527 research outputs found
Bulk and surface-sensitive high-resolution photoemission study of Mott-Hubbard systems SrVO and CaVO
We study the electronic structure of Mott-Hubbard systems SrVO and
CaVO with bulk and surface-sensitive high-resolution photoemission
spectroscopy (PES), using a VUV laser, synchrotron radiation and a discharge
lamp ( = 7 - 21 eV). A systematic suppression of the density of states
(DOS) within 0.2 eV of the Fermi level () is found on decreasing
photon energy i.e. on increasing bulk sensitivity. The coherent band in
SrVO and CaVO is shown to consist of surface and bulk derived
features, separated in energy. The stronger distortion on surface of CaVO
compared to SrVO leads to higher surface metallicity in the coherent DOS
at , 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
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 A phonon mode of bismuth
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 A
phonon mode is suppressed at a temperature 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
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
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
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
<p>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.</p></p
Thermal acclimation of leaf photosynthetic traits in an evergreen woodland, consistent with the coordination hypothesis
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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Functional trait variation related to gap dynamics in tropical moist forests: a vegetation modelling perspective
The conventional representation of Plant Functional Types (PFTs) in Dynamic Global Vegetation Models (DGVMs) is increasingly recognized as simplistic and lacking in predictive power. Key ecophysiological traits, including photosynthetic parameters, are typically assigned single values for each PFT while the substantial trait variation within PFTs is neglected. This includes continuous variation in response to environmental factors, and differences linked to spatial and temporal niche differentiation within communities. A much stronger empirical basis is required for the treatment of continuous plant functional trait variation in DGVMs. We analyse 431 sets of measurements of leaf and plant traits, including photosynthetic measurements, on evergreen angiosperm trees in tropical moist forests of Australia and China. Confining attention to tropical moist forests, our analysis identifies trait differences that are linked to vegetation dynamic roles. Coordination theory predicts that Rubisco- and electron-transport limited rates of photosynthesis are co-limiting under field conditions. The least-cost hypothesis predicts that air-to-leaf CO2 drawdown minimizes the combined costs per unit carbon assimilation of maintaining carboxylation and transpiration capacities. Aspects of these predictions are supported for within-community trait variation linked to canopy position, just as they are for variation along spatial environmental gradients. Trait differences among plant species occupying different structural and temporal niches may provide a basis for the ecophysiological representation of vegetation dynamics in next-generation DGVMs
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