196 research outputs found
Characterization of PRLR and PPARGC1A genes in buffalo (Bubalus bubalis)
More than 40 million households in India depend at least partially on livestock production. Buffaloes are one of the major milk producers in India. The prolactin receptor (PRLR) gene and peroxisome proliferators activated receptor-γ coactivator 1-alpha (PPARGC1A) gene are reportedly associated with milk protein and milk fat yields in Bos taurus. In this study, we sequenced the PRLR and PPARGC1A genes in the water buffalo Bubalus bubalis. The PRLR and PPARGC1A genes coded for 581 and 819 amino acids, respectively. The B. bubalis PRLR gene differed from the corresponding Bos taurus at 21 positions and four differences with an additional arginine at position 620 in the PPARGC1A gene were found in the amino acid sequence. All of the changes were confirmed by cDNA sequencing. Twelve buffalo-specific single nucleotide polymorphisms (SNPs) were identified in both genes, with five of them being non-synonymous
Characterization of GPX1 and DIO1 Genes in Bubalus Bubalis
Selenoprotein genes contain selenium in the form of selenocysteine which is involved in protecting the cells from oxidative stress. Soils in India differ greatly in selenium concentrations affecting feed stuffs for selenium availability. Selenoproteins have recently been identified in variety of living organisms including humans which have 25 selenoprotein genes. Among these families of selenoprotein genes, we sequenced Gpx1 gene (Glutathione peroxidases1) and Dio1 gene (Iodothyronine deiodinases) in Bubalus bubalis. Gpx1 is most abundant and ubiquitously expressed selenoprotein which helps to protect against the damaging effects of hydrogen peroxide and oxygen rich free radicals whereas Dio1 is expressed mainly in liver, thyroid gland and adipose tissue, its main function is to convert tetraiodothyronine (T4) to its active form thyroxine (T3) in the presence of deiodinases enzyme. The main aim of the study was to characterize these two genes and to find out the buffalo specific SNPs. This was accomplished by designing primers using cattle database and sequencing a panel of 24 samples consisting of 6 diverse breeds of buffalo. Gpx1 consisted of 2 exons (Accession ID: JQ031269) while Dio1 comprised 4 exons (Accession ID: JQ791197). In Gpx1 gene, 9 SNPs were recorded and 4 were non synonymous, changing amino acid were distributed equally in both exon. In exon 1, A141G (aa Q5R) and G161A (aa A12T); and in exon 2 C785T (aa R132W) and A808T (aa S139R). In Dio1 gene, 3 non synonymous SNPs were identified at A188G (aa H22R), C215G (aa T31R) and G941A (aa V146I). These SNPs are novel and reported for the first time in Indian buffalo and has a potential for their use in diversity analysis and association with various selenium related traits
Herschel Observations of a Newly Discovered UX Ori Star in the Large Magellanic Cloud
The LMC star, SSTISAGE1C J050756.44-703453.9, was first noticed during a
survey of EROS-2 lightcurves for stars with large irregular brightness
variations typical of the R Coronae Borealis (RCB) class. However, the visible
spectrum showing emission lines including the Balmer and Paschen series as well
as many Fe II lines is emphatically not that of an RCB star. This star has all
of the characteristics of a typical UX Ori star. It has a spectral type of
approximately A2 and has excited an H II region in its vicinity. However, if it
is an LMC member, then it is very luminous for a Herbig Ae/Be star. It shows
irregular drops in brightness of up to 2 mag, and displays the reddening and
"blueing" typical of this class of stars. Its spectrum, showing a combination
of emission and absorption lines, is typical of a UX Ori star that is in a
decline caused by obscuration from the circumstellar dust. SSTISAGE1C
J050756.44-703453.9 has a strong IR excess and significant emission is present
out to 500 micron. Monte Carlo radiative transfer modeling of the SED requires
that SSTISAGE1C J050756.44-703453.9 has both a dusty disk as well as a large
extended diffuse envelope to fit both the mid- and far-IR dust emission. This
star is a new member of the UX Ori subclass of the Herbig Ae/Be stars and only
the second such star to be discovered in the LMC.Comment: ApJ, in press. 9 pages, 5 figure
SPITZER SAGE Observations of Large Magellanic Cloud Planetary Nebulae
We present IRAC and MIPS images and photometry of a sample of previously
known planetary nebulae (PNe) from the SAGE survey of the Large Magellanic
Cloud (LMC) performed with the Spitzer Space Telescope. Of the 233 known PNe in
the survey field, 185 objects were detected in at least two of the IRAC bands,
and 161 detected in the MIPS 24 micron images. Color-color and color-magnitude
