1,961 research outputs found
Functional K ATP channels in the rat retinal microvasculature: topographical distribution, redox regulation, spermine modulation and diabetic alteration
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66207/1/jphysiol.2009.169003.pd
First-principles study on the intermediate compounds of LiBH
We report the results of the first-principles calculation on the intermediate
compounds of LiBH. The stability of LiBH and LiBH has been examined with the ultrasoft pseudopotential method based on
the density functional theory. Theoretical prediction has suggested that
monoclinic LiBH is the most stable among the candidate
materials. We propose the following hydriding/dehydriding process of LiBH
via this intermediate compound : LiBHLiBH LiH HLiH B H. The hydrogen content and enthalpy of the first
reaction are estimated to be 10 mass% and 56 kJ/mol H, respectively, and
those of the second reaction are 4 mass% and 125 kJ/mol H. They are in good
agreement with experimental results of the thermal desorption spectra of
LiBH. Our calculation has predicted that the bending modes for the
-phonon frequencies of monoclinic LiBH are lower than
that of LiBH, while stretching modes are higher. These results are very
useful for the experimental search and identification of possible intermediate
compounds.Comment: 7 pages, 5 figures, submitted to PR
Microstructural characterization of AISI 431 martensitic stainless steel laser-deposited coatings
High cooling rates during laser cladding of stainless steels may alter the microstructure and phase constitution of the claddings and consequently change their functional properties. In this research, solidification structures and solid state phase transformation products in single and multi layer AISI 431 martensitic stainless steel coatings deposited by laser cladding at different processing speeds are investigated by optical microscopy, Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), orientation imaging microscopy (OIM), ternary phase diagram, Schaeffler and TTT diagrams. The results of this study show how partitionless solidification and higher solidification rates alter the microstructure and phase constitution of martensitic stainless steel laser deposited coatings. In addition, it is shown that while different cladding speeds have no effect on austenite–martensite orientation relationship in the coatings, increasing the cladding speed has resulted in a reduction of hardness in deposited coatings which is in contrast to the common idea about obtaining higher hardness values at higher cladding speeds.
Localization properties of a one-dimensional tight-binding model with non-random long-range inter-site interactions
We perform both analytical and numerical studies of the one-dimensional
tight-binding Hamiltonian with stochastic uncorrelated on-site energies and
non-fluctuating long-range hopping integrals . It was argued recently [A.
Rodriguez at al., J. Phys. A: Math. Gen. 33, L161 (2000)] that this model
reveals a localization-delocalization transition with respect to the disorder
magnitude provided . The transition occurs at one of the band edges (the upper
one for and the lower one for). The states at the other band edge are always
localized, which hints on the existence of a single mobility edge. We analyze
the mobility edge and show that, although the number of delocalized states
tends to infinity, they form a set of null measure in the thermodynamic limit,
i.e. the mobility edge tends to the band edge. The critical magnitude of
disorder for the band edge states is computed versus the interaction exponent
by making use of the conjecture on the universality of the normalized
participation number distribution at transition.Comment: 7 pages, 6 postscript figures, uses revtex
Metal Enrichment of the Intergalactic Medium in Cosmological Simulations
Observations have established that the diffuse intergalactic medium (IGM) at
z ~ 3 is enriched to ~0.1-1% solar metallicity and that the hot gas in large
clusters of galaxies (ICM) is enriched to 1/3-1/2 solar metallicity at z=0.
Metals in the IGM may have been removed from galaxies (in which they presumably
form) during dynamical encounters between galaxies, by ram-pressure stripping,
by supernova-driven winds, or as radiation-pressure driven dust efflux. This
study develops a method of investigating the chemical enrichment of the IGM and
of galaxies, using already completed cosmological simulations. To these
simulations, we add dust and (gaseous) metals, distributing the dust and metals
in the gas according to three simple parameterized prescriptions, one for each
enrichment mechanism. These prescriptions are formulated to capture the basic
ejection physics, and calibrated when possible with empirical data. Our results
indicate that dynamical removal of metals from >~ 3*10^8 solar mass galaxies
cannot account for the observed metallicity of low-column density Ly-alpha
absorbers, and that dynamical removal from >~ 3*10^10 solar mass galaxies
cannot account for the ICM metallicities. Dynamical removal also fails to
produce a strong enough mass-metallicity relation in galaxies. In contrast,
either wind or radiation-pressure ejection of metals from relatively large
galaxies can plausibly account for all three sets of observations (though it is
unclear whether metals can be distributed uniformly enough in the low-density
regions without overly disturbing the IGM, and whether clusters can be enriched
quite as much as observed). We investigate in detail how our results change
with variations in our assumed parameters, and how results for the different
ejection processes compare. (Abridged)Comment: Minor revision, 1 figure added addressing diffusion of metals after
their ejection. Accepted by ApJ. 31 EmulateApj Pages with 13 embedded
postscript figure
Localized induction equation and pseudospherical surfaces
We describe a close connection between the localized induction equation
hierarchy of integrable evolution equations on space curves, and surfaces of
constant negative Gauss curvature.Comment: 21 pages, AMSTeX file. To appear in Journal of Physics A:
Mathematical and Genera
Pressure formulas for liquid metals and plasmas based on the density-functional theory
At first, pressure formulas for the electrons under the external potential
produced by fixed nuclei are derived both in the surface integral and volume
integral forms concerning an arbitrary volume chosen in the system; the surface
integral form is described by a pressure tensor consisting of a sum of the
kinetic and exchange-correlation parts in the density-functional theory, and
the volume integral form represents the virial theorem with subtraction of the
nuclear virial. Secondly on the basis of these formulas, the thermodynamical
pressure of liquid metals and plasmas is represented in the forms of the
surface integral and the volume integral including the nuclear contribution.
From these results, we obtain a virial pressure formula for liquid metals,
which is more accurate and simpler than the standard representation. From the
view point of our formulation, some comments are made on pressure formulas
derived previously and on a definition of pressure widely used.Comment: 18 pages, no figur
Hole Dynamics in the Orthogonal-Dimer Spin System
The dynamics of a doped hole in the orthogonal-dimer spin system is
investigated systematically in one, two and three dimensions. By combining the
bond-operator method with the self-consistent
Born approximation, we argue that a dispersive quasi-particle state in the
dimer phase is well defined even for quasi-two-dimensional systems. On the
other hand, a doped hole in the plaquette-singlet phase hardly itinerates,
forming an almost localized mode. We further clarify that although the
quasi-particle weight in the dimer phase is decreased in the presence of the
interchain coupling, it is not suppressed but even enhanced upon the
introduction of the interlayer coupling.Comment: 8 pages, 10 figure
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