Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35836 Publications

2D MOFs: A New Platform for Optics?

Arora, H.; Park, S.; Dong, R.; Erbe, A.

With the research on inorganic 2D semiconductors reaching its zenith, the search for new materials beyond these traditional 2D materials is at a rapid pace. In this article, we present an emerging class of 2D semiconductors, so-called metal-organic frameworks, in terms of their synthesis, intrinsic properties, and underlying charge transport mechanisms. Further, we discuss their potential as active elements in optical applications.

Keywords: Metal-organic frameworks; Two-dimensional semiconductors; Photonics; optical applications; photodetectors; high-mobility materials; sensors

Permalink: https://www.hzdr.de/publications/Publ-31584
Publ.-Id: 31584


Protonen als Alternative zur konventionellen Strahlentherapie – Unterschiede und Herausforderungen

Spautz, S.; Stützer, K.

Die externe Strahlentherapie ist eine wesentliche Komponente bei der Behandlung von Tumoren. Üblicherweise wird dafür Photonenstrahlung verwendet. Jedoch hat sich die Protonentherapie auf Grund ihrer physikalischen Eigenschaften zu einer attraktiven Alternative entwickelt. Vor allem ihre überlegene Dosisverteilung ermöglicht im Vergleich zur herkömmlichen Strahlentherapie eine bessere Normalgewebsschonung, wodurch potentiell das Risiko von Nebenwirkungen und Toxizitäten sinkt. Wir geben hier einen einleitenden Überblick zu den physikalischen Protoneneigenschaften und den Möglichkeiten der Dosisformierung. Insbesondere werden auch spezielle Herausforderungen in der Protonentherapie und damit verbundene aktuelle Forschungsschwerpunkte vorgestellt.

Keywords: Protonentherapie; Physikalische Grundlagen; Herausforderungen; Forschungsschwerpunkte

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  • Secondary publication expected from 01.11.2021

Permalink: https://www.hzdr.de/publications/Publ-31582
Publ.-Id: 31582


Optimal allocation of proton therapy slots in combined proton-photon radiotherapy

Loizeau, N.; Fabiano, S.; Papp, D.; Stützer, K.; Jakobi, A.; Bandurska-Luque, A.; Troost, E. G. C.; Richter, C.; Unkelbach, J.

Purpose: Proton therapy is a limited resource, which is not available to all patients who may benefit from it. We investigate combined proton-photon treatments, in which some fractions are delivered with protons and the remaining fractions with photons, as an approach to maximize the benefit of limited proton therapy resources at a population level.
Methods: To quantify differences in normal tissue complication probability (NTCP) between protons and photons, we consider a cohort of 45 head-and-neck cancer patients for which IMRT and IMPT plans were previously created, in combination with NTCP models for xerostomia and dysphagia considered in the Netherlands for proton patient selection. Assuming limited availability of proton slots, we develop methods to optimally assign proton fractions in combined proton-photon treatments to minimize the average NTCP on a population level. Such combined treatments are compared to patient selection strategies in which patients are assigned to single-modality proton or photon treatments.
Results: There is a benefit of combined proton-photon treatments over patient selection due to the nonlinearity of NTCP functions, i.e. the initial proton fractions are the most beneficial whereas additional proton fractions have a decreasing benefit when a flatter part of the NTCP curve is reached. This effect was small for the patient cohort and NTCP models considered, but may be larger if dose-response relationships are better known. In addition, when proton slots are limited, patient selection methods face a tradeoff between leaving slots unused and blocking slots for future patients who may have a larger benefit. Combined proton-photon treatments with flexible proton slot assignment provide a method to make optimal use of all available resources.
Conclusions: Combined proton-photon treatments allow for a better utilization of limited proton therapy resources. The benefit over patient selection schemes depends on the NTCP models and the dose differences between protons and photons.

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  • Secondary publication expected from 09.04.2022

Permalink: https://www.hzdr.de/publications/Publ-31581
Publ.-Id: 31581


New reaction rates for the destruction of 7Be during big bang nucleosynthesis measured at CERN/n_TOF and their implications on the cosmological lithium problem

Mengoni, A.; Damone, L. A.; Barbagallo, M.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, 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.; 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.; Krtička, 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.; 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.

New measurements of the 7Be(n,α)4He and 7Be(n,p)7Li reaction cross sections from thermal to keV neutron energies have been recently performed at CERN/n_TOF. Based on the new experimental results, astrophysical reaction rates have been derived for both reactions, including a proper evaluation of their uncertainties in the thermal energy range of interest for big bang nucleosynthesis studies. The new estimate of the 7Be destruction rate, based on these new results, yields a decrease of the predicted cosmological 7Li abundance insufficient to provide a viable solution to the cosmological lithium problem.

Permalink: https://www.hzdr.de/publications/Publ-31579
Publ.-Id: 31579


Status and perspectives of the neutron time-of-flight facility n_TOF at CERN

Chiaveri, E.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, M.; 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.; 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.; Krtička, 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.

Since the start of its operation in 2001, based on an idea of Prof. Carlo Rubbia [1], the neutron time of-flight facility of CERN, n_TOF, has become one of the most forefront neutron facilities in the world for wide-energy spectrum neutron cross section measurements. Thanks to the combination of excellent neutron energy resolution and high instantaneous neutron flux available in the two experimental areas, the second of which has been constructed in 2014, n_TOF is providing a wealth of new data on neutron-induced reactions of interest for nuclear astrophysics, advanced nuclear technologies and medical applications. The unique features of the facility will continue to be exploited in the future, to perform challenging new measurements addressing the still open issues and long-standing quests in the field of neutron physics. In this document the main characteristics of the n_TOF facility and their relevance for neutron studies in the different areas of research will be outlined, addressing the possible future contribution of n_TOF in the fields of nuclear astrophysics, nuclear technologies and medical applications. In addition, the future perspectives of the facility will be described including the upgrade of the spallation target, the setup of an imaging installation and the construction of a new irradiation area.

Permalink: https://www.hzdr.de/publications/Publ-31578
Publ.-Id: 31578


Measurement of the energy-differential cross-section of the 12C(n,p)12B and 12C(n,d)11B reactions at the n_TOF facility at CERN

Barbagallo, M.; Aberle, O.; Alcayne, V.; Amaducci, S.; Andrzejewski, J.; Audouin, L.; Babiano-Suarez, V.; Bacak, 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.; Krtička, 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.

Although the 12C(n,p)12B and 12C(n,d)11B reactions are of interest in several fields of basic and applied Nuclear Physics the present knowledge of these two cross-sections is far from being accurate and reliable, with both evaluations and data showing sizable discrepancies. As part of the challenging n_TOF program on (n,cp) nuclear reactions study, the energy differential cross-sections of the 12C(n,p)12B and 12C(n,d)11 B reactions have been measured at CERN from the reaction thresholds up to 30 MeV neutron energy. Both measurements have been recently performed at the long flight-path (185 m) experimental area of the n_TOF facility at CERN using a pure (99.95%) rigid graphite target and two silicon telescopes. In this paper an overview of the experiment is presented together with a few preliminary results.

Permalink: https://www.hzdr.de/publications/Publ-31577
Publ.-Id: 31577


Measurement of the 242Pu(n, γ) cross section from thermal to 500 keV at the Budapest research reactor and CERN n_TOF-EAR1 facilities

Lerendegui-Marco, J.; Guerrero, C.; Mendoza, E.; Quesada, J. M.; Eberhardt, K.; Junghans, A.; Krtiička, M.; Belgya, T.; Maróti, B.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bécares, V.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Barros, S.; Bečvář, F.; Beinrucker, C.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Furman, V.; Göbel, K.; García, A. R.; Gawlik, A.; Glodariu, T.; Gonçalves, I. F.; González-Romero, E.; Goverdovski, A.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heftrich, T.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Knapova, I.; Kokkoris, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Musumarra, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, J. I.; Praena, J.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Weigand, M.; Weiss, C.; Wolf, C.; Woods, P. J.; Wright, T.; Žugec, P.; The N_TOF Collaboration

The design and operation of innovative nuclear systems requires a better knowledge of the capture and fission cross sections of the Pu isotopes. For the case of capture on 242Pu, a reduction of the uncertainty in the fast region down to 8-12% is required. Moreover, aiming at improving the evaluation of the fast energy range in terms of average parameters, the OECD NEA High Priority Request List (HPRL) requests high-resolution capture measurements with improved accuracy below 2 keV. The current uncertainties also affect the thermal point, where previous experiments deviate from each other by 20%. A fruitful collaboration betwen JGU Mainz and HZ Dresden-Rossendorf within the EC CHANDA project resulted in a 242Pu sample consisting of a stack of seven fission-like targets making a total of 95(4) mg of 242Pu electrodeposited on thin (11.5 μm) aluminum backings. This contribution presents the results of a set of measurements of the 242Pu(n, γ) cross section from thermal to 500 keV combining different neutron beams and techniques. The thermal point was determined at the Budapest Research Reactor by means of Neutron Activation Analysis and Prompt Gamma Analysis, and the resolved (1 eV - 4 keV) and unresolved (1 - 500 keV) resonance regions were measured using a set of four Total Energy detectors at the CERN n_TOF-EAR1.

Permalink: https://www.hzdr.de/publications/Publ-31576
Publ.-Id: 31576


Co(NO3)2 as an inverted umbrella-type chiral noncoplanar ferrimagnet

Danilovich, I. L.; Deeva, E. B.; Bukhteev, K. Y.; Vorobyova, A. A.; Morozov, I. V.; Volkova, O. S.; Zvereva, E. A.; Maximova, O. V.; Solovyev, I. V.; Nikolaev, S. A.; Phuyal, D.; Abdel-Hafiez, M.; Wang, Y. C.; Lin, J.-Y.; Chen, J. M.; Gorbunov, D.; Puzniak, K.; Lake, B.; Vasiliev, A. N.

The low-dimensional magnetic systems tend to reveal exotic spin-liquid ground states or form peculiar types of long-range order. Among systems of vivid interest are those characterized by the triangular motif in two dimensions. The realization of either ordered or disordered ground state in triangular, honeycomb, or kagome lattices is dictated by the competition of exchange interactions, also being sensitive to anisotropy and the spin value of magnetic ions.While the low-spin Heisenberg systems may arrive to a spin-liquid long-range entangled quantum state with emergent gauge structures, the high-spin Ising systems may establish the rigid noncollinear structures. Here, we present the case of chiral noncoplanar inverted umbrella-type ferrimagnet formed in cobalt nitrate Co(NO3)2 below TC = 3 K with the comparable spin and orbital contributions to the total magnetic moment.

Permalink: https://www.hzdr.de/publications/Publ-31575
Publ.-Id: 31575


Recent progress in contact, mobility, and encapsulation engineering of InSe and GaSe

Arora, H.; Erbe, A.

The field of two-dimensional (2D) materials has stimulated considerable interest in the scientific community. Owing to quantum confinement in one direction, intriguing properties have been reported in 2D materials that cannot be observed in their bulk form. The advent of semiconducting 2D materials with a broad range of electronic properties has provided fascinating opportunities to design and configure next-generation electronics. One such emerging class is the family of III–VI monochalcogenides, the two prominent members of which are indium selenide (InSe) and gallium selenide (GaSe). In contrast to transition metal dichalcogenides (TMDCs), their high intrinsic mobility and the availability of a direct bandgap at small thicknesses have attracted researchers to investigate the underlying physical phenomena as well as their technological applications. However, the sensitivity of InSe and GaSe to environmental influences has limited their exploitation in functional devices. The lack of methods for their scalable synthesis further hinders the realization of their devices. This review article outlines recent advancements in the synthesis and understanding of the charge transport properties of InSe and GaSe for their integration into technological applications. A detailed summary of the improvements in the device structure by optimizing extrinsic factors such as bottom substrates, metal contacts, and device fabrication schemes is provided. Furthermore, various encapsulation techniques that have been proven effective in preventing the degradation of InSe and GaSe layers under ambient conditions are thoroughly discussed. Lastly, this article presents an outlook on future research ventures with respect to ongoing developments and practical viability of these materials.

Keywords: 2D materials; indium selenide; gallium selenide; electronic properties; vdW semiconductors; 2D transistors

Permalink: https://www.hzdr.de/publications/Publ-31574
Publ.-Id: 31574


Dataset for: Morphology of flashing feeds at critical fluid properties in larger pipes

Döß, A.; Schubert, M.; Hampel, U.
DataManager: Wiezorek, Michael

This data set contains cross-sectional averaged vapor fraction data obtained for flashing refrigerant in the horizontal feed section (inner pipe diameter of 200 mm) of the TERESA facility. The data was obtained with the Wire-mesh Sensor Framework GUI (Version 1.3.0). The archive 'void' contains .epst-files which are organized as a two column table (ASCII). The first column denotes the time step (in seconds), the second column is the cross-sectional averaged vapor fraction in percent.

Allocation of the files to the operational conditions is included separate .csv-file (overview.csv), which contains 12 columns for each measurement. Here the averaged values of the .epst-files are included as well.

In this study, two wire-mesh sensors were operated simultaneously. WMS1 (*_X_Sensor_1.epst) was located in an axial distance of L = 2.5 D from the flash nozzle and WMS2 (*_Y_Sensor_2.epst) was located L = 17.5 D away from the flash nozzle.  

Keywords: TERESA; Flashing feed; Wire-mesh sensor

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-10-01
    DOI: 10.14278/rodare.418
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31573
Publ.-Id: 31573


Detection of REEs with lightweight UAV-based hyperspectral imaging.

Booysen, R.; Jackisch, R.; Lorenz, S.; Zimmermann, R.; Kirsch, M.; Nex, P. A. M.; Gloaguen, R.

Rare Earth Elements (REEs) supply is important to ensure the energy transition, e-mobility and ultimately to achieve the sustainable development goals of the United Nations. Conventional exploration techniques usually rely on substantial geological field work including dense in-situ sampling with long delays until provision of analytical results. However, this approach is limited by land accessibility, financial status, climate and public opposition. Efficient and innovative methods are required to mitigate these limitations. The use of lightweight Unmanned Aerial Vehicles (UAVs) provides a unique opportunity to conduct rapid and non-invasive exploration even in socially sensitive areas and in relatively inaccessible locations. We employ drones with hyperspectral sensors to detect REEs at the Earth’s surface and thus contribute to a rapidly evolving field at the cutting edge of exploration technologies. We showcase for the first time the direct mapping of REEs with lightweight hyperspectral UAV platforms. Our solution has the advantage of quick turn-around times (<1d), low detection limits (<200ppm for Nd) and is ideally suited to support exploration campaigns. This procedure was successfully tested and validated in two areas: Marinkas Quellen, Namibia, and Siilinjärvi, Finland. This strategy should invigorate the use of drones in exploration and for the monitoring of mining activities.

Permalink: https://www.hzdr.de/publications/Publ-31572
Publ.-Id: 31572


Reducing entrainment in ultrafine particle flotation by selective flocculation of gangue material

Sygusch, J.; Rudolph, M.

Froth flotation is an efficient and well-established separation technique for particles with sizes ranging from 10 µm to 200 µm, but when it comes to the separation of ultrafine particles (< 10 µm) there are still some challenges. This research is part of the German research foundation priority programme DFG-SPP 2045 “MehrDimPart” and aims at developing a method for the separation of ultrafine particles based on multiple particle properties, such as wettability, morphology (shape or roughness) and size. In this study, the focus lies on the investigation of the effect of particle size on the flotation outcome.
A system consisting of ultrafine size fractions of glass particles as the valuable material and magnetite as the gangue material is used for testing. Wettability analysis is carried out using inverse gas chromatography, whereas size and shape properties are obtained via a combination of laser diffraction and microscopic analysis. In order to investigate the effect of particle size, the magnetite is selectively flocculated using macromolecules as flocculants. A novel flotation apparatus, designed for the flotation of ultrafine particles by combining advantages from column flotation and machine-type froth flotation, is used for all flotation tests.

Keywords: Ultrafine Particles; Flotation; Selective flocculation; Entrainment

  • Poster (Online presentation)
    10. ProcessNet-Jahrestagung und 34. DECHEMA-Jahrestagung der Biotechnologen 2020, 21.-24.09.2020, Online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31571
Publ.-Id: 31571


Zur Mineralogie von Vulkaniten und Lithophysen im Bereich des unterpermischen Leisniger Porphyrs (Nordwestsächsisches Becken)

Götze, J.; Möckel, R.; Breitkreuz, C.; Georgi, U.; Klein, A.

