Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41396 Publications

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

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

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

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


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

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

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

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

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


Fluid Mechanics of Liquid Metal Batteries

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

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

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

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

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


Polyoxometalates in Extraction and Sorption Processes

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

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

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

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


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

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

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

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

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


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

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

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

Keywords: Mössbauer spectroscopy; corrosion

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


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

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

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

Keywords: gELBE; dosimetry

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


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

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

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

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

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


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

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

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

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

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


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

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

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

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

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


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

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

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

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


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

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

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

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

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


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

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

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

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


Classical and robust regression analysis with compositional data

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

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

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

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


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

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

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

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

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


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

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

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

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

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


The absence of metamictisation in natural monazite

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

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

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


Experimental gas phase hydrodynamic data of lab scale bubble column

Kipping, R.; Hampel, U.

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

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

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

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


Analytical Approach to Phonon Calculations in the SCC-DFTB Framework

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

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

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


Deutschlands Ausstieg aus der Atomkraft - Wie entsorgen wir den Müll und welche Rolle spielen Mikroorganismen?

Matschiavelli, N.

Zur Zeit werden in Deutschland noch 6 Kernkraftwerke zur Stromerzeugung betrieben. Bis 2022 soll das letzte Kernkraftwerk abgeschaltet werden – Deutschlands Ausstieg aus der Atomkraft. Der Atomausstieg ist ein wichtiger Schritt für die Energiewende mit dem Ziel einer langfristigen und vollständigen Umstellung auf erneuerbare Energien wie z. B. Wasserkraft, Sonnen- und Windenergie.
Der Ausstieg aus der Kernenergie bringt auch einige Konsequenzen mit sich, für welche wir die Verantwortung übernehmen müssen. Eine der größten Herausforderungen ist dabei die sichere und langfristige Lagerung des Atommülls. Weltweit hat sich hierbei das Konzept einer tiefen-geologischen Lagerung – etwa 500 m bis 1000 m unter der Erde – durchgesetzt. Die unterschiedlichen Materialien und Gesteine werden momentan auf ihre Eignung für das Endlager in Deutschland untersucht. Viele verschiedene Fachdisziplinen sind dafür relevant: Geologie, Mineralogie, (Radio-)Chemie, Physik, Mathematik, Materialwissenschaften, Architektur – um hier nur einige zu nennen.
Interessanterweise spielt auch die Biologie bei der Planung des Endlagers eine Rolle. Lebewesen können auf verschiedene Art und Weise mit den hier verwendeten Materialien – sogar mit dem Atommüll selbst – interagieren. Zu den hauptsächlich hier betrachteten Lebewesen zählen Pflanzen, Pilze und Mikroorganismen (Bakterien, Archaeen, einzellige Eukaryota). Bedingt durch ihren Stoffwechsel sind Mikroorganismen in der Lage, Materialien und deren Eigenschaften zu verändern. Da die Lagerung des Atommülls sicher und langfristig sein muss, ist es wichtig zu erforschen, inwiefern Mikroorganismen die verwendeten Materialien verändern und deren Eigenschaften möglicherweis beeinflussen.

Der Vortrag gibt einen Einblick in die faszinierende Welt der Mikroorganismen und zeigt zugleich deren Relevanz für die sichere und langfristige Lagerung des Atommülls.

  • Invited lecture (Conferences)
    Tag der Wissenschaften, 23.11.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31527
Publ.-Id: 31527


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

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

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

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

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


Microcosm studies for evaluating the microbial influence on metal corrosion

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

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

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

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


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

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

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

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

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


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

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

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

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


Neutronics Benchmark of CEFR Start-Up Tests: Temperature Coefficient, Sodium Void Worth, and Swap Reactivity

Choe , J.; Batki , B.; Davies , U.; Hyuck Won , J.; Jae Lee , M.; Batra , C.; Kriventsev , V.; Bodi , J.; Mikityuk , K.; Zheng, Y.; Du , X.; Lee , D.; Quoc Tran , T.; Pataki , I.; Tóth , M.; Fridman, E.; Kyum Kim , T.; Jarrett , M.; Miguel Gomez Torres , A.; Lopez , R.; Taninaka , H.; Szogradi , M.; Giusti , V.; Di Pasquale , S.; Petruzzi , A.

The China Institute of Atomic Energy (CIAE) proposed some of the China Experimental Fast Reactor (CEFR) neutronics start-up test data for the IAEA benchmark within the scope of the IAEA’s coordinated research activity. The coordinated research project (CRP) on “Neutronics Benchmark of CEFR Start-Up Tests” was launched in 2018. This benchmark aims to perform validation and verification of the physical models and the neutronics simulation codes by comparing calculation results against collected experimental data. Twenty-nine participating research organizations finished performing independent blind calculations and are refining their calculation results by referring to measurement data. The main objective of this benchmark is to improve understanding of the start-up of SFRs and validate the state-of-the-art fast reactor analysis computer codes against the recent experimental data obtained at the modern experimental SFR.
This paper introduces the following three kinds of reactivity measurements in the CEFR start-up test and presents the results by participants: temperature coefficient, sodium void reactivity, and swap reactivity. The measurements were done at the basic core in operation loading with fuel assemblies. First, for the measurement of temperature coefficients, ten sets of data were obtained by increasing and decreasing the temperature. For each temperature, the control rod position is changed to maintain the reactor as a critical. Second, sodium void reactivity is measured by replacing a fuel SA by vacuum-sealed SA and searching for the critical position of control rods. Third, for the measurement of the swap reactivity, fuel subassembly is replaced by SS subassembly, and SS subassembly is switched with one fuel subassembly. Swap reactivities are measured in two ways, with more than two control rods moving to find the criticality of the core in ‘Multiple Rods’ case, and only one control rod moving in the ‘Single Rod’ case. All three reactivities are obtained by a combination of control rod worth for changed rod position and criticality difference. Therefore, accuracy on control rod worth is important for benchmark calculation.
The comparison shows that uncertainty of calculations, modeling errors, and inaccurately determined control assembly worths make it challenging to calculate the temperature coefficient precisely. Depending on how modeling a vacuum-sealed fuel SA, the sodium void reactivity results from participants show large deviations. For swap reactivity calculation, the reactivity induced by the assembly swap is relatively larger than the temperature coefficient measurement. The swap reactivity calculation results from participants have similar trends and show good agreement with measurement.

  • Contribution to proceedings
    International Conference on Fast Reactors and Related Fuel Cycles (FR22), 19.-22.04.2022, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-31522
Publ.-Id: 31522


Neutronics Benchmark of CEFR Start-Up Tests: Control rods worths results

Levchenko , A.; Duginov , O.; Fridman, E.; Hyuck Won , J.; Lopez , R.; Dařílek , P.; Seubert , A.; Choe , J.; Taninaka , H.; Batki , B.; Visan , I.; Moise , A.; Kunhiraman , D.; Sciora , P.; Davies , U.; Huo , X.; Quoc Tran , T.; Malovytsia , M.

