Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

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.   

The coordination chemistry of the hexadentate ligand, tris(2-thiosalicylamidoethyl)amine, (LH3), was studied. The reaction of the ligand trianion with iron(III) and indium(III) yields monomeric hexacoordinate complexes, LFe·HCl and LIn. The complexes were characterized by spectroscopic, magnetic and electrochemical methods.   

A general identification procedure is given, for first and second orders plus time delay models, that uses two or three arbitrary points over the process reaction curve. Two simplified versions of the methods are described: the three points 123c identification method that uses the times required to arrive to the 25, 50 and 75% of the output total change, and the symmetrical method that uses points symmetrically distributed over the reaction curve. It is also described the use of the identification methods to obtain the optimal times for the model parameters identification. Using an example, the goodness of the models identified is compared.   

Three new sesquiterpenes lactonaes were isolated from the aerial parts of Perymenium grande Hemsl. (Asteraceae), collected around Rincón de la Vieja  Volcano, Costa Rica. In addition to the three new lactones 1, 3 and 5; were isolated the additional five known sesquiterpenes lactones. The separation were performed with chromatographic techniques and the structures were elucidated by one- and two-dimensional nuclear magnetic resonance techniques.

The Radiation Safety Program (RSP) of the University of Costa Rica established in 1990, handles the radioactive waste generated at the University. A centralized storage waste room is used by the Atomic, Nuclear and Molecular Research Center, Health Research Institute, Molecular and Cellular Biology Research Center and the Environmental Contamination Research Center. The RSP has pre-storage procedures, internal controls, protocols for storage, withdrawal of sources and discharges to the environment, according to national and international legislation. The main radionuclides in liquid and solid wastes are P32, I125, S35 y C14; which after a storage period will be disposed of as exempted materials. The waste room also permanently stores sources with the following radionuclides Cs137, U238, Th232, Sr90, Ra226, Cd109, Cf252 and Am241. It has 96 permanent sources and 52 that will be disposed of. The RSP allows the University to have a centralized facility for the safe management of all radioactive waste generated locally.  

From the aerial parts of Zanthoxylum acuminatum (Rutaceae) collected in Upala, Alajuela, Costa Rica were isolated the known lignans hinokinin, (+)-asarinin, (+)- piperitol, (+)-kobusin, and epi-kobusin. In addition to the lignans were isolated the triterpen lupeol and the steroid campesterol. All the separations were performed with chromatographic techniques and the structures were elucidated using 1D and 2D NMR techniques.   

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.

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.

Using thermoluminiscent dosimeters (Harshaw TLD-200) the first set of Costa Rica data on absorbed doses in air from natural radiation is obtained. During the period September 1996 through October 2000 eight different sites throughout the country were chosen to install the TLD stations. Each station had 8 cards (five were changed every 3 months and 3 were changed annually). The dosimeters were read in the Atomic, Nuclear and Molecular Research Center using a 4000 Harshaw reader. Through a mathematical algorithm and its calibration factors the absorbed dose rate in air (nGy. h-1) was calculated. The national average is 108.9 ± 32.4 nGy.h-1, the lowest values (in nGy.h-1) were obtained at sea level at Quebrada Honda with 53 ± 11 and the highest values (in nGy.h-1) at Cartago with 160 ± 19. A slight increase with altitude is observed even though the Cartago station was always the highest. The values found agree with values reported worldwide.   

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.