Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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43570 Publications

Understanding the Timelines of Developing a By-Product Mining Operation: the case of Nickel, Cobalt (and Copper)

Buarque Andrade, L.; Frenzel, M.; Bookhagen, B.; Kresse, C.

Abstract

The projected increase in electric vehicle demand over the next few decades raised some concerns about whether the mining industry can meet the growing need for battery metals like nickel and cobalt, which are essential for this shift in energy technology. These metals are commonly obtained as secondary products of other metals like copper, and their future availability relies on the mining progress of the primary metal. From exploration to production, the projects go through several stages of characterisation and evaluation, and the interconnection between host and secondary metal adds complexity to understanding which mining projects advance to production. Even projects with similar geological and technical characteristics may take very different trajectories. The present study uses a retrospective analysis model to investigate the dynamics of this process for Copper, Nickel and Cobalt exploration projects. A global database of over 6,000 projects was compiled, covering their progression through major development stages over the past 20 years. Ordinal logistic regression was used for the statistical analysis of this data. Different explanatory variables, including economic, geological, technical, and geographic factors, were tested to identify the best predictors for project progress at each development stage and final product definition. The results provide essential insights into the dynamics of nickel and cobalt supply and will eventually allow more realistic forecasts to be made for future market dynamics

  • Lecture (Conference)
    8th Freiberg PhD Conference, 07.06.2024, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-39896


Quantitative assessment of global future Lithium supply: Simulating which mining projects and when will they start production

Buarque Andrade, L.; Frenzel, M.; Bookhagen, B.; Kresse, C.

Abstract

Whether primary lithium (Li) sources will be able to supply the rapidly growing needs of the electric mobility
transition has recently caused considerable controversy. Existing assessments need to be improved by a lack
of consideration for the decision-making processes occurring at the level of individual mining projects. In the
present contribution, we demonstrate how these processes and associated uncertainties can be incorporated
into an assessment of the likely future evolution of the global Li market. Our method uses Monte Carlo simulations
to achieve this goal. A global database of existing Li mining projects (all development stages, including case
histories) is used to build models to estimate the likelihood of each project proceeding to the next development
stage in any given year, depending on specific project characteristics such as location, deposit type, and ore
grade, as well as market conditions, i.e., Li price and demand. Iterative stochastic simulations are then run, in
which projects are moved through the development pipeline according to these estimated likelihoods, year-by year,
up to 2050. Discoveries are also included in the model to achieve realistic results over the relatively long
period covered. Simple, functional models estimate future Li demand, including uncertainty. The simulations
generate a large set of equally probable scenarios (1,000 or more) of which projects enter production when,
whether primary supply can meet demand in any given year, and what the likely mean Li price is for that year.
Summarising the data from all scenarios provides an impression of the likely evolution of the Li market up to
2050. Besides this likely market evolution, the simulation outputs can be used further to assess the probable
environmental impacts of future primary Li supply
213

  • Lecture (Conference)
    Helmholtz Energy Conference 2023 Tackling the Global Challenges for the Energy Transition, 12.-13.06.2023, Koblenz, Germany

Permalink: https://www.hzdr.de/publications/Publ-39895


Quantitative assessment of global future Lithium supply: Simulating mining projects and predicting production start times

Buarque Andrade, L.; Frenzel, M.; Bookhagen, B.; Kresse, C.

Abstract

Whether primary lithium (Li) sources will be able to supply the rapidly growing needs of the electric mobility
transition has recently caused considerable controversy. Existing assessments need to be improved by a lack
of consideration for the decision-making processes occurring at the level of individual mining projects. In the
present contribution, we demonstrate how these processes and associated uncertainties can be incorporated
into an assessment of the likely future evolution of the global Li market. Our method uses Monte Carlo simulations
to achieve this goal. A global database of existing Li mining projects (all development stages, including case
histories) is used to build models to estimate the likelihood of each project proceeding to the next development
stage in any given year, depending on specific project characteristics such as location, deposit type, and ore
grade, as well as market conditions, i.e., Li price and demand. Iterative stochastic simulations are then run, in
which projects are moved through the development pipeline according to these estimated likelihoods, year-by year,
up to 2050. Discoveries are also included in the model to achieve realistic results over the relatively long
period covered. Simple, functional models estimate future Li demand, including uncertainty. The simulations
generate a large set of equally probable scenarios (1,000 or more) of which projects enter production when,
whether primary supply can meet demand in any given year, and what the likely mean Li price is for that year.
Summarising the data from all scenarios provides an impression of the likely evolution of the Li market up to
2050. Besides this likely market evolution, the simulation outputs can be used further to assess the probable
environmental impacts of future primary Li supply
213

  • Lecture (Conference)
    11th International Conference on Industrial Ecology, 02.-05.07.2023, Leiden, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-39894


From exploration to production: Understanding the development dynamics of lithium mining projects

Buarque Andrade, L.; Frenzel, M.; Bookhagen, B.; Kresse, C.; Nassar, N.; Alonso, E.; Shojaeddini, E.; Sandmann, D.; Schmidt, M.

Abstract

There has been considerable recent controversy whether current and new lithium mines will be able to supply the rapidly growing needs of the electric mobility transition. Mineral exploration projects are typically active for many years, and only some become operational mines. From exploration to production, the projects go through several stages of characterisation and evaluation. At each stage, decisions are made by companies and stakeholders to advance, continue or stop the project. This is a complex process, and even projects with very similar geological and technical characteristics may take very different trajectories, depending on external factors such as global market conditions and local regulatory environments. The present study investigates the dynamics of this process for lithium exploration projects. A global database of 397 lithium projects was compiled, covering their progression through major development stages between 2004 and 2022. Ordinal logistic regression was used for the statistical analysis of this data. Different explanatory variables were tested, including economic, geological, technical, and geographic factors, to identify the best predictors for project progress at each development stage. The results suggest an essential role for lithium carbonate prices, and a variable role for other factors at each stage. Critically, the already elapsed lead time and project economics, which are traditionally considered important for the prediction of the start-up of individual mines, do not appear to be relevant in all cases. The results provide important insights into the dynamics of lithium supply and will eventually allow more realistic forecasts to be made for future lithium market dynamics.

Keywords: Mine life cycle; Mine development lead times; Metal supply; Logistic Regression; Econometrics; Mineral Economics

Related publications

Permalink: https://www.hzdr.de/publications/Publ-39893


Predicting daily net ecosystem production in shallow lakes from dissolved oxygen saturation levels: a pan-European mesocosm experiment and modelling approach

Cao, Y.; Scharfenberger, U.; Shatwell, T.; Adrian, R.; Agasild, H.; Angeler, D. G.; Beklioğlu, M.; Çakıroğlu, A. l.; Hejzlar, J.; Papastergiadou, E.; Šorf, M.; Stefanidis, K.; Søndergaard, M.; Zingel, P.; Jeppesen, E.

Abstract

Net ecosystem production (NEP) is an important indicator of lake ecosystem function and integrity. An earlier study, restricted to one geographical region, indicated that oxygen saturation levels (DO%) might be used to predict daily NEP in shallow lakes. To test the generality of the method, we used DO% data collected in a standardised pan-European mesocosm experiment with contrasting trophic states and water levels covering a large climate gradient (from Sweden to Turkey). We corroborated these data with process-based DO simulations. The NEP ~ DO% relation depended on factors influencing gas transfer: water depth and wind. The NEP ~ DO% relation per volume became weaker with increasing depth (1–2 m) but was independent of depth when area based. Simulations indicated that the marginalisation of the depth was sensitive to wind conditions. Trophic status, temperature and light showed no or only marginal (climate zone) effects (experimental data), while the simulations indicated influence of those factors under particular wind–depth conditions. We confirmed that when considering also wind and depth effects, midday DO% potentially provides reliable estimates of daily NEP. Therefore, historical monitoring data of DO% might be used to estimate NEP, and process-based oxygen models may be valuable tool therein. We encourage further tests.

Keywords: Shallow lakes; Metabolism; Statistical model; Process-based model; Cross-system analyses

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Permalink: https://www.hzdr.de/publications/Publ-39891


Training data for "Harnessing Machine Learning for Single-Shot Measurement of Free Electron Laser Pulse Power"

Korten, T.; Steinbach, P.; Mirian, N. S.

Abstract

This repository contains data for the NeurIPS conference paper titled "Harnessing Machine Learning for Single-Shot Measurement of Free Electron Laser Pulse Power".

Raw data is provided in the following files:

  • PBD2_VRFD_pbd2_stream_6_run52040_file114_20240227T153103.hdf5
  • PBD2_VRFD_pbd2_stream_6_run52040_file115_20240227T153214.hdf5
  • PBD2_VRFD_pbd2_stream_6_run52040_file116_20240227T153325.hdf5
  • PBD2_VRFD_pbd2_stream_6_run52040_file117_20240227T153436.hdf5

The raw data contains 23 machine parameters as well as the longitudinal phase space images of 2826 shots in the lasing-off regime of the FLASH2 beamline at DESY Hamburg.

Training data for the MLP model is contained in "electron_power_data_files_114_115_116_117.hdf5"

The training data contains 23 machine parameters as well as the temporal power profiles of 2826 electron bunches.

Keywords: machine learning; free electron laser; linear accelerator

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Permalink: https://www.hzdr.de/publications/Publ-39889


Novel radiofluorinated analogues of GSK321 for PET imaging of mIDH1 in gliomas

Kaur, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Toussaint, M.; Wenzel, B.; Kopka, K.; Moldovan, R.-P.

Abstract

Objectives
Mutant isocitrate dehydrogenase (mIDH) has become an important biomarker for effective diagnosis, prognosis, treatment planning and patient stratification in patients with mIDH. Currently, mIDH status is determined by an invasive immunohistochemical method. A non-invasive PET imaging method for the detection of isocitrate dehydrogenase mutations represents a potentially better alternative. To date, there is no clinically available PET radiotracer targeting mIDH. In this study, we have developed [18F]SK60 and [18F]SK87 (Fig. 1) and are currently investigating their ability to visualise mIDH1.1
Methods
A SAR study was carried out starting from the structure of the mIDH inhibitor GSK321.2 Our medicinal chemistry program led to the development of dimethylated GSK321 analogues, SK60 and SK87 which were radiofluorinated in view of their high potency and selectivity towards the mIDH1R13H. To develop [18F]SK60 and [18F]SK87, various reaction parameters were investigated, for instance: fluorination agents, solvent, temperature and molar ratios between precursor and copper complex. For [18F]SK60, the ex vivo metabolic stability was investigated in female CD-1 mice at 30 min post-injection (p.i) and the biodistribution was evaluated ex vivo at 5, 15, 30 and 60 min as well as by dynamic PET scan studies (60 min) in healthy female CD-1 mice.
Results
The structural optimization and medicinal chemistry on GSK321 resulted in SK60 (IC50 mIDH1R132H = 14.5 ± 3.3 nM and IC50 wtIDH1 = 374 ± 59 nM) and SK87 (IC50 mIDH1R132H = 25.9  7.1 nM and IC50 wtIDH1 > 10,000 nM). Compounds [18F]SK60 and [18F]SK87 were successfully synthesized by copper-mediated radiofluorination from the respective Bpin and BEpin precursors, respectively. In vivo studies conducted in healthy female CD-1 mice, exhibited the excellent metabolic stability of [18F]SK60, with parent fractions of 80% and 100% in plasma and brain at 30 min p.i., respectively. The ex vivo biodistribution studies and dynamic PET scan showed a low brain uptake (0.6 % ID/g 15 min p.i.) and hepatobiliary excretion of [18F]SK60 in healthy mice.
Conclusions
This study resulted in the development of a novel series of fluorinated mIDHR132H inhibitors. Consequently, [18F]SK60 and [18F]SK87 were successfully radiofluorinated. Our preclinical evaluation of [18F]SK60 demonstrated high metabolic stability, limited brain uptake and hepatobiliary excretion in vivo in healthy mice. In general, further structural modifications in [18F]SK60 are required to enhance the brain uptake diagnosis and treatment of glioma and other tumours associated with mIDH. Currently, we are conducting the biological evaluation of [18F]SK87, the analogue with reduced lipophilicity.
References
1. Patent application number: DE 10 2024 110 434.1 (15 April 2024)
2. Okoye-Okafor, U. C.; et al. Nat. Chem. Bio. 2015, 11 (11), 878–886.

  • Lecture (Conference)
    CAFACHEM 2024, 17.-20.07.2024, Ann Arbor, Michigan, USA

Permalink: https://www.hzdr.de/publications/Publ-39887


Protodeboronation: A major challenge in copper-mediated radiofluorination

Kaur, S.; Wenzel, B.; Kopka, K.; Moldovan, R.-P.

Abstract

Introduction:

Copper-Mediated Radiofluorination (CMRF) is one of the most significant developments of the last decade in the production of 18F-aryl-containing radiopharmaceuticals.1 Despite extensive research and improved radiolabelling conditions, the generation of H-side product (Fig. 1) continues to be an issue in these CMRF reactions. In our research, we focused on the identification of the sources and reaction parameters influencing the “H”-side product formation in these CMRF reactions.

Methods:

The CMRF of pinacol boronic esters was optimized by varying the following parameters: solvent (DMA, DMI, n-BuOH), reaction time (5 - 20 min), temperature (110 - 130 °C), base (K2CO3) and molar ratio of precursor to Cu-complex (1:3, 2:3, 1:8). To investigate the source of protons, deuterated reagents (D2O, n-BuOD-d10, TBADCO3, K2CO3 in D2O) were used. The influence of different leaving groups of precursors [B(OH)2, Bpin, BEpin and SnBu3] was also evaluated. The effect of amounts of different eluting phase transfer catalyst (PTC) (TBAHCO3, TEHCO3, TBAOTf, DMAPHCO3) was also investigated. A time-dependent (2 to 30 min) formation of H-side product was investigated.
Results:
[18F]Biphenyl was achieved with a high radiochemical conversion of 85 % using 2 mg of biphenyl boronic ester, 10 mg of [Cu(OTf)2(Py)4] (molar ratio of 1:4) in n-BuOH:DMI (1:2, v/v) at 110 °C for 5 min. The H-side product was successfully separated from the radiofluorinated product using a ReproSil C18 PFP column (250 x 10 mm) and 54 % MeCNaq. Our deuterated experiments revealed that quenching the reaction with D2O had no influence on the H-side product formation, but the use of n-BuOD-d10 increased its generation by four folds. The different eluting PTCs (TBAHCO3, TEHCO3, TBAOTf, DMAPHCO3) implied no significant influence on the H-side product formation, however, the exclusion of K2CO3 not only improved RCC but also decreased the H-side product formation. The use of boronic acid precursor lead to an increased H-side product formation by several folds as compared to the use of pinacol boronic ester bearing precursor. Moreover, the use of a precursor with acidic protons (e.g. NH) enhance the H-side product formation. The yield of the H-side product formation reached a plateau at 10 min of reaction.
Conclusion:
Despite a number of hurdles, the CMRF reactions are currently being widely employed for the production of radiopharmaceuticals embodying a wide variety of 18F-aryl scaffolds. To overcome the purification difficulties of the 18F-radioligands due to H-side product formation, further improvements and mechanistic studies need to be undertaken.
LITERATURE
[1] Wright JS, Kaur T, Preshlock S, et al. Clin Transl Imaging. 2020 Jun;8(3):167-206.

  • Lecture (Conference)
    CAFACHEM 2024, 17.-20.07.2024, Ann Arbor, Michigan, USA

Permalink: https://www.hzdr.de/publications/Publ-39886


Synthesis and evaluation of radiofluorinated GSK321 analogues as candidate radiotracers for imaging mutant IDH1 expression in gliomas

Kaur, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Toussaint, M.; Wenzel, B.; Kopka, K.; Moldovan, R.-P.

Abstract

Aim
Mutant isocitrate dehydrogenase (mIDH) has become an important biomarker for effective diagnosis, prognosis, treatment planning and patient stratification in patients with mIDH. Currently, mIDH status is determined by an invasive immunohistochemical method. A non-invasive PET imaging method for the detection of isocitrate dehydrogenase mutations represents a potentially better alternative. To date, there is no clinically available PET radiotracer targeting mIDH. In this study, we have developed [18F]SK60 and [18F]SK87 and are currently investigating their ability to visualise mIDH1.1
Methods
A SAR study was carried out starting from the structure of the mIDH inhibitor GSK321.2 Our medicinal chemistry program led to the development of dimethylated GSK321 analogues, SK60 and SK87 which were radiofluorinated in view of their high potency and selectivity towards the mIDH1R13H. To develop [18F]SK60 and [18F]SK87, various reaction parameters were investigated, for instance: fluorination agents, solvent, temperature and molar ratios between precursor and copper complex. For [18F]SK60, the ex vivo metabolic stability was investigated in female CD-1 mice at 30 min post-injection (p.i) and the biodistribution was evaluated ex vivo at 5, 15, 30 and 60 min as well as by dynamic PET scan studies (60 min) in healthy female CD-1 mice.

Results
The structural optimization and medicinal chemistry on GSK321 resulted in SK60 (IC50 mIDH1R132H = 14.5 ± 3.3 nM and IC50 wtIDH1 = 374 ± 59 nM) and SK87 (IC50 mIDH1R132H = 25.9  7.1 nM and IC50 wtIDH1 > 10,000 nM). Compounds [18F]SK60 and [18F]SK87 were successfully synthesized by copper-mediated radiofluorination from the respective Bpin and BEpin precursors, respectively. In vivo studies conducted in healthy female CD-1 mice, exhibited the excellent metabolic stability of [18F]SK60, with parent fractions of 80% and 100% in plasma and brain at 30 min p.i., respectively. The ex vivo biodistribution studies and dynamic PET scan showed a low brain uptake (0.6 % ID/g 15 min p.i.) and hepatobiliary excretion of [18F]SK60 in healthy mice.
Conclusions
This study resulted in the development of a novel series of fluorinated mIDHR132H inhibitors. Consequently, [18F]SK60 and [18F]SK87 were successfully radiofluorinated. Our preclinical evaluation of [18F]SK60 demonstrated high metabolic stability, limited brain uptake and hepatobiliary excretion in vivo in healthy mice. In general, further structural modifications in [18F]SK60 are required to enhance the brain uptake diagnosis and treatment of glioma and other tumours associated with mIDH. Currently, we are conducting the biological evaluation of [18F]SK87, the analogue with reduced lipophilicity.
References
1. Patent application number: DE 10 2024 110 434.1 (15 April 2024)
2. Okoye-Okafor, U. C.; et al. Nat. Chem. Bio. 2015, 11 (11), 878–886.

  • Poster
    EANM 2024, 19.-23.10.2024, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-39885


Synthesis and evaluation of [18F]SK60 and [18F]SK87 as potential radiotracers to image mutant IDH1 in gliomas

Kaur, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Toussaint, M.; Wenzel, B.; Kopka, K.; Moldovan, R.-P.

