2,083 research outputs found
The genus Elasmopus on the coast of Brazil with description of Elasmopus besnardi n. sp., and E. fusimanus n. sp. (Crustacea, amphipoda)
Neste trabalho apresentamos os anfÃpodos do gênero Elasmopus, que são representados na coleção da Estação de Hidrobiologia do Instituto Oswaldo Cruz, e entre eles temos a honra de dedicar uma espécie ao Prof. W. Besnard. Assim este trabalho representa, de certo modo, uma contribuição aos resultados da Expedição do navio 'Baependi', realizada em 1950, à Ilha da Trindade
Influence of Logging on Douglas Fir Beetle Populations
All species of bark beetles of economic importance prefer to attack freshly-killed host material. Logging slash, wind-throw, and fire-killed timber provide ideal breeding grounds for bark beetles. A few species, mostly in the Dendroctonus group, are able to kill living trees. When beetles in the group, raised in preferred host material, cannot find any or enough freshly-killed trees, logs, or slash to enter, they may attack living trees. In the interior of British Columbia, infestations of the Douglas fir beetle can often be traced to logging disturbance
Gaia broad band photometry
The scientific community needs to be prepared to analyse the data from Gaia,
one of the most ambitious ESA space missions, to be launched in 2012. The
purpose of this paper is to provide data and tools in order to predict in
advance how Gaia photometry is expected to be. To do so, we provide
relationships among colours involving Gaia magnitudes and colours from other
commonly used photometric systems (Johnson-Cousins, SDSS, Hipparcos and Tycho).
The most up-to-date information from industrial partners has been used to
define the nominal passbands and based on the BaSeL3.1 stellar spectral energy
distribution library, relationships were obtained for stars with different
reddening values, ranges of temperatures, surface gravities and metallicities.
The transformations involving Gaia and Johnson-Cousins V-I_C and Sloan DSS g-z
colours have the lowest residuals. A polynomial expression for the relation
between the effective temperature and the colour G_BP-G_RP was derived for
stars with T > 4500 K. Transformations involving two Johnson or two Sloan DSS
colours yield lower residuals than using only one colour. We also computed
several ratios of total-to-selective absorption including absorption A_G in the
G band and colour excess E(G_BP-G_RP) for our sample stars. A relationship,
involving A_G/A_V and the intrinsic (V-I_C) colour, is provided. The derived
Gaia passbands have been used to compute tracks and isochrones using the Padova
and BASTI models. Finally, the performances of the predicted Gaia magnitudes
have been estimated according to the magnitude and the celestial coordinates of
the star. The provided dependencies among colours can be used for planning
scientific exploitation of Gaia data, performing simulations of the Gaia-like
sky, planning ground-based complementary observations and for building
catalogues with auxiliary data for the Gaia data processing and validation.Comment: 15 pages and 19 figure (accepted in A&A
Characterizing normal crossing hypersurfaces
The objective of this article is to give an effective algebraic
characterization of normal crossing hypersurfaces in complex manifolds. It is
shown that a hypersurface has normal crossings if and only if it is a free
divisor, has a radical Jacobian ideal and a smooth normalization. Using K.
Saito's theory of free divisors, also a characterization in terms of
logarithmic differential forms and vector fields is found and and finally
another one in terms of the logarithmic residue using recent results of M.
Granger and M. Schulze.Comment: v2: typos fixed, final version to appear in Math. Ann.; 24 pages, 2
figure
Microsurgical neurovascular anastomosis: The example of superficial temporal artery to middle cerebral artery bypass. Technical principles
AbstractThe superficial temporal artery to the middle cerebral artery (STA-MCA) bypass is a good example of cerebrovascular anastomosis. In this article, we describe the different stages of the procedure: patient installation, superficial temporal artery harvesting, recipient artery exposure, microsurgical anastomosis, and closure of the craniotomy. When meticulously performed, with the observance of important details at each stage, this technique offers a high rate of technical success (patency>90%) with a very low morbi-mortality (respectively 3% and 1%). Some anesthetic parameters have to be considered to insure perioperative technical and clinical success. STA-MCA bypass is a very useful technique for the management of complex or giant aneurysms where surgical treatment sometimes requires the sacrifice and revascularization of a main arterial trunk. It is also a valuable option for the treatment of chronic and symptomatic hemispheric hypoperfusion (Moyamoya disease, carotid or middle cerebral artery occlusion)
The photometric evolution of dissolving star clusters: II. Realistic models. Colours and M/L ratios
Evolutionary synthesis models are the prime method to construct models of
stellar populations, and to derive physical parameters from observations. One
of the assumptions for such models so far has been the time-independence of the
stellar mass function. However, dynamical simulations of star clusters in tidal
fields have shown the mass function to change due to the preferential removal
of low-mass stars from clusters. Here we combine the results from dynamical
simulations of star clusters in tidal fields with our evolutionary synthesis
code GALEV to extend the models by a new dimension: the total cluster
disruption time. We reanalyse the mass function evolution found in N-body
simulations of star clusters in tidal fields, parametrise it as a function of
age and total cluster disruption time and use this parametrisation to compute
GALEV models as a function of age, metallicity and the total cluster disruption
time. We study the impact of cluster dissolution on the colour (generally, they
become redder) and magnitude (they become fainter) evolution of star clusters,
their mass-to-light ratios (off by a factor of ~2 -- 4 from standard
predictions), and quantify the effect on the cluster age determination from
integrated photometry (in most cases, clusters appear to be older than they
are, between 20 and 200%). By comparing our model results with observed M/L
ratios for old compact objects in the mass range 10^4.5 -- 10^8 Msun, we find a
strong discrepancy for objects more massive than 10^7 Msun (higher M/L). This
could be either caused by differences in the underlying stellar mass function
or be an indication for the presence of dark matter in these objects. Less
massive objects are well represented by the models. The models for a range of
total cluster disruption times are available online. (shortened)Comment: MNRAS, in press, data are available at
http://www.phys.uu.nl/~anders/data/SSP_varMF/, http://data.galev.org and soon
also from CDS ... sorry for the sometimes strange layout, that's LaTe
- …