IST Austria: PubRep (Institute of Science and Technology)
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Artificial intelligence-assisted workflow for transmission electron microscopy: From data analysis automation to materials knowledge unveiling
No full text(Scanning) transmission electron microscopy ((S)TEM) has significantly advanced materials science but faces challenges in correlating precise atomic structure information with the functional properties of devices due to its time-intensive nature. To address this, an analytical workflow is introduced for the holistic characterization, modelling, and simulation of device heterostructures. This workflow automates the experimental (S)TEM data analysis, providing an in-depth characterization of crystallographic information, 3D orientation, elemental composition, and strain distribution. It reduces a process that typically takes days for a trained human into an automatic routine solved in minutes. Utilizing a physics-guided artificial intelligence model, it generates representative descriptions of materials and samples. The workflow culminates in creating digital twins of systems limited with at least one axis of translational invariance –3D finite element and atomic models of millions of atoms–enabling simulations that provide crucial insights into device behavior in practical applications. Demonstrated with SiGe planar heterostructures for scalable spin qubits, the workflow links digital twins to theoretical properties, revealing how atomic structure impacts materials and functional properties such as spatially-resolved phononic or electronic characteristics, or (inverse) spin orbit lengths. The versatility of the workflow is demonstrated through its application to a wide array of materials systems, device configurations, and sample morphologies
ABP1/ABL3-TMK1 cell-surface auxin signaling targets PIN2-mediated auxin fluxes for root gravitropism
No full textPhytohormone auxin and its directional transport mediate much of the remarkably plastic development of higher plants. Positive feedback between auxin signaling and transport is a prerequisite for (1) self-organizing processes, including vascular tissue formation, and (2) directional growth responses such as gravitropism. Here, we identify a mechanism by which auxin signaling directly targets PIN auxin transporters. Via the cell-surface AUXIN-BINDING PROTEIN1 (ABP1)-TRANSMEMBRANE KINASE 1 (TMK1) receptor module, auxin rapidly induces phosphorylation and thus stabilization of PIN2. Following gravistimulation, initial auxin asymmetry activates autophosphorylation of the TMK1 kinase. This induces TMK1 interaction with and phosphorylation of PIN2, stabilizing PIN2 at the lower root side, thus reinforcing asymmetric auxin flow for root bending. Upstream of TMK1 in this regulation, ABP1 acts redundantly with the root-expressed ABP1-LIKE 3 (ABL3) auxin receptor. Such positive feedback between cell-surface auxin signaling and PIN-mediated polar auxin transport is fundamental for robust root gravitropism and presumably for other self-organizing developmental phenomena
Tropics-wide intraseasonal oscillations
No full textThe tropical climate variability is characterized by various oscillations across a range of timescales. Oscillations that imprint the tropical mean state are generally attributed to slow processes, such as the seasonal cycle or interannual variability. Here, we identify a pronounced tropics-wide intraseasonal oscillation (TWISO) in satellite observations and reanalyses. This oscillation, with a period of 30 to 60 d, is evident across multiple variables and involves interactions between convection, radiation, surface fluxes, and large-scale circulation. It is primarily manifested as convective perturbations in the tropical Indo-Pacific warm pool accompanied by oscillations in the large-scale tropical overturning circulation. Here, we examine the relationship between TWISO, the Madden–Julian Oscillation (MJO), and the instability of radiative-convective equilibrium. Certain phases of TWISO coincide with specific phases of the MJO, suggesting a potential connection between the two. However, although the MJO can amplify the oscillation amplitude of TWISO, it is not essential for TWISO to occur. Finally, due to its broad manifestation across the tropics, TWISO potentially exerts widespread influence on tropical weather and climate at regional scales
PMLR
No full textClustering is a cornerstone of data analysis that is particularly suited to identifying coherent subgroups or substructures in unlabeled data, as are generated continuously in large amounts these days. However, in many cases traditional clustering methods are not applicable, because data are increasingly being produced and stored in a distributed way, e.g. on edge devices, and privacy concerns prevent it from being transferred to a central server. To address this challenge, we present FedDP-KMeans, a new algorithm for
-means clustering that is fully-federated as well as differentially private. Our approach leverages (potentially small and out-of-distribution) server-side data to overcome the primary challenge of differentially private clustering methods: the need for a good initialization. Combining our initialization with a simple federated DP-Lloyds algorithm we obtain an algorithm that achieves excellent results on synthetic and real-world benchmark tasks. We also provide a theoretical analysis of our method that provides bounds on the convergence speed and cluster identification success
Sets with arbitrary Hausdorff and packing scales in infinite dimensional Banach spaces
