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Search Results: 1 - 10 of 395610 matches for " R. P.; Pereira "
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PET Oligomer Waste to Modify CAP Characteristics  [PDF]
L. C. Mendes, M. L. Dias, P. S. C. Pereira, L. M. R. Albuquerque
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.38082
Abstract: To develop an improved method of reusing poly(ethylene terephthalate) (PET) waste in the production chain, it was chemically modified with pentaerythritol (PENTE), resulting in PET/PENTE (60/40) oligomer. This was added to petroleum asphalt cement (CAP) in different proportions—5, 10 and 20 wt%—as a modifier of bitumen characteristics. The mixture was evaluated by thermogravimetry (TG/DTG), differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR), optical microscopy (OM) and the adhesion-peel test. The oligomer enhanced substantially the asphalt thermal stability-Tonset. OM images showed strong compatibility between components and PET’s amorphization. PET oligomer increased CAP’s wettability and the mixture presented cohesive fracture through the peel test. The mixture has excellent potential as paving material.
Effect of local mate competition on fig wasp sex ratios
Pereira, R. A. S.;Prado, A. P.;
Brazilian Journal of Biology , 2006, DOI: 10.1590/S1519-69842006000400004
Abstract: in fig wasps, mating takes place among the offspring of one or a few foundress mothers inside the fig from which mated females disperse to found new broods. under these conditions, related males will compete with each other for mating and several studies have shown female bias in brood sex ratios as a response to local mate competition (lmc). studying pegoscapus tonduzi which pollinates ficus citrifolia in brazil, we analysed the effect of lmc (number of foundresses) on the sex ratio of the offspring of pollinating wasps. the relationship between the foundress number and brood sex ratio qualitatively followed the theory, however the empirical sex ratio was more female biased than expected from theoretical values. the model for an optimal sex ratio considers that each foundress wasp contributes the same number of eggs to be bred and that the violation of this assumption may explain the lack of adjustment in relation to the theory.
Gravitational Collapse of Cylindrical Shells Made of Counter-Rotating Dust Particles
P. R. C. T. Pereira,Anzhong Wang
Physics , 2000, DOI: 10.1103/PhysRevD.67.129902
Abstract: The general formulas of a non-rotating dynamic thin shell that connects two arbitrary cylindrical regions are given using Israel's method. As an application of them, the dynamics of a thin shell made of counter-rotating dust particles, which emits both gravitational waves and massless particles when it is expanding or collapsing, is studied. It is found that when the models represent a collapsing shell, in some cases the angular momentum of the dust particles is strong enough to halt the collapse, so that a spacetime singularity is prevented from forming, while in other cases it is not, and a line-like spacetime singularity is finally formed on the symmetry axis.
Dynamics of Rotating Cylindrical Shells in General Relativity
P. R. C. T. Pereira,Anzhong Wang
Physics , 2000, DOI: 10.1023/A:1001954604324
Abstract: Cylindrical spacetimes with rotation are studied using the Newmann-Penrose formulas. By studying null geodesic deviations the physical meaning of each component of the Riemann tensor is given. These spacetimes are further extended to include rotating dynamic shells, and the general expression of the surface energy-momentum tensor of the shells is given in terms of the discontinuation of the first derivatives of the metric coefficients. As an application of the developed formulas, a stationary shell that generates the Lewis solutions, which represent the most general vacuum cylindrical solutions of the Einstein field equations with rotation, is studied by assuming that the spacetime inside the shell is flat. It is shown that the shell can satisfy all the energy conditions by properly choosing the parameters appearing in the model, provided that $ 0 \le \sigma \le 1$, where $\sigma$ is related to the mass per unit length of the shell.
Spinning process variables and polymer solution effects in the die-swell phenomenon during hollow fiber membranes formation
Pereira, C.C.;Nobrega, R.;Borges, C.P.;
Brazilian Journal of Chemical Engineering , 2000, DOI: 10.1590/S0104-66322000000400024
Abstract: during hollow fiber spinning many variables are involved whose effects are still not completely clear. however, its understanding is of great interest because the control of these variables may originate membranes with the desired morphologies and physical properties. in this work, the phase inversion process induced by the immersion precipitation technique was applied to prepare hollow fibers membranes. it was verified that some of the variables involved, can promote a visco-elastic polymer solution expansion, called die-swell phenomenon, which is undesired since it may lead to low reproducibility of the permeation properties. the effects of the distance between spinneret and precipitation bath, the bore liquid composition, and the polymer solution composition were analyzed and discussed in order to avoid this phenomenon. according to the results, it was verified that the parameters investigated might promote a delay precipitation, which restrained the visco-elastic expansion.
