Revista de Ciencia y Tecnología

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A model of chemical association in binary mixtures
(2009-04-29 00:00:00) Castellón Elizondo, Erick
A general model of chemical association is presented for the correlation of activities of components of a binary mixture A + B with negative deviation from Raoult's law. The model takes into account the coexistence in solution of the species A, B, AB and AB2. The model is applied to the mixture of propanonetrichloromethane, resulting in a satisfactory correlation of the activities. For this system the deviation from ideality can be explained simply by the formation of the AB complex, with H° = (-1.2±0.4) kJ mol-1 and as the standard enthalpy and entropy of association S° = (-34±1) J K-1 mol-1, for the hydrogen bond formation in this system.
Acerca de si pudo o no ser el universo anisotrótipico
(2011-02-15 00:00:00) Alvarado Marín, Rodrigo Eduardo
The theoretical and experimetnal problem concerning the origin and formations of the universe is establish in this paper, specially by developing some theories that try to explain this phenomena, and also to settle the reasons why the universe could have been anisotropic and homogeneous at the very beginning, envolving in time later on in what we see today. Besides some other posibilities are studied in order to avoid the singularyty at the beginning of the universe. Some exact solutions are obtained by autoconsistency with the Einstein equations utilizing for that purpose different types of interactions among the spinor and the scalar fields, with and without matter.
Acumulación de cobre en plantas silvestres de zonas agrícolas contaminadas con el metal
(2013-06-28 15:00:39) Hernández Colorado, Ramón Rigoberto; Alvarado Gámez, Ana Lorena; Romero Chacón, Rosaura María
Copper is an essential nutrient that is known to result in toxic damages to organisms. Copper salts have been utilized as fungicide because of its protective effect against several diseases in plants, but the repeated use of it has caused contamination of many Costa Rican agricultural lands. This study evaluated the potential of twenty most abundant species growing on two contaminated sites in Alajuela and Siquirres. Plants and associated soil samples were collected and analyzed for total metal concentrations using flame atomic adsorption technique. None of the species was identified as hyperaccumulator. Plant total Cu concentration varied from 19,0 to 170 mg kg-1 and in the soil ranged from 60,0 to 307 mg kg-1 . Among the plants, Portulaca oleracea had the higher bioconcentration factor (BCF): 2,5. This specie could be suitable for phytoextracting of sites contaminated with copper.
Álgebras-MV artinianas y noetherianas
(2011-02-11 00:00:00) Belluce, L. P.
We study MV-algebras that satisfacy tha ascending of descending chain conditions on ideals. We demostrarted, for example, if an MV-algebra is artianan, then it has a finite number of minimal prime ideals. We also show the set of impoicative ideals of an MV-algebra satisfies bothchain conditions provided the algebra, modulo its radical is noetherian. Other results relate tha chain conditions to semi-locality.
Álgebras-MV artinianas y noetherianas
(2011-02-14 00:00:00) Belluce, L. P.
Estudiamos álgebras-MV que satisfacen las condiciones de cadena ascendente o de cadena descendente por ideales. Por ejemplo, si un álgebra es artiana, entonces tiene un número finito de ideales primos y minimales. También demostramos que el conjunto de ideales implicativos de un álgebra-MV satisface ambas condiciones de cadena si esta álgebra, módulo su radical, es noetheriana. Otros resultados relacionan las condiciones de cadea con la propiedad de ser semi-local.
