Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41397 Publications

GSTools v1.3: A toolbox for geostatistical modelling in Python

Müller, S.; Schüler, L.; Zech, A.; Heße, F.

Geostatistics as a subfield of statistics accounts for the spatial correlations encountered in many applications of e.g. Earth Sciences. Valuable information can be extracted from these correlations, also helping to address the often encountered burden of data scarcity. Despite the value of additional data, the use of geostatistics still falls short of its potential. This problem is often connected to the lack of user-friendly software hampering the use and application of geostatistics. We therefore present GSTools, a Python-based software suite for solving a wide range of geostatistical problems. We chose Python due to its unique balance between usability, flexibility, and efficiency and due to its adoption in the scientific community. GSTools provides methods for generating random fields, it can perform kriging and variogram estimation and much more. We demonstrate its abilities by virtue of a series of example application detailing their use.

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Permalink: https://www.hzdr.de/publications/Publ-33530
Publ.-Id: 33530


Measurement of the photon strength function in ¹¹⁵In at the gELBE facility

Makinaga, A.; Schwengner, R.; Beyer, R.; Grieger, M.; Hammer, S.; Hensel, T.; Junghans, A.; Ludwig, F.; Trinh, T. T.; Turkat, S.

The photon strength function (PSF) in 115In is an important parameter for the estimate of the neutron capture cross section on 114In in the field of astrophysics and nuclear engineering. Until now, the so-called PSF method for 115In was applied only above the neutron-separation energy (Sn), and the evaluated 114In (n,g) cross section has uncertainties caused by the lack of the PSF below Sn. We studied the dipole strength distribution of 115In with a photon-scattering experiment using bremsstrahlung produced by an electron beam of an energy of 10.3 MeV at the linear accelerator ELBE at HZDR.

Keywords: ELBE; gELBE; NRF; photon-scattering; bremsstrahlung; 115In

Related publications

  • Open Access Logo Contribution to proceedings
    2019 Symposium on Nuclear Data, 28.-30.11.2019, Fukuoka, Japan
    Proceedings of the 2019 Symposium on Nuclear Data, 101-105
    DOI: 10.11484/jaea-conf-2020-001

Permalink: https://www.hzdr.de/publications/Publ-33529
Publ.-Id: 33529


Dose Rate Measurements in Pulsed Radiation Fields by Means of an Organic Scintillator

Werner, T.; Beyer, R.; Biedermann, R.; Gerber, M.; Götze, J.; Herzig, P.; Melzer, V.; Metzner, E.; Weinberger, D.; Kormoll, T.

A deficiency in the implementation of current radiation protection is the determination of the ambient dose equivalent H*(10) and the directional dose equivalent H ́(0.07) in pulsed radiation fields. Conventional dosimeter systems are not suitable for measurements in photon fields comprising short radiation pulses, which consequently leads to high detector loads in short time periods. Nevertheless, due to the implementation of advanced medical accelerators for cancer therapy, new medical diagnostic devices as well as various laser machining systems, there is an urgent need for suitable dosimeter systems for real time dosimetry. In this paper, a detector concept based on an organic scintillator and a full digital data analysis with the aim of developing a portable, battery powered measurement system is presented.

Keywords: ELBE; gELBE; radiation protection; dose rate measurements; pulsed radiation fields; organic scintillation detector

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33528
Publ.-Id: 33528


Active Dosimetry with the Ability to Distinguish Pulsed and Non-Pulsed Dose Rate Contributions

Makarevich, K.; Beyer, R.; Henniger, J.; Ma, Y.; Polter, S.; Sommer, M.; Teichmann, T.; Weinberger, D.; Kormoll, T.

This paper presents the concept of an active dosimetry system and its operational regime for pulsed radiation dose rate measurements. The plastic scintillator is suggested to be used for absorbed dose rate measurements. As long as the detector can be considered tissue equivalent, the energy weighting of pile-up events in terms of the dose is achieved. The real-time distinction of pulsed and non-pulsed dose rate contributions is based on the time structure of a single interaction and requires only basic information about the beam time structure (pulses duration and period). The detector connected to a fully digital signal processing board creates an active dosimetry system with adjustable parameters. Such a system was used for absorbed dose rate measurements in pulsed photon field mimicking radiation field outside the bunker of a medical LINAC, but also in the presence of a constant radiation component. The results show a linear dependence of a pulsed radiation contribution on the accelerator current in the investigated range of the total dose rate up to 8 μGy/h.

Keywords: ELBE; gELBE; Dosimetry; pulsed radiation fields

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33527
Publ.-Id: 33527


Organotin derivatives as versatile precursors for the radioiodination and radiofluorination of 1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid (TIC(OH)) analogues

Maisonial-Besset, A.; Noelia Chao, M.; Debiton, E.; Canitrot, D.; Witkowski, T.; Degoul, F.; Tarrit, S.; Wenzel, B.; Miot-Noirault, E.; Serre, A.; Chezal, J.-M.

Objective: Organotin compounds are well known as efficient precursors for reliable radioiodination of aromatic derivatives, with high molar activities, via electrophilic aromatic substitution reaction. They can be easily prepared from corresponding halogenated derivatives using metalation or palladium-catalyzed reactions. In the last years, organotin derivatives, together with boronic acid or ester precursors, were also successfully applied to the direct radiolabelling of electron-rich aromatic structures from [18F]F- via Cu-mediated radiofluorination. As evidenced with the progresses reported for the radiosynthesis of the [18F]FDOPA for example, these major developments in the fluorine-18 radiochemistry field created new opportunities to produce radiofluorinated arenes that could not be routinely accessed even a few years ago. Surprisingly, the [123I]8-iodo-L-TIC(OH), a promising radiotracer for SPECT imaging of prostatic tumours, did not benefit from these methodological advances and no corresponding radiofluorinated derivatives, which could allow the use of the TIC(OH) scaffold to PET imaging, were reported so far.

Methods: A convergent synthetic route was developed to produce radioiodinated [125I]iodo-L-TIC(OH), and radiofluorinated [18F]fluoro-L-TIC(OH) tracers from common organotin intermediates, synthesized from iodinated analogues via palladium catalyzed I/SnMe3 exchange. The [125I]iodo-L-TIC(OH) radiotracers were obtained by electrophilic radioiododestannylation with [125I]I+, while the radiofluorinated analogues [18F]fluoro-L-TIC(OH) were produced from the organotin precursors by a copper-mediated aromatic radiofluorination using nucleophilic [18F]F-. For control of the purity, molar activity and enantiomeric excess, corresponding non-radiolabelled iodinated and fluorinated derivatives from the L and D series were synthesized.

Results: Organotin compounds were radiolabelled using no-carrier-added [125I]NaI in the presence of Chloramine-T as mild oxidative agent at room temperature for 5 min with excellent labelling efficiencies (> 95%). After a two-step deprotection sequence and semipreparative RP-HPLC purification, [125I]iodo-L-TIC(OH) compounds were isolated with good radiochemical yields (RCY = 51-78%), high radiochemical purities (RCP, > 98%), molar activities (MA > 1.5 GBq/µmol) and enantiomeric excess (e.e. > 99%). [18F]fluoro-L-TIC(OH) derivatives were obtained by radiofluorination of organotin compounds in presence of tetrakis(pyridine)copper(II) triflate and nucleophilic [18F]F- at 110 °C for 10 min with high labelling efficiencies (54-92%). After purification by C18 solid phase extraction, deprotection under acidic conditions and semipreparative RP-HPLC purification, [18F]fluoro-L-TIC(OH) radiotracers were produced with good RCY (23-37% d.c.), high RCP (> 99%), MA (20-107 GBq/µmol) and e.e. (> 99%).

Conclusion: A short and efficient synthetic pathway was developed to easily produce [125I]iodo-L-TIC(OH) and [18F]fluoro-L-TIC(OH) analogues from common organotin intermediates. Such radiofluorination process could be easily implemented on radiopharmacy automatic synthesis modules and could pave the way to the development of novel radiopharmaceuticals containing the TIC(OH) core.

Acknowledgments : This work was partially funded by the Cancéropôle Lyon Auvergne Rhône Alpes (CLARA), the Auvergne Rhône Alpes Region, the ARTP (Association pour la Recherche sur les Tumeurs de la Prostate), and the Fondation de la Maison de la Chimie.

  • Lecture (Conference)
    International Symposium of Radiopharmaceutical Sciences, 2022, 29.05.-02.06.2022, Nantes, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-33526
Publ.-Id: 33526


From helical to standard magnetorotational instability: predictions for upcoming liquid sodium experiments

Mishra, A.; Mamatsashvili, G.; Stefani, F.

We conduct a linear analysis of axisymmetric magnetorotational instability (MRI) in a magnetized
cylindrical Taylor-Couette (TC) flow for its standard version (SMRI) with a purely axial background
magnetic field and two further types – helically modified SMRI (H-SMRI) and helical MRI (HMRI)
– in the presence of combined axial and azimuthal magnetic fields. This study is intended as
preparatory for upcoming large-scale liquid sodium MRI experiments planned within the DRESDYN
project at Helmholtz-Zentrum Dresden-Rossendorf, so we explore these instability types for typical
values of the main parameters: the magnetic Reynolds number, the Lundquist number and the ratio
of the angular velocities of the cylinders, which are attainable in these experiments. In contrast to
previous attempts of detecting MRI in the lab, our results demonstrate that SMRI and its helically
modified version can in principle be detectable in the DRESDYN-TC device for the range of the
above parameters, including the astrophysically most important Keplerian rotation, despite the
extremely small magnetic Prandtl number of liquid sodium. Since in the experiments we plan to
approach (H-)SMRI from the previously studied HMRI regime, we characterise the continuous and
monotonous transition between the both regimes. We show that H-SMRI, like HMRI, represents
an overstability (travelling wave) with non-zero frequency linearly increasing with azimuthal field.
Because of its relevance to finite size flow systems in experiments, we also analyse the absolute form
of H-SMRI and compare its growth rate and onset criterion with the convective one.

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Permalink: https://www.hzdr.de/publications/Publ-33525
Publ.-Id: 33525


Using a digital phantom for quality control of ExploreASL image processing

Stritt, M.; Padrela, B.; Dijsselhof, M.; Oliver-Taylor, A.; Barkhof, F.; Golay, X.; Gunther, M.; Gregori, J.; Mutsaerts, H. J.; Petr, J.

In recent years, there has been an increasing focus on
open-science and reproducible research, including reliable and robust
software. To this end, methods of requirements engineering and
quality control were integrated in the ExploreASL pipeline and
development workflow. Here, we used the recently developed digital
reference object (DRO) ’’ASL-DRO‘‘ to evaluate the reliability of
ExploreASL with a main focus on motion correction [1, 2].

  • Contribution to proceedings
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual
  • Poster
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33524
Publ.-Id: 33524


Quantification of background suppressed arterial spin labeling images without an M0 image

Prysiazhniuk, Y.; Dijsselhof, M.; van de Ven, K. C. C.; Baas, K. P. A.; Oliver-Taylor, A.; Thomas, D. L.; Mutsaerts, H. J.; Petr, J.

Arterial spin labeling (ASL) is a non-invasive perfusion MRI scan technique used in pathologies such as Alzheimer’’s
disease, cerebrovascular disease, and brain tumors [3]. To obtain
absolute quantification of cerebral blood flow (CBF) in mL/100 g/
min, the blood equilibrium magnetization (M0b) is required [1]. For
that, M0-scan acquisition is recommended [1]; however, in practice,
clinical studies often lack an M0-scan. A control image can be used as
an alternative only when background suppression (BSup) is not used.
Here, we investigate the possibility to reconstruct an M0 scan from a
control image with BS and compare it with acquired M0 scans from
the same patients.

  • Contribution to proceedings
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual
  • Poster
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33523
Publ.-Id: 33523


An ExploreASL toolbox for DICOM to BIDS conversion

Stritt, M.; Padrela, B.; Dijsselhof, M.; Clement, P.; Oliver-Taylor, A.; Barkhof, F.; Golay, X.; Gunther, M.; Gregori, J.; Petr, J.; Mutsaerts, H. J.

Most data scientists spend about 45% of their time on
tasks like data loading and cleansing [1]. This is especially problematic in ASL-MRI, which is available in a variety of acquisition
flavors, export forms, and differs between vendors and laboratories.
ASL-BIDS [2] has recently addressed this issue by defining a standardized data structure. Current DICOM to BIDS conversion tools are
still working on a complete support of ASL-BIDS [3]. Here, we
introduce a tool within ExploreASL [4], that converts DICOMs to
ASL-BIDS using DCMTK [5] and dcm2niiX [6].

  • Contribution to proceedings
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual
  • Poster
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33522
Publ.-Id: 33522


Assessment of cerebral perfusion symmetry in retired Canadian Football League players

Danielli, E.; Padrela, B.; Doughty, M.; Petr, J.; Mutsaerts, H. J.; Noseworthy, M. D.

High contact sports such as American football can
result in athletes sustaining concussions and countless sub-concussive
blows, leading to cumulative neurological damage [1]. This study
aimed to use cerebral blood flow (CBF) measured with ASL and a
Z-scoring approach to quantify focal brain damage and left/right
symmetry in retired Canadian Football League (rCFL) players. It was
hypothesized that subjects would have asymmetric CBF and regional
hypoperfusion due to their history of repetitive head trauma.

  • Contribution to proceedings
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual
  • Poster
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33521
Publ.-Id: 33521


ExploreASL GUI: processing large arterial spin labeling datasets without programming skills

Pasternak, M.; Keil, V.; Clement, P.; Pinter, N.; Dijsselhof, M.; Stritt, M.; Petr, J.; Mutsaerts, H. J.

While several arterial spin labelling (ASL) processing
pipelines are freely available, programming skills are usually needed
to efficiently process large datasets (1), deterring clinicians from analyzing ASL data. Leaving data unanalysed reduces the speed of
progress in medical research and this unavailability keeps research
restricted to a select few specialized academic institutions. These
hurdles are addressed by ExploreASL, an ASL processing pipeline
that analyzes ASL data on an individual and population level, and is
free for non-commercial purposes (2). To enable its use for
researchers without any coding knowledge, a graphical user interface
(GUI) was developed in collaboration with clinical radiologists to
specifically address their needs (3).

  • Contribution to proceedings
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual
  • Lecture (Conference)
    European Society for Magnetic Resonance in Medicine and Biology, 07.10.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33520
Publ.-Id: 33520


Using ASL perfusion images for spatial normalization in a pediatric population with craniosynostosis

de Planque, C.; Mutsaerts, H.; Keil, V.; Erler, N.; Dremmen, M.; Mathijssen, I.; Petr, J.

Spatial normalization is an important step for image processing and quantification of regional brain perfusion values using arterial spin labeling (ASL) MRI and is typically performed via high-resolution structural scans. Structural segmentation and/or registration is complicated when gray-white matter T1w contrast is low and changing in early phases of myelination in newborns. Craniosynostosis is a condition where the decision for surgical treatment in the first years of life is supported by brain imaging. In this study, we investigate if ASL CBF image contrast can be directly used for spatial normalization, in both healthy controls and a non-syndromic type of craniosynostosis.

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33519
Publ.-Id: 33519


The Open Source Initiative for Perfusion Imaging (OSIPI): ASL Pipeline inventory

Dolui, S.; Fan, H.; Croal, P.; Buchanan, C.; Hirschler, L.; Anazodo, U.; Thomas, D.; Mutsaerts, H.; Petr, J.

As a part of the Open Source Initiative for Perfusion Imaging (OSIPI), we have created an inventory of software for automated processing of Arterial Spin Labeling (ASL) perfusion MRI data. We contacted the ASL community through different channels, inviting software developers to list their pipelines by completing a questionnaire covering different aspects and features of a desired pipeline. We received inputs from 18 developers and have summarized the main characteristics of their pipelines based on the information they provided. We expect that this inventory will facilitate ASL-related research, reduce duplicate development, and enable translation of ASL to clinical practice.

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33518
Publ.-Id: 33518


The Open Source Initiative for Perfusion Imaging (OSIPI) ASL MRI Challenge

Anazodo, U.; Pinto, J.; Kennedy McConnell, F.; Dounavi, M.-E.; Gould Van Praag, C.; Mutsaerts, H.; Oliver-Taylor, A.; Paschoal, A.; Petr, J.; Pineda-Ordóñez, D.; Woods, J.; Zhao, M.; Croal, P.

The OSIPI ASL MRI Challenge is a community-led initiative aiming to establish the range of approaches used for ASL image analysis and cerebral blood flow (CBF) quantification. Challenge data will consist of population-based and synthetic pseudo-continuous ASL images, with participants analysing the data and submitting resulting CBF maps and mean tissue CBF, along with documentation. Entries will be scored on accuracy, reproducibility and documentation quality. Through documenting the analysis choices made within the community, we will begin to better understand sources of variability, ultimately identifying an optimum pipeline, and moving towards the much-needed consensus of ASL image processing standards.

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33517
Publ.-Id: 33517


The Open Source Initiative for Perfusion Imaging (OSIPI)

Bell, L.; Mutsaerts, H.; Fedorov, A.; Ahmed, Z.; Clement, P.; Levy, S.; Zollner, F.; Petr, J.; Dolui, S.; Schmainda, K.; Prah, M.; Schabel, M.; Madhuranthakam, A.; Zhao, L.; Thrippleton, M.; van Houdt, P.; Holmes, J.; Quarles, C.; Cron, G.; Thomas, D.; Suzuki, Y.; Kompan, I.; Buckley, D.; Croal, P.; Anazodo, U.; Fathi Kazerooni, A.; Saligheh Rad, H.; Debus, C.; Sourbron, S.

Open Source Initiative for Perfusion Imaging (OSIPI) was founded by the ISMRM Perfusion Study Group as a community-driven initiative. Supported by six distinct aims, its mission is “to promote the sharing of perfusion imaging open-source software in order to eliminate the practice of duplicate development, improve the reproducibility of perfusion imaging research, and speed up the translation into tools for discovery science, drug development, and clinical practice”. OSIPI seeks to provide centralized resources to deliver reproducible perfusion research. In addition, it provides a platform for exchange where new and more advanced methods may be validated for perfusion accuracy.

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33516
Publ.-Id: 33516


Neuroimaging Pre-Processing and Quality Control for The European Prevention of Alzheimer's Dementia (EPAD) Cohort Study

Lorenzini, L.; Ingala, S.; Wink, A. M.; Kuijer, J.; Wottschel, V.; Sudre, C.; Haller, S.; Molinuevo, J. L.; Gispert, J. D.; Cash, D.; Thomas, D.; Vos, S.; Prados Carrasco, F.; Petr, J.; Wolz, R.; Palombit, A.; Schwarz, A.; Chételat, G.; Payoux, P.; Di Perri, C.; Pernet, C.; Giovanni, F.; Fox, N.; Ritchie, C.; Wardlaw, J.; Waldman, A.; Barkhof, F.; Mutsaerts, H.

The neuroimaging community strives to obtain large data cohorts, usually through association within consortia spanning different sites and countries. This results in increased variability of acquisition parameters and scan quality, which can affect image processing and statistical analyses. We propose a semi-automatic data management pipeline to process raw data, assess quality and compute image-derived phenotypes from multi-modal MRI scans, as developed for the multi-centre European Prevention of Alzheimer Dementia longitudinal cohort study (EPAD LCS).

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33515
Publ.-Id: 33515


Generating virtual brains for MRI-based 3D cerebral blood flow simulations

Józsa, T.; Petr, J.; Wink, A. M.; Barkhof, F.; Mutsaerts, H.; Payne, S.

Human brain perfusion simulations have been limited to less than five patient-specific cases. We propose a pipeline based on MRI to overcome this limitation. Computational geometry is adjusted using T1-weighted MRI, and the perfusion model parameters are tuned based on arterial spin labeling perfusion MRI. A cohort of 75 patients is used to demonstrate that the pipeline is suitable to generate virtual patients with statistically accurate and precise cerebral blood flow maps. Our findings encourage future studies on in silico clinical trials using similar virtual cohorts to improve ischaemic stroke interventions.

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33514
Publ.-Id: 33514


ASLDRO: Digital reference object software for Arterial Spin Labelling

Oliver-Taylor, A.; Hampshire, T.; Smith, N.; Stritt, M.; Petr, J.; Gregori, J.; Günther, M.; Mutsaerts, H.; Golay, X.

ASLDRO is digital reference object software for Arterial Spin Labelling. Here we present the development and demonstration of the DRO software, and its use in a sensitivity and uncertainty analysis of the single-subtraction equation for ASL perfusion quantification.The DRO software was written in python, and can generate synthetic ASL control, label and M0 data in ASL BIDS format. Pulsed and continuous labelling are supported, and patient motion and instrument noise are accurately simulated. It can be used both for testing and validation of image processing software, and for investigating ASL quantification models.

