4,430 research outputs found
Evaluating LANDSAT-4 MSS and TM data
Interband line pixel misregistrations were determined for the four MSS bands of the Mistassini, Ontario scene and multitemporal registration of LANDSAT-4 products were tested for two different geocoded scenes. Line and pixel misregistrations are tabulated as determined by the manual ground control points and the digital band to band correlation techniques. A method was developed for determining the spectral information content of TM images for forestry applications
Bulge mass is king: The dominant role of the bulge in determining the fraction of passive galaxies in the Sloan Digital Sky Survey
We investigate the origin of galaxy bimodality by quantifying the relative
role of intrinsic and environmental drivers to the cessation (or `quenching')
of star formation in over half a million local Sloan Digital Sky Survey (SDSS)
galaxies. Our sample contains a wide variety of galaxies at z=0.02-0.2, with
stellar masses of 8 < log(M*/M_sun) < 12, spanning the entire morphological
range from pure disks to spheroids, and over four orders of magnitude in local
galaxy density and halo mass. We utilise published star formation rates and add
to this recent GIM2D photometric and stellar mass bulge + disk decompositions
from our group. We find that the passive fraction of galaxies increases steeply
with stellar mass, halo mass, and bulge mass, with a less steep dependence on
local galaxy density and bulge-to-total stellar mass ratio (B/T). At fixed
internal properties, we find that central and satellite galaxies have different
passive fraction relationships. For centrals, we conclude that there is less
variation in the passive fraction at a fixed bulge mass, than for any other
variable, including total stellar mass, halo mass, and B/T. This implies that
the quenching mechanism must be most tightly coupled to the bulge. We argue
that radio-mode AGN feedback offers the most plausible explanation of the
observed trends.Comment: Accepted to MNRAS. 32 pages, 27 figures. [This version is virtually
identical to v1
A new species in the major malaria vector complex sheds light on reticulated species evolution
Complexes of closely related species provide key insights into the rapid and independent evolution of adaptive traits. Here, we described and studied Anopheles fontenillei sp.n., a new species in the Anopheles gambiae complex that we recently discovered in the forested areas of Gabon, Central Africa. Our analysis placed the new taxon in the phylogenetic tree of the An. gambiae complex, revealing important introgression events with other members of the complex. Particularly, we detected recent introgression, with Anopheles gambiae and Anopheles coluzzii, of genes directly involved in vectorial capacity. Moreover, genome analysis of the new species allowed us to clarify the evolutionary history of the 3La inversion. Overall, An. fontenillei sp.n. analysis improved our understanding of the relationship between species within the An. gambiae complex, and provided insight into the evolution of vectorial capacity traits that are relevant for the successful control of malaria in Africa
Recovering 3D structural properties of galaxies from SDSS-like photometry
Because of the 3D nature of galaxies, an algorithm for constructing spatial
density distribution models of galaxies on the basis of galaxy images has many
advantages over surface density distribution approximations. We present a
method for deriving spatial structure and overall parameters of galaxies from
images and estimate its accuracy and derived parameter degeneracies on a sample
of idealised model galaxies. The test galaxies consist of a disc-like component
and a spheroidal component with varying proportions and properties. Both
components are assumed to be axially symmetric and coplanar. We simulate these
test galaxies as if observed in the SDSS project through ugriz filters, thus
gaining a set of realistically imperfect images of galaxies with known
intrinsic properties. These artificial SDSS galaxies were thereafter remodelled
by approximating the surface brightness distribution with a 2D projection of a
bulge+disc spatial distribution model and the restored parameters were compared
to the initial ones. Down to the r-band limiting magnitude 18, errors of the
restored integral luminosities and colour indices remain within 0.05 mag and
errors of the luminosities of individual components within 0.2 mag. Accuracy of
the restored bulge-to-disc ratios (B/D) is within 40% in most cases, and
becomes worse for galaxies with low B/D, but the general balance between bulges
and discs is not shifted systematically. Assuming that the intrinsic disc axial
ratio is < 0.3, the inclination angles can be estimated with errors < 5deg for
most of the galaxies with B/D < 2 and with errors < 15deg up to B/D = 6. Errors
of the recovered sizes of the galactic components are below 10% in most cases.
In general, models of disc components are more accurate than models of
spheroidal components for geometrical reasons.Comment: 15 pages, 13 figures, accepted for publication in RA
Role of the mitochondria on the paradoxical effect of red wine polyphenols on angiogenesis
Red wine polyphenol (RWPC) extracts has been reported to possess vasoprotective properties that involve nitric oxide (NO) release from endothelial cells via a redox- sensitive pathway. Besides, the molecular target of RWPC to release NO has been recently revealed and it involves the activation of the estrogen receptor alpha (ERα). Paradoxical effects of RWPC have been shown with regard to angiogenesis. Indeed in a rat model of postischemic neovascularization, low- dose is pro- whereas high dose is anti- angiogenic. NO and ERα
 are key regulators of mitochondrial function. Furthermore, angiogenesis is a highly energetic process associated with mitochondrial biogenesis. However, whether RWPC induces changes in mitochondrial function has never been addressed and it is the aim of this study.
The effects of RWPC at low concentration (10- 4 g/l, LCP) and high concentration (10- 2 g/l, HCP) after 48 hours time exposure were investigated on human endothelial cells. Mitochondrial respiration, expression of biogenesis factors and DNA content was assessed using oxygraphy and qRT- PCR, respectively. In vitro capillary formation using Matrigel® was performed. The mechanism involved with respect to ER using the ER- antagonist fulvestrant was studied. The involvement of both NADPH oxidase and NO synthase was addressed using apocynin and L- NA respectively.