Paper considers results of control rods worth calculation tests which have been done in IAEA coordinate research project (CRP) of China Experimental Fast Reactor (CEFR). Obtained results of more than 20 participants from 17 countries include neutronic calculations by using deterministic and stochastic codes. During RCM these results been compared by method of calculation and between it.
Calculation performed for all types of control rods used in CEFR as “light” for power control and “heavy” rods for shutdown and fuel burning compensation. Summary values of k-eff and rods worth are closed to each other, of course the some difference can be seen in comparison of two different methods of calculation but, in general, this difference not more 2 percent. For light rods relative deviation from average value is not more 10 % mostly. For heavy rods such deviation is not more 5%. Considering calculation results for group rods worth can be saying that difference between codes not more 2% in most cases.

  • Contribution to proceedings
    International Conference on Fast Reactors and Related Fuel Cycles (FR21), 19.-22.04.2022, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-31521
Publ.-Id: 31521


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

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

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

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


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

Ulbricht, A.

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

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

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


Nanoindentation testing and TEM observations of irradiated F/M alloys

Bergner, F.

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

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

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

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


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

Chekhonin, P.

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

Keywords: ENTENTE project

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

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


ENTENTE WP2 Task 2.4: Data Collection

Chekhonin, P.

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

Keywords: ENTENTE project

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

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


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

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

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

Keywords: SiC; AlN; Raman spectroscopy; Stress

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


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

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

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

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


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

Podlipec, R.

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

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


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

Podlipec, R.

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

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


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

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

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

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

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


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

Huste, T.

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

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

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

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


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

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

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

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

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


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

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

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

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

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


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

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

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

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


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

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

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

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

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


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

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

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

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

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


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

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

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

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

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


Time refraction of spin waves

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

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

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

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


Experimental observation of the curvature-induced asymmetric spin-wave dispersion in hexagonal nanotubes

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

Theoretical and numerical studies on curved magnetic nano-objects predict numerous exciting effects that can be referred to as magneto-chiral effects, which do not originate from the intrinsic Dzyaloshinskii-Moriya interaction or surface-induced anisotropies. The origin of these chiral effects is the isotropic exchange or the dipole-dipole interaction present in all magnetic materials but renormalized by the curvature. Here, we demonstrate experimentally that curvature induced effects originating from the dipole-dipole interaction are directly observable by measuring spin-wave propagation in magnetic nanotubes with hexagonal cross section using time resolved scanning transmission X-ray microscopy. We show that the dispersion relation is asymmetric upon reversal of the wave vector when the propagation direction is perpendicular to the static magnetization. Therefore counter-propagating spin waves of the same frequency exhibit different wavelenghts. Hexagonal nanotubes have a complex dispersion, resulting from spin-wave modes localised to the flat facets or to the extremely curved regions between the facets. The dispersion relations obtained experimentally and from micromagnetic simulations are in good agreement. %The asymmetric spin-wave transport is present for all modes, promoting hexagonal nanotubes for magnonic applications. These results show that spin-wave transport is possible in 3D, and that the dipole-dipole induced magneto-chiral effects are significant.

Keywords: spin wave; nanotube; STXM; dispersion; hexagonal; micromagnetic simulations

Permalink: https://www.hzdr.de/publications/Publ-31500
Publ.-Id: 31500


Effect of nanoscale surface topography on the adsorption of globular proteins

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

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

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

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


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

Scheinost, A. C.

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

Keywords: nuclear waste; XAFS; Redox

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    GFZ Talk, 17.09.2020, Postdam, Germany
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Permalink: https://www.hzdr.de/publications/Publ-31498
Publ.-Id: 31498


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

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

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

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


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

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

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

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


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

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

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

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

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


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

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

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

Keywords: LWFA

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


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

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

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

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

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


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

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

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

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

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

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


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

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

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

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

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


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

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

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

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

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


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

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

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

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


THz nonlinear electronic response in GaAs/InGaAs semiconductor nanowires

Schneider, H.

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

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


Ion-implanted Ge photoconductive antennae for terahertz emission

Schneider, H.

This talk does not have an abstract.

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

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


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

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

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

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


Determination of the crystal field parameters in SmFe11Ti

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

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

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


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

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

We report on a comprehensive characterization of the newly synthesized Cu2+-based molecular magnet Cu(pz)2 (2-HOpy)2 K, as revealed by μ+SR. In applied magnetic fields, our 1H-NMR data reveal a strong increase of the magnetic anisotropy, manifested by a pronounced enhancement of the transition temperature to commensurate long-range order at TN = 2.8 K and 7 T.

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


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

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

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

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


Feasibility of metal pad roll instability experiments at room temperature

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

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

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


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

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

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

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


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

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

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

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


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

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

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

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


Room-Temperature Infrared Photoresponse from Ion Beam–Hyperdoped Silicon

Wang, M.; Berencen, Y.

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

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


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

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

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

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


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

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

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

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


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

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

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

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


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

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

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

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

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


How robust are landslide susceptibility estimates?

Ozturk, U.; Pittore, M.; Behling, R.; Roessner, S.; Andreani, L.; Korup, O.

Much of contemporary landslide research is concerned with predicting and mapping susceptibility to slope failure. Many studies rely on generalised linear models with environmental predictors that are trained with data collected from within and outside of the margins of mapped landslides. Whether and how the performance of these models depends on sample size, location, or time remains largely untested. We address this question by exploring the sensitivity of a multivariate logistic regression—one of the most widely used susceptibility models—to data sampled from different portions of landslides in two independent inventories (i.e. a historic and a multi-temporal) covering parts of the eastern rim of the Fergana Basin, Kyrgyzstan. We find that considering only areas on lower parts of landslides, and hence most likely their deposits, can improve the model performance by >10% over the reference case that uses the entire landslide areas, especially for landslides of intermediate size. Hence, using landslide toe areas may suffice for this particular model and come in useful where landslide scars are vague or hidden in this part of Central Asia. The model performance marginally varied after progressively updating and adding more landslides data through time. We conclude that landslide susceptibility estimates for the study area remain largely insensitive to changes in data over about a decade. Spatial or temporal stratified sampling contributes only minor variations to model performance. Our findings call for more extensive testing of the concept of dynamic susceptibility and its interpretation in data-driven models, especially within the broader framework of landslide risk assessment under environmental and land-use change.

Keywords: landslide susceptibility; logistic regression; Southern Kyrgyzstan; Landslide inventory; Remote sensing

Permalink: https://www.hzdr.de/publications/Publ-31472
Publ.-Id: 31472


Ferromagnetism in B2-Ordered Alloys Induced via Lattice Defects

Bali, R.