Mineralogische und geochemische Untersuchungen an Proben des Leisniger Porphyrs sowie von Gangporphyren, Pechsteinen und Lithophysen (Hochtemperatur-Kristallisationsdomänen) im entsprechenden Verbreitungsgebiet wurden durchgeführt, um eine mineralogisch-petrographische Charakteristik dieser vulkanischen Bildungen und deren Zuordnung zu möglichen vulkanischen Edukten zu erarbeiten. Phasenanalytische Untersuchungen (Röntgendiffraktometrie, Mikroskopie, Kathodolumineszenz - KL) erbrachten eine monotone Mineralzusammensetzung, die von Quarz, den beiden Kalifeldspat-Phasen Sanidin und Orthoklas sowie Biotit dominiert ist. Anhand der geochemischen Charakteristika (Röntgenfluoreszenzanalyse - RFA) lassen sich die untersuchten Vulkanite überwiegend als Rhyolithe einstufen. Das Vorkommen von hypidiomorphen Quarzphänokristen, z.T. mit Einbuchtungen, gut erhaltenen Kalifeldspäten, sowie das Fehlen von Glas-Shards und Fiamme (Bimsfetzen) deuten darauf hin, dass es sich bei den vulkanischen Ablagerungen im Untersuchungsgebiet um keine Pyroklastite (Ignimbrite) handelt. Neuere Untersuchungen (Rehda 2018) gehen davon aus, dass es sich bei den Gesteinen nicht um klassische Fließlaven handelt, sondern um einen Lakkolith, der sich unter den Rochlitz-Ignimbrit eingeschoben hat. Damit müsste auch die bisherige stratigraphische Einordnung des Leisniger Porphyrs in die KohrenFormation korrigiert werden und eine Einordnung in die frühe Oschatz-Formation erfolgen. Die deutlichen Übereinstimmungen aller Gesteinstypen hinsichtlich mineralogischer Zusammensetzung, chemischer Charakteristik, Ausbildung der Phänokristen sowie deren KL-Eigenschaften deuten auf die Herkunft aus einem gemeinsamen Magmenreservoir hin. Auftretende Unterschiede sind im Wesentlichen auf sekundäre Alterationen zurückzuführen. Allerdings zeigen Geländebefunde und vertikal ausgerichtete Gefüge in Pechsteinen und Gangporphyren, dass diese vulkanischen Bildungen den eigentlichen Leisniger Porphyr wahrscheinlich zu einem späteren Zeitpunkt in Form vertikaler Gangstrukturen durchschlagen haben. Aufgrund der mineralogischen und geochemischen Ähnlichkeiten der Kristallisationsdomänen der Lithophysen und aller Gesteinstypen im Verbreitungsbereich des Leisniger Porphyrs kann bisher keine eindeutige Zuordnung
der Lithophysen- und Achatbildungen zu einer speziellen Gesteinsgruppe erfolgen. Aus Geländebefunden ist eine Häufung in Kreuzungsbereichen von Gangporphyren und Pechsteinen mit dem eigentlichen Leisniger Porphyr zu beobachten, was allerdings im Anstehenden oder in Bohrproben nicht direkt nachgewiesen werden
konnte. Die Bildung der Lithophysen im Bereich einer glasigen Fazies konnte ebenfalls bisher nicht bestätigt werden, da keine randlichen Anhaftungen von Pechsteinrelikten an den Lithophysen (wie im Fall des Kemmlitzer Porphyrs) beobachtet wurden. Auf Grund spezifischer textureller und mineralogischer Unterschiede kann allerdings eine Zuordnung der Lithophysen zum Seifersdorfer Porphyr im Liegenden bzw. zum Rochlitz-Ignimbrit im Hangenden ausgeschlossen werden.

Mineralogical and geochemical investigations were carried out on samples of the Leisnig porphyry including certain vein-like porphyries, pitchstones and lithophysae (HTCD - high temperature crystallization domains) in the distribution area to get information about mineralogical and petrographical characteristics of the volcanic rocks and their origin. Analytical results of X-ray diffraction, microscopy and cathodoluminescence (CL) revealed a monotonous mineral composition dominated by quartz, orthoclase/sanidine and biotite. The volcanic rocks can be classified as rhyolite according to geochemical characteristics (X-ray fluorescence – XRF). Hypidiomorphic quartz phenocrysts, partially with embayments, well preserved K-feldspar, and the absence of glass shards and fiamme disclose a pyroclastic formation (ignimbrite) of the rocks of the Leisnig porphyry in contrast to the Rochlitz ignimbrite in the same area. Recent results of Rehda (2018) indicate that the volcanic rocks of the Leisnig porphyry were not formed by flowing lava, but represent a laccolith that emplaced below the volcanic rocks of the Rochlitz ignimbrite. This consideration would result in a stratigraphic position of the Leisnig porphyry in the early Oschatz Formation instead of the previously assumed position in the Kohren Formation. The common mineralogical and chemical composition of all rock types, as well as similar characteristics of phenocrysts including their CL properties, indicate an origin from the same magma chamber or at least a melt with similar composition. Detected differences can mainly be related to secondary alteration processes. Field observations and vertically oriented textures in pitchstones and vein porphyries show that these volcanic rocks subsequently penetrated the Leisnig porphyry as vertical vein structures. Up to now, no unambiguous assignment of the lithopysae and associated agates can be done to one of the rock types in the distribution area of the Leisnig porphyry because of their similarities in mineralogy and geochemistry with the crystallization domains of the lithophysae. Based on field observations, a preferred occurrence of lithophysae in cross areas of vein porphyries and pitchstones with the Leisnig porphyry is assumed. However, this assumption could not be proven directly in outcrops or drilling samples. Although the formation of lithophysae in a glassy facies is most likely (as it was proven for the Kemmlitz porphyry), this assumption could not be confirmed due to the lack of adherent pitchstone relics on the lithophysae. However, mineralogical and textural differences to the underlying Seifersdorf porphyry and the overlying Rochlitz ignimbrite disclose an assignment of the lithophysae in the area of the Leisnig porphyry to these volcanic rocks.

  • Veröffentlichungen des Museums für Naturkunde Chemnitz 43(2020)-5-44

Permalink: https://www.hzdr.de/publications/Publ-31570
Publ.-Id: 31570


Better Together: Ilmenite/Hematite Junctions for Photoelectrochemical Water Oxidation

Berardi, S.; Kesavan, J. K.; Amidani, L.; Meloni, E. M.; Marelli, M.; Boscherini, F.; Caramori, S.; Pasquini, L.

Hematite (α-Fe₂O₃) is an Earth-abundant indirect n-type semiconductor displaying a band gap of about 2.2 eV, useful for collecting a large fraction of visible photons, with frontier energy levels suitably aligned for carrying out the photoelectrochemical water oxidation reaction under basic conditions. The modification of hematite mesoporous thin film photoanodes with Ti(IV), as well as their functionalization with an oxygen evolving catalyst, leads to a six-fold increase in photocurrent density with respect to the unmodified electrode. In order to provide a detailed understanding of this behavior, we report a study of Ti-containing phases within the mesoporous film structure. Using X-ray absorption fine structure and high-resolution transmission electron microscopy coupled with electron energy loss spectroscopy, we find that Ti(IV) ions are incorporated within ilmenite (FeTiO₃) near-surface layers, thus modifying the semiconductor-electrolyte interface. To the best of our knowledge, this is the first time that a FeTiO₃/α -Fe₂O₃ composite is used in a photoelectrochemical set-up for water oxidation. In fact, previous studies of Ti(IV)-modified hematite photoanodes reported the formation of pseudobrookite (Fe₂TiO₅) at the surface. By means of transient absorption spectroscopy, transient photocurrent experiments, and electrochemical impedance spectroscopy, we show that the formation of the Fe₂O₃/FeTiO₃ interface passivates deep traps at the surface and induce a large density of donor levels, resulting in a strong depletion field that separates electron and holes, favoring hole injection in the electrolyte. Our results provide the identification of a phase coexistence with enhanced photoelectrochemical performance, allowing for the rational design of new photoanodes with improved kinetics.

Keywords: Photoelectrochemistry; Hematite; Titanium; EXAFS; Electron Microscopy; Transient Absorption Spectroscopy; Heterointerface; Oxygen Evolution Catalyst

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-31569
Publ.-Id: 31569


Formation and crystallographic orientation of NiSi2-Si interfaces

Fuchs, F.; Khan, B.; Deb, D.; Pohl, D.; Schuster, J.; Weber, W. M.; Mühle, U.; Löffler, M.; Georgiev, Y. M.; Erbe, A.; Gemming, S.

The transport properties of novel device architectures depend strongly on the morphology and the quality of the interface between contact and channel materials. In silicon nanowires with nickel silicide contacts, NiSi 2-Si interfaces are particularly important as NiSi 2 is often found as the phase adjacent to the silicide-silicon interface during and after the silicidation. The interface orientation of these NiSi 2-Si interfaces as well as the ability to create abrupt and flat interfaces, ultimately with atomic sharpness, is essential for the properties of diverse emerging device concepts. We present a combined experimental and theoretical study on NiSi 2-Si interfaces. Interfaces in silicon nanowires were fabricated using silicidation and characterized by high-resolution (scanning) transmission electron microscopy. It is found that {111} interfaces occur in 〈110»nanowires. A tilted interface and an arrow-shaped interface are observed, which depends on the nanowire diameter. We have further modeled NiSi 2-Si interfaces by density functional theory. Different crystallographic orientations and interface variations, e.g., due to interface reconstruction, are compared with respect to interface energy densities. The {111} interface is energetically most favorable, which explains the experimental observations. Possible ways to control the interface type are discussed.

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Publ.-Id: 31568


Detection of manufactured nanomaterials in complex environmental compartments – An expert review

Schymura, S.; Hildebrand, H.; Völker, D.; Schwirn, K.; Franke, K.; Fischer, C.

Manufactured nanomaterials (NMs) are materials in which 50% or more of the particles have one or more dimensions between 1 nm and 100 nm. These NMs show interesting properties. However, the same properties that motivate their use in applications are also reason for concern, as NMs can cause toxic reactions and have mobilities in the environment different from bulk materials of the same elements. Despite considerable scientific efforts, the selective detection of manufactured NMs in environmental compartments is still a very complex and challenging task. An expert review of the literature has been conducted on behalf of the German Environment Agency (UBA) to identify relevant methods for nanomaterial detection in complex media in the context of environmental monitoring and a need for action was concluded from the existing body of work.

Keywords: Nanoparticle detection; Environment; complex systems

  • Poster (Online presentation)
    Nanosafety 2020, 05.-07.10.2020, Saarbrücken, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31567
Publ.-Id: 31567


Radiolabeling of nanoparticles - A versatile tool in nanosafety research

Schymura, S.; Hildebrand, H.; Rybkin, I.; Strok, M.; Franke, K.

The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. The monitoring of nanoparticles (NPs) in such complex natural systems as soil, natural waters, plants, sewage sludge, etc. very is challenging using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by the use of radiolabeling which provides an easy way of accurately quantifying nanoparticles in complex systems without extensive sample preparation, regardless of any particulate or elemental background.
We have developed various methods of introducing radiotracers into the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles.

Keywords: Radiolabeling; nanoparticles

  • Poster (Online presentation)
    Nanosafety 2020, 05.-07.10.2020, Saarbrücken, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31566
Publ.-Id: 31566


Monitoring laser-induced magnetization in FeRh by transient terahertz emission spectroscopy

Awari, N.; Semisalova, A.; Deinert, J.-C.; Lenz, K.; Lindner, J.; Fullerton, E.; Uhlir, V.; Li, J.; Clemens, B.; Carley, R.; Scherz, A.; Kovalev, S.; Gensch, M.

In this study, a conceptually different approach for investigating magnetic phase transitions in ultra-thin films is presented. THz emission from a laser-excited material is used to monitor the magnetization dynamics during the laser-driven antiferromagnetic to ferromagnetic transition in FeRh. The emitted THz signal is calibrated against static magnetometry data measurements, giving a direct measure of the absolute magnetic moment of the sample on the sub-picosecond timescale. The technique is, therefore, highly complementary to conventional time-resolved experiments such as time resolved magneto-optic Kerr effect (MOKE) or x-ray magnetic circular dichroism.

Keywords: Magnetization dynamics; terahertz; ultrafast; FeRh

  • Open Access Logo Applied Physics Letters 117(2020), 122407-1-122407-6
    Online First (2020) DOI: 10.1063/5.0019663

Permalink: https://www.hzdr.de/publications/Publ-31565
Publ.-Id: 31565


Grating-graphene metamaterial as a platform for terahertz nonlinear photonics

Deinert, J.-C.; Alcaraz Iranzo, D.; Perez, R.; Jia, X.; Hafez, H. A.; Ilyakov, I.; Awari, N.; Chen, M.; Bawatna, M.; Ponomaryov, O.; Germanskiy, S.; Bonn, M.; Koppens, F. H. L.; Turchinovich, D.; Gensch, M.; Kovalev, S.; Tielrooij, K.-J.

Nonlinear optics is an increasingly important field for scientific and technological applications, owing to its relevance and potential for optical and optoelectronic technologies. Currently, there is an active search for suitable nonlinear material systems with efficient conversion and small material footprint. Ideally, the material system should allow for chip-integration and room-temperature operation. Two-dimensional materials are highly interesting in this regard. Particularly promising is graphene, which has demonstrated an exceptionally large nonlinearity in the terahertz regime. Yet, the light-matter interaction length in two-dimensional materials is inherently minimal, thus limiting the overall nonlinear-optical conversion efficiency. Here we overcome this challenge using a metamaterial platform that combines graphene with a photonic grating structure providing field enhancement. We measure terahertz third-harmonic generation in this metamaterial and obtain an effective third-order nonlinear susceptibility with a magnitude as large as 3·10−⁸ m² /V² , or 21 esu, for a fundamental frequencyof 0.7 THz. This nonlinearity is 50 times larger than what we obtain for graphene without grating. Such an enhancement corresponds to third-harmonic signal with an intensity that is three orders of magnitude larger due to the grating. Moreover, we demonstrate a field conversion efficiency for the third harmonic of up to ∼1% using a moderate field strength of ∼30 kV/cm. Finally we show that harmonics beyond the third are enhanced even more strongly, allowing us to observe signatures of up to the 9th harmonic. Grating-graphene metamaterials thus constitute an outstanding platform for commercially viable, CMOS compatible, room temperature, chip-integrated,THz nonlinear conversion applications.

Keywords: terahertz; harmonics; graphene; nonlinear; field enhancement; metamaterial

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Permalink: https://www.hzdr.de/publications/Publ-31564
Publ.-Id: 31564


Experimental data of the ROCOME2.3 experiment

Kliem, S.
DataManager: Grahn, Alexander

The experiment ROCOM E2.3 represents a boron dilution event in a KONVOI-type pressurized lightwater reactor. It was conducted at room temperature with de-mineralized water without boric acid. Underborated water slugs were modelled by adding Ethanol in order to adjust a density difference of 1.22% with respect to the regular coolant inventory. At the beginning of the experiment, the slugs are enclosed between two valves in the cold legs of loops 1 and 2. The volume of the two water slugs accounts for 0.0576 m 3 (57.6 l) each and the slug fronts are located at 1.8 m upstream of the pressure vessel inlet nozzles. The experiment is started by opening the loop valves and running up the circulation pumps. The time dependency of the volumetric flow rates in all four coolant loops can be found in https://doi.org/10.1016/j.nucengdes.2020.110776. During the experiment, the mixing process was recorded by wire-mesh conductivity sensors at various positions within the coolant loops and the pressure vessel.  The nomenclature of the data files as well as the format of the tables are described in the accompanying document DataDescription_ROCOME23.pdf.

Keywords: boron dilution; coolant mixing; pressurized water reactor

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-25
    DOI: 10.14278/rodare.527
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31562
Publ.-Id: 31562


Presence of Bradyrhizobium sp. under continental conditions in Central Europe

Griebsch, A.; Matschiavelli, N.; Lewandowska, S.; Schmidtke, K.

Soil samples from different locations with varied cultivation histories of soybeans were taken from arable fields in 2018 in East Germany and Poland (Lower Silesia) to evaluate the specific microsymbionts of the soybean, Bradyrhizobium japonicum, over the years after inoculation. Soybean was grown in the selected farms between 2011 and 2017. The aim of the experiment is to investigate whether there is a difference in rhizobia content in soils in which soybean was grown over a different period of time and whether this might lead to differences in plant growth of soybean. The obtained soil samples were directly transferred into containers, then sterilized soybean seeds were sown into pots in the greenhouse. After 94 days of growth, the plants were harvested and various parameters such as nodular mass, number of nodules and dry matter in the individual plant parts were determined. In addition, the relative abundance of Bradyrhizobium sp. in soil samples was determined identified by sequencing. No major decline in Bradyrhizobia could be observed due to a longer interruption of soybean cultivation. Soil properties such as pH, P and Mg content had no significant influence on the formation of nodule mass and number, but seem to have an influence on the relative abundance of Bradyrhizobium sp. The investigations have shown that Bradyrhizobium japonicum persists longer in arable soils even under the site conditions of Central Europe and forms an effective symbiosis with soybeans.

Permalink: https://www.hzdr.de/publications/Publ-31561
Publ.-Id: 31561


Zur Untersuchung schwerer Erdalkalimetalle für die radiopharmazeutische Anwendung

Bauer, D.