LCP, but not HCP, increased mitochondrial respiration. The effect of LCP was associated with an increase of both expression of several mitochondrial biogenesis factors (NRF- 1, NRF- 2, ERRα, Tfam, PolG) and mitochondrial DNA content whereas HCP had no effect on these parameters. All the effects of LCP on mitochondrial respiration are prevented by fulvestrant, apocynin and L- NA. LCP also promoted in vitro capillary elongation that was prevented by fulvestrant, apocynin and L- NA. Finally, the inhibition of mitochondrial protein synthesis using chloramphenicol suppressed the pro- angiogenic property of LCP.
The present study highlights the implication of the axis ER, NADPH oxidase and NOS pathways on both increase mitochondrial function and capillary elongation in response to RWPC at low concentration. They explain the paradoxical effect of RWPC depending on the concentration with respect to angiogenesis, mitochondria being key targets for its pro- angiogenic properties
What shapes a galaxy? - Unraveling the role of mass, environment and star formation in forming galactic structure
We investigate the dependence of galaxy structure on a variety of galactic
and environmental parameters for ~500,000 galaxies at z<0.2, taken from the
Sloan Digital Sky Survey data release 7 (SDSS-DR7). We utilise bulge-to-total
stellar mass ratio, (B/T)_*, as the primary indicator of galactic structure,
which circumvents issues of morphological dependence on waveband. We rank
galaxy and environmental parameters in terms of how predictive they are of
galaxy structure, using an artificial neural network approach. We find that
distance from the star forming main sequence (Delta_SFR), followed by stellar
mass (M_*), are the most closely connected parameters to (B/T)_*, and are
significantly more predictive of galaxy structure than global star formation
rate (SFR), or any environmental metric considered (for both central and
satellite galaxies). Additionally, we make a detailed comparison to the
Illustris hydrodynamical simulation and the LGalaxies semi-analytic model. In
both simulations, we find a significant lack of bulge-dominated galaxies at a
fixed stellar mass, compared to the SDSS. This result highlights a potentially
serious problem in contemporary models of galaxy evolution.Comment: Accepted to MNRAS. 31 pages, 15 figure
Transcatheter Tricuspid Valve Intervention: Current Perspective
Tricuspid regurgitation (TR) adversely impacts both quality of life and long-term survival, which generates interest in therapeutic approaches to mitigate these effects. Historically, therapeutic options for TR were limited to surgical approaches, which are often complicated by significant morbidity and mortality in elderly patients with multiple comorbidities. This gap in therapeutic options led to the rapid evolution of transcatheter tricuspid valve intervention (TTVI), with a wide variety of approaches pursued and early results suggesting that TTVI improves clinical outcomes. Numerous strategies, including edge-to-edge repair, annular reduction, spacers, caval valve implantation, and transcatheter tricuspid valve replacement form the basis of TTVI today. In this review, the authors discuss the current state of each approach
Quantitative Morphology of Galaxies in the Hubble Deep Field
We measure quantitative structural parameters of galaxies in the Hubble Deep
Field (HDF) on the drizzled F814W images. Our structural parameters are based
on a two-component surface brightness made up of a S\'ersic profile and an
exponential profile. We compare our results to the visual classification of van
den Bergh et al. (1996) and the classification of Abraham et al. (1996a).
Our morphological analysis of the galaxies in the HDF indicates that the
spheroidal galaxies, defined here as galaxies with a dominant bulge profile,
make up for only a small fraction, namely 8% of the galaxy population down to
m = 26.0. We show that the larger fraction of early-type systems
in the van den Bergh sample is primarily due to the difference in
classification of 40% of small round galaxies with half-light radii <
0\arcsecpoint 31. Although these objects are visually classified as elliptical
galaxies, we find that they are disk-dominated with bulge fractions < 0.5.
Given the existing large dataset of HDF galaxies with measured spectroscopic
redshifts, we are able to determine that the majority of distant galaxies
() from this sample are disk-dominated. Our analysis reveals a subset of
HDF galaxies which have profiles flatter than a pure exponential profile.Comment: 35 pages, LaTeX, 18 Postscript Figures, Tables available at
http://astro.berkeley.edu/~marleau/. Accepted for Publication in The
Astrophysical Journa
Localization of Candidate Regions Maintaining a Common Polymorphic Inversion (2La) in Anopheles gambiae
Chromosomal inversion polymorphisms are thought to play a role in adaptive divergence, but the genes conferring adaptive benefits remain elusive. Here we study 2La, a common polymorphic inversion in the African malaria vector Anopheles gambiae. The frequency of 2La varies clinally and seasonally in a pattern suggesting response to selection for aridity tolerance. By hybridizing genomic DNA from individual mosquitoes to oligonucleotide microarrays, we obtained a complete map of differentiation across the A. gambiae genome. Comparing mosquitoes homozygous for the 2La gene arrangement or its alternative (2L+a), divergence was highest at loci within the rearranged region. In the 22 Mb included within alternative arrangements, two ∼1.5 Mb regions near but not adjacent to the breakpoints were identified as being significantly diverged, a conclusion validated by targeted sequencing. The persistent association of both regions with the 2La arrangement is highly unlikely given known recombination rates across the inversion in 2La heterozygotes, thus implicating selection on genes underlying these regions as factors responsible for the maintenance of 2La. Polymorphism and divergence data are consistent with a model in which the inversion is maintained by migration-selection balance between multiple alleles inside these regions, but further experiments will be needed to fully distinguish between the epistasis (coadaptation) and local adaptation models for the maintenance of 2La
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