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arXiv 2024年

作者： Garaud, Pascale Chini, Gregory P. Cope, Laura Shah, Kasturi Caulfield, Colm-Cille P. Department of Applied Mathematics and Theoretical Physics University of Cambridge CambridgeCB3 0WA United Kingdom Department of Applied Mathematics Baskin School of Engineering University of California Santa Cruz Santa CruzCA95064 United States Program in Integrated Applied Mathematics Department of Mechanical Engineering University of New Hampshire DurhamNH03824 United States School of Mathematics University of Leeds LeedsLS2 9JT United Kingdom Department of Earth Atmospheric and Planetary Sciences Massachusetts Institute of Technology CambridgeMA02139 United States Institute for Energy and Environmental Flows University of Cambridge CambridgeCB3 0EZ United Kingdom

Recent theoretical progress using multiscale asymptotic analysis has revealed various possible regimes of stratified turbulence. Notably, buoyancy transport can either be dominated by advection or diffusion, depending on the effective Péclet number of the flow. Two types of asymptotic models have been proposed, which yield measurably different predictions for the characteristic vertical velocity and length scale of the turbulent eddies in both diffusive and non-diffusive regimes. The first, termed a ‘single-scale model’, is designed to describe flow structures having large horizontal and small vertical scales, while the second, termed a ‘multiscale model’, additionally incorporates flow features with small horizontal scales, and reduces to the single-scale model in their absence. By comparing predicted vertical velocity scaling laws with direct numerical simulation data, we show that the multiscale model correctly captures the properties of strongly stratified turbulence within regions dominated by small-scale isotropic motions, whose volume fraction decreases as the stratification increases. Meanwhile its single-scale reduction accurately describes the more orderly, layer-like, quiescent flow outside those regions. Copyright © 2024, The Authors. All rights reserved.

关键词： Asymptotic analysis

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Low Temperature Spin Seebeck Effect in Non-Magnetic Vanadium Dioxide

arXiv

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arXiv 2023年

作者： Luo, Renjie Legvold, Tanner J. Chen, Liyang Navarro, Henry Basaran, Ali C. Hong, Deshun Liu, Changjiang Bhattacharya, Anand Schuller, Ivan K. Natelson, Douglas Department of Physics and Astronomy Rice University HoustonTX77005 United States Applied Physics Graduate Program Rice Quantum Institute Rice University HoustonTX77005 United States Department of Physics Center for Advanced Nanoscience University of California La Jolla San DiegoCA92093 United States Materials Science Division Argonne National Laboratory LemontIL60439 United States Department of Electrical and Computer Engineering Department of Materials Science and NanoEngineering Rice University HoustonTX77005 United States

The spin Seebeck effect (SSE) is sensitive to thermally driven magnetic excitations in magnetic insulators. Vanadium dioxide in its insulating low temperature phase is expected to lack magnetic degrees of freedom, as vanadium atoms are thought to form singlets upon dimerization of the vanadium chains. Instead, we find a paramagnetic SSE response in VO2 films that grows as the temperature decreases below 50 K. The field and temperature dependent SSE voltage is qualitatively consistent with a general model of paramagnetic SSE response and inconsistent with triplet spin transport. Quantitative estimates find a spin Seebeck coefficient comparable in magnitude to that observed in strongly magnetic materials. The microscopic nature of the magnetic excitations in VO2 requires further examination. Copyright © 2023, The Authors. All rights reserved.

关键词： Paramagnetism

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A Whole Head Ultra-High Density Diffuse Optical Tomography System for Naturalistic and Resting State Functional Human Brain Mapping

A Whole Head Ultra-High Density Diffuse Optical Tomography S...

