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Energy landscape of ZnO clusters and low-density polymorphs

Physical Review B 2017年第6期96卷 064108-064108页

作者： Robabe Rasoulkhani Hossein Tahmasbi S. Alireza Ghasemi Somayeh Faraji Samare Rostami Maximilian Amsler Department of Physics Institute for Advanced Studies in Basic Sciences (IASBS) Zanjan 45137-66731 Iran Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA

We report on an extensive study of ZnO materials with cagelike motifs in clusters and bulk phases through structural searches using the minima hopping method. A novel putative ground state was discovered for the (ZnO)32 cluster with a tubelike structure, closely related to the previously reported (ZnO)24 ground-state cage geometry. Furthermore, the effect of ionization on the geometries and energetic ordering of (ZnO)n clusters with n=3–10,12 was studied by directly sampling the energy landscape of the ionized system. Our results indicate that the transition from ring and planar structures to three-dimensional cages occurs at larger cluster sizes than in the neutral system. Inspired by the bottom-up design philosophy and the predominance of cagelike structures in medium-sized clusters, a search for crystalline ZnO was conducted aimed specifically at low-density polymorphs, resulting in the discovery of 57 novel metastable phases. The voids in these low-density materials closely resemble the hollow cage structures of small (ZnO)n/(ZnO)n+ clusters with n<16. Analogous to clathrate materials, these voids could serve to accommodate guest atoms to tailor the materials properties for various applications.

关键词： Crystal structure Semiconductors Artificial neural networks Density functional theory

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Hyperuniformity and anti-hyperuniformity in one-dimensional substitution tilings

arXiv

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arXiv 2018年

作者： Oguz, Erdal C. Socolar, Joshua E.S. Steinhardt, Paul J. Torquato, Salvatore School of Mechanical Engineering Sackler Center for Computational Molecular and Materials Science Tel Aviv University Tel Aviv Israel Physics Department Duke University DurhamNC27708 United States Department of Physics Princeton Center for Theoretical Science Princeton University PrincetonNJ08544 United States Center for Cosmology and Particle Physics Department of Physics New York University New YorkNY10003 United States Department of Chemistry Department of Physics Princeton Institute for the Science and Technology of Materials Program in Applied and Computational Mathematics Princeton University PrincetonNJ08540 United States

We consider the scaling properties characterizing the hyperuniformity (or anti-hyperuniformity) of long wavelength fluctuations in a broad class of one-dimensional substitution tilings. We present a simple argument that predicts the exponent α governing the scaling of Fourier intensities at small wavenumbers, tilings with α > 0 being hyperuniform, and confirm with numerical computations that the predictions are accurate for quasiperiodic tilings, tilings with singular continuous spectra, and limit-periodic tilings. Tilings with quasiperiodic or singular continuous spectra can be constructed with α arbitrarily close to any given value between −1 and 3. Limit-periodic tilings can be constructed with α between −1 and 1 or with Fourier intensities that approach zero faster than any power law. Copyright © 2018, The Authors. All rights reserved.

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Polybenzimidazole membranes with nanophase-separated structure induced by non-ionic hydrophilic side chains for vanadium flow batteries

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Journal of materials Chemistry A 2017年第9期6卷 3895-3905页

作者： Sangshan Peng Xuemei Wu Xiaoming Yan Li Gao Yangzhi Zhu Daishuang Zhang Jie Li Qian Wang Gaohong He State Key Laboratory of Fine Chemicals R&D Center of Membrane Science and Technology School of Chemical Engineering Dalian University of Technology Dalian China School of Petroleum and Chemical Engineering Dalian University of Technology Panjin China Department of Chemical and Environmental Engineering Materials Science Engineering Program Bourns College of Engineering University of California Riverside California 92521 USA

