Volumen 25, Números 1 y 2

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https://hdl.handle.net/10669/14627

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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.
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.
Estructura hidrográfica de la Bahía de Bluefields, Nicaragua
(2009-04-29 00:00:00) Brenes, C. L.; Ballestero Sakson, Daniel; Hernández, A.
In March and October of 2000, under the DIPAL II project (Proyecto para el Desarrollo Integral de la Pesca Artesanal en la Región Autónoma del Atlántico Sur), two hydrographic surveys were carried out in the Bay of Bluefields to study their hydrography during the dry and rainy seasons. Water temperature, salinity and turbidity were determined both at the surface and the bottom of the bay. The results obtained are consistent with previous studies carried out in this area. In March, water temperature and salinity were lower and higher, respectively, than in October. Water turbidity increased with increased fresh water input as a result of a greater movement of suspended sediments and organic matter into the water body. Saline wedges were observed in deep strata during the two months of sampling in the adjacent areas to the bars of The Bluff and Hone Sound. In the first case the wedge extended to the northwest up to the area of Bluefields, while in the second case it extended to the west reaching the western coast of the bay. The vertical gradient of salinity was stronger in October, when the superficial flow of fresh water in the whole bay was more intense. A circulation pattern related to the salinity field was recognised: fresh water introduced by the Caño Negro and Escondido rivers moves along the western coast of the bay, while sea water enters the bay towards the northwest, throughout the whole water column, at the bars of The Bluff and Hone Sound. Fresh water introduced by the River Torsuani moves along the eastern coast towards the open sea at the southern end of the bay.
Evaluación de la uniformidad intrínseca en gamma cámaras del servicio de medicina nuclear del Hospital San Juan de Dios
(2009-04-29 00:00:00) Mora Ramírez, Erick
The quality assurance program in a Nuclear Medicine Department aims to minimize errors and artifacts that cover all aspects of clinical practice. The quality control can be seen such as one particular procedure used to meet measurements that can be followed along the time. The intrinsic flood-field uniformity is one of the quality control procedures to evaluate the response of a gamma camera to a spatially uniform flux of an incident gamma radiation over the field of view. The purpose of this study is to test our gamma cameras, recording the integral and differential uniformity figures of the intrinsic uniformity during the 2007 in order to establish how well the instruments were working. At the beginning we perform an evaluation of our acquisition protocol which implies the variation of the acquired counts, the energy window width and its placement. After that we analyze the recording data creating plots which are showing the performance of the systems. Using an energy window placed at 140 keV at 20%, with matrix size of 512 x 512, acquiring 15 million counts and the source activity close to 700 °C; we think that we get a good enough images and both uniformities are within the manufacture's requirements, however, increasing the number of acquired counts, images are much better and an improvement in the evaluated parameters can be seen. The performance evaluation, of the three gamma cameras, was taking into account for approximately 240 days, showing an integral uniformity range of 1.04 ± 3.5 % and the range for differential uniformity vary from 0.88 up to 2.7 %. We conclude that the gamma cameras were working quite well, we do not need to vary our acquisition protocol because it is good enough to perform this test; also factors affecting the quality of the images are radioactive waste material not very well shielded and temperature room variations, especially at the beginning of our workday.
Importancia de la batimetría de las planicies basales en la propagación de tsunamis transoceánicos
(2009-04-29 00:00:00) Chacón Barrantes, Silvia E.
The initial form of a tsunami originated by an homogeneous seismic source consists on a simple wave front. While the tsunami propagates in deep water, this simple form suffers several modifications by the tsunami's interaction with the ocean basin's bathymetry. When the tsunami climbs the continental slope, it suffers more modifications due to the bathymetry and topography of the coastal region. The manner in which these local features modify the tsunami's form depends on the tsunami's form itself, i.e., different tsunamis arriving at the same location do not have the same form, though resemblances can be identified among them, and also among the same tsunami arriving to different regions. In this paper the importance that these modifications on the tsunami's form acquires when it approaches to the coast, is identified for the arrival of the Alaska 1964's tsunami to Hilo Bay in Hawaii and of the Indonesia 2004 and 2005's tsunamis to Colombo in Sri Lanka.
La tierra moler o "diatomita" como sistema de remoción de sustancias químicas en el laboratorio.
(2009-04-29 00:00:00) Alfaro Vargas, Ariel
Experiments were carried out, to determine the capability of diatomite for the disposal of laboratory residues. Experimentation with different organic solvents (ethyl ether, acetone, ethyl acetate, hexane and ethanol) verified that there is no solvent absorption in the mineral material. Experiments were also carried out with heavy metal cations, in order to quantify their absorption or adsorption in the porous mineral. Ion sequestration was determined and the following order resulted: Cr3+ > Pb2+ > Ag+ > Ni2+ > Zn2+ > Cr2O7 2-. The effect of pH was also studied with nickel, 99,5% removal was observed at pH 7, SO4 2- was 98% removed, followed by Cl - and NO3-. The ideal cation concentration was 4 ppm with a removal efficiency of 99,5%. It is possible to conclude that the absorption material can be used as effusion containment system, rather than a material to eliminate laboratory residues.
Modelización directa y comparación de los principales dispositivos geoeléctricos
(2009-04-29 00:00:00) Arias Salguero, Mario Enrique
With the purpose of comparing the main geolectrics arrays used for the realization of vertical electrical sounding, a direct simulation is presented, considering two geologic models. The investigation depth, precision in the determination of the thickness of the layers, the effects of the presence of a superficial layer, the geometric similarity and the sensibility to the mensuration of the potential difference are evaluated. It is considered that the most appropriate arrays for vertical electrical sounding are those of Wenner and of Schlumberger. On the other hand; the pole-pole and the dipole-dipole should be used preferably for geolectrics profiles (constant separation transversing) and electrics pseudosections.
Nuevo método para la obtención de quitina
(2009-04-29 00:00:00) Díaz Sánchez, Luisa M.
A simple method for the isolation of chitin is described. It is based on the solubility of the biopolymer in concentrated aqueous HCl at low temperature. The solubility diagram of the system chitin-HCl-H2O is discussed as well as the kinetics of the acid-catalyzed hydrolysis of the biomaterial. The hydrolytic degradation of the polymer is estimated to be less than 0,3 %, during the procedure.

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