51 research outputs found
Low-mass pre--main-sequence stars in the Magellanic Clouds
[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar
stars form in very large numbers. Most attractive places for catching low-mass
star formation in the act are young stellar clusters and associations, still
(half-)embedded in star-forming regions. The low-mass stars in such regions are
still in their pre--main-sequence (PMS) evolutionary phase. The peculiar nature
of these objects and the contamination of their samples by the evolved
populations of the Galactic disk impose demanding observational techniques for
the detection of complete numbers of PMS stars in the Milky Way. The Magellanic
Clouds, the companion galaxies to our own, demonstrate an exceptional star
formation activity. The low extinction and stellar field contamination in
star-forming regions of these galaxies imply a more efficient detection of
low-mass PMS stars than in the Milky Way, but their distance from us make the
application of special detection techniques unfeasible. Nonetheless, imaging
with the Hubble Space Telescope yield the discovery of solar and sub-solar PMS
stars in the Magellanic Clouds from photometry alone. Unprecedented numbers of
such objects are identified as the low-mass stellar content of their
star-forming regions, changing completely our picture of young stellar systems
outside the Milky Way, and extending the extragalactic stellar IMF below the
persisting threshold of a few solar masses. This review presents the recent
developments in the investigation of PMS stars in the Magellanic Clouds, with
special focus on the limitations by single-epoch photometry that can only be
circumvented by the detailed study of the observable behavior of these stars in
the color-magnitude diagram. The achieved characterization of the low-mass PMS
stars in the Magellanic Clouds allowed thus a more comprehensive understanding
of the star formation process in our neighboring galaxies.Comment: Review paper, 26 pages (in LaTeX style for Springer journals), 4
figures. Accepted for publication in Space Science Review
TRY plant trait database â enhanced coverage and open access
Plant traitsâthe morphological, anatomical, physiological, biochemical and phenological characteristics of plantsâdetermine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of traitâbased plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traitsâalmost complete coverage for âplant growth formâ. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and traitâenvironmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives
Suplemento mineral aniĂŽnico para vacas no periparto: parĂąmetros sanguĂneos, urinĂĄrios e incidĂȘncia de patologias de importĂąncia na bovinocultura leiteira
Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures
Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo
Effects of different doses of medetomidine and tiletamineâzolazepam on the duration of induction and immobilization in free-ranging yearling brown bears ( Ursus arctos
The Nature of the Cold Filaments in the California Current System
Data from the Coastal Transition Zone (CTZ) experiment axe used to describe the velocity
fields and water properties associated with cold filaments in the California Current. Combined
with previous field surveys and satellite imagery, these show seasonal variability with maximum
dynamic height ranges and velocities in summer and minimum values in late winter and early
spring. North of Point Arena (between 39 degrees N and 42 degrees N) in spring-summer the flow field on the
outer edge of the cold water has the character of a meandering jet, carrying fresh, nutrient-poor
water from farther north on its offshore side and cold, salty, nutrient-rich water on its inshore
side. At Point Arena in midsummer, the jet often flows offshore and continues south without
meandering back onshore as strongly as it does farther north. The flow field south of Point Arena
in summer takes on more of the character a field of mesoscale eddies, although the meandering
jet from the north continues to be identifiable. The conceptual model for the May-July period
between 36 degrees N and 42 degrees N is thus of a surface jet that meanders through and interacts with a field
of eddies; the eddies are more dominant south of 39 degrees N, where the jet broadens and where multiple
jets and filaments are often present. At the surface, the jet often separates biological communities
and may appear as a barrier to cross-jet transport, especially north of Point Arena early in the
season (March-May). However, phytoplankton pigment and nutrients are carried on the inshore
flank of the jet, and pigment maxima are sometimes found in the core of the jet. The biological
effect of the jet is to define a convoluted, 100 to 400-km-wide region next to the coast, within
which much of the richer water is contained, and also to carry some of that richer water offshore
in meanders along the outer edge of that region.The CTZ program was funded by the Coastal Sciences Program of the Office of Naval Research (Code 1122CS). Support for PTS was provided by ONR grants N00014-87K0009 and N00014-90J1115, with additional support provided by NASA grants NAGW-869 and NAGW-1251
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