198 research outputs found
Properties of the PCygni wind found using the Self Absorption Curve method
We have used the optical lines of N II and Fe III to study the wind of the
luminous blue variable P Cyg. This was performed by applying a version of the
Self Absorption Curve (SAC) method, involving few assumptions, to lines whose
flux can be measured. A rather surprising result was obtained; the lines of
more excited multiplets without blue shifted absorption components appear to be
optically thick, while the lines of the most excited multiplets may show some
indications of being optically thicker than the lines of less excited ones.
Explanations of such effects are discussed, including possible inhomogeneities
in the wind.Comment: accepted by Astronomy & Astrophysic
Analysis of the circumstellar environment of the B[e] star HD 45677 (FS CMa)
We studied the circumstellar environment of the B[e] star HD 45677 through
the analysis of the emission lines from ionized metals. We used the statistical
approach of the self absorption curve method (SAC) to derive physical
parameters of the line emitting region. The Fe II and Cr II double-peaked
emission line structure is explained by the presence of a thin absorption
component red shifted by ~3 km/s. This absorption component can be interpreted
geometricaly as being due to infalling material perpendicularly to the disk
seen nearly pole-on, as indicated by the emission line structure. The Cr II and
Fe II emission lines have a complex structure with two (narrow and broad)
components, of 45 and 180 km/s FWHM for the permitted lines and 25 and 100 km/s
FWHM for the forbidden ones, respectively. We argue that the narrow components
are principaly emitted by an optically thin disk seen nearly pole-on, in a
region whose minimum radius is estimated to be 4 10^12 cm, while the broad ones
are formed in a disk-linked wind.Comment: 14 pages, submitted to Astronomy and Astrophysic
Detecting short spatial scale local adaptation and epistatic selection in climate-related candidate genes in European beech (Fagus sylvatica) populations
Detecting signatures of selection in tree populations threatened by climate change is currently a major research priority. Here, we investigated the signature of local adaptation over a short spatial scale using 96 European beech (Fagus sylvatica L.) individuals originating from two pairs of populations on the northern and southern slopes of Mont Ventoux (south-eastern France). We performed both single and multi-locus analysis of selection based on 53 climate-related candidate genes containing 546 SNPs. FST outlier methods at the SNP level revealed a weak signal of selection, with three marginally significant outliers in the northern populations. At the gene-level, considering haplotypes as alleles, two additional marginally significant outliers were detected, one on each slope. To account for the uncertainty of haplotype inference, we averaged the Bayes Factors over many possible phase reconstructions. Epistatic selection offers a realistic multi-locus model of selection in natural populations. Here, we used a test suggested by Ohta based on the decomposition of the variance of linkage disequilibrium. Over all populations, 0.23% of the SNP pairs (haplotypes) showed evidence of epistatic selection, with nearly 80% of them being within genes. One of the between gene epistatic selection signals arose between an FST outlier and a non-synonymous mutation in a drought response gene. Additionally, we identified haplotypes containing selectively advantageous allele combinations which were unique to high or low-elevations and northern or southern populations. Several haplotypes contained non-synonymous mutations situated in genes with known functional importance for adaptation to climatic factor
Disk winds of B[e] supergiants
The class of B[e] supergiants is characterized by a two-component stellar
wind consisting of a normal hot star wind in the polar zone and a slow and
dense disk-like wind in the equatorial region. The properties of the disk wind
are discussed using satellite UV spectra of stars seen edge-on, i.e. through
the equatorial disk. These observations show that the disk winds are extremely
slow, 50-90 km/s, i.e. a factor of about 10 slower than expected from the
spectral types. Optical emission lines provide a further means to study the
disk wind. This is discussed for line profiles of forbidden lines formed in the
disk.Comment: 7 pages, LaTeX, 3 ps figures, uses lamuphys.sty from Springer-Verlag,
to be published in the proceedings of IAU Coll. 169 "Variable and
Non-spherical Stellar Winds in Luminous Hot Stars" held in Heidelberg 199
Looking for local adaptation:Convergent microevolution in aleppo pine (pinus halepensis)
Finding outlier loci underlying local adaptation is challenging and is best approached by suitable sampling design and rigorous method selection. In this study, we aimed to detect outlier loci (single nucleotide polymorphisms, SNPs) at the local scale by using Aleppo pine (Pinus halepensis), a drought resistant conifer that has colonized many habitats in the Mediterranean Basin, as the model species. We used a nested sampling approach that considered replicated altitudinal gradients for three contrasting sites. We genotyped samples at 294 SNPs located in genomic regions selected to maximize outlier detection. We then applied three different statistical methodologies-Two Bayesian outlier methods and one latent factor principal component method-To identify outlier loci. No SNP was an outlier for all three methods, while eight SNPs were detected by at least two methods and 17 were detected only by one method. From the intersection of outlier SNPs, only one presented an allelic frequency pattern associated with the elevational gradient across the three sites. In a context of multiple populations under similar selective pressures, our results underline the need for careful examination of outliers detected in genomic scans before considering them as candidates for convergent adaptation