Ein maßgebliches medizinisches Problem unserer Gesellschaft sind Krebs- und Tumor-erkrankungen. Aus diesem Grund sind die verbesserte Diagnose und Früherkennung von Krebserkrankungen sowie die Entwicklung neuer und effizienterer Therapiemöglichkeiten ein wichtiger Aspekt der gegenwärtigen medizinischen Forschung.
Die zielgerichtete α-Partikel Therapie (TAT, engl. Targeted Alpha-particle Therapy) ist eine spezielle Form der nuklearmedizinischen Behandlung von Krebserkrankungen und ordnet sich im Feld der Radionuklidtherapie ein. Die TAT hebt sich gegenüber anderen Radionuklidtherapien, wie der Behandlung mit β--oder Auger-Elektronen-Emittern, dadurch hervor, dass sie Chemo- und Strahlungsresistenzen überwinden kann, eine hohe biologische Wirksamkeit zeigt, und dabei gesundes Gewebe vergleichsmäßig wenig belastet.
Bei der TAT werden α-emittierende Radionuklide, hauptsächlich Radiometalle, mittels eines Radiopharmakons zielgerichtet an oder in die Krebszellen transportiert, welche dort hochenergetische α-Partikel emittieren, die zum Absterben des entarteten Gewebes führen. Um ein Radiopharmakon auf Basis eines Radiometalls herzustellen, werden die entsprechenden Radionuklide mittels eines Chelators stabil gebunden, welcher wiederum mit einem Vektormolekül verknüpft ist. Vektormoleküle können dabei monoklonale Antikörper oder niedermolekulare Verbindungen sein, welche spezifische Eigenschaften der Krebszelle adressieren und damit das selektive Binden an diese ermöglichen.
Nur wenige α-Emitter erfüllen die Voraussetzungen, um in der TAT eingesetzt werden zu können. Aus der Reihe der schweren Erdalkalimetalle stammen die beiden α-Emitter Radium 223 und Radium-224, welche großes Potential für eine solche radiopharmazeutische Anwendung besitzen. Zusätzlich kann der γ Emitter Barium 131, dessen Element das nächst leichtere Homologe des Radiums ist, zum Therapie-Monitoring eingesetzt werden. Aufgrund der chemischen Ähnlichkeit der Elemente Barium und Radium können beide mittels des gleichen Chelators gebunden und deren Radionuklide im Rahmen eines kombinierten diagnostischen und therapeutischen – eines so genannten theranostischen – Ansatzes in der Onkologie genutzt werden. Da von Radium keine stabilen Isotope existieren, dient Barium auch als ein nicht-radioaktives Surrogat, um Chelatoren initial bezüglich ihrer Komplex-bildungseigenschaften zu untersuchen.
Ziel dieser Arbeit war es, das Potential ausgewählter Radionuklide aus der Gruppe der schweren Erdalkalimetalle für die radiopharmazeutische Anwendung zu erschließen, und dafür die Möglichkeit ihrer stabilen Bindung in einem Radiopharmakon mittels eines geeigneten Chelators zu untersuchen. Der Fokus lag dabei auf Barium 131 und Radium 224. Als potentielle Chelatoren wurden die beiden Substanzklassen der Calix[4]aren-krone-6-Derivate und der Cavitanden untersucht.
Bei diesen Verbindungen handelt es sich um Makrozyklen, welche aus vier aromatischen Einheiten aufgebaut sind. Ihre Anordnung formt eine Kavität, welche auf die Ionengrößen von Barium und Radium zugeschnitten ist. Die beiden Grundstrukturen verfügen jeweils über acht Sauerstoffatome, die für die Koordination an Ba2+- beziehungsweise Ra2+-Ionen, ideale Donoratome darstellen.
Um die Interaktion der Liganden mit (nicht-radioaktiven) Bariumionen untersuchen zu können, wurden analytische Verfahren auf der Basis von NMR- und UV/Vis-Spektroskopie etabliert. Bei diesen Untersuchungen wurde für die Cavitanden trotzt weitreichender Optimierungsversuche keine Einlagerung von Bariumionen festgestellt.
Für die Calix[4]krone-6-basierten Derivate wurden die entsprechenden 1:1 Metallion-Ligand-Chelate mit Bariumionen hergestellt und nachgewiesen. Die Stabilität der Chelate wurde mit einer Titrationsmethode auf Basis von NMR- und UV/Vis Detektion bestimmt. Aufgrund der geringen Wasserlöslichkeit der gewählten Verbindungen wurden die initialen Versuche im Lösungsmittel Acetonitril durchgeführt. In nachfolgenden Optimierungsschritten wurden Calix[4]krone-6-basierte Chelatoren hergestellt, welche in Hinblick auf das HSAB-Konzept noch besser auf schwere Erdalkalimetalle abgestimmt waren. Zusätzlich wurden diese Chelatoren über funktionelle Gruppen mit einem Vektormolekül verknüpft, welches die Wasserlöslichkeit erhöhte.
Für nachfolgende Radiomarkierungsversuche wurden Dünnschichtchromatographie-Systeme etabliert, welche die Untersuchung von [131Ba]Ba2+- und [224Ra]Ra2+-Chelaten im wässrigen Medium sowie unter kompetitiven Bedingungen ermöglichten. Es konnten jedoch für alle Calix[4]krone-6-Derivate unter wässrigen Bedingungen keine Chelate nachgewiesen werden. Anschließende Untersuchungen legten nahe, dass das Radiometall kinetisch nicht ausreichend stabil in den Calix[4]krone-6-Derivate gebunden ist

Keywords: Radium-223; Barium-131; Makrozyklen; targetd Alpha-Therrapy

  • Doctoral thesis
    TU Dresden, 2020
    Mentor: PD Dr. habil. Constantin Mamat
    162 Seiten

Permalink: https://www.hzdr.de/publications/Publ-31560
Publ.-Id: 31560


Nanocytometer for smart analysis of peripheral blood and acute myeloid leukemia: a pilot study

Schütt, J.; Sandoval Bojorquez, D. I.; Avitabile, E.; Oliveros Mata, E. S.; Milyukov, G.; Colditz, J.; Delogu, L. G.; Rauner, M.; Feldmann, A.; Koristka, S.; Middeke, J. M.; Sockel, K.; Faßbender, J.; Bachmann, M.; Bornhäuser, M.; Cuniberti, G.; Baraban, L.

We realize an ultracompact nanocytometer for real-time impedimetric detection and classification of subpopulations ofliving cells. Nanoscopic nanowires in a microfluidic channel act asnanocapacitors and measure in real time the change of theamplitude and phase of the output voltage and, thus, the electricalproperties of living cells. We perform the cell classification in thehuman peripheral blood (PBMC) and demonstrate for thefirsttime the possibility to discriminate monocytes andsubpopulationsof lymphocytes in a label-free format. Further, we demonstrate thatthe PBMC of acute myeloid leukemia and healthy samples grantthe label free identification of the disease. Using the algorithmbased on machine learning, we generatedspecific data patternstodiscriminate healthy donors and leukemia patients. Such a solutionhas the potential to improve the traditional diagnostics approaches with respect to the overall cost and time effort, in a label-freeformat, and restrictions of the complex data analysis.

Keywords: mpedance cytometer; nanosensor; POC diagnostics; PBMCs; acute myeloid leukemia (AML); machine learning for data treatment

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Permalink: https://www.hzdr.de/publications/Publ-31558
Publ.-Id: 31558


Tailoring the Electronic and Magnetic Properties of Hematene by Surface Passivation: Insights from First-principles Calculations

Wei, Y.; Ghorbani Asl, M.; Krasheninnikov, A.

Exfoliation of atomically-thin layers from non-van der Waals bulk solids gave rise to the emergence of a new class of two-dimensional (2D) materials, such as hematene (Hm), a structure just a few atoms thick obtained from hematite. Due to a large number of unsaturated sites, Hm surface can be passivated under ambient conditions. Using density functional theory calculations, we investigate the effects of surface passivation with H and OH groups on Hm properties and demonstrate that the passivated surfaces are energetically favorable under oxygen-rich conditions. While the bare sheet is antiferromagnetic and possesses an indirect band gap of 0.93 eV, the hydrogenated sheets are half-metallic with a ferromagnetic ground state, and the fully hydroxylated sheets are antiferromagnetic with a larger band gap as compared to the bare system. The electronic structure of Hm can be further tuned by mechanical deformations. The band gap of fully passivated Hm increases monotonically with biaxial strain, hinting at potential applications of Hm in electromechanical devices.

Keywords: Two-dimensional materials; Hematene; Surface Passivation; First-principles Calculations

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Permalink: https://www.hzdr.de/publications/Publ-31557
Publ.-Id: 31557


Eddy Current Flow Meter performance in liquid metal flows inclined to the sensor axis

Krauter, N.; Galindo, V.; Wondrak, T.; Eckert, S.; Gerbeth, G.

The Eddy Current Flow Meter is a reliable and robust inductive sensor for the measurement of flowrates in liquid metal flows. This kind of sensor is usually being used in pipe flows where the flow is mostly parallel to the sensor axis. When this sensor is used as part of the safety instrumentation above the subassemblies in liquid metal cooled fast reactors, the flow angle may change rapidly according to the conditions within the reactor. In this paper we investigate the performance of the Eddy Current Flow Meter in flows inclined to the sensor axis by numerical simulations as well as model experiments. We demonstrate that the Eddy Current Flow Meter yields reliable results for flow angles up to 30° while the sensitivity of the sensor is significantly reduced for larger angles.

Keywords: inductive measurements; flow velocity; flow angle; Eddy Current Flow Meter

  • Journal of Nuclear Engineering and Radiation Science 8(2022)1, 011303
    Online First (2021) DOI: 10.1115/1.4050420

Permalink: https://www.hzdr.de/publications/Publ-31556
Publ.-Id: 31556


Depth selective magnetic phase coexistence in FeRh thin films

Griggs, W.; Eggert, B.; Liedke, M. O.; Butterling, M.; Wagner, A.; Kentsch, U.; Hirschmann, E.; Grimes, M.; Caruana, A. J.; Kinane, C.; Wende, H.; Bali, R.; Thomson, T.

We demonstrate the manipulation of magnetic phasesin FeRh thin filmsthrough atomic displacementsand the distributionof structural defects. Atomic scale disorder can be controlled via irradiation withlight noble gas ions, producingdepth-varying nanoscale phase configurationsof distinct antiferromagnetic, ferromagnetic and paramagnetic regions. Here, we perform a spatial characterization of the magnetic phasesandthe local magnetic environment around the Fe atoms,as well as the variation ofthe open-volumes around atomic sites. Thus,a direct correspondence between the existence of the three magnetic phases andlattice defects is revealed. By careful selection of the irradiating fluence, we show that it is possible to produce simple and thermally stable magnetic configurations, such as uniform magnetisation or a bilayer phase structure.Furthermore, the thin film surface and interfaces are observed as the nucleation sites for the transitions between the phases. These results demonstrate a sensitive nanoscale manipulation of magnetic properties, shedding light on magnetic ordering in alloy lattices and broadening the scope for applications.

Keywords: Magnetic modification; PNR; Induced disorder; Phase transitions; FeRh

Permalink: https://www.hzdr.de/publications/Publ-31555
Publ.-Id: 31555


Guideline on current good radiopharmacy practice (cGRPP) for the small-scale preparation of radiopharmaceuticals

Gillings, N.; Hjelstuen, O.; Ballinger, J.; Béhé, M.; Decristoforo, C.; Elsinga, P.; Ferrari, V.; Kolenc Peitl, P.; Koziorowski, J.; Laverman, P.; Mindt, T.; Neels, O.; Ocak, M.; Patt, M.; Todde, S.

This guideline on current good radiopharmacy practice (cGRPP) for small-scale preparation of radiopharmaceuticals represents the view of the Radiopharmacy Committee of the European Association of Nuclear Medicine (EANM). The guideline is laid out in the format of the EU Good Manufacturing Practice (GMP) guidelines as defined in EudraLex volume 4. It is intended for non-commercial sites such as hospital radiopharmacies, nuclear medicine departments, research PET centres and in general any healthcare establishments. In the first section, general aspects which are applicable to all levels of operations are discussed. The second section discusses the preparation of small-scale radiopharmaceuticals (SSRP) using licensed generators and kits. Finally, the third section goes into the more complex preparation of SSRP from non-licensed starting materials, often requiring a purification step and sterile filtration. The intention is that the guideline will assist radiopharmacies in the preparation of diagnostic and therapeutic SSRP´s safe for human administration.

Keywords: cGRPP; GMP; radiopharmaceuticals; radiopharmacy

Permalink: https://www.hzdr.de/publications/Publ-31554
Publ.-Id: 31554


Anisotropy of the magnetocaloric effect: Example of Mn5Ge3

Maraytta, N.; Voigt, J.; Salazar Mejia, C.; Friese, K.; Scurschii, I.; Perßon, J.; Salman, S. M.; Brückel, T.

We have investigated the field direction dependence of thermo-magnetic behavior in single crystalline Mn5Ge3. The adiabatic temperature change ΔTad in pulsed fields, the isothermal entropy change ΔSiso calculated from static magnetization measurements, and heat capacity have been determined for fields parallel and perpendicular to the easy magnetic direction [001]. The isothermal magnetization measurements yield, furthermore, the uniaxial anisotropy constants in second and fourth order, K1 and K2. We discuss how the anisotropy affects the magneto-caloric effect (MCE) and compare the results to the related compound MnFe4Si3, which features an enhanced MCE, too, but instead exhibits strong easy plane anisotropy. Our study reveals the importance of magnetic anisotropy and opens new approaches for optimizing the performance of magnetocaloric materials in applications.

Permalink: https://www.hzdr.de/publications/Publ-31553
Publ.-Id: 31553


Pulsed laser deposition of Fe-oxypnictides: Co- and F-substitution

Haindl, S.; Sato, M.; Wurmehl, S.; Büchner, B.; Kampert, W. A. G.

The majority of thin film studies that were devoted to Fe-oxyarsenides has focused so far on F-substituted (i.e. indirectly electron doped) LnOFeAs (Ln = La, Nd, Sm). Here we turn our attention towards Co-substituted (i.e. directly electron doped) LaOFeAs and SmOFeAs in order to investigate its growth on different substrate materials by using pulsed laser deposition (PLD). We detected dominant LnOFeAs phase formation and discuss the occurrence of minor impurity phases in the different films on different substrates. The lack of a superconducting transition in LnOFe0.85Co0.15As films on MgO(100) could be due to strain, since we observe an onset of superconductivity in SmOFe1−xCoxAs (x = 0.07, 0.15) films on other oxide substrates. In addition, Co-substitution (i.e. within the Fe2As2 layers) and F-substitution (i.e. within the Ln2O2 layers) leading to direct and indirect electron doping respectively, appears for films deposited on CaF2 substrates. In contrast to the F-substituted but Co-free Fe-oxyarsenides, the co-doped SmO1−xFxFe0.85Co0.15As film has experimentally accessible upper critical fields down to the lowest temperatures and may serve as an ideal test bed for further theoretical modeling of Fe-oxyarsenides.

Permalink: https://www.hzdr.de/publications/Publ-31552
Publ.-Id: 31552


Preparation of γ-Al₂O₃/α-Al₂O₃ ceramic foams as catalyst carriers via the replica technique

Shumilov, V.; Kirilin, A.; Tokarev, A.; Boden, S.; Schubert, M.; Hampel, U.; Hupa, L.; Salmi, T.; Murzin, D. Y.

This work describes an effective method for the preparation of open-cell ceramic foams for their further use as catalyst supports. The polyurethane sponge replica technique was applied using a ceramic suspension based on a mixture of α-alumina, magnesia and titania and polyvinyl alcohol solution as a liquid component. The polyurethane sponge was etched with NaOH and covered with colloidal silica to obtain better adhesion of the slurry to the walls of the polymeric material onto it. The surface area of the ceramic carrier was increased by adding a layer of γ-alumina. Deposition of an active catalytic phase (Pt) was done by impregnation. Properties of the carriers and the final catalyst were investigated by a number of physico-chemical methods such as TEM, SEM, XRD and computer tomography. Hydrogenation of ethyl benzoylformate was performed to elucidate the catalytic properties of foam catalysts illustrating their applicability.

Keywords: γ-Al₂O₃/α-Al₂O₃; catalytic foams; macroporous ceramics; hydrogenation of ethylbenzoylformate

Permalink: https://www.hzdr.de/publications/Publ-31551
Publ.-Id: 31551


Single-Shot Measurement of Post-Pulse-GeneratedPre-Pulse in High-Power Laser Systems

Kon, A.; Nishiuchi, M.; Kiriyama, H.; Kando, M.; Bock, S.; Ziegler, T.; Püschel, T.; Zeil, K.; Schramm, U.; Kondo, K.

In this study, a detailed investigation of the dynamics of the generation of pre-pulse bypost-pulses is presented, using single-shot self-referenced spectral interferometry (SRSI). The capabilityof SRSI in terms of the single-shot measurement of the temporal contrast of high-power lasersystems has been experimentally demonstrated. The results confirm that the energy levels of thepre-pulses increase proportional to the square of the B-integral parametrizing the nonlinearity of theamplifier chain.

Keywords: laser pulse contrast; high-intensity lasers; B-integral

Permalink: https://www.hzdr.de/publications/Publ-31549
Publ.-Id: 31549


Supplementary simulations for laser foil experiments on TOD variation

Göthel, I.

Simulations made with PIConGPU in 2d geometry with a longitudinally modified gaussian laser on a foil.
The laser has been modified to reproduce the main features of the pulse shape seen in the experiments as a result of modifying TOD and GVD.
The three main features, which were enabled with varying strength in the simulations:
 - an exponential ramp on the timescale of 300fs before the gaussian main pulse
 - a postpulse with around 100fs delay and around 0.2 of the total pulse energy
 - a skewness of the gaussian - modelled by two gaussian halves for the rising and falling part

From the spectra of the accelerated protons the cutoff energy is measured. The main result is, that the variations of the spectra are much smaller than those observed in the experiments, suggesting more complex mechanisms than those modelled here.

Keywords: laser particle acceleration

  • Software in the HZDR data repository RODARE
    Publication date: 2020-09-22
    DOI: 10.14278/rodare.521
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31548
Publ.-Id: 31548


Single-shot diagnostics development for high power laser driven relativistic plasma experiments at the Helmholtz-Zentrum Dresden-Rossendorf

Bock, S.; Püschel, T.; Helbig, U.; Gebhardt, R.; Oksenhendler, T.; Bernert, C.; Couperus Cabadağ, J. P.; Ziegler, T.; Schöbel, S.; Zeil, K.; Irman, A.; Toncian, T.; Cowan, T.; Schramm, U.

At the HZDR TO-AC contrast measurement tools and newly developed single-shot diagnostics characterizing laser pulses are applied for laser improvements and particle acceleration experiments. An overview of the applied techniques and recent results is presented.

  • Invited lecture (Conferences) (Online presentation)
    CLEO 2020, 11.-15.05.2020, San Jose, California, USA

Permalink: https://www.hzdr.de/publications/Publ-31547
Publ.-Id: 31547


Control of magneto-optical properties of cobalt-layers by adsorption of α-helical polyalanine self-assembled monolayers

Sharma, A.; Matthes, P.; Soldatov, I.; Arekapudi, S. S. P. K.; Böhm, B.; Lindner, M.; Selyshchev, O.; Thi, N. H. N.; Mehring, M.; Tegenkamp, C.; Schulz, S. E.; Zahn, D. R. T.; Paltiel, Y.; Hellwig, O.; Salvan, G.