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33513
Publ.-Id: 33513


Advanced image processing outside the academia: The integration of ExploreASL into the workflow of an outpatient imaging center

Pinter, N.; Ganji, S.; Petr, J.; Ajtai, B.; Friel, H.; Fritz, J.; Mechtler, L.; Fischer, A.; Barkhof, F.; Mutsaerts, H.

While neurological imaging is mostly done in non-academic centers, the lack of academic resources, special image processing skillset and the fast paced
workflow prevent radiologists in these data-rich environments from engaging in high quality clinical research that utilizes quantitative imaging. Clinical
adoption of Arterial Spin Labeling could benefit from providing easy-to-use, PACS connected image processing solutions that do not require
neuroscience background and provide truly quantified Cerebral Blood Flow values in any outpatient center or public hospital. Our goal is to create such
a solution and bridge the gap between academic research and real world practice.

  • Contribution to proceedings
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual
  • Poster
    ISMRM '21: Proceedings of the ISMRM 29th Annual Meeting & Exhibition, 15.-20.05.2021, Virtual, Virtual

Permalink: https://www.hzdr.de/publications/Publ-33512
Publ.-Id: 33512


Die Rolle des TRPC6 Kanals im Rahmen der akuten Nierenschädigung

Zheng, Z.; Tsvetkov, D.; Bartolomaeus, T. U. P.; Erdogan, C.; Krügel, U.; Schleifenbaum, J.; Schaefer, M.; Nürnberg, B.; Chai, X.; Ludwig, F.-A.; N’Diaye, G.; Köhler, M.-B.; Wu, K.; Gollasch, M.; Marko, L.

Aims: Transient receptor potential (TRP) channels are non-selective cation channels that promote influx of Ca2+, Mg2+ and monovalent cations into cells. TRP channel subfamily C, member 6 (TRPC6) is widely expressed - next to several other tissues - in the kidney, and gene variations were linked to fibrosing renal disease. Here we aimed to investigate the putative role of TRPC6 channels in acute kidney injury (AKI). Since ischemia/reperfusion injury is known relate to Ca2+ overload, we hypothesized that inhibition of TRPC6 ameliorates AKI.
Methods: We used Trpc6-/- mice and SH045, a pharmacological inhibitor of TRPC6, to evaluate short-term AKI outcomes. Ischemia was induced after right–sided nephrectomy by clipping the renal pedicle of the left kidney for 20 or 17.5 minutes. SH045 was used for intravenous injection (2 mg/kg) 30 minutes before I/R surgery in the pharmacological studies with WT mice.
Results: Here, we demonstrate that neither Trpc6 deficiency nor pharmacological inhibition of TRPC6 influence the short-term outcomes of AKI. Blood markers (Creatinine in WT [131.4±33.3 µmol/l] vs Trpc6-/- [159.6±41.7 µmol/l] mice after 24 hours of reperfusion and in the pharmacological study: 17.5 min-I/R vehicle [199.5±21.8 µmol/l] versus 17.5 min-I/R SH045 [172.6±31.6 µmol/l], and 20 min-I/R vehicle [212.2±8.4 µmol/l] versus 20 min-I/R SH045 [226.2±28.6 µmol/l], all comparisons are n.s.), renal expression of epithelial damage markers, tubular injury and renal inflammatory response assessed by histological analysis were similar in wild-type mice compared to Trpc6-/- mice as well as in vehicle-treated versus SH045-treated mice. In addition, our results also found no effect of TRPC6 modulation on renal myogenic tone by using SH045 to perfuse isolated kidneys.
Conclusion: Therefore, we conclude that TRPC6 does not play role on the acute phase of AKI. Further studies should focus if TRPC6 inhibition could be protective in terms of long-term outcome of an AKI.

  • Poster
    Kongress für Nephrologie 2021, 23.-26.09.2021, Rostock, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33510
Publ.-Id: 33510


Rapid Detection of SARS-CoV-2 Antigens and Antibodies Using OFET Biosensors Based on a Soft and Stretchable Semiconducting Polymer

Ditte, K.; Nguyen Le, T. A.; Ditzer, O.; Isabel Sandoval Bojorquez, D.; Chae, S.; Bachmann, M.; Baraban, L.; Lissel, F.

In the midst of the COVID-19 pandemic, adaptive solutions are needed to allow us to make fast decisions and take effective sanitation measures, e.g., the fast screening of large groups (employees, passengers, pupils, etc.). Although being reliable, most of the existing SARS-CoV-2 detection methods cannot be integrated into garments to be used on demand. Here, we report an organic field-effect transistor (OFET)-based biosensing device detecting of both SARS-CoV-2 antigens and anti-SARS-CoV-2 antibodies in less than 20 min. The biosensor was produced by functionalizing an intrinsically stretchable and semiconducting triblock copolymer (TBC) film either with the anti-S1 protein antibodies (S1 Abs) or receptor-binding domain (RBD) of the S1 protein, targeting CoV-2-specific RBDs and anti-S1 Abs, respectively. The obtained sensing platform is easy to realize due to the straightforward fabrication of the TBC film and the utilization of the reliable physical adsorption technique for the molecular immobilization. The device demonstrates a high sensitivity of about 19%/dec and a limit of detection (LOD) of 0.36 fg/mL for anti-SARS-Cov-2 antibodies and, at the same time, a sensitivity of 32%/dec and a LOD of 76.61 pg/mL for the virus antigen detection. The TBC used as active layer is soft, has a low modulus of 24 MPa, and can be stretched up to 90% with no crack formation of the film. The TBC is compatible with roll-to-roll printing, potentially enabling the fabrication of low-cost wearable or on-skin diagnostic platforms aiming at point-of-care concepts.

Permalink: https://www.hzdr.de/publications/Publ-33509
Publ.-Id: 33509


Quantitation of the A2A adenosine receptor density in the striatum of mice and pigs with [18F]FLUDA by positron emission tomography

Gündel, D.; Toussaint, M.; Lai, T. H.; Deuther-Conrad, W.; Cumming, P.; Schröder, S.; Teodoro, R.; Moldovan, R.-P.; Pan-Montojo, F.; Sattler, B.

The cerebral expression of the A2A adenosine receptor (A2AAR) is altered in neurodegenerative disorders diseases such as Parkinson's (PD) or Huntington’s (HD) diseases, making these recep-tors an attractive diagnostic and therapeutic target. We aimed to further investigate the pharma-cokinetic properties in the brain of our recently developed A2AAR specific antagonist radioligand [18F]FLUDA. For this purpose, we retrospectively analysed dynamic PET studies of healthy mice and rotenone-treated mice, and undertook dynamic PET studies with healthy pigs. We performed analysis of mouse brain time-activity curves to calculate the mean residence time (MRT) by non-compartmental analysis and the binding potential (BPND) of [18F]FLUDA using the simplified reference tissue model (SRTM). For the pig studies, we performed a Logan graphical analysis to calculate the radiotracer distribution volume (VT) at baseline and under blocking conditions with tozadenant. The MRT of [18F]FLUDA in the striatum of mice was decreased by 30 % after treatment with the A2AAR antagonist, istradefylline. Mouse results showed the highest BPND (3.9 to 5.9) in the striatum. SRTM analysis showed a 20% lower A2AAR availability in the rotenone-treated mice compared to the control-aged group. Tozadenant treatment significantly decreased the VT (14.6 vs. 8.5 mL · g-1) and BPND values (1.3 vs. 0.3) in pig striatum. This study confirms the target specificity and a high BPND of [18F]FLUDA in the striatum. We conclude that [18F]FLUDA is a suitable tool for the non-invasive quantitation by PET of altered A2AAR expression in neurodegenerative diseases such as PD and HD.

Keywords: [18F]FLUDA; A2A adenosine receptor (A2AAR); Parkinson’s disease; Huntington’s disease; kinetic analysis; preclinical positron emission tomography; simplified reference tissue model; 7-(3-(4-(2-[18F]fluoroethoxy-1,1,2,2-d4)phenyl)propyl)-2-(furan-2-yl)-7H-pyrazolo[4,3-e][1,2,4]triaz

Permalink: https://www.hzdr.de/publications/Publ-33508
Publ.-Id: 33508


First evaluation of [18F]RM273 for sigma2 receptor imaging in a pre-clinical brain tumour model

Gündel, D.; Toussaint, M.; Moldovan, R.-P.; Teodoro, R.; Schepmann, D.; Wünsch, B.; Ludwig, F.-A.; Fischer, S.; Brust, P.; Deuther-Conrad, W.

Introduction: The sigma2 receptor (TMEM97) expression correlates well with the Ki67 expression in tumours [1, 2] and therefore represents an attractive marker for the proliferative status. An assessment of the sigma2 receptors in brain tumours by a non-invasive technique as PET depends on the radioligand’s suitability to cross the blood-brain barrier (BBB), which is actually one of the major challenges. Our aim was to develop an 18F-labelled radioligand for sigma2 receptor imaging in brain tumours, based on the well-described 2-(4-(1H-indol-1-yl)butyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline class of compounds. On the basis of a series of novel fluorinated derivatives for 18F-labelling the promising sigma2 receptor ligand [18F]RM273 was synthesized and investigated in healthy mice and an orthotopic rat glioma model.
Methods: [18F]RM273 (2-[4-(6-[18F]fluoro-1H-pyrrolo[2,3-b]pyridin-1-yl)butyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) has been obtained by automated synthesis by Cu-mediated oxidative radiofluorination of the aryl boronic acid pinacol ester precursor. Radiometabolite analysis was performed ex vivo in mouse plasma samples 30 min p.i. The target specificity was investigated by in vitro autoradiographic studies with or without the sigma2 receptor antagonist ISO-1 in rat brain cryosections with a stereotactically implanted F98 glioma [3]. The biodistribution of [18F]RM273 in healthy mice (female, CD1; n = 4, 7.2 ± 1.1 MBq) and the tumour uptake into the F98 glioma (male, F344; n = 2; 21 – 25 MBq) were investigated by dynamic PET imaging for 60 min (nanoScan®PET-1T MRI, Mediso Kft., Hungary).
Results: [18F]RM273 has been produced with a molar activity of 69 – 233 GBq/μmol at moderate radiochemical yield (8%) and high purity (≥99%). Polar radiometabolites of [18F]RM273, detected in blood plasma samples of mice, were not crossing the BBB, as 100 % parent fraction were detected in brain extracts at 30 min p.i.). We validated the target-specific binding of [18F]RM273 towards the F98 glioma in vitro and determined a 3-times higher density of binding sites in comparison to the healthy brain [3]. PET studies revealed a peak value of the time activity curve of 1.3 at 2.25 min p.i. with a t1/2 of 13.1 min after peak time and a peak-to-endpoint ratio of 6.4 ± 0.9 in the brain of healthy mice [3], whereas in the F98 glioma an SUVmean of 0.8 – 1.3 at 30 – 60 min p.i. was found, which was two times higher than measured in the contralateral brain region.
Conclusions: The reasonable brain penetration in rodents and the tumour specific accumulation of [18F]RM273 in the F98 glioma indicate the suitability of this radioligand for future imaging studies regarding the role of sigma2 receptors in neuro-oncological diseases. Our preliminary finding of a high density of sigma2 receptors in highly proliferative brain tumour cells deserves further investigation by use of larger sample sizes and complementation with immunohistochemistry.
Acknowledgements: This work was supported by the Deutsche Forschungsgemeinschaft (DFG: BR 1360/13-1).
References: [1] Shoghi et al. Plos One 2013, 8: e74188; [2] Yang et al. Molecules 2020, 25 (22): 5439 [3] Moldovan et al. Int. J. Mol. Sci. 2021, 22: 5447

  • Poster
    EMIM 2022, 15.-18.03.2022, Thessaloniki, Greece

Permalink: https://www.hzdr.de/publications/Publ-33507
Publ.-Id: 33507


Multidisciplinary Characterization of Uranium Mine Waters: A Bioremediation Perspective.

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

An intensive uranium mining took place for decades in East Germany. These intensive mining activities have left many uranium contaminated areas. For a remediation purpose, the mine water has to be pumped to the surface and treated by a conventional chemical wastewater treatment plant. However, such chemical treatments are time- and cost-intensive. The resulting release of the soluble uranium into the mine water represents a major health risk. Remediation approaches using indigenous microbial communities are an efficient strategy [1,2]. In this study, we have characterized the microbial diversity and geochemistry of water samples from a german former uranium mine to design bioremediation approach based on uranium enzymatic reduction.

Inductively Coupled Plasma-Mass Spectrometry and Ion-Chromatography studies showed that the mine water exhibited a high concentration of uranium (1.01 mg/L), sulfate (335 mg/L), iron (0.99 mg/L) and manganese (144 mg/L). Cryo-Time-resolved Laser-induced Fluorescence Spectroscopy studies identified an aqueous uranyl carbonate species [UO2(CO3)3]. The 16S and ITS1 rRNA gene sequencing revealed an extensive microbial diversity. The total bacterial community composition indicated a high relative abundance of sulfate-reducing-bacteria (e.g., Desulfovibrio) and iron-oxidizing-bacteria (e.g., Gallionella, Sideroxydans). These bacterial groups are reported to be involved in uranium (VI) reduction as a key process in the bioremediation of anoxic uranium contaminated sites [2].

To design a bioremediation strategy for this uranium-contaminated mine water, the original mine water was used directly as a reference to set up anoxic microcosms. Concretely, uranium-reducing-bacteria were stimulated by glycerol (10mM) as electron donor. ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease of uranium (≈90%), sulfate (≈60%), iron (≈86%) and manganese (≈88%). In addition, a drop of Eh and pH of the system was detected. A theoretical thermodynamic Eh-pH predominance diagram was calculated by Geochemist ́s Workbench, indicating the formation of uranium (IV) precipitates, probably uraninite, after 3 months at the latest. Finally, uranium (IV) was detected by UV-Visible spectroscopy in the precipitate at the end of the experiment.

These results show that the uranium reduction of soluble uranium (VI) to insoluble uranium (IV) is favoured by the addition of an electron donor (glycerol) in low concentrated uranium contaminated mines water by biostimulating their native microbial community.

Keywords: Uranium; Bioremediation; Reduction; Spectroscopy

  • Poster (Online presentation)
    Mineralogical Society. New Topics in Mineralogy 2: The mineral–microbe interface through time and space., 02.-03.12.2021, Manchester, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-33506
Publ.-Id: 33506


Non-invasive assessment of locally overexpressed human adenosine 2A receptors in the heart of transgenic mice

Gündel, D.; Lai, T. H.; Dukic-Stefanovic, S.; Teodoro, R.; Deuther-Conrad, W.; Toussaint, M.; Moldovan, R.-P.; Kopka, K.; Boknik, P.; Hofmann, B.; Gergs, U.; Neumann, J.; Brust, P.

Abstract: A2A adenosine receptors (A2A-AR) have a cardio-protective function upon ischemia and reperfusion, but on the other hand, their stimulation could lead to arrhythmias. Our aim was to investigate the potential use of the PET radiotracer [18F]FLUDA to determine the A2A-AR availability non-invasively for diagnosis of the A2AR status. Therefore, we compared mice with a cardiomyocyte-specific overexpressing of the human A2A-AR (A2A-AR TG) with the respective wild type (WT). We determined: (1) the functional impact of FLUDA on the contractile function of atrial mouse samples, (2) the binding parameters (Bmax and KD) of [18F]FLUDA on mouse and additionally on human atrial tissue samples by autoradiographic studies, and investigated (3) the in vivo uptake of the radiotracer by dynamic PET imaging in the two A2A-AR TG and WT. After A2A-AR stimulation by CGS 21680 in isolated atrial preparations antagonistic effects of FLUDA were found in A2A-AR-TG animals but not in WT mice. Radiolabeled [18F]FLUDA exhibited a KD of 5.9 ± 1.6 nM and a Bmax of 455 ± 78 fmol/mg protein in cardiac samples of A2A-AR TG, whereas in WT, as well as in human atrial preparations only low specific binding could was found. Dynamic PET studies revealed a significantly higher initial uptake of [18F]FLUDA into the myocardium of A2A-AR TG compared to WT. The hA2A-AR-specific binding of [18F]FLUDA in vivo was verified by pre-administration of the highly affine A2AAR-specific antagonist istradefylline.
Conclusion: [18F]FLUDA is a promising PET probe for the non-invasive assessment of the A2A-AR as a marker for pathologies linked to an increased A2A-AR density in the heart, as shown in patients with heart failure.

Keywords: [18F]FLUDA; A2A adenosine receptor; PET; myocardium

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Permalink: https://www.hzdr.de/publications/Publ-33505
Publ.-Id: 33505


Turbulent fluid flow in a precessing cylinder

Pizzi, F.; Giesecke, A.; Stefani, F.

In the framework of DRESDYN (DREsden Sodium facility for DYNnamo and thermohydraulic studies) we study the hy-
drodynamics of a fluid contained in a precessing cylinder. Here we focus on turbulence properties of the flow in dependence of the
precession angle as well as Reynolds number and Poincaré number (ratio of the frequency of the precessional system and the cylinder
itself). The main result is a characteristic peak in the dissipation around Po = 0.1 which goes along with a local maximum of turbulent
kinetic energy.

Keywords: precession; turbulence

  • Poster (Online presentation)
    25th International Congress of Theoretical and Applied Mechanics, 22.-27.08.2021, Milano, Italia

Permalink: https://www.hzdr.de/publications/Publ-33504
Publ.-Id: 33504


Nondiffusive Transport and Anisotropic Thermal Conductivity in High-Density Pt/Co Superlattices

Shahzadeh, M.; Andriyevska, O.; Salikhov, R.; Fallarino, L.; Hellwig, O.; Pisana, S.

Despite the numerous reports over the last two decades dedicated to the study of interfacial thermal transport,
physics of thermal transport across nanoscale metallic multilayers is less explored. This is in part due to the relatively
high conductance characteristic of these interfaces, which renders them difficult to characterize.
Interfacial transport in these systems has so far appeared to be diffusive, a surprising behavior when the interface density
increases and the layer thicknesses become comparable with the mean free path of electrons.
To address the limit of diffusive theories describing heat transport across high-density metallic interfaces,
we systematically investigate heat transport in and across Pt/Co multilayers via frequency domain thermoreflectance.
Sensitivity gained from offsetting the laser beam and reducing the laser spot size allows for the
measurement of anisotropic thermal conductivity of the multilayers. By changing the number of interfaces while keeping the overall
thickness of Pt and Co in the multilayer structure constant, the effect of interface density on the multilayers’ effective thermal
conductivity is studied. The extracted Pt/Co interface thermal boundary conductance is then compared to the calculations from the
electronic diffuse mismatch model and experimental data available in the literature. We show that as the multilayer period thickness
becomes much smaller than the electron mean free path, measurements markedly deviate from the diffusive transport theory. We
attribute this deviation to the nondiffusive nature of heat transport in subnanometric scales at interface densities above 1/nm.

Keywords: heat transport; metallic multilayers; anisotropic thermal conductivity; nondiffusive transport; frequency domain thermoreflectance

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Permalink: https://www.hzdr.de/publications/Publ-33503
Publ.-Id: 33503


Single Atom Counting of Stellar and r-Process Nuclei in Time-Resolved Deep-Sea Archives

Koll, D.; Wallner, A.; Hotchkis, M.; Child, D.; Fifield, K.; Froehlich, M.; Hartnett, M.; Lachner, J.; Merchel, S.; Pavetich, S.; Rugel, G.; Slavkovská, Z.; Tims, S.

Stars are the major element factories in the universe. In 1999, live supernova Fe-60 (t1/2 =2.6 Myr)
was detected in a deep-sea ferromanganese crust (1 ) indicating the accumulation of supernova
dust on Earth about 2 million years ago. This was followed by several projects reinforcing the
initial evidence for a global influx of supernova Fe-60. Recently, a much younger continuous
influx was found in Antarctic snow and in deep-sea sediments (2 –4 ) and an older peak around
6 - 8 Myr in deep-sea crusts (5 , 6 ).
In contrast to the well-known production mechanism and synthesis site of Fe-60, the long-lived
plutonium isotope Pu-244 (t1/2 =80 Myr) is a pure r-process nucleus. The nucleosynthesis site for
the astrophysical r-process is still debated in the astrophysics community. Potential candidates
involve rare supernovae and neutron star mergers. To date no evidence was presented that would
point to an exclusive r-process site and combinations of different sites are considered.
Experimentally, we can search for Pu-244 signatures in samples with known Fe-60 signatures to
test for either common influx patterns or independent Pu-244 influxes disentangled from stellar
Fe-60. Accordingly, this information provides a unique and direct experimental approach for
identifying the production site of the heavy elements.
Based on the recent publication of the first detection of interstellar Pu-244 in a ferromanganese
crust with a time resolution of 4.5 Myr (integrating over much shorter Fe-60 influxes) (6 ), we are
now working on a highly time-resolved profile of Fe-60 and Pu-244 in the large ferromanganese
crust VA13/237KD. This direct experimental input will further constrain models for r-process
nucleosynthesis in the galaxy. The recently determined profile of Fe-60 clearly shows two influxes,
one at 2 Myr, the other at 7 Myr, confirming and refining previous results. Preliminary data on
Pu-244 and an outlook for future measurement campaigns will be given.

