1,580 research outputs found
Differences in the epidemiology of theileriosis on smallholder dairy farms in contrasting agro-ecological and grazing strata of highland Kenya
A prospective cohort study was conducted in five purposively-sampled agro-ecological zone (AEZ)-grazing system strata in Murang’a District, Kenya, between March 1995 and June 1996. The study strata were selected based on a preliminary characterization study to represent the widest range of risks to East Coast fever (ECF) in the District and included zero-grazing and open-grazing farms. In total, 225 calves from 188 smallholder farms were examined from birth to 6 months of age and visited within the first 2 weeks of life and thereafter at bi-weekly intervals for up to 14 visits.
The purpose of the study was to characterize the differences in epidemiology (risks of infection, morbidity and mortality) and potential control of ECF between the selected strata. Evidence of Theileria parva infection was assessed by increased antibody levels as measured in an indirect ELISA assay by the percent positivity (PP) of serum samples relative to a strong positive reference serum.
Sero-conversion risks of T. parva were highest in the open-grazing strata. Antibody prevalence in adult cattle and ECF morbidity and mortality risks were also highest in open-grazing strata. While different, all five AEZ-grazing strata were considered to be endemically unstable for ECF. East Coast fever challenge was low in all zero-grazing strata and this challenge is likely to remain low due to continuing intensification of smallholder farming in the central highlands. In the open-grazing strata, there was higher challenge and a greater impact of ECF.
ILRI publication no.: 99017
Turbulent Pressure Spectrum Measurements on a Compliant Surface
Experimental results obtained by measuring the drag, wall pressure fluctuations, and radiated sound from a compliantly coated cylinder, 21 inches in diameter, and rotating in water are described. The compliant layer was a 1/4-inch thick closed cell, air-filled neoprene which was mounted on the 3/8-inch thick aluminum cylinder walls. Results are presented for four speed conditions; one condition is below the speed where a sudden increase in drag is obtained, and the other speed conditions are at and above this critical speed. In general, the results indicate a surface which becomes increasingly more roughened as the critical speed is exceeded
Identification of Quantitative Trait Loci for Flowering Time in a Field-Grown \u3cem\u3eLolium Perene x Lolium Multiflorum\u3c/em\u3e Mapping Population
Perennial ryegrass (L. perenne) and annual, or Italian, ryegrass (L. multiflorum) are considered to be separate species by the seed trade, and are used and bred for distinct purposes. However, the two species are cross-fertile. Seed producers rely on the different flowering times of the two species to produce pure seed. Flowering times can overlap, leading to genetic mixing. Contamination of perennial ryegrass seed lots with annual types is an expensive problem for grass seed producers in western Oregon, USA
Ab initio calculation of the dynamical properties of PPP and PPV
In this work, we have calculated the vibrational modes and frequencies of the
crystalline PPP (in both the Pbam and Pnnm symmetries) and PPV (in the P21/c
symmetry). Our results are in good agreement with the available experimental
data. Also, we have calculated the temperature dependence of their specific
heats at constant volume, and of their vibrational entropies. Based on our
results, at high temperatures, the PPP is more stable in the Pnnm structure
than in the Pbam one.Comment: 5 pages, 7 figures, accepted for publication in Braz. J. Phys.,
special number, Proceedings of BWSP-12, 12th Brazilian Workshop on
Semiconductor Physic
Long-Range Excitons in Optical Absorption Spectra of Electroluminescent Polymer Poly(para-phenylenevinylene)
The component of photoexcited states with large spatial extent is
investigated for poly(para-phenylenevinylene) using the intermediate exciton
theory. We find a peak due to long-range excitons at the higher-energy side of
the lowest main feature of optical spectra. The fact that the onset of
long-range excitons is located near the energy gap is related to the mechanisms
of large photocurrents measured in such energy regions. We show that a large
value of the hopping integral is realistic for characterizing optical
excitations.Comment: To be published in J. Phys. Soc. Jpn. (Letters
The Role of Color-Magnetic Monopoles in a Gluonic Plasma
The role of color-magnetic monopoles in a pure gauge plasma at high
temperature is considered. In this temperature regime, monopoles can
be considered heavy, rare objects embedded into matter consisting mostly of the
usual "electric" quasiparticles, quarks and gluons. The gluon-monopole
scattering is found to hardly influence thermodynamic quantities, yet it
produces a large transport cross section, significantly exceeding that for pQCD
gluon-gluon scattering up to quite high . This mechanism keeps viscosity
small enough for hydrodynamics to work at LHC.Comment: 4 pages, 4 figures, Talk presented at the Quark Matter 2009
Conference, Knoxville, T
Effect of Intra-molecular Disorder and Inter-molecular Electronic Interactions on the Electronic Structure of Poly-p-Phenylene Vinylene (PPV)
We investigate the role of intra-molecular conformational disorder and
inter-molecular electronic interactions on the electronic structure of disorder
clusters of poly-p-phenylene vinylene (PPV) oligomers. Classical molecular
dynamics is used to determine probable molecular geometries, and
first-principle density functional theory (DFT) calculations are used to
determine electronic structure. Intra-molecular and inter-molecular effects are
disentangled by contrasting results for densely packed oligomer clusters with
those for ensembles of isolated oligomers with the same intra-molecular
geometries. We find that electron trap states are induced primarily by
intra-molecular configuration disorder, while the hole trap states are
generated primarily from inter-molecular electronic interactions.Comment: 4 pages, 4 figures. Compile with pdflate
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