Implementação Matlab do método dos elementos finitos móveis para resolução de problemas de convecção-difusão-reacção

No presente trabalho apresentamos uma aplicação computacional desenhadaem Matlab para a resolução de sistemas de equações diferenciais com derivadas parciais,dependentes do tempo em domínios espaciais de dimensão 1. O algoritmo numéricobaseia-se na formulação do método dos Elementos Finitos Móveis (MEFM) com funçõesde base não lineares e malhas adaptativas associadas a cada uma das variáveisdependentes. O principal objectivo desta nova implementação do MEFM é que possa serutilizada de modo simples por um utilizador que não domine as técnicas da linguagemFORTRAN para resolver de modo eficiente uma grande variedade de problemasevolutivos, incluindo problemas com fronteiras móveis. Os exemplos numéricos queapresentamos permitem avaliar a robuste

Nanoemulsions of β-carotene using a high-energy emulsification-evaporation technique

Nanoemulsions of β-carotene were prepared using a high-energy emulsification-evaporation technique based on a 23 level factorial design. Results show that it is possible to obtain dispersions at a nanoscale range. Process parameters such as time and shear rate of homogenization affected significantly particle size distribution in terms of volume-weighted mean diameter and surface-weighted mean diameter. The obtained nanoemulsions presented a volume-surface diameter ranging from 9 to 280 nm immediately after the production of particles, displaying in all cases a monomodal size distribution. Those nanoemulsions showed a good physical stability during 21 days storage. The stability was evaluated by the maintenance of size distribution. However, β-carotene retention inside the micelles and color were affected by storage. Processing conditions also influenced storage stability.Fundação para a Ciência e a Tecnologia (FCT)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brasil)Conselho Nacional de Ciência e Tecnologia (CNPq, Brasil

Anti-de Sitter curvature radius constrained by quasars in brane-world scenarios

This paper is intended to investigate the luminosity due to accretion of gas in supermassive black holes (SMBHs) in the center of quasars, using a brane-world scenario naturally endowed with extra dimensions, whereon theories formulated introduce corrections in the field equations at high energies. SMBHs possess the necessary highly energetic environment for the introduction of these corrections, which are shown to produce small deviations in all SMBH properties and, consequentely, corrections in the accretion theory that supports quasars radiative processes. The radiative flux observed from quasars indicates these deviations, from which the magnitude of the AdS$_5$ bulk curvature radius, and consequently the extra dimension compactification radius is estimated.Comment: 11 pages, RevTeX, Eq.(2) and (3) expanded, and comments thereon update

Production of β-carotene nanoemulsions prepared by a high-speed blender: characterization and stability evaluation

An efficient implementation of nanotechnology at the industrial level depends on the development of new tools for the application of strategies aimed at improving food quality and human health. Such strategies should offer the potential to significantly improve the solubility and bioavailability of many functional ingredients. The aim of the present work was to prepare -carotene stable nanoemulsions as potential active ingredients for food formulations. -carotene nanoemulsions were prepared using an emulsification-evaporation technique trough a high-speed blender. Promoting homogenization between -carotene dissolved in n-hexane with Tween 20 dispersed in mili-Q water, removing the n-hexane trough evaporation. The emulsions were prepared based on a 23 level factorial design, being the time (2, 5 and 8 min) and shear rate of the homogenization (3500, 5500 and 6500 rpm) and the cycles between the each homogenization (1, 2 and 3) the independent variables. Particle size distribution of -carotene nanoemulsions was determined by Dynamic Light Scattering. The stability of the nanoemulsions was determined at a storage temperature of 4 ºC, in the absence of light, through monitoring the concentration of -carotene during storage by spectrophotometry. The color of the nano-emulsions was evaluated with a colorimeter using the parameters CIE L* a* b*. The particle size ranged from 9.24 and 219.72 nm and between 9.78 and 259.68 nm for the weight-mean diameter (D3,2) and volume-surface diameter (D4,3), respectively. These diameters were measured immediately after the production of the particles. The concentration of -carotene decreased during 21 days of storage time. Particle size parameters suffered a statistically significant influence (p < 0.05) from the blending time and from the interaction of blending time and shear rate. These results show that it is possible to prepare oil-in-water nanoemulsions of -carotene using the emulsification-evaporation technique, without the use of high-pressure homogenization