Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34121 Publications

cupla-docker

Ehrig, S.

Dockerfiles which provide environments for building and running Cupla applications.

Keywords: Docker; Cupla; Alpaka

Permalink: https://www.hzdr.de/publications/Publ-29212
Publ.-Id: 29212


Thermal expansion of magnetron sputtered TiCxN1-x coatings studied by high-temperature X-ray diffraction

Saringer, C.; Kickinger, C.; Munnik, F.; Mitterer, C.; Schalk, N.; Tkadletz, M.

The coefficient of thermal expansion (CTE) of TiCxN1-x can be adjusted by changing the value x between 0 (i.e. pure TiN) and 1 (pure TiC), which makes this material exceptionally useful as base layer to adapt the mismatch between the CTEs of substrate and coating. However, no comprehensive data on the CTE of sputtered TiCxN1-x has been reported up to now. Thus, in this work eleven coatings with compositions ranging from pure TiN to pure TiC were deposited using non-reactive magnetron sputtering. The elemental and phase composition were obtained by elastic recoil detection analysis and Raman spectroscopy, respectively. Powders of the coating material were analyzed using high-temperature X-ray diffraction between room temperature and up to 1000 °C to determine the temperature dependent lattice parameters. Subsequently, these lattice parameters were fitted using second order polynomials with coefficients linearly depending on the carbon content. Thus, a formula for the CTE of TiCxN1-x valid between 25 and 1000 °C was deduced which showed that at room temperature TiN has the highest CTE of 8.12 × 10-6 K-1. The CTE gradually decreases with increasing carbon content to 7.55 × 10-6 K-1 for pure TiC. While the value for TiC only shows a small increase with temperature, the CTE of TiN increases strongly up to 11.1 × 10-6 K-1 at 1000 °C. The presented formula for the temperature dependent CTE of sputtered TiCxN1-x coatings allows to calculate the required composition for TiCxN1-x base layers, in order to tune their thermal expansion for the use in complex multilayered coatings.

Keywords: Thermal expansion; Titanium carbonitride; High-temperature X-ray diffraction; Physical vapor deposition; Hard coatings

Permalink: https://www.hzdr.de/publications/Publ-29211
Publ.-Id: 29211


Modeling of the FFTF isothermal physics tests with the Serpent and DYN3D codes

Nikitin, E.; Fridman, E.

In this study, the isothermal physics tests performed on the fully loaded core of the Fast Flux Test Facility (FFTF) are analyzed with the Monte Carlo code Serpent and with the deterministic core simulator DYN3D. The selected tests comprise two neutron spectra measurements and a multitude of reactivity effect measurements (32 cases with control rod movements and one case for isothermal temperature coefficient). While the flux spectra are calculated only with the Monte Carlo code, the reactivity effects are evaluated with both codes, Serpent and DYN3D. The homogenized few-group cross sections for DYN3D calculations are generated with Serpent. The obtained numerical results are in a very good agreement as compared to the experimental data. Additionally, a comparison of radial power distributions is presented between DYN3D and Serpent calculations, demonstrating an adequate performance of the nodal code DYN3D. This paper provides an additional contribution to the validation of both codes for neutronic analyses of Sodium cooled Fast Reactor cores.

Keywords: Group constant generation; SFR; nodal diffusion; Monte Carlo; SPH; Serpent; DYN3D

Permalink: https://www.hzdr.de/publications/Publ-29210
Publ.-Id: 29210


The UniCAR system: A modular CAR T cell approach to improve the safety of CAR T cells

Bachmann, M.

The idea to eliminate tumor cells via our own immune system is more than a hundred years old. However, a real break through came first with the development of check point inhibitors, bispecific antibodies (bsAbs) and T cells genetically modified to express Chimeric Antigen Receptors (CARs). Eventhough the clinical application of T cells equipped with CARs can lead to a complete remission, unfortunately, their application can also cause severe or even life threatening side effects as their activity can no more be adjusted once given to the patient. For targeting of tumor cells expressing tumor associated antigens (TAAs) which are not limited to tumor cells but also accessible on healthy tissues CAR T cells should not be permanently in a killing mode but be equipped with some kind of a switch whereby the activity of CAR T cells can reversely be turned “on and off “. Moreover, in case of cytokine release syndrome (CRS), tumor lysis syndrome (TLS), or other deadly side effects the possibility of an emergency shut down of the CAR T cell activity should exist. Modular CAR variants such as the UniCAR system may fulfill these requirements.

Keywords: Immunotherapy; Chimeric antigen receptor; T cells; UniCAR; BiTE; Bispecific antibody

Permalink: https://www.hzdr.de/publications/Publ-29209
Publ.-Id: 29209


Formation of calix[4]arenes with acyloxycarboxylate functions

Bauer, D.; Stipurin, S.; Köckerling, M.; Mamat, C.

Calix[4]arenes are an exciting class of multifunctional compounds. Their ability to bind small molecules and ions actively make them useful tools in many scopes of application. While looking for a suitable chelating agent, a particular modification of the calix[4]arene lead to an unexpected side reaction. In this work, we will describe the selective formation of the observed acyloxy-acetate derivatives, which can be tuned by the choice of wet solvents. This side reaction is not described in the literature so far. All new compound were obtained in yields >45% and fully characterized by NMR, MS, and X-ray crystallography. Using the monomeric derivatives of calixarenes and X-ray data, an explanation for the reaction mechanism was postulated. Further, we report on different reaction conditions that were investigated to verify and elaborate this type of reaction. Finally, two additional derivatives of this class were synthesized according to this mechanism to support our considerations.

Keywords: Calix[4]arenes; Esterification; O-alkylation; Complexation; Selective bromination

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  • Secondary publication expected from 21.08.2021

Permalink: https://www.hzdr.de/publications/Publ-29208
Publ.-Id: 29208


Reconstruction of the Landscape Evolution of South Central Africa: A Case Study on Waterfalls of Northern Zambia and South-Eastern D.R. Congo

Olivotos, S.; Niedermann, S.; Mouslopoulou, V.; Merchel, S.; Cotterill, F.; Flugel, T.; Gärtner, A.; Rugel, G.; Scharf, A.; Bookhagen, B.; Nadeau, M.-J.; Braucher, R.

Northern Zambia and the south-eastern Katanga Province of D.R. Congo lie within the southwest extension of the East African Rift System, which is one of the most significant present-day examples of active tectonics. Seismotectonic research in the area has been scarce, despite the fundamental impacts of neotectonics, which controls landscape evolution southwest of the Tanganyika graben. Nevertheless, the formation of the Congo-Zambezi watershed has been constrained from the combination of geological and biological evidence at ~2 Ma (Cotterill & de Wit 2011).
A preliminary Google Earth mapping has revealed two major sets of fault systems (Mweru and Upemba). Analysis of the seismicity patterns recorded within the two fault systems during the last 35 years provides indications for fault interactions over earthquake timescales, highlighting the fact that they are currently active.
This study is part of an interdisciplinary project combining DNA sequencing of selected fish groups to define molecular clocks together with surface exposure dating of key landforms using in-situ produced cosmogenic nuclides. This technique can be applied to quantify how long rocks have been exposed at “knickpoints” since they were first formed (Burbank & Anderson 2012). For that purpose, quartz-rich samples were collected from selected waterfalls with the aim of quantifying exposure ages and erosion/retreat rates. Expecting complex exposure scenarios both radionuclides ¹⁰Be and ²⁶Al and the stable noble gas ²¹Ne were combined in all samples.
Preliminary results from Northern Zambia indicate burial for at least several hundred thousand years. This specific burial may confirm the existence of a significantly deeper and larger Paleo-Lake Mweru before the modern drainage evolved (Dixey, 1944). More results are expected soon to confirm or dismiss this hypothesis. Furthermore, samples taken at different distances below the Kiubo and Luvilombo Waterfalls (D.R.C.) yield preliminary ages between ~7 and 40 ka, increasing with distance from the falls and thus reflecting waterfall retreat. Extrapolating to the original knickpoint location should enable us to estimate the age of its formation.
References
Burbank D.W. & Anderson R.S. 2012. Tectonic Geomorphology. Second Edition. Wiley‐Blackwell, Chichester.
Cotterill F.P.D. & de Wit M.J. 2011. South African Geographical Journal 114: 489-514.
Dixey F. 1944. South African Geographical Journal 47, 01: 9-45.

  • Lecture (Conference)
    GeoMünster 2019 "Earth! Past, Present, Future", 22.-25.09.2019, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29207
Publ.-Id: 29207


Bulk analysis of meteorites using INAA at FRM II

Li, X.; Merchel, S.; Lierse Von Gostomski, C.

In March 2017, the 49th German meteorite was found lying on top of a rock pile on the side of a potato field, near the city of Cloppenburg, Lower Saxony, Germany [1,2]. With two other meteorites (Oldenburg (fall in 1930), Benthullen (find in 1948 or 1951)) from the same region and meteorites from other countries, we started a program to analyze extraterrestrial samples in 2017. We have analyzed in total three chondrites, three achondrites of the HED
group (Howardite-Eucrite-Diogenite) (Dhofar 1675, NWA 2690, NWA 2698), a lunar and a Martian meteorite (NWA 7986, NWA 4925), two iron meteorites (Gibeon, yet unnamed new find from Libya/Chad in 2019) and six potential micrometeorites. The bigger samples (10-20 mg) were normally irradiated twice: for 3-5 min and for a long time up to 1 h in the rabbit position. The much smaller micrometeorites (9-38 μg) were irradiated for 24 h in the high-flux capsule irradiation position (Φth>1E14 cm-2s-1). We used the k0-method for the analysis [3].
With the high and pure thermal neutron flux at the FRM II, up to 45 elements could be determined in most samples [3]. According to the element compositions, the meteorites could be classified or earlier classifications could be confirmed. Although, the sample weights of the micrometeorites are very small and manipulating them was challenging, we could determine up to 16 elements. All of them show a rather high Fe concentration, i.e. 55-70 weight-%. However, for Ni and Ir, we can only give a detection limit of about 0.4% and 2 ng/g, respectively. Their potential origin are under discussion.
Acknowledgments
We thank A. Muszynski and M. Szyszko (Poznan, PL), A. Bischoff (Uni. Münster), D. Heinlein, J. Feige (TU Berlin) and A. Gärtner (Senckenberg Dresden) for providing and preparation of samples and the TUM-Kolleg program for financial supports.
References
1. J. Gattacceca et al., Meteorit. Planet. Sci., 2019, 54, 469-471.
2. J. Storz et al., www.paneth.eu/PanethKolloquium/2017/0075.pdf (Jan. 2019)
3. X. Li et al., J. Radioanal. Nucl. Chem. 2014, 300, 457-463.

Keywords: INAA; k0-method; meteorite; micrometeorite

  • Lecture (Conference)
    2nd International Conference on Radioanalytical and Nuclear Chemistry (RANC 2019), 05.-10.05.2019, Budapest, Hungary

Permalink: https://www.hzdr.de/publications/Publ-29206
Publ.-Id: 29206


Preliminary Report on the Study of Beam-induced Background Effects at a Muon Collider

Bartosik, N.; Bertolin, A.; Casarsa, M.; Collamati, F.; Ferrari, A.; Ferrari, A.; Gianelle, A.; Lucchesi, D.; Mokhov, N.; Müller, S.; Pastrone, N.; Sala, P.; Sestini, L.; Striganov, S.

Physics at a multi-TeV muon collider needs a change of perspective for the detector design due to the large amount of background induced by muon beam decays. Preliminary studies, based on simulated data, on the composition and the characteristics of the particles originated from the muon decays and reaching the detectors are presented here. The reconstruction performance of the physics processes H→bb¯ and Z→bb¯ has been investigated for the time being without the effect of the machine induced background. A preliminary study of the environment hazard due to the radiation induced by neutrino interactions with the matter is presented using the FLUKA simulation program.

Keywords: Detectors in high-intensity environments; future accelerators; muon beams; neutrino-induced radiation

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Permalink: https://www.hzdr.de/publications/Publ-29205
Publ.-Id: 29205


Vertical Organic Thin-Film Transistors with an Anodized Permeable Base for Very Low Leakage Current

Dollinger, F.; Lim, K.-G.; Li, Y.; Guo, E.; Formánek, P.; Hübner, R.; Fischer, A.; Kleemann, H.; Leo, K.

The organic permeable base transistor (OPBT) is currently the fastest organic transistor with a transition frequency of 40 MHz. It relies on a thin aluminum base electrode to control the transistor current. This electrode is surrounded by a native oxide layer for passivation, currently created by oxidation in air. However, this process is not reliable and leads to large performance variations between samples, slow production, and relatively high leakage currents. Here, for the first time it is demonstrated that electrochemical anodization can be conveniently employed for the fabrication of high-performance OPBTs with vastly reduced leakage currents and more controlled process parameters. Very large transmission factors of 99.9996 % are achieved, while excellent on/off ratios of 5 × 105 and high on-currents greater than 300 mA cm−2 show that the C60 semiconductor layer can withstand the electrochemical anodization. These results make anodization an intriguing option for innovative organic transistor design.

Keywords: aluminum oxide; anodization; organic permeable base transistors (OPBTs); organic transistors; organic thin-film transistors (OTFTs); vertical transistors

Permalink: https://www.hzdr.de/publications/Publ-29204
Publ.-Id: 29204


The influence of microstructure on the fracture behaviour of ferritic ODS steels

Das, A.

Oxide dispersion strengthened (ODS) steels are candidate materials for cladding tube and structural components in Generation IV nuclear fission reactors and as candidate materials for structural components in fusion devices. Fracture toughness is an important parameter required for the structural integrity and workability of a material. Despite having high strength at high temperatures and high irradiation swelling resistance, ODS steels have been known to possess lower fracture toughness than non-ODS ferritic martensitic steels, their immediate competitor. They also exhibit anisotropic fracture behaviour, especially for the hot-rolled and hot-extruded variants. In addition, ODS steels tend to form secondary cracks, which absorb energy but can lead to design problems.
In the present work, the microstructural features which cause low fracture toughness, anisotropic fracture behaviour and secondary cracking are investigated. This information can help manufacturers develop ODS steels with better fracture properties. Fracture toughness testing on three different batches of ODS steels are performed using miniature fracture toughness C(T) specimens using the unloading compliance method. The basic microstructure, fracture surfaces and crack propagation are investigated using techniques such as SEM, TEM and EBSD and compared with the fracture behaviour. A quantitative assessment of the microstructural parameters affecting fracture toughness is made using a critical strain based fracture toughness expression.
It was observed that the low fracture toughness of ODS steels is predominantly affected by the bond strength between the void initiating particle and the matrix. The size and inter-particle spacing of void initiating particles along with the yield stress did not dominantly affect the fracture toughness. The anisotropic fracture behaviour in ODS steels was found to be predominantly affected by the anisotropic grain morphology. Crystallographic anisotropy and anisotropy in void initiating particle distribution did not dominantly affect the fracture anisotropy. Secondary cracking favoured hot-rolled over hot-extruded specimens due to higher degree of microstructural anisotropy. Secondary cracks could stabilize primary crack propagation as well as prevent cleavage fracture at low temperatures. However, the drawback with secondary cracks was that they initiated earlier or at lower loads than the primary crack.

Keywords: fracture; fracture toughness; microstructure-mechanical property correlation; ODS steels; material characterization

  • Doctoral thesis
    University of Siegen, 2019
    Mentor: Prof. Dr.-Ing. habil. H.-J. Christ

Permalink: https://www.hzdr.de/publications/Publ-29202
Publ.-Id: 29202


Wave-shaped polycyclic hydrocarbons with controlled aromaticity

Ma, J.; Zhang, K.; Schellhammer, S.; Fu, Y.; Komber, H.; Xu, C.; Popov, A. A.; Hennersdorf, F.; Weigand, J. J.; Zhou, S.; Pisula, W.; Ortmann, F.; Berger, R.; Liu, J.; Feng, X.

Controlling the aromaticity and electronic properties of curved π-conjugated systems has been increasingly attractive for the development of novel functional materials for organic electronics. Herein, we demonstrate an efficient synthesis of two novel wave-shaped polycyclic hydrocarbons (PHs) 1 and 2 with 64 π-electrons. Among them, the wave-shaped π-conjugated carbon skeleton of 2 is unambiguously revealed by single-crystal X-ray crystallography analysis. The wave-shaped geometry is induced by steric congestion in the cove and fjord regions. Remarkably, the aromaticity of these two structural isomers can be tailored by the annulated direction of cyclopenta[b]fluorene units. Isomer 1 (Eoptg = 1.13 eV) behaves as a closed-shell compound with weakly antiaromatic feature, whereas its structural isomer 2 displays a highly stable tetraradical character (y0 = 0.23; y1 = 0.22; t1/2 = 91 days) with a narrow optical energy gap of 0.96 eV. Moreover, the curved PH 2 exhibits remarkable ambipolar charge transport in solution-processed organic thin-film transistors. Our research provides a new insight into the design and synthesis of stable functional curved aromatics with multiradical characters.

Permalink: https://www.hzdr.de/publications/Publ-29201
Publ.-Id: 29201


Flash Lamp Annealing: From Basics to Applications

Rebohle, L.; Prucnal, S.; Reichel, D.

The work gives a detailed introduction to the technology of flash lamp annealing, the corresponding physical background and an overview of the various applications of flash lamp annealing found in literature. It discusses a couple of issues which are relevant for process management with the focus on temperature measurement and temperature simulation. The application-related chapters include, inter alia, ultra-shallow junctions and hyperdoping in silicon, doping and superconductivity in germanium, silicon carbide, III-V semiconductors, diluted magnetic semiconductors, the crystallization of thin amorphous silicon films, semiconductor nanostructures, high-k materials, flash lamp annealing for monocrystalline, polycrystalline and thin film solar cells, transparent conducting oxides and flexible substrates.

Keywords: Thermal processing; semiconductors; flash lamp annealing; thin films; millisecond annealing

Permalink: https://www.hzdr.de/publications/Publ-29200
Publ.-Id: 29200


Measurement-Protocol Dependence of the Magnetocaloric Effect in Ni-Co-Mn-Sb Heusler Alloys

Salazar Mejia, C.; Kumar, V.; Felser, C.; Skourski, Y.; Wosnitza, J.; Nayak, A. K.

Ni-Co-Mn-Sb-based Heusler shape-memory alloys that undergo a martensitic-structural transition around room temperature are well known for exhibiting large magnetic entropy change and elastocaloric effect. Here, we report the observation of a large adiabatic temperature change of −11 K in a Ni-Co-Mn-Sb system by using direct adiabatic temperature-change measurements in pulsed magnetic fields. We show that a large magnetic cooling can be achieved in a wide temperature range spanning from 120 to 270 K by purposefully varying the chemical composition. The temperature- and field-dependent irreversibility of the effect is analyzed through a detailed experimental study of the protocol-dependent magnetocaloric effect. The present study is an important contribution towards the understanding of irreversible magnetocaloric effects in materials with magnetostructural transition.

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Permalink: https://www.hzdr.de/publications/Publ-29199
Publ.-Id: 29199


Magnetocaloric effect of gadolinium in high magnetic fields

Gottschall, T.; Kuz'Min, M. D.; Skokov, K. P.; Skourski, Y.; Fries, M.; Gutfleisch, O.; Ghorbani Asl, M.; Schlagel, D. L.; Mudryk, Y.; Pecharsky, V.; Wosnitza, J.

The magnetocaloric effect of gadolinium has been measured directly in pulsed magnetic fields up to 62 T. The maximum observed adiabatic temperature change is ΔTad = 60.5 K, the initial temperature T0 being just above 300 K. The field dependence of ΔTad is found to follow the usual H2/3 law, with a small correction in H4/3. However, as H is increased, a radical change is observed in the dependence of ΔTad on T0, at H = const. The familiar caret-shaped peak situated at T0 = TC becomes distinctly asymmetric, its high-temperature slope becoming more gentle and evolving into a broad plateau. For yet higher magnetic fields, μ0H ≥ 140 T, calculations predict a complete disappearance of the maximum near TC and an emergence of a new very broad maximum far above TC.

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Permalink: https://www.hzdr.de/publications/Publ-29198
Publ.-Id: 29198


Field-induced instability of the quantum spin liquid ground state in the Jeff = 1/2 triangular-lattice compound NaYbO2

Ranjith, K. M.; Opherden, D.; Khim, S.; Sichelschmidt, J.; Luther, S.; Ehlers, D.; Yasuoka, H.; Wosnitza, J.; Tsirlin, A. A.; Kühne, H.; Baenitz, M.