Golfe: os hábitos alimentares dos jogadores séniores
A.P. Ferreira de Brito,R.G. Pereira
Motricidade , 2008,
Abstract: EXCERTO:O objectivo deste estudo é apresentar o contexto que justifica a liga o das performances dos jogadores de golfe com os seus hábitos alimentares. A alimenta o influencia inequivocamente a saúde e o desempenho desportivo dos jogadores. Uma ingest o nutricional adequada contribui para optimizar a composi o corporal e reservas energéticas em fun o do desporto. A ausência de estudos nesta área, despoletou o interesse da investiga o, de forma a contribuir cientificamente para um aplanar de conhecimentos e uma abertura para a interven o da abordagem por outras áreas científicas tais como a nutri o. (...)
Les o perianal atípica em Doen a de Crohn
A. Vieira,R. Loureiro,V. Fernandes,P. Moniz Pereira
Jornal Português de Gastrenterologia , 2007,
Abstract:
STUDY OF PHYSICAL-CHEMICAL VARIABLE IN THE SEE WATER AND THE TANK WATER OF LIVE BAIT IN TUNA FISHING VESSEL ESTUDO DAS VARIáVEIS FíSICO-QUíMICAS DA áGUA DO MAR E DAS TINAS DE ISCA VIVA EM BARCOS ATUNEIROS
A. F. CAMPOS,P. R SCHWINGEL,K. C. PEREIRA
Brazilian Journal of Aquatic Science and Technology , 2002,
Abstract: The main purpose of the present work is to determine physico-chemical differences (dissolved oxygen, pH, salinity, nitrite, ammonia, temperature) between sea water and the tank water used for keeping live bait in a tuna fishing vessel. The study was conducted onboard the tuna vessel “Kowalski V”, around the Macuco island and Bombinhas coast (Santa Catarina, Brazil) in January 2000. The main live bait were clupeid fishes (Sardinella brasiliensis and Anchoa spp.). The results revealed the presence of ammonia in tank water, which, associated with high values of pH, can reduce the fish immunity and increase mortality. In general, the dissolved oxygen in the tank indicated a negative anomaly of 2 mg/l. Temperature, salinity and pH showed nonsignificant differences. Esse trabalho tem como objetivo determinar diferen as nas variáveis físico-químicas (oxigênio dissolvido, salinidade, pH, nitrito, am nia, temperatura) entre a água das tinas e do mar durante a captura e manuten o das iscas vivas em barcos da frota atuneira. O trabalho foi realizado durante o cruzeiro do barco “Kowalski V”, na enseada de Bombinhas e entorno da ilha do Macuco, SC, entre 13 a 21 de janeiro de 2000. Os peixes utilizados como isca viva foram sardinha-verdadeira (Sardinella brasiliensis) e boqueir o (Anchoa spp). O resultado das análises de água das tinas mostrou a presen a de am nia, que associada a valores altos de pH pode ocasionar queda de imunidade e causar a mortalidade de peixes devido sua toxidez. Em geral, o oxigênio dissolvido nas tinas apresentou uma diferen a negativa de 2 mg/l em rela o a água do mar. Temperatura, salinidade e pH n o mostraram diferen as significativas.
Spinning process variables and polymer solution effects in the die-swell phenomenon during hollow fiber membranes formation
Pereira C.C.,Nobrega R.,Borges C.P.
Brazilian Journal of Chemical Engineering , 2000,
Abstract: During hollow fiber spinning many variables are involved whose effects are still not completely clear. However, its understanding is of great interest because the control of these variables may originate membranes with the desired morphologies and physical properties. In this work, the phase inversion process induced by the immersion precipitation technique was applied to prepare hollow fibers membranes. It was verified that some of the variables involved, can promote a visco-elastic polymer solution expansion, called die-swell phenomenon, which is undesired since it may lead to low reproducibility of the permeation properties. The effects of the distance between spinneret and precipitation bath, the bore liquid composition, and the polymer solution composition were analyzed and discussed in order to avoid this phenomenon. According to the results, it was verified that the parameters investigated might promote a delay precipitation, which restrained the visco-elastic expansion.
First report of Uredo crepidis-japonicae and Septoria crepidis on Crepis japonica in Brazil
PEREIRA OLINTO L.,CAVALLAZZI JOSé R. P.,BARRETO ROBERT W.
Fitopatologia Brasileira , 2002,
Abstract:
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