This chapter considers the case of B2-ordered alloys that are initially non-ferromagnetic and where the introduction of lattice defects can cause the onset of ferromagnetism. This disorder-induced ferromagnetism is confined to the regions where the defects are concentrated. In general, the lattice can be thermally re-ordered, removing the defects and erasing the magnetized regions. Using B2 Fe60Al40 thin films as a prototype, the use of ion irradiation as well as pulsed laser irradiation for inducing antisite defects in the crystalline lattice is demonstrated. Ion beams can be applied as broad beams in combination with shadow masks for printing magnetic patterns over large areas, or focused down to approximately nanometer diameters for stylus-like writing of nanomagnets of desired geometries. The patterning resolution is limited by the lateral scattering of ions and can be estimated by semi-empirical modelling, described in this chapter. In the case of laser pulsing, disordering can be induced at thin film surfaces for pulse fluences above the melting threshold. Pulsing below the threshold can lead to surface re-ordering, erasing the magnetic regions and achieving all-laser re-writeable patterning. Localized disordering of B2 ordered systems thus enables a versatile path to embedding highly resolved non-volatile magnets at room temperature, with potential in magnetic device applications.

Related publications

  • Book chapter
    Francis Chi-Chung Ling, Shengqiang Zhou, Andrej Kuznetsov: Defects in Functional Materials, Hong Kong: World Scientific Publishing Co Pte Ltd, 2020, 978-981-120-316-9, 201-239
    DOI: 10.1142/11352
    Cited 2 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-31471
Publ.-Id: 31471


Normal tissue reaction following proton irradiation of the mouse brain

Beyreuther, E.; Suckert, T.; Müller, J.; Azadegan, B.; Bodenstein, E.; Haase, R.; Schürer, M.; Krause, M.; Lühr, A.; von Neubeck, C.; Dietrich, A.

Background: Due to the beneficial inverse physical depth-dose profile, proton radiotherapy (PT) offers the potential to reduce normal tissue toxicity by depositing the maximum dose within the tumor volume while sparing the surrounding tissue. However, range uncertainties and necessary clinical safety margins in combination with varying relative biological effectiveness may result in a critical dose in the normal tissue. Dedicated preclinical studies are needed to assess and better understand potential adverse effects of PT and to develop potential biomarkers and countermeasures for backtranslation into clinics.
For this purpose, a high-precision image-guided proton irradiation setup for small animals was established at the University Proton Therapy Dresden that mimics the clinical workflow, including pre-treatment imaging, treatment planning and image-guided brain irradiation.
The right hippocampus of C57BL/6 and C3H/HeN mice was irradiated to study the dose- and time-dependent radiation response of mouse brain tissue after short or long-term follow-up analysis. A Monte Carlo model of the proton beam was designed in the simulation toolkit TOPAS to calculate the dose distributions in vivo and to correlate the outcome with proton dose and LET.
The geometric accuracy of proton irradiation, detailed dose simulations on mouse CT and cell-based assessment enable a biologically and spatially resolved analysis of short-term radiation response and RBE. In addition, the long-term follow up over six month provides first insights into the formation of normal tissue damage in mouse brain after PT.

  • Lecture (Conference) (Online presentation)
    digital-ERRs, 13.-17.09.2020, Lund, Sweden

Permalink: https://www.hzdr.de/publications/Publ-31470
Publ.-Id: 31470


Late side effects in normal mouse brain tissue after proton irradiation

Suckert, T.; Beyreuther, E.; Müller, J.; Azadegan, B.; Meinhardt, M.; Raschke, F.; Bodenstein, E.; von Neubeck, C.; Lühr, A.; Krause, M.; Dietrich, A.

Radiation induced late side effects such as cognitive decline and normal tissue complications can severely affect quality of life and outcome in long-term survivors of brain tumors. Proton therapy offers a favorable depth-dose deposition with the potential to spare tumor-surrounding normal tissue, thus potentially reducing such side effects. In this study, we describe a preclinical model to reveal underlying biological mechanisms caused by precise high-dose proton irradiation of a brain subvolume.
We studied the dose- and time-dependent radiation response of mouse brain tissue, using a high-precision image-guided proton irradiation setup for small animals established at the University Proton Therapy Dresden. The right hippocampal area of ten C57BL/6 and ten C3H/He mice was irradiated. Both strains consisted of four groups treated with increasing doses (0 – 85 Gy and 0 – 80 Gy, respectively). Follow-ups were performed up to six months, including longitudinal monitoring of general health status and regular contrast-enhanced magnetic resonance imaging (MRI) of mouse brains. These findings were related to comprehensive final histological analysis.
In mice of the highest dose group, first symptoms of blood-brain barrier (BBB) damage appeared one week after irradiation, while a dose-dependent delay in onset was observed for lower doses. MRI contrast agent leakage occurred in the irradiated brain areas and was progressive in the higher dose groups. Mouse health status and survival corresponded to the extent of contrast agent leakage. Histological analysis revealed tissue changes such as vessel abnormalities, gliosis, and granule cell dispersion, which also partly affected the non-irradiated contralateral hippocampus.
All observed effects depended strongly on the prescribed radiation doses and the outcome, i.e. survival, image changes and tissue alterations, within an experimental dose cohort was very consistent. A derived dose-response model will determine doses in future experiments and may support the formulation of clinical hypotheses on brain toxicity after proton therapy.

Keywords: Proton therapy; brain irradiation; preclinical mouse model; magnetic resonance imaging (MRI); late side effects; blood-brain barrier; brain tissue toxicity; radiation dose modelling

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Permalink: https://www.hzdr.de/publications/Publ-31469
Publ.-Id: 31469


Damages induced by synchrotron radiation-based X-ray microanalysis in chrome yellow paints and related Cr-compounds: assessment, quantification and mitigation strategies

Monico, L.; Cotte, M.; Vanmeert, F.; Amidani, L.; Janssens, K.; Nuyts, G.; Garrevoet, J.; Falkenberg, G.; Glatzel, P.; Romani, A.; Miliani, C.

Synchrotron radiation (SR)-based X-ray methods are powerful analytical tools for several purposes and we widely use them for probing the degradation mechanisms of inorganic artists’ pigments in paintings, including chrome yellows (PbCr1-xSxO4; 0 ≤x≤0.8), a class of compounds often found in Van Gogh masterpieces. However, the high intensity and brightness of SR beams raise important issues regarding potential damages of the analyzed samples. A thorough knowledge of the SR X-ray sensitivity of each class of pigment in the painting matrix is therefore required to find analytical strategies that contribute to minimize the damage for preserving the integrity of the analyzed sample and to avoid misinterpretation of the data. Here, we employ a combination of Cr K-edge X-ray absorption near edge structure (XANES) spectroscopy, Cr-Kβ X-ray emission spectroscopy (XES) and X-ray diffraction (XRD) to monitor and quantify the effects of SR X-rays on the stability of chrome yellows and related Cr-compounds and to define strategies for mitigating their damage. We found that the SR X-ray beam exposure induces changes in the oxidation state and local coordination environment of Cr-ions and leads to a loss of the compound’s crystalline structure. The extent of X-ray damage depends on some intrinsic properties of the samples (chemical composition of the pigment as well as the presence/absence and nature of the binder) and it can be minimized by optimizing the overall fluence/dose released to the samples and by working in vacuum and cryogenic conditions.

