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Topology of three-dimensional Dirac semimetals and quantum spin Hall systems without gapless edge modes

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Physical Review Research 2023年第1期5卷 L012019-L012019页

作者： Alexander C. Tyner Shouvik Sur Danilo Puggioni James M. Rondinelli Pallab Goswami Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208USA Department of Physics and Astronomy Northwestern University Evanston Illinois 60208 USA Department of Materials Science and Engineering Northwestern University Illinois 60208 USA Northwestern Argonne Institute for Science and Engineering Evanston Illinois 60208 USA

The quantum spin Hall states are usually expected to possess gapless, helical edge modes. We show that the generic, n-fold-symmetric, momentum planes of three-dimensional, stable Dirac semimetals, which are orthogonal to the direction of nodal separation are examples of generalized quantum spin Hall systems, that possess quantized, spin or relative Chern numbers as bulk topological invariants, and gapped edge modes. We demonstrate these planes and the celebrated Bernevig-Zhang-Hughes model support identical quantized, non-Abelian Berry flux of magnitude 2π. Hence, they display identical quantized, topological response such as spin-charge separation and pumping of one Kramers-pair or SU(2) doublet, when probed with a magnetic flux tube. The Dirac points are identified as unit-strength, monopoles of SO(5) Berry connection, describing topological phase transitions between generalized quantum spin Hall and trivial insulators. Our work identifies precise bulk invariant and quantized response of Dirac semimetals, which are not diagnosed by nested Wilson loops and filling anomaly of corner-localized-states, and shows that many two-dimensional higher-order topological insulators can be understood as generalized quantum spin Hall systems.

关键词： Fractionalization Geometric & topological phases Spintronics Topological insulators Topological phase transition Topological phases of matter

The Effects of Growth Environments on Ws2 in Electrocatalytic Hydrogen Evolution Reaction

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SSRN 2023年

作者： Chang, Yung-Huang Huang, Chien-Sheng Chen, Yuan-Tsung Bachelor Program in Industrial Technology National Yunlin University of Science and Technology Yunlin Taiwan Department of Electronic Engineering National Yunlin University of Science and Technology Yunlin Taiwan Graduate School of Materials Science National Yunlin University of Science and Technology Yunlin Taiwan

Transition metal dichalcogenides (TMDs) recently have attracted much attention because of their outstanding catalytic activity, low cost, and earth abundance in the hydrogen evolution reaction (HER). Among these TMDs, MoS2 and WS2 are recognized as promising HER electrocatalysts and have been explored to be one of the candidates for replacing precious metals. In this work, the electrocatalytic activity of WS2 grown in Ar-only, Ar + H2, and ambient environments were studied, where the WS2 was synthesized by thermolysis from (NH4)2WS4 precursor. Different surface morphologies are shown under the different growth atmospheres. The structures of pure WS2, WS2 and WO3 mixed, and almost WO3 grow under the growth atmospheres of Ar-only, Ar + H2, and ambient environment, respectively. All the materials prepared in these different environments exhibit high crystalline characteristic. Especially, the pure WS2 grown in an Ar-only environment presents the preferred (103) lattice plane. The pure WS2 performs the best H2 evolution efficiency, indicating that high crystallinity and preferred (103) lattice plane are relative to the electrocatalytic activity. The studies provide fundamental insight for further design and preparation of electrocatalysts, useful in the development of clean energy. © 2023, The Authors. All rights reserved.

关键词： Electrocatalysts

Transferable screened range-separated hybrid functionals for electronic and optical properties of van der Waals materials

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Physical Review materials 2023年第10期7卷 104001-104001页

作者： María Camarasa-Gómez Ashwin Ramasubramaniam Jeffrey B. Neaton Leeor Kronik Department of Molecular Chemistry and Materials Science Weizmann Institute of Science Rehovoth 7610001 Israel Department of Mechanical and Industrial Engineering University of Massachusetts Amherst Amherst Massachusetts 01003 USA Materials Science and Engineering Graduate Program University of Massachusetts Amherst Amherst Massachusetts 01003 USA Department of Physics University of California Berkeley California 94720 USA Materials Sciences Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Kavli Energy NanoSciences Institute at Berkeley University of California Berkeley California 94720 USA

