2,522 research outputs found
Model reconstructions for the Si(337) orientation
Although unstable, the Si(337) orientation has been known to appear in
diverse experimental situations such as the nanoscale faceting of Si(112), or
in the case of miscutting a Si(113) surface. Various models for Si(337) have
been proposed over time, which motivates a comprehensive study of the structure
of this orientation. Such a study is undertaken in this article, where we
report the results of a genetic algorithm optimization of the Si(337)- surface. The algorithm is coupled with a highly optimized empirical
potential for silicon, which is used as an efficient way to build a set of
possible Si(337) models; these structures are subsequently relaxed at the level
of ab initio density functional methods. Using this procedure, we retrieve most
of the (337) reconstructions proposed in previous works, as well as a number of
novel ones.Comment: 5 figures (low res.); to appear in J. Appl. Phy
Rapid communication: Mapping of the \u3ci\u3eCa\u3csup\u3e2+\u3c/sup\u3e ATPase of fast twitch 1 skeletal muscle sarcoplasmic reticulum (ATP2A1)\u3c/i\u3e gene to porcine chromosome 3
Locus Name. Ca2+ ATPase of fast twitch 1 skeletal muscle sarcoplasmic reticulum.
Species. Sus scrofa.
Locus Symbol. ATP2A1.
Source of Primers. Two sets of PCR primers were designed based on human ATP2A1 sequences (Gen- Bank accession numbers U96773 and U96777) available in the GenBank database. Using pig genomic DNA as a template we used set A primers to amplify approximately 1,100 bp spanning exon 1 to exon 2 and set B primers to amplify 1,200 bp gene segment covering some of exon 8 through part of exon 9. These sequences were deposited in GenBank, accession number AY027797-AY027799
Ground states of a mixture of two species of spin-1 Bose gases with interspecies spin exchange in a magnetic field
We consider a mixture of two species of spin-1 atoms with both interspecies
and intraspecies spin exchanges in a weak magnetic field. Under the usual
single mode approximation, it can be reduced to a model of coupled giant spins.
We find most of its ground states. This is a complicated problem of energy
minimization, with three quantum variables under constraints, i.e. the total
spin of each species and the total spin of the whole mixture, as well as four
parameters, including intraspecies and interspecies spin coupling strengths and
the magnetic field. The quantum phase diagram is very rich. Compared with the
case without a magnetic field, the ground states are modified by a magnetic
field, which also modifies the ground state boundaries or introduces new
crossover regimes on the phase diagram. Without interspecies spin coupling, the
quantum phase transitions existing in absence of a magnetic field disappear
when a magnetic field is applied, which leads to crossover regimes in the phase
diagram. Under ferromagnetic interspecies spin coupling, the ground states
remain disentangled no matter whether there is a magnetic field. For
antiferromagnetic interspecies spin coupling, a magnetic field entangles the
ground states in some parameter regimes. When the intraspecies spin couplings
are both ferromagnetic, the quantum phase transition between antiferromagnetic
and zero interspecies spin couplings survives the magnetic field. When the
intraspecies spin couplings are both antiferromagnetic, a magnetic field
induces new quantum phase transitions between antiferromagnetic and zero
interspecies spin couplings.Comment: 17 pages, initially submitted to Phys. Rev. A on September 15 2010,
to appear in Int. J. Mod. Phys.
Understanding single-top-quark production and jets at hadron colliders
I present an analysis of fully differential single-top-quark production plus
jets at next-to-leading order. I describe the effects of jet definitions,
top-quark mass, and higher orders on the shapes and normalizations of the
kinematic distributions, and quantify all theoretical uncertainties. I explain
how to interpret next-to-leading-order jet calculations, and compare them to
showering event generators. Using the program ZTOP, I show that HERWIG and
PYTHIA significantly underestimate both s-channel and t-channel
single-top-quark production, and propose a scheme to match the relevant samples
to the next-to-leading-order predictions.Comment: 40 pgs., revtex4, 35 ps figs; added Fig. 4, 1 Ref., minor
clarifications, to appear in Phys. Rev.
New alleles in calpastatin gene are associated with meat quality traits in pigs
Suggestive QTL affecting raw firmness scores and average Instron force, tenderness, juiciness, and chewiness on cooked meat were mapped to pig chromosome 2 using a three-generation intercross between Berkshire and Yorkshire pigs. Based on its function and location, the calpastatin (CAST) gene was considered to be a good candidate for the observed effects. Several missense and silent mutations were identified in CAST and haplotypes covering most of the coding region were constructed and used for association analyses with meat quality traits. Results demonstrated that one CAST haplotype was significantly associated with lower Instron force and cooking loss and higher juiciness and, therefore, this haplotype is associated with higher eating quality. Some of the sequence variation identified may be associated with differences in phosphorylation of CAST by adenosine cyclic 3′, 5′-monophosphate- dependent protein kinase and may in turn explain the meat quality phenotypic differences. The beneficial haplotype was present in all the commercial breeds tested and may provide significant improvements for the pig industry and consumers because it can be used in marker-assisted selection to produce naturally tender and juicy pork without additional processing steps
Elastic constants of beta-eucryptite: A density functional theory study
The five independent elastic constants of hexagonal -eucryptite have
been determined using density functional theory (DFT) total energy
calculations. The calculated values agree well, to within 15%, with the
experimental data. Using the calculated elastic constants, the linear
compressibility of -eucryptite parallel to the c-axis, , and
perpendicular to it, , have been evaluated. These values are in close
agreement to those obtained from experimentally known elastic constants, but
are in contradiction to the direct measurements based on a three-terminal
technique. The calculated compressibility parallel to the c-axis was found to
positive as opposed to the negative value obtained by direct measurements. We
have demonstrated that must be positive and discussed the implications
of a positive in the context of explaining the negative bulk thermal
expansion of -eucryptite.Comment: 3 eps figures, submitted for publicatio
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