A Spitzer Space Telescope far-infrared spectral atlas of compact sources in the Magellanic Clouds. I. The Large Magellanic Cloud
[abridged] We present 52-93 micron spectra obtained with Spitzer in the
MIPS-SED mode, of a representative sample of luminous compact far-IR sources in
the LMC. These include carbon stars, OH/IR AGB stars, post-AGB objects and PNe,
RCrB-type star HV2671, OH/IR red supergiants WOHG064 and IRAS05280-6910, B[e]
stars IRAS04530-6916, R66 and R126, Wolf-Rayet star Brey3a, Luminous Blue
Variable R71, supernova remnant N49, a large number of young stellar objects,
compact HII regions and molecular cores, and a background galaxy (z~0.175). We
use the spectra to constrain the presence and temperature of cold dust and the
excitation conditions and shocks within the neutral and ionized gas, in the
circumstellar environments and interfaces with the surrounding ISM. Evolved
stars, including LBV R71, lack cold dust except in some cases where we argue
that this is swept-up ISM. This leads to an estimate of the duration of the
prolific dust-producing phase ("superwind") of several thousand years for both
RSGs and massive AGB stars, with a similar fractional mass loss experienced
despite the different masses. We tentatively detect line emission from neutral
oxygen in the extreme RSG WOHG064, with implications for the wind driving. In
N49, the shock between the supernova ejecta and ISM is revealed by its strong
[OI] 63-micron emission and possibly water vapour; we estimate that 0.2 Msun of
ISM dust was swept up. Some of the compact HII regions display pronounced
[OIII] 88-micron emission. The efficiency of photo-electric heating in the
interfaces of ionized gas and molecular clouds is estimated at 0.1-0.3%. We
confirm earlier indications of a low nitrogen content in the LMC. Evidence for
solid state emission features is found in both young and evolved object; some
of the YSOs are found to contain crystalline water ice.Comment: Accepted for publication in The Astronomical Journal. This paper
accompanies the Summer 2009 SAGE-Spec release of 48 MIPS-SED spectra, but
uses improved spectrum extraction. (Fig. 2 reduced resolution because of
arXiv limit.
Spatial and temporal population genetic variation and structure of Nothotsuga longibracteata (Pinaceae), a relic conifer species endemic to subtropical China
High genetic diversity with moderate differentiation in Juniperus excelsa from Lebanon and the eastern Mediterranean region
Juniperus excelsa constitutes a precious woody species of high ecological value able to grow up to Mountain treeline around the Mediterranean. Nuclear microsatellites were used to shed light on genetic diversity and differentiation of different Mediterranean populations. This information is essential in planning conservation strategies and reforestation programs
El laberinto de la autonomía indígena en el Ecuador: las circunscripciones territoriales indígenas en la Amazonía Central, 2010-2012
¿Cuáles son los avatares y desencuentros presentes en el proceso de constitución de las
Circunscripciones Territoriales Indígenas (CTIs) en relación a la vigencia del derecho a la
autodeterminación y autogestión territorial de las nacionalidades indígenas en el Ecuador? Para
responder a dicha interrogante, el artículo considera el reconocimiento al derecho a la
autonomía y autodeterminación de las nacionalidades y pueblos indígenas en Ecuador.
Posteriormente, analiza el alcance de los procedimientos establecidos tanto en la Constitución
Política como en el Código Orgánico de Ordenamiento Territorial y Descentralización
(COOTAD), y su alcance potencial en generar un nuevo tipo de institucionalidad y una nueva
organización territorial en el marco de la definición del Estado plurinacional Ecuatoriano. Esta
contribución analiza además el proceso derivado de una hoja de ruta acordada entre el Estado y
las nacionalidades amazónicas en el periodo comprendido entre 2010 y 2012, y analiza las
diferentes acciones desplegadas desde entonces, enfatizando en los avances y contradicciones,
tanto a lo interno del movimiento indígena como en su relación con otras instancias estatales
centrales y locales. Se examinan los desencuentros y tensiones a lo interno del aparato Estatal y
los sectores mestizos, que no se plantean ningún reparo al momento de obstaculizar los avances
del proceso. El artículo analiza el desafío de crear las CTIs en el territorio de los Kichwa de las
provincias de Napo y Orellana y en los territorios Kichwa y Achuar en la provincia de Pastaza,
en la Amazonía central. Finalmente, el texto puntualiza críticamente algunas de las perspectivas
y dilemas que dicho proceso plantea al futuro de la relación Estado-nacionalidades indígenas y
al proceso de construcción del Estado plurinacional e intercultural en Ecuador
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