527 research outputs found

    Bulk and surface-sensitive high-resolution photoemission study of Mott-Hubbard systems SrVO3_3 and CaVO3_3

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    We study the electronic structure of Mott-Hubbard systems SrVO3_{3} and CaVO3_3 with bulk and surface-sensitive high-resolution photoemission spectroscopy (PES), using a VUV laser, synchrotron radiation and a discharge lamp (hνh\nu = 7 - 21 eV). A systematic suppression of the density of states (DOS) within \sim 0.2 eV of the Fermi level (EFE_F) is found on decreasing photon energy i.e. on increasing bulk sensitivity. The coherent band in SrVO3_{3} and CaVO3_3 is shown to consist of surface and bulk derived features, separated in energy. The stronger distortion on surface of CaVO3_{3} compared to SrVO3_{3} leads to higher surface metallicity in the coherent DOS at EFE_F, consistent with recent theory.Comment: 4 pages 5 figures (including 2 auxiliary figures); A complete analysis of the spectra based on the surface and bulk analysis shows in auxiliary figures Fig. A1 and A

    Creation and Reproduction of Model Cells with Semipermeable Membrane

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    A high activity of reactions can be confined in a model cell with a semipermeable membrane in the Schl\"ogl model. It is interpreted as a model of primitive metabolism in a cell. We study two generalized models to understand the creation of primitive cell systems conceptually from the view point of the nonlinear-nonequilibrium physics. In the first model, a single-cell system with a highly active state confined by a semipermeable membrane is spontaneously created from an inactive homogeneous state by a stochastic jump process. In the second model, many cell structures are reproduced from a single cell, and a multicellular system is created.Comment: 11 pages, 7 figure

    Suppression of atomic displacive excitation in photo-induced A1g_{\mathrm{1g}} phonon mode of bismuth

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    Atomic motion of a photo-induced coherent phonon of bismuth (Bi) is directly observed with time-resolved x-ray diffraction under a cryogenic temperature. It is found that displacive excitation in a fully symmetric A1g_{\mathrm{1g}} phonon mode is suppressed at a temperature T=9T = 9 K. This result implies a transfer of the phonon-generation mechanism from displacive to impulsive excitation with decreasing the temperature. It is comprehensively understandable in a framework of stimulated Raman scattering. The suppression of displacive excitation also indicates that the adiabatic potential surface at the photo-excited state deviates from a parabolic one, which is assumed to be realized at room temperature. This study points out important aspects of phonon generation in transient phonon-induced quantum phenomena

    Nonlinearity of Mechanochemical Motions in Motor Proteins

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    The assumption of linear response of protein molecules to thermal noise or structural perturbations, such as ligand binding or detachment, is broadly used in the studies of protein dynamics. Conformational motions in proteins are traditionally analyzed in terms of normal modes and experimental data on thermal fluctuations in such macromolecules is also usually interpreted in terms of the excitation of normal modes. We have chosen two important protein motors - myosin V and kinesin KIF1A - and performed numerical investigations of their conformational relaxation properties within the coarse-grained elastic network approximation. We have found that the linearity assumption is deficient for ligand-induced conformational motions and can even be violated for characteristic thermal fluctuations. The deficiency is particularly pronounced in KIF1A where the normal mode description fails completely in describing functional mechanochemical motions. These results indicate that important assumptions of the theory of protein dynamics may need to be reconsidered. Neither a single normal mode, nor a superposition of such modes yield an approximation of strongly nonlinear dynamics.Comment: 10 pages, 6 figure

    European society of urogenital radiology (ESUR) guidelines: MR imaging of pelvic endometriosis