References
1. K. Knie et al., Phys. Rev. Lett. 83, 18–21 (1999).
2. D. Koll et al., Phys. Rev. Lett. 123, 072701 (2019).
3. A. Wallner et al., Proceedings of the National Academy of Sciences 117, 21873–21879 (2020).
4. D. Koll et al., EPJ Web Conf. 232, 02001 (2020).
5. A. Wallner et al., Nature 532, 69–72 (2016).
6. A. Wallner et al., Science 372, 742–745 (2021).

Keywords: 60Fe; 244Pu; AMS; Stars; Supernovae; r-process

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  • Lecture (Conference) (Online presentation)
    Schools on Nuclear Astrophysics Questions, 13.10.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33501
Publ.-Id: 33501


Neutronenfluss in Untertagelaboren

Grieger, M.

Das Felsenkellerlabor ist ein neues Untertagelabor im Bereich der nuklearen Astrophysik. Es befindet sich unter 47 m Hornblende-Monzonit Felsgestein im Stollensystem der ehemaligen Dresdner Felsenkellerbrauerei.

Im Rahmen dieser Arbeit wird der Neutronenuntergrund in Stollen IV und VIII untersucht. Gewonnene Erkenntnisse aus Stollen IV hatten direkten Einfluss auf die geplanten Abschirmbedingungen fur Stollen VIII. Die Messung wurde mit dem Hensa-Neutronenspektrometer durchgeführt, welches aus polyethylenmoderierten 3He-Zählrohren besteht.

Mit Hilfe des Monte-Carlo Programmes Fluka zur Simulation von Teilchentransport werden für das Spektrometer die Neutronen-Ansprechvermögen bestimmt. Fur jeden Messort wird außerdem eine Vorhersage des Neutronenflusses erstellt und die Labore hinsichtlich der beiden Hauptkomponenten aus myoneninduzierten Neutronen und Gesteinsneutronen aus (α,n)-Reaktionen und Spaltprozessen kartografiert.

Die verwendeten Mess- und Analysemethoden finden in einer neuen Messung am tiefen Untertagelabor Lsc Canfranc Anwendung. Erstmalig werden im Rahmen dieser Arbeit
vorläufige Ergebnisse vorgestellt.

Des Weiteren werden Strahlenschutzsimulationen fur das Felsenkellerlabor präsentiert, welche den strahlenschutztechnischen Rahmen für die wissenschaftliche Nutzung definieren. Dabei werden die für den Sicherheitsbericht des Felsenkellers verwendeten Werte auf die Strahlenschutzverordnung 2018 aktualisiert.

Letztlich werden Experimente an der Radiofrequenz-Ionenquelle am Felsenkeller vorgestellt, die im Rahmen dieser Arbeit technisch betreut wurde. Dabei werden Langzeitmessungen am übertägigen Teststand am Helmholtz-Zentrum Dresden-Rossendorf präsentiert.

Keywords: Neutronen; Untertagelabor; Spektrometer; Entfaltung; FLUKA; Monte-Carlo; HENSA

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-117 2022
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-33500
Publ.-Id: 33500


Fe-60 and Mn-53: The Radionuclide System to Study Meteorites, the Solar Neighborhood and Past Supernova Activity

Koll, D.; Faestermann, T.; Korschinek, G.; Ingo, L.; Merchel, S.; Wallner, A.

Astrophysical studies on extraterrestrial samples often involve long-lived radionuclides to study the evolution
of the solar system and the galaxy on long timescales. Dyadic radionuclide/stable nuclide systems such as
U-Pb, Sm-Nd or Rb-Sr are well-established and widely used for dating and characterization of meteorites and
lunar rocks. Such systems rely on the decay of a long-lived radionuclide and the resulting isotopic anomalies
of the daughter isotope compared to natural abundances.
In contrast, in this talk, the two live radionuclides Fe-60 and Mn-53 are shown to be versatile tools to study
meteorites and past supernova activity. Both radionuclides with half-lives around 3 Myr are produced in massive
stars as well as by spallation in extraterrestrial materials, planetary surfaces and cosmic dust. Measured
and modelled production rates [1,2] and the first use as a dyadic system to disentangle the origin of supernovaproduced
Fe-60 on the surface of the moon [3] and in Antarctic snow [4] will be presented amongst recent
discoveries of the individual radionucides in geological archives.

[1] Leya et al., Meteoritics & Planetary Science 55, 818–831 (2020)
[2] Merchel et al., Nucl. Instr. Meth. Phys. Res. B 172, 806-811 (2000)
[3] Fimiani et al., Phys. Rev. Lett. 116, 151104 (2016)
[4] Koll et al., Phys. Rev. Lett. 123, 072701 (2019)

Keywords: Meteorites; 60Fe; 53Mn; Supernova; Interstellar; Interplanetary

  • Poster (Online presentation)
    The 16th International Symposium on Nuclei in the Cosmos, 21.09.2021, Chengdu, China

Permalink: https://www.hzdr.de/publications/Publ-33499
Publ.-Id: 33499


Time-Resolved Interstellar Pu-244 and Fe-60 Profiles in a Be-10 Dated Ferromanganese Crust

Koll, D.; Wallner, A.; Hotchkis, M.; Child, D.; Fifield, K.; Froehlich, M.; Hartnett, M.; Lachner, J.; Merchel, S.; Pavetich, S.; Rugel, G.; Slavkovská, Z.; Tims, S.

More than 20 years have passed since the first attempts to find live supernova Fe-60
(t1/2 = 2.6 Myr) in a deep-sea ferromanganese crust [1]. Within these 20 years, strong evidence was presented for a global influx of supernova dust into several geological samples around 2 Myr ago. Recently, a much younger continuous influx was found in Antarctic snow and in deep-sea sediments [2-4] and an older peak around 7 Myr in deep-sea crusts [5,6].

The long-lived isotope Pu-244 (t1/2 = 80 Myr) is produced in the astrophysical r-process similarly to most of the heaviest elements. Although the production mechanism is believed to be understood, the astrophysical site is heavily disputed. Most likely scenarios involve a combination of rare supernovae and neutron star mergers. The search for Pu-244 signatures in samples with known Fe-60 signatures allows to test for either common influx patterns or a independent Pu-244 influxes disentangled from stellar Fe-60. Accordingly, this information provides a unique and direct experimental approach for identifying the production site of the heavy elements.

Very recently and first reported in the AMS-14 conference, the first detection of interstellar Pu-244 was published [6]. This was only feasible by achieving the highest detection efficiencies for plutonium in AMS ever reported [7]. The achieved time resolution of 4.5 Myr integrates over the supernova influxes and is therefore not high enough to unequivocally show a correlated influx pattern of Fe-60 and Pu-244.
Based on this progress, we are now aiming to measure highly time-resolved profiles of Fe-60 and Pu-244 in the largest ferromanganese crust used so far. Results on the characterisation of the crust including cosmogenic Be-10 (t1/2 = 1.4 Myr) dating and a 10 Myr profile of interstellar Fe-60 including the confirmation of the 7 Myr influx will be presented along with first data on interstellar Pu-244.

[1] Knie et. al., Phys. Rev. Lett. 83 (1999).
[2] Koll et al., Phys. Rev. Lett. 123 (2019).
[3] Koll et al., EPJ 232 (2020).
[4] Wallner et al., PNAS 117 (2020).
[5] Wallner et al., Nature 532 (2016)
[6] Wallner et al., Science 372 (2021)
[7] Hotchkis et al., NIMB 438 (2019)

Keywords: Supernova; 60Fe; 244Pu; 10Be; r-process; ferromanganese crust; pacific; AMS

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  • Lecture (Conference) (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry, 19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33498
Publ.-Id: 33498


Manipulating magnetic and magnetoresistive properties by oxygen vacancy complexes in GCMO thin films

Beiranvand, A.; Liedke, M. O.; Haalisto, C.; Lähteenlahti, V.; Schulman, A.; Granroth, S.; Palonen, H.; Butterling, M.; Wagner, A.; Huhtinen, H.; Paturi, P.

The effect of in situ annealing is investigated in Gd0.1Ca0.9MnO3 (GCMO) thin films in oxygen and vacuum atmospheres. We show that the reduction of oxygen content in GCMO lattice by vacuum annealing induced more oxygen complex vacancies in both subsurface and interface regions and larger grain domains when compared with the pristine one. Consequently, the double exchange interaction is suppressed and the metallic-ferromagnetic state below Curie temperature turned into spin-glass insulating state. In contrast, the magnetic and resistivity measurements show that the oxygen treatment increases ferromagnetic phase volume, resulting in greater magnetization (MS) and improved magnetoresistivity properties below Curie temperature by improving the double exchange interaction. The threshold field to observe the training effect is decreased in oxygen treated film. In addition, the positron annihilation spectroscopy analysis exhibits fewer open volume defects in the subsurface region for oxygen treated film when compared with the pristine sample. These results unambiguously demonstrate that the oxygen treated film with significant spin memory and greater magnetoresistance can be a potential candidate for the future memristor applications.

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; GaCaMnO3; oxygen vacancy; spin-glass

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Publ.-Id: 33497


Band-selective third-harmonic generation in superconducting MgB2: Possible evidence for the Higgs amplitude mode in the dirty limit

Kovalev, S.; Dong, T.; Shi, L.-Y.; Reinhoffer, C.; Xu, T.-Q.; Wang, H.-Z.; Wang, Y.; Gan, Z.-Z.; Germanskiy, S.; Deinert, J.-C.; Ilyakov, I.; van Loosdrecht, P. H. M.; Wu, D.; Wang, N.-L.; Demsar, J.; Wang, Z.

We report on time-resolved linear and nonlinear terahertz spectroscopy of the two-band superconductor MgB2
with a superconducting transition temperature Tc ≈ 36 K. Third-harmonic generation (THG) is observed below
Tc by driving the system with intense narrow-band THz pulses. For the pump-pulse frequencies f = 0.3, 0.4,
and 0.5 THz, the temperature-dependent evolution of the THG signals exhibits a resonance maximum at the
temperatures with the resonance conditions 2 f = 2Delta π (T ) fulfilled, for the dirty-limit superconducting gap
2Delta π . In contrast, for f = 0.6 and 0.7 THz with 2 f > 2Delta π (T → 0) = 1.03 THz, the THG intensity increases
monotonically with decreasing temperature. Moreover, for 2 f < 2Delta π (T → 0) the THG is found nearly isotropic
with respect to the pump-pulse polarization. These results suggest a predominant contribution of the driven
Higgs amplitude mode of the dirty-limit π -band superconducting gap, pointing to the importance of scattering
for observation of the Higgs mode in superconductors.

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Publ.-Id: 33496


Radiosynthesis and first preclinical evaluation of an 18F-radiolabelled ligand for cancer stem cells by non-invasive PET imaging

Toussaint, M.; Moldovan, R.-P.; Teodoro, R.; Gündel, D.; Deuther-Conrad, W.; Brust, P.

Objectives: Cancer stem cells (CSCs) are a multipotent cells subpopulation playing a critical role in tumor initiation, therapy resistance and recurrence1. Therefore, their therapeutic targeting is of relevance for highly aggressive entities with poor prognosis such as glioblastoma (NCT02654964). To support the development of such targeted therapy we intended to develop a radiotracer enabling the non-invasive imaging of the CSCs population. Based on the work of Lucki et al.2 who discovered a promising prodrug termed RIPGBM selective of cancer stem cells (CSC), we aimed at developing an 18F-radiolabelled RIPGBM, and to preliminary assess its potential as non-invasive imaging agent of a low-density population such as the CSC in a mouse model of human glioblastoma. We report in this first exploratory study on the synthesis, radiosynthesis, in vivo metabolism and pharmacokinetics of [18F]RIPGBM.
Methods: The reference compound N-(3-(benzylamino)-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-N-(4-fluorobenzyl)acetamide (RIPGBM) and the corresponding boronic acid pinacol ester precursor for radiofluorination (RM361) were obtained by following the synthetic procedure reported by Lucki and co-workers2. The radiosynthesis of [18F]RIPGBM was performed on an automated module in presence of CU(OTf)2(Py)4, [18F]TBAF and DMA/tBuOH. The fraction of radiometabolites was quantified in mice plasma and brain at 30 min post injection (p.i.). Dynamic PET studies (60 min, nanoScan® PET/MRI, MEDISO, Budapest, Hungary) were performed using an orthotopic xenogenic U87 glioblastoma model in nude mice (n=2) presenting a stem cell-like population3,4.
Results: [18F]RIPGBM was obtained with a radiochemical yield of 6.0 ± 1.3% (EOB), a radiochemical purity >99% and a molar activity of 60-200 GBq/µMol (EOS). It shows a similar stability in both mice at 30 p.i. with 26-30% of intact radiotracer in plasma and 73-74% in the brain. About 70% of intact radiotracer was found in the tumor hemisphere. The PET-derived time-activity curves (TACs) of the whole brain, tumor and contralateral regions displayed a sufficient brain uptake (TAC peak value of 1.0-1.4 SUV). Furthermore, [18F]RIPGBM displays a fast washout from all the above mentioned region.
Conclusion: A fully automated copper-mediated radiosynthetic procedure was developed for the promising prodrug RIPGBM targeting CSCs. A first exploration in vivo demonstrates the presence of 30 % of radiometabolites in the brain/tumor region, no high unspecific retention as shown by the fast washout, but also no observable specific retention in the target area presumably due to the lack of affinity of this radioligand given the low density of the targeted cell population in this model.
References: 1. Lathia, J. D., Mack, S. C., Mulkearns-Hubert, E. E., Valentim, C. L. L. & Rich, J. N. Cancer stem cells in glioblastoma. Genes Dev. 29, 1203–1217 (2015).
2. Lucki, N. C. et al. A cell type-selective apoptosis-inducing small molecule for the treatment of brain cancer. PNAS 116, 6435–6440 (2019).
3. Yu, S. et al. Isolation and characterization of cancer stem cells from a human glioblastoma cell line U87. Cancer Letters 265, 124–134 (2008).
4. Toda, Y. et al. DJ-1 Contributes to Self-renewal of Stem Cells in the U87-MG Glioblastoma Cell Line. Anticancer Res 39, 5983–5990 (2019).

Keywords: RIPGBM; 18F-radiolabelled ligand; Positron emission tomography; cancer stem cells

  • Open Access Logo Poster
    International symposium on radiopharmaceutical sciences, 29.05.-02.06.2022, Nantes, France

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Data publication: Temperature-induced surface faceting of M-plane Al₂O₃: An in-situ GISAXS study

Erb, D.; Perlich, J.; Roth, S.; Röhlsberger, R.; Schlage, K.

-- raw data of GISAXS experiment

-- AFM data

-- GISAXS simulation files

Keywords: crystal surface reconstruction; nanofaceted Al₂O₃; pattern formation; in-situ GISAXS; AFM

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Publ.-Id: 33492


Mode conversion and period doubling in a liquid rubidium Alfvén-wave experiment with coinciding sound and Alfvén speeds

Stefani, F.; Forbriger, J.; Gundrum, T.; Herrmannsdörfer, T.; Wosnitza, J.

We report Alfvén-wave experiments with liquid rubidium at the Dresden High Magnetic Field Laboratory (HLD). Reaching up to 63 T, the pulsed magnetic field exceeds the critical value of 54 T at which the Alfvén speed coincides with the sound speed. At this threshold we observe a period doubling of an applied 8 kHz CW excitation, which is consistent with the theoretical expectation of a parametric resonance between magnetosonic waves and Alfvén waves. Similar mode conversions are discussed as a possible mechanism for heating the solar corona.

Keywords: Alfvén waves; Solar physics; Corona heating

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Molecular Response to Combined Molecular- and External Radiotherapy in Head and Neck Squamous Cell Carcinoma (HNSCC).

Rassamegevanon, T.; Feindt, L.; Koi, L.; Müller, J.; Freudenberg, R.; Löck, S.; Sihver, W.; Çevik, E.; Christel Kühn, A.; von Neubeck, C.; Linge, A.; Pietzsch, H.-J.; Kotzerke, J.; Baumann, M.; Krause, M.; Dietrich, A.

Combination treatment of molecular targeted and external radiotherapy is a promising strategy and was shown to improve local tumor control in a HNSCC xenograft model. To enhance the therapeutic value of this approach, this study investigated the underlying molecular response. Subcutaneous HNSCC FaDuDD xenografts were treated with single or combination therapy (X-ray: 0, 2, 4 Gy; anti-EGFR antibody (Cetuximab) (un-)labeled with Yttrium-90 (90Y)). Tumors were excised 24 h post respective treatment. Residual DNA double strand breaks (DSB), mRNA expression of DNA damage response related genes, immunoblotting, tumor histology, and immunohistological staining were analyzed. An increase in number and complexity of residual DNA DSB was observed in FaDuDD tumors exposed to the combination treatment of external irradiation and 90Y-Cetuximab relative to controls. The increase was observed in a low oxygenated area, suggesting the expansion of DNA DSB damages. Upregulation of genes encoding p21cip1/waf1 (CDKN1A) and GADD45α (GADD45A) was determined in the combination treatment group, and immunoblotting as well as immunohistochemistry confirmed the upregulation of p21cip1/waf1. The increase in residual γH2AX foci leads to the blockage of cell cycle transition and subsequently to cell death, which could be observed in the upregulation of p21cip1/waf1 expression and an elevated number of cleaved caspase-3 positive cells. Overall, a complex interplay between DNA damage repair and programmed cell death accounts for the potential benefit of the combination therapy using 90Y-Cetuximab and external radiotherapy.

Keywords: Cetuximab; DNA damage response; cell death induction; external beam radiotherapy; molecular targeted radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-33490
Publ.-Id: 33490


Spin-wave focusing induced by dipole-dipole interaction in synthetic antiferromagnets

Gallardo, R. A.; Alvarado-Seguel, P.; Kákay, A.; Lindner, J.; Landeros, P.

Under certain conditions, spin waves can be channeled into a broad angular spectrum of wave vectors, where the direction
of the group velocity becomes independent of those wave vectors. Such highly focused waves are called caustic waves,
whose properties can be manipulated by anisotropies or chiral interactions, like the Dzyaloshinskii-Moriya interaction. In this
paper, we theoretically study the focusing features of the spin waves induced by the dipole-dipole interaction in synthetic
antiferromagnets. For stacked systems, the dipolar interaction causes a noticeable frequency nonreciprocity when the
magnetizations in both films are antiparallelly aligned, and then the focusing properties of the spin waves are enhanced. The
role of thicknesses and magnetic graduation along the film's normal are systematically analyzed. We found that the degree
of focalization of the spin waves can be manipulated by increasing the layers' thickness. Also, we show that the low- and
high-frequency modes exhibit different focalization properties; the low-frequency mode manifests a similar behavior to the
heavy-metal/ferromagnet systems with interfacial Dzyaloshinskii-Moriya interaction, while the high-frequency one tends the
generate almost reciprocal interference patterns along one axis. In the case of magnetization-graded synthetic
antiferromagnets, we demonstrate that the graduation slightly influences the low-frequency mode, while the focusing and
nonreciprocal dynamic properties of the high-frequency ones are notoriously altered. The theoretical calculations are
compared with micromagnetic simulations, where a good agreement is found between both methods. Our results
demonstrate that a synthetic antiferromagnetic system allows for controlling the propagation of spin waves, assisting in the
transfer of angular momentum and energy.

Keywords: Spin waves; Wave focusing; synthetic antiferromagnets; Dzyaloshinskii-Moriya interaction; Spectrum analysis; dipole-dipole interaction; multilayers

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Publ.-Id: 33489


Evaluation of [18F]RM273 for sigma2-receptor imaging in an experimental orthotopic glioblastoma model

Gündel, D.; Toussaint, M.; Moldovan, R.-P.; Teodoro, R.; Schepmann, D.; Wünsch, B.; Ludwig, F.-A.; Fischer, S.; Brust, P.; Deuther-Conrad, W.

