Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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39109 Publications

Superphénix Benchmark Part I: Results of Static neutronics

Ponomarev, A.; Mikityuk, K.; Zhang, L.; Nikitin, E.; Fridman, E.; Álvarez-Velarde, F.; Romojaro-Otero, P.; Jiménez-Carrascosa, A.; García-Herranz, N.; Lindley, B.; Davies, U.; Seubert, A.; Henry, R.

n the paper, the specification of a new neutronics benchmark for a large Sodium cooled Fast Reactor
(SFR) core and results of modelling by different participants are presented. The neutronics benchmark describes
the core of the French sodium cooled reactor Superphénix at its startup configuration, which in particular was
used for experimental measurement of reactivity characteristics. The benchmark consists of the detailed
heterogeneous core specification for neutronic analysis and results of the reference solution. Different core
geometries and thermal conditions from cold “as fabricated” up to full power were considered. The reference
Monte Carlo solution of Serpent 2 includes data on multiplication factor, power distribution, axial and radial
reaction rates distribution, reactivity coefficients and safety characteristics, control rods worth, kinetic data.
The results of modelling with seven other solutions using deterministic and Monte Carlo methods are also
presented and compared to the reference solution. The comparisons results demonstrate appropriate
agreement of evaluated characteristics. The neutronics results will be used in the second phase of the
benchmark for evaluation of transient behaviour of the core.

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Permalink: https://www.hzdr.de/publications/Publ-32426
Publ.-Id: 32426


Unser Rohstoffbedarf – Forschung für eine nachhaltige Rohstoffsuche in Europa im Spannungsfeld von Umwelt und Wirtschaft

Pospiech, S.

Vortrag für Schüler des Heidelberger Life-Science Labs (HLSL) am Deutschen Krebsforschungszentrum (DKFZ) im Rahmen der Freitagsvorträge, einer öffentlichen Vortragsreihe

Keywords: Schüler; Rohstoffe; Critical raw materials; Exploration; EU-Projekt

  • Lecture (others) (Online presentation)
    Freitagsvorträge des Heidelberger Life-Science Labs, 12.03.2021, Heidelberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-32425
Publ.-Id: 32425


Dissolution-based uptake of CeO2 nanoparticles by fresh water shrimp – A dual-radiolabelling study of the fate of anthropogenic cerium in water organisms

Schymura, S.; Rybkin, I.; Uygan, S. S. S.; Drev, S.; Podlipec, R.; Rijavec, T.; Mansel, A.; Lapanje, A.; Franke, K.; Strok, M.

Manufactured nanoparticles, such as CeO2, give rise to novel risks when released into the environment. To assess these risks it is important to quantify the nanoparticle mass flows, as well as their speciation and the mechanisms of their transformation. We developed an innovative dual-radiolabelling strategy for CeO2 nanoparticles using neutron activation and in-diffusion labelling to radiolabel CeO2 nanoparticles with both Ce-141 and Ce-139. The different distribution of the radiolabels in the particles does not only allow easy dose determination in uptake studies but also enables us to track the uptake pathways of the anthropogenic cerium. By measuring the activity as well as the isotope ratio we tracked the uptake, transformation and excretion of CeO2 nanoparticles in freshwater shrimp. We found that 99.99 % of the uptaken particles are excreted, leaving the gut with excrement. The remaining 0.01 % was internalized via a dissolution based pathway and accumulated in the hepatopancreas of the shrimp at a dose range of pg CeO2 per shrimp. Most importantly, our results show that dissolution is not only coincidental but instrumental in the uptake of the cerium into the internal organs of the shrimp.

Keywords: CeO2 nanoparticles; radiolabelling; Uptake; Dissoltution

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Permalink: https://www.hzdr.de/publications/Publ-32424
Publ.-Id: 32424


Particle resuspension from monolayered deposits: evidence of collision-induced phenomenon

Lecrivain, G.; Banari, A.; Henry, C.; Hampel, U.

We present here new experimental and numerical results for the resuspension of microscopic glass particles from a monolayer bed into a turbulent gas flow. With an intermediate surface coverage, here about 10 % of the field of
view, we report two distinct detachment mechanisms: collision-induced resuspension at low flow velocities and individual particle resuspension at higher fluid velocities.

Keywords: Particle resuspension

  • Invited lecture (Conferences)
    Institute Seminar at Institut National de Recherche en Sciences et Technologies du Numérique (INRIA), 11.03.2021, Sophia Antipolis - Méditerranée, France

Permalink: https://www.hzdr.de/publications/Publ-32423
Publ.-Id: 32423


Data-Driven Shadowgraph Simulation of a 3D Object

Willmann, A.; Stiller, P.; Debus, A.; Irman, A.; Pausch, R.; Chang, Y.-Y.; Bussmann, M.; Hoffmann, N.

In this work we propose a deep neural network based surrogate model for a plasma shadowgraph - a technique for visualization of perturbations in a transparent medium. We are substituting the numerical code by a computationally cheaper projection based surrogate model that is able to approximate the electric fields at a given time without computing all preceding electric fields as required by numerical methods. This means that the projection based surrogate model allows to recover the solution of the governing 3D partial differential equation, 3D wave equation, at any point of a given compute domain and configuration without the need to run a full simulation. This model has shown a good quality of reconstruction in a problem of interpolation of data within a narrow range of simulation parameters and can be used for input data of large size.

  • Contribution to proceedings
    ICLR 2021 - Ninth International Conference on Learning Representations, 03.-07.05.2021, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-32422
Publ.-Id: 32422


Robust Magnetoelectric Effect in Decorated Graphene/In2Se3 Heterostructure

Shang, J.; Tang, X.; Gu, Y.; Krasheninnikov, A.; Picozzi, S.; Chen, C.; Kou, L.

The magnetoelectric effect is a fundamental physical phenomenon that synergizes electric and magnetic degrees of freedom to generate distinct material responses like electrically tuned magnetism, which serves as a key foundation of the emerging field of spintronics. Here, we show by first-principles studies that ferroelectric (FE) polarization of an In2Se3 monolayer can modulate the magnetism of an adjacent transition-metal (TM)-decorated graphene layer via a ferroelectrically induced electronic transition. The TM nonbonding d-orbital shifts downward and hybridizes with carbon-p states near the Fermi level, suppressing the magnetic moment, under one FE polarization, but on reversed FE polarization this TM d-orbital moves upward, restoring the original magnetic moment. This finding of robust magnetoelectric effect in the TM-decorated graphene/In2Se3 heterostructure offers powerful insights and a promising avenue for experimental exploration of ferroelectrically controlled magnetism in two-dimensional (2D) materials.

Keywords: 2D materials; First-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-32421
Publ.-Id: 32421


Formation of Highly Doped Nanostripes in 2D Transition Metal Dichalcogenides via a Dislocation Climb Mechanism

Lin, Y.; Karthikeyan, J.; Chang, Y.; Li, S.; Kretschmer, S.; Komsa, H.; Chiu, P.; Krasheninnikov, A.; Suenaga, K.

Doping of materials beyond the dopant solubility limit remains a challenge, especially when spatially nonuniform doping is required. In 2D materials with a high surface‐to‐volume ratio, such as transition metal dichalcogenides, various post‐synthesis approaches to doping have been demonstrated, but full control over spatial distribution of dopants remains a challenge. A post‐growth doping of single layers of WSe2 is performed by adding transition metal (TM) atoms in a two‐step process, which includes annealing followed by deposition of dopants together with Se or S. The Ti, V, Cr, and Fe impurities at W sites are identified by using transmission electron microscopy and electron energy loss spectroscopy. Remarkably, an extremely high density (6.4–15%) of various types of impurity atoms is achieved. The dopants are revealed to be largely confined within nanostripes embedded in the otherwise pristine WSe2. Density functional theory calculations show that the dislocations assist the incorporation of the dopant during their climb and give rise to stripes of TM dopant atoms. This work demonstrates a possible spatially controllable doping strategy to achieve the desired local electronic, magnetic, and optical properties in 2D materials.

Keywords: 2D materials; doping; first-principles simulations

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Permalink: https://www.hzdr.de/publications/Publ-32420
Publ.-Id: 32420


Atomistic Simulations of Defect Production in Monolayer and Bulk Hexagonal Boron Nitride under Low- and High-Fluence Ion Irradiation

Ghaderzadeh, S.; Kretschmer, S.; Ghorbani Asl, M.; Hlawacek, G.; Krasheninnikov, A.

Controlled production of defects in hexagonal boron nitride (h-BN) through ion irradiation has recently been demonstrated to be an effective tool for adding new functionalitites to this material such as single photon generation and for developing optical quantum applications. Using analytical potential molecular dynamics, we study the mechanisms of vacancy creation in single- and multi-layer h-BN under low- and high-fluence ion irradiation. Our results quantify the densities of defects produced by noble gas ions in a wide range of ion energies and elucidate the types and distribution of defects in the target. The simulation data can directly be used to guide the experiment aimed at the creation of defects of particular types in h-BN targets for single-photon emission, spin-selective optical transitions and other applications by using beams of energetic ions.

Keywords: Two-dimensional materials; ion irradiation; atomistic simulations; defects

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Permalink: https://www.hzdr.de/publications/Publ-32419
Publ.-Id: 32419


Supporting data to the publication: Impact of surface charge on the motion of light-activated Janus micromotors

Baraban, L.

These video set (Video 1-5) summarizes the all experimental results. these videos were analyzed to get the dynamics of the Janus particle in the article further reflected in the figures.

Keywords: Janus particles; particle tracking

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Permalink: https://www.hzdr.de/publications/Publ-32418
Publ.-Id: 32418


Data (15/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

- Simulationsdaten für den ROFEX 1 zum Vergleich unterschiedlicher Detektorgrößen mit dem USRBIN-Kommando

Keywords: Electron beam; Beam position; FLUKA; ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-32417
Publ.-Id: 32417


Data (14/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

- Simulationsdaten für den ROFEX 1 zum Vergleich unterschiedlicher Detektorgrößen mit dem USRBIN-Kommando

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32416
Publ.-Id: 32416


Data (13/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

- Simulationsdaten für den ROFEX 1 mit dem FLUKA-USRBDX-Kommando (Ro1_Pos_*)
- Simulationsdaten für den ROFEX 1 mit dem USRBIN-Kommando zum Vergleich unterschiedlicher Detektorgrößen

Keywords: ROFEX; Electron beam; FLUKA; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32415
Publ.-Id: 32415


Data (12/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

- Simulationsdaten für den ROFEX 1 mit dem USRBDX-FLUKA-Kommando

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32414
Publ.-Id: 32414


Data (11/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

- Pos_* Simulationsdaten für den ROFEX 3 für verschiedene USRBINs mit EMFCUT=10keV
- Ro1_* Simulationsdaten für den ROFEX 1 mit EMFCUT = 100keV

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32413
Publ.-Id: 32413


Data (10/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Untersuchung des Einflusses verschiedener USRBDX-Strukturen auf den Elektronenfluss.

Keywords: FLUKA; ROFEX; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32412
Publ.-Id: 32412


Data (9/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandtd, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Untersuchung des Einflusses verschiedener USRBDX-Strukturen auf den Elektronenfluss.

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32411
Publ.-Id: 32411


Data (8/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Untersuchung des Einflusses verschiedener USRBDX-Strukturen auf den Elektronenfluss.

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32410
Publ.-Id: 32410


Data (7/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Untersuchung des Einflusses verschiedener USRBDX-Strukturen auf den Elektronenfluss.

Keywords: ROFEX; FLUKA; Electron Beam

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Permalink: https://www.hzdr.de/publications/Publ-32409
Publ.-Id: 32409


Data (6/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Untersuchung des Einflusses verschiedener USRBDX-Strukturen auf den Elektronenfluss.

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32408
Publ.-Id: 32408


Data (5/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Untersuchung des Einflusses verschiedener USRBDX-Strukturen auf den Elektronenfluss.

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32407
Publ.-Id: 32407


Data for (4/15): Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Untersuchung des Einflusses verschieder USRBDX-Strukturen auf den Elektronenfluss.

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32406
Publ.-Id: 32406


Data (3/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Pos_17* enthält die Elektronenflusssimulationen für den ROFEX 3 mit EMFCUT=10keV

Keywords: ROFEX; Electron beam; FLUKA; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32405
Publ.-Id: 32405


Data (2/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

FLUKA-Daten für den ROFEX 3:
- Pos_18_* wurden zur Erstellung des Gleichungssystems Elektronenfluss(r, phi) verwendet.

Messdaten für den ROFEX 1:
-DC_4_2kHz* aufgenommen mit dem Präzisionsmessgerät LTT24

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32404
Publ.-Id: 32404


Data (1/15) for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Simulationsdaten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Daten für den ROFEX 3:
- Pos_17 bzw. Pos_19 wurden zur Bestimmung des Gleichungssystems Elektronenfluss(r, phi) verwendet
- groessenvgl diente dem Vergleich verschiedener USRBIN-Größen bei den ROFEX-3-Simulationen
- USRBIN70_Ro3 zeigte den Elektronenfluss an einer weiteren Detektorposition
- 66_21_Ro3 untersuchte einen leicht verschobenen USRBIN 66.

Daten für den ROFEX 1:
-Ro1_USRBIN_gekippt wurde für den Vergleich von USRBINs mit unterschiedlichen Winkeln verwendet

Keywords: ROFEX; FLUKA; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32403
Publ.-Id: 32403


Scripts for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Skripte und FLUKA-Eingangsdateien ohne Strahlposition für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Keywords: FLUKA; ROFEX; Electron beam; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32402
Publ.-Id: 32402


Results for: Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, M.
Supervisor: Barthel, Frank

Auswertungen der Daten für die Masterarbeit Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Keywords: Electron beam; ROFEX; Beam position

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Permalink: https://www.hzdr.de/publications/Publ-32401
Publ.-Id: 32401


Analysen zur Anwendbarkeit verschiedener Strahlbahn-Monitoring-Konzepte für die ultraschnelle Röntgencomputertomografie

Brandt, Mira

Deutsch:

Die vorliegende Arbeit beschäftigt sich mit der Suche nach einem für die ultraschnelle Röntgencomputertomografie geeigneten Strahlbahn-Monitoring-Konzept. Mehrere Sekundäreffekte, die durch den Primärelektronenstrahl ausgelöst werden, wurden analysiert und aus ihnen die Rückstreuelektronenverteilung als Parameter für das Monitoring ausgewählt. Auf Grundlage von für verschiedene Strahlpositionen durchgeführten Simulationen des Elektronenflusses mit dem Monte-Carlo-Simulationspaket FLUKA wurden geeignet positionierte Kupferelektroden als Elektronendetektoren verwendet. Mit diesen Elektroden wurden Testmessungen durchgeführt. Die aufgenommenen Spannungskurven wurden mit den simulierten Elektronenflusskurven verglichen, wobei die Kurvenformen ähnlich waren. Das Spannungssignal wurde dagegen von den Simulationen unterschätzt. Da es während der ersten Messungen zu Spannungsüberschlägen kam, wurde ein zweites, verbessertes System entwickelt, das diese vermeiden soll.

English:

This thesis shows the search for a beam path monitoring concept suitable for ultrafast X-ray computed tomography. Several secondary effects triggered by the primary electron beam were analysed and from them the backscattered electron distribution was selected as a parameter to monitor the beam position. Based on simulations of the electron fluence, carried out for different beam positions with the Monte Carlo simulation package FLUKA, well positioned copper electrodes were used as electron detectors. Test measurements were done with these electrodes. The recorded voltage curves were compared with the simulated electron fluence curves which showed that the curve shapes are similar. However, the voltage signal was underestimated by the simulations. Because voltage flashovers occurred during the first measurements, a second improved system was developed to avoid them.

