Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34110 Publications

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

Publ.-Id: 31541

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.

Publ.-Id: 31534

Experimental gas phase hydrodynamic data of lab scale bubble column

Kipping, R.; Hampel, U.

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

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


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

Related publications

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


Publ.-Id: 31529

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

Mousley, M.; Moeller, 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

Publ.-Id: 31526

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.

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

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

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

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

Publ.-Id: 31514

4 f 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.


Publ.-Id: 31512

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

Podlipec, R.

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

Related publications

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


Publ.-Id: 31511

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

Podlipec, R.

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

Related publications

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


Publ.-Id: 31510

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

Publ.-Id: 31508

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

Podlipec, R.

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.

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


Publ.-Id: 31505

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

Publ.-Id: 31499

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

Scheinost, A. C.

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

Keywords: nuclear waste; XAFS; Redox

  • Invited lecture (Conferences) (Online presentation)
    GFZ Talk, 17.09.2020, Postdam, Germany

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.

Publ.-Id: 31497

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

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

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

Related publications

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


Publ.-Id: 31496

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

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

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

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

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


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


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


Publ.-Id: 31493

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

Publ.-Id: 31490

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

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

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

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

Publ.-Id: 31489

THz nonlinear electronic response in GaAs/InGaAs semiconductor nanowires

Schneider, H.

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

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

Publ.-Id: 31488

Ion-implanted Ge photoconductive antennae for terahertz emission

Schneider, H.

This talk does not have an abstract.

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

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.

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 A02 and A06 are essentially nonzero. A comparison with an isomorphous compound DyFe11Ti reveals a dramatic disparity of their crystal fields, especially as regards A44, nearly zero in SmFe11Ti but outstandingly large in DyFe11Ti.

Publ.-Id: 31485

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

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

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


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.


Publ.-Id: 31483

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.

Publ.-Id: 31479

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.

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.


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, Mao; 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.

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.

Publ.-Id: 31474

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

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.

  • 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
    DOI: 10.1142/11352

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

Publ.-Id: 31470

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

Publ.-Id: 31467

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
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

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

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

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

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

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

  • Patent
    DE102018125822 - Erteilung 02.01.2020

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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-08-27
    DOI: 10.14278/rodare.465
    License: CC-BY-4.0


Publ.-Id: 31459

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.

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

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, C.; 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 1855−1, 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

Publ.-Id: 31452

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.

Related publications


Publ.-Id: 31450

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

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


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


Publ.-Id: 31443

Liquid Metal Alloy Ion Sources for magnetic nano-structures

Bischoff, L.; Pilz, W.; Klingner, N.; Hlawacek, G.; Mazarov, P.; Meyer, F.

Focused Ion Beam (FIB) is a modern tool for µm and sub-µm structure fabrication and analysis. Commercial systems work mostly with a Gallium - Liquid Metal Ion Source (LMIS) and can achieve a resolution lower than 10 nm and current densities more than 10 Acm-2. The use of alloy LMIS, mainly developed at HZDR, opens a broad field of new applications. In combination with modern FIB systems, like the VELION (Raith) the application field can be extended due to a broad spectrum of available ion species in high resolution ion beams and the stage properties. All these aspects will be concentrated to the ZIM project GRANT No.-ZF4330902 DF7 dealing with the prospective modern topic of nano-magnetic structures from basic research up to new applications. Main topics are: i) the local modification of magnetic single nano-structures using a FIB with Co, Ni, Fe, … ions and ii) the fabrication and investigation of magnonic crystals, made by writing FIB implantation with rare earth ions (Nd, Dy, Ho, Er, …).

Keywords: Focused Ion Beam; ion sources; magnetic nanostructures; magnonic crystals

  • Lecture (others)
    Kick-off meeting, ZIM Project No.-ZF4494801 DF7, 14.-16.09.2020, Dortmund, Germany

Publ.-Id: 31442

Simulation of hard x-rays source produced by a picosecond laser irradiated solid target for Compton radiography

Meng-Ting, L.; Guang-Yue, H.; Huang, L.; Jian, Z.

A bremsstrahlung radiation hard x-ray source, produced by a picosecond intense laser irradiated solid target, was used to diagnose an implosion capsule at stagnation phase via Compton radiography in experiments. By performing Monte Carlo and particle-in-cell simulation, we investigated the influence of target materials and laser intensity on the >70 keV bremsstrahlung hard x-ray emission. We found that the brightness of the hard x-rays is proportional to the atomic number multiplied by area density (ZρL), which indicates that the higher Z and higher density gold or uranium material will produce the brightest hard x-rays source at the same thickness. In relativistic laser solid interactions, hot electron recirculation plays an important role in hard x-ray emission. Without recirculation, hard x-ray conversion efficiency decays when increasing the laser intensity. While the hard x-ray emission comes to the maximal saturated conversion efficiency at relativistic laser intensity if considering the electron recirculation.
These results provide valuable insights into the experimental design of Compton radiography

Keywords: Inertial confined fusion; Compton radiography; Numerical modeling


  • Secondary publication expected from 22.07.2021

Publ.-Id: 31440

Trapped-ion toolkit for studies of quantum harmonic oscillators under extreme conditions

Wittemer, M.; Schröder, J.-P.; Hakelberg, F.; Kiefer, P.; Fey, C.; Schützhold, R.; Warring, U.; Schaetz, T.

Many phenomena described in relativistic quantum field theory are inaccessible to direct observations, but analogue processes studied under well-defined laboratory conditions can present an alternative perspective. Recently, we demonstrated an analogy of particle creation using an intrinsically robust motional mode of two trapped atomic ions. Here, we substantially extend our classical control techniques by implementing machine-learning strategies in our platform and, consequently, increase the accessible parameter regime. As a proof of methodology, we present experimental results of multiple quenches and parametric modulation of an unprotected motional mode of a single ion, demonstrating the increased level of real-time control. In combination with previous results, we enable future experiments that may yield entanglement generation using a process in analogy to Hawking radiation. This article is part of a discussion meeting issue 'The next generation of analogue gravity experiments'.

Keywords: Trapped Ions; Qubits; Ion Traps (Instrumentation)

Publ.-Id: 31436

Prognostic value of baseline [18F]-fluorodeoxyglucose positron emission tomography parameters MTV, TLG and asphericity in an international multicenter cohort of nasopharyngeal carcinoma patients

Zschaeck, S.; Li, Y.; Lin, Q.; Beck, M.; Amthauer, H.; Bauersachs, L.; Hajiyianni, M.; Rogasch, J.; Ehrhardt, V. H.; Kalinauskaite, G.; Weingärtner, J.; Hartmann, V.; van den Hoff, J.; Budach, V.; Stromberger, C.; Hofheinz, F.


[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) parameters have shown prognostic value in nasopharyngeal carcinomas (NPC), mostly in monocenter studies. The aim of this study was to assess the prognostic impact of standard and novel PET parameters in a multicenter cohort of patients.

The established PET parameters metabolic tumor volume (MTV), total lesion glycolysis (TLG) and maximal standardized uptake value (SUVmax) as well as the novel parameter tumor asphericity (ASP) were evaluated in a retrospective multicenter cohort of 114 NPC patients with FDG-PET staging, treated with (chemo)radiation at 8 international institutions. Uni- and multivariable Cox regression and Kaplan-Meier analysis with respect to overall survival (OS), event-free survival (EFS), distant metastases-free survival (FFDM), and locoregional control (LRC) was performed for clinical and PET parameters.

When analyzing metric PET parameters, ASP showed a significant association with EFS (p = 0.035) and a trend for OS (p = 0.058). MTV was significantly associated with EFS (p = 0.026), OS (p = 0.008) and LRC (p = 0.012) and TLG with LRC (p = 0.019). TLG and MTV showed a very high correlation (Spearman’s rho = 0.95), therefore TLG was subesequently not further analysed. Optimal cutoff values for defining high and low risk groups were determined by maximization of the p-value in univariate Cox regression considering all possible cutoff values. Generation of stable cutoff values was feasible for MTV (p<0.001), ASP (p = 0.023) and combination of both (MTV+ASP = occurrence of one or both risk factors, p<0.001) for OS and for MTV regarding the endpoints OS (p<0.001) and LRC (p<0.001). In multivariable Cox (age >55 years + one binarized PET parameter), MTV >11.1ml (hazard ratio (HR): 3.57, p<0.001) and ASP > 14.4% (HR: 3.2, p = 0.031) remained prognostic for OS. MTV additionally remained prognostic for LRC (HR: 4.86 p<0.001) and EFS (HR: 2.51 p = 0.004). Bootstrapping analyses showed that a combination of high MTV and ASP improved prognostic value for OS compared to each single variable significantly (p = 0.005 and p = 0.04, respectively). When using the cohort from China (n = 57 patients) for establishment of prognostic parameters and all other patients for validation (n = 57 patients), MTV could be successfully validated as prognostic parameter regarding OS, EFS and LRC (all p-values <0.05 for both cohorts).