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Optics and the Brain, BRAIN 2023 - Part of Optica Biophotonics Congress: Optics in the Life Sciences 2023

作者： Fogarty, Morgan Rafferty, Sean M. O’Sullivan, Anthony C. Svoboda, Calamity F. Markow, Zachary E. Richter, Edward J. George, Tessa King, Kelsey Wilhelm, Dana Tripathy, Kalyan Trobaugh, Jason W. Eggebrecht, Adam T. Culver, Joseph P. Imaging Science Program Washington University in St. Louis 1 Brookings Drive St. LouisMO63130 United States Department of Biomedical Engineering Washington University in St. Louis 1 Brookings Drive St. LouisMO63130 United States Department of Neuroscience Washington University in St. Louis 1 Brookings Drive St. LouisMO63130 United States Department of Electrical and Systems Engineering Washington University in St. Louis 1 Brookings Drive St. LouisMO63130 United States Department of Radiology Washington University in St. Louis 1 Brookings Drive St. LouisMO63130 United States Department of Physics Washington University in St. Louis 1 Brookings Drive St. LouisMO63130 United States

High-density diffuse optical tomography uses a dense array of overlapping measurements that provides functional brain images validated against fMRI. We doubled this optode density, improving resolution and expanding t... 详细信息

ISBN: (纸本)9781957171210

关键词： Diffuse optical tomography Functional imaging Image quality Magnetic resonance imaging Near infrared spectroscopy Optical imaging

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Increasing the mobility and power-electronics figure of merit of AlGaN with atomically thin AlN/GaN digital-alloy superlattices

arXiv

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arXiv 2022年

作者： Pant, Nick Lee, Woncheol Sanders, Nocona Kioupakis, Emmanouil Applied Physics Program University of Michigan Ann ArborMI48109 United States Department of Materials Science and Engineering University of Michigan Ann ArborMI48109 United States Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109 United States

Alloy scattering in random AlGaN alloys drastically reduces the electron mobility and therefore the power-electronics figure of merit. As a result, Al compositions greater than 75% are required to obtain even a two-fold increase of the Baliga figure of merit compared to GaN. However, beyond approximately 80% Al composition, donors in AlGaN undergo the DX transition which makes impurity doping increasingly more difficult. Moreover, the contact resistance increases exponentially with increasing Al content, and integration with dielectrics becomes difficult due to the upward shift of the conduction band. Atomically thin superlattices of AlN and GaN, also known as digital alloys, are known to grow experimentally under appropriate growth conditions. These chemically ordered nanostructures could offer significantly enhanced figure of merit compared to their random-alloy counterparts due to the absence of alloy scattering, as well as better integration with contact metals and dielectrics. In this work, we investigate the electronic structure and phonon-limited electron mobility of atomically thin AlN/GaN digital-alloy superlattices using first-principles calculations based on density-functional and many-body perturbation theory. The band gap of the atomically thin superlattices reaches 4.8 eV, and the in-plane (out-of-plane) mobility is 369 (452) cm2 V-1 s-1. Using the modified Baliga figure of merit that accounts for the dopant ionization energy, we demonstrate that atomically thin AlN/GaN superlattices with a monolayer sublattice periodicity have the highest modified Baliga figure of merit among several technologically relevant ultra-wide band-gap materials, including random AlGaN, β-Ga2O3, cBN, and diamond. Copyright © 2022, The Authors. All rights reserved.

关键词： Aluminum gallium nitride

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Computational Characterization of the Recently Synthesized Pristine and Porous 12-Atom-Wide Armchair Graphene Nanoribbon

arXiv

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arXiv 2025年

作者： da Gomes, Djardiel S. Felix, Isaac M. Radel, Willian F. Dias, Alexandre C. Ribeiro Junior, Luiz A. Pereira Junior, Marcelo L. State University of Campinas Gleb Wataghin Institute of Physics Department of Applied Physics Campinas São Paulo13083-859 Brazil University of Brasília Faculty UnB Planaltina Materials Science Postgraduate Program Federal District Brasília Brazil Center for Agri-food Science and Technology Federal University of Campina Grande Paraíba Pombal58840-000 Brazil University of Brasília Institute of Physics Physics Postgraduate Program Federal District Brasília70910900 Brazil Institute of Physics International Center of Physics University of Brasília Federal District Brasília70910-900 Brazil Institute of Physics University of Brasília Federal District Brasília70910-900 Brazil Computational Materials Laboratory University of Brasília Federal District Brasília70910900 Brazil University of Brasília College of Technology Department of Electrical Engineering Federal District Brasília70910-900 Brazil