Objectives
The proven suitability of the sigma2 receptor as marker for the proliferative status of solid tumors of the body [1] has promoted efforts to develop brain-targeted radioligands for sigma2 receptor imaging in neuro-oncological diseases as well. Accordingly, based on the well described 2-(4-(1H-indol-1-yl)butyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline class of compounds we designed a series of novel fluorinated derivatives for 18F-labelling and investigated the most promising sigma2 receptor ligand in a rat model for glioma.
Methods
[18F]RM273 (2-[4-(6-[18F]fluoro-1H-pyrrolo[2,3-b]pyridin-1-yl)butyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) has been obtained by automated synthesis by Cu-mediated oxidative radiofluorination of the aryl boronic acid pinacol ester precursor. Wildtype mice (female, CD1; n = 4) and rats with intracranial implanted orthotopic F98 glioma (male, F344; n = 2) were injected with the radiotracer (mice: 7.2±1.1 MBq; rats: 21–25 MBq) and investigated by dynamic PET (nanoScan®PET-1T MRI). Complementary ex vivo metabolite as well as in vitro autoradiographic studies were performed in mice after intravenous injection and in rat with cryosections of the brain of one F98 bearing animal, respectively [2].
Results
[18F]RM273 has been produced with a molar activity of 69–233 GBq/μmol at moderate radiochemical yield (8%) and high purity (≥99%). A mean standardized uptake value (SUV) of 1.3 at 2.25 min p.i. in the brain of wildtype CD1 mice indicates fast and adequate penetration of the blood-brain barrier. The polar radiometabolites of [18F]RM273 discovered in blood plasma of mice were not detectable in the brain extracts (100 % parent fraction at 30 min p.i.). The binding pattern of [18F]RM273 in vitro in cryosections of the glioma brain indicates target-specific binding towards the F98 glioma (complete displacement by co-incubation with 1 µM ISO-I) with an about 3-fold higher density of binding sites in comparison to the healthy brain [2]. Also by PET the F98 glioma could be delineated clearly with mean SUVs at 30–60 min p.i. of 0.8–1.3 in the tumor and 0.5 in the contralateral region.
Conclusions
The reasonable brain penetration in rodents as well as the tumor specific accumulation of [18F]RM273 in the F98 glioma indicates the suitability of this radioligand for future imaging studies regarding the role of sigma2 receptors in neuro-oncological diseases. Our preliminary finding of a high density of sigma2 receptors in highly proliferative brain tumor cells deserves further investigation by larger sample sizes and complementation with immunohistochemistry.
Acknowledgements
This work was supported by the Deutsche Forschungsgemeinschaft (DFG: BR 1360/13-1).
References
[1] Shoghi et al. Plos One 2013, 8: e74188
[2] Moldovan et al. Int. J. Mol. Sci. 2021, 22: 5447

  • Abstract in refereed journal
    Nuclear Medicine and Biology 108-109(2022)Suppl., S184
    DOI: 10.1016/S0969-8051(22)00384-5
  • Poster
    International Symposium on Radiopharmaceutical Sciences iSRS, 29.05.-02.06.2022, Nantes, Frankreich

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Data to 18F-AW09

Wodtke, R.; Löser, R.

radio-TLC, radio-HPLC, radio-SDS, in vitro autoradiography

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NMR data FBz/FBn polyamines

Wodtke, R.; Löser, R.

Files of NMR data for the different fluorobenz(o)ylated polyamines and radiosynthesis data

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Americium preferred: LanM, a natural lanthanide-binding protein favors an actinide over lanthanides

Singer, H.; Drobot, B.; Zeymer, C.; Steudtner, R.; Daumann, L.

The separation and recycling of lanthanides is an active area of research with a growing demand that calls for more environmentally friendly lanthanide sources. Likewise, the efficient and industrial separation of lanthanides from the minor actinides (Np, Am - Fm) is one of the key questions for closing the nuclear fuel cycle; reducing costs and increasing safety. With the advent of the field of lanthanide dependent bacterial metabolism, bio-inspired applications are in reach. Here, we utilize the natural lanthanide chelator Lanmodulin and the luminescent probes Eu3+ and Cm3+ to investigate the inter-metal competition behavior of all lanthanides (except Pm) and the major actinide plutonium as well as three minor actinides neptunium, americium and curium to Lanmodulin. Using time resolved laser induced fluorescence spectroscopy we show that Lanmodulin has the highest relative binding affinity to Nd3+ and Eu3+ among the lanthanide series. When equimolar mixtures of Cm3+ and Am3+ are added to Lanmodulin, Lanmodulin preferentially binds to Am3+ over Cm3+ whilst Nd3+ and Cm3+ bind with similar relative affinity. The results presented show that a natural lanthanide binding protein can bind a major and various minor actinides with high relative affinity, paving the way to bio inspired separation applications. In addition, an easy and versatile method was developed, using the fluorescence properties of only two elements, Eu and Cm, for inter-metal competition studies regarding lanthanides and selected actinides and their binding to biological molecules.

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Development of “clickable” albumin binders and application to theranostic radioligands for somatostatin receptor subtype 2

Brandt, F.; Ullrich, M.; Löser, R.; Pietzsch, H.-J.; Kopka, K.; Pietzsch, J.; Wodtke, R.

Despite given high affinity and selectivity towards their distinct biological targets, theranostic radioligands can suffer strongly from fast blood clearance and metabolism, which limits the enrichment of the compounds in the tumour tissue. A viable strategy to increase the bioavailability of substances is the conjugation to human serum albumin (HSA). In this context, Nε-4-(4-iodophenyl)butanoyllysine (Nε-IPB-lysine) was recently discovered as potent albumin binder.[1] However, conjugation of Nε-IPB-lysine via its α-amino group to proteins, peptides or small molecules is challenging, as a free α-carboxyl group is required to maintain good binding to HSA.
To allow the broad applicability and late-stage introduction of Nε-IPB-lysine we present a novel approach of Cu-catalyzed azide-alkyne cycloaddition (CuAAC) using Nε-IPB-lysine derivatives with azide/alkyne bearing moieties at the α-amino group. For small scales, a solid phase synthesis strategy starting from Fmoc-Lys(Alloc)-OH was developed. For upscaling, a 3-step synthesis starting from Boc-Lys-OH has been established. The HSA binding affinities were determined using microscale thermophoresis and a fluorescence-based competition assay. A library of azide/alkyne containing compounds with a binding affinity to HSA ranging from 0.4 µM to 100 µM could be obtained.
To demonstrate the suitability of the novel albumin binders, Nα-5-azidopentanoyl-Nε-IPB-D-lysine (Kd = 8 µM) was coupled to the somatostatin receptor subtype 2 ligand NODAGA-Pra-O2Oc-TATE 1 by on-resin CuAAC. For radiolabelling, copper-64 was used. The resulting conjugate [64Cu]Cu-2 showed significantly improved binding to HSA compared to [⁶⁴Cu]Cu-1, [⁶⁴Cu]Cu-NODAGA-TATE, and [⁶⁴Cu]Cu-DOTA-TATE. All TATE derivatives were studied by PET imaging using a mouse phaechromocytoma (MPC)-allograft model highlighting an increased blood circulation time of [⁶⁴Cu]Cu-2 and higher tumor uptake at late time points (24 h) compared to the other radiotracers. Current studies aim to further optimise the biodistribution by selecting HSA binders of higher or lower binding affinity.

Literature:

[1] Dumelin et al. Angew. Chem. Int. Ed. Engl. 2008, 47(17), 3196-3201.

  • Poster (Online presentation)
    Frontiers in Medicinal Chemistry, 08.-10.03.2021, Darmstadt, Deutschland

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Publ.-Id: 33484


Synthesis and characterisation of irreversible transglutaminase 2-inhibitors with albumin binding moiety

Wodtke, R.; Schlitterlau, P.; Brandt, F.; Laube, M.; Kopka, K.; Pietzsch, H.-J.; Pietzsch, J.; Löser, R.

The development of radiotracers for transglutaminase 2 (TGase 2) based on irreversible inhibitors appears highly attractive to further uncover the role of that enzyme for the emergence and progression of various tumours. [1] In this context, the ¹⁸F-labelled analogue of Nε-acryloyl-L-lysine 1, developed in our lab, showed great potential as radiometric tool for in vitro investigations. However, application for in vivo imaging is strongly limited by its unfavourable pharmacokinetic properties such as fast blood clearance and metabolism. A common approach to improve biodistribution and blood circulation time of drugs is the reversible conjugation to human serum albumin (HSA). Recently, compound 2 was identified as HSA binder with good affinity (Kd = 3.2 µM). [2] Successful application of 2 was demonstrated for pharmacokinetic tuning of various radiolabelled compounds, but rather for hydrophilic than for hydrophobic molecules. [3] Moreover, compound 2 offers the possibility for radiolabelling with iodine-123. [4]
For the purpose to develop radiotracers for TGase 2 with HSA binding capability, we designed compound 3 as lead structure containing the HSA binding moiety of 2 linked via a triazole ring as an amide bioisostere to the part of the TGase 2-inhibitor. Conjugation of alkyne-functionalised Nε-acryloyl-L-lysines and Boc-protected (R)-6-amino-2-azidohexanoic acid by copper-catalysed azide/alkyne cycloaddition followed by Boc deprotection and introduction of 4-(4-iodophenyl)butanoic acid via the respective N-hydroxysuccinimide ester gave access to 3 and two further derivatives with 3,5 and 2,5 substitution pattern at the pyridine ring. Evaluation of these compounds (and their alkyne precursors) by in-house assay methods revealed excellent inhibitory potencies towards TGase 2 (kinact/KI = 10,800 and 3,880 M-1s-1 for 3 and 1, respectively) and good binding affinities to HSA (Kd = 2.3 µM for 3). Overall, this indicates a promising basis for the application of this dual-targeting approach. Current studies focus on the radiolabelling of compound 3 with iodine-123 using the respective arylboronic acid as precursor which can be obtained via the same synthetic route.

Literature:

[1] Pietsch et al. Bioorg. Med. Chem. Lett. 2013, 23, 6528. [2] Dumelin et al. Angew. Chem. Int. Ed. 2008, 47, 3196. [3] Brandt et al. Nucl. Med. Biol. 2019, 70, 46. [4] Wen et al. Mol. Pharmaceutics 2019, 16, 816.

  • Lecture (Conference) (Online presentation)
    Frontiers in Medicinal Chemistry, 08.-10.03.2021, Darmstadt, Deutschland

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Publ.-Id: 33483


18F-Chemistry in HPLC vials - a microliter scale radiofluorination approach

Laube, M.; Wodtke, R.; Kopka, K.; Knieß, T.; Pietzsch, J.

Abstract:

Objectives: Finding optimal 18F-fluorination conditions represents a critical and often time-consuming step in radiotracer development. Microfluidic or lab-on-a-chip devices are modern tools for that purpose but not accessible everywhere. Inspired by 18F-chemistry in low volumes based on a MAX/MCX-trapping technique for one complete 18F-batch,[1] we herein present an 18F-labeling approach using low volume aliquots (<100 µL) of defined QMA-eluates in HPLC vials as reaction vessels for optimizations as well as the preparation of radiotracers for preclinical studies.

Methods: For optimization experiments, 1-80 MBq [18F]fluoride was eluted from QMA cartridges with defined mixtures of phase transfer catalyst (Kryptofix®222), base (such as K2CO3, KHCO3, KH2PO4), and 2-3% water in acetonitrile[2]. 25 or 50 µL aliquots of the eluates were pipetted into 1.5 mL HPLC vials and the sealed vials were consecutively dried once at 90°C for 3 min with a helium stream. After processing up to 15 vials in one batch, 25 or 50 µL precursor stock solution (1-20 mg/mL in MeCN, DMF, or DMSO) was added and the sealed vials were heated at defined temperatures (60-140°C) and times (5-15 min) by using three heaters equipped with aluminum blocks. Samples were 4-fold diluted with acetonitrile/water 50/50 for analysis by radio-TLC/radio-HPLC. 18F-trapping/elution at higher activity levels (~20 GBq [18F]fluoride) was performed by using a radiosynthesizer (Tracerlab FXFN) followed by transfer into a lead container having three small bores as inlet, vent needle and withdrawal port. A self-made pipet tip-to-cannula adapter allowed withdrawal of defined 25-100 µL aliquots at an activity level of ~13 MBq/µL for further processing under optimized conditions as described above.

Results: The use of small reaction volumes and HPLC vials enabled an efficient 18F-optimization workflow to examine rapidly a variety of reaction parameters (>50 reactions/day) using minimal amounts of precursor. Utilizing mixtures of 2-3% water in acetonitrile for 18F-elution allowed for radiolabeling even without azeotropic drying in certain cases, which can further accelerate the entire labeling process. For more demanding radiolabeling reactions, drying of only 3 min with helium furnished highly reactive [18F]fluoride with comparable reactivity even several hours after the elution step. This optimization workflow was used successfully to identify high yielding reaction conditions for a variety of precursor molecules like aliphatic tosylates or mesylates as well as aromatic sydnones, boronic acids or trimethylammonium salts. As examples, optimization results for 18F-labeling of the FDG mannose triflate precursor and the tosylate precursor of celecoxib-derivative [18F]A[3] are shown in Figure 1. Transfer into isolated RCY at activity levels suitable for preclinical evaluations was achieved (e.g. for [18F]A: 25-30% after 18F-labeling in acetonitrile at 90°C and purification) and turned out to be comparable to results from conventional automated radiosyntheses.

Conclusion: This microliter scale optimization and labeling procedure can easily be adapted and transferred to the synthesis of known and new radiotracers. The straightforward approach represents a valuable radiochemistry tool to enter rapidly into subsequent preclinical studies.

References: [1] Iwata (2018), J.Labelled.Comp.Radiopharm., 61, 540; [2] Kniess (2017), Appl.Radiat.Isot 127, 260; [3] Laube (2020), RSC Advances, 10, 38601.

Figure 1. Setup of HPLC vial experiments and representative results of optimization.

  • Poster (Online presentation)
    eSRS 2021, 17.-19.05.2021, Online, -

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Publ.-Id: 33482


Development of ¹²³I-labelled acrylamides as radiotracer candidates for transglutaminase 2

Laube, M.; Brandt, F.; Kopka, K.; Pietzsch, H.-J.; Pietzsch, J.; Löser, R.; Wodtke, R.

Objectives: The development of radiotracers for transglutaminase 2 (TGase 2) based on irreversible inhibitors appears highly attractive to further uncover the role of this enzyme for the emergence and progression of various tumour entities. However, the present imaging probes labeled with carbon-11 or fluorine-18 suffer from unfavourable pharmacokinetic properties such as fast blood clearance and metabolism. [1] Furthermore, incorporation of radionuclides with a longer half-life is desirable as the irreversible reaction between the molecular target and the probe might lead to a better signal-to-noise ratio at later time points. To tackle these two aspects, we developed the potent inhibitors 1 and 2 (Scheme) containing pyridine-3-yl residues with electron withdrawing groups and a iodinated phenylacetyl moiety. Herein, we present the radiosynthesis of [¹²³I]1 and [¹²³I]2 using their respective boronic acid pinacol esters as precursors.
Methods: Compounds 1 and 2 and the precursors 1-P and 2-P were synthesised starting from Nα-Boc-L-lysine in a sequence consisting of Nε-acrylation, PyBOP-mediated amide bond formation, Boc deprotection and HATU-mediated Nα-acylation. [2] For optimisation of radioiodination, reactions were performed in HPLC vials as reaction vessels applying 0.5-2 MBq [¹²³I]iodide in 50-100 µL of solvent. In addition to varying additive/precursor/water concentrations, the storage life and premixing time of reagent solutions were investigated. Radiolabelling at higher activity levels (up to 600 MBq) was conducted using 15-50 µL [¹²³I]iodide in total reaction volumes of 200-300 µL. Radiotracers were separated by semi-preparative HPLC. Solid-phase extraction was performed to provide [¹²³I]1 and [¹²³I]2 in suitable formulations for preclinical studies.
Results: 80-100 mg of each reference and precursor compound were obtained in sufficient purities (>95%). While chloramine T did not lead to the formation of [¹²³I]1 and [¹²³I]2, both compounds were accessible by the use of copper(II) trifluoroacetate and 1,10-phenanthroline [3] or tetrakis(pyridine)copper(II) triflate (Cu(OTf)₂(py)₄) [4]. In this context, Cu(OTf)₂(py)₄ in a 4-fold excess to precursor appeared to be most favourable leading to radiochemical conversions of >90% already after 10 min at room temperature (Scheme). These conditions allow for efficient radioiodinations even at 0.1 mM of precursor as well as with a water portion of up to 26%. Furthermore, the reagent solutions can be stored up to 3 month (at -20°C) without significant loss of radiochemical conversion. [¹²³I]1 and [¹²³I]2 were obtained as solutions in ethanol (2 MBq/µL) with (radio)chemical purities of ≥98% and radiochemical yields of >80%.
Conclusion: ¹²³I-labelled irreversible inhibitors of TGase 2 were prepared for the first time. The use of boronic acid pinacol ester as precursor and Cu(OTf)₂(py)₄ as catalyst facilitated the efficient radiolabelling with [¹²³I]iodide. This enables the radiopharmacological characterisation of these potential radiotracers towards their target TGase 2 in vitro and in vivo.
Acknowledgments: The authors thank ROTOP Radiopharmacy for continuously providing [¹²³I]iodide. Financial support by “Europäischer Fonds für regionale Entwicklung (EFRE)” (ML, HJP, and RW) is gratefully acknowledged.
References: [1] van der Wildt et al. Amino Acids 2017, 49, 585; [2] Wodtke et al. J. Med. Chem. 2018, 61, 4528; [3] Wilson et al. Chem. Comm. 2016, 52, 13277; [4] Reilly et al. Org. Lett. 2018, 20, 1752.

  • Lecture (Conference) (Online presentation)
    eSRS 2021, 17.-19.05.2021, Fredericksburg, United States of America
    DOI: 10.1016/S0969-8051(21)00396-6

Permalink: https://www.hzdr.de/publications/Publ-33481
Publ.-Id: 33481


Transition-metal-free reductive coupling of an 18F-labeled nitro-arene with boronic acids as a potential access to 18F-labeled fenamates

Laube, M.; Roscales Garcia, S.; Pietzsch, J.; Csákÿ, A. G.

Objectives

A recently developed synthetic route for the transition metal-free reductive coupling of aryl boronic acids with nitro1 or nitroso2 substituted arenes gives access to a variety of diaryl amines like fenamates.3 Radiotracers targeting COX-2 have been developed and tested as PET tracer but no clinically approved radiotracer emerged up to now. Aim of this project is to evaluate this novel synthetic route as a general access to 18F-labeled N,N-diaryl amines which are principally not activated for 18F-labeling by nucleophilic aromatic substitution, and by that access to fenamates like flufenamic acid as COX-targeting radiotracers in a wider sense. In this report, we present first results with focus on radiolabeling and reactivity of an asymmetric 18F-labeled nitro-arene.

Methods

The asymmetric sydnone-substituted nitroarene was radiolabeled under optimized conditions with fluorine-18 using K222/K2CO3 in DMF at 90°C and was purified by a C18-based solid phase extraction (SPE). Elution from the dried C18 SPE-cartridge with ortho-dichlorobenzene over a SEP-Pak Dry cartridge provided the intermediate [18F]A for further testing and optimization of the reductive coupling step. Subsequent radiochemical conversion of [18F]A with different boronic acids was monitored via radio-UHPLC. 3-Cyanophenyl boronic acid was used to optimize the coupling reaction with [18F]A with respect to the parameters base/reducing agent, temperature, reaction time. Furthermore, [18F]A was subjected to the reaction with other ortho-, meta-, and para-substituted boronic acids to get a first impression about the scope of this reaction.

Results

[18F]A was isolated after radiolabeling and purification by SPE in 16-54% isolated RCY (n=4). Optimizations using aliquots of 50 µL allowed for optimization of several reaction conditions with one batch of [18F]A. Triphenylphosphine but not triethylphosphite was found to mediate the reductive coupling of 3-cyanophenylboronic acid at reaction temperatures of 140°C and 170°C. Compared to 170°C, radiochemical conversion of [18F]A was found to be slightly higher at 180°C. A clear rationale for the amount of boronic acid and PPh3 was not found since both ratios of 5.4 to 2.5 as well as 2.4 to 4.2 gave highest RCC at 180°C. [18F]A was found to react with a variety of different boronic acids, although proof of identity for the reaction products to the respective diarylamines has still to be performed. In general, however, reaction kinetics were found to be slow leading to radiochemical conversions above 80% only after a reaction time of 80 min which represents a main limitation for radiochemical reactions using fluorine-18.

Conclusion

18F-labeling of N,N-diarylamines represents a challenge for classical nucleophilic aromatic substitution approaches. The use of an 18F-labeled nitroarene and a transition-metal free reductive coupling methodology gave access to this type of compounds but slow reaction kinetics likely hinders the general use in 18F-chemistry. Hence, the evaluation of a respective nitrosoarene is currently under the way representing a highly attractive alternative in this regard due to the much faster reaction kinetics.

References

1. a) Nykaza, J.Am.Chem.Soc. 2020, 142, 6786. b) Roscales, Adv.Synth.Catal. 2020, 362, 111.

