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arXiv 2024年

作者： Lim, Seongjoon Singh, Sobhit Huang, Fei-Ting Pan, Shangke Wang, Kefeng Kim, Jaewook Kim, Jinwoong Vanderbilt, David Cheong, Sang-Wook Rutgers Center for Emergent Materials Department of Physics and Astronomy PiscatawayNJ08854 United States Department of Mechanical Engineering University of Rochester RochesterNY14627 United States Materials Science Program University of Rochester RochesterNY14627 United States State Key Laboratory Base of Novel Function Materials and Preparation Science School of Material Sciences and Chemical Engineering Ningbo University Zhejiang Ningbo315211 China Department of Physics and Astronomy Rutgers University PiscatawayNJ08854 United States

Electric currents have the intriguing ability to induce magnetization in nonmagnetic crystals with sufficiently low crystallographic symmetry. Some associated phenomena include the non-linear anomalous Hall effect in polar crystals and the nonreciprocal directional dichroism in chiral crystals when magnetic fields are applied. In this work, we demonstrate that the same underlying physics is also manifested in the electronic tunneling process between the surface of a nonmagnetic chiral material and a magnetized scanning probe. In the paramagnetic but chiral metallic compound Co1/3NbS2, the magnetization induced by the tunneling current is shown to become detectable by its coupling to the magnetization of the tip itself. This results in a contrast across different chiral domains, achieving atomic-scale spatial resolution of structural chirality. To support the proposed mechanism, we used first-principles theory to compute the chirality-dependent current-induced magnetization and Berry curvature in the bulk of the material. Our demonstration of this magnetochiral tunneling effect opens up a new avenue for investigating atomic-scale variations in the local crystallographic symmetry and electronic structure across the structural domain boundaries of low-symmetry nonmagnetic crystals. © 2024, CC BY.

关键词： Magnetization

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Minimizing finite viscosity enhances relative kinetic energy absorption in bistable mechanical metamaterials but only with sufficiently fine discretization: a nonlinear dynamical size effect

arXiv

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arXiv 2024年

作者： Xiu, Haning Fancher, Ryan Frankel, Ian Ziemke, Patrick Fermen-Coker, Müge Begley, Matthew Boechler, Nicholas Department of Mechanical and Aerospace Engineering University of California La Jolla San DiegoCA United States Department of Mechanical Engineering University of California Santa Barbara Santa BarbaraCA United States Materials Department University of California Santa Barbara Santa BarbaraCA United States DEVCOM Army Research Laboratory Aberdeen Proving GroundMD United States Program in Materials Science and Engineering University of California La Jolla San DiegoCA United States

Bistable mechanical metamaterials have shown promise for mitigating the harmful consequences of impact by converting kinetic energy into stored strain energy, offering an alternative and potentially synergistic approach to conventional methods of attenuating energy transmission. In this work, we numerically study the dynamic response of a one-dimensional bistable metamaterial struck by a high speed impactor (where the impactor velocity is commensurate with the sound speed), using the peak kinetic energy experienced at midpoint of the metamaterial compared to that in an otherwise identical linear system as our performance metric. We make five key findings: 1) The bistable material can counter-intuitively perform better (to nearly 103× better than the linear system) as the viscosity decreases (but remains finite), but only when sufficiently fine discretization has been reached (i.e. the system approaches sufficiently close to the continuum limit);2) This discretization threshold is sharp, and depends on the viscosity present;3) The bistable materials can also perform significantly worse than linear systems (for low discretization and viscosity or zero viscosity);4) The dependence on discretization stems from the partition of energy into trains of solitary waves that have pulse lengths proportional to the unit cell size, where, with intersite viscosity, the solitary wave trains induce high velocity gradients and thus enhanced damping compared to linear, and low-unit-cell-number bistable, materials;and 5) When sufficiently fine discretization has been reached at low viscosities, the bistable system outperforms the linear one for a wide range of impactor conditions. The first point is particularly important, as it shows the existence of a nonlinear dynamical "size effect", where, given a protective layer of some thickness and otherwise identical quasi-static mechanical properties and total mass, e.g., a 1 mm thick layer having 200 unit cells of 5 µm thickness is predicte

关键词： Kinetic energy

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Development and Validation of a Portable Optical Instrument for Estimating Leaf Nitrogen in Maize (Zea Mays L.)

