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35670 Publications

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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-03-10
    DOI: 10.14278/rodare.837

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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

Related publications

  • Software in the HZDR data repository RODARE
    Publication date: 2021-03-08
    DOI: 10.14278/rodare.835

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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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-03-10
    DOI: 10.14278/rodare.845

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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

Related publications

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

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


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.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-03-10
    DOI: 10.14278/rodare.843

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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.

Related publications

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


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.

Related publications

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

  • Software in the HZDR data repository RODARE
    Publication date: 2021-03-09
    DOI: 10.14278/rodare.839
    License: GPL-3.0

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


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

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


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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  • Secondary publication expected from 04.03.2022

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


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.

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


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

  • 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.

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


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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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-03-04
    DOI: 10.14278/rodare.829

Downloads:

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

Related publications

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.

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.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-03-02
    DOI: 10.14278/rodare.827
    License: CC-BY-4.0

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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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-06
    DOI: 10.14278/rodare.825
    License: CC-BY-4.0

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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: Upadhyay, Kartik; Other: Mohite, Onkar; Other: Kriebitzsch, Sebastian

HZDR Multiphase Case Collection for OpenFOAM contains simulation setups for the open-source CFD software OpenFOAM with the HZDR multiphase addon. The simulation setups are separated into polydisperse bubbly flows utilising the HZDR Baseline model set according to Liao et al. (Chem Eng Sci, 2019, Vol. 202, 55-69), setups for a hybrid modelling approach (disperse and resolved interfaces) according to Meller et al. (Int J Numer Meth Fluids, 2021, Vol. 93, 748–773) and miscellaneous cases.

Cases using the HZDR Baseline model set

baseline/1998_Liu

baseline/2005_Lucas_et_al

baseline/2008_Shawkat

baseline/2009_Hosokawa

baseline/2013_Hosokawa_and_Tomiyama

baseline/2016_Kim_et_al

Cases using the hybrid modelling approach

hybrid/wenka/2D-MP3-23

hybrid/risingBubbleHysingEtAl2009

hybrid/risingBubbleBalcazarEtAl2015

hybrid/risingBubbleMellerEtAl2021

  • Reference for case setup: Meller et al., Flow Turbul Combust (submitted)

Miscellaneous cases

misc/multiphase/HZDRmultiphaseEulerFoam/1991_Akhtar_et_al

Keywords: Multiphase Flow; Numerical Simulations; OpenFOAM; CFD; Baseline model; Multi-field two-fluid model; Eulerian-Eulerian model; Free Surface

Related publications

  • Software in the HZDR data repository RODARE
    Publication date: 2021-07-01
    DOI: 10.14278/rodare.811
    License: CC-BY-4.0

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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. 

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-03-01
    DOI: 10.14278/rodare.823

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


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

Related publications

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


ASTRID-DYN3D

Fridman, Emil

ASTRID-DYN3D: XS generation and full core simulations

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-25
    DOI: 10.14278/rodare.821

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


Spatially resolved Eu(III) environments by chemical microscopy

Drobot, B.

Archiv of research data for the manuscript

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-24
    DOI: 10.14278/rodare.819

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


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.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-23
    DOI: 10.14278/rodare.817

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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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  • Secondary publication expected from 15.04.2022

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

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.

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

  • 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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  • Secondary publication expected from 11.02.2022

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

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

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

  • 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.

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


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.

  • Journal of the American Chemical Society 143(2021), 2353-2360
    Online First (2021) DOI: 10.1021/jacs.0c12116

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  • Secondary publication expected from 27.01.2022

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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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-18
    DOI: 10.14278/rodare.815
    License: CC-BY-4.0

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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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  • Secondary publication expected from 03.02.2022

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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  • Secondary publication expected from 01.06.2022

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


2020 Roadmap on Plasma Accelerators

Albert, F.; Couprie, M.-E.; Debus, A.; Downer, M.; Faure, J.; Flacco, A.; Gizzi, L.; Grismayer, T.; Huebl, A.; Joshi, C.; Labat, M.; Leemans, W.; Maier, A.; Mangles, S.; Mason, P.; Mathieu, F.; Muggli, P.; Nishiuchi, M.; Osterhoff, J.; Rajeev, P.; Schramm, U.; Schreiber, J.; Thomas, A.; Vay, J.-L.; Vranic, M.; Zeil, K.

Plasma-based accelerators use the strong electromagnetic fields that can be supported by plasmas to accelerate charged particles to high energies. Accelerating field structures in plasma can be generated by powerful laser pulses or charged particle beams. This research field has recently transitioned from involving a few small-scale efforts to the development of national and international networks of scientists supported by substantial investment in large-scale research infrastructure. In this New Journal of Physics 2020 Plasma Accelerator Roadmap, perspectives from experts in this field provide a summary overview of the field and insights into the research needs and developments for an international audience of scientists, including graduate students and researchers entering the field.

Permalink: https://www.hzdr.de/publications/Publ-32318
Publ.-Id: 32318


Photons or protons for reirradiation in (non-)small cell lung cancer: Results of the multicentric ROCOCO in silico study

Troost, E. G. C.; Wink, K. C. J.; Roelofs, E.; Simone Ii, C. B.; Makocki, S.; Löck, S.; van Kollenburg, P.; Dechambre, D.; Minken, A. W. H.; van der Stoep, J.; Avery, S.; Jansen, N.; Solberg, T.; Bussink, J.; de Ruysscher, D.

Objective: Locally recurrent disease is of increasing concern in (non-) small cell lung cancer [(N)SCLC] patients. Local reirradiation with photons or particles may be of benefit to these patients. In this multicentre in silico trial performed within the Radiation Oncology Collaborative Comparison (ROCOCO) consortium, the doses to the target volumes and organs at risk (OARs) were compared when using several photon and proton techniques in patients with recurrent localised lung cancer scheduled to undergo reirradiation. Methods: 24 consecutive patients with a second primary (N)SCLC or recurrent disease after curative-intent, standard fractionated radio(chemo)therapy were included in this study. The target volumes and OARs were centrally contoured and distributed to the participating ROCOCO sites. Remaining doses to the OARs were calculated on an individual patient’s basis. Treatment planning was performed by the participating site using the clinical treatment planning system and associated beam characteristics. Results: Treatment plans for all modalities (five photon and two proton plans per patient) were available for 22 patients (N = 154 plans). 3D-conformal photon therapy and double-scattered proton therapy delivered significantly lower doses to the target volumes. The highly conformal techniques, i.e., intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), CyberKnife, TomoTherapy and intensity-modulated proton therapy (IMPT), reached the highest doses in the target volumes. Of these, IMPT was able to statistically significantly decrease the radiation doses to the OARs. Conclusion: Highly conformal photon and proton beam techniques enable high-dose reirradiation of the target volume. They, however, significantly differ in the dose deposited in the OARs. The therapeutic options, i.e., reirradiation or systemic therapy, need to be carefully weighed and discussed with the patients. Advances in knowledge: Highly conformal photon and proton beam techniques enable high-dose reirradiation of the target volume. In light of the abilities of the various highly conformal techniques to spare specific OARs, the therapeutic options need to be carefully weighed and patients included in the decision-making process.

Permalink: https://www.hzdr.de/publications/Publ-32317
Publ.-Id: 32317


Specific requirements for translation of biological research into clinical radiation oncology

Krause, M.; Alsner, J.; Linge, A.; Bütof, R.; Löck, S.; Bristow, R.

Radiotherapy has been optimized over the last decades not only through technological advances, but also through the translation of biological knowledge into clinical treatment schedules. Optimization of fractionation schedules and/or the introduction of simultaneous combined systemic treatment have significantly improved tumour cure rates in several cancer types.
With modern techniques, we are currently able to measure factors of radiation resistance or radiation sensitivity in patient tumours; the definition of new biomarkers is expected to further enable personalized treatments. In this Review article, we overview important translation paths and summarize the quality requirements for preclinical and translational studies that will help to avoid bias in trial results.

Keywords: biomarkers; clinical trials; personalized treatment; quality; radiotherapy; translational research

Permalink: https://www.hzdr.de/publications/Publ-32316
Publ.-Id: 32316


Quantum-mechanical calculations of novel heterocycles as building blocks of 2D-COFs with extended π-conjugation

Asteriadis, A.

For more than a decade, Covalent Organic Frameworks (COFs) have been investigated for various applications. Recently, focus is especially on 2D COFs, a field which is constantly under development. They exhibit very interesting properties, for example, for gas storage, drug delivery, or more recently for electronic transport.

