Repository for natural sciences and technology

The repository is used for the free publication of scientific publications from the fields of natural sciences and technology in the sense of Open Access and is open to all authors. The publications placed in the repository are permanently freely available and citable worldwide. The repository is operated by the Technical Information Library (TIB).
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Now showing 1 - 10 of 13717
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    Lebensqualität bei Krebserkrankungen – Integration in die Versorgung (working paper von Versorgern und Betroffenen)
    (Hannover : Technische Informationsbibliothek, 2024) Beutter, C. N. L.; Block, N.; Berger, S.; Edo-Ferrando, P.; Heinz, B.; Läufer, K.; Lang, B.; Mächtlen, K.; Münkel, S.; Rannert, D.; Zwerenz-Kopp, F.; Fegeler, C.
    Im Rahmen einer Projektgruppe haben sich sowohl Versorger (ÄrztInnen, KrebsberatungsstellenmitarbeiterInnen oder PsychoonkologInnen) sowie Betroffene mit einer regulären Integration von Lebensqualitätsdaten in der Versorgung befasst. Dabei wurde ein digitales System konzipiert, dass eine alltagsnahe und longitudinale Erhebung ermöglicht. Im working paper wurde über alle Teilnehmenden hinweg eine Problemidentifikation der derzeitigen IST-Situation integriert, um anhand dieser Probleme und Hemmschwellen ein übergreifendes Lösungskonzept zu erarbeiten. Im Lösungsraum wurden sowohl spezifische Anforderungen seitens der Versorger als auch PatientInnen zusammengefasst und gegenübergestellt. Dabei wurde ebenfalls die Vernetzung der einzelnen Akteure untereinander beleuchtet sowie die Thematik der Datenspende angerissen.
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    Bridging the Gap Between (AI-) Services and Their Application in Research and Clinical Settings Through Interoperability: the OMI-Protocol
    (Hannover : Technische Informationsbibliothek, 2024-02) Sigle, Stefan; Werner, Patrick; Schweizer, Simon; Caldeira, Liliana; Hosch, René; Dyrba, Martin; Fegeler, Christian; Sigle, Stefan; Werner, Patrick; Schweizer, Simon; Caldeira, Liliana; Hosch, René; Dyrba, Martin; Fegeler, Christian; Grönke, Ana; Seletkov, Dmitrii; Kotter, Elmar; Nensa, Felix; Wehrle, Julius; Kaufmes, Kevin; Scherer, Lucas; Nolden, Marco; Boeker, Martin; Schmidt, Marvin; Pelka, Obioma; Braren, Rickmer; Stump, Shura-Roman; Graetz, Teresa; Pogarell, Tobias; Susetzky, Tobias; Wieland, Tobias; Parmar, Vicky; Wang, Yuanbin
    Artificial Intelligence (AI) in research and clinical contexts is transforming the areas of medical and life sciences permanently. Aspects like findability, accessibility, interoperability, and reusability are often neglected for AI-based inference services. The Open Medical Inference (OMI) protocol aims to support remote inference by addressing the aforementioned aspects. Key component of the proposed protocol is an interoperable registry for remote inference services, which addresses the issue of findability for algorithms. It is complemented by information on how to invoke services remotely. Together, these components lay the basis for the implementation of distributed inference services beyond organizational borders. The OMI protocol considers prior work for aspects like data representation and transmission standards wherever possible. Based on Business Process Modeling of prototypical use cases for the service registry and common inference processes, a generic information model for remote services was inferred. Based on this model, FHIR resources were identified to represent AI-based services. The OMI protocol is first introduced using AI-services in radiology but is designed to be generalizable to other application domains as well. It provides an accessible, open specification as blueprint for the introduction and implementation of remote inference services.
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    RIXS interferometry and the role of disorder in the quantum magnet Ba3 Ti3-x Irx O9
    (College Park, MD : APS, 2023) Magnaterra, M.; Moretti Sala, M.; Monaco, G.; Becker, P.; Hermanns, M.; Warzanowski, P.; Lorenz, T.; Khomskii, D. I.; van Loosdrecht, P. H. M.; van den Brink, J.; Grüninger, M.
    Motivated by several claims of spin-orbit-driven spin-liquid physics in hexagonal Ba3Ti3-xIrxO9 hosting Ir2O9 dimers, we report on resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge for different x. We demonstrate that magnetism in Ba3Ti3-xIrxO9 is governed by an unconventional realization of strong disorder, where cation disorder affects the character of the local moments. RIXS interferometry, studying the RIXS intensity over a broad range of transferred momentum q, is ideally suited to assign different excitations to different Ir sites. We find pronounced Ir-Ti site mixing. Both ions are distributed over two crystallographically inequivalent sites, giving rise to a coexistence of quasimolecular singlet states on Ir2O9 dimers and spin-orbit-entangled j=1/2 moments of 5d5Ir4+ ions. RIXS reveals different kinds of strong magnetic couplings for different bonding geometries, highlighting the role of cation disorder for the suppression of long-range magnetic order in this family of compounds.
