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.

Methods for the study of marine biodiversity

Abstract: Recognition of the threats to biodiversity and its importance to society has led to calls for globally coordinated sampling of trends in marine ecosystems. As a step to defining such efforts, we review current methods of collecting and managing marine biodiversity data. A fundamental component of marine biodiversity is knowing what, where, and when species are present. However, monitoring methods are invariably biased in what taxa, ecological guilds, and body sizes they collect. In addition, the data need to be placed, and/or mapped, into an environmental context. Thus a suite of methods will be needed to encompass representative components of biodiversity in an ecosystem. Some sampling methods can damage habitat and kill species, including unnecessary bycatch. Less destructive alternatives are preferable, especially in conservation areas, such as photography, hydrophones, tagging, acoustics, artificial substrata, light-traps, hook and line, and live-traps. Here we highlight examples of operational international sampling programmes and data management infrastructures, notably the Continuous Plankton Recorder, Reef Life Survey, and detection of Harmful Algal Blooms and MarineGEO. Data management infrastructures include the World Register of Marine Species for species nomenclature and attributes, the Ocean Biogeographic Information System for distribution data, Marine Regions for maps, and Global Marine Environmental Datasets for global environmental data. Existing national sampling programmes, such as fishery trawl surveys and intertidal surveys, may provide a global perspective if their data can be integrated to provide useful information. Less utilised and emerging sampling methods, such as artificial substrata, light-traps, microfossils and eDNA also hold promise for sampling the less studied components of biodiversity. All of these initiatives need to develop international standards and protocols, and long-term plans for their governance and support.

Directed Unfolding of Petri Nets

Abstract: The key to efficient on-the-fly reachability analysis based on unfolding is to focus the expansion of the finite prefix towards the desired marking. However, current unfolding strategies typically equate to blind (breadth-first) search. They do not exploit the knowledge of the marking that is sought, merely entertaining the hope that the road to it will be short. This paper investigates directed unfolding , which exploits problem-specific information in the form of a heuristic function to guide the unfolding towards the desired marking. In the unfolding context, heuristic values are estimates of the distance between configurations. We show that suitable heuristics can be automatically extracted from the original net. We prove that unfolding can rely on heuristic search strategies while preserving the finiteness and completeness of the generated prefix, and in some cases, the optimality of the firing sequence produced. We also establish that the size of the prefix obtained with a useful class of heuristics is never worse than that obtained by blind unfolding. Experimental results demonstrate that directed unfolding scales up to problems that were previously out of reach of the unfolding technique.

A linear programming methodology for the optimization of electric power-generation schemes

Abstract: A mathematical model, based upon the application of a linear-integer programming algorithm, is presented for the optimum selection of independent electric power generation schemes in industrial power systems, taking into account reliability considerations. The problem is formulated as a mathematical programming problem, considering investment costs, fuel costs, operation and maintenance costs, power balance, maximum and minimum limits on the generated power of the units, as well as reliability considerations such as the unavailability of the generation scheme. These considerations include assumptions taken and simplifications performed in order to obtain an accurate enough linear model. The problem is solved using a conventional branch and bound algorithm for linear-integer programming, yielding to the optimum number of units, as well as the correspondent size and type. Results are presented for the application of the proposed methodology to a real case of an industrial power system. The technique is proved as a valuable tool for the planning engineer.

Comparative Study of Brain Morphology in Ants

Abstract: Brain morphology, with special attention to the three dimensional form of the corpora pedunculata, was studied in thirteen species of ants, representing four subfamilies of Formicidae. The results can

Food Insecurity of Children and Shame of Others Knowing They Are Without Food

Abstract: We studied the association of shame when children experience food insecurity and management strategies. The cross-sectional study assessed food insecurity in 404 children using 2 instruments with 10 and 11 items for food insecurity and management strategies. Food insecurity in children was associated with shame of others knowing that they were out of food (γ = 0.37, P < .01). Nine out of 11 management strategies were associated (P < 0.05) with feeling of shame of being out of food. Older girls were most likely to report shame when they reported lack of food (P < .01). Understanding these relations may increase access to food in socially acceptable ways.