COFs are generally built of organic molecules, such as benzene or naphthalene, which act as linkers, and inorganic heterocycles, such as borazine or boroxine, which are the so-called connectors. Since the first synthesis of COFs back in 2005 by Yaghi, many molecules were used to build these materials with various properties. These properties can be tuned by stoichiometry, size, and functionalization of the building blocks.

The main idea of this project is to investigate the geometries and electronic properties of novel building blocks, especially the connectors, which can be used to build 2D COFs. For this purpose, four novel inorganic heterocyclic molecules, namely B₃N₃H₆, N₃S₃H₃, B₃S₃H₃ and Al₃N₃H₆, as proposed by our experimental collaborator from TU Dresden (Dr. A. Schneemann) were used as connectors. These were expected to provide good π-conjugations within the heterocycles. These molecules, joint together with the organic linkers, are expected to offer extended conjugation over the periodic COFs, providing interesting electronic transport properties.

In this study, we used these four new heterocycle molecules together with nine well-known organic linkers and calculated their geometric and electronic properties, including the single building blocks, finite models, and 2D COFs. All calculations were carried out using TZP basis set and PBE exchange-correlation functional as implemented in the AMS-code, settings selected after extended benchmarking of methods. All of the investigated finite fragments and periodic COFs showed extended π-conjugation, indicating that the electronic properties of finite building blocks are retained in the extended systems upon formation of the 2D COF. The latter were also investigated for their band structures, which showed interesting properties: i) light electrons and heavy holes or vice versa, depending on the heterocycle molecule, which are interesting for transport applications; ii) the expected signatures of kagome (kgm) and honeycomb (hcb) lattices are presented in the band structures of COFs and the interesting points could be reached by doping or functionalization.

  • Master thesis
    Leipzig University, 2021
    Mentor: PD Dr. A. B. Kuc
    68 Seiten

Permalink: https://www.hzdr.de/publications/Publ-32314
Publ.-Id: 32314


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.

Colloidal Janus microparticles can be propelled by controlled chemical reactions on their surfaces. Such microswimmers have been used as model systems for the behavior on the microscale and ascarriers for cargo to well-defined positions in hard-to-access areas. Here we demonstrate the propagation motion of clusters of magnetic Janus particles driven by the catalytic decomposition of H₂O₂ on their metallic caps. The magnetic moments of their caps lead to certain spatial arrangements of Janus particles, which can be influenced by external magnetic fields. We investigate how the arrangement of the particles and caps determines the driven motion of the particle clusters. In addition, we show the influence ofconfining walls on the cluster motion, which will be encountered in any real-life biological system.

Keywords: Janus particles; Magnetic caps; Hydrogen peroxide propulsion; Catalytic propulsion; Magnetic manipulation

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Permalink: https://www.hzdr.de/publications/Publ-32313
Publ.-Id: 32313


X-ray Spectroscopic Studies of a Solid-Density Germanium Plasma Created by a Free Electron Laser

Perez-Callejo, G.; Vinko, S. M.; Ren, S.; Royle, R.; Humphries, O. S.; Preston, T. R.; Hammel, B. A.; Chung, H.-K.; Burian, T.; Vozda, V.; Lin, M.-F.; Brandt Van Driel, T.; Wark, J. S.

The generation of solid-density plasmas in a controlled manner using an X-ray free electron laser (XFEL) has opened up the possibility of diagnosing the atomic properties of hot, strongly coupled systems in novel ways. Previous work has concentrated on K-shell emission spectroscopy of low Z (<= 14) elements. Here, we extend these studies to the mid-Z(=32) element Germanium, where the XFEL creates copious L-shell holes, and the plasma conditions are interrogated by recording of the associated L-shell X-ray emission spectra. Given the desirability of generating as uniform a plasma as possible, we present here a study of the effects of the FEL photon energy on the temperatures and electron densities created, and their uniformity in the FEL beam propagation direction. We show that good uniformity can be achieved by tuning the photon energy of the XFEL such that it does not overlap significantly with L-shell to M-shell bound-bound transitions, and lies below the L-edges of the ions formed during the heating process. Reasonable agreement between experiment and simulations is found for the emitted X-ray spectra, demonstrating that for these higher Z elements, the selection of appropriate XFEL parameters is important for achieving uniformity in the plasma conditions.

Keywords: High energy density; Plasma opacity; XFEL; spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-32312
Publ.-Id: 32312


Mineral Dissolution Rates: Importance of Surface Reactivity

Schabernack, J.; Fischer, C.

Mineral dissolution plays a key role in many environmental and technical fields, e.g., weathering, building materials, as well as host rock characterization for potential nuclear waste repositories. The rate of mineral dissolution in water is controlled by two parameters: (1) transport of dissolved species over and from the interface determined by advective fluid flow and diffusion (transport control) and (2) crystal surface reactivity (surface reactivity control). Current reactive transport models (RTM) simulating species transport commonly calculate mineral dissolution by using rate laws [1]. These rate laws solely depend on species concentration in the fluid and therefore do not include intrinsic variability of surface reactivity. Experimental studies under surface-controlled conditions have shown a heterogeneous distribution of reaction rates [2]. This rate heterogeneity is caused by nanotopographical structures on the crystal surface, such as steps and etch pits that are generated at lattice defects. At these structures, the high density of reactive kink sites is leading to a local increase in dissolution rates.
In this study, we test whether experimentally observed rate heterogeneities can be reproduced by using current RTMs. We apply a standard RTM approach combined with the measured surface topography of a calcite single crystal [2]. Calcite is one of the larger mineral components in the sandy facies of the Opalinus clay formation, that is under consideration for nuclear waste storage. The calculated surface dissolution rate maps are compared to experimentally derived rate maps. The results show that the measured rate heterogeneities cannot be reproduced with the existing RTM approach. To improve the predictive capabilities of RTMs, the surface reactivity that is intrinsic to the mineral needs to be implemented into rate calculations. Investigating calcite surface reactivity in the context of dissolution can also yield information about other kinetic surface processes such as the adsorption of radionuclides. We discuss parameterization of surface reactivity via proxy parameters, such as surface roughness or surface slope. The implementation of these proxy parameters will allow for a more precise prediction of host rock-fluid interaction over large time scales in RTMs, relevant for safety assessment.
[1] P. Agrawal, A. Raoof, O. Iliev and M. Wolthers, Evolution of pore-shape and its impact on pore conductivity during CO2 injection in calcite: Single pore simulations and microfluidic experiments, Advances in Water Resources, 136, 103480 (2020).
[2] I. Bibi, R.S. Arvidson, C. Fischer and A. Luttge: Temporal Evolution of Calcite Surface Dissolution Kinetics, Minerals, 8, 256 (2018).

Keywords: Reactive Transport Model; Mineral Dissolution; Crystal Surface Reactivity

  • Poster (Online presentation)
    2. Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-32309
Publ.-Id: 32309


U(VI) and Eu(III) bioassociation behavior and uptake mechanisms of plant cells

Jessat, J.; Moll, H.; Bilke, M.-L.; John, W.; Hübner, R.; Steudtner, R.; Drobot, B.; Bok, F.; Stumpf, T.; Sachs, S.

For a safety assessment of nuclear waste repositories, it is necessary to consider accident scenarios through which radionuclides (RN) can enter the biosphere up to the food chain via groundwater and soil. It is necessary to generate detailed knowledge about the uptake pathways and the interaction of RN with plants to contribute to the molecular process understanding required for a reliable biogeochemical modeling. We investigated the uptake and immobilization (bioassociation) of U(VI) and Eu(III) as a non-radioactive analogue for trivalent actinides by two typical crop plant cell cultures as model systems: canola (Brassica napus) and carrot (Daucus carota). For both metals a time- and concentration-dependent bioassociation behavior was observed, which shows differences between the two plant cell types. U(VI) and Eu(III) were used as luminescence probes to explore their speciation in the two systems. Therefore, time-resolved laser-induced fluorescence spectroscopy (TRLFS) was performed under cryogenic conditions. For an investigation of possible uptake pathways of the metals, it must be considered that both U and Eu are non-essential heavy metals for plants. Therefore, it can be assumed that they have no specific uptake pathway into the plant cells. Possible uptake routes are the use of transport systems of essential micronutrients, whose homeostasis can be disturbed by U(VI) and Eu(III), but uptake via endocytosis and mechanosensitive ion channels is also possible. Experiments were performed to investigate whether the metals can be unspecifically taken up into the cells by blocking Ca(II) ion channels with GdCl3. The investigations are supplemented by transmission electron microscopy combined with energy-dispersive X-ray spectroscopy (TEM with EDX mapping), which contribute to an improved understanding of the processes taking place by localizing the metals in the plant cell.

