Ma C.,University of California at San Diego |
Xu J.,University of California at San Diego |
Xu J.,Lawrence Berkeley National Laboratory |
Alvarado J.,University of California at San Diego |
And 5 more authors.
Chemistry of Materials | Year: 2015
Tin sulfide-reduced graphene oxide (SnS2-rGO) composite material is investigated as an advanced anode material for Na-ion batteries. It can deliver a reversible capacity of 630 mAh g-1 with negligible capacity loss and exhibits superb rate performance. Here, the energy storage mechanism of this SnS2-rGO anode and the critical mechanistic role of rGO will be revealed in detail. A synergistic mechanism involving conversion and alloying reactions is proposed based on our synchrotron X-ray diffraction (SXRD) and in situ X-ray absorption spectroscopy (XAS) results. Contrary to what has been proposed in the literature, we determined that Na2S2 forms instead of Na2S at the fully discharge state. The as-formed Na2S2 works as a matrix to relieve the strain from the huge volume expansion of the Na-Sn alloy reaction, shown in the high resolution transmission electron microscope (HRTEM). In addition, the Raman spectra results suggest that the rGO not only assists the material to have better electrochemical performance by preventing particle agglomeration of the active material but also coordinates with Na-ions through electrostatic interaction during the first cycle. The unique reaction mechanism in SnS2-rGO offers a well-balanced approach for sodium storage to deliver high capacity, long-cycle life, and superior rate capability. (Chemical Equation Presented). © 2015 American Chemical Society.
Saranathan V.,Yale University |
Saranathan V.,University of Oxford |
Saranathan V.,Linacre College |
Forster J.D.,Yale University |
And 7 more authors.
Journal of the Royal Society Interface | Year: 2012
Non-iridescent structural colours of feathers are a diverse and an important part of the phenotype of many birds. These colours are generally produced by three-dimensional, amorphous (or quasi-ordered) spongy b-keratin and air nanostructures found in the medullary cells of feather barbs. Two main classes of three-dimensional barb nanostructures are known, characterized by a tortuous network of air channels or a close packing of spheroidal air cavities. Using synchrotron small angle X-ray scattering (SAXS) and optical spectrophotometry, we characterized the nanostructure and optical function of 297 distinctly coloured feathers from 230 species belonging to 163 genera in 51 avian families. The SAXS data provided quantitative diagnoses of the channel- and sphere-type nanostructures, and confirmed the presence of a predominant, isotropic length scale of variation in refractive index that produces strong reinforcement of a narrow band of scattered wavelengths. The SAXS structural data identified a new class of rudimentary or weakly nanostructured feathers responsible for slate-grey, and blue-grey structural colours. SAXS structural data provided good predictions of the single-scattering peak of the optical reflectance of the feathers. The SAXS structural measurements of channel- and sphere-type nanostructures are also similar to experimental scattering data from synthetic soft matter systems that self-assemble by phase separation. These results further support the hypothesis that colour-producing protein and air nanostructures in feather barbs are probably self-assembled by arrested phase separation of polymerizing β-keratin from the cytoplasm of medullary cells. Such avian amorphous photonic nanostructures with isotropic optical properties may provide biomimetic inspiration for photonic technology. © 2012 The Royal Society.
Head C.E.I.,University of Oxford |
Head C.E.I.,Linacre College |
Bonsall M.B.,University of Oxford |
Bonsall M.B.,St Peters College |
And 4 more authors.
Coral Reefs | Year: 2015
Small and cryptic organisms that live within the interstices of reef habitats contribute greatly to coral reef biodiversity, but are poorly studied. Many species of cryptofauna have seemingly obligate associations with live coral and are therefore considered to be very vulnerable to coral mortality. Here we report the unanticipated prevalence of obligate coral-dwelling decapod crustaceans on dead colonies of branching corals in the Chagos Archipelago (British Indian Ocean Territory) in the central Indian Ocean. A total of 205 obligate coral-dwelling decapods, including Trapezia crabs, were recorded from 43 (out of 54) dead coral colonies of Acropora and Pocillopora collected across five different atolls. Trapezia individuals found on dead corals were mainly juveniles, and the few adults were almost exclusively male. Among the shrimps (Pontoniinae), however, it was predominantly adult females found on dead corals. Obligate coral-dwelling species that typically occur only on live Pocillopora hosts (e.g., Trapezia spp.) were recorded on dead Acropora. These findings suggests that these obligate coral-dwelling decapods are not simply persisting on coral hosts that have died, but may be explicitly recruiting to or moving to dead coral hosts at certain stages in their life cycle. Variation in the abundance of live coral among sites had no affect on the presence or abundance of obligate coral-dwelling decapods on dead corals. This study shows that habitat associations of obligate coral-dwelling organisms, and their reliance on different habitat types, are complex and further work is required to establish their vulnerability to widespread habitat degradation on coral reefs. © 2015, The Author(s).
Harre R.,Linacre College
Hyle | Year: 2014
Three concepts have recently been added to the resources of the philosophy of chemistry - 'affordance' from J.J. Gibson's (1967) perception studies, 'hinge' from Ludwig Wittgenstein's later philosophy (Wittgenstein 1974), and the 'mereological fallacies' from the critical discussion of neuropsychology by M.R. Bennett and P.M.S. Hacker (2003). Together they have to some extent opened the way for a reshaping of the materialist metaphysics of chemistry. When made use of in the philosophy of chemistry they also represent a renewed emphasis on chemical practice and its relation to the products of chemical activity. In addition to that shift of emphasis, the analytical use of the three concepts reveals the extent to which the environment of chemical processes is an essential component in chemical explanations. The analytical tool kit is completed by the revival of the model centered approach to the understanding of how the content of theories is established, changes, and grows. The fourth concept, that of the 'iconic model' (Hesse 1963), completes the equipment needed to examine the intelligibility of chemical discourse and practice in more detail than heretofore. © 2014 by HYLE and Rom Harré.
Nikitenko L.L.,University College London |
Nikitenko L.L.,Keble College |
Nikitenko L.L.,Linacre College |
Shimosawa T.,University of Tokyo |
And 8 more authors.
Journal of Investigative Dermatology | Year: 2013
Secondary lymphedema is a debilitating condition, and genetic factors predisposing to its development remain largely unknown. Adrenomedullin (AM) is peptide encoded, together with proadrenomedullin N-terminal peptide (PAMP), by the Adm gene (adrenomedullin gene). AM and its putative receptor calcitonin receptor-like receptor (CLR) are implicated in angiogenesis and lymphangiogenesis during embryogenesis and wound healing, suggesting their possible involvement in secondary lymphedema. To investigate whether AM deficiency predisposes to secondary lymphedema, we used heterozygous adult mice with Adm gene-knockin stop mutation, which selectively abrogated AM, but preserved PAMP, expression (Adm AM+/Δ animals). After hind limb skin incision, Adm messenger RNA expression was upregulated in wounded tissue of both Adm AM+/+ and Adm AM+/Δ mice. However, only Adm AM+/Δ animals developed limb swelling and histopathological lymphedematous changes, including epidermal thickening, elevated collagen fiber density, and increased microvessel diameter. Secondary lymphedema was prevented when circulating AM levels in Adm AM+/Δ mice were restored by systemic peptide delivery. In human skin, CLR was expressed in tissue components affected by lymphedema, including epidermis, lymphatics, and blood vessels. Our study identified a previously unrecognized role for endogenous AM as a key factor in secondary lymphedema pathogenesis and provided experimental in vivo evidence of an underlying germ-line genetic predisposition to developing this disorder. © 2013 The Society for Investigative Dermatology.