Recently synthesized Porous 12-Atom-Wide Armchair Graphene Nanoribbons (12-AGNRs) [Nano Lett. 2024, 24, 10718-10723]exhibit tunable properties through periodic porosity, enabling precise control over their electronic, optical, thermal, and mechanical behavior. This work presents a comprehensive theoretical characterization of pristine and porous 12-AGNRs based on density functional theory (DFT) and molecular dynamics (MD) simulations. DFT calculations reveal substantial electronic modifications, including band gap widening and the emergence of localized states. Analyzed within the Bethe–Salpeter equation (BSE) framework, optical properties highlight strong excitonic effects and significant absorption shifts. Thermal transport simulations indicate a pronounced reduction in conductivity due to enhanced phonon scattering at nanopores. At the same time, MD-based mechanical analysis shows decreased stiffness and strength while maintaining structural integrity. Despite these modifications, porous 12-AGNRs remain mechanically and thermally stable. These findings establish porosity engineering as a powerful strategy for tailoring graphene nanoribbons’ functional properties, reinforcing their potential for nanoelectronic, optoelectronic, and thermal management *** Codes 00-xx © 2025, CC BY.

关键词： Nanoribbons

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Two-step electronic response to magnetic ordering in a van der Waals ferromagnet

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Physical Review B 2024年第4期109卷 045416-045416页

作者： Han Wu Jian-Xin Zhu Lebing Chen Matthew W. Butcher Ziqin Yue Dongsheng Yuan Yu He Ji Seop Oh Bin Gao Jianwei Huang Shan Wu Cheng Gong Yucheng Guo Sung-Kwan Mo Jonathan Denlinger Donghui Lu Makoto Hashimoto Matthew B. Stone Alexander I. Kolesnikov Songxue Chi Junichiro Kono Andriy H. Nevidomskyy Robert J. Birgeneau Pengcheng Dai Ming Yi Department of Physics and Astronomy and Rice Center for Quantum Materials Rice University Houston Texas 77005 USA Theoretical Division Los Alamos National Laboratory Los Alamos New Mexico 87545 USA Center for Integrated Nanotechnologies Los Alamos National Laboratory Los Alamos New Mexico 87545 USA Department of Physics University of California at Berkeley Berkeley California 94720 USA Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston Texas 77005 USA Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA National Institute for Materials Science 1-1 Namiki Tsukuba Ibaraki 305-0044 Japan Department of Applied Physics Yale University New Haven Connecticut 06511 USA Department of Electrical and Computer Engineering and Quantum Technology Center University of Maryland College Park Maryland 20742 USA Advanced Light Source Lawrence Berkeley National Laboratory Berkeley California 94720 USA Stanford Synchrotron Radiation Lightsource SLAC National Accelerator Laboratory Menlo Park California 94025 USA Neutron Scattering Division Oak Ridge National Laboratory Oak Ridge Tennessee 37831 USA Department of Electrical and Computer Engineering Rice University Houston Texas 77005 USA Smalley-Curl Institute Rice University Houston Texas 77005 USA Department of Material Science and Nanoengineering Rice University Houston Texas 77005 USA Department of Materials Science and Engineering University of California Berkeley California 94720 USA

The two-dimensional material Cr2Ge2Te6 is a member of the class of insulating van der Waals (vdW) magnets. Here, using high resolution angle-resolved photoemission spectroscopy in a detailed temperature dependence study, we identify a clear response of the electronic structure to a dimensional crossover in the form of two distinct temperature scales marking onsets of modifications in the electronic structure. Specifically, we observe Te p-orbital-dominated bands to undergo changes at the Curie transition temperature TC while the Cr d-orbital-dominated bands begin evolving at a higher temperature scale. Combined with neutron scattering, density functional theory calculations, and Monte Carlo simulations, we find that the electronic system can be consistently understood to respond sequentially to the distinct temperatures at which in-plane and out-of-plane spin correlations exceed a characteristic length scale. Our findings reveal the sensitivity of the orbital-selective electronic structure for probing the dynamical evolution of local moment correlations in vdW insulating magnets.

关键词： Electronic structure Magnetic order Magnetic phase transitions Van der Waals systems Angle-resolved photoemission spectroscopy

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Graph Neural Networks for Radiological/Nuclear Detection with Static Detector Networks

Graph Neural Networks for Radiological/Nuclear Detection wit...