Polycrystalline samples of NaYbO2 are investigated by bulk agnetization and specific-heat measurements, as well as by nuclear magnetic resonance (NMR) and electron spin resonance (ESR) as local probes. No signatures of long-range magnetic order are found down to 0.3 K, evidencing a highly frustrated spin-liquid-like ground state in zero field. Above 2 T, signatures of magnetic order are observed in thermodynamic measurements, suggesting the possibility of a field-induced quantum phase transition. The 23Na NMR relaxation rates reveal the absence of magnetic order and persistent fluctuations down to 0.3 K at very low fields and confirm the bulk magnetic order above 2 T. The H-T phase diagram is obtained and discussed along with the existing theoretical concepts for layered spin- 1/2 triangular-lattice antiferromagnets.

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Permalink: https://www.hzdr.de/publications/Publ-29197
Publ.-Id: 29197


Electronic Properties of Defective MoS2 Monolayers Subject to Mechanical Deformations: A First-Principles Approach

Bahmani, M.; Faghihnasiri, M.; Lorke, M.; Kuc, A. B.; Frauenheim, T.

Monolayers (MLs) of group-6 transition-metal dichalcogenides (TMDs) are semiconducting 2D materials with direct bandgap, showing promising applications in various fields of science and technology, such as nanoelectronics and optoelectronics. These MLs can undergo strong elastic deformations, up to about 10%, without any bond breaking. Moreover, the electronic structure and transport properties, which define the performance of these TMD MLs in nanoelectronic devices, can be strongly affected by the presence of point defects, which are often present in the synthetic samples. Thus, it is important to understand both effects on the electronic properties of such MLs. Herein, the electronic structure and energetic properties of defective MoS2 MLs are investigated as subject to various strains, using density functional theory simulations. The results indicate that strain leads to strong modifications of the defect levels inside the bandgap and their orbital characteristics. Strain also splits the degenerate defect levels up to an amount of 450 meV, proposing novel applications.

Permalink: https://www.hzdr.de/publications/Publ-29196
Publ.-Id: 29196


Single Plane Compton Imaging for Radionuclide and Prompt Gamma-Ray Imaging

Kögler, T.; Berthold, J.; Deneva, B.; Enghardt, W.; Römer, K.; Straessner, A.; Wagner, A.; Werner, T.; Pausch, G.

The contribution reports on first attempts to prove the concept of Single Plane Compton Imaging (SPCI), which was recently proposed in [1]. SPCI combines electronic collimation as known from conventional Compton cameras with a much simpler detector design: Multiple scintillator pixels are arranged alongside in a single detection plane. Imaging information is encoded in a set of ‘conditional’ spectra meaning energy deposition distributions in single pixels obliged with the condition of a coincident detection in another (adjacent) pixel. The activity distribution is iteratively reconstructed from the measured projections (the bin contents of the conditional spectra) by using the Maximum Likelihood Expectation Maximization (MLEM) algorithm.
This concept has been approached experimentally with three distinct setups addressing the application fields of radionuclide imaging in nuclear medicine, and of prompt-gamma based range verification in radiooncology with proton beams.
The first setup consists of two Directional Gamma-Ray Detectors [2], each consisting of two monolithic CeBr3 scintillators of 2”x1” and 2”x2”, arranged facing each other in close geometry. Those were exposed to prompt gamma radiation produced by a 90 MeV proton beam in a beam-stopping polymethyl acrylate (PMMA) target.
The third setup, aiming to be applied in radionuclide imaging, is a combination of a 4×4 pixel array of about 7 × 7 × 20 mm3 GAGG scintillator pixels read out with a Philips STEK module comprising 4×4 digital silicon photomultiplier dies. Data were taken with radioactive point sources arranged in few-cm distance from the scintillator pixels. Though data analyses are not yet finished, the effects enabling imaging are clearly visible. Preliminary plots exemplify the applicability of SPCI in both applications. The experimental activities have been closely accompanied with appropriate imaging methods and modeling using the Geant4 toolkit.

Bibliography

[1] G. Pausch, C. Golnik, A. Schulz and W. Enghardt, "A Novel Scheme of Compton Imaging for Nuclear Medicine," in IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD), Strasbourg, 2016.
[2] A. Gueorguiev, J. Preston, l. Hoy, G. Pausch, C. Herbach and J. Stein, "A novel method to determine the directionality of radiation sources with two detectors based on coincidence measurements," in IEEE Nuclear Science Symposuim & Medical Imaging Conference, Knoxville, 2010.

Keywords: proton therapy; radiotherapy; range verification; single plane Compton imaging

  • Invited lecture (Conferences)
    International Conference on Nuclear Data for Science and Technology 2019, 19.-24.05.2019, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-29195
Publ.-Id: 29195


Proton-induced Prompt Gamma-Ray Yield of Carbon for Range Verification in Hadron Therapy

Kögler, T.; Buch, F.; Römer, K.; Urlaß, S.; Pausch, G.; Wagner, A.

With particle therapy, more and more patients around the world are benefiting from precise dose deposition in the tumor. Due to the characteristic depth dose distribution, however, hadron therapy is particularly susceptible to range inaccuracies. Particle range verification is the subject of current research, but not yet a clinical standard. To circumvent this problem, safety margins are currently being defined around the tumor volume, which nullify the potential precision of particle compared to conventional photon therapy.
The use of the prompt gamma radiation resulting from the deceleration of hadrons in tissue for range verification is a promising approach here. At present, various methods exist (for example, prompt gamma-ray imaging, prompt gamma-ray spectroscopy, prompt gamma-ray timing, prompt gamma-ray peak integration), which attempt to obtain information regarding the range from the temporal and / or spatial distribution of these high-energy photons. However, all methods are based directly or indirectly on the results of particle transport calculations. But their results show significant discrepancies compared to the experimental data [1] - [7].
Photon production cross sections are particularly important for range verification with prompt gamma radiation, although there is hardly any experimental data for the clinically relevant isotopes to check and optimize the underlying models. The importance of prompt photon yields in clinical research was therefore also the subject of the 2nd ESTRO Physics Workshop Science and Development "Improving Range Accuracy in Particle Therapy" and will soon be emphasized again in a position paper of the society.
At the University Proton Therapy Dresden, the prompt emission spectrum of homogeneous graphite targets of different thickness was determined by irradiation with 90, 150 and 226 MeV protons. The detector response of the CeBr3 scintillation detectors (placed below 55 °, 90 ° and 125 ° with respect to the beam axis) was determined by Geant 4 simulations and verified by measurements with radioactive emitters. The emission spectrum was then obtained by unfolding the detector response using two different deconvolution algorithms (gold deconvolution and spectrum stripping). Scattered protons, which were detected in a YAP / BGO-Phoswich detector below 35°, were used to determine the incident proton fluence. The yields thus obtained are in good agreement with the available experimental data.

Bibliography

[1] J. Berthold, Single Plane Compton Imaging for Range Verification in Proton Therapy - A Proof-of-Principle Study, Dresden: Technische Universität Dresden, 2018.
[2] L. Kelleter, A. Wronska, J. Besuglow, A. Konefał, K. Laihem, J. Leidner und A. Magiera, „Spectroscopic study of prompt-gamma emission for range verification in proton therapy,“ Physica Med., Bd. 34, pp. 7-17, 2017.
[3] M. Pinto, D. Dauvergne, N. Freud, J. Krimmer, J. Létang und E. Testa, „Assessment of Geant4 Prompt-Gamma Emission Yields in the Context of Proton Therapy Monitoring,“ Frontiers in Oncology, Bd. 6, 2016.
[4] J. Jeyasugiththan und S. Peterson, „Evaluation of proton inelastic reaction models in Geant4 for prompt gamma production during proton radiotherapy,“ Phys. Med. Biol., Bd. 60, p. 7617–7635, 2015.
[5] A. Schumann, J. Petzoldt, P. Dendooven, W. Enghardt, C. Golnik, F. Hueso-González, T. Kormoll, G. Pausch, K. Roemer und F. Fiedler, „Simulation and experimental verification of prompt gamma-ray emissions during proton irradiation,“ Phys. Med. Biol., Bd. 60, pp. 4197-4207, 2015.
[6] J. Verburg, Reducing Range Uncertainty In Proton Thearpy, Eindhoven: Technische Universiteit Eindhoven, 2015.
[7] J. Dudouet, D. Cussol, D. Durand und M. Labalme, „Benchmarking Geant4 nuclear models for hadron therapy with 95 MeV/nucleon carbon ions,“ Phys. Rev. C, Bd. 89, p. 054616, 2014.

Keywords: proton therapy; range verification; prompt gamma yield; spectrum stripping; gold deconvolution

  • Poster
    International Conference on Nuclear Data for Science and Technology 2019, 19.-24.05.2019, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-29194
Publ.-Id: 29194


Solubility of Se in saline solutions – towards a consistent polythermal Pitzer dataset

Bok, F.; Moog, H. C.

Selenium (with the isotope Se-79 being an important fission product) can occur in oxidation states varying between +VI and –II. Most often negatively charged species are formed rendering them extraordinarily mobile in groundwater systems. For a correct calculation of the solubilities of Se(VI) and Se(IV) phases, the Pitzer ion-ion interaction model is essential for solutions with high ionic strengths.
Beside solubility calculations – mostly relevant for low soluble earth alkali selenites – reliable thermodynamic data sets for selenium are also of importance for chemotoxicity estimations or as boundary system in S-Se-solid solutions.
The state-of-the-art thermodynamic data for Selenium are given in the OECD/NEA Chemical Thermodynamics. This compilation does not address the Pitzer ion-ion interaction model. A polythermal set of Pitzer interaction parameters was compiled by GRS. However, both compilations hold solubility data for T = 25 °C only.
Here, to enable the calculation of selenium solubility at various temperatures in high saline solutions, temperature functions for the solubility products of alkaline and earth alkaline selenium phases are presented.

The experimental solubility data of various alkaline and earth alkaline selenates and selenites have been collected. The temperature function’s parameters of the solubility products were fitted to these solubility data using the geochemical speciation code PHREEQC in combination with the parameter estimation software Ucode2014.
Beside the solubility data, also temperature function’s parameters for the relevant redox reactions have been determined. The THEREDA database was used for all auxiliary reactions. Thus, the obtained data are consistent with their actual Pitzer model.

Temperature function’s parameters for the solubility products of seven selenate and four selenite mineral phases as well as for the relevant redox reactions could be obtained. In all cases, simplified functions with only two parameters were sufficient to fit the data within the range of experimental uncertainty.
With this new temperature-dependent parameter set, the solubility of selenium(IV) and (VI) an be calculated over the temperature range (T = 0 – 100 °C) relevant for a nuclear waste disposal.
The literature on directly measured selenide solubility data is very limited and not sufficient to derive solubility products or Pitzer interaction parameters – even at 25 °C. Thus, for the Se(−II) system the solubility data for alkaline and earth alkaline solid phases were taken from thermochemical measurements. For the Pitzer interaction coefficients data from chemical analogs have been used (Br or H2S). For the selenide system, this dataset is valid for T = 25 °C only.
The new temperature functions provide a redox-enabled and self-consistent dataset for the solubility calculations of selenium within the oceanic salt system including carbonates from the binary up to ternary and some quaternary systems.
For oxidizing to light reducing conditions, this dataset is valid between T = 0 – 100 °C, for stronger reducing conditions, the dataset is valid at T = 25 °C only.

Keywords: THEREDA; Selenium; Solubility; Löslichkeit; Pitzer

  • Lecture (Conference)
    Workshop on Actinide-Brine-Chemistry and Workshop on High Temperature Aqueous Chemistry, 25.-27.06.2019, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29193
Publ.-Id: 29193


Size effects in nanocrystalline thoria

Plakhova, T.; Romanchuk, A.; Lykhosherstova, D.; Baranchikov, A.; Dorovatovskii, P.; Svetogorov, R.; Shatalova, T.; Egorova, T.; Trigub, A.; Kvashnina, K.; Ivanov, V.; Kalmykov, S.

The facile chemical precipitation method and subsequent thermal treatment were shown to be suitable for preparation of crystalline ThO2 nanoparticles (NPs) in a wide range of particle sizes (from 2.5 to 34.3 nm). The obtained NPs were investigated with X-ray diffraction, high-resolution transmission electron microscopy and X-ray absorption techniques to find out the possible size effects associated with nanocrystalline thoria. The lattice parameter of ThO2 was found to increase by up to 1.1 %, in comparison with the bulk material whose particle size decreased to 2.5 nm. The decrease in the particle size was also accompanied by a significant decrease in the Th-Th coordination number

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Permalink: https://www.hzdr.de/publications/Publ-29192
Publ.-Id: 29192


New insights into the mechanism of graphene oxide and radionuclide interaction through vacancy defects

Kuzenkova, A.; Romanchuk, A.; Trigub, A.; Maslakov, K.; Egorov, A.; Amidani, L.; Kittrelle, C.; Kvashnina, K.; Toure, J.; Talyzin, A.; Kalmykov, S.

The sorption of U(VI), Am(III)/Eu(III) and Cs(I) radionuclides by graphene oxides (GOs) synthesized by Hummers’s, Brodie’s and Tour’s methods was studied through a combination of batch experiments with characterization by microscopic and spectroscopic techniques such as XPS, ATR-FTIR, HERFD-XANES, EXAFS and HRTEM. Remarkably different sorption capacity and affinity of radionuclides was found towards GOs synthesized by Hummers’s and Brodie’s methods reflecting different structure and oxidation state of these materials. Mechanism underlying GO –radionuclide interaction is determined using variety of experimental techniques. For the first time it is shown here that GO - radionuclides interaction takes place on the small holes or vacancy defects in the GO sheets. Mechanism of GO’s interaction with radionuclides was analysed and specific functional groups responsible for this interaction were identified. Therefore, new strategy to produce improved materials with high capacity for radionuclides suggests to use perforated and highly defected GO with larger proportion of carboxylic functional groups

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29191
Publ.-Id: 29191


Ion Sources for Focused Ion Beams – Present Status and Prospective Developments

Bischoff, L.; Mazarov, P.; Pilz, W.; Klingner, N.; Gierak, J.

Focused Ion Beam (FIB) processing has been developed into a well-established, irreplaceable and still promising technique in nearly all fields of nano-technology in particular for direct patterning and proto-typing on the μm scale and well below as well as sample preparation for further investigations, using SEM or TEM.
At the moment nearly exclusively gallium Liquid Metal Ion Sources (LMIS) are used for ion beam generation. Therefore, the Liquid Metal Alloy Ion Sources (LMAIS) represent a promising new alternative research area to expand the global FIB application fields. Here, especially, IBL (Ion Beam Lithography) - a direct, resistless and threedimensional patterning - enables a simultaneous in-situ process control by crosssectioning and inspection. Thanks to this, nearly half of the elements of the periodic table are made available in the FIB technology as a result of continuous research in this area during the last forty years [1]. Key features of a LMAIS are long life-time, high brightness and stable ion current. Recent developments could make these sources as an alternative technology feasible for nano patterning challenges e.g. to tune electrical, optical, magnetic or mechanic properties. In this contribution the operation principle, the preparation and testing
technology as well as prospective domains for modern FIB applications will be presented. As an example we will introduce a Ga35Bi60Li5 LMAIS in detail. It enables high resolution imaging with light Li ions, obtained with a VELION FIB/SEM system (Raith GmbH), as well as heavy Bi ions or polyatomic clusters, all coming from one ion source [2]. Additionally, also new ion source developments based on gas field emission (GFIS), on ionic liquids (ILIS), on magneto-optical traps (MOTIS) or on ICP or ECR high current sources for Xe-FIB are presented. Combined with an optimized FIB optics design they can open a bright field of new employments. These alternative ion sources will be introduced and briefly described.
[1] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources - An Alternative
for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
[2] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium Ion Beams from Liquid Metal
Alloy Ion Sources, J. Vac. Sci. Technol. B 37 (2019) 021802-1.

Keywords: Ion sources; Focused Ion Beam; Nanopatterning

  • Invited lecture (Conferences)
    European FIB Network, 3rd EuFN Workshop 2019, 12.-14.06.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29190
Publ.-Id: 29190


Studying of plutonium nanoparticles with various synchrotron metods

Gerber, E.; Romanchuk, A.; Hennig, C.; Trigub, A.; Scheinost, A.; Roßberg, A.; Vaughan, G.; Amidani, L.; Pidchenko, I.; Weiß, S.; Kalmykov, S.; Kvashnina, K.

Plutonium is one of the most significant elements among actinides due to its high radiotoxicity and long period of high-decay. The migration of plutonium in the environment is a challenging and global problem. Plutonium migrates at scale of kilometers from previously contaminated sites in the form of intrinsic colloids or “pseudocolloids”.1-2 In the last few years it was found that so called “colloidal Pu(IV) polymers” actually represents as aggregates of PuO2 nanoparticles with size ~ 2 nm.3-5 The revealing of the mechanism of these particles formation (including the consideration of different factors which may have an influence), as well as their characterization is a key to understanding the conditions for long-term storages for the nuclear waste.
With the combination of different laboratory and synchrotron techniques it was found that small (2 nm) nanoparticles are formed from Pu(III), Pu(IV), Pu(V) aqueous solutions at pH 8-12, with the crystal structure close to PuO2, and with only Pu(IV) oxidation state present. Any other Pu-O contributions except Pu(IV)-O (in oxide) were not revealed.

  • Lecture (Conference)
    XXI Mendeleev Congress on General and Applied Chemistry, 09.-13.09.2019, Saint Petersburg, Russia

Permalink: https://www.hzdr.de/publications/Publ-29189
Publ.-Id: 29189


Minimizing betatron coupling of energy spread and divergence in laser-wakefield accelerated electron beams

Köhler, A.; Pausch, R.; Couperus Cabadağ, J. P.; Zarini, O.; Krämer, J. M.; Bussmann, M.; Debus, A.; Schramm, U.; Irman, A.

Matched beam loading in laser wakefield acceleration (LWFA), characterizing the state of flattening of the accelerating electric field along the bunch, leads to the minimization of energy spread at high bunch charges. Here, we demonstrate by independently controlling injected charge and accelerating gradients, using the self-truncated ionization injection scheme, that minimal energy spread coincides with a reduction of the normalized beam divergence. With the simultaneous confirmation of a constant beam radius at the plasma exit, deduced from betatron radiation spectroscopy, we attribute this effect to the reduction of chromatic betatron decoherence. Thus, beam loaded LWFA enables highest longitudinal and transverse phase space densities.

Keywords: Laser wakefield acceleration; laser plasma accelerator; high bunch charge; beam loading; bunch size measurement; betatron radiation; betatron spectroscopy; Transverse phase space dynamic; beam divergence; beam decoherence; betatron phase mixing; betatron decoherence

Related publications

  • Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop, 15.-21.09.2019, Isola d'Elba, Italia
  • Contribution to WWW
    arXiv:1905.02240 [physics.acc-ph]: https://arxiv.org/abs/1905.02240

Permalink: https://www.hzdr.de/publications/Publ-29188
Publ.-Id: 29188


Geometry description in the FLUKA MC transport code

Müller, S.

Geometry description in the FLUKA MC transport code

Keywords: FLUKA; MU2E; CLFV

  • Lecture (others)
    MU2E SimWG meeting, 11.04.2019, Fermilab, Batavia, USA

Permalink: https://www.hzdr.de/publications/Publ-29187
Publ.-Id: 29187


Ultrafast Anisotropic Disordering in Graphite Driven by Intense Hard X-ray Pulses

Hartley, N.; Grenzer, J.; Lu, W.; Huang, L.; Inubushi, Y.; Kamimura, N.; Katagiri, K.; Kodama, R.; Kon, A.; Lipp, V.; Makita, M.; Matsuoka, T.; Medvedev, N.; Nakajima, S.; Ozaki, N.; Pikuz, T.; Rode, A. V.; Rohatsch, K.; Sagae, D.; Schuster, A.; Tono, K.; Vorberger, J.; Yabuuchi, T.; Kraus, D.