The accurate description of electronic properties and optical absorption spectra is a long-standing challenge for density functional theory. Recently, the introduction of screened range-separated hybrid (SRSH) functionals for solid-state materials has allowed for the calculation of fundamental band gaps and optical absorption spectra that are in very good agreement with many-body perturbation theory. However, since solid-state SRSH functionals are typically tuned to reproduce the properties of bulk phases, their transferability to low-dimensional structures, which experience substantially different screening than in the bulk, remains an open question. In this work, we explore the transferability of SRSH functionals to several prototypical van der Waals materials, including transition-metal sulfides and selenides, indium selenide, black phosphorus, and hexagonal boron nitride. Considering the bulk and a monolayer of these materials as limiting cases, we show that the parameters of the SRSH functional can be determined systematically, using only the band-edge quasiparticle energies of these extremal structural phases as fitting targets. The resulting SRSH functionals can describe both electronic band structures and optical absorption spectra with accuracy comparable to more demanding ab initio many-body perturbation theory (GW and Bethe-Salpeter equation) approaches. Selected examples also demonstrate that the SRSH parameters, obtained from the bulk and monolayer reference structures, display good accuracy for band structures and optical spectra of bilayers, indicating a degree of transferability that is independent of the fitting procedure.

关键词： 2-dimensional systems Density functional theory First-principles calculations GW method

Corrosion-Resistant and Ultrafine-Grained Boron-Containing Stainless Steel Produced by Laser Powder Bed Fusion

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SSRN 2024年

作者： Freitas, Brenda Juliet Martins Koga, Guilherme Yuuki de Traglia Amancio-Filho, Sergio Bolfarini, Claudemiro Federal University of São Carlos Graduate Program in Materials Science and Engineering São Carlos13.565-905 Brazil Graz University of Technology Institute of Materials Science Joining and Forming Graz8010 Austria Federal University of São Carlos Department of Materials Engineering São Carlos13.565-905 Brazil Rod. Washington Luis SP São CarlosCEP 13565-905 Brazil

Ultrafine-grained stainless steel armored with borides was produced by laser powder bed fusion (L-PBF). The in-situ formed composite was characterized by refined grains of high-alloyed ferritic stainless steel matrix with hard and rigid nanoborides along the grain boundaries. Besides being hard and wear resistant, the resulted material was unsensitized and resistant against pitting corrosion, with corrosion resistance comparable to a SAF 2205 duplex stainless steel. Besides unveiling the microstructural and electrochemical nexus, this work opens positive perspectives to surpass the corrosion-wear resistance trade-off upon the in-situ formation of stainless steel matrix reinforced by hard Cr-containing nanoborides using additive manufacturing technologies. © 2024, The Authors. All rights reserved.

关键词： Steel corrosion

Improved camptothecin encapsulation and efficacy by environmentally sensitive block copolymer/chitosan/fucoidan nanoparticles for targeting lung cancer cells

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International Journal of Biological Macromolecules 2024年第Part2期277卷 133901页

作者： Don, Trong-Ming Hong, Yu-Ting Jheng, Pei-Ru Chuang, Er-Yuan Huang, Yi-Cheng Department of Chemical and Materials Engineering Tamkang University New Taipei City Taiwan College of Life Sciences Department of Food Science National Taiwan Ocean University Keelung Taiwan Graduate Institute of Biomedical Materials and Tissue Engineering International PhD Program in Biomedical Engineering Taipei Medical University Taipei Taiwan Cell Physiology and Molecular Image Research Center Taipei Medical University–Wan Fang Hospital Taipei Taiwan