Abstract

Aim
Mutant isocitrate dehydrogenase (mIDH) has become an important biomarker for effective diagnosis, prognosis, treatment planning and patient stratification in patients with mIDH. Currently, mIDH status is determined by an invasive immunohistochemical method. A non-invasive PET imaging method for the detection of isocitrate dehydrogenase mutations represents a potentially better alternative. To date, there is no clinically available PET radiotracer targeting mIDH. In this study, we have developed [18F]SK60 and [18F]SK87 and are currently investigating their ability to visualise mIDH1.1
Methods
A SAR study was carried out starting from the structure of the mIDH inhibitor GSK321.2 Our medicinal chemistry program led to the development of dimethylated GSK321 analogues, SK60 and SK87 which were radiofluorinated in view of their high potency and selectivity towards the mIDH1R13H. To develop [18F]SK60 and [18F]SK87, various reaction parameters were investigated, for instance: fluorination agents, solvent, temperature and molar ratios between precursor and copper complex. For [18F]SK60, the ex vivo metabolic stability was investigated in female CD-1 mice at 30 min post-injection (p.i) and the biodistribution was evaluated ex vivo at 5, 15, 30 and 60 min as well as by dynamic PET scan studies (60 min) in healthy female CD-1 mice.
Results
The structural optimization and medicinal chemistry on GSK321 resulted in SK60 (IC50 mIDH1R132H = 14.5 ± 3.3 nM and IC50 wtIDH1 = 374 ± 59 nM) and SK87 (IC50 mIDH1R132H = 25.9  7.1 nM and IC50 wtIDH1 > 10,000 nM). Compounds [18F]SK60 and [18F]SK87 were successfully synthesized by copper-mediated radiofluorination from the respective Bpin and BEpin precursors, respectively. In vivo studies conducted in healthy female CD-1 mice, exhibited the excellent metabolic stability of [18F]SK60, with parent fractions of 80% and 100% in plasma and brain at 30 min p.i., respectively. The ex vivo biodistribution studies and dynamic PET scan showed a low brain uptake (0.6 % ID/g 15 min p.i.) and hepatobiliary excretion of [18F]SK60 in healthy mice.
Conclusions
This study resulted in the development of a novel series of fluorinated mIDHR132H inhibitors. Consequently, [18F]SK60 and [18F]SK87 were successfully radiofluorinated. Our preclinical evaluation of [18F]SK60 demonstrated high metabolic stability, limited brain uptake and hepatobiliary excretion in vivo in healthy mice. In general, further structural modifications in [18F]SK60 are required to enhance the brain uptake diagnosis and treatment of glioma and other tumours associated with mIDH. Currently, we are conducting the biological evaluation of [18F]SK87, the analogue with reduced lipophilicity.
References
1. Patent application number: DE 10 2024 110 434.1 (15 April 2024)
2. Okoye-Okafor, U. C.; et al. Nat. Chem. Bio. 2015, 11 (11), 878–886.

  • Poster
    CJKSRS 2024 - The 12th China - Japan - Korea Symposium on Radiopharmaceutical Sciences, 19.-20.09.2024, Kanazawa, Japan

Permalink: https://www.hzdr.de/publications/Publ-39884


Data publication: Gas flow rate measurement in two-phase flows using an optical channel body flow sensor. Design and validation of the single-channel prototype

Condriuc, I.; Kipping, R.; Schleicher, E.

Abstract

This publication presents the measurement data, including temporal signal changes at measuring points, and validation data, including gas and liquid flow rate measurements, absolute pressure, pressure losses, and temperature, used for the development and investigation of an Optical Channel Body Flow Sensor (OCBFS). The sensor is designed for the simultaneous measurement of gas and liquid flow rates. Experimental validation of the OCBFS was conducted across a range of superficial velocities, with liquid velocities between vl,s = 0.14 0.31 m/s and gas velocities between vg,s = 0.015-0.95 m/s. The results showed deviations of less than 10% from reference values, confirming the sensor’s accuracy and reliability in measuring gas flow rates

Keywords: Gas-liquid flow; Flow patterns; Taylor-Bubbles; Flow rate measurement; Optical fiber

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Permalink: https://www.hzdr.de/publications/Publ-39883


Wechselwirkung eines tongesteinsrelevanten Mikroorganismus mit Uran und Europium

Hilpmann, S.

Abstract

Tongesteine stellen mögliche Wirtsgesteine für die Endlagerung des hochradioaktiven Abfalls in einem geologischen Tiefenlager dar. Bentonit soll dabei als Verfüllmaterial nicht nur für ein Endlager in Tonformationen, sondern auch in kristallinem Ge-stein dienen. Für ein umfassendes Sicherheitskonzept müssen neben den geologischen, geochemischen und geophysikalischen Eigenschaften eines Endlagers auch der Einfluss natürlich vorkommender Mikroorganismen in dessen Umgebung betrachtet werden. Diese können im Falle eines Wassereinbruchs mit den freigesetzten Radionukliden wechselwirken und dadurch bspw. die chemische Speziation oder den Oxidationszustand verändern.
Neben weiteren sulfatreduzierenden Mikroorganismen spielen Bakterien der Gattung Desulfosporosinus eine wichtige Rolle in den mikrobiellen Gemeinschaften sowohl in Tongestein als auch in Bentonit. Desulfosporosinus hippei DSM 8344T ist ein naher Verwandter der aus Bentonit isolierten Bakterien und wurde im Rahmen dieser Arbeit ausgewählt, um dessen Wechselwirkungen mit Uran und Europium mit Hilfe verschiedener mikroskopischer und spektroskopischer Methoden näher zu untersuchen.
Zeitabhängige Untersuchungen in synthetischer Opalinustonporenlösung (100 µM Uran(VI), pH 5,5) zeigten eine fast vollständige Entfernung des Urans aus den Über-ständen innerhalb einer kurzen Zeitspanne. TEM Aufnahmen gekoppelt mit element-spezifischer EDX-Spektroskopie zeigten eine Assoziation von Uran vorrangig auf der Zelloberfläche. Darüber hinaus bildeten die Zellen Membranvesikel als mögliche Abwehrreaktion aus, um eine Verkrustung der Zellen zu verhindern.
Außerdem konnte die Reduktion von Uran(VI) mithilfe verschiedener spektroskopischer Methoden nachgewiesen werden. Zunächst wurden die aufgelösten Zellpellets mit Hilfe der UV/Vis-Spektroskopie untersucht. Dabei zeigte sich ein ansteigender An-teil an Uran(IV) mit der Zeit. Eine vollständige Reduktion konnte allerdings nicht beobachtet werden. Dies deutet darauf hin, dass es sich bei dem Wechselwirkungsmechanismus um einen gekoppelten Sorptions-Reduktionsmechanismus handelt. HERFD-XANES-Messungen bestätigten die Reduktion von Uran(VI) in den Zellpellets. Darüber hinaus konnte die Anwesenheit von Uran(V) während des Reduktionsprozesses beobachtet werden. Dabei handelte es sich um den erstmaligen Nachweis dieser Oxidationsstufe in einem Bioreduktionsexperiment von Uran(VI) mit sulfatreduzierenden Bakterien.
Bei den Untersuchungen mit Europium zeigten TEM Aufnahmen eine Biopräzipitation von Europium mit Phosphaten auf der Zelloberfläche und lumineszenzspektroskopische Untersuchungen konnten eine Anbindung von Europium an Carboxyl- oder Phosphatgruppen auf der Zelloberfläche nachweisen.
Zusammenfassend erweitert diese Arbeit unser Verständnis für die Komplexität von Redoxprozessen in der Umwelt und trägt zu einem Sicherheitskonzept für nukleare Endlager in Tongestein bei. Darüber hinaus liefert sie neue Erkenntnisse über die Mechanismen der Uran(VI)-Reduktion durch sulfatreduzierende Bakterien.

Keywords: Mikrobielle Uran(VI)-Reduktion; Sulfatreduzierende Bakterien; Opalinustonporenwasser

  • Invited lecture (Conferences)
    GDCh Fachgruppentagung Nuklearchemie, 05.-07.11.2024, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39882


CT image sequences of sandwich packings: B1-250 plus B1-500 at constant liquid rate of 50 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; Researcher: Sohr, Johanna; DataManager: Sprewitz, Uwe; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-500 (specific geometric surface area is 500 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packing; two-phase flow; ultrafast electron beam X-ray computed tomography

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39881


CT image sequences of sandwich packings: B1-250 plus B1-500 at constant liquid rate of 20 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; Researcher: Sohr, Johanna; DataManager: Sprewitz, Uwe; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-500 (specific geometric surface area is 500 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packing; two-phase flow; ultrafast electron beam X-ray computed tomography

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39880


CT image sequences of sandwich packings: B1-250 plus B1-500 at constant liquid rate of 10 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; Researcher: Sohr, Johanna; DataManager: Sprewitz, Uwe; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-500 (specific geometric surface area is 500 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packing; two-phase flow; ultrafast electron beam X-ray computed tomography

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39879


CT image sequences of sandwich packings: B1-250 plus B1-1000 at constant liquid rate of 50 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; Researcher: Sohr, Johanna; DataManager: Sprewitz, Uwe; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-1000 (specific geometric surface area is 1000 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packing; two-phase flow; ultrafast electron beam X-ray computed tomography

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39878


CT image sequences of sandwich packings: B1-250 plus B1-1000 at constant liquid rate of 20 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; Researcher: Sohr, Johanna; DataManager: Sprewitz, Uwe; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-1000 (specific geometric surface area is 1000 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packing; two-phase flow; ultrafast electron beam X-ray computed tomography

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39877


CT image sequences of sandwich packings: B1-250 plus B1-1000 at constant liquid rate of 10 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; Researcher: Sohr, Johanna; DataManager: Sprewitz, Uwe; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-1000 (specific geometric surface area is 1000 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packing; two-phase flow; ultrafast electron beam X-ray computed tomography

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39876


Diffusion Models Meet Remote Sensing: Principles, Methods, and Perspectives

Liu, Y.; Yue, J.; Xia, S.; Ghamisi, P.; Xie, W.; Fang, L.

Abstract

As a newly emerging advance in deep generative models, diffusion models have achieved state-of-the-art results in many fields, including computer vision, natural language processing, and molecule design. The remote sensing (RS) community has also noticed the powerful ability of diffusion models and quickly applied them to a variety of tasks for image processing. Given the rapid increase in research on diffusion models in the field of RS, it is necessary to conduct a comprehensive review of existing diffusion model-based RS papers, to help researchers recognize the potential of diffusion models and provide some directions for further exploration. Specifically, this article first introduces the theoretical background of diffusion models, and then systematically reviews the applications of diffusion models in RS, including image generation, enhancement, and interpretation. Finally, the limitations of existing RS diffusion models and worthy research directions for further exploration are discussed and summarized.

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Permalink: https://www.hzdr.de/publications/Publ-39875


Cross Hyperspectral and LiDAR Attention Transformer: An Extended Self-Attention for Land Use and Land Cover Classification

Roy, S. K.; Sukul, A.; Jamali, A.; Haut, J. M.; Ghamisi, P.

Abstract

The successes of attention-driven deep models like the vision transformer (ViT) have sparked interest in cross-domain exploration. However, current transformer-based techniques in remote sensing (RS) primarily focus on single-modal data, limiting their potential to exploit the growing array of multimodal Earth observation (EO) data fully. Enhancing these models for multimodal integration is crucial for comprehensive RS applications. To achieve this, we extend the traditional self-attention mechanism by introducing cross hyperspectral and light detection and ranging (LiDAR) (Cross-HL) attention. We present a novel multimodal deep learning framework that effectively fuses RS data, intending to improve land use and land cover (LULC) recognition. To enhance the accurate exchange of information across different modalities, we fuse their patch projections using the Cross-HL self-attention module. In this process, LiDAR patch tokens serve as queries (Q), while keys (K) and values (V) are derived from HS patch tokens. To demonstrate the superiority of Cross-HL in the proposed multimodal deep learning framework, we conducted extensive experiments on three multimodal RS benchmark datasets: Houston, Trento, and MUUFL. These datasets contain hyperspectral (HS) and LiDAR data. The source code for Cross-HL will be made available publicly at https://github.com/AtriSukul1508/Cross-HL .

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  • Secondary publication expected from 12.03.2025

Permalink: https://www.hzdr.de/publications/Publ-39874


SpectralGPT: Spectral Remote Sensing Foundation Model

Hong, D.; Zhang, B.; Li, X.; Li, Y.; Li, C.; Yao, J.; Yokoya, N.; Li, H.; Ghamisi, P.; Jia, X.; Plaza, A.; Gamba, P.; Benediktsson, J. A.; Chanussot, J.

Abstract

The foundation model has recently garnered significant attention due to its potential to revolutionize the field of visual representation learning in a self-supervised manner. While most foundation models are tailored to effectively process RGB images for various visual tasks, there is a noticeable gap in research focused on spectral data, which offers valuable information for scene understanding, especially in remote sensing (RS) applications. To fill this gap, we created for the first time a universal RS foundation model, named SpectralGPT, which is purpose-built to handle spectral RS images using a novel 3D generative pretrained transformer (GPT). Compared to existing foundation models, SpectralGPT 1) accommodates input images with varying sizes, resolutions, time series, and regions in a progressive training fashion, enabling full utilization of extensive RS Big Data; 2) leverages 3D token generation for spatial-spectral coupling; 3) captures spectrally sequential patterns via multi-target reconstruction; and 4) trains on one million spectral RS images, yielding models with over 600 million parameters. Our evaluation highlights significant performance improvements with pretrained SpectralGPT models, signifying substantial potential in advancing spectral RS Big Data applications within the field of geoscience across four downstream tasks: single/multi-label scene classification, semantic segmentation, and change detection.

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Permalink: https://www.hzdr.de/publications/Publ-39873


Spatially Resolved Phase Transition and Characterization of Gallium Oxide

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

Abstract

Gallium Oxide (Ga2O3) is a promising ultra-wide bandgap semiconductor material that has garnered significant attention due to its ease of large-scale production through melt growth and its high break-down voltage. Beta (β)-Ga2O3 is the most thermally and chemically stable polymorph among the vari-ous forms of Ga2O3. Unfortunately, the control and manufacturing of other phases on the nanoscale remain immature due to the metastable nature of those phases. Azarov et al. demonstrated that β to gamma (γ)-Ga2O3 phase transition is possible after reaching a certain critical damage level (dpa) induced by ion irradiation. Various ion implantation experiments have shown that the phase transition is independent of the chemical nature of the implanted ion. Interestingly, the structure retains its crystal order up to 260 dpa before amorphization, which is quite higher than most radiation-tolerant materials (AlN, SiC). The stability of the oxygen lattice against ion irradiation is the main reason for the high radiation tolerance of Ga2O3. Here, helium ion microscopy (HIM) and plasma FIB are used to locally irradiate the (-201)-oriented β-Ga2O3 with neon and argon ions, respectively. Spatially resolved texture analysis was performed by electron backscatter diffraction (EBSD) and confirmed the β to γ phase transition. Transmission elec-tron microscopy (TEM) was also performed to observe the depth profile and interface between two polymorphs. We see a certain fluence where the β to γ-Ga2O3 phase transition is completed for both neon (figure 1) and argon implantation. Using Positron Annihilation Lifetime Spectroscopy (PALS) and Doppler Broadening Variable Energy Positron Annihilation Spectroscopy (DB-VEPAS) on broad-beam irradiated samples, we observed a reduction in defect concentration and relaxation of accumulated defects after the phase transition. Moreover, a sharp interface between two phases makes local noble gas FIB implantation a promising method to fabricate double polymorph Ga2O3 nanostructures. This work is supported by the state of Saxony.

Keywords: Gallium Oxide; Defects in Gallium Oxide; Positron Annihilation Lifetime Spectroscopy; Doppler broadening spectroscopy; Focused Ion Beam; Transmission Electron Microscopy

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  • Open Access Logo Lecture (others)
    Fit4Nano workshop, 15.-20.09.2024, Durres, Albania

Permalink: https://www.hzdr.de/publications/Publ-39870


Polymorph Conversion and Defect Analysis in Gallium Oxide

Bektas, U.; Hlawacek, G.

Abstract

Gallium Oxide (Ga2O3) is a promising ultra-wide bandgap semiconductor material that has garnered
significant attention due to its advantages in melt growth and high breakdown voltage compared to GaN and
SiC. The main focus is on the Beta polymorph, which is the most thermally and chemically stable polymorph
among other polymorphs of Ga2O3. Unfortunately, controlling and manufacturing other phases is immature
due to the metastable structure of those phases and their conversion back to the beta phase at high
temperatures. Conversion between polymorph phases of Ga2O3 can be achieved by adjusting temperature and
pressure during growth.
In a previous study, our project partners Kuznetsov et.al. [1] demonstrated the ion-beam-induced β-to-κ
phase transformation in Ga2O3 as shown in Figure 1. β-Ga2O3 single crystal wafers were implanted with
different ions, specifically 58Ni+ (400 keV), 69Ga+(500 keV), and 197Au+ (1.2 MeV). Above a critical fluence, a
polymorph conversion can be induced independent of the used primary ion species [1]. The formed
polymorph is stable against further amorphization by very high fluences on the order of 1016 Ni/cm2. From
the multi-species implantation experiments we conclude that it is the induced strain by the defects and not
the chemical nature of the implanted ions that drives the transition. Later, it is found that actual transition is
not to Kappa phase but actually into defective spinel gamma phase. Additionally, our recent publication
demonstrates that strain induced by ion irradiation can cause a transition from beta to gamma phase [2],
which is highly radiation tolerant crystal. We also showed that the induced gamma phase is not affected by
the type of ion, but rather by the displacement per atom (DPA) in the crystal.
However, these irradiations are done using a broad beam, which means that the entire surface of the material
is irradiated by energetic ions. Our goal is to understand and induce polymorphic transitions in Ga2O3 using a
focused ion beam. This will enable us to establish new technologies and devices at the nanoscale. Therefore,
Gas field ion source focus ion beam (GFIS-FIB) with Neon source, commercially known as Helium ion
microscopy, and Liquid metal ion source focus ion beam (LMIS-FIB) were used to locally irradiate the Beta-
Ga2O3 surface. Different ions were used, such as silicon and tin for n-type conductive features, cobalt for
semi-insulating features, and noble gas neon for preserving electrical and thermal properties.
Here, we perform spatially resolved FIB to find resolution limit of the phase transition and analyzed the
defect formation during the beta-Ga2O3 to gamma-Ga2O3 phase transition. Characterization of the samples
was conducted by Electron Backscatter Diffraction (EBSD), Positron annihilation lifetime spectroscopy
(PALS), Doppler broadening variable energy positron annihilation spectroscopy (DB-VEPAS), Transmission
electron microscopy (TEM), and X-ray Diffraction (XRD). The first results indicate that the defect size and
concentration depend on the implanted ion type, fluence, and annealing temperature. This work is supported
by the state of Saxony.

Keywords: Gallium Oxide; Defects in Gallium Oxide; Positron Annihilation Lifetime Spectroscopy; Doppler broadening spectroscopy; X-ray diffraction

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  • Poster
    IWGO 2024 Berlin, 26.-31.05.2024, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-39869


Focused Ion Beam Induced Polymorph Conversion and Defect Analysis in Gallium Oxide

Bektas, U.; Hlawacek, G.

Abstract

Gallium Oxide (Ga2O3) is a promising ultra-wide bandgap semiconductor material that has garnered
significant attention due to its easy large scale production via melth growth and high breakdown voltage
compared to GaN and SiC. The main focus is on the Beta polymorph among other polymorphs, which is the
most thermally and chemically stable polymorph among other polymorphs of Ga2O3. Unfortunately,
controlling and manufacturing other phases is immature due to the metastable structure of those phases and
their conversion back to the beta phase at elevated temperatures.
Above a damage level (dpa), a polymorph conversion from beta to gamma phase can be induced independent
of the used primary ion species [1]. The formed polymorph is highly resistant against amorphization for very
high damage levels upto 265 dpa. From the multi-species implantation experiments (Ni+, Au+, Ga+, Ne+) we
conclude that it is the induced strain by the defects and not the chemical nature of the implanted ions that
drives the transition.
Here, we present a multi method analysis approach with the the aim to better understand and characterize the
role of atomic defects before, during and after the beta to gamma conversion. We employed Ne+, Ni+ and
Al+ irradiation at damage levels hgher than what other semiconductors can endure. We performed X-ray
diffraction (XRD) to confirm a successful conversion, Transmission electron microscopy (TEM) to observe
depth profile and Rutherford backscattering spectroscopy (RBS) to investigate high crystallinity after
conversion and exceptional radiation hardness of the gamma layer. Based on positron annihilation lifetime
spectroscopy (PALS) and Doppler broadening variable energy positron annihilation spectroscopy (DBVEPAS),
we see clear change in defect size in particular after phase transition, while seeing a change in
defect concentration by changing implanted ion fluence. This work is supported by the state of Saxony.