We present results from the SPring-8 Angstrom Compact free electron LAser (SACLA) X-ray free electron laser (XFEL) facility, using an X-ray pump, X-ray probe scheme to observe ultrafast changes in the structure of heated graphite. The 9.8 keV XFEL beam was focused to give an intensity on the order of 10^19 W/cm2, and the evolution of the diffraction pattern observed up to delays of 300 fs. The interplanar diffraction peaks weaken significantly within 10s of femtoseconds, but in-plane diffraction orders i.e. those with Miller Index (hk0), persist up to 300 fs, with the observed signal increasing. We interpret this as nonthermal damage through the breaking of interplanar bonds, which at longer timescales leads to ablation by removal of intact graphite sheets. Post-experiment examination of the graphite samples shows damage which is comparable in size to the range of the excited photoelectrons. These results highlight the challenges of accurately modelling X-ray driven heating, as it becomes a routine approach to generating high energy density states.

Permalink: https://www.hzdr.de/publications/Publ-29186
Publ.-Id: 29186


Tunable disorder and localization in the rare-earth nickelates

Wang, C.; Chang, C.-H.; Huang, A.; Wang, P.-C.; Wu, P.-C.; Yang, L.; Xu, C.; Pandey, P.; Zeng, M.; Böttger, R.; Jeng, H.-T.; Zeng, Y.-J.; Helm, M.; Chu, Y.-H.; Ganesh, R.; Zhou, S.

We demonstrate that transport in metallic rare-earth nickelates can be engineered by directly tuning the electronic mean free path. Using irradiation as a tool to induce disorder, we drive this system from a metallic phase into an Anderson insulator. This proceeds via an intermediate regime which shows a thermal crossover from insulating to metallic behavior. We argue that this phase falls within the paradigm of weak localization in three dimensions. We develop a theoretical model for the temperature dependence of resistivity which shows good agreement with our data. The three-dimensional weak localization picture is supported by magnetoconductivity, which scales as ∼B2 up to several tesla. Interestingly, our data indicate that this phase lies in the Mott-Ioffe-Regel regime with the mean free path approaching the lattice constant. Upon further increasing disorder, the charge carriers are localized, leading to insulating behavior at all temperatures. Our results show that irradiation provides a “clean” tuning knob for the mean free path, without altering other system parameters. This suggests promising directions for studies of Anderson localization.

Keywords: Anderson localization; Metal-insulator transition; Weak localization; Magnetoresistance

  • Physical Review Materials 3(2019)053801
    DOI: 10.1103/PhysRevMaterials.3.053801
  • Poster
    26th International Workshop on Oxide Electronics, 29.09.-02.10.2019, Kyoto, Japan

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Permalink: https://www.hzdr.de/publications/Publ-29185
Publ.-Id: 29185


Light and Heavy Ions from New Non-classical Liquid Metal Ion Sources for Advanced Nanofabrication

Mazarov, P.; Richter, T.; Bruchhaus, L.; Jede, R.; Yu, Y.; Sanabia, J. E.; Bischoff, L.; Gierak, J.

Nanofabrication requirements for FIB technologies are specifically demanding in terms of patterning resolution, stability and the support of new processing techniques. Moreover the type of ion defines the nature of the interaction mechanism with the sample and thus has significant consequences on the resulting nanostructures [1]. Therefore, we have extended the technology towards the stable delivery of multiple ion species selectable into a nanometer scale focused ion beam by employing a liquid metal alloy ion source (LMAIS) [2]. This provides single and multiple charged species of different masses, resulting in significantly different interaction mechanisms. Nearly half of the elements of the periodic table are made available in the FIB technology as a result of continuous research in this area [3]. This range of ion species with different mass or charge can be beneficial for various nanofabrication applications. Recent developments could make these sources to an alternative technology feasible for nanopatterning challenges. In this contribution the operation principle, the preparation and testing process as well as prospective domains for modern FIB applications will be presented. As example we will introduce a GaBiLi LMAIS [4]. It enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB or the AuSiGe-FIB could benefit of providing additional ion species in a mass separated FIB without changing the ion source.
[1] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of technologies for nano device prototyping with a special focus on ion beams: A review, Appl. Phys. Rev. 4, 011302 (2017).
[2] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for
Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
[3] J. Gierak, P. Mazarov, L. Bruchhaus, R. Jede, L. Bischoff, Review of electrohydrodynamical ion sources and their applications to focused ion beam technology, JVSTB 36, 06J101 (2018).
[4] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37, 021802 (2019).

Keywords: Nanofabrication; FIB technology; Liquid Metal Alloy Ion Source

  • Invited lecture (Conferences)
    AVS 66th International Symposium & Exhibition, 20.-25.10.2019, Columbus, Ohio, USA

Permalink: https://www.hzdr.de/publications/Publ-29184
Publ.-Id: 29184


Numerical simulation of an electromagnetic flow excitation in a liquid metal volume using OpenFOAM

Röhrborn, S.; Jüstel, P.; Schindler, F.; Galindo, V.; Stefani, F.

To prepare an experiment on the potential resonance effect between the Rayleigh-Bénard convection and weak tidal forcing in a liquid metal, the influence of electromagnetic forcing on the eutectic metal Ga-In-Sn simulated in OpenFOAM will be the main topic of this work [1].
A modulated tidal m=2 Lorentz forcing will be produced by two opposing Helmholtz-like coils outside a Ga-In-Sn filled cylinder with an aspect ratio of one. Considering future analyses with additional Rayleigh-Bénard convection two Cu-plates installed at the bottom and the top of the volume are also taken into account for the simulation of the AC magnetic field. With a small magnetic flux density of a few mT a flow speed up to several centimeters per second can be produced. The results of the numerical simulations will be compared with experimental data.

Keywords: Magnetohydrodynamics; OpenFOAM; Rayleigh-Bénard convection; electromagnetic forcing; liquid metal

  • Lecture (Conference)
    9th European Postgraduate Fluid Dynamics Conference, 16.-19.07.2019, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29183
Publ.-Id: 29183


Electromagnetic flow excitation in a liquid metal volume using a Helmholtz-like coil setup

Jüstel, P.; Röhrborn, S.; Schindler, F.; Galindo, V.; Stefani, F.

We present first results of our experiment involving electromagnetic forcing of a liquid metal volume. The experiment consist of a cylinder filled with eutectic GaInSn alloy and two magnetic coils placed on opposite sides of the cylinder. An alternating current in the coils excites Lorentz forces in the fluid, generating a flow field. Using ultrasound doppler velocimetry (UDV), we mapped this flow field. Maximum velocities of a few centimetres per second were reached. Numerical studies of the problem were also conducted and show good agreement. As a next step, the experimental setup shall be used to periodically disturb a Rayleigh-Bénard convection. The Rayleigh-Bénard flow structure occurs, when a layer of fluid is heated from below. The resulting flow is a convection roll about a horizontal axis. Point of interest is a possible resonance effect between the introduced forces and this flow structure.

Keywords: Electromagnetic forcing; liquid metal; Rayleigh-Bénard convection; resonance

  • Poster
    9th European Postgraduate Fluid Dynamics Conference, 16.07.2019, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29182
Publ.-Id: 29182


Experimental investigation of magnetorotational instability in hydromagnetic Taylor-Couette flows

Ogbonna, J. E.; Seilmayer, M.; Stefani, F.

Magnetorotational instability (MRI) is believed to be largely responsible for the formation of protostars and black holes by introducing turbulence and facilitating an outward angular momentum transport in accretion disks. MRI is replicable in Taylor-Couette flows of electrically conducting fluids in the presence of externally applied magnetic fields. The Potsdam Rossendorf Magnetic Instability Experiment (PROMISE) at Helmholtz-Zentrum Dresden-Rossendorf is one of several existing facilities where an experimental approach towards understanding MRI takes place. PROMISE creates a magnetized Taylor-Couette flow of GaInSn alloy between concentric copper cylinders. Using PROMISE, the azimuthal MRI (AMRI), which is obtained when an azimuthal magnetic field is applied to the flow, have been demonstrated. The azimuthal magnetic field is induced by a strong central current along the cylinder axis. PROMISE has also shown evidence of the helical MRI (HMRI), which is obtained when an axial magnetic field is applied in addition to the azimuthal magnetic field. The axial magnetic field is induced by current through a coil wound around the outer cylinder. Recently, a symmetry breaking of AMRI due to thermal convection in the GaInSn alloy was discovered. In future, the transition from AMRI to HMRI will be investigated.

Keywords: Magnetorotational instability; Taylor-Couette flows; hydromagnetic flows

  • Lecture (Conference)
    9th European Postgraduate Fluid Dynamics Conference, 16.-19.07.2019, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29181
Publ.-Id: 29181


Solid target irradiation at the cyclotron Cyclone 18/9® at the HZDR in Leipzig

Franke, K.; Mansel, A.

Different research projects within the fields of resource ecology and neuroradiopharamceutical research make use of the cyclotron Cyclone 18/9® (IBA RadioPharma Solutions) at the HZDR in Leipzig. Aside liquid (2x F-18) and gas targets ([C-14]CH4, [C-14]CO2, [O-15]O2) two Nirta® Solid irradiation systems (IBA RadioPharma Solutions) are used. A broad spectrum of radionuclides (Ti-45, V-48, Cr-51, Co-56, Cu-64, Sr-85, Y-86, Zr-89, La-135, Ce-139, Au-194) is produced with these Nirta® Solid irradiation systems. Here we give an overview about the used target designs, irradiation parameters and target processing.
The Nirta® Solid irradiation system 1 (SIS1) is mounted at a 2m beam transfer line at port 3 of the cyclotron. The second irradiation system (SIS2) is mounted at port 4 of the cyclotron via a short tube. The cyclotron Cyclone 18/9 provides protons with an energy of 18 MeV and deuterons with energy of 9 MeV. The required energy of the incident particle for the nuclear reaction is set by the appropriate choice of the vacuum (Ti) and the entrance window (Al) of the target. SIS2 can hold coin like target disks (Ø 24 mm x 2mm). The maximal effective target size is Ø 12 mm x 1 mm. The SIS2 is used for the irradiation of metal foils, which are crimped inside the disk in between a cover and a backing plate. SIS1 can operate target capsules with a maximal effective target size of Ø 12 mm x 4 mm. This enables the irradiation of powders and pellets aside its use for metal foils. Both irradiation systems can be pre-loaded with 3 targets for consecutive irradiations. Different target materials are used for irradiation, like metal foils (Sc-45(p,n)Ti-45, Ti-48(p,n)V-48, V-nat(p,n)Cr-51, Ni-64(p,n)Cu-64, Y 89(p,n)Zr-89), metal powders (Ti-48(p,n)V-48, Pt-nat(p,n)Au-194), oxides (La-139(p,n)Ce-139), carbonates (Sr 86(p,n)Y-86) and chlorides (Rb-85(p,n)Sr-85). If required electroplating or pellet pressing is applied for target preparation. After irradiation the targets are transferred out of the vault by a conveyer system. Different techniques, like liquid/liquid extraction, liquid/solid extraction and chromatography are applied for target processing and the recovery of the enriched target material. Gamma-ray spectrometry is used to prove the radionuclidical purity of the product. The presented methods allow a straightforward and reliable production of n.c.a. radionuclides for research purposes. Irradiation parameters, target preparation and processing are easily adaptable to the experimental needs.

  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29180
Publ.-Id: 29180


AMS at Big Accelerators: 53Mn and 60Fe in Meteorites

Rugel, G.; Faestermann, T.; Fimiani, L.; Korschinek, G.; Leya, I.; Ludwig, P.; Pavetich, S.; Smith, T.; Wallner, A.

The poster describes that big tandem accelerators are essential to measure 53Mn and 60Fe in meteorites.

Keywords: AMS Accelerator Fe-60 Mn-53 Meteorites

  • Poster
    KIMM Workshop 2019, 02.05.2019, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29179
Publ.-Id: 29179


Interaction of O-Y and O-Y-Ti clusters embedded in bcc Fe with He, vacancies and self-interstitial atoms

Vallinayagam, M.; Posselt, M.; Faßbender, J.

Calculations based on Density Functional Theory are performed to investigate the interaction of O-Y and O-Y-Ti clusters in bcc Fe with He atoms, vacancies (V) and self-interstitial atoms (SIA). The four different cluster structures studied in our previous work (J Phys Condens Matter 31 095701) are considered. He, V and SIA are inserted on different positions inside and in the environment of the clusters, the total energy of the corresponding supercell is minimized and the binding and incorporation energy of the three kinds of defects is determined. He in the center of a cage-like (CL) cluster is more stable than on interfacial vacant sites (IVS). In CL O-Y clusters He on an IVS is more stable than in the cluster structure with oxygen in the center (OC), whereas there is no significant difference between the two kinds for clusters with Ti. Up to a distance of 1.5 times the iron lattice constant from the cluster center He is not stable on most of the octahedral and tetrahedral interstitial sites in the Fe matrix near the interface. Instead He is shifted towards positions closer to the cluster. Relaxation occurs to known IVS as well as to previously unknown interfacial interstitial sites (IIS). Moreover, two or three He atoms are placed on sites found to be stable after adding a single He. The corresponding binding and incorporation energies obtained after relaxation are nearly equal to the sum of the values for the interaction with a single He atom. However, placing He dimers or trimers in the environment of a vacancy may also lead to relatively low values of the incorporation energy. Also, barriers for jumps of He atoms between interfacial sites and the center of CL clusters are determined. In the CL O-Y cluster the barriers are lower than in the CL O-Y-Ti cluster, i.e. trapping and release of He is easier in the former than in the latter. V and SIA interaction with the clusters is also attractive. The binding energy of V strongly depends on the site where V is inserted while in all the studied cases the SIA is annihilated at the cluster-iron interface. Present results clearly demonstrate that the oxide-based nanoclusters are strong traps for irradiation induced defects which is in agreement with experimental findings.

Keywords: density functional theory calculations; oxide dispersion strengthened steels; interaction with He; vacancies and self-interstitial atoms

Permalink: https://www.hzdr.de/publications/Publ-29178
Publ.-Id: 29178


Magnetic Orders and Origin of Exchange Bias in Co Clusters Embedded Oxide Nanocomposite Films

Li, H.; Wang, C.; Li, D.-Y.; Pereira, L. M. C.; Homm, P.; Menghini, M.; Locquet, J.-P.; Temst, K.; Vantomme, A.; van Haesendonck, C.; van Bael, M. J.; Ruan, S.; Zeng, Y.-J.

Magnetic nanoparticles embedded oxide semiconductors are interesting candidates for spintronics in view of combining ferromagnetic (FM) and semiconducting properties. Co-ZnO and Co-V2O3 nanocomposite thin films are synthesized by Co ion implantation in crystalline thin films. Magnetic order varies with the implantation fluence in Co-ZnO, where the superparamagnetic (SPM) order appears in the low-fluence films (2×1016 and 4×1016 ions/cm2) while the FM order coexists with the SPM phase in high-fluence ones (1×1017 ions/cm2). The exchange bias (EB) effect is evident in high-fluence films, which gives an EB field of about 100 Oe at 2 K and a blocking temperature of around 100 K. In parallel, 3.5×1016 ions/cm2 Co-V2O3 hybrid thin film exhibits a clear antiferromagnetic (AFM) coupling at low temperature with a weak EB effect. The different magnetic behaviors in the two Co-implanted systems lead us to believe on one hand, that the observed EB effect in the Co-ZnO system is the result of the FM/AFM coupling between large Co nanoparticles and their CoO/Co3O4 surroundings in the (Zn,Co)O matrix. While, on the other hand, the EB effect in Co-V2O3 system originates from the interaction between FM Co nanoparticles and AFM V2O3 matrix. Detailed studies of magnetic orders as well as EB effect in magnetic nanocomposite semiconductors pave the way for their application in spintronics.

Keywords: nanocomposite; exchange bias; antiferromagnetic; superparamagnetic

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Permalink: https://www.hzdr.de/publications/Publ-29176
Publ.-Id: 29176


Thermal stability of Te-hyperdoped Si: Atomic-scale correlation of the structural, electrical, and optical properties

Wang, M.; Hübner, R.; Xu, C.; Xie, Y.; Berencen, Y.; Heller, R.; Rebohle, L.; Helm, M.; Prucnal, S.; Zhou, S.

Si hyperdoped with chalcogens (S,Se,Te) is well known to possess unique properties such as an insulator-tometal transition and a room-temperature sub-band-gap absorption. These properties are expected to be sensitive to a postsynthesis thermal annealing, since hyperdoped Si is a thermodynamically metastable material. Thermal stability of the as-fabricated hyperdoped Si is of great importance for the device fabrication process involving temperature-dependent steps such as Ohmic contact formation. Here, we report on the thermal stability of the as-fabricated Te-hyperdoped Si subjected to isochronal furnace anneals from 250 to 1200 °C. We demonstrate that Te-hyperdoped Si exhibits thermal stability up to 400 °C for 10 min, which even helps to further improve the crystalline quality, the electrical activation of Te dopants, and the room-temperature sub-band-gap absorption. At higher temperatures, however, Te atoms are found to move out from the substitutional sites with a maximum migration energy of EM = 2.3 eV forming inactive clusters and precipitates that impair the structural, electrical, and optical properties. These results provide further insight into the underlying physical state transformation of Te dopants in a metastable compositional regime caused by postsynthesis thermal annealing. They also pave the way for the fabrication of advanced hyperdoped Si-based devices.

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Permalink: https://www.hzdr.de/publications/Publ-29175
Publ.-Id: 29175


Controllable defect driven symmetry change and domain structure evolution in BiFeO3 with enhanced tetragonality

Chen, C.; Wang, C.; Cai, X.; Xu, C.; Li, C.; Zhou, J.; Luo, Z.; Fan, Z.; Qin, M.; Zeng, M.; Lu, X.; Gao, X.; Kentsch, U.; Yang, P.; Zhou, G.; Wang, N.; Zhu, Y.; Zhou, S.; Chen, D.; Liu, J.

Defect engineering has been a powerful tool to enable the creation of exotic phases and the discovery of intriguing phenomena in ferroelectric oxides. However, the accurate control of the concentration of defects remains a big challenge. In this work, ion implantation, which can provide controllable point defects, allows us to produce a controlled defect driven true super-tetragonal (T) phase with a single-domain-state in ferroelectric BiFeO3 thin films. This point-defect engineering is found to drive the phase transition from the as-grown mixed rhombohedral-like (R) and tetragonal-like (MC) phase to true tetragonal (T) symmetry and induce the stripe multi-nanodomains to a single domain state. By further increasing the injected dose of the He ion, we demonstrate an enhanced tetragonality super-tetragonal (super-T) phase with the largest c/a ratio of ∼1.3 that has ever been experimentally achieved in BiFeO3. A combination of the morphology change and domain evolution further confirms that the mixed R/MC phase structure transforms to the single-domain-state true tetragonal phase. Moreover, the re-emergence of the R phase and in-plane nanoscale multi-domains after heat treatment reveal the memory effect and reversible phase transition and domain evolution. Our findings demonstrate the reversible control of R-Mc-T-super T symmetry changes (leading to the creation of true T phase BiFeO3 with enhanced tetragonality) and multidomain-single domain structure evolution through controllable defect engineering. This work also provides a pathway to generate large tetragonality (or c/a ratio) that could be extended to other ferroelectric material systems (such as PbTiO3, BaTiO3 and HfO2) which might lead to strong polarization enhancement.

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Permalink: https://www.hzdr.de/publications/Publ-29174
Publ.-Id: 29174


Channeling effects in gold nano-clusters under He ion irradiation: insights from molecular dynamics simulations

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

The interpretation of helium ion microscopy (HIM) images of crystalline metal clusters requires microscopic understanding of the effects of He ion irradiation on the system, including energy deposition and associated heating, as well as channeling patterns. While channeling in bulk metals has been studied at length, there is no quantitative data for small clusters. We carry out molecular dynamics simulations to investigate the behavior of gold nano-particles with diameters of 5–15 nm under 30 keV He ion irradiation. We show that impacts of the ions can give rise to substantial heating of the clusters through deposition of energy into electronic degrees of freedom, but it does not affect channeling, as clusters cool down between consecutive impact of the ions under typical imaging conditions. At the same time, high temperatures and small cluster sizes should give rise to fast annealing of defects so that the system remains crystalline. Our results show that ion-channeling occurs not only in the principal low-index, but also in the intermediate directions. The strengths of different channels are specified, and their correlations with sputtering-yield and damage production is discussed, along with size-dependence of these properties. The effects of planar defects, such as stacking faults on channeling were also investigated. Finally, we discuss the implications of our results for the analysis of HIM images of metal clusters.

