15,736 research outputs found
Maior tempo de exposição à progesterona associado ao uso de agonista de GnRH na superovulação e produção de embriões ovinos.
Condensation of Vortex-Strings: Effective Potential Contribution Through Dual Actions
Topological excitations are believed to play an important role in different
areas of physics. For example, one case of topical interest is the use of dual
models of quantum cromodynamics to understand properties of its vacuum and
confinement through the condensation of magnetic monopoles and vortices. Other
applications are related to the role of these topological excitations,
nonhomogeneous solutions of the field equations, in phase transitions
associated to spontaneous symmetry breaking in gauge theories, whose study is
of importance in phase transitions in the early universe, for instance. Here we
show a derivation of a model dual to the scalar Abelian Higgs model where its
topological excitations, namely vortex-strings, become manifest and can be
treated in a quantum field theory way. The derivation of the nontrivial
contribution of these vacuum excitations to phase transitions and its analogy
with superconductivity is then made possible and they are studied here.Comment: 7 pages. Based on a talk given by R. O. Ramos at the Infrared QCD in
Rio conference, Rio de Janeiro, Brazil, June 5-9, 200
VISIR-VLT high resolution study of the extended emission of four obscured post-AGB candidates
The onset of the asymmetry of planetary nebulae (PNe) is expected to occur
during the late Asymptotic Giant Branch (AGB) and early post-AGB phases of low-
and intermediate-mass stars. Among all post-AGB objects, the most heavily
obscured ones might have escaped the selection criteria of previous studies
detecting extreme axysimmetric structures in young PNe. Since the most heavily
obscured post-AGB sources can be expected to descend from the most massive PN
progenitors, these should exhibit clear asymmetric morphologies. We have
obtained VISIR-VLT mid-IR images of four heavily obscured post-AGB objects
barely resolved in previous Spitzer IRAC observations to analyze their
morphology and physical conditions across the mid-IR. The VISIR-VLT images have
been deconvolved, flux calibrated, and used to construct RGB composite pictures
as well as color and optical depth maps that allow us to study the morphology
and physical properties of the extended emission of these sources. We have
detected extended emission from the four objects in our sample and resolved it
into several structural components that are greatly enhanced in the temperature
and optical depth maps. They reveal the presence of asymmetry in three young
PNe (IRAS 15534-5422, IRAS 17009-4154, and IRAS 18454+0001), where the
asymmetries can be associated with dusty torii and slightly bipolar outflows.
The fourth source (IRAS 18229-1127), a possible post-AGB star, is better
described as a rhomboidal detached shell. The heavily obscured sources in our
sample do not show extreme axisymmetric morphologies. This is at odds with the
expectation of highly asymmetrical morphologies in post-AGB sources descending
from massive PN progenitors. The sources presented in this paper may be
sampling critical early phases in the evolution of massive PN progenitors,
before extreme asymmetries develop.Comment: 9 pages, 4 figure
A search for water maser emission toward obscured post-AGB star and planetary nebula candidates
Water maser emission at 22 GHz is a useful probe to study the transition
between the nearly spherical mass-loss in the AGB to a collimated one in the
post-AGB phase. In their turn, collimated jets in the post-AGB phase could
determine the shape of planetary nebulae (PNe) once photoionization starts. We
intend to find new cases of post-AGB stars and PNe with water maser emission,
including water fountains or water-maser-emitting PNe. We observed water maser
emission in a sample of 133 objects, with a significant fraction being post-AGB
and young PN candidate sources with strong obscuration. We detected this
emission in 15 of them, of which seven are reported here for the first time. We
identified three water fountain candidates: IRAS 17291-2147, with a total
velocity spread of ~96 km/s in its water maser components and two sources (IRAS
17021-3109 and IRAS 17348-2906) that show water maser emission outside the
velocity range covered by OH masers. We have also identified IRAS 17393-2727 as
a possible new water-maser-emitting PN. The detection rate is higher in
obscured objects (14%) than in those with optical counterparts (7%), consistent
with previous results. Water maser emission seems to be common in objects that
are bipolar in the near-IR (43% detection rate). The water maser spectra of
water fountain candidates like IRAS 17291-2147 show significantly less maser
components than others (e.g., IRAS 18113-2503). We speculate that most
post-AGBs may show water maser emission with wide enough velocity spread (> 100
km/s) when observed with enough sensitivity and/or for long enough periods of
time. Therefore, it may be necessary to single out a special group of "water
fountains", probably defined by their high maser luminosities. We also suggest
that the presence of both water and OH masers in a PN is a better tracer of its
youth, rather than the presence of just one of these species.Comment: To be published in Astronomy & Astrophysics. 16 pages, 1 figure
(spanning 5 pages). This version includes some minor language corrections and
fixes some errors in Table
Sinostosis húmero-radio-cubital: a propósito de un caso
Se presenta aparentemente el primer caso en la literatura mundial de Sinostosis
Húmero-Radio-Cubital unilateral, no asociado a ninguna entidad patológica congénita, observando
un crecimiento y desarrollo del resto del organismo dentro de parámetros normales. Siendo
este un miembro superior funcional se decide no aplicar ningún tratamiento.We report the first case in the world's literature of unilateral Húmero-Radio-Ulnar
Synostosis, not associated to other congenital pathology entity; we observed a normal growth and development
of the rest of the body; due to be a funtional upper lim b we decided not give treatment
Utilização de FSH:LH como alternativa para estimular o crescimento folicular na sincronização do estro ovino.
201
Sound and light from fractures in scintillators
Prompted by intriguing events observed in certain particle-physics searches
for rare events, we study light and acoustic emission simultaneously in some
inorganic scintillators subject to mechanical stress. We observe
mechanoluminescence in , and ,
in various mechanical configurations at room temperature and ambient pressure.
We analyze how the light emission is correlated to acoustic emission during
fracture. For , we set a lower bound on the energy of
the emitted light, and deduce that the fraction of elastic energy converted to
light is at least
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