Keywords: Gallium Oxide; Defects in Gallium Oxide; Positron Annihilation Lifetime Spectroscopy; Doppler broadening spectroscopy; X-ray diffraction

Involved research facilities

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  • Poster
    EPS Forum, 24.03.-26.11.2024, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-39868


Defect Analysis During Ion Beam Induced β to γ Phase Transition in Ga2O3

Bektas, U.; Liedke, M. O.; Ganss, F.; Hübner, R.; Klingner, N.; Hlawacek, G.

Abstract

Gallium oxide (Ga2O3) is a unique material for power electronics,
optoelectronics, and batteries. However, controlling the metastable
polymorph phases of Ga2O3 is challenging, and the fabrication technology
at the nanoscale is immature. We aim to understand and control
the polymorph conversion to establish new fabrication methods of
single-phase polymorph coatings, buried layers, multilayers, and different
nanostructures in Ga2O3.
Under ion beam irradiation, most semiconductors show the transformation
from crystalline to amorphous structure due to ion beam induced
damage. However, we showed that this transformation is suppressed
in Ga2O3, and a polymorph conversion is observed instead.
Here, we analyzed the defect formation during the beta-Ga2O3 to
gamma-Ga2O3 phase transition, induced by ion implantation with
different ions and fluences. Characterization of the samples was conducted
by Positron annihilation lifetime spectroscopy (PALS), Doppler
broadening variable energy positron annihilation spectroscopy (DBVEPAS),
and X-ray Diffraction (XRD). The first results indicate that
the defect size and concentration depend on the implanted ion type,
fluence, and annealing temperature. This work is supported by the
state of Saxony.

Keywords: Gallium Oxide; Defects in Gallium Oxide; Positron Annihilation Lifetime Spectroscopy; Doppler broadening spectroscopy; X-ray diffraction

Involved research facilities

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  • Poster
    DPG Spring 2024, 17.-22.03.2024, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-39867


Lattice dynamics of LiNb1-xTaxO3 solid solutions: Theory and experiment

Bernhardt, F.; Gharat, S.; Kapp, A.; Pfeiffer, F.; Buschbeck, R.; Hempel, F.; Pashkin, O.; Kehr, S. C.; Rüsing, M.; Sanna, S.; Eng, L. M.

Abstract

Lithium niobate (LNO) and lithium tantalate (LTO) see widespread use in fundamental research and commercial technologies reaching from electronics over classical optics to integrated quantum communication. In recent years, the mixed crystal system lithium niobate tantalate (LNT) allows for the dedicate engineering of material properties by combining the advantages of the two parental materials LNO and LTO. Vibrational spectroscopies such as Raman spectroscopy or (Fourier transform) infrared spectroscopy are vital techniques to provide detailed insight into the material properties, which is central to the analysis and optimization of devices. In this work, we present a joint experimental-theoretical approach allowing to unambiguously assign the spectral features in the LNT material family through both Raman and IR spectroscopy, as well as to provide an in-depth explanation for the observed scattering efficiencies based on first-principles calculations. The phononic contribution to the static dielectric tensor is calculated from the experimental and theoretical data using the generalized Lyddane-Sachs-Teller relation and compared with the results of the first-principles calculations. The joint methodology can be readily expanded to other materials and serves, e.g., as the basis for studying the role of point defects or doping.

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Permalink: https://www.hzdr.de/publications/Publ-39866


MineNetCD: A Benchmark for Global Mining Change Detection on Remote Sensing Imagery

Yu, W.; Zhang, X.; Gloaguen, R.; Xiang Zhu, X.; Ghamisi, P.

Abstract

Monitoring land changes triggered by mining activities is crucial for industrial control, environmental management and regulatory compliance, yet it poses significant challenges due to the vast and often remote locations of mining sites. Remote sensing technologies have increasingly become indispensable to detect and analyze these changes over time. We thus introduce MineNetCD, a comprehensive benchmark designed for global mining change detection using remote sensing imagery. The benchmark comprises three key contributions. First, we establish a global mining change detection dataset featuring more than 70k paired patches of bitemporal high-resolution remote sensing images and pixel-level annotations from 100 mining sites worldwide. Second, we develop a novel baseline model based on a change-aware Fast Fourier Transform (ChangeFFT) module, which enhances various backbones by leveraging essential spectrum components within features in the frequency domain and capturing the channel-wise correlation of bitemporal feature differences to learn change-aware representations. Third, we construct a unified change detection (UCD) framework that currently integrates 20 change detection methods. This framework is designed for streamlined and efficient processing, utilizing the cloud platform hosted by HuggingFace. Extensive experiments have been conducted to demonstrate the superiority of the proposed baseline model compared with 19 state-of-the-art change detection approaches. Empirical studies on modularized backbones comprehensively confirm the efficacy of different representation learners on change detection. This benchmark represents significant advancements in the field of remote sensing and change detection, providing a robust resource for future research and applications in global mining monitoring.

Keywords: Mining change detection; remote sensing; benchmark; frequency domain learning; unified framework

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Permalink: https://www.hzdr.de/publications/Publ-39865


Data publication: MineNetCD: A Benchmark for Global Mining Change Detection on Remote Sensing Imagery

Yu, W.; Zhang, X.; Gloaguen, R.; Zhu, X. X.; Ghamisi, P.
DataCollector: Shi, Yasong; DataCollector: Deng, Yilong

Abstract

This is the full version of the MineNetCD dataset. The paper has been published in IEEE TGRS 2024 (https://ieeexplore.ieee.org/document/10744421). The dataset contains 100 sites, and the metadata can also be found in the zip archive.

The cropped version can also be found in Huggingface Hub (https://huggingface.co/datasets/HZDR-FWGEL/MineNetCD256).

Keywords: Mining change detection; remote sensing; benchmark; frequency domain learning; unified framework

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Permalink: https://www.hzdr.de/publications/Publ-39864


Data for bubble column reactor at offshore floating conditions

Heydari, N.; Kipping, R.

Abstract

This set contains experimental data obtained for the investigation of hydrodynamics of a bubble column under offshore floating conditions. The motions roll, pitch, roll and pitch as well as the static bubble column have been investigated. The frequency of the motion has been varried while the flow rate of the gas was set constant to 3 l/min. Experiments were performed in a bubble column with 100 mm inner diameter and hydrodynamics were investigated by meas of wire-mesh sensor measurements. Experiments were perfomed at ambient temperature and pressure conditions.

Keywords: bubble column; offshore conditions; moving column

Involved research facilities

  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-39860


Radiative corrections and Monte Carlo tools for low-energy hadronic cross sections in $e^+ e^-$ collisions

Aliberti, R.; Beltrame, P.; Budassi, E.; Carloni Calame, C. M.; Colangelo, G.; Cotrozzi, L.; Denig, A.; Driutti, A.; Engel, T.; Flower, L.; Gurgone, A.; Hoferichter, M.; Ignatov, F.; Kollatzsch, S.; Kubis, B.; Kupść, A.; Lange, F.; Lusiani, A.; Müller, S.; Paltrinieri, J.; Petit Rosàs, P.; Piccinini, F.; Price, A.; Punzi, L.; Rocco, M.; Shekhovtsova, O.; Siódmok, A.; Signer, A.; Stagnitto, G.; Stoffer, P.; Teubner, T.; Torres Bobadilla, W. J.; Ucci, F. P.; Ulrich, Y.; Venanzoni, G.

Abstract

We present the results of Phase I of an ongoing review of Monte Carlo tools relevant
for low-energy hadronic cross sections. This includes a detailed comparison of Monte Carlo
codes for electron–positron scattering into a muon pair, pion pair, and electron pair, for
scan and radiative-return experiments. After discussing the various approaches that are used
and effects that are included, we show differential cross sections obtained with AfkQed,
BabaYaga@NLO, KKMC, MCGPJ, McMule, Phokhara, and Sherpa, for scenarios that
are inspired by experiments providing input for the dispersive evaluation of the hadronic vac-
uum polarisation

Keywords: Radiative corrections; Monte Carlo; e+e- scattering; Radiative return

Involved research facilities

  • Data Center

Permalink: https://www.hzdr.de/publications/Publ-39859


Lanthanide-binding peptides as sustainable tools for the recovery of rare earth metals from waste streams

Techert, G.; Drobot, B.; Schönberger, N.; Lederer, F.

Abstract

Lanthanides are essential trace elements of today’s technological age and are indispensable for the corresponding economic, scientific and social structures. These elements' unique properties find application not only in the high-tech industry, but are also increasingly being utilized in the emerging GreenTech sector, which focuses on the development of sustainable products and technologies. Consequently, the demand for rare earth elements (REE) will continue to rise in the future. REE mining and production are associated with enormous environmental impacts, such as the release of arsenic, heavy metals and acids. Secondary waste streams containing these valuable metals are constantly increasing, which has turned the attention to alternative extraction strategies such as the Ln recycling from end-of-life products or industrial and mining wastewater. However, due to their similar chemical and physical characteristics as well as their low concentrations in wastewater and electronic scrap, REE separation processes are challenging in terms of costs and efficiency. For this reason, there is a high demand for new recycling technologies enabling a cost-effective and environmentally friendly recovery, which consequently conserves primary resources. A biohybrid separation platform consisting of Ln-selective peptides immobilized on a suitable carrier material would be such a novel recycling technology and is being targeted in our current project PepTight. For the identification of Ln-binding peptides, we used the combination of phage surface display and next generation sequencing [1,2]. In parallel in vitro-binding incubations, so-called biopannings, on the target ion and the immobilization material, we were able to enrich and identify peptide sequences showing an affinity for europium ions (Eu3+). Characterization of enriched peptide variants in terms of their Eu3+ affinity was carried out by time-resolved laser-induced fluorescence spectroscopy and isothermal titration calorimetry. Calmodulin’s EF hand 4 peptide, one of four binding sites of the naturally occurring Ln-binding protein [3], serves as a reference system.

  • Lecture (Conference)
    2nd Metal-Binding Peptides conference, 12.07.2024, Toulouse, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-39858


RSAdapter: Adapting Multimodal Models for Remote Sensing Visual Question Answering

Wang, Y.; Ghamisi, P.

Abstract

In recent years, with the rapid advancement of transformer models, transformer-based multimodal architectures have found wide application in various downstream tasks, including, but not limited to, image captioning, visual question answering (VQA), and image–text generation. However, contemporary approaches to remote sensing (RS) VQA often involve resource-intensive techniques, such as full fine-tuning of large models or the extraction of image–text features from pretrained multimodal models, followed by modality fusion using decoders. These approaches demand significant computational resources and time, and a considerable number of trainable parameters are introduced. To address these challenges, we introduce a novel method known as RSAdapter, which prioritizes runtime and parameter efficiency. RSAdapter comprises two key components: the parallel adapter and an additional linear transformation layer inserted after each fully connected (FC) layer within the adapter. This approach not only improves adaptation to pretrained multimodal models but also allows the parameters of the linear transformation layer to be integrated into the preceding FC layers during inference, reducing inference costs. To demonstrate the effectiveness of RSAdapter, we conduct an extensive series of experiments using three distinct RS-VQA datasets and achieve state-of-the-art results on all three datasets. The code for RSAdapter is available online at https://github.com/Y-D-Wang/RSAdapter .

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Permalink: https://www.hzdr.de/publications/Publ-39853


Formation of multinucleated osteoclasts depends on an oxidized species of cell surface-associated La protein

Leikina, E.; Whitlock, J. M.; Melikov, K.; Zang, W.; Bachmann, M.; Chernomordik, L.

Abstract

The bone-resorbing activity of osteoclasts plays a critical role in the life-long remodeling of our bones that is perturbed in many bone loss diseases. Multinucleated osteoclasts are
formed by the fusion of precursor cells, and larger cells – generated by an increased number of cell fusion events – have higher resorptive activity. We find that osteoclast fusion and bone resorption are promoted by reactive oxygen species (ROS) signaling and by an unconventional low molecular weight species of La protein, located at the osteoclast surface. Here, we develop the hypothesis that La’s unique regulatory role in osteoclast multinucleation and function is controlled by an ROS switch in La trafficking. Using antibodies that recognize reduced or oxidized species of La, we find that differentiating osteoclasts enrich an oxidized species of La at the cell surface, which is distinct from the reduced La species conventionally localized within cell nuclei. ROS signaling triggers the shift from reduced to oxidized La species, its dephosphorylation and delivery to the surface of osteoclasts, where La promotes multinucleation and resorptive activity. Moreover, intracellular ROS signaling in differentiating osteoclasts oxidizes critical cysteine residues in the C-terminal half of La,
producing this unconventional La species that promotes osteoclast fusion. Our findings suggest that
redox signaling induces changes in the location and function of La and may represent a promising
target for novel skeletal therapies.

Permalink: https://www.hzdr.de/publications/Publ-39849


Dimensional Dilemma: Navigating the Fusion of Hyperspectral and Lidar Point Cloud Data for Optimal Precision – 2D vs. 3D

Rizaldy, A.; Afifi, A. J. M.; Ghamisi, P.; Gloaguen, R.

Abstract

Despite the extensive body of research conducted on the fusion of lidar and hyperspectral data for land cover classification in urban areas, the predominant approach has been the utilization of rasterized lidar data merged with hyperspectral data. This image-centric methodology tends to overlook the primary advantage inherent in lidar technology—namely, the production of 3D point cloud data. In our work, we present a framework demonstrating how we infer semantic information from 3D point cloud data, comprising both lidar and hyperspectral features—a concept we refer to as a 3D hyperspectral point cloud. We illustrate the generation of hyperspectral point clouds and evaluate the performance of various deep learning models for point learning. Our findings on the original test data of the 2018 IEEE GRSS Data Fusion Challenge, disclosed by IEEE Image Analysis and Data Fusion Technical Committee, indicate that recent deep learning models not only produce better shapes for predicted objects but also yield more precise semantic information. Finally, we plan to release the 3D hyperspectral point cloud data to the community, hoping to inspire future studies on data fusion in the point cloud domain.

Keywords: machine learning; deep learning; hyperspectral; point cloud; lidar; fusion; 3D

Permalink: https://www.hzdr.de/publications/Publ-39848


Data publication: Magnetic imaging of thermally switchable antiferromagnetic/ferromagnetic modulated thin films

Griggs, W.; Peasey, A.; Schedin, F.; Anwar, M. S.; Eggert, B.; Mawass, M.-A.; Kronast, F.; Wende, H.; Bali, R.; Thomson, T.

Abstract

Compiled raw data for the following measurements: MFM, VSM, XPEEM, XRD & XRR as well as simulation data.

Keywords: Magnetic thin films; Magnetic patterning; Implantation/irradiation; Magnetic domains; Magnetic phase

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Permalink: https://www.hzdr.de/publications/Publ-39847


ChangeMinds: Multi-task Framework for Detecting and Describing Changes in Remote Sensing

Wang, Y.; Yu, W.; Kopp, M.; Ghamisi, P.

Abstract

Recent advancements in Remote Sensing (RS) for Change Detection (CD) and Change Captioning (CC) have seen substantial success by adopting deep learning techniques. Despite these advances, existing methods often handle CD and CC tasks independently, leading to inefficiencies from the absence of synergistic processing. In this paper, we present ChangeMinds, a novel unified multi-task framework that concurrently optimizes CD and CC processes within a single, end-to-end model. We propose the change-aware long short-term memory module (ChangeLSTM) to effectively capture complex spatiotemporal dynamics from extracted bi-temporal deep features, enabling the generation of universal change-aware representations that effectively serve both CC and CD tasks. Furthermore, we introduce a multi-task predictor with a cross-attention mechanism that enhances the interaction between image and text features, promoting efficient simultaneous learning and processing for both tasks. Extensive evaluations on the LEVIR-MCI dataset, alongside other standard benchmarks, show that ChangeMinds surpasses existing methods in multi-task learning settings and markedly improves performance in individual CD and CC tasks. Codes and pre-trained models will be available online.

Keywords: multi-task learning; xLSTM; change captioning; change detection; deep learning; remote sensing

Permalink: https://www.hzdr.de/publications/Publ-39846


MineNet-CD: Global Mining Change Detection Dataset

Yu, W.; Das, S.; Rizaldy, A.; Zhang, X.; Gloaguen, R.; Ghamisi, P.

Abstract

Mining change detection requires dedicated datasets because it includes unique objects such as pits or quarries, tailings dams, overburden, processing plants, haul roads, access roads, buildings/sheds, mining and blasting equipment, and plants, among others. This paper introduces a benchmark, large dataset for mining change detection, termed the MineNet-CD, to facilitate large-scale change detection. The proposed dataset contains a total of 100 high-resolution bi-temporal mining images from all over the world with corresponding ground truth. Unlike existing datasets, the images of MineNet-CD exhibit significant background, topological variation, and well-defined ground truth that ignores insignificant change maps. The work analyzes the efficacy of state-of-the-art deep learning methods for change detection. The results demonstrate that more efficient and advanced networks are required to accurately predict the change maps. The dataset and code are available at https://github.com/EricYu97/MineNet-CD.

Keywords: Sustainable Mining; Benchmark Dataset; Deep Learning; Mining Change Detection; MineNet-CD; Remote Sensing

  • Open Access Logo Contribution to proceedings
    IGARSS 2024 - 2024 IEEE International Geoscience and Remote Sensing Symposium, 07.-12.07.2024, Athens, Greece
    DOI: 10.1109/IGARSS53475.2024.10640520

Permalink: https://www.hzdr.de/publications/Publ-39845


Path of a pair of deformable bubbles rising initially in line and close to a vertical wall

Huang, H.; Shi, P.; Elkina, N.; Schulz, H.; Zhang, J.

Abstract

This work numerically examines the stability of this configuration in the presence of a nearby vertical wall. The focus is on moderately inertial regimes, where two bubbles rising initially in line typically separate laterally from each other under unbounded conditions. In the presence of the wall, our results indicate that while the path of the bubble pair predominantly separates laterally, the plane of separation largely depends on the wall-bubble interaction. This interaction involves a competition between two distinct effects, with the dominance determined by the ratios of buoyancy-to-viscous and buoyancy-to-capillary forces, which define the Galilei $(\Ga)$ and Bond $(\Bo)$ numbers, respectively. When $\Bo$ is below a critical $\Ga$-dependent threshold, irrotational effects dominate, initially stabilizing both bubbles near the wall until horizontal separation among them occurs in the wall-parallel plane. Conversely, at higher $\Bo$, vortical effects dominate such that both bubbles migrate away from the wall. During the departure, asymmetric interactions cause the wall-normal velocities of the two bubbles to differ, leading to horizontal separation in the wall-normal plane. These two separation motions, both newly identified in the present study, are found to result from two distinct mechanisms: one associated with the shear flow generated in the gap separating the wall and the leading bubble, which attracts the trailing bubble toward the wall, and the other linked to vortex shedding from the leading bubble, which promotes the trailing bubble’s faster escape from the wall. A slight angular deviation favours separation in the wall-parallel plane, promoting the formation of a near-wall, bubble-rich layer as observed in prior investigations of buoyancy-driven, bubble-laden flows.

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Permalink: https://www.hzdr.de/publications/Publ-39844


Photocathode study in SRF Gun-II at HZDR

Xiang, R.; Arnold, A.; Gatzmaga, S.; Hallilingaiah, G.; Hoffmann, A.; Murcek, P.; Niemczyk, R.; Ryzhov, A.; Teichert, J.