In this analysis, PET parameters were associated with outcome of NPC patients. MTV showed a robust association with OS, EFS and LRC. Our data suggest that combination of MTV and ASP may potentially further improve the risk stratification of NPC patients.

Publ.-Id: 31435

Unusual scandium enrichments of the Tørdal pegmatites, south Norway. Part I: Garnet as Sc exploration pathfinder

Steffenssen, G.; Müller, A.; Munnik, F.; Friis, H.; Erambert, M.; Kristoffersen, M.; Rosing-Schow, N.

The granitic pegmatites of the Tørdal area in southern Norway have been known for their Sc enrichment for about 100 years. Scandium is a compatible element in garnet. In this study, 32 garnet samples from 16 pegmatite localities across the Tørdal pegmatite field were investigated to determine the Sc distribution within garnets (crystal scale), within pegmatite bodies (pegmatite scale) and across the Tørdal pegmatite field (regional scale). In the Tørdal pegmatites, Sc content in garnet is representative for the Sc bulk composition of pegmatites, defining garnet as a reliable pathfinder mineral for the exploration of Sc mineralization in pegmatite fields. Garnets with highest Sc concentrations of up to 2197 µg/g have a spessartine component ranging from 50 to 60 mol.%. Since most garnets crystallized during the early stage of pegmatite formation (wall zone stage) Sc decreases in the remaining pegmatite melt, as documented by generally decreasing Sc from core to rim of crystals and by the occurrence of late-stage garnets (albite zone stage) with low Sc. Thus, with progressing crystallization Sc decreases in the melt. The regional Sc distribution in the Tørdal pegmatite field revealed that the Skardsfjell-Heftetjern-Høydalen pegmatites have highest Sc enrichments to sub-economic levels, with an average bulk Sc content of 53 µg/g and an average Sc content in garnet of about 1900 µg/g in the Heftetjern 2 pegmatite.
The assumed resources of the Skardsfjell-Heftetjern-Høydalen area are about 125,000 t ore grading c. 50 µg/g Sc resulting in a total of 625 t Sc, which is too small to have economic potential. However, the strong Sc enrichment of the Tørdal pegmatites is unusual for granitic pegmatites, making them a specific Sc deposit type. The amphibolitic host rocks of the Tørdal pegmatites are identified as the source rocks of Sc. The host rocks, which are part of the Nissedal Outlier supracrustals, are enriched in Sc (mean 34 µg/g) compared to average crustal compositions (mean 14 µg/g). Scandium of amphiboles was preferentially released at the onset of partial melting of the amphibolites. Thus, the Sc content in the pegmatite is strongly dependent on the degree of partial melting.

Keywords: scandium; pegmatite; garnet; Sveconorwegian orogeny; Tørdal

Publ.-Id: 31434

Coherent Optical Signatures of Electron Microbunching in Laser-Driven Plasma Accelerators

Lumpkin, A. H.; Laberge, M.; Rule, D. W.; Zgadzaj, R.; Hannasch, A.; Zarini, O.; Bowers, B.; Irman, A.; Couperus Cabadağ, J. P.; Debus, A.; Köhler, A.; Schramm, U.; Downer, M. C.

We report observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched∼200-MeV electrons as they emerge from a laser-driven plasma accelerator. The divergence of the microbunched portion of electrons, deduced by comparison to a COTRI model, is ∼9× smaller than the ∼3 mrad ensemble beam divergence, while the radius of the microbunched beam, obtained from COTR images on the same shot, is <3 μm. The combined results show that the microbunched distribution has estimated transverse normalized emittance∼0.4mm mrad.

Keywords: Beam diagnostics; LWFA; COTRI; CTR; transition radiation


Publ.-Id: 31431

Freestanding and Supported MoS2 Monolayers under Cluster Irradiation: Insights from Molecular Dynamics Simulation

Ghaderzadeh, S.; Ladygin, V.; Ghorbani Asl, M.; Hlawacek, G.; Schleberger, M.; Krasheninnikov, A.

Two-dimensional (2D) materials with nanometer-size holes are promising systems for DNA sequencing, water purification, and molecule selection/separation. However, controllable creation of holes with uniform sizes and shapes is still a challenge, especially when the 2D material consists of several atomic layers as, e.g., MoS2, the archetypical transition metal dichalcogenide.We use analytical potential molecular dynamics simulations to study the response of 2D MoS2tocluster irradiation. We model both freestanding and supported sheets and assess the amount of damage created in MoS2by the impacts of noble gas clusters in a wide range of cluster energies and incident angles. We show that cluster irradiation can be used to produce uniform holes in 2DMoS2with the diameter being dependent on cluster size and energy. Energetic clusters can also beused to displace sulfur atoms preferentially from either top or bottom layers of S atoms in MoS2and also clean the surface of MoS2sheets from adsorbents. Our results for MoS2, which should be relevant to other 2D transition metal dichalcogenides, suggest new routes toward cluster beam engineering of devices based on 2Dinorganic materials.

Keywords: two-dimensional materials; MoS2; cluster irradiation; pore formation; sputtering yield; atomistic simulation


  • Secondary publication expected from 28.07.2021

Publ.-Id: 31430

Drill-Core Hyperspectral and Geochemical Data Integration in a Superpixel-Based Machine Learning Framework

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tolosana Delgado, R.; Gloaguen, R.

The analysis of drill-core samples is one of the most important steps in the mining industry for the exploration and discovery of mineral resources. Geochemical assays are a common approach to represent the abundance of different chemical elements and aid at quantifying the concentrations of the important ore accumulations. However, their acquisition is time-consuming and usually averages of long core portions. Hyperspectral data are increasingly being used in the mining industry to complement the analysis of drill-cores due to their efficiency and fast turn-around time. Moreover, hyperspectral imaging is a technique able to provide data with high spatial resolution. In this article, we propose to integrate the complementary information derived from hyperspectral and geochemical data via a superpixel-based machine learning framework. This framework considers the difference in spatial resolution through segmentation. We extract labels from the geochemical assays and select, from the hyperspectral data, representative samples for each measurement. A supervised machine learning classification (composite kernel support vector machine) is then used to extrapolate the elements relative abundance to the entire core length. We propose an innovative integration of hyperspectral data covering different regions of the electromagnetic spectrum in a kernel-based framework to facilitate the identification of a larger amount of elements. A qualitative and quantitative evaluation of the results demonstrates the capabilities of the proposed method, which provides approximately 20% more accurate results than the pixel-based approach. Results also imply that the method could be beneficial for the reduction of geochemical assays needed for the detailed analysis of the cores.

Keywords: Data integration; drill-cores; geochemical data; hyperspectral data; machine learning; superpixel segmentation

  • Open Access Logo IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 13(2020), 4214-4228
    Online First (2020) DOI: 10.1109/JSTARS.2020.3011221

Publ.-Id: 31425

Mass Spectrum of Pseudo-Scalar Glueballs from a Bethe–Salpeter Approach with the Rainbow–Ladder Truncation

Kaptari, L. P.; Kämpfer, B.

We suggest a framework based on the rainbow approximation to the Dyson–Schwinger and Bethe–Salpeter equations with effective parameters adjusted to lattice QCD data to calculate the masses of the ground and excited states of pseudo-scalar glueballs. The structure of the truncated Bethe–Salpeter equation with the gluon and ghost propagators as solutions of the truncated Dyson–Schwinger equations is analyzed in Landau gauge. Both, the Bethe–Salpeter and Dyson–Schwinger equations, are solved numerically within the same rainbow–ladder truncation with the same effective parameters which ensure consistency of the approach. We found that with a set of parameters, which provides a good description of the lattice data within the Dyson–Schwinger approach, the solutions of the Bethe–Salpeter equation for the pseudo-scalar glueballs exhibit a rich mass spectrum which also includes the ground and excited states predicted by lattice calculations. The obtained mass spectrum contains also several intermediate excitations beyond the lattice approaches. The partial Bethe–Salpeter amplitudes of the pseudo-scalar glueballs are presented as well.


