239 research outputs found
CMB anisotropy: deviations from Gaussianity due to non-linear gravity
Non-linear evolution of cosmological energy density fluctuations triggers
deviations from Gaussianity in the temperature distribution of the cosmic
microwave background. A method to estimate these deviations is proposed. N-body
simulations -- in a CDM cosmology -- are used to simulate the strongly
non-linear evolution of cosmological structures. It is proved that these
simulations can be combined with the potential approximation to calculate the
statistical moments of the CMB anisotropies produced by non-linear gravity.
Some of these moments are computed and the resulting values are different from
those corresponding to Gaussianity.Comment: 6 latex pages with mn.sty, 3 eps figures. Accepted in MNRA
Comportamiento biológico intraarticular de distintos aloinjertos tendinosos: estudio experimental
Se ha efectuado un estudio experimental comparativo, con valoración macro y microscópica,
de la supervivencia, dentro de la articulación de la rodilla del conejo, de tendones flexores
sobre extensores y dentro de estos, entre tendones conservados en fresco, congelados,
liofilizados y fijados en solución de glutaraldehido al 0,2%. Los tendones se mantuvieron libres en
la articulación receptora durante periodos distintos de tiempo. Entre los resultados destaca la pérdida
de volumen, en el tiempo, de la masa tendinosa (18% de despariciones totales, con un 28%
de pérdida final global). Los tendones fijados en glutaraldehido fueron los que presentaron menor
pérdida de volumen. Los tendones implantados en fresco y los congelados presentaron una mayor
tasa de infección. La mejor respuesta de supervivencia se detectó en los tendones conservados en
glutaraldehido y los congelados. Así mismo, tenían más posibilidades de sobrevivir los flexores que
los extensores. Desde el punto de vista histológico, los tendones conservados en fresco desencadenaron
una mayor respuesta inflamatoria, con gran alteración estructural. Desde el punto de vista
microscópico no se han hallado diferencias significativas entre flexores y extensores.Different groups of flexor and extensor tendons have been compared in their
abitihty survive within the rabbit knee joint. Tendons were grouped and compared according
four different storage procedures like freezing, lyophylization and fixation in 0,2% glutaraldehid.
Some of them were used in fresh. All tendons have been kept inside the joint as free
graft. All specimens lost weight along the study (18% of total loosing of specimen, and 28% of
global loosing). Tendons fixed in disclosed less loosing of volume. Allograft infection was
related to the method o glutaraildehid of storage, relationship being statistically significant (fresh tendons
and frozen tendons were infected more easily). The best survival was found in both frozen
and glutaraldehid fixed tendons. Flexor tendons show more chances of survival than extensors
tendons. Histologically, fresh tendons disclosed the greatest inflammatory reaction. Opposite to
the macroscopic findings, there were no significant differences between flexors and extensors
tendons in the microscopical study
The Tully-Fisher relation of intermediate redshift field and cluster galaxies from Subaru spectroscopy
We have carried out spectroscopic observations in 4 cluster fields using
Subaru's FOCAS multi-slit spectrograph and obtained spectra for 103 bright disk
field and cluster galaxies at . Seventy-seven of these
show emission lines, and 33 provide reasonably-secure determinations of the
galaxies' rotation velocity. The rotation velocities, luminosities, colours and
emission-line properties of these galaxies are used to study the possible
effects of the cluster environment on the star-formation history of the
galaxies. Comparing the Tully-Fisher relations of cluster and field galaxies at
similar reshifts we find no measurable difference in rest-frame -band
luminosity at a given rotation velocity (the formal difference is mag). The colours of the cluster emission line galaxies are only marginally
redder in rest-frame (by mag) than the field galaxies in
our sample. Taken at face value, these results seem to indicate that bright
star-forming cluster spirals are similar to their field counterparts in their
star-formation properties. However, we find that the fraction of disk galaxies
with absorption-line spectra (i.e., with no current star formation) is larger
in clusters than in the field by a factor of --5. This suggests that the
cluster environment has the overall effect of switching off star formation in
(at least) some spiral galaxies. To interpret these observational results, we
carry out simulations of the possible effects of the cluster environment on the
star-formation history of disk galaxies and thus their photometric and
