38,025 research outputs found
Intestinal Microbial Ecology of Broilers Vaccinated and Challenged With Mixed Eimeria Species, and Supplemented with Essential Oil Blends
Intestinal microbiota is an important component in the development of defense mechanisms in the gut mucosa. This project determined the dynamics of intestinal microbial communities (MC) of broilers vaccinated at first day of age with live oocysts of Eimeria species and fed diets supplemented with 2 specific essential oil (EO) blends, Crina Poultry (CP) and Crina Alternate (CA). Five treatments were analyzed: 1) unmedicated-uninfected (UU) control; 2) unmedicated-infected (UI) control; 3) vaccinated with Advent cocci-vaccine and without feed additive (COV) supplements; 4) vaccinated with Advent and supplemented with CP; and 5) vaccinated with Advent and supplemented with CA. The EO blends were added at 100 ppm to the same basal diets. Chicks were gavage-infected at 19 d of age with Eimeria acervulina, Eimeria maxima, and Eimeria tenella. Duodenal, ileal, and cecal samples were taken from 12 birds per treatment just before the infection and 7 d after the challenge, pooled in 6 samples, and frozen. Denaturing gradient gel electrophoresis was used to examine PCR-amplified fragments of the bacterial 16S ribosomal DNA variable region. Results are presented as percentages of similarity coefficients (SC). Dendrograms of amplicon patterns indicated MC differences due to intestinal location, feed additives, and cocci infection. The EO blends CP and CA did affect MC in all gut sections. The cocci-infection caused drastic MC population shifts in duodenal, ileal, and cecal sections (36.7, 55.4, and 36.2% SC, respectively). The CP-supplemented birds had higher SC between pre- and postchallenge MC in duodenal and ileal (73.3, 81.8%) than COV (66.4, 66.5%). However, COV broilers had the smallest changes in cecal MC after infection (79.5% SC). We concluded that cocci-vaccination causes small changes in intestinal MC, but challenge causes drastic shifts. The EO blend supplementation modulates MC in cocci-vaccinated broilers, avoiding drastic shifts after a mixed coccidia infection. Correlations between MC dynamics and host responses are discussed
Bound state of dimers on a spherical surface
The study of particle motion on spherical surfaces is relevant to adsorption
on buckyballs and other solid particles. This paper reports results for the
binding energy of such dimers, consisting of two light particles (He atoms or
hydrogen molecules) constrained to move on a spherical surface. The binding
energy reaches a particularly large value when the radius of the sphere is
about 3/4 of the particles' diameter.Comment: 6 pages, 3 figures, submitted to JLTP, conference proceedings QFS
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Two-dimensional Bloch electrons in perpendicular magnetic fields: an exact calculation of the Hofstadter butterfly spectrum
The problem of two-dimensional, independent electrons subject to a periodic
potential and a uniform perpendicular magnetic field unveils surprisingly rich
physics, as epitomized by the fractal energy spectrum known as Hofstadter's
Butterfly. It has hitherto been addressed using various approximations rooted
in either the strong potential or the strong field limiting cases. Here we
report calculations of the full spectrum of the single-particle Schr\"{o}dinger
equation without further approximations. Our method is exact, up to numerical
precision, for any combination of potential and uniform field strength. We
first study a situation that corresponds to the strong potential limit, and
compare the exact results to the predictions of a Hofstadter-like model. We
then go on to analyze the evolution of the fractal spectrum from a Landau-like
nearly-free electron system to the Hofstadter tight-binding limit by tuning the
amplitude of the modulation potential
On piecewise isomorphism of some varieties
Two quasi-projective varieties are called piecewise isomorphic if they can be
stratified into pairwise isomorphic strata. We show that the m-th symmetric
power of the complex affine space is piecewise isomorphic to
and the m-th symmetric power of the infinite
dimensional complex projective space is piecewise isomorphic to the infinite
dimensional Grassmannian
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