Abstract

HZDR’s SRF Gun-II is an excellent demonstration of SRF technology application in the field of electron sources operating in continuous wave mode. As well known, quality of the photocathode is crucial for operational stability and reliability of an SRF gun. In this contribution, various studies on Cs2Te cathodes, including cleaning, preparation, transport/insertion, RF and beam operation will be summarised. We will look back at the achievements and open issues, and discuss possible improvements and further development.

Keywords: SRF gun; Photocathode; continuous wave mode

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Permalink: https://www.hzdr.de/publications/Publ-39842


Prototypical Unknown-Aware Multiview Consistency Learning for Open-Set Cross-Domain Remote Sensing Image Classification

Zhang, X.; Wu, W.; Zhang, M.; Yu, W.; Ghamisi, P.

Abstract

Abstract—Developing a cross-domain classification model for
remote sensing images has drawn significant attention in the
literature. By leveraging the open-set Unsupervised Domain
Adaptation (UDA) technique, the generalization performance of
deep learning models has been improved with the capability to
recognize unknown categories. However, it remains challenging
to explore distribution patterns in the target domain using
uncertain category-wise supervision from unlabeled datasets
while reducing negative transfer caused by unknown samples. To
develop a robust open-set UDA framework, this paper presents
Prototypical Unknown-aware Multiview Consistency Learning
(PUMCL) designed for remote sensing scene classification across
heterogeneous domains. Specifically, it employs a consistency
learning scheme with multiview and multilevel perturbations
to improve feature learning from unlabeled target samples. An
entropy separation strategy is utilized to facilitate open-set detection
and recognition during adaptation, enabling unknown-aware
feature alignment. Furthermore, the introduction of prototypical
constraints optimizes pseudo-label generation through online
denoising and promotes a compact category-wise feature subspace
for improved class separation across domains. Experiments
conducted on six cross-domain scenarios using AID, NWPU, and
UCMD datasets demonstrate the method’s superior performance
compared to nine state-of-the-art approaches, achieving a gain
of 4.5% to 21.2% in mIoU. More importantly, it shows promising
class separability with clear boundaries between different classes
and compact clustering of unknown samples in the feature space.
The source code will be available at https://github.com/zxk688.

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  • Secondary publication expected from 18.10.2025

Permalink: https://www.hzdr.de/publications/Publ-39840


Curvilinear magnetism: fundamentals and applications

Makarov, D.

Abstract

Curvilinear magnetism is a framework, which helps understanding the impact of geometric curvature on complex magnetic responses of curved 1D wires and 2D shells [1-3]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films and nanowires [3]. In this talk, we will address fundamentals of curvature-induced effects in magnetism and review the envisioned application scenarios. In particular, we will demonstrate that curvature allows tailoring fundamental anisotropic and chiral magnetic interactions and enables fundamentally new nonlocal chiral symmetry breaking effect [4]. The topology of the geometry of 3D shaped magnetic objects allows stabilizing multiple solitons within a confined nanoarchitecture [5]. Those are relevant for numerous research and technology fields ranging from non-conventional computing and spin-wave splitters for low-energy magnonics. The application potential of geometrically curved magnetic architectures is being explored as mechanically reshapeable magnetic field sensors for automotive applications, spin-wave filters, high-speed racetrack memory devices, magnetic soft robots [6] as well as on-skin interactive electronics relying on thin films [7-9] as well as printed magnetic composites [10,11] with appealing self-healing performance [12]. This opens perspectives for magnetoelectronics in smart wearables, interactive printed electronics and motivates further explorations towards the realization of eco-sustainable magnetic field sensing relying on biocompatible and biodegradable materials [13-15].

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
[2] P. Makushko et al., A tunable room-temperature nonlinear Hall effect in elemental bismuth thin films. Nature Electronics 7, 207 (2024).
[3] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
[4] O. M. Volkov et al., Chirality coupling in topological magnetic textures with multiple magnetochiral parameters. Nature Communications 14, 1491 (2023).
[5] O. Volkov et al., Three-dimensional magnetic nanotextures with high-order vorticity in soft magnetic wireframes. Nature Communications 15, 2193 (2024).
[6] M. Ha et al., Reconfigurable Magnetic Origami Actuators with On-Board Sensing for Guided Assembly. Advanced Materials 33, 2008751 (2021).
[7] G. S. Canon Bermudez et al., Magnetosensitive e-skins for interactive devices. Advanced Functional Materials (Review) 31, 2007788 (2021).
[8] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[9] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[10] M. Ha et al., Printable and Stretchable Giant Magnetoresistive Sensors for Highly Compliant and Skin-Conformal Electronics. Advanced Materials 33, 2005521 (2021).
[11] E. S. Oliveros Mata et al., Dispenser printed bismuth-based magnetic field sensors with non-saturating large magnetoresistance for touchless interactive surfaces. Advanced Materials Technologies 7, 2200227 (2022).
[12] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).
[13] X. Wang et al., Printed magnetoresistive sensors for recyclable magnetoelectronics. J. Mater. Chem. A 12, 24906 (2024).
[14] E. S. Oliveros Mata et al., Magnetically aware actuating composites: Sensing features as inspiration for the next step in advanced magnetic soft robotics. Phys. Rev. Appl. (Review) 20, 060501 (2023).
[15] L. Guo et al., Printable magnetoresistive sensors: A crucial step toward unconventional magnetoelectronics. Chinese Journal of Structural Chemistry (Review) 100428 (2024).

Keywords: curvilinear magnetism; shapeable magnetoelectronics; magnetic composites

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  • Lecture (others)
    Seminar of the Laboratoire des Sciences des Procédés et des Matériaux at the Université Sorbonne Paris Nord, 09.12.2024, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-39838


Magnetic composites: from soft robotics to eco-sustainable magnetoelectronics

Makarov, D.

Abstract

Composites consisting of magnetic fillers in polymers and elastomers enable new types of applications in soft robotics, reconfigurable actuation and sensorics. We will introduce lightweight, durable, untethered and ultrafast soft-bodied robots that can walk, swim, levitate, transport cargo, and perform collaborative tasks being driven using magnetic far fields [1,2] and near fields [3,4]. Reconfigurable magnetic origami actuators [2] can be equipped with ultrathin magnetosensitive e-skins [5] to decide on and control the actuation pattern. The on-board sensing adds awareness to soft-bodied magnetic actuators enabling them to act and be controlled similar to conventional robotic devices [6]. Magnetic composites containing functional fillers with high degree of spin polarization can be readily used to realise not only actuators but also solution-processable magnetic field sensors [7]. We will demonstrate that printed magnetoelectronics can be stretchable, skin-conformal, capable of detection in low magnetic fields and withstand extreme mechanical deformations [8,9]. The use of Bi as a functional filler of a composite [9] acts as a green alternative to conventional environmentally polluting Ni-based sensors [8]. We show that printed Bi sensors reveal a linear nonsaturating magnetoresistive response, which is a fingerprint of the electronic band structure of the Bi material - a higher order topological insulator. We feature the potential of printed magnetic field sensors to turn any object into an interactive surface via the realization of a smart magnetosensitive wallpaper or in-mold magnetoelectronics [9]. We will present a technology to realize self-healable magnetic field sensors, which can be repaired upon mechanical damage, hence extending the life-time of magnetoelectronics and reducing the amount of toxic magnetic waste [10]. This opens new perspectives for magnetoelectronics in smart wearables, interactive printed electronics and motivates further explorations towards the realization of recyclable magnetoelectronics [11]. For the latter, we will discuss eco-sustainable, namely biocompatible and biodegradable magneto sensitive devices, which can help to minimise electronic waste and bring magnetoelectronics to new application fields in medical implants and health monitoring [6].

[1] X. Wang et al., Untethered and ultrafast soft-bodied robots. Commun. Mater. 1, 67 (2020).
[2] M. Ha et al., Reconfigurable magnetic origami actuators with on-board sensing for guided assembly. Adv. Mater. 33, 2008751 (2021).
[3] M. Richter et al., Locally addressable energy efficient actuation of magnetic soft actuator array systems. Advanced Science 2302077 (2023).
[4] L. Masjosthusmann et al., Miniaturized variable stiffness gripper locally actuated by magnetic fields. Advanced Intelligent Systems 6, 2400037 (2024).
[5] G. S. Canon Bermudez et al., Magnetosensitive e-skins for interactive devices. Adv. Funct. Mater. (Review) 31, 2007788 (2021).
[6] E. S. Oliveros Mata et al., Magnetically aware actuating composites: Sensing features as inspiration for the next step in advanced magnetic soft robotics. Phys. Rev. Appl. (Review) 20, 060501 (2023).
[7] L. Guo et al., Printable magnetoresistive sensors: A crucial step toward unconventional magnetoelectronics. Chinese Journal of Structural Chemistry (Review) 100428 (2024).
[8] M. Ha et al., Printable and stretchable giant magnetoresistive sensors for highly compliant and skin-conformal electronics. Adv. Mater. 33, 2005521 (2021).
[9] E. S. Oliveros Mata et al., Dispenser printed bismuth-based magnetic field sensors with non-saturating large magnetoresistance for touchless interactive surfaces. Adv. Mater. Technol. 7, 2200227 (2022).
[10] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).
[11] X. Wang et al., Printed magnetoresistive sensors for recyclable magnetoelectronics. J. Mater. Chem. A 12, 24906 (2024).

Keywords: flexible magnetic field sensors; shapeable magnetoelectronics; printed magnetoelectronics; soft magnetic composites; magnetic soft robots

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  • Lecture (others)
    Colloquium of the Collaborative Research Center (CRC) 1261, 16.01.2025, Kiel, Germany

Permalink: https://www.hzdr.de/publications/Publ-39836


RADEKOR: Speciation and Transfer of Radionuclides (RN) in the Human Organism Especially Taking into Account Decorporation Agents (DA) – a Joint Project, Part II

Heller, A.; Senwitz, C.; Acker, M.; Taut, S.; Stumpf, T.; Barkleit, A.

Abstract

When radionuclides (RN) enter the food chain and are ingested by humans, they pose a potential health risk due to their radio- and chemotoxicity. To minimize the health risk, decorporation agents (DA), which are usually strong complexants, are used after the accidental incorporation of RN to increase their excretion. In order to accurately assess the health risk after oral ingestion and to apply effective decontamination methods, it is essential to understand the processes of (bio)chemistry and speciation of RN at the molecular and cellular level. Within the joint research project RADEKOR: “Speciation and transfer of radionuclides in the human organism especially taking into account decorporation agents”, molecular speciation studies of RN in artificial biofluids of the digestive system of humans and cytotoxicity studies with respective human and rat renal cell lines in vitro both in the absence and presence of DA were performed.

As DA we investigated i) aminopolycarboxylate diethylenetriaminepentaacetic acid DTPA as the only approved and commercially used DA and ii) some promising new chelators like the hydroxypyridinone 3,4,3-(LI-1,2-HOPO) (HOPO) and 1-hydroxy-ethylidene-1,1-diphosphonic acid (HEDP), which was formerly used as a pharmaceutical. First, the complex formation of the non-radioactive An(III) analogue Eu(III) with HEDP in aqueous solution and cell culture medium was studied. Second, Eu(III) and Am(III) cytotoxicity onto kidney cells was investigated in absence and presence of DTPA and HOPO. Finally, the molecular speciation of Eu(III) and Am/Cm(III) with and w/o DTPA and HOPO was studied in both cell culture medium and exposed renal cells. The results of this work contribute to a better understanding of the effect of DA after RN incorporation at the molecular level and support making them more effective in the future.

  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2024, 05.-07.11.2024, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39835


RADEKOR: Speciation and Transfer of Radionuclides (RN) in the Human Organism Especially Taking into Account Decorporation Agents (DA) – a Joint Project, Part I

Barkleit, A.; Friedrich, S.; Butscher, D.; Kretzschmar, J.; Stumpf, T.; Heller, A.

Abstract

When radionuclides (RN) enter the food chain and are ingested by humans, they can present significant health risks due to their radiotoxic and chemotoxic properties. To mitigate these risks, decorporation agents (DA), which are typically strong chelators, are employed after accidental RN exposure to facilitate their removal from the body. A thorough understanding of the (bio)chemical behavior and speciation of RN at both the molecular and cellular levels is essential for assessing health impacts and applying effective decontamination techniques. In the joint BMBF project RADEKOR, studies were conducted to investigate the molecular speciation of RN in artificial digestive biofluids, alongside with in vitro cytotoxicity assessments using human and rat kidney cell lines, with and without DA.

As DA we investigated i) aminopolycarboxylate diethylenetriaminepentaacetic acid (DTPA) as the only approved and commercially used DA, ii) alternative aminocarboxylates like ethylenediaminetetraacetic acid (EDTA) or ethyleneglycoltetraacetic acid (EGTA), and iii) some promising new chelators like the hydroxypyridinone 3,4,3-(LI-1,2-HOPO) (HOPO) and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), which was formerly used as a pharmaceutical. The complex formation of Eu(III) as a non-radioactive analogue for An(III) with EGTA was studied along with its molecular speciation in simulated body fluids in presence and absence of DTPA, EGTA, and HOPO. Furthermore, the molecular speciation of U(VI) in simulated body fluids and cell culture medium as well as its cytotoxicity onto kidney cells was investigated in absence and presence of DTPA, HEDP, and HOPO. The results of this work contribute to a better understanding of the effect of DA after RN incorporation at the molecular level and support making them more effective in the future.

  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2024, 05.-07.11.2024, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39834


Unidirectional ray polaritons in twisted asymmetric stacks

Álvarez-Cuervo, J.; Obst, M.; Dixit, S.; Carini, G.; Tresguerres-Mata, A. I. F.; Lanza, C.; Terán-García, E.; Álvarez-Pérez, G.; Álvarez-Tomillo, L. F.; Diaz-Granados, K.; Kowalski, R.; Senerath, A. S.; Mueller, N. S.; Herrer, L.; de Teresa, J. M.; Wasserroth, S.; Klopf, J. M.; Beechem, T.; Wolf, M.; Eng, L. M.; Folland, T. G.; Tarazaga Martín-Luengo, A.; Martín-Sánchez, J.; Kehr, S. C.; Nikitin, A. Y.; Caldwell, J. D.; Alonso-González, P.; Paarmann, A.

Abstract

The vast repository of van der Waals (vdW) materials supporting polaritons offers numerous possibilities to tailor electromagnetic waves at the nanoscale. The development of twistoptics—the modulation of the optical properties by twisting stacks of vdW materials—enables directional propagation of phonon polaritons (PhPs) along a single spatial direction, known as canalization. Here we demonstrate a complementary type of directional propagation of polaritons by reporting the visualization of unidirectional ray polaritons (URPs). They arise naturally in twisted hyperbolic stacks with very different thicknesses of their constituents, demonstrated for homostructures of -MoO3 and heterostructures of -MoO3 and -Ga2O3. Importantly, their ray-like propagation, characterized by large momenta and constant phase, is tunable by both the twist angle and the illumination frequency. Apart from their fundamental importance, our findings introduce twisted asymmetric stacks as efficient platforms for nanoscale directional polariton propagation, opening the door for applications in nanoimaging, (bio)-sensing, or polaritonic thermal management.

Keywords: s-SNOM; FEL; THz; MIR; nanoscopy; phonon polaritons; 2D materials; van der Waals (vdW) materials

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Permalink: https://www.hzdr.de/publications/Publ-39833


Molecular to Macroscopic Insights: Technetium immobilization through iron(II) phosphate

Börner, C.; Roßberg, A.; Müller, K.; Schild, D.; Seewald, F.; Stumpf, T.; Mayordomo, N.

Abstract

Technetium (Tc) is an element originating mostly from the fission of ²³⁵U and ²³⁹Pu with a yield of 6%.¹ Therefore, ⁹⁹Tc is mainly found in high-level radioactive waste, e.g. from nuclear power or reprocessing plants.² The waste disposal is the subject of numerous studies due to the long half-life of many radionuclides (e.g. ⁹⁹Tc: 2.1 · 10⁵ years)¹ and their high radiotoxicity. One of the most widely accepted strategies is the deep geological underground repository. This approach relies on a multi-barrier system designed to minimize the risk of a worst-case scenario, where water intrusion could lead to the corrosion of the waste canister and the subsequent release of radionuclides. For the long-term safety, including the construction of effective barriers, it is essential to study the interaction of radionuclides with the various minerals present in the repository at a fundamental level. Tc poses a particular challenge due to its complex redox chemistry high mobility in its oxidized form TcO₄¯, under oxidising conditions. However, Tc migration decreases significantly when Tc(VII) is reduced to Tc(IV), as it then forms precipitates or becomes immobilized by mineral surfaces such as Fe(II) minerals.³ Vivianite (Fe₃(PO₄)₂ · 8 H₂O) is a naturally occurring Fe(II) mineral under reducing conditions⁵ and can be formed by microorganisms.⁶ Phosphate phases are already being considered as an immobilisation matrix for other radionuclides relevant in deep geological repositories (e.g. ²³⁵U, ²³⁷Np, ²³⁹Pu, ²⁴³Am).⁷ ⁸

This study investigates the retention of Tc by synthetic vivianite particles as a function of pH, Tc concentration and ionic strength on a macroscopic and molecular scale. In addition, Tc(IV) reoxidation experiments were performed.⁴

The synthesis of vivianite was carried out by precipitation from a solution mixture of an iron(II) sulphate and ammonium hydrogen phosphate, as described by Roldán et al..⁹ The product was characterised by Raman microscopy, Mössbauer spectroscopy, powder X-ray diffraction and solubility studies with regard to the pH-dependent behaviour under N₂ atmosphere. The identified phase at pH 5.0 and pH 8.0 is vivianite. At pH 12.0 vivianite transforms into Fe(II)(OH)₂. The change in solid morphology due to the mineralogical modification was also observed with scanning electron microscopy.

Batch contact experiments at N₂ atmosphere were carried out to determine the interaction between vivianite particles suspended in water and KTcO₄. The Tc concentrations in solution were determined by liquid scintillation counting, while the Tc-loaded solids were analysed by X-ray photoelectron spectroscopy (XPS). Kinetic contact experiments of 1 µM TcO₄¯ show that Tc uptake by vivianite increases with longer contact time at pH 8.0 and is complete after 20 days, while no Tc retention takes place at pH 6.5. The XPS results of Tc-containing solids from experiments at pH 5.0 and pH 12.0 show that Tc(IV) was present on the solid surface. It indicates that Tc removal at high pH values is due to the reductive immobilization of Tc(VII) to Tc(IV) by vivianite. In contrast, at acidic pH values (pH 5.0), Tc(VII) reduction occurs without decreasing the Tc concentration in solution, but by XPS, formerly dissolved Tc(IV) could be detected on the solid surface. Further X-ray absorption spectroscopy (XAS) measurements were performed to determine the molecular environment of Tc when it was directly presence in the vivianite synthesis (coprecipitate) and after interaction with vivianite at pH 8.5 and 11.0. The first preliminary results indicate that Tc(IV) coordination environment drastically differs when changing pH and Tc concentration. Their final structural rearrangement is yet to be deciphered.

To investigate the remobilisation of reduced Tc(IV), samples obtained after completion of Tc retention experiments at different pH were exposed to ambient atmosphere and Tc concentration was monitored for six months. Under oxidising conditions, no remobilisation of Tc takes place at pH values above pH 8.0. The immobilisation of Tc by vivianite remains complete over the course of six months. This shows a slower Tc(IV) reoxidation than in Tc(IV)-containing FeS₂ mineral phases, where reoxidation starts after 64 days.¹⁰ Additionally, an increase of Tc retention was determined at pH 2.0 and pH 3.0. This can be explained by a time-delayed immobilisation of Tc by the dissolved Fe(II).¹¹
Those promising results show a high affinity of vivianite towards Tc, aided by the reduction of Tc(VII) to Tc(IV) by structural Fe(II).