diagrams are presented using several combinations of IRAC, MIPS, and 2MASS
magnitudes. The location of an individual PN in the color-color diagrams is
seen to depend on the relative contributions of the spectral components which
include molecular hydrogen, polycyclic aromatic hydrocarbons (PAHs), infrared
forbidden line emission from the ionized gas, warm dust continuum, and emission
directly from the central star. The sample of LMC PNe is compared to a number
of Galactic PNe and found to not significantly differ in their position in
color-color space. We also explore the potential value of IR PNe luminosity
functions (LFs) in the LMC. IRAC LFs appear to follow the same functional form
as the well-established [O III] LFs although there are several PNe with
observed IR magnitudes brighter than the cut-offs in these LFs.Comment: 18 pages, 10 figures, 3 tables, to be published in the Astronomical
Journal. Additional online data available at
http://www.cfa.harvard.edu/irac/publications
Spitzer Sage Survey of the Large Magellanic Cloud. III. Star Formation and ~1000 New Candidate Young Stellar Objects
We present ~1000 new candidate Young Stellar Objects (YSOs) in the Large Magellanic Cloud selected from Spitzer Space Telescope data, as part of the Surveying the Agents of a Galaxy's Evolution (SAGE) Legacy program. The YSOs, detected by their excess infrared (IR) emission, represent early stages of evolution, still surrounded by disks and/or infalling envelopes. Previously, fewer than 20 such YSOs were known. The candidate YSOs were selected from the SAGE Point Source Catalog from regions of color-magnitude space least confused with other IR-bright populations. The YSOs are biased toward intermediate- to high-mass and young evolutionary stages, because these overlap less with galaxies and evolved stars in color-magnitude space. The YSOs are highly correlated spatially with atomic and molecular gas, and are preferentially located in the shells and bubbles created by massive stars inside. They are more clustered than generic point sources, as expected if star formation occurs in filamentary clouds or shells. We applied a more stringent color-magnitude selection to produce a subset of "high-probability" YSO candidates. We fitted the spectral-energy distributions (SEDs) of this subset and derived physical properties for those that were well fitted. The total mass of these well-fitted YSOs is ~2900 M_☉ and the total luminosity is ~2.1 × 10^6 L_☉ . By extrapolating the mass function with a standard initial mass function and integrating, we calculate a current star-formation rate of ~0.06 M_☉ yr^(–1), which is at the low end of estimates based on total ultraviolet and IR flux from the galaxy (~0.05 – 0.25 M_☉ yr^(–1)), consistent with the expectation that our current YSO list is incomplete. Follow-up spectroscopy and further data mining will better separate the different IR-bright populations and likely increase the estimated number of YSOs. The full YSO list is available as electronic tables, and the SEDs are available as an electronic figure for further use by the scientific community
Spitzer SAGE survey of the Large Magellanic Cloud II: Evolved Stars and Infrared Color Magnitude Diagrams
Color-magnitude diagrams (CMDs) are presented for the Spitzer SAGE (Surveying
the Agents of a Galaxy's Evolution) survey of the Large Magellanic Cloud (LMC).
IRAC and MIPS 24 um epoch one data are presented. These data represent the
deepest, widest mid-infrared CMDs of their kind ever produced in the LMC.
Combined with the 2MASS survey, the diagrams are used to delineate the evolved
stellar populations in the Large Magellanic Cloud as well as Galactic
foreground and extragalactic background populations. Some 32000 evolved stars
brighter than the tip of the red giant branch are identified. Of these,
approximately 17500 are classified as oxygen-rich, 7000 carbon-rich, and
another 1200 as ``extreme'' asymptotic giant branch (AGB) stars. Brighter
members of the latter group have been called ``obscured'' AGB stars in the
literature owing to their dusty circumstellar envelopes. A large number (1200)
of luminous oxygen--rich AGB stars/M supergiants are also identified. Finally,
there is strong evidence from the 24 um MIPS channel that previously
unexplored, lower luminosity oxygen-rich AGB stars contribute significantly to
the mass loss budget of the LMC (1200 such sources are identified).Comment: LaTex, 31 pages, 10 figures. Accepted for publication in the
Astronomical Journa
The Dust-to-Gas Ratio in the Small Magellanic Cloud Tail
The Tail region of the Small Magellanic Cloud (SMC) was imaged using the MIPS
instrument on the Spitzer Space Telescope as part of the SAGE-SMC Spitzer
Legacy. Diffuse infrared emission from dust was detected in all the MIPS bands.