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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： M. D. Verlie D. T. Murnane A. Butko R. Cooper M. Kiran E. Rofors K. Vetter Department of Nuclear Engineering University of California Berkeley Berkeley California United Statesof America Applied Nuclear Physics Program Lawrence Berkeley National Laboratory (LBNL) Berkeley California United States of America Computational Research Division Lawrence Berkeley National Laboratory (LBNL) Berkeley California United States of America

To address the threat posed by the nefarious use of radiological/nuclear sources, there is a growing interest in deploying connected static detector networks in cities. Connected detector networks can have improved detection sensitivity over unconnected networks by using the correlations between detectors. We explore the use of graph neural networks (GNNs) to exploit such correlations in a minimal detector network of two nodes and one edge in downtown Chicago. We compare a GNN model with and without message passing, and find that the model with message passing performs significantly better (p = 0.03), suggesting that it is leveraging spatiotemporal relationships to improve detection performance. Future work includes assessing the performance of GNN models on larger detector networks and benchmarking them against existing algorithms.

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Doping ratio between ZnO/MgO tunes antimicrobial, osteogenic, and anti-osteoclast activity of CaO-MgO-ZnO-SiO2 bioactive glass-ceramics

引用

Ceramics International 2025年

作者： Hung, Guan-Yi Xia, Yun-Ze Chen, Pin-Yi Lai, Po-Liang Feng, Kuei-Chih Tu, Chi-Shun Cheng, I.-C. Wang, Chi-Yun International Ph.D. Program in Innovative Technology of Biomedical Engineering and Medical Devices Ming Chi University of Technology New Taipei City24301 Taiwan Department of Physics Fu Jen Catholic University New Taipei City24205 Taiwan Department of Mechanical Engineering Ming-Chi University of Technology New Taipei City24301 Taiwan Bone and Joint Research Center Department of Orthopaedic Surgery Chang Gung Memorial Hospital Taoyuan City33305 Taiwan College of Medicine Chang Gung University Taoyuan City33305 Taiwan Department of Mechanical Engineering Chang Gung University Taoyuan City33305 Taiwan Research Center for Intelligent Medical Devices Ming Chi University of Technology New Taipei City243303 Taiwan

Limitations such as donor site morbidity hamper autologous bone grafts. On the other hand, allogeneic grafts, sourced from cadavers, pose risks of viral transmission and rejection. While hydroxyapatite is a prevalent synthetic graft material, antibiotic-laden fillers addressing infection face challenges with antibiotic-resistant pathogens, driving the emergence of nonantibiotic materials to combat persistent bone infections. Bioactive glass is a potential bone void filler superior to hydroxyapatite. Thus, to improve the antibacterial efficacy and bioactivity, we adjusted the doping ratio of the novel CaO-(1-x) MgO-(x) ZnO-SiO2 glass-ceramics (x = 0, 0.25, 0.50, 0.75, 1). Using XRD, we found a typical amorphous structure alongside polycrystalline diopside (CaMgSi2O6), hardystonite (Ca2ZnSi2O7), and petedunnite (CaZnSi2O6) formations. Raman spectroscopy revealed the silicate-glass matrix structure in all the Zn(100x) glass-ceramics and confirmed that the Zn ions replaced the Mg ions. Zn-doped glass-ceramics promoted apatite layer formation and had greater antibacterial efficacy against E. coli and S. aureus. Zn25 glass-ceramic were biocompatible with L929 and MC3T3-E1 cells. Furthermore, Zn25 glass-ceramic promoted bone cell mineralization and reduced osteoclast formation without affecting ALP activity. In vivo, the Zn25 glass-ceramic exhibited greater osteointegration ability than the HAP and Zn0 glass-ceramic. Taken together, the present study demonstrated that bioactive glass-ceramics with a doping ratio between ZnO and MgO (25:75) can enhance antibacterial and osteogenic activity while impeding osteoclastogenic activity. © 2025

关键词： Escherichia coli

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Mapping in situ the assembly and dynamics in aqueous supramolecular polymers

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Nature Communications 2025年第1期16卷 1-13页

