1,687 research outputs found
Superbubble evolution including the star-forming clouds: Is it possible to reconcile LMC observations with model predictions?
Here we present a possible solution to the apparent discrepancy between the
observed properties of LMC bubbles and the standard, constant density bubble
model. A two-dimensional model of a wind-driven bubble expanding from a
flattened giant molecular cloud is examined. We conclude that the expansion
velocities derived from spherically symmetric models are not always applicable
to elongated young bubbles seen almost face-on due to the LMC orientation. In
addition, an observational test to differentiate between spherical and
elongated bubbles seen face-on is discussed.Comment: 25 pages, 7 figures, accepted to ApJ (September, 1999 issue
Galaxy evolution in nearby groups. II. Galaxy evolution in nearby loose groups. II. Photometric and kinematic characterization of USGC U268 and USGC U376 group members in the Leo cloud
We present the photometric and kinematic characterization of two groups, USGC
U268 and USGC U376 located in different regions of the Leo cloud. U268,
composed of 10 catalogued members and 11 new added members, has a small
fraction (~24%) of early-type galaxies (ETGs). U376 has 16 plus 8 new added
members, with ~38% of ETGs. We find the presence of significant substructures
in both groups suggesting that they are likely accreting galaxies. U268 is
located in a more loose environment than U376. For each member galaxy, broad
band integrated and surface photometry have been obtained in far-UV and near-UV
with GALEX, and in u,g, r, i, z (SDSS) bands. H_alpha imaging and 2D high
resolution kinematical data have been obtained using PUMA Scanning Fabry-Perot
interferometer at the 2.12 m telescope in San Pedro M\'artir, (Baja California,
M\'exico). We improved the galaxy classification and we detected morphological
and kinematical distortions that may be connected to either on-going and/or
past interaction/accretion events or environmental induced secular evolution.
U268 appears more active than U376, with a large fraction of galaxies showing
interaction signatures (60% vs. 13%). The presence of bars among late-type
galaxies is ~10% in U268 and ~$29% in U376. The cumulative distribution of (FUV
- NUV) colours of galaxies in U268 is significantly different than that in U376
with galaxies in U268 bluer than those in U376. In the (FUV-r vs. M_r) and
(NUV-r vs. M_r) planes no members of U268 are found in the `red sequence', even
early-type galaxies lie in the `blue sequence' or in the `green valley'. Most
(80%) of the early-type members in U376 inhabits the `red sequence, a large
fraction of galaxies, of different morphological types, are located in the
`green valley', while the `blue sequence' is under-populated with respect to
U268.Comment: 27 pages, 11 figures, 8 tables, accepted for publication in MNRAS
(abridged abstract
Structure of Supergiant Shells in the Large Magellanic Cloud
Nine supergiant shells (SGSs) have been identified in the Large Magellanic
Cloud (LMC) based on H-alpha images, and twenty-three SGSs have been reported
based on HI 21-cm line observations, but these sets do not always identify the
same structures. We have examined the physical structure of the optically
identified SGSs using HI channel maps and P-V diagrams to analyze the gas
kinematics. There is good evidence for seven of the nine optically identified
SGSs to be true shells. Of these seven H-alpha SGSs, four are the ionized inner
walls of HI SGSs, while three are an ionized portion of a larger and more
complex HI structure. All of the H-alpha SGSs are identified as such because
they have OB associations along the periphery or in the center, with younger OB
associations more often found along the periphery. After roughly 12 Myrs, if no
new OB associations have been formed a SGS will cease to be identifiable at
visible wavelengths. Thus, the presence and location of ionizing sources is the
main distinction between shells seen only in HI and those also seen in H-alpha.