Keywords: Electron beam; Computed tomography; Beam position; Beam monitoring; ROFEX

  • Master thesis
    TU Dresden, 2021
    Mentor: Dr.-Ing. Frank Barthel
    151 Seiten

Permalink: https://www.hzdr.de/publications/Publ-32400
Publ.-Id: 32400


Towards high-rate RPC-based thermal neutron detectors using low-resistivity electrodes

Margato, L. M. S.; Morozov, A.; Blanco, A.; Fonte, P.; Lopes, L.; Saraiva, J.; Zeitelhack, K.; Hall-Wilton, R.; Höglund, C.; Lai, C.-C.; Robinson, L.; Svensson, P.; Naumann, L.; Römer, K.; Stach, D.; Wilpert, T.

We present experimental results on the counting rate measurements for several single-gap ¹⁰B‑RPCs with anodes made from standard float glass, low-resistivity glass and ceramic. The measurements were performed at the V17 monochromatic neutron beamline (3.35 Å) at the Helmholtz-Zentrum Berlin. For the ¹⁰B-RPCs with 0.28 mm thick float glass a maximum counting rate density of about 8×10³ Hz/cm² was obtained. In the case of low resistivity glass and ceramic, the counting rate density did not deviate from linear dependence on the neutron flux up to the maximum flux available at this beamline and exceeded a value of 3×10⁴ Hz/cm².

Keywords: RPC; neutron detection

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Permalink: https://www.hzdr.de/publications/Publ-32399
Publ.-Id: 32399


Research data "Fluorination of graphene leads to susceptibility for nanopore formation by highly charged ion impact"

Creutzburg, S.; Hübner, R.; Facsko, S.

The depository contains STEM images, experimental data from charge exchange measurements and data from charge exchange simulations.

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Permalink: https://www.hzdr.de/publications/Publ-32397
Publ.-Id: 32397


Fluorination of graphene leads to susceptibility for nanopore formation by highly charged ion impact

Creutzburg, S.; Mergl, M.; Hübner, R.; Jirka, I.; Erb, D.; Heller, R.; Niggas, A.; Grande, P. L.; Aumayr, F.; Wilhelm, R. A.; Kalbac, M.; Facsko, S.

The formation of nanopores by highly charged ion impacts on freestanding fluorine-functionalized graphene is demonstrated. The process is driven by potential sputtering, which becomes active by changing the semi-metallic properties of graphene into a strongly insulating state by fluorination. The interaction of fluorographene with highly charged ions is also studied in terms of charge exchange and kinetic energy loss. A higher number of captured electrons and a larger kinetic energy loss than in pristine graphene are observed, which can be well explained by an increase in the ion's neutralization length and in the atomic areal density of the target, respectively. Using a computer code based on a time-dependent scattering potential model, a connection between the efficiency of charge exchange and the fluorine coverage is revealed. Our results suggest a competition of two distinct nanostructure formation processes leading either to pore formation or fluorine desorption.

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Permalink: https://www.hzdr.de/publications/Publ-32396
Publ.-Id: 32396


Flexible magnetoreceptor with tunable intrinsic logic for on-skin touchless human-machine interfaces

Makushko, P.; Oliveros Mata, E. S.; Canon Bermudez, G. S.; Hassan, M.; Laureti, S.; Rinaldi, C.; Fagiani, F.; Barucca, G.; Schmidt, N.; Zabila, Y.; Kosub, T.; Illing, R.; Volkov, O.; Vladymyrskyi, I.; Faßbender, J.; Albrecht, M.; Varvaro, G.; Makarov, D.

Artificial magnetoception is a new and yet to be explored path for humans to interact with our surroundings. This technology is enabled by thin film magnetic field sensors embedded in a soft and flexible format to constitute magnetosensitive electronic skins (e-skins). Being limited by the sensitivity to in-plane magnetic fields, magnetosensitive e-skins are restricted to basic proximity and angle sensing and are not used as switches or logic elements of interactive wearable electronics. Here, we demonstrate a novel magnetoreceptive platform for on-skin touchless interactive electronics based on flexible spin valve switches with the sensitivity to out-of-plane magnetic fields. The technology relies on all-metal Co/Pd-based spin valves with a synthetic antiferromagnet possessing perpendicular magnetic anisotropy. The flexible magnetoreceptors act as logic elements, namely momentary and permanent (latching) switches. The switches maintain their performance even upon severe bending to a radius of less than 5 mm and withstand repetitive bending for hundreds of cycles. We integrated flexible switches in on-skin interactive electronics and demonstrated their performance as touchless human-machine interfaces, which are intuitive to use, energy efficient, and insensitive to external magnetic disturbances. This technology offers qualitatively new functionalities for electronic skins and paves the way towards full-fledged on-skin touchless interactive electronics.

Keywords: flexible electronics; magnetic field sensors; flexible spin valve; skin-conformal; sensor

Permalink: https://www.hzdr.de/publications/Publ-32395
Publ.-Id: 32395


Impact of surface charge on the motion of light-activated Janus micromotors

Huang, T.; Ibarlucea, B.; Caspari, A.; Synytska, A.; Cuniberti, G.; de Graaf, J.; Baraban, L.

Control over the motion of micromotors is of high relevance for lab-on-a-chip and biomedical engineering, wherein such particles encounter complex microenvironments. Here, we introduce an efficient way to influence the direction of motion and speed of Janus micromotors by modifying their surface properties and those of their immediate surroundings. We fabricated light-responsive Janus micromotors with positive and negative surface charge, both driven by ionic self-diffusiophoresis. These were used to observe direction-of-motion reversal in proximity to glass substrates for which we varied the surface charge. Quantitative analysis allowed us to extract the dependence of the particle velocity on the surface charge density at the substrate. This constitutes the first quantitative demonstration of the substrate’s surface charge on the motility of the light-activited diffusiophoretic motors in water. We provide qualitative understanding of these observations in terms of osmotic flow along the substrate generated through the ions released by the propulsion mechanism. Our results constitute a crucial step in moving toward practical application of self-phoretic artificial micromotors.

Permalink: https://www.hzdr.de/publications/Publ-32393
Publ.-Id: 32393


PIConGPU setup: LPWFA downramp injection

Pausch, R.; Couperus Cabadag, J. P.; Bastrakov, S.; Bussmann, M.; Irman, A.; Kurz, T.; Schöbel, S.; Schramm, U.; Steiniger, K.; Ufer, P.; Widera, R.; Debus, A.

PIConGPU source code and setup files used for the LPWFA downramp injection simulation study

Keywords: PIConGPU; LWFA; PWFA; LPWFA; hybrid

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Permalink: https://www.hzdr.de/publications/Publ-32392
Publ.-Id: 32392


In-vivo assessment of tissue parameters with intra- and inter-patient variation using dual-energy CT

Peters, N.; Kieslich, A.; Wohlfahrt, P.; Hofmann, C.; Richter, C.

Purpose/Objective:

The precise and reliable knowledge of radiological tissue properties is essential for a multitude of radiotherapeutic applications, such as input parameters for Monte Carlo simulation, stoichiometric CT calibration as well as for tissue-mimicking phantoms. However, so far only limited data based on ex-vivo experimental studies is available, summarized in ICRU46. Utilizing a clinically validated Dual-Energy-CT (DECT)-based tissue characterization approach (DirectSPR), we present a precise in-vivo assessment of relative electron density (RED), effective atomic number (EAN) and stopping-power ratio (SPR) for organs in the head and pelvis in a patient cohort analysis of clinical DECT scans.
Material/Methods:
Organ-specific tissue parameters were obtained from clinical DECT scans of 107 brain-tumour and 103 pelvic cancer patients applying the DirectSPR approach. DirectSPR is characterised by a voxel-wise, patient-specific parameter determination based on a specific superposition of low- and high-energy DECT scans. In total, six structures in the head (brain, brainstem, spinal cord, chiasm, optical nerve, lens) and four in the pelvic region (prostate, kidney, liver, bladder) were investigated. To minimise contamination from surrounding tissues, clinical contours were shrunk and smoothed in 2D. Image slices with artefacts (e.g. due to metal implants) were omitted from analysis. Organ tissue parameters were characterised regarding the cohort mean value as well as the variation within each patient (2σ_intra) and between the investigated patients (2σ_inter).
Results:
For 10 organs, including 4 organs not listed in ICRU46, the mean RED, EAN and SPR as well as their respective intra- and inter-patient variation were determined (Table 1). Results are exemplarily illustrated for SPR, crucial for proton therapy planning (Figure 1). SPR intra-patient variation was higher than 1.4% (1.4-5.3%) in all organs and always exceeded the inter-patient variation of the organ mean SPR (0.5-2.0%). The largest intra-patient variation was observed in the kidney, where renal parenchyma and calyx were included in the contours. The average inter-patient variation over all organs was 1.2%, highlighting the potential benefit of considering variation in tissue parameters instead of using tabulated mean values. For brain, lens, liver and urine the ICRU46 values are within the determined 2σ_inter interval around the respective mean value, while for prostate and kidney the ICRU46 values are outside this interval. For kidney, cohort mean SPR was 2.3% below ICRU46.
Conclusion:
Radiological tissue parameters in the head and pelvis were characterised in-vivo in a large patient cohort using dual-energy CT. This substantially expands and reassesses the current standard database defined in ICRU46 by smaller substructures in the brain as well as by the quantification of organ-specific inter- and intra-patient variation. Our results can be used as input to simulate intra- and inter-patient variability e.g. in Monte Carlo simulations.

  • Lecture (Conference) (Online presentation)
    ESTRO 21, 27.-31.08.2021, Madrid, Spain
  • Abstract in refereed journal
    Radiotherapy and Oncology 161(2021)Suppl. 1, S587-S588
    DOI: 10.1016/S0167-8140(21)07035-3

Permalink: https://www.hzdr.de/publications/Publ-32391
Publ.-Id: 32391


Patterns Of Practice in Adaptive and Real-Time Particle Therapy (POP-ART PT), Part I: intrafractional respiratory motion

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

Purpose/objectives: For particle therapy, the clinical implementation of Real-time Respiratory Motion Management (RRMM) is of vital importance to mitigate the detrimental effects of motion on dose delivery. We introduced a worldwide questionnaire on the Patterns of Practice for Adaptive and Real-time Particle Therapy (POP-ART PT), aiming to determine the current status and the potential barriers for motion management implementation in clinical practice at particle therapy centers. Here we summarize the result of RRMM implementation at European centers.
Material and methods: A questionnaire was distributed worldwide to evaluate the current clinical practice, wishes for expansion and barriers to new implementation. Two types of RRMM technique were considered: 1) passive, using volumetric/layered rescanning, 2) active, using free-breathing gating, breath-hold (BH), or tracking/synchronization where beam and target are continuously re-aligned. The tumor sites breast, lung, liver, pancreas, esophagus, and lymphoma were specifically surveyed.
Results: Answers from 44 centers from 16 countries worldwide have been received so far. Here we present the results for 23 European centers from 13 countries (92% response rate). RRMM was used in 16(69%) centers clinically, of which 5(22%) have both passive and active method implemented (figure 1). Of the 22 centers using pencil beam scanning, 13(56%) were applying rescanning, 7(31%) indicated the plan to implement it in the future, and 2(9%) reported rescanning incompatibility due to machine limitations. However, no clear agreement on an optimal rescanning method was found, as 6/7 centers used layered/volumetric rescanning with large variations in rescan numbers (2-6 times). Only 8(34%) centers have been using BH/gating as active RRMM in at least one tumour site (Lymphoma: 100%), but all centers wished to implement it in the future. Surface motion or breathing volume monitoring was the most common method to guide active RRMM. Four centers (…% of those using active RRMM) provided audio/visual feedback to the patient with 2 acquiring additional images to verify surrogate accuracy during dose delivery. No center conducted separate coaching for BH/gating. No center used or wished to use tracking/motion synchronization in the future. Furthermore, 12(54%) and 20(87%) centers wished to extend the use of active RRMM for current tumour sites and to implement it for new tumour sites, respectively. Priority was given to lung (58% and 83%). The main barriers (figure 2) to extend/implement RRMM for current/new tumour sites were technical limitations, limited equipment and human resources.
Conclusion: 69% of particle therapy centers in Europe have implemented RRMM to mitigate the effects of intrafractional respiratory motion in clinical practice. A significant interest was reported to implement more active RRMM in the future, in particular for lung cancer, requiring more support to address technical limitations.

  • Lecture (Conference)
    ESTRO 2021, 27.-31.08.2021, Madrid, Spain
  • Abstract in refereed journal
    Radiotherapy and Oncology 161(2021)Suppl. 1, S129-S130
    DOI: 10.1016/S0167-8140(21)06815-8

Permalink: https://www.hzdr.de/publications/Publ-32390
Publ.-Id: 32390


Patterns Of Practice in Adaptive and Real Time Particle Therapy part II: interfractional changes

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

Purpose/objectives: Adaptive particle therapy (APT) allows to account for anatomical changes throughout the treatment course resulting in more conformal target coverage and better sparing of organ at risk (OAR). Different types of APT ranging from weekly to daily to real-time adaptation have been proposed. Based on the POP-ART RT questionnaire [1], the Patterns Of Practice for Adaptive and Real-time Particle Therapy (POP-ART PT) questionnaire aims to determine the status of APT implementation worldwide. Here we focus on APT for interfractional anatomical changes in European centers.
Material/Methods: An institutional questionnaire was sent to particle therapy centers worldwide to determine the current extent of APT implementation in clinical practice. Respondents were asked if and which type of APT was used for selected treatment sites as well as details about the implemented workflow. Additionally, questions regarding the barriers to implementation and wishes for the future were addressed.
Results: Answers from 44 particle therapy centers worldwide have been received so far. Here we present the results for 23 European particle therapy centers from 13 countries, representing a 92% response rate for Europe. All responding centers except one use APT for at least one treatment site. The number of centers using APT for selected sites are shown in Table 1. None of the centers uses online APT (plan libraries or daily adaptation). The plan adaptation was in all cases motivated by both, target and OAR dose considerations. Reasons for adaptation are presented in Figure 1.
Three institutes are satisfied with their implemented adaptive workflows but would like to increase the number of treatment sites treated with APT. All other institutes would like to improve the plan adaptation workflow for a treatment site already treated with APT and 13 of those institutes would like to introduce APT to a new treatment site. One center explicitly stated that they would like to introduce an online adaptive workflow, first applied to skull base patients. Another center explicitly stated the aim to improve adaptive workflow efficiency. Other centers did not specify the type of improvement they wish for. The main barriers in the implementation of APT are presented in Figure 2. The biggest issues were the lack of integrated and efficient workflows and the lack of human resources.
Conclusion: Comprehensive data about APT implementation in clinical practice at particle centers were collected. Currently, no center uses online APT and more research and development for integrated and efficient workflow is needed to bring it to clinical practice. Until the end of the year, we will conclude data collection worldwide and summarize the results in a comprehensive report.

  • Lecture (Conference)
    ESTRO 2021, 27.-31.08.2021, Madrid, Spain
  • Abstract in refereed journal
    Radiotherapy and Oncology 161(2021)Suppl. 1, S476-S478
    DOI: 10.1016/S0167-8140(21)06970-X

Permalink: https://www.hzdr.de/publications/Publ-32389
Publ.-Id: 32389


Reaction Pathways for Atomic Layer Deposition with Lithium Hexamethyl Disilazide, Trimethyl Phosphate, and Oxygen Plasma

Werbrouck, A.; Mattelaer, F.; Minjauw, M.; Nisula, M.; Julin, J. A.; Munnik, F.; Dendooven, J.; Detavernier, C.

Atomic layer deposition (ALD) of lithium-containing films is of interest for the development of next-generation energy storage devices. Lithium hexamethyl disilazide (LiHMDS) is an established precursor to grow these types of films. The LiHMDS molecule can either be used as a single-source precursor molecule for lithium or as a dual-source precursor molecule for lithium and silicon. Single-source behavior of LiHMDS is observed in the deposition process with trimethylphosphate (TMP) resulting in the deposition of crystalline lithium phosphate (Li3PO4). In contrast, LiHMDS exhibits dual-source behavior when combined with O-2 plasma, resulting in a lithium silicate. Both processes were characterized with in situ ellipsometry, in situ time-resolved full-range mass spectrometry, X-ray photoelectron spectroscopy (XPS), and elastic recoil detection analysis (ERDA). When we combined both reactants into a three-step LiHMDS-TMP-O-2* or LiHMDS-O-2*-TMP process, the dual-source nature of LiHMDS emerged again. By carefully combining our measurements, it is shown that film growth with LiHMDS (in combination with TMP and O-2 plasma) is driven by dipole-driven self-saturated surface interactions combined with dissociative chemisorption. We show that when hydroxyl groups are present on the surface, silicon will be incorporated in the films. These insights benefit the general understanding of the behavior of the LiHMDS and TMP precursors and may facilitate their effective use in ternary or quaternary processes.