Keywords: gold nano structures; ion irradiation; channeling effect; sputtering-yield; Helium ion microscope

Permalink: https://www.hzdr.de/publications/Publ-29173
Publ.-Id: 29173


High spin-wave propagation length consistent with low damping in a metallic ferromagnet

Flacke, L.; Liensberger, L.; Althammer, M.; Huebl, H.; Geprägs, S.; Schultheiß, K.; Buzdakov, A.; Hula, T.; Schultheiß, H.; Edwards, E. R. J.; Nembach, H. T.; Shaw, J. M.; Gross, R.; Weiler, M.

We report ultra-low intrinsic magnetic damping in Co25Fe75 heterostructures, reaching the low 10E−4 regime at room temperature. By using a broadband ferromagnetic resonance technique, we extracted the dynamic magnetic properties of several Co25Fe75-based heterostructures with varying ferromagnetic layer thickness. By estimating the eddy current contribution to damping, measuring radiative damping and spin pumping effects, we extrapolated an intrinsic damping of α0 ≤ 3.05 × 10E−4. Furthermore, using Brillouin light scattering microscopy we measured spin-wave propagation lengths of up to (21 ± 1) μm in a 26 nm thick Co25 Fe75 heterostructure at room temperature, which is in excellent agreement with the measured damping.

Keywords: spin-wave propagation; low magnetic damping; ferromagnetic resonance; Brillouin light scattering

Permalink: https://www.hzdr.de/publications/Publ-29172
Publ.-Id: 29172


Nonlinear ferromagnetic resonance in the presence of 3-magnon scattering in magnetic nanostructures

Slobodianiuk, D. V.; Melkov, G. A.; Schultheiß, K.; Schultheiß, H.; Verba, R. V.

Bulk and patterned ferromagnets can exhibit various nonlinear phenomena at moderate excitation power, making them a nice test bed for study of nonlinear dynamics. We investigate nonlinear ferromagnetic resonance in magnetic nanostructures with discrete spectra of spin-wave modes in the case of allowed 3-magnon scattering processes. These processes result in the splitting of a directly driven spin-wave mode into two secondary modes if a certain excitation threshold is overcome. The 3-magnon splitting manifests itself as a characteristic distortion of the resonance curve, which can be detected in a simple ferromagnetic resonance experiment. Theoretical results are also compared to the experimental study of nonlinear spin-wave dynamics in a vortex-state magnetic disk, in which 3-magnon splitting is confirmed by direct measurements using Brillouin light scattering microscopy.

Keywords: nonlinear ferromagnetic resonance; 3-magnon scattering; spin-wave modes; magnetic vortex; Brillouin light scattering; magnetic nanoelements

Permalink: https://www.hzdr.de/publications/Publ-29171
Publ.-Id: 29171


Absorption edge, Urbach tail, and electron-phonon interactions in topological insulator Bi2Se3 and band insulator (Bi0.89In0.11)2Se3

Zhu, J.; Xia, Y.; Li, G.; Zhou, S.; Wimmer, S.; Springholz, G.; Pashkin, O.; Helm, M.; Schneider, H.

We employ infrared transmission spectroscopy to explore the temperature-dependent absorption edge and electron-phonon (e-ph) interaction in topological insulator Bi2Se3 and band insulator (Bi0.89In0.11)2Se3 films. Upon heating from 5 K to 300 K, the absorption edge shifts from 262 to 249 meV for Bi2Se3 and from 367 to 343 meV for (Bi0.89In0.11)2Se3. By analyzing the temperature dependence of the Urbach tail, the significant role of Raman-active phonon mode E2g in e-ph interaction is identified, which agrees well with the ab initio calculation.

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Permalink: https://www.hzdr.de/publications/Publ-29170
Publ.-Id: 29170


Electron-Beam-Driven Structure Evolution of Single-Layer MoTe2 for Quantum Devices

Lehnert, T.; Ghorbani Asl, M.; Köster, J.; Lee, Z.; Krasheninnikov, A.; Kaiser, U.

40 kV high-resolution transmission electron microscopy (TEM) experiments are performed to understand defect formation and evolution of their atomic structure in single-layer 2H MoTe2 under electron beam irradiation. We show that Te vacancies can agglomerate either in single Te-vacancy lines or in extended defects composed of column Te vacancies, including rotational trefoil-like defects, with some of them being never reported before. The formation of inversion domains with mirror twin boundaries of different types, along with the islands of the metallic T’ phase was also observed. Our first-principles calculations provide insights into the energetics of the transformations as well as the electronic structure of the system with defects and point out that some of the observed defects have localized magnetic moments. Our results indicate that various nano-scale structures, including metallic quantum dots consisting of T’-phase islands and one-dimensional metallic quantum systems such as vacancy lines and mirror twin boundaries embedded into a semiconducting host material can be realized in single-layer 2H MoTe2, and defect-associated magnetism can also be added, which may allow prospective control of optical and electronic properties of two-dimensional materials.

Keywords: Defects; 2D MoTe2; transmission electron microscopy; transition metal dichalcogenide; DFT; quantum devices

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Permalink: https://www.hzdr.de/publications/Publ-29169
Publ.-Id: 29169


Impact of Extrinsic and Intrinsic Hypoxia on Catecholamine Biosynthesis in Absence or Presence of Hif2α in Pheochromocytoma Cells

Bechmann, N.; Poser, I.; Seifert, V.; Greunke, C.; Ullrich, M.; Qin, N.; Walch, A.; Peitzsch, M.; Robledo, M.; Pacak, K.; Pietzsch, J.; Richter, S.; Eisenhofer, G.

Abstract: Pheochromocytomas and paragangliomas (PPGLs) with activated pseudohypoxic pathways are associated with an immature catecholamine phenotype and carry a higher risk for metastasis. For improved understanding of the underlying mechanisms we investigated the impact of hypoxia and pseudohypoxia on catecholamine biosynthesis in pheochromocytoma cells naturally lacking Hif2α (MPC and MTT) or expressing both Hif1α and Hif2α (PC12). Cultivation under extrinsic hypoxia or in spheroid culture (intrinsic hypoxia) increased cellular dopamine and norepinephrine contents in all cell lines. To distinguish further between Hif1α- and Hif2α-driven effects we expressed Hif2α in MTT and MPC-mCherry cells (naturally lacking Hif2α). Presence of Hif2α resulted in similarly increased cellular dopamine and norepinephrine under hypoxia as in the control cells. Furthermore, hypoxia resulted in enhanced phosphorylation of tyrosine hydroxylase (TH). A specific knockdown of Hif1α in PC12 diminished these effects. Pseudohypoxic conditions, simulated by expression of Hif2α under normoxia resulted in increased TH phosphorylation, further stimulated by extrinsic hypoxia. Correlations with PPGL tissue data led us to conclude that catecholamine biosynthesis under hypoxia is mainly mediated through increased phosphorylation of TH, regulated as a short-term response
(24–48 h) by HIF1α. Continuous activation of hypoxia-related genes under pseudohypoxia leads to a HIF2α-mediated phosphorylation of TH (permanent status).

Keywords: hypoxia; pseudohypoxia; spheroids; HIF; EPAS1; catecholamine; pheochromocytoma and paraganglioma; phosphorylation tyrosine hydroxylase

Permalink: https://www.hzdr.de/publications/Publ-29168
Publ.-Id: 29168


Silver Particles with Rhombicuboctahedral Shape and Effective Isotropic Interactions with Light

Steiner, A. M.; Mayer, M.; Schletz, D.; Wolf, D.; Formanek, P.; Hübner, R.; Dulle, M.; Förster, S.; König, T. A. F.; Fery, A.

Truly spherical silver nanoparticles are of great importance for fundamental studies including plasmonic applications, but their direct synthesis in aqueous media is not feasible. Using the commonly employed copper-based etching processes, an isotropic plasmonic response can be achieved by etching well-defined silver nanocubes. Whilst spherical-like shape is typically prevailing in such processes, we established that there is a preferential growth toward silver rhombicuboctahedra, which is the thermodynamically most stable product of this synthesis. The rhombicuboctahedral morphology is further evidenced by comprehensive characterization with small-angle X-ray scattering in combination with transmission electron microscopy (TEM) tomography and high-resolution TEM. We also elucidate the complete reaction mechanism based on UV-vis kinetic studies, and the postulated mechanism can also be extended to all copper-based etching processes.

Permalink: https://www.hzdr.de/publications/Publ-29167
Publ.-Id: 29167


Carboranyl analogues of ketoprofen with cytostatic activity against human melanoma and colon cancer cell lines

Buzharevski, A.; Paskas, S.; Laube, M.; Lönnecke, P.; Neumann, W.; Murganic, B.; Mijatovic, S.; Maksimovic-Ivanic, D.; Pietzsch, J.; Hey-Hawkins, E.

Ketoprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) that also exhibits cytotoxic activity against various cancers. This makes ketoprofen an attractive structural lead for the development of new NSAIDs and cytotoxic agents. Recently, the incorporation of carboranes as phenyl mimetics in structures of established drugs has emerged as an attractive strategy in drug design. Herein, we report the synthesis and evaluation of four novel carborane-containing derivatives of ketoprofen, two of which are prodrug esters with an nitric oxide-releasing moiety. One of these prodrug esters exhibited high cytostatic activity against melanoma and colon cancer cell lines. The most pronounced activity was found in cell lines that are sensitive to oxidative stress, which was apparently induced by the ketoprofen analogue.

Permalink: https://www.hzdr.de/publications/Publ-29166
Publ.-Id: 29166


General guideline for closure model development for gas-liquid flows in the multi-fluid framework

Lucas, D.; Krepper, E.; Liao, Y.; Rzehak, R.; Ziegenhein, T.

The two- or multi-fluid approach is frequently used for Nuclear Reactor Safety (NRS)-related simulations of gas-liquid flows. To enable reliable predictions the closure models have to reflect the involved local physical phenomena at the non-resolved scale properly. To consolidate the CFD-modelling in the frame of the multi-fluid approach the so-called baseline model strategy was recently proposed (Lucas et al., 2016). The present technical note discusses a long-term strategy for the baseline model development and ways to obtain or improve closure models. Guidelines for the model development are given by listing requirements for appropriate closure models as well as frequently made mistakes. This is illustrated by examples for recent developments done for HZDR baseline models for poly-disperse bubbly flows.

Keywords: CFD; multi-fluid model; closure models

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  • Secondary publication expected from 31.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29165
Publ.-Id: 29165


A Five-MicroRNA Signature Predicts Survival and Disease Control of Patients with Head and Neck Cancer Negative for HPV Infection

Hess, J.; Unger, K.; Maihoefer, C.; Schuettrumpf, L.; Wintergerst, L.; Heider, T.; Weber, P.; Marschner, S.; Braselmann, H.; Samaga, D.; Kuger, S.; Pflugradt, U.; Baumeister, P.; Walch, A.; Woischke, C.; Kirchner, T.; Werner, M.; Werner, K.; Baumann, M.; Budach, V.; Combs, S. E.; Debus, J.; Grosu, A.-L.; Krause, M.; Linge, A.; Roedel, C.; Stuschke, M.; Zips, D.; Zitzelsberger, H.; Ganswindt, U.; Henke, M.; Belka, C.

Purpose: Human papillomavirus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) is associated with unfavorable prognosis, while independent prognostic markers remain to be defined.
Experimental Design: We retrospectively performed miRNA expression profiling. Patients were operated for locally advanced HPV-negative HNSCC and had received radiochemotherapy in eight different hospitals (DKTK-ROG; n = 85). Selection fulfilled comparable demographic, treatment, and follow-up characteristics. Findings were validated in an independent single-center patient sample (LMU-KKG; n = 77). A prognostic miRNA signature was developed for freedom from recurrence and tested for other endpoints. Recursivepartitioning analysis was performed on the miRNA signature, tumor and nodal stage, and extracapsular nodal spread.
Technical validation used qRT-PCR. An miRNA-mRNA target network was generated and analyzed.
Results: For DKTK-ROG and LMU-KKG patients, the median follow-up was 5.1 and 5.3 years, and the 5-year freedom from recurrence rate was 63.5% and 75.3%, respectively. A five-miRNA signature (hsa-let-7g-3p, hsamiR- 6508-5p, hsa-miR-210-5p, hsa-miR-4306, and hsa-miR-7161-3p) predicted freedom from recurrence in DKTK-ROG [hazard ratio (HR) 4.42; 95% confidence interval (CI), 1.98-9.88, P < 0.001], which was confirmed in LMU-KKG (HR 4.24; 95% CI, 1.40-12.81, P = 0.005). The signature also predicted overall survival (HR 3.03; 95% CI, 1.50-6.12, P = 0.001), recurrence-free survival (HR 3.16; 95% CI, 1.65-6.04, P < 0.001), and disease-specific survival (HR 5.12; 95% CI, 1.88-13.92, P < 0.001), all confirmed in LMU-KKG data. Adjustment for relevant covariates maintained the miRNA signature predicting all endpoints. Recursive- partitioning analysis of both samples combined classified patients into low (n = 17), low-intermediate (n = 80), high-intermediate (n = 48), or high risk (n = 17) for recurrence (P < 0.001).
Conclusions: The five-miRNA signature is a strong and independent prognostic factor for disease recurrence and survival of patients with HPV-negative HNSCC.

Permalink: https://www.hzdr.de/publications/Publ-29164
Publ.-Id: 29164


Thermal Transport in MoS2 from Molecular Dynamics using Different Empirical Potentials

Xu, K.; Gabourie, A. J.; Hashemi, A.; Fan, Z.; Wei, N.; Farimani, A. B.; Komsa, H.-P.; Krasheninnikov, A.; Pop, E.; Ala-Nissila, T.

Thermal properties of molybdenum disulfide (MoS2) have recently attracted attention related to fundamentals of heat propagation in strongly anisotropic materials, and in the context of potential applications to optoelec- tronics and thermoelectrics. Multiple empirical potentials have been developed for classical molecular dynamics (MD) simulations of this material, but it has been unclear which provides the most realistic results. Here, we calculate lattice thermal conductivity of single- and multilayer pristine MoS2 by employing three different thermal transport MD methods: equilibrium, nonequilibrium, and homogeneous nonequilibrium ones. We mainly use the Graphics Processing Units Molecular Dynamics code for numerical calculations, and the Large-scale Atomic/Molecular Massively Parallel Simulator code for crosschecks. Using different methods and computer codes allows us to verify the consistency of our results and facilitate comparisons with previous studies, where different schemes have been adopted. Our results using variants of the Stillinger-Weber potential are at odds with some previous ones and we analyze the possible origins of the discrepancies in detail. We show that, among the potentials considered here, the reactive empirical bond order (REBO) potential gives the most reasonable predictions of thermal transport properties as compared to experimental data. With the REBO potential, we further find that isotope scattering has only a small effect on thermal conduction in MoS2 and the in-plane thermal conductivity decreases with increasing layer number and saturates beyond about three layers. We identify the REBO potential as a transferable empirical potential for MD simulations of MoS2 which can be used to study thermal transport properties in more complicated situations such as in systems containing defects or engineered nanoscale features. This work establishes a firm foundation for understanding heat transport properties of MoS2 using MD simulations.

Keywords: 2D materials; thermal transport; atomistic simulations

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Permalink: https://www.hzdr.de/publications/Publ-29163
Publ.-Id: 29163


Tomonaga-Luttinger liquid in a box: electrons confined within MoS2 mirror twin boundaries

Jolie, W.; Murray, C.; Weiß, P. S.; Hall, J.; Portner, F.; Atodiresei, N.; Krasheninnikov, A.; Busse, C.; Komsa, H.-P.; Rosch, A.; Michely, T.

Two- or three-dimensional metals are usually well described by weakly interacting, fermionic quasiparticles. This concept breaks down in one dimension due to strong Coulomb interactions. There, low-energy electronic excitations are expected to be bosonic collective modes, which fractionalize into independent spin- and charge-density waves. Experimental research on one-dimensional metals is still hampered by their difficult realization, their limited accessibility to measurements, and by competing or obscuring effects such as Peierls distortions or zero bias anomalies. Here we overcome these difficulties by constructing a well-isolated, one-dimensional metal of finite length present in MoS2 mirror-twin boundaries. Using scanning tunneling spectroscopy we measure the single-particle density of the interacting electron system as a function of energy and position in the 1D box. Comparison to theoretical modeling provides unambiguous evidence that we are observing spin-charge separation in real space.

Keywords: 2D materials; Tomonaga-Luttinger liquid; First-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-29162
Publ.-Id: 29162


Room temperature ferromagnetism in MoTe2 by post-growth incorporation of vanadium impurities

Coelho, P. M.; Komsa, H.-P.; Lasek, K.; Kalappattil, V.; Karthikeyan, J.; Phan, M.-H.; Krasheninnikov, A.; Batzill, M.

Post-synthesis doping of 2D materials is demonstrated by incorporation of vapor-deposited transition metals into a MoTe2 lattice. Using this approach, vanadium doping of 2H-MoTe2 produces a 2D ferromagnetic semiconductor with a Curie temperature above room temperature (RT). Surprisingly, ferromagnetic properties can be induced with very low vanadium concentrations, down to ≈0.2%. The vanadium species introduced at RT are metastable, and annealing to above ≈500 K results in the formation of a thermodynamically favored impurity configuration that, however, exhibits reduced ferromagnetic properties. Doping with titanium, instead of vanadium, shows a similar incorporation behavior, but no ferromagnetism is induced in MoTe2. This indicates that the type of impurities in addition to their atomic configuration is responsible for the induced magnetism. The interpretation of the experimental results is consistent with ab initio calculations, which confirm that the proposed vanadium impurity configurations exhibit magnetic moments, in contrast to the same configurations with titanium impurities. This study illustrates the possibility to induce ferromagnetic properties in layered van der Waals semiconductors by controlled magnetic impurity doping and thus to add magnetic functionalities to 2D materials.

Keywords: 2D materials; STM; electronic structure calculations; doping

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Permalink: https://www.hzdr.de/publications/Publ-29161
Publ.-Id: 29161


Efficient method for calculating Raman spectra of solids with impurities and alloys and its application to two-dimensional transition metal dichalcogenides

Hashemi, A.; Krasheninnikov, A.; Puska, M.; Komsa, H.

Raman spectroscopy is a widely used, powerful, and nondestructive tool for studying the vibrational properties of bulk and low-dimensional materials. Raman spectra can be simulated using first-principles methods but due to the high computational cost calculations are usually limited only to fairly small unit cells, which makes it difficult to carry out simulations for alloys and defects. Here, we develop an efficient method for simulating Raman spectra of alloys, benchmark it against full density-functional theory calculations, and apply it to several alloys of two-dimensional (2D) transition metal dichalcogenides. In this method, the Raman tensor for the supercell mode is constructed by summing up the Raman tensors of the pristine system weighted by the projections of the supercell vibrational modes to those of the pristine system. This approach is not limited to 2D materials and should be applicable to any crystalline solid with defects and impurities. To efficiently evaluate vibrational modes of very large supercells, we adopt mass approximation, although it is limited to chemically and structurally similar atomic substitutions. To benchmark our method, we first apply it to the MoxW(1-x)S2 monolayer in the H phase where several experimental reports are available for comparison. Second, we consider MoxW(1-x)Te2 in the T' phase, which has been proposed to be a 2D topological insulator but where experimental results for the monolayer alloy are still missing. We show that the projection scheme also provides a powerful tool for analyzing the origin of the alloy Raman-active modes in terms of the parent system eigenmodes. Finally, we examine the trends in characteristic Raman signatures for dilute concentrations of impurities in MoS2.

Keywords: 2D materials; atomistic simulation

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Permalink: https://www.hzdr.de/publications/Publ-29160
Publ.-Id: 29160


Cathepsin B-Activatable Cell-Penetrating Peptides

Kuhne, K.; Behring, L.; Belter, B.; Wodtke, R.; Pietzsch, J.; Löser, R.