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Permalink: https://www.hzdr.de/publications/Publ-31468
Publ.-Id: 31468


Development of PSMA-1007 - Related Series of 18F-Labeled Glu-ureido type PSMA inhibitors.

Cardinale, J.; Roscher, M.; Schaefer, M.; Geerlings, M.; Benešová, M.; Bauder-Wüst, U.; Remde, Y.; Eder, M.; Novakova, Z.; Motlová, L.; Bařinka, C.; Giesel, F.; Kopka, K.

In recent years, a number of drugs targeting the prostate specific-membrane antigen (PSMA) have become important tools in the diagnosis and treatment of prostate cancer. In the present work, we report on the synthesis and preclinical evaluation of a series of 18F-labeled PSMA ligands for diagnostic application based on the theragnostic ligand PSMA-617. By applying modifications to the linker-structure, insight into the structure-activity relationship could be gained highlighting the importance of hydrophilicity and stereoselectivity on interaction with PSMA and hence the biodistribution. Selected compounds were co-crystallized with the PSMA-protein and analyzed by X-ray with mixed results. Amongst these, PSMA-1007 (compound 5) showed the best interaction with the PSMA protein. The respective radiotracer [18F]PSMA-1007 was translated into the clinic and is in the meantime subject of advanced clinical trials.

Keywords: PET Tracer; PSMA ligands; prostate cancer; PSMA-1007; PSMA inhibitors

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Permalink: https://www.hzdr.de/publications/Publ-31467
Publ.-Id: 31467


Atomic Physics in Particle in Cell Algorithms(PIC)

Marre, B. E.; Garten, M.; Bussmann, M.; Kluge, T.

Simulations allow us to get a detailed understanding of processes inside plasmas not directly accessible to experiments. They are therefore a very important tool for theoretical and experimental research and are continually being improved.
One improvement in development is the direct inclusion of atomic physics in Particle in Cell(PIC) simulations, a specific simulation technic used for non fluid-like plasmas.
In this talk I will describe possible approaches to realise atomic physics in PIC and give a short introduction to PIC algorithms and atomic physics in plasmas.

Keywords: atomic physics; particel in cell; Atomphysik in Plasmen; plasma; PIConGPU

  • Lecture (others)
    Numerics Seminar, 06.08.2020, Görlitz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-31466
Publ.-Id: 31466


P1826 - Calix[n]aren-Derivate zur Komplexierung von Erdalkalimetallkationen

Mamat, C.; Bauer, D.; Reissig, F.; Pietzsch, H.-J.; Steinbach, J.

Die Erfindung betrifft eine Verbindung, die

  • eine Calixaren-Einheit, die n Phenoleinheiten aufweist, wobei n 4, 5, 6 oder 8 ist;
  • eine Ethereinheit, die unter Ausbildung eines Kronenethers an die Calixaren-Einheit gebunden ist; und
  • zumindest eine Sulfonsäureamid-Einheit der Formel
-O-(CH)ₚ-C(O)-NH-S(O)₂-R¹
aufweist, wobei
die zumindest eine Sulfonsäureamid-Einheiten jeweils an die Calixaren-Einheit gebunden ist und R¹ jeweils aus der Gruppe ausgewählt ist, die aus einer perfluorierten verzweigten oder unverzweigten C₂-C₈-Alkylgruppe, einer perfluorierten Arylgruppe, und einer Gruppe Ar besteht, p eine Ganzzahl von 1 bis 4 ist und Ar eine Phenylgruppe ist, die mit einer oder mehreren perfluorierten verzweigten oder unverzweigten C₁-C₈-Alkylgruppen substituiert ist.
  • Patent
    DE102018132293 - Offenlegung 18.06.2020; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-31465
Publ.-Id: 31465


P1825 - Tomographievorrichtung und Tomographieverfahren

Iskander, K.; Bieberle, A.; Schleicher, E.

Die Erfindung betrifft eine Tomographievorrichtung und ein Tomographieverfahren zum Abbilden der inneren Struktur eines Untersuchungsobjekts, wobei aufeinanderfolgend in einer ersten, einer zweiten und einer dritten Scanebene Strahlung zum tomographischen Untersuchen des Untersuchungsobjekts erzeugt wird und die Strahlung mittels einer Detektorvorrichtung mit mehreren Detektorsegmenten erfasst wird, wobei jedes Detektorsegment einen in der ersten Scanebene angeordneten ersten Strahlungsdetektor, einen in der zweiten Scanebene angeordneten zweiten Strahlungsdetektor und einen in der dritten Scanebene angeordneten dritten Strahlungsdetektor zum Erfassen der Strahlung unter Erzeugung von Detektorsignalen aufweist, und wobei die Detektorsignale des ersten und des dritten Strahlungsdetektors mittels eines ersten Verstärkers verstärkt werden und die Detektorsignale des zweiten Strahlungsdetektors mittels eines zweiten Verstärkers verstärkt werden.

  • Patent
    DE102018131497 - Offenlegung 10.06.2020

Permalink: https://www.hzdr.de/publications/Publ-31464
Publ.-Id: 31464


P1824 - Rippenrohrwärmeübertrager mit konvexen Aussparungen der Rippenflächen und integrierten Materialaufdickungen

Unger, S.; Hampel, U.

Die Erfindung betrifft einen Wärmeübertrager mit wenigstens einer Trennwand und wenigstens von einer Seite der Trennwand abstehenden und die Oberfläche der Trennwand vergrößernden Oberflächenelementen, die von einem Fluid umströmbar sind. Dabei weisen die Oberflächenelemente Verstärkungswülste und zwischen den Verstärkungswülsten befindliche Flächenbereiche auf, wobei sich die Verstärkungswülste von der Trennwand ausgehend erstrecken und eine kreisrunde oder ovale Querschnittform haben. Die Verstärkungswülste erstrecken sich ausgehend von der Trennwand über mindestens einen Teil der Höhe des Oberflächenelementes und verjüngen sich von der Trennwand aus entlang der Höhe der Oberflächenelemente. Die Oberflächenelemente weisen eine Vielzahl konvexer Aussparungen auf, wobei jede der konvexen Aussparungen in einem der Flächenbereiche zwischen zwei Verstärkungswülsten angeordnet ist und sich von einer Außenkante des Oberflächenelementes erstreckt. Der Scheitelpunkt der konvexen Aussparung liegt bei einer Höhe größer als oder gleich 30% und kleiner als oder gleich 70% der gesamten Höhe des Oberflächenelementes, wobei die Höhe ausgehend von der Trennwand gemessen ist.

  • Patent
    DE102018129788 - Erteilung 24.10.2019; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-31463
Publ.-Id: 31463


P1823 - Pyrrolopyridin-Derivate und deren Verwendung

Moldovan, R.-P.; Fischer, S.; Ludwig, F.-A.; Deuther-Conrad, W.; Brust, P.

