6,071 research outputs found
de Broglie-Proca and Bopp-Podolsky massive photon gases in cosmology
We investigate the influence of massive photons on the evolution of the
expanding universe. Two particular models for generalized electrodynamics are
considered, namely de Broglie-Proca and Bopp-Podolsky electrodynamics. We
obtain the equation of state (EOS) for each case using
dispersion relations derived from both theories. The EOS are inputted into the
Friedmann equations of a homogeneous and isotropic space-time to determine the
cosmic scale factor . It is shown that the photon non-null mass does not
significantly alter the result valid for a massless photon
gas; this is true either in de Broglie-Proca's case (where the photon mass
is extremely small) or in Bopp-Podolsky theory (for which is extremely
large).Comment: 8 pages, 2 figures; v2 matches the published versio
Percepções leigas sobre as desigualdades na saúde e no ambiente e suas associações com a saúde mental
Health inequalities are very well documented in epidemiological research: rich people live longer and have less diseases than poor persons. Recently, a growing amount of evidence from environmental sciences confirms that poor people are also more exposed to pollution and other environmental threats. However, research in the social sciences has shown a wide unawareness of health inequalities. In this paper, based on data collected in Portugal, we will analyse the consciousness of both health and environmental injustices and test one hypothesis for this social blindness. The results show, even more clearly than before, that public opinion tends to see rich and poor people equally susceptible to health and environmental events. Besides, those who have this equal view of the world present lower levels of depression and anxiety. Following cognitive adaptation theory, this “belief in an equal world” can be interpreted as a protective positive illusion about social justice, particularly relevant in one of the most unequal countries in Europe.info:eu-repo/semantics/publishedVersio
Current-driven and field-driven domain walls at nonzero temperature
We present a model for the dynamics of current- and field-driven domain-wall
lines at nonzero temperature. We compute thermally-averaged drift velocities
from the Fokker-Planck equation that describes the nonzero-temperature dynamics
of the domain wall. As special limits of this general description, we describe
rigid domain walls as well as vortex domain walls. In these limits, we
determine also depinning times of the domain wall from an extrinsic pinning
potential. We compare our theory with previous theoretical and experimental
work
Combined effects of chemical dip and/or edible coating and/or controlled atmosphere on quality of fresh-cut banana
Emergent sources of prebiotics: seaweeds and microalgae
In recent years, scientists have become aware that human microbiota, in general, and gut microbiota, in particular, play a major role in human health and diseases, such as obesity and diabetes, among others. A large number of evidence has come to light regarding the beneficial effects, either for the host or the gut microbiota, of some foods and food ingredients or biochemical compounds. Among these, the most promising seem to be polysaccharides (PS) or their derivatives, and they include the dietary fibers. Some of these PS can be found in seaweeds and microalgae, some being soluble fibers, such as alginates, fucoidans, carrageenans and exopolysaccharides, that are not fermented, at least not completely, by colonic microbiota. This review gives an overview of the importance of the dietary fibers, as well as the benefits of prebiotics, to human health. The potential of the PS from marine macro- and microalgae to act as prebiotics is discussed, and the different techniques to obtain oligosaccharides from PS are presented. The mechanisms of the benefits of fiber, in general, and the types and benefits of algal fibers in human health are highlighted. The findings of some recent studies that present the potential effects of prebiotics on animal models of algal biomass and their extracts, as well as oligo- and polysaccharides, are presented. In the future, the possibility of using prebiotics to modulate the microbiome, and, consequently, prevent certain human diseases is foreseen.info:eu-repo/semantics/publishedVersio
Influence of growth regulators kinetin and 2,4-D on the growth of two Chlorophyte Microalgae, Haematococcus pluvialis and Dunaliella salina
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