17,708 research outputs found
Pure infiniteness, stability and C*-algebras of graphs and dynamical systems
Pure infiniteness (in sense of E.Kirchberg and M.R{\o}rdam) is considered for
C*-algebras arising from singly generated dynamical systems. In particular,
Cuntz-Krieger algebras and their generalizations, i.e., graph-algebras and O_A
of an infinite matrix A, admit characterizations of pure infiniteness. As a
consequence, these generalized Cuntz-Krieger algebras are traceless if and only
if they are purely infinite. Also, a characterization of AF-algebras among
these C*-algebras is given. In the case of graph-algebras of locally finite
graphs, characterizations of stability are obtained.Comment: 31 page
Blister patterns and energy minimization in compressed thin films on compliant substrates
This paper is motivated by the complex blister patterns sometimes seen in
thin elastic films on thick, compliant substrates. These patterns are often
induced by an elastic misfit which compresses the film. Blistering permits the
film to expand locally, reducing the elastic energy of the system. It is
natural to ask: what is the minimum elastic energy achievable by blistering on
a fixed area fraction of the substrate? This is a variational problem involving
both the {\it elastic deformation} of the film and substrate and the {\it
geometry} of the blistered region. It involves three small parameters: the {\it
nondimensionalized thickness} of the film, the {\it compliance ratio} of the
film/substrate pair and the {\it mismatch strain}. In formulating the problem,
we use a small-slope (F\"oppl-von K\'arm\'an) approximation for the elastic
energy of the film, and a local approximation for the elastic energy of the
substrate.
For a 1D version of the problem, we obtain "matching" upper and lower bounds
on the minimum energy, in the sense that both bounds have the same scaling
behavior with respect to the small parameters. For a 2D version of the problem,
our results are less complete. Our upper and lower bounds only "match" in their
scaling with respect to the nondimensionalized thickness, not in the dependence
on the compliance ratio and the mismatch strain. The upper bound considers a 2D
lattice of blisters, and uses ideas from the literature on the folding or
"crumpling" of a confined elastic sheet. Our main 2D result is that in a
certain parameter regime, the elastic energy of this lattice is significantly
lower than that of a few large blisters
Reaction rate in a heat bath
We show in detail how the presence of a heat bath of photons effectively
gives charged particles in the final state of a decay process a
temperature-dependent mass, and changes the effective strength of the force
responsible for the decay. At low temperature, gauge invariance causes both
these effects to be largely cancelled by absorption of photons from the heat
bath and by stimulated emission into it, but at high temperature the
temperature-dependent mass is the dominant feature.Comment: 9 pages plus one figur
Optical Hyperlens: Far-field imaging beyond the diffraction limit
We propose an approach to far-field optical imaging beyond the diffraction
limit. The proposed system allows image magnification, is robust with respect
to material losses and can be fabricated by adapting existing metamaterial
technologies in a cylindrical geometry
Regional Trends in U.S. Milk Production: Analysis and Projections
Livestock Production/Industries,
Comparison of serum immunoglobulin G half-life in dairy calves fed colostrum, colostrum replacer or administered with intravenous bovine plasma.
In calves, passive immunity of immunoglobulins can be acquired through ingestion of colostrum or colostrum replacers. Plasma can been used to supplement immunoglobulins in healthy or sick calves. Serum half-life of colostral derived immuglobulin G (IgG) is estimated to be 20 days. Half-life of IgG is important in determining response to antigens and timing of vaccination in calves. To date studies evaluating half-life of colostrum replacer or plasma derived IgG are lacking. The objectives of this study were to compare the serum half-life of IgG derived from colostrum, colostrum replacer and plasma in dairy calves reared up to 35 days of age. Thirty Jersey calves were randomly assigned to receive colostrum or colostrum replacer by oroesophageal tubing or plasma by intravenous administration. Serum samples were collected at 2, 5, 7, 10, 14, 21, 28 and 35 days. Serum IgG concentrations were determined by radial immunodiffusion. The results indicated that half-life for IgG in colostrum fed (28.5 days) or plasma transfused calves (27.3 days) was longer than colostrum replacer fed calves (19.1 days). Further studies are required to evaluate pathogen specific immunoglobulins in order to recommend vaccination timing in calves fed colostrum replacers
Triplet supercurrent due to spin-active zones in a Josephson junction
Motivated by a recent experiment evidencing triplet superconductivity in a
ferromagnetic Josephson junction with a CuMnAl-Heusler barrier, we
construct a theoretical model accounting for this observation. The key
ingredients in our model which generate the triplet supercurrent are
\textit{spin-active zones}, characterised by an effective canted interface
magnetic moment. Using a numerical solution of the quasiclassical equations of
superconductivity with spin-active boundary conditions, we find qualitatively
very good agreement with the experimentally observed supercurrent. Further
experimental implications of the spin-active zones are discussed.Comment: 4 pages, 4 figures. Revised version with additional results. Accepted
for publication in PRB Rapid Communication
Triplet proximity effect and odd-frequency pairing in graphene
We study the interplay between proximity-induced superconductivity and
ferromagnetism in graphene by self-consistently solving the Bogoliubov-de
Gennes equations on the honeycomb lattice. We find that a strong triplet
proximity effect is generated in graphene, leading to odd-frequency pairing
correlations. These odd-frequency correlations are clearly manifested in the
local density of states of the graphene sheet, which can be probed via
STM-measurements. Motivated by recent experiments on SNS graphene
Josephson junctions, we also study the spectrum of Andreev-bound states formed
in the normal region due to the proximity effect. Our results may be useful for
interpreting spectroscopic data and can also serve as a guideline for future
experiments.Comment: 4 pages, 3 figures. Submitted to Physical Review
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