The Tail gas-to-dust ratio was measured to be 1200 +/- 350 using the MIPS
observations combined with existing IRAS and HI observations. This gas-to-dust
ratio is higher than the expected 500-800 from the known Tail metallicity
indicating possible destruction of dust grains. Two cluster regions in the Tail
were resolved into multiple sources in the MIPS observations and local
gas-to-dust ratios were measured to be ~440 and ~250 suggests dust formation
and/or significant amounts of ionized gas in these regions. These results
support the interpretation that the SMC Tail is a tidal tail recently stripped
from the SMC that includes gas, dust, and young stars.Comment: 6 pages, 3 figures, ApJ Letters, in press, (version with full
resolution figures at
http://www.stsci.edu/~kgordon/papers/PS_files/sage-smc_taildust_v1.62.pdf
Thirty Years After Michael E. Porter: What Do We Know About Business Exit?
Although a business exit is an important corporate change initiative, the buyer’s side seems to be more appealing to management researchers than the seller’s because acquisitions imply growth, i.e., success. Yet from an optimistic viewpoint, business exit can effectively create value for the selling company. In this paper we attempt to bring the relevance of the seller’s side back into our consciousness by asking: What do we know about business exit? We start our exploration with Porter (1976), focusing on literature that investigates the antecedents of, barriers to, and outcomes of business exit. We also include studies from related fields such as finance and economics.1 Through this research we determine three clusters of findings: factors promoting business exit, exit barriers, and exit outcomes. Overall, it is the intention of this paper to highlight the importance of business exit for research and practice. Knowing what we know about business exits and their high financial value we should bear in mind that exit need not mean failure but a new beginning for a corporation
Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator
HII regions are the birth places of stars, and as such they provide the best
measure of current star formation rates (SFRs) in galaxies. The close proximity
of the Magellanic Clouds allows us to probe the nature of these star forming
regions at small spatial scales. We aim to determine the monochromatic IR band
that most accurately traces the bolometric IR flux (TIR), which can then be
used to estimate an obscured SFR. We present the spatial analysis, via
aperture/annulus photometry, of 16 LMC and 16 SMC HII region complexes using
the Spitzer IRAC and MIPS bands. UV rocket data and SHASSA H-alpha data are
also included. We find that nearly all of the LMC and SMC HII region SEDs peak
around 70um, from ~10 to ~400 pc from the central sources. As a result, the
sizes of HII regions as probed by 70um is approximately equal to the sizes as
probed by TIR (about 70 pc in radius); the radial profile of the 70um flux,
normalized by TIR, is constant at all radii (70um ~ 0.45 TIR); the 1-sigma
standard deviation of the 70um fluxes, normalized by TIR, is a lower fraction
of the mean (0.05 to 0.12 out to ~220 pc) than the normalized 8, 24, and 160um
normalized fluxes (0.12 to 0.52); and these results are invariant between the
LMC and SMC. From these results, we argue that 70um is the most suitable IR
band to use as a monochromatic obscured star formation indicator because it
most accurately reproduces the TIR of HII regions in the LMC and SMC and over
large spatial scales. We also explore the general trends of the 8, 24, 70, and
160um bands in the LMC and SMC HII region SEDs, radial surface brightness
profiles, sizes, and normalized (by TIR) radial flux profiles. We derive an
obscured SFR equation that is modified from the literature to use 70um
luminosity, SFR(Mo/yr) = 9.7(0.7)x10^{-44} L(70)(ergs/s), which is applicable
from 10 to 300 pc distance from the center of an HII region.Comment: 21 pages, 12 figures, 4 tables. Will be published in ApJ
Variable Evolved Stars and YSOs Discovered in the Large Magellanic Cloud using the SAGE Survey
We present initial results and source lists of variable sources in the Large
Magellanic Cloud (LMC) for which we detect thermal infrared variability from
the SAGE (Surveying the Agents of a Galaxy's Evolution) survey, which had 2
epochs of photometry separated by three months. The SAGE survey mapped a 7
degree by 7 degree region of the LMC using the IRAC and the MIPS instruments on
board Spitzer. Variable sources are identified using a combination of the IRAC
3.6, 4.5, 5.8, 8.0 \micron bands and the MIPS 24 \micron bands. An
error-weighted flux difference between the two epochs is used to assess the
variability. Of the ~ 3 million sources detected at both epochs we find ~ 2,000
variable sources for which we provide electronic catalogs. Most of the variable
sources can be classified as asymptotic giant branch (AGB) stars. A large
fraction (> 66%) of the extreme AGB stars are variable and only smaller
fractions of carbon-rich (6.1%) and oxygen-rich (2.0%) stars are detected as
variable. We also detect a population of variable young stellar object
candidates.Comment: Accepted for publication in A
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