Keywords: plant cells; radionuclides; uptake mechanisms

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

Permalink: https://www.hzdr.de/publications/Publ-32307
Publ.-Id: 32307


Recovery of nanodiamonds produced by laser-induced shock compression of polystyrene

Schuster, A.; Hartley, N.; Lütgert, B. J.; Voigt, K.; Vorberger, J.; Zhang, M.; Benad, A.; Eychmüller, A.; Klemmed, B.; Gericke, D. O.; Rack, A.; Bagnoud, V.; Blazevic, A.; Brabetz, C.; Eisenbarth, U.; Götte, S.; Reemts, D.; Schumacher, D.; Toimil Molares, M. E.; Tomut, M.; Kraus, D.

Hydrocarbons are highly abundant in icy giant planets like Uranus and Neptune and their interior conditions can be created in the laboratory on a nanosecond timescale by applying the technique of laser-induced shock compression using high energy lasers. Based on this method, nanodiamond formation in a simplified hydrocarbon representative, polystyrene (C₈H₈), was observed via in situ X-ray diffraction (XRD). The goal is to physically recover the nanodiamonds that are ejected at hypervelocities upon shock-break out to un-derstand the underlying hydrocarbon separation mechanism by analysing their shape, size, surface mod-ifications and defects. This work is important for planetary interior modelling and may present an additional route for nanodiamond production.

  • Open Access Logo Contribution to external collection
    in: News and Reports from High Energy Density generated by Heavy Ion and Laser Beams 2019, Darmstadt: GSI, 2020
    DOI: 10.15120/GSI-2020-01321

Permalink: https://www.hzdr.de/publications/Publ-32305
Publ.-Id: 32305


How Hyperspectral Image Unmixing and Denoising Can Boost Each Other

Rasti, B.; Koirala, B.; Scheunders, P.; Ghamisi, P.

Hyperspectral linear unmixing and denoising are highly related hyperspectral image (HSI) analysis tasks. In particular, with the assumption of Gaussian noise, the linear model assumed for the HSI in the case of low-rank denoising is often the same as the one used in HSI unmixing. However, the optimization criterion and the assumptions on the constraints are different. Additionally, noise reduction as a preprocessing step in hyperspectral data analysis is often ignored. The main goal of this paper is to study experimentally the influence of noise on the process of hyperspectral unmixing by: (1) investigating the effect of noise reduction as a preprocessing step on the performance of hyperspectral unmixing; (2) studying the relation between noise and different endmember selection strategies; (3) investigating the performance of HSI unmixing as an HSI denoiser; (4) comparing the denoising performance of spectral unmixing, state-of-the-art HSI denoising techniques, and the combination of both. All experiments are performed on simulated and real datasets.

Keywords: hyperspectral image; unmixing; denoising; linear mixing model; low-rank model; noise reduction; abu

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Permalink: https://www.hzdr.de/publications/Publ-32304
Publ.-Id: 32304


Feature Extraction for Hyperspectral Imagery: The Evolution From Shallow to Deep: Overview and Toolbox

Rasti, B.; Hong, D.; Hang, R.; Ghamisi, P.; Kang, X.; Chanussot, J.; Benediktsson, J. A.

Hyperspectral images (HSIs) provide detailed spectral information through hundreds of (narrow) spectral channels (also known as dimensionality or bands), which can be used to accurately classify diverse materials of interest. The increased dimensionality of such data makes it possible to significantly improve data information content but provides a challenge to conventional techniques (the so-called curse of dimensionality) for accurate analysis of HSIs.

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Permalink: https://www.hzdr.de/publications/Publ-32303
Publ.-Id: 32303


Direct observation of shock‐induced disordering of enstatite below the melting temperature

Hernandez, J.-A.; Morard, G.; Guarguaglini, M.; Alonso-Mori, R.; Benuzzi-Mounaix, A.; Bolis, R.; Fiquet, G.; Galtier, E.; Gleason, A. E.; Glenzer, S.; Guyot, F.; Ko, B.; Lee, H. J.; Mao, W. L.; Nagler, B.; Ozaki, N.; Schuster, A.; Shim, S. H.; Vinci, T.; Ravasio, A.

We report in situ structural measurements of shock‐compressed single crystal orthoenstatite up to 337 ± 55 GPa on the Hugoniot, obtained by coupling ultrafast X‐ray diffraction to laser‐driven shock compression. Shock compression induces a disordering of the crystalline structure evidenced by the appearance of a diffuse X‐ray diffraction signal at nanosecond timescales at 80 ± 13 GPa on the Hugoniot, well below the equilibrium melting pressure (>170 GPa). The formation of bridgmanite and post‐perovskite have been indirectly reported in microsecond‐scale plate‐impact experiments. Therefore, we interpret the high‐pressure disordered state we observed at nanosecond scale as an intermediate structure from which bridgmanite and post‐perovskite crystallize at longer timescales. This evidence of a disordered structure of MgSiO₃ on the Hugoniot indicates that the degree of polymerization of silicates is a key parameter to constrain the actual thermodynamics of shocks in natural environments.

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Permalink: https://www.hzdr.de/publications/Publ-32302
Publ.-Id: 32302


Comparing the optical properties and thermal stability of green (TbPO4), yellow (DyPO4), and red (PrPO4) emitting single crystal samples

Sharma, S.; Beyer, J.; Gloaguen, R.; Heitmann, J.

Blue, green and red-emitting phosphors for near-UV/blue based phosphor blend converted white-light emitting devices have been investigated extensively over the past years. Herein, we present our results on the optical spectroscopy of single crystal samples of TbPO4, DyPO4 and PrPO4 exhibiting prominent emission at green (545 nm), yellow (574 nm) and red (616 nm) region of the electromagnetic spectrum, respectively. We study the temperature dependence of their emission spectra for excitations at 365 and 455 nm, to mimic experimental conditions for phosphor converted light emitting diodes, to show that their thermal quenching temperature is 730 K for TbPO4 (excitation 365 nm), 490 and 520 K for DyPO4 (excitation at 365 and 455 nm), and 540 K for PrPO4 (excitation 455 nm). The TbPO4 emission does not show any considerable blue/red shift at elevated temperatures, while DyPO4 emission is observed close to the center of CIE coordinate diagram. The PrPO4 sample possesses high color purity which shows slight yellow-shift at elevated temperatures. The ground state of Pr3+ and Tb3+ are found to be within the band gap suggesting that both are able to trap holes from the valence band as evinced from the thermoluminescence glow curve data which shows peak maxima at 422 and 437 K due to hole release from the Pr4+ and Tb4+, respectively. The result suggests that the samples have large potential for solid state lighting devices upon choice of an appropriate excitation wavelength.

Permalink: https://www.hzdr.de/publications/Publ-32301
Publ.-Id: 32301


Library of UV-Visible Absorption Spectra of Rare Earth Orthophosphates, LnPO4 (Ln = La-Lu, except Pm)

Sharma, S. K.; Behm, T.; Köhler, T.; Beyer, J.; Gloaguen, R.; Heitmann, J.

In recent times, rare earth orthophosphates ( Ln PO 4 ) have shown great potential as efficient optical materials. They possess either monazite or xenotime –type structures. These light or heavy rare earth bearing orthophosphates also exhibit an extraordinary stability over geological time scale in nature, ∼10 9 years. In the present contribution, we measure, collect, and present a library of absorption spectra of all the Ln PO 4 hosts ( Ln = La–Lu, except Pm) using their single crystal samples, to conclude that the observed spectral features for wavelengths longer than 200 nm were attributable to either Ln- or defect related centers, which corroborate the fact that they have a bandgap higher than 8.0 eV. The absorption band around wavelength, 275 nm, corresponds to defect absorption related to PO 3 centers and/or oxygen vacancies. The hosts can potentially be used to study and interpret unperturbed rare earth emissions due to absence of host related absorption above 300 nm. The information presented herein is expected to serve as a library of absorption spectra for geologists, physicists, material scientists, and chemists working in the field of rare earths.