作者： Du, Huachuan Qiu, Ruomeng Lou, Xianwen Jansen, Stef A. H. Sai, Hiroaki Wang, Yuyang Markvoort, Albert J. Meijer, E.W. Stupp, Samuel I. Center for Regenerative Nanomedicine Northwestern University Chicago IL United States Institute for Complex Molecular Systems Eindhoven University of Technology Eindhoven Netherlands Department of Chemistry and Chemical Engineering and Laboratory of Macromolecular and Organic Chemistry Eindhoven University of Technology Eindhoven Netherlands Department of Chemistry Northwestern University Evanston IL United States Department of Applied Physics and Science Education Eindhoven University of Technology Eindhoven Netherlands Department of Biomedical Engineering and Synthetic Biology Group Eindhoven University of Technology Eindhoven Netherlands School of Chemistry and RNA Institute University of New South Wales Sydney NSW Australia Department of Medicine Northwestern University Chicago IL United States Department of Biomedical Engineering Northwestern University Evanston IL United States Department of Materials Science and Engineering Northwestern University Evanston IL United States

Supramolecular polymers, bonded through directional non-covalent interactions, closely mimic dynamic behaviors of biological nanofibers. However, the complexity of assembly pathways makes it highly challenging to unravel the nature of supramolecular dynamics in aqueous environments. Here we introduce a precise combinatorial titration methodology to probe in situ the assembly of peptide amphiphiles (PAs). This approach reveals a binary assembly mechanism governed by equilibrium between spheroidal micelles and β-sheet polymers. Weakening hydrogen bonding shifts the equilibrium towards micelles and decreases the internal structural order of filamentous polymers, promoting supramolecular dynamics. Extending this methodology to two-component copolymerization systems, we find a surprising tendency to form blocky nanostructures with reduced internal phase separation as the mismatch in peptide sequence decreases. Interestingly, while well-mixed copolymers acquire different dynamics, mismatched ones retain the characteristic supramolecular motion of their homopolymer counterparts. These critical insights into supramolecular dynamics offer strategies to tailor the dynamic functions of supramolecular nanomaterials. © The Author(s) 2025.

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Giant Thermomechanical Bandgap engineering in Quasi-two-dimensional Tellurium

arXiv

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arXiv 2023年

作者： Hussain, Naveed Ahmed, Shehzad Tep, Hüseyin U. Ullah, Kaleem Shahzad, Khurram Wu, Hui Shcherbakov, Maxim R. Department of Electrical Engineering and Computer Science University of California Irvine IrvineCA92697 United States State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing100084 China College of Physics and Optoelectronic Engineering Shenzhen University Guangdong518060 China Micro and Nano-Technology Program School of Natural and Applied Sciences Middle East Technical University Ankara06800 Turkey Department of Electrical and Computer Engineering University of Delaware NewarkDE19711 United States Department of Physics Middle East Technical University Ankara06800 Turkey

Mechanical straining-induced bandgap modulation in two-dimensional (2D) materials has been confined to volatile and narrow modulation due to substrate slippage and poor strain transfer. We report the thermomechanical modulation of the inherent bandgap in quasi-2D tellurium nanoflakes (TeNFs) via non-volatile strain induction during hot-press synthesis. We leveraged the coefficient of thermal expansion (CTE) mismatch between TeNFs and growth substrates by maintaining a high-pressure enforced non-slip condition during thermal relaxation (623 to 300K) to achieve the optimal biaxial compressive strain of -4.6 percent in TeNFs/sapphire. This resulted in an enormous bandgap modulation of 2.3 eV, at a rate of up to ~600 meV/%, which is two-fold larger than reported modulation rate. Strained TeNFs display robust band-to-band radiative excitonic blue photoemission with an intrinsic quantum efficiency (IQE) of c.a. 79.9%, making it promising for energy efficient blue LEDs and nanolasers. Computational studies reveal that biaxial compressive strain inhibits exciton-exciton annihilation by evading van-Hove singularities, hence promoting radiative-recombination. Bandgap modulation by such nonvolatile straining is scalable to other 2D semiconductors for on-demand nano(opto)-electronics. Copyright © 2023, The Authors. All rights reserved.

关键词： Energy gap

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