Polybenzimidazole (PBI) membranes with nanophase-separated structure induced by non-ionic hydrophilic side chain are designed and fabricated for vanadium flow batteries (VFBs). The designed PBI membranes are prepared by grafting non-ionic hydrophilic side chains via an N-substitution reaction. This molecular modification induces nanophase separation and formation of hydrophilic clusters, which act as effective proton transfer pathways, hence dramatically improving the proton conductivity. Meanwhile, the vanadium permeability is inappreciable due to the appropriate size of hydrophilic clusters and Donnan exclusion of protonated grafted-PBI membranes (GPBI). Free from ion exchange groups, GPBI membranes maintain the good chemical stability of the pristine PBI membrane. As a result, the designed membrane exhibits an impressive performance, combining ultrahigh proton conductivity, ion selectivity and chemical stability. The GPBI-based VFB exhibits a coulombic efficiency of over 99% and an energy efficiency of 84% at 120 mA cm⁻², the highest reported for dense PBI membranes for VFB applications. The decent stability of GPBI membranes is demonstrated by the stable performance over 200 charge–discharge cycles and the ex situ immersion test. This work provides a new insight into the design of high-performance PBI membranes for VFB applications.

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The ELIMÄKI Locus is Required for Vertical Proprioception in Birch Trees

SSRN

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SSRN 2019年

作者： Alonso-Serra, Juan Shi, Xueping Peaucelle, Alexis Rastas, Pasi Bourdon, Matthieu Immanen, Juha Takahashi, Junko Koivula, Hanna Eswaran, Gugan Muranen, Sampo Help, Hanna Smolander, Olli-Pekka Su, Chang Safronov, Omid Gerber, Lorenz Salojärvi, Jarkko Hagqvist, Risto Mähonen, Ari Pekka Nieminen, Kaisa Helariutta, Ykä Organismal and Evolutionary Biology Research Program Faculty of Biological and Environmental Sciences Viikki Plant Science Centre University of Helsinki Helsinki Finland Institute of Biotechnology HiLIFE University of Helsinki Helsinki Finland Key Laboratory of Horticultural Plant Biology of Ministry of Education College of Horticulture and Forestry Sciences Huazhong Agricultural University Wuhan430070 China Sainsbury Laboratory University of Cambridge Cambridge United Kingdom Institut Jean-Pierre Bourgin INRA AgroParisTech CNRS Université Paris-Saclay Versailles78000 France Helsinki Finland Umeå Plant Science Center Department of Forest Genetics and Plant Physiology Swedish University of Agricultural Sciences Umeå Sweden Department of Food and Nutrition Faculty of Agriculture and Forestry University of Helsinki Finland Department of Physics Division of Materials Sciences X-ray Laboratory University of Helsinki Helsinki Finland Department of Chemistry and Biotechnology School of Science Tallinn University of Technology Tallinn Estonia Genome Institute of Singapore Singapore138672 Singapore Singapore Centre for Environmental Life Sciences Engineering Nanyang Technological University Singapore63755 Singapore

Tree architecture has evolved to support a top-heavy above-ground biomass, but this integral feature poses a weight-induced challenge to trunk stability. Maintaining an upright stem is expected to require vertical proprioception through feedback between sensing stem weight and modulating radial growth. Despite its apparent importance, the principle by which plant stems respond to vertical loading forces remains largely unknown. Here, by manipulating the stem weight of downy birch (Betula pubescens) trees, we show that cambial development is modulated systemically along the stem. We carried out a genetic study on the underlying regulation by combining an accelerated birch flowering program with a recessive mutation at the ELIMÄKI locus (EKI), which causes a mechanically defective response to weight stimulus resulting in stem collapse after just three months. We observed delayed wood morphogenesis in eki compared with WT, along with a more mechanically elastic cambial zone and radial compression of xylem cell size, indicating that timely tissue differentiation is critical for cambial growth under mechanical stress. Furthermore, the touch-induced mechanosensory pathway was transcriptionally misregulated in eki, indicating that the ELIMÄKI locus is required to integrate the weight-growth feedback regulation. By studying this birch mutant, we were able to dissect vertical proprioception from the gravitropic response associated with reaction wood formation. Taken together, our study provides evidence for both local and systemic responses to mechanical stimuli during secondary plant development. © 2019, The Authors. All rights reserved.