  • Secondary publication expected from 28.07.2021

Publ.-Id: 31424

Highly ordered silicide ripple patterns induced by medium-energy ion irradiation

Redondo-Cubero, A.; Palomares, F. J.; Hübner, R.; Gago, R.; Vázquez, L.

We study the nanopatterning of silicon surfaces under near-normal 40-keV Ar+ sputtering with simultaneous Fe oblique codeposition. The ion-beam incidence was kept at 15°, for which no pattern is produced in the absence of metal incorporation. Morphological and compositional analyses were performed by atomic force microscopy, in its morphological and electrical modes, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, scanning Auger, as well as transmission and scanning electron microscopy. Initially, nanodot structures randomly emerge, which, with increasing ion fluence, become progressively aligned along the perpendicular direction to the Fe flux. With increasing fluence, they coalesce, leading to a ripple pattern. The pattern dynamics and characteristics are faster and enhanced, respectively, as the distance to the metal source decreases (i.e., as the metal content increases). For the highest metal flux, the ripples can become rather large (up to 18 μm) and straighter, with few defects, and a pattern wavelength close to 500 nm, while keeping the surface roughness close to 15 nm. Furthermore, for a fixed ion fluence, the pattern order is improved for higher metal flux. In contrast, the pattern order enhancement rate with ion fluence does not depend on the metal flux. Our experimental observations agree with the predictions and assumptions of the model by Bradley [R. M. Bradley, Phys. Rev. B 87, 205408 (2013)] Several compositional and morphological studies reveal that the ripple pattern is also a compositional one, in which the ripple peaks have a higher iron silicide content, in agreement with the model. Likewise, the ripple structures develop along the perpendicular direction to the Fe flux, and the pattern wavelength increases as the metal flux decreases with a behavior qualitatively consistent with the model predictions.

Publ.-Id: 31422

Towards Bacteria Counting in DI Water of Several Microliters or Growing Suspension Using Impedance Biochips

Kiani, M.; Tannert, A.; Du, N.; Hübner, U.; Skorupa, I.; Bürger, D.; Zhao, X.; Blaschke, D.; Rebohle, L.; Cherkouk, C.; Neugebauer, U.; Schmidt, O. G.; Schmidt, H.

We counted bacterial cells of E. coli strain K12 in several-microliter DI water or in several-microliter PBS in the low optical density (OD) range (OD = 0.05-1.08) in contact with the surface of Si-based impedance biochips with ring electrodes by impedance measurements. The multiparameter fit of the impedance data allowed calibration of the impedance data with the concentration cb of the E. coli cells in the range of cb = 0.06 to 1.26 × 109 cells/mL. The results showed that for E. coli in DI water and in PBS, the modelled impedance parameters depend linearly on the concentration of cells in the range of cb = 0.06 to 1.26 × 109 cells/mL, whereas the OD, which was independently measured with a spectrophotometer, was only linearly dependent on the concentration of the E. coli cells in the range of cb = 0.06 to 0.50 × 109 cells/mL.

Publ.-Id: 31421

Sorption of trivalent actinides (Cm, Am) and their rare earth analogues (Lu, Y, Eu, Nd, La) onto orthoclase: Batch experiments, Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) and Surface Complexation Modeling (SCM)

Brinkmann, H.; Neumann, J.; Britz, S.; Brendler, V.; Stumpf, T.; Schmidt, M.

Sorption is one of the main processes, which determine the retention of radionuclides (RN) in a repository for nuclear waste. In a multi-barrier system, the host rock poses the ultimate barrier retarding the release of RN into the environment. Feldspars (e.g. orthoclase) are one of the main constituents of crystalline rock (e.g. granite), which is considered one potential host rock type in many countries (e.g. Finland, Sweden, Germany). In this study, the sorption of trivalent actinides (Cm, Am) and their rare earth analogues (Lu, Y, Eu, Nd, La) onto orthoclase (K feldspar) is investigated. For reliable predictions concerning the migration of RN, a process understanding on the molecular level of such processes is necessary. To achieve this, batch sorption experiments are combined with TRLFS and SCM.
Batch experiments were performed covering a broad range of experimental conditions (pH 4-11, oxic and anoxic conditions, [M3+] = 10-6-10-4 M, 3-50 g/L orthoclase (grain size: < 21 and 63-200 µm; SSA: 4.2 and 0.2 m2g-1)). Weak retardation below pH 5, followed by a strong increase between pH 5 and 7 and complete removal from solution at pH ≥ 8 was observed for all investigated metals. Cm- and Eu-TRLFS-measurements suggested the formation of an outer-sphere surface complex at lower (pH<5) and two different inner-sphere surface complexes at higher pH values (pH > 5 and pH > 7.5, respectively). Surface precipitation was observed for higher metal concentrations (10-4 M). As the investigated metals revealed a similar behavior over a broad range of conditions, a generic approach was used for the SCM to describe the system as a whole. Experimental data of different series with different metals were simultaneously fitted by coupling PHREEQC with UCODE using the same underlying speciation model. Resulting generic stability constants for the involved surface complexes will be presented.
The identification of comparable processes and their unified description with one suitable model is important to map the complexity of natural systems onto simplified geochemical models. This step is crucial for large-scale reactive transport calculations needed for a reliable safety assessment of potential repository sites, as they require enormous computing efforts.

Keywords: Actinides; Sorption; Orthoclase; Spectroscopy; Modeling

Publ.-Id: 31420

Studies of Big Data Processing at Linear Accelerator Sources Using Machine Learning

Bawatna, M.; Green, B. W.

In linear accelerator sources such as the electron beam of the super-conducting linear accelerator at the radiation source Electron Linear accelerator for beams with high Brilliance and low Emittance (ELBE), different kinds of secondary radiation can be produced for various research purposes from materials science up to medicine. A variety of different beam detectors generate a huge amount of data, which take a great deal of computing power to capture and analyse. In this contribution, we will discuss the possibilities of using Machine Learning method to solve the big data challenges. Moreover, we will present a technique that employ the machine learning strategy for the diagnostics of high-field terahertz pulses generated at the ELBE accelerator with extremely flexible parameters such as repetition rate, pulse form and polarization.

Keywords: Cloud computing; Machine learning; Big data; Deep neural networks

  • Contribution to proceedings
    Computer Science On-line Conference, CSOC 2020: Artificial Intelligence and Bioinspired Computational Methods, 20.-24.05.2020, Berlin, Germany
    Advances in Intelligent Systems and Computing, Volume 1225 AISC, 2020, Pages 450-460: Springer, 978-3-030-51970-4
    DOI: 10.1007/978-3-030-51971-1_37

Publ.-Id: 31417

Real-Time Data Compression System for Data-Intensive Scientific Applications Using FPGA Architecture

Bawatna, M.; Knodel, O.; Spallek, R.

Particle accelerators are continually advancing and offer insights into the world of molecules, atoms, and particles on the ever shorter length and timescales. A variety of detectors, which are connected to different front-end electronics are installed in various kinds of Data Acquisition (DAQ) systems, to collect a huge amount of raw data. This goes along with a rapid and highly accurate transformation of analog quantities into discrete values for electronic storage and processing with exponentially increasing amounts of data. Therefore, data reduction or compression is an important feature for the DAQ systems to reduce the size of the data transmission path between the detectors and the computing units or storage devices. The flexibility of the Field Programmable Gate Arrays (FPGAs) allows the implementation of real-time data compression algorithms inside these DAQ systems. In this contribution, we will present our developed real-time data compression technique for continuous data recorded by high-speed imaging detectors at the terahertz source facility at ELBE particle accelerator. The hardware implementation of the algorithm proved its real-time suitability by compressing one hundred thousand consecutive input signals without introducing dead time.