Protease activity is increasingly drawn into the spotlight as a crucial modulator in cancer angiogenesis, invasion, and metastasis [1]. Elevated activity of multiple members of the family of cysteine cathepsins has been shown to correlate with increased metastasis and therapy resistance [2, 3]. Especially high expression levels of extracellular cathepsin B (CatB) indicate poor prognosis in neoplastic diseases, making CatB an interesting target for functional characterization of cancers by activity-based molecular imaging. It is our aim to develop such an imaging probe for CatB by combination of a polyarginine-based, activatable cell-penetrating peptide [4] (ACPP) and an optimised endopeptidase substrate for CatB. Substrate optimisation proofed to be challenging as two entirely opposite factors needed to be balanced – high stability against serum proteases to prevent premature cleavage of the activation sequence, while retaining efficient and specific endoproteolytic cleavability by CatB. We have generated a CatB-endoprotease substrate by C-terminally elongating the CatB carboxydipeptidase substrate Abz GIVR*AK(Dnp) OH [5] (Abz – amino-benzoyl, Dnp – dinitrophenyl, * – cleavage site) to the octapeptide Abz GIVR*AK(Dnp)GX CONH2, which could be used as activation site in the final ACPP. Introduction of any amino acid other than glycine at the P4’ position resulted in hysteretic kinetics for the CatB-catalysed hydrolysis of the octapeptides, which might indicate the displacement of the occluding loop from the active site upon interaction with the substrates. Using LC-ESI-MS-based analysis of serum-incubated substrates, the positions P1 and P3’ where determined to be primary determinants of serum stability. After suppression of the P3’ instability by Nα-methylation and optimisation within the positions P1-P3, we were able to increase serum half-life from < 5 min to > 24 h under concomitant improvement of kinetic substrate efficiency towards CatB. Based on this optimised CatB-endopeptidase substrate, we have synthesised a fluorescently labelled ACPP with which we were able to demonstrate CatB-dependent uptake and subsequent nucleolar accumulation of the activated peptide in human U87 MG glioma cells. Radiolabelling of the probe with copper-64 was enabled by conjugating the ACPP to NODAGA as chelating moiety. Its evaluation in vivo using PET imaging is under current investigation.

[1] Yang et al., Cancer Growth Metastasis 2009, 2, 13
[2] Aggarwal and Sloane, Proteomics Clin. Appl. 2014, 8, 427
[3] Löser and Pietzsch, Front. Chem. 2015, 3, article 37
[4] Jiang et al., PNAS, 2004, 101, 17867
[5] Cotrin et al., Anal. Biochem. 2004, 335, 244

  • Poster
    Frontiers in Medicinal Chemistry, 24.-27.03.2019, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29159
Publ.-Id: 29159


Optical properties of ZnSxTe1-x synthesized by sulfur implantation

Zhang, X.; Xu, M.; Li, Q.; Wang, M.; Akhmadaliev, S.; Zhou, S.; Wu, Y.; Guo, B.

ZnSxTe1-x thin films were prepared by sulfur implantation into ZnTe grown by molecular beam epitaxy and subsequent pulsed laser melting. The chemical composition and layer thickness of the ZnSxTe1-x layer have been analyzed based on Rutherford backscattering spectrometry. Raman and photoluminescence spectroscopies were employed to reveal the optical properties of the ZnSxTe1-x layer. Raman spectra exhibit a redshift of the longitudinal optical photon modes with increasing sulfur concentration. The room temperature photoluminescence measurement indicates the appearance of the sulfur induced energy state in the bandgap.

Permalink: https://www.hzdr.de/publications/Publ-29158
Publ.-Id: 29158


Dipeptide-derived Alkynes as Irreversible Inhibitors of Cysteine Cathepsins

Behring, L.; Trapp, C.; Morales, M.; Wodtke, R.; Kuhne, K.; Belter, B.; Pietzsch, J.; Löser, R.

Even though the C-C triple bond is largely considered as a bioinert functional group, two research groups observed the irreversible inhibition of a cysteine protease by an alkyne-functionalised substrate derivative: both EKKEBUS et al. and SOMMER et al. independently described the unexpected inactivation of de-ubiquitinating enzymes by ubiquitin or ubiquitin-like modifiers bearing propargylamine in place of C-terminal glycine by covalent targeting of the active-site cysteine residue [1, 2]. We intended to harness that finding for the design of inhibitor-based probes for the imaging of tumour-associated cysteine proteases.
All 11 human cysteine cathepsins have been linked to tumour progression. Especially high expression levels of the cathepsins B, K, L, S and X are correlated with an increased metastatic potential and poor prognosis. [3] Therefore, those enzymes represent promising targets for the therapy and imaging of tumours.
GREENSPAN et al. reported a potent, highly selective dipeptidyl nitrile-based cathepsin B inhibitor (1, structure shown above) [4]. Based on that lead compound, dipeptide alkynes were designed by isoelectronic replacement of the nitrile nitrogen atom by a methine group (2) and consecutive variation of the 2,4-difluorobenzoyl group and the amino acid-derived side chains. Formation of the C-C triple bond by reaction of the corresponding open-chain serine-derived aldehyde with the Bestmann-Ohira reagent was accompanied by partial enantiomerisation. Therefore, the synthesis was performed via Garner’s aldehyde to ensure high stereochemical purity of the final compounds.
By investigating the inhibitory potential against cathepsin B, S, L and K potent alkyne-based inhibitors were identified for all tested cathepsins, with second-order inactivation constants (kinact/KI) up to 10133 M-1s-1 and interesting selectivity profiles. Based on these promising results and considering their absent indiscriminate thiol reactivity, dipeptidyl alkynes have the potential to be translated into activity-based probes for molecular imaging in vivo. In further studies, selected inhibitors will be labelled with suitable radionuclides such as fluorine-18, which will in turn enable further pharmacological evaluations.
[1] Ekkebus et al., J. Am. Chem. Soc., 2013, 135, 2867-2870.
[2] Sommer et al., Bioorg. Med. Chem., 2013, 21, 2511-2517.
[3] Löser and Pietzsch, Front. Chem., 2015, 3, 37.
[4] Greenspan et al., J. Med. Chem., 2001, 44, 4524-4534.

  • Lecture (Conference)
    Frontiers in Medicinal Chemistry, 24.-27.03.2019, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29157
Publ.-Id: 29157


Deciphering the Crystal Structure of a Scarce 1D Polymeric Thorium Peroxo Sulfate

Bonato, L.; Virot, M.; Dumas, T.; Mesbah, A.; Lecante, P.; Prieur, D.; Le Goff, X.; Hennig, C.; Dacheux, N.; Moisy, P.; Nikitenko, S.

The preparation and structural characterization of an original Th peroxo sulfate dihydrate crystallizing at room temperature in the form of stable 1D polymeric microfibers is described. A combination of laboratory and synchrotron techniques allowed to solve the structure of Th(O2)(SO4)(H2O)2 compound which crystallizes in a new structure type in the Pna21 space group of the orthorhombic system. Particularly, peroxide ligand coordinates Th cations in a scarce μ3–η2:η2:η2 bridging mode forming an infinite 1D chain decorated with sulfato ligands exhibiting simultaneously both monodentate and bidentate coordination modes.

Permalink: https://www.hzdr.de/publications/Publ-29156
Publ.-Id: 29156


Collective flow and correlations measurements with HADES in Au plus Au collisions at 1.23 AGeV

Kardan, B.; Adamczewski-Musch, J.; Arnold, O.; Arnoldi-Meadows, B.; Belounnas, A.; Belyaev, A.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chlad, L.; Chudoba, P.; Ciepal, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gillitzer, A.; Golosov, O.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hoehne, C.; Holzmann, R.; Ierusalimov, A.; Ivanov, V.; Ivashkin, A.; Kaempfer, B.; Kajetanowicz, M.; Kampert, K.-H.; Kardan, B.; Khomyakov, V.; Koenig, I.; Koenig, W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kozela, A.; Kubos, J.; Kugler, A.; Kunz, T.; Kurilkin, P.; Kushpil, V.; Ladygin, V.; Lalik, R.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Lykasov, G.; Mahmoud, T.; Malakhov, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Muentz, C.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Patel, V.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pereira, A.; Petousis, V.; Petukhov, O.; Pfeifer, D.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Ritman, L.; Rodriguez-Ramos, P.; Rost, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Silva, L.; Smyrski, J.; Sobiella, M.; Spataro, S.; Spies, S.; Strikhanov, M.; Stroebele, H.; Stroth, J.; Strzempek, P.; Svoboda, O.; Szala, M.; Taranenko, A.; Tlusty, P.; Traxler, M.; Troyan, A.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wintz, P.; Wirth, J.; Wloch, B.; Zhilin, A.; Zinchenko, A.; Zumbruch, P.

The HADES experiment provides a large acceptance combined with a high mass resolution and therefore makes it possible to study dielectron and hadron production in heavy-ion collisions with unprecedented precision. With the high statistics of seven billion Au+Au collisions at 1.23 AGeV recorded in 2012 the investigation of collective effects and particle correlations is possible with unprecedented accuracy. We present multi-differential data on directed (v(1)) and elliptic (v(2)) flow, and the first measurement of triangular flow (v(3)), of protons and deuterons.

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Permalink: https://www.hzdr.de/publications/Publ-29155
Publ.-Id: 29155


Multi-differential pattern of low-mass e(+)e(-) excess from root S-NN=2.4 GeV Au+Au collisions with HADES

Harabasz, S.; Adamczewski-Musch, J.; Arnold, O.; Arnoldi-Meadows, B.; Belounnas, A.; Belyaev, A.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chlad, L.; Chudoba, P.; Ciepal, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gillitzer, A.; Golosov, O.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hoehne, C.; Holzmann, R.; Ierusalimov, A.; Ivanov, V.; Ivashkin, A.; Kaempfer, B.; Kajetanowicz, M.; Kampert, K.-H.; Kardan, B.; Khomyakov, V.; Koenig, I.; Koenig, W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kozela, A.; Kubos, J.; Kugler, A.; Kunz, T.; Kurilkin, P.; Kushpil, V.; Ladygin, V.; Lalik, R.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Lykasov, G.; Mahmoud, T.; Malakhov, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Muentz, C.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Patel, V.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pereira, A.; Petousis, V.; Petukhov, O.; Pfeifer, D.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Ritman, L.; Rodriguez-Ramos, P.; Rost, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Silva, L.; Smyrski, J.; Sobiella, M.; Spataro, S.; Spies, S.; Strikhanov, M.; Stroebele, H.; Stroth, J.; Strzempek, P.; Svoboda, O.; Szala, M.; Taranenko, A.; Tlusty, P.; Traxler, M.; Troyan, A.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wintz, P.; Wirth, J.; Wloch, B.; Zhilin, A.; Zinchenko, A.; Zumbruch, P.

The matter formed in central heavy-ion collisions at a few GeV per nucleon is commonly understood as resonance matter, a gas of nucleons and excited baryon states with a substantial contribution from mesonic, mostly pionic excitations. Yet, in the initial phase of the reaction the system is compressed to beyond nuclear ground state density and hence substantial modifications of the hadron properties are expected to occur. The spectral distribution of virtual photons measured in Au+Au collisions at 2.4 GeV center of mass energy indicates strong medium effects beyond pure superposition of individual NN collisions. We present multi-differential distributions of low-mass electron pairs. This radiation is remarkably well described assuming emission from a thermalized system. To gain deeper understanding of the microscopic origin of the radiation, we extracted the centrality dependent true (not blue-shifted) temperature, its azimuthal distribution, as well as mass-dependent effective slope parameter. Virtual photon spectra are confronted with available model calculations.

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Permalink: https://www.hzdr.de/publications/Publ-29154
Publ.-Id: 29154


Sub-threshold strangeness production measured with HADES

Kornakov, G.; Adamczewski-Musch, J.; Arnold, O.; Arnoldi-Meadows, B.; Belounnas, A.; Belyaev, A.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chlad, L.; Chudoba, P.; Ciepal, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gillitzer, A.; Golosov, O.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hoehne, C.; Holzmann, R.; Ierusalimov, A.; Ivanov, V.; Ivashkin, A.; Kaempfer, B.; Kajetanowicz, M.; Kampert, K.-H.; Kardan, B.; Khomyakov, V.; Koenig, I.; Koenig, W.; Korcyl, G.; Kornas, F.; Kotte, R.; Kozela, A.; Kubos, J.; Kugler, A.; Kunz, T.; Kurilkin, P.; Kushpil, V.; Ladygin, V.; Lalik, R.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Lykasov, G.; Mahmoud, T.; Malakhov, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Muentz, C.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Patel, V.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pereira, A.; Petousis, V.; Petukhov, O.; Pfeifer, D.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Ritman, L.; Rodriguez-Ramos, P.; Rost, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Silva, L.; Smyrski, J.; Sobiella, M.; Spataro, S.; Spies, S.; Strikhanov, M.; Stroebele, H.; Stroth, J.; Strzempek, P.; Svoboda, O.; Szala, M.; Taranenko, A.; Tlusty, P.; Traxler, M.; Troyan, A.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wintz, P.; Wirth, J.; Wloch, B.; Zhilin, A.; Zinchenko, A.; Zumbruch, P.

At energies below sqrt(sNN) approximate to 2.55 GeV, strange quarks cannot be produced in binary nucleon-nucleon collisions because of the higher production threshold of the lightest hadrons carrying strangeness. Hence, the investigation of sub-threshold strangeness production in heavy-ion collisions is one of the most promising probes, to access the properties of the created system, as the missing energy must be provided by the latter one. For the first time, a nearly complete set of strange particles has been reconstructed in the 40% most central Au+Au collisions at sqrt(sNN) = 2.42 GeV. The data sample includes multi-differential representations of charged and neutral particles containing strangeness (K+,-,Ks0, φ, Λ). To achieve a better understanding of strangeness production the properties of the short-lived resonances have to be investigated. The first steps in this direction are presented here, including the reconstruction of baryon resonances using a new iterative technique, comparison to microscopic transport model calculations and interpretation of the pion transverse momentum distribution.

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Permalink: https://www.hzdr.de/publications/Publ-29153
Publ.-Id: 29153


Ferromagnetic (In,Ga,Mn)As films prepared by ion implantation and pulsed laser melting

Xu, C.; Wang, M.; Zhang, X.; Yuan, Y.; Zhou, S.

In the present work, we show the preparation of (In,Ga,Mn)As films with different Ga concentration by Mn ion implantation and pulsed laser melting. All films are confirmed to be well recrystallized by Rutherford backscattering spectrometry/channeling and to be ferromagnetic by magnetometry measurements, respectively. Their Curie temperatures depend on the Ga concentration. Our results show the perspective of ion implantation in the preparation of different III-Mn-V quaternary alloys as new members of diluted ferromagnetic semiconductors.

Keywords: Thin film; Ion implantation; Pulsed laser melting; III-V compounds

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Permalink: https://www.hzdr.de/publications/Publ-29152
Publ.-Id: 29152


Coupled dissolution-precipitation reactive transport modeling at the pore scale

Karimzadeh, L.; Fischer, C.

Coupled dissolution-precipitation processes are of critical importance for the evolution of porosity and permeability in materials and for multiple applications, such as waste management, reservoir rocks, and corrosion. Here, we study the impact of saturation and fluid flow velocity with high spatial resolution, i.e., in the micrometer to submicrometer scale. Utilizing a time series of datasets of corroded crystal surfaces, collected using interferometry techniques, we analyze the impact of local fluid flow heterogeneity and resulting saturation variability. Systematically, the series of surface data is used (i) to constrain the initial topography for reactive transport modeling, and (ii) to compare the model vs. experimental results.
In this work, a reactive transport model is presented which simulates the complex chemical reaction of mineral dissolution/precipitation and subsequent pore-geometry evolution at a single pore scale [1]. We used the finite element package COMSOL Multiphysics® 5.4 for the simulation, utilizing the arbitary-Lagrangian Eulerian (ALE) method for the free-moving domain boundary.
Experimental and modeling studies have shown both the spatial [2] and temporal [3] heterogeneity of reaction rates and their impact on topography evolution at the pore scale. We expect an improved predictability of reactive transport modeling by using an approach combining the heterogeneities of surface reactivity and flow velocity at the pore scale.


[1] Karimzadeh, L., et al., 2018. Benchmark 3D reactive transport modelling of leaching of fractured calcareous sulfide ores, in: Lottermoser, B.G. (Ed.), Aachen International Mining Symposia (AIMS 2018), Aachen, Germany, p. 88 pp.
[2] Fischer, C., and Luttge, A., 2018, Pulsating dissolution of crystalline matter. PNAS 115.
[3] Fischer, C., Kurganskaya, I., and Luttge, A., 2018, Inherited control of crystal surface reactivity. Applied Geochemistry 91, 140.

  • Poster
    EGU General Assembly 2019, 08.-12.04.2019, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-29151
Publ.-Id: 29151


Improving fracture-flow models by experimental evidence from process tomography

Kulenkampff, J.; Karimzadeh, L.; Jankovsky, F.; Zuna, M.; Havlova, V.; Fischer, C.

Advective fluid flow transport controls the migration of radionuclides in fractured crystalline rocks. Thus, the
safety assessment of deep geological repositories in crystalline rocks relies critically on fracture flow properties
and the reliability of transport modelling approaches. Here, we focus on heterogeneity and complexity of transport
processes, typically of limited predictability. In order to tackle this issue, we suggest experimental observations by
using tomographic methods, as well as feedback with and improvement of existing transport modelling approaches.
As an example, tracer propagation through fractured crystalline rock cores from the Czech Republic (Bukov URL,
depth of 500 m below the surface), was studied in collaboration between HZDR (Germany) and UJV (Czech
Republic). Spatiotemporal data of the tracer concentration during conservative transport are based on positron
emission tomography (PET), and the underlying fracture structure was characterized by microCT-imaging. The latter
yields a structural model for reactive transport modelling. The PET data sequences provide (i) the validation of
existing simulation approaches, and (ii) serve as input or the parameterization of advanced simulation concepts.
First results underscore the outlined approach. In particular, the PET measurements clearly show preferential and
localized pathways, a feature of the process that significantly reduces the effect of interactions at the fracture
surface (and thus retention by adsorption); although repeat experiments are suggesting that the identified pathways
are not constant over the experimental periods.
As a consequence of the combined experimental and simulation approach, we expect (i) advanced model concepts
based on experimental insights and (ii) an improved understanding of reactive transport processes with a focus on
temporal heterogeneity of preferential pathways.

  • Poster
    EGU General Assembly 2019, 08.-12.04.2019, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-29150
Publ.-Id: 29150


Photoconductive germanium antenna emitting broadband THz pulses

Pashkin, O.; Singh, A.; Winnerl, S.; Helm, M.; Schneider, H.

The spectral range between 5 and 10 THz is hardly accessible for time-resolved THz spectroscopy due to strong phonon absorption in many polar materials utilized for the generation of THz transients. We demonstrate that non-polar germanium is a promising semiconductor for a realization of a photoconductive THz emitter with a continuous spectrum spanning well above 10 THz.

  • Invited lecture (Conferences)
    AES 2019, the 7th Advanced Electromagnetics Symposium, 24.-26.07.2019, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-29149
Publ.-Id: 29149


A correlation study of layer growth rate, thickness uniformity, stoichiometry, and hydrogen impurity level of ALD grown HfO2 thin films

Blaschke, D.; Munnik, F.; Grenzer, J.; Rebohle, L.; Zahn, P.; Schmidt, H.; Gemming, S.

Hafnium oxide was deposited from tetrakis(dimethylamino)hafnium (TDMAHf) and water by atomic layer deposition (ALD) on heated 400 Si wafers covered with native oxide in the temperature range from 100 C to 350 C. Optimized self-limiting ALD reaction and smallest hydrogen impurity level have been realized for a substrate temperature of 300 C. The stoichiometry of deposited films and hydrogen impurity level were measured by elastic recoil detection analysis. The hafnium to oxygen ratio showed the expected 1:2 value. Besides hydrogen, no other impurities could be detected.
Furthermore, a strong correlation between the growth rate per cycle (GPC), film uniformity and level of hydrogen impurities was observed. Based on this result, the easily accessible GPC can be used as a first indication for the hydrogen impurity level in ALD grown thin films.
Furthermore, the characterization of the crystal structure showed the appearance of some crystallites in an amorphous matrix already for a growth temperature of 250 C and a pure crystalline layer at a growth temperature of 350 C. The increased crystallinity with increasing growth temperature was attributed to a higher seed concentration and a constant crystal size.

Keywords: ALD; TDMAHf; HfO₂; growth rate per cycle; thickness uniformity; ERDA; H impurity level; GIXRD; AFM

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  • Secondary publication expected from 26.11.2020

Permalink: https://www.hzdr.de/publications/Publ-29148
Publ.-Id: 29148


Simulación numérica en pilas de combustible PEMFC tipo Air-Breathing

Weber, N.; Chaparro, A.; Ferreira Aparicio, P.

Der Vortrag gibt eine Übersicht über die Simulation von Luft atmenden Brennstoffzellen.

  • Lecture (others)
    Institutsseminar am CIEMAT, 24.04.2019, Madrid, Spanien

Permalink: https://www.hzdr.de/publications/Publ-29147
Publ.-Id: 29147


Maximizing magnetic field generation in high power laser–solid interactions

Huang, L.; Takabe, H.; Cowan, T.

