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

The groundwater of the Barva, Upper Colima, and Lower Colima aquifers, located in the western part of the Central Valley of Costa Rica represents the main source of drinking water in this region. The purpose of this study was to design a monitoring network to evaluate groundwater quality in these aquifers within the sub-basins of the Bermúdez, Ciruelas and Río Segundo rivers, and to encourage the participation of stakeholders. Five proposed sites exceeded, in between two and four occasions, the Alert Value of 25 mg/l nitrate as NO3-. These sites, which capture water from the Barva aquifer, were located in areas where urban use and coffee crops predominated. The sites that collected water from this aquifer with the lowest concentrations, below 2 mg/l, were found in the upper sub-basins, where forest and pastures predominate, while those that collected water from the Colima aquifers showed concentrations below 20 mg/l. At least semi-annual monitoring of electrical conductivity, pH, temperature, nitrates and chlorides is recommended. The operation of these networks provides an opportunity for monitoring groundwater quality by stakeholders at basin level as one of the first steps in developing sustainable management of this resource.

This investigation was carried out to evaluate the effect of two cytokinins: 6-benzilaminopurine (BAP) (6.5 mg l-1) and kinetin (K) (2.5 mg l-1), as well as the growth inhibitor abscisic acid (ABA) (1.0 mg l-1) on the in vitro tuberization capacity of two potato varieties: Atlantic and Alpha. The basal culture medium MS (1962) was used as a control. The responses were different between varieties. In cv. Atlantic, the analysis of the number (NM), weight (WM) and diameter (DM) of microtubers indicated that the addition of growth regulators did not affect induction and development of microtubers. However, when BAP was used, a non-significant increment of 41 % was observed in the number of the microtubers compared to the control treatment, from 2.6 to 4.4. The addition of cytokinins and ABA to the medium did not have a significant impact on the development of microtubers. In cv. Alpha the cytokinins used without ABA increased the number of microtubers, which were larger and heavier than those of the control treatment. In this variety, ABA significantly reduced the values of the NM, WM and DM variables. The exogenous action of cytokinins in the culture medium is likely to have caused an endogenous hormonal imbalance in the Atlantic and Alpha genotypes which interfered with their innate microtuberization ability, a result that was even more evident for cv. Alpha, which showed the need to continue optimizing protocols of genotype-specific systems in potato tissue culture to increase yield and seed quality.

Aloin is an anthraquinone found in a wide variety of food products made from aloe, which can cause laxative effects and prolonged ingestion increases the risk of gastrointestinal cancer. In this study, parameters for aloin analysis and extraction methodology were validated using High Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD). Aloin concentration was determined in 14 commercial products consumed in Costa Rica. The quality values evaluated were linearity (R = from 0.9995 to 0.999995), reproducibility (recovery percentage = from 96.7% to 99.9%), intra-day precision (coefficient of variation = from 0.24% to 1.47%), inter-day precision (coefficient of variation = from 1.65% to 2.68%), limit of detection (from 0.063 mg/L to 0.228 mg/L), limit of quantification (from 0.126 mg/L to 0.452 mg/L) and selectivity (≤ 0.063 mg/L). The majority of the evaluated food products showed a concentration below the maximum value allowed (10 mg/L), with values between 0.2 ± 0.1 mg/L and 4.8 ± 0.1 mg/L of aloin, with an average standard deviation of 0.41 mg/L. Liquid samples presented higher values than the rest of the matrices. Two of the samples (RU/BT1/39A and RU/BT1/45B) were reported with concentrations higher than the maximum aloin value allowed (14.2 ± 0.1 mg/L and 19.0 ± 0.1 mg/L). The consumption of these products could have a long-term harmful effect on health, since they exceed the limit mentioned above.

The color of white acrylic lacquers utilized to touch up automotive paint was characterized in this paper using the CIELab color space and the whiteness index, with standard illuminant D65 and the standard observer at ten degrees. Based on this information, the color trends used in this type of product in the national market were recognized. In addition, the chemometric techniques of the Principal Component Analysis, Cluster Analysis, and Hierarchical Analysis allowed for recognition of similarities between the observed colors, which found, among other aspects, the greatest visual difference in the pearl white lacquer. On the other hand, the Alaskan white lacquer from Mazda and the universal white lacquer from Nissan were the most similar. It is also concluded that the chromatic and chemometric analyses of spectral data complemented each other; therefore, both are recommended for quality control purposes.

