20,913 research outputs found
Geographical origin discrimination of the green coffee bean and analytical qualification of the roasting profilles
Tese de doutoramento, QuĂmica (QuĂmica AnalĂtica), Universidade de Lisboa, Faculdade de CiĂȘncias, 2011ADI Agency (AgĂȘncia de Inovação), project POCTI Med. 2.4 - Projecto ORITOCAFĂ (2004-2006); Fundação para a CiĂȘncia e a Tecnologia (FCT, SFRH/BD/28354/2006), project PTDC/AGR-AAM/104357/2008 (IsoGeoCoffee), (2010-2012
The origin of Scorpius X-1
We have used multi-wavelength observations of high precision to derive the
space velocity and compute the orbit around the Galactic Centre of the
prototype X-ray binary Scorpius X-1. An origin in the local spiral arm of the
Milky Way is ruled out. The galactocentric kinematics of Scorpius X-1 is
similar to that of the most ancient stars and globular clusters of the inner
Galactic halo. Most probably, this low-mass X-ray binary was formed by a close
encounter in a globular cluster. However, it cannot be ruled out that a natal
supernova explosion launched Scorpius X-1 into an orbit like this from a birth
place in the galactic bulge. In any case, the Galactocentric orbit indicates
that Scorpius X-1 was formed more than 30 Myrs ago.Comment: 4 pages, 1 figure. Animation and high resolution figures can be
retrived from the NRAO press release:
http://www.aoc.nrao.edu/epo/pr/2003/scox1
Can Punctured Rate-1/2 Turbo Codes Achieve a Lower Error Floor than their Rate-1/3 Parent Codes?
In this paper we concentrate on rate-1/3 systematic parallel concatenated
convolutional codes and their rate-1/2 punctured child codes. Assuming
maximum-likelihood decoding over an additive white Gaussian channel, we
demonstrate that a rate-1/2 non-systematic child code can exhibit a lower error
floor than that of its rate-1/3 parent code, if a particular condition is met.
However, assuming iterative decoding, convergence of the non-systematic code
towards low bit-error rates is problematic. To alleviate this problem, we
propose rate-1/2 partially-systematic codes that can still achieve a lower
error floor than that of their rate-1/3 parent codes. Results obtained from
extrinsic information transfer charts and simulations support our conclusion.Comment: 5 pages, 7 figures, Proceedings of the 2006 IEEE Information Theory
Workshop, Chengdu, China, October 22-26, 200
Sustainable forest management of miombo woodlands in Niassa National Reserve, northern Mozambique: a multidisciplinary approach of fire resistance analysis.
Poster presented at XIII World Forestry Congress. Buenos Aires (Argentina). 18 - 23 Oct 2009
Imagery and long-slit spectroscopy of the Polar-Ring Galaxy AM2020-504
Interactions between galaxies are very common. There are special kinds of
interactions that produce systems called Polar Ring Galaxies (PRGs), composed
by a lenticular, elliptical, or spiral host galaxy, surrounded by a ring of
stars and gas, orbiting in an approximately polar plane. The present work aims
to study AM2020-504, a PRG with an elliptical host galaxy, and a narrow and
well defined ring, probably formed by accretion of material from a donor
galaxy, collected by the host galaxy. Our observational study was based on BVRI
broad band imagery as well as longslit spectroscopy in the wavelenght range
4100--8600\AA, performed at the 1.6m telescope at the Observat\'orio do Pico
dos Dias (OPD), Brazil. We estimated a redshift of z= 0.01683, corresponding a
heliocentric radial velocity of 5045 +/-23 km/s. The (B-R) color map shows that
the ring is bluer than the host galaxy, indicating that the ring is a younger
structure. Standard diagnostic diagrams were used to classify the main ionizing
source of selected emission-line regions (nucleus, host galaxy and ring). It
turns out that the ring regions are mainly ionized by massive stars while the
nucleus presents AGN characteristics. Using two empirical methods, we found
oxygen abundances for the HII regions located in the ring in the range
12+log(O/H)=8.3-8.8 dex, the presence of an oxygen gradient across the ring,
and that AM2020-504 follows the metallicity-luminosity relation of spiral
galaxies. These results support the accretion scenario for this object and
rules out cold accretion as source for the HI gas in the polar ring
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