2. Roscales, Org.Lett. 2018, 20, 1667; 3. Roscales, J.Chem.Educ. 2019, 96, 1738.

Figure 1. Radiosynthesis of flufenamic acid derivates by transition metal-free reductive coupling with [18F]A

  • Poster (Online presentation)
    eSRS 2021, 17.-19.05.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33480
Publ.-Id: 33480


“Clickable” albumin binders for modulating the tumor uptake of targeted radiopharmaceuticals

Brandt, F.; Ullrich, M.; Laube, M.; Kopka, K.; Bachmann, M.; Löser, R.; Pietzsch, J.; Pietzsch, H.-J.; van den Hoff, J.; Wodtke, R.

The intentional binding of radioligands to albumin gains increasing attention in the context of radiopharmaceutical cancer therapy as it can lead to an enhanced radioactivity uptake into the tumor lesions and thus, to a potentially improved therapeutic outcome. However, the influence of the radioligand’s albumin binding affinity on the time profile of tumor uptake depending on the particular albumin-binding affinity have been only partly addressed so far. Based on the previously identified Nε-4-(4-iodophenyl)butanoyl-lysine scaffold, we designed “clickable” lysine-derived albumin binders (cLABs) and determined their dissociation constants towards albumin by novel assay methods. Structure-activity relationships were derived and selected cLABs were applied for the modification of the somatostatin receptor subtype-2 ligand (Tyr³)octreotate (TATE). These novel conjugates were radiolabeled with copper-64 and subjected to a detailed in vitro and in vivo radiopharmacological characterization. Overall, the results of this study provide an incentive for further investigations of albumin binders for applications in endoradionuclide therapies.

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Permalink: https://www.hzdr.de/publications/Publ-33477
Publ.-Id: 33477


An interdisciplinary view of the long-term evolution of repository systems across scales: the iCROSS project

Bosbach, D.; Geckeis, H.; Heberling, F.; Kolditz, O.; Kühn, M.; Müller, K.; Stumpf, T.; Heberling, F.

The interdisciplinary project “Integrity of nuclear waste repository systems – Cross-scale system understanding and analysis (iCROSS)” combines research competencies of Helmholtz scientists related to the topics of nuclear, geosciences, biosciences and environmental simulations in collaborations overarching the research fields energy and earth and environment. The focus is to understand and analyze close-to-real long-term evolutionary pathways of radioactive waste repositories across nanoscales to repository scales.

The project is subdivided into work packages dealing with laboratory studies, field experiments in underground research laboratories (URLs), advanced modelling studies and the integration and alignment of data and information using virtual reality methods. In this sense, the project structure aims at a holistic view on relevant processes across scales in order to comprehensively simulate potential repository evolutions.

Within the multi-barrier system of a repository for heat-generating radioactive waste, a number of complex reactions proceed, including dissolution, redox processes, biochemical reactions, gas evolution and solid/liquid interface and (co)precipitation reactions. At the same time, thermal and external mechanical stress has an impact on the conditions in a deep geological repository. All those processes are highly coupled, with multiple interdependencies on various scales and have a strong impact on radionuclide mobility and retention. In recent years, substantial progress was achieved in describing coupled thermal-hydro-mechanical-chemical-biological (THM/CB) processes in numerical simulations. A realistic and concise description of these coupled processes on different time and spatial scales is, at present, a largely unresolved scientific and computational challenge. The close interaction of experimental and simulation teams aims at a more accurate quantification and assessment of processes and thus, the reduction of uncertainties and of conservative assumptions and eventually to a close-to-real perception of the repository evolution.

One focus of iCROSS is directed to relevant processes in a clay rock repository. In this context, the iCROSS team became a full member of the international Mont Terri consortium and worked in close collaboration with international and German institutions in URL projects. Respective experiments specifically deal with coupled processes at the reactive interfaces in a repository near field (e.g. the steel/bentonite and bentonite/concrete interfaces). Within iCROSS, the impact of secondary phase formation on radionuclide transport is investigated. At Mont Terri, experiments are in preparation to study radionuclide transport phenomena in clay rock formations within temperature gradients and in facies exhibiting significant heterogeneities on different scales (nm to cm). Beside those studies, high resolution exploration methods for rock characterization are developed and tested and the effect of temperature and other boundary conditions on the strength, creep properties and healing of faults within Opalinus clay are quantified. Multiphysics models coupled to reactive transport simulation have been further developed and applied to laboratory and field experiments. Results are digitally analyzed and illustrated in a visualization center, in order to enhance the comprehension of coupled processes in repository systems across scales.

The present contribution provides an overview on the project and reports selected results. The impact of considering complex coupled processes in repository subsystems for the assessment of the integrity of a given (generic) repository arrangement is discussed.
How to cite.

Bosbach, D., Geckeis, H., Heberling, F., Kolditz, O., Kühn, M., Müller, K., Stumpf, T., and the iCROSS team: An interdisciplinary view of the long-term evolution of repository systems across scales: the iCROSS project, Saf. Nucl. Waste Disposal, 1, 85–87, https://doi.org/10.5194/sand-1-85-2021, 2021.

------------------

Im interdisziplinären Projekt iCROSS („Integrität von Endlagern für nukleare Abfälle – Übergreifendes Systemverständnis und Analyse“) werden Forschungskompetenzen von Wissenschaftlern der Helmholtz-Institute mit den Themen Nuklearwissenschaften, Geowissenschaften, Biowissenschaften und Umweltsimulationen in einer die Forschungsbereiche Energie sowie Erde und Umwelt übergreifenden Zusammenarbeit kombiniert. Der Fokus richtet sich darauf, realitätsnahe Langzeitentwicklungspfade von Endlagern für radioaktive Abfälle von der Nano- bis zur Endlagerskala zu verstehen und auszuwerten.

Das Projekt ist unterteilt in Arbeitspakete zu Laborstudien, Feldexperimenten in unterirdischen Forschungslaboren (URL), fortgeschrittenen Modellierungsstudien und der Integration sowie der Ausrichtung von Daten und Informationen unter Verwendung von Methoden der virtuellen Realität. In diesem Sinne zielt die Projektstruktur auf eine ganzheitliche Sicht auf relevante Prozesse über Skalen hinweg ab, um potenzielle Entwicklungen von Endlagern umfassend zu simulieren.

Innerhalb des Multi-Barrieren-Systems eines Endlagers für wärmeerzeugende radioaktive Abfälle laufen eine Reihe komplexer Reaktionen, einschließlich Zerfallsreaktionen, Redoxreaktionen, biochemischer Reaktionen, Gasentwicklung und Fest-Flüssig-Grenzflächen- sowie (Ko-)Präzipitationsreaktionen ab. Gleichzeitig haben thermische und externe mechanische Belastungen einen Einfluss auf die Bedingungen in einem geologischen Tiefenlager. Sämtliche dieser Prozesse sind eng miteinander verbunden – mit multiplen Interdependenzen auf verschiedenen Ebenen – und haben einen großen Einfluss auf die Radionuklidmobilität und -retention. In den vergangenen Jahren wurden wesentliche Fortschritte bei der Beschreibung gekoppelter thermo-hydromechanisch-chemisch-biologischer (THM/CB-)Prozesse in numerischen Simulationen erzielt. Eine realistische Beschreibung dieser gekoppelten Prozesse auf unterschiedlichen Zeit- und Raumskalen ist zum gegenwärtigen Zeitpunkt eine großenteils ungelöste wissenschaftliche und rechnerische Herausforderung. Die enge Interaktion von Experimentier- und Simulationsteams zielt auf eine genauere Quantifizierung und Beurteilung von Prozessen ab und somit auf die Verminderung von Ungewissheiten und von konservativen Annahmen und schließlich auf eine realitätsnahe Wahrnehmung der Entwicklung des Endlagers.

Ein Fokus von iCROSS richtet sich auf relevante Prozesse in einem Tongestein-Endlager. In diesem Zusammenhang wurde das iCROSS-Team Vollmitglied des internationalen Mont-Terri-Konsortiums und arbeitet in enger Kooperation mit internationalen und deutschen Institutionen in URL-Projekten zusammen. Die entsprechenden Experimente befassen sich insbesondere mit gekoppelten Prozessen an den reaktiven Grenzflächen im Nahfeld eines Endlagers (z. B. die Stahl-Bentonit- und Bentonit-Beton-Grenzflächen). Innerhalb von iCROSS werden die Auswirkungen der Sekundärphasenbildung auf den Radionuklidtransport untersucht. Im Mont-Terri-Labor befinden sich Experimente in Vorbereitung, um Radionuklidtransportphänomene in Tongesteinsformationen innerhalb von Temperaturgradienten und angesichts erheblicher Heterogenitäten in unterschiedlichen Maßstäben (nm bis cm) zu untersuchen. Neben diesen Untersuchungen werden hochauflösende Untersuchungsmethoden für die Gesteinscharakterisierung entwickelt und geprüft, und die Auswirkungen von Temperatur und anderen Randbedingungen auf die Festigkeit, Kriecheigenschaften und Heilung von Verwerfungen innerhalb von Opalinus-Ton werden quantifiziert. Multiphysikalische Modelle in Kombination mit reaktiver Transportsimulation werden weiterentwickelt worden und in Labor- sowie Feldexperimenten eingesetzt. Die Ergebnisse werden digital ausgewertet und in einem Visualisierungszentrum dargestellt, um das Verständnis gekoppelter Prozesse in Endlagersystemen skalenübergreifend zu verbessern.

Der vorliegende Beitrag bietet einen Überblick über das Projekt und legt ausgewählte Ergebnisse dar. Die Auswirkungen der Betrachtung komplexer gekoppelter Prozesse in Endlager-Subsystemen auf die Beurteilung der Integrität einer gegebenen exemplarischen Endlageranordnung werden erörtert.

Related publications

  • Lecture (Conference)
    SafeND Interdisziplinäres Forschungssymposium für die Sicherheit der nuklearen Entsorgung, 10.-12.11.2021, Berlin, Deutschland
  • Contribution to proceedings
    SafeND Interdisziplinäres Forschungssymposium für die Sicherheit der nuklearen Entsorgung, 10.-12.11.2021, Berlin, Deutschland
    Saf. Nucl. Waste Disposal: Copernicus Publications, 85-87
    DOI: 10.5194/sand-1-85-2021

Permalink: https://www.hzdr.de/publications/Publ-33476
Publ.-Id: 33476


Data publication: Symmetry and curvature effects on spin waves in vortex-state hexagonal nanotubes

Körber, L.; Zimmermann, M.; Wintz, S.; Finizio, S.; Kronseder, M.; Bougeard, D.; Dirnberger, F.; Weigand, M.; Raabe, J.; Otálora, J. A.; Schultheiß, H.; Josten, E.; Lindner, J.; Kézsmárki, I.; Back, C. H.; Kakay, A.

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The dynamic matrix data contains eparam.yaml and sparam.yaml files containing the simulation and sample parameters used for micromagnetic modeling.

Keywords: spin wave; dispersion; curvature; micromagnetic modeling; hexagonal; symmetry; STXM

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Permalink: https://www.hzdr.de/publications/Publ-33475
Publ.-Id: 33475


Modular Machine Timing System for the ELBE accelerator based on MRF MicroTCA.4 series 300 hardware

Kuntzsch, M.; Zenker, K.; Schwarz, A.; Justus, M.; Oven, Z.; Jesensek, J.; Krmpotic, L.

At the ELBE accelerator center a new timing system is being developed based on the MRF hardware platform. It uses two mTCA-EVM-300 configured as masters and a scalable number of connected receivers (mTCA-EVR-300U, PCIe-EVR-300) to generate flexible pulse patterns for operating the machine. It allows for independent operation of two electron injectors and offers the opportunity for a combined injection into ELBE.
The control software is tailored to ELBE’s requirements based on mrfioc2. All machine operations modes as well as plausibility checks have been implemented. The communication interface to the ELBE control system is provided by a Siemens PLC that is at the same time integral part of the machine safety system. It sets the allowed parameter space for the timing system according to the current machine state and interlock signals.
The system will provide timing signals on few picosecond level to machine subsystems as LLRF and diagnostics as well as to user labs allowing for individual trigger generation based on the machine event signals. Universal IO modules offer a variety of logic levels on the receiver front panel while the MicroTCA backplane can be used to trigger hardware installed.

Keywords: ELBE; Timing; accelerator

Related publications

  • Lecture (Conference) (Online presentation)
    10th MicroTCA Workshop for Industry and Research, 07.-09.12.2021, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-33474
Publ.-Id: 33474


Magnetotactic bacteria as an effective sorbent for uranium in contaminated water.

Krawczyk-Bärsch, E.; Ramtke, J.; Drobot, B.; Steudtner, R.; Hübner, R.; Raff, J.

There are many ideas for using radionuclide- and heavy metal-binding microorganisms to remediate contaminated waters after e.g. uranium mining and processing. In particular, magnetotactic bacteria are moving into the focus of interest since they are able to survive in environments with very limited oxygen. Due to their organelles containing magnetic crystals, they can align themselves along the Earth's magnetic field for reaching regions of optimal oxygen concentrations. In laboratory studies we used the α-proteobacterium Magnetospirillum magneticum AMB-1, which is a motile, magnetotactic, gram-negative bacterium. It is facultative anaerobe and usually found in oxic-anoxic transition zones. In kinetic batch sorption experiments, cells of Magnetospirillum magneticum AMB-1 were contacted with different uranium concentrations and different pH. Independent of the initial U concentration, the cells were able to remove most of the uranium from the solution during the first hours of incubation. Microscopic studies, such as Transmission Electron Microscopy (TEM) in combination with Energy-Dispersive X-ray Spectroscopy (EDXS), clearly indicated that uranium is entirely accumulated in the cell membrane. Using spectroscopic methods like Time-Resolved Laser-Induced Fluorescence Spectroscopy at low temperature (cryo-TRLFS at 153 K), it was shown that uranium is mainly bound to the carboxylic functionality groups of peptidoglycan at the outer membrane of Magnetospirillum magneticum AMB-1 cells. With the obtained results we demonstrate that magnetotactic bacteria may play an important role in the bioremediation of contaminated sites, and probably not only for uranium, but also for other heavy metals.

Keywords: Magnetotactic bacteria; Uranium; Sorption; Remediation; TRLFS; TEM

  • Lecture (Conference) (Online presentation)
    4th International Caparica Conference on Pollutant Toxic Ions and Molecules 2021, 31.10.-04.11.2021, Caparica, Portugal

Permalink: https://www.hzdr.de/publications/Publ-33473
Publ.-Id: 33473


Bioremediación de aguas contaminadas: Estudio multidisciplinar de la reducción microbiana de uranio (U) en aguas de mina.

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

Tras el cese de la minería en Alemania oriental, restos de U y otros metales pesados siguen contaminando el territorio. Actualmente, estas minas están en proceso de remediación mediante estrategias convencionales. En este estudio, hemos caracterizado la geoquímica y la diversidad microbiana del agua de dos antiguas minas de U (Schlema-Alberoda y Pöhla) con el objetivo de diseñar una estrategia de biorremediación. Los análisis de ICP-MS y cromatografía iónica (CI) mostraron en el agua una alta concentración de U, sulfato, hierro y manganeso en Schlema-Alberoda respecto a Pöhla (U: 1,01 y 0,11mg/L;
Sulfato: 335 y 0,26mg/L; Hierro: 0,99 y 0,13mg/L; Manganeso: 1,44 y 0,16mg/L, respectivamente). El estudio de los genes 16S del ARNr e ITS1 de ambas minas reveló una gran diversidad microbiana implicada en la biorremediación de U(VI), destacando una abundanciarelativa de bacterias sulfatorreductoras (p.ej., Sulfuricuvum, Sulfurimonas y Sulfurovum) y bacterias hierro-oxidadoras (p.ej., Gallionella y Sideroxydans). Además, se diseñaron microcosmos-anóxicos-bioestimulados (glicerol [10mM]) tomando agua original de Schlema-Alberoda. Los análisis de ICP-MS y CI de los microcosmos revelaron aproximadamente una disminución del 90% de U, sulfato, hierro y manganeso, junto a un descenso del Eh y pH del sistema. Se calculó un diagrama termodinámico de predominio Eh-pH que indica la formación de precipitados de U(IV) insolubles. Estos resultados muestran que la reducción enzimática del U(VI), es favorecida por la adición de un donador de electrones en aguas mineras contaminadas. Por ende, podría ser un enfoque eficiente de biorremediación para las aguas contaminadas con U, bioestimulando su comunidad microbiana nativa.

Keywords: uranium; bacteria; bioremediation; uranium reduction

  • Lecture (Conference) (Online presentation)
    XXVIII Congreso Nacional de Microbiología (SEM21), 28.06.-02.07.2021, virtuell, Espana

Permalink: https://www.hzdr.de/publications/Publ-33472
Publ.-Id: 33472


Electrical and structural properties of NixGey thin films made by Magnetron sputtering and flash lamp annealing

Begeza, V.; Rebohle, L.; Mehner, E.; Zhou, S.

Due to its higher charge carrier mobility compared to silicon, germanium belongs to the promising materials to surpass the physical limitations of the silicon based CMOS technology. For the integration of germanium into the CMOS process, the ohmic contact material with sufficiently low resistivity plays a crucial role. One of the promising candidates is nickel-germanide (NiGe) with a specific resistivity of (13.5 – 22) cm. Those values are comparable with the nickel-silicides used in the CMOS process with electrical resistivities of around 17 cm
This work is focused on the formation process of NiGe films on different germanium layer morphologies, by the flash lamp annealing approach. Furthermore, the investigation on the NixGey phase formation at different annealing temperatures was performed by grazing incidence X-ray diffraction and cross section transmission electron microscopy. The electrical properties were investigated by the application of four-point-probe, Hall effect and circular transfer length measurement techniques.

Keywords: Germanium; Nickel-germanide; Thin films; Flash Lamp Annealing; Millisecond Thermal Treatment; Phase Formation

  • Open Access Logo Poster (Online presentation)
    From Matter to Materials and Life 2021, 22.-24.11.2021, Online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33471
Publ.-Id: 33471


Probing ultrafast laser plasma processes inside solids with resonant small angle X-ray scattering

Gaus, L.; Bischoff, L.; Bussmann, M.; Cunningham, E.; Curry, C. B.; E, Juncheng; Galtier, E.; Gauthier, M.; Laso García, A.; Garten, M.; Glenzer, S.; Grenzer, J.; Gutt, C.; Hartley, N.; Huang, L.; Hübner, U.; Kraus, D.; Lee, H. J.; McBride, E. E.; Metzkes-Ng, J.; Nagler, B.; Nakatsutsumi, M.; Nikl, J.; Ota, M.; Pelka, A.; Prencipe, I.; Randolph, L.; Rödel, M.; Sakawa, Y.; Schlenvoigt, H.-P.; Smid, M.; Treffert, F.; Voigt, K.; Zeil, K.; Cowan, T.; Schramm, U.; Kluge, T.

Extreme states of matter exist throughout the universe e.g. inside planetary cores, stars or astrophysical jets. Such conditions can be generated in the laboratory in the interaction of powerful lasers with solids.
Yet, the measurement of the subsequent plasma dynamics with regard to density, temperature and ionization is a major experimental challenge. However, ultra-short X-ray pulses provided by X-ray free electron lasers (XFELs) allow for dedicated studies, which are highly relevant to study laboratory astrophysics, laser-fusion research or laser-plasma-based particle acceleration.
Here, we report on experiments that employ a novel ultrafast method, which allows to simultaneously access temperature, ionization state and nanometer scale expansion dynamics in high-intensity laser-driven solid-density plasmas with a single X-ray detector.
Using this method, we gain access to the expansion dynamics of a buried layer in compound samples, and we measure opacity changes arising from bound-bound resonance transitions in highly ionized copper. The presence of highly ionized copper leads to a temperature estimate of at least 2 million Kelvin already after the first 100 femtoseconds following the high-intensity laser irradiation.
More specifically, we make use of asymmetries in small-angle X-ray scattering (SAXS) patterns, which arise from different spatial distributions of absorption and scattering cross sections in nanostructured grating samples when we tune an XFEL to atomic resonant energies of copper.
Thereby, changes in asymmetry can be connected with the evolution of the plasma expansion and ionization dynamics.
The potential of XFEL-based resonant SAXS to obtain three-dimensional ultrafast, nanoscopic information on density and opacity may offer a unique path for the characterization of dynamic processes in High Energy Density plasmas.

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Permalink: https://www.hzdr.de/publications/Publ-33470
Publ.-Id: 33470


Plasmonic terahertz nonlinearity in graphene disks

Han, J.; Chin, M. L.; Matschy, S.; Poojali, J.; Seidl, A.; Winnerl, S.; Hafez, H. A.; Kumar, G.; Myers-Ward, R. L.; Dejarld, M. T.; Daniels, K. M.; Drew, H. D.; Murphy, T. E.; Mittendorff, M.

"Analysis_code_Final" contains the theoretical calculations. "FELmeasurements" contains the raw data of the pump-probe measurements with the FEL. "LabBook" contains the corresponding lab book pages.