The authors acknowledge the German Federal Ministry of Education and Research (BMBF) for the financial support of the NukSiFutur TecRad young investigator group (02NUK072).¹²

References:

1 NDS-Datenbank, https://www-nds.iaea.org, (accessed 4 June 2024).
2 A. H. Meena, Y. Arai, Environ. Chem. Lett., 2017, 15, 241–263.
3 C. I. Pearce, R. C. Moore, J. W. Morad, R. M. Asmussen, S. Chatterjee, A. R. Lawter, T. G. Levitskaia, J. J. Neeway, N. P. Qafoku, M. J. Rigali, S. A. Saslow, J. E. Szecsody, P. K. Thallapally, G. Wang, V. L. Freedman, Sci. Total Environ., 2020, 716, 132849.
4 C. Börner, Masterarbeit, Technische Universität Dresden, 2023.
5 A. Al-Borno, M. B. Tomson, Geochim. Cosmochim. Acta, 1994, 58, 5373–5378.
6 J. M. McBeth, J. R. Lloyd, G. T. W. Law, F. R. Livens, I. T. Burke, K. Morris, Mineral. Mag., 2011, 75, 2419–2430.
7 P. Sengupta, J. Hazard. Mater., 2012, 235–236, 17–28.
8 M. R. Rafiuddin, G. Donato, S. McCaugherty, A. Mesbah, A. P. Grosvenor, ACS Omega, 2022, 7, 39482–39490.
9 R. Roldán, V. Barrón, J. Torrent, Clay Miner., 2002, 37, 709–718.
10 D. M. Rodríguez, N. Mayordomo, D. Schild, S. Shams Aldin Azzam, V. Brendler, K. Müller, T. Stumpf, Chemosphere, 2021, 281, 130904.
11 J. M. Zachara, S. M. Heald, B. H. Jeon, R. K. Kukkadapu, C. Liu, J. P. McKinley, A. C. Dohnalkova, D. A. Moore, Geochim. Cosmochim. Acta, 2007, 71, 2137–2157.
12 TecRad-group, https://www.hzdr.de/db/Cms?pNid=1375, (accessed 4 June 2024).

Keywords: technetium; iron(II); mineral; vivianite; reduction

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  • Lecture (Conference)
    Rising Stars Workshop, 25.-26.11.2024, Joint Research Center, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-39832


Data publication: Boosting electrode performance and bubble management via Direct Laser Interference Patterning

Rox, H.; Ränke, F.; Mädler, J.; Marzec, M. M.; Sokolowski, K.; Baumann, R.; Hamedimastanabad, H.; Yang, X.; Mutschke, G.; Urbas, L.; Lasagni, A. F.; Eckert, K.

Abstract

Direct Laser Intereference Patterning is a promising approach to structure electrodes for alkaline water electrolysis to improve the electrode performance. By increasing the electrochemical active surface area and apply a superhydrophilic surface structure, the overpotential could be decreased significantly. The present data set compares three different spatial period and aspect ratios, defined as the ratio between structure depth and period, at applied current densities of j = 10, 31.62 and 100 mA/cm² in terms of electrode potential, detached bubble size and number of nucleation sites. As electrolyte 1 M KOH was used. All experiments were carried out under ambient conditions (T = 293 K,p = 1 bar).

A.) Description of Data.zip:

An overview of all performed experiments is given in the file Summary.csv. The data is analyzed as described in the corresponding journal publication Boosting electrode performance and bubble management via Direct Laser Interference Patterning. Each data set is stored in a .hdf5-file, with the relevant metadata incorporated into the attributes assigned to the groups/datasets within the .hdf5-file. The data files are structured in groups as follows:

  • Electrochemical Measurement Data
    • Galvanostatic Measurement Data
    • CV double-layer capacitance
    • LSV onset potential
  • Results
    • Detected Bubbles Sideview
    • Detected Bubbles Topview
  • Sideview Raw Images (only for SH2_LS_DoE_01.hdf5)
  • Topview Raw Images (only for SH2_LS_DoE_01.hdf5)

With the exception of a single comprehensive data set comprising unprocessed images (SH2_LS_DoE_01.hdf5), the remaining raw images from all performed measurements can be made available upon request.

B.) Description of Videos.zip:

Example videos for non-structured and laser-structured electrodes at a current density of j = 100 mA/cm² are given for both, sideview and topview. The provided characteristic videos are named after following scheme:

  • Perspective_Electrode_CurrentDensity
  • E.g.: Sideview_#1_NSE_100mAcm-2

Keywords: Alkaline water electrolysis; Bubble dynamics; Direct laser interference patterning; Oxygen evolution reaction

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  • Data Center

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Permalink: https://www.hzdr.de/publications/Publ-39830


Nuclear magnetic resonance spectroscopy in pulsed magnetic fields

Kühne, H.; Ihara, Y.

Abstract

This article provides an introduction to nuclear magnetic resonance spectroscopy in pulsed magnetic fields (PFNMR), focussing on its capabilities, applications, and future developments in research involving high magnetic fields. It highlights the significance of PFNMR in enhancing the understanding of solid-state materials, with particular emphasis on those exhibiting complex interactions and strong electronic correlations. Several technical aspects are discussed, including the challenges associated with high-frequency NMR experiments. The power of PFNMR is showcased through several examples, including studies on the topical materials LiCuVO4, SrCu2(BO3)2, and CeIn3, offering insights into their magnetic and electronic properties at high magnetic fields. The article also discusses possible future directions for the technique, including improvements in PFNMR instrumentation and the exploration of materials under extreme conditions. This exposition underscores the role of PFNMR in advancing the frontiers of materials-science research.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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  • Secondary publication expected from 05.09.2025

Permalink: https://www.hzdr.de/publications/Publ-39827


Data publication: Curvature-induced parity loss and hybridization of magnons: Exploring the connection of flat and tubular magnetic shells

Brevis, F.; Landeros, P.; Lindner, J.; Kakay, A.; Körber, L.

Abstract

This archive contains the raw data as well as the Tetrax (www.tetrax.software) Jupyter notebooks to produce the data that has been analyzed and used for the manuscript: Curvature-induced parity loss and hybridization of magnons: Exploring the connection of flat and tubular magnetic shells, Physical Review B 110, 134428 (2024), published on 17 October, 2024.

Keywords: curvature-induced; spin waves; mignons; hybridization; parity

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Permalink: https://www.hzdr.de/publications/Publ-39826


Unusual metallic state in superconducting A15-type La4H23

Guo, J.; Semenok, D.; Shutov, G.; Zhou, D.; Chen, S.; Wang, Y.; Zhang, K.; Wu, W.; Luther, S.; Helm, T.; Huang, X.; Cui, T.

Abstract

Hydride superconductors continue to fascinate the communities of condensed matter physics and material scientists because they host the promising near room-temperature superconductivity. Current research has concentrated on the new hydride superconductors with the enhancement of the superconducting transition temperature (Tc). The multiple extreme conditions (high pressure/temperature and magnetic field) will introduce new insights into hydride superconductors. The study of transport properties under very high magnetic fields facilitates the understanding of superconductivity in conventional hydride superconductors. In the present work, we report experimental evidence of an unusual metal state in a newly synthesized cubic A15-type La4H23 that exhibits superconductivity with a Tc reaching 105 K at 118 GPa. A large negative magnetoresistance is observed in strong pulsed magnetic fields in the non-superconducting state of this compound below 40 K. Moreover, we construct the full magnetic phase diagram of La4H23 up to 68 T at high pressure. The present work reveals anomalous electronic structural properties of A15-La4H23 under high magnetic fields, and therefore has great importance with regard to advancing the understanding of quantum transport behaviors in hydride superconductors.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-39825


Possible realization of a randomness-driven quantum disordered state in the S = 1/2 antiferromagnet Sr3CuTa2O9

Sana, B.; Barik, M.; Lee, S.; Jena, U.; Baenitz, M.; Sichelschmidt, J.; Luther, S.; Kühne, H.; Sethupathi, K.; Ramachandra Rao, M. S.; Choi, K. Y.; Khuntia, P.

Abstract

Collective behavior of spins, frustration-induced strong quantum fluctuations, and subtle interplay between competing degrees of freedom in quantum materials can lead to correlated quantum states with exotic excitations that are essential ingredients for establishing paradigmatic models and have immense potential for quantum technologies. Disorder is ubiquitous in real materials, and the detailed insights into the role of disorder on the intriguing ground state borne out of quenched randomness provide a route towards the design and discovery of functional quantum materials. Herein we report magnetization, specific heat, electron spin resonance, and muon spin resonance studies on a 3d-electron-based antiferromagnet Sr3CuTa2O9. The negative value of Curie-Weiss temperature, obtained from the Curie-Weiss fit of high-temperature magnetic susceptibility data indicates the presence of antiferromagnetic interaction between Cu2+ moments. Specific heat data show the absence of long-range magnetic ordering down to 64 mK despite a reasonably strong exchange interaction between Cu2+ (S = 1/2) spins as reflected from a Curie-Weiss temperature of −27 ± 1 K. The power-law behavior and the data collapse of specific heat and magnetization data evince the emergence of a random-singlet state in Sr3CuTa2O9. The power-law-like spin autocorrelation function and the data collapse of muon polarization asymmetry with longitudinal field dependence of t/(μ0H)γ further support credence to the presence of a randomness-induced quantum disordered state. Our results suggest that randomness induced by disorder is an alternate route to realize quantum spin disordered state in this antiferromagnet.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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Permalink: https://www.hzdr.de/publications/Publ-39824


Quasistatic magnetism in the breathing pyrochlore antiferromagnets LiGa1−xInxCr4O8 (x = 0.2, 0.5)

Lee, W.; Yoon, S.; Choi, Y.-S.; Do, S.-H.; Ponomaryov, O.; Zvyagin, S.; Gorbunov, D.; Wosnitza, J.; Koda, A.; Chen, W.-T.; Lee, S.

Abstract

We report magnetic susceptibility, high-field magnetization, muon spin relaxation, and electron spin resonance measurements of the breathing pyrochlore antiferromagnets LiGa1−xInxCr4O8 (x = 0.2, 0.5). Unlike the previously proposed spin-glass-like phase for 0.1 < x < 0.75, we find no signature for spin glassiness and phase segregation in both the x = 0.2 and 0.5 compounds. Instead, we identify a two-step magnetic transition with a partial spin freezing at T = 12 K (x = 0.2) and 9 K (x = 0.5) followed by quasistatic order at Tm = 6 K (x = 0.2) and 3 K for (x = 0.5). In addition, for Tm < T < T, we observe evidence of a competition between fast and slow spin dynamics, suggesting a thermal and temporal distribution of spin correlations. Our findings underscore the possibility of realizing novel magnetic phases by tuning bond alternation and introducing bond disorder through chemical substitution.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-39823


Giant magnetocaloric effect of Ni-Co-Mn-Ti all-d Heusler alloys in high magnetic fields

Beckmann, B.; Taubel, A.; Gottschall, T.; Pfeuffer, L.; Koch, D.; Staab, F.; Bruder, E.; Scheibel, F.; Skokov, K. P.; Gutfleisch, O.

Abstract

Ni-Co-Mn-Ti all-d Heusler alloys are attracting considerable attention for solid-state caloric cooling applications due to their promising combination of excellent caloric and mechanical properties. Here, we report on the maximum attainable magnetocaloric effect in Ni37Co13Mn34.5Ti15.5, which shows a first-order magnetostructural martensitic transformation around room temperature. Heat capacity measurements reveal a giant transition entropy change of 43.5 J(kgK)−1 and are utilized to estimate the magnetocaloric effect as well as the magnetic fields required to saturate it in isothermal and adiabatic conditions. Confirming the results based on this approach, we achieve maximum isothermal entropy changes and directly measured adiabatic temperature changes of 37.8 J(kgK)−1 and −20.2 K, respectively. Thus, the herein reported maximum attainable magnetocaloric effect outperforms classical Ni-Mn-based Heusler alloys, such as Ni(-Co)-Mn-In. Especially the saturated adiabatic temperature change surpasses all previously published values of magnetic field-induced first-order phase transitions measured around room temperature in pulsed magnetic fields in recent years. Thereby, we demonstrate that Ni(-Co)-Mn-Ti Heusler alloys are particularly suitable for the application of sufficiently large external stimuli to fully induce the phase transition and exploit their intrinsically large caloric effect.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-39822


Absence of Fermi surface reconstruction in pressure-driven overdoped YBCO

Tozer, S. W.; Coniglio, W. A.; Förster, T.; Bonn, D. A.; Hardy, W. N.; Liang, R.; Kampert, W. A. G.; Grockowiak, A. D.

Abstract

The evolution of the critical superconducting temperature and field, quantum oscillation frequencies, and effective mass m∗ in underdoped YBa2Cu3O7−δ (YBCO) crystals (p = 0.11, with p the hole concentration per Cu atom) points to a partial suppression of the charge orders with increasing pressure up to 7 GPa, mimicking doping. Application of pressures up to 25 GPa pushes the sample to the overdoped side of the superconducting dome. In contrast to other cuprates, or to doping studies on YBCO, the frequencies of the quantum oscillations measured in that pressure range do not support the picture of a Fermi-surface reconstruction in the overdoped regime, but possibly point to the existence of a new charge order.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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Permalink: https://www.hzdr.de/publications/Publ-39821


RandomCells: Julia package for the generation of random convex polytopes

Ballani, F.

Abstract

RandomCells is a Julia package that provides implementations of some standard models for random convex polytopes that arise from random tessellations of the plane or space and are therefore also intended to serve in part as simple models for particles in random breakage for subsequent investigations. The package also implements some standard statistics such as volume, surface area and mean width.

Keywords: random polytopes; random particles; random breakage; tessellations; Julia

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Permalink: https://www.hzdr.de/publications/Publ-39819


Curvature-induced parity loss and hybridization of magnons: Exploring the connection of flat and tubular magnetic shells

Brevis, F.; Landeros, P.; Lindner, J.; Kakay, A.; Körber, L.

Abstract

This paper delves into the connection between flat and curvilinear magnetization dynamics. For this, we numerically study the evolution of the magnon spectrum of rectangular waveguides upon rolling its cross section up to a full tube. Magnon spectra are calculated over a wide range of magnetization states using a finite-element dynamic-matrix method, which allows us to trace the evolution of the magnon frequencies and several critical magnetic fields with increasing curvature. By analyzing the parity of the higher-order magnon modes, we find a curvature-induced mode heterosymmetry that originates from a chiral contribution to the exchange interaction and is related to the Berry phase of magnons in closed loops. Importantly, this curvature-induced parity loss has profound consequences for the linear coupling between different propagating magnons, allowing for hybridization between initially orthogonal modes. In this context, we demonstrate the integral role of edge modes in forming the magnon spectrum in full tubes. Our findings provide theoretical insights into curvilinear magnetization dynamics and are relevant for interpreting and designing experiments in the field.

Keywords: Curvature-induced; parity; hybridization; spin waves

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Permalink: https://www.hzdr.de/publications/Publ-39818


Vegetation clustering and self-organization in inhomogeneous environments

Pinto Ramos, D. I.; Clerc, M. G.; Makhoute, A.; Tlidi, M.

Abstract

Due to climatic changes, excessive grazing, and deforestation, semi-arid and arid ecosystems are vulnerable to desertification and land degradation. Adversely affected biological productivity has a negative impact on social, economic, and environmental factors. The term 'arid ecosystems' refers not only to water-scarce landscapes but also to nutrient-poor environments. Specifically, the vegetation cover loses spatial homogeneity as aridity increases, and the self-organized heterogeneous vegetation patterns developed could eventually collapse into a bare state. It is still unclear whether this transition would be gradual or abrupt, leading to the often-called catastrophic shift of ecosystems. Several studies suggest that environmental inhomogeneities in time or space can promote a gradual transition to bare soil, thus avoiding catastrophic shifts. Environmental inhomogeneities include non-uniformities in the spatial distribution of precipitation, spatial irregularities in topography and other external factors. Employing a generic mathematical model including environmental inhomogeneities in space, we show how two branches of vegetation patterns create a hysteresis loop when the effective mortality level changes. These two branches correspond to qualitatively distinct vegetation self-organized responses. In an increasing mortality scenario, one observes an equilibrium branch of high vegetation biomass forming self-organized patterns with a well-defined wavelength. However, reversing the mortality trend, one observes a low biomass branch lacking a wavelength. We call this phenomenon the clustering of vegetation patches. This behavior can be connected to historically significant trends of climate change in arid ecosystems.

Keywords: Vegetation pattern formation; Spatial inhomogeneities

Permalink: https://www.hzdr.de/publications/Publ-39816


Vegetation banded patterns and their dislocations

Pinto Ramos, D. I.

Abstract

Self-organization and pattern formation are ubiquitous processes in nature. We study the properties of migrating banded vegetation patterns in arid landscapes, usually presenting dislocation topological defects. Vegetation patterns with dislocations are investigated in three different ecosystems. We show through remote sensing data analysis and theoretical modeling that the number of dislocations N(x) decreases in space according to the law N ∼ log(x/B)/x, where x is the coordinate in the opposite direction to the water flow and B is a suitable constant. A sloped topography explains the origin of banded vegetation patterns with permanent dislocations. Theoretically, we considered well-established approaches to describe vegetation patterns. All the models support the law. This contrasts with the common belief that the dynamics of dislocations are transient. In addition, regimes with a constant distribution of defects in space are predicted. We analyze the different regimes depending on the aridity level and water flow speed. The reported decay law of defects can warn of imminent ecosystem collapse.

  • Invited lecture (Conferences)
    Dynamics Days Europe 2024, 29.07.2024, Bremen, Germany

Permalink: https://www.hzdr.de/publications/Publ-39815


How range residency and velocity correlations impact encounter rates

Surendran, A.

Abstract

Encounters between individuals are fundamental for many ecological processes such as mate finding, predation, and disease transmission, among others. Computing encounter rates in these scenarios provides insight into how individual movement strategies lead to population-level consequences. Many previous studies, focused on tying individual movement behavior to encounters, suggest that directionally persistent movement (ballistic movement) strategies improve encounter rates. However, these models often ignore the effect of range residency of animals, where the individuals use space non-uniformly and occupy a home range that is considerably smaller than the population range. Here we show that when we consider the range resident behavior, the ballistic movement strategy does not always result in increased encounter as previously thought. Rather, we show that the effect of ballistic movement on encounter rates is influenced by the spatial distribution of the individual home ranges. We demonstrate these features by deriving exact analytical expressions for encounter rates under the Ornstein-Uhlenbeck movement with foraging (OUF), which is a movement model that allows directional persistence (correlations in velocity) along with range residency.

Keywords: Animal movement; Animal encounters; Ornstein-Uhlenbeck movement with foraging

  • Invited lecture (Conferences)
    Brin MRC Workshop - Applied Stochastic Processes for Encounter Problems, 05.-09.02.2024, University of Maryland, Collage Park, USA

Permalink: https://www.hzdr.de/publications/Publ-39814


Topological defect law for migrating banded vegetation patterns

Pinto Ramos, D. I.

Abstract

Large-scale vegetation patterns, with wavelengths up to hundreds of meters, have inspired scientists to understand their origin and their influence on ecosystems. One global observation is that banded patterns generally appear on sloped territories, where the environment imposes a clear break of symmetry, favoring stripes with well-defined directions. Most models predict a perfect stripe pattern as the asymptotic state. Including the break of symmetry in mathematical models and realistic boundary conditions enables the formation of banded structures characterized by showing dislocations throughout the pattern. The pattern as a whole acquires a group velocity, propagating as a nonlinear wave with singularities, which is permanently sustained by boundaries. This same bifurcation from perfect bands to bands with dislocations is observed in three different models of vegetation biomass spatiotemporal evolution proposed in the literature. Surprisingly, this new dynamical regime could leave an imprint in the spatial distribution of dislocations, which is observed in actual vegetation banded patterns from Chile, Sudan, and North America, where we analyzed the distribution of dislocations together with the topography of the territory to unveil a clear break of symmetry, in line with our theory. We explore how ecologically relevant parameters could mediate the transition between the different dynamical regimes. Our work proposes that the break of symmetry due to the environment and the boundary conditions could play a crucial role in understanding these complex systems.