Die Erfindung betrifft eine Verbindung der allgemeinen Formel I worin Ar ein Pyridin-Ring ist; R¹ Wasserstoff oder Fluor ist; R² aus der Gruppe ausgewählt ist, die aus Wasserstoff, Hydroxy, Halogen, -CN, -NO₂, -N(R³R⁴), -(CR⁹R¹⁰)ₚ-C(O)-N(R⁵R⁶), -(CR⁹R¹⁰)q-CHO, -(CR⁹R¹⁰)r-C(O)-(CR⁹R¹⁰)s-R⁷, -(CR⁹R¹⁰)t-O-(CR⁹R¹⁰)v-R⁸ oder einer verzweigten oder unverzweigten, substituierten oder unsubstituierten C₁-C₁₂-Alkylgruppe besteht; R³, R⁴, R⁵, R⁶ und R⁷ unabhängig voneinander jeweils Wasserstoff oder eine verzweigte oder unverzweigte, substituierte oder unsubstituierte C₁-C₁₂-Alkylgruppe sind; R⁸ eine verzweigte oder unverzweigte, substituierte oder unsubstituierte C₁-C₁₂-Alkylgruppe ist; R⁹ und R¹⁰ unabhängig voneinander bei jedem Vorkommen Wasserstoff, Halogen, verzweigtes oder unverzweigtes, unsubstituiertes oder substituiertes C₁-C₁₂-Alkyl oder unsubstituiertes oder substituiertes C₂-C₆-Alkenyl sind; 1 1, 2, 3 oder 4 ist m 0, 1 oder 2 ist, mit der Maßgabe, dass 1 + m nicht größer als 4 ist; n 1, 2 oder 3 ist; und p, q, r, s, t und v unabhängig voneinander 0 oder eine Ganzzahl von 1 bis 6 sind. Außerdem ist eine Präkursor-Verbindung zur Herstellung einer Verbindung der Formel I vorgesehen, die anstelle einer Gruppe R¹ eine Abgangsgruppe aufweist.

  • Patent
    DE102018129693 - Offenlegung 28.05.2020; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-31462
Publ.-Id: 31462


P1821 - Markierungsvorläufer mit Quadratsäure-Kopplung

Bergmann, R.; Johannes-Gutenberg-Universität Mainz

Ein Markierungsvorläufer umfasst einen Chelator oder eine Fluorierungsgruppe für die Radiomarkierung mit ⁴⁴Sc, ⁴⁷Sc, ⁵⁵Co, ⁶²Cu, ⁶⁴Cu, ⁶⁷Cu, ⁶⁶Ga, ⁶⁷Ga, ⁶⁸Ga, ⁸⁹Zr, ⁸⁶Y, ⁹⁰Y, ⁹⁰Nb, ⁹⁹ᵐTc, ¹¹¹In, ¹³⁵Sm, ¹⁴⁰Pr, ¹⁵⁹Gd, ¹⁴⁹Tb, ¹⁶⁰Tb, ¹⁶¹Tb, ¹⁶⁵Er, ¹⁶⁶Dy, ¹⁶⁶Ho, ¹⁷⁵Yb, ¹⁷⁷Lu, ¹⁸⁶Re, ¹⁸⁸Re, ¹¹³Bi und ¹¹⁵Ac beziehungsweise mit ¹⁸F, ¹³¹I oder ¹¹¹At und einen oder zwei biologische Targetingvektoren, die über eine oder mehrere Quadratsäuregruppen mit dem Chelator oder der Fluorierungsgruppe gekoppelt sind.

  • Patent
    DE102018126558 - Offenlegung 30.04.2020; Nachanmeldungen: WO

Permalink: https://www.hzdr.de/publications/Publ-31461
Publ.-Id: 31461


P1820 - Tomographievorrichtung und Tomographieverfahren

Barthel, F.

Die Erfindung betrifft eine Tomographievorrichtung und ein Tomographieverfahren zum Abbilden der inneren Struktur eines Untersuchungsobjekts, wobei ein Elektronenstrahl derart über ein erstes Target mit mehreren Durchtrittsöffnungen geführt wird, dass der Elektronenstrahl nacheinander mehrere der Durchtrittsöffnungen überstreicht, wobei an dem ersten Target erste Röntgenstrahlung zum Durchstrahlen des Untersuchungsobjekts entsteht, wenn der Elektronenstrahl abseits der Durchtrittsöffungen auf das erste Target trifft, und wobei der Elektronenstrahl durch das erste Target hindurchtritt und mittels einer zwischen das erste Target und ein zweites Target angelegten elektrischen Spannung auf das zweite Target beschleunigt wird, wenn der Elektronenstrahl auf eine der Durchtrittsöffnungen gerichtet ist, wobei an dem zweiten Target zweite Röntgenstrahlung zum Durchstrahlen des Untersuchungsobjekts
entsteht.

  • Patent
    DE102018125822 - Erteilung 02.01.2020

Permalink: https://www.hzdr.de/publications/Publ-31460
Publ.-Id: 31460


Data for: Enantiomerically pure Tetravalent Neptunium Amidinates: Synthesis and Characterization

Fichter, S.; Kaufmann, S.; Kaden, P.; Brunner, T. S.; Stumpf, T.; Roesky, P. W.; März, J.

The synthesis of a tetravalent neptunium amidinate [NpCl((S)‐PEBA)3] (1) ((S)‐PEBA=(S,S)‐N,N′‐bis‐(1‐phenylethyl)‐benzamidinate) is reported. This complex represents the first structurally characterized enantiopure transuranic compound. Reactivity studies with halide/pseudohalides yielding [NpX((S)‐PEBA)3] (X=F (2), Br (3), N3 (4)) have shown that the chirality‐at‐metal is preserved for all compounds in the solid state. Furthermore, they represent an unprecedented example of a structurally characterized metal–organic Np complex featuring a Np−Br (3) bond. In addition, 4 is the only reported tetravalent transuranic azide. All compounds were additionally characterized in solution using para‐magnetic NMR spectroscopy showing an expected C3‐symmetry at low temperatures.

Keywords: transuranium chemistry; actinides; neptunium; coordination chemistry; amidinates

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Permalink: https://www.hzdr.de/publications/Publ-31459
Publ.-Id: 31459


How does iron storage protein ferritin interact with plutonium (and thorium) ?

Zurita, C.; Tsushima, S.; Bresson, C.; Garcia-Cortes, M.; Solari, P. L.; Jeanson, A.; Creff, G.; Den Auwer, C.

The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the 1950s. But to date still little is understood. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring and a ferrihydric core at the center. This work sheds light on the interactions of early actinides (Th, Pu) at oxidation state +IV with ferritin and its ability to store those elements at physiological pH compared to Fe. The Ferritin ‐ thorium load curve suggests that Th(IV) saturates the protein (2840 Th atoms per ferritin) in a similar way that Fe does on the protein ring. Complementary spectroscopic techniques (Spectrophotometry, Infrared Spectroscopy and X‐ray Absorption Spectroscopy) were combined with Molecular Dynamics to provide a structural model of the interaction of Th(IV) and Pu(IV) with ferritin. Comparison of spectroscopic data together with MD calculations suggests that Th(IV) and Pu(IV) are complexed mainly on the protein ring and not on the ferrihydric core. Indeed from XAS data, there is no evidence of Fe neighbors in the Th and Pu environments. On the other hand, carboxylates from amino acids of the protein ring and a possible additional carbonate anion are shaping the cation coordination spheres. This thorough description from a molecular view point of Th(IV) and Pu(IV) interaction with ferritin, an essential iron storage protein, is a cornerstone in comprehensive nuclear toxicology.