One of the great advances in nanotechnology has been the development of the scanning tunneling microscope, a tool that permits the manipulation of atoms and molecules, the study of electron transport in a single atom, and the generation of images with atomic precision in electrically conductive surfaces. In this paper we describe the tunneling microscope, its operation, a calibration methodology, and how to make topographic measurements on flat surfaces with atomic resolution at room conditions. This is done from a didactic point of view, intended to assist new users or researchers unfamiliar with the technique. Depending on the type of measurement and calibration, we used two conductive samples, gold (111) oriented along the crystallographic direction, and highly oriented pyrolytic graphite (HOPG).

A bioprospection was conducted of santol fruit exocarp (Sandoricum koetjape), in order to evaluate its main antioxidant and antibiotic properties.  In addition, total polyphenols and proanthocyanidins present were characterized. In order to obtain pure metabolites or more concentrated blends, dry and ground exocarp was subjected to different quantitative tests and chromatographic fractions with various resins. Fractions and extracts were analyzed using the Folin-Ciocalteu (total polyphenols), DMAC (total proanthocyanidins) and DPPH (antioxidant activity) method, using a traditional pattern and one from the sample. Results obtained with the latter were up to 80% higher compared to traditional patterns. It was also determined that fractions with a higher proanthocyanidin content have a higher antibiotic activity, that is 73 ± 4% on the S. Aureus battery and 42 ± 2% on Bacilus spp., both analyzed using the Kirby-Bauer method.

Costa Rica is a small country in Central America with a recent history of fungal research. However, comparative differences with other territories in the Mesoamerican Biodiversity Hotspot region have promoted the study of fungi and the integration of fungal information with natural resource management. Even though there is still a large number of multidisciplinary aspects to cover in Costa Rica for robust incorporation of fungal data in conservation and political and developmental agendas, regional advantages have allowed this country to move towards such goal more rapidly than other countries in this part of the world. Mycoliteracy-centered and citizen science initiatives seem to be the next step in order to normalize disparities in fungal perception across regions within the country and promote social interaction with fungi. However, in general terms, the Costa Rican society seems to be aware of the potential of fungi as a source of food and medicines and their remarkable contribution through ecosystem services. In this manner, fungal conservation and management seem easier to conduct in this territory than in other regions of the world where less information on fungi has reached the general population.

The pedagogical and didactic trends present in the Costa Rica math curriculum have led the style of the lesson organization proposed by the Ministry of Public Education since 2012. Every step in the class is based on ideas from different sources: constructivism, socioculturalism, realistic pragmatism, realistic mathematical education, as well as Japanese, French and American ideas. This paper aims to present the link between theory and the actions that can be performed with students by posing a problem, solving it, and having the teacher’s assistance, as proposed in the Costa Rican curriculum. It can be established that each trend is present and produces an impact when performing each step proposed for classwork since the foundation and the historical and theoretical backgrounds are solid; therefore, the methodological proposal can be trusted.

In this paper we describe in detail an algorithm for the efficient computational implementation of the finite difference method (FDM) in the two-dimensional time-dependent heat equation with non-homogeneous Dirichlet boundary conditions. The MATLAB® software was used to validate the method mentioned here; however, the processes are presented independently from the programming language. Finally, numerical results are presented to validate the proposed algorithm.

After harvesting, barley grains (Hordeum vulgare L.) can show dormancy and water sensitivity, which delays industrial use. Both effects depend on the barley genotype and environmental conditions during grain maturation. In order to analyze the effect of the average temperature and the total rainfall accumulated during and in the final third of the grain filling, on the dormancy and water sensitivity and the relationship between them, three cultivars of barley were sownin four dates in 2009 and two in 2011. Temperature and daily rainfall were recorded from anthesis to physiological maturity. The dormancy was evaluated as germination at 12 days post physiological maturity and the water sensitivity as germination in water excess conditions at 100 days post physiological maturity. The variables that presented a higher correlation with germination and water sensitivity were average temperature and accumulated rainfall during grain maturity. Environments with average high temperature during grain filling, reduced dormancy, but on water sensitivity decrease was cultivar dependent. The increase of rainfall during grain filling, decreased dormancy, but increased water sensitivity in all three cultivars.