Keywords: Lossless data compression; FPGA; Real-time; Data-intensive

  • Contribution to proceedings
    Computer Science On-line Conference, Applied Informatics and Cybernetics in Intelligent Systems, 20.-24.05.2020, Berlin, Germany
    CSOC 2020: Applied Informatics and Cybernetics in Intelligent Systems: Springer, 978-3-030-51974-2, 304-313
    DOI: 10.1007/978-3-030-51974-2_29

Publ.-Id: 31416

Possibilities and Challenges for Reconfigurable Hardware and Cloud Architectures in Data-Intensive Scientific Applications

Bawatna, M.; Knodel, O.; Spallek, R.

Advances in process technology and new design tools have expanded the scope of embedded systems. This ranges from the implementation in several chips on board to module groups in integrated circuits. Reconfigurable hardware and, in particular, FPGAs are used more frequently in scientific applications, where they enable the development of complex and intelligent field devices. Furthermore, this increased the use of a platform-based design approach that facilitates the development and verification of complex FPGAs through the full reuse of hardware and software modules. Especially in the area of heterogeneous accelerators, which can improve the exploitation of modern data centers. Another critical aspect in the evolution of embedded systems is the trend towards networking embedded nodes using specialized computational and networking technologies called cloud computing. In this paper, we will present our data-intensive experiments at the terahertz source at ELBE accelerator-based light source, and its integration into a reproducible data management workflow at the heterogeneous cluster in our data centre

Keywords: Reconfigurable computing; cloud; data-intensive scientific applications

  • Contribution to proceedings
    Seventh International Conference on Software Defined Systems (SDS), 20.-23.04.2020, Paris, France
    Proceedings of Seventh International Conference on Software Defined Systems: IEEE, 978-1-7281-7218-7
    DOI: 10.1109/SDS49854.2020.9143904

Publ.-Id: 31415

In silico finding of key interaction mediated α3β4 and α7 nicotinic acetylcholine receptor ligand selectivity of quinuclidine-triazole chemotype

Arunrungvichian, K.; Chongruchiroj, S.; Sarasamkan, J.; Schüürmann, G.; Brust, P.; Vajragupta, O.

The selective binding of six (S)-quinuclidine-triazole and their (R)-enantiomers to nicotinic acetylcholine receptor (nAChR) subtypes α3β4 and α7, respectively, was analyzed by in silico docking to provide the insight into the molecular basis for the observed stereospecific subtype discrimination. Homology modeling follwed by molecular docking and molecular dynamics (MD) simulations revealed that unique amino acid residues in the complementary subunits of the nAChR subtypes are involved in subtype-specific selectivity profiles. In the complementary β4-subunit of the α3β4 nAChR binding pocket, non-conserved AspB173 through a salt bridge was found to be the key determinant for the α3β4 selectivity of the quinuclidine-triazole chemotype, explaining the 47-327-fold affinity of the (S)-enantiomers as compared to their (R)-enantiomer counterparts. Regarding the α7 nAChR subtype, the aminio acids promoting a however significantly lower preference for the (R)-enantiomers were the conserved TyrA93, TrpA149 and TrpB55 residues. The non-conserved amino acid residue in the complementary subunit of nAChR subtypes appeard to play a significant role for the nAChR subtype-selective binding, particularly at the heteropentameric subtype, wheras the conserved amino acid residues in both principal and complementary subunits are essential for ligand potency and efficacy.

Keywords: stereoselectivity; anti-1,2,3-triazole; α7 nAChR; α3β4 nAChR; quinuclidine

Publ.-Id: 31414

Data for: An analysis for detecting potential relocation of the inventory of dry storage containers during prolonged interim storage via changes in the wall temperature fields

Wagner, M.; Reinicke, S.

Geometry files of the performed simulations (ANSYS Fluent).

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-08-06
    DOI: 10.14278/rodare.416
    License: CC-BY-4.0


Publ.-Id: 31409

A convolutional neural network for fully automated blood SUV determination in oncological FDG-PET

Nikulin, P.; Hofheinz, F.; Maus, J.; Pietsch, J.; Li, Y.; Bütof, R.; Lange, C.; Furth, C.; Kreissl, M. C.; Kotzerke, J.; van den Hoff, J.

Aim: The standardized uptake value (SUV) is widely used for quantitative evaluation in oncological FDG-PET but has well-known shortcomings as a measure of the tumor's glucose consumption. The standard uptake ratio (SUR) of tumor SUV and arterial blood SUV (BSUV) possesses an increased prognostic value but requires image-based BSUV determination, typically in the aortic lumen. However, accurate manual ROI delineation requires care and imposes an additional workload which makes the SUR approach less attractive for clinical routine. The goal of the present work was the development of a fully automated method for BSUV determination in whole-body PET/CT.

Methods: Automatic delineation of the aortic lumen was performed with a convolutional neural network (CNN), namely U-Net. 632 FDG PET/CT scans from 4 different sites were used for network training (N=208) and testing (N=424). For all scans, the aortic lumen was manually delineated, avoiding areas affected by motion-induced attenuation artifacts or potential spill-over from adjacent FDG-avid regions. Performance of the network was assessed using the fractional deviations of automatically and manually derived BSUVs in the test data.

Results: The trained U-Net yields BSUVs in close agreement with those obtained from manual delineation. Notably, using both CT and PET data as input for network training allows the trained network to derive unbiased BSUVs by detecting and excluding aorta segments affected by attenuation artifacts or spill-over. Comparison of manually (M) and automatically (A) derived BSUVs shows excellent concordance: the mean paired M-A difference in the 424 test cases is (mean +/- SD)=(0.2 +/- 3.1)% with a 95% confidence interval of [-6.6, 5.7]%. For a single test case the M-A difference exceeded 10%.

Conclusion: CNNs offer a viable approach for automatic BSUV determination. Our trained network exhibits a performance comparable to an experienced human observer and might already be considered suitable for supervised clinical use.

Keywords: FDG-PET; standardized uptake value; SUV; standardized uptake ratio; SUR; convolutional neural network

  • Poster (Online presentation)
    Nuklearmedizin 2020, 07.-09.07.2020, Online, Online


Publ.-Id: 31407

Thermal kinetics of free volume in porous spin-on dielectrics: exploring the network- and pore-properties

Elsherif, A. G. A.; Koehler, N.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Ecke, R.; Schulz, S. E.; Wagner, A.

Comprehensive ex-situ and in-situ investigations of thermal curing processes in spin-on ultra-low-k thin films conducted by positron annihilation spectroscopy and Fourier transform infrared spectroscopies are presented. Positron annihilation lifetime spectroscopy of ex-situ cured samples reveals an onset of the curing process at about 200 °C, which advances with increasing curing temperature. Porogen agglomeration followed by diffusive migration to the surface during the curing process leads to the generation of narrow channels across the film thickness. The size of those channels is determined by a pore size distribution analysis of positron lifetime data. Defect kinetics during in-situ thermal curing has been investigated by means of Doppler broadening spectroscopy of the annihilation radiation, showing several distinct partially superposed and subsequent curing stages, i.e., moisture and residual organic solvents removal, SiOx network cross-linking, porogen decomposition, and finally creation of a stable porous structure containing micropore channels interconnecting larger mesopores formed likely due to micelle like interaction between porogen molecules, for curing temperatures not larger than 500 °C. Static (sequencing curing) states captured at specific temperature steps confirm the conclusions drawn during the dynamic (continuous curing) measurements. Moreover, the onset of pore inter-connectivity is precisely estimated as pore interconnectivity sets in at 380–400 °C.

Keywords: In-situ curing; Positron annihilation spectroscopy; Porogen removal; Porosimetry; FTIR; Dielectrics; Pore size distribution; Positronium

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Publ.-Id: 31402

Strengthening of ods silver wires

Wasserbäch, W.; Skrotzki, W.; Chekhonin, P.

The present work is part of an experimental program in which the mechanical behavior and the evolution of microstructure and texture of different industrially manufactured oxide-dispersion strengthened silver alloys upon different processing steps like hot-extrusion, cold-working and further annealing have been investigated. The investigations reveal that the incoherent oxide particles strongly influence the evolution of microstructure and texture during processing and consequently the deformation behavior at room temperature. Small oxide particles cause a high strengthening of the material but only a small change of the microstructure and texture. Increasing the oxide particle size subsequently reduces the strength and changes the original microstructure and texture in a more pronounced way. The yield strength at room temperature can be explained with a linear superposition of the Orowan stress for bypassing of oxide particles by dislocations and grain boundary strengthening according to Hall-Petch. The impact of texture of the materials on the yield strength is accounted for.