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Permalink: https://www.hzdr.de/publications/Publ-31457
Publ.-Id: 31457


Numerical ferromagnetic resonance experiments in nanosized elements

Wagner, K.; Körber, L.; Stienen, S.; Lindner, J.; Farle, M.; Kakay, A.

We present a numerical approach to obtain the Ferromagnetic Resonance (FMR) spectra of micrometer- and nano-sized magnetic elements by micromagnetic simulations. Mimicking common experimental conditions, a static magnetic field is applied and a linearly polarized oscillating magnetic field is used to excite magnetization dynamics. A continuous single-frequency excitation is utilized, which permits to study the steady-state dynamics in space- and time-domain. This gives direct access to resonance fields, line widths and relative amplitudes as observed in the experiments, which is not easily accessible in pulsed schemes and allows for a one-to-one identification between simulation and experiment. Similar to numerical approaches using pulsed excitations the phases, ellipticity and spatial mode profiles of the spin-wave excitations may also be accessed. Using large excitation powers we then showcase that one can additionally study nonlinear responses by this method such as the nonlinear shift of the resonance fields and the fold-over of the absorption lines. Since the dynamic susceptibility is directly determined from standard outputs of common micromagnetic codes, the presented method is robust, efficient and easy-to-use, adding to its practical importance.

Keywords: Ferromagnetic resonance; Micromagnetic simulations; line width; nonlinear; fold-over

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Permalink: https://www.hzdr.de/publications/Publ-31456
Publ.-Id: 31456


Non-linear Breit-Wheeler process with linearly polarized beams

Titov, A.; Kämpfer, B.

We study the non-linear Breit-Wheeler process γ⃗ ′+L⃗ →e++e− in the interaction of linearly polarized probe photons (γ⃗ ′) with a linearly polarized laser beam (L⃗ ). In particular, we consider the asymmetry of the total cross section and the azimuthal electron distributions when the polarizations of the photon and laser beams in the initial state are mutually perpendicular or parallel. Considering intense laser beams and the strong field asymptotic we explore essentially the multi-photon dynamics. The asymmetry exhibits some non-monotonic behavior depending on initial kinematic conditions; it depends sensitively on the laser pulse duration. Our results provide additional knowledge for studying non-linear multi-photon effects in quantum electrodynamics and may be used in planning experiments in upcoming laser facilities.

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Permalink: https://www.hzdr.de/publications/Publ-31455
Publ.-Id: 31455


Quarkonia formation in a holographic gravity-dilaton background describing QCD thermodynamics

Zöllner, R.; Kämpfer, B.

A holographic model of probe quarkonia is presented, where the dynamical gravity-dilaton background is adjusted to the thermodynamics of 2 +1 flavor QCD with physical quark masses. The quarkonia action is modified to account for a systematic study of the heavy-quark mass dependence. We focus on the J/ψ and Υ spectral functions and relate our model to heavy quarkonia formation as a special aspect of hadron phenomenology in heavy-ion collisions at LHC.

Permalink: https://www.hzdr.de/publications/Publ-31454
Publ.-Id: 31454


Brittle-ductile transition temperature of recrystallized tungsten following exposure to fusion relevant cyclic high heat load

Shah, V.; van Dommelen, J. A. W.; Altstadt, E.; Das, A.; Geers, M. G. D.

The lifetime of tungsten (W) monoblocks under fusion conditions is ambivalent. In this work, the microstructure dependent mechanical behaviour of pulsed high heat flux (HHF) exposed W monoblock is investigated. Two different microstructural states, i.e. initial (deformed) and recrystallized, both machined from HHF exposed monoblocks are tested using tensile and small punch tests. The initial microstructural state reveals a higher fraction of low angle boundaries along with a preferred orientation of crystals. Following HHF exposure, the recrystallized state exhibits weakening of initial texture along with a higher fraction of high angle boundaries. Irrespective of the testing methodology, both the microstructural states display brittle failure for temperatures lower than 400∘C. For higher temperatures (>400∘C), the recrystallized microstructure exhibits more ductile behaviour as compared to the initial state. The observed microstructural state-dependent mechanical behaviour is further discussed in terms of different microstructural features. The estimated brittle-to-ductile transition temperature (BDTT) range is noticed to be lower for the recrystallized state as compared to the initial state. The lower BDTT in the recrystallized state is attributed to the high purity of the W in combination with its low defect density, thereby preventing segregation of impurities at the recrystallized boundaries and the related premature failure. Based on this observation, it is concluded that the common opinion of the aggravation of BDTT in W due to recrystallization is not unerring, and as a matter of fact, recrystallization in W could be instrumental for preventing the self-castellation of the monoblocks.

Keywords: Tungsten; High heat flux exposure; Tensile test; Small punch test; Recrystallization and embrittlement; Brittle-to-ductile transition temperature

Permalink: https://www.hzdr.de/publications/Publ-31453
Publ.-Id: 31453


An integrated approach combining soil profile, records and tree ring analysis to identify the origin of environmental contamination in a former uranium mine (Rophin, France)

Martin, A.; Hassan-Loni, Y.; Fichtner, A.; Péron, O.; David, K.; Chardon, P.; Larrue, S.; Gourgiotis, A.; Sachs, S.; Arnold, T.; Grambow, B.; Stumpf, T.; Montavon, G.

Uranium mining and milling activities raise environmental concerns due to the release of radioactive and other toxic elements. Their long-term management thus requires a knowledge of past events coupled with a good understanding of the geochemical mechanisms regulating the mobility of residual radionuclides. This article presents the results on the traces of anthropic activity linked to previous uranium (U) mining activities in the vicinity of the Rophin tailings storage site (Puy de Dôme, France). Several complementary approaches were developed based on a study of the site's history and records, as well as on a radiological and chemical characterization of soil cores and a dendrochronology. Gamma survey measurements of the wetland downstream of the Rophin site revealed a level of 1050 nSv.h−1. Soil cores extracted in the wetland showed U concentrations of up to 1855 mg.kg−1, which appears to be associated with the presence of a whitish silt loam (WSL) soil layer located below an organic topsoil layer. Records, corroborated by prior aerial photographs and analyses of 137Cs and 14C activities, suggest the discharge of U mineral particles while the site was being operated. Moreover, lead isotope ratios indicate that contamination in the WSL layer can be discriminated by a larger contribution of radiogenic lead to total lead. The dendroanalysis correlate U emissions from Rophin with the site's history. Oak tree rings located downstream of the site contain uranium concentrations ten times higher than values measured on unaffected trees. Moreover, the highest U concentrations were recorded not only for the operating period, but more surprisingly for the recent site renovations as well. This integrated approach corroborates that U mineral particles were initially transported as mineral particles in Rophin's watershed and that amajority of the deposited uranium appears to have been trapped in the topsoil layer, with high organic matter content.