In order to understand the transport of fast electrons within solid density targets driven by an optical high power laser, wehave numerically investigated the dynamics and structure of strong self-generated magnetic fields in such experiments.Here we present a systematic study of the bulk magnetic field generation due to the ponderomotive current, Weibel-likeinstability and resistivity gradient between two solid layers. Using particle-in-cell simulations, we observe the effect ofvarying the laser and target parameters, including laser intensity, focal size, incident angle, preplasma scale length, targetthickness and material and experimental geometry. The simulation results suggest that the strongest magnetic field isgenerated with laser incident angles and preplasma scale lengths that maximize laser absorption efficiency. The recentcommissioning of experimental platforms equipped with both optical high power laser and X-ray free electron laser(XFEL), such as European XFEL-HED, LCLS-MEC and SACLA beamlines, provides unprecedented opportunities toprobe the self-generated bulk magnetic field by X-ray polarimetry via Faraday rotation with simultaneous high spatialand temporal resolution. We expect that this systematic numerical investigation will pave the way to design and optimizenear future experimental setups to probe the magnetic fields in such experimental platforms

Keywords: laser–plasmas interaction; high energy density physics; X-ray free electron laser probi

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Permalink: https://www.hzdr.de/publications/Publ-29146
Publ.-Id: 29146


Kinetic Simulations of Target Heating, Ionization and Micro-Explosion with High Intensity XFEL Beams

Huang, L.; Hartley, N.; Hau-Riege, S.; Inubushi, Y.; Kamimura, N.; Katagiri, K.; Kodama, R.; Kon, A.; Makita, M.; Matsuoka, T.; Nakajima, S.; Pikuz, T.; Rode, A.; Rohatsch, K.; Sagae, D.; Schuster, A.; Tono, K.; Lu, W.; Yabuuchi, T.; Ozaki, N.; Kraus, D.; Cowan, T.

High intensity X-ray Free Electron Lasers (XFEL) are an ideal tool to heat materials directly and isochorically, which can cause them to be modified and damaged irreversibly. During XFEL-matter interactions, the energy of an XFEL beam will be mainly absorbed by photoionization, creating numerous high-energy photo- and Auger electrons. Modelling this process is quite complex since both atomic physics and plasma physics are involved. Atomic collisional-radiative (CR) codes such as FLYCHK are widely used to simulate such processes. However, the CR codes typically assume local thermodynamic equilibrium (LTE) and are limited to zero dimension.
In order to understand the sample damaging mechanisms, we performed two-dimensional kinetic particle-in-cell simulations with radiation transport (PIC-RT) to retrieve the temporal processes of XFEL-matter interactions. The dynamics of XFEL-Matter interactions can roughly divide into three different time scales: 1) electron heating and photoionization by XFEL in ~ 10 fs ; 2) collisional heating and ionization by high-energy photo- and Auger electrons with several keV energy in tens of fs to sub-ps; and 3) collective hydrodynamic explosion driven by ~ TPa thermal pressure from ~100 fs to nanoseconds.
The simulation results are compared to our recent experiment that a variety of samples were irradiated by Japanese XFEL SACLA with intensities on the order of 10^20 W/cm^2. The post-analysis of the irradiated samples showed that large holes with radius sizes more than one order of magnitude higher than the XFEL spot were created for metallic samples. The hole size is also much larger than the stopping range of high energy electrons. According to our PIC-RT simulations, we attribute the generation of such large holes to the micro-explosion process. Kinect simulation of the hole generation with multiple time scales is also useful and complementary to understand the change of X-Ray diffraction pattern in the experiment that infers significant material structural change on femtosecond timescales.

Keywords: XFEL; Pump-Probe Experiment; Kinect Simulations; Radiation Transport

  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 01.-04.04.2019, Prague, Czech Republic
    DOI: 10.1117/12.2520565

Permalink: https://www.hzdr.de/publications/Publ-29145
Publ.-Id: 29145


Uncertainty limits of range verification in proton therapy by means of prompt gamma-ray timing (PGT)

Werner, T.; Kögler, T.; Permatasari, F. F.; Petzoldt, J.; Römer, K.; Wagner, A.; Enghardt, W.; Pausch, G.

Range verification during clinical treatments is a key for further improving the precision and for reducing the normal-tissue toxicity of radiotherapy with proton beams. In spite of the breakthrough achieved with IBA’s knife-edge slit camera, capable of imaging single beam spots in pencil-beam scanning (PBS) treatment fractions delivered to cancer patients, there are ongoing activities aiming at systems distinguished by lower expense, lower weight, easier integration in the therapy facility, and potentially higher precision. In this context, OncoRay’s Prompt Gamma-Ray Timing (PGT) technology has been further explored with the focus on quantifying uncertainty contributions in potential clinical applications. Experimental data acquired in the treatment room of the University Proton Therapy Dresden (UPTD) during single pencil beam delivery to a polymethyl methacrylate (PMMA) target with arbitrary air cavities have been carefully analyzed. Besides the limited number of events the instable phase relation between proton-beam bunches and accelerating RF turned out to be the weakest point at the given facility. Technical means for monitoring this phase relation at a time scale of split seconds without touching the medical beamline are being developed and will be discussed in the paper. Altogether PGT could provide range verification with 3 mm accuracy at PBS spot level, if (at least) eight PGT detection units are deployed. Technically even a larger number of detectors could be arranged around the nozzle, which would further reduce the uncertainty.

Keywords: proton therapy; treatment verification; range verification; prompt gamma ray; prompt gamma-ray imaging; PGI; prompt gamma-ray timing; PGT

  • Lecture (Conference)
    2019 IEEE Nuclear Science Symposium and Medical Imaging Conference, 26.10.-02.11.2019, Manchester, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-29144
Publ.-Id: 29144


Fast 2D laser-induced fluorescence spectroscopy mapping of rare earth elements in rock samples

Seidel, P.; Lorenz, S.; Heinig, T.; Zimmermann, R.; Booysen, R.; Beyer, J.; Heitmann, J.; Gloaguen, R.

Due to the rapidly increasing use of energy-efficient technologies, the need for complex materials containing rare earth elements (REEs) is steadily growing. The high demand for REEs requires the exploration of new mineral deposits of these valuable elements, as recovery by recycling is still very low. Easy-to-deploy sensors technologies featuring high sensitivity to REE are required to overcome limitations by traditional techniques such as X-ray fluorescence. We demonstrate the ability of laser-induced fluorescence (LIF) to detect REEs rapidly in relevant geological samples. We introduce two-dimensional LIF mapping to scan rock samples from two Namibian REE deposits and cross-validate the obtained results by employing mineral liberation analysis (MLA) and hyperspectral imaging (HSI). Technique-specific parameters, such as acquisition speed, spatial resolution, and detection limits, are discussed and compared to established analysis methods. We also focus on the attribution of REEs occurrences to mineralogical features, which may helpful for the further geological interpretation of the deposit. This study sets the basis for the development of a combined mapping sensor for HSI and 2D LIF measurements, which could be used for drill-core logging in REE exploration as well as in recovery plants.

Keywords: laser-induced fluorescence; rare earth elements; imaging sensor, optical spectroscopy, reflectance spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-29143
Publ.-Id: 29143


Successful immunotherapy and irradiation in a HIV-positive patient with metastatic Merkel cell carcinoma

Linge, A.; Rauschenberg, R.; Blum, S.; Spornraft-Ragaller, P.; Meier, F.; Troost, E. G. C.

This case report presents a HIV-positive 60-year old male with Merkel cell carcinoma of his right forearm and pulmonary sarcoidosis, who, after excisions and irradiations of the primary tumour site and subsequent lymph node metastases developed distant metastases. He received radiotherapy to symptomatic mediastinal lymph node metastases followed by Doxorubicin and, after two cycles, by the PD-1 Inhibitor Pembrolizumab due to mixed response. Re-staging showed a para-mediastinal, radiotherapy-induced pneumonitis, which was treated by prednisolone due to clinical symptoms. In September 2017, the patient developed a solitary lymph node metastasis next to the right atrium, for which he received stereotactic radiotherapy. The systemic treatment with Pembrolizumab was replaced by the PD-L1 inhibitor Avelumab and is being continued since. The patient has been in complete remission for one year now and the HIV-infection is well-controlled.

Keywords: Merkel cell carcinoma; Avelumab; Immunotherapy; Pembrolizumab; Immune checkpoint Inhibition; Radiotherapy; HIV; Sarcoidosis

Permalink: https://www.hzdr.de/publications/Publ-29142
Publ.-Id: 29142


Implementierung von CT-basierten Schwächungskarten am PET/MRT für die Bestrahlungsplanung von Prostatakrebspatienten

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

Einleitung:
Das Ziel der Einbindung von PSMA-PET/MRT-Daten in die Bestrahlungsplanung (RT) von Prostatakrebspatienten ist es, die Tumorabgrenzung zu verbessern und eventuell die
Dosisverschreibung zu individualisieren. Da diese Scans in Behandlungsposition aufgenommen werden müssen, ist eine Schwächungskorrektur für die RT-Positionierungshilfsmittel erforderlich. Die hier vorgestellte Methode implementiert CT-basierte Schwächungskarten von RT-Positionierungshilfsmitteln in die Rekonstruktion von PET/MRT-Bildern und wird anschließend hinsichtlich der Genauigkeit ihrer Schwächungskorrektur analysiert.

Material & Methode:
Eine RT-Tischplattenauflage (hausinterne Herstellung) wurde an einem CT (SOMATOM Definition Flash, Siemens) mit einer Röhrenspannung von 120 kV und einem effektiven Röhrenstrom von 320 mAs gescannt. Basierend auf den CT-Bildern wurde eine Schwächungskarte der RT-Tischplattenauflage berechnet. Anschließend wurde die RT-Tischplattenauflage auf den Patiententisch des PET/MRTs (Biograph mMR, Siemens) montiert. PET-Messungen mit (RT-Scan) und ohne (Referenzscan) RT-Tischplattenauflage wurden mithilfe eines aktiven, homogen gefüllten 68Ge-Phantoms (32 MBq, 10 Minuten Scanzeit) aufgenommen. Beide Scans wurden mit identischen Rekonstruktionsparametern rekonstruiert. Die Rekonstruktion des RT-Scans wurde mit (korrigiert) und ohne (unkorrigiert) Implementierung der Schwächungskarte der RT-Tischplattenauflage durchgeführt. Die PET-Aktivitäten der RT- und Referenzscans wurden verglichen, indem die Mittelwerte der ROIs im Abstand von 10 Schichten entlang des Phantoms in Längsrichtung ausgewertet wurden.

Ergebnisse:
Tabelle 1 zeigt den Vergleich der gemessenen PET-Aktivitäten des unkorrigiertem und des korrigiertem RT-Scans mit dem Referenzscan. Der mittlere prozentuale Unterschied zwischen dem unkorrigierten RT- und dem Referenzscan beträgt 4,8%. Zwischen dem korrigierten RT- und dem Referenzscan wurde eine mittlere prozentuale Differenz von 0,5% ermittelt.

Zusammenfassung:
Die PET-Signalschwächung durch die RT-Tischplattenauflage ist mit durchschnittlich 5% klinisch relevant und kann mithilfe von CT-basierten Schwächungskarten erfolgreich korrigiert werden. Dieser Schritt ist Voraussetzung für die Integration von PET/MRT-Daten in die Bestrahlungsplanung.

  • Lecture (Conference)
    50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e. V., 18.-21.09.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29141
Publ.-Id: 29141


Midostaurin abrogates CD33-directed UniCAR and CD33-CD3 bispecific antibody therapy in acute myeloid leukemia

Fasslrinner, F.; Arndt, C.; Koristka, S.; Feldmann, A.; Altmann, H.; von Bonin, M.; Schmitz, M.; Bornhäuser, M.; Bachmann, M.

Combinatory therapeutic approaches of different targeted therapies in acute myeloid leukemia (AML) are currently under preclinical and early clinical investigation. To enhance anti-tumor effects, we combined tyrosine kinase inhibitor (TKI) Midostaurin and T cell-mediated immunotherapy directed against CD33. We show that clinically relevant concentrations of Midostaurin abrogate T cell-mediated cytotoxicity both after activation with bispecific antibodies (bsAbs) and chimeric antigen receptor (CAR) T cells. This information is of relevance for clinicians exploring T cell-mediated immunotherapy in early clinical trials. Given the profound inhibition of T cell functionality and anti-tumor activity, we recommend favoring specific fms-like tyrosine kinase 3 (FLT3) TKIs for further clinical testing of combinatory approaches with T cell-based immunotherapy.

Permalink: https://www.hzdr.de/publications/Publ-29140
Publ.-Id: 29140


T Cell Based Immunotherapy of Acute Myeloid Leukemia is Abrogated by the Tyrosine Kinase Inhibitor Midostaurin

Fasslrinner, F.; Arndt, C.; Koristka, S.; Feldmann, A.; Altmann, H.; von Bonin, M.; Schmitz, M.; Bornhäuser, M.; Bachmann, M.

Background
Induction chemotherapy is currently the standard of care for treatment of acute myeloid leukemia (AML) with 5-year disease-free survival of 33%. Given the large proportion of non-responders and relapsed patients, novel adjuvant drugs are urgently needed. Especially, targeted therapies including small molecules and T cell based immunotherapies are under intensive preclinical and clinical investigation. The tyrosine kinase inhibitor Midostaurin recently received approval for treatment of FLT3-positive AML. In addition to chemotherapy, it significantly deepens remission rates and improves overall survival of patients. In light of future combinatorial approaches, simultaneous application of different targeted therapies should theoretically augment anti-tumor effects.

Aims
Therefore, we questioned whether Midostaurin could strengthen cytotoxic effector mechanisms of redirected switchable UniCAR T cells or bispecific antibody-redirected T cells against primary AML cells.

Methods/Results
By performing in vitro co-cultivation assays with patient-derived AML cells, it was shown that Midostaurin concentrations ≥ 1 µM significantly impair the activation, proliferation, cytokine production and cytotoxicity of autologous and allogeneic T cells after engagement via bsAb or the UniCAR system. Data could be also verified in a solid tumor model.

Summary/Conclusion
At concentrations ranging between 0.1 and 10 M, it was shown that Midostaurin and its metabolites are indeed able to inhibit several components of the TCR signaling pathway including LcK, Zeta-chain-associated protein kinase 70 (ZAP-70), mitogen-activated protein kinase (MAPK) and Protein kinase C (PKC) in vitro. Therefore, we argue that the observed T cell inhibition by Midostaurin in our studies is caused by the inhibition of several of these kinases. This hypothesis is supported by the work of two individual research groups that were able to show synergistic effects by combining FLT3 selective TKIs with different T cell-based immunotherapies. Because Midostaurin through concentrations above ≥ 1 µM have been observed in earlier performed dose finding studies, we speculate that current standard Midostaurin therapy will inhibit T cell function in vivo.
In summary, our data underline that combination of Midostaurin and T cell-based immunotherapies in FLT3-positive AML patients is not recommended due to the suppressive effect of Midostaurin on T cells. Therefore, more selective TKI or other small molecules should be chosen to avoid impairment of T cell functions.

  • Poster
    1st European CAR T Cell Meeting, 14.-16.02.2019, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-29139
Publ.-Id: 29139


Integriertes Management und Publikation von wissenschaftlichen Artikeln, Software und Forschungsdaten am Helmholtz-Zentrum Dresden-Rossendorf (HZDR)

Reschke, E.; Konrad, U.

Mit dem Ziel, das Publizieren von Artikeln, Forschungsdaten und wissenschaftlicher Software gemäß den FAIR-Prinzipien zu unterstützen, wurde am HZDR ein integriertes Publikationsmanagement aufgebaut. Insbesondere Daten- und Softwarepublikationen erfordern die Entwicklung bedarfsgerechter organisatorischer und technischer Strukturen ergänzend zu bereits sehr gut funktionierenden Services im Publikationsmanagement. In der Zusammenarbeit mit Wissenschaftlern des HZDR und internationalen Partnern in ausgewählten Projekten wurde der Bedarf an Unterstützung im Forschungsdatenmanagement analysiert. Darauf aufbauend wurde schrittweise ein integriertes System von Infrastrukturen und Services entwickelt und bereitgestellt. In einer seit Mai 2018 gültigen Data Policy wurden die Rahmenbedingungen und Regelungen sowohl für wissenschaftliche Mitarbeiter als auch für externe Messgäste definiert.
Zusammenfassend werden unsere Erfahrungen im integrierten Publikationsmanagement für Artikel, Forschungsdaten und Forschungssoftware vorgestellt. Es wird ein Ausblick auf die nächsten Schritte und Aufgaben gegeben und Aspekte der Integration im Kontext der europäischen und nationalen Forschungsorganisationen herausgearbeitet.

Keywords: Publikationsmanagement; Forschungsdaten; Forschungssoftware; publication management; research data; research software; FAIR; Open Access

  • Open Access Logo Contribution to proceedings
    WissKom2019: Forschungsdaten - Sammeln, sichern, strukturieren, 04.-06.06.2019, Jülich, Deutschland
    WissKom2019: Forschungsdaten - Sammeln, sichern, strukturieren. 8. Konferenz der Zentralbibliothek, Forschungszentrum Jülich, Jülich: Forschungszentrum Jülich, 978-3-95806-405-8, 167-177
  • Open Access Logo Invited lecture (Conferences)
    WissKom2019 – Forschungsdaten: Sammeln, sichern, strukturieren. 8. Konferenz der Zentralbibliothek, Forschungszentrum Jülich, 04.-06.06.2019, Jülich, Deutschland
    DOI: 10.13140/RG.2.2.14789.19683

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Permalink: https://www.hzdr.de/publications/Publ-29138
Publ.-Id: 29138


X-ray radioscopic visualization of bubbly flows injected through a top submerged lance into a liquid metal

Akashi, M.; Keplinger, O.; Anders, S.; Shevchenko, N.; Reuter, M.; Eckert, S.

We present an experimental study on the formation and behaviour of a liquid metal bubbly flow arising from a downward gas injection through a top submerged lance (TSL). A visualization of the bubble dynamics was achieved by the X-ray radiography combined with high-speed imaging. The experiments were carried out in a parallelepiped container (144×144×12 mm3) using GaInSn, a ternary alloy that is liquid at room temperature. The gas flow rate Qgas was adjusted in a range between 0.033 and 0.1 l/s. Three different injection positions were considered with respect to the submergence depth L. X-ray images allow for a characterization of the flow regimes and provide the properties of the individual bubbles such as size, shape and trajectory. Formation and entrainment of smaller gas bubbles are observed at the free surface. These small bubbles can be trapped in the fluid for a long time by recirculation vortices. Bubbles size distributions are determined for different Qgas. The bubble detachment frequency is measured as a function of Qgas and L. The results are compared with previously published data for water. The X-ray radiography offers an effective method for determining the local void fraction and allows for an estimation of the bubble volume.

Keywords: Two phase flow; X-ray radiography; Top submerged lance

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  • Secondary publication expected from 29.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29137
Publ.-Id: 29137


An oligo-His-tag of a targeting module does not influence its biodistribution and the retargeting capabilities of UniCAR T cells

Jureczek, J.; Bergmann, R.; Berndt, N.; Koristka, S.; Kegler, A.; Puentes-Cala, E.; Soto, J. A.; Arndt, C.; Bachmann, M.; Feldmann, A.

Recently, we established the controllable modular UniCAR platform technology to advance the efficacy and safety of CAR T cell therapy. The UniCAR system is composed of (i) target modules (TMs) and (ii) UniCAR armed T cells. TMs are bispecific molecules that are able to bind to the tumor cell surface and simultaneously to UniCAR T cells. For interaction with UniCAR T cells, TMs contain a peptide epitope sequence which is recognised by UniCAR T cells. So far, a series of TMs against a variety of tumor targets including against the prostate stem cell antigen (PSCA) were constructed and functionally characterised. In order to facilitate their purification all these TMs are expressed as recombinant proteins equipped with an oligo-His-tag. The aim of the here presented manuscript was to learn whether or not the oligo-His-tag of the TM influences the UniCAR system. For this purpose, we constructed TMs against PSCA equipped with or lacking an oligo-His-tag. Both TMs were compared side by side including for functionality and biodistribution. According to our data, an oligo-His-tag of a UniCAR TM has only little if any effect on its binding affinity, in vitro and in vivo killing capability and in vivo biodistribution.