Keywords: graphene; terahertz; nonlinearity

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Permalink: https://www.hzdr.de/publications/Publ-33469
Publ.-Id: 33469


Helmholtz AI Consulting for matter research at HZDR

Steinbach, P.; Hoffmann, H.; Pape, D.; Schmerler, S.; Starke, S.

In this presentation, I'd like to present the current status of Helmholtz AI consultancy for matter research in Helmholtz. I'd provide sneak previews into past and ongoing vouchers we embarked upon for the accelerator physics community and other collaborators. I'll try my best to give some insights on what we use our cluster for and why. Last but not least, I'll discuss challenges we faced along the way and will highlight some future directions if time allows.

Keywords: machine learning; HPC; history; artificial intelligence

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Hardware & Numerics Seminar at HZDR, 23.11.2021, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-33467
Publ.-Id: 33467


Asymptotic properties of Dirichlet kernel density estimators

Ouimet, F.; Tolosana Delgado, R.

We study theoretically, for the first time, the Dirichlet kernel estimator introduced by Aitchison and Lauder (1985) for the estimation of multivariate densities supported on the d-dimensional simplex. The simplex is an important case as it is the natural domain of compositional data and has been neglected in the literature on asymmetric kernels. The Dirichlet kernel estimator, which generalizes the (non-modified) unidimensional Beta kernel estimator from Chen (1999), is free of boundary bias and non-negative everywhere on the simplex. We show that it achieves the optimal convergence rate O(n−4/(d+4)) for the mean squared error and the mean integrated squared error, we prove its asymptotic normality and uniform strong consistency, and we also find an asymptotic expression for the mean integrated absolute error. To illustrate the Dirichlet kernel method and its favorable boundary properties, we present a case study on minerals processing.

Keywords: Asymmetric kernel; Asymptotic normality; Beta kernel; Boundary bias; Density estimation; Dirichlet kernel; Mean integrated absolute error; Multivariate associated kernel; Simplex; Strong consistency

Permalink: https://www.hzdr.de/publications/Publ-33466
Publ.-Id: 33466


Data publication: MHT-X: Offline Multiple Hypothesis Tracking with Algorithm X

Akashi, M.; Eckert, S.

There are images of bubbles in the liquid metal obtained through X-ray radiography. Bubbles are injected by a top-submerged lance. Experiments were performed in ELBE in HZDR.

Keywords: Algorithm X; two-phase flow; bubble dynamics; liquid metal; X-ray radiography; neutron imaging; image processing

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Permalink: https://www.hzdr.de/publications/Publ-33465
Publ.-Id: 33465


Data publication: Prograde and retrograde precession of a fluid-filled cylinder

Pizzi, F.; Giesecke, A.; Simkanin, J.; Stefani, F.

This dataset included the data and figures for the associated publication "Prograde and retrograde precession of a fluid-filled cylinder".

Keywords: precession; core flow; dynamo; instability; transition

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Permalink: https://www.hzdr.de/publications/Publ-33464
Publ.-Id: 33464


On the wettability of glass particles with different morphologies hydrophobized via esterification with alcohols

Sandbrink, J.; Rudolph, M.

The separation of fine particles is a challenging task, which requires a fundamental understanding of the interfacial properties. In our research, we focus on the selective separation of ultrafine particles by flotation, a well-established and efficient particle processing technique in the mineral’s sector based mainly on particle wettabilities. Flotation works best for particle size ranges of 10 μm to 200 μm, but when it comes to the separation of ultrafine particles (< 10 μm) there is still lots of room for understanding and improvement. Within the German research foundation priority programme DFG-SPP 2045 “MehrDimPart” we aim at developing a novel multidimensional separation device for such ultrafine particles based on the particle parameters of wettability, morphology (shape or roughness) and size.
In this study, three differently shaped fractions of glass particles are used, among them spheres, fibres and fragments. The glass particles are functionalised by an esterification reaction with alcohols, where the wettability of the esterified particles is controlled by the length of the alkyl chain, at water contact angles ranging from approx. 40° to 100°. By liquid-liquid phase transfer, using water as the aqueous phase and cyclohexane as the organic phase, the success of the particle functionalization is studied. Glass slides, esterified in the same way as the glass particles, are analysed by measuring static and dynamic contact angles against water using the sessile drop method. Additionally, the functionalized glass particles are studied with inverse gas chromatography, which results in their specific surface free energies, as that is related to the contact angle via Young’s equation. The correlation of the various methods shed light on both the wettability heterogeneity and how it is changed through functionalization but also on the effect the morphologies have on the wettability and phase-transferability characteristics.
The obtained information on the particle wettability after esterification is set into context with their particle morphology and particle sizes.

Keywords: Wettability; Ultrafine Particles; Surface Modification; Esterification of Glass Particles; Hydrophobisation; Surface Energy Distribution; Inverse Gas Chromatography; Contact angle measurement; Flotation

  • Lecture (Conference) (Online presentation)
    Jahrestreffen der ProcessNet-Fachgruppen "Lebensmittelverfahrenstechnik, Mischvorgänge und Grenzflächenbestimmte Systeme und Prozesse", 11.-12.03.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33463
Publ.-Id: 33463


Ultrafine particle separation based on multiple particle properties by means of froth-flotation and their characterization using MLA and flow cytometry

Sandbrink, J.; Rudolph, M.

The separation of fine particles is a challenging task for which a fundamental understanding of the interfacial properties is inevitable. One of the most important techniques in the mining sector to separate fine particles (10 μm to 200 μm) from unwanted gangue material is froth flotation, which is based on the difference in particle wettabilities. As nowadays, particles need to be milled down to finer size fractions to obtain sufficient liberation of the valuable minerals as well as the fact that particles used in electronic devices become finer, existing techniques need to be adapted. For that reason, this project, which is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart”, aims at developing a method for the separation of ultrafine particles based on multiple particle properties, such as size, morphology, surface energy or state of dispersion.
In this study, a system consisting of ultrafine size fractions of glass particles as the valuable material and magnetite as the gangue material is used for testing and the particle properties of wettability and state of gangue dispersion are modified. Said glass particles are hydrophobised via an esterification reaction using alcohols with differing chain length and the resulting wettability states are analysed using inverse gas chromatography as well as analytic particle solvent extraction. The particle properties of size and shape (multiple shape factors) are characterised via a combination of laser diffraction and microscopic analysis. Flow cytometry is introduced as a new method for multidimensional particle characterization, as it allows for size and shape analysis, as well as wettability analysis via fluorescent marking of particles with dyes. Selective flocculation of magnetite is carried out using macromolecules as flocculants. For all flotation tests, a novel flotation apparatus, specifically designed for the flotation of ultrafine particles, is used, which combines advantages from machine-type froth flotation and column flotation. Flotation tests are run in batch mode to study the influence of certain particle properties on the outcome, as well as in continuous stationary mode to study the behaviour of the particles during the process in more depth. For this, samples will be taken at different heights along the flotation column to analyse in which parts certain particles accumulate.
The investigation of the separation of ultrafine particles based on multiple particle properties by means of froth flotation will help to further understand how certain particle properties influence flotation, as well as other separation processes. In this way, the separation of ultrafine particles can be optimized and adjusted to be more efficient, which will play an important role in the recycling of secondary materials.

Keywords: Ultrafine Particles; multidimensional separation; Flotation; particle characterization; flow cytometry

  • Lecture (Conference) (Online presentation)
    13th European Congress of Chemical Engineering, 20.-23.09.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33462
Publ.-Id: 33462


Wettability and wetting characterisation of ultrafine glass particles for particle separation technologies

Sandbrink, J.; Rudolph, M.

Many particle separation processes are based on differences in wettabilities. Therefore, one needs to understand the interfacial properties and micro processes taking place on the material surface. The main quantity to account for wettability is the Young contact angle. However, this method requiring homogeneous flat and smooth substrates has drawbacks when analysing particles and is rather system specific as particles are not planar and exhibit rough surfaces. Here, we demonstrate the challenges of proper wettability analysis of particulate material as available methods are influenced strongly by multiple particle properties such as shape and size. Three fractions of glass particles with different shapes are investigated, fibres, fragments, spheres, and their wettability is modified by esterification with alcohols. These particle systems are characterised via analytic particle solvent extraction, static and dynamic contact angle measurements, and inverse gas chromatography. Alcohols with longer alkyl chains result in more hydrophobic particles with more homogeneous wettability characteristics in terms of surface energy. Comparing the characterisation methods reveals the influence of particle morphology on the interfacial wetting behaviour. Applying inverse gas chromatography for wettability characterisation in combination with the other methods underlines its potentials as well as limitations in understanding particulate surface properties.

Keywords: Wettability; Hydrophobicity; Surface heterogeneity; Surface free energy; Inverse gas chromatography; Contact angle

  • Invited lecture (Conferences) (Online presentation)
    2nd European Sorption Science Symposium 2021, 22.-23.09.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33461
Publ.-Id: 33461


Numerical and experimental methods for the analysis of complex particulate systems

Lecrivain, G.; Hampel, U.

In this presentation, experimental and numerical tools available at HZDR are presented for the analysis of complex particulate systems. Energy-intensive particulate systems includes, for example, high-temperature reactors, mixers for the mineral and cement industries, flotation apparatuses for the selective of separation minerals, textile fibers, micro-algae as well as plastics.

Keywords: Particle transport; Resource efficiency; Particulate systems

  • Lecture (Conference)
    M0-Workshop des Topic 5 „Ressourcen- und Energieeffizienz“ des Helmholtz-Programms Materialien und Technologien für die Energiewende, 18.11.2021, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-33460
Publ.-Id: 33460


Particle deposition and resuspension in turbulent gas flows - An industrial and environnemental application

Lecrivain, G.

The talk will focus on the transport, deposition and resuspension of particles in the micron size in air systems. Expertise of the Helmholtz-Zentrum Dresden-Rossendorf in the experimental and numerical investigation of particle-laden flow will be presented. A first application includes the transport of dust particles in industrial systems. A second application is the resuspension of toxic micronparticles in urban system by strong winds. In these two scenarios, experimental tests are first used to study small-scale mechanisms. Simulations are then used to extrapolate the much larger systems.

Keywords: Particle transport; Microplastics; Turbulent flows

  • Lecture (others) (Online presentation)
    Workshop on microplastics in the atmosphere, 22.11.2021, Valbonne, France

Permalink: https://www.hzdr.de/publications/Publ-33459
Publ.-Id: 33459


Estimating uncertainties of radionuclide migration in crystalline host rock - an interdisciplinary approach

Pospiech, S.; Brendler, V.

Estimating uncertainties of radionuclide migration in crystalline host rock - an interdisciplinary approach

  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2022
    119
    41 Seiten
    ISSN: 2191-8708, eISSN: 2191-8716
    ISSN: 2191-8716
    ISSN: 2191-8708

Permalink: https://www.hzdr.de/publications/Publ-33458
Publ.-Id: 33458


Autocorrected off-axis holography of two-dimensional materials

Kern, F.; Linck, M.; Wolf, D.; Alem, N.; Arora, H.; Gemming, S.; Erbe, A.; Zettl, A.; Büchner, B.; Lubk, A.

The reduced dimensionality in two-dimensional materials leads to a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high-resolution microscopy techniques are indispensable. Here we report on the development of an electron holography (EH) transmission electron microscopy (TEM) technique, which facilitates high spatial resolution by an automatic correction of geometric aberrations. Distinguished features of EH beyond conventional TEM imaging are gap-free spatial information signal transfer and higher dose efficiency for certain spatial frequency bands as well as direct access to the projected electrostatic potential of the two-dimensional material. We demonstrate these features with the example of h-BN, for which we measure the electrostatic potential as a function of layer number down to the monolayer limit and obtain evidence for a systematic increase of the potential at the zig-zag edges.

Permalink: https://www.hzdr.de/publications/Publ-33457
Publ.-Id: 33457


Radiosynthesis and biological investigation of an 18F-labeled triazolopyridopyrazine-based inhibitor for imaging of the phosphodiesterase 2A enzyme (PDE2A) in brain

Wenzel, B.; Fritzsche, S. R.; Deuther-Conrad, W.; Toussaint, M.; Briel, D.; Kopka, K.; Brust, P.; Scheunemann, M.

Objectives: The cyclic nucleotide phosphodiesterase 2A is an intracellular enzyme which hydrolyzes the second messengers cAMP and cGMP and therefore plays an important role in signaling processes. It is highly expressed in distinct brain areas associated with emotion, memory and learning. Therefore, it is assumed that the PDE2A is involved in the pathophysiology of neurodegenerative and neuropsychiatric diseases. To enable a specific imaging of this enzyme in the brain by PET, we are developing fluorine-18 labeled radioligands with high inhibitory potency and selectivity toward other phosphodiesterases, in particular the PDE10A, which is also located in typical PDE2A-rich brain regions.

Methods: Out of a series of 12 tricyclic triazolopyridopyrazine-based derivatives with high inhibitory potency toward PDE2A and selectivity vs. PDE10A [1], the most promising candidate 1 was selected for radiofluorination. The radiolabeling was performed in a two-step one-pot procedure via nucleophilic aromatic substitution of the nitro group (precursor 2) by [18F]fluoride followed by the reduction of the activating ketone function to obtain the desired radiotracer [18F]1 (Figure 1). The product was isolated using semi-preparative HPLC followed by final purification with solid-phase extraction and formulation in isotonic saline containing 10% ethanol. In vitro autoradiography studies with cryosections of rat brain and PET studies in female Sprague-Dawley rats (30 min dynamic PET imaging after intravenous injection, nanoScan® PET/MRI, MEDISO, Budapest, Hungary) were performed. The in vivo metabolism of [18F]1 was investigated by radio-HPLC analysis of extracts obtained from blood plasma and homogenized brain of rats at 30 min p.i.

Results: The new derivative 1 inhibits PDE2A with high potency (IC50 PDE2A3 = 1.99 nM) and superior selectivity against PDE10A (IC50 PDE10A1 = 1910 nM). [18F]1 was obtained with a radiochemical yield of 2.1 ± 0.7% (EOB), molar activities of 10–20 GBq/µmol (EOS) and radiochemical purities of ≥ 99% (n=7). The distribution pattern of [18F]1 detected by in vitro autoradiography corresponds to the anatomical distribution of PDE2A in rat brain with prominent expression in the superficial layers of the somatosensory cortex, in hippocampal structures, and in basal ganglia, and with nearly no expression in the cerebellum. By co-incubation with compound 1 as well as two structurally different well-established PDE2A inhibitors, the binding of [18F]1 was completely inhibited, confirming the high specific interaction with PDE2A. In vivo PET-MR studies revealed a good brain uptake (SUV peak = 1.0); however, a considerable enrichment in PDE2A-specific regions was not detectable (15 min p.i.: SUVcaudate putamen = 0.51 vs. SUVcerebellum = 0.40). Furthermore, in vivo metabolism studies of [18F]1 revealed unneglectable fractions of radiometabolites in blood plasma and brain at 30 min p.i. (parent compound: 50 and 66%, resp.).

Conclusions: [18F]1 is a suitable and high specific probe for the investigation of the PDE2A expression in vitro. However, further work is needed to explore the reasons for the poor in vivo imaging capability of this radiotracer.

Acknowledgment: Deutsche Forschungsgemeinschaft (German Research Foundation, SCHE 1825/3-1).

References: [1] S. R. Fritzsche et al. „Triazolopyridopyrazine-based Inhibitors of Phosphodiesterase 2A – Synthesis and SAR-Exploration“, Annual Meeting of the German Pharmaceutical Society – DPhG 2021, Poster

  • Poster
    24th International Symposium on Radiopharmaceutical Sciences, 29.05.-02.06.2022, Nantes, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-33456
Publ.-Id: 33456


Prograde and retrograde precession of a fluid-filled cylinder

Pizzi, F.; Giesecke, A.; Simkanin, J.; Stefani, F.

We numerically study precession driven flows in a cylindrical container whose nutation angle varies between 60 and 90 degrees for prograde and retrograde precession. For prograde precession we observe sharp transitions between a laminar and a turbulent flow state with low and high geostrophic axisymmetric flow components related with a centrifugal instability, while for retrograde precession a rather smooth transition between a low state and a high state occurs. At the same time prograde and perpendicular precession shows an abrupt breakdown of the flow directly excited by the forcing mechanism, which is not the case for retrograde motion. We characterize the corresponding flow states in terms of the directly driven, non-axisymmetric Kelvin mode, the axisymmetric geostrophic mode, and an axisymmetric poloidal flow which is promising for precession-driven dynamo action. The latter issue is discussed with particular view on an optimal parameter choice for the DRESDYN dynamo project.

Keywords: precession; core flow; dynamo; instability; transition

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Permalink: https://www.hzdr.de/publications/Publ-33455
Publ.-Id: 33455


Oxidation of Micro- and Nanograined UO2Pellets by in Situ Synchrotron X-ray Diffraction

de Bona, E.; Popa, K.; Walter, O.; Cologna, M.; Hennig, C.; Scheinost, A.; Prieur, D.

When in contact with oxidising media, UO2 pellets used as nuclear fuel may transform into U4O9, U3O7, and U3O8. The latter starts forming by stress-induced phase transformation only upon cracking of the pristine U3O7, and is associated with a 36 % volumetric expansion with respect to the initial UO2. This may pose a safety issue for spent nuclear fuel (SNF) management as it could imply a confinement failure and hence dispersion of radionuclides within the environment. In this work, UO2 with different grain sizes (representative of the grain size in different radial positions in the SNF) were oxidised in air at 300 °C, and the oxidation mechanisms were investigated using in-situ synchrotron XRD. The formation of U3O8 was detected only in UO2 pellets with larger grains (3.08 ± 0.06 µm and 478 ± 17 nm), while U3O8 did not develop in sintered UO2 with a grain size of 163 ± 9 nm. This result shows that, in dense materials, a sufficiently fine microstructure inhibits both the cracking of U3O7 and the subsequent formation of U3O8. Hence, the nanostructure prevents the material from undergoing significant volumetric expansion. Considering that the peripheral region of SNF is constituted by the High Burnup Structure (HBS), characterised by 100-300 nm sized grains and micrometric porosity, these findings are relevant for a better understanding of the spent nuclear fuel behaviour and hence for the safety of the nuclear waste storage.

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Permalink: https://www.hzdr.de/publications/Publ-33454
Publ.-Id: 33454


Higher harmonics in complex plasmas with alternating screening

Moldabekov, Z.; Aldakul, Y. K.; Bastykova, N. K.; Sundar, S.; Cangi, A.

We report how higher harmonics of collective excitations emerge in a 2D layer of strongly correlated charged microparticles in a complex plasma with a periodically alternating screening.
The simulation results of the radio frequency discharge and the charged microparticles are obtained using a highly accurate multi-scale and multi-physics approach based on the particle-in-cell technique, Monte Carlo collision calculations, and molecular dynamics simulations.
We also devise a simple phenomenological expression for the dispersion relation of higher harmonics.
Furthermore, our analysis reveals that the periodically alternating screening causes a self-conjugate state with negative refraction.
In doing so, we demonstrate how complex plasmas can serve as a testbed for studying the fundamental physics of a self-conjugate state in strongly correlated systems.

Keywords: plasma physics; strongly correlated plasmas; complex plasmas

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Permalink: https://www.hzdr.de/publications/Publ-33453
Publ.-Id: 33453


Data publication: Controlled Silicidation of SiNW using FLA

Khan, M. B.; Prucnal, S.; Ghosh, S.; Deb, D.; Hübner, R.; Pohl, D.; Rebohle, L.; Mikolajick, T.; Erbe, A.; Georgiev, Y.

The folder contains the following: 1. all the SEM and TEM images. 2. The schematics of fabrication 3. comparison of silicidation with FLA and RTA and 4. temperature simulations to estimate temperature during FLA process.

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Permalink: https://www.hzdr.de/publications/Publ-33452
Publ.-Id: 33452


Effect of Interfacial Defects on the Electronic Properties of MoS₂ Based Lateral T-H Heterophase Junctions

Bahmani, M.; Ghorbani Asl, M.; Frauenheim, T.

The coexistence of semiconducting (2H) and metallic (1T) phases of MoS₂ monolayers have further pushed their strong potential for applications in the next generation of electronic devices based on two-dimensional lateral heterojunctions. Structural defects have considerable effects on the properties of these 2D devices. In particular, the interfaces of two phases are often imperfect and may contain numerous vacancies created by phase engineering techniques, e.g. under the electron beam. Here, the transport behaviors of the heterojunctions in the existence of point defects are explored by means of first-principles calculations and non-equilibrium Green's function approach. While vacancies in semiconducting MoS₂ act as scattering centers, their presence at the interface improves the flow of the charge carriers. In the case of Vmo, the current has been increased by two orders of magnitude in comparison to the perfect device. The enhancement of transmission was explained by changes in the electronic densities at the T-H interface, which open new transport channels for electron conduction.

