2,545 research outputs found
Quality assurance and histopathological lesions of laboratory animals
No abstract availabl
Polarimetry of an Intermediate-age Open Cluster: NGC 5617
We present polarimetric observations in the UBVRI bands of 72 stars located
in the direction of the medium age open cluster NGC 5617. Our intention is to
use polarimetry as a tool membership identification, by building on previous
investigations intended mainly to determine the cluster's general
characteristics rather than provide membership suitable for studies such as
stellar content and metallicity, as well as study the characteristics of the
dust lying between the Sun and the cluster. The obsevations were carried out
using the five-channel photopolarimeter of the Torino Astronomical Observatory
attached to the 2.15m telescope at the Complejo Astron\'omico El Leoncito
(CASLEO; Argentina. We are able to add 32 stars to the list of members of NGC
5617, and review the situation for others listed in the literature. In
particular, we find that five blue straggler stars in the region of the cluster
are located behind the same dust as the member stars are and we confirm the
membership of two red giants. The proposed polarimetric memberships are
compared with those derived by photometric and kinematical methods, with
excellent results. Among the observed stars, we identify 10 with intrinsic
polarization in their light. NGC 5617 can be polarimetrically characterized
with and . The spread in polarization
values for the stars observed in the direction of the cluster seems to be
caused by the uneven distribution of dust in front of the cluster's face.
Finally, we find that in the direction of the cluster, the interstellar medium
is apparently free of dust, from the Sun's position up to the
Carina-Sagittarius arm, where NGC 5617 seems to be located at its farthest
border
Klossiella cobayae associated With Chronic Interstitial Nephritis in Guinea Pigs
Infection with the renal coccidian parasite K. cobayae was detected in 6 conventionally kept Dunkin-Hartley guinea pigs, submitted for routine health monitoring at The National Veterinary Intsitute, Uppsala. Chronic inflammatory lesions were microscopically observed in the kidneys and the lungs of all animals
Health monitoring of purpose bred laboratory rabbits in Sweden: Major findings
Post-mortem examinations were performed on groups of 12 rabbits from nine colonies. The most frequent pathological changes found were chronic inïŹammatory processes in lungs and intestines. Bordetella bronchiseptica was frequently isolated and Pasteurella spp. were not observed. Most cases of enteritis were associated with Eimeria spp., but Trichomonas spp. and Coronaviruses were also noticed. The pinworm Passalums ambiguus was found in seven groups and the nematode Trichostrongylus retortaeformis in one. Rabbits from five colonies evidenced hepatic coccidiosis. Among ectoparasites, Cheyletiellaparasitivorax was found in seven groups and Listrophorus gibbus in four. The ear mite Psoroptes cuniculii was recorded in two groups. One rabbit exhibited Encephalitozoon cum'culi antibodies and another one Toxoplasma gondii antibodies. Among other findings, the ascending aorta and are displayed calcified plaques in eight rabbits from three colonies and the appendiceal lymphoid tissues evidenced multinucleated giant cells in adult rabbits of three groups. A good correlation was found between the health of the rabbits and the hygienic standards at the colonies
Study of perturbed periodic systems of differential equations - The Stroboscopic method
Stroboscopic method for solving perturbed periodic systems of differential equation
Inhomogeneous String Cosmology Solutions with Regular Spacetime Curvature
In this work cosmological models are considered for the low energy string
cosmological effective action (tree level) in the absence of dilaton potential.
A two parametric non-diagonal family of analytic solutions is found. The
curvature is non singular, however the string coupling diverges exponentially.Comment: LaTeX, 6 pge
Initial Conditions and the Structure of the Singularity in Pre-Big-Bang Cosmology
We propose a picture, within the pre-big-bang approach, in which the universe
emerges from a bath of plane gravitational and dilatonic waves. The waves
interact gravitationally breaking the exact plane symmetry and lead generically
to gravitational collapse resulting in a singularity with the Kasner-like
structure. The analytic relations between the Kasner exponents and the initial
data are explicitly evaluated and it is shown that pre-big-bang inflation may
occur within a dense set of initial data. Finally, we argue that plane waves
carry zero gravitational entropy and thus are, from a thermodynamical point of
view, good candidates for the universe to emerge from.Comment: 18 pages, LaTeX, epsfig. 3 figures included. Minor changes; paragraph
added in the introduction, references added and typos corrected. Final
version published in Classical and Quantum Gravit
Radiative transport analysis of electromagnetic propagation in isotropic plasma turbulence
The problem of electromagnetic wave propagation in a turbulent plasma is formulated in terms of the radiative transport equation. A singular eigenfunction solution is obtained for the case of isotropic plasma turbulence, and detailed numerical calculations are presented. The intensity distribution is studied as a function of the turbulent spectrum and relative strength of scattering attenuation to total attenuation. For a highly forward peaked scattering law characteristic of many physical situations it is found that the reflected backscatter intensity is relatively insensitive to the angle of incidence, except as grazing incidence is approached. The importance of multiple scatter is studied as a function of the properties of the medium
Inhomogeneous Einstein-Rosen String Cosmology
Families of anisotropic and inhomogeneous string cosmologies containing
non-trivial dilaton and axion fields are derived by applying the global
symmetries of the string effective action to a generalized Einstein-Rosen
metric. The models exhibit a two-dimensional group of Abelian isometries. In
particular, two classes of exact solutions are found that represent
inhomogeneous generalizations of the Bianchi type VI_h cosmology. The
asymptotic behaviour of the solutions is investigated and further applications
are briefly discussed.Comment: Minor extension of concluding section; 18 pages, to appear in
Phys.Rev.
The Extended Line Region of 3C 299
We present results of HST observations of the radio galaxy 3C 299. The
broad-band F702W (R) and F555W (V) images (WFPC2/PC) show an elliptical galaxy,
with a comet-like structure extending to the NE in the radio jet direction. The
[OIII]5007 emission line map, shows a bi-conical structure centered on
the nucleus, that overlaps the structure found in the broad-band filters. The
radio core coincides with the center of the bi-conical structure and the radio
axes are aligned with the direction of the cones. These data show clear
evidence of a strong interaction between the radio jet and the NE morphology of
the galaxy. We show evidence that this NE region is an ENLR; the line-ratio
diagnostics show that models involving gas shocked by the radio-jet plus
ionization from a precursor HII region, produced itself by the ionizing photons
of the postshocked gas on the preshocked gas provide a good match to the
observations. We investigate the spatial behavior of the ionizing parameter
, by determining the [OIII]/[OII] line ratio which is sensitive to the
change of the ionization parameter, and trace its behavior over the ENLR along
the radio jet direction. We find that [OIII]/[OII] does not follow a simple
dilution model, but rather that it is approximately constant over a large range
of distance from the nucleus thus requiring a local source of ionization which
seems to be compatible with the shock models driven by the radio jet.Comment: 17 pages, 9 Postscript figures, ApJ accepted, uses aaspp.st
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