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

The effect generated by the def iciency of Selenium (Se) in the soil and in the forages on the yields of sheep production justif ies the analysis of the levels of this microelement in the soil, pasture and sheep in dif ferent regions of the State of Mexico from of the evaluation of the enzymatic activity of GHS-Px and the inf luence of Se supplementation on IgG concentration in pregnant ewes and lambs. The results show that Mexiquense soils and forages present Se def iciencies at levels of ±0.02 and 0.03±0.12 mg kg-1, respectively. The levels of Se and the average GSH-Px activity in the blood of sheep subjected only to grazing were equally def icient with values of 0.02 ± 0.04 mg kg-1 and 51.54 ± 24.55 U g-1 Hb. Statistically signif icant GSH-Px values were observed between groups from different regions and sheep breeds, being higher in creole sheep compared to Suf folk (P < 0.05). There were no statistically signif icant dif ferences in Se values in soil and grass, according to soil type, pH, organic matter content or stages of higher rainfall. The sodium selenite supplement at a rate of 5 mg mL-1 x 100 kilograms of weight in pregnant sheep allowed to identify signif icant statistical dif ferences (P < 0.01) in the Se levels of the treated animals in relation to the negative control, but enough for the supplemented animals to consistently reach the recommended levels of this element. IgG levels increased in animals supplemented with Se but no statistical dif ferences were observed between groups. From the foregoing, it follows that it is an important nutrient in sheep farming, so adequate doses should be administered to the herds to improve productivity in the Mexican production units.

Cinnamon (Cinnamomum sp.) is a species with few but significant health limitations, of which Phytophthora cinnamomi and Fusarium sp. are the most important ones that affect the root. Their control based on synthetic fungicides has favored resistance due to poor handling, so their control with essential oils is a viable alternative. The objective of this study is to determine the antifungal potential of thyme and clove – essential oils for the control of P. cinnamomi and Fusarium sp. isolated from Cinnamomum verum. Concentrations of 60, 120 and 300 μL L-1 were evaluated for both oils and phytopathogens. Data recorded on the mycelial growth rate of pathogens after incubation of Fusarium sp. at 25 ± 1 °C and 28 ± 1 °C had a significant difference in the concentrations tested. When clove essential oil was used in P. cinnamomi, the pathogen did not grow with the concentration of 300 μL L-1; with 120 μL L-1 growth rate was 0.06 mm per day, and with the concentration of 60 μL L-1, it reached a growth rate of 1.16 mm per day. With respect to Fusarium sp. mycelial growth was completely inhibited with doses of 120 and 300 μL L-1 of essential oils; with thyme oil a similar trend was observed at concentrations of 120 and 300 μL L-1 greatly inhibiting effects of the two pathogens. It is noteworthy that the doses of 300 μL L-1 of the two essential oils are able to inhibit in their entirety (P ≤ 0.05) growth of both pathogens. The use of thyme and clove essential oils can be an alternative in preventive control of cinnamon root diseases.

The best agricultural soils in Venezuela are located in the Valencia lake basin, but unfortunately for various reasons, such as the use of recycled gray water with or without treatment from urban and industrial origin, they have been subjected to accelerated degradation processes. Detecting the causes of soil deterioration in early stages with biochemical indicators will allow timely corrective measures to be applied. In this work, three suitable measurement tools were adopted with the following mathematical indexes: alteration index (AI3), enzymatic geometric mean and radar diagram area. The quality of the alluvial and lacustrine soils of the lake Valencia basin cultivated with sugar cane and banana was evaluated. The calculation of the indexes was based on the determinations of dehydrogenase, arginine ammonif ication, acid phosphomonoesterase, alkaline phosphomonoesterase, β-glucosidase, urease and protease activities. The estimated quality indexes showed that agricultural use causes a disturbance of the natural balance, the order being: natural vegetation> sugar cane> banana. The alteration index (AI3) and the enzyme geometric mean (MGe) correlated signif icantly with the metabolic ef f iciency quotient. The radar plots for each soil type (lacustrine and alluvial) under both types of land use (sugar cane and banana) conf irmed the results of the other indexes. Soils planted with both crops showed a lower quality compared to the reference soils under native vegetation.