Keywords: orthophosphate; lanthanide; monazite/xenotime-structure; absorption spectra

Permalink: https://www.hzdr.de/publications/Publ-32300
Publ.-Id: 32300


Development of Sustainable Test Sites for Mineral Exploration and Knowledge Spillover for Industry

Kesselring, M.; Wagner, F.; Kirsch, M.; Ajjabou, L.; Gloaguen, R.

In mineral exploration, pressure is growing to develop innovative technologies and methods with a lower impact on the social and physical environment. To assess the performance and impact of these technologies and methods, test sites are required. Embedded in the literature on sustainable development, this paper explores how social and environmental measures can be implemented in the design of test sites and what industry stake can learn from sustainable test sites. Through qualitative research, two value networks were developed, one for a sustainable test site approach and another for the existing business practice in mineral exploration. Respondents include public sector officials as well as experts in the social, environmental, business, geoscience, and industry fields. The analysis identifies key drivers for the development of socially and environmentally accepted test sites, thus drawing up actionable points for the mineral exploration industry to increase sustainability. The findings of this paper suggest that the integration of experts and partners from social, as well as environmental, sciences drives sustainability at test sites. For industry application, this results in the need to adapt the activities performed, align resource use with sustainability indicators, and also reconfigure the network of partners towards more socially and environmentally oriented business practices.

Keywords: mineral exploration; sustainable development; test sites

Permalink: https://www.hzdr.de/publications/Publ-32299
Publ.-Id: 32299


Large-Scale Neural Solvers for Partial Differential Equations

Stiller, P.; Bethke, F.; Böhme, M.; Pausch, R.; Debus, A.; Torge, S.; Vorberger, J.; Bussmann, M.; Hoffmann, N.

Solving partial differential equations (PDE) is an indispensable part of many branches of science as many processes can be modelled in terms of PDEs. However, recent numerical solvers require manual discretization of the underlying equation as well as sophisticated, tailored code for distributed computing. Scanning the parameters of the underlying model significantly increases the runtime as the simulations have to be cold-started for each parameter configuration. Machine Learning based surrogate models denote promising ways for learning complex relationship among input, parameter and solution. However, recent generative neural networks require lots of training data, i.e. full simulation runs making them costly. In contrast, we examine the applicability of continuous, mesh-free neural solvers for partial differential equations, physics-informed neural networks (PINNs) solely requiring initial/boundary values and validation points for training but no simulation data. The induced curse of dimensionality is approached by learning a domain decomposition that steers the number of neurons per unit volume and significantly improves runtime. Distributed training on large-scale cluster systems also promises great utilization of large quantities of GPUs which we assess by a comprehensive evaluation study. Finally, we discuss the accuracy of GatedPINN with respect to analytical solutions- as well as state-of-the-art numerical solvers, such as spectral solvers.

Keywords: PDE solving; Physics-informed Neural Networks; Machine Learning; HPC

  • Contribution to proceedings
    SMC 2020: Driving Scientific and Engineering Discoveries Through the Convergence of HPC, Big Data and AI pp, 26.-28.08.2020, Virtual Conference, Virtual Conference
    Driving Scientific and Engineering Discoveries Through the Convergence of HPC, Big Data and AI: Springer Nature Switzerland AG 2020, 978-3-030-63393-6
    DOI: 10.1007/978-3-030-63393-6

Permalink: https://www.hzdr.de/publications/Publ-32298
Publ.-Id: 32298


FuseVis: Interpreting Neural Networks for Image Fusion Using Per-Pixel Saliency Visualization

Kumar, Nishant; Gumhold, Stefan

Image fusion helps in merging two or more images to construct a more informative single fused image. Recently, unsupervised learning-based convolutional neural networks (CNN) have been used for different types of image-fusion tasks such as medical image fusion, infrared-visible image fusion for autonomous driving as well as multi-focus and multi-exposure image fusion for satellite imagery. However, it is challenging to analyze the reliability of these CNNs for the image-fusion tasks since no groundtruth is available. This led to the use of a wide variety of model architectures and optimization functions yielding quite different fusion results. Additionally, due to the highly opaque nature of such neural networks, it is difficult to explain the internal mechanics behind its fusion results. To overcome these challenges, we present a novel real-time visualization tool, named FuseVis, with which the end-user can compute per-pixel saliency maps that examine the influence of the input image pixels on each pixel of the fused image. We trained several image fusion-based CNNs on medical image pairs and then using our FuseVis tool we performed case studies on a specific clinical application by interpreting the saliency maps from each of the fusion methods. We specifically visualized the relative influence of each input image on the predictions of the fused image and showed that some of the evaluated image-fusion methods are better suited for the specific clinical application. To the best of our knowledge, currently, there is no approach for visual analysis of neural networks for image fusion. Therefore, this work opens a new research direction to improve the interpretability of deep fusion networks. The FuseVis tool can also be adapted in other deep neural network-based image processing applications to make them interpretable

Keywords: image fusion; convolutional neural networks (CNN); saliency visualization; jacobians; graphical use interface (GUI)

Permalink: https://www.hzdr.de/publications/Publ-32296
Publ.-Id: 32296


Deep white matter analysis (DeepWMA): Fast and consistent tractography segmentation

Zhang, F.; Karayumak, S. C.; Hoffmann, N.; Rathi, Y.; Golby, A. J.; O’Donnell, L. J.

White matter tract segmentation, i.e. identifying tractography fibers (streamline trajectories) belonging to anatomically meaningful fiber tracts, is an essential step to enable tract quantification and visualization. In this study, we present a deep learning tractography segmentation method (DeepWMA) that allows fast and consistent identification of 54 major deep white matter fiber tracts from the whole brain. We create a large-scale training tractography dataset of 1 million labeled fiber samples, and we propose a novel 2D multi-channel feature descriptor (FiberMap) that encodes spatial coordinates of points along each fiber. We learn a convolutional neural network (CNN) fiber classification model based on FiberMap and obtain a high fiber classification accuracy of 90.99% on the training tractography data with ground truth fiber labels. Then, the method is evaluated on a test dataset of 597 diffusion MRI scans from six independently acquired populations across genders, the lifespan (1 day - 82 years), and different health conditions (healthy control, neuropsychiatric disorders, and brain tumor patients). We perform comparisons with two state-of-the-art tract segmentation methods. Experimental results show that our method obtains a highly consistent tract segmentation result, where on average over 99% of the fiber tracts are successfully identified across all subjects under study, most importantly, including neonates and patients with space-occupying brain tumors. We also demonstrate good generalization of the method to tractography data from multiple different fiber tracking methods. The proposed method leverages deep learning techniques and provides a fast and efficient tool for brain white matter segmentation in large diffusion MRI tractography datasets.

Permalink: https://www.hzdr.de/publications/Publ-32295
Publ.-Id: 32295


Visualisation of Medical Image Fusion and Translation for Accurate Diagnosis of High Grade Gliomas

Kumar, N.; Hoffmann, N.; Kirsch, M.; Gumhold, S.

The medical image fusion combines two or more modalities into a single view while medical image translation synthesizes new images and assists in data augmentation. Together, these methods help in faster diagnosis of high grade malignant gliomas. However, they might be untrustworthy due to which neurosurgeons demand a robust visualisation tool to verify the reliability of the fusion and translation results before they make pre-operative surgical decisions. In this paper, we propose a novel approach to compute a confidence heat map between the source-target image pair by estimating the information transfer from the source to the target image using the joint probability distribution of the two images. We evaluate several fusion and translation methods using our visualisation procedure and showcase its robustness in enabling neurosurgeons to make finer clinical decisions.

Keywords: Visualisation; Medical Image Fusion; Medical Image Translation; Mutual information

  • Open Access Logo Contribution to proceedings
    2020 IEEE 17th International Symposium on Biomedical Imaging (ISBI), 03.-07.04.2020, Iowa City, USA
    2020 IEEE 17th International Symposium on Biomedical Imaging (ISBI): IEEE
    DOI: 10.1109/ISBI45749.2020.9098504

Permalink: https://www.hzdr.de/publications/Publ-32294
Publ.-Id: 32294


Review and new concepts for neutron-capture measurements of astrophysical interest

Domingo-Pardo, C.; Babiano-Suarez, V.; Balibrea-Correa, J.; Caballero, L.; Ladarescu, I.; Lerendegui-Marco, J.; Tain, J. L.; Calviño, F.; Casanovas, A.; Segarra, A.; Tarifeño-Saldivia, A. E.; Guerrero, C.; Millán-Callado, M. A.; Quesada, J. M.; Rodríguez-González, M. T.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Calviani, M.; Cano-Ott, D.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Gunsing, F.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krticka, M.; Kurtulgil, D.; Lederer-Woods, C.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Maugeri, E.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Ramos Doval, D.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.; The, N. T. C.