Algunas características de las mareas en la costa Pacífica y Caribe de Centroamérica
(2006) Lizano Rodríguez, Omar Gerardo
Tidal levels were studied in 48 stations using tidal predictions along the coasts of the Pacific and Caribbean of Central America. Statistics of basic mean values were analyzed to characterize the stations. These values are useful in coastal design structures as marines, ports, breakwaters, and for planning of marine operations in ports and piers. The tidal wave in the Pacific is simidiurnal, while in the Caribbean varies according to the latitude and the bathymetric basin in which it is found. In this last region the tidal wave can be mixed (a combination of semidiurnal and diurnal types) or semidiurnal pure. Some stations may show seasonal variations in the tidal wave according to the phases of the moon. It was found that the stations positioned in open coasts in the Pacific Ocean had smaller tidal range than those stations inside of semi-enclosed bodies of waters as bays and gulfs. Some stations in the interior of the Gulf of Panama showed very high tidal ranges associated possibly to resonance interactions of the tidal wave with the continental shelf and the geometry of the gulf. In the Caribbean Sea the tides seemed to resonance according to the basin and sea floor batimetry in which they are found. In some stations the oceanic and atmospheric forces as wind, atmospheric pressure, waves and currents, might generate the so called “weather tides” that could explain the major tidal range found in some of them.
Aplicación de la tomografía axial computarizada para la detección de bolsas de humedad en madera seca de gmelina arborea (roxb.)
(2009-01-13 00:00:00) Moya, Róger; Muñoz A., Freddy; Escalante, Iván
Due to its excellent growth rate and productivity, Gmelina arborea (Roxb.) is widely used for commercial reforestation in Costa Rica. However during the lumber drying process, the wooden boards show non-uniform values of final moisture content (MC). The low uniformity in final MC is caused by the presence of "wet pockets", originated during the growing process of the tree. During the wood drying process, the regions with wet pockets present zones with a high MC, which are hard to detect with traditional methods for MC measurements. This article shows that it is possible to detect and to set the limits of the presence of wet wood in Gmelina arborea boards using scanning computed tomography (CT-scanning), a technique applied in medical diagnostic.
Aplicación de las técnicas de punto fijo
(2011-02-15 00:00:00) Azofeifa Z., Carlos E.
This article will develop a computacional procedure for approximating a fixed point of continuos functions of the simplex into itself using the Brouwer`theorem. We also shows the different applications of the theory of fixed point in the economic area.
Aproximación de sucesiones definidas por recurrencia
(2011-02-11 00:00:00) Durán, Ana Lía
It is established that recurrent sequences, xn+1 = f(xn),which converge to a fixed point L where the derivative α = f '(L) satisfies 0 < |α| < 1 and where the rest r(x) = f(x) - L - α(x-L) satisfies r(x) = O(|x - L|1+ s), for some s > 0, can be approximated as xn ~ L + cαn for a certain constant c. It is shown that such approximation might fail if only the condition 0 < |α| < 1 is assumed.
Calculations of chemical equilibrium with symbolic computation
(2014-07-07 10:11:02) Hidalgo, Ricardo
We show how a processor for symbolic computation can readily enable extensive calculations to describe the equilibria involving gases, the pH of an aqueous solution in the titration of a polyprotic acid, and complex ions as a function of concentration of ligand in aqueous solution.
Cálculo de las integrales radiales en dispersión de electrones
(2011-02-11 00:00:00) Soto Vargas, C. W.
The radial integrals which arise from the distorted wave treatment of photon emission process in electron and positron scattering, involve products of the electron`s (or positron`s) ingoing and outgoing wave functions and the radial part of the electromagnetic Green`s function. They can be performed analytically for point Dirac-Coulorab wave functions, but are difficult to evaluate because they involve slowly converging doubly infinite series. We present a discussion and review of the formulation and methods employed to calculate these basic integral at a given value of the energy trafer.
Caracterización del producto del proceso de viscoreducción, para la conversión de aceite vegetal, aceite de alga y búnker
(2013-06-28 15:00:39) Davis Barquero, Alexander; Ulate Brenes, Adolfo Mauricio
Through the use of a high pressure and high temperature reactor conditions a visbreaking is simulated, with the purpose of producing green fuels, replacing a fraction fuel oil #6 with vegetable oils. A 25% (m/m) of palm (Elaeis guineensis), castor (Ricinus communis), jatropha (Jatropha curcas) and 10% algae (Undaria pinatifida) oils, 450 ° C and 5 min of reaction time were utilize and the products were compared with the standards used by RECOPE. The replacement of 25% m/m by vegetable oil, increases by 6,1% the fraction of total diesel oil, improves the cetane index, decreases viscosity the amount of aromatic material and the amount of sulphur respect to 100% bunker The use of fluidized bed reactors or hydrogen mix for increase the saturated products are recommended for future research.
