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.

Analysis of the influence of substrate variables on coral reef fish communities

Abstract: A simple field technique to obtain a gross estimate of the surface area of a quadrat on a coral reef is described. This measure, termed the substrate rugosity index, was determined, in conjunction with two other substrate variables (vertical relief and coral species richness), in a series of 4 quadrats (10 to 40 m depth) along 4 transects. The mean substrate rugosity and vertical relief of a quadrat were highly correlated. A correlation analysis was made of the substrate variables and several reef fish community parameters (species richness, number of fishes and diversity). Species richness was highly correlated with substrate rugosity. This relationship was tested in two experimental quadrats and the results were generally in accord with those predicted. Stratification of the fish communities by body size revealed that the correlation with substrate rugosity was scale-dependent. The fish community parameters were poorly correlated with percentage substrate cover by corals (ramose and glomerate) and by sand. A significant area effect was determined for two species of sand-dwelling goby.

Impact of an augmented reality system on students' motivation for a visual art course

Abstract: In this paper, the authors show that augmented reality technology has a positive impact on the motivation of middle-school students. The Instructional Materials Motivation Survey (IMMS) (Keller, 2010) based on the ARCS motivation model (Keller, 1987a) was used to gather information; it considers four motivational factors: attention, relevance, confidence, and satisfaction. Motivational factors of attention and satisfaction in an augmented-reality-based learning environment were better rated than those obtained in a slides-based learning environment. When the impact of the augmented reality system was analyzed in isolation, the attention and confidence factors were the best rated. The usability study showed that although this technology is not mature enough to be used massively in education, enthusiasm of middle-school students diminished most of the barriers found.

Caribbean corals in crisis: record thermal stress, bleaching, and mortality in 2005.

Abstract: Background: The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin. Methodology/Principal Findings: Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the iming and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles. Conclusions/Significance: Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.

Molecular-Based Equations of State for Associating Fluids: A Review of SAFT and Related Approaches

Abstract: We present a review of recent advances in the statistical associating fluid theory (SAFT). In contrast to the “chemical theory”, in which nonideality is explained in terms of chemical reactions between the species, SAFT and similar approaches relate nonideality to the intermolecular forces involved. Such physical theories can be tested against molecular simulations, and improvements to the theory can be made where needed. We describe the original SAFT approach and more recent modifications to it. Emphasis is placed on pointing out that SAFT is a general method and not a unique equation of state. Applications to a wide variety of fluids and mixtures are reviewed, including aqueous mixtures and electrolytes, liquid−liquid immiscible systems, amphiphilic systems, liquid crystals, polymers, petroleum fluids, and high-pressure phase equilibria.