49 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
Densidade da madeira de ĂĄrvores em savanas do norte da AmazĂŽnia brasileira
Densidade da madeira (DM) Ă© uma variĂĄvel importante para estimativas de estoques de carbono arbĂłreo em ecossistemas terrestres. Este tema Ă© pobremente investigado em ĂĄreas de savana da AmazĂŽnia brasileira. O objetivo deste estudo foi investigar a DM das oito principais espĂ©cies arbĂłreas que ocorrem na savana aberta de Roraima, a maior ĂĄrea de savana do norte do bioma AmazĂŽnia. Foram verificadas as variaçÔes na DM em função da espĂ©cie e dos diferentes diĂąmetros observados ao longo da dimensĂŁo vertical de 75 indivĂduos amostrados em seis sĂtios de coleta. Foi utilizado o mĂ©todo direto para obtenção de peças de madeira do fuste e da copa. Os resultados indicaram discrepĂąncia significativa interespecĂfica, sendo Roupala montana Aubl. a espĂ©cie de maior DM mĂ©dia (0,674 g cm-3). Foi detectado que existe variação significativa da DM entre as peças do fuste e da copa, independente da espĂ©cie e do sĂtio de coleta. A densidade da madeira de peças da copa com diĂąmetro entre 5 e 10 cm pode ser utilizada como preditora da DM mĂ©dia do indivĂduo arbĂłreo. NĂłs concluimos que a DM das oito espĂ©cies arbĂłreas investigadas possui variabilidade interespecĂfica, com discrepĂąncias entre a DM do fuste e das partes lenhosas da copa. As distinçÔes aqui detectadas devem ser considerados como uma importante ferramenta para melhorar as estimativas de estoque de carbono em ĂĄreas de savanas na AmazĂŽnia
US hegemony and the origins of Japanese nuclear power : the politics of consent
This paper deploys the Gramscian concepts of hegemony and consent in order to explore the process whereby nuclear power was brought to Japan. The core argument is that nuclear power was brought to Japan as a consequence of US hegemony. Rather than a simple manifestation of one state exerting material âpower over' another, bringing nuclear power to Japan involved a series of compromises worked out within and between state and civil society in both Japan and the USA. Ideologies of nationalism, imperialism and modernity underpinned the process, coalescing in post-war debates about the future trajectory of Japanese society, Japan's Cold War alliance with the USA and the role of nuclear power in both. Consent to nuclear power was secured through the generation of a psychological state in the public mind combining the fear of nuclear attack and the hope of unlimited consumption in a nuclear-fuelled post-modern world
Suplemento mineral aniĂŽnico para vacas no periparto: parĂąmetros sanguĂneos, urinĂĄrios e incidĂȘncia de patologias de importĂąncia na bovinocultura leiteira
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
Hypoxic Pulmonary Vasoconstriction in Humans:Tale or Myth
Hypoxic Pulmonary vasoconstriction (HPV) describes the physiological adaptive process of lungs to preserves systemic oxygenation. It has clinical implications in the development of pulmonary hypertension which impacts on outcomes of patients undergoing cardiothoracic surgery. This review examines both acute and chronic hypoxic vasoconstriction focusing on the distinct clinical implications and highlights the role of calcium and mitochondria in acute versus the role of reactive oxygen species and Rho GTPases in chronic HPV. Furthermore it identifies gaps of knowledge and need for further research in humans to clearly define this phenomenon and the underlying mechanism