5,951 research outputs found
Restricted dog leucocyte antigen (DLA) class II haplotypes and genotypes in Beagles
AbstractBeagles are commonly used in vaccine trials as part of the regulatory approval process. Genetic restriction within this breed and the impact this might have on vaccine responses are rarely considered. This study was designed to characterise diversity of dog leucocyte antigen (DLA) class II genes in a breeding colony of laboratory Beagles, whose offspring are used in vaccine studies. DLA haplotypes were determined by PCR and sequence-based typing from genomic DNA extracted from blood. Breeding colony Beagles had significantly different DLA haplotype frequencies in comparison with pet Beagles and both groups showed limited DLA diversity. Restricted DLA class II genetic variability within Beagles might result in selective antigen presentation and vaccine responses that are not necessarily representative of those seen in other dog breeds
Reversible enhancement of the magnetism of ultrathin Co films by H adsorption
By means of ab initio calculations, we have investigated the effect of H
adsorption in the structural, electronic and magnetic properties of ultrathin
Co films on Ru(0001). Our calculations predict that H occupies hollow sites
preserving the two-dimensional 3-fold symmetry. The formation of a complete H
overlayer leads to a very stable surface with strong H-Co bonds. H tends to
suppress surface features, in particular, the enhancement of the magnetic
moments of the bare film. The H-induced effects are mostly confined to the Co
atoms bonded to H, independent of the H coverage or of the thickness and the
structure of the Co film. However, for partial H coverages a significant
increase occurs in the magnetic moment for the surface Co atoms not bonded to
H, leading to a net enhancement of surface magnetism.Comment: 6 pages, 4 figures, 3 table
A minor-merger origin for inner disks and rings in early-type galaxies
Nuclear disks and rings are frequent galaxy substructures, for a wide range
of morphological types (from S0 to Sc). We have investigated the possible
minor-merger origin of inner disks and rings in spiral galaxies through
collisionless N-body simulations. The models confirm that minor mergers can
drive the formation of thin, kinematically-cold structures in the center of
galaxies out of satellite material, without requiring the previous formation of
a bar. Satellite core particles tend to be deposited in circular orbits in the
central potential, due to the strong circularization experienced by the
satellite orbit through dynamical friction. The material of the satellite core
reaches the remnant center if satellites are dense or massive, building up a
thin inner disk; whereas it is fully disrupted before reaching the center in
the case of low-mass satellites, creating an inner ring instead.Comment: 2 pages, 2 figures, Proceedings of the conference "Hunting for the
Dark: The Hidden Side of Galaxy Formation", held in Malta, 19-23 Oct. 2009,
ed. V. Debattista and C. C. Popescu, AIP Conf. Ser., in pres
Surface roughness and thermal conductivity of semiconductor nanowires: going below the Casimir limit
By explicitly considering surface roughness at the atomic level, we
quantitatively show that the thermal conductivity of Si nanowires can be lower
than Casimir's classical limit. However, this violation only occurs for deep
surface degradation. For shallow surface roughness, the Casimir formula is
shown to yield a good approximation to the phonon mean free paths and
conductivity, even for nanowire diameters as thin as 2.22 nm. Our exact
treatment of roughness scattering is in stark contrast with a previously
proposed perturbative approach, which is found to overpredict scattering rates
by an order of magnitude. The obtained results suggest that a complete
theoretical understanding of some previously published experimental results is
still lacking.Comment: 11 pages, 4 figure
Scaling of Local Slopes, Conservation Laws and Anomalous Roughening in Surface Growth
We argue that symmetries and conservation laws greatly restrict the form of
the terms entering the long wavelength description of growth models exhibiting
anomalous roughening. This is exploited to show by dynamic renormalization
group arguments that intrinsic anomalous roughening cannot occur in local
growth models. However some conserved dynamics may display super-roughening if
a given type of terms are present.Comment: To appear in Phys. Rev. Lett., 4 pages in RevTeX style, no fig
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