SSRN

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SSRN 2024年

作者： Nogueira, Felipe Hermínio Meireles Ribeiro, Sharon Gomes Lima, Guilherme Santos Moreira, Luís Clênio Jario da Rocha Neto, Odílio Coimbra Nogueira, Ricardo Emílio Ferreira Quevedo dos Santos Teixeira, Adunias Department of Agricultural Engineering Federal University of Ceara Fortaleza60455-760 Brazil Soil Science Graduate Program Federal University of Ceara Fortaleza60455-760 Brazil Department of Agronomy Federal Institute of Education Science and Technology of Ceara Limoeiro do Norte62930-000 Brazil Department of Metallurgical and Materials Engineering Federal University of Ceara Fortaleza60455-760 Brazil

This study proposes the development and evaluation of a new portable multispectral instrument to estimate the leaf nitrogen concentration in maize crops in the field. The MSPAT (Multispectral Soil Plant Analysis Tools) includes the AS7265x sensor, which has 18 bands and covers the spectrum from 410 to 940 nm. The device was designed to be portable, using the ESP32 microcontroller and incorporating such functionality as data storage on a MicroSD card, communication with a smartphone via WiFi and geolocation of the acquired data. The MSPAT was evaluated in an experiment conducted at the Federal University of Ceará (UFC), where the maize was subjected to different doses of nitrogen fertiliser (0, 60, 90, 120, 150 and 180 ***−1 N). Spectral readings were taken at three phenological stages (V5, V10, R2) using the MSPAT, the SPAD-502 chlorophyll meter and the FieldSpec PRO FR3 spectroradiometer. After taking the optical measurements, the nitrogen content of the leaves was determined in the laboratory using the method proposed by Kjeldahl. The data analysis included the calculation of normalised ratio indices (NRIs) for the estimation using linear regression, and the application of multivariate statistical methods (PLSR and PCR) for predicting the leaf nitrogen concentration (LNC). The results showed that the MSPAT index with the best performance used the 900 nm band in a normalised ratio with the 560 nm band (R2 = 0.64) at stage V10. In the validation, the MSPAT presented an R2 of 0.79, demonstrating superior performance to the SPAD-502, which achieved an R2 of 0.70. This confirms the potential of the MSPAT compared to commercial equipment, and made it possible to obtain similar results to the reference spectroradiometer. The PLSR model with data from the FieldSpec 3 provided important validation metrics when using reflectance data with first-derivative transformation (R2 = 0.88, RMSE = 1.94 and MAE = 1.28). When using the MSPAT, PLSR (R2 = 0.75, RMSE = 2.77 and MAE = 2

关键词： Network security

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Flexible, charged biopolymers in monovalent and mixed-valence salt: Regimes of anomalous electrostatic stiffening and of salt insensitivity

引用

Physical Review E 2021年第1期104卷 014504-014504页

作者： Sarah N. Innes-Gold David R. Jacobson Philip A. Pincus Mark J. Stevens Omar A. Saleh Materials Department and Biomolecular Science and Engineering Program University of California Santa Barbara California 93106 USA

The conformations of biological polyelectrolytes (PEs), such as polysaccharides, proteins, and nucleic acids, affect how they behave and interact with other biomolecules. Relative to neutral polymers, PEs in solution are more locally rigid due to intrachain electrostatic repulsion, the magnitude of which depends on the concentration of added salt. This is typically quantified using the Odijk-Skolnick-Fixman (OSF) electrostatic-stiffening model, in which salt-dependent Debye-Hückel (DH) screening modulates intrachain repulsion. However, the applicability of this approach to flexible PEs has long been questioned. To investigate this, we use high-precision single-molecule elasticity measurements to infer the scaling with salt of the local stiffness of three flexible biopolymers (hyaluronic acid, single-stranded RNA, and single-stranded DNA) in both monovalent and mixed-valence salt solutions. In monovalent salt, we collapse the data across all three polymers by accounting for charge spacing, and find a common power-law scaling of the electrostatic persistence length with ionic strength with an exponent of 0.66±0.02. This result rules out simple OSF pictures of electrostatic stiffening. It is roughly compatible with a modified OSF picture developed by Netz and Orland; alternatively, we posit the exponent can be explained if the relevant electrostatic screening length is the interion spacing rather than the DH length. In mixed salt solutions, we find a regime where adding monovalent salt, in the presence of multivalent salt, does not affect PE stiffness. Using coarse-grained simulations, and a three-state model of condensed, chain-proximate, and bulk ions, we attribute this regime to a “jacket” of ions surrounding the PE that regulates the chain's effective charge density as ionic strength varies. The size of this jacket in simulations is again consistent with a screening length controlled by interion spacing rather than the DH length. Taken together, our results describ