Based on our analysis, H-alpha observations alone cannot unambiguously identify
SGSs, especially in distant galaxies.Comment: 26 pages, 16 figures, accepted for publication in the Astrophysical
Journal Supplemen
Water Quality of Cisterns and Underground Dams in Semiarid Regions: Case Study of Afogados da Ingazeira, Pernambuco – Northeast Brazil
In semiarid regions water resources are limited and irregularly distributed over space and time. As a result, water scarcity is a reality emphasized by the high evaporation rate recorded in these
regions (2000 mm per year). In consequence, the management of water use is a subject that
requires priority, especially in the regions where water is a scarce resource. There should be orientation towards its rational use through storage in appropriate places – as cisterns, and underground dams. Additionally, these techniques represent an advantage since they have low costs and can be developed and maintained by individual or community programmes. The social mobilization that occurs with families involved on the construction and maintenance of these structures guaranty the sustainability of these techniques. Although several local populations continued to use water without any treatment, is essential to promote the sanitary security of those
waters, which must achieve the human consumption standards, defined on Brazilian legislations. The main goals of this work are: (i) to analyze the maintenance of these structures and the facilities of their implementation; (ii) to calculate the costs involved; (iii) and finally to discuss the
importance of improve water quality in cisterns and groundwater dams
Elaboration of Essential Oil From the Oregano for Medicinal Use Sheet
The extraction and industrialization of the oregano oil in Ecuador can represent an important source of work, from the harvest to the transformation of the raw material into finished product. The oregano is a plant known from many years back and has always been used for medicinal purposes and is currently being used in many fields such as perfumery, gastronomy, toiletries; But its main use is in medicine. The work proposes a methodology that allows extracting the essential oil of the plant for different medical uses such as: anti - inflammatory, analgesic, antioxidant and antibiotic, being of social benefit representing an economic impact in its industrializatio
Ocorrência de três espécies de coleoptera do gênero Homalinotus (Curculionidae: Molytinae) em pupunha (Bactris gasipaes).
EVINCI. Resumo
Genetic parameters and variability in physic nut accessions during early developmental stages.
The objective of this work was to estimate the genetic parameters and variability among accessions (half?sib families) of physic nut (Jatropha curcas) during the early stages of development. For this study, 110 accessions in the first year of development of the physic nut germplasm bank, maintained at Embrapa Cerrados, DF, Brazil, were evaluated in situ. The experiment was established in a randomized complete block design, with two replicates and five plants per plot arranged in rows at 4x2 m spacing. Grain yield, total number of branches per plant, plant height, stem diameter, canopy projection on the row, canopy projection between rows, canopy volume, number of days until first flowering and height of the first inflorescence were evaluated. Estimates of vegetative genetic parameters showed the existence of genetic variability in the physic nut germplasm bank. Physic nut accessions of the germplasm bank were grouped into five similarity groups based on character divergence. Although preliminary, the obtained results are promising for showing potential for Jatropha improvement with selective efficiency
Cruzamentos dialéticos e capacidade combinatória em pinhão-manso na fase jovem.
O presente trabalho objetivou avaliar cruzamentos em esquema dialélicos e estimar a capacidade de combinação para caracteres vegetativos em pinhão-manso na fase jovem
X-Ray Synchrotron Emitting Fe-Rich Ejecta in SNR RCW 86
Supernova remnants may exhibit both thermal and nonthermal X-ray emission. We
present Chandra observations of RCW 86. Striking differences in the morphology
of X-rays below 1 keV and above 2 keV point to a different physical origin.
Hard X-ray emission is correlated fairly well with the edges of regions of
radio emission, suggesting that these are the locations of shock waves at which
both short-lived X-ray emitting electrons, and longer-lived radio-emitting
electrons, are accelerated. Soft X-rays are spatially well-correlated with
optical emission from nonradiative shocks, which are almost certainly portions
of the outer blast wave. These soft X-rays are well fit with simple thermal
plane-shock models. Harder X-rays show Fe K alpha emission and are well
described with a similar soft thermal component, but a much stronger
synchrotron continuum dominating above 2 keV, and a strong Fe K alpha line.
Quantitative analysis of this line and the surrounding continuum shows that it
cannot be produced by thermal emission from a cosmic-abundance plasma; the
ionization time is too short, as shown both by the low centroid energy (6.4
keV) and the absence of oxygen lines below 1 keV. Instead, a model of a plane
shock into Fe-rich ejecta, with a synchrotron continuum, provides a natural
explanation. This requires that reverse shocks into ejecta be accelerating
electrons to energies of order 50 TeV. We show that maximum energies of this
order can be produced by radiation-limited diffusive shock acceleration at the
reverse shocks.Comment: ApJ, accepted; full resolution images in
http://spider.ipac.caltech.edu/staff/rho/rcw86chandra.p
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