The adsorption of chiral molecules was recently shown to trigger a change in the magnetisation of mesoscopic magnetic domains in a ferromagnetic underlayer. In this work, we investigated the macroscopic (magneto-)optical response of chemisorbed α-helical polyalanine self-assembled monolayers (SAMs) on a gold and gold-capped-cobalt thin film on Au substrates using spectroscopic ellipsometry and magneto-optical Kerr effect spectroscopy and microscopy. The optical and magneto-optical spectra reveal selective chemisorption of the α-helical polyalanine molecules depending on the orientation of the substrate remanent magnetisation during the SAMs process. Moreover, a sign change of the magneto-optical response was observed in some of the magnetic substrates after the chiral SAMs formation.

Permalink: https://www.hzdr.de/publications/Publ-31546
Publ.-Id: 31546


Characterization of Accumulated B-Integral of Regenerative Amplifier Based CPA Systems

Bock, S.; Marie Herrmann, F.; Püschel, T.; Helbig, U.; Gebhardt, R.; Johannes Lötfering, J.; Pausch, R.; Zeil, K.; Ziegler, T.; Irman, A.; Oksenhendler, T.; Kon, A.; Nishuishi, M.; Kiriyama, H.; Kondo, K.; Toncian, T.; Schramm, U.

We report on a new approach to measure the accumulated B-integral in the regenerative and multipass amplifier stages of ultrashort-pulse high-power laser systems by B-integral-induced coupling between delayed test post-pulses and the main pulse. A numerical model for such non-linear pulse coupling is presented and compared to data taken at the high-power laser Draco with self-referenced spectral interferometry (SRSI). The dependence of the B-integral accumulated in the regenerative amplifier on its operation mode enables optimization strategies for extracted energy vs. collected B-integral. The technique presented here can, in principle, be applied to characterize any type of ultrashort pulse laser system and is essential for pre-pulse reduction.

Keywords: Petawatt laser; temporal pulse contrast; B-integral; self-referenced spectral interferometry

Permalink: https://www.hzdr.de/publications/Publ-31545
Publ.-Id: 31545


Fluid Mechanics of Liquid Metal Batteries

Weier, T.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Weber, N.

The quest for renewable energy sources entails an increasingly intermittent electricity supply.
Transmission grid updates can only partially account for balancing the resulting variations and large-scale stationary storage will gain importance in future energy landscapes dominated by volatile sources.
Today’s battery technologies were, with the notable exception of redox-flow batteries, mainly designed for and driven by mobile applications. Those prioritize properties (energy density, power rating) that are less important for stationary storage. Thus, battery technologies developed from the ground up to meet the needs of stationary storage have the potential to much better address the specifics of huge capacity installations.
Liquid metal batteries (LMBs) are a new technology for grid-scale energy storage, see [1] for a comprehensive review. They consist of all liquid cells that operate with liquid metals as electrodes and molten salts as electrolytes. The liquids separate into three stably stratified layers by virtue of density and mutual immiscibility (see the two upper left inserts in Fig. 1a). This conceptually very simple and self-assembling structure has the unique advantage to allow for an easy scale-up at the cell level: single-cell cross sections can potentially reach several square-meters. Such cell sizes enable highly favourable and otherwise unattainable ratios of active to construction material because of the cubic scaling (volume) of the former and the quadratic scaling (surface) of the latter. The total costs should therefore largely be determined by those of the active materials.
The talk will start with a general introduction to LMBs and then focus on the fluid mechanics in these devices [2]. Electric currents, magnetic fields, and heat and mass transfer are tightly coupled with the cells’ electrochemistry. First a number of fluid dynamic instabilities will be discussed in relation to operational safety. The remainder of the talk will deal with transport phenomena in the positive electrode. While transport in most modern battery systems is typically dominated by diffusion and migration in micrometer-scale liquid layers and solids, convection - with exception of the aforementioned redox-flow batteries - rarely plays a role. This is in stark contrast to LMBs were mediated by the fully liquid interior fluid flow can be driven by various mechanisms. The influence of solutal convection on the cycling behavior of a cell (Fig. 1a) will be demonstrated. Electromagnetically induced convection can be used to improve mixing (Fig. 1b) thereby mitigating diffusion overpotentials.

Keywords: liquid metal batteries; electro-vortex flows; mass transfer; solutal convection

  • Invited lecture (Conferences) (Online presentation)
    Department Seminar Mechanical Engineering Department, 16.10.2020, Dearborn, MI, USA

Permalink: https://www.hzdr.de/publications/Publ-31544
Publ.-Id: 31544


Polyoxometalates in Extraction and Sorption Processes

Jelinek, L.; Mištová, E.; Kubeil, M.; Stephan, H.

Polyoxometalates (POMs) represent a fascinating class of inorganic cluster compounds. Due to the almost unlimited possibilities to tailor size, shape and charge of this compound class and to perform various surface functionalization, they are discussed for different applications, especially in the fields of catalysis, material sciences and biomedicine. In contrast, the systematic study of extraction and sorption properties of POMs has received relatively little attention so far. This review article provides a brief overview of relevant POM structures used for effective and selective phase transfer of metal ions from aqueous into organic media as well as for the development of efficient sorption processes. The use of inorganic-organic POM-based hybrid materials for extraction and sorption processes is also discussed.

Keywords: cluster compounds; POM hybrid materials; inclusion; metal ions; phase transfer; sorption efficacy

Permalink: https://www.hzdr.de/publications/Publ-31543
Publ.-Id: 31543


Highly Conductive Collagen by Low-Temperature Atomic Layer Deposition of Platinum

Bishal, A. K.; Anderson, N. D.; Hung, S. K. H.; Jokisaari, J. R.; Klie, R. F.; Koh, A.; Abdussalam, W.; Sukotjo, C.; Takoudis, C. G.

In modern biomaterial-based electronics, conductive and flexible biomaterials are gaining increasing attention for their wide range of applications in biomedical and wearable electronics industries. The ecofriendly, biodegradable, and self-resorbable nature of these materials makes them an excellent choice in fabricating green and transient electronics. Surface functionalization of these biomaterials is required to cater to the need of designing electronics based on these substrate materials. In this work, a low-temperature atomic layer deposition (ALD) process of platinum (Pt) is presented to deposit a conductive thin film on collagen biomaterials, for the first time. Surface characterization revealed that a very thin ALD-deposited seed layer of TiO2 on the collagen surface prior to Pt deposition is an alternative for achieving a better nucleation and 100% surface coverage of ultrathin Pt on collagen surfaces. The presence of a pure metallic Pt thin film was confirmed from surface chemical characterization. Electrical characterization proved the existence of a continuous and conductive Pt thin film (∼27.8 ± 1.4 nm) on collagen with a resistivity of 295 ± 30 μΩ cm, which occurred because of the virtue of TiO2. Analysis of its electronic structures showed that the presence of metastable state due to the presence of TiO2 enables electrons to easily flow from valence into conductive bands. As a result, this turned collagen into a flexible conductive biomaterial.

Keywords: collagen; atomic layer deposition; platinum thin films; conductive biomaterials; electronic structures

Permalink: https://www.hzdr.de/publications/Publ-31542
Publ.-Id: 31542


Investigation of Mild Steel Corrosion in the Cement Production Associated with the Usage of Secondary Fuels

Thieme, M.; Bergmann, U.; Kiesewetter, A.; Wehry, T.; Potzger, K.; Zarzycki, A.; Marszalek, M.; Worch, H.

The present work deals with the corrosion of mild steel (1.0037) used as the outer construction material of the preheater of a modern industrial cement production facility. The facility uses secondary fuels, which introduce considerable amounts of corrosive species. The situation at the examination sites in the preheater zone is tracked over a period of two years including operation and shut-down periods. The investigation is focused on (i) the acquisition of the underlying physicochemical conditions, such as moisture, temperature, and contamination data at the examination site of the preheater, (ii) the multianalytical identification of the formed corrosion products using scanning electron microscopy combined with energy-dispersive X-ray analysis, infrared spectrometry, Raman spectrometry, X-ray diffractometry, and Möβbauer spectrometry, and (iii) voltammetric and EIS laboratory investigations using model solutions. It was evidenced that corrosion takes place at a temperature level of about 100°C in the presence of moisture and oxygen as well as chloride ion as a consequence of the usage of secondary fuels. Typical hot-gas corrosion could be excluded under the current conditions. Appearance, structure, and nature of the corrosion products were found to be not mainly dependent on the varied length of exposure, but on the conditions of the hosting preheater intake. In addition to different FeOOH phases and hematite, magnetite was found, dependent on the oxygen concentration in the process gas. The decisive role of oxygen as key factor for the corrosion rate was electrochemically confirmed.

Keywords: Mössbauer spectroscopy; corrosion

Permalink: https://www.hzdr.de/publications/Publ-31541
Publ.-Id: 31541


Dosimetry with the ability to distinguish pulsed and non-pulsed dose contributions

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

The concept of an active dosimetry system for pulsed radiation dose rate measurements is presented. Real-time distinction of pulsed and non-pulsed radiation contributions is based on the time structure of a single interaction. A fast tissue equivalent plastic scintillator is exploited to minimize the pile-up effect influence on absorbed energy measurements. Being connected to a fully digital signal processing board, the detector creates an active dosimetry system with adjustable parameters. With this system, absorbed dose rate measurements were carried out in a photon field with a time structure mimicking a radiotherapeutic beam, but also in the presence of a constant radiation field. Measurements show a linear dependence of a pulsed radiation contribution on the accelerator current in the investigated range of the total dose rate up to 8 μGy h⁻¹. While increasing the accelerator current by 1 μA, the pulsed radiation dose rate grows by (26.2±0.9) nGy h⁻¹ when considering pile-up events.

Keywords: gELBE; dosimetry

Permalink: https://www.hzdr.de/publications/Publ-31540
Publ.-Id: 31540


Comprehensive analysis of tumour sub-volumes for radiomic risk modelling in locally advanced HNSCC

Leger, S.; Zwanenburg, A.; Leger, K.; Lohaus, F.; Linge, A.; Schreiber, A.; Kalinauskaite, G.; Tinhofer, I.; Guberina, N.; Guberina, M.; Balermpas, P.; Von, D. G. J.; Ganswindt, U.; Belka, C.; Peeken, J.; Combs, S.; Böke, S.; Zips, D.; Richter, C.; Krause, M.; Baumann, M.; Troost, E. G. C.; Löck, S.

Radiomics aims to characterise the tumour phenotype using advanced image features to predict patient-specific outcome. ...

Keywords: radionmic; image-based risk modelling; machine learning; personalised therapy; radiation oncology

Permalink: https://www.hzdr.de/publications/Publ-31539
Publ.-Id: 31539


Identification of patient benefit from proton beam therapy in brain tumour patients based on dosimetric and NTCP analyses

Dutz, A.; Lühr, A.; Troost, E. G. C.; Agolli, L.; Bütof, R.; Valentini, C.; Baumann, M.; Vermeren, X.; Geismar, D.; Timmermann, B.; Krause, M.; Löck, S.

Background
The limited availability of proton beam therapy (PBT) requires individual treatment selection strategies, such as the model-based approach. We compared PBT and photon therapy using several normal tissue complication probability (NTCP) models to assess the feasibility of this approach in brain tumour patients.
Methods
For 92 patients treated at two PBT centres, volumetric modulated arc therapy treatment plans were retrospectively created for comparison with the clinically applied PBT plans. Several dosimetric parameters for the brain excluding tumour and margins, cerebellum, brain stem, frontal and temporal lobes, hippocampi, cochleae, chiasm, optic nerves, lacrimal glands, lenses, pituitary gland, and skin were compared between both modalities using Wilcoxon signed-rank tests. NTCP differences (ΔNTCP) were calculated for 11 models predicting brain necrosis, delayed recall, temporal lobe injury, hearing loss, tinnitus, blindness, ocular toxicity, cataract, endocrine dysfunction, alopecia, and erythema. A patient was assumed to be selected for PBT if ΔNTCP exceeded a threshold of 10 percentage points for at least one of the side-effects.
Results
PBT substantially reduced the dose in almost all investigated OARs, especially in the low and intermediate dose ranges and for contralateral organs. In general, NTCP predictions were significantly lower for PBT compared to XRT. Considering ΔNTCP of all models, 80 patients (87.0%) would have been selected for PBT in this in-silico study, mainly due to predictions of a model on delayed recall (51 patients). In contrast to the dosimetric analysis, NTCP was substantially reduced in ipsilateral organs.
Conclusion
This study underlines that physical dose-volume parameters alone may not be sufficient to describe the clinical relevance between different reatment techniques and highlights potential benefits of NTCP models. Further NTCP models for different modern treatment techniques are mandatory and existing models have to be externally validated in order to implement the model-based approach in clinical practice.

Keywords: cranial radiotherapy; model-based-approach; proton beam therapy; NTCP models

Permalink: https://www.hzdr.de/publications/Publ-31538
Publ.-Id: 31538


Toxicity of L19-Interleukin 2 combined with Stereotactic Body Radiation Therapy: A phase I study

van Limbergen Ej, H. A.; Lieverse, R.; Houben, R.; Overhof, C.; Jacobi, L.; Postma, A.; Zindler, J.; Verhelst, F.; Dubois, L.; De, R. D.; Troost, E. G. C.; Lambin, P.

Introduction
The immunocytokine L19-IL2 delivers interleukin-2 to the tumor by exploiting the selective L19-dependent binding of extradomain B of fibronectin on tumor blood vessels. In preclinical models, L19-IL2 has been shown to enhance the local and abscopal effects of radiotherapy. The clinical safety of L19-IL2 monotherapy has been established previously. In this study, the safety and tolerability of L19-IL2 following Stereotactic Body Radiotherapy (SBRT) was assessed.
Materials and methods
Patients with oligometastatic solid tumors received radical SBRT to all visible metastases. Within one week following SBRT, intravenous L19-IL2 using a 3+3 dose escalation design was administered. Safety and tolerability were analyzed as the primary endpoint using the CTCAE4.03 scoring system, progression-free and overall survival as secondary endpoints.
Results
A total of 6 patients in two L19-IL2 dose levels were included. The 15 Mio International Units (IU) dose level was well tolerated with no dose limiting toxicity. The most frequently reported adverse events were chills, noninfectious fever, fatigue, edema, erythema, pruritus, nausea/vomiting as well as cough and dyspnea. Blood analysis revealed abnormalities in liver function tests, anemia, hypoalbuminemia, and hypokalemia. At the second dose level (i.e., 22.5 Mio IU), which is the recommended dose for L19-IL2 monotherapy, all three included patients experienced dose-limiting toxicity, but toxicities recovered without sequelae. We documented two long-term progression-free responders both having non-small cell lung cancer as primary tumor.
Conclusion
Based in the results of this phase I clinical trial, the recommended phase II dose for SBRT combined with L19-IL2 is 15 Mio IU. The therapeutic efficacy of this combination is currently being evaluated in the multicentric EU-funded phase II clinical trial, ImmunoSABR.

Keywords: L19-IL2; SBRT; oligometastatic cancer; toxicity; safety; phase I

Permalink: https://www.hzdr.de/publications/Publ-31537
Publ.-Id: 31537


CT-based attenuation correction of whole-body radiotherapy treatment positioning devices in PET/MRI hybrid imaging

Taeubert, L.; Berker, Y.; Beuthien-Baumann, B.; Hoffmann, A. L.; Troost, E. G. C.; Kachelrieß, M.; Gillmann, C.

Objective To implement Computed Tomography (CT)-based attenuation maps of radiotherapy (RT) positioning hardware and radiofrequency (RF) coils to enable hybrid positron emission tomography/magnetic resonance imaging (PET/MRI)-based RT treatment planning. Materials and Methods The RT positioning hardware consisted of a flat RT table overlay, coil holders for abdominal scans, coil holders for head and neck scans and an MRI compatible hip and leg immobilization system. CT images of each hardware element were acquired on a CT scanner. Based on the CT images, attenuation maps of the devices were created. Validation measurements were performed on a PET/MR scanner using a 68Ge phantom (48 MBq, 10 min scan time). Scans with each device in treatment position were performed. Then, reference scans containing only the phantom were taken. The scans were reconstructed online (at the PET/MRI scanner) and offline (via e7tools on a PC) using identical reconstruction parameters. Average reconstructed activity concentrations of the device and reference scans were compared. Results The device attenuation maps were successfully implemented. The RT positioning devices caused an average decrease of reconstructed PET activity concentration in the range between -8.3 ± 2.1 % (mean ± SD) (head and neck coil holder with coils) to -1.0 ± 0.5 % (abdominal coil holder). With attenuation correction taking into account RT hardware, these values were reduced to -2.0 ± 1.2 % and 0.6 ± 0.5 %, respectively. The results of the offline and online reconstructions were nearly identical, with a difference of up to 0.2 %. Conclusion The decrease in reconstructed activity concentration caused by the RT positioning devices is clinically relevant and can successfully be corrected using CT-based attenuation maps. Both the offline and online reconstruction methods are viable options.

Permalink: https://www.hzdr.de/publications/Publ-31536
Publ.-Id: 31536


Dead time corrections for Bonner sphere measurements of secondary neutrons at a proton therapy facility

Dommert, M.; Reginatto, M.; Zbořil, M.; Lutz, B.