Keywords: Uranium mining; Wetland; Records; Dendroanalysis; Radiochronology; U decay chain

Permalink: https://www.hzdr.de/publications/Publ-31452
Publ.-Id: 31452


Photoluminescence and Raman Spectroscopy Study on Color Centers of Helium Ion-Implanted 4H–SiC

Song, Y.; Xu, Z.; Li, R.; Wang, H.; Fan, Y.; Rommel, M.; Liu, J.; Astakhov, G.; Hlawacek, G.; Li, B.; Xu, J.; Fang, F.

Color centers in silicon carbide (SiC) are promising candidates for quantum technologies. However, the richness of the poly-type and defect coniguration of SiC makes the accurate control of the types and position of defects in SiC still challenging. In this study, helium ion-implanted 4H–SiC was characterized by atomic force microscopy (AFM), confocal photoluminescence (PL), and Raman spectroscopy at room temperature. PL signals of silicon vacancy were found and analyzed using 638-nm and 785-nm laser excitation by means of depth proiling and SWIFT mapping. Lattice defects (C–C bond) were detected by continuous laser excitation at 532 nm and 638 nm, respectively. PL/Raman depth proiling is helpful in revealing the three-dimensional distribution of produced defects. Diferences in the depth proiling results and SRIM simulation results were explained by considering the depth resolution of the confocal measurement setup, helium bubbles, as well as swelling.

Keywords: Helium ion implantation; Silicon Carbid (SiC); Color Center; Point defect; Silicon vacancy; Confocal photoluminescence spectroscopy; Raman spectroscopy; Atomic force Microscopy (AFM); Helium Ion Microscopy

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Permalink: https://www.hzdr.de/publications/Publ-31451
Publ.-Id: 31451


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

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

We observe third-harmonic generation (THG) in boron-doped silicon (Si:B) upon pumping with picosecond 1.56 THz pulses from a free-electon laser with a peak electric field strength of up to 12 kV/cm. The measurements are performed at cryogenic temperatures where the majority of holes are bound to the acceptor dopants. The dependence of the THG on the pump intensity exhibits a threshold-free power-law behavior with an exponent close to 4. The observations can be explained by THz emission by free holes accelerated in the non-parabolic valence band, under the assumption that the density of free holes increases with the pump intensity. A quantitative treatment supports that these carriers are generated by impact ionization, initiated by the population of thermally ionized carriers , as opposed to direct tunneling ionization. In addition, we also observe intracavity THG by embedding the Si:B in a one-dimensional photonic crystal cavity. The THG efficiency is increased by a factor of eight due to the field enhancement in the cavity, with the potential to reach a factor of more than 100 for pump pulses with a spectrum narrower than the linewidth of the cavity resonance.

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Permalink: https://www.hzdr.de/publications/Publ-31450
Publ.-Id: 31450


Measurement of the 2H(p, γ)3He S-factor at 265 - 1094 keV

Turkat, S.; Hammer, S.; Masha, E.; Akhmadaliev, S.; Bemmerer, D.; Grieger, M.; Hensel, T.; Julin, J.; Koppitz, M.; Ludwig, F.; Möckel, C.; Reinicke, S.; Schwengner, R.; Stöckel, K.; Szücs, T.; Wagner, L.; Zuber, K.

Recent astronomical data have provided the primordial deuterium abundance with percent pre- cision. As a result, Big Bang nucleosynthesis may provide a constraint on the universal baryon to photon ratio that is as precise as, but independent from, analyses of the cosmic microwave back- ground. However, such a constraint requires that the nuclear reaction rates governing the production and destruction of primordial deuterium are sufficiently well known.
Here, a new measurement of the 2H(p,γ)3He cross section is reported. This nuclear reaction dominates the error on the predicted Big Bang deuterium abundance. A proton beam of 400- 1650keV beam energy was incident on solid titanium deuteride targets, and the emitted γ-rays were detected in two high-purity germanium detectors at angles of 55◦ and 90◦, respectively. The deuterium content of the targets has been obtained in situ by the 2H(3He,p)4He reaction and offline using the Elastic Recoil Detection method.
The astrophysical S-factor has been determined at center of mass energies between 265 and 1094 keV, addressing the uppermost part of the relevant energy range for Big Bang nucleosynthesis and complementary to ongoing work at lower energies. The new data support a higher S-factor at Big Bang temperatures than previously assumed, reducing the predicted deuterium abundance.

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Permalink: https://www.hzdr.de/publications/Publ-31449
Publ.-Id: 31449


Fate of contaminants from repositories for radioactive waste based in clay-rock?

Marques Fernandes, M.; Baeyens, B.; Daehn, R.; Scheinost, A. C.; Churakov, S. V.

Safe disposal of radioactive waste is one of the big challenges of modern society. The concept of final storage in deep geological formations has become internationally accepted as a means of safe waste management waste in order to isolate it from the Biosphere for hundreds of thousands of years. The safety case has hence to prove that migration from the disposal site into the Biosphere can be effectively prevented across this time span. The potential migration is primarily controlled by sorption/desorption processes onto mineral surfaces along the migration path. Clay minerals are major constituents in both the engineered barriers and in the argillaceous host rock formations being considered for the deep high-level radioactive waste (HLW) repository in Switzerland. Therefore it is critically important to develop an understanding of the uptake processes of radionuclides on clay minerals and other minerals under a wide range of relevant geochemical conditions, to quantify and characterize them with the aim of strengthening the confidence in the safety case. An overview of the work performed at the Laboratory for Waste Management on the retention of radionuclides on clay rich materials will be presented.

Keywords: nuclear waste; clay rock; XAFS; ROBL

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  • Invited lecture (Conferences) (Online presentation)
    18th Swiss Geoscience Meeting, 06.-07.11.2020, Zurich, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-31448
Publ.-Id: 31448


CRISPR/Cas9 mediated knockout of cyclooxygenase-2 gene inhibits invasiveness in A2058 melanoma cells

Haase-Kohn, C.; Laube, M.; Donat, C.; Belter, B.; Pietzsch, J.

The inducible isoenzyme cyclooxygenase-2 (COX-2) is an important hub in cellular signaling, which contributes to tumor progression by modulating and enhancing a pro-inflammatory tu-mor microenvironment, tumor growth, apoptosis resistance, angiogenesis, and metastasis. In order to understand the role of COX-2 expression in melanoma, we investigated the effect of functional knockout of COX-2 in A2058 human melanoma cells. COX-2 knockout was validated by western blot and flow cytometry analysis. When comparing COX-2 knockout cells to con-trols, we observed significantly reduced invasion, colony and spheroid formation potential in cell monolayers and three-dimensional models in vitro, and significantly reduced tumor devel-opment in xenograft mouse models in vivo. Moreover, COX-2 knockout alters the metabolic ac-tivity of cells under normoxia and experimental hypoxia as demonstrated by using the radio-tracers [18F]FDG and [18F]FMISO. Finally, a pilot protein array analysis in COX-2 knockout cells verified significantly altered downstream signaling pathways that can be linked to cellular and molecular mechanisms of cancer metastasis closely related to the enzyme. Given the complexity of the signaling pathways and the multifaceted role of COX-2, targeted suppression of COX-2 in melanoma cells, in combination with modulation of related signaling pathways, appears to be a promising therapeutic approach.