关键词： Forestry

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Contraction of polymer gels created by the activity of molecular motors

arXiv

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arXiv 2018年

作者： Bacca, Mattia Saleh, Omar A. McMeeking, Robert M. Mechanical Engineering Department University of British Columbia VancouverBCV6T 1Z4 – Canada Materials Department University of California Santa BarbaraCA93106 – United States Biomolecular Science & Engineering Program University of California Santa BarbaraCA93106 – United States Mechanical Engineering Departments University of California Santa BarbaraCA93106 – United States School of Engineering University of Aberdeen King’s College AberdeenAB24 3FX – United Kingdom INM—Leibniz Institute for New Materials Campus D2 2 Saarbrücken66123 Germany

We propose a theory based on non-equilibrium thermodynamics to describe the mechanical behavior of an active polymer gel created by the inclusion of molecular motors in its solvent. When activated, these motors attach to the chains of the polymer network and shorten them creating a global contraction of the gel, which mimics the active behavior of a cytoskeleton. The power generated by these motors is obtained by ATP hydrolysis reaction, which transduces chemical energy into mechanical work. The latter is described by an increment of strain energy in the gel due to an increased stiffness. This effect is described with an increment of the cross-link density in the polymer network, which reduces its entropy. The theory then considers polymer network swelling and species diffusion to describe the transient passive behavior of the gel. We finally formulate the problem of uniaxial contraction of a slab of gel and compare the results with experiments, showing good agreement. Copyright © 2018, The Authors. All rights reserved.

关键词： Gels

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Modified Transport-of-Intensity Approach for Mapping In-situ Magnetic Induction

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Microscopy and Microanalysis 2017年第S1期23卷 930-931页

作者： C. Phatak V. Brajuskovic F. Barrows A. Petford-Long Materials Science Division Argonne National Laboratory Lemont IL 60439 USA Department of Materials Science and Engineering Northwestern University Evanston IL 60208 USA Applied Physics Program Northwestern University Evanston IL 60208 USA

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Properties of selected structural and flat flexible cabling materials for low temperature applications

arXiv

引用

arXiv 2018年

作者： Daal, M. Zobrist, N. Kellaris, N. Sadoulet, B. Robertson, M. Department of Physics University of California Santa BarbaraCA93106-9530 United States Department of Physics University of California BerkeleyCA94720-7300 United States Department of Physics University of California DavisCA95616-8677 United States Department of Mechanical Engineering University of Colorado Boulder80309-0427 United States Materials Science and Engineering Program University of Colorado Boulder80309-0596 United States

We present measurements of the low temperature thermal conductivity for materials useful in the construction of cryogenic supports for scientific instrumentation and in the fabrication of flat flexible cryogenic cabling. The materials we measure have relatively low thermal conductivity. We present a method for measuring the heat transfer coefficient of flat cabling and show, using an example, that the thermal conductivity of a flex cable is reasonably well predicted by composing the thermal conductivities of its constituent material layers. Room temperature physical and mechanical data is given for the materials studied, as well as an overview of relevant materials science and manufacturing details. materials include Timet Ti 15-3 and Ti 21S, Materion alloy vit105 (LM105) in amorphous state, ATI Metals Nb-47Ti, Johnson Matthey nitinol (NiTi), Mersen graphite grade 2020, DuPont Pyralux coverlay and Vespel SCP-5050, and Fralock Cirlex polyimide sheets. All data is in the temperature range 0.05 to 2 K, and up to 5 K for SCP-5050. Copyright © 2018, The Authors. All rights reserved.

关键词： Temperature

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Single shot ultrafast all optical magnetization switching of ferromagnetic Co/Pt multilayers

Single shot ultrafast all optical magnetization switching of...

引用

Berkeley Symposium on Energy Efficient Electronic Systems (E3S)

作者： Jon Gorchon Charles-Henri Lambert Yang Yang Akshay Pattabi Richard B. Wilson Sayeef Salahuddin Jeffrey Bokor Lawrence Berkeley National Laboratory Berkeley CA USA Department of Electrical Engineering and Computer Sciences University of California Berkeley CA USA Department of Materials Science and Engineering University of California Berkeley CA USA Department of Mechanical Engineering and Materials Science and Engineering Program University of California Riverside CA USA