Radiation therapy with proton beams allows the deposition of high doses to the tumour while minimising dose to the surrounding tissue. During such treatment the patient is also exposed to secondary radiation which produces an out-of-field dose that affects healthy tissue. The largest contribution to this out-of-field dose comes from neutron radiation; therefore, it is of interest to fully characterise the neutron field in the therapy room with measurements. This is usually done with Bonner sphere spectrometers using active detectors, typically ³He-filled proportional counters, as central thermal neutron sensors. Under the experimental conditions encountered in proton therapy facilities, a proper analysis of the measurements is impossible unless dead time corrections are implemented. In this paper, we present a method using a paralysable dead time model for carrying out such corrections for Bonner sphere measurements with ³He-filled proportional counters and apply it to data taken at the University Proton Therapy Dresden (UPTD) facility in double scattering mode. The neutron events were recorded with time stamps and, based on this time-resolved data, the measured neutron rate distribution was sampled. Since the neutron flux is proportional to the proton flux, the integral neutron flux is directly related to the proton dose. Hence, we were able to estimate the detector dead time from the measured rate distributions recorded for a set of measurements with different proton dose rates. Experimental measurements with different intensities of the proton field show that the corrections are in agreement within 0.5% for measured signal rates smaller than 15×10³ counts per second and do not exceed 1% at 25×10³ counts per second.

Keywords: Neutron detectors; Instrumentation for hadron therapy; Data processing methods; Radiation monitoring

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  • Secondary publication expected from 30.03.2022

Permalink: https://www.hzdr.de/publications/Publ-31535
Publ.-Id: 31535


Wafer-scale 4H-silicon carbide-on-insulator (4H–SiCOI) platform for nonlinear integrated optical devices

Yi, A.; Zheng, Y.; Huang, H.; Lin, J.; Yan, Y.; You, T.; Huang, K.; Zhang, S.; Shen, C.; Zhou, M.; Huang, W.; Zhang, J.; Zhou, S.; Ou, H.; Ou, X.

4H-silicon carbide-on-insulator (4H–SiCOI) serves as a novel and high efficient integration platform for nonlinear optics and quantum photonics. The realization of wafer-scale fabrication of single-crystalline semi-insulating 4H–SiC film on Si (100) substrate using the ion-cutting and layer transferring technique was demonstrated in this work. The thermodynamics of 4H–SiC surface blistering is investigated via observing the blistering phenomenon with a series of implanted fluences and annealing temperatures. Surface tomography and the depth dependent film quality of the 4H–SiC have been extensively studied by employing scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, X-ray diffraction (XRD) was carried out and the diffraction spectrum reveals a narrow peak with a full width at half maximum (FWHM) of 75.6 arcsec, indicating a good maintenance of the single-crystalline phase for the prepared thin film of 4H–SiC as compared to its bulk counterpart. With the single-crystalline 4H–SiCOI, we have successfully fabricated a micro-ring resonator with a quality factor as high as 6.6 × 104. The reported 4H–SiCOI wafer provides a feasible monolithic platform for integrated photonic applications.

Permalink: https://www.hzdr.de/publications/Publ-31534
Publ.-Id: 31534


Classical and robust regression analysis with compositional data

van den Boogaart, K. G.; Filzmoser, P.; Hron, K.; Templ, M.; Tolosana Delgado, R.

Compositional data carry their relevant information in the relationships (logratios) between the compositional parts. It is shown how this source of information can be used in regression modeling, where the composition could either form the response, or the explanatory part, or even both. An essential step to set up a regression model is the way how the composition(s) enter the model. Here, balance coordinates will be constructed that support an interpretation of the regression coefficients and allow for testing hypotheses of subcompositional independence. Both classical least-squares regression and robust MM regression are treated, and they are compared within different regression models at a real data set from a geochemical mapping project.

Keywords: Balances; Robust regression; GEMAS project; Hypothesis testing; Robust bootstrap

Permalink: https://www.hzdr.de/publications/Publ-31533
Publ.-Id: 31533


High carrier mobility epitaxially aligned PtSe2 films grown by one-zone selenization

Sojkova, M.; Dobročka, E.; Hutár, P.; Tašková, V.; Pribusová-Slušná, L.; Stoklas, R.; Píš, I.; Bondino, F.; Munnik, F.; Hulman, M.

Few-layer PtSe2 films are promising candidates for applications in high-speed electronics, spintronics and photodetectors. Reproducible fabrication of large-area highly crystalline films is, however, still a challenge. Here, we report the fabrication of epitaxially aligned PtSe2 films using one-zone selenization of pre-sputtered platinum layers. We have studied the influence of growth conditions onstructural and electrical properties of the films prepared from Pt layers with different initial thickness. The best results were obtained for the PtSe2 layers grown at elevated temperatures (600 °C). The films exhibit signatures for a long-range in-plane ordering resembling an epitaxial growth. The charge carrier mobility determined by Hall-effect measurements is up to 24 cm²/V.s

Keywords: PtSe2; epitaxial films; Laue oscillations; Raman spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-31532
Publ.-Id: 31532


Series of Tetravalent Actinide Amidinates: Structure Determination and Bonding Analysis.

Kloditz, R.; Fichter, S.; Kaufmann, S.; Brunner, T. S.; Kaden, P.; Patzschke, M.; Stumpf, T.; Roesky, P. W.; Schmidt, M.; März, J.

Two series of isostructural tetravalent actinide amidinates [AnX((S)-PEBA)3] (An = Th, U, Np; X = Cl, N3) bearing the chiral (S,S)-N,N’-bis-(1-phenylethyl)benzamidinate ((S)- PEBA) ligand have been synthesized and thoroughly characterized in solid and in solution. This study expands the already reported tetravalent neptunium complexes to the lighter actinides thorium and uranium. Furthermore, a rare Ce(IV) amidinate [CeCl((S)-PEBA)3] was synthesized to compare its properties to those of the analogous tetravalent actinide complexes. All compounds were characterized in the solid state using single crystal XRD and infrared spectroscopy and in solution using NMR spectroscopy. Quantum chemical bonding analysis including also the isostructural Pa and Pu complexes was used to characterize the covalent contributions to any bond involving the metal cation. Th shows the least covalent character throughout the series, even substantially smaller than for the Ce complex. For U, Np, and Pu similar covalent bonding contributions are found, but a natural population analysis reveals different origins. The 6d participation is the highest for U and decreases afterwards, whereas the 5f participation increases continuously from Pa to Pu.

Keywords: actinides; coordination chemistry; bonding; NMR; DFT; transuranium chemistry; QTAIM; NPA

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Permalink: https://www.hzdr.de/publications/Publ-31531
Publ.-Id: 31531


The absence of metamictisation in natural monazite

Nasdala, L.; Akhmadaliev, S.; Burakov, B. E.; Chanmuang N, C.; Škoda, R.

The actinide-containing mineral monazite–(Ce) is a common accessory rock component that bears petrogenetic information, is widely used in geochronology and thermochronology, and is considered as potential host material for immobilisation of radioactive waste. Natural samples of this mineral show merely moderate degrees of radiation damage, despite having sustained high self-irradiation induced by the decay of Th and U (for the sample studied herein 8.9 ± 0.3 × 1019 α/g). This is assigned to low damage-annealing temperature of monazite–(Ce) and “alpha-particle-assisted reconstitution”.
Here we show that the response of monazite–(Ce) to alpha radiation changes dramatically, depending on the damage state. Only in radiation-damaged monazite–(Ce), 4He ions cause gradual structural restoration. In contrast, its high-temperature annealed (i.e. well crystalline) analogue and synthetic CePO4 experience He-irradiation damage. Alpha-assisted annealing contributes to preventing irradiation-induced amorphisation (“metamictisation”) of monazite–(Ce); however, this process is only significant above a certain damage level.

Permalink: https://www.hzdr.de/publications/Publ-31530
Publ.-Id: 31530


Experimental gas phase hydrodynamic data of lab scale bubble column

Kipping, R.; Hampel, U.

For the investigation of bubble column hydrodynamics an experimental study using ultrafast electron beam X-ray tomography (UFXCT) has been carried out. Local hydrodynamic parameters were measured in a DN100 bubble column using two types of capillary gas sparger, which are named as 'Type A' and 'Type B' . Nitrogen is used as gas phase and deionized water as liquid phase. For Type B sparger additionally, experiments with sodium hydroxide of different concentrations are given. Experiments were carried out at two different measurement heights, which are located at 10 (L/D = 1) and 70 cm (L/D = 7) above the gas sparger

An additional readme.txt file provides all required information and is necessary for the interpretation of the experimental data.

Keywords: Bubble column hydrodynamics; Uniform bubbly flow; Ultrafast X-ray computed tomography; SPP1740

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-02
    DOI: 10.14278/rodare.282

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Permalink: https://www.hzdr.de/publications/Publ-31529
Publ.-Id: 31529


Analytical Approach to Phonon Calculations in the SCC-DFTB Framework

Bacic, V.; Heine, T.; Kuc, A. B.

Detailed derivation of the analytical, reciprocal-space approach of Hessian calculation within the self- consistent-charge density functional based tight-binding framework (SCC-DFTB) is presented. This ap- proach provides an accurate and efficient way for obtaining the SCC-DFTB Hessian of periodic systems. Its superiority with respect to the traditional numerical force differentiation method is demonstrated for doped graphene, graphene nanoribbons, boron-nitride nanotubes, bulk zinc-oxide and other systems.

  • Open Access Logo Journal of Chemical Physics 153(2020), 144109
    Online First (2020) DOI: 10.1063/5.0023666

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Permalink: https://www.hzdr.de/publications/Publ-31528
Publ.-Id: 31528


Structural and chemical evolution of Au-silica core-shell nanoparticles during 20 keV helium ion irradiation: a comparison between experiment and simulation

Mousley, M.; Möller, W.; Philipp, P.; Hlawacek, G.; Wirtz, T.; Eswara, S.

Au-silica core-shell nanoparticles have been irradiated with 20 keV He+ ions up to a maximum fluence of 4.7x10(17) ions/cm(2). The nanoscale structural and crystallographic evolution induced by He+ ion irradiation was followed at various stages using Transmission Electron Microscopy (TEM). During irradiation satellite Au clusters are formed around the main Au core, which remained crystalline even after the maximum He+ ion fluence. The spherical silica shell deformed into a hemisphere due to He+ ion irradiation. Three dimensional Monte-Carlo simulations, based on the binary collision approximation, have been performed on stacked infinite layers and an individual particle. The stacked layers results show that the He+ beam interacts with most of the nanoparticle and Au migrates in the direction of beam incidence agreeing with experimental findings. The individual particle results match the experiment in terms of the volume which is sputtered away however additional mechanisms, not included in the simulations, are present in the experiment during the satellite formation and silica shell deformation. These results show the ability for 20 keV He+ ions to be used for the modification of nanostructures. Furthermore, these results contribute to a quantitative understanding of the dynamic evolution of materials observed using microscopy techniques based on He+ ions.

Keywords: nanoparticles; ion irradiation; He-Ne microscope; computer simulation; TRI3DYN

Permalink: https://www.hzdr.de/publications/Publ-31526
Publ.-Id: 31526


Microcosm studies for evaluating the microbial influence on metal corrosion

Sushko, V.; Dressler, M.; Neubert, T.; Kühn, L.; Cherkouk, A.; Schierz, A.; Stumpf, T.; Matschiavelli, N.

A deep geological disposal by using multiple barriers is favored for the long-term storage of high-level radioactive waste. A safe long-term storage means to analyze the applied materials according to their structural properties and stability in order to identify potential risks that could evolve during the operational phase and on the long run. So far, several concepts in Europe prefer cast iron and copper as canister materials (technical barrier) and bentonite as backfill- and buffering-/sealing material in between the canister and the host rock formation. In order to analyze the influence of naturally occurring microorganisms in bentonite on the respective barrier materials, different microcosm experiments were set up. These slurry experiments contain the Bavarian B25 bentonite, synthetic Opalinus Clay pore water or cap rock solution as well as copper- or cast iron plates in various combinations. During an incubation time of 400 days under anaerobic conditions at 37 °C, several bio-geochemical parameters (e.g. pH, redox potential and the concentration of minerals, sulfate, iron(II/III) and organic acids) were analyzed as well as the development of microbial diversity and incubated metal plates in the respective experiments. The obtained results provide insights into the complex interplay between bentonite, pore water, metals and microorganisms and can help to get a deeper understanding of the corrosion process of canister materials under the applied conditions.

  • Lecture (others) (Online presentation)
    European MIC Network, 20.10.2020, Dresden-Webinar, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31525
Publ.-Id: 31525


The pyrazolo[3,4-d]pyrimidine-based kinase inhibitor NVP-BHG712: Effects of regioisomers on tumor growth, perfusion, and hypoxia in EphB4-positive A375 melanoma xenografts

Neuber, C.; Tröster, A.; Löser, R.; Belter, B.; Schwalbe, H.; Pietzsch, J.

In a previous study, EphB4 was demonstrated to be a positive regulator of A375 melanoma growth but a negative regulator of tumor vascularization and perfusion. To distinguish between EphB4 forward and ephrinB2 reverse signaling, we used the commercially available EphB4 kinase inhibitor NVP BHG712 (NVP), which was later identified as its regioisomer NVPiso. Since there have been reported significant differences between the inhibition profiles of NVP and NVPiso, we compared the influence of NVP and NVPiso on tumor characteristics under the same experimental conditions. Despite of different inhibitory profiles of NVP and NVPiso, the comparative study conducted here showed the same EphB4-induced effects in vivo as in the previous investigation. This confirmed the conclusion that EphB4-ephrinB2 reverse signaling is responsible for increased tumor growth as well as decreased tumor vascularization and perfusion. These results are further substantiated by microarrays showing differences between mock-transfected and EphB4-transfected (A375-EphB4) cells with respect to at least 9 angiogenesis-related proteins. Decreased expression of VEGF, Ang-1, and Akt/PKB, together with the increased expression of TIMP-1 and TGF-2, is consistent with the impaired vascularization of A375-EphB4 xenografts. Functional overexpression of EphB4 in A375-EphB4 cells was confirmed by activation of a variety of signaling pathways including JAK/STAT, Ras/Raf/MEK, and NFkB.

Keywords: Eph receptor tyrosin kinase family; ephrins; tyrosine kinase inhibitors; regioisomers; tumor angiogenesis; tumor hypoxia; tumor perfusion

Permalink: https://www.hzdr.de/publications/Publ-31524
Publ.-Id: 31524


Experimental investigation of the return flow instability in magnetic spherical Couette flow

Ogbonna, J. E.; Garcia Gonzalez, F.; Gundrum, T.; Seilmayer, M.; Stefani, F.

We conduct magnetic spherical Couette (MSC) flow experiments in the return flow instability regime with GaInSn as the working fluid, and the ratio of the inner to the outer sphere radii rᵢ/rₒ= 0.5, the Reynolds number Re = 1000, and the Hartmann number Ha ∈ [27.5, 40]. Rotating waves with different azimuthal wavenumbers m ∈ {2, 3, 4} manifest in certain ranges of Ha in the experiments, depending on whether the values of Ha were fixed or varied from different initial values. These observations demonstrate the multistability of rotating waves, which we attribute to the dynamical system representing the state of the MSC flow tending to move along the same solution branch of the bifurcation diagram when Ha is varied. In experiments with both fixed and varying Ha, the rotation frequencies of the rotating waves are consistent with the results of nonlinear stability analysis. A brief numerical investigation shows that differences in the azimuthal wavenumbers of the rotating waves that develop in the flow also depend on the azimuthal modes that are initially excited.

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Permalink: https://www.hzdr.de/publications/Publ-31523
Publ.-Id: 31523


Band structure of a HgTe-based three-dimensional topological insulator

Gospodaric, J.; Dziom, V.; Shuvaev, A.; Dobretsova, A. A.; Mikhailov, N. N.; Kvon, Z. D.; Novik, E. G.; Pimenov, A.

From the analysis of the cyclotron resonance, we experimentally obtain the band structure of the threedimensional topological insulator based on a HgTe thin film. Top gating was used to shift the Fermi level in the film, allowing us to detect separate resonance modes corresponding to the surface states at two opposite film interfaces, the bulk conduction band, and the valence band. The experimental band structure agrees reasonably well with the predictions of the k · p model. Due to the strong hybridization of the surface and bulk bands, the dispersion of the surface states is close to parabolic in the broad range of the electron energies.

Permalink: https://www.hzdr.de/publications/Publ-31518
Publ.-Id: 31518


STRUctural MATerials research for safe Long Term Operation of LWR NPPs (STRUMAT-LTO) Work Package 3: Synergetic effects of Ni, Mn and Si on RPV embrittlement at high fluences

Ulbricht, A.

The objective of this WP is to identify and explain synergetic effects of VVER-1000 typical alloying elements in terms of irradiation-induced microstructures and mechanical property changes. Suitable materials are available in the neutron-irradiated condition from the LYRA-10 irradiation experiment. The approach is based on the application of complementary microstructural characterization techniques such as SEM, (S)TEM, APT, SANS, PAS to study low-Cu base and weld materials of intentionally varied contents of Ni, Mn and Si. In order to identify a synergetic effect of elements X and Y, low-X/low-Y, high-X/low-Y, low-X/high-Y and high-X/high-Y materials are to be compared and statistically evaluated with respect to mechanical property changes as well as type, composition, volume fraction, number density and size of irradiation-induced nano-features. Post-irradiation annealing allows the thermal stability of the defects to be evaluated. An additional objective is to provide a link between irradiated microstructures and mechanical property changes for highly irradiated VVER-1000 type steels.

  • Lecture (Conference) (Online presentation)
    STRUMAT-LTO Kick-off Meeting, 07.-08.09.2020, online, online

Permalink: https://www.hzdr.de/publications/Publ-31517
Publ.-Id: 31517


Nanoindentation testing and TEM observations of irradiated F/M alloys

Bergner, F.