Keywords: Reaction products; Adsorption; Precursors; Molecules; Plasma

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Permalink: https://www.hzdr.de/publications/Publ-32388
Publ.-Id: 32388


Reduzierung von respirationsbedingter Pankreasbewegung mittels eines MRT- und Partikeltherapie-kompatiblen abdominellen Korsetts

Schneider, S.; Stefanowicz, S.; Jentsch, C.; Lohaus, F.; Valentini, C.; Platzek, I.; Troost, E.; Hoffmann, A.

Fragestellung:

Die intrafraktionelle Bewegung von abdominellen Tumoren erfordert entsprechend große Sicherheitssäume in der Radioonkologie und führt zu einer erhöhten Strahlenbelastung des umliegenden gesunden Gewebes. Für die geplante Magnetresonanztomographie (MRT)-geführte Partikeltherapie (PT) von Pankreaskarzinomen wurde ein innovatives, patientenspezifisches abdominelles Korsett zur Reduktion der atmungsbedingten Pankreasbewegung entwickelt, welches die hohen Materialansprüche der MRT sowie der PT erfüllt. Das Maß an Bewegungsreduktion durch das Korsetts und dessen Verträglichkeit wurde in einer Patientenstudie untersucht.

Methodik:

Vorbereitend wurden drei abdominelle Korsetts unterschiedlicher Beschaffenheit und Patientenindividualität in ihrer Anwendbarkeit für die MRT-geführte PT bei abdominellen Tumoren untersucht. Das Modell, das die höchste Reproduzierbarkeit in der PT bei Oberbauchtumoren ermöglichte und so eine konformale Strahlentherapie ermöglichte, wurde in einer durch die lokale Ethikkommissioin gebilligte Patientenstudie getestet. Für 12 Patienten (neun weiblich, Alter 71.6±8.6 Jahre) mit Tumoren des Oberbauchs wurde ein Polyethylene-Korsett individuell hergestellt. An einem 3T MRT Scanner wurden von den Patienten sowohl mit Korsett als direkt darauffolgend auch ohne Korsett unter freier Atmung zeitauflösende Bildsequenzen (orthogonale 2D-cine MRT und retrospektiv rekonstruierte 4D-MRT) akquiriert. Das Pankreas wurde in allen Bildern manuell konturiert und die Bewegung des Massenschwerpunktes zwischen maximaler Inspiration und Exspiration in 3D analysiert. Basierend auf einem detaillierten Erhebungsbogen wurde die Verträglichkeit des Korsetts in klinischer Anwendung untersucht.

Ergebnis:

Durch Applikation des Korsetts wurde bei hoher Patientenverträglichkeit eine Reduktion der Pankreasbewegung vorwiegend in der Hauptrichtung der Atmung (inferior-superior) um 49% (p<0.05) erreicht, während kein signifikanter Effekt auf die Bewegung anterior-posterior und links-rechts gefunden wurde. Des Weiteren konnte eine Reduzierung der Bewegungsvariabilität von 36% (p<0.01) festgestellt werden.

Schlussfolgerung
Ein patienten-spezifisches Korsett konnte entwickelt werden, das den Materialansprüchen und dem klinischen Workflow der MRT-geführten PT genügt und die respirationsbedingte Pankreasbewegung in IS Richtung signifikant reduzieren konnte. Dies stimmt mit den Ergebnissen überein, die mit einem Korsett für die Photonentherapie gefunden wurden [1], dessen Beschaffenheit jedoch für die Protonentherapie ungeeignet ist. Bei hoher Patientenverträglichkeit konnte das Korsett so als innovatives Hilfsmittel in den klinischen Workflow überführt werden.

Keywords: MRT geführte Partikeltherapie; intrafraktionelle Bewegung; Pankreaskarzinom

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Permalink: https://www.hzdr.de/publications/Publ-32387
Publ.-Id: 32387


Development and Validation of a GMP-Compliant High-Pressure Liquid Chromatography Method for the Determination of the Chemical and Radiochemical Purity of [18F]PSMA-1007, a PET Tracer for the Imaging of Prostate Cancer

Katzschmann, I.; Marx, H.; Kopka, K.; Hennrich, U.

For the PET imaging of prostate cancer, radiotracers targeting the prostate-specific membrane antigen (PSMA) are nowadays used in clinical practice. [18F]PSMA-1007, a radiopharmaceutical labeled with fluorine-18, has excellent properties for the detection of prostate cancer. Essential for the human use of a radiotracer is its production and quality control under GMP-compliance. For this purpose, all analytical methods have to be validated. [18F]PSMA-1007 is easily radiosynthesized in a one-step procedure and isolated using solid phase extraction (SPE) cartridges followed by formulation of a buffered injection solution and for the determination of its chemical and radiochemical purity a robust, fast and reliable quality control method using radio-HPLC is necessary. After development and optimizations overcoming problems in reproducibility, the here described radio-HPLC method fulfills all acceptance criteria-for e.g., specificity, linearity, and accuracy-and is therefore well suited for the routine quality control of [18F]PSMA-1007 before release of the radiopharmaceutical. Recently a European Pharmacopeia monograph for [18F]PSMA-1007 was published suggesting a different radio-HPLC method for the determination of its chemical and radiochemical purity. Since the here described method has certain advantages, not least of all easier technical implementation, it can be an attractive alternative to the monograph method. The here described method was successfully validated on several radio-HPLC systems in our lab and used for the analysis of more than 60 batches of [18F]PSMA-1007. Using this method, the chemical and radiochemical purity of [18F]PSMA-1007 can routinely be evaluated assuring patient safety.

Keywords: GMP; PSMA; [18F]PSMA-1007; high performance liquid chromatography (HPLC); positron emission tomography (PET); prostate cancer; validation

Permalink: https://www.hzdr.de/publications/Publ-32386
Publ.-Id: 32386


Synthesis and application of a thiol-reactive HBED-type chelator for development of easy-toproduce Ga-radiopharmaceutical kits and imaging probes

Klika, K.; Da, P. C.; Kopka, K.; Smith, G.; Makarem, A.

In radiopharmaceutical syntheses, maleimide is commonly used for linking thiol-bearing bioactive molecules to metal-complexing ligands (chelators). However, due to instability of the resulting linkage, phenyloxadiazolyl methylsulfone (PODS) was developed as an alternative to maleimide. This coupling strategy has never been attempted with HBED which is a powerful chelator for gallium-radiolabeling especially at ambient temperature. Here we present HBED-CC-PODS as a bifunctional chelator scaffold for the site-selective conjugation of thiol-bearing vectors and [68Ga]Ga-radiolabeling.

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Permalink: https://www.hzdr.de/publications/Publ-32385
Publ.-Id: 32385


Benefit of 4D robustly optimized proton plans for NSCLC patients with intrafractional motion > 5mm

Spautz, S.; Haase, L.; Tschiche, M.; Makocki, S.; Troost, E. G. C.; Richter, C.; Stützer, K.

Purpose/Objective
The inclusion of breathing-induced variation using 4D robust plan optimization (RO) may yield more robust proton plans for non-small cell lung cancer (NSCLC) patients. Here, we analysed the benefit of 4DRO in terms of robustness against different motion effects.

Material/Methods
Five NSCLC patients with relevant intrafractional motion in the primary (CTVp; on average 3.2-11.1mm) and nodal clinical target volumes (CTVn; 0.9-7.4mm) were included. CTVs and organs at risk (OARs) were contoured on the planning (pCT) and up to two control 4DCTs (cCT). In RayStation 7.99 (RaySearch, Sweden), we optimized three robust normo-fractionated plans [dose: 66Gy(RBE)]with our clinical criteria of 5mm setup and 3.5%+2mm range uncertainty: RO on the average CT with density override of the primary integral gross tumour volume (3DRO); RO on the average, minimum, maximum and mid inspiration CT image (4DRO3); and RO on the average CT and all eight 4DCT phases (4DRO8).
On each of the average, minimum and maximum inspiration pCT, 16 setup and range error scenarios were analysed. To assess the influence of intrafractional changes, a 4D dose was calculated for the pCT and compared to those for the cCTs assuming equal weights of all breathing phases. Interplay effects were simulated by 4D dynamic dose (4DDD) scenarios on the pCT using a logfile-based dose reconstruction with machine logfiles from mock treatments with and without 5 layered rescans and the breathing signals from 4DCT acquisition. To account for a possible fractionation effect within the first fractions, we accumulated 4DDD scenarios with 4 different starting times.

Results
All nominal plans fulfilled target coverage (D98%>95%) and OAR sparing; 3DRO achieved lower mean lung dose [up to 0.3 Gy(RBE)] in 4 patients and lower V5Gy of contralateral lung (up to 4pp). CTVp/CTVn coverage failed setup and range robustness on average in 7%/17% (3DRO), 9%/10% (4DRO3) and 9%/12% (4DRO8) of the scenarios, respectively. 4D dose target coverage on the pCT remained >97% and within 0.5pp difference to the nominal results for both CTVp and CTVn for all planning strategies; however, interfractional changes in the cCTs reduced mainly the CTVp coverage by about 2.5pp, 2.7pp and 2.5pp in the case of 3DRO, 4DRO3 and 4DRO8 plans, respectively. Compared to the nominal plans, single 4DDD scenarios showed a larger mean loss of CTVp/CTVn coverage in 3DRO plans (2.9pp/2.0pp) than in 4DRO plans (4DRO3: 2.2pp/1.6pp, 4DRO8: 2.2pp/1.9pp). Rescanning improved the D98% values by less than 1pp on average, but was even worse for single scenarios. Irrespective of rescanning, target coverage was restored to clinical acceptance (>95%) in all cases when considering potential fractionation on the pCT.

Conclusion
4DRO provided superior robustness for target coverage in some patients. However, 3DRO demands less workload, offers better healthy lung sparing and yields similar interplay effect reduction when combined with rescanning.

  • Lecture (Conference) (Online presentation)
    ESTRO 2021, 27.-31.08.2021, Madrid, Spain
  • Abstract in refereed journal
    Radiotherapy and Oncology 161(2021)Sup 1, S21-S22
    DOI: 10.1016/S0167-8140(21)07228-5

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-32384
Publ.-Id: 32384


Development of an 18F-labelled irreversible inhibitor of transglutaminase 2 as radiometric tool for quantitative expression profiling in cells and tissues

Wodtke, R.; Wodtke, J.; Hauser, S.; Laube, M.; Bauer, D.; Rothe, R.; Neuber, C.; Pietsch, M.; Kopka, K.; Pietzsch, J.; Löser, R.

The transamidase activity of transglutaminase 2 (TGase 2) is considered to be important for several pathophysiological processes including fibrotic and neoplastic tissue growth, whereas in healthy cells this enzymatic function is predominantly latent. Methods that enable the highly sensitive detection of TGase 2, such as application of radiolabelled activity-based probes, will support the exploration of the enzyme’s function in various diseases. In this context, the radiosynthesis and detailed in vitro radiopharmacological evaluation of an 18F-labelled Nε-acryloyllysine piperazide is reported. Robust and facile detection of the radiotracer-TGase 2 complex by autoradiography of thin layer plates and polyacrylamide gels after chromatographic and electrophoretic separation owing to irreversible covalent bond formation was demonstrated for the isolated protein, cell lysates and living cells. Using this radiotracer, quantitative data on the expression profile of activatable TGase 2 in mouse organs and selected tumours were obtained for the first time by autoradiography of tissue sections.

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Permalink: https://www.hzdr.de/publications/Publ-32383
Publ.-Id: 32383


Influence of surfactant contaminations on the lift force of ellipsoidal bubbles in water

Heßenkemper, H.; Ziegenhein, T.; Lucas, D.; Tomiyama, A.

The shear-induced lift force is known to influence the lateral distribution of gas bubbles in bubbly flows. Although the hydrodynamic behavior of a bubble can be greatly affected by surfactants that are present in the liquid bulk, their influence on the lift force has only been investigated to a limited extent. In our previous work we investigated the influence of impurities on the lift force in air-water flows and could reveal non-negligible changes even without a modification of the bubble drag or shape. To bring further insight on changes caused by higher surfactant concentrations, the lift coefficient of single ellipsoidal bubbles of different sizes, which rise in water with varying degree of contamination are experimentally determined in this work. For this purpose, different amounts of 1-Pentanol as well as Triton X-100 were added to the flow. The results reveal a strong dependency of the lift coefficient on the bubble shape, where different findings in the literature for bubbles with lower Reynolds numbers could also be observed for ellipsoidal bubbles in water.

Keywords: Lift coefficient; Draf coefficient; Bubbly flows; Contamination; Surfactant

Permalink: https://www.hzdr.de/publications/Publ-32382
Publ.-Id: 32382


Passive magnetic shielding for in-beam MR imaging during proton pencil beam irradiation

Semioshkina, E.; Oborn, B.; Hoffmann, A. L.

Introduction
Dynamic magnetic fringe fields produced by the scanning magnets (SMs) of a proton pencil beam scanning (PBS) research beamline have shown to cause severe image artefacts during in-beam MR imaging [1]. In this study we investigate the effect of different design parameters of a passive magnetic shield positioned around the SMs on the reduction in magnitude of the magnetic fringe fields the SMs produce.

Methods
A finite element model of the PBS beamline was used to calculate the magnetic fringe fields produced by the SMs. Parameters investigated for a carbon steel magnetic shield included: geometry, material thickness, number of material layers, size of the air gap between layers. The shielding factor (SF) at the projected position of the MR isocenter was calculated. Previous measurements at our facility showed that a SF of at least 20 is required for artefact-free MR imaging during PBS dose delivery.

Results
A cost-efficient way to achieve the required SF was to use a multilayer cylindrical shield. A SF of 21 was achieved for two concentric layers of 10 mm thickness with a 10 mm air gap. The SF can be further increased to 25 by an additional layer. Setting the air gap equal to the layer thickness gave the highest shielding performance.

Conclusion
Computer simulations showed that a passive magnetic shield around the SM can provide the required SF using a multilayer cylindrical geometry with an interlayer air gap equal to the layer thickness.

References
[1] S. Gantz et al. 2020 Phys. Med. Biol.

  • Contribution to proceedings
    The 59th Annual Conference of the Particle Therapy Co-Operative Group (PTCOG 59), 04.-07.06.2021, Online Meeting, Online Meeting

Permalink: https://www.hzdr.de/publications/Publ-32381
Publ.-Id: 32381


Neutron noise patterns from coupled fuel-assembly vibrations

Viebach, M.; Lange, C.; Seidl, M.; Bilodid, Y.; Hurtado, A.

The neutron flux fluctuation magnitude of KWU-built PWRs shows a hitherto unexplained correlation with the types of loaded fuel assemblies. Also, certain measured long-range neutron flux fluctuation patterns in neighboring core quadrants still lack a closed understanding of their origin. The explanation of these phenomena has recently revived a new interest in neutron noise research.

The contribution at hand investigates the idea that a synchronized coolant-driven vibration of major parts of the fuel-assembly ensemble leads to these phenomena. Starting with an assumed mode of such collective vibration, the resulting effects on the time-dependent neutron-flux distribution are analyzed via a DYN3D simulation. A three-dimensional representation of the time-dependent bow of all fuel assemblies is taken into account as a nodal DYN3D feedback parameter by time-dependent variations of the fuel-assembly pitch. The impact of its variation on the cross sections is quantified using a cross-section library that is generated from the output of corresponding CASMO5 calculations.
The DYN3D simulation qualitatively reproduces the measured neutron-flux fluctuation patterns. The magnitude of the fluctuations and its radial dependence are comparable to the measured details. The results imply that collective fuel-assembly vibrations are a promising candidate for being the key to understand long-known fluctuation patterns in KWU built PWRs. Further research should elaborate on possible excitation mechanisms of the assumed vibration modes.