In this study, thermo-sensitive poly(N-isopropyl acrylamide) (PNP) was polymerized with pH-sensitive poly(acrylic acid) (PAA) to prepare a PAA-b-PNP block copolymer. Above its cloud point, the block copolymer self-assembled into nanoparticles (NPs), encapsulating the anticancer drug camptothecin (CPT) in situ. Chitosan (CS) and fucoidan (Fu) further modified these NPs, forming Fu-CPT-NPs to enhance biocompatibility, drug encapsulation efficiency (EE), and loading content (LC), crucially facilitating P-selectin targeting of lung cancer cells through a drug delivery system. The EE and LC reached 82 % and 3.5 %, respectively. According to transmission electron microscope observation, these Fu-CPT-NPs had uniform spherical shapes with an average diameter of ca. 250 nm. They could maintain their stability in a pH range of 5.0–6.8. In vitro experimental results revealed that the Fu-CPT-NPs exhibited good biocompatibility and had anticancer activity after encapsulating CPT. It could deliver CPT to cancer cells by targeting P-selectin, effectively increasing cell uptake and inducing cell apoptosis. Animal study results showed that the Fu-CPT-NPs inhibited lung tumor growth by increasing tumor cell apoptosis without causing significant tissue damage related to generating reactive oxygen species in lung cancer cells. This system can effectively improve drug-delivery efficiency and treatment effects and has great potential for treating lung cancer. © 2024 Elsevier B.V.

关键词： Nanoparticles

Optimizing cultivation strategies and scaling up for fucoxanthin production using Pavlova sp.

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Bioresource Technology 2024年 399卷 130609页

作者： Chen, Chun-Yen Liu, Ping-Yung Chang, Yu-Han Nagarajan, Dillirani Latagan, Mary Joy D. de Luna, Mark Daniel G. Chen, Jih-Heng Chang, Jo-Shu University Center for Bioscience and Biotechnology National Cheng Kung University Tainan Taiwan Department of Biotechnology and Bioindustry Sciences National Cheng Kung University Tainan701 Taiwan Department of Chemical Engineering National Cheng Kung University Tainan Taiwan Institute of Aquatic Science and Technology College of Hydrosphere Science National Kaohsiung University of Science and Technology Nanzih Campus Kaohsiung City Taiwan Energy Engineering Program National Graduate School of Engineering University of the Philippines Diliman Quezon City1101 Philippines Environmental Engineering Program National Graduate School of Engineering University of the Philippines Quezon City Diliman1101 Philippines Department of Chemical Engineering University of the Philippines Diliman Quezon City1101 Philippines Department of Chemical and Materials Engineering National Kaohsiung University of Science and Technology Kaohsiung807 Taiwan Department of Chemical and Materials Engineering Tunghai University Taichung407 Taiwan Research Center for Smart Sustainable Circular Economy Tunghai University Taichung407 Taiwan Department of Chemical Engineering and Materials Science Yuan Ze University Chung-Li Taiwan

The microalgal-based production of fucoxanthin has emerged as an imperative research endeavor due to its antioxidant, and anticancer properties. In this study, three brown marine microalgae, namely Skeletonema costatum, Chaetoceros gracilis, and Pavlova sp., were screened for fucoxanthin production. All strains displayed promising results, with Pavlova sp. exhibiting the highest fucoxanthin content (27.91 mg/g) and productivity (1.16 mg/L·day). Moreover, the influence of various cultivation parameters, such as culture media, salinity, sodium nitrate concentration, inoculum size, light intensity, and iron concentration, were investigated and optimized, resulting in a maximum fucoxanthin productivity of 7.89 mg/L·day. The investigation was further expanded to large-scale outdoor cultivation using 50 L tubular photobioreactors, illustrating the potential of Pavlova sp. and the cultivation process for future commercialization. The biomass and fucoxanthin productivity for the large-scale cultivation were 70.7 mg/L·day and 4.78 mg/L·day, respectively. Overall, the findings demonstrated considerable opportunities for fucoxanthin synthesis via microalgae cultivation and processing. © 2024 Elsevier Ltd

关键词： Microalgae

Plasma Surface Treatment of Cocr and Nicr Alloys for Dental Applications: A Comparative Study of Tin Thin Film Plasma Deposition Techniques

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SSRN 2024年

作者： Balica, Naasson Matheus Pereira Almeida, Larissa Solano Rossino, Luciana Sgarbi Pupim, Denise Monção, Renan Matos Costa, Thércio Henrique de Carvalho Santos, Rafaela Luiz Pereira Sousa, Rômulo Ribeiro Magalhães Nunes, Lívio César Cunha Federal University of Piauí Technology Center Graduate Program in Materials Science and Engineering Avenida Universitária s/n Ininga PI Teresina Brazil Federal University of São Carlos Graduate Program in Materials Science SP Sorocaba Brazil University of São Paulo Ribeirão Preto School of Dentistry Avenida do Café SP Ribeirão Preto Brazil Federal University of Rio Grande do Norte Technology Center Department of Mechanical Engineering University Campus Natal RN Lagoa Nova Brazil