Keywords: chemosensitivity; CRISPR/Cas9-knockout; 3D-tumor spheroid models; malignant melanoma; radiosensitivity; selective COX-2 inhibitors; tumor hypoxia

Permalink: https://www.hzdr.de/publications/Publ-31447
Publ.-Id: 31447


Crystal structure, phase transition and properties of indium (III) sulfide

Wyżga, P.; Carrillo-Cabrera, W.; Akselrud, L.; Veremchuk, I.; Wagler, J.; Hennig, C.; Tsirlin, A.; Leithe-Jasper, A.; Kroke, E.; Gumeniuk, R.

Poly- and single-crystalline samples of In0.670.33In2S4 thiospinel were obtained by various powder metallurgical and chemical vapor transport methods, respectively. All synthesized samples contained β-In0.670.33In2S4 modification only, independent from synthesis procedure. High-resolution powder X-ray diffraction (PXRD) experiment at 80 K enabled observation of split tetragonal reflections (completely overlapped at room temperature), which proves the correctness of crystal structure model accepted for β-polymorph. Combined single-crystal XRD, transmission electron microscopy and selected-area electron diffraction confirmed the presence of three twin domains in as-grown crystals. High temperature PXRD study revealed both abrupt (in full width at half maximum) and gradual (in intensity of satellites, c/a ratio and unit-cell volume) changes in the vicinity of the α-β phase transition. On the other hand, clear thermal effect in heat capacity, magnitude of enthalpy/entropy change and temperature dependence of electrical resistivity, associated with hysteresis, hinted towards the 1st order type of the transition. Two scenarios, based on Rietveld refinement analysis, were proposed for the description of crystal structure evolution from β- to α-modification. Seebeck coefficient, electrical resistivity and thermal conductivity were shown to be influenced not only by phase transition, but also by annealing conditions (S-poor or S-rich atmosphere). Theoretical density functional calculations predicted n-type semiconducting behavior of In0.670.33In2S4, as well as instability of fictitious InIn2S4 thiospinel.

Keywords: In2S3; synchrotron diffraction; single-crystal diffraction; twinning; DFT calculations

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Permalink: https://www.hzdr.de/publications/Publ-31446
Publ.-Id: 31446


Anisotropic spin-acoustic resonance in silicon carbide at room temperature

Hernandez-Minguez, A.; Poshakinskiy, A. V.; Hollenbach, M.; Santos, P. V.; Astakhov, G.

We report on acoustically driven spin resonances in atomic-scale centers in silicon carbide at room temperature. Specifically, we use a surface acoustic wave cavity to selectively address spin transitions with magnetic quantum number differences of 1 and 2 in the absence of external microwave electromagnetic fields. These spin-acoustic resonances reveal a nontrivial dependence on the static magnetic field orientation, which is attributed to the intrinsic symmetry of the acoustic fields combined with the peculiar properties of a half-integer spin system. We develop a microscopic model of the spin-acoustic interaction, which describes our experimental data without fitting parameters. Furthermore, we predict that traveling surface waves lead to a chiral spin-acoustic resonance that changes upon magnetic field inversion. These results establish silicon carbide as a highly promising hybrid platform for on-chip spin-optomechanical quantum control enabling engineered interactions at room temperature.

Keywords: Spin qubits; surface acoustic waves; quantum technology; SiC

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Permalink: https://www.hzdr.de/publications/Publ-31445
Publ.-Id: 31445


Experimental and numerical analysis of the complex permittivity of open-cell ceramic foams

Hernandez, J. N. C.; Link, G.; Soldatov, S.; Füssel, A.; Schubert, M.; Hampel, U.

Open-cell ceramic foams are promising materials in the field of microwave heating. They can be manufactured from susceptor materials and can, therefore, be used as selective heating elements. In this study, the complex permittivities of ceramic foam materials, including silicon-infiltrated silicon carbide (SiSiC), pressureless sintered silicon carbide (SSiC), silicate bonded silicon carbide (SBSiC), and cordierite were determined. The dielectric properties of the foams were determined by the cavity perturbation technique using a TE104 WR340 waveguide resonator at 2.45 GHz. Samples were preheated in a tubular furnace, enabling temperature-dependent permittivity measurements up to 200 °C. The effective dielectric constant and effective loss factor were found to depend on the porosity and material composition of the foam. The SiSiC material had a higher effective dielectric constant than the SSiC and SBSiC ceramics. The effective dielectric constant of the foams showed a trend of gradual increase with increasing temperature. Some selected dielectric mixing relations were then applied to describe the effective permittivity of the foams and compare them with predictions from finite element simulations performed using the CST Studio Suite. The foam morphologies and simple block inclusions were used in the simulations.

Keywords: microwave processing; dielectric properties; silicon carbide; cordierite

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Publ.-Id: 31444


Dimensional crossover in spin Hall oscillators

Smith, A.; Sobotkiewich, K.; Khan, A.; Montoya, E. A.; Yang, L.; Duan, Z.; Schneider, T.; Lenz, K.; Lindner, J.; An, K.; Li, X.; Krivorotov, I. N.

Auto-oscillations of magnetization driven by direct spin current have been previously observed in multiple quasi-zero-dimensional (0D) ferromagnetic systems such as nanomagnets and nanocontacts. Recently, it was shown that pure spin Hall current can excite coherent auto-oscillatory dynamics in quasi-one-dimensional (1D) ferromagnetic nanowires but not in quasi-two-dimensional (2D) ferromagnetic films. Here we study the 1D to 2D dimensional crossover of current-driven magnetization dynamics in wire-based Pt/Ni80Fe20 bilayer spin Hall oscillators via varying the wire width.We find that increasing the wire width results in an increase of the number of excited auto-oscillatory modes accompanied by a decrease of the amplitude and coherence of each mode. We also observe a crossover from a hard to a soft onset of the auto-oscillations with increasing wire width. The amplitude of auto-oscillations rapidly decreases with increasing temperature suggesting that interactions of the phase-coherent auto-oscillatory modes with incoherent thermal magnons play an important role in suppression of the auto-oscillatory dynamics. Our measurements set the upper limit on the dimensions of an individual spin Hall oscillator and elucidate the mechanisms leading to suppression of coherent auto-oscillations with increasing oscillator size.

Keywords: Spin hall oscillators; ferromagnetism; spin currents; magnetization dynamics; spin waves

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Publ.-Id: 31443


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