The idea of slow-neutron capture nucleosynthesis formulated in 1957 triggered a tremendous experimental effort in different laboratories worldwide to measure the relevant nuclear physics input quantities, namely (n, γ) cross sections over the stellar temperature range (from few eV up to several hundred keV) for most of the isotopes involved from Fe up to Bi. A brief historical review focused on total energy detectors will be presented to illustrate how advances in instrumentation have led to the assessment of new aspects of s-process nucleosynthesis and to the progressive refinement of stellar models. A summary will be presented on current efforts to develop new detection concepts, such as the Total-Energy Detector with γ-ray imaging capability (i-TED). The latter is based on the simultaneous combination of Compton imaging with neutron time-of-flight (TOF) techniques, in order to achieve a superior level of sensitivity and selectivity in the measurement of stellar neutron capture rates.

Permalink: https://www.hzdr.de/publications/Publ-32293
Publ.-Id: 32293


Neutron capture measurement at the n TOF facility of the 204Tl and 205Tl s-process branching points

Casanovas, A.; Tarifeño-Saldivia, A. E.; Domingo-Pardo, C.; Calviño, F.; Maugeri, E.; Guerrero, C.; Lerendegui-Marco, J.; Dressler, R.; Heinitz, S.; Schumann, D.; Tain, J. L.; Quesada, J. M.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Caballero, L.; Calviani, M.; Cano-Ott, D.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Gunsing, F.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krticka, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; J. Lonsdale, S.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Millán-Callado, M. A.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Doval, D. R.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.; Koester, U.

Neutron capture cross sections are one of the fundamental nuclear data in the study of the s (slow) process of nucleosynthesis. More interestingly, the competition between the capture and the decay rates in some unstable nuclei determines the local isotopic abundance pattern. Since decay rates are often sensible to temperature and electron density, the study of the nuclear properties of these nuclei can provide valuable constraints to the physical magnitudes of the nucleosynthesis stellar environment. Here we report on the capture cross section measurement of two thallium isotopes, 204Tl and 205Tl performed by the time-of-flight technique at the n TOF facility at CERN. At some particular stellar s-process environments, the decay of both nuclei is strongly enhanced, and determines decisively the abundance of two s-only isotopes of lead, 204Pb and 205Pb. The latter, as a long-lived radioactive nucleus, has potential use as a chronometer of the last s-process events that contributed to final solar isotopic abundances.

Permalink: https://www.hzdr.de/publications/Publ-32292
Publ.-Id: 32292


Neutron Capture Cross Section for 10Be

Volknandt, M.; Eberhardt, K.; Endres, A.; Erbacher, P.; Fix, M.; Göbel, K.; Heftrich, T.; Heinitz, S.; Hrivula, E.; Junghans, A.; Käppeler, F.; Kivel, N.; Langer, C.; Mengoni, A.; Reifarth, R.; Schmidt, S.; Schumann, D.; Thomas, B.; Veltum, D.; Weigand, M.; Wiehl, N.; Wolf, C.

The determination of the involved reaction cross sections is essential for the understanding of how the big bang nucleosynthesis and nuclear reactions in stars contribute to the observed abundances. One of those, which has not been measured so far, is the 10Be(n,γ) cross section.

A 10BeO sample, provided by PSI Villigen, was irradiated in a cyclic activation at the TRIGA reactor in Mainz. The characteristic γ-rays following the decay of 11Be were measured using LaBr3 scintillation detectors. The thermal neutron cross section and the resonance integral were experimentally determined for the first time.

Permalink: https://www.hzdr.de/publications/Publ-32291
Publ.-Id: 32291


80Se(n,γ) cross-section measurement at CERN n_TOF

Babiano-Suarez, V.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea-Correa, J.; Barbagallo, M.; Bennett, S.; Berthoumieux, E.; Bosnar, D.; Brown, A. S.; Busso, M.; Caamaño, M.; Caballero, L.; Calviani, M.; Calviño, F.; Cano-Ott, D.; Casanovas, A.; Cerutti, F.; Chiaveri, E.; Colonna, N.; Cortés, G. P.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Damone, L. A.; Davies, P. J.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Ducasse, Q.; Dupont, E.; Durán, I.; Eleme, Z.; Fernández-Domíngez, B.; Ferrari, A.; Ferro-Gonçalves, I.; Finocchiaro, P.; Furman, V.; Garg, R.; Gawlik, A.; Gilardoni, S.; Göbel, K.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Jiri, U.; Junghans, A.; Kadi, Y.; Käppeler, F.; Kimura, A.; Knapová, I.; Kokkoris, M.; Kopatch, Y.; Krticka, M.; Kurtulgil, D.; Ladarescu, I.; Lederer-Woods, C.; Lerendegui-Marco, J.; Lonsdale, S.-J.; Macina, D.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P. F.; Mastromarco, M.; Maugeri, E.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Michalopoulou, V.; Milazzo, P. M.; Millán-Callado, M. A.; Mingrone, F.; Moreno-Soto, J.; Musumarra, A.; Negret, A.; Ogállar, F.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Petrone, C.; Piersanti, L.; Pirovano, E.; Porras, I.; Praena, J.; Quesada, J. M.; Ramos Doval, D.; Reifarth, R.; Rochman, D.; Rubbia, C.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N.; Sprung, P.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A. E.; Tassan-Got, L.; Thomas, B.; Torres-Sánchez, P.; Tsinganis, A.; Urlass, S.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Wright, T. J.; Žugec, P.

Radiative neutron capture cross section measurements are of fundamental importance for the study of the slow neutron capture (s-) process of nucleosynthesis. This mechanism is responsible for the formation of most elements heavier than iron in the Universe. Particularly relevant are branching nuclei along the s-process path, which are sensitive to the physical conditions of the stellar environment. One such example is the branching at 79Se (3.27 × 105 y), which shows a thermally dependent β-decay rate. However, an astrophysically consistent interpretation requires also the knowledge of the closest neighbour isotopes involved. In particular, the 80Se(n,γ) cross section directly affects the stellar yield of the "cold" branch leading to the formation of the s-only 82Kr. Experimentally, there exists only one previous measurement on 80Se using the time of flight (TOF) technique. However, the latter suffers from some limitations that are described in this presentation. These drawbacks have been significantly improved in a recent measurement at CERN n TOF. This contribution presents a summary of the latter measurement and the status of the data analysis.

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Permalink: https://www.hzdr.de/publications/Publ-32290
Publ.-Id: 32290


Radiotherapy enhances uptake and efficacy of 90Y-cetuximab: A preclinical trial

Dietrich, A.; Andreeff, M.; Koi, L.; Bergmann, R.; Schubert, M.; Schreiner, L.; Löck, S.; Sihver, W.; Freudenberg, R.; Hering, S.; Pietzsch, H.-J.; Steinbach, J.; Kotzerke, J.; Baumann, M.; Krause, M.

Background and purpose

Systemic molecular radiotherapy utilizes internal irradiation by radionuclide-labeled tumor-targeting agents with the potential to destroy (micro-)metastases. However, doses that are applicable in solid tumors do not reach the levels nessecary for tumor control. Thus, the combination of molecular and external radiotherapy is a promising treatment strategy, as enhanced tumor doses can be delivered with and without minor overlapping toxicities. Here, we combined a 90Y-labeled anti-EGFR antibody (Cetuximab) with clinically relevant fractionated radiotherapy in a preclinical trial using head and neck squamous cell carcinoma xenograft tumors.
Materials and methods

To model 90Y-Cetuximab uptake for treatment schedule optimization, FaDu-bearing mice were injected with near-infrared-labeled-Cetuximab at different time points during radiotherapy with differing doses. Cetuximab uptake was longitudinally followed by in vivo-optical imaging. Tumor control probability experiments with fractionated radiotherapy (30 fx, 6 weeks, 8 dose groups/ arm) in combination with 90Y-Cetuximab were performed to test the curative potential.