  • Invited lecture (Conferences)
    European Conference on Mathematical and Theoretical Biology (ECMTB), 22.07.2024, Toledo, Spain

Permalink: https://www.hzdr.de/publications/Publ-39813


NiPS3 and CrPS4 – Interplay between structure and magnetic ordering

Costa Guedes, B.

Abstract

Magnetic van der Waals materials, such as transition metal phosphorous chalcogenides MPS3 and MPS4 (M = Mn, Fe, Co, and Ni), offer potential for coupled spintronic and optoelectronic applications due to their wide band gap (1.2 - 3.5 eV) [1] and efficient light absorption. While both belong to the C2/m space group, they differ in magnetic ordering, with MPS3 preserving antiferromagnetic (AFM) ordering [1] and CrPS4 changing from AFM to ferromagnetic (FM) in the monolayer limit [2]. However, the mechanism and role of exchange interaction still need to be clarified, especially in the case of MPS4. Our methodology involved using VASP with PAW and PBE+D3, optB86-vdW functionals, and the SCAN functional. For the magnetic structure, we adopted the GGA+U approach with Dudarev formalism [3]. The exchange parameters for a Heisenberg Hamiltonian were then derived with the TB2J Python package [4] by downfolding the DFT bands in the vicinity of the Fermi energy employing Wannier functions. First, we studied CrPS4 and found an FM ground state with a magnetic moment of 3.0 µB/magnetic
atom, in agreement with the literature [5]. The exchange parameters of CrPS4 were analyzed in detail, providing insight into the competition between different exchange-interaction mechanisms.

  • Poster
    Saxony meets Lower Silesia: Science across Borders, 17.-18.06.2024, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-39812


Nonreciprocal feedback induces migrating oblique and horizontal banded vegetation patterns in hyperarid landscapes

Hidalgo-Ogalde, B.; Pinto Ramos, D. I.; Clerc, M. G.; Tlidi, M.

Abstract

In hyperarid environments, vegetation is highly fragmented, with plant populations exhibiting non‐random biphasic structures where regions of high biomass density are separated by bare soil.
In the Atacama Desert of northern Chile, rainfall is virtually nonexistent, but fog pushed in from the interior sustains patches of vegetation in a barren environment. Tillandsia landbeckii, a plant with
no functional roots, survives entirely on fog corridors as a water source. Their origin is attributed to interaction feedback among the ecosystem agents, which have different spatial scales, ultimately generating banded patterns as a self‐organising response to resource scarcity. The interaction feedback between the plants can be nonreciprocal due to the fact that the fog flows in a well‐
defined direction. Using remote sensing analysis and mathematical modelling, we characterise the orientation angle of banded vegetation patterns with respect to fog direction and topographic slope gradient. We show that banded vegetation patterns can be either oblique or horizontal to the fog flow rather than topography. The initial and boundary conditions determine the type of the pattern. The bifurcation diagram for both patterns is established. The theoretical predictions are in agreement with observations from remote sensing image analysis.

Keywords: Vegetation patterns; Nonlinear dynamics; Nonreciprocal coupling

Permalink: https://www.hzdr.de/publications/Publ-39811


Interplay between structure and magnetism in MPS4

Costa Guedes, B.

Abstract

Magnetic van der Waals materials, such as transition metal phosphorus chalcogenides MPS3 and MPS4 (M = Mn, Fe, Co, Ni), offer potential for spintronic and optoelectronic applications
due to their wide band gaps (1.2 - 3.5 eV) [1] and efficient light absorption. Both belong to the C2/m space group but differ in magnetic ordering: MPS3 maintains antiferromagnetic (AFM)
ordering [1], while CrPS4 shifts from AFM to ferromagnetic (FM) in the monolayer limit [2].However, the mechanisms involving ligand field theory and exchange interactions are still
unclear, necessitating further research on the magnetic states in FePS4, CoPS4, MnPS4, and NiPS4, and their instability factors.
We studied the stability and electronic properties of the MPS4 family using DFT, focusing on magnetic properties. VASP with PAW, PBE+D3, optB86-vdW functionals, and the SCAN
functional were employed with the GGA+U approach with Dudarev formalism. Analysis was done using a Heisenberg model derived using TB2J [3] and bond analysis using LOBSTER [4].
First, we studied CrPS4 and found an FM ground state with a magnetic moment of 3.0 μB per magnetic atom, consistent with the literature [5]. Detailed analysis of CrPS4's exchange
parameters provided insight into the competition between exchange interaction mechanisms, explaining why it exhibits FM order in the monolayer. We also studied FePS4, CoPS4, MnPS4,
and NiPS4. The exchange parameters, combined with structural and COHP analysis, suggest these materials are unstable due to a structure favoring FM ordering. However, the electron distribution in these MPS4 compounds, except CrPS4, favors AFM coupling.
In conclusion, our study of CrPS4 confirmed the FM ground state and magnetic moment reported in previous literature. We now understand why CrPS4 exhibits FM behavior and
envision that this property can be influenced through targeted modifications. Additionally, we provide insights into the instability of other MPS4 compounds, which can guide experimentalists in modifying these materials to enhance their stability.

  • Poster
    Flatlands 2024, 09.-13.09.2024, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-39810


Data publication: Current vs voltage raw data

Herrer, L.; Hlawacek, G.

Abstract

Current vs. Voltage data including the raw data

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Permalink: https://www.hzdr.de/publications/Publ-39808


Data publication: Fabrication of palladium-enriched metallic structures by direct focused He+ and Ne+ beam nanowriting from organometallic thin films: a com- parison with Ga+ and e− beams

Herrer, L.; Hlawacek, G.

Abstract

All Images produced by the Helium Ion Microscope (*.czi) including the pattering files created by NPVE from FIBICS (tif and xml)

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Permalink: https://www.hzdr.de/publications/Publ-39807


Fabrication of palladium-enriched metallic structures by direct focused He+ and Ne+ beam nanowriting from organometallic thin films: a com- parison with Ga+ and e− beams

Herrer, L.; Salvador-Porroche, A.; Hlawacek, G.; Cea, P.; María De Teresa, J.

Abstract

A direct nanowriting procedure using helium- and neon-focused ion beams and spin-coated organo-
metallic thin films is introduced and applied to the fabrication of Pd-enriched metallic structures in a
single lithography step. This process presents significant advantages over multi-step resist-based lithogra-
phy and focused beam-induced deposition using gaseous precursors, such as its simplicity and speed,
respectively. The optimized process leads to Pd-rich structures with low electrical resistivity values of 141
and 152 μΩ cm under Ne+ or He+ fluences of 1000 and 5000 μC cm−2, respectively. These resistivity
values correlate well with compositional and microstructural studies, indicating a high Pd metallic content
in a dense structure with a few-nm grain size. The obtained results are compared to similar structures fab-
ricated by direct electron and gallium beam nanowriting, demonstrating the full potential of nanopat-
terned Pd-based organometallic thin films under the most common focused charged beams. The practi-
cal applications of combining spin-coated organometallic thin films with focused beam nanowriting in
micro- and nano-lithography modern procedures are also discussed in this contribution.

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Permalink: https://www.hzdr.de/publications/Publ-39806


Helium-Ion Microscopy and Its Applications in Nanoscale Devices

Ogawa, S.; Hlawacek, G.; Liu, F.; Nakaharai, S.; Sarkar, N.; Cybart, S.

Abstract

The term “Helium-Ion Microscope (HIM)” is still unfamiliar to many people. HIM is a type of gas field ion source (GFIS) microscope based on the principle of the projection microscope proposed by E.W. Muller of the University of Pennsylvania in 1951. It utilizes a needle-shaped metal tip, sharpened to the atomic level, as the ion source filament. In 1975, W.H. Escovitz et al. proposed a microscope using hydrogen gas for GFIS, and in 1978, J. Orloff et al. developed the current GFIS. Around the same time, a liquid metal ion source (LMIS) was also developed, enabling more stable beam extraction than GFIS. However, as the research, development, and commercialization of Ga Focused Ion Beam (Ga FIB) microscopes using LMIS progressed, the advancements of GFIS were temporarily overshadowed. In 2006, more than a decade after the maturity of Ga FIB microscopy technology, HIM, which utilizes helium gas for GFIS, was commercialized. Since then, there has been steady progress in the research and development of HIM technology applications, as well as advancements in HIM equipment. These applications include surface imaging using secondary electrons emitted from the near-surface region of the sample irradiated by helium ions, which closely resembles observations made by secondary electron microscopy (SEM). Additionally, analysis techniques such as backscattering spectrometry are employed. Furthermore, HIM technology enables nano-level fabrication and modification of materials, leading to numerous new applications.

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  • Book chapter
    Simon Deleonibus: Outlooking beyond Nanoelectronics and Nanosystems, New York: Jenny Stanford Publishing, 2024, 9781003509905, 139-213
    DOI: 10.1201/9781003509905

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Permalink: https://www.hzdr.de/publications/Publ-39805


Focused electron beam induced deposition of magnetic tips for improved magnetic force microscopy

Escalante-Quiceno, A. T.; Fernández, V. V.; Martín, J. I.; Hierro-Rodriguez, A.; Hlawacek, G.; Jaafar, M.; Asenjo, A.; Magén, C.; de Teresa, J. M.

Abstract

The combination of focused electron beam induced deposition (FEBID) and magnetic force microscopy (MFM) has opened up new possibilities in nanoscale magnetic imaging. FEBID offers precise control over the dimensions and magnetic properties of the MFM probes, enabling the development of high-performance magnetic tips with enhanced capabilities compared to conventional ones. These improved tips offer superior resolution, sensitivity, and versatility in nanoscale magnetic surface characterization. Here, we compare the performance of a commercial MFM tip and a FEBID-grown Fe tip in a Ni80Fe20/NdCo5 film. The FEBID tip exhibited superior lateral resolution for topography imaging, likely due to its sharper and well-defined geometry, with a tip diameter of approximately 20 nm. MFM measurements further confirmed this advantage, revealing better-defined magnetic domains and higher magnetic contrast with the FEBID-functionalized probes compared to the commercial tip. This improvement can be attributed to the possibility to optimize the tip-sample magnetic interaction for the FEBID tip. By reducing the lift height of the second pass, we were able to bring the tip closer to the sample, enhancing the magnetic signal without introducing significant topographic artifacts. Overall, these findings highlight the potential of FEBID for creating high-resolution and high-sensitivity MFM tips.

Keywords: Magnetic anisotropy; Magnetic materials; Image processing; Electron beam-induced deposition; Alloys

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Permalink: https://www.hzdr.de/publications/Publ-39804


FLAIM: A reduced volume ignition model for the compression and thermonuclear burn of spherical fuel capsules

Essamade Saufi, A.; Bellenbaum, H.; Read, M.; Niasse, N.; Barrett, S.; Hawker, N.; Joiner, N.; Chapman, D.

Abstract

We present the ‘‘First Light Advanced Ignition Model" (FLAIM), a reduced model for the implosion, adiabatic
compression, volume ignition and thermonuclear burn of a spherical DT fuel capsule utilising a high-Z
metal pusher. FLAIM is characterised by a highly modular structure, which makes it an appropriate tool
for optimisations, sensitivity analyses and parameter scans. One of the key features of the code is the 1D
description of the hydrodynamic operator, which has a minor impact on the computational efficiency, but
allows us to gain a major advantage in terms of physical accuracy. We demonstrate that a more accurate
treatment of the hydrodynamics plays a primary role in closing most of the gap between a simple model and
a general 1D rad-hydro code, and that only a residual part of the discrepancy is attributable to the heat losses.
We present a detailed quantitative comparison between FLAIM and 1D rad-hydro simulations, showing good
agreement over a large parameter space in terms of temporal profiles of key physical quantities, ignition maps
and typical burn metrics.

Permalink: https://www.hzdr.de/publications/Publ-39803


A 2D predictive geometallurgical model of a tailings storage facility

Tolosana Delgado, R.; Pereira, L.; Ghebreyesus, S. T.; Frenzel, M.; Hoang, D. H.; Rudolph, M.; van den Boogaart, K. G.; Gutzmer, J.

Abstract

Historical tailings storage facilities (TSFs) are being revisited everywhere in the World for their potential in commodities of recent interest, such as Indium, Lithium or REEs, as well as to mitigate their environmental risks. This interest has sparked the development of methods to quantify their value. In this contribution we present one such method for estimating both the grade and recoverability of target commodities, i.e. not just how much of the component is present in the tailings and where, but also how much is expected to be recovered with a specified minerals processing route. The method exploits (i) particulate data from automated mineralogy systems (such as e.g. mineral liberation analysis, MLA) covering the TSF of interest, plus (ii) MLA analyses of the results of beneficiation tests on a handful of samples. A machine learning method (lasso regularised multinomial logistic regression) is trained on this second data set (ii) for predicting the chances of any particle to be recovered into the concentrate product as a function of its properties as measured by the MLA. This allows to calculate the expected proportion of mass of each component (both commodities and waste components) reporting to each output stream, not only for each MLA sample of the training set (ii) but also of the samples (i) from the TSF. These can then be interpolated with a geostatistical analysis. We applied this framework to a TSF in the Ore Mountains, near Freiberg (Saxony, Germany). We applied an n-fold validation strategy, showing significant agreement between predictions and actually observed behaviour. This supports our claim that the proposed method has a strong predictive power.

Keywords: Tailings; Predictive Geometallurgy; Machine Learning; Geostatistics

  • Lecture (Conference)
    37th International Geological Congress 2024, 25.-31.08.2024, Busan, South Korea

Permalink: https://www.hzdr.de/publications/Publ-39802


A training image-free direct mulitpoint algorithm based on Artificial Neural Networks

Tolosana Delgado, R.; Khojasteh, E. R.; van den Boogaart, K. G.

Abstract

Multipoint simulation (MPS) algorithms exploit the dependence structure of the target variable at a series of k-nearest points around each simulation location. Most of the algorithms require the usage of a training image (TI) to either estimate and draw realisations from the conditional distribution of the target variable at an unsampled location, or else directly draw from the TI at the earliest occurrence of a sufficiently similar pattern as the conditioning one. The innovation from the TI (i.e. the ability to produce patterns not strictly found in it) happens because of a certain tolerance embedded into these algorithms. We present an MPS that can be trained on extensive conditioning data as well as on a TI. The method has three steps. In a first step, the training data is so to say "folded"" in a pre-specified series of ways to produce long lists of patterns containing (k+1)-tuples of nearest and near observations to each sample location: not just tuples of the target variable are created, but also information about the constellation of the corresponding (k+1) locations of these tuples is added to the patterns. In a second step, the folded dataset is fed into the training of an artificial neural network (ANN) to predict the target variable at the reference point conditional on the surrounding k-point pattern. Once the ANN is trained, in the third step we follow a random path through the simulation grid, each time finding the k-nearest data points and using the trained ANN to predict the conditional target value at each grid node. In this contribution, we discuss the details of the proposed algorith with an illustration example and discuss its properties and applicability.

Keywords: geostatistics; simulation; multipoint; Artificial neural networks

  • Lecture (Conference)
    37th International Geological Congress 2024, 25.-31.08.2024, Busan, South Korea

Permalink: https://www.hzdr.de/publications/Publ-39801


Principal Component Analysis for Distributions Observed by Samples in Bayes Spaces

Pavlú, I.; Machalová, J.; Tolosana Delgado, R.; Hron, K.; Bachmann, K.; van den Boogaart, K. G.

Abstract

Particle or grain size distributions often play an important role in understanding processes in geosciences. Functional data analysis allows applying multivariate methods like principal component analysis directly to such distributions. These are however often observed in the form of samples, and thus with a sampling error. This additional sampling error changes the properties of the multivariate variance and thus the number of relevant principal components and their direction. The result of the principal component analysis becomes an artefact of the sampling error and can negatively affect the following data analysis. This work presents a way of estimating this sampling error and how to confront it in the context of principal component analysis. The effect of the sampling error and the effectiveness of the correction is demonstrated with a series of simulations. It is shown how the interpretability and reproducibility of the principal components improve and become independent of the selection of the basis. The proposed method is then applied on a dataset of grain size distributions in a geometallurgical dataset from Thaba mine in the Bushveld complex.

Keywords: Principal component analysis; Errors in Observations; ZB-splines; Orthogonal ZB-Splines

Permalink: https://www.hzdr.de/publications/Publ-39800


Entropy Analysis for Raw Material Processes

Schach, E.; Buchwald, T.; Leißner, T.; Peuker, U.; Tolosana Delgado, R.

Abstract

Several definitions of entropy have been used in literature to assess the efficiency of processes in the raw material industry. These definitions are based on tracking substance- or material concentrations within anthropogenic systems such as processing plants or analyzing partition values for characterizing separation processes. This work presents a common framework for entropy analysis for particulate systems, combining these existing definitions and, for the first time, taking the disperse state of particles, described by size and intergrowth, into account. Consequently, the same characteristic measure can evaluate both comminution and separation processes, allowing for combined optimization.

  • Lecture (Conference)
    XXXI IMPC-International Mineral Processing Congress, 29.09.-03.10.2024, Washington, USA
  • Contribution to proceedings
    XXXI IMPC-International Mineral Processing Congress, 29.09.-03.10.2024, Washington, USA
    Proceedings of the XXXI IMPC-International Mineral Processing Congress, 978-0-87335-518-6, 1011-1017

Permalink: https://www.hzdr.de/publications/Publ-39799


Development and Application of Scalable Density Functional Theory Machine Learning Models

Fiedler, L.

Abstract

Electronic structure simulations allow researchers to compute fundamental properties of materials without the need for experimentation. As such, they routinely aid in propelling scientific advancements across materials science and chemical applications. Over the past decades, density functional theory (DFT) has emerged as the most popular technique for electronic structure simulations, due to its excellent balance between accuracy and computational cost. Yet, pressing societal and technological questions demand solutions for problems of ever-increasing complexity. Even the most efficient DFT implementations are no longer capable of providing answers in an adequate amount of time and with available computational resources. Thus, there is a growing interest in machine learning (ML) based approaches within the electronic structure community, aimed at providing models that replicate the predictive power of DFT at negligible cost. Within this work it will be shown that such ML-DFT approaches, up until now, do not succeed in fully encapsulating the level of electronic structure predictions DFT provides. Based on this assessment, a novel approach to ML-DFT models is presented within this thesis. An exhaustive framework for training ML-DFT models based on a local representation of the electronic structure is developed, including minute treatment of technical issues such as data generation techniques and hyperparameter optimization strategies. Models found via this framework recover the wide array of predictive capabilities of DFT simulations at drastically reduced cost, while retaining DFT levels of accuracy. It is further demonstrated how such models can be used across differently sized atomic systems, phase boundaries and temperature ranges, underlining the general usefulness of this approach.

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

Related publications

  • Doctoral thesis
    TU Dresden, 2024
    Mentor: Prof. Dr. Thomas Cowan, Dr. Attila Cangi
    199 Seiten

Permalink: https://www.hzdr.de/publications/Publ-39797


Real-time ligand binding of near-infrared dyes using LigandTracer Green

Donat, C.; Buijs, J.; Bondza, S.