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    Endometriosis is a common gynaecological condition of unknown aetiology that primarily affects women of reproductive age. The accepted first-line imaging modality is pelvic ultrasound. However, magnetic resonance imaging (MRI) is increasingly performed as an additional investigation in complex cases and for surgical planning. There is currently no international consensus regarding patient preparation, MRI protocols or reporting criteria. Our aim was to develop clinical guidelines for MRI evaluation of pelvic endometriosis based on literature evidence and consensus expert opinion. This work was performed by a group of radiologists from the European Society of Urogenital Radiology (ESUR), experts in gynaecological imaging and a gynaecologist expert in methodology. The group discussed indications for MRI, technical requirements, patient preparation, MRI protocols and criteria for the diagnosis of pelvic endometriosis on MRI. The expert panel proposed a final recommendation for each criterion using Oxford Centre for Evidence Based Medicine (OCEBM) 2011 levels of evidence.info:eu-repo/semantics/publishedVersio

    Quest for a potent antimalarial drug lead: synthesis and evaluation of 6,7-dimethoxyquinazoline-2,4-diamines

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    Quinazolines have long been known to exert varied pharmacologic activities that make them suitable for use in treating hypertension, viral infections, tumors, and malaria. Since 2014, we have synthesized approximately 150 different 6,7-dimethoxyquinazoline-2,4-diamines and evaluated their antimalarial activity via structure-activity relationship studies. Here, we summarize the results and report the discovery of 6,7-dimethoxy-N(4)-(1-phenylethyl)-2-(pyrrolidin-1-yl)quinazolin-4-amine (20, SSJ-717), which exhibits high antimalarial activity as a promising antimalarial drug lead

    Observation of a superconducting gap in boron-doped diamond by laser-excited photoemission spectroscopy

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    &lt;p&gt;We investigate the temperature (T)-dependent low-energy electronic structure of a boron-doped diamond thin film using ultrahigh resolution laser-excited photoemission spectroscopy. We observe a clear shift of the leading edge below T=11 K, indicative of a superconducting gap opening (Delta~0.78 meV at T=4.5 K). The gap feature is significantly broad and a well-defined quasiparticle peak is lacking even at the lowest temperature of measurement (=4.5 K). We discuss our results in terms of disorder effects on the normal state transport and superconductivity in this system.&lt;/p&gt;</p

    Thermal acclimation of leaf photosynthetic traits in an evergreen woodland, consistent with the coordination hypothesis

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    Ecosystem models commonly assume that key photosynthetic traits, such as carboxylation capacity measured at a standard temperature, are constant in time. The temperature responses of modelled photosynthetic or respiratory rates then depend entirely on enzyme kinetics. Optimality considerations, however, suggest this assumption may be incorrect. The coordination hypothesis (that Rubisco- and electron-transport-limited rates of photosynthesis are co-limiting under typical daytime conditions) predicts, instead, that carboxylation (Vcmax) capacity should acclimate so that it increases somewhat with growth temperature but less steeply than its instantaneous response, implying that Vcmax when normalized to a standard temperature (e.g. 25 °C) should decline with growth temperature. With additional assumptions, similar predictions can be made for electron-transport capacity (Jmax) and mitochondrial respiration in the dark (Rdark). To explore these hypotheses, photosynthetic measurements were carried out on woody species during the warm and the cool seasons in the semi-arid Great Western Woodlands, Australia, under broadly similar light environments. A consistent proportionality between Vcmax and Jmax was found across species. Vcmax, Jmax and Rdark increased with temperature in most species, but their values standardized to 25 °C declined. The ci : ca ratio increased slightly with temperature. The leaf N  :  P ratio was lower in the warm season. The slopes of the relationships between log-transformed Vcmax and Jmax and temperature were close to values predicted by the coordination hypothesis but shallower than those predicted by enzyme kinetics.This research was funded by the Terrestrial Ecosystem Research Network (TERN), Macquarie University and the Australian National University. Henrique Fürstenau Togashi was supported by an international Macquarie University International Research Scholarship (iMQRES). Iain Colin Prentice, Bradley John Evans, and Henrique Fürstenau Togashi were funded by the Ecosystem Modelling and Scaling Infrastructure (eMAST, part of TERN). TERN and eMAST have been supported by the Australian Government through the National Collaborative Research Infrastructure Strategy (NCRIS). Owen Atkin acknowledges the support of the Australian Research Council (DP130101252 and CE140100008)
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