spectroscopic properties. Finally, we evaluate the evolution of the rest-frame
absolute -band magnitude per unit redshift at fixed rotation velocity.Comment: 21 pages, 13 figures, accepted for publication in MNRA
UV completion of an axial, leptophobic,
The -portal is one of most popular and well-explored scenarios of dark
matter (DM). To avoid the strong constraints coming from dilepton resonance
searches at the LHC and direct detection of DM, it is usually required that in
addition to being leptophobic, the is axially coupled to either the
(fermionic) DM or the standard model (SM) quarks. The first possibility has
been extensively studied both in the context of simplified model and UV
complete scenarios. However, the studies on the second possibiliy are largely
confined to simplified models only. Here, we construct the minimal UV
completion of these models satisfying both the criteria of leptophobia and
purely axial quark coupling. The anomaly cancellation conditions demand
highly non-trivial structures, not only in the dark sector, but also in the
Higgs sector.Comment: 15 pages. Improved version with phenomenological implications
addressed and references adde
The star formation activity in cosmic voids
Using a sample of cosmic voids identified in the Sloan Digital Sky Survey Data Release 7, we study the star formation activity of void galaxies. The properties of galaxies living in voids are compared with those of galaxies living in the void shells and with a control sample, representing the general galaxy population. Void galaxies appear to form stars more efficiently than shell galaxies and the control sample. This result cannot be interpreted as a consequence of the bias towards low masses in underdense regions, as void galaxy subsamples with the same mass distribution as the control sample also show statistically different specific star formation rates. This highlights the fact that galaxy evolution in voids is slower with respect to the evolution of the general population. Nevertheless, when only the star-forming galaxies are considered, we find that the star formation rate is insensitive to the environment, as the main sequence is remarkably constant in the three samples under consideration. This fact implies that environmental effects manifest themselves as fast quenching mechanisms, while leaving the non-quenched galaxies almost unaffected, as their star formation activity is largely regulated by the mass of their halo. We also analyse galaxy properties as a function of void-centric distance and find that the enhancement in the star formation activity with respect to the control sample is observable up to a radial distance 1.5Rvoid. This result can be used as a suitable definition of void shells. Finally, we find that larger voids show an enhanced star formation activity in the shells with respect to their smaller counterparts, which could be related to the different dynamical evolution experienced by voids of different size
Efecto de la congelación en rodillas animales. Estudio biomecánico experimental
Se estudia el comportamiento mecánico de rodillas animales que han sido congeladas en 1 o varias ocasiones mediante la aplicación de cargas axiales hasta la fractura o test destructivos. Se analizan el tipo y localización de fracturas aparecidas mediante un estudio radiográfico.We study the mechanical behavior in animal knees who are fresh frozen in one or various times. Axial loading are applied until the final fracture ( destructive test). Also it evaluates the tipe and localization of the fractures with radiological study
A Catalogue and Analysis of X-ray luminosities of Early-type galaxies
We present a catalogue of X-ray luminosities for 401 early-type galaxies, of
which 136 are based on newly analysed ROSAT PSPC pointed observations. The
remaining luminosities are taken from the literature and converted to a common
energy band, spectral model and distance scale. Using this sample we fit the
L_X:L_B relation for early-type galaxies and find a best fit slope for the
catalogue of ~2.2. We demonstrate the influence of group-dominant galaxies on
the fit and present evidence that the relation is not well modeled by a single
powerlaw fit. We also derive estimates of the contribution to galaxy X-ray
luminosities from discrete sources and conclude that they provide
L_discrete/L_B = 29.5 erg/s/L_solar. We compare this result to luminosities
from our catalogue. Lastly, we examine the influence of environment on galaxy
X-ray luminosity and on the form of the L_X:L_B relation. We conclude that
although environment undoubtedly affects the X-ray properties of individual
galaxies, particularly those in the centres of groups and clusters, it does not
change the nature of whole populations.Comment: 33 pages, 16 postscript figures, accepted for publication in MNRA
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