Abstract

Surgical resection of tumours is a balance between sparing healthy and completely removing cancerous tissue. Fluorescently labelled cancer-specific ligands, such as Fibroblast activation protein (FAP), could aid the surgeon in differentiating healthy from cancerous tissue during surgery. When these compounds can also be radiolabelled, bimodal ligands are the result. These can then also be used for an initial diagnosis, e.g. via molecular imaging using Positron Emission Tomography. Combining both approaches allows for a better alignment of diagnostic and surgical outcomes and ultimately improve the patient’s quality of life.
Development of such bimodal ligands requires careful assessment of binding kinetics. Real-time ligand binding using the LigandTracer® platform, allows to assess binding kinetics either via the radioactive or the fluorescent signal. Together with the industry partner, Ridgeview Instruments AB, we investigated the binding kinetics (association and dissociation) of new bimodal FAP ligands (IRDye800CW and 68Ga via NODA-GA ) in a FAP-expressing cell model. Binding was measured using fluorescence with a new near-infrared detector for LigandTracer Green. This was then simultaneously compared to radioactive detection using LigandTracer Grey/Yellow.
During the first association phase, binding curves from fluorescent and radioactive detection were very
similar. As more timed passed, the fluorescence signal decayed with more than 10% per hour, while the radioactive signal remained stable. This difference might be attributed to internalization and/or degradation of the fluorophore, whereas the radioactive signal is unaffected by such processes. Nevertheless, fitted kinetic parameters still showed a suitable agreement, indicating that both approaches can be utilized for the testing of such bimodal ligands.

Keywords: real-time ligand binding; near-infrared dye; LigandTracer

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-39796


Utility of Interchangeable Coordination Modes of N,N’-Dialkyl-2,6-Pyridinediamide Tridentate Pincer Ligands for Efficient and Selective Separation of Pd(II) and Zr(IV) from High-level Radioactive Liquid Waste

Orino, T.; Cao, Y.; Tashiro, R.; Takeyama, T.; Gericke, R.; Tsushima, S.; Takao, K.

Abstract

A new class of ligands, N,N’-dialkyl-2,6-pyridinediamide (DRPDA), has been designed with the specific intention of exhibiting interchangeable diversity in coordination modes, including organometallic interactions, for the purpose of solvent extraction of elements relevant to the proper treatment of high-level radioactive liquid waste (HLLW) generated after nuclear fuel reprocessing. Consequently, DRPDA has been observed to extract Pd(II) and Zr(IV) from HNO3(aq) to 1-octanol in nearly quantitative yields when the selected ligand is sufficiently hydrophobic. However, concomitance of some of other HLLW components were also found. The extraction selectivity towards Pd(II) and Zr(IV) was markedly enhanced by employing ndodecane instead of 1-octanol as evidenced by good distribution ratios (DM) of Pd(II) (DPd = 72.5) and Zr(IV) (DZr = 12.9), which is several orders of magnitude greater than DM’s of other HLLW components (10−3-10−2), where addition of 20 vol% 1-octanol is still required to accelerate the extraction kinetics. Despite direct contact with the highly acidic aqueous phase, deprotonation from one of the amide NH moieties of DRPDA proceeds to form [Pd(DRPDA−)(NO3)] as a good extractables in the current biphasic system. This Pd(II) complex with a rather unique asymmetric N−^N^O tridentate coordination was characterized by SCXRD, elemental analysis and 1H NMR, and theoretically corroborated by DFT calculations and NBO analysis. In contrast, DRPDA also interacts with Zr4+ in different tridentate O^N^O mode without any deprotonation. Based on mechanistic differences in the extraction chemistry we clarified, Pd(II) and Zr(IV) co-extracted to the organic phase were recovered stepwise by using appropriate stripping agents such as 1.0 M HCl(aq) and 0.10 M HNO3(aq), respectively.

Permalink: https://www.hzdr.de/publications/Publ-39792


Ionization potential depression and charge state of warm dense hydrogen from ab initio path integral Monte Carlo simulations

Bellenbaum, H.; Schwalbe, S.; Böhme, M.; Gawne, T. D.; Moldabekov, Z.; Vorberger, J.; Chapman, D.; Fletcher, L.; Doeppner, T.; Kraus, D.; Bonitz, M.; Dornheim, T.

Abstract

Research into Warm Dense Matter (WDM) has recently become more important with
advances in inertial confinement fusion and astrophysics. The complex nature of matter under
these conditions remains however, making it extremely difficult to describe theoretically, due
to the interplay between quantum degeneracy and Coulomb interactions, and the transition
of condensed and plasma phases. Several methods exist to describe matter at these
conditions, with recent extensions to Path Integral Monte Carlo (PIMC) allowing the
calculation of the Laplace of the dynamic structure factors. This allows quasi-exact calculations
for warm dense hydrogen, but does not give access to other important physical quantities
describing a plasma state, like the ionisation and ionisation potential depression (IPD). Since
both are difficult to measure experimentally, we instead compare the imaginary time
correlation function (ITCF) from PIMC simulations with synthetic X-Ray Thomson Scattering
(XRTS) spectra to obtain a best estimate for the ionisation state. The IPD is then directly
calculated using the Saha equation and compared against other commonly used models. We
expect this work to be relevant for future inertial confinement energy developments,
particularly in validating equation of state models.

  • Poster
    Physics of Non-ideal Plasmas 18, 15.-19.09.2024, Oxford, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-39791


Ionization potential depression and charge state of warm dense hydrogen from ab initio path integral Monte Carlo simulations

Bellenbaum, H.; Schwalbe, S.; Gawne, T. D.; Vorberger, J.; Fletcher, L.; Böhme, M.; Moldabekov, Z.; Chapman, D.; Doeppner, T.; Bonitz, M.; Dornheim, T.

Abstract

Research into Warm Dense Matter (WDM) has become more important with recent advances in inertial confinement fusion and astrophysics. The interplay between quantum degeneracy and Coulomb interactions, and the transition of condensed and plasma phases occurring under these conditions, however, make WDM extremely difficult to describe theoretically. Several methods exist to describe matter at these conditions, with recent extensions to Path Integral Monte Carlo (PIMC) allowing the calculation of the Laplace transform of the dynamic structure factor, i.e. the imaginary time correlation function (ITCF), of warm dense hydrogen [1]. While PIMC is quasi-exact, it does not give access to other important physical quantities describing a plasma state, like the ionisation and ionisation potential depression (IPD). Moreover, both are difficult to measure experimentally. To remedy this, we instead compare the ITCF from PIMC simulations with synthetic X-Ray Thomson Scattering spectra [2], computed from a Chihara decomposition [3], to obtain a best estimate for the ionisation state. The IPD is then directly calculated using the Saha equation and compared against other commonly used models. We expect this work to be relevant for future inertial confinement energy developments, particularly in validating equation of state models, and for the refinement of astrophysical models.

[1] T. Dornheim et.al., arXiv preprint arXiv:2403.08570 (2024)

[2] T. Dornheim et.al., Phys. Plasmas 30, 042707 (2023)

[3] G. Gregori et.al., Phys. Rev. E 67, 026412 (2003)

  • Lecture (Conference)
    66th Annual Meeting of the APS Division of Plasma Physics, 07.-11.10.2024, Atlanta, USA

Permalink: https://www.hzdr.de/publications/Publ-39790


Evidence of free-bound transitions in warm dense matter and their impact on equation-of-state measurements

Böhme, M.; Fletcher, L.; Doeppner, T.; Kraus, D.; Baczewski, A.; Preston, T.; MacDonald, M.; Graziani, F.; Moldabekov, Z.; Vorberger, J.; Dornheim, T.

Abstract

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

*This work was partly funded by the Center for Advanced Systems Understanding (CASUS) which is financed by Germany's Federal Ministry of Education and Research (BMBF) and by the Saxon Ministry for Science, Culture and Tourism (SMWK) with tax funds on the basis of the budget approved by the Saxon State Parliament.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-NA0003525.The work of Ti.~D., M.~J.~M, and F.R.G.~was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  • Lecture (Conference)
    66th Annual Meeting of the APS Division of Plasma Physics, 07.-11.10.2024, Atlanta, USA

Permalink: https://www.hzdr.de/publications/Publ-39789


Towards highly accurate diagnostics of extreme states of matter with x-ray Thomson scattering

Dornheim, T.

Abstract

Matter under extreme densities, temperatures and pressures is ubiquitous throughout our universe
and naturally occurs in a variety of astrophysical objects, including giant planet interiors (e.g.
Jupiter, but also exoplanets), brown dwarfs, white dwarf atmospheres, in the outer layer of neutron
stars and during meteor impacts. On Earth, such extreme states are important for technological
applications such as the discovery and synthesis of novel materials. A particularly important
application is given by inertial fusion energy (IFE), where both the fuel capsule and the ablator
material have to traverse this warm dense matter regime in a controlled way to reach ignition.
Indeed, the recent spectacular news from the National Ignition Facility (NIF) at the Lawrence
Livermore National Laboratory in California, USA, who have reported a net energy gain of the
burning plasma with respect to the compression energy [1], opens up the intriguing possibility to
develop IFE into a clean, safe and nigh abundant source of energy in the future.
In the laboratory, warm dense matter is created in large research facilities such as the European
XFEL in Germany, SACLA in Japan, and the NIF, SLAC, and the OMEGA laser in the USA using a
variety of techniques. Here, a key challenge is given by the accurate diagnostics of the created
samples due to the extreme conditions and the ultrafast time scales. Over the last years, the X-ray
Thomson scattering (XRTS) technique---also known as inelastic X-ray scattering---has emerged as
a promising method of diagnostics as it is, in principle, capable of giving microscopic insights into
the probed sample in the form of the electronic dynamic structure factor [2]. In practice, however,
the interpretation of XRTS measurements has relied on theoretical models that are based on a
number of de-facto uncontrolled assumptions. Consequently, the quality of the thus inferred system
parameters has remained unclear.
Here, I present an overview of a new approach that allows for the model-free interpretation of
XRTS spectra in the imaginary-time domain [3-5]. The latter naturally emerges in Feynman’s
celebrated path integral formulation of statistical mechanics and, by definition, contains the same
information as the usual spectral representation, only in an a-priori unfamiliar representation. At the
same time, working in the imaginary-time allows one to deconvolve the physical information from
effects due to the X-ray source and the detector. This, in turn, opens up the way for the model-free
extraction of important system parameters such as the temperature [3] without the need for any
approximations or simulations.

[1] The Indirect Drive ICF Collaboration, Achievement of Target Gain Larger than Unity in an
Inertial Fusion Experiment, Phys. Rev. Lett. 132, 065102 (2024)
[2] S. H. Glenzer and R. Redmer, X-ray Thomson scattering in high energy density plasmas, Rev.
Mod. Phys. 81, 1625 (2009)
[3] T. Dornheim et al., Accurate temperature diagnostics for matter under extreme conditions,
Nature Commun. 13, 7911 (2022)
[4] T. Dornheim et al., Physical insights from imaginary-time correlation functions, Matt. Radiat.
Extremes 8, 056601 (2023)
[5] T. Dornheim et al., X-ray Thomson scattering absolute intensity from the f-sum rule in the
imaginary-time domain, Sci. Reports 14, 14377 (2024)

  • Invited lecture (Conferences)
    12th International Symposium "Optics & its applications" (OPTICS-12), 15.-19.10.2024, Yerevan, Armenia

Permalink: https://www.hzdr.de/publications/Publ-39788


Ab initio path integral Monte Carlo simulations of warm dense hydrogen

Dornheim, T.

Abstract

Understanding the properties of warm dense hydrogen [1] is of paramount importance for the modeling of astrophysical objects (giant planets, brown dwarfs, etc) and for the development of technological applications such as inertial fusion energy. Yet, the simultaneous presence of Coulomb correlations, partial ionization, quantum degeneracy and strong thermal excitations renders its accurate theoretical description challenging: a holistic approach that takes into account all of these effects without uncontrolled approximations is needed.

Here, I present new ab initio path integral Monte Carlo (PIMC) simulations of warm dense hydrogen [2,3], which have been obtained without the usual fixed-node approximation. While being computationally costly, these simulations give us access to a host of observables, most notably the linear density response and the related local field factors [3]. Finally, I discuss the direct connection between our simulations and upcoming x-ray Thomson scattering (XRTS) experiments with hydrogen, and the potential utility of the static density response function as a physical observable to quantify electronic localization around the ions.

[1] M. Bonitz et al., arXiv:2405.10627

[2] T. Dornheim et al., Journal of Chemical Physics 160, 164111 (2024)

[3] T. Dornheim et al., arXiv:2403.08570

*This work has received funding from the European Union's Just Transition Fund (JTF) within the project "Roentgenlaser-Optimierung der Laserfusion" (ROLF), contract number 5086999001, co-financed by the Saxon state government out of the State budget approved by the Saxon State Parliament.This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2022 research and innovation programme(Grant agreement No. 101076233, "PREXTREME").Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them

  • Lecture (Conference)
    66th Annual Meeting of the APS Division of Plasma Physics, 07.-11.10.2024, Atlanta, USA

Permalink: https://www.hzdr.de/publications/Publ-39787


Data publication: Real-time 3D Particle Tracking using Ultrafast Electron Beam X-ray Computed Tomography

Windisch, D.; Barthel, F.; Bieberle, A.; Hampel, U.

Abstract

This dataset includes all raw data used in the linked publication "Real-time 3D Particle Tracking using Ultrafast Electron Beam X-ray Computed Tomography".

Keywords: Particle tracking; ultrafast X-ray imaging; real-time control

Involved research facilities

  • ROFEX

Downloads

Permalink: https://www.hzdr.de/publications/Publ-39785


Integration of Python WebApps into the Draco Laser Shot Tracking Pipeline, and Provision of Data and Metadata in the HZDR Data Patchwork

Tippey, K. E.; Knodel, O.; Schlenvoigt, H.; Kluge, T.; Pape, D.; Gruber, T.; Müller, S.; Juckeland, G.

Abstract

The HZDR team has harnessed the power of Python, Flask, Dash, ZeroMQ and Kafka in tandem with MongoDB, to create a suite of web-based applications that simplify the extraction of laser shot data and metadata from various distinct, heterogeneous, semi-automated data acquisition systems.

The Shotsheet apps play a central role in manual logging, especially in a facility with highly flexible but manual operation modes. These apps also connect to other data sources like the Mediawiki ELN system. To enable further automation, we’ve developed the Experimental Shot Counter and enrichment app (escape), which handles incoming ZeroMQ messages from the Draco Laser system (experiment driver) and provides tailored ZeroMQ and Kafka messages within the Lab intranet. These messages can automate the readout and processing of measurements, as well as trigger mechanical actions.

In the subsequent landscape of data management, navigating the diverse array of metadata catalogs – such as SciCat, data publications on Invenio derivatives, and internal archives – presents a formidable challenge. However, with the right strategies, this mosaic of data can be effectively combined and represented to unlock its full potential. In the HZDR data management ecosystem , we delve into the intricacies of data fusion, exploring innovative approaches to seamlessly harmonize metadata catalogs, data publications, and archives.

Keywords: Python; Flask; HZDR

  • Contribution to proceedings
    DAPHNE Annual Meeting 2024, 11.-13.03.2024, Dresden, Germany
    Proceedings of DAPHNE Annual Meeting 2024

Permalink: https://www.hzdr.de/publications/Publ-39784


Magnetic imaging of thermally switchable antiferromagnetic/ferromagnetic modulated thin films

Griggs, W.; Peasey, A.; Schedin, F.; Anwar, M. S.; Eggert, B.; Mawass, M.-A.; Kronast, F.; Wende, H.; Bali, R.; Thomson, T.

Abstract

Nanoscale magnetic patterning can lead to the formation of a variety of spin textures, depending on the intrinsic properties of the material and the microstructure. Here we report on the spin textures formed in laterally patterned antiferromagnetic (AF)/ferromagnetic (FM) thin film stripes with a period of 200 nm (100 nm FM/100 nm AF). We make use of the AF to FM phase transition in FeRh thin films at ~100 °C, thereby creating a nanoscale pattern that is thermally switchable between AF/FM stripes and uniformly FM. A combination of spin-resolved photoemission electron microscopy, magnetic force microscopy, and magnetometry measurements allow direct nanoscale observations of the stray magnetic fields emergent from the nanopattern as well as the underlying magnetization. Our measurements reveal pinning centres resistant to temperature cycling that govern the modulated spin-texture as well as a sub-texture consisting of grain-driven nanoscale magnetization structure directed out of the film plane. The nanoscale magnetic structure is thus strongly influenced by the film microstructure. Signatures of exchange bias are not observed, most likely due to the small contact area between the AF and FM regions. These results show that temperature controllable spin textures can be created in FeRh thin films which could find application in domain wall, microwave, or magnonic devices.

Keywords: Magnetic thin films; Magnetic patterning; Implantation/irradiation; Magnetic domains; Magnetic phase

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-39783


Multi-section fission ionization chamber for measurement of 239Pu(n,gamma) reaction in fission tagging method

Perkowski, J.; Alcayne, V.; Andrzejewski, J.; Cano-Ott, D.; Gawlik-Ramięga, A.; Mendoza, E.; Sánchez-Caballero, A.; Sibbens, G.; Vanleeuw, D.; Aberle, O.; Altieri, S.; Amaducci, S.; Babiano-Suarez, V.; Bacak, M.; Balibrea Correa, J.; Beltrami, C.; Bennett, S.; Bernardes, A. P.; Berthoumieux, E.; Beyer, R.; Boromiza, M.; Bosnar, D.; Caamaño, M.; Calviño, F.; Calviani, M.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Cescutti, G.; Chasapoglou, S.; Chiaveri, E.; Colombetti, P.; Colonna, N.; Console Camprini, P.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Dellmann, S.; Di Castro, M.; Di Maria, S.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Eleme, Z.; Fargier, S.; Fernández, B.; Fernández-Domínguez, B.; Finocchiaro, P.; Fiore, S.; Furman, V.; García-Infantes, F.; Gervino, G.; Gilardoni, S.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Gustavino, C.; Heyse, J.; Hillman, W.; Jenkins, D. G.; Jericha, E.; Junghans, A.; Kadi, Y.; Kaperoni, K.; Kaur, G.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krtička, M.; Kyritsis, N.; Ladarescu, I.; Lederer-Woods, C.; Lerendegui-Marco, J.; Lerner, G.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Mucciola, R.; Murtas, F.; Musacchio-Gonzalez, E.; Musumarra, A.; Negret, A.; Pérez de Rada Fiol, A.; Pérez-Maroto, P.; Patronis, N.; Pavón-Rodríguez, J. A.; Pellegriti, M. G.; Petrone, C.; Pirovano, E.; Plaza del Olmo, J.; Pomp, S.; Porras, I.; Praena, J.; Quesada, J. M.; Reifarth, R.; Rochman, D.; Romanets, Y.; Rubbia, C.; Sabaté-Gilarte, M.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N. V.; Stamati, M. E.; Sturniolo, A.; Tagliente, G.; Tarifeño-Saldivia, A.; Tarrío, D.; Torres-Sánchez, P.; Vagena, E.; Valenta, S.; Variale, V.; Vaz, P.; Vecchio, G.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T.; Zarrella, R.; Žugec, P.

Abstract

Abstract: The 239Pu(n,γ) reaction cross section is very important for operation of both thermal and fast reactors, when loaded with MOX fuels. According to the NEA/OECD High Priority Request List the precision of cross section data for this reaction should be improved. The cross section of (n,f) reaction is much higher compared to (n,γ) for this isotope. In such conditions the fission tagging technique could be applied to identify the fission background. In the past, this technique was successfully used for capture measurements at the n_TOF facility at CERN. The multi-section fission ionization chamber was constructed and used in the combination with Total Absorption Calorimeter (TAC) for detecting gamma rays for the precise measurement of 239Pu(n,γ) reaction cross section at the n_TOF facility.