No full textFor every couple of Hausdorff functions ψ and φ verifying some mild assumptions, there exists a compact subset K of the Baire space such that the φ-Hausdorff measure and the ψ-packing measure on K are both finite and positive. Such examples are then embedded in any infinite dimensional Banach space to answer positively a question of Fan on the existence of metric spaces with arbitrary scales
Efficient near room temperature thermoelectric cooling and power generation with CuAgSe
No full textCuAgSe-based materials are attractive for low-temperature thermoelectric (TE) applications but are limited by bipolar conduction and relatively high thermal conductivity. Herein, we report a ligand-free aqueous synthesis of Te-doped CuAgSe (CuAgSe1-xTex), where structural and electronic modulation improve carrier transport and suppress phonon propagation. Ex-situ time-resolved X-ray diffraction reveals a spontaneous growth mechanism, while density functional theory calculations show that Te-5s and 5p orbitals hybridization generates localized states and an asymmetric density of states, thereby enhancing the Seebeck coefficient. Electron microscopy and strain analyses confirm that Te-doping introduces a high density of lattice dislocations and grain boundaries, leading to a reduced lattice thermal conductivity of 0.11 W m−1K−1 at 443 K. These synergistic effects translate into device-level performance—the first integrated CuAgSe thermoelectric modules, exhibit a maximum cooling temperature difference of 27.3 K, and power density of 0.34 W cm−2 with a conversion efficiency of 3.6% at a modest temperature gradient of 136 K. These results demonstrate that CuAgSe1-xTex enables efficient energy harvesting and localized cooling under small temperature gradient, underscoring the importance of structural and electronic design beyond conventional zT benchmarks
Efficient and rapid sunlight-driven photocatalytic degradation of methylene blue dye using multiferroic BiFeO3 nanoparticles
No full textThe current investigation presents a facile and cost-effective sol-gel approach for the synthesis of phase-pure multiferroic bismuth ferrite (BiFeO3) nanoparticles (BFO NPs) by using propylene glycol as a complexing agent, intended for use as a photocatalyst to efficiently degrade organic dyes in aqueous solutions under natural sunlight. Characterization techniques, including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD), elucidated a plausible reaction pathway for the formation of phase-pure BFO NPs. Rietveld refinement of the XRD data, in conjunction with transmission electron microscopy (TEM) and Raman spectroscopy, confirmed the synthesis of single-phase BFO NPs at 400 °C, displaying a space group of R3c and an average crystallite size of 25 nm. UV–visible diffuse reflectance spectroscopy revealed an absorption cut-off wavelength near 590 nm, corresponding to a band gap of 2.08 eV, indicating the capability of BFO NPs to absorb visible light within the 400–590 nm range. BFO NPs have shown efficient and rapid photocatalytic degradation of methylene blue (MB) in acidic, neutral, and basic pH conditions under natural sunlight. This is attributed to the intrinsic ferroelectric and ferromagnetic ordering present in synthesized BFO NPs which facilitates the separation and migration of photoinduced charges through band bending phenomena at the interface
Structural insights into brassinosteroid export mediated by the Arabidopsis ABC transporter ABCB1
No full textBrassinosteroids (BRs) are steroidal phytohormones indispensable for plant growth, development, and responses to environmental stresses. The export of bioactive BRs to the apoplast is essential for BR signalling initiation, which requires binding of BR molecule to the extracellular domains of the plasma membrane-localized receptor complex. We have previously shown that the Arabidopsis thaliana ATP-binding cassette (ABC) transporter, ABCB19, functions as a BR exporter, and together with its close homologue, ABCB1, positively regulate BR signalling. Here, we demonstrate that ABCB1 is another BR transporter. The ATP hydrolysis activity of ABCB1 was stimulated by bioactive BRs, and its transport activity was confirmed in proteoliposomes and protoplasts. Structures of ABCB1 in substrate-unbound (apo), brassinolide (BL)-bound, and ATP plus BL-bound states were determined. In the BL-bound structure, BL was bound to the hydrophobic cavity formed by the transmembrane domain, and triggered local conformational changes. Together, our data provide additional insights into the ABC transporter-mediated BR export
Polyharmonic fields and Liouville quantum gravity measures on tori of arbitrary dimension: From discrete to continuous
No full textFor an arbitrary dimension (Formula presented.), we study: the polyharmonic Gaussian field (Formula presented.) on the discrete torus (Formula presented.), that is the random field whose law on (Formula presented.) given by (Formula presented.) where (Formula presented.) is the Lebesgue measure and (Formula presented.) is the discrete Laplacian; the associated discrete Liouville quantum gravity (LQG) measure associated with it, that is, the random measure on (Formula presented.) (Formula presented.) where (Formula presented.) is a regularity parameter. As (Formula presented.), we prove convergence of the fields (Formula presented.) to the polyharmonic Gaussian field (Formula presented.) on the continuous torus (Formula presented.), as well as convergence of the random measures (Formula presented.) to the LQG measure (Formula presented.) on (Formula presented.), for all (Formula presented.)