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.

Second Quantization of the Free Electromagnetic Field as Quantum Mechanics in the Loop Space

Abstract: The quantum field theory of electromagnetism in a vacuum is formulated as quantum mechanics in the loop space. A precise statement of the incompatibility field loop is given in terms of generalized momentum-position uncertainty relations. The loop-dependent wave functions of the basic states are obtained, and a physically satisfactory geometrical interpretation is given.

A survey of bond graphs : Theory, applications and programs

Abstract: This paper presents a survey of the bond graph method from its conception and creation by Prof. Henry Paynter to the present. A thematic classification of the bibliographical material is given depending on whether work deals with the definition of theoretical details of bond graphs, applications of bond graphs to particular fields, or if it deals with a computer program developed using the bond graph theory. A list of journals which publish bond graph related articles, as well as textbooks is also presented. The survey, though exhaustive, does not pretend to be all inclusive. Some works may have been unintentionally omitted due to obvious limitations on accessing and listing all the relevant literature concerning the topic.

Narcissism Guides Mate Selection: Humans Mate Assortatively, as Revealed by Facial Resemblance, following an Algorithm of “Self Seeking Like”

Abstract: Theoretical studies suggest that mating and pair formation is not likely to be random. Computer simulations suggested that sex among genetically complex organisms requires mate choice strategies for its evolutionary maintenance, to reduce excessive genetic variance produced by out-crossing. One strategy achieving this aim efficiently in computer simulations is assortative mating modeled as “self seeking like”. Another one is selection of “good genes”. Assortative mating increases the probability of finding a genetically similar mate, without fomenting inbreeding, achieving assortative mating without hindering the working of other mate selection strategies which aim to maximize the search for “good genes”, optimizing the working of sex in evolutionary terms. Here we present indirect evidence that in a significant proportion of human reproductive couples, the partners show much higher facial resemblances than can be expected by random pair formation, or as the outcome of “matching for attractiveness” or the...

Antinucleation Effect of the Polyethylene Block on the Polycaprolactone Block in ABC Triblock Copolymers

Abstract: Polystyrene-block-poly(ethylene-co-butylene)-block-poly(∈-caprolactone triblock copolymers (SEC ) were prepared by hydrogenating polystyrene-block-polybutadiene-block-poly(∈-caprolactone triblock copolymers (SBC) previously prepared by sequential anionic polymerization. The effect of the crystallization of the polyethylene block (PE) upon cooling from a phase-segregated melt on the crystallization process of the adjacent polycaprolactone block (PCL) was investigated by means of differential scanning calorimetry and polarized optical microscopy. It was found that there was no nucleation effect of the PE block on the PCL block under controlled cooling conditions in the DSC. On the contrary, an antinucleation effect was detected when nucleation of the PCL block crystals within the SEC triblock copolymers was attempted. It was demonstrated that such an antinucleation effect was induced by the annealing of the polyethylene block crystals of the SEC copolymers. By the application of the successive self-nucleation and annealing technique (SSA) the possibility of producing a distribution of lamellar thickness within the PCL and the PE blocks of the SEC triblock copolymers was shown. These results, together with the spherulitic morphology displayed by the SEC copolymers with more than 50 wt.-% PCL, are consistent with previous morphological observations in SBC triblock copolymers. Those observations indicate that the chain stems within the lamellar crystals in the PCL blocks could be perpendicular to the interphase of the block copolymer domains, even though the crystallization occurred from a heterogeneous melt.