Results

Imaging of near-infrared-labeled-Cetuximab uptake revealed that low to moderate external beam doses can enhance antibody uptake. Using the optimized schedule, combination of molecular and external radiotherapy using 90Y-Cetuximab at a dose that did not result in permanent tumor inactivation in previous experiments, led to substantially increased tumor control compared to radiotherapy alone.
Conclusion

Our results indicate that combination of radiolabeled therapeutics with clinically relevant fractionated radiotherapy has a remarkable potential to improve curative treatment outcome. Application of some radiation dose prior to injection may improve drug uptake and enable patient stratification and treatment personalization via a corresponding PET-tracer during therapy.

Keywords: Molecular radiotherapy Combination therapy Cetuximab Preclinical imaging Radiation therapy Radioimmu

Permalink: https://www.hzdr.de/publications/Publ-32289
Publ.-Id: 32289


On-shot dosimetry setup for radiobiology studies on volumetric in-vivo samples with laser accelerated proton beams

Reimold, M.

Laser plasma-based accelerators promise to provide proton sources for radiobiological studies with extended possibilities compared to conventional accelerators due to short acceleration lengths, high pulse doses, high dose rates and the usage of compact magnets for beam guiding operated in pulsed mode. For the generation of radiobiological relevant proton energies, Petawatt (PW) class laser powers are required, which can be provided at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) by the DRACO laser system and the upcoming PENELOPE laser system. Both laser systems will be used to perform radiobiological in-vivo studies which require precise absolute dosimetry for three-dimensional depth-dose profiles on a millimeter scale. This presentation gives an overview of the dosimetry setup developed for radio-biological studies on volumetric samples consisting of a combination of several different detector types for on-shot dose measurement (ionization chambers, time-of-flight spectrometer), absolute calibration (radiochromic films) and spatial dose profile optimization (scintillators). Additionally, a recently developed detector system design based on scintillator emission tomography for the full reconstruction of an arbitrary proton depth profile generated by a single proton bunch will be presented. Details on the reconstruction of the 3D dose distribution inside the scintillator volume and the reverse calculation of the angularly resolved proton energy spectrum are discussed.

  • Lecture (Conference) (Online presentation)
    LaPlaSS, 18.09.2020, Salamanca/ Dresden, Spanien/ Deutschland
  • Lecture (Conference) (Online presentation)
    BLIN4, 29.06.2020, München/ Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32288
Publ.-Id: 32288


Beam monitoring and dosimetry for in vivo studies with laser-driven protons at Draco PW

Reimold, M.

Petawatt laser-plasma based proton sources, capable of providing multi-10 MeV proton pulses at ultra-high dose rates of 10^9 Gy/s, are unique sources for radiobiological studies of ~mm size 3D in vivo samples in the recently strongly investigated FLASH regime.
At Draco PW (HZDR), a compact and tunable pulsed power beamline is utilized for efficient beam transport and spectral filtering for dose deposition in a sample. The setup was successfully used for in vivo radiobiological studies with up to 20 Gy single shot doses as well as for accumulative multi-shot low dose (~500 mGy) schemes for %-level accuracy of dose delivery.
Regarding beam monitoring and dosimetry, the inherent fluctuations of the laser-driven source, the ultra-high dose rate and the experimental environment (pulsed power, EMP) pose challenges for established dosimetry methods.
In this presentation, we present a non-invasive scintillator-based time-of-flight spectrometer as a unique tool for single-shot online beam optimization and monitoring of laser-driven proton pulses in application experiments. Calibration of the device against established dosimeters (here radiochromic film) in combination with Monto Carlo simulations additionally allows dosimetric use, overcoming saturation issues with dose rate or linear energy transfer present in other devices.
To illustrate the suitability of the time-of-flight spectrometer as a beam monitor and absolute dosimeter for laser-based protons, the time-of-flight data of two radiobiological in vivo irradiation campaigns performed at the implemented beamline at the DRACO PW facility are presented.

Keywords: time-of-flight spectrometer

  • Lecture (Conference) (Online presentation)
    WHELMI-Meeting, 17.-18.12.2020, Dresden-Rossendorf/ Rechovot, Deutschland/ Israel
  • Lecture (Conference) (Online presentation)
    Gruppenseminar, 08.02.2021, Dresden, Deutschland
  • Lecture (Conference) (Online presentation)
    M&T Student Retreat, 01.02.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-32287
Publ.-Id: 32287


Nanoparticle-Stabilized Perforated Lamellar Morphology in Block Copolymer/Quantum Dot Hybrids

Singh, S.; Horechyy, A.; Yadav, S.; Formanek, P.; Hübner, R.; Srivastava, R. K.; Sapra, S.; Fery, A.; Nandan, B.

We report on the surprising observation of a unique perforated lamellar (PL) morphology in a mixture of an asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer and CdSe−CdS quantum dots (QDs). The PL morphology formed by the PS-b-P4VP/CdSe−CdS composites consisted of alternating layers of PS and P4VP, where the layer formed by the minority PS block contained cylindrical perforations of the majority P4VP block. Most interestingly, the CdSe−CdS QDs were localized exclusively in the P4VP perforations. The swelling of the bulk samples in a P4VP selective solvent also allowed the isolation of the perforated PS nanosheets, with QDs localized in the perforations, which further provided strong evidence for the formation of the unique PL morphology. The observed PL morphology was, plausibly, energetically stabilized because of the localization of QDs within the P4VP perforations, which allowed for the conformational entropy minimization of the majority P4VP block. The present work reveals possibilities for the discovery of novel hierarchical structures in block copolymer/nanoparticle composite systems and also provides new opportunities for the application of such materials in nanotechnology.

Permalink: https://www.hzdr.de/publications/Publ-32286
Publ.-Id: 32286


Assessment of column tray flow patterns and separation efficiencies on large-scale distillation trays

Vishwakarma, V.; Marchini, S.; Abdul Haq, S.; Schleicher, E.; Bieberle, A.; Schubert, M.; Hampel, U.

Thorough characterization of mixing behavior and separation efficiencies of large-scale distillation trays is important especially in their design phase. A precise account of the tray operation would allow modifying their mixing and mass-transfer characteristics (via design modifications) for better separation efficiencies (see design strategy in Fig. 1, left).
Fig. 1. Design strategy for distillation trays (left), and relevant data on the distributions of liquid holdup, residence time, RTD variance, and species concentration (right).
The existing literature lacks a thorough hydrodynamic description of large-scale distillation trays. Thus, the CFD studies have relied either on trivial measurements (such as those of pressure drop, liquid weeping and entrainment, visual froth height, etc.) or the available low-resolution residence time data for model validation rather than on refined data on flow path and local mixing.
Meanwhile, an extensive description of the tray hydrodynamics can be made available using the recently proposed flow profiler.1 Based on recent developments in that regard, the distributions of liquid holdup, residence time and mixing are obtained over the entire deck (see Fig. 1, right) for several gas and liquid loadings at high resolution.
The acquired data permits to predict the tray efficiency by applying models that relate liquid flow patterns with the tray performance, such as the recently proposed ‘Refined RTD (RRTD) model’ that considers the mixing behavior at intermediary tray locations.2
Eventually, experimental data on air stripping of isobutyl acetate from the aqueous solution at tray loadings same as those during the hydrodynamic experiments can be applied to validate the proposed efficiency model. An example of species concentration distribution (i.e., examined using UV spectroscopy) over the tray deck is also shown in Fig. 1 (right).

[1] Vishwakarma, V., Schleicher, E., Schubert, M., Tschofen, M. and Löschau, M., 2020. Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten. Deutsches Patent und Markenamt, DE 10 2018 124 501.
[2] Vishwakarma, V., Schubert, M. and Hampel, U., 2019. Development of a refined RTD-based efficiency prediction model for cross-flow trays. Ind. Eng. Chem. Res., 58(8), pp.3258-3268.

  • Lecture (Conference) (Online presentation)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Wärme- und Stoffübertragung, 24.-26.02.2021, Online event, Germany

Permalink: https://www.hzdr.de/publications/Publ-32285
Publ.-Id: 32285


Experimental analysis of the hydrodynamic performance of an industrial-scale cross-flow sieve tray

Vishwakarma, V.; Abdul Haq, S.; Schleicher, E.; Schubert, M.; Hampel, U.

This work reports the hydrodynamic description of a large-scale sieve tray equipped in an air/water column mockup. The test tray accommodates a multi-probe flow profiler for simultaneous conductivity measurements. 3D liquid holdup distribution, liquid residence time distribution and effective froth height distribution are obtained at high spatiotemporal resolution for several gas and liquid loadings. The liquid flow and mixing patterns are visualized via tracer-based experiments. The methodologies used for acquiring these distributions are discussed in this work. Thorough examination of the processed experimental data reveals the hydrodynamic characteristics of an operational sieve tray for the studied loadings.

