2,675 research outputs found

    Strong, lightweight, and recoverable three-dimensional ceramic nanolattices

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    Ceramics have some of the highest strength- and stiffness-to-weight ratios of any material but are suboptimal for use as structural materials because of their brittleness and sensitivity to flaws. We demonstrate the creation of structural metamaterials composed of nanoscale ceramics that are simultaneously ultralight, strong, and energy-absorbing and can recover their original shape after compressions in excess of 50% strain. Hollow-tube alumina nanolattices were fabricated using two-photon lithography, atomic layer deposition, and oxygen plasma etching. Structures were made with wall thicknesses of 5 to 60 nanometers and densities of 6.3 to 258 kilograms per cubic meter. Compression experiments revealed that optimizing the wall thickness-to-radius ratio of the tubes can suppress brittle fracture in the constituent solid in favor of elastic shell buckling, resulting in ductile-like deformation and recoverability

    Crosslinked poly(acrylic acid) enhances adhesion and electrochemical performance of Si anodes in Li-ion batteries

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    Water-soluble binders such as poly (acrylic acid) (PAA) possess many advantages in the slurry and electrode preparation due to their low-cost and environmental friendliness. However, due to the linear nature of these binders, they are susceptible to slide under the continuous volume variation of Si-containing anodes during cycling. Therefore, a three-dimensional (3D) interconnected polymeric network is required to provide robust mechanical adhesion with the Si particles to maintain the electrode integrity for excellent cycle stability. Here, pentaerythritol (PER) is used as a crosslinking agent to connect the linear PAA binder to enhance its adhesion strength for Si anodes, which is systematically confirmed using Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric (TG) measurements. Si electrodes with crosslinked PAA-PER binder show enhanced adhesion and elasticity, exhibiting a more robust electrode integrity than purely PAA-based Si electrodes. Galvanostatic cycling shows that Si-PAA-5%PER electrodes maintain a higher discharge capacity of 514.3 mAh g-1 (after 10 cycles) for micro-sized and 1502.1 mAh g-1 (after 105 cycles) for nano-sized Si particles compared to 257.6 mAh g-1 and 1413.9 mAh g-1 for micro- and nano-sized Si in Si-PAA electrodes, respectively. XPS analyses on cycled electrodes confirmed that crosslinked PAA-PER binder has no negative effects on the SEI formation and its functionality in Si electrodes. SEM cross-sections reveal that Si-PAA-5%PER electrodes show reduced electrode thickness variation (micro-/nano-: 114.2%/182.2%) than that of Si-PAA electrodes (micro-/nano-: 134.1%/212.0%) after cycling, which indicates that crosslinked PAA-PER binder can enhance the electrode integrity due to its 3D interconnected network. This work provides meaningful insight into the exploration of novel binders and their impact on the SEI formation and functionality, especially for high-capacity alloy-type anode materials

    Anthropocentric Ocean Connectivity: A Pluralistic Legal-Regulatory Model

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    This article proposes a model of anthropocentric ocean connectivity based on the concept of human perspective as location. Within this location, anthropocentrism can be, but is not necessarily, an exclusive or dominant valuation of the human. In fact, conceptions of both anthropocentrism and of ocean connectivity are pluralistic. These and other pluralisms are borne out in this article’s content and structure, which takes the form of explorations of anthropocentric connectivity in relation to four specific ocean-related human activities. First, Jan Solski applies understandings of connectivity as “flow” in the context of strategic ocean geopolitics. Second, Iva Parlov analyzes current doctrinal issues and interactions at the international level with respect to the legal regime for places of refuge for ships in need of assistance. Third, Maria Madalena das Neves examines ocean connectivity in the context of transboundary energy trade and market integration, with particular attention to geopolitical and ecological connectivity. Finally, Julia Gaunce proposes that the making and application of transnational rules and standards for ships in polar waters enhances certain connections and disrupts others, to the detriment of oceans and people, and that broadening connectivity especially in respect of Arctic Indigenous people(s) could help address challenges faced by oceans and ocean governance

    Relations between institutional environment and level of social disclosure in the banking sector: evidence from Latin America

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    The companies seek to legitimize their activities in corporate social responsibility through the dissemination of sustainability reports. The present study aims to verify the existence of relations between the institutional environment and the social disclosure of the Latin American banks listed in Forbes Global 2000, between 2015 and 2017. For this purpose, we analyzed 26 social indicators of the Global Reporting Initiative (GRI) to characterize social disclosure. The institutional environment was characterized by six indicators of the World Economic Forum. In order to relate the dependent variable to the independent variables, four hypotheses were formulated, which were tested using statistical techniques. Evidence obtained in the research indicates that there is a positive relationship between the institutional environment and social disclosure. The results show that the higher the firm's profitability and its age, the higher the level of disclosure. We conclude that the results of the research corroborate previous findings

    Cardiac Repair and Regenerative Potential in the Goldfish (Carassius auratus) Heart

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    The remarkable ability of the heart to regenerate has been demonstrated in the zebrafish and giant danio, two fish members of the cyprinid family. Here we use light and electron microscopy to examine the repair response in the heart of another cyprinid, the goldfish (Carassius auratus), following cautery injury to a small portion of its ventricularmyocardium. We observed a robust inflammatory response in the first two weeks consisting primarily of infiltrating macrophages, heterophils, and melanomacrophages. These inflammatory cells were identified in the lumen of the spongy heart, within the site of the wound, and attached to endocardial cells adjacent to the site of injury. Marked accumulation of collagen fibers and increased connective tissue were also observed during the first and second weeks in a transition zone between healthy and injured myocardium as well as in adjacent sub-epicardial regions. The accumulation of collagen and connective tissue however did not persist. The presence of capillaries was also noted in the injured area during repair. The replacement of the cauterized region of the ventricle by myocardial tissue was achieved in 6 weeks. The presence of ethynyl deoxyuridinepositive cardiac myocytes and partially differentiated cardiac myocytes during repair suggest effective cardiac myocyte driven regeneration mechanisms also operate in the injured goldfish heart, and are similar to those observed in zebrafish and giant danio. Our data suggest the ability for cardiac regeneration may be widely conserved among cyprinids

    OURIKA: NOTÍCIAS DE UMA NARRATIVA DO SÉCULO XIX

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    Monodromy Matrix in the PP-Wave Limit

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    We construct the monodromy matrix for a class of gauged WZWN models in the plane wave limit and discuss various properties of such systems.Comment: 16 page
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