Permalink: https://www.hzdr.de/publications/Publ-29136
Publ.-Id: 29136


Eulerian/Lagrangian formulation for the elasto-capillary deformation of a flexible fibre

Lecrivain, G.; Grein, T. B. P.; Yamamoto, R.; Hampel, U.; Taniguchi, T.

The capillary-induced bending of flexible fibres, a process also known as elasto-capillary deformation, is central to a variety of industrial and non-industrial applications, among which stand out textile flotation, stabilization of emulsions, micro-folding of elastic structures, and clogging of feather fibres by oil droplets. A consistent formulation for the direct numerical simulation of a flexible fibre interacting with a fluidic interface is presently suggested. The fibre is geometrically decomposed into a chain of spherical beads, which undergo stretching, bending, and twisting. interactions. The capillary force, acting at the three-phase contact line, is calculated using a ternary diffuse-interface model. In a first stage, the fibre deformation model and the ternary diffuse-interface model are validated against theoretical solutions. In a second stage, the two- and three-dimensional elasto-capillary bending of a fibre by an immersed droplet are numerically investigated. Partial wrapping and complete encapsulation could be simulated. The results show that the fibre curvature increases linearly with the square of the elasto-capillary length, for both low and large structural deformation.

Keywords: Elasto-capillary deformation; fibre at fluidic interface; ternary diffuse interface model; direct numerical simulation; droplet encapsulation

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  • Secondary publication expected from 17.02.2021

Permalink: https://www.hzdr.de/publications/Publ-29135
Publ.-Id: 29135


Fluid Flow and Transport Phenomena in Liquid Metal Batteries

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

Fluid flows in liquid metal batteries can be generated by a number of effects. We start with a short overview of different driving mechanisms and then address questions specific to the metal pad role instabilities in three-layer systems. Besides introducing a term accounting for the interfacial tension that should be considered for smaller cells, we focus on the role of the conductivity distribution in the cell.

Keywords: Liquid metal batteries; metal pad roll; sloshing

  • Contribution to proceedings
    11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich, 188-192
  • Lecture (Conference)
    11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-29134
Publ.-Id: 29134


Mass Transport in the Positive Electrode of a Liquid Metal Battery

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

Liquid metal electrodes are one of the key components of different electrical energy storage technologies. The understanding of transport phenomena behind liquid electrodes is mandatory in order to ensure efficient operation, however it would certainly gain by further investigations. In the present study we focus our attention on the positive electrode of a Li||Bi liquid metal battery. Starting from a real experimental setup, we investigate mass transport with numerical simulations. During the charge of the cell, compositional convection becomes apparent. The time evolution of the fluid flow and the flow structure are studied. First results on compositional convection are presented, highlighting its capability to affect the flow in the positive electrode.

Keywords: electrorefining; liquid electrode; liquid metal batteries; mass transport; solutal convection

  • Contribution to proceedings
    11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France
    Mass Transport in the Positive Electrode of a Liquid Metal Battery
  • Poster
    11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France

Permalink: https://www.hzdr.de/publications/Publ-29133
Publ.-Id: 29133


Oscillating hydrogen bubbles at Pt microelectrodes

Bashkatov, A.; Hossain, S. S.; Yang, X.; Mutschke, G.; Eckert, K.

The dynamics of hydrogen bubbles produced via electrolysis in acidic electrolytes is studied in a combination of experiments and numerical simulations.
A transition from monotonous to oscillatory bubble growth is observed after 2/3 of the bubble lifetime, if the electric potential exceeds -3V. This work analyzes characteristic features of the oscillations in terms of bubble geometry, the thickness of the microbubble carpet and the oscillation frequency. An explanation of the oscillation mechanisms is provided by the competition between buoyancy and electric force, the magnitude of which depends on the carpet thickness. Both the critical carpet thickness at detachment and the oscillation frequencies of the bubble as predicted by the model agree well with the experiment.

Keywords: electrolysis; hydrogen bubble; oscillations; charged bubble; electric force

Permalink: https://www.hzdr.de/publications/Publ-29132
Publ.-Id: 29132


Integral multi-scenario robustness evaluation of anatomical robust optimization in head and neck

Cubillos Mesías, M.; Troost, E. G. C.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.

Purpose/Objective
Classical robust optimization considers uncertainties in patient setup and particle range. Usually plan robustness is evaluated from calculation of perturbed dose distributions based on the planning CT, without considering potential anatomical changes that may occur during the treatment course. Our aim was to compare the overall plan robustness of classical robust optimization (cRO) with the recently proposed anatomical robust optimization (aRO) based on an integral multi-scenario evaluation, considering all types of uncertainties including anatomical variations.

Material/Methods
Datasets for 20 head and neck cancer patients, including a planning CT and weekly control CTs, were analyzed. Two intensity-modulated proton therapy (IMPT) plans were calculated: cRO, using solely the planning CT, and aRO, including additionally the first two control CTs in the plan optimization. For the robustness analysis, perturbed dose distributions with random setup uncertainties and fixed range uncertainty values of -3.5%, 0% and +3.5% were generated, drawing for each fraction n a random number from a Gaussian distribution around 0 mm with a standard deviation of 2.5 mm for the isocenter shift in each cardinal direction (xn, yn, zn). Moreover, in each fraction n the correspondent weekly control CT was used to consider the anatomical changes during therapy. 33 single-fraction perturbed doses were calculated and summed to generate a perturbed whole-treatment dose distribution. The procedure was repeated 10 times for each of the three range uncertainty values, resulting in 30 perturbed dose distributions per plan (Figure 1).

Results
Both nominal plans fulfilled the clinical objective for target coverage (D98% ≥ 95% of the prescribed dose). The median values calculated from the 30 perturbed dose distributions for each patient showed a reduction in the target coverage for the cRO plan, with mean (minimum) values of 94.9% (88.1%) and 95.4% (89.3%) for the low- and high-risk CTV, respectively, in comparison with 96.6% (92.0%) and 96.8% (93.6%), respectively, for aRO (Figure 2a). The variation in CTV coverage between the 30 scenarios, i.e. the width of the perturbed dose distributions, was found to be larger for cRO plans, with median (maximum) values of 1.9 (8.3) and 1.4 (5.6) for low- and high-risk CTV, respectively, in comparison with 1.4 (3.4) and 0.9 (5.2) for aRO plans, respectively. Moreover, the cRO case showed reduced robustness in comparison with aRO for some patients, where certain scenarios violate the clinical objective, as shown in Figure 2b.

Conclusion
Anatomical robust optimization showed superior plan robustness in comparison with the classical approach in a comprehensive multi-scenario evaluation. Anatomical variations play an important role in the overall plan robustness together with setup and range uncertainties, therefore their effect should not be underestimated or neglected.

  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 133(2019)Sup 1, S488-S489
    DOI: 10.1016/S0167-8140(19)31335-0

Permalink: https://www.hzdr.de/publications/Publ-29131
Publ.-Id: 29131


Quantification of plan robustness against different uncertainty sources for classical and anatomical robust optimized treatment plans in head and neck cancer proton therapy

Cubillos-Mesías, M.; Troost, E. G. C.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.

Objective: Classical robust optimization (cRO) in intensity-modulated proton therapy (IMPT) considers isocenter position and particle range uncertainties; anatomical robust optimization (aRO) aims to consider additional non-rigid positioning variations. This work compares the influence of different uncertainty sources on the robustness of cRO and aRO IMPT plans for head and neck squamous cell carcinoma (HNSCC).
Methods: Two IMPT plans were optimized for twenty HNSCC patients who received weekly control CTs (cCT): cRO, using solely the planning CT, and aRO, including two additional cCTs. The robustness of the plans in terms of clinical target volume (CTV) coverage and organ at risk (OAR) sparing was analyzed considering stepwise the influence of (1) non-rigid anatomical variations given by the weekly cCT, (2) with fraction-wise added rigid random setup errors and (3) additional systematic proton range uncertainties.
Results: cRO plans presented significantly higher nominal CTV coverage but are outperformed by aRO plans when considering non-rigid anatomical variations only, as cRO and aRO plans presented a median target coverage (D98%) decrease for the low-risk/high-risk CTV of 1.8/1.1 percentage points (pp) and -0.2pp/-0.3pp, respectively. Setup and range uncertainties had larger influence on cRO CTV coverage, but led to similar OAR dose changes in both plans. Considering all error sources, 10/2 cRO/aRO patients missed the CTV coverage and a limited number exceeded some OAR constraints in both plans.
Conclusions: Non-rigid anatomical variations are mainly responsible for critical target coverage loss of cRO plans, whereas the aRO approach was robust against such variations. Both plans provide similar robustness of OAR parameters.
Advances in knowledge: The influence of different uncertainty sources was quantified for robust IMPT HNSCC plans.

Keywords: Robust optimization; robustness analysis; head and neck cancer; proton therapy

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Permalink: https://www.hzdr.de/publications/Publ-29130
Publ.-Id: 29130


Bestimmung der Gas-Flüssigkeits-Grenzfläche in Anstaupackungen mittels ultraschneller Röntgentomographie

Sohr, J.; Bieberle, M.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.

Durch die alternierend angeordneten Packungslagen mit unterschiedlichen geometrischen Oberflächen bilden sich in Anstaupackungen abhängig von den Betriebsbedingungen Filmströmung und Sprudelschicht gleichzeitig aus. Der intensive Kontakt zwischen der Gas- und Flüssigkeitsphase in den sprudelnden Bereichen der Anstaupackung führt zu einer Trenneffizienzsteigerung von bis zu 30 % im Vergleich zu konventionell gepackten Kolonnen [1]. Zur Abschätzung der Beiträge der jeweiligen Bereiche mit unterschiedlichen Strömungsregimen zur Gesamttrennleistung ist die Kenntnis der Gas-Flüssigkeits-Grenzfläche erforderlich. Die Grenzfläche kann mittels ultraschneller Röntgentomographie bestimmt werden, welche die dynamischen Strömungsstrukturen mit einer Bildrate von 1000 Bildern pro Sekunde erfasst. Mithilfe eines modifizierten Level-set-Algorithmus wird die Phasengrenze zwischen Gas einerseits und Flüssigkeit sowie Metallpackung andererseits in den Querschnittsbildern detektiert (Abb.1).
In diesem Beitrag werden sowohl die Methodik zur Bestimmung der Phasengrenzfläche als auch Ergebnisse für unterschiedliche Gas- und Flüssigkeitsbelastungen bei verschiedenen Packungskombinationen präsentiert.
Wir danken der DFG für die finanzielle Unterstützung des Kooperationsprojekts "Experimentelle und theoretische Untersuchung der Fluiddynamik und des Stofftrennverhaltens von Anstaupackungen" (KE 837/26-1, HA 3088/10-1).
[1] M. Jödecke, T. Friese, G. Schuch, B. Kaibel, H. Jansen, Institution of Chemical Engineers Symposium Series, Institution of Chemical Engineers, 2006, Vol.152, pp. 786–789.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29129
Publ.-Id: 29129


Partieller Einsatz von teilweise gefluteten Packungen

Flechsig, S.; Utchenko, Y.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.

Ein Weg zur Reduzierung des hohen Energiebedarfs thermischer Trennverfahren ist die Prozessintegration. Ein Beispiel dafür ist die Integration verschiedener Strömungsformen in einem Trennapparat durch den Einsatz von Anstaupackungen, wodurch eine Erhöhung der Trennleistung im Vergleich zu Strukturpackungen erzielt wird. Anstaupackungen bestehen aus zwei alternierend angeordneten Lagen von industriell verfügbaren Standardpackungen mit unterschiedlichen spezifischen Oberflächen. Die untere Anstaulage weist eine geringere Lastgrenze als die darüber angeordnete Abscheidelage auf, wodurch im Betrieb zwischen den Flutpunkten
beider Lagen ein heterogenes Strömungsmuster entsteht. Dabei bildet sich in der gezielt gefluteten Anstaulage eine bis in die Abscheidelage hineinreichende Sprudelschicht, die durch eine intensive Phasenvermischung und große
Phasengrenzflächen geprägt ist.
Um die Leistungscharakteristik von Anstaupackungen mit der von anderen Einbauten vergleichen zu können, wurde in einer vorherigen Arbeit [1] ein rate-based-Modell entwickelt, welches die Auswirkungen der belastungsabhängig auftretenden Regime in Anstaupackungen berücksichtigt. Basierend auf experimentellen Daten zur CO2-Absorption mit wässrigen Aminlösungen im Technikumsmaßstab sowie tomographischen Untersuchungen wurden Abhängigkeiten der modellspezifischen Parameter identifiziert und anschließend regimespezifisch ins Modell implementiert. Mittels Prozesssimulationen der CO2-Absorption aus Abgasen gasbefeuerter Kraftwerke im industriellen Maßstab werden im Rahmen dieser Arbeit Anstaupackungen und Strukturpackungen hinsichtlich der benötigten Kolonnenabmessungen und des zu überwindenden Druckverlustes verglichen. Um eine abschließende Bewertung durchzuführen, wurden mithilfe von Aspen Process Economic AnalyzerTM die Anlagen- und Betriebskosten für die CO2-Abscheidung bestimmt. Zusätzlich wurde zur Ermittlung eines optimalen Designs der Einfluss der wesentlichen Geometrieparameter von Anstaupackungen auf die Kosten untersucht.
[1] S. Flechsig, J. Sohr, M. Schubert, U. Hampel, E.Y. Kenig, Chem. Eng. Trans., 2018, 69, 169-174, DOI: 10.3303/CET1869029.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29128
Publ.-Id: 29128


Mass transfer and electrolyte flow during electrodeposition on a conically shaped electrode under the influence of a magnetic field

Huang, M.; Marinaro, G.; Yang, X.; Fritzsche, B.; Lei, Z.; Uhlemann, M.; Eckert, K.; Mutschke, G.

The electrodeposition of copper on a conically shaped diamagnetic electrode was studied under the influence of a vertical magnetic field. Numerical simulations combined with measurements of the velocity and the concentration field were conducted to provide understanding of the influence of the Lorentz force on the deposition process. The secondary flow caused by the magnetic field is directed downward along the cone surface and thus supporting conical growth. Since the cathode is placed at the bottom of the electrochemical cell, natural convection is counteracting the influence of the Lorentz force. However, the different time scales of both forces involved allow to utilize the beneficial influence of the Lorentz force, e.g. in pulsed deposition regimes.

Keywords: copper electrodeposition; magnetic field; surface-structured electrode; Mach-Zehnder interferometry; shadowgraphy; numerical simulation

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Permalink: https://www.hzdr.de/publications/Publ-29127
Publ.-Id: 29127


Degradation of natural uranium containing micro-mineral phases: Implications to contaminats transport at abandoned mining sites

Pidchenko, I.; Bauterns, S.; Amidani, L.; Kvashnina, K.

In this work a combination of multiple synchrotron and laboratory based micro-techniques is utilized to unveil the speciation, heterogeneities and degradation of uranium (U) micro-mineral phases accumulated on rock outcrop from natural U deposit area. The investigated system is sampled from the abandoned Krunkelbach U mine in Southern Germany with 2-3 km surrounding area which represents a natural analogue site with an unique accumulation of U minerals suitable for investigations of potential mobilization-immobilization processes expected in a real spent nuclear fuel repository. A specific feature of the site is the occurrence of more than forty secondary U minerals, from uraninite, mixed U oxy-hydroxides to uranyl silicates, representing a wide scale of U ore weathering events. Available data on the age of the secondary U mineralization indicates that oxidizing processes at the site started some 340,000 years ago and continues up to date. Several phases close to Cu(UO2)2(PO4)2-x(AsO4)x·8H2O are identified on 1×2 mm2 area with presumably older, more evenly distributed uranyl silicate and uranyl tungstate mineralization. Based on a multi-technique investigation 10-200 μm Cu(UO2)2(PO4)2-x(AsO4)x·8H2O particles with widely varying arsenic-phosphorus (As-P) content are analyzed. The evidences of a degradation on some zones of selected crystals are found which are associated with higher As content. This observation can be apparently attributed to different degradation properties of the mixed As-P phases depending on As-P ratio and originate from drastically different solubility properties of Cu(UO2)2(PO4)2·8H2O and Cu(UO2)2(AsO4)2·8H2O species. The conditions for preferential formation of As rich Cu(UO2)2(XO4)2·8H2O [X=As, P] phases and its possible role on U transport in environment under oxidizing conditions are discussed.

  • Lecture (Conference)
    21st Mendeleev Congress on General and Applied Chemistry, 09.-13.09.2019, Saint Petersburg, Russia

Permalink: https://www.hzdr.de/publications/Publ-29126
Publ.-Id: 29126


Multidimensional fluid mixing study during an asymmetric injection of cold water in the primary side of a generic PWR KONVOI with ATHLET 3.1A

Diaz Pescador, E.; Schäfer, F.; Kliem, S.

The presented paper gathers the insights obtained during the study of the multidimensional fluid mixing in the reactor pressure vessel (RPV) during an asymmetric injection of cold or overcooled water in the primary side of a generic German PWR KONVOI reactor by means of the thermal-hydraulic system code ATHLET 3.1A. With this aim, the paper provides first an overview on the selection procedure of the accident scenarios to be studied together with the plant model development, with special emphasis on the pseudo multidimensional RPV configuration. Later on the fluid mixing study in the RPV is performed during an overcooling transient by means of two different developed vessel configurations and the obtained results are assessed against experimental data from analogous tests carried out at the ROCOM test facility, showing good agreement to each other.

  • Contribution to proceedings
    50th Annual Meeting on Nuclear Technology (AMNT) 2019, 07.05.2019, Berlin, Germany
  • Lecture (Conference)
    50th Annual meeting on Nuclear Technology (AMNT) 2019, 07.-08.05.2019, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-29125
Publ.-Id: 29125


Accelerated time-of-flight scatter correction for whole-body PET

Nikulin, P.; Maus, J.; Hofheinz, F.; van den Hoff, J.

Utilization of Time-Of-Flight (TOF) information allows to improve image quality and convergence rate in PET image reconstruction. In order to obtain quantitatively correct images accurate scatter correction (SC) is required that accounts for the study-specific scatter time distribution.
The currently accepted TOF-SC gold standard - the TOF extension of the single scatter simulation approach (TOF-SSS), see [1] - is computationally demanding and can substantially slow down the reconstruction which becomes a substantial problem in whole-body investigations. On the other hand, the accuracy of existing simplified TOF-SC algorithms is limited in many cases. We have developed a new TOF-SC algorithm in order to improve this situation.

Our TOF-SC method is based on a separate estimation of scatter spatial distribution (via SSS) and scatter time distribution via a dedicated fast algorithm. The key idea of the algorithm is the use of an immediate scatter approximation (ISA) for scatter time distributions calculation. The underlying assumption is that for this calculation a distinction between the emission point from which the annihilation event originates and actual scatter point is not crucial.
The proposed approach was evaluated in phantom measurements providing challenging high activity contrast conditions as well as in representative clinical patient data sets.

The reconstructed images are in excellent quantitative agreement with those obtained with TOF-SSS while scatter estimation time was reduced by a factor of four and overall reconstruction time by a factor of two in whole-body studies, even when using a listmode reconstruction not optimized for speed.

Our results show that ISA is a viable alternative to TOF-SSS offering a factor of four TOF scatter estimation acceleration without compromising the image quality.

[1] C. C. Watson, Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET, IEEE Transations Nucl. Sci., vol. 54(5), pp. 1679–1686, 2007

Keywords: PET; TOF; TOF-SC; TOF-SSS; ISA

  • Lecture (Conference)
    57. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 03.-06.04.2019, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29121
Publ.-Id: 29121


Predictive Geometallurgy- State of the Art

Birtel, S.; Büttner, P.; Frenzel, M.; Bachmann, K.; Tolosana Delgado, R.; Gutzmer, J.

The 45 minutes talk gives a brief overview of the approach of the Helmholtz Institute Freiberg for Resource Technology, followed by an introduction into Geometallurgy, Predictive Geometallurgy respectively. From the analytical perspective there will be a focus on SEM based automated image analysis. This data is the basis for further data processing, statistical assesment and interpretations. Depending on data availability, operational stage (exploration extraction) different levels of geometallurgical models can be created. This will be illustrated in case studies, showing the work flow and result for the development of 1) 3D resource potential model of a historic tailings dam to recover Sn, 2) Methodology for mineralogical deportment prediction of In as a by- product from complex ore types, 3) 3D first order geomet model of a primary deposit to recover PGE as by product

Keywords: Geometallurgy; predictive geometallurgical model; SEM based automated mineralogy; data analysis

  • Invited lecture (Conferences)
    InRec Stakeholder Meeting (Geometallurgy applied to industrial Mineral operations), 24.-25.04.2019, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-29120
Publ.-Id: 29120


Geostatistical Compositional Analysis of Regional Geochemical Stream Sediments of West Java, Indonesia

Selia, S. R. R.; Rus, A. M. M.; Tolosana Delgado, R.; Sendjaja, P.; van den Boogaart, K. G.; Schaeben, H.