Keywords: column tray; hydrodynamics; effective froth height; 3D liquid holdup; tracer-response analysis

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-32284
Publ.-Id: 32284


Nonlinear response in warm dense matter

Vorberger, J.

Talk at Hirschegg workshop "41th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams"

Keywords: warm dense matter; nonlinear response; quantum Monte Carlo; Green's function

  • Lecture (Conference) (Online presentation)
    41th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams, 01.-05.02.2021, Hirschegg, Austria

Permalink: https://www.hzdr.de/publications/Publ-32282
Publ.-Id: 32282


Nonequilibrium in general and in warm dense matter

Vorberger, J.

Talk given at CASUS

Keywords: non-equilibrium; warm dense matter; Boltzmann; kadanoff-baym; two temperature model

  • Lecture (others) (Online presentation)
    MEC Seminar at CASUS, 26.01.2021, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-32281
Publ.-Id: 32281


The Impact of Barium Isotopes in Radiopharmacy and Nuclear Medicine – from Past to Presence

Reissig, F.; Kopka, K.; Mamat, C.

With the exception of beryllium, every alkaline earth metal is characterized by a calcimimetic behavior. Thus, in vivo biodistribution mostly occurs in form of a massive accumulation in bone tissues, consisting of hydroxyapatite to a major extent. Apart from the lightest elements beryllium and magnesium, animal studies and human studies regarding the overall in vivo behavior were carried out by using radioisotopes of the elements calcium, strontium, barium, and radium. To date, only strontium with its radioisotopes gained importance for applications in nuclear medicine, mainly for pain-reducing and palliative treatment of bone metastases. In contrast, barium isotopes can be useful imaging agents and possible diagnostic analogues for theranostic approaches. This review focuses on the characteristic and chemical behavior of barium compounds, possible radioactive barium isotopes for future applications in nuclear medicine and radiopharmacy as well as recent results regarding barium-131 as diagnostic match for radium isotopes used in targeted alpha therapy.

Keywords: Barium isotopes; bone seeker; alkaline earth metals; brachytherapy

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  • Secondary publication expected from 26.05.2022

Permalink: https://www.hzdr.de/publications/Publ-32280
Publ.-Id: 32280


Dependence of the damage in optical metal/dielectric coatings on the energy of ions in irradiation experiments for space qualification

Pelizzo, M. G.; Corso, A. J.; Santi, G.; Hübner, R.; Garoli, D.; Doyle, D.; Lubin, P.; Cohen, A. N.; Erlikhman, J.; Favaro, G.; Bazzan, M.; Drobny, J.; Curreli, D.; Umansky, M.

Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. In this work, a TiO2/Al bi-layer coating has been irradiated with a He+ beam at three different energies. The same flux and dose have been used in order to investigate the damage dependence on the energy. The energies were selected to be in the range 4-100 keV, in order to consider those associated to the quiet solar wind and to the particles present in the near-Earth space environment. The optical, morphological and structural modifications have been investigated by using various techniques. Surprisingly, the most damaged sample is the one irradiated at the intermediate energy, which, on the other hand, corresponds to the case in which the interface between the two layers is more stressed. Results demonstrate that ion energies for irradiation tests must be carefully selected to properly qualify space components.

Permalink: https://www.hzdr.de/publications/Publ-32279
Publ.-Id: 32279


Annual Report 2020 - Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A.

The institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden –Rossendorf (HZDR). Our research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Ra-diation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. The program NUSAFE, and therefore all work which is done at IRE, belong to the research field “Energy” of the HGF.

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-113 2021
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-32278
Publ.-Id: 32278


Data for: Spin-wave dynamics and symmetry breaking in an artificial spin ice

Saha, S.; Zhou, J.; Hofhuis, K.; Kakay, A.; Scagnoli, V.; Heyderman, L. J.; Gliga, S.

These data are related to the https://arxiv.org/abs/2011.04505 publication entitled: Spin-wave dynamics and symmetry breaking in an artificial spin ice

The archive-files.txt contains a detailed description of the files stored in the repository-files-paper.tar file.

The geometry .bmp files are also included, thus anyone can reproduce the results by using mumax3 from https://mumax.github.io

Keywords: nanomagnetism; artificial spin ice; spin wave; magnetization dynamics; magnonic crystal

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-08
    DOI: 10.14278/rodare.799

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Permalink: https://www.hzdr.de/publications/Publ-32277
Publ.-Id: 32277


Sub-20 nm multilayer nanopillar patterning for hybrid SET/CMOS integration: Figs. 1a, 1b and 5

Engelmann, H.-J.
Project Leader: von Borany, Johannes

Energy-filtered transmission electron microscopy (EFTEM) images of stacked Si/SiO2/Si nanopillars

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-09
    DOI: 10.14278/rodare.806
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-32276
Publ.-Id: 32276


Data file for manuscript on Interfacial Properties of Tridecyl Dimethyl Phosphine Oxide Adsorbed at the Surface of a Solution Drop in Hexane Saturated Air

Javadi, A.

Experimental data for paper: Interfacial Properties of Tridecyl Dimethyl Phosphine Oxide Adsorbed at the Surface of a Solution Drop in Hexane Saturated Air.

The presented data are measured dynamic surface tension of Tridecyl Dimethyl Phosphine Oxide in water against air and alkane vapors, by profile analysis tensiometry. It also includes data analysis standard deviation from Young-Laplace fitting, and theoretical analysis illustrating isotherm of adsorption.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-02-08
    DOI: 10.14278/rodare.804

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Permalink: https://www.hzdr.de/publications/Publ-32274
Publ.-Id: 32274


Data File for Drop Size Dependence of the Apparent Surface Tension of Aqueous Solutions in Hexane Vapor

Javadi, A.

Experimental data file for Paper on "Drop Size Dependence of the Apparent Surface Tension of Aqueous Solutions in Hexane Vapor as Studied by Drop Profile Analysis Tensiometry".

These data are measured dynamic surface tension and variations of deviations from Young Laplace fitting, of different drop size of surfactants solution Tridecyl dimethyl phosphine oxide C13DMPO and Oxyethylated alcohol С14ЕО8 in water against air and hexane vapor. 

Related publications

  • Software in the HZDR data repository RODARE
    Publication date: 2021-02-08
    DOI: 10.14278/rodare.802

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Permalink: https://www.hzdr.de/publications/Publ-32273
Publ.-Id: 32273


Characterization of lithium ion battery recycling processes and estimation of liberation efficiency of electrodes using automated mineralogy

Vanderbruggen, A.; Hayagan, N. L.; Bachmann, K.; Rudolph, M.

Lithium-ion batteries (LIBs) are currently one of the most important electrochemical energy storage devices, powering electronic mobile devices and electric vehicles. Growing global demands for Co, Mn, Ni, Li, and graphite which are all used and present in LIBs as energy storage added difficulties to the already deficit and imbalance supply of sources of raw materials worldwide, which resulted to supply risks, price fluctuations and monopoly of market. In fact, Co and natural graphite are listed as critical raw materials (CRMs) in Europe since 2010 and Mn, and Li are on the boundary of criticality. While recycling is identified as a solution to potentially reduce the gap between the demand and supply. Recycling of lithium ion battery (LIB) has attracted a lot of attention in the recent years and focuses primarily on valuable metals such as cobalt, nickel and lithium. During the recycling processes, considerable amount of the components are lost like electrolyte, separator or graphite. For instance, graphite can either be slagged-off or consumed as a reductant agent during pyrometallurgical treatment. Some other loses are due to a lack of liberation of the targeted particles, elements such as Co are lost in the coarse fractions and a not recovered in the right product. Hence, there is a need to find innovative and comprehensive LIB recycling operations.
For understanding and be able to quantify the loses and recycling process efficiency a deeper characterization is required. This research proposes a new characterization method based on automated mineralogy. In this study, the particles morphologies (size, composition and phases associations) are analysed. The liberation of active materials from electrodes is quantified by comparing two recycling processes: mechanical and thermochemical-mechanical. The mechanical route operates with an impact shear crusher while for the thermomechanical operation the batteries were vacuum pyrolyzed at 500-650oC before to be crushed. The black mass, fraction below 1 mm from the recycling processes, were classified in 4 size fractions based on the particles size distribution. Each fraction was characterized by various analytical methods, including X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Atomic Absorption Spectrometry (AAS) and SEM-based automated mineralogy. The latter consists in the combination of a scanning electron microscopy (SEM) image analysis and energy dispersive X-ray spectroscopy (EDS). It is a powerful and well-known method for primary material characterization; however, it has not yet been applied to secondary material such as black mass, which is a challenging material to analyse due fine alloys particles and to the lack of an existing dedicated database.
In this research, a database for battery characterization is also aimed aside from the determination of the liberation efficiency of the processes employed. Furthermore, a unique procedure was used in preparing the grain mounts for SEM-EDS analysis. Here, iodoform is added to modify the grey level of resin, which improves the contrast with the carbon phases. This technic allows the quantification of the carbon phases which is also a limitation of XRF and XRD aside from the fact that these methods cannot provide images for qualitative evaluation. This study showed that the thermo-mechanical process liberates more active particles from the foils than only a mechanical process. For both processes, a liberation selectivity of the electrode foils was observed. Cu foil is better liberated than Al foils. By consequence, most of the graphite particles are concentrated in the <63μm fraction. However, it was
found that the process type has different effects on Al foil liberation. The thermomechanical process liberates more metal oxides from the Al foil than only mechanical process, but Al breakage is more affected by thermal treatment, which creates finer Al particles, which can be problematic for further hydrometallurgy routes.