Keywords: Neutron noise; KWU; PWR

Permalink: https://www.hzdr.de/publications/Publ-32379
Publ.-Id: 32379


Effect of the Uniform Fission Source method on local power variance in full core Serpent calculation

Bilodid, Y.; Leppänen, J.

One of challenges of the Monte Carlo full core simulations is to obtain acceptable statistical variance of local parameters throughout the whole reactor core at a reasonable computation cost. The statistical variance tends to be larger in low-power regions. To tackle this problem, the Uniform-Fission-Site method was implemented in Monte Carlo code MC21 and its effectiveness was demonstrated on NEA Monte Carlo performance benchmark. The very similar method is also implemented in Monte Carlo code Serpent under the name Uniform Fission Source (UFS) method.

In this work the effect of UFS method implemented in Serpent is studied on the BEAVRS benchmark which is based on a real PWR core with relatively flat radial power distribution and also on 3x3 PWR mini-core simulated with thermo-hydraulic and thermo-mechanic feedbacks. It is shown that the application of the Uniform Fission Source method has no significant effect on radial power variance but equalizes axial distribution of variance of local power.

Keywords: Serpent; Monte Carlo; Uniform Fission Source; variance reduction

Permalink: https://www.hzdr.de/publications/Publ-32378
Publ.-Id: 32378


SERPENT/SUBCHANFLOW coupled calculations for a VVER core at hot full power

Ferraro, D.; García, M.; Imke, U.; Valtavirta, V.; Tuominen, R.; Bilodid, Y.; Leppänen, J.; Sanchez-Espinoza, V.

An increasing interest on the development of highly accurate methodologies in reactor physics is nowadays observed, mainly stimulated by the availability of vast computational resources. As a result, an on-going development of a wide range of coupled calculation tools is observed within diverse projects worldwide. Under this framework, the McSAFE European Union project is a coordinated effort aimed to develop multiphysics tools based on Monte Carlo neutron transport and subchannel thermal-hydraulics codes. These tools are aimed to be suitable for high-fidelity calculations both for PWR and VVER reactors, with the final goal of performing pin-by-pin coupled calculations at full core scope including burnup. Several intermediate steps are to be analyzed in-depth before jumping into this final goal in order to provide insights and to identify resources requirements. As part of this process, this work presents the results for a pin-by-pin coupling calculation using the Serpent 2 code (developed by VTT, Finland) and the subchannel code SUBCHANFLOW (SCF, developed by KIT, Germany) for a full-core VVER model. For such purpose, a recently refurbished master-slave coupling scheme is used within a High Performance Computing architecture. A full-core benchmark for a VVER-1000 that provides experimental data is considered, where the first burnup step (i.e. fresh core at hot-full rated power state) is calculated. For such purpose a detailed (i.e. pin-by-pin) coupled Serpent-SCF model is developed, including a simplified equilibrium xenon distribution (i.e. by fuel assembly). Comparisons with main global reported results are presented and briefly discussed, together with a raw estimation of resources requirements and a brief demonstration of the inherent capabilities of the proposed approach. The results presented here provide valuable insights and pave the way to tackle the final goals of the on-going high-fidelity project.

Keywords: full-core VVER; Serpent; SCF; code coupling; high-fidelity

Permalink: https://www.hzdr.de/publications/Publ-32377
Publ.-Id: 32377


Ancient permafrost of the Batagay megaslump (East Siberia) – first insights into chronostratigraphy

Wetterich, S.; Murton, J. B.; Toms, P.; Wood, J.; Blinov, A.; Opel, T.; Fuchs, M.; Merchel, S.; Rugel, G.; Gärtner, A.; Savvinov, G.

Age information from ancient permafrost is key for understanding permafrost formation, stability and decay, and allows for interpreting past climate and environmental conditions over Pleistocene timescales. However, reliable permafrost geochronology is challenging, especially for deposits beyond the radiocarbon dating limit at about 50,000 years before present.
The headwall of the world’s largest retrogressive thaw slump at Batagay in the Yana Upland, East Siberia (67.58 °N, 134.77 °E), exposes four generations of ice and sand–ice (composite) wedges that formed synchronously with permafrost aggradation (Opel et al., 2019). The exposed Batagay stratigraphy separates into a lower ice complex that is covered by a lower sand unit, an upper ice complex and an upper sand unit. Two woody beds below and above the lower sand are remarkable (Murton et al., 2017).
We apply four dating methods to disentangle the chronology of the Batagay permafrost archive: optically-stimulated luminescence (OSL) dating of quartz and post-infrared-stimulated luminescence (pIR-IRSL) dating of feldspar as well as accelerator mass spectrometry-based Cl-36/Cl dating of wedge ice and radiocarbon dating of organic material (Murton et al., under review). All four chronometers produce stratigraphically consistent and comparable ages. However, OSL appears to date Marine Isotope Stage (MIS) 3 to MIS 2 deposits more reliably than pIR-IRSL, whereas the latter is more consistent with Cl-36/Cl ages for older deposits.
The age information obtained so far indicates that the Batagay permafrost sequence is discontinuous. The lower ice complex developed at least 650,000 years ago, potentially during MIS 16 and represents the oldest dated permafrost in western Beringia and the second oldest known ice in the Northern Hemisphere. The age of the overlying lower sand is poorly constrained, indicating formation some time during MIS 16–4. The upper ice complex formed during MIS 4–2 and the upper sand during MIS 3–2, respectively. Thus, the ancient permafrost at Batagay potentially provides one of the longest terrestrial records of Pleistocene environments in western Beringia.
Additional sampling for all dating approaches presented here took place in spring 2019, and is part of ongoing research to enhance the geochronology of the exceptional palaeoenvironmental archive of the Batagay megaslump.

References
Murton, J.B., Edwards, M.E., Lozhkin, A.V., Anderson, P.M., Savvinov, G.N., Bakulina, N., Bondarenko, O.V., Cherepanova, M., Danilov, P.P., Boeskorov, V., Goslar, T., Grigoriev, S., Gubin, S.V., Korzun, J., Lupachev, A.V., Tikhonov, A., Tsygankova, V.I., Vasilieva, G.V., & Zanina, O.G. (2017) - Preliminary palaeoenvironmental analysis of permafrost deposits at Batagaika megaslump, Yana Uplands, northern Siberia. Quat. Res., 87, 314–330
Murton, J.B., Toms, P., Blinov, A., Opel, T., Fuchs, M., Wood, J., Gärtner, A., Merchel, S., Rugel, G., Savvinov, G., & Wetterich, S. (under review) - A multi-method pilot dating study of ancient permafrost, Batagay megaslump, East Siberia. Quat. Res.
Opel, T., Murton, J.B., Wetterich, S., Meyer, H., Ashastina, K., Günther, F., Grotheer, H., Mollenhauer, G., Danilov, P., Boeskorov, V., Savvinov, G.N., & Schirrmeister, L. (2019) - Past climate and continentality inferred from ice wedges at Batagay megaslump in the Northern Hemisphere’s most continental region, Yana Highlands, interior Yakutia. Clim. Past, 15, 1443–1461.

Keywords: permafrost; chronology; western Beringia; Batagay megaslump

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  • Poster
    2nd International Conference on ‘Processes and Palaeo-environmental changes in the Arctic: from past to present (PalaeoArc), 24.-28.05.2021, Pisa, Italia

Permalink: https://www.hzdr.de/publications/Publ-32376
Publ.-Id: 32376


Radiation Studies for Mu2e and Mu2e-II - brief status report

Müller, S.

Presentation at "MU2E-II workshop" (virtuell)

  • Open Access Logo Lecture (Conference) (Online presentation)
    Mu2e-II Snowmass22 Workshop, 03.03.2021, Chicago (virtual), USA

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Permalink: https://www.hzdr.de/publications/Publ-32375
Publ.-Id: 32375


Highlight selection of radiochemistry and radiopharmacy developments by editorial board

Aime, S.; Al-Qahtani, M.; Behe, M.; Bormans, G.; Carlucci, G.; Dasilva, J.; Decristoforo, C.; Duatti, A.; Elsinga, P.; Kopka, K.; Li, X.; Liu, Z.; Mach, R.; Middel, O.; Passchier, J.; Patt, M.; Penuelas, I.; Rey, A.; Scott, P.; Todde, S.; Toyohara, J.; Vugts, D.; Yang, Z.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to update the readership on trends in the field of radiopharmaceutical development.
Results: This commentary of highlights has resulted in 23 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals.
Conclusion: Trends in radiochemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.

Permalink: https://www.hzdr.de/publications/Publ-32374
Publ.-Id: 32374


Field-induced valence fluctuations in YbB12

Kurihara, R.; Miyake, A.; Tokunaga, M.; Ikeda, A.; Matsuda, Y. H.; Miyata, A.; Gorbunov, D.; Nomura, T.; Zherlitsyn, S.; Wosnitza, J.

We performed high-magnetic-field ultrasonic experiments on YbB12 up to 59 T to investigate the valence fluctuations in Yb ions. In zero field, the longitudinal elastic constant C11, the transverse elastic constants C44 and (C11 −C12)/2, and the bulk modulus CB show a hardening with a change of curvature at around 35 K indicating a small contribution of valence fluctuations to the elastic constants. When high magnetic fields are applied at low temperatures, CB exhibits a softening above a field-induced insulator-metal transition signaling field-induced valence fluctuations. Furthermore, at elevated temperatures, the field-induced softening of CB takes place at even lower fields and CB decreases continuously with field. Our analysis using the multipole susceptibility based on a two-band model reveals that the softening of CB originates from the enhancement of multipole-strain interaction in addition to the decrease of the insulator energy gap. This analysis indicates that field-induced valence fluctuations of Yb cause the instability of the bulk modulus CB.

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Permalink: https://www.hzdr.de/publications/Publ-32373
Publ.-Id: 32373


Background analysis of actinide and 99Tc tracers in the frame of an in-situ bentonite diffusion experiment at the Grimsel Test Site

Quinto, F.; Blechschmidt, I.; Faestermann, T.; Hain, K.; Koll, D.; Korschinek, G.; Kraft, S.; Pitters, J.; Plaschke, M.; Rugel, G.; Schäfer, T.; Steier, P.; Geckeis, H.

A bentonite engineered barrier will be used in deep geological repositories in granitic host rock to retard the transport of radionuclides possibly released from corroded canisters to the geo- and biosphere. Thus, it is relevant to investigate the diffusion of radionuclides through bentonite and their consequent migration through water-conductive features in granitic rock.
Such scenario in the case of glacial melt water intrusion has been simulated at the Grimsel Test Site with the Long-Term in-situ Test (LIT). A packer-system containing bentonite rings spiked with radionuclide tracers was emplaced in the crystalline rock in contact with a water-conducting shear zone [1]. The bentonite pore-water mixing with Grimsel groundwater was collected at sampling points 5.6 cm from the bentonite for ca. 4.5 years. In these samples, we have determined the concentration of the actinide tracers 233U, 237Np, 242Pu, 241Am and 99Tc. The expected ultra-trace radionuclide concentrations could only be addressed via the high analytical sensitivity of Accelerator Mass Spectrometry. Actinide tracers were analyzed at the 3 MV tandem accelerator of VERA, while 99Tc at the 14 MV tandem accelerator of TUM, enabling quantification at the level of 25 at/g and 0.5 fg/g, respectively [2, 3]. In order to identify radionuclides originating from the LIT, an extensive analysis of the background originating from previous in-situ radionuclide tracer tests [2] was undertaken. First results suggest, that 242Pu release from the bentonite could not be detected. Concentrations of 233U, 237Np and 241Am were found slightly above background for samples collected within 600 days. The levels of 99Tc were always above background indicating the possible release of ca. 8.5 × 10-3 % of the total 99Tc within the experimental time frame. Such early appearance of tracers is unexpected. Further analysis is ongoing in order to identify the possible transport mechanism.

References:

[1] NAB 14-48. GTS Phase VI – CFM Phase 3. February 2015
[2] Quinto et al., (2017) Anal. Chem. 2017, 89, 7182-7189
[3] Quinto et al., (2019) Anal. Chem. 2019, 91, 4585-4591
Acknowledgments: German Federal Ministry for Economic Affairs and Energy, BMWi, grant number 02E11759B & international consortium of the CFM project

  • Lecture (Conference) (Online presentation)
    Goldschmidt 2021, 04.-09.07.2021, Lyon (online), Frankreich

Permalink: https://www.hzdr.de/publications/Publ-32372
Publ.-Id: 32372


SC-XRD data of U13 cluster

Fichter, S.; Radoske, T.; Ikeda-Ohno, A.

Collected frames of SC-XRD measurement of crystal consisting of U13 cluster. Refined cif file is also included.

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Permalink: https://www.hzdr.de/publications/Publ-32371
Publ.-Id: 32371


Structure of the {U₁₃} poly-oxo cluster, U₁₃O₈Clₓ(MeO)₃₈₋ₓ (x = 2.3, MeO: methoxide)

Fichter, S.; Radoske, T.; Ikeda, A.

The structure of a new type of poly-oxo cluster complex that contains thirteen uranium atoms, {U13}, is reported. The complex crystallises from methanol containing tetravalent uranium (U(IV)) with a basic organic ligand, and is characterised as [U13(μ4-Ooxo)8(μ4-OMeO)2(μ2-OMeO)24Clx(OMeO)12-x] (x = 2.3, MeO: methoxide) (I) by single crystal X-ray diffraction. The characterised {U13} poly-oxo cluster complex (I) possesses a single cubic uranium polyhedron at the centre of the cluster core. To be best of our knowledge, this is the very first example of a poly-oxo f-element complex that maintains a single unit of cubic polyhedron in the structure. The cubic polyhedron in (I) is well comparable with those in bulk UO2 in shape. The U-O bonds in the cubic polyhedron of (I) are, however, significantly shorter than those not only in bulk UO2 but also in another cluster analogue of the {U38} cluster. This shortening of UO bonds, together with BVS calculations and the overall negative charge (2-) of (I), suggests that the central uranium atom in (I), that forms the single cubic polyhedron, is presumably oxidised to the pentavalent state (U(V)) from the original tetravalent state (U(IV)). Hence, (I) is a rare example possessing a single cubic coordination polyhedron of U(V). The {U13} cluster (I) is also a new member of the poly-oxo polymer/cluster family of f-elements, contributing to further development of the polymer/cluster chemistry of f-elements.

Keywords: poly-oxo cluster; actinide; uranium; tetravalent; crystal structure

Permalink: https://www.hzdr.de/publications/Publ-32370
Publ.-Id: 32370


Towards Targeted Alpha Therapy with Actinium 225: Chelators for Mild Condition Radiolabeling and Targeting PSMA – a Proof of Concept Study

Reissig, F.; Bauer, D.; Zarschler, K.; Novy, Z.; Bendova, K.; Kopka, K.; Pietzsch, H.-J.; Petrik, M.; Mamat, C.

Currently, targeted alpha therapy is one of the most investigated topics in radiopharmaceutical cancer management. Especially, the alpha emitter 225 Ac provides excellent nuclear properties and is gaining increasing popularity for the treatment of various tumor entities. We herein report on the synthesis of two universal 225Ac-chelators for mild condition radiolabeling and binding sites to conjugate biomolecules via the copper-mediated click chemistry. A convenient radiolabeling procedure was investigated as well as the complex stability proved for both chelators and two PSMA-targeting model radioconjugates. Studies regarding affinity and cell survival were per-formed on LNCaP cells followed by biodistribution studies, which were performed using LNCaP tumor-bearing mice. High efficiency radiolabeling for all conjugates was demonstrated. Cell binding studies revealed a fourfold lower cell affinity for the PSMA conjugate with one targeting vector compared to the conjugate owing two targeting vectors. Additionally, these differences were verified by in vitro cell survival evaluation and biodistribution studies, both showing a higher therapeutic efficiency for the same dose on a cellular leve, a higher tumor up-take (15%ID/g) and a rapid whole body clearance after 24 hours. The synthesized chelators will overcome obstacles of lacking stability and worse labeling needs regarding 225Ac complexation using the DOTA chelator. Moreover, the universal functionalization expands the coverage of these chelators in combination with any sensitive bio(macro)molecule, thus improving treat-ment of any addressable tumor target.

