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.

Cautiously Approaching SWRL

Abstract: The Semantic Web Rules Language (SWRL) has recently been proposed as the basic rules language for the Semantic Web. SWRL is unusual in being an undecidable superset of a very expressive description logic - OWL DL (SHOIN(D)) and a simple rules language, Datalog. In this paper, we attempt to evolve OWL DL toward SWRL, but cautiously and carefully. We strive to retain practical decidability. We seek to meet identifiable needs as simply as possible. We also attempt to make use of existing work on integrating rules systems, especially Datalog, with expressive description logics. We want to build a rules system that people with a large commitment to OWL will find understandable and useful. With such an aim, we explore different ways to give the users what they want, while staying “close” to OWL, and “cautiously far” from the full expressivity of SWRL.

Approximate analytical expression for equation of ideal diode with series and shunt resistances

Abstract: A simple and continuous analytical approximation for the equation of an ideal diode with a series resistance and shunt conductance is proposed. When compared to the exact numerical solution, the approximate expression produces relative errors smaller than 3%, for any values of series resistance and shunt conductance.

Molecular Mobilities in Biodegradable Poly(dl-lactide)/Poly(ε-caprolactone) Blends

Abstract: The miscibility of poly(dl-lactide) and poly(e-caprolactone) (PDLLA/PCL) blends in a wide composition range was studied by the thermally stimulated depolarization currents technique by following the local and segmental dielectric relaxations changes as the blend composition is varied. The PCL primary relaxation is slightly shifted to higher temperatures as the PDLLA content increases, thus demonstrating the existence of a rich PCL phase and partial miscibility with PDLLA. Wide-angle X-ray scattering showed that neat PDLLA was amorphous, as expected for a sample with 12 mol % d-lactide isomer; nevertheless, the presence of 3D order was detected in the PDLLA that was melt blended with PCL. Differential scanning calorimetry also evidenced chain interaction by the decrease in the melting and crystallization temperatures as well as in the PCL crystallization kinetics which becomes slower in the presence of increasing amounts of PDLLA.

Biosurfactant-mediated biodegradation of straight and methyl-branched alkanes by Pseudomonas aeruginosa ATCC 55925

Abstract: Accidental oil spills and waste disposal are important sources for environmental pollution. We investigated the biodegradation of alkanes by Pseudomonas aeruginosa ATCC 55925 in relation to a rhamnolipid surfactant produced by the same bacterial strain. Results showed that the linear C11-C21 compounds in a heating oil sample degraded from 6% to 100%, whereas the iso-alkanes tended to be recalcitrant unless they were exposed to the biosurfactant; under such condition total biodegradation was achieved. Only the biodegradation of the commercial C12-C19 alkanes could be demonstrated, ranging from 23% to 100%, depending on the experimental conditions. Pristane (a C19 branched alkane) only biodegraded when present alone with the biosurfactant and when included in an artificial mixture even without the biosurfactant. In all cases the biosurfactant significantly enhanced biodegradation. The electron scanning microscopy showed that cells depicted several adaptations to growth on hydrocarbons, such as biopolymeric spheres with embedded cells distributed over different layers on the spherical surfaces and cells linked to each other by extracellular appendages. Electron transmission microscopy revealed transparent inclusions, which were associated with hydrocarbon based-culture cells. These patterns of hydrocarbon biodegradation and cell adaptations depended on the substrate bioavailability, type and length of hydrocarbon.