Keywords: Silver; Metal matrix composites; Cold-working; Strain hardening; Texture


  • Secondary publication expected from 09.07.2021

Publ.-Id: 31397

Atomic-Scale Carving of Nanopores into a van der Waals Heterostructure with Slow Highly Charged Ions

Schwestka, J.; Inani, H.; Tripathi, M.; Niggas, A.; Mcevoy, N.; Libisch, F.; Aumayr, F.; Kotakoski, J.; Wilhelm, R. A.

The growing family of 2D materials led not long ago to combining different 2D layers and building artificial systems in the form of van-der-Waals heterostructures. Tailoring of heterostructure properties post-growth would greatly benefit from a modification technique with a monolayer precision. However, appropriate techniques for material modification with this precision are still missing. To achieve such control, slow highly charged ions appear ideal as they carry high amounts of potential energy, which is released rapidly upon ion neutralization at the position of the ion. The resulting potential energy deposition is thus limited to just a few atomic layers (in contrast to the kinetic energy deposition). Here, we irradiated a freestanding van-der-Waals MoS2/graphene heterostructure with 1.3 keV/amu xenon ions in high charge states of 38, which led to nm-sized pores that appear only in the MoS2 facing the ion beam, but not in graphene beneath the hole. Reversing the stacking order leaves both layers undamaged, which we attribute to the high conductivity and carrier mobility in graphene acting as a shield for the MoS2 underneath. Our main focus is here on monolayer MoS2, but we also analyzed areas with few-layer structures, and observed that the perforation is limited to the two topmost MoS2 layers, whereas deeper layers remain intact. Our results demonstrate that in addition to already being a valuable tool for materials processing, the usability of ion irradiation can be extended to mono(or bi-)layer manipulation of van-der-Waals heterostructures when also the localized potential energy deposition of highly charged ions is added to the toolbox.

Keywords: 2d material modification; ion beam surface modification; monolayer precision; van der Waals heterostructure

Publ.-Id: 31392

The role of contaminations in ion beam spectroscopy with freestanding 2D materials: A study on thermal treatment

Niggas, A.; Schwestka, J.; Creutzburg, S.; Gupta, T.; Eder, D.; Bayer, B. C.; Aumayr, F.; Wilhelm, R. A.

As surface-only materials, freestanding 2D materials are known to have a high level of contamination—mostly in the form of hydrocarbons, water, and residuals from production and exfoliation. For well-designed experiments, it is of particular importance to develop effective clean- ing procedures, especially since standard surface science techniques are typically not applicable. We perform ion spectroscopy with highly charged ions transmitted through freestanding atomically thin materials and present two techniques to achieve clean samples, both based on thermal treatment. Ion charge exchange and energy loss are used to analyze the degree of sample contamination. We find that even after cleaning, heavily contaminated spots remain on single layer graphene. The contamination coverage, however, clusters in strand-like structures leaving large clean areas. We present a way to discriminate clean from contaminated areas with our ion beam spectroscopy if the heterogeneity of the surface is increased sufficiently enough. We expect a similar discrimination to be necessary in most other experimental techniques.

Publ.-Id: 31391

PIMC data for the nonlinear electronic density response in warm-dense matter (WDM)

Dornheim, T.

This repository contains the PIMC raw data for the actual density response of the harmonically perturbed electron gas.


The data can be freely re-used. Please cite:

T. Dornheim, J. Vorberger, and M. Bonitz, Nonlinear Electronic Density Response in Warm Dense Matter, Phys. Rev. Lett. (in press), arXiv:2004.03229

Keywords: PIMC, density response, warm dense matter

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-08-03
    DOI: 10.14278/rodare.408
    License: CC-BY-4.0


Publ.-Id: 31390

Tumor markers as an entry for SARS-CoV-2 infection?

Pu, X.; Dubrovska, A.

Coronavirus disease 2019 (COVID-19), the highly contagious illness caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread across the globe, becoming one of the most challenging public health crisis of our times. SARS-CoV-2 can cause severe disease associated with multiple organ damage. Cancer patients have a higher risk of SARS-CoV-2 infection and death. While the virus uses angiotensin-converting enzyme 2 (ACE2) as the primary entry receptor, the recent experimental and clinical findings suggest that some tumor markers, including CD147 (Basigin), can provide a new entry for SARS-CoV-2 infection through binding to the viral spike (S) protein. In the absence of specific viral drugs, blocking of CD147 might be a way to prevent virus invasion. Identifying other target proteins is of high importance as targeting the alternative receptors for SARS-CoV-2 might open up a promising avenue for the treatment of COVID-19 patients, including those who have cancer.

Keywords: SARS-CoV-2; COVID-19; CD147; Basigin; Emmprin; spike protein

Publ.-Id: 31388

Quantitative isotopic fingerprinting of thallium associated with potentially toxic elements (PTEs) in fluvial sediment cores with multiple anthropogenic sources

Liu, J.; Zhou, Y.; She, J.; Tsang, D. C. W.; Lippold, H.; Wang, J.; Jiang, Y.; Wei, X.; Yuan, W.; Luo, X.; Zhai, S.; Song, L.

Thallium (Tl) is a dispersed trace metal showing remarkable toxicity. Various anthropogenic activities may generate Tl contamination in river sediments, posing tremendous risks to aquatic life and human health. This paper aimed to provide insight into the vertical distribution, risk assessment and source tracing of Tl and other potentially toxic elements (PTEs) (lead, cadmium, zinc and copper) in three representative sediment cores from a riverine catchment impacted by multiple anthropogenic activities (such as steel-making and Pb-Zn smelting). The results showed high accumulations of Tl combined with associated PTEs in the depth profiles. Calculations according to three risk assessment methods by enrichment factor (EF), geoaccumulation index (Igeo) and the potential ecological risk index (PERI) all indicated a significant contamination by Tl in all the sediments. Furthermore, lead isotopes were analyzed to fingerprint the contamination sources and to calculate their quantitative contributions to the sediments using the IsoSource software. The results indicated that a steel-making plant was the most important contamination source (~56%), followed by a Pb-Zn smelter (~20%). The natural parental bedrock was found to contribute ~24%. The findings highlight the importance of including multiple anthropogenic sources for quantitative fingerprinting of Tl and related metals by the lead isotopic approach in complicated environmental systems.

Keywords: Thallium contamination; Spatial distribution; Pollution risk assessment; Multiple end-members; Isotopic tracing

Publ.-Id: 31386

Data for: The influence of negatively charged silica nanoparticles on the surface properties of anionic surfactants: electrostatic repulsion or the effect of ionic strength?

Eftekhari, M.; Schwarzenberger, K.; Javadi, A.; Eckert, K.

The presence of negatively charged nanoparticles affects the surface activity of anionic surfactants in an aqueous phase. Recent studies suggest that electrostatic repulsive forces play an important role in increasing the surface activity of surfactants. However, the addition of nanoparticles also increases the ionic strength of the system, which has a significant impact on the surfactant's properties, e.g. its critical micelle concentration (CMC). To investigate how and to what extent electrostatic forces and ionic strength influence the behavior of ionic surfactants, the surface tension and elasticity of different solutions were measured using drop profile tensiometry as a function of the surfactant (SDBS), nanoparticle (silica) and salt (KNO3) concentration. It is observed that the surface activity of the surfactants is mainly influenced by the change in the system's ionic strength due to the presence of nanoparticles. Several characteristic parameters including the equivalent concentration of the surfactant, the CMC and the apparent partial molar area of the adsorbed surfactant are theoretically calculated and further employed to validate experimental observations. Both the nanoparticles and electrolyte decrease the CMC, while the equivalent concentration of the surfactant remains nearly constant. This paper presents a criterion to estimate the possible influence of such forces for nanoparticles of different sizes and mass fractions.

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    Publication date: 2020-01-09
    DOI: 10.14278/rodare.406


Publ.-Id: 31383

All-THz pump-probe spectroscopy of the intersubband AC-Stark effect in a wide GaAs quantum well

Schmidt, J.; Winnerl, S.; Dimakis, E.; Hübner, R.; Schneider, H.; Helm, M.

