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.

Polyphenols and antioxidant capacity of Phaseolus vulgaris stored under extreme conditions and processed

Abstract: Phaseolus vulgaris is a foodstuff that not only supplies nutrients, but also bioactive compounds with antioxidant capacity; however, bad post-harvest storage or processing can diminish the antioxidant capacity. In this work, the effect of storage under extreme conditions, of thermal processing and of fermentation on the content of phenolic compounds and their antioxidant capacity (AA) in beans of just harvested P. vulgaris were evaluated. Combination of temperatures of 30 and 50 °C and relative humidity of 11% and 80% for 150 days were evaluated. Extreme storage conditions drastically decreased the AA, demonstrating that post-harvest storage at low temperature and humidity preserves the antioxidant capacity of the beans. Regarding processing, cooking decreased the scavenging effect and the AA by 63.5% and 56.8%, while fermentation decreased them by only 14% and 22%, respectively. It was concluded that the loss of antioxidant capacity due to heating is less in fermented beans.

Development of amorphous PLA-montmorillonite nanocomposites

Abstract: The large amounts of plastics that are produced mainly from fossil fuels, once they are consumed and discarded into the environment, finally end up as undegradable wastes, and therefore contribute greatly to global pollution. For this reason, there is an urgent need to produce renewable source-based environmentally benign plastic materials, specially in short term packaging and disposable applications that could allow the composting of naturally occurring degradation products. One of the most promising candidates in this direction is poly(lactic acid) (PLA), produced from renewable resources and readily biodegradable. PLA is a linear thermoplastic polyester produced by the ringopening polymerization of lactide. Lactide is a cyclic dimmer prepared by the controlled depolymerization of lactic acid, which is obtained from the fermentation of sugar feedstocks, corn, etc. [1, 2]. In general commercial PLA grades are copolymers of poly(L-lactic acid) and poly(D,L-lactic acid), which are produced from L-lactides and D,L-lactides respectively. The ratio of L-enantiomers to D,L-enantiomers is known to affect the properties of PLA [3], i.e. if the materials are semicrystalline or amorphous; until now all the efforts reported in order to improve the properties of PLA are focused on the semicrystalline material [3], e.g. D-content less than 6%. There is increasing interest in using PLA for disposable degradable plastic articles; however, there are properties such as flexural properties, gas permeability, impact strength, processability, etc. that are often not good enough for some end use applications [4]. On the other hand confinement of polymer in a two-dimensional silicate gallery, so-called polymer nanocomposite, is one of the effective ways to improve material performance [5]. The most widely utilized clay is the montmorillonite (MMT) for its large cation exchange capacity [5]. Ogata et al. [4] first prepared

Efficient evaluation of queries in a mediator for WebSources

Abstract: We consider an architecture of mediators and wrappers for Internet accessible WebSources of limited query capability. Each call to a source is a WebSource Implementation (WSI) and it is associated with both a capability and (a possibly dynamic) cost. The multiplicity of WSIs with varying costs and capabilities increases the complexity of a traditional optimizer that must assign WSIs for each remote relation in the query while generating an (optimal) plan. We present a two-phase Web Query Optimizer (WQO). In a pre-optimization phase, the WQO selects one or more WSIs for a pre-plan; a pre-plan represents a space of query evaluation plans (plans) based on this choice of WSIs. The WQO uses cost-based heuristics to evaluate the choice of WSI assignment in the pre-plan and to choose a good pre-plan. The WQO uses the pre-plan to drive the extended relational optimizer to obtain the best plan for a pre-plan. A prototype of the WQO has been developed. We compare the effectiveness of the WQO, i.e., its ability to efficiently search a large space of plans and obtain a low cost plan, in comparison to a traditional optimizer. We also validate the cost-based heuristics by experimental evaluation of queries in the noisy Internet environment.

The Synthesis of Substituted 2-Aryl 4(3H)-Quinazolinones using Nahso3/Dma. Steric Effect upon the Cyclisation-Dehydrogenation Step:

Abstract: A number of 2-aryl substituted 6-pyrrolidino-4(3H)-quinazolinones are reported. They were synthesised in four steps starting from commercially available 5-chloro-2-nitrobenzoic acid. The key cyclis...