1,036 research outputs found
Tendencias en la normalización de nombres de autores en publicaciones científicas
Se analizan las tendencias actuales sobre normalización de los nombres de autores. Se revisan las ventajas de utilizar un nombre bibliográfico único y se revisan las recomendaciones más habituales para que se elijan los de cada autor
Non-circular rotating beams and CMB experiments
This paper is concerned with small angular scale experiments for the
observation of cosmic microwave background anisotropies. In the absence of
beam, the effects of partial coverage and pixelisation are disentangled and
analyzed (using simulations). Then, appropriate maps involving the CMB signal
plus the synchrotron and dust emissions from the Milky Way are simulated, and
an asymmetric beam --which turns following different strategies-- is used to
smooth the simulated maps. An associated circular beam is defined to estimate
the deviations in the angular power spectrum produced by beam asymmetry without
rotation and, afterwards, the deviations due to beam rotation are calculated.
For a certain large coverage, the deviations due to pure asymmetry and
asymmetry plus rotation appear to be very systematic (very similar in each
simulation). Possible applications of the main results of this paper to data
analysis in large coverage experiments --as PLANCK-- are outlined.Comment: 13 pages, 9 figures, to appear in A&
A Biophysically-Based Model of the Optical Properties of Skin Aging
This paper presents a time-varying, multi-layered biophysically-based model of the optical properties of human skin, suitable for simulating appearance changes due to aging. We have identified the key aspects that cause such changes, both in terms of the structure of skin and its chromophore concentrations, and rely on the extensive medical and optical tissue literature for accurate data. Our model can be expressed in terms of biophysical parameters, optical parameters commonly used in graphics and rendering (such as spectral absorption and scattering coefficients), or more intuitively with higher-level parameters such as age, gender, skin care or skin type. It can be used with any rendering algorithm that uses diffusion profiles, and it allows to automatically simulate different types of skin at different stages of aging, avoiding the need for artistic input or costly capture processes
Is Sugar Sweeter at the Pump? The Macroeconomic Impact of Brazil's Alternative Energy Program
The recent world energy crisis raises serious questions about the extent to which the United States should increase domestic oil production and develop alternative sources of energy. We examine the energy developments in Brazil as an important experiment. Brazil has reduced its share of imported oil more than any other major economy in the world in the last 30 years, from 70 percent in the 1970s to only 10 percent today. Brazil has largely achieved this goal by: (1) increasing domestic oil production and (2) developing one of the world's largest and most competitive sources of renewable energy -- sugarcane ethanol -- that now accounts for 50 percent of Brazil's total gasoline consumption. A counterfactual analysis of economic growth in Brazil from 1980-2008 suggests that GDP is almost 35 percent higher today because of increased domestic oil production and the development of sugarcane ethanol. We also find a notable reduction in business-cycle volatility as a result of Brazil's progression to a more diversified energy program. Nearly three-fourths of the welfare benefits have come from domestic oil drilling, however, as rents have been paid to domestic factors of production during a time of rising oil prices. We discuss the potential implications of Brazil's energy program for the U.S. economy by conducting historical counterfactual exercises on U.S. real GDP growth since the 1970s.
CMB anisotropy: deviations from Gaussianity due to non-linear gravity
Non-linear evolution of cosmological energy density fluctuations triggers
deviations from Gaussianity in the temperature distribution of the cosmic
microwave background. A method to estimate these deviations is proposed. N-body
simulations -- in a CDM cosmology -- are used to simulate the strongly
non-linear evolution of cosmological structures. It is proved that these
simulations can be combined with the potential approximation to calculate the
statistical moments of the CMB anisotropies produced by non-linear gravity.
Some of these moments are computed and the resulting values are different from
those corresponding to Gaussianity.Comment: 6 latex pages with mn.sty, 3 eps figures. Accepted in MNRA
High temperature susceptibility in electron doped Ca1-xYxMnO3: Double Exchange vs Superexchange
We present a study of the magnetic properties of the electron doped
manganites Ca1-xYxMnO3 (for 0<=x<=0.25) in the paramagnetic regime. For the
less doped samples (x<=0.1) the magnetic susceptibility, c(T), follows a
Curie-Weiss (CW) law only for T > 450 K and, below this temperature, c^-1(T)
shows a ferrimagnetic-like curvature. We approached the discussion of these
results in terms of a simple mean-field model where double exchange,
approximated by a ferromagnetic Heisenberg-like interaction between Mn3+ and
Mn4+ ions, competes with classical superexchange. For higher levels of doping
(x>=0.15), the CW behaviour is observed down to the magnetic ordering
temperature (Tmo) and a better description of c(T) was obtained by assuming
full delocalization of the eg electrons. In order to explore the degree of
delocalization as a function of T and x, we analyzed the problem through
Montecarlo simulations. Within this picture we found that at high T the
electrons doped are completely delocalized but, when Tmo is approached, they
form magnetic polarons of large spin that cause the observed curvature in
c^-1(T) for x<=0.1.Comment: 15 pages, 10 figures, Submitted to J. Physics: Condensed Matter
(06/28/02
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