4,277 research outputs found
SO(5) superconductor in a Zeeman magnetic field: Phase diagram and thermodynamic properties
In this paper we present calculations of the SO(5) quantum rotor theory of
high-T superconductivity in Zeeman magnetic field. We use the spherical
approach for five-component quantum rotors in three-dimensional lattice to
obtain formulas for critical lines, free energy, entropy and specific heat and
present temperature dependences of these quantities for different values of
magnetic field. Our results are in qualitative agreement with relevant
experiments on high-T cuprates.Comment: 4 pages, 2 figures, to appear in Phys. Rev. B, see http://prb.aps.or
Transition in a numerical model of contact line dynamics and forced dewetting
We investigate the transition to a Landau-Levich-Derjaguin film in forced
dewetting using a quadtree adaptive solution to the Navier-Stokes equations
with surface tension. We use a discretization of the capillary forces near the
receding contact line that yields an equilibrium for a specified contact angle
called the numerical contact angle. Despite the well-known
contact line singularity, dynamic simulations can proceed without any explicit
additional numerical procedure. We investigate angles from to
and capillary numbers from to where the mesh size
is varied in the range of to of the capillary length
. To interpret the results, we use Cox's theory which involves a
microscopic distance and a microscopic angle . In the numerical
case, the equivalent of is the angle and we find
that Cox's theory also applies. We introduce the scaling factor or gauge
function so that and estimate this gauge function by
comparing our numerics to Cox's theory. The comparison provides a direct
assessment of the agreement of the numerics with Cox's theory and reveals a
critical feature of the numerical treatment of contact line dynamics: agreement
is poor at small angles while it is better at large angles. This scaling factor
is shown to depend only on and the viscosity ratio . In the
case of small , we use the prediction by Eggers [Phys. Rev. Lett.,
vol. 93, pp 094502, 2004] of the critical capillary number for the
Landau-Levich-Derjaguin forced dewetting transition. We generalize this
prediction to large and arbitrary and express the critical
capillary number as a function of and . An analogy can be drawn
between and the numerical slip length.Comment: This version of the paper includes the corrections indicated in Ref.
[1
Biologia de Cinara pinivora (Hemoptera: Aphididae), em duas temperaturas, em laboratĂłrio.
Organizado por PatrĂcia PĂłvoa de Mattos, Celso Garcia Auer, Paulo CĂ©sar Botosso e Rejane Stumpf Sberze
A momentum-conserving, consistent, Volume-of-Fluid method for incompressible flow on staggered grids
The computation of flows with large density contrasts is notoriously
difficult. To alleviate the difficulty we consider a consistent mass and
momentum-conserving discretization of the Navier-Stokes equation.
Incompressible flow with capillary forces is modelled and the discretization is
performed on a staggered grid of Marker and Cell type. The Volume-of-Fluid
method is used to track the interface and a Height-Function method is used to
compute surface tension. The advection of the volume fraction is performed
using either the Lagrangian-Explicit / CIAM (Calcul d'Interface Affine par
Morceaux) method or the Weymouth and Yue (WY) Eulerian-Implicit method. The WY
method conserves fluid mass to machine accuracy provided incompressiblity is
satisfied which leads to a method that is both momentum and mass-conserving. To
improve the stability of these methods momentum fluxes are advected in a manner
"consistent" with the volume-fraction fluxes, that is a discontinuity of the
momentum is advected at the same speed as a discontinuity of the density. To
find the density on the staggered cells on which the velocity is centered, an
auxiliary reconstruction of the density is performed. The method is tested for
a droplet without surface tension in uniform flow, for a droplet suddenly
accelerated in a carrying gas at rest at very large density ratio without
viscosity or surface tension, for the Kelvin-Helmholtz instability, for a
falling raindrop and for an atomizing flow in air-water conditions
Di-ÎŒ-acetato-bisÂ(dimethylÂformamide)ÂpentaÂkisÂ(ÎŒ-N,2-dioxidobenzene-1-carÂboximidato)tetraÂkisÂ(1-ethylÂimidazole)ÂpentaÂmanganese(III)Âmanganese(II)âdiethyl etherâdimethylÂforamideâmethanolâwater (1/1/1/1/0.12)
The title compound [Mn6(C7H4NO3)5(CH3CO2)2(C5H8N2)4(C3H7NO)2]·(C2H5)2O·C3H7NO·CH3OH·0.12H2O, abbreviated as MnII(OAc)2[15-MCMnIII(N)shi-5](EtIm)4(DMF)2·diethyl ether·DMF·MeOH·0.12H2O (where âOAc is acetate, MC is metallacrown, shi3â is salicylhydroximate, EtIM is n-ethylimidazole, DMF is N,N-dimethylformamide, and MeOH is methanol) contains five MnIII ions as members of the metallacrown ring and an MnII ion bound in the central cavity. The central MnII ion is seven-coordinate with a distorted face-capped trigonalâprismatic geometry. The five MnIII ions of the metallacrown ring are six-coordinate with distorted octaÂhedral geometries. The configuration of the MnIII ions about the metallacrown ring follow a ÎÎÎPP pattern, with P representing planar. The four 1-ethylÂimidazole ligands are bound to four different MnIII ions. A diethyl ether solvent molÂecule was found to be disordered over two mutually exclusive sites with an occupancy ratio of 0.568â
(7):0.432â
(7). A methanol solvent molÂecule was found to be disordered over two mutually exclusive sites by being hydrogen bonded either to a dimethylÂformamide solvent molÂecule (major occupancy component) or to an O atom of the main molÂecule (minor occupancy component). The occupancy ratio refined to 0.678â
(11):0.322â
(11). Associated with the minor component is a partially occupied water molÂecule [total occupancy 0.124â
(15)]
Relativity and the lead-acid battery
The energies of the solid reactants in the lead-acid battery are calculated
ab initio using two different basis sets at non-relativistic, scalar
relativistic, and fully relativistic levels, and using several
exchange-correlation potentials. The average calculated standard voltage is
2.13 V, compared with the experimental value of 2.11 V. All calculations agree
in that 1.7-1.8 V of this standard voltage arise from relativistic effects,
mainly from PbO2 but also from PbSO4
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