In this talk, selected results of nanoindentation testing of unirradiated, neutron irradiated and ion irradiated (1 and 5 MeV) Fe-based materials are presented. The Nix-Gao approach is applied in order to extract the bulk-equivalent hardenss. Cross-sectional transmission electron microscopy shows how ion-irradiated microstructures look like. The available information is used to develop a microstructure-informed prediction model of irradiation hardening.

Keywords: Nanoindentation; TEM; Ferritic/martensitic steels; Ion irradiation; Irradiation hardening; Dislocation loops

  • Lecture (others) (Online presentation)
    ONLINE M4F Plenary Project Meeting, 16.-17.06.2020, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-31516
Publ.-Id: 31516


ENTENTE WP3 Task 3.2: Task 3.2: Microstructural Examinations in RPV Steels and Model Alloys

Chekhonin, P.

The talk presents the goals and intended work within the EU ENTENTE project. The focus is on work package 3, task 3.2 regarding microstructural characterisation planned within the project.

Keywords: ENTENTE project

  • Lecture (Conference) (Online presentation)
    ENTENTE Kickoff Meeting, 09.-10.09.2020, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-31515
Publ.-Id: 31515


ENTENTE WP2 Task 2.4: Data Collection

Chekhonin, P.

The talk presents the goals and intended work within the EU ENTENTE project. The focus is on work package 2, task 2.4 regarding the data collection contribution within the project.

Keywords: ENTENTE project

  • Lecture (Conference) (Online presentation)
    ENTENTE Kickoff Meeting, 09.-10.09.2020, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-31514
Publ.-Id: 31514


Stress distribution at the AlN/SiC heterointerface probed by Raman spectroscopy

Breev, I. D.; Likhachev, K. V.; Yakovleva, V. V.; Hübner, R.; Astakhov, G.; Mokhov, E. N.; Baranov, P. G.; Anisimov, A. N.

We investigate AlN grown on 4H- and 6H-SiC substrates using Raman spectroscopy. We obtain the Raman peak shifts in 4H- and 6H-SiC substrates across the heterointerface and along the entire depth of the SiC layer. Using the earlier experimental prediction for the phonon deformation potential constants, we determine the stress tensor components in the 4H-SiC layer as a function of the distance from the AlN/SiC heterointerface and estimate the stress tensor value along the entire depth of the 6H-SiC layer. The maximum compressing stress values lie in the range of -1.7 GPa for the 4H-SiC/AlN heterostructure and in the range of -1.5 GPa for the 6H-SiC/AlN heterostructure.

Keywords: SiC; AlN; Raman spectroscopy; Stress

  • Journal of Applied Physics 129(2021), 055304
    Online First (2021) DOI: 10.1063/5.0029682

Permalink: https://www.hzdr.de/publications/Publ-31513
Publ.-Id: 31513


4f spin driven ferroelectric-ferromagnetic multiferroicity in PrMn2O5 under a magnetic field

Chattopadhyay, S.; Balédent, V.; Panda, S. K.; Yamamoto, S.; Duc, F.; Herrmannsdörfer, T.; Uhlarz, M.; Gottschall, T.; Mathon, O.; Wang, Z.

In contrast to all other members of the RMn2O5 family with nonzero 4 f electrons (R = Nd to Lu), PrMn2O5 does not show any spin driven ferroelectricity in the magnetically ordered phase. By means of high-field electric polarization measurements up to 45 T, we have found that this exceptional candidate undergoes a spin driven multiferroic phase under magnetic field. X-ray magnetic circular dichroism studies up to 30 T at the Pr L2 edge show that this ferroelectricity originates from and directly couples to the ferromagnetic component of the Pr3+spins. Experimental observations along with our generalized gradient-approximation+U calculations reveal that this exotic ferroelectric-ferromagnetic combination stabilizes through the exchange-striction mechanism solely driven by a 3d-4f-type coupling, as opposed to the other RMn2O5 members with 3d-3d driven ferroelectric-antiferromagnetic-type conventional type-II multiferroicity.

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Permalink: https://www.hzdr.de/publications/Publ-31512
Publ.-Id: 31512


Videos for: Characterization of blood coagulation dynamics and oxygenation in ex‐vivo retinal vessels by fluorescence hyperspectral imaging

Podlipec, R.

Videos are showing experimental results of the blood coagulation dynamics study in ex‐vivo retinal vessels.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-08
    DOI: 10.14278/rodare.511
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31511
Publ.-Id: 31511


Images for: Characterization of blood coagulation dynamics and oxygenation in ex-vivo retinal vessels by fluorescence hyperspectral imaging

Podlipec, R.

Images for the manuscript/paper titled Characterization of blood coagulation dynamics and oxygenation in ex-vivo retinal vessels by fluorescence hyperspectral imaging

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-08
    DOI: 10.14278/rodare.509
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31510
Publ.-Id: 31510


Analysis of aerosol particles collected in Ljubljana, Slovenia, using Particle Induced X-ray Emission with a focused proton beam and a Helium Ion Microscope

Podlipec, R.; Munnik, F.; Klingner, N.; Rigler, M.; Heller, R.

The correlative approach of real-time aerosol measurements with offline filter analysis and ParticleInduced X-ray Emission (PIXE) can significantly enhance the scope of aerosol studies. Aerosol particles have diverse physical and chemical properties, thus having a direct impact on air quality, cloud nucleation the planetary radiation balance, public health, etc. Essential information on the chemical composition of aerosol particles can be deduced from the elemental concentrations measured simultaneously for many elements by non-destructive and undemanding PIXE (Lucarelli, 2018). Furthermore, PIXE measurements can be performed with a focused beam allowing the analysis of individual particles (Biancato, 2006). Determining elemental concentrations is also important input information for aerosol source apportionment models and consequently abatement measures in order to improve air quality (Artaxo, 1999). Complementary information of aerosol particles structure down to nm scale, can be obtained with a Helium Ion Microscope (HIM), which, to our knowledge, has never been used before for aerosol characterization. The detection of secondary electrons and backscattered ions enables sub nm lateral resolution and large depth-of-field, also on insulating samples. In addition, a concurrent secondary ion mass spectrometry (ToF-SIMS) integrated in the HIM can provide insights of the composition of elements and molecules with imaging capabilities of sub 8 nm (Klingner, 2019).
In this study we coupled real-time measurements of optical properties of aerosols with an Aethalometer (Drinovec, 2015) and their carbon content with a Total Carbon Analyzer (Rigler, 2019) with PIXE and HIM analysis. Ambient aerosols were collected on quartz filters and quartz filters with Teflon coating during different pollution events (traffic or biomass burning dominated, Saharan dust dominated, etc.) at an urban background sampling site in Ljubljana, Slovenia (46o04’17’’N, 14o30’06’’E). The PM2.5 inlet was used for sampling carbonaceous aerosol while a virtual impactor was used for concentrating coarse particles during Saharan dust events.
PIXE measurements have been performed on these collected samples and compared to optical properties and source apportionment obtained by the online instruments. The PIXE measurements were performed across several hundred-micrometer regions and on individual points and results are presented including a description of the procedures for quantification. Complementary high-resolution imaging and sputtered ion analysis on single black carbon and Saharian dust aerosol particles was done on the HIM to study their structure and coating composition. The combination of all methods yields a comprehensive view of the aerosol particles.

  • Poster
    European Aerosol Conference (EAC), 31.08.-04.09.2020, Virtual Event, Virtual Event

Permalink: https://www.hzdr.de/publications/Publ-31509
Publ.-Id: 31509


HIFIS - Platform, Training and Support for a Sustainable Software Development

Huste, T.

HIFIS aims to ensure an excellent information environment for outstanding research in all Helmholtz research fields and a seamless and performant IT-infrastructure connecting knowledge from all centres. It will build a secure and easy-to-use collaborative environment with efficiently accessible ICT services from anywhere. HIFIS will also support the development of research software with a high level of quality, visibility and sustainability.
In this talk we will present current offers of the HIFIS platform. The focus is on the Software Services pillar of HIFIS.

Keywords: HIFIS; Software Engineering; Cloud; Consulting; Education; Training

  • Invited lecture (Conferences) (Online presentation)
    Wissensaustausch-Workshop Software Engineering (WAW SE VII), 09.09.2020, Online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31508
Publ.-Id: 31508


Application of Next Generation Sequencing (NGS) in Phage Displayed Peptide Selection to Support the Identification of Arsenic-Binding Motifs

Braun, R.; Schönberger, N.; Vinke, S.; Lederer, F.; Kalinowski, J.; Pollmann, K.

Next generation sequencing (NGS) in combination with phage surface display (PSD) are powerful tools in the newly equipped molecular biology toolbox for the identification of specific target binding biomolecules. Application of PSD led to the discovery of manifold ligands in clinical and material research. However, limitations of traditional phage display hinder the identification process. Growth-based library biases and target-unrelated peptides often result in the dominance of parasitic sequences and the collapse of library diversity. This study describes the effective enrichment of specific peptide motifs potentially binding to arsenic as proof-of-concept using the combination of PSD and NGS. Arsenic is an environmental toxin, which is applied in various semiconductors as gallium arsenide and selective recovery of this element is crucial for recycling and remediation. The development of biomolecules as specific arsenic-binding sorbents is a new approach for its recovery. Usage of NGS for all biopanning fractions allowed for evaluation of motif enrichment, in-depth insight into the selection process and the discrimination of biopanning artefacts, e.g., the amplification-induced library-wide reduction in hydrophobic amino acid proportion. Application of bioinformatics tools led to the identification of an SxHS and a carboxy-terminal QxQ motif, which are potentially involved in the binding of arsenic. To the best of our knowledge, this is the first report of PSD combined with NGS of all relevant biopanning fractions.

Keywords: phage display; peptide; biopanning; target-unrelated peptide; arsenic; motif; NGS; Illumina; interaction; oxyanion

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Permalink: https://www.hzdr.de/publications/Publ-31507
Publ.-Id: 31507


Scanning transmission imaging in the helium ion microscope using a microchannel plate with a delay line detector

Serralta Hurtado De Menezes, E.; Klingner, N.; de Castro, O.; Mousley, M.; Eswara, S.; Duarte Pinto, S.; Wirtz, T.; Hlawacek, G.

A detection system based on a microchannel plate with a delay line readout structure has been developed to perform scanning transmission ion microscopy (STIM) in the helium ion microscope (HIM). This system is an improvement over other existing approaches since it combines the information of the scanning beam position on the sample with the position (scattering angle) and time of the transmission events. Various imaging modes such as bright and dark field or the direct image of the transmitted signal can be created by post-processing the collected STIM data. Furthermore, the detector has high spatial and time resolution, is sensitive to both ions and neutral particles over a wide energy range, and shows robustness against ion beam-induced damage. A special in-vacuum movable support gives the possibility of moving the detector vertically, placing the detector closer to the sample for the detection of high-angle scattering events, or moving it down to increase the angular resolution and distance for time-of-flight measurements. With this new system, we show composition-dependent contrast for amorphous materials and the contrast difference between small and high angle scattering signals. We also detect channeling related contrast on polycrystalline silicon, thallium chloride nanocrystals, and single crystalline silicon by comparing the signal transmitted at different directions for the same data set

Keywords: helium ion microscopy; Scanning transmission ion microscopy; delay line detector; channeling; bright field; dark field

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Permalink: https://www.hzdr.de/publications/Publ-31506
Publ.-Id: 31506


Chronic Inflammation Prediction for Inhaled Particles, the Impact of Material Cycling and Quarantining in the Lung Epithelium

Podlipec, R.
WorkPackageLeader: Rok Podlipec; ContactPerson: Gregor Hlawacek; ContactPerson: Nico Klingner

Correlative optical (STED) and ion (HIM) high-resolution images of lung epithelial cells interacting with metal oxide nanoparticles where the mechanism of material cycling and quarantining is studied.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-08
    DOI: 10.14278/rodare.513
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31505
Publ.-Id: 31505


Chronic Inflammation Prediction for Inhaled Particles, the Impact of Material Cycling and Quarantining in the Lung Epithelium

Kokot, H.; Kokot, B.; Sebastijanović, A.; Voss, C.; Podlipec, R.; Zawilska, P.; Berthing, T.; Ballester López, C.; Høgh Danielsen, P.; Contini, C.; Ivanov, M.; Krišelj, A.; Čotar, P.; Zhou, Q.; Ponti, J.; Zhernovkov, V.; Schneemilch, M.; Doumandji, Z.; Pušnik, M.; Umek, P.; Pajk, S.; Joubert, O.; Schmid, O.; Urbančič, I.; Irmler, M.; Beckers, J.; Lobaskin, V.; Halappanavar, S.; Quirke, N.; Lyubartsev, A. P.; Vogel, U.; Koklič, T.; Stoeger, T.; Štrancar, J.

We are daily exposed to a multitude of health hazardous airborne particulate matter with notable deposition in the fragile alveolar region of our lungs. Hence, there is a great need for identification and prediction of material-associated diseases, currently hindered due to the lack of in-depth understanding of causal relationships, in particular between acute exposures and chronic symptoms. By applying advanced microscopies and omics to in vitro and in vivo systems, together with in silico molecular modelling, we have here determined that the long-lasting response to a single exposure can originate from the interplay between the newly discovered nanomaterial quarantining and nanomaterial cycling between different lung cell types. This new insight finally allows us to predict the spectrum of lung inflammation associated with materials of interest using only in vitro measurements and in silico modelling potentially relating outcomes to material properties for large number of materials thus boosting safe-by-design-based material development. Because of its profound implications for animal-free predictive toxicology, our work paves the way to a more efficient and hazard-free introduction of numerous new advanced materials into our lives.

Keywords: material safety and health hazards; adverse outcome pathway; mode of action; disease prediction; advanced microscopies

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31504
Publ.-Id: 31504


Experimental validation of an inductive system for magnesium level detection in a titanium reduction reactor

Krauter, N.; Eckert, S.; Gundrum, T.; Stefani, F.; Wondrak, T.; Khalilov, R.; Dimov, R.; Frick, P.

In order to determine the magnesium level in a titanium reduction retort by inductive methods, many interfering influences have to be considered to achieve precise measurement results. By using a look-up-table method, the magnesium level can be identified while taking into account the interfering effects of titanium sponge rings that are forming at the walls of the retort during the reduction process with their unknown geometrical and electrical parameters. This new method uses a combination of numerical simulations and measurements, whereby the simulation model is calibrated so that it represents the experimental setup as closely as possible. Previously we have presented purely theoretical studies on this method. Here, we demonstrate the practical feasibility of that method by performing measurements on a model experiment. This method is not limited to the production of titanium but can also be applied to other applications in metal production and processing.

Keywords: Kroll process; numerical simulation; inductive measurements; Titanium; level detection

Permalink: https://www.hzdr.de/publications/Publ-31503
Publ.-Id: 31503


Generating a tide-like flow in a cylindrical vessel by electromagnetic forcing - datasets and software

Jüstel, P.; Röhrborn, S.; Galindo, V.; Schindler, F.
Project Member: Frick, Peter; Project Member: Gundrum, Thomas; Project Leader: Stefani, Frank; Project Member: Stepanov, Rodion; Project Member: Vogt, Tobias

The two 7z Archives contain experimental data and the corresponding evaluation software, as well as the code and setup of the numerical part of the paper "Generating a tide-like flow in a cylindrical vessel by electromagnetic forcing".

Keywords: Ultrasound-Doppler-Velocimetry (UDV); Python; openFOAM

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-08
    DOI: 10.14278/rodare.507
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-31502
Publ.-Id: 31502


Time refraction of spin waves

Schultheiß, K.; Sato, N.; Matthies, P.; Körber, L.; Wagner, K.; Hula, T.; Gladii, O.; Pearson, J. E.; Hoffmann, A.; Helm, M.; Faßbender, J.; Schultheiß, H.

We present an experimental study of time refraction of spin waves propagating in microscopic waveguides under the influence of time-varying magnetic fields. Using space- and time-resolved Brillouin light scattering microscopy, we demonstrate that the broken translational symmetry along the time coordinate can be used to in- or decrease the energy of spin waves during their propagation. This allows for a broadband and controllable shift of the spin-wave frequency. Using an integrated design of spin-wave waveguide and microscopic current line for the generation of strong, nanosecond-long, magnetic field pulses, a conversion efficiency up to 39% of the carrier spin-wave frequency is achieved, significantly larger compared to photonic systems. Given the strength of the magnetic field pulses and its strong impact on the spin-wave dispersion relation, the effect of time refraction can be quantified on a length scale comparable to the spin-wave wavelength. Furthermore, we utilize time refraction to excite spin-wave bursts with pulse durations in the nanosecond range and a frequency shift depending on the pulse polarity.

Keywords: magnetization dynamics; spin waves; time refraction; Brillouin light scattering

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Permalink: https://www.hzdr.de/publications/Publ-31501
Publ.-Id: 31501


Effect of nanoscale surface topography on the adsorption of globular proteins

Yang, Y.; Yu, M.; Böke, F.; Qin, Q.; Hübner, R.; Knust, S.; Schwiderek, S.; Grundmeier, G.; Fischer, H.; Keller, A.