关键词： Biomolecules Polyelectrolytes Single polymer chains

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Exploring the Potential of Tesla Valve for Filtering and Sorting Microscale Active Swimmers: A Computational Study

SSRN

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SSRN 2023年

作者： Rogers, Ariel He, Zhiyao Wang, Yong Department of Physics University of Arkansas FayettevilleAR72701 United States Department of Computer Science and Computer Engineering University of Arkansas FayettevilleAR72701 United States Materials Science & Engineering Program University of Arkansas FayettevilleAR72701 United States Cell & Molecular Biology Program University of Arkansas FayettevilleAR72701 United States

An interesting connection between shark spiral intestines and the Tesla valve was proposed recently;however, how Tesla valves interact with active matters and the potential applications of Tesla valves in biology remain largely unexplored. Here, we present a computational study on the potential use of Tesla valves for filtering and sorting microscale active swimmers such as bacteria. We investigated the behavior of microswimmers passing through the Tesla valve at different linear and angular velocities using numerical simulations, and quantified the diodicity of the Tesla valve for active swimmers. Our results demonstrate that the Tesla valve can effectively filter and sort microscale swimmers based on their swimming behavior. The findings of this study suggest that Tesla valves could have potential applications in microscale sorting and chromatography, with significant implications for biomedical and environmental engineering. © 2023, The Authors. All rights reserved.

关键词： Bacteria

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Electronic Structures and Thermoelectric Properties of Heavily Doped N-Type Zrcobi from First Principles Calculations

SSRN

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SSRN 2022年

作者： Ibrahim, Nura Ahmed, Ridwan A. Adri, Huda Reisya, Ichwani Department of Physics Ahmadu Bello University Zaria Nigeria Materials Science and Engineering Program Department of Mechanical Engineering Worcester Polytechnic Institute WorcesterMA01609 United States

We present a theoretical investigation on the electronic structures and the thermoelectric properties of doped ZrCoBi half-Heusler compound using a combination of density functional theory calculations, semi classical Boltzmann transport theory and deformation potential theory. The effect of doping is described by a combination of rigid band approximation (RBA) and a model that explicitly includes the dopant atom within the lattice of ZrCoBi. The results demonstrate a high power factor with considerable n- and p-doping concentrations at high temperatures. Our findings further reveal that the electronic transport coefficients of ZrCo0.75M0.25Bi (M = Ni, Pd, Pt) are comparable because of their identical electronic structures. At 900 K, a high figure of merit (ZT) of ~ 0.35, ~ 0.38, and ~ 0.40 are obtained for ZrCo0.75Ni0.25Bi, ZrCo0.75Pd0.25Bi and ZrCo0.75Pt0.25Bi respectively. © 2022, The Authors. All rights reserved.

关键词： Electronic structure

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Impact damage and injection repair strength restoration 36

Impact damage and injection repair strength restoration

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36th Technical Conference of the American Society for Composites 2021: Composites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021

作者： Massey, Justin Romasko, Barrett Kim, Hyonny Materials Science and Engineering Program University of California San Diego La Jolla CA92093 United States Department of Structural Engineering University of California San Diego La Jolla CA92093 United States

ISBN: (纸本)9781713837596

Impact damage to composite structures can lead to a range of damage modes. Of interest is modest damage composed of delaminations less than 50 mm in size, and no visible impact-side fiber breakage. While resin injection is a current-practice repair technique that can be used to address these damage modes in a manner that is much less invasive than bonded scarf patch repair, the injection technique is not currently credited as one restoring strength back to laminate. Issues of quantifying the removal of any internal contamination, assessing degree of resin fill, and demonstration of how much strength is restored are being addressed within the scope of this research activity. Resin injection will be conducted and the resulting strength restoration assessed in local fracture tests (end-notch flexure). The formation of actual impact damage morphologies, namely multiple planes of delamination interconnected with matrix cracks, is a critical aspect of this problem. Three 25-ply composite panel types having varying percentage of 0o fiber content have been impacted under low velocity at a range of energy levels. Resulting force vs. time and ultrasonic mapping of damage extent. Damage produced by such impacts will be used in subsequent injection repair studies. Intentional contamination will be introduced, and then removal will be achieved via injected solvents and atmospheric plasma, with monitoring of contaminant presence achieved by in-line quantitative chemical analysis. © 36th Technical Conference of the American Society for Composites 2021: Composites Ingenuity Taking on Challenges in Environment-Energy-Economy, ASC 2021.