Keywords: Targeted Alpha Therapy; click labeling; Actinium-225; PSMA; Biodistribution

Permalink: https://www.hzdr.de/publications/Publ-32369
Publ.-Id: 32369


Characterization of the LUNA neutron detector array for the measurement of the 13C(alpha,n)16O reaction

Csedreki, L.; Ciani, G. F.; Balibrea-Correa, J.; Best, A.; Aliotta, M.; Barile, F.; Bemmerer, D.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Chillery, T.; Colombetti, P.; Corvisiero, P.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Janas, Z.; Junker, M.; Kochanek, I.; Lugaro, M.; Marigo, P.; Masha, E.; Mazzocchi, C.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Piatti, D.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Takács, M. P.; Terrasi, F.; Zavatarelli, S.

We introduce the LUNA neutron detector array developed for the investigation of the 13C(𝛼, 𝑛)16O reaction towards its astrophysical 𝑠-process Gamow peak in the low-background environment of the Laboratori Nazionali del Gran Sasso (LNGS). Eighteen 3He counters are arranged in two different configurations (in a vertical and a horizontal orientation) to optimize neutron detection efficiency, target handling and target cooling over the investigated energy range E𝛼,lab = 300 − 400 keV (En = 2.2 − 2.6 MeV in emitted neutron energy). As a result of the deep underground location, the passive shielding of the setup and active background suppression using pulse shape discrimination, we reached a total background rate of 1.23 ± 0.12 counts/hour. This resulted in an improvement of two orders of magnitude over the state of the art allowing a direct measurement of the 13C(𝛼, 𝑛)16O cross-section down to E𝛼,lab = 300 keV. The absolute neutron detection efficiency of the setup was determined using the 51V(p,n)51Cr reaction and an AmBe radioactive source, and completed with a Geant4 simulation. We determined a (34 ± 3)% and (38 ± 3)% detection efficiency for the vertical and horizontal configurations, respectively, for En = 2.4 MeV neutrons.

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Permalink: https://www.hzdr.de/publications/Publ-32368
Publ.-Id: 32368


SERPENT2-SUBCHANFLOW-TRANSURANUS pin-by-pin depletion calculations for a PWR fuel assembly

Garcia, M.; Tuominen, R.; Gommlich, A.; Ferraro, D.; Valtavirta, V.; Imke, U.; van Uffelen, P.; Mercatali, L.; Sanchez-Espinoza, V.; Leppänen, J.; Kliem, S.

This work presents the results for a coupled neutronic-thermalhydraulic-thermomechanic pin-level depletion calculation of a PWR fuel assembly using Serpent2-SUBCHANFLOWTRANSURANUS. This tool is based on a semi-implicit depletion scheme with pin-by-pin feedback, mesh-based field exchange and an object-oriented software design. The impact of including fuel-performance capabilities is analyzed, with focus on high-burnup effects. The treatment of the Doppler feedback to the neutronics is examined as well, in particular the use of radial fuel-temperature profiles or radially averaged values.

Keywords: SERPENT2; SUBCHANFLOW; TRANSURANUS; Multiphysics; PWR

Permalink: https://www.hzdr.de/publications/Publ-32367
Publ.-Id: 32367


Data for: Experimental studies on bubble aspect ratio and corresponding correlations under bubble swarm condition

Liu, L.; Zhang, H.; Yan, H.; Ziegenhein, T.; Heßenkemper, H.; Zhou, P.; Lucas, D.

Zip-file that contains the raw images on a study on bubble aspect ratio under swarm condition. Further information can be found in the respective paper.

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Permalink: https://www.hzdr.de/publications/Publ-32366
Publ.-Id: 32366


Data for: Bremsstrahlung emission and plasma characterization driven by moderately relativistic laser–plasma interactions

Singh, S.; Armstrong, C. D.; Kang, N.; Ren, L.; Liu, H.; Hua, N.; Rusby, D. R.; Klimo, O.; Versaci, R.; Zhang, Y.; Sun, M.; Zhu, B.; Lei, A.; Ouyang, X.; Lancia, L.; Laso Garcia, A.; Wagner, A.; Cowan, T. E.; Zhu, J.; Schlegel, T.; Weber, S.; McKenna, P.; Neely, D.; Tikhonchuk, V.; Kumar, D.

Relativistic electrons generated by the interaction of petawatt-class short laser pulses with solid targets can be used to generate bright x-rays via bremsstrahlung. The efficiency of laser energy transfer into these electrons depends on multiple parameters including the focused intensity and pre-plasma level. This paper reports experimental results from the interaction of a high intensity petawatt-class glass laser pulses with solid targets at a maximum intensity of 1019 W cm−2. In-situ measurements of specularly reflected light are used to provide an upper bound of laser absorption and to characterize focused laser intensity, the pre-plasma level and the generation mechanism of second harmonic light. The measured spectrum of electrons and bremsstrahlung radiation provide information about the efficiency of laser energy transfer.

Keywords: Plasma physics; Bremsstrahlung; Laser-plasma

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Permalink: https://www.hzdr.de/publications/Publ-32365
Publ.-Id: 32365


HZDR Multiphase Case Collection for OpenFOAM

Hänsch, S.; Draw, M.; Evdokimov, I.; Khan, H.; Krull, B.; Lehnigk, R.; Liao, Y.; Lyu, H.; Meller, R.; Schlegel, F.; Tekavčič, M.
Other: Couteau, Arthur; Other: Kriebitzsch, Sebastian; Other: Kumaresh, Pramodh; Other: Mohite, Onkar; Other: Upadhyay, Kartik

HZDR Multiphase Case Collection for OpenFOAM contains simulation setups for the open-source CFD software OpenFOAM extended by the HZDR Multiphase Addon for OpenFOAM. The simulation setups are separated into mono- and polydisperse bubbly flows utilising the HZDR Baseline model set, setups for a hybrid modelling approach (disperse and resolved interfaces) and miscellaneous cases.

Keywords: Multiphase Flow; Numerical Simulations; OpenFOAM; Computational Fluid Dynamics; Baseline model; Multi-field two-fluid model; Partial elimination algorithm; Free Surface; Euler-Euler Method; Shell; Python; Gnuplot; C++

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Permalink: https://www.hzdr.de/publications/Publ-32364
Publ.-Id: 32364


Control Over Self-Assembled Janus Clusters by the Strength of Magnetic Field in H₂O₂

Alsaadawi, Y.; Eichler-Volf, A.; Heigl, M.; Zahn, P.; Albrecht, M.; Erbe, A.

Microscope video of capped Janus particles propelled in Hydrogen peroxide under influence of varying magnetic fields. The caps compose of ferromagnetic (Co) and paramagnetic (Pd, H2O2 catalyst) elements carefully deposited onto one hemisphere of silica particles, which will later exhibit aligned magnetic moments upon saturation in 1 T magnetic field. The videos demonstrate different motion profiles depending on cluster shapes, with the later determined by cap-cap interaction of individual particles. 

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Permalink: https://www.hzdr.de/publications/Publ-32363
Publ.-Id: 32363


Complex metal nanostructures with programmable shapes from simple DNA building blocks

Ye, J.; Aftenieva, O.; Bayrak, T.; Jain, A. R.; König, T. A. F.; Erbe, A.; Seidel, R.

Advances in DNA nanotechnology allow to design and fabricate highly complex DNA structures, which uses specific programmable interactions between smaller nucleic acid building blocks. To convey this concept to the fabrication of metallic nanoparticles, an assembly platform was developed based on a few basic DNA structures that can serve as molds. Programming specific interactions between these elements allowed the assembly of mold superstructures with a range of different geometries. Subsequent seeded growth of gold within the mold cavities enabled the synthesis of complex metal structures including tightly DNA-caged particles, rolling pin- and dumbbell-shaped particles as well as T-shaped and loop particles with high continuity. The method further supports the formation of higher-order assemblies of the obtained metal geometries. Based on electrical and optical characterizations, we expect that the developed platform is a valuable tool for a self-assembly-based fabrication of nanoelectronic and nanooptic devices.

Keywords: Gold nanoparticles; DNA origami; DNA templating; Shape programming; Seeded growth

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Permalink: https://www.hzdr.de/publications/Publ-32362
Publ.-Id: 32362


Terahertz signatures of ultrafast Dirac fermion relaxation at the surface of topological insulators

Kovalev, S.; Tielrooij, K.-J.; Deinert, J.-C.; Ilyakov, I.; Awari, N.; Chen, M.; Ponomaryov, O.; Bawatna, M.; de Oliveira, T.; Eng, L. M.; Kuznetsov, K. A.; Safronenkov, D. A.; Kitaeva, G. K.; Kuznetsov, P. I.; Hafez, H. A.; Turchinovich, D.; Gensch, M.

Topologically-protected surface states present rich physics and promising
spintronic, optoelectronic and photonic applications that require a proper
understanding of their ultrafast carrier dynamics. Here, we investigate
these dynamics in topological insulators (TIs) of the bismuth and antimony
chalcogenide family, where we isolate the response of Dirac fermions at the
surface from the response of bulk carriers by combining photoexcitation
with below-bandgap terahertz (THz) photons with TI samples with vary-
ing Fermi level, including one sample with the Fermi level located within
the bandgap. We identify distinctly faster relaxation of charge carriers
in the topologically-protected Dirac surface states (few hundred femtosec-
onds), compared to bulk carriers (few picoseconds). In agreement with
such fast cooling dynamics, we observe THz harmonic generation without
any saturation effects for increasing incident fields, unlike graphene which
exhibits strong saturation. This opens up promising avenues for increased
THz nonlinear conversion effciencies, and high-bandwidth optoelectronic
and spintronic information and communication applications.

Keywords: Terahertz; Ultrafast; Harmonic Generation; Topological Insulators; Surface Science; Dirac Material

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Permalink: https://www.hzdr.de/publications/Publ-32361
Publ.-Id: 32361


Preparation of calix[4]arenes for chelation of selected divalent cations

Blumberg, M.; Al-Ameed, K.; Eiselt, E.; Luber, S.; Mamat, C.

Two sets of calix[4]arenes either with a 1,3-crown ether bridge or with an open-chained oligo ether moiety in 1,3-position were prepared and further functionalized with additional deprotonizable sulfonamide groups to form chelating systems for selected cations Sr2+, Ba2+, and Pb2+. To improve the complexation behaviour towards these cations, calix[4]arenes with oligo ether groups and modified crowns in different size were synthesized. Association constants were determined by UV/Vis titration in acetonitrile using the respective perchlorate salts and logK values between 3.2 and 8.0 were obtained. These findings were supported by the calculation of the binding energy exemplarily for Ba2+.

Keywords: Barium; Calix[4]arene; complexation; Radium

Permalink: https://www.hzdr.de/publications/Publ-32360
Publ.-Id: 32360


Compositional modelling of element cycling in soil and plants - a case study from Northern Finland

Pospiech, S.; van den Boogaart, K. G.; Tolosana Delgado, R.; Sarala, P.; Kinnunen, J.; Middleton, M.

Modelling element enrichment into upper soil and uptake from soil to the plant organs in natural systems is challenged by the complexity due to mutual interaction of numerous processes and parameters. These parameters include the elemental composition of the sources like different soil horizons or underlying bedrock, varying availabilities of ions, redox conditions in the rhizosphere, and the characteristics of the plant species and their reaction to environmental changes like weather and climate. In this study, we present statistical models based on the principles of compositional data analysis (CoDa-principle) to decipher in a multi-variate and multi-parameter data set the major factors for element cycling between soil and plants.

The test site is located in an natural boreal forest area in Northern Finland and covers an area of ca. 4 km2. A stratified random sampling approach had been used to determine 90 sampling locations. For each location, soil samples of B-horizon and Ah-horizon and plant samples of Common Juniper, Norway Spruce and Scots Pine had been collected. The B-horizon samples had been analysed with XRF methods, Aqua regia and Ionic Leach. The Ah-horizon samples had been analysed by modified Aqua regia and Sodium pyrophosphate leach. Additionally, for each sampling location the soil conductivity, soil dielectric permittivity and pH had been measured. For the plants, the subsamples of twigs, needles and barks had been separately analysed. The elemental composition of all data sets is given as concentration values.
Because the concentrations are by definition constraint data and the uptake of one element often depends on concentration of other elements, the data analysis is performed on log-ratios scores of the elements instead of concentration values to avoid spurious effects in the data analysis. Three different statistical models had been defined: Specific, plant controlled uptake, regulated uptake and unspecific, source controlled uptake. These uptake models can be represented by compositional (Aitchison-space) linear models. It is shown, how this approach can be used to model the influence of elemental composition of sources, the availability of elements in aqueous solutions and the influence of pH and conductivity on the uptake in the various plant organs.

Keywords: compositional data; geochemistry; plant-soil uptake; exploration

  • Open Access Logo Lecture (Conference) (Online presentation)
    Goldschmidt2021, 04.-09.07.2021, Virtual, France
    DOI: 10.7185/gold2021.6037

Permalink: https://www.hzdr.de/publications/Publ-32358
Publ.-Id: 32358


Sub-grid scale modelling and a-posteriori tests with a morphology adaptive multifield two-fluid model considering rising gas bubbles

Meller, R.; Schlegel, F.; Klein, M.

The predictive simulation of gas-liquid multiphase flows at industrial scales reveals the challenging task to consider turbulence and interfacial structures, which span a large range of length scales. For simulation of relevant applications, a hybrid model can be utilised, which combines the Euler-Euler model for the description of small interfacial structures with a Volume-of-Fluid model as a scale-resolving multiphase approach. Such a hybrid model needs to be able to simulate interfaces, which are hardly resolved on a coarse numerical grid. The goal of this work is to improve the prediction of interfacial gas-liquid flows on a numerical grid with comparably large grid spacing. From the low-pass filtering of the two-fluid model five unclosed sub-grid scale terms arise. The convective and the surface tension part of the aforementioned contributions are individually modelled with multiple closure formulations. Those models are a-posteriori assessed in cases of two- and three-dimensional gas bubbles rising in stagnant liquid. It is demonstrated, that predictions on interfacial flows on coarse numerical grids can be improved.

Keywords: Large Eddy Simulation; Multiphase Flow; Sub-grid scale modelling; Multifield two-fluid model; Hybrid model

Permalink: https://www.hzdr.de/publications/Publ-32356
Publ.-Id: 32356


Using perfusion contrast for spatial normalization of ASL MRI images in a pediatric craniosynostosis population

de Planque, C. A.; Mutsaerts, H. J. M. M.; Keil, V. C. W.; Erler, N. S.; Dremmen, M. H. G.; Mathijssen, I. M. J.; 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 brain scans. However, structural segmentation and/or registration to standard space is complicated when gray-white matter contrast in structural images is low due to on-going myelination in newborns and infants. This problem is particularly of clinical relevance for imaging infants with inborn or acquired disorders that impair normal brain development. We investigated if the ASL MRI perfusion contrast is a viable alternative for spatial normalization. Four registration approaches have been compared: 1) using the structural image contrast, or perfusion contrast with 2) rigid, 3) affine, and 4) non-linear transformations - in 16 healthy controls (median age 0.83 years, IQR ± 0.56) and 36 trigonocephaly patients (median age 0.50 years, IQR ± 0.30) - a non-syndromic type of craniosynostosis. Registration performance was compared quantitatively using the Tanimoto coefficient (TC), visually by three blinded readers, and eventually by the impact on regional CBF values. For both patients and controls, non-linear registration using perfusion contrast showed the highest TC, a 17.51 (CI 6.66-49.38) times more likely to have a higher rating, and 17.45-18.88 mL/100g/min higher CBF compared to the standard registration. Using perfusion based contrast improved spatial registration compared to the use of structural images, significantly affected the regional CBF, and may open up new possibilities for future large pediatric ASL brain studies.

