Simón Bolívar University

About: Simón Bolívar University is a education organization based out in Caracas, Venezuela. It is known for research contribution in the topics: Population & Crystallization. The organization has 5912 authors who have published 8294 publications receiving 126152 citations.

Stellar models in brane worlds

Abstract: We consider here a full study of stellar dynamics from the brane-world point of view in the case of constant density and of a polytropic fluid. We start our study cataloguing the minimal requirements to obtain a compact object with a Schwarzschild exterior, highlighting the low and high energy limit, the boundary conditions, and the appropriate behavior of Weyl contributions inside and outside of the star. Under the previous requirements we show an extensive study of stellar behavior, starting with stars of constant density and its extended cases with the presence of nonlocal contributions. Finally, we focus our attention to more realistic stars with a polytropic equation of state, especially in the case of white dwarfs, and study their static configurations numerically. One of the main results is that the inclusion of the Weyl functions from brane-world models allows the existence of more compact configurations than within general relativity.

Bayesian time-varying autoregressions: Theory, methods and applications

Abstract: We review the class of time-varying autoregressive (TVAR) models and a range of related recent developments of Bayesian time series modelling.

Synthesis and rheological properties of hydrophobically modified polyacrylamides with lateral chains of poly(propylene oxide) oligomers.

Abstract: Hydrophobically modified polyacrylamides (HMPAM) were synthesized by aqueous micellar copolymerization using poly(propylene glycol) monomethacrylate, PPGMA, as hydrophobic monomer and sodium dodecyl sulfate, SDS, as surfactant. The hydrophobic monomer to surfactant ratio was varied during micellar synthesis to obtain different hydrophobic block lengths. It was found that the rheology of HMPAM/SDS solutions depends both on the ratio of PPGMA to surfactant and on the concentration of surfactant used in the micellar copolymerization. Also, the rheological behavior of the copolymer solutions was studied as a function of SDS addition and temperature. In the presence of SDS, an increase in zero-shear viscosity was observed that depended on polymer and surfactant concentration. At the highest SDS concentration, the copolymer did not reach the viscosity value exhibited by the solution without surfactant. In the presence of surfactant, HMPAM solutions exhibited a small thermo-thickening behavior when the temperature increases from 25 to 50 degrees C. Our rheological results evidence that the properties of HMPAM aqueous solution as a function of temperature, are a consequence of the rheological response of both components within the copolymer chain, i.e., hydrophilic (acrylamide) and lateral lower critical solution temperature (LCST) sequences (PPO).

Role of Endocrine-Disrupting Chemicals in the Pathogenesis of Non-Alcoholic Fatty Liver Disease: A Comprehensive Review.

Abstract: Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disorder, affecting around 25% of the population worldwide. It is a complex disease spectrum, closely linked with other conditions such as obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome, which may increase liver-related mortality. In light of this, numerous efforts have been carried out in recent years in order to clarify its pathogenesis and create new prevention strategies. Currently, the essential role of environmental pollutants in NAFLD development is recognized. Particularly, endocrine-disrupting chemicals (EDCs) have a notable influence. EDCs can be classified as natural (phytoestrogens, genistein, and coumestrol) or synthetic, and the latter ones can be further subdivided into industrial (dioxins, polychlorinated biphenyls, and alkylphenols), agricultural (pesticides, insecticides, herbicides, and fungicides), residential (phthalates, polybrominated biphenyls, and bisphenol A), and pharmaceutical (parabens). Several experimental models have proposed a mechanism involving this group of substances with the disruption of hepatic metabolism, which promotes NAFLD. These include an imbalance between lipid influx/efflux in the liver, mitochondrial dysfunction, liver inflammation, and epigenetic reprogramming. It can be concluded that exposure to EDCs might play a crucial role in NAFLD initiation and evolution. However, further investigations supporting these effects in humans are required.