O efeito “dominó” na Interacção Homem-Computador

A colaboração multidisciplinar é essencial para uma interacção homem-computador (IHC) efectiva. Historicamente a ciência dos computadores, a psicologia e as ciências sociais actuavam como disciplinas independentes, mas com o aumento da frequência na utilização das tecnologias da informação e comunicação em vários aspectos do dia-a-dia, a funcionalidade e acessibilidade assumiram uma importância cada vez maior. Neste artigo é apresentada uma reflexão sobre a multidisciplinaridade e transversalidade da IHC em termos tecnológicos e tendências futuras

VELOCITY PROFILE MODELING FOR NON-ISOTHERMAL FLOWS INSIDE A CIRCULAR TUBE

This research proposes a new method to establish the velocity field and the dimensionless velocity profile for Newtonian and non-Newtonian flows inside a circular tube. Several studies developed regarding different fluid types (such as potency law fluid, Bingham and Herschel-Bulkley, among others) observed that a rational or irrational polynomial was used for the dependent velocity field variable. Thus, a rational polynomial was established as a starting point for this research as the dependent velocity field variable. Dimensionless velocity profiles obtained from the proposed fluid-dynamics model were experimentally compared only with dimensionless velocity profiles for non-isothermal Newtonian flows of glycerol, in cooling as well as heating. On the other hand, it was possible to calculate that RMS errors found using relative dimensionless velocity data obtained from the proposed fluid-dynamics model creates very small errors, which are comparable to RMS errors found using data obtained from application of a numerical method. Finally, the proposed fluid-dynamics model was validated with a dimensionless velocity profile obtained from the flow of a cooling process, resulting in the validity of the proposed model

Global warming will affect the maximum potential abundance of boreal plant species

Forecasting the impact of future global warming on biodiversity requires understanding how temperature limits the distribution of species. Here we rely on Liebig's Law of Minimum to estimate the effect of temperature on the maximum potential abundance that a species can attain at a certain location. We develop 95%‐quantile regressions to model the influence of effective temperature sum on the maximum potential abundance of 25 common understory plant species of Finland, along 868 nationwide plots sampled in 1985. Fifteen of these species showed a significant response to temperature sum that was consistent in temperature‐only models and in all‐predictors models, which also included cumulative precipitation, soil texture, soil fertility, tree species and stand maturity as predictors. For species with significant and consistent responses to temperature, we forecasted potential shifts in abundance for the period 2041–2070 under the IPCC A1B emission scenario using temperature‐only models. We predict major potential changes in abundance and average northward distribution shifts of 6–8 km yr−1. Our results emphasize inter‐specific differences in the impact of global warming on the understory layer of boreal forests. Species in all functional groups from dwarf shrubs, herbs and grasses to bryophytes and lichens showed significant responses to temperature, while temperature did not limit the abundance of 10 species. We discuss the interest of modelling the ‘maximum potential abundance’ to deal with the uncertainty in the predictions of realized abundances associated to the effect of environmental factors not accounted for and to dispersal limitations of species, among others. We believe this concept has a promising and unexplored potential to forecast the impact of specific drivers of global change under future scenarios.202

Origin of the diffuse 4–8 keV emission in M 82

We present the first spatially resolved, X-ray spectroscopic study of the 4−8 keV diffuse emission found in the central part of the nearby starburst galaxy M 82 on a few arcsecond scales. The new details that we see allow a number of important conclusions to be drawn on the nature of the hot gas and its origin as well as feedback on the interstellar medium. We use archival data from the Chandra X-ray Observatory with an exposure time of 570 ks. The Fe XXV emission at 6.7 keV, expected from metal-enriched hot gas, is enhanced only in a limited area close to the starburst disc and is weak or almost absent over the rest of the diffuse emission, resulting in spatial variations in equivalent width from < 0.1 keV to 1.9 keV. This shows the presence of non-thermal emission due to inverse Compton scattering of the far-infrared photons by radio emitting cosmic ray electrons. The morphological resemblance between the diffuse X-ray, radio, and far-infrared emission maps support this concept. Our decomposition of the diffuse emission spectrum indicates that ∼70% of the 4−8 keV luminosity originates from the inverse Compton emission. The metal-rich hot gas with a temperature of ≃5 keV makes a minor contribution to the 4−8 keV continuum, but it accounts for the majority of the observed Fe XXV line. This hot gas appears to emerge from the circumnuclear starburst ring and fill the galactic chimneys identified as mid-infrared and radio emission voids. The energetics argument suggests that much of the supernova energy in the starburst site has gone into creating of the chimneys and is transported to the halo. We argue that a hot, rarefied environment produced by strong supernova feedback results in displacing the brightest X-ray and radio supernova remnants which are instead found to reside in giant molecular clouds. We find a faint X-ray source with a radio counterpart, close to the kinematic centre of the galaxy and we carefully examine the possibility that this source is a low-luminosity active galactic nucleus in an advection-dominated accretion flow phase

Papel de la glucógeno sintetasa cinasa 3β (GSK-3β) en el pre y postacondicionamiento isquémicos en ratas hipertensas espontánea

Estudios recientes en animales normotensos muestran que la enzima glucógeno sintetasa cinasa 3β (GSK-3β) es una de las potenciales cinasas que pueden regular la formación y/o apertura del poro de transición mitocondrial (PTM). La GSK-3β es constitutivamente activa y es inactivada por fosforilación en Ser 9. En estas condiciones es capaz de interactuar con los principales componentes del PTM e impedir su apertura

Scaling Analysis of Improved Actions for Pure SU(3) Gauge Theory

We have explored the behaviour of some improved actions based on a nonperturbative renormalization group (RG) analysis in coupling space. We calculate the RG flow in two-coupling space (\boneone,\bonetwo) and examine the restoration of rotational invariance and the scaling of physical quantities $(T_c/\sqrt{\sigma})$.Comment: LATTICE98(improvement

Adiabatic Compression of Soliton Matter Waves

The evolution of atomic solitary waves in Bose-Einstein condensate (BEC) under adiabatic changes of the atomic scattering length is investigated. The variations of amplitude, width, and velocity of soliton are found for both spatial and time adiabatic variations. The possibility to use these variations to compress solitons up to very high local matter densities is shown both in absence and in presence of a parabolic confining potential.Comment: to appear in J.Phys.

One-mode Bosonic Gaussian channels: a full weak-degradability classification

A complete degradability analysis of one-mode Gaussian Bosonic channels is presented. We show that apart from the class of channels which are unitarily equivalent to the channels with additive classical noise, these maps can be characterized in terms of weak- and/or anti-degradability. Furthermore a new set of channels which have null quantum capacity is identified. This is done by exploiting the composition rules of one-mode Gaussian maps and the fact that anti-degradable channels can not be used to transfer quantum information.Comment: 23 pages, 3 figure

Stochastic Resonance in a Dipole

We show that the dipole, a system usually proposed to model relaxation phenomena, exhibits a maximum in the signal-to-noise ratio at a non-zero noise level, thus indicating the appearance of stochastic resonance. The phenomenon occurs in two different situations, i.e. when the minimum of the potential of the dipole remains fixed in time and when it switches periodically between two equilibrium points. We have also found that the signal-to-noise ratio has a maximum for a certain value of the amplitude of the oscillating field.Comment: 4 pages, RevTex, 6 PostScript figures available upon request; to appear in Phys. Rev.