We report the observation of the intersubband AC-Stark effect in a single wide GaAs/AlGaAs quantum well. In a three-level configuration, the n = 2 to n = 3 intersubband transition is resonantly pumped at 3:5 THz using a free-electron laser. The induced spectral changes are probed using THz time-domain spectroscopy with a broadband pulse extending up to 4 THz. We observe an Autler Townes splitting at the 1 -> 2 intersubband transition as well as an indication of a Mollow triplet at the 2 -> 3 transition, both evidencing the dressed states. For longer delay times, a relaxation of the hot-electron system with a time constant of around 420 ps is measured.

Keywords: AC Stark effect, Autler Townes splitting, high-field physics, intersubband transitions

Publ.-Id: 31382

Practice recommendations for lung cancer radiotherapy during the COVID-19 pandemic: An ESTRO-ASTRO consensus statement

Troost, E. G. C.; Nestle, U.; Putora, P.; Bussink, J.

COVID-19 Rapid Letter

Publ.-Id: 31378

Nonlinear Electronic Density Response in Warm Dense Matter

Dornheim, T.; Vorberger, J.; Bonitz, M.

Warm dense matter (WDM)—an extreme state with high temperatures and densities that occurse.g. in astrophysical objects—constitutes one of the most active fields in plasma physics and materials science. These conditions can be realized in the lab by shock compression or laser excitation, and the most accurate experimental diagnostics is achieved with lasers and free electron lasers which is theoretically modeled using linear response theory. Here, we present first ab initio path integral Monte Carlo results for the nonlinear density response of correlated electrons in WDM and show that for many situations of experimental relevance nonlinear effects cannot be neglected.

Keywords: Warm dense matter; Nonlinear effects; path integral Monte Carlo

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Publ.-Id: 31377

Benchmark hyperspectral field and laboratory data against X-ray diffraction (XRD), Portable X-ray fluorescence (pXRF) and Scanning Electron Microscopy with Mineral Liberation Analysis (SEM-MLA) data.

de La Rosa Ferna; Tolosana Delgado, R.; Gloaguen, R.

A benchmarking databank based on different spectral, multiscale, multisensor exploration technologies was created. The benchmarking is composed of 63 rock samples from drill cores from a polymetallic (Cu-Zn-Pb) massive sulphide deposit in the Iberian Pyrite Belt. The samples had been analyzed by portable XRF, point hyperspectral spectrometer, portable FTIR, VNIR-SWIR imaging hyperspectral sensor and a LWIR imaging thermal hyperspectral sensor.

The mineralogical information from the boreholes will be complemented with mineral chemistry extracted from the spectral features of the alteration minerals that display chemical variations. The chemical variations in minerals generate shifts on the position of the metal-OH vibrational absorptions. This systematic variation can be recorded using the SWIR wavelength region of hyperspectral data. The shifts sometimes occur systematically with respect to ore deposits and hence mineral chemical information extracted from hyperspectral surveys can be used for mineral exploration. The mineral chemistry of the samples will be validated using scanning electron microscopy data integrated with the mineral liberation analysis (SEM-MLA).

In order to apply this type of research techniques aiming at a 3D model of the alteration areas of the entire deposit based on the hyperspectral data, it is essential to have the availability of drill cores along the whole extension of the mineral deposit. Consequently, the research was focused in a study area in the Southern Spain, the Elvira deposit of the MATSA–VALORIZA mining company, where 7 km of drill core were scanned with the hyperspectral sensors.

New exploration technologies (NEXT) is a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement nº 776804.

Keywords: Benchmarking; Hyperspectral; Drill core scanner; pFTIR; PXRF; VNIR - SWIR - LWIR

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-07-02
    DOI: 10.14278/rodare.392


Publ.-Id: 31373

Advanced Sandwich Composite Cores for Patient Support in Advanced Clinical Imaging and Oncology Treatment

Morris, R. H.; Geraldi, N. R.; Pike, L. C.; Pawelke, J.; Hoffmann, A. L.; Doy, N.; Stafford, J. L.; Spicer, A.; Newton, M. I.

Ongoing advances in both imaging and treatment for oncology purposes have seen a significant rise in the use of not only the individual imaging modalities, but also their combination in single systems such as PET-CT and PET-MRI when planning for advanced oncology treatment, the most demanding of which is proton therapy. This has identified issues in the availability of suitable materials upon which to support the patient undergoing imaging and treatment owing to the differing requirements for each of the techniques. Sandwich composites are often selected to solve this issue but there is little information regarding optimum materials for their cores. In this paper we present a range of materials which are suitable for such purposes and evaluate the performance for use in terms of PET signal attenuation, proton beam stopping, MRI signal shading and X-Ray CT visibility. We find that Extruded Polystyrene offers the best compromise for patient support and positioning structures across all modalities tested, allowing for significant savings in treatment planning time and delivering more efficient treatment with lower margins.

Keywords: Composite; Core; Clinical imaging; PET; CT; MRI; Proton

Publ.-Id: 31372

Brain geometry matters in Alzheimer disease progression: a simulation study

Hoore, M.; Kelling, J.; Sayadmanesh, M.; Mitra, T.; Schips, M.; Meyer-Hermann, M.

The Amyloid cascade hypothesis (ACH) for Alzheimer's disease (AD) is modeled over the whole brain tissue with a set of partial differential equations. Our results show that the amyloid plaque formation is critically dependent on the secretion rate of amyloid β(Aβ), which is proportional to the product of neural density and neural activity. Neural atrophy is similarly related to the secretion rate of Aβ. Due to a heterogeneous distribution of neural density and brain activity throughout the brain, amyloid plaque formation and neural death occurs heterogeneously in the brain. The geometry of the brain and microglia migration in the parenchyma bring more complexity into the system and result in a diverse amyloidosis and dementia pattern of different brain regions. Although the pattern of amyloidosis in the brain cortex from in-silico results is similar to experimental autopsy findings, they mismatch at the central regions of the brain, suggesting that ACH is not able to explain the whole course of AD without considering other factors, such as tau-protein aggregation or neuroinflammation.

Keywords: Neurdegenerative disease; Alzheimer's disease; Amyloid cascade hypothesis; mult-phase model


Publ.-Id: 31371

Multiscale Tomographic Analysis for Micron-Sized Particulate Samples

Ditscherlein, R.; Furat, O.; de Langlard, M.; Martins De Souza E. Silva, J.; Sygusch, J.; Rudolph, M.; Leißner, T.; Schmidt, V.; Peuker, U. A.

The three-dimensional characterization of distributed particle properties in the micro- and nanometer range is essential to describe and understand highly specific separation processes in terms of selectivity and yield. Both performance measures play a decisive role in the development and improvement of modern functional materials. In this study, we mixed spherical glass particles (0.4–5.8 μm diameter) with glass fibers (diameter 10 μm, length 18–660 μm) to investigate a borderline case of maximum difference in the aspect ratio and a significant difference in the characteristic length to characterize the system over several size scales. We immobilized the particles within a wax matrix and created sample volumes suitable for computed tomographic (CT) measurements at two different magnification scales (X-ray micro- and nano-CT). Fiber diameter and length could be described well on the basis of the low-resolution micro-CT measurements on the entire sample volume. In contrast, the spherical particle system could only be described with sufficient accuracy by combining micro-CT with high-resolution nano-CT measurements on subvolumes of reduced sample size. We modeled the joint (bivariate) distribution of fiber length and diameter with a parametric copula as a basic example, which is equally suitable for more complex distributions of irregularly shaped particles. This enables us to capture the multidimensional correlation structure of particle systems with statistically representative quantities.

Keywords: multidimensional particle characterization; multiscale X-ray tomography; parametric copula; statistical image analysis

Publ.-Id: 31370

Yu-Shiba-Rusinov bands in ferromagnetic superconducting diamond

Zhang, G.; Samuely, T.; Iwahara, N.; Kačmarčík, J.; Wang, C.; May, P. W.; Jochum, J. K.; Onufriienko, O.; Szabó, P.; Zhou, S.; Samuely, P.; Moshchalkov, V. V.; Chibotaru, L. F.; Rubahn, H.-G.