Keywords: Radiative neutron capture cross section; Fission Ionization chamber; 239Pu; n_TOF facility; CERN

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Permalink: https://www.hzdr.de/publications/Publ-39782


The microbial communities in bentonites and its influence on cast iron corrosion

Matschiavelli, N.

Abstract

Online-workshop with focus on overviews. On the one hand, present national research topics are addressed. On the other hand, the diversity of specific aspects is covered by a number of dedicated, short technical presentations that span the evolution of the bentonite from mining to the far future of the barrier.

  • Invited lecture (Conferences) (Online presentation)
    Bentonite in crystalline rock, 03.-04.12.2024, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-39780


UAV and field hyperspectral imaging for Sphagnum discrimination and vegetation modelling in Finnish aapa mires

Wolff, F.; Lorenz, S.; Korpelainen, P.; Eltner, A.; Kumpula, T.

Abstract

Detailed knowledge of vegetation patterns allows to evaluate mire ecosystems and their dynamics. The use of hyperspectral information has the benefits of exploring spectral characteristics of species and vegetation modelling. Our study employed multi-scale and multi-source hyperspectral imaging with a handheld camera in the field and an UAV (Unoccupied Aerial Vehicle) sensor covering the wavelengths of 400 – 1000 nm. Plot-level spectra acquired with a UAV and field spectra collected at 1 m height were combined to develop a spectral library for Sphagnum moss species. This library was then used to map dominant Sphagnum species in a Finnish Aapa mire complex using the Spectral Angle Mapper (SAM) classifier. Classification performance assessment was supported by calculating a water index from the UAV-information. Additionally, we examined the transferability of site-specific spectral libraries to an aapa mire with similar vegetation. The results showed little spectral variation in the plot spectrum between the sensors. A fusion of species- and plot-level libraries yielded the highest accuracy of 62 %. For both mires, there was a great variation among the class accuracies. Floating mosses had an accuracy of 86 %, followed by lawn-forming Sphagnum balticum with 77 %. For the test site, the latter species was mapped with an accuracy of 59 %. Red moss species achieved low accuracies of 45 % and 38 %, likely due to effects from sub-pixel and mixed-pixel effects of neighbouring graminoid species and the presence of litter. This might have also enhanced the contrast of adjacent pixels contributing to spectral alterations. Water table depth measurements and the water index revealed a hydrological preference for most species, with classification performance notably improving with higher water index values. We recommend collecting on-site hyperspectral information at varying hydrological circumstances to build a comprehensive spectral library for mire vegetation and modelling.

Permalink: https://www.hzdr.de/publications/Publ-39779


Relaxation to persistent currents in a Hubbard trimer coupled to fermionic baths

Szpak, N.; Schaller, G.; Schützhold, R.; König, J.

Abstract

We consider a ring of fermionic quantum sites, modeled by the Fermi-Hubbard Hamiltonian, in which electrons can move and interact strongly via the Coulomb repulsion. The system is coupled to fermionic cold baths, which by the exchange of particles and energy induce relaxation in the system. We eliminate the
environment and describe the system effectively by Lindblad master equations in various versions valid for different coupling parameter regimes. The early relaxation phase proceeds in a universal way, irrespective of the relative couplings and approximations. The system settles down to its low-energy sector and is consecutively well approximated by the Heisenberg model. We compare different Lindblad approaches, which, in the late relaxation, push the system towards different final states with opposite, extreme spin orders, from ferromagenetic to antiferromagnetic. Due to spin frustration in the trimer (a three site ring), degenerate ground states are formed by spin waves (magnons). The system described by the global coherent version of the Lindblad operators relaxes
towards the final states carrying directed persistent spin currents. We numerically confirm these predictions.

Keywords: Lindblad equation; Fermi-Hubbard Hamiltonian; relaxation dynamics; Heisenberg model; coherent approximation

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Permalink: https://www.hzdr.de/publications/Publ-39778


Julia in high-energy physics: A paradigm shift or just another tool?

Hernandez Acosta, U.

Abstract

The Julia programming language was designed for scientific computing and with its claimed usability („walks like Python“) and speed („runs like C“), it seems to be a scientists‘ software dream come true. Julia appears to be particularly well-suited for high-energy physics (HEP), where reliable software tools and rapid development cycles are crucial for everyday work. Whether it’s data processing, or the simulation of the whole experiment, or the final data analysis and interactive visualization, the Julia ecosystem — with over ten thousand packages — might be a modern and high-performance software solution and the right set of tools to easily build any missing pieces.
In this talk, we will discuss, if the Julia programming language meets these requirements and can withstand testing on the workbenches of HEP. Additionally, we give an overview of current contributions in Julia to the HEP-related software stack and its potential trajectory. Moreover, we explore how the software development process itself can benefit from Julia, as it strikes an ideal balance between high-performance technology and student-friendly training — an especially valuable combination for the rapidly moving high-energy physics community.

Keywords: Julia Programming Language; High-Energy Physics; HPC

  • Open Access Logo Invited lecture (Conferences)
    JuliaHEP 2024 Workshop, 30.09.-04.10.2024, CERN, Switzerland

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Permalink: https://www.hzdr.de/publications/Publ-39776


IntegrationTests.jl: a framework for the automatic generation of integration tests for Julia projects and eco systems

Ehrig, S.; Hernandez Acosta, U.; Reinhard, A.

Abstract

To be successor, every larger software project needs to be tested to verify the correct functionality and to enable its functionality to be extended flawlessly. The type of tests can be very different and depends on the kind of software project. Software projects, that are divided into several sub-projects require integration tests to verify that the individual parts work together correctly.
At JuliaHEP 2023, I gave the talk “Unit and Integration testing in modularized julia package eco-systems” and talked about the problems that need to be solved when developing integration tests for a Julia package ecosystem. With the feedback from the talk, I developed IntegrationTests.jl [1], a framework to dynamically generate GitHub Action or GitLab CI integration jobs for a given Julia Project.toml. The talk explains the different problems to solve when adding integration tests in a Julia project and how IntegrationTests.jl solves them.

[1] https://github.com/QEDjl-project/IntegrationTests.jl

Keywords: QED; Automatic testing; Integration tests; Julia; JuliaHEP

  • Open Access Logo Lecture (Conference)
    JuliaHEP 2024 Workshop, 30.09.-04.10.2024, CERN, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-39775


Structural transformations in two-dimensional noble chalcogenides

Ghorbani Asl, M.

Abstract

Platinum chalcogenides have received great attention among layered materials due to their peculiar physical properties. The strong layer-dependent electronic properties cause a band gap opening in monolayer PtTe₂, while the system is (semi)metallic otherwise. Here we show that starting with PtTe₂ films, other compositions such as Pt₃Te₄ and P₂Te₂ can be obtained by a post-growth desorption of tellurium or vapor-deposited Pt atoms. The experiments combined with DFT calculations provide insights into these transformation mechanisms and the stabilization of the new phases. The partially converted monolayer flakes exhibit PtTe₂-Pt₂Te₂ heterojunctions, which enable the formation of the in-plane semiconductor-metal interface. We further studied the electronic structure of edges and point defects in PtSe₂ monolayer where metallic 1D states with spin-polarized bands were found. In addition to stoichiometry, combining different Pt-chalcogenides in vertical heterostructures provides an additional degree of engineering of materials properties. Our results showed the variation of the interlayer interaction within the moire structure locally modulates the electronic structure of PtSe₂/PtTe₂ heterostructures.

Keywords: two-dimensional materials; noble chalcogenides; scanning tunneling microscopy; first-principles calculations; heterostructures

Involved research facilities

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  • Invited lecture (Conferences)
    Journées de la Matière Condensée" (JMC) 2024, 28.-31.10.2024, Marseille, France

Permalink: https://www.hzdr.de/publications/Publ-39774


Generating Feynman Diagrams for QED in Julia

Reinhard, A.; Hernandez Acosta, U.; Ehrig, S.

Abstract

Calculating differential cross-sections of scattering processes is a crucial observable in high-energy physics, used to predict experimental outcomes and test theoretical models. For perturbative quantum field theories, this involves generating all possible Feynman diagrams for a given scattering process and translating them into computable functions. This becomes cumbersome very rapidly, especially for high-multiplicity processes. In this talk, we introduce a method implemented in Julia for generating these functions for arbitrary scattering processes in perturbative QED, utilizing the ComputableDAGs.jl library. Our approach incorporates novel results and reuse optimizations, which could be extended to other theories or even the entire Standard Model and beyond.

Keywords: Julia; HPC; Feynman; QED; Diagrams; DAG; scattering

  • Open Access Logo Lecture (Conference)
    JuliaHEP 2024 Workshop, 30.09.-04.10.2024, Genf, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-39773


Ion-irradiation induced phenomena in two-dimensional materials: insights from atomistic simulations

Ghorbani Asl, M.

Abstract

While the response of graphene to ion beams has been studied in detail, much less is known about the effects of ion irradiation on other two-dimensional (2D) materials such as MoS2, h-BN, and CrSBr. We have studied the effects of ion irradiation on free-standing and supported targets using molecular dynamics (MD) combined with density functional theory (DFT) calculations. We characterize the types and assess the abundance of point defects in our structures as a function of ion energy, mass, and incident angle. Our simulations, combined with experimental data, show that controlled production of defects by ion irradiation is an effective tool to tune the electrical properties of MoS2 or add new functionalities to h-BN, such as single-photon generation. In the case of CrSBr, a ferromagnetic phase transition occurs upon intentionally introducing defects via ion irradiation. Our results help to understand the fundamental physical mechanisms underlying ion irradiation of low-dimensional materials and finding optimum parameters for defect engineering of 2D
materials with optimized properties.

Keywords: Ion-irradiation; two-dimensional materials; atomistic simulations

Involved research facilities

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  • Open Access Logo Lecture (Conference)
    FIT4NANO and EuFN workshop 2024, 16.-20.09.2024, Durres, Albania

Permalink: https://www.hzdr.de/publications/Publ-39772


Simulation of irradiation effects in solids

Ghorbani Asl, M.

Abstract

Ion beam irradiation has proven to be an efficient technique for introducing defects and impurities to tailor the properties of both bulk and nanomaterials. However, this requires a thorough microscopic understanding of how the target reacts to ion irradiation. The behavior of solids under the influence of energetic ions has been extensively studied over the last 50 years using various theoretical approaches. These methods can provide details on ion ranges, energy losses, as well as on the types, stabilities, and evolution of irradiation-induced defects. We give a brief introduction to the computational methods that are commonly used to simulate the effects of radiation on solids. We discuss the fundamental physics that underlies both binary collision approximation (BCA) and more advanced molecular dynamics (MD) simulation techniques. Finally, the main advantages and limitations of both simulation methods are discussed for studying ion irradiation damage in solids.

Keywords: ion irradiation; solids; binary collision approximation; molecular dynamics simulation

Involved research facilities

Related publications

  • Lecture (Conference)
    FIT4NANO and EuFN workshop 2024, 16.-20.09.2024, Durres, Albania

Permalink: https://www.hzdr.de/publications/Publ-39771


CT image sequences of sandwich packings: B1-250 plus B1-750 at constant liquid rate of 50 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; DataManager: Sprewitz, Uwe; Researcher: Sohr, Johanna; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-750 (specific geometric surface area is 750 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packings; two-phase flow; ultrafast electron-beam X-ray CT

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39769


CT image sequences of sandwich packings: B1-250 plus B1-750 at constant liquid rate of 20 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; DataManager: Sprewitz, Uwe; Researcher: Sohr, Johanna; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract

This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-750 (specific geometric surface area is 750 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packings; two-phase flow; ultrafast electron-beam X-ray CT

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39768


Structural and Compositional Optimization of Bimetallic NiCo Nanoalloys for Promotion of Alkaline Hydrogen Evolution Reaction

Mohanty, B.; Pradhan, L.; Satpati, B.; Rajput, P.; Ghorbani Asl, M.; Wei, Y.; Menezes, P. W.; Krasheninnikov, A.; Kumar Jenaa., B.

Abstract

Alkaline hydrogen evolution reaction (HER) is highly desired due to its economic utility as well as its basic significance in the study of all electrocatalytic processes taking place on cathode electrodes. Herein, we report the nickel and cobalt-based bimetallic alloy nanoparticles embedded in nitrogen-doped carbon (NiₓCo₁₋ₓ@NC) starting from novel metal-organic complexes. Among the synthesized alloy nanoparticle catalysts, Ni₁Co₃@NC exhibits the best performance for HER, reaching a current density of 10 mA/cm² merely at an overpotential of 28 mV, outperforming state-of-the-art noble Pt-based, as well as non-noble metal-based catalysts. Remarkably, this catalyst displays a high turnover frequency (TOF) of 32.44 s⁻¹ and even long-term durability at higher current density (50 mA/cm²) up to 175 hours with negligible decay. A series of advanced characterizations reveal that Ni₁Co₃@NC undergoes minimal near-surface restructuring, majorly retaining its structure during longer operations. In order to comprehend the interaction between the inherent HER activity and the metal center, we conducted further experiments for several bimetallic alloy nanoparticles by alloying Co nanoparticles with Mn, Fe, and Zn. This work sheds important light on the structure-function link for bimetallic alloy nanoparticles made of non-noble metals that exhibit electrocatalytic HER activity in an alkaline medium.

Keywords: Bimetallic alloy nanoparticles; NiCo; Alkaline solutions; Hydrogen evolution reaction; Improved hydrogen adsorption

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-39767


CT image sequences of sandwich packings: B1-250 plus B1-750 at constant liquid rate of 10 m³/(m²h) and various gas rates

Sohr, J.; Barthel, F.; Sprewitz, U.; Schubert, M.
Producer: Barthel, Frank; DataManager: Sprewitz, Uwe; Researcher: Sohr, Johanna; Project Leader: Schubert, Markus; DataCurator: Bieberle, André

Abstract
This repository contains sequences of CT images of the two-phase flow in sandwich packings that are alternately arranged in a packing stack using B1-250 (specific geometric surface area is 250 m² /m³) for de-entrainment layer and B1-750 (specific geometric surface area is 750 m² /m³) for holdup layer. As measurement system the ultrafast electron beam X-ray computed tomography scanner was applied in dual plane scanning mode with a dual-imaging frequency of 1000 Hz. Operating parameters, the scanning plane as well as the tags "AB" for de-entrainment layer, "AN" for hold-up layer and "DRIVE" for an axial scan are encoded in the name of the data files.

Keywords: sandwich packings; two-phase flow; ultrafast electron-beam X-ray CT

Involved research facilities

  • TOPFLOW Facility
  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-39766


Preclinical assessment of enhanced blood retention and tumor uptake PSMA-targeting 225Ac-labeled radioconjugates

Novy, Z.; Hajduova, K.; Petrik, M.; Bendova, K.; Reissig, F.; Zarschler, K.; Kopka, K.; Kurfurstova, D.; Bouchal, J.; Mamat, C.; Hajduch, M.

Abstract

Aim: The prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancer at significantly higher levels compared to healthy tissue. Therefore, PSMA has emerged as very suitable target for molecular imaging as well as targeted radionuclide therapy of metastatic castration-resistant prostate cancer (mCRPC). In this study, we have investigated the in vivo behavior of two novel macropa-based PSMA inhibitors, namely [225Ac]Ac-mcp-D-PSMA and [225Ac]Ac-mcp-M-alb-PSMA modified with albumin binding moiety. The main motivation behind this project was to improve tumor uptake and thus therapeutic efficacy of those novel 225Ac-labeled PSMA inhibitors.
Materials and methods: We have performed in vivo studies involving long-term toxicity study in healthy mice with subsequent immunohistochemical examinations of kidneys and salivary glands. We have also done therapeutic efficacy study in LNCaP-tumor bearing animals employing three different doses (5/15/45 kBq/mouse). Kidneys, livers and tumors were examined using immunohistochemical staining methods to detect PSMA expression, DNA damage (γH2AX), proliferation status (Ki67) and necrosis (H&E).
Results: The toxicity study have not revealed any significant toxic effect in studied parameters. Insignificant DNA damage was observed in the kidney tissue compared to the untreated controls. The therapy study showed no significant effect of two lower doses (5 and 15 kBq/animal) onto tumor volume or survival. The dose of 45 kBq/mouse had significant impact to both mentioned parameters, whereas [225Ac]Ac-mcp-M-alb-PSMA performed better than other two 225Ac-labeled PSMA inhibitors.
Conclusion: In vivo experiments in healthy mice showed very low toxicity of tested PSMA inhibitors. Histological examination of the organs in therapy study confirmed substantial DNA damage in the tumor tissue of mice injected with both studied novel 225Ac-compounds, on the other hand the same parameter revealed only low DNA harm in the kidneys. The therapeutic efficacy of novel compounds was comparable to gold standard [225Ac]Ac-PSMA-617, in case of [225Ac]Ac-mcp-M-alb-PSMA seemed to be even higher.

Keywords: Actinium-225; alpha therapy; therapeutic outcome

  • Lecture (Conference)
    21st European Symposium on Radiopharmacy and Radiopharmaceuticals, 18.-21.04.2024, Coimbra, Portugal
  • Open Access Logo Abstract in refereed journal
    EJNMMI Radiopharmacy and Chemistry 9(2024), OP30
    DOI: 10.1186/s41181-024-00294-8

Permalink: https://www.hzdr.de/publications/Publ-39765


Synthesis, stability determination and radiolabeling of new diazabenzene-based azamacrocycles with barium-131, actinium-225, lanthanum-133, and lead-212

Blei, M. K.; Drobot, B.; Stadlbauer, S.; Kopka, K.; Kretzschmar, J.; Mamat, C.

Abstract

Aim: The radium isotopes radium-223/-224 with their diagnostic gamma emitter barium-131 (SPECT) are ideal candidates for targeted alpha therapy. However, in order to use radium as + 2 metal ion in radioconjugates, it must be stably bound. The chelator macropa (mcp) has been found to form the most stable complexes so far, but they are not stable enough for in vivo applications.[1,2] Therefore, novel macrocyclic chelators based on macropa were developed with an additional application for lanthanum, actinium, and lead radionuclides.
Materials and methods: Starting from the diazamacrocycle K2.2, 4 new chelators were prepared in which the picolinic acid side arm was replaced by 3 regioiosomeric diazabenzenes with carboxylic acid moiety. All new tendentate chelators and nonradioactive metal complexes were synthesized and characterized by NMR spectroscopy. The stability of the complexes was determined using ITC and radiolabeling was performed with barium-131, lanthanum-133, actinium-225 and lead-212.
Results: The 4 pym chelators were obtained in yields ranging from 19 to 74% including deprotection. Compared to Ba-mcp, a higher stability was found for all Ba-pym complexes. For barium-131, quantitative radiolabeling of all pym chelators was possible down to c = 10 µM, and for actinium-225, lanthanum-133, and lead-212 down to c = 0.1 µM. In competition experiments with the new radiometal complexes using 50 mM EDTA, consistently higher complex stabilities were found in contrast to the respective mcp complexes (barium-131: > 99% intact complex down to 0.1 mM; actinium-225, lanthanum-133 and lead-212: > 99% intact complex down to 0.1 µM).
Conclusion: Four new pym chelators were synthesized, which show a higher stability than macropa due to their modification. They are therefore better suited for complexation with barium-131, as well as for actinium-225, lanthanum-133 and lead-212 and thus also have the potential to form more stable radium-223 complexes.

Keywords: theranostic concept; alpha therapy; lanthanum-133; actinium-225

  • Open Access Logo Lecture (Conference)
    21st European Symposium on Radiopharmacy and Radiopharmaceuticals, 18.-21.04.2024, Coimbra, Portugal
  • Open Access Logo Abstract in refereed journal
    EJNMMI Radiopharmacy and Chemistry 9(2024), OP15
    DOI: 10.1186/s41181-024-00294-8

Permalink: https://www.hzdr.de/publications/Publ-39764


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