Keywords: two-dimensional materials; defects; lateral heterostructure; conductivity; quantum transport; DFT

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Permalink: https://www.hzdr.de/publications/Publ-33451
Publ.-Id: 33451


Direct visualization of highly resistive areas in GaN by means of low-voltage scanning electron microscopy

Jóźwik, I.; Jagielski, J.; Caban, P.; Kamiński, M.; Kentsch, U.

The damage-induced voltage alteration (DIVA) contrast mechanism in scanning
electron microscope (SEM) at low electron energy has been presented as a fast and
convenient method of direct visualization of increased resistivity induced by energetic
ions irradiation in gallium nitride (GaN). Epitaxially grown GaN layers on sapphire
covered with a metallic masks with etched windows were subjected to He 2+
irradiations at 600 keV energy. The resulting two-dimensional damage profiles at the
samples cross-sections were imaged at SEM at different e-beam energies and scan
speeds. The gradual development of image contrast was observed with the increase of
cumulative charge deposited by electron beam irradiation, to finally reach the
saturation level of the contrast related to the local resistivity of the ion-irradiated part of
GaN.
The presented method allows one to directly visualize the ion-irradiated zone even for
the lowest resistivity changes resulting from ion damage, i.e. all levels of insulation
build-up in GaN upon irradiation with ions. Taking into account that it is not possible to
apply the etch-stop technique by wet chemistry to GaN, it makes the presented
technique the only available method of visualization of highly resistant and insulating
regions in GaN-based electronic devices.
Main aim of the presented work is to get a deeper insight into a DIVA contrast in GaN
with the special emphasize to discuss the role of rastering speed and electron beam
current, i.e. details of charge build-up ion the sample surface.

Keywords: GaN; Ion damage; Ion implantation; Low-kV SEM

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Permalink: https://www.hzdr.de/publications/Publ-33450
Publ.-Id: 33450


Small-angle neutron scattering applied to low-dose neutron-irradiated Fe–Cr alloys and ferritic martensitic steel Eurofer97

Ulbricht, A.; Heinemann, A.; Bergner, F.

Abstract Experimental results reported before for neutron-irradiated binary Fe-Cr alloys and high-dose neutron-irradiated ferritic/martensitic (F/M) Cr steels do not unfold a complete understanding of the irradiation behaviour required for the application of F/M steels in nuclear components. Gaps are related to the effect of secondary alloying and impurity elements, such as Ni and Si, as well as the dose dependence at lower neutron doses, e.g. the range 0.1 – 1 displacements per atom (dpa). Such input is essential for both multiscale modelling of irradiation effects and the evaluation of nuclear fission or fusion components at the first stages of operation. Using magnetic small-angle neutron scattering, three pieces are added to the puzzle: (1) The effect of Cr undersaturation (5% Cr) and supersaturation (14% Cr) on the formation of irradiation-induced solute atom clusters/precipitates in the presence of intentionally added levels of Ni, Si, and P; (2) the effect of irradiation temperature, 290 °C versus 450 °C; and (3) a comparison of two heats of Eurofer 97, one of them neutron-irradiated to 0.06, 0.1 and 0.6 dpa. We have found that the irradiation-enhanced formation of Cr-rich α’-phase particles is the dominant effect for supersaturated Fe-14Cr-NiSiP. In contrast, α’ formation is impossible in Fe-5Cr-NiSiP, for which the pronounced irradiation effects observed at 0.1 dpa are mainly due to added Ni, Si and P. Finally, the 9Cr steel Eurofer 97 exhibits a much smaller irradiation effect than Fe-9Cr-NiSiP. The reasons of this exceptional irradiation resistance are discussed.

Keywords: Small-angle neutron scattering; Fe-Cr alloys; Ferritic-martensitic steel; Neutron irradiation

Permalink: https://www.hzdr.de/publications/Publ-33449
Publ.-Id: 33449


Process simulation for comprehensive sustainability assessment of the silicon photovoltaic life cycle

Bartie, N.; Cobos-Becerra, L.; Froehling, M.; Schlatmann, R.; Reuter, M.

Over the last decade, the global solar PV industry has grown at a rate of more than 35% annually, reaching record levels and outpacing annual conventional power capacity additions and will continue its trajectory to reach terawatt-level deployment by 2022-2023 and an estimated 8.5 TW (cumulative) by 2050. The global c-Si cell and PV module production capacity at the end of 2020 is assumed to have further increased to over 200 GWp due to continued PERC capacity expansion. To assess the potential contribution photovoltaics (PV) can make to decarbonization, and to achieving the European and global sustainable development and circular economy goals, the resource efficiency and sustainability of photovoltaic life cycle systems need to be evaluated. Using process simulation, we create detailed digital representations of entire PV life cycles. These include all raw material and PV production steps, as well as recycling processes that close material loops and aim to recover valuable materials from end-of-life modules. The simulations make use of the physical, chemical, and thermodynamic processes that govern each step in the life cycle to deliver a robust foundation from which to determine the potential impacts of individual processes and the system on resource consumption, resource efficiency, the environment, and technoeconomic parameters. In this paper, we focus on the assessment of potential recycling, wafer thickness, and carbon tax effects on the resource efficiency, carbon footprint, and technoeconomic performance of the system.

Keywords: Silicon PV system; LCOE; MSP; resource efficiency; carbon footprint; recycling; simulation

Permalink: https://www.hzdr.de/publications/Publ-33448
Publ.-Id: 33448


Coordination and Electrochemical Switching on Paddle-Wheel Complexes Containing an As−Ru or a Sb−Ru Axis

Gericke, R.; Wagler, J.

Inspired by the known complex [PhP(μ-PyO)₄Ru(CO)] (PyO = 2-pyridyloxy), the family of group 15 paddle-wheel complexes has been expanded to [PhPn(μ-PyO)₄Ru(L)] (Pn = P, As, Sb; L = NCMe, CO). Solvent-dependent reversible switching between [PhAs(μ-PyO)₄Ru(NCMe)] and [PhAs(μ-PyO)₃Ru(κ²-PyO)] was detected. Electrochemical investigations of the [PhPn(μ-PyO)₄Ru(L)] complexes showed reversible oxidation of the complexes with L = NCMe and back-formation of the complexes with L = NCMe upon oxidation of the complexes with L = CO in NCMe. In the series of [PhPn(μ-PyO)₄RuL)] complexes, the Pn→Ru bonding mode is shifted from L-type Pn to X-type upon going from Pn = P and As to Pn = Sb, resulting in a pronounced electron-rich Ru site in the latter case. The easily accessible complex [PhSb(μ-PyO)₄RuCl] exhibits reversible electrochemical and coordinative exchange with its reduced analogue [PhSb(μ-PyO)₄Ru(NCMe)] under retention of the paddle-wheel motif and Sb−Ru bond properties.

Keywords: ambidentate ligands; ruthenium; pnictogen; hetero bimetallic; electrochemical switching

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-33447
Publ.-Id: 33447


The precession dynamo experiment at HZDR

Giesecke, A.; Pizzi, F.; Kumar, V.; Anders, S.; Ratajczak, M.; Gundrum, T.; Stefani, F.

Cosmic magnetic fields exist on all scales, from planets and stars to
galaxies and beyond. The generation of these fields via the
hydromagnetic dynamo effect involves the formation of electrical
currents by means of complex flows of conducting fluids or plasmas. At
HZDR a related experiment is under construction within the project
DRESDYN. In that experiment a precessing flow of liquid sodium will
provide the required energy for magnetic field generation.

Here we address preliminary numerical and experimental studies aimed
at the identification of parameter ranges where a dynamo can be
expected. Our kinematic dynamo models show that dynamo action is
possible just before the transition from a laminar flow state to
vigorous turbulence where the flow structure is determined by a
combination of axisymmetric and nonaxisymmetric large scale modes. By
applying the derived scaling laws, the results can be directly applied
to the parameters of the planned large device.

Keywords: Dynamo

  • Poster (Online presentation)
    MML-Workshop 2021, 22.-24.11.2021, virtuell, virtuell

Permalink: https://www.hzdr.de/publications/Publ-33446
Publ.-Id: 33446


Polyoxoplatinates as Covalently Dynamic Electron Sponges and Molecular Electronics Materials

Kondinski, A.; Ghorbani Asl, M.

Dynamic covalent chemistry is an adaptive approach that utilizes thermodynamic equilibriums towards tailoring the structural and the electronic properties of molecular assemblies. The primary application of the latter approach lies in the design of organic self-healing materials, sensors, and actuators. Herein we apply density functional theory (DFT) to explore the structural, electronic and transport properties of the [Pt₁₂O8(SO₄)₁₂]⁴⁻ cluster and its derivatives. The cluster is a polyoxometalate (POM) that exhibits six {O−Pt−Pt−O} moieties. The latter moieties are redox responsive and covalently dynamic, allowing the POM to store up to twelve electrons. In our proposed Au/POM/Au junction, the simulations show that the electron conduction strongly depends on the redox of POM but more weakly on its rotations with respect to the Au surface. Moreover, the POM shows promising spin-polarized current behaviour, which can be modulated using bias and gate voltages.

Keywords: polyoxometalates (POMs); platinum; computational modelling; DFT; charge storage; molecular electronics

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Permalink: https://www.hzdr.de/publications/Publ-33445
Publ.-Id: 33445


Resonant SAXS data used in publication: "Probing ultrafast laser plasma processes inside solids with resonant small angle X-ray scattering"

Gaus, L.; Bischoff, L.; Bussmann, M.; Cunningham, E.; Curry, C. B.; E, Juncheng; Galtier, E.; Gauthier, M.; Laso García, A.; Garten, M.; Glenzer, S.; Grenzer, J.; Gutt, C.; Hartley, N.; Huang, L.; Hübner, U.; Kraus, D.; Lee, H. J.; McBride, E. E.; Metzkes-Ng, J.; Nagler, B.; Nakatsutsumi, M.; Nikl, J.; Ota, M.; Pelka, A.; Prencipe, I.; Randolph, L.; Rödel, M.; Sakawa, Y.; Schlenvoigt, H.-P.; Smid, M.; Treffert, F.; Voigt, K.; Zeil, K.; Cowan, T.; Schramm, U.; Kluge, T.

Resonant Small-angle x-ray scattering raw data obtained in measurements at MEC at LCLS and evalutation of the asymmetry in the scattering patterns. The data set is structured in case 1/Si-Cu-compound targets and case 2/Cu-only-targets as presented in the publication for on- and off-resonant XFEL probe energies.

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Permalink: https://www.hzdr.de/publications/Publ-33444
Publ.-Id: 33444


Dynamo action of the large scale flow in a precessing cylinder

Giesecke, A.; Pizzi, F.; Stefani, F.

Precession is a well known phenomenon that (in a very general sense) paraphrases the
temporal change of the orientation of the spin axis of rotating objects. In rotating celestial bodies
with liquid interior precession causes a volume force that directly drives a non-axisymmetric fluid
flow [1]. Paradigmatic example is the liquid core of the Earth [2], for which the forcing is
considerably strong due to the rather large angle between rotation axis and precession axis. An even
stronger forcing is assumed for the ancient moon three to four billion years ago [3]. Precessional
forcing of the fluid interior of planets or moons is of interest because the resulting internal flows in
terms of inertial modes or turbulence back-react on the rotation of the whole body, which may
become evident for example in length of day variations or periodic changes of the nutation angle.
Furthermore a precession-driven flow of an electrically conductive fluid is capable of generating a
large scale magnetic field [4]. From an energetic point of view, the directly driven non-
axissymmetric flow is not sufficient to generate a magnetic field [5], however, multifaceted
instabilities of the primary flow provide the possibility to extract a large a amount of kinetic energy
from the rotational fluid motions into a fluid flow, which may be more suitable of generating a
magnetic field via electromagnetic induction [6].
In order to investigate to what extent a precession-driven flow can power a dynamo, and what
properties the related magnetic field would have, an experiment is currently being constructed at
HZDR, in which 6 tons of liquid sodium will precess in a cylinder with 2 meters height and 2
meters in diameter [7]. The design of the experiment is attended by comprehensive numerical
simulations, which showed that at the edge of the transition between a complex but still laminar
flow to a fully developed turbulent state, onset of dynamo action can be expected [8]. This state of
flow is characterized by an almost complete transformation of the original rotation into large-scale
inertial waves and small-scale turbulent flow. The dynamo effect found in the simulations is mainly
due to an evolving axially symmetric flow component and the strong shear layer near the outer
walls due to the massive extraction of rotational energy [9]. Free inertial waves in the form of
triadic resonances as the first instability, which describe the transition from the stationary to the
time-dependent state, do not seem to play any special role for the dynamo-effect. Open questions
concern the role of this triadic instability as a trigger for the transition to turbulence, the character of
the turbulence itself (is it three-dimensional or quasi-geostrophic) and the very mechanism that
causes the redistribution of the internal angular momentum and/or torque that goes along with the
significant modification of the large scale pattern of the velocity field.

1.
2.
3.
4.
5.
6.
7.
8.
9.
Stewartson & Roberts 1963, J. Fluid Mech. 17 (1), 1-20.
Malkus 1968, Science, 160, 259
Cebron et al. 2019, Geophys. J. Int., 219 (1), 34-57
Tilgner 2005, Phys. Fluids, 17, 034104
Loper 1975, Phys. Earth Planet. Inter. 11 (1), 43-60
Kerswell 1999, J. Fluid Mech. 382, 283-306
Stefani et al. 2015, Magnetohydrodynamics, 51 (2), 275-284
Giesecke et al. 2018, Phys. Rev. Lett. 120, 024502
Giesecke et al. 2018, Geophys. Astrophys. Fluid Mech., 113 (1-2), 235-255

Keywords: Dynamo

  • Invited lecture (Conferences)
    IV Russian Conference on Magnetohydrodynamics, 20.-22.09.2021, Perm, Russland

Permalink: https://www.hzdr.de/publications/Publ-33443
Publ.-Id: 33443


Rational Linker Design to Accelerate Excretion and Reduce Background Uptake of Peptidomimetic PSMA-Targeting Hybrid Molecules.

Eder, A.; Schäfer, M.; Schmidt, J.; Bauder-Wüst, U.; Roscher, M.; Leotta, K.; Haberkorn, U.; Kopka, K.; Eder, M.

The evolution of peptidomimetic hybrid molecules for preoperative imaging and guided surgery targeting the prostate-specific membrane antigen (PSMA) significantly progressed over the past few years, and some approaches are currently being evaluated for further clinical translation. However, accumulation in nonmalignant tissue such as kidney, bladder, spleen, or liver might limit tumor-to-background contrast for precise lesion delineation, particularly in a surgical setting. To overcome these limitations, a rational linker design aims at the development of a second generation of PSMA-11-based hybrid molecules with an enhanced pharmacokinetic profile and improved imaging contrast. Methods: A selection of rationally designed linkers was introduced to the PSMA-targeting hybrid molecule Glu-urea-Lys-HBED-CC-IRDye800CW, resulting in a second-generation peptidomimetic hybrid molecule library. The biologic properties were investigated in cell-based assays. In a preclinical proof-of-concept study with the radionuclide 68Ga, the impact of the modifications was evaluated by determination of specific tumor uptake, pharmacokinetics, and fluorescence imaging in tumor-bearing mice. Results: The modified hybrid molecules carrying various selected linkers revealed high PSMA-specific binding affinity and effective internalization. The highest tumor-to-background contrast of all modifications investigated was identified for the introduction of a histidine- (H) and glutamic acid (E)-containing linker ((HE)3-linker) between the PSMA-binding motif and the chelator. In comparison to the parental core structure, uptake in nonmalignant tissue was significantly reduced to a minimum, as exemplified by an 11-fold reduced spleen uptake from 38.12 ± 14.62 percentage injected dose (%ID)/g to 3.47 ± 1.39 %ID/g (1 h after injection). The specific tumor uptake of this compound (7.59 ± 0.95 %ID/g, 1 h after injection) was detected to be significantly higher than that of the parental tracer PSMA-11. These findings confirmed by PET and fluorescence imaging are accompanied by an enhanced pharmacokinetic profile with accelerated background clearance at early time points after injection. Conclusion: The novel generation of PSMA-targeting hybrid molecules reveals fast elimination, reduced background organ enrichment, and high PSMA-specific tumor uptake meeting the key demands for potent tracers in nuclear medicine and fluorescence-guided surgery. The approach's efficacy in improving the pharmacokinetic profile highlights the strengths of rational linker design as a powerful tool in strategic hybrid-molecule development.

Keywords: PSMA; guided surgery; hybrid molecules; pharmacokinetic profile; prostate cancer

Permalink: https://www.hzdr.de/publications/Publ-33442
Publ.-Id: 33442


Spectroscopic and modeling study of the sorption of Ln³⁺ (Eu) and An³⁺ (Am, Cm) on Ca-feldspars

Lessing, J.; Neumann, J.; Bezzina, J. P.; Bok, F.; Lützenkirchen, J.; Brendler, V.; Stumpf, T.; Schmidt, M.

INTRODUCTION
Deep geological repositories are considered as a safe disposal strategy for radioactive waste due their ability to isolate toxic components from the biosphere over hundreds of thousands of years. Minor actinides and Pu dominate the radiotoxicity of spent nuclear fuel over these long time scales. Due to the expected reducing conditions in the underground repository, the trivalent oxidation state is dominant for Am and Cm, and will also be relevant for Pu. For investigations of the mobility of the trivalent actinides Am(III) and Cm(III), the less toxic trivalent rare earth elements, in particular Eu(III), are commonly used.
In Germany and many other countries, crystalline rock is being considered as a possible host rock. Therefore, there is a need for understanding the sorption behavior of radionuclides on this material. Crystalline rock (e.g. granite), consists mainly of quartz, feldspars, and mica. Recently, the retention of trivalent actinides by K-feldspar was investigated from a thermodynamic and structural point of view.[1] Here, we extend this study towards Ca-feldspars (plagioclases), which may show a different sorption behavior due to their different elemental composition, crystal structure, and surface charge behavior.
DESCRIPTION OF THE WORK
Synthetic Ca-feldspar and natural plagioclases of different Ca amounts were used for zeta potential measurements and batch sorption experiments under different geochemical conditions ([M³⁺] = 52 nM – 10 μM; solid-liquid ratio = 1 – 3 g/L, I = 0,1 M NaCl, pH = 3 – 9) to quantify the uptake of Am(III) and Eu(III). For analysis of the sorption structure of trivalent f-elements on the molecular level, time-resolved laser-induced spectroscopy (TRLFS) using Cm(III) as a luminescent probe was carried out on synthetic Ca-feldspar. The obtained data were used to develop a surface complexation model (SCM) and to derive surface complexation parameters for the spectroscopically identified surface complexes.
RESULTS AND DISCUSSION
Zeta potential investigations of all Ca-feldspars show a decrease of the potential for pH = 2 – 4 due to surface site deprotonation. In contrast to the previously reported trend for K-feldspar, the zeta potential increases for pH = 4 – 7, with a stronger increase with higher Ca²⁺ concentration in the crystal lattice of the investigated plagioclases, even reaching positive values in the case of the synthetic Ca-feldspar. This effect can be traced to dissolved Al³⁺: Due to differences in solubility, Al³⁺ concentration in solution increases with increasing Ca²⁺ in the crystal lattice. Experiments on K-feldspar with added Al³⁺ reveal a connection between its concentration and the increase of the zeta potential.
All observed Ca-feldspars show a strong sorption uptake of trivalent f-elements for pH > 6. K- and Ca-feldspars seem to have a similar sorption behavior for low [M³⁺].[1] In contrast, Ca-feldspar has a slightly stronger sorption affinity when the metal concentrations is increased. This leads to a steeper sorption edge with increasing Ca²⁺ concentration in the crystal lattice of the mineral.
Spectroscopic studies with Cm(III) on synthetic Ca-feldspar reveal three sorption complexes: one inner sphere complex (IS) and its two hydrolysis forms, which have the same band positions as previously determined for K-feldspar.[1] Therefore, it can be concluded that the structure of the formed IS complexes is independent on the feldspar type. Differences are only observed for the quantitative contributions of the surface complexes. In particular, hydrolysis of the IS complex is stronger in the case of the Ca-feldspar.
Batch sorption data and the information about spectroscopically identified surface complexes were then combined to develop a SCM for Ca-feldspar that describes the experimental data. The formation constants of the surface complexes were determined to be −8.37; −10.81, and −16.35, respectively and are very similar to those of the K-feldspar.[1]
From the applied multi-method approach, we conclude that the sorption of trivalent f-elements on K- and Ca-feldspar is most likely comparable for relevant, natural conditions. Therefore, it may be possible not to distinguish between the two minerals in reactive transport simulations, which will reduce calculation resources needed for a reliable risk assessment of repositories for radioactive waste.
REFERENCES
[1] J. Neumann et al., “A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar,” Journal of Colloid Interface Science, vol. 591, pp. 490–499 (2021)
[2] Neumann and Lessing et al., “Structural and modeling study of the retention of trivalent f-elements (Am, Cm, Eu) by natural and synthetic Ca-feldspars”, in preparation.