Permalink: https://www.hzdr.de/publications/Publ-32355
Publ.-Id: 32355


Experimental studies on bubble aspect ratio and corresponding correlations under bubble swarm condition

Liu, L.; Zhang, H.; Yan, H.; Ziegenhein, T.; Heßenkemper, H.; Zhou, P.; Lucas, D.

The bubble shape affects the gas-liquid interface momentum, heat and mass transfer, as well as the flow field around the bubble. Correctly predicting the bubble shape is challenging but indispensable under bubble swarm conditions. In this work, the bubble aspect ratio, which is adopted for the characterization of the bubble shape, is obtained through high-speed photography combined with an image processing algorithm from several experiments with an oscillating bubble plume. The results show that the bubble aspect ratio tends to be a constant value with increasing the bubble diameter, rather than decreasing as predicted by various empirical correlations developed in single bubble experiments. None of the available empirical correlations can accurately correlate the bubble aspect ratio with Weber number or Tadaki number. Among the available correlations in literature, Eo based correlation proposed by Besagni and Inzoli (2016) and Eo-Re based correlation proposed by Besagni and Deen (2019) show a better performance. The predicted values of Eo-Re based correlation developed in this work are the closest to the experimental data compared with others.

Keywords: bubble shape; bubble aspect ratio; bubble swarm; dimensionless number; emperical correlation

Permalink: https://www.hzdr.de/publications/Publ-32354
Publ.-Id: 32354


ASTRID-DYN3D

Fridman, Emil

ASTRID-DYN3D: XS generation and full core simulations

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Permalink: https://www.hzdr.de/publications/Publ-32353
Publ.-Id: 32353


International Standardization of Basic Industrial Radiotracer and Radiation Applications

Jentsch, T.; Thereska, J.; Brisset, P.; Jin, J.-H.

The International Atomic Energy Agency (IAEA) in cooperation with the International Society for Tracer and Radiation Applications (ISTRA) promotes the international standardization of basic industrial radiotracer and radiation applications. On behalf of IAEA and ISTRA experts from many countries employed in leading research centers and renowned industrial companies analyze existing international standards regarding the necessity of their update or amendment as well as the need for new standards in this field.
In June 2020 a new international standard on “Non-destructive testing - Gamma ray scanning method on process columns” was published as ISO 23159. About three years ago, the experts detected the need to standardize this method meanwhile widely used in petrochemical and chemical process plants as a possibility to check the interior and to locate the cause of malfunction in tray and packed bed columns to avoid basic errors at the application of this method.
In the field of flow rate measurements of fluids in conduits using radioactive tracers several international standards are known:
 Measurement of water flow in closed conduits (ISO 2975)
 Measurement of gas flow in conduits (ISO 4053)
 Measurement of liquid flow in open channels (ISO 9555).
All three standards describe more or less the same measuring methods. Therefore, there is no reason to maintain three independent standards on similar subjects. To bundle the existing diversity experts proposed a new international standard on “Measurement of Fluid Flow Rate in Closed Conduits – Radioactive Tracer Methods” which is under development just now. As soon as finalized, this standard will be published as ISO 24460.
The experts are planning further international standards using radioactive tracer methods for the near future. One of them will deal with leak testing in pressured vessels and underground pipelines, another one will be on determination of concentration or density of suspended and deposited sediment in water bodies by radiometric methods. For the last one, the working draft is already prepared, submitted to the responsible ISO Technical Committee 113 and got the number 6640.
ISO standards are part of accreditation of radiotracer and radiation applications groups, facilitating the promotion and implementation of these competitive technologies in national, regional and international scale.

Keywords: ISO; International standards; Radiotracer; Industrial Application; Gamma Column Scanning; Flow Rate Measurement; Leak Testing

  • Lecture (Conference)
    Tenth International Conference on Radiation in Various Fields of Research, 13.-17.06.2022, Herceg Novi, Montenegro

Permalink: https://www.hzdr.de/publications/Publ-32352
Publ.-Id: 32352


Semimetallic square-octagon two-dimensional polymer with high mobility

Liu, T.-J.; Springer, M.; Heinsdorf, N.; Kuc, A. B.; Valenti, R.; Heine, T.

The electronic properties of π -conjugated two-dimensional (2D) polymers near the Fermi level are determined by structural topology and chemical composition. Thus tight-binding (TB) calculations of the corresponding fundamental network can be used to explore the parameter space to find configurations with intriguing properties before designing the atomistic 2D polymer network. The vertex-transitive fes lattice, which is also called a square-octagon, 4-8, or 4.82<\sup> lattice, is rich in interesting topological features including Dirac points and flat bands. Herein, we study its electronic and topological properties within the TB framework using representative parameters for chemical systems. Secondly, we demonstrate that the rational implementation of band structure features obtained from TB calculations in 2D polymers is feasible with a family of 2D polymers possessing fes structure. A one-to-one band structure correspondence between the fundamental network and 2D polymers is found. Moreover, changing the relative length of linkers connecting the triangulene units in the 2D polymers reflects tuning of hopping parameters in the TB model. These perturbations allow sizable local band gaps to open at various positions in the Brillouin zone. From analysis of the Berry curvature flux, none of the polymers exhibits a large topologically nontrivial band gap. However, we find a particular configuration of semimetallic characteristics with separate electron and hole pockets, which possess very low effective masses
both for electrons (as small as m∗<\sup> e<\sub> = 0.05) and for holes (as small as m∗<\sup> h<\sub> = 0.01).

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Permalink: https://www.hzdr.de/publications/Publ-32351
Publ.-Id: 32351


Spatially resolved Eu(III) environments by chemical microscopy

Drobot, B.

Archiv of research data for the manuscript

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Permalink: https://www.hzdr.de/publications/Publ-32350
Publ.-Id: 32350


Spatially resolved Eu(III) environments by chemical microscopy

Vogel, M.; Steudtner, R.; Fankhänel, T.; Raff, J.; Drobot, B.

Chemical microscopy combines high-resolution emission spectra with Abbe-limited spatial resolution and is used for studies of inhomogeneous samples at the nanoscale. The spatial distinction of multiple Eu(III) coordination sites allows for a comprehensive understanding of environmental samples and highlights the applicability of Eu(III) as molecular probe in medicine and biology

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Permalink: https://www.hzdr.de/publications/Publ-32349
Publ.-Id: 32349


Microfocus X-ray Computed Tomography of a Plastic Toy ("HIPPO"): Projection Data

Boden, S.

Raw and preprocessed projection data from a microfocus X-ray CT of a plastic toy ("HIPPO"). To be used as demo dataset for the PARIS reconstruction framework.

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Permalink: https://www.hzdr.de/publications/Publ-32348
Publ.-Id: 32348


Cytoplasmic localization of prostate-specific membrane antigen inhibitors may confer advantages for targeted cancer therapies.

Matthias, J.; Engelhardt, J.; Schäfer, M.; Bauder-Wüst, U.; Meyer, P.; Haberkorn, U.; Eder, M.; Kopka, K.; Hell, S.; Eder, A.

Targeted imaging and therapy approaches based on novel prostate-specific membrane antigen (PSMA) inhibitors have fundamentally changed the treatment regimen of prostate cancer. However, the exact mechanism of PSMA inhibitor internalization has not yet been studied, and the inhibitors' subcellular fate remains elusive. Here we investigated the intracellular distribution of peptidomimetic PSMA inhibitors and of PSMA itself by stimulated emission depletion (STED) nanoscopy, applying a novel non-standard live cell staining protocol. Imaging analysis confirmed PSMA cluster formation at the cell surface of prostate cancer cells and clathrin-dependent endocytosis of PSMA inhibitors. Following the endosomal pathway, PSMA inhibitors accumulated in prostate cancer cells at clinically relevant time points. In contrast to PSMA itself, PSMA inhibitors were found to eventually distribute homogeneously in the cytoplasm, a molecular condition that promises benefits for treatment as cytoplasmic and in particular perinuclear enrichment of the radionuclide carriers may better facilitate the radiation-mediated damage of cancerous cells. This study is the first to reveal the subcellular fate of PSMA/PSMA inhibitor complexes at the nanoscale and aims to inspire the development of new approaches in the field of prostate cancer research, diagnostics, and therapeutics.

Keywords: Prostate Cancer; Prostate-Specific Membrane Antigen; Dual-Labeled PSMA Inhibitors; Stimulated Emission Depletion Nanoscopy; Theranostics

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Permalink: https://www.hzdr.de/publications/Publ-32347
Publ.-Id: 32347


Emerging radionuclides in a regulatory framework for medicinal products – how do they fit?

Decristoforo, C.; Neels, O.; Patt, M.

Recent years have seen the establishment of several radionuclides as medicinal products in particular in the setting of theranostics and PET. [177Lu]Lutetium Chloride or [64Cu]Copper Chloride have received marketing authorization as radionuclide precursor [68Ga]Gallium Chloride has received regulatory approval in the form of different 68Ge/68Ga generators. This is a formal requirement by the EU directive 2001/83, even though for some of these radionuclide precursors no licensed kit is available that can be combined to obtain a final radiopharmaceuticals, as it is the case for Technetium-99m. In view of several highly promising, especially metallic radionuclides for theranostic applications in a wider sense, the strict regulatory environment poses the risk of slowing down development, in particular for radionuclide producers that want to provide innovative radionuclide for clinical research purposes, which is the basis for their further establishment. In this position paper we address the regulatory framework for novel radionuclides within the EU, the current challenges in particular related to clinical translation and potential options to support translational development within Europe and worldwide.

Keywords: Radionuclides; Regulatory; Medicinal Product; Directive 2001/83; Radionuclide Precursor; Theranostics; European Pharmacopoeia

Permalink: https://www.hzdr.de/publications/Publ-32346
Publ.-Id: 32346


Controlled Generation of Luminescent Centers in Hexagonal Boron Nitride by Irradiation Engineering

Fischer, M.; Caridad, J. M.; Sajid, A.; Ghaderzadeh, S.; Ghorbani Asl, M.; Gammelgaard, L.; Bøggild, P.; Thygesen, K. S.; Krasheninnikov, A.; Xiao, S.; Wubs, M.; Stenger, N.

Luminescent centres in the two-dimensional material hexagonal boron nitride have the potential to enable quantum applications at room temperature. In order to be utilized for applications it is crucial to generate these centres in a controlled manner and to identify their microscopic nature. Here we present a novel method inspired by irradiation engineering with oxygen atoms. We explore systematically the influence of the kinetic energy and the irradiation fluence on the generation of luminescent centres. We find modifications of their density for both parameters while a five-fold enhancement is observed with increasing fluence. Molecular dynamics simulations clarify the generation mechanism of these centres and their microscopic nature. We infer that V_N C_B and V_B are the most likely centres formed. Ab initio calculations of their optical properties show excellent agreement with our experiments. Our methodology generates quantum emitters in a controlled manner and provides new insights into their microscopic nature.

Keywords: two-dimensional materials; hexagonal boron nitride; defect engineering; ion irradiation; luminescent centre; quantum emitter

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Permalink: https://www.hzdr.de/publications/Publ-32345
Publ.-Id: 32345


Fractional Quantum Conductance Plateaus in Mosaic-Like Conductors and Their Similarities to the Fractional Quantum Hall Effect

Kisslinger, F.; Rienmüller, D.; Ott, C.; Kampert, W. A. G.; Weber, H. K.

A simple route to generate magnetotransport data is reported that results in fractional quantum Hall plateaus in the conductance without invoking strongly correlated physics. Ingredients to the generating model are conducting tiles with integer quantum Hall effect and metallic linkers, further irchhoff rules. When connecting few identical tiles in a mosaic, fractional steps occur in the conductance values. Richer spectra representing several fractions occur when the tiles are parametrically varied. Parts of the simulation data are supported with purposefully designed graphene mosaics in high magnetic fields. The findings emphasize that the occurrence of fractional conductance values, in particular in two-terminal measurements, does not necessarily indicate interaction-driven physics. The importance of an independent determination of charge densities is underscored and similarities with and differences to the fractional quantum Hall effect are critically discussed.

Permalink: https://www.hzdr.de/publications/Publ-32344
Publ.-Id: 32344


Magnetic anisotropy and spin dynamics in the kagome magnet Fe4Si2Sn7O16: NMR and magnetic susceptibility study on oriented powder

Dengre, S.; Sarkar, R.; Opherden, L.; Herrmannsdörfer, T.; Allison, M.; Söhnel, T.; Ling, C. D.; Gardner, J. S.; Klauss, H.-H.

Fe4Si2Sn7O16 hosts an undistorted kagome lattice of Fe2+ (3d6, S = 2) ions. We present results of bulk magnetization and Sn nuclear magnetic resonance (NMR) measurements on an oriented Fe4Si2Sn7O16 powder sample oriented in geometries parallel (II) and perpendicular (⊥) to the external applied magnetic field used for orienting the powder (Bori). The bulk susceptibility χ shows a broad peak at TN ∼ 3 K associated with antiferromagnetic ordering. NMR spectra indicate the presence of planar anisotropy in the kagome planes. From an analysis of the static NMR shift (K) and dynamic spin-lattice relaxation rate (1/T1) we conclude the presence of dominant magnetic fluctuations in the kagome planes. For the II orientation, K scales linearly with the bulk susceptibility for temperatures down to ∼4 K, while in the ⊥ orientation K starts to deviate strongly below T ∼ 30 K. We associate this deviation with the onset of spin-tilting towards the kagome planes. These correlations are also reflected in the 1/T1 data for the II orientation, which starts to decrease below T ∼ 30 K. In this correlated regime, TN < T < ∼30 K, we discuss the formation of positive chiral spin correlations in the kagome planes.

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Permalink: https://www.hzdr.de/publications/Publ-32343
Publ.-Id: 32343


Robustness of the remanent magnetic domain pattern formation and associated stripe-bubble transitions in Co/Pt multilayers against field sequencing

Gentillon, A.; Richards, C.; Ortiz-Flores, L. A.; Metzner, J.; Montealegre, D.; Healey, M.; Cardon, K.; Westover, A.; Hellwig, O.; Chesnel, K.

Thin ferromagnetic [Co/Pt] multilayers with perpendicular magnetic anisotropy exhibit a variety of nanoscopic magnetic domain patternsat remanence, from long interlaced stripes to lattices of bubbles, depending on the multilayer structure but also on the magnetic historyof the sample. For optimized structural parameters, stripe-bubble transitions accompanied by drastic increases in domain density havebeen observed when the magnitude of the previously applied perpendicular fieldHmis finely tuned throughout the hysteresis loop. Here, we investigate the robustness of these morphological transitions against field sequencing and field cycling. We conducted this study on[Co(x)/Pt(7Å)]N=50where x varies from 4 to 60 Å. We mapped the morphological transition withHmvarying from 0 to 9 T, following bothan ascending sequence (0→9 T) and a descending sequence (9 T→0). We found that the optimal fieldHm=H∗at which the domain densityis maximized and its associated maximal density n∗ are not significantly affected by the field sequencing direction. We have also investigatedpossible pumping effects when cycling the applied field at the value H∗. We found that n∗ remains relatively stable through field cycling, andmuch more stable in the bubble state, compared to longer stripe states. The observed robustness of these morphological transitions againstfield sequencing and field cycling is of crucial importance for potential magnetic recording applications.

Permalink: https://www.hzdr.de/publications/Publ-32342
Publ.-Id: 32342


Magnetic and structural dimer networks in layered K2Ni(MoO4)2

Murugan, G. S.; Ramesh Babu, K.; Sankar, R.; Chen, W. T.; Panneer Muthuselvam, I.; Chattopadhyay, S.; Choi, K.-Y.

