Browsing Facultad de Ciencias Exactas y Naturales by Title
Now showing items 98-117 of 2541
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Amenazas químico-tecnológicas en la Gran Área Metropolitana de Costa Rica
(Universidad Nacional (Costa Rica), 2013)Los accidentes químico-tecnológicos son eventos inesperados que con llevan la liberación no controlada de una o más sustancias químicas con graves repercusiones en la salud humana y, en ocasiones, impactos irreversibles ... -
Ampliación de la base geodésica Barranca
(Universidad Nacional (Costa Rica), 1991)La Red Geodésica Nacional se estableció por medio de una triangulación entre 1945 y 1955. El trabajo geodésico consistió en la medición de las bases Barranca y Bataan, la determinación de las bases de dichas bases, la ... -
Amplitud de hábitat y su relación con la masa corporal, gremio trófico y riesgo de extinción en murciélagos filostómidos (Chiroptera: Phyllostomidae) de distribución continental
(Universidad Nacional (Costa Rica), 2021)La amplitud de hábitat representa la variación en el número de ambientes en los que una especie logra ejercer su forma de vida. Esta medida a su vez es un indicador de la tolerancia de las especies ante la variación de ... -
An anatomical comparison between bunch and fruit of oil palm with pineapple leaf and three woods from plantations in Costa Rica
(Journal of Oil Palm Research, 2013-04)Elaeis guineensis, Ananas comusus and forest plantations are planted widely in Costa Rica; however their residues (8000 t) are not utilised. The main objective of this work was to undertake an anatomical description of the ... -
An approach to rheological and electrokinetic behaviour of lipidic vesicles covered with chitosan biopolymer
(Elsevier, 2008)The rheological and electrokinetic properties of soybean lecithin vesicles prepared from concentrated soy lecithin dispersions (250 g/L) obtained by slow swelling under shear conditions and mixed with chitosan biopolymer ... -
An evaluation of variables affecting the stability and performance of down-flow anaerobic fixed bed reactors treating piggery wastewater
(Taylor & Francis, 2006)The influence of the most important variables on the stability and performance of down-flow anaerobic fixed bed reactors treating piggery wastewater after primary sedimentation was evaluated at HRT in the range of 1-6 d ... -
An in vivo model to study the anti-malaric capacity of plant extracts
(Universidad de Costa Rica, 1998)An in vivo model to study the antimalaric effect of plant extracts is described. White mice (25-30g body weight) are treated subcutaneously with 0.6ml of the diluted extract starting seven days before P. berghei infection; ... -
An undescribed species of velvet worm from Chiapas, Mexico (Onychophora: Peripatidae)
(Universidad Estatal a Distancia (Costa Rica), 2018-06)Onychophoran worms are considered “living fossils” because their basic body structure has changed little in 500 million years. Only two species have been properly recorded from Mexico: Macroperipatus perrieri from ... -
Analogías y Metáforas: Caminos que conducen a la construcción de los conceptos y al desarrollo del razonamiento científico
(Universidad Nacional (Costa Rica), 2000)Explora el papel de las analogías y metáforas en la conformación de oportunidades de aprendizaje en química. Es una investigación cualitativa, se realiza en tres colegios académicos diurnos, los sujetos fueron 230 estudiantes ... -
Analysis of an Augmented HDG Method for a Class of Quasi-Newtonian Stokes Flows
(Springer, 2015)In this paper we introduce and analyze a hybridizable discontinuous Galerkin (HDG) method for numerically solving a class of nonlinear Stokes models arising in quasi-Newtonian fluids. Similarly as in previous papers dealing ... -
Analysis of an augmented pseudostress-based mixed formulation for a nonlinear Brinkman model of porous media flow
(Elsevier, 2015)In this paper we introduce and analyze an augmented mixed finite element method for the two-dimensional nonlinear Brinkman model of porous media flow with mixed boundary conditions. More precisely, we extend a previous ... -
Analysis of energy transfer and ternary non-covalent filler/matrix/UV stabilizer interactions in carbon nanofiber and oxidized carbon nanofiber filled poly(methyl methacrylate) composites
(Elsevier, 2011-10-27)Ternary non-covalent interactions between carbon nanofibers (CNFs), oxidized carbon nanofibers (ox- CNFs), poly(methyl methacrylate) (PMMA) chains, and benzotriazole-containing UV stabilizers were analyzed using ... -
Analysis of non-covalent interactions between the nanoparticulate fillers and the matrix polymer as applied to shape memory performance
(The Royal Society of Chemistry, 2010)Non-covalent interactions between filler particles and polyurethanes were investigated using fluorescence emission spectroscopy. The results were used in the analysis of shape memory (SM) performance of polyurethanes. ... -
Analysis of the contaminant “microplastics” in marine and freshwater ecosystems in the World Heritage Site Cocos Island National Park, Costa Rica
(Universidad Nacional (Costa Rica), 2023) -
Analysis of the educational resources used in the course Fundamentals of Informatics in the face of the COVID-19 pandemic
(Universidad Nacional (Costa Rica), 2022)Technology brought several advancements to the Educational area in the past few years, including digital resources such as Open Educational Resources (OER). However, higher demand associated with the lack of platforms that ... -
Analysis of the HDG method for the stokes–darcy coupling
(Numerical Methods for Partial Differential Equations, 2017-02-03)In this article, we introduce and analyze a hybridizable discontinuous Galerkin (HDG) method for numerically solving the coupling of fluid flow with porous media flow. Flows are governed by the Stokes and Darcy equations, ... -
Analysis of the influence of GLONASS signals in the processing of one regional geodestic Network
(Universidad Nacional, Costa Rica, 2018-01-31)In recent years, there has been an increase in the number of satellites available for positioning using space techniques, highlighting the GPS and GLONASS systems. The comparative analysis of the results ... -
Analysis of the threat of groundwater contamination in the Jacó aquifer, Central Pacific, Costa Rica
(Universidad Nacional (Costa Rica), 2021-07-01)[Introduction]: In Costa Rica, more than 70 % of the public drinking water supply comes from groundwater sources. In the coastal city of Jacó, on the Central Pacific Coast of Costa Rica, tourism activity ... -
Analysis performed by Pre-Service Teachers in an Emerging Technological Environment in Mathematics Education
(REDIMAT © HipatiaPress, 2024-02-22)El objetivo de esta investigación es describir la forma en que una profesora de matemática en formación analiza lo que ocurre en una clase de matemáticas virtual videograbada en un entorno emergente. Para esto, se diseñó ... -
Analyzing a Five-year Failure Record of a Leadership-class Supercomputer
(Institute of Electrical and Electronics Engineers, Incorporated (IEEE), 2019-10-18)Extreme-scale computing systems are required to solve some of the grand challenges in science and technology. From astrophysics to molecular biology, supercomputers are an essential tool to accelerate scientific discovery. ...