Keywords: Sorption; Trivalent metal ions; Actinides; Ca-feldspar; Surface complexation model; TRLFS; Zeta potential

  • Poster
    TransRet2020, 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33441
Publ.-Id: 33441


The disappearance and return of nanoparticles upon low energy ion irradiation

Choupanian, S.; Nagel, A.; Möller, W.; Pacholski, C.; Ronning, C.

Ion irradiation of bulk and thin film materials is tightly connected to well described effects such as sputtering or/and ion beam mixing. However, when a nanoparticle is ion irradiated and the ion range is comparable to the nanoparticle size, these effects are to be reconsidered essentially. This study investigates the morphology changes of silver nanoparticles on top of silicon substrates, being irradiated with Ga+ ions in an energy range from 1 to 30 keV. The hemispherical shaped nanoparticles become conical due to an enhanced and curvature-dependent sputtering, before they finally disappear. The sputter yield and morphology changes can be well described by 3D Monte Carlo TRI3DYN simulations. However, the combination of sputtering, ion beam mixing, ion beam induced diffusion, and Ostwald ripening at ion energies lower than 8 keV results in the reappearance of new particles. These newly formed nanoparticles appear in various structures depending on the material and ion energy

Keywords: Ag nanoparticles; Ion beam mixing; Ion-nanoparticle interaction; Ostwald ripening; Phase sepereation

Permalink: https://www.hzdr.de/publications/Publ-33440
Publ.-Id: 33440


Deterministic Shallow Dopant Implantation in Silicon with Detection Confidence Upper-Bound to 99.85% by Ion–Solid Interactions

Jakob, A. M.; Robson, S. G.; Schmitt, V.; Mourik, V.; Posselt, M.; Spemann, D.; Johnson, B. C.; Firgau, H. R.; Mayes, E.; McCallum, J. C.; Morello, A.; Jamieson, D. N.

Silicon chips containing arrays of single dopant atoms can be the material of choice for classical and quantum devices that exploit single donor spins. For example, group-V donors implanted in isotopically purified 28Si crystals are attractive for large-scale quantum computers. Useful attributes include long nuclear and electron spin lifetimes of 31P, hyperfine clock transitions in 209Bi or electrically controllable 123Sb nuclear spins. Promising architectures require the ability to fabricate arrays of individual near-surface dopant atoms with high yield. Here, an on-chip detector electrode system with 70 eV root-mean-square noise (≈20 electrons) is employed to demonstrate near-room-temperature implantation of single 14 keV 31P+ ions. The physics model for the ion–solid interaction shows an unprecedented upper-bound single-ion-detection confidence of 99.85 ± 0.02% for near-surface implants. As a result, the practical controlled silicon doping yield is limited by materials engineering factors including surface gate oxides in which detected ions may stop. For a device with 6 nm gate oxide and 14 keV 31P+ implants, a yield limit of 98.1% is demonstrated. Thinner gate oxides allow this limit to converge to the upper-bound. Deterministic single-ion implantation can therefore be a viable materials engineering strategy for scalable dopant architectures in silicon devices.

Keywords: Deterministic single-ion implantation; Near-surface dopant location; Quantum computers; Ion Beam Induced Charge Collection

Permalink: https://www.hzdr.de/publications/Publ-33439
Publ.-Id: 33439


Investigation of a buoyancy-driven instability during horizontal miscible displacement*

Stergiou, G.; Dezso, H.; Eckert, K.; Schwarzenberger, K.

Hydrodynamic instabilities in miscible reactive systems have significant impact on applications such as: CO2 sequestration, soil reparation, or particle formation in precipitation systems. A buoyancy-induced instability has been observed when a fluid horizontally displaces another miscible fluid of different density, resulting in a complex flow field. With this study, we intended to characterize the flow patterns in such systems and to investigate their dependence on parameters such as the injection flow rate and the fluids density difference. We performed reactive and non-reactive experiments in a microscale geometry and explored the intricate 3D flow conditions of the system, using micro-Particle Image Velocimetry. The results evidence the existence of flow structures present in equivalent numerical studies and reveal the dependency of the instability on the direction of the displacement.

*Funded by the German Aerospace Center (DLR) provided by BMWi, Grant No. 50WM2061.

  • Lecture (Conference)
    74th APS Division of Fluid Dynamics Meeting, 21.-23.11.2021, Phoenix, USA

Permalink: https://www.hzdr.de/publications/Publ-33438
Publ.-Id: 33438


Atomic layer etching of SiGe nanowires

Khan, M. B.; Shakeel, S.; Richter, K.; Ghosh, S.; Deb, D.; Hübner, R.; Mikolajick, T.; Erbe, A.; Georgiev, Y.

Developments in the fabrication techniques like lithography, etching, thin-film deposition, and metallization, etc. have enhanced device the performance of the complementary metal-oxide-semiconductor (CMOS) transistors mainly by the scaling-down. Innovative concepts need to be incorporated to further improve the device performance as the scaling limits are being reached.
We report on the development of the atomic layer etching (ALE) process to fabricate smooth SiGe-on-insulator (SiGeOI) nanowire using the conventional dry etching tool. First, nano-patterns were made on SiGeOI samples using electron beam lithography. Then these patterns were transferred into the SiGeOI layer using an inductively coupled plasma reactive ion etching (ICP-RIE) process. Subsequently, the ALE process was developed to smoothen the nanowire and to reduce their widths. For the surface modification step, SF6 was used, while Ar+ was used for the subsequent modified layer removal step. The ALE cycle sequence was: modification with 60 sccm SF6 for 20 s, 60 sccm Ar purge for 15 s, layer removal with 60 sccm Ar for 10 s using 25 W platen power, and 40 sccm Ar purge for 10 s.
Various ALE cycles were performed to investigate the effect of ALE on the nanowire roughness and width. The surface of etched features was studied using the atomic force microscopy (AFM) (figure 1 (a)). A reduction in the width of the wire was seen with the increasing number of the ALE cycles. Figure 1 (b) shows the root mean square (r.m.s) surface roughness of the buried oxide after certain numbers of the ALE cycles. The roughness went down from ca. 6 nm to 1 nm or below (exact value could not be calculated due to limitation of the AFM tip) as the number of ALE cycles was increased from 78 to 102.
Figure 2 shows sub-12 nm nanowires with smooth sidewalls fabricated after performing 63 ALE cycles. An etch per cycle of 1.1 Å was attained. This process, developed on a conventional ICP-RIE tool, can be used to further scale down the nanowires.

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  • Poster (Online presentation)
    Micro and Nano Engineering Conference, 2021, 20.-23.09.2021, Turin, Italy

Permalink: https://www.hzdr.de/publications/Publ-33437
Publ.-Id: 33437


Controlled Silicidation of Silicon Nanowires using Flash Lamp Annealing

Khan, M. B.; Prucnal, S.; Ghosh, S.; Deb, D.; Hübner, R.; Pohl, D.; Rebohle, L.; Mikolajick, T.; Erbe, A.; Georgiev, Y.

Among other new device concepts, nickel silicide (NiSix)-based Schottky barrier nanowire transistors are projected to supplement down-scaling of the complementary metal-oxide-semiconductor (CMOS) technology as its physical limits are reached. Control over the NiSix phase and its intrusions into the nanowire are essential for superior performance and down-scaling of these devices. Several works have shown control over the phase, but control over the intrusion lengths has remained a challenge. To overcome this, we report a novel millisecond-range flash-lamp-annealing (FLA)-based silicidation process. Nanowires are fabricated on silicon-on-insulator substrates using a top-down approach. Subsequently, Ni silicidation experiments are carried out using FLA. It is demonstrated that this silicidation process gives unprecedented control over the silicide intrusions. Scanning electron microscopy and high-resolution transmission electron microscopy are performed for structural characterization of the silicide. FLA temperatures are estimated with the help of simulations.

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Permalink: https://www.hzdr.de/publications/Publ-33436
Publ.-Id: 33436


Stable acceleration of intense proton beams to energies beyond 80 MeV at rep-rated laser systems

Ziegler, T.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Kiriyama, H.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

We report on experimental investigations of proton acceleration from laser-irradiated solid foils with the Draco-PW laser, where highest proton cut-off energies were achieved for temporal pulse parameters that varied significantlyfrom those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal shape ofthe last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that short and asymmetric pulses generated by positive third order dispersion values are favourable for proton acceleration and can lead to maximum energies above 60 MeV at 18 J laser energy for thin plastic foils, effectively doubling the maximum energy compared to ideally compressed FTL pulses. This performance optimization was the key to perform worlds first dose-controlled in-vivo studies with laser accelerated protons.

The talk will further report on experiments we have carried out in the relativistically induced transparancy regime where the target turns transparent during the laser pulse interaction. We show recent data how the experimental signatures of the accelerated protons in this regime change compared to standard TNSA conditions and how we could reproduce those results at another similar laser laser system.

  • Invited lecture (Conferences)
    5th European Advanced Accelerator Concepts Workshop, 20.-23.09.2021, Rome, Italy

Permalink: https://www.hzdr.de/publications/Publ-33435
Publ.-Id: 33435


Assessment of the validity of a log-law for wall-bounded turbulent bubbly flows

Bragg, A.; Liao, Y.; Fröhlich, J.; Ma, T.

There has been considerable discussion in recent years concerning whether a log-law exists for wall-bounded,
turbulent bubbly flows. Previous studies have argued for the existence of such a log-law, with a modified von
K´arm´an constant, and this is used in various modelling studies. We provide a critique of this idea, and present
several theoretical reasons why a log-law need not be expected in general for wall-bounded, turbulent bubbly
flows. We then demonstrate using recent data from interface-resolving Direct Numerical Simulations that when
the bubbles make a significant contribution to the channel flow dynamics, the mean flow profile of the fluid can
deviate significantly from the log-law behaviour that approximately holds for the single-phase case. The departures
are not surprising and the basic reason for them is simple, namely that for bubbly flows, the mean flow is
affected by a number of additional dynamical parameters, such as the void fraction, that do not play a role for the
single-phase case. As a result, the inner/outer asymptotic regimes that form the basis of the derivation of the loglaw
for single-phase flow do not exist in general for bubbly turbulent flows. Nevertheless, we do find that for
some cases, the bubbles do not cause significant departures from the unladen log-law behaviour. Moreover, we
show that if departures occur these cannot be understood simply in terms of the averaged void fraction, but that
more subtle effects such as the bubble Reynolds number and the competition between the wall-induced turbulence
and the bubble-induced turbulence must play a role.

Keywords: Bubbly flow; Log-law; Wall-bounded turbulent flows

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Permalink: https://www.hzdr.de/publications/Publ-33434
Publ.-Id: 33434


Origin and avoidance of double peaks in the induced voltage of a thermomagnetic generator for harvesting low-grade waste heat

Dzekan, D.; Kischnik, T. D.; Diestel, A.; Kornelius, N.; Fähler, S.

Thermomagnetic harvesting is an emerging approach to convert low-grade
waste heat to electricity, which recently obtained a boost due to the development of both,
more efficient functional materials and innovative device concepts. Here we examine a
thermomagnetic generator which utilizes Gadolinium as thermomagnetic material and report
on double peaks of the induced voltage. By a combination of experiments and theory we
show that these double peaks originate from the interaction of an asymmetric magnetization
curve and a pretzel like magnetic field topology. Double peaks are detrimental for the output
power and can be avoided by matching the magnetization change by adjusting cold and hot
fluid flow.

Keywords: Thermomagnetic Energy Harvesting; Thermomagnetic Generator; Magnetocaloric Refrigeration; Magnetic Materials

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Permalink: https://www.hzdr.de/publications/Publ-33433
Publ.-Id: 33433


A Machine-Learning Surrogate Model for ab initio Electronic Correlations at Extreme Conditions

Dornheim, T.; Moldabekov, Z.; Cangi, A.

The electronic structure in matter under extreme conditions is a challenging complex system prevalent in astrophysical objects and highly relevant for technological applications. We show how machine-learning surrogates in terms of neural networks have a profound impact on the efficient modeling of matter under extreme conditions. We demonstrate the utility of a surrogate model that is trained on \emph{ab initio} quantum Monte Carlo data for various applications in the emerging field of warm dense matter research.

Keywords: Machine Learning; Surrogate model; warm dense matter

Permalink: https://www.hzdr.de/publications/Publ-33432
Publ.-Id: 33432


Fermion Sign Problem in Path Integral Monte Carlo Simulations: Grand-canonical ensemble

Dornheim, T.

We present a practical analysis of the fermion sign problem in fermionic path integral Monte Carlo (PIMC) simulations in the grand-canonical ensemble (GCE). As a representative model system, we consider electrons in a harmonic trap. We find that the sign problem in the GCE is even more severe than in the canonical ensemble at the same conditions, which, in general, makes the latter the preferred option. Despite these difficulties, we show that fermionic PIMC simulations in the GCE are still feasible in many cases, which potentially gives access to important quantities like the compressiblity or the Matsubara Greens function. This has important implications for contemporary fields of research such as warm dense matter, ultracold atoms, and electrons in quantum dots.

Keywords: path integral Monte Carlo; Fermion sign problem

Permalink: https://www.hzdr.de/publications/Publ-33431
Publ.-Id: 33431


Ab initio path integral Monte Carlo approach to the momentum distribution of the uniform electron gas at finite temperature without fixed nodes

Dornheim, T.; Böhme, M.; Militzer, B.; Vorberger, J.

We present extensive new ab initio path integral Monte Carlo results for the momentum distribution function n(k) of the uniform electron gas in the warm dense matter regime over a broad range of densities and temperatures. This allows us to study the nontrivial exchange-correlation-induced increase of low-momentum states around the Fermi temperature, and to investigate its connection to the related lowering of the kinetic energy compared to the ideal Fermi gas. In addition, we investigate the impact of quantum statistics on both n(k) and the off-diagonal density matrix in coordinate space, and find that it cannot be neglected even in the strongly coupled electron liquid regime. Our results were derived without any nodal constraints, and thus constitute a benchmark for other methods and approximations.

Keywords: path integral Monte Carlo; uniform electron gas; momentum distribution; warm dense matter

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Permalink: https://www.hzdr.de/publications/Publ-33430
Publ.-Id: 33430


Momentum distribution of the Uniform Electron Gas at finite temperature: Effects of spin-polarization

Dornheim, T.; Vorberger, J.; Militzer, B.; Moldabekov, Z.

We carry out extensive direct path integral Monte Carlo (PIMC) simulations of the uniform electron gas (UEG) at finite temperature for different values of the spin-polarization ξ. This allows us to unambiguously quantify the impact of spin-effects on the momentum distribution function n(k) and related properties. We find that interesting physical effects like the interaction-induced increase in the occupation of the zero-momentum state n(0) substantially depend on ξ. Our results further advance the current understanding of the UEG as a fundamental model system, and are of practical relevance for the description of transport properties of warm dense matter in an external magnetic field.
All PIMC results are freely available online and can be used as a benchmark for the development of new methods and applications.

Keywords: path integral Monte Carlo; uniform electron gas; momentum distribution; spin-effects; warm dense matter

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Permalink: https://www.hzdr.de/publications/Publ-33429
Publ.-Id: 33429


Nonlinear density response from imaginary-time correlation functions: Ab initio path integral Monte Carlo simulations of the warm dense electron gas

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

The \emph{ab initio} path integral Monte Carlo (PIMC) approach is one of the most successful methods in quantum many-body theory. A particular strength of this method is its straightforward access to imaginary-time correlation functions (ITCF). For example, the well-known density-density ITCF F(q,τ) allows one to estimate the linear response of a given system for all wave vectors q from a single simulation of the unperturbed system. Moreover, it constitutes the basis for the reconstruction of the dynamic structure factor S(q,ω) -- a key quantity in state-of-the-art scattering experiments. In this work, we present analogous relations between the nonlinear density response in quadratic and cubic order of the perturbation strength and generalized ITCFs measuring correlations between up to four imaginary-time arguments. As a practical demonstration of our new approach, we carry out simulations of the warm dense electron gas and find excellent agreement with previous PIMC results that had been obtained with substantially larger computational effort. In addition, we give a relation between a cubic ITCF and the triple dynamic structure factor S(q1,ω1;q2,ω2), which evokes the enticing possibility to study dynamic three-body effects on an \emph{ab initio} level.

Keywords: Nonlinear response; path integral Monte Carlo; imaginary-time correlation functions

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Permalink: https://www.hzdr.de/publications/Publ-33428
Publ.-Id: 33428


Nonlinear electronic density response of the ferromagnetic uniform electron gas at warm dense matter conditions

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

In a recent Letter [T.~Dornheim \emph{et al.}, Phys.~Rev.~Lett.~\textbf{125}, 085001 (2020)], we have presented the first \emph{ab initio} results for the nonlinear density response of electrons in the warm dense matter regime. In the present work, we extend these efforts by carrying out extensive new path integral Monte Carlo (PIMC) simulations of a \emph{ferromagnetic} electron gas that is subject to an external harmonic perturbation. This allows us to unambiguously quantify the impact of spin-effects on the nonlinear density response of the warm dense electron gas. In addition to their utility for the description of warm dense matter in an external magnetic field, our results further advance our current understanding of the uniform electron gas as a fundamental model system, which is important in its own right.

Keywords: Nonlinear response; path integral Monte Carlo

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Permalink: https://www.hzdr.de/publications/Publ-33427
Publ.-Id: 33427


Classical bridge functions in classical and quantum plasma liquids

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

Bridge functions, the missing link in the exact description of strong correlations, are indirectly extracted from specially designed molecular dynamics simulations of classical one-component plasma liquids and accurately parameterized. Their incorporation into an advanced integral equation theory description of Yukawa one-component plasma liquids and a novel dielectric formalism scheme for quantum one-component plasma liquids leads to an unprecedented agreement with available molecular dynamics simulations and new ab initio path integral Monte Carlo simulations, respectively.

Keywords: Dielectric theory; Bridge functions; path integral Monte Carlo

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Permalink: https://www.hzdr.de/publications/Publ-33426
Publ.-Id: 33426


Path integral Monte Carlo approach to the structural properties and collective excitations of liquid 3He without fixed nodes

Dornheim, T.; Moldabekov, Z.; Vorberger, J.; Militzer, B.

Due to its nature as a strongly correlated quantum liquid, ultracold helium is characterized by the nontrivial interplay of different physical effects. Bosonic 4He exhibits superfluidity and Bose-Einstein condensation. Its physical properties have been accurately determined on the basis of ab initio path integral Monte Carlo (PIMC) simulations. In contrast, the corresponding theoretical description of fermionic 3He is severely hampered by the notorious fermion sign problem, and previous PIMC results have been derived by introducing the uncontrolled fixed-node approximation. In this work, we present extensive new PIMC simulations of normal liquid 3He without any nodal constraints. This allows us to to unambiguously quantify the impact of Fermi statistics and to study the effects of temperature on different physical properties like the static structure factor S(q) , the momentum distribution n(q) , and the static density response function χ(q). In addition, the dynamic structure factor S(q, ω) is rigorously reconstructed from imaginary-time PIMC data. From simulations of 3He , we derived the familiar phonon–maxon–roton dispersion function that is well-known for 4He and has been reported previously for two-dimensional 3He films (Nature 483:576–579 (2012)). The comparison of our new results for both S(q) and S(q, ω) with neutron scattering measurements reveals an excellent agreement between theory and experiment.

Keywords: path integral Monte Carlo; Helium; ultracold atoms

Permalink: https://www.hzdr.de/publications/Publ-33425
Publ.-Id: 33425


Nonlinear interaction of external perturbations in Warm Dense Matter

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

We present extensive new ab initio path integral Monte Carlo (PIMC) results for an electron gas at warm dense matter conditions that is subject to multiple harmonic perturbations. In addition to the previously investigated nonlinear effects at the original wave number [Dornheim \emph{et al.}, PRL \textbf{125}, 085001 (2020)] and the excitation of higher harmonics [Dornheim \emph{et al.}, PRR \textbf{3}, 033231 (2021)], the presence of multiple external potentials leads to mode-coupling effects, which constitute the dominant nonlinear effect and lead to a substantially more complicated density response compared to linear response theory. One possibility to estimate mode-coupling effects from a PIMC simulation of the unperturbed system is given in terms of generalized imaginary-time correlation functions that have been recently introduced by Dornheim \emph{et al.}~[JCP \textbf{155}, 054110 (2021)]. In addition, we extend our previous analytical theory of the nonlinear density response of the electron gas in terms of the static local field correction [Dornheim \emph{et al.}, PRL \textbf{125}, 235001 (2020)], which allows for a highly accurate description of the PIMC results with negligible computational cost.

Keywords: Nonlinear response; warm dense matter; path integral Monte Carlo; mode coupling

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Permalink: https://www.hzdr.de/publications/Publ-33424
Publ.-Id: 33424


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