As analytical tools evolve, more geochemical data are obtained so that effective and robust tools are demanded for capturing detailed information of underlying geological processes such as alteration, mineralization and weathering. The data are formed by a number of elements, whose concentrations are interdependent due to the fact that their total sum is bounded to a constant (e.g. 100%). Classical statistical analysis of this type of data may provide misleading results because it does not consider the closure effects: for instance, one of the correlation coefficients will always be negative regardless of whether the two elements with negative correlation are incompatible or not. Consequently, methods employing variance cannot be used on the raw dataset. To manage this problem, one can adopt Compositional Data Analysis (CoDa) which acknowledges the compositional nature of the data.

In the last decade, CoDa has been widely applied to geochemical data. Thus, combined with geological information, we apply CoDa to the regional geochemical stream sediment data of West Java to address our understanding of the underlying geological processes of the area. The first process carried out is a log-ratio transformation to eliminate both constant-sum constraints and non-negativity problems. Then to distinguish features in the data a Principal Component Analysis (PCA) can be performed. Here we can get linear components that have a large effect on variations in the data. The final stage is the spatial estimation of important PCA components through experimental variogram calculation, variogram modeling, and geostatistical estimation. The interpolated maps can be back-transformed to obtain maps of the original components. In this way, the results will not violate the compositional nature of the data, while spatially representing the captured processes.

Keywords: Geochemical exploration; Geology of Java; Mining

  • Lecture (Conference)
    HAGI-IAGI-IAFMI-IATMI Joint Convention 2019, 25.-28.11.2019, Yogyakarta, Indonesia

Permalink: https://www.hzdr.de/publications/Publ-29119
Publ.-Id: 29119


Mid-Treatment Gd-EOB-DTPA-Enhanced MRI and Interleukin 6 Cytokine as Biomarkers of Radiation-induced Liver Toxicity in Metastatic Liver Patients

Ajdari, A.; Xie, Y.; Richter, C.; Hong, T.; Bortfeld, T.

Purpose: In the era of precision medicine and personalized radiation treatment (RT), there is an ever-growing need to find predictive biomarkers of treatment response in patients. Here we investigate the potentials of using mid-treatment MR images and inflammatory cytokines as biomarkers of liver toxicity.

Method and Materials: Eleven intrahepatic metastatic patients who had proton stereotactic body radiotherapy (SBRT) to the liver lesion were retrospectively analyzed. Two Gd-EOB-DTPA (a hepatobiliary-directed contrast agent)-enhanced MR scans as well as three inflammatory cytokines (interleukin 6 [IL-6], IL-8, and tumor necrosis factor α [TNF- α]) were acquired during the RT course. Deformable image registrations were done among mid-treatment (fx4 and 5) MR images and the planning CT. MR signal changes and delivered dose were then calculated for each voxel. Mid-treatment changes in the expression of the cytokines were calculated with respect to the pre-treatment baseline. Liver toxicity was assessed at 3 months post-RT, using Child-Pugh (CP) and ALBI score. Patients were subsequently classified into high-risk (HR) and low-risk (LR) groups. Statistical analysis was performed to compare the changes in the MR signals and cytokine expressions between these groups.

Results: On average, high-risk patients had lower high-dose/low-dose mid-treatment signal changes (i.e., decreased/increased signal in high-dose/low-dose). In CP classification, there was a significant difference in MR signal change between two group means (0.61 and 1.04 for HR and LR groups; p-value=0.005). The ALBI classification showed more pronounced difference (0.61 vs. 1.11, p-value = 0.002). High-risk patients also showed larger IL-6 changes during their treatment (86% vs. 0.33%, p-value=0.01).

Conclusion: Using mid-treatment MR scans and interleukin 6 as biomarkers, it is possible to predict the risk of acute liver toxicity, already during the RT course. This biomarker information can be potentially used for adaptive planning and RT plan personalization.

Keywords: Liver metastasis; MR; mid-treatment; adaptations; biomarker; cytokine

  • Lecture (Conference)
    2019 AAPM Annual Meeting, 14.-18.07.2019, San Antonio, USA
  • Abstract in refereed journal
    Medical Physics 46(2019)6, E499-E499
    DOI: 10.1002/mp.13589

Permalink: https://www.hzdr.de/publications/Publ-29118
Publ.-Id: 29118


Late life brain perfusion after prenatal famine exposure

de Rooij, S. R.; Mutsaerts, H. M.; Petr, J.; Asllani, I.; Caan, M. W.; Groot, P.; Nederveen, A.; Schwab, M.; Roseboom, T. J.

Early nutritional deprivation may cause irreversible damage to the brain and seems to affect cognitive function in older age. We investigated whether prenatal undernutrition was associated with brain perfusion differences in older age. We acquired Arterial spin labelling scans in 118 Dutch famine birth cohort members. Cerebral blood flow (CBF) was compared between exposed and unexposed groups in grey and white matter, perfusion territories, neurodegeneration-related regions anterior and posterior cingulate cortex and precuneus. Furthermore, we compared the GM/WM-ratio and the spatial coefficient of variation (CoV) as a proxy of overall cerebrovascular health. The WM ASL signal and the GM/WM-ratio were significantly lower and higher respectively among exposed participants. Exposed men had lower CBF in anterior and posterior cingulate cortices and higher spatial CoV. The latter seemed largely mediated by higher 2h-glucose levels at age 50. Our findings suggest that overall brain perfusion was worse in exposed participants, especially men exposed to undernutrition in early gestation. These results provide further evidence for life-long effects of undernutrition during early brain development.

Keywords: brain perfusion; prenatal famine; fetal programming

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29117
Publ.-Id: 29117


Numerical optimization of a finned tube bundle heat exchanger arrangement for passive spent fuel pool cooling to ambient air

Unger, S.; Krepper, E.; Beyer, M.; Hampel, U.

The passive cooling of nuclear spent fuel pools is a promising alternative to active cooling. Since such systems work even in safety-critical situations, e.g. station blackout, the reliability of nuclear power plants would be enhanced. As in such systems heat needs to be transfer to the environment, the heat exchanger to air has a crucial influence on the system performance. This paper describes investigations of the Nusselt number, the achievable efficiency and the volumetric heat flux density of the tube bundle heat exchangers for a passive cooling system located at the bottom of a chimney. The effect of tube bundle configuration, tube shape, longitudinal tube pitch, transversal tube pitch and tube row number on natural convection heat transfer was numerical studied. These parameters were varied to optimize the heat transfer performance of the heat exchanger. It was found, that the staggered configuration performs better than the inline arrangement, since the flow mixing is higher. Furthermore circular tube shape and an oval tube shape with the aspect ratio of 1:2.1 were optimum for the inline and staggered configuration respectively. The longitudinal and transversal tube pitches of 63 mm and 65 mm performed best, since higher values reduced heat transfer. A tube row number greater than 5 did not improve the heat transfer and therefore a tube row number of 5 is recommended. The Nusselt number and volumetric heat flux density of the optimized tube bundle arrangement enhanced by 15.4 % and 47.8 % respectively at a temperature difference of 40 K compared to the initial design.

Keywords: passive cooling; spent fuel pool; natural convection; tube bundle heat exchanger; air cooling; design optimization

Related publications

Permalink: https://www.hzdr.de/publications/Publ-29116
Publ.-Id: 29116


Quantifying the value of geometallurgical information and optimization

van den Boogaart, K. G.

Predictive Geometallurgy can use thorough quantitative characterisation of the ores microstructure and mineralogy to predict and adaptively optimize the processing and blending of the ore. Adaptive processing allows to exploit this variation to achieve higher overall recovery at lower costs, e.g. by adapting milling to mineral grain sizes or grades.

The geometallurgical properties of the ore are however typically only known with some geostatistical uncertainty. The talk demonstrates in model calculation, that naive optimization of processing parameters based on expected ore properties might lead to performance losses relative to non-adaptive processing, while overestimating its own expected performance. The contribution shows how to outperform non-adpative processsing decissions substantially based on a stochastic optimization approach and how to quantify the value of geometallurgical information in a certain setting.

Indeed in the context of predictive geometallurgy the value of a blend is no longer defined only by its acutally physical properties, but also by the information we have about it at the time of processing. This makes geometallurgical exploration activity a relevant part of the mine plan, which can actually change and on average increase the value of blocks.

Keywords: Geometallurgy; Mine Scheduling; Stochastic Optimization; Geostatistics

  • Lecture (Conference)
    2019 COSMO Technical Day, 27.-28.06.2019, Montreal, Canada

Permalink: https://www.hzdr.de/publications/Publ-29115
Publ.-Id: 29115


Nuclear Data Sensitivity and Uncertainty Analysis of Critical VENUS-F Cores with the Serpent Monte Carlo Code

Fridman, E.; Valtavirta, V.; Aufiero, M.

In the framework of the FP7 Euratom project FREYA, the Serpent Monte Code was used to characterize a number of critical VENUS-F core configurations. Several neutronic parameters calculated by Serpent were compared to the available experimental data and reported in a previous study. Although a generally reasonable agreement between the calculated and experimental values was obtained, the study also revealed some important issues related to the numerical results such as a systematic overestimation of reactivity and a systematic underestimation of U238 to U235 fission rate ratio (designated as F28/F25 spectral index).
The objective of the current follow-up study is to quantify the effect of nuclear data uncertainties on the Monte Carlo estimates of reactivity and spectral indices. The analysis is carried out for two critical VENUS-F cores using a recently upgraded version of Serpent which is capable to perform sensitivity analysis based on the collision history method and to propagate and quantify nuclear data uncertainties using multi-group covariance libraries in an automated way. The criticality calculations were performed using the ENDV/B-VII.1 based cross sections while the uncertainties due to nuclear data were obtained using 56-group neutron cross section covariance library from the SCALE-6.2 package.
The estimated uncertainties due to nuclear data are of the order of 2200 pcm and 8% on k-eff and F28/F25 spectral index respectively. It was found that the major contributor to the k-eff uncertainty is capture cross section of U235. In the F28/F25 case, the total uncertainty is dominated by inelastic cross section of U238, fission spectrum of U235, and capture cross section of U235.

Keywords: Serpent; Monte Carlo; uncertainty quantification; FREYA; VENUS-F; critical experiments

Downloads:

  • Secondary publication expected from 15.11.2020

Permalink: https://www.hzdr.de/publications/Publ-29114
Publ.-Id: 29114


Simulating air-breathing fuel cells using openFuelCell

Weber, N.; Chaparro, A. M.; Ferreira-Aparicio, P.; Zhang, S.; Reimer, U.; Beale, S.

The talk will be dedicated to modelling polymer electrolyte fuel cells. In the first part, the theory of the fuel cell model is presented. Details on its implementation in the open source library openFuelCell will be given. Secondly, numerical results on modelling an air-breathing fuel cell operated at CIEMAT will be shown and discussed.

  • Lecture (Conference)
    OpenFOAM Workshop, 23.07.2019, Duisburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-29113
Publ.-Id: 29113


Modelling electric potential distributions in batteries and fuel cells: an overview

Weber, N.; Personnettaz, P.; Weier, T.; Sadoway, D.

The talk will give an overview on simulating electric potential and current distributions in the frame of the finite volume method. Special attention will be paid to modelling internal discontinuities of the electric potential, as they appear at the electrode-electrolyte interface in fuel cells, electrolysers and batteries. The theoretical background will be explained and illustrated with simple examples.

  • Lecture (Conference)
    OpenFOAM Workshop, 23.07.2019, Duisburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29112
Publ.-Id: 29112


Interaction of uranium with halophilic microorganisms

Bader, M.; Hilpmann, S.; Swanson, J. S.; Steudtner, R.; Drobot, B.; Schmidt, M.; Roßberg, A.; Ikeda-Ohno, A.; Stumpf, T.; Cherkouk, A.

Rock salts are considered as potential host rocks for the long-term storage of highly radioactive waste in a deep geological repository. In addition to bacteria and fungi, extremely halophilic archaea, e.g. Halobacterium species, are predominantly present in this habitat. For long-term risk assessment it is of high interest to study how these microorganisms can potentially interact with radionuclides if the radionuclides are released from the waste repository. Given this fact, the interactions of extremely halophilic archaea from the genus Halobacterium and the moderately halophilic bacterium Brachybacterium sp. G1 with uranium, one of the major radionuclides of concern in the geological repository of radioactive wastes, were investigated in detail in batch experiments. The archaea and the bacterium showed different association mechanisms with uranium. Brachybacterium sp. G1 cells sorbed uranium within a short time, whereas a much longer and a multi-stage bioassociation process, dependent on the uranium concentration, occurred with the archaea. Furthermore, a multi-spectroscopic (time-resolved laser-induced fluorescence spectroscopy and X-ray absorption spectroscopy) and -microscopic (scanning electron microscopy coupled with energy-dispersive X-ray analysis for elemental mapping) approach was used to elucidate the U(VI) bioassociation behavior. By using these spectroscopic and microscopic tools, the formation of a U(VI) phosphate mineral, such as meta-autunite, by the Halobacterium species was demonstrated. These findings offer new insights into the microbe-actinide interactions at highly saline conditions relevant to the disposal of nuclear waste.

  • Lecture (Conference)
    Halophiles 2019, 24.-28.06.2019, Cluj-Napoca, Romania

Permalink: https://www.hzdr.de/publications/Publ-29110
Publ.-Id: 29110


Prediction of Bubble Departure in Forced Convection Boiling with a Mechanistic Model that Considers Dynamic Contact Angle and Base Expansion

Setoodeh, H.; Ding, W.; Lucas, D.; Hampel, U.

A mechanistic model for bubble dynamics in flow boiling that is based on a force balance approach for a growing bubble is introduced. It considers evaporation of the microlayer underneath the bubble, thermal diffusion and condensation around the bubble cap as well as dynamic inclination and contact angles between the bubble and the heating wall. It requires no recalibration of parameters to predict the bubble growth. Validation against different experimental flow boiling data was carried out with no case-dependent recalibration and yielded good agreement. The simulations confirmed the dependency of bubble departure and lift-off diameters on different parameters, such as heat flux, liquid properties, subcooling temperature, system pressure, inclination angle of channel, channel geometry and mass flow rate.

Keywords: flow boiling; bubble growth; bubble departure; force balance

Permalink: https://www.hzdr.de/publications/Publ-29109
Publ.-Id: 29109


Mechanical compliancy for magnetic field sensors

Makarov, D.

Augmented reality gadgets are becoming common for our information intensive society assisting us to acquire and process the data. Although impressive in the realization and demonstrations, the obvious drawback of the state-of-the-art augmented and virtual reality devices relying on optical detection systems is their bulkiness, energy inefficiency and the stringent requirement for an operator to be at the line of sight of the device.
We envision that prospective augmented reality systems will strongly benefit from the recent developments in compliant on-skin electronics [1-3]. The fabrication of highly conformable gadgets requires the realization of the electronic replica of the exteroceptive sensory system of humans as well as calls for the acquiring new perception skills beyond those prescribed by the evolution. The representative example of the missing exteroceptive sense of humans is the magnetoception, which allows some of the mammals but not humans perceiving the location in space or directions based on the detection of magnetic fields. The first crucial step towards the realization of this vision was accomplished with the development of interactive magnetosensitive skins [4-6]. The key enabler for this technology is the shapeable magnetoelectronics [7] –namely, flexible [5,6], stretchable [8,9] and imperceptible [4,10-12]– magnetic field sensorics.
Here, we present the first on-skin gadgets, which replicate our natural proprioceptive sensory ability of detecting the motion [4,10-12]. The technology is put forth to realize distributed arrays of magnetic field sensors on ultra-thin polymeric foils. Relying on this magnetically enabled electronic proprioception, we visualize the bodily motion and demonstrate the touchless manipulation of virtual objects for augmented reality systems.
Those highly conformable interactive devices possess great potential to extend the portfolio of tasks, which can be performed in virtual or augmented reality. The integration of gadgets in imperceptible electronic skins will open not only exciting possibilities for business or gaming industry but is also beneficial for safety and security applications, where the somatic manipulation of objects, e.g. turning regulation knobs located in a restricted environment is undesirable or even prohibited.


References
1. J. A. Rogers et al., Nature 477, 45 (2011).
2. S. Bauer et al., Adv. Mater. 26, 149 (2014).
3. M. Kaltenbrunner et al., Nature 499, 458 (2013).
4. M. Melzer et al., Nature Commun. 6, 6080 (2015).
5. M. Melzer et al., Adv. Mater. 27, 1274 (2015).
6. N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
7. D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
8. M. Melzer et al., Nano Lett. 11, 2522 (2011).
9. M. Melzer et al., Adv. Mater. 27, 1333 (2015).
10. G. S. Canon Bermudez et al., Science Advances 4, eaao2623 (2018).
11. G. S. Canon Bermudez et al., Nature Electronics 1, 589 (2018).
12. P. Granell et al., npj Flexible Electronics 3, 3 (2019).

Keywords: flexible electronics; flexible magnetic field sensors

  • Invited lecture (Conferences)
    Magnetic Frontiers 2019: Magnetic Sensors, 24.-27.06.2019, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-29108
Publ.-Id: 29108


Curvilinear magnetism

Makarov, D.

There is one aspect, which is in common to the majority of fundamentally appealing and technologically relevant novel magnetic materials, namely their non-collinear magnetic textures like spin spirals, chiral domain walls or skyrmions [1]. These textures are typically driven by the Dzyaloshinskii-Moriya interaction (DMI). Recently, curvature effects emerged as a novel mean to design chiral magnetic properties by relying on extrinsic parameters, e.g. geometry of thin films [2]. In particular, novel effects occur when the magnetization is modulated by curvature leading to new magnetization configurations and is implications on the spin dynamics due to topological constraints. Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films [3,4] and nanowires [5]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [6,7]. The application potential of 3D-shaped objects is currently being explored as mechanically reshapeable magnetic field sensorics [8] for flexible interactive electronics [9,10], spin-wave filters and high-speed racetrack memory devices [11]. The fundamentals as well as application relevant aspects of curvilinear nanomagnets will be covered in this presentation.
References:
[1] “The 2017 Magnetism Roadmap”, D. Sander et al., J. Phys. D 50, 363001 (2017).
[2] “Magnetism in curved geometries”, R. Streubel, et al., J. Phys. D 49, 363001 (2016).
[3] “Curvature Effects in Thin Magnetic Shells”, Y. Gaididei et al., Phys. Rev. Lett. 112, 257203 (2014).
[4] “Multiplet of Skyrmion States on a Curvilinear Defect: Reconfigurable Skyrmion Lattices”, V. Kravchuk et al., Phys. Rev. Lett. 120, 067201 (2018).
[5] “Mesoscale Dzyaloshinskii-Moriya interaction: geometrical tailoring of the magnetochirality”, O. M. Volkov et al., Scientific Reports 8, 866 (2018).
[6] “Coupling of Chiralities in Spin and Physical Spaces: The Möbius Ring as a Case Study”, O. V. Pylypovskyi et al., Phys. Rev. Lett. 114, 197204 (2015).
[7] “Curvature-Induced Asymmetric Spin-Wave Dispersion”, J. A. Otalora et al., Phys. Rev. Lett. 117, 227203 (2016).
[8] “Shapeable magnetoelectronics”, D.Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[9] “Magnetosensitive e-skins with directional perception for augmented reality”, S. Canon Bermudez et al., Science Advances 4, eaao2623 (2018).
[10] “Electronic-skin compasses for geomagnetic field driven artificial magnetoreception and interactive electronics”, S. Canon Bermudez et al., Nature Electronics 1, 589 (2018).
[11] “Beating the Walker Limit with Massless Domain Walls in Cylindrical Nanowires”, M. Yan et al., Phys. Rev. Lett. 104, 057201 (2010).

Keywords: curvature effects in magnetism; curved magnetic thin films

  • Invited lecture (Conferences)
    6th International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems, 30.06.-03.07.2019, Corfu, Greece

Permalink: https://www.hzdr.de/publications/Publ-29107
Publ.-Id: 29107


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