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    Electron holographic mapping of structural reconstruction at mono- and bilayer steps of h−BN
    (College Park, MD : APS, 2023) Subakti, Subakti; Daqiqshirazi, Mohammadreza; Wolf, Daniel; Linck, Martin; Kern, Felix L.; Jain, Mitisha; Kretschmer, Silvan; Krasheninnikov, Arkady V.; Brumme, Thomas; Lubk, Axel
    Here, by making use of medium and high resolution autocorrected off-axis electron holography, we directly probe the electrostatic potential as well as in-plane structural reconstruction at edges and steps in multilayer hexagonal boron nitride. In combination with ab initio calculations, the data allows revealing the formation of folded zigzag edges at steps comprising two monolayers and their absence at monolayer steps.
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    Berry curvature associated to Fermi arcs in continuum and lattice Weyl systems
    (College Park, MD : APS, 2023) Wawrzik, Dennis; van den Brink, Jeroen
    Recently it has been discovered that in Weyl semimetals the surface state Berry curvature can diverge in certain regions of momentum. This occurs in a continuum description of tilted Weyl cones, which for a slab geometry results in the Berry curvature dipole associated to the surface Fermi arcs growing linearly with slab thickness. Here we investigate analytically incarnations of lattice Weyl semimetals and demonstrate this diverging surface Berry curvature by solving for their surface states and connect these to their continuum descriptions. We show how the shape of the Fermi arc and the Berry curvature hot-line is determined and confirm the 1/k2 divergence of the Berry curvature at the end of the Fermi arc as well as the finite-size effects for the Berry curvature and its dipole, using finite-slab calculations and surface Green's function methods. We further establish that apart from affecting the second-order, nonlinear Hall effect, the divergent Berry curvature has a strong impact on other transport phenomena as the Magnus-Hall effect and the nonlinear chiral anomaly.
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    Resonating holes vs molecular spin-orbit coupled states in group-5 lacunar spinels
    ([London] : Nature Publishing Group UK, 2023) Petersen, Thorben; Bhattacharyya, Pritam; Rößler, Ulrich K.; Hozoi, Liviu
    The valence electronic structure of magnetic centers is one of the factors that determines the characteristics of a magnet. This may refer to orbital degeneracy, as for jeff = 1/2 Kitaev magnets, or near-degeneracy, e.g., involving the third and fourth shells in cuprate superconductors. Here we explore the inner structure of magnetic moments in group-5 lacunar spinels, fascinating materials featuring multisite magnetic units in the form of tetrahedral tetramers. Our quantum chemical analysis reveals a very colorful landscape, much richer than the single-electron, single-configuration description applied so far to all group-5 GaM4X8 chalcogenides, and clarifies the basic multiorbital correlations on M4 tetrahedral clusters: while for V strong correlations yield a wave-function that can be well described in terms of four V4+V3+V3+V3+ resonant valence structures, for Nb and Ta a picture of dressed molecular-orbital jeff = 3/2 entities is more appropriate. These internal degrees of freedom likely shape vibronic couplings, phase transitions, and the magneto-electric properties in each of these systems.
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    Magnetoelectricity induced by rippling of magnetic nanomembranes and wires
    (College Park, MD : APS, 2023) Ortix, Carmine; van den Brink, Jeroen
    Magnetoelectric crystals have the interesting property that they allow electric fields to induce magnetic polarizations, and vice versa, magnetic fields to generate ferroelectric polarizations. Having such a magnetoelectric coupling usually requires complex types of magnetic textures, e.g., of spiraling type. Here, we establish a previously unknown approach to generate linear magnetoelectric coupling in ferromagnetic insulators with intrinsic Dzyaloshinskii-Moriya interaction (DMI). We show that the effect of nanoscale curved geometries combined with the intrinsic DMI of the magnetic shell lead to a reorganization of the magnetic texture that spontaneously breaks inversion symmetry and thereby induces macroscopic magnetoelectric multipoles. Specifically, we prove that structural deformation in the form of controlled ripples activates a magnetoelectric monopole in the recently synthesized two-dimensional magnets. We also demonstrate that in zigzag-shaped ferromagnetic wires in planar architectures, a magnetic toroidal moment triggers direct linear magnetoelectric coupling.