Cobalt-chromium and nickel-chromium metal alloys have been widely used as biomaterials in the dental field due to their excellent physical-mechanical properties and biocompatibility, as well as the low cost of the material. However, in unfavorable environments, such as the oral cavity, these dental prostheses composed of these alloys can suffer alterations in their structure where they can undergo rapid changes with the surface corrosion process, which can vary with pH and temperature, typically related to changes in the patient's diet. The aim of this work is to carry out a comparative study between the cathodic cage (CC) and hollow cathode (HC) methods, in which a plasma deposition treatment of titanium nitride (TiN) thin films was carried out on CoCr and NiCr samples, in order to subsequently evaluate their surface characteristics and tribological properties in relation to each method. The samples were characterized using X-ray diffractometry (XRD), scanning electron microscopy (SEM/EDS) and micro abrasive wear tests on each sample from the three groups of alloys mentioned. It was observed that the TiN films provided greater resistance to the wear mechanism of all the samples, where through the characterizations, it can be inferred that the two types of treatments carried out on the samples are suitable for dental applications. © 2024, The Authors. All rights reserved.

关键词： Chromium alloys

New Insights into the Effects of Solidification Process on The Thermodynamic Parameters and Mechanical Properties of Cualbenbni Shape Memory Alloy

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SSRN 2023年

作者： Silva, David D.S. Vieira, Rafael T. Falcão, Gabriely M.S. Brito, Ieverton C.A. Caluête, Rafael E. Gomes, Rodinei M. Oliveira, Danniel F. Federal University of São Carlos Graduate Program in Materials Science and Engineering SP São Carlos13565-905 Brazil Colorado School of Mines George S. Ansell Department of Metallurgical and Materials Engineering GoldenCO80401 United States Federal University of Paraíba Graduate Program in Materials Science and Engineering PB João Pessoa58051-900 Brazil Federal University of Paraíba Department of Materials Engineering PB João Pessoa58051-900 Brazil Federal University of Paraíba Department of Mechanical Engineering PB João Pessoa58051-900 Brazil

In this work, the influence of the solidification process on the microstructure, thermodynamic parameters and mechanical properties of CuAlBeNbNi shape memory alloy (SMA) was investigated. While directional solidification has been used to improve functional properties in Cu-based SMAs, the squeeze casting process has not yet been explored. The results indicate that the processes of unidirectional solidification and squeeze casting offer an alternative method to modify the thermodynamic parameters, mechanical properties, and microstructural properties of the CuAlBeNbNi SMA while keeping the composition constant. This study aims to fill the knowledge gap regarding the impact of solidification processes on the properties of Cu-based SMAs, specifically investigating CuAlBeNbNi SMAs. © 2023, The Authors. All rights reserved.

关键词： Microstructural evolution

Formation and Oer Properties of Nano-Porous Concentrated Tivzrnbcofe Alloy

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SSRN 2024年

作者： Jorge, Alberto M. Chatenet, Marian Roche, Virginie Berthomé, Gregory Champion, Yannick LEPMI Grenoble38000 France Univ. Grenoble Alpes CNRS Grenoble INP SIMaP Grenoble38000 France Federal University of Sao Carlos Graduate Program of Materials Science and Engineering DEMa Sao Carlos13565-905 Brazil

A nano-porous Ti25 V0.5Zr13Nb51Co6Fe4 metallic alloy was produced by de-alloying (Ti31V26Zr12Nb26Co5)50Fe50. The material was characterized using X-ray diffraction and SEM imaging showing complex concentrated solid solution and interesting OER properties were revealed from cyclic voltammetry. X-ray photoelectron spectroscopy shows a significant content of Fe-doped Co(OH)2 at the surface of the nanoporous alloy that explains the high OER activity. Nanoporous structure in particular nanosized ligaments and surface curvature are identified in connexion to the OER properties. © 2024, The Authors. All rights reserved.

关键词： Cyclic voltammetry