关键词： Restoration

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Bacterial Mobility and Motility in Porous Media Mimicked By Microspheres

SSRN

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SSRN 2022年

作者： Shrestha, Diksha Ou, Jun Rogers, Ariel Jereb, Amani Wang, Yong Department of Physics Cell and Molecular Graduate Program Materials Science and Engineering Program University of Arkansas FayettevilleAR72701 United States Department of Environmental Resources Engineering Mechanical Engineering Program California State Polytechnic University Humboldt ArcataCA95521 United States

Bacterial motion in porous media are essential for their survival, proper functioning, and variousapplications. Here we investigated the motion of Escherichia coli bacteria in microsphere-mimicked porousmedia. We observed reduced bacterial velocity and enhanced directional changes of bacteria as the densityof microspheres increased, while such changes happened mostly around the microspheres and due to thecollisions with the microspheres. More importantly, we established and quantified the correlation betweenthe bacterial trapping in porous media and the geometric confinement imposed by the microspheres. In addition,numerical simulations showed that the active Brownian motion model in the presence of microspheresresulted in bacterial motion that are consistent with the experimental observations. Our study suggested thatit is important to distinguish the ability of bacteria to move easily – bacterial mobility – from the abilityof bacteria to move independently – bacteria motility. Our results showed that bacterial motility remainssimilar in porous media, but bacterial mobility was significantly affected by the pore-scale confinement. © 2022, The Authors. All rights reserved.

关键词： Microspheres

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Emergent Magnetic Phases and Piezomagnetic Effects in MnxNi1−xF2 Thin Film Alloys

arXiv

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arXiv 2023年

作者： Van Haren, Ryan Hald, Nessa Lederman, David Department of Physics University of California Santa Cruz Santa CruzCA95064 United States Materials Science and Engineering Program School for Engineering of Energy Matter and Transport Arizona State University TempeAZ85287 United States

The effect of random competing single-ion anisotropies in antiferromagnets was studied using epitaxial MnxNi1−xF2 antiferromagnetic thin film alloys grown via molecular beam epitaxy. The crystal structure of this material is tetragonal for all values of x, and the Mn sites have a magnetic easy axis single-ion anisotropy while the Ni sites have an easy plane anisotropy perpendicular to the Mn easy axis. Crystallographic and magnetization measurements demonstrated that the thin film alloys were homogeneously mixed and did not phase-separate into their constituent parts. Pure MnF2 thin films epitaxially grown on MgF2 exhibited compressive strain along all three crystallographic axes which resulted in piezomagnetic effects. The piezomagnetism disappeared if the film was grown on a (MnNi)F2 graded buffer layer. A mean-field theory fit to the transition temperature as a function of the Mn concentration x, which takes into account piezomagnetic effects, gave a magnetic exchange constant between Mn and Ni ions of JMnNi = 0.305±0.003 meV. Mean-field theory calculations also predicted the existence of an oblique antiferromagnetic phase in the MnxNi1−xF2 alloy which agreed with the experimental data. A magnetic phase diagram for MnxNi1−xF2 thin film alloys was constructed and showed evidence for the existence of two unique magnetic phases, in addition to the ordinary antiferromagnetic and paramagnetic phases: an oblique antiferromagnetic phase, and an emergent magnetic phase proposed to be either a magnetic glassy phase or a helical phase. The phase diagram is quantitatively different from that of FexNi1−xF2 because of the much larger single-ion anisotropy of Fe2+ compared to Mn2+ © 2023, CC BY.

关键词： Ions

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Empowering Machines to Think Like Chemists: Unveiling Molecular Structure-Polarity Relationships with Hierarchical Symbolic Regression

arXiv

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arXiv 2024年

作者： Lou, Siyu Liu, Chengchun Chen, Yuntian Mo, Fanyang Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai200240 China Ningbo Institute of Digital Twin Eastern Institute of Technology Ningbo315200 China School of Materials Science and Engineering Peking University Beijing100871 China -Preferred Program Peking University Shenzhen Graduate School Shenzhen518500 China

Thin-layer chromatography (TLC) is a crucial technique in molecular polarity analysis. Despite its importance, the interpretability of predictive models for TLC, especially those driven by artificial intelligence, remains a challenge. Current approaches, utilizing either high-dimensional molecular fingerprints or domain-knowledge-driven feature engineering, often face a dilemma between expressiveness and interpretability. To bridge this gap, we introduce Unsupervised Hierarchical Symbolic Regression (UHiSR), combining hierarchical neural networks and symbolic regression. UHiSR automatically distills chemical-intuitive polarity indices, and discovers interpretable equations that link molecular structure to chromatographic behavior. Copyright © 2024, The Authors. All rights reserved.

关键词： Thin layer chromatography

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