Caracterización y determinación del potencial Aterogénico de quesos producidos en Costa Rica
(2009-01-13 00:00:00) Chavarría Sánchez, Jéssica; Herrera Ramírez, Carlos Hernán; Lutz Cruz, Giselle
Cardiovascular diseases have been one of the main causes of mortality during the past years in Costa Rica. Many risk factors associated to these disorders include the intake of high-fat diets, being cheese an example of such a dietary component. Thus, the fatty-acid characterization of different cheeses was needed, in order to obtain a more ample scope of this public health issue. Cheeses derived from both bovine and caprine milks were included in this study. The Laboratorio Costarricense de Metrología of the Ministry of Economy, Industry and Commerce carried out the sampling needed for this work. The chemical parameters determined in the samples studied were: fatty acid composition (by GC and NMR techniques), saponification and iodine numbers, average triacylglycerol molecular weight, polyunsaturated fatty acids / saturated fatty acids ratio, atherogenic index and number of allylic hydrogens. The experimental values of water and lipid content found were compared with the data in the nutritional-fact labels, designed according to existing national and international food regulations.
Ciencia, tecnología y educación en Costa Rica en el período 2010-2014
(2017-09) Granados Carvajal, Rafael Evelio; Calvo Solano, Oscar David
En este artículo se analizaron las distintas redes vinculadas a la formulación de políticas públicas en la Comisión de Ciencia y Tecnología del Congreso de Costa Rica, entre el 2010 y 2014, con el propósito de describir el abordaje realizado y la incidencia sobre el estilo de desarrollo costarricense. Se encontró que las principales redes presentan propuestas cerradas y un Poder Ejecutivo con más cercanía a los distintos sectores, pero no suficiente. A raíz de lo anterior, se concluye que existe una limitada coordinación y cohesión de los actores relacionados con la ciencia, la tecnología y la educación en Costa Rica, determinando limitados alcances en educación, empleo, competitividad y desarrollo; especialmente, pensando en la dinámica que ejercen la ciencia y la tecnología en el mediano y largo plazo en el proceso de desarrollo económico y social.
Climatología del viento y oleaje frente a las costas de Costa Rica, parte 1.
(2009-04-29 00:00:00) Lizano Rodríguez, Omar Gerardo
The climatologically behavior of the wind and waves is studied around the Costa Rica's coasts using re-analysis data from wave forecasting numeric model. It is found that the wind in the Caribbean coasts of Costa Rica is predominantly from northeast direction all the year. This wind is projected to the north Pacific of Costa Rica through the topographical depression north of Costa Rica and south of Nicaragua generating high wave conditions. The strong trade winds in the boreal winter (north hemisphere) dominate the behavior of the wind in the central and south Pacific coasts of Costa Rica in the first months of the year. This pattern is modified as the Inter-tropical Convergence Zone (ITCZ) migrating to north and then, the westerly wind is intensified over the Pacific coast reaching their maximum expression during September. In respect to waves, it is found that in the Caribbean wave heights are in relationship with the trade wind force over the sea. The relatively short wave period (7 seg) identifies the local wave origin, called "ea", which is chaotic in general and with short wave crests. In the Pacific coast, it is found that the predominant wave direction for all the three distinguishable Costa Rican regions is from the Southwest continued by the south. In the north Pacific, although the predominance of the wind is the zonal component and there is a local wave generation in that direction, it prevails waves with direction from the southwest, indicating that its main wave origin is remote, mainly generated in the south Pacific, like New Zealand , called "well", which are smooth and long wave crests. The monthly climatological analysis of the wave height shows that the Caribbean waves has more energy as the trade wind is intensified (November to April) in the boreal winter. In this time the wave heights in the Pacific coasts is low, changing their pattern when the Caribbean wind weaken (September to October) and the equatorial tropical western is present.