The magnetic and thermodynamic properties of layered single-crystal K2Ni(MoO4)2 having both structural and magnetic dimers have been investigated. The crystal structure of K2Ni(MoO4)2 is composed of edge-sharing NiO6-octahedral pairs bridged by the MoO4 2− polyatomic ion groups in a plane, and the K+ ions sit in the van der Waals gap between the layers. The temperature dependence of magnetic susceptibility shows a spin-singlet ground state with an activation gap of Δ/kB ≈ 38 K. A high-field magnetization study at T = 1.5 K exhibits a half-magnetization plateau at μ0H ∼ 25 T, corresponding to a level crossing of the singlet ground state with the lowest triplet state. Further, we have performed density functional theory calculations to determine magnetic exchange interactions. The nearest-neighbor coupling constant J1 ∼ 10 K between the Ni spins turns out to be an order of magnitude larger than all interdimer couplings. Our experimental and theoretical results suggest that K2Ni(MoO4)2 constitutes a nearly isolated two-dimensional S = 1 dimer model.

Permalink: https://www.hzdr.de/publications/Publ-32341
Publ.-Id: 32341


Experimental evidence for Zeeman spin–orbit coupling in layered antiferromagnetic conductors

Ramazashvili, R.; Grigoriev, P. D.; Helm, T.; Kollmannsberger, F.; Kunz, M.; Biberacher, W.; Kampert, W. A. G.; Fujiwara, H.; Erb, A.; Wosnitza, J.; Gross, R.; Kartsovnik, M. V.

Most of solid-state spin physics arising from spin–orbit coupling, from fundamental phenomena to industrial applications, relies on symmetry-protected degeneracies. So does the Zeeman spin–orbit coupling, expected to manifest itself in a wide range of antiferromagnetic conductors. Yet, experimental proof of this phenomenon has been lacking. Here we demonstrate that the Néel state of the layered organic superconductor κ-(BETS)2FeBr4 shows no spin modulation of the Shubnikov–de Haas oscillations, contrary to its paramagnetic state. This is unambiguous evidence for the spin degeneracy of Landau levels, a direct manifestation of the Zeeman spin–orbit coupling. Likewise, we show that spin modulation is absent in electron-doped Nd1.85Ce0.15CuO4, which evidences the presence of Néel order in this cuprate superconductor even at optimal doping. Obtained on two very different materials, our results demonstrate the generic character of the Zeeman spin–orbit coupling.

Permalink: https://www.hzdr.de/publications/Publ-32340
Publ.-Id: 32340


Intense Positron Sources driven by a Superconducting Electron LINAC

Wagner, A.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Liedke, M. O.; Krause-Rehberg, R.

The Helmholtz-Center Dresden-Rossendorf operates several user beamlines for materials research using positron annihilation energy and lifetime spectroscopy. The superconducting electron LINAC ELBE [1] drives a hard X-ray source which is used to generate positrons through pair production. The unique setup Gamma-induced Positron Source GiPS generates electron-positron pairs inside the sample under investigation directly [2] making it well suited for annihilation lifetime studies of materials which are not qualified for vacuum conditions or because they impose hazards or intrinsic radioactivity.
The high-intensity Mono-energetic Positron Source MePS utilizes moderated positrons with adjustable kinetic energies ranging from 500 eV to 18 keV [3] for depth profiling in thin films. A magnetic beam transport system consisting of a beam chopper, a beam buncher, and a post-accelerator guides the positron beam towards the sample under investigation. Full-digital data processing of positron annihilation lifetime events generates spectra nearly free from background and free from distortions with timing resolutions down to about 210 ps and count rates in excess of 120 kcps.
The MePS facility is currently complemented by an additional beamline named Apparatus for In-situ Defect Analysis, AIDA-II, where in-situ defect studies are to be performed in a wide temperature range during thin film growth and under ion irradiation. A complimentary but functionally similar setup, AIDA-I [4], is operated at a 22Na-based mono-energetic continuous positron beam [5] used for in-situ (coincidence) Doppler-broadening positron annihilation spectroscopy experiments.
All facilities serve as user facilities to the international scientific community. Recent developments at all beam lines and some exemplary experiments will be presented [6-8].

The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). The initial AIDA system was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox). The AIDA facility was funded through the Helmholtz Energy Materials Characterization Platform.

References
[1] F. Gabriel, et al., Nucl. Instr. Meth. B 161 (2000) 1143.
[2] M. Butterling, et al., Nucl. Instr. Meth. B 269 (2011) 2623.
[3] A. Wagner, et al., AIP Conference Proceedings 1970 (2018) 040003.
[4] M. O. Liedke, et al., Journal of Applied Physics 117 (2015) 163908.
[5] W. Anwand, et al., Defect and Diffusion Forum Vl. 331 (2012) 25.
[6] M. Reiner, et al., Scientific Reports 6 (2016) 29109.
[7] A. Quintana, et al., ACS Nano 12 (2018) 10291.
[8] J. Ji, et al., Scientific Reports 6 (2016) 31238.

Keywords: positron annihilation lifetime spectroscopy ELBE MePS EPOS GiPS defects porosity

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Positron Studies of Defects, 01.-05.03.2021, Mumbai, India

Permalink: https://www.hzdr.de/publications/Publ-32339
Publ.-Id: 32339


Challenges on cyclic nucleotide phosphodiesterases imaging with positron emission tomography: Novel radioligands and (pre-)clinical insights since 2016

Schröder, S.; Scheunemann, M.; Wenzel, B.; Brust, P.

Cyclic nucleotide phosphodiesterases (PDEs) represent one of the key targets in the research field of intracellular signaling related to the second messenger molecules cyclic adenosine monophosphate (cAMP) and/or cyclic guanosine monophosphate (cGMP). Hence, non-invasive imaging of this enzyme class by positron emission tomography (PET) using appropriate isoform-selective PDE radioligands is gaining importance. This methodology enables the in vivo diagnosis and staging of numerous diseases associated with altered PDE density or activity in the periphery and the central nervous system as well as the translational evaluation of novel PDE inhibitors as therapeutics. In this follow-up review, we summarize the efforts in the development of novel PDE radioligands and highlight (pre-)clinical insights from PET studies using already known PDE radioligands since 2016.

Keywords: positron emission tomography; cyclic nucleotide phosphodiesterases; PDE inhibitors; PDE radioligands; radiochemistry; imaging; recent (pre-)clinical insights

Permalink: https://www.hzdr.de/publications/Publ-32338
Publ.-Id: 32338


CTF and FLOCAL Thermal Hydraulics Validations and Verifications within a Multiscale and Multiphysics Software Development

Davies, S.; Rohde, U.; Litskevich, D.; Merk, B.; Bryce, P.; Levers, A.; Detkina, A.; Atkinson, S.; Ravindra, V.

Simulation codes allow to reduce the high conservativism in nuclear reactor design improving the reliability and sustainability associated to nuclear power. Full core coupled reactor physics at the rod level are not provided by most simulation codes. This has led in the UK to the development of a multiscale and multiphysics software development focused on LWRS. In terms of the thermal hydraulics, simulation codes suitable for this multiscale and multiphysics software development include the subchannel code CTF and the thermal hydraulics module FLOCAL of the nodal code DYN3D. In this journal article, CTF and FLOCAL thermal hydraulics validations and verifications within the multiscale and multiphysics software development have been performed to evaluate the accuracy and methodology available to obtain thermal hydraulics at the rod level in both simulation codes. These validations and verifications have proved that CTF is a highly accurate sub-channel code for thermal hydraulics. Also, these verifications have proved that CTF provides a wide range of crossflow and turbulent mixing methods while FLOCAL provides in general the simplified no crossflow method as the rest of the methods were only tested during its implementation into DYN3D.

Keywords: Nuclear Reactor; Thermal Hydraulics; Simulation; Subchannel Code; CTF; FLOCAL; PSBT

Permalink: https://www.hzdr.de/publications/Publ-32337
Publ.-Id: 32337


Effect of deposition current density on the Co–Ni/SiO2 alloy composite coatings Using Scanning Jet Electrodeposition

Jiang, W.; Qiu, M.; Shen, L.; Lou, G.; Yang, X.; Eckert, K.; Tian, Z.

Co–Ni/SiO2 alloy composite coatings were electrodeposited on copper substrate by scanning jet electrodeposition at various current densities to study its effect on the deposite morphologies, texture orientation, microhardness, adhesion force, wear resistance and corrosion resistance of Co–Ni/SiO2 alloy composite coatings. The structure and performance of the material were characterized using scanning electron microscope, XRD diffractometer, nanoindentation, scratch tester, friction and wear tester and electrochemical methods. The morphologies of the Co–Ni/SiO2 alloy composite coatings changed from sparse and slender structures to dense starfish structures with an increase in current density. A part of Co precipitated in the form of a face-centered cubic structure and formed a solid solution with Ni, while another part of Co precipitated in the structure of the composite coating in the form of a hexagonal close-packed structure. The Co–Ni/SiO2 alloy composite coating exhibited excellent adhesion force, wear resistance and corrosion resistance when the deposition current density was 130 A/dm2. Once the current density was exceeded, some microcracks appeared on the surface of the composite coating, after which the adhesion force and corrosion resistance decreased. The present study suggests that current density at 130 A/dm2 is more suitable than low current density for jet electrodeposition to prepare high-density and high-quality composite coating.

Keywords: Co–Ni/SiO2; Scanning jet electrodeposition; Deposition current density

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Permalink: https://www.hzdr.de/publications/Publ-32336
Publ.-Id: 32336


Treatment verification with prompt-gamma-imaging: Detection of anatomical changes in prostate-cancer proton therapy

Berthold, J.; Piplack, N.; Traneus, E.; Pietsch, J.; Khamfongkhruea, C.; Thiele, J.; Hölscher, T.; Janssens, G.; Smeets, J.; Stützer, K.; Richter, C.

Introduction
We present results of the worldwide first systematic study on the sensitivity of prompt-gamma-imaging (PGI) to detect anatomical changes in proton therapy for the ongoing evaluation in prostate-cancer treatments.

Materials&Methods
Spot-wise range shifts were monitored with a PGI-slit-camera during 40 fractions of hypo-fractionated prostate-cancer treatments (5 patients, 2 fields, each 1.5GyE). In-room CTs were acquired for these fractions and range shifts of spot-wise integrated depth-dose (IDD) profiles serve as ground-truth. For both PGI and IDD data, spots were clustered based on Bragg-peak position and proton number to mitigate statistical uncertainty in the PGI measurement using a low-dose spot cut-off at 5e7 protons, a minimum number of 3e9 protons per cluster, and a minimum/maximum cluster volume of 1cm3/8cm3. Clusters with absolute range shift ≥5mm were classified as relevant anatomical changes.

Results
A strong correlation (rPearson=0.72) was found between ground-truth IDD and PGI range shifts per cluster with an average absolute deviation of 1.3mm over all fractions. In total, 245/7143 (3.4%) clusters (found within 24/72 fields) contained relevant IDD-based range shifts. PGI detected these changes with a sensitivity of 68%, specificity of 96%, and accuracy of 95%. The results might be affected by potential intra-fractional changes between in-room CT acquisition and treatment delivery. A higher sensitivity is also expected for a gantry-mounted camera system with decreased positioning uncertainty.

Conclusion
Our systematic investigation on the sensitivity of a PGI-slit-camera with a first quantitative comparison of range shifts from PGI and IDD profiles demonstrates the capability to locally detect relevant anatomical changes in patients.

  • Lecture (Conference) (Online presentation)
    59th annual conference of the particle therapy co-operative group (PTCOG), 04.-07.06.2021, online, online
  • Open Access Logo Abstract in refereed journal
    International Journal of Particle Therapy (2022)
    DOI: 10.14338/IJPT-22-PTCOG59-9.3

Permalink: https://www.hzdr.de/publications/Publ-32335
Publ.-Id: 32335


First-In-Human Validation of CT-Based Proton Range Prediction Using Prompt Gamma Imaging in Prostate Cancer Treatments

Berthold, J.; Khamfongkhruea, C.; Petzoldt, J.; Thiele, J.; Hölscher, T.; Wohlfahrt, P.; Peters, N.; Jost, A.; Hofmann, C.; Janssens, G.; Smeets, J.; Richter, C.

Purpose
Uncertainty in computed tomography (CT)-based range prediction substantially impairs the accuracy of proton therapy. Direct determination of the stopping-power ratio (SPR) from dual-energy CT (DECT) has been proposed (DirectSPR), and initial validation studies in phantoms and biological tissues have proven a high accuracy. However, a thorough validation of range prediction in patients has not yet been achieved by any means. Here, we present the first systematic validation of CT-based proton range prediction in patients using prompt gamma imaging (PGI).

Methods and Materials
A PGI slit camera system with improved positioning accuracy, using a floor-based docking station, was used. Its overall uncertainty for range prediction validation was determined experimentally with both x-ray and beam measurements. The accuracy of range prediction in patients was determined from clinical PGI measurements during hypofractionated treatment of 5 patients with prostate cancer - in total 30 fractions with in-room control-CTs. For each pencil-beam-scanning spot, the range shift was obtained by comparing the PGI measurement to a control-CT-based PGI simulation. Three different SPR prediction approaches were applied in simulations: a standard CT-number-to-SPR conversion (Hounsfield look-up table [HLUT]), an adapted HLUT (DECT optimized), and DirectSPR. The spot-wise weighted mean range shift from all spots served as a measure for the accuracy of the respective range prediction approach.

Results
A mean range prediction accuracy of 0.0% ± 0.5%, 0.3% ± 0.4%, and 1.8% ± 0.4% was obtained for DirectSPR, adapted HLUT, and standard HLUT, respectively. The overall validation uncertainty of the second-generation PGI slit camera is about 1 mm (2σ) for all approaches, which is smaller than the range prediction uncertainty for deep-seated tumors.

Conclusions
For the first time, range prediction accuracy was assessed in clinical routine using PGI range verification in prostate cancer treatments. Both DECT–derived range prediction approaches agree well with the measured proton range from PGI verification, whereas the standard HLUT approach differs relevantly. These results endorse the recent reduction of clinical safety margins in DirectSPR-based treatment planning in our institution.

Keywords: proton therapy; range verification; prompt gamma imaging; SPR prediction; DECT

Permalink: https://www.hzdr.de/publications/Publ-32334
Publ.-Id: 32334


Which is the best ⁹Be carrier for ¹⁰Be/⁹Be accelerator mass spectrometry?

Merchel, S.; Braucher, R.; Lachner, J.; Rugel, G.

Commercial ⁹Be solutionss used for chemical preparation of samples for accelerator mass spectrometry contain the cosmogenic long-lived radionuclide ¹⁰Be at elevated but different ¹⁰Be/⁹Be levels. Within a systematic study of recently produced solutions, comparison to published data and new data on customised solutions from minerals, we recommend - if no customised solution is available - the ⁹Be solutions from Australian Chemical Reagents (ACR) or from LGC. They contain ¹⁰Be/⁹Be at the 3.4 x 10-15 level, which is still suitable for the majority of Earth science applications, compared to customised solutions at the 10-16 level for lowest-level studies. Commercial solutions from Scharlab having different lot numbers, i.e. an identification number assigned to a particular lot of material from a single manufacturer, vary in ¹⁰Be/⁹Be by up to a factor of nine. Hence, it seems an advisable strategy to buy a bigger quantity of a single production batch (such as 10 x 100 ml bottles of ⁹BeBe at 1 g l-1) and have them tested once at any AMS facility before first use.

  • The best ⁹Be carrier for low-level ¹⁰Be/⁹Be applications is a customised one from minerals like phenakite.
  • The best ⁹Be carriers for medium- and high-level ¹⁰Be/⁹Be applications are currently from Australian Chemical Reagents (ACR) or from LGC.
  • As ⁹Be carriers from Scharlab of different batches (LOT) contain ¹⁰Be/⁹Be at different levels, it is advisable to buy a bigger number of bottles of the same LOT of commercial carriers after being identified to have reasonably low isotope ratios.