The combination of different exotic properties in materials paves the way for the emergence of their new potential applications. An example is the recently found coexistence of the mutually antagonistic ferromagnetism and superconductivity in hydrogenated boron-doped diamond, which promises to be an attractive system with which to explore unconventional physics. Here, we show the emergence of Yu-Shiba-Rusinov (YSR) bands with a spatial extent of tens of nanometers in ferromagnetic superconducting diamond using scanning tunneling spectroscopy. We demonstrate theoretically how a two-dimensional (2D) spin lattice at the surface of a three-dimensional (3D) superconductor gives rise to the YSR bands and how their density-of-states profile correlates with the spin lattice structure. The established strategy to realize new forms of the coexistence of ferromagnetism and superconductivity opens a way to engineer the unusual electronic states and also to design better-performing superconducting devices.

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    Publication date: 2020-05-25
    DOI: 10.14278/rodare.341
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Publ.-Id: 31369

Tailoring Magnetic Features in Zigzag-Edged Nanographenes by Controlled Diels–Alder Reactions

Ajayakumar, M.; Fu, Y.; Liu, F.; Komber, H.; Tkachova, V.; Xu, C.; Zhou, S.; Popov, A.; Liu, J.; Feng, X.

Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0=0.72; half-life, t1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y0=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.

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    Publication date: 2020-05-25
    DOI: 10.14278/rodare.343
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Publ.-Id: 31366

Dynamics of Bubble Formation at Micro-orifices under Constant Gas Flow Conditions

Mohseni, E.; Jose Kalayathine, J.; Reinecke, S.; Hampel, U.

Fine gas dispersion into a liquid is requested in a number of industrial applications. One way to achieve fine gas dispersion is to downsize the openings from which gas bubbles are generated. Accordingly, we have investigated the dynamics of bubble formation from submerged orifices ranging from 0.04 to 0.8 mm at a comprehensive range of gas flow rates for a system of air and deionized water. In this range of orifice size, we observe a different mechanism of bubble formation compared with millimeter-range orifices. We discuss the observations on the basis of temporal change of the bubble shape, bubble base expansion, and detachment criteria. At submillimeter orifices, the mechanism of bubble formation is highly influenced by the capillary pressure and the gas kinetic energy. The latter results in congregation of small bubbles in the vicinity of the orifice, even at very small gas flow rates. Moreover, we studied the evolution of individual forces applied to the surface of bubbles during their formation. We have found that the formation of bubbles at submillimeter orifices cannot be described with a quasi-static force balance. Finally, we present a bubbling regime map using relevant dimensionless numbers.

Keywords: Bubble Formation; Submillimeter Orifices; Bubbling Regime; Bubbling Dynamics; Stainless Steel Orifice

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Publ.-Id: 31363

Magnetocaloric effect in GdNi2 for cryogenic gas liquefaction studied in magnetic fields up to 50 T

Taskaev, S.; Khovaylo, V.; Skokov, K.; Liu, W.; Bykov, E.; Ulyanov, M.; Bataev, D.; Basharova, A.; Kononova, M.; Plakhotskiy, D.; Bogush, M.; Gottschall, T.; Gutfleisch, O.

Natural gases have played a significant role in different sectors of the global economy. Recent analyses have shown that the world’s gas consumption doubled over the last three decades; further growth of the gas consumption is predicted, rising to be 23%–28% of the total primary energy demand by 2030. Therefore, liquefaction of natural gases rapidly gains global importance. In this context, magnetic refrigeration emerges as a modern energy-saving technique, which is an alternative to the traditional gas-compression refrigeration. This paper is devoted to the study of the magnetocaloric effect in magnetic fields up to 10 T on a representative of the Laves phase alloys, GdNi2, which is considered as a perspective material for liquefaction of natural gases. For a magnetic field change of 10 T, the magnetic entropy change ΔSm≈−17 J/kg K and the adiabatic temperature change ΔTad ≈ 6.8 K was attained around Curie temperature TC = 70 K. The maximal value of the adiabatic temperature change measured directly in pulsed magnetic fields up to 50 T is ΔTad ≈ 15 K.

Publ.-Id: 31361

Effect of uniaxial stress on the electronic band structure of NbP

Schindler, C.; Noky, J.; Schmidt, M.; Felser, C.; Wosnitza, J.; Gooth, J.

The Weyl semimetal NbP exhibits a very small Fermi surface consisting of two electron and two hole pockets, whose fourfold degeneracy in k space is tied to the rotational symmetry of the underlying tetragonal crystal lattice. By applying uniaxial stress, the crystal symmetry can be reduced, which successively leads to a degeneracy lifting of the Fermi-surface pockets. This is reflected by a splitting of the Shubnikov–de Haas frequencies when the magnetic field is aligned along the c axis of the tetragonal lattice. In this study, we present the measurement of Shubnikov–de Haas oscillations of single-crystalline NbP samples under uniaxial tension, combined with state-of-the-art calculations of the electronic band structure. Our results show qualitative agreement between calculated and experimentally determined Shubnikov–de Haas frequencies, demonstrating the robustness of the band-structure calculations upon introducing strain. Furthermore, we predict a significant shift of the Weyl points with increasing uniaxial tension, allowing for an effective tuning to the Fermi level at only 0.8% of strain along the a axis.

Publ.-Id: 31360

Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation

Konstantinovic, M. J.; Ulbricht, A.; Brodziansky, T.; Castin, N.; Malerba, L.

Origin-files, data for figure 3 and figure 4 of publication in J. Nucl. Mater.

Keywords: Neutron irradiation, FeCr alloys and steels

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    Publication date: 2020-07-21
    DOI: 10.14278/rodare.400
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Publ.-Id: 31356

CFD Modeling and Experimental Validation of Top-Submerged-Lance Gas Injection in Liquid Metal

Reuter, M. A.; Akashi, M.; Kriebitzsch, S.; Meyer, B.; Obiso, D.; Eckert, S.; Richter, A.

In the present work, the dynamics of a downward gas injection into a liquid metal bath is studied using a numerical modeling approach, and validated with experimental data. As in a top-submerged-lance (TSL) smelter, gas is injected through the lance into the melt. By this means, the properties of the liquid are closer to the actual industrial process than the typically used water/glycerol–air/helium systems. The experimental activity was carried out in a quasi-2D vessel (144 x 144 x 12 mm3) filled with GaInSn, a metal alloy with eutectic at room temperature. Ar was used as the inert gas. The structure and behavior of the gas phase were visualized and quantitatively analyzed by X-ray radiography and high-speed imaging. Computational Fluid Dynamics (CFD) was applied to simulate the multiphase flow in the vessel and the Volume Of Fluid (VOF) model chosen to track the interface using a geometric reconstruction of the interface. Three different vertical lance positions were investigated, applying a gas flow rate of Qgas = 6850 cm³/min: The CFD model is able to predict the bubble detachment frequency, the average void fraction distributions, and the bubble size and hydrodynamic behavior, demonstrating its applicability to simulate such complex multiphase systems. The use of numerical models also provides a deep insight into fluid dynamics to study particular phenomena such as bubble break-up and free surface oscillations.

Keywords: top-submerged-lance (TSL),; X-ray,; Computational Fluid Dynamics (CFD),; Volume Of Fluid (VOF),

Publ.-Id: 31353

Engineering telecom single-photon emitters in silicon for scalable quantum photonics

Hollenbach, M.; Berencen, Y.; Kentsch, U.; Helm, M.; Astakhov, G.

We create and isolate single-photon emitters with a high brightness approaching 10⁵ counts per second in commercial silicon-on-insulator (SOI) wafers. The emission occurs in the infrared spectral range with a spectrally narrow zero phonon line in the telecom O-band and shows a high photostability even after days of continuous operation. The origin of the emitters is attributed to one of the carbon-related color centers in silicon, the so-called G center, allowing purification with the ¹²C and ²⁸Si isotopes. Furthermore, we envision a concept of a highly-coherent scalable quantum photonic platform, where single-photon sources, waveguides and detectors are integrated on the same SOI chip. Our results provide a route towards the implementation of quantum processors, repeaters and sensors compatible with the present-day silicon technology.