COMPARACIÓN DE METODOLOGÍAS DE EXTRACCIÓN PARA LIMONENO Y CARVONA EN Lippia alba USANDO CROMATOGRAFÍA DE GASES.
(2012-11-26 00:00:00) Medina López, Ligia A.; Araya Barrantes, Juan José; Tamayo Castillo, Giselle; Romero Chacón, Rosaura María
Abstract Different plants drying procedures, hydrodistillation and solvent extraction by sonication were evaluated for the essential oil extraction of Lippia alba. Quantitative analysis of the markers limonene and carvone was performed in the extracts by gas chromatograph with flame ionization detection (GC-FID). Experimental precision, accuracy, specificity, linearity, limits of detection and quantitation were addressed. Lyophilization as a drying procedure and solvent extraction by sonication using ethyl acetate showed the best results regarding the highest concentration for marker compounds.
Control de calidad en espectrometría gamma de bajo nivel
(2011-02-07 00:00:00) Salazar Matarrita, Alfonso; Loría Salazar, Luis Guillermo
Low level gamma spectrometry is a very precise techniqueto measure the concentration of nuclides present in different samples in Bq kg-1. The quality control of the procedure and method used be carried out by intercomparison exercises with world reconized institutios. During the last three years the Nuclear Physics Laboratory of the University of Costa Rica (LAFNA) has been participating in the international quality assessment program (QAP) carried out by the Environmental Measurements Laboratory (EML), Department of Energy, USA. The results show a very good agreement with the rest of the participant laboratories. This provide a very objetive evaluation of the high precision of the methods used by LAFNA in low leel spectroscopy measurements.
Curvatura en teorías generalizadas de Yang-Mills
(2009-01-13 00:00:00) Chaves, Max
The curvature in R1+3 spaces with a generalized Yang-Mills connection is studied and the results are analyzed. Other options borne by modifications of the base space are also studied and commented. The present situation of the problem is reviewed.
Desórdenes del sistema musculoesquelético por trauma acumulativo en estudiantes universitarios de computación e informática
(2011-07-18 00:00:00) Fonseca Barrantes, Melissa
The main objective of this research was to establish the correlation of Musculoskeletal Disorders (MSD ́s) by accumulative damage, among university ́s students from the computer science school (ECCI) at the Universidad de Costa Rica (UCR). The study group included 129 computer users with an average age of 21,9 years old. Neck pain was the most commonly reported symptom (81 cases), followed by lumbar region (71 cases) and wrist pain (63 cases). The women perceived the higher stress, and the computer laboratory, followed by home environment, seem to have the higher risk factor associated with the symptoms. At least 90 % of students use the computer 6 or 7 days per week and 31 % report to use the computer 8 or more hours per day. In general, the symptoms increased according to the time of exposition. The level of perception of computer-‐‑related health risks among the students was low.
Determinación de un modelo para el consumo de energía con suspensión total de sólidos en fluidos newtonianos
(2011-07-18 00:00:00) Ulate Brenes, Adolfo Mauricio; Vásquez, Alexander
The development of a model for the power consumption in a mixing process for the suspension solids in a Newtonian liquid is proposed in this study. As a first step of this research, the critical variables were determined using an alternative method: the kind and size of the impellers (propeller and turbine, Da/Dt 0,333 and 0,433), the kind, size and quantity of solid (sand, volcanic stone and silica, 1,68x10-3 m and 7,07x10‑4 m in diameters); and the fluid. Two equations were developed to fix the experimental data, both using the same dimensionless numbers (One for Reynolds numbers lower than 60 000 and the other for Reynolds numbers between 60 000 and 150 000). These equations have similarities with the reported in the literature.

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