Keywords: AMS; phenakite; carrier; blank; beryl

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Permalink: https://www.hzdr.de/publications/Publ-32333
Publ.-Id: 32333


Proton range verification with prompt gamma-ray timing and on-line proton bunch monitoring

Permatasari, F.; Lutz, B.; Pausch, G.; Römer, K.; Schellhammer, S.; Wagner, A.; Werner, R.-D.; Weinberger, D.; Werner, T.; Kögler, T.

Range verification is an important prerequisite to unfold the full potential of the finite range of proton beams and to improve treatment precision. The prompt gamma-ray timing (PGT) technique offers a non-invasive approach for range verification using the measured time distribution of the prompt gamma rays produced in the patient. PGT dispenses with a heavy collimator and can be integrated into existing treatment gantries. However, the high sensitivity of this technique to any instabilities in the proton bunch periodicity is a major challenge and demands online monitoring of the proton bunch arrival time. Therefore, we have developed a proton bunch monitor (PBM) comprising fast-scintillating fibers with a double-sided silicon photomultiplier readout. Placing the PBM in the beam halo allows the direct measurement of the proton arrival time at clinical beam intensities while maintaining a processable trigger rate. In a proof-of-principle experiment with a thick acrylic glass target and defined cylindrical air cavities as well as tissue equivalent inserts, a direct monitoring of proton bunches was carried out together with a PGT measurement. With the use of the PBM, another important step towards the clinical translation of the PGT method was taken.

Keywords: proton therapy; treatment verification; radiation detector development

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  • Poster (Online presentation)
    59th Annual Conference of the Particle Therapy Co-operative Group, 04.-07.06.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-32332
Publ.-Id: 32332


Complexation of Cm(III) and Eu(III) with aqueous phosphates at elevated temperatures

Jordan, N.; Huittinen, N. M.; Jessat, I.; Réal, F.; Vallet, V.; Starke, S.; Eibl, M.

Thermodynamic databases are essential for the safety assessments of radioactive waste repositories. They have to be reliable, comprehensive, and describe the key mechanisms controlling the mobility of contaminants in the environment. However, in many cases these prerequisites are not fulfilled. An important example is the complexation of actinides and lanthanides with aqueous phosphates, for which this work provides complexation constants for spectroscopically identified species at 298K and at elevated temperature.
The complexation of Cm(III) and Eu(III) was studied at submicromolar concentrations by laser-induced luminescence spectroscopy as a function of total phosphate concentration (0-0.06 M ΣPO₄) in the temperature range of 298-363K, using NaClO₄ as a background electrolyte at –log[H⁺] ranging from 2.5 to 3.6. The formation of both CmH₂PO₄²⁺/EuH₂PO₄²⁺ and Cm(H₂PO₄)₂⁺/Eu(H₂PO₄)₂⁺ complexes was revealed, the latter being spectroscopically evidenced for the first time. Complexation constants were found to increase when raising the ionic strength from 0.5 to 3.0 M.
Temperature-dependent complexation constants for the identified species were derived and recalculated to standard conditions using the van´t Hoff equation and the Specific Ion Interaction Theory. Endothermic and entropy driven reactions were established for both Cm(III) and Eu(III) phosphate complexes.
In addition, relativistic quantum chemical investigations were performed to study the complexation strength of Cm(III) with aqueous phosphates, to provide insight into potential changes of the coordination number with increasing temperature and to probe the character of the Cm water and Cm phosphate bonds.

Keywords: curium; phosphate; complexation; temperature; luminescence spectroscopy; thermodynamics; ab initio

  • Lecture (Conference) (Online presentation)
    Goldschmidt2021, 04.-09.07.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-32331
Publ.-Id: 32331


Comparison of Elemental Analysis Techniques for the Characterization of Commercial Alloys

Seidel, P.; Ebert, D.; Schinke, R.; Möckel, R.; Raatz, S.; Chao, M.; Niederschlag, E.; Kreschel, T.; Gloaguen, R.; Renno, A.

Better quality control for alloy manufacturing and sorting of post-consumer scraps relies heavily on the accurate determination of their chemical composition. In recent decades, analytical tech-niques, such as X-ray fluorescence spectroscopy (XRF), laser-induced breakdown spectroscopy (LIBS), and spark optical emission spectroscopy (spark-OES), found widespread use in the metal industry, though only a few studies were published about the comparison of these techniques for commercially available alloys. Hence, we conducted a study on the evaluation of four analytical techniques (energy-dispersive XRF, wavelength-dispersive XRF, LIBS, and spark-OES) for the de-termination of metal sample composition. It focuses on the quantitative analysis of nine commer-cial alloys, representing the three most important alloy classes: copper, aluminum, and steel. First, spark-OES is proven to serve as a validation technique in the use of certified alloy reference sam-ples. Following an examination of the lateral homogeneity by XRF, the results of the techniques are compared, and reasons for deviations are discussed. Finally, a more general evaluation of each technique with its capabilities and limitations is given, taking operation-relevant parameters, such as measurement speed and calibration effort, into account. This study shall serve as a guide for the routine use of these methods in metal producing and recycling industries.

Permalink: https://www.hzdr.de/publications/Publ-32330
Publ.-Id: 32330


B20-MnSi films grown on Si(100) substrates with magnetic skyrmion signature

Li, Z.; Yuan, Y.; Hübner, R.; Begeza, V.; Rebohle, L.; Helm, M.; Nielsch, K.; Prucnal, S.; Zhou, S.

Magnetic skyrmions have been suggested as information carriers for future spintronic devices. As the first material with experimentally confirmed skyrmions, B20-type MnSi has the research focus for decades. Although B20-MnSi films have been successfully grown on Si(111) substrates, there is no report about B20-MnSi films on Si(100) substrates, which would be more preferred for practical applications. In this letter, we present the first preparation of B20-MnSi on Si(100) substrates. It is realized by sub-second solid-state reaction between Mn and Si via flash-lamp annealing at ambient pressure. The regrown layer shows an enhanced Curie temperature of 43 K compared with bulk B20-MnSi. The magnetic skyrmion signature is proved in our films by magnetic and transport measurements. The millisecond-range flash annealing provides a promising avenue for the fabrication of Si-based skyrmionic devices.

Keywords: Skyrmions; B20-MnSi; Flash-lamp annealing

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Permalink: https://www.hzdr.de/publications/Publ-32329
Publ.-Id: 32329


Defective Nanographenes Containing Seven-Five-Seven (7–5–7)-Membered Rings

Fei, Y.; Fu, Y.; Bai, X.; Du, L.; Li, Z.; Komber, H.; Low, K.-H.; Zhou, S.; Lee Phillips, D.; Feng, X.; Liu, J.

Defects have been observed in graphene and are expected to playa key role in its optical, electronic, and magnetic properties. However, becausemost of the studies focused on the structural characterization, the implications oftopological defects on the physicochemical properties of graphene remain poorlyunderstood. Here, we demonstrate a bottom-up synthesis of three novelnanographenes (1−3) with well-defined defects in which seven-five-seven (7−5−7)-membered rings were introduced to their sp2carbon frameworks. From theX-ray crystallographic analysis, compound1adopts a nearly planar structure.Compound2, with an additionalfive-membered ring compared to1, possesses aslightly saddle-shaped geometry. Compound3, which can be regarded as the“head-to-head”fusion of1with two bonds, features two saddles connectedtogether. The resultant defective nanographenes1−3were well-investigated byUV−vis absorption, cyclic voltammetry, and time-resolved absorption spectra and further corroborated by density functional theory(DFT) calculations. Detailed experimental and theoretical investigations elucidate that these three nanographenes1−3exhibit ananti-aromatic character in their ground states and display a high stability under ambient conditions, which contrast with the reportedunstable biradicaloid nanographenes that contain heptagons. Our work reported herein offers insights into the understanding ofstructure-related properties and enables the control of the electronic structures of expanded nanographenes with atomically precise defects.

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Permalink: https://www.hzdr.de/publications/Publ-32328
Publ.-Id: 32328


Effect of PAA-induced surface etching on the adhesion properties of ZnO nanostructured films

Meinderink, D.; Kielar, C.; Sobol, O.; Ruhm, L.; Rieker, F.; Nolkemper, K.; Orive, A. G.; Ozcan, O.; Grundmeier, G.

Zinc oxide - polymer interfaces are known to exhibit interesting properties regarding molecular adhesion. This work is aimed at the investigation of the effect of the morphology and surface chemistry on the macroscopic adhesion of a model epoxy-based adhesive to nanorod (ZnO NR) and nanocrystalline (ZnO NC) ZnO-modified surfaces. Both ZnO films have been prepared using hydrothermal synthesis on hot-dip galvanized steel (HDG) surfaces by varying the precursor chemistry in order to control the film morphology. Poly (acrylic acid) (PAA) was used to improve the interfacial adhesion by modifying the morphology and surface chemistry of ZnO nanostructured films. The strong interaction of PAA from a dilute and neutral aqueous solution with the ZnO nanocrystallites was shown to significantly improve the interfacial adhesion by means of a nanoetching process. It was shown that the wet peel-forces correlate well with the considered morphology and surface chemistry.

Keywords: ZnO nanorods; Nanocrystalline ZnO films; Adhesion by mechanical interlocking; Poly(acrylic acid); Morphology control; Interfacial stability

Permalink: https://www.hzdr.de/publications/Publ-32327
Publ.-Id: 32327


Convergent Synthesis of Diversified Reversible Network Leads to Liquid Metal-Containing Conductive Hydrogel Adhesives

Xu, Y.; Rothe, R.; Voigt, D.; Hauser, S.; Cui, M.; Miyagawa, T.; Patino Gaillez, M.; Kurth, T.; Bornhäuser, M.; Pietzsch, J.; Zhang, X.

Many features of extracellular matrices, e.g., self-healing, adhesiveness, viscoelasticity, and conductivity, are associated with the intricate networks composed of many different covalent and non-covalent chemical bonds. Whereas a reductionism approach would have the limitation to fully recapitulate various biological properties with simple chemical structures, mimicking such sophisticated networks by incorporating many different functional groups in a macromolecular system is synthetically challenging. Herein, we propose a strategy of convergent synthesis of complex polymer networks to produce biomimetic electroconductive liquid metal hydrogels. Four precursors could be individually synthesized in one to two reaction steps and characterized, then assembled to form hydrogel adhesives. The convergent synthesis allows us to combine materials of different natures to generate matrices with high adhesive strength, enhanced electroconductivity, good cytocompatibility in vitro and high biocompatibility in vivo. The reversible networks exhibit self-healing and shear-thinning properties, thus allowing for 3D printing and minimally invasive injection for in vivo experiments.

Permalink: https://www.hzdr.de/publications/Publ-32326
Publ.-Id: 32326


Comprehensive Bonding Analysis of Tetravalent f-Element Complexes of the Type [M(salen)2]

Kloditz, R.; Radoske, T.; Schmidt, M.; Heine, T.; Stumpf, T.; Patzschke, M.

Zip-File with the xyz-files of the optimized structures of the studied complexes. Further information can be found in the respective paper and supplementary information.

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Permalink: https://www.hzdr.de/publications/Publ-32325
Publ.-Id: 32325


Comprehensive Bonding Analysis of Tetravalent f-Element Complexes of the Type [M(salen)₂]

Kloditz, R.; Radoske, T.; Schmidt, M.; Heine, T.; Stumpf, T.; Patzschke, M.

Key questions for the study of chemical bonding in actinide compounds are the degree of covalency that can be realized in the bonds to different donor atoms and the relative participation of 5f and 6d orbitals. A manifold of theoretical approaches is available to address these questions, but hitherto no comprehensive assessments are available. Here, we present an in-depth analysis of the metal–ligand bond in a series of actinide metal–organic compounds of the [M(salen)₂] type (M = Ce, Th, Pa, U, Np, Pu) with the Schiff base N,N′-bis(salicylidene)ethylenediamine (salen). All compounds except the Pa complex (only included in the calculations) have been synthesized and characterized experimentally. The experimental data are then used as a basis to quantify the covalency of bonds to both N- and O-donor atoms using simple electron-density differences and the quantum theory of atoms in molecules (QTAIM) with interacting quantum atoms. In addition, the orbital origin of any covalent contributions was studied via natural population analysis (NPA). The results clearly show that the bond to the hard, charged O-donor atoms of salen is consistently not only stronger but also more covalent than bonds to the softer N-donor atoms. On the other hand, in a comparison of the metals, Th shows the most ionic bond character even compared to its 4f analogue Ce. A maximum of the covalency is found for Pa or Np by their absolute and relative covalent bond energies, respectively. This trend also correlates with a significant f- and d-orbital occupation for Pa and Np. These results underline that only a comprehensive computational approach is capable of fully characterizing the covalency in actinide complexes.

Keywords: Actinides; Covalency; QTAIM; Coordination Chemistry; Metal-organic Chemistry; DFT; Electron Density

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Permalink: https://www.hzdr.de/publications/Publ-32324
Publ.-Id: 32324


A workflow for the sustainable development of closure models for bubbly flows

Hänsch, S.; Evdokimov, I.; Schlegel, F.; Lucas, D.

Many years of research in developing closure models for polydisperse bubbly flows have produced a plethora of empirical and semi-empirical models.
The continuous development and analysis of such models requires their constant validation with the steadily increasing number of validation cases in
the literature.
In this paper we present a pipeline for the fully-automated analysis of OpenFOAM simulations using the Snakemake workflow management system. The pipeline is applied to an extensive collection of well-established validation cases for bubbly flows and allows the fast and efficient production of large amounts of results that are summarized in well-structured reports. An optional post-processing step introduces a fuzzy-logic controller developed for the detailed analysis of these results by quantifying the agreement of the simulation with the available experimental data. It is demonstrated how such quantification enables the systematic evaluation of new closure models and contributes to a more sustainable model development.

Keywords: Baseline; bubbly flow; OpenFOAM; workflow; Artificial Intelligence

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Permalink: https://www.hzdr.de/publications/Publ-32323
Publ.-Id: 32323


Multilayer interfacial wave dynamics in upright circular cylinders with application to liquid metal batteries

Horstmann, G. M.

Liquid metal batteries (LMBs) are discussed today as an economic grid-scale energy storage, as required for the deployment of fluctuating renewable energies. These batteries consist of three stably stratified liquid layers: two liquid metal electrodes are separated by a thin molten salt electrolyte, this way forming an electrochemical concentration cell. Their completely liquid interior, which is on the one hand very beneficial for the energy efficiency, also poses some major challenges on the other hand. Strong cell currents in combination with electromagnetic fields make liquid metal batteries highly susceptible to various kinds of magnetohydrodynamic instabilities. In particular, the so-called metal pad roll instability (MPRI), which can drive uncontrollable wave motions in both interfaces, was identified as a key limiting factor for the batteries' operational safety.
In this seminar talk, I will present the key results of my PhD thesis, where I was concerned with multilayer interfacial wave dynamics in cylindrical LMB models. In the fist part, I will show the results of a potential flow theory describing gravity–capillary waves in three-layer stratifications. The theory is used to classify different wave coupling states, which comprise different manifestations of the MPRI. Accompanying numerical simulations substantiate that coupling effects will be present in most future LMBs. In the second part, a multilayer sloshing experiment will be introduced, which allows to mechanically excite the same interfacial wave motions as induced by the MPRI. Different sets of experiments emphasize the crucial role of the contact line as well as of viscous damping, both having a strong impact on instability onsets of cylindrical LMBs. In the final part, I will present a new hybrid interfacial sloshing model, which accounts for viscous damping and can explain the experimentally observed resonance dynamics. As a further unexpected result, the sloshing theory predicts the formation of novel spiral wave patterns under the effect of strong damping in higher wave modes.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Online seminars of the Morelia Unit of the Materials Research Institute at the National University of Mexico, 12.02.2021, Mexico City, Mexico

Permalink: https://www.hzdr.de/publications/Publ-32322
Publ.-Id: 32322


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