Protein adsorption is the initial step in the response of biological systems to artificial surfaces and thus a ubiquitous phenomenon in biomedicine and tissue engineering. Here, we investigate the adsorption of the three globular proteins myoglobin (MGB), thyroglobulin (TGL), and bovine serum albumin (BSA) at flat and nanorippled SiOx/Si and TiOx/Ti surfaces. Despite having lateral and vertical dimensions of only about 30 nm and less than 2 nm, respectively, these nanoripples influence protein adsorption and adsorption-induced protein denaturation in a highly protein- and material-specific way. Adsorption of small, positively charged MGB results in preferential protein alignment along the nanoripples on both oxide surfaces. The larger and strongly negatively charged TGL forms layers of similar thickness on all four surfaces except the nanorippled TiOx/Ti surface. Here, a smaller layer thickness is attributed to different denaturation states of the adsorbed proteins. Similarly, the smaller and less negatively charged BSA shows different degrees of denaturation on the flat and rippled SiOx/Si surfaces. Our results thus demonstrate that topographic surface features with vertical dimensions well below 10 nm may have a surprisingly strong effect on protein adsorption and thus need to be considered in the interaction of biological systems even with apparently flat surfaces.

Keywords: Protein adsorption; Biomaterials; Biointerfaces; Nanopatterning; Surface topography

Permalink: https://www.hzdr.de/publications/Publ-31499
Publ.-Id: 31499


Interfacial redox reactions, X-ray absorption spectroscopy, and how they can contribute to the safety of radioactive-waste repositories

Scheinost, A. C.

The safe enclosure of nuclear waste in deep-geological repositories is not only a challenge for engineers to build it, but also for geoscientist to predict that the eventually forming leaks do not lead to a contamination of the biosphere – and this for a period of up to one million years, as dictated by the slow decay of long-lived radionuclides. A precise, molecular-scale understanding of the retention processes at water/mineral interfaces is one of the fundamental requirements to improve the prediction of radionuclide migration by (reactive) transport models. These processes include physical and chemical sorption, and structural incorporation by existing or neoforming mineral phases. Interfacial redox reactions with structural or sorbed Fe(II) play a pivotal role during these processes, since Fe(II) is the most ubiquitous redox agent in the deep anoxic underground, and is released from steel canisters corroding under radiolytic H2 production. Synchrotron-based X-ray absorption spectroscopy is ideally suited to elucidate such processes, since it provides information on oxidation state, bonding and short-range structure of an element at the same time, and this in situ due to the high penetration depth and element-specifity of the used synchrotron radiation. I will show selected examples for a range of metals occurring in radwaste (Tc, U, Np, Pu, Am), while the observed processes are transferable to many other metals and metalloids of general geochemical interest.

Keywords: nuclear waste; XAFS; Redox

  • Invited lecture (Conferences) (Online presentation)
    GFZ Talk, 17.09.2020, Postdam, Germany
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Azeotrope Chemistry Seminar at National Institute of Technology (NIT) Rourkela, 25.11.2020, Rourkela, India

Permalink: https://www.hzdr.de/publications/Publ-31498
Publ.-Id: 31498


Electrochemical detection of ascorbic acid in artificial sweat using a flexible alginate/CuO-modified electrode

Ibarlucea, B.; Pérez, R. A.; Belyaev, D.; Baraban, L.; Cuniberti, G.

A flexible sensor is presented for electrochemical detection of ascorbic acid in sweat based on single-step modified gold microelectrodes. The modification consists of electrodeposition of alginate membrane with trapped CuO nanoparticles. The electrodes are fabricated at a thin polyimide support and the soft nature of the membrane can withstand mechanical stress beyond requirements for skin monitoring. After characterization of the membrane via optical and scanning electron microscopy and cyclic voltammetry, the oxidative properties of CuO are exploited toward ascorbic acid for amperometric measurement at micromolar levels in neutral buffer and acidic artificial sweat, at ultralow applied potential (− 5 mV vs. Au pseudo-reference electrode). Alternatively, measurement of the horizontal shift of redox peaks by cyclic voltammetry is also possible. Obtaining a limit of detection of 1.97 μM, sensitivity of 0.103 V log (μM)−1 of peak shift, and linear range of 10–150 μM, the effect of possible interfering species present in sweat is minimized, with no observable cross-reaction, thus maintaining a high degree of selectivity despite the absence of enzymes in the fabrication scheme. With a lateral flow approach for sample delivery, repeated measurements show recovery in few seconds, with relative standard deviation of about 20%, which can serve to detect increased loss or absence of vitamin, and yet be improved in future by optimized device designs. This sensor is envisioned as a promising component of wearable devices for e.g. non-invasive monitoring of micronutrient loss through sweat, comprising features of light weight, low cost, and easy fabrication needed for such application.

Permalink: https://www.hzdr.de/publications/Publ-31497
Publ.-Id: 31497


Intracavity third-harmonic generation in Si:B pumped by intense terahertz pulses

Meng, F.; Thomson, M. D.; Ul-Islam, Q.; Klug, B.; Pashkin, O.; Schneider, H.; Roskos, H. G.

Raw experimental data: emission interferograms, FEL spectra and FEL spots

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-03
    DOI: 10.14278/rodare.502

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Permalink: https://www.hzdr.de/publications/Publ-31496
Publ.-Id: 31496


Data for: Lattice dynamics and ultrafast energy flow between electrons, spins, and phonons in a 3d ferromagnet

Zahn, D.; Jakobs, F.; William Windsor, Y.; Seiler, H.; Vasileiadis, T.; Butcher, T. A.; Qi, Y.; Engel, D.; Atxitia, U.; Vorberger, J.; Ernstorfer, R.

The ultrafast dynamics of magnetic order in a ferromagnet are governed by the interplay between electronic, magnetic and lattice degrees of freedom. In order to obtain a microscopic understanding of ultrafast demagnetization, information on the response of all three subsystems is required. A consistent description of demagnetization and microscopic energy flow, however, is still missing. Here, we combine a femtosecond electron diffraction study of the ultrafast lattice response of nickel to laser excitation with ab initio calculations of the electron-phonon interaction and energy conserving atomistic spin dynamics simulations. Our model is in agreement with the observed lattice dynamics and previously reported electron and magnetization dynamics. Our approach reveals that the spin system is the dominating heat sink in the initial few hundreds of femtoseconds and implies a transient non-thermal state of the spins. Our results provide a clear picture of the microscopic energy flow between electronic, magnetic and lattice degrees of freedom on ultrafast timescales and constitute a foundation for theoretical descriptions of demagnetization that are consistent with the dynamics of all three subsystems.

Keywords: magnetization; relaxation; laser; phonon; spin; DFT; electron beam; femtosecond

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-03
    DOI: 10.14278/rodare.500
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31495
Publ.-Id: 31495


Water-Window X-Ray Pulses from a Laser-Plasma Driven Undulator

Maier, A. R.; Kajumba, N.; Guggenmos, A.; Werle, C.; Wenz, J.; Delbos, N.; Zeitler, B.; Dornmair, I.; Schmidt, J.; Gullikson, E. M.; Krausz, F.; Schramm, U.; Kleineberg, U.; Karsch, S.; Gruner, F.

Femtosecond (fs) x-ray pulses are a key tool to study the structure and dynamics of matter on its natural length and time scale. To complement radio-frequency accelerator-based large-scale facilities, novel laser-based mechanisms hold promise for compact laboratory-scale x-ray sources. Laser-plasma driven undulator radiation in particular offers high peak-brightness, optically synchronized few-fs pulses reaching into the few-nanometer (nm) regime. To date, however, few experiments have successfully demonstrated plasma-driven undulator radiation. Those that have, typically operated at single and comparably long wavelengths. Here we demonstrate plasma-driven undulator radiation with octave-spanning tuneability at discrete wavelengths reaching from 13 nm to 4 nm. Studying spontaneous undulator radiation is an important step towards a plasma-driven free-electron laser. Our specific setup creates a photon pulse, which closely resembles the plasma electron bunch length and charge profile and thus might enable novel methods to characterize the longitudinal electron phase space.

Keywords: LWFA

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Permalink: https://www.hzdr.de/publications/Publ-31494
Publ.-Id: 31494


Worldline master formulas for the dressed electron propagator, part 1: Off-shell amplitudes

Ahmadiniaz, N.; Guzman, V. M. B.; Bastianelli, F.; Corradini, O.; Edwards, J. P.; Schubert, C.

In the firrst-quantised worldline approach to quantum field theory, a long-standing problem has been to extend this formalism to amplitudes involving open fermion lines while maintaining the efficiency of the well-tested closed-loop case. In the present series of papers, we develop a suitable formalism for the case of quantum electrodynamics (QED) in vacuum (part one and two) and in a constant external electromagnetic field (part three), based on second-order fermions and the symbol map. We derive this formalism from standard field theory, but also give an alternative derivation intrinsic to the worldline theory. In this first part, we use it to obtain a Bern-Kosower type master formula for the fermion propagator, dressed with N photons in configuration as well as in momentum space.

Keywords: Worlline formalism; QED; Scattering Amplitudes; Gauge Symmetry

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Permalink: https://www.hzdr.de/publications/Publ-31493
Publ.-Id: 31493


T-Staging and Target Volume Definition by Imaging in Head and Neck Tumors

Platzek, I.; Agolli, L.; Beuthien-Baumann, B.; Troost, E. G. C.

Anatomical and functional imaging by means of computed tomography, magnetic resonance imaging, and positron emission tomography are, besides a thorough physical examination, of utmost importance for accurate staging of primary tumors in the head and neck region. This chapter deals with the particular advan-tages and disadvantages of those imaging techniques and gives practical guidance on how to employ these in radiation treatment planning.

Keywords: CT,; Head and neck squamous cell carcinoma; Multiparametric MRIPETT-staging; Tumor characterization

  • Book chapter
    Regina G.H. Beets-TanWim J. G. OyenVincenzo Valentini: Imaging and Interventional Radiology for Radiation Oncology, Switzerland: Springer, 2020, 978-3-030-38260-5, 169-181
    DOI: 10.1007/978-3-030-38261-2_12

Permalink: https://www.hzdr.de/publications/Publ-31492
Publ.-Id: 31492


A new approach for estimating the effective froth height on column trays

Vishwakarma, V.; Wiedemann, P.; Schleicher, E.; Schubert, M.; Hampel, U.

The present work proposes a new approach for measuring the effective froth height on column trays. This approach is applied on the two-phase dispersion data gathered by a novel multi-probe sensor installed inside a large-scale tray column mockup. A physical explanation of the proposed approach describes how to distinguish between the liquid-continuous and gas-continuous regions in the froth. Accordingly, the effective froth height distributions are reported for selected tray loadings.

Keywords: Effective froth height; Column tray; Two-phase dispersion; Conductivity probes

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  • Secondary publication expected from 13.11.2021

Permalink: https://www.hzdr.de/publications/Publ-31491
Publ.-Id: 31491


Small-scale diagenetic facies heterogeneity controls porosity and permeability pattern in reservoir sandstones

Heidsiek, M.; Butscher, C.; Blum, P.; Fischer, C.

The fluvial-aeolian Upper Rotliegend sandstones from the Bebertal outcrop (Flechtingen High, Germany) are the famous reservoir analog for the deeply-buried Upper Rotliegend gas reservoirs of the Southern Permian Basin (SPB). While most diagenetic and reservoir quality investigations are conducted on a meter scale, there is an emerging consensus that significant reservoir heterogeneity is inherited from diagenetic complexity at smaller scales. In this study, we utilize information about diagenetic products and processes at the pore-and plug-scale and analyze their impact on the heterogeneity of porosity, permeability, and cement patterns. Eodiagenetic poikilitic calcite cements, illite/iron oxide grain coatings, and the amount of infiltrated clay are responsible for mm-to cm-scale reservoir heterogeneities in the Parchim formation of the Upper Rotliegend sandstones. Using the Petrel E&P software platform, spatial fluctuations and spatial variations of permeability, porosity, and calcite cements are modeled and compared, offering opportunities for predicting small-scale reservoir rock properties based on diagenetic constraints.

Keywords: Sandstone diagenesis; calcite cement; reservoir quality; high-resolution diagenetic modeling; Upper Rotliegend sandstone

Permalink: https://www.hzdr.de/publications/Publ-31490
Publ.-Id: 31490


70 THz bandwidth from a Au-implanted Ge photoconductive emitter pumped by a modelocked Er:fibre laser

Singh, A.; Winnerl, A. P. S.; Welsch, M.; Beckh, C.; Sulzer, P.; Leitenstorfer, A.; Helm, M.; Schneider, H.

Germanium is a nonpolar semiconductor with missing one-phonon absorption. The absence of a Reststrahlen band enables the generation of a gapless THz spectrum spreading up to 13 THz [1], limited only by the duration of the excitation and detection laser pulses. However, in spite of other promising properties including low bandgap and small effective mass, the long, µs-scale recombination time arising from the indirect bandgap of intrinsic germanium has been prohibitive for practical application as photoconductive THz emitters. Although not essential for broadband THz emission, shorter recombination times are necessary to ensure complete carrier recombination between subsequent laser pulses and to make these emitters compatible with standard modelocked laser systems operating at pulse repetition rates up to hundreds of MHz.
By introducing deep traps into germanium via gold implantation, we have reduced the carrier lifetime to sub-nanosecond values. Fabricated on this Au-implanted Ge material, we have demonstrated a photoconductive THz antenna which is compatible with modelocked fibre lasers operating at wavelengths of 1.1 and 1.55 m and with pulse repetition rates of 78 MHz [2] and potentially up to several hundreds of MHz. Reaching up to 70 THz bandwidth, which is almost one order of magnitude higher than that of existing state-of–the-art photoconductive THz emitters fabricated on GaAs or InGaAs, our approach points towards the possibility of compact, high-bandwidth THz photonic devices compatible with Si CMOS technology.
[1] A. Singh et al., ACS Photonics 5, 2718 (2018).
[2] A. Singh et al., Light Science & Applications 9, 30 (2020).

  • Invited lecture (Conferences) (Online presentation)
    SPIE Optics + Photonics Digital Forum, 24.-28.08.2020, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-31489
Publ.-Id: 31489


THz nonlinear electronic response in GaAs/InGaAs semiconductor nanowires

Schneider, H.

This presentation reviews some recent experiments using free-electron-laser-based narrow-band as well as tabletop-laser-based single-cycle terahertz (THz) fields for exploring electronic properties in semiconducting GaAs/InGaAs core/shell nanowires (NW) [1]. In undoped NW, charge carriers are optically excited by near-infrared pulses and probed by strong single-cycle THz fields up to 0.6 MV/cm. The photoexcited charge carriers exhibit a pronounced plasmon resonance, which undergoes a systematic redshift and a suppression of its spectral weight, which indicates a drop of the electron mobility at the highest fields to about half of the original value [2]. In n-type NWs, intense narrowband THz excitation causes a nonlinear plasmonic response, which manifests itself by a similar pronounced red shift of the plasma resonance. This nonlinearity is investigated by scattering-type scanning near-field infrared microscopy on individual NWs. For NW doped with Si to a concentration of 9x10^18 cm^-3, a spectrally sharp plasma resonance, located at a photon energy of 125 meV for weak excitation, undergoes a power-dependent redshift to about 95 meV [3]. In these experiments, the observed behavior is attributed to a pronounced increase of the average electron effective mass caused by transient carrier heating and electron intervalley transfer. The results quantify the nonlinear transport regime in GaAs-based nanowires and show their high potential for development of nanodevices operating at THz frequencies.
[1] L. Balaghi et al., Widely tunable GaAs band gap via strain engineering in core/shell nanowires, Nature Comm. 10, 2793 (2019)
[2] R. Rana et al., Nonlinear terahertz field-induced charge transport and transferred-electron effect in InGaAs nanowires, Nano Lett. 20, 3225 (2020)
[3] D. Lang et al., Nonlinear plasmonic response of doped nanowires observed by infrared nanospectroscopy, Nanotechnol. 30, 084003 (2019)

  • Invited lecture (Conferences) (Online presentation)
    Synchrotron and Free electron laser Radiation: generation and application (SFR-2020), 13.-16.07.2020, Novosibirsk, Russische Föderation

Permalink: https://www.hzdr.de/publications/Publ-31488
Publ.-Id: 31488


Ion-implanted Ge photoconductive antennae for terahertz emission

Schneider, H.

This talk does not have an abstract.

  • Invited lecture (Conferences)
    Radiation Effects of Materials and Devices (REMD-2020), 12.-15.01.2020, Harbin, China

Permalink: https://www.hzdr.de/publications/Publ-31487
Publ.-Id: 31487


Non-monotonic pressure dependence of high-field nematicity and magnetism in CeRhIn5

Helm, T.; Grockowiak, A. D.; Balakirev, F. F.; Singleton, J.; Betts, J. B.; Shirer, K. R.; König, M.; Förster, T.; Bauer, E. D.; Ronning, F.

CeRhIn5 provides a textbook example of quantum criticality in a heavy fermion system: Pressure suppresses local-moment antiferromagnetic (AFM) order and induces superconductivity in a dome around the associated quantum critical point (QCP) near pc ≈ 23 kbar. Strong magnetic fields also suppress the AFM order at a field-induced QCP at Bc ≈ 50 T. In its vicinity, a nematic phase at B* ≈ 28 T characterized by a large in-plane resistivity anisotropy emerges. Here, we directly investigate the interrelation between these phenomena via magnetoresistivity measurements under high pressure. As pressure increases, the nematic transition shifts to higher fields, until it vanishes just below p. While pressure suppresses magnetic order in zero field as pc is approached, we find magnetism to strengthen under strong magnetic fields due to suppression of the Kondo effect. We reveal a strongly nonmean-field-like phase diagram, much richer than the common local-moment description of CeRhIn would suggest.

Permalink: https://www.hzdr.de/publications/Publ-31486
Publ.-Id: 31486


Determination of the crystal field parameters in SmFe11Ti

Diop, L. V. B.; Kuz'Min, M. D.; Scurschii, I.; Skokov, K. P.; Radulov, I. A.; Gutfleisch, O.