ISBN: (纸本)9781538632918

The ability to control magnetism in sub-picosecond timescales using laser pulses has potential applications in fast magnetic devices. It has been demonstrated that a single femto-second laser pulse can reverse the magnetization of a film within a few picoseconds [1], a phenomenon called as all-optical switching (AOS). However, this phenomenon thus far has been observed only in ferrimagnetic GdFeCo films. On the other hand, ferromagnetic films, which are of greater interest than ferrimagnets in many technological applications, need multiple laser pulses for magnetization reversal [2], making the overall effect slow and energy inefficient. Fast, single-shot switching of a ferromagnet can open up new avenues for spintronic devices that operate at unprecedented picosecond timescales, thereby making them viable non-volatile replacements for silicon based RAMs and logic devices.

关键词： Optical switches Magnetization Ultrafast optics Magnetic separation Optical films Optical pulses

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Appropriate feeding for early juvenile stages of eunicid polychaete Marphysa sanguinea

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Fisheries and Aquatic sciences 2017年第1期20卷 1-9页

作者： Kim, Kyeong Hun Kim, Byoung Kwon Kim, Sung Kyun Phoo, War War Venmathi Maran, B.A. Kim, Chang-Hoon Pukyong National University Interdisciplinary Program of Biomedical Engineering Busan 48513 South Korea Pukyong National University Department of Marine Bio-materials and Aquaculture Busan 48513 South Korea Pukyong National University Fisheries Science and Technology Centre Goseong-gun Gyeongsangnam-do 52957 South Korea

Survival rate (SR) and growth rate (GR) were tested with various feed sources to identify an appropriate feed to improve the productivity in the early life stage of the rock worm Marphysa sanguinea (Montagu, 1813) (Eunicidae: Polychaeta). In addition, feed supply rates were also examined. Three experiments were performed to identify the appropriate feed for the juvenile stages of M. sanguinea. Experiment 1 was done using seven different feed sources and without feed as well for the first 20days of M. sanguinea culture. Decapsulated Artemia and extruded pellet for shrimp were showed with high SR and GR in the experiment 1. Experiment 2 was performed with five different feed sources. Two feeds were selected from experiment 1 in addition to eel feed, mixed micro-algae, and benthic diatom. Four different quantities of each feed were supplied to 3000 individuals of early juvenile stage of M. sanguinea. High quantity of decapsulated Artemia and shrimp feed resulted with a relatively good SR and GR. In experiment 3, we provided 20, 50, and 75mg of decapsulated Artemia and shrimp feed to 3000 individuals of M. sanguinea. Our results demonstrated that after 3months, decapsulated Artemia showed high survival rate and 75mg/3000 inds provided the best quantity of feed in the earlier life stage culture of M. sanguinea. © 2017 The Author(s).

关键词： Decapsulated Artemia Feed Feeding rate Marphysa sanguinea Polychaete

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Using probe molecule FTIR spectroscopy to identify and characterize Pt-group metal based single atom catalysts

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Chinese Journal of Catalysis 2017年第9期38卷 1473-1480页

作者： Chithra Asokan Leo DeRita Phillip Christopher Department of Chemical and Environmental Engineering University of California Riverside Riverside CA 92521 USA Program in Materials Science University of CaliforniaRiverside Riverside CA 92521 USA UCR Center for Catalysis University of California RiversideRiverside CA 92521 USA

单原子催化是提高贵金属利用率的有效手段,而表征单原子催化剂是理解单原子催化的基础.探针分子红外光谱可用于识别和定量催化剂样品中孤立的Pt族金属物种的浓度,从而得到负载的孤立的Pt族金属物种的局部几何形状、稳定性、活性及其分散... 详细信息

单原子催化是提高贵金属利用率的有效手段,而表征单原子催化剂是理解单原子催化的基础.探针分子红外光谱可用于识别和定量催化剂样品中孤立的Pt族金属物种的浓度,从而得到负载的孤立的Pt族金属物种的局部几何形状、稳定性、活性及其分散性.本文讨论了该技术用于识别和表征含负载型孤立的Pt族金属原子催化剂的效能、应用、以及未来的发展方向.

关键词：单原子催化剂铂族金属红外光谱表征载体效应

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