Keywords: Signe photon source; telecommunication window; silicon photonics; quantum communication; color centers

Publ.-Id: 31352

Adenosine/A2B Receptor Signaling Ameliorates the Effects of Aging and Counteracts Obesity

Gnad, T.; Navarro, G.; Lahesmaa, M.; Reverte-Salisa, L.; Copperi, F.; Cordomi, A.; Naumann, J.; Hochh€Auser, A.; Haufs-Brusberg, S.; Wenzel, D.; Suhr, F.; Zenius Jespersen, N.; Scheele, C.; Tsvilovskyy, V.; Brinkmann, C.; Rittweger, J.; Dani, C.; Kranz, M.; Deuther-Conrad, W.; Eltzschig, H. K.; Niemi, T.; Taittonen, M.; Brust, P.; Nuutila, P.; Pardo, L.; Fleischmann, B. K.; Bleuher, M.; Franco, R.; Bloch, W.; Virtanen, K. A.; Pfeifer, A.

The combination of aging populations with the obesity pandemic results in an alarming rise in non-communicable diseases. Here, we show that the enigmatic adenosine A2B receptor (A2B) is abundantly expressed in skeletal muscle (SKM) as well as brown adipose tissue (BAT) and might be targeted to counteract age-related muscle atrophy (sarcopenia) as well as obesity. Mice with SKM-specific deletion of A2B exhibited sarcopenia, diminished muscle strength, and reduced energy expenditure (EE), whereas pharmacological A2B activation counteracted these processes. Adipose tissue-specific ablation of A2B exacerbated age-related processes and reduced BAT EE, whereas A2B stimulation ameliorated obesity. In humans, A2B expression correlated with EE in SKM, BAT activity, and abundance of thermogenic adipocytes in white fat. Moreover, A2B agonist treatment increased EE from human adipocytes, myocytes, and muscle explants. Mechanistically, A2B forms heterodimers required for adenosine signaling. Overall, adenosine/A2B signaling links muscle and BAT and has both anti-aging and anti–obesity potential.

Publ.-Id: 31349

Numerical study of the appearance of short-circuits in liquid metal batteries

Benard, S.

The report gives an overview on small-scale interface instabilities in liquid metal batteries.

  • Other
    École normale supérieure Paris-Saclay, 2020

Publ.-Id: 31347

Magnetoelectric coupling in a frustrated spinel studied using high-field scanning probe microscopy

Rossi, L.; Brüning, D.; Ueda, H.; Scurschii, I.; Lorenz, T.; Bryant, B.

Below its Neél temperature, the frustrated magnet CdCr2O4 exhibits an antiferromagnetic spin-spiral ground state. Such states can give rise to a sizable magnetoelectric coupling. In this report, we measure the electric polarization induced in single-crystalline CdCr2O4 by large applied magnetic field. Because the detection of a macroscopic polarization is hindered by the structural domains in the tetragonal spin-spiral phase, we have pioneered an alternative method of measuring polarization induced by high magnetic fields, using electrostatic force microscopy. This method enables us to measure polarization from nanoscale areas of the sample surface, as well as imaging how charge inhomogeneities change with magnetic field.

Publ.-Id: 31346

Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation

Konstantinovic, M. J.; Ulbricht, A.; Brodziansky, T.; Castina, N.; Malerba, L.

Vacancy-solute clustering in neutron irradiated Fe-Cr alloys with various concentrations of Cr and minor solutes (Ni, Si and P) were studied by using
coincidence Doppler broadening spectroscopy and small angle neutron scattering techniques. The results from both experiments, supported by an object kinetic Monte Carlo model, show in a very consistent way the existence and formation of vacancy-CrNiSiP clusters that play detrimental role in irradiation hardening. Similar solute cluster number density of about 30 to 50 x10^16cm-3 and an average diameter of about 1 nm were estimated for all alloys containing minor solutes, irrespectively of the chromium content. In Fe9Cr ferritic and Fe9Cr ferritic/martensitic alloys, with significantly reduced concentration of minor solute elements, the main defects are vacancy clusters, with an average cluster size size of about 10 and 2 vacancies, respectively. Large concentration of alpha'-precipitates was observed in Fe14Cr(NiSiP). However, both vacancy clusters and alpha'-precipitates provide significantly less impact to hardening in comparison to vacancy-CrNiSiP clusters. The fact that vacancy clustering in Fe9Cr ferritic alloy resembles that of pure iron suggests that Cr solutes may play lesser role in irradiation hardening of ferritic alloys and steels than previously believed.

Keywords: Neutron irradiation; FeCr alloys; Steels

Related publications


  • Secondary publication expected from 24.07.2021

Publ.-Id: 31344

Band Bending and Valence Band Quantization at Line Defects in MoS2

Murray, C.; van Efferen, C.; Jolie, W.; Fischer, J. A.; Hall, J.; Rosch, A.; Krasheninnikov, A.; Komsa, H.-P.; Michely, T.

The variation of the electronic structure normal to 1D defects in quasi-freestanding MoS2, grown by molecular beam epitaxy, is investigated through high resolution scanning tunneling spectroscopy at 5K. Strong upward bending of valence and conduction bands toward the line defects is found for the 4|4E mirror twin boundary and island edges but not for the 4|4P mirror twin boundary. Quantized energy levels in the valence band are observed wherever upward band bending takes place. Focusing on the common 4|4E mirror twin boundary, density functional theory calculations give an estimate of its charging, which agrees well with electrostatic modeling. We show that the line charge can also be assessed from the filling of the boundary-localized electronic band, whereby we provide a measurement of the theoretically predicted quantized polarization charge at MoS2 mirror twin boundaries. These calculations elucidate the origin of band bending and charging at these 1D defects in MoS2. The 4|4E mirror twin boundary not only impairs charge transport of electrons and holes due to band bending, but holes are additionally subject to a potential barrier, which is inferred from the independence of the quantized energy landscape on either side of the boundary.

Keywords: 2D materials; Line defects; first-principles calculations


  • Secondary publication expected from 30.06.2021

Publ.-Id: 31342

Strain robust spin gapless semiconductors/half-metals in transition metal embedded MoSe2 monolayer

Yang, Q.; Kou, L.; Hu, X.; Wang, Y.; Lu, C.; Krasheninnikov, A.; Sun, L.

The realization of spin gapless semiconductor (SGS) and half-metal (HM) behavior in two-dimensional (2D) transition metal (TM) dichalcogenides is highly desirable for their applications in spintronic devices. Here, using density functional theory calculations, we demonstrate that Fe, Co, Ni substitutional impurities can not only induce magnetism in MoSe2 monolayer, but also convert the semiconducting MoSe2 to SGS/HM system. We also study the effects of mechanical strain on the electronic and magnetic properties of the doped monolayer. We show that for all TM impurities we considered, the system exhibits the robust SGS/HM behavior regardless of biaxial strain values. Moreover, it is found that the magnetic properties of TM–MoSe2 can effectively be tuned under biaxial strain by controlling the spin polarization of the 3d orbitals of Fe, Co, Ni atoms. Our findings offer a new route to designing the SGS/HM properties and modulating magnetic characteristics of the TM–MoSe2 system and may also facilitate the implementation of SGS/HM behavior and realization of spintronic devices based on other 2D materials.

Keywords: 2D materials, first-principles simulations, magnetism


  • Secondary publication expected from 17.06.2021

Publ.-Id: 31341

Reversible crystalline-to-amorphous phase transformation in monolayer MoS under grazing ion irradiation

Valerius, P.; Kretschmer, S.; V. Senkovskiy, B.; Wu, S.; Hall, J.; Herman, A.; Ehlen, N.; Ghorbani Asl, M.; Grüneis, A.; Krasheninnikov, A.; Michely, T.

By combining scanning tunneling microscopy, low-energy electron diffraction, photoluminescence and Raman spectroscopy experiments with molecular dynamics simulations, a comprehensive picture of the structural and electronic response of a monolayer of MoS2 to 500 eV Xe+ irradiation is obtained. The MoS2 layer is epitaxially grown on graphene/Ir(1 1 1) and analyzed before and after irradiation in situ under ultra-high vacuum conditions. Through optimized irradiation conditions using low-energy ions with grazing trajectories, amorphization of the monolayer is induced already at low ion fluences of 1.5 × 1014 ions cm−2 and without inducing damage underneath the MoS2 layer. The crystalline-to-amorphous transformation is accompanied by changes in the electronic properties from semiconductor-to-metal and an extinction of photoluminescence. Upon thermal annealing, the re-crystallization occurs with restoration of the semiconducting properties, but residual defects prevent the recovery of photoluminescence.

Keywords: 2D materilas, irradiation, defects, atomistic simulations


  • Secondary publication expected from 06.01.2021

Publ.-Id: 31340

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