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    Experimental and numerical characterization of imperfect additively manufactured lattices based on triply periodic minimal surfaces
    (Amsterdam [u.a.] : Elsevier Science, 2023) Günther, Fabian; Pilz, Stefan; Hirsch, Franz; Wagner, Markus; Kästner, Markus; Gebert, Annett; Zimmermann, Martina
    Lattices based on triply periodic minimal surfaces (TPMS) are attracting increasing interest in seminal industries such as bone tissue engineering due to their excellent structure-property relationships. However, the potential can only be exploited if their structural integrity is ensured. This requires a fundamental understanding of the impact of imperfections that arise during additive manufacturing. Therefore, in the present study, the structure-property relationships of eight TPMS lattices, including their imperfections, are investigated experimentally and numerically. In particular, the focus is on biomimetic network TPMS lattices of the type Schoen I-WP and Gyroid, which are fabricated by laser powder bed fusion from the biocompatible alloy Ti-42Nb. The experimental studies include computed tomography measurements and compression tests. The results highlight the importance of process-related imperfections on the mechanical performance of TPMS lattices. In the numerical work, firstly the as-built morphology is artificially reconstructed before finite element analyses are performed. Here, the reconstruction procedure previously developed by the same authors is used and validated on a larger experimental matrix before more advanced calculations are conducted. Specifically, the reconstruction reduces the numerical overestimation of stiffness from up to 341% to a maximum of 26% and that of yield strength from 66% to 12%. Given a high simulation accuracy and flexibility, the presented procedure can become a key factor in the future design process of TPMS lattices.
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    Symmetry‐Induced Selective Excitation of Topological States in Su–Schrieffer–Heeger Waveguide Arrays
    (Weinheim : Wiley-VCH, 2023) Tang, Min; Wang, Jiawei; Valligatla, Sreeramulu; Saggau, Christian N.; Dong, Haiyun; Saei Ghareh Naz, Ehsan; Klembt, Sebastian; Lee, Ching Hua; Thomale, Ronny; van den Brink, Jeroen; Fulga, Ion Cosma; Schmidt, Oliver G.; Ma, Libo
    The investigation of topological state transition in carefully designed photonic lattices is of high interest for fundamental research, as well as for applied studies such as manipulating light flow in on-chip photonic systems. Herein, the topological phase transition between symmetric topological zero modes (TZM) and antisymmetric TZMs in Su–Schrieffer–Heeger mirror symmetric waveguides is reported. The transition of TZMs is realized by adjusting the coupling ratio between neighboring waveguide pairs, which is enabled by selective modulation of the refractive index in the waveguide gaps. Bidirectional topological transitions between symmetric and antisymmetric TZMs can be achieved with proposed switching strategy. Selective excitation of topological edge mode is demonstrated owing to the symmetry characteristics of the TZMs. The flexible manipulation of topological states is promising for on-chip light flow control and may spark further investigations on symmetric/antisymmetric TZM transitions in other photonic topological frameworks.
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    Surfactant stabilization of vanadium iron oxide derived from Prussian blue analog for lithium-ion battery electrodes
    (Cambridge : Royal Society of Chemistry, 2023) Bornamehr, Behnoosh; El Gaidi, Hiba; Arnold, Stefanie; Pameté, Emmanuel; Presser, Volker
    Due to their high energy density, Li-ion batteries have become indispensable for energy storage in many technical devices. Prussian blue and its analogs are a versatile family of materials. Apart from their direct use as an alkali-ion battery electrode, they are a promising source for templating other compounds due to the presence of carbon, nitrogen, and metallic elements in their structure, ease of synthesis, and high tunability. In this study, homogeneous iron vanadate derivatization from iron vanadium Prussian blue was successfully carried out using an energy efficient infrared furnace utilizing CO2 gas. Iron-vanadate is an inherently unstable electrode material if cycled at low potentials vs. Li/Li+. Several parameters were optimized to achieve a stable electrochemical performance of this derivative, and the effect of surfactants, such as tannic acid, sodium dodecylbenzene sulfonate, and polyvinylpyrrolidone were shown with their role in the morphology and electrochemical performance. While stabilizing the performance, we demonstrate that the type and order of addition of these surfactants are fundamental for a successful coating formation, otherwise they can hinder the formation of PBA, which has not been reported previously. Step-by-step, we illustrate how to prepare self-standing electrodes for Li-ion battery cells without using an organic solvent or a fluorine-containing binder while stabilizing the electrochemical performance. A 400 mA h g−1 capacity at the specific current of 250 mA g−1 was achieved after 150 cycles while maintaining a Coulombic efficiency of 99.2% over an extended potential range of 0.01–3.50 V vs. Li/Li+.