The magnetization of SmFe11Ti single crystals has been measured along the principal crystallographic directions in steady (14 T) and pulsed (43 T) magnetic fields. The fourfold symmetry axis [001] is an easy magnetization direction. The magnetization curves measured in directions perpendicular to [001] are remarkable in two ways: (i) They do not depend on orientation of H within the basal plane; (ii) at low temperature they are S shaped, with an inflection point at about 0.6 times saturation magnetization. These two facts enable us to conclude that three out of five crystal field parameters of SmFe11Ti are negligibly small; only A0 2 and A0 6 are essentially nonzero. A comparison with an isomorphous compound DyFe11Ti reveals a dramatic disparity of their crystal fields, especially as regards A4 4, nearly zero in SmFe11Ti but outstandingly large in DyFe11Ti.

Permalink: https://www.hzdr.de/publications/Publ-31485
Publ.-Id: 31485


Extremely well isolated two-dimensional spin-1/2 antiferromagnetic Heisenberg layers with a small exchange coupling in the molecular-based magnet CuPOF

Opherden, D.; Nizar, N.; Richardson, K.; Monroe, J. C.; Turnbull, M. M.; Polson, M.; Vela, S.; Blackmore, W. J. A.; Goddard, P. A.; Singleton, J.; Choi, E. S.; Xiao, F.; Williams, R. C.; Lancaster, T.; Pratt, F. L.; Blundell, S. J.; Scurschii, I.; Uhlarz, M.; Ponomaryov, O.; Zvyagin, S.; Wosnitza, J.; Baenitz, M.; Heinmaa, I.; Stern, R.; Kühne, H.; Landee, C. P.

We report on a comprehensive characterization of the newly synthesized Cu2+-based molecular magnet [Cu(pz)2 (2-HOpy)2](PF6)2 (CuPOF), where pz = C4H4N2 and 2-HOpy = C5H4NHO. From a comparison of theoretical modeling to results of bulk magnetometry, specific heat, μ+SR, ESR, and NMR spectroscopy, this material is determined as an excellent realization of the two dimensional square-lattice S = 1/2 antiferromagnetic Heisenberg model with a moderate intraplane nearest-neighbor exchange coupling of J/kB = 6.80(5) K, and an extremely small interlayer interaction of about 1 mK. At zero field, the bulk magnetometry reveals a temperature-driven crossover of spin correlations from isotropic to XY type, caused by the presence of a weak intrinsic easy-plane anisotropy. A transition to long-range order, driven by the low-temperature XY anisotropy under the influence of the interlayer coupling, occurs at TN = 1.38(2) K, as revealed by μ+SR. In applied magnetic fields, our 1H-NMR data reveal a strong increase of the magnetic anisotropy, manifested by a pronounced enhancement of the transition temperature to commensurate long-range order at TN = 2.8 K and 7 T.

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Permalink: https://www.hzdr.de/publications/Publ-31484
Publ.-Id: 31484


Changes in elastic moduli as evidence for quadrupolar ordering in the rare-earth frustrated magnet Tb2Ti2O7

Gritsenko, Y.; Mombetsu, S.; Cong, P. T.; Stöter, T.; Green, E. L.; Salazar Mejia, C.; Wosnitza, J.; Ruminy, M.; Fennell, T.; Zvyagin, A. A.; Zherlitsyn, S.; Kenzelmann, M.

Numerous materials feature unexplained phases with invisible or hidden order of electronic origin. A particularly mysterious case is that of Tb2Ti2O7, which avoids magnetic order to the lowest temperatures, but nevertheless has an unexplained second-order phase transition near T = 0.5 K. Our ultrasound measurements of Tb2Ti2O7 provide direct evidence of a huge softening followed by strong hardening of the structural lattice below T = 0.5 K. In the absence of magnetic order at this temperature, our results provide conclusive evidence for the proposed quadrupolar order and emphasize the importance of higher-order multipolar interactions in rare-earth frustrated magnets.

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Permalink: https://www.hzdr.de/publications/Publ-31483
Publ.-Id: 31483


Feasibility of metal pad roll instability experiments at room temperature

Nore, C.; Cappanera, L.; Guermond, J.-L.; Weier, T.; Herreman, W.

We propose a solution to the longstanding problem of experimentally reproducing the metal pad roll instability at room temperature. Combining theoretical arguments with numerical simulations we show that the instability can occur in a centimeter scale set-up, with reasonable values of the magnetic field and electrical current and using either gallium with mercury (immiscible fluid pair) or gallium with GaInSn eutectic alloy (miscible fluid pair).

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Permalink: https://www.hzdr.de/publications/Publ-31482
Publ.-Id: 31482


Efficient Modulation of Photonic Bandgap and Defect Modes in All-Dielectric Photonic Crystals by Energetic Ion Beams

Du, G.; Zhou, X.; Pang, C.; Zhang, K.; Zhao, Y.; Lu, G.; Liu, F.; Wu, A.; Akhmadaliev, S.; Zhou, S.; Chen, F.

The photonic bandgap and localization in photonic crystals can be effectively modulated by energetic ion beams owing to the induced modification of the thickness and refractive indices of the materials. In this work, the modulation of photonic bandgap and defect modes in 1D all-dielectric photonic crystals is investigated theoretically and experimentally by using carbon (C5+) ion irradiation. It is found that the photonic bandgap and defect mode have a remarkable hypsochromic shift under the C5+ ion irradiation. The degree of the blueshift mainly depends on the reduction of the material thickness that is nearly proportional to the fluences of C5+ ions. The blueshift of the band edges and defect modes shows a step-like behavior from transparency to opacification (near-zero transmittance or high reflectance) or a converse trend. The work paves a new way to tailor the photonic crystals toward the development of novel devices with tunable specific wavelengths and wavebands.

Permalink: https://www.hzdr.de/publications/Publ-31481
Publ.-Id: 31481


How public health services pay for radiotherapy in Europe: an ESTRO-HERO analysis of reimbursement

Lievens, Y.; Defourny, N.; Corral, J.; Gasparotto, C.; Grau, C.; Borras, J.; Chauvet, B.; Coffey, M.; Coza, O.; Daisne, J.; Hadjieva, T.; Jarusevicius, L.; Karadjinovic, V.; Kouloulias, V.; Kozma, E.; Kristensen, B.; Lopez, A.; Mohammed, N.; Petera, J.; Rolles, M.; Roques, T.; Russi, E.; Sedlmayer, F.; Slobina, E.; Smichkoska, S.; Takácsi-Nagy, Z.; Trigo, L.; Troost, E. G. C.; Untereiner, M.; Valgma, M.; van Loon, J.

Reimbursement is a key factor in defining which resources are made available to ensure quality, efficiency, availability,
and access to specific health-care interventions. This Policy Review assesses publicly funded radiotherapy
reimbursement systems in Europe. We did a survey of the national societies of radiation oncology in Europe, focusing
on the general features and global structure of the reimbursement system, the coverage scope, and level for typical
indications. The annual expenditure covering radiotherapy in each country was also collected. Most countries have a
predominantly budgetary-based system. Variability was the major finding, both in the components of the treatment
considered for reimbursement, and in the fees paid for specific treatment techniques, fractionations, and indications.
Annual expenses for radiotherapy, including capital investment, available in 12 countries, represented between 4·3%
and 12·3% (average 7·8%) of the cancer care budget. Although an essential pillar in multidisciplinary oncology,
radiotherapy is an inexpensive modality with a modest contribution to total cancer care costs. Scientific societies and
policy makers across Europe need to discuss new strategies for reimbursement, combining flexibility with incentives
to improve productivity and quality, allowing radiation oncology services to follow evolving evidence.

Permalink: https://www.hzdr.de/publications/Publ-31479
Publ.-Id: 31479


Electron dose rate and oxygen depletion protect zebrafish embryo from radiation damage

Beyreuther, E.; Brand, M.; Hans, S.; Karsch, L.; Leßmann, E.; Löck, S.; Schürer, M.; Pawelke, J.

The combination of the beneficial effects of high dose-rate Flash-RT and proton depth dose distribution promise the differential sparing of normal tissue under similar tumour treating efficacy. However, of the two published attempts [1,2] made at clinical proton facilities, one in vivo study on zebrafish embryo was not able to measure a Flash effect [2]. In the discussion of this experiment, the zebrafish model, a non-ideal pulse-time-regime and an uncertain oxygen level during irradiation were identified as potential explanations for the missing Flash effect. In order to investigate these parameters in detail an experiment was scheduled at the research electron accelerator ELBE at HZDR, because an electron Flash effect was already demonstrated for zebrafish embryo [3]. The highly variable pulse structure of ELBE enables to deliver the dose either in therapy like quasi-continuous (cw) beams or as electron Flash irradiation.
Zebrafish embryo were irradiated with 40 Gy with pulse dose rates of 109 Gy/s and mean dose rates of 106 Gy/s in comparison to 0.1 Gy/s with cw irradiation. In addition to this, the Oxylite system was applied to measure and control oxygen depletion kinetics in sealed embryo samples. A protective Flash effect was seen for most endpoints ranging from 4 % less reduction in embryo length to about 20 – 25 % less embryo with spinal curvature and pericardial oedema, relative to cw-irradiation. The reduction of partial oxygen pressure below atmospheric levels results in higher protection, the more the lower the oxygen level.
In conclusion, the Flash experiment at ELBE show that the zebrafish embryo model is appropriate for the study of the radiobiological response of high dose rate irradiation. A sufficiently pulse dose seems to be more important than pulse dose rate and the partial oxygen pressure during irradiation plays a pivotal role.
[1] Diffenderfer et al.: https://doi.org/10.1016/j.ijrobp.2019.10.049
[2] Beyreuther et al.: https://doi.org/10.1016/j.radonc.2019.06.024
[3] Vozenin et al.: https://doi.org/10.1016/j.clon.2019.04.001

  • Invited lecture (Conferences) (Online presentation)
    European Radiation Research Meeting, 13.-17.09.2020, Lund, Sweden
  • Invited lecture (Conferences) (Online presentation)
    VHEE/FLASH meeting - virtual, 05.-07.10.2020, CERN, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-31478
Publ.-Id: 31478


Room-Temperature Infrared Photoresponse from Ion Beam–Hyperdoped Silicon

Wang, M.; Berencen, Y.

Room-temperature broadband infrared photoresponse in Si is of great interest for the development of on-chip complementary metal-oxide-semiconductor (CMOS)-compatible photonic platforms. One effective approach to extend the room-temperature photoresponse of Si to the mid-infrared range is the so-called hyperdoping. This consists of introducing deep-level impurities into Si to form an intermediate band within its bandgap enabling a strong intermediate band-mediated infrared photoresponse.Typically, impurity concentrations in excess of the equilibrium solubility limit can be introduced into the Si host either by pulsed laser melting of Si with a gas-phase impurity precursor, by pulsed laser mixing of a thin-film layer of impurities atop the Si surface or by ion implantation followed by a sub-second annealing step. In this review, a conspectus of the current status of room-temperature infrared photoresponse in hyperdoped Si by ion implantation followed by nanosecond-pulsed laser annealing is provided. The possibilities of achieving room-temperature broadband infrared photoresponse in ion beam-hyperdoped Si with different deep-level impurities are discussed in terms of material fabrication and device performance. The thermal stability of hyperdoped Si with deep-level impurities is addressed with special emphasis on the structural and the opto-electronic material properties. The future perspectives of achieving room-temperature Si-based broadband infrared photodetectors are outlined.

Permalink: https://www.hzdr.de/publications/Publ-31477
Publ.-Id: 31477


Critical behavior of the insulator-to-metal transition in Te-hyperdoped Si

Wang, M.; Debernardi, A.; Zhang, W.; Xu, C.; Yuan, Y.; Xie, Y.; Berencén, Y.; Prucnal, S.; Helm, M.; Zhou, S.

Hyperdoping Si with chalcogens is a topic of great interest due to the strong sub-band-gap absorption exhibited by the resulting material, which can be exploited to develop broadband room-temperature infrared photodetectors using fully Si-compatible technology. Here, we report on the critical behavior of the impurity-driven insulator-tometal transition in Te-hyperdoped Si layers fabricated via ion implantation followed by nanosecond pulsed-laser melting. Electrical transport measurements reveal an insulator-to-metal transition, which is also confirmed and understood by density functional theory calculations. We demonstrate that the metallic phase is governed by a power-law dependence of the conductivity at temperatures below 25 K, whereas the conductivity in the insulating phase is well described by a variable-range hopping mechanism with a Coulomb gap at temperatures in the range of 2–50 K. These results show that the electron wave function in the vicinity of the transition is strongly affected by the disorder and the electron-electron interaction.

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Permalink: https://www.hzdr.de/publications/Publ-31476
Publ.-Id: 31476


Phthalocyanine-Based 2D Conjugated Metal-Organic Framework Nanosheets for High-Performance Micro-Supercapacitors

Wang, M.; Shi, H.; Zhang, P.; Liao, Z.; Wang, M.; Zhong, H.; Schwotzer, F.; Shaygan Nia, A.; Zschech, E.; Zhou, S.; Kaskel, S.; Dong, R.; Feng, X.

2D conjugated metal-organic frameworks (2D c-MOFs) are emerging as a novel class of conductive redox-active materials for electrochemical energy storage. However, developing 2D c-MOFs as flexible thin-flm electrodes have been largely limited, due to the lack of capability of solution-processing and integration into nanodevices arising from the rigid powder samples by solvothermal synthesis. Here, the synthesis of phthalocyanine-based 2D c-MOF (Ni2[CuPc(NH)8]) nanosheets through ball milling mechanical exfoliation method are reported. The nanosheets feature with average lateral size of ≈160 nm and mean thickness of ≈7 nm (≈10 layers), and exhibit high crystallinity and chemical stability as well as a p-type semiconducting behavior with mobility of ≈1.5 cm2 V−1 s−1 at room temperature. Benefting from the ultrathin feature, the nanosheets allow high utilization of active sites and facile solution-processability. Thus, micro-supercapacitor (MSC) devices are fabricated mixing Ni2[CuPc(NH)8] nanosheets with exfoliated graphene, which display outstanding cycling stability and a high areal capacitance up to 18.9 mF cm−2; the performance surpasses most of the reported conducting polymers-based and 2D materials-based MSCs.

Permalink: https://www.hzdr.de/publications/Publ-31475
Publ.-Id: 31475


Ultrathin two-dimensional conjugated metal–organic framework single-crystalline nanosheets enabled by surfactant-assisted synthesis

Wang, Z.; Wang, G.; Qi, H.; Wang, M.; Wang, M.; Park, S.; Wang, H.; Yu, M.; Kaiser, U.; Fery, A.; Zhou, S.; Dong, R.; Feng, X.

Two-dimensional conjugated metal–organic frameworks (2D c-MOFs) have recently emerged for potential applications in (opto-)electronics, chemiresistive sensing, and energy storage and conversion, due to their excellent electrical conductivity, abundant active sites, and intrinsic porous structures. However, developing ultrathin 2D c-MOF nanosheets (NSs) for facile solution processing and integration into devices remains a great challenge, mostly due to unscalable synthesis, low yield, limited lateral size and low crystallinity.
Here, we report a surfactant-assisted solution synthesis toward ultrathin 2D c-MOF NSs, including HHBCu (HHB ¼ hexahydroxybenzene), HHB-Ni and HHTP-Cu (HHTP ¼ 2,3,6,7,10,11-hexahydroxytriphenylene). For the first time, we achieve single-crystalline HHB-Cu(Ni) NSs featured with a thickness of 4–5 nm (~8–10 layers) and a lateral size of 0.25–0.65 mm2, as well as single-crystalline HHTP-Cu NSs with a thickness of ~5.1 + 2.6 nm (~10 layers) and a lateral size of 0.002–0.02 mm2.Benefiting from the ultrathin feature, the synthetic NSs allow fast ion diffusion and high utilization of active sites. As a proof of concept, when serving as a cathode material for Li-ion storage, HHB-Cu NSs
deliver a remarkable rate capability (charge within 3 min) and long-term cycling stability (90% capacity retention after 1000 cycles), superior to the corresponding bulk materials and other reported MOF cathodes.

Permalink: https://www.hzdr.de/publications/Publ-31474
Publ.-Id: 31474


Precision modeling of the IBA Universal Nozzle double scattering mode at the University Proton Therapy Dresden

Lutz, B.; Eulitz, J.; Haneke-Swanson, R.; Enghardt, W.; Lühr, A.

Monte Carlo (MC) simulations are indispensable for many research and advanced clinical questions in proton therapy (PT). However, the necessary site-specifc modeling of a double scattering (DS) PT system is extensive and challenging and requires a clear strategy. This work describes a comprehensive method for precise and accurate modeling of a DS nozzle that minimizes additional measurement effort. A detailed model of the IBA universal nozzle is created within the TOPAS simulation framework. This model is subsequently fine-tuned using a step by step procedure to match the same dose profiles used for the commissioning of the treatment planning system. In the proposed bottom-up approach, the geometry of beam-shaping elements is first adjusted to measured quantities and then the beam and model properties are optimized using iterative methods. The resulting dose distributions are validated with a set of independent measurement data to estimate the achieved quality. The resulting simulated dose distributions agree well with the data and show residual range diifferences typically better than 0.5 mm. The shape of the SOBP plateau regions is accurately reproduced with a spread of the residuals below 1% (i.e., near to the statistical limit) over a large part of the machine settings. The simulated lateral dose profiles, although not directly included in the optimization, match the shape of the validation data better than 0.14 mm. The minimal measurement effort and high-precision proton field modeling make this method attractive, in particular, for retrospective beam modeling needed in clinical outcome studies after DS treatment.

Keywords: radiation therapy; protons; Monte Carlo simulation; SOBP fields; nozzles; double scattering

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  • Secondary publication expected from 25.03.2022

Permalink: https://www.hzdr.de/publications/Publ-31473
Publ.-Id: 31473


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