Keywords: Recycling; Lithium ion battery; Automated mineralogy; critical raw material; Graphite

Permalink: https://www.hzdr.de/publications/Publ-32271
Publ.-Id: 32271


Highlight selection of radiochemistry and radiopharmacy developments by editorial board (January-June 2020).

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

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to describe trends in the field.
Results: This commentary of highlights has resulted in 19 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-32266
Publ.-Id: 32266


Curvilinear magnetism: fundamentals and applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring geometrical curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-4]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral responses and topologically induced magnetization patterning [5-7]. The possibility to tailor magnetic responses by geometry of the object is a new approach to material science, which allows to obtain a desired functionality of spintronic and spin-orbitronic devices yet without the need to rely on the optimization of the intrinsic material properties. The application potential of 3D-shaped magnetic thin films is currently being explored as mechanically shapeable magnetic field sensors [8] for automotive applications, magnetoelectrics for memory devices, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive electronics [9-11]. The magnetosensitive smart skins allow digitizing the bodily motion and offer new means of touchless manipulation of virtual objects based on the interaction with magnetic stray fields of small permanent magnets [9,11] but also with geomagnetic field [10]. The fundamentals as well as application relevant aspects of curvilinear magnetism will be covered in this presentation.

[1] R. Streubel et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Sheka et al., Nonlocal chiral symmetry breaking in curvilinear magnetic shells. Communications Physics 3, 128 (2020)
[5] V. Kravchuk et al., Multiplet of Skyrmion states on a curvilinear defect: Reconfigurable Skyrmion lattices. Phys. Rev. Lett. 120, 067201 (2018)
[6] O. Pylypovskyi et al., Chiral Skyrmion and Skyrmionium States Engineered by the Gradient of Curvature. Phys. Rev. Appl. 10, 064057 (2018)
[7] O. Pylypovskyi et al., Coupling of chiralities in spin and physical spaces: The Möbius ring as a case study. Phys. Rev. Lett. 114, 197204 (2015)
[8] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[9] G. S. Cañón Bermúdez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[10] G. S. Cañón Bermúdez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[11] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).

Keywords: flexible electronics; curvilinear magnetism; magnetosensitive smart skins

  • Lecture (others) (Online presentation)
    Seminar at the University of Kiel, 11.02.2021, Kiel, Germany

Permalink: https://www.hzdr.de/publications/Publ-32265
Publ.-Id: 32265


Mechanisms of pyrite biodepression with Acidithiobacillus ferrooxidans in seawater flotation

San Martin, F.; Kracht, W.; Vargas, T.; Rudolph, M.

It has been shown that bacterium Acidithiobacillus ferrooxidans can be used to depress pyrite in seawater flotation at natural pH, which opens the possibility for its use as an alternative to lime to depress pyrite in copper sulfide flotation. In order to have a better understanding of the mechanisms involved in pyrite depression with A. ferrooxidans, different kind of experiments were carried out, including, contact angle, attachment kinetics, and streaming potential measurements. All these experiments were carried out in seawater. Biodepression of pyrite was improved by increasing the pH from 4 to 8, with a decrease in recovery from 92% to 36%. This increase in depressing capability was accompanied by an increase in attachment density of bacteria on pyrite, from bacteria/g to bacteria/g at pH 4 and 8, respectively. These results suggest that the mechanism of depression is related to the attachment of bacteria to the pyrite surface. The streaming potential measurements showed that both bacteria and pyrite were negatively charged at pH 8. This indicates that electrostatic forces are mainly repulsive, therefore other forces cause the attachment of bacteria to the mineral. The contact angle of pyrite conditioned with seawater at pH 8 was 16, which increased to 54 when collector (sodium isopropyl xanthate) was added, indicating an increase in hydrophobicity. Nevertheless, when pyrite was previous conditioned with bacteria, the contact angle increased only to 44 when collector was added. Thus, the collector has a lower influence in the hydrophobicity of pyrite when the mineral has interacted with bacteria A. ferrooxidans.

Keywords: Flotation; Seawater; Pyrite; Biodepression; Acidithiobacillus ferrooxidans

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Permalink: https://www.hzdr.de/publications/Publ-32264
Publ.-Id: 32264


Advanced Analysis of Bubble Columns: Comparison of Euler/Lagrange Simulations and Experiments under CO2 chemisorption conditions

Taborda, M. A.; Kipping, R.; Hampel, U.; Sommerfeld, M.

The chemical absorption reaction of CO2 in a circular bubble column reactor was simulated with an Euler/Lagrange CFD method and results were compared with data from a laboratory scale bubble column. The experimental data comprises gas holdup and bubble size distributions obtained with ultrafast X-ray tomography and hydroxide ion conversion obtained with a wire-mesh sensor. Large Eddy Simulation (LES) is used for calculating the fluid flow and modelling the turbulence in the continuous phase, considering the effect of sub-grid-scale (SGS) turbulence on bubble motion, and also SGS turbulence modification by bubbles. Lagrangian bubble tracking is conducted considering all relevant forces, bubble oscillation via stochastic generation of eccentricity and motion angle and consequently non-steady mass transfer via a dynamic Sherwood number. The comparison of experimental and simulation results shows very good agreement for the given data.

Keywords: Euler/Lagrange approach; bubble dynamics model; reactive two-phase flow; dynamic Sherwood number; wire-mesh sensor; ultrafast X-ray computed tomography

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Permalink: https://www.hzdr.de/publications/Publ-32261
Publ.-Id: 32261


Study of the parameter dependence of laser-accelerated protons from a hydrogen cluster source

Aurand, B.; Schwind, K. M.; Toncian, T.; Aktan, E.; Cerchez, M.; Lessmann, L.; Mannweiler, C.; Prasad, R.; Khoukaz, A.; Willi, O.

We present a study on laser-driven proton acceleration from a hydrogen cluster target. Aiming for the optimisation of the proton source, we performed a detailed parametric scan of the interaction conditions by varying different laser and the target parameters. While the underlying process of a Coulomb-explosion delivers moderate energies, in the range of 100 s of keV, the use of hydrogen as target material comes with the benefit of a debris-free, single-species proton acceleration scheme, enabling high repetition-rate experiments, which are very robust against shot-to-shot fluctuations.

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Permalink: https://www.hzdr.de/publications/Publ-32260
Publ.-Id: 32260


Direct laser acceleration of electrons assisted by strong laser-driven azimuthal plasma magnetic fields

Gong, Z.; Mackenroth, F.; Wang, T.; Yan, X. Q.; Toncian, T.; Arefiev, A. V.

A high-intensity laser beam propagating through a dense plasma drives a strong current that robustly sustains a strong quasistatic azimuthal magnetic field. The laser field efficiently accelerates electrons in such a field that confines the transverse motion and deflects the electrons in the forward direction. Its advantage is a threshold rather than resonant behavior, accelerating electrons to high energies for sufficiently strong laser-driven currents. We study the electron dynamics via a test-electron model, specifically deriving the corresponding critical current density. We confirm the model's predictions by numerical simulations, indicating energy gains two orders of magnitude higher than achievable without the magnetic field.

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Permalink: https://www.hzdr.de/publications/Publ-32259
Publ.-Id: 32259


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