chemical environments, so that such investigations should always be complemented by microscopic assessments of nanostructure integrity.

Keywords: circular dichroism; AFM; DNA melting; ionic interactions; DNA hydration

Permalink: https://www.hzdr.de/publications/Publ-37550
Publ.-Id: 37550


Strategic wafer-scale creation of telecom single-photon emitters in silicon for large-scale quantum photonic integrated circuits

Berencen, Y.

Indistinguishable single-photon sources at telecom wavelengths are the key photonic qubits for transmitting quantum information over long distances in standard optical fibers with minimal transmission losses and high fidelity. This enables secure quantum communication over the quantum internet and, in turn, a modular approach to quantum computing. The monolithic integration of single-photon sources with reconfigurable photonic elements and single-photon detectors in a silicon chip is a key enabling step toward demonstrating scalable quantum hardware such as quantum photonic integrated circuits (QPICs). Nowadays, nearly all the necessary components for QPICs are available such as superconducting single-photon detectors, low-loss photonic waveguides, delay lines, modulators, phase shifters, and low-latency electronics. Yet, the practical implementation of scalable quantum hardware has been largely hampered by the lack of on-chip single-photon emitters in silicon that can be created at desired locations on the nanoscale.
Here, we demonstrate two complementary wafer-scale protocols for the quasi-deterministic creation of single G and W telecom-wavelength color centers in silicon with a probability exceeding 50%. Both approaches are fully compatible with current silicon technology and enable the fabrication of single telecom quantum emitters at desired nanoscale positions on a silicon chip. These results unlock a clear and easily exploitable pathway for industrial-scale photonic quantum processors with technology nodes below 100 nm.

Keywords: Telecom-wavelength single-photon sources; Color centers in silicon; Focused ion beam

Related publications

  • Invited lecture (Conferences)
    2023 RAISIN – Roadmap for Applications of Implanted Single Impurities Network, 06.-08.09.2023, University of Surrey, Guildford, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-37549
Publ.-Id: 37549


HELPMI: HElmholtz Laser-Plasma Metadata Initiative

Bagnoud, V.; Bussmann, M.; Debus, A.; Hornung, J.; Kaluza, M.; Kessler, A.; Pöschel, F.; Schlenvoigt, H.-P.; Schramm, U.

HELPMI is a 2-year project, subsidized by the Helmholtz Metadata Collaboration, conducted by GSI, HI Jena and HZDR (lead). The aim is to start the development of a F.A.I.R. data standard for experimental data of the entire laser-plasma (LPA) community. Such standard does not yet exist. It will facilitate management and analysis of usually quite heterogeneous experimental data and logs by rich and machine-actionable metadata, allowing automated processing of broad and long data sets. To date, the LPA community is widely using openPMD, an open meta-standard, well-established for simulations. NeXus is a similarly hierarchical and extensible standard for various experimental methods of the Photon and Neutron science community. Within HELPMI, we plan to adopt NeXus for LPA experimental data and simultaneously to make openPMD and its API extensible for custom hierarchies like NeXus. Thereby we can achieve interoperability of the standards, circumventing the need for another standard. Alongside we will start developing a glossary of LPA experimental terms in order to achieve re-usability. The glossary shall be community-driven and technically open, extensible and implementation-independent.

Keywords: data standard; metadata; data management

  • Lecture (Conference)
    6th European Advanced Accelerator Concepts workshop, 18.-22.09.2023, La Biodola Bay, Isola d'Elba, Italy

Permalink: https://www.hzdr.de/publications/Publ-37547
Publ.-Id: 37547


Exploring the Potential of Nanogels: From Drug Carriers to Radiopharmaceutical Agents

Kubeil, M.; Suzuki, Y.; Casulli, M. A.; Kamal, R.; Hashimoto, T.; Bachmann, M.; Hayashita, T.; Stephan, H.

Nanogels open up access to a wide range of applications and offer among others hopeful approaches for use in the field of biomedicine. This review provides a brief overview of current developments of nanogels in general, particularly in the fields of drug delivery, therapeutic applications, tissue engineering and sensor systems. Specifically, cyclodextrin (CD)-based nanogels are important because they have exceptional complexation properties and are highly biocompatible. Nanogels as a whole and CD-based nanogels in particular can be customized in a wide range of sizes and equipped with a desired surface charge as well as containing additional molecules inside and outside, such as dyes, solubility-mediating groups or even biological vector molecules for pharmaceutical targeting. Currently, biological investigations are mainly carried out in vitro, but more and more in vivo applications are gaining importance. Modern molecular imaging methods are increasingly being used for the latter. Due to an extremely high sensitivity and the possibility of obtaining quantitative data on pharmacokinetic and pharmacodynamic properties, nuclear methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiolabeled compounds are particularly suitable here. The use of radiolabeled nanogels for imaging, but also for therapy, is being discussed.

Keywords: nanogels; cyclodextrin; drug delivery; radiolabeling; molecular imaging; theranostics

Permalink: https://www.hzdr.de/publications/Publ-37546
Publ.-Id: 37546


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