Tropical forest soils store a third of the global terrestrial carbon and control carbon dioxide (CO2) terrestrial effluxes to the atmosphere produced by root and microbial respiration. Soil CO2 efflux varies in time and space and is known to be strongly influenced by soil temperature and water content. However, little is known about the influence of seasonality on soil CO2 efflux, especially in tropical dry forests. This study evaluated soil CO2 efflux, soil temperature, and soil volumetric water content in a semideciduous tropical forest of the Yucatan Peninsula under two sites (flat areas close to and far from hills), and three seasons: dry, wet, and early dry (a transition between the rainy and dry seasons) throughout a year. Additionally, six 24-h periods of soil CO2 efflux were measured within these three seasons. The mean annual soil CO2 efflux was 4±2.2 μmol CO2 m-2 s-1, like the mean soil CO2 efflux during the early dry season. In all seasons, soil CO2 efflux increased linearly with soil moisture, which explained 45% of the spatial-temporal variation of soil CO2 efflux. Soil CO2 efflux was higher close to than far from hills in some months. The daily variation of soil CO2 efflux was less important than its spatial and seasonal variation likely due to small diel variations in temperature. Transition seasons are common in many tropical dry forests, and they should be taken into consideration to have a better understanding of the annual soil CO2 efflux, especially under future climate-change scenarios.

Jatropha curcas L. has a great potential which lies in its high oil content for the production of biodiesel. To extract J. curcas oil, it is necessary to peel the seeds, and since this coproduct represents 2.0% of the total weight, it is important to look for options for its use. The previous step to any action in this sense is to know its bromatological values and the presence of total phenolic compounds. During a period of two years (2017-2018) at the Experimental Station of Pastures and Forages Indio Hatuey a study was carried out on the determination of the chemical composition of the fruit shell of J. curcas. The objective of this work was to characterize the chemical composition of the fruit shell of J. curcas. The samples were obtained randomly from a plantation with more than two years of established from ripe fruits dehydrated in the sun. The values obtained were, in percentage, humidity 12.35; ashes 5.48; crude protein 3.71; crude f iber 77.17; cellulose 33.71; hemicellulose 9.65; holocellulose 43.36; lignin 47.53; extractive 5.55; Na 0.78; K 4.51; Ca 0.59; Si 0.08; S 0.03; P 0.72 and total phenolic compounds 1.89. The results indicate the f ibrous components as predominant, the contents of acceptable minerals, and the contributions of crude protein discrete. The high phenolic composition suggested the need to deepen, from the qualitative and quantitative point of view, the organic elements that compose it and determine if there is presence of phorbol esters on it.

A study was carried out at the in agroecological transition El Renacer farm, in the Perico municipality, Matanzas, with the objective of evaluating the functionality of some of the components of ecological biodiversity and the sustainability of its economic dimension. The farm has a total area of 43.5 ha; 40 of them dedicated to livestock. The rest is dedicated to crops (0.5 ha), fruit trees (1.5 ha), forestry (1.0) and facilities (0.5 ha). The functionality of biodiversity was evaluated, based on an analysis model that included the components: tree diversity, production diversity and species richness. Through a diagnosis, which included tours, semi-structured interviews and observation, the number of individuals of each species was quantif ied, which were characterized according to their functionality within the system. For the calculation of economic sustainability, the indicators were standardized and weighted according to their importance. Shannon’s indices for tree diversity (2.06) and Margalef’s for species richness (4.50) demonstrated that the system can be considered as high species richness and sustainable, while the diversity index production (1.46) showed that the farm is not self-sufficient, from the point of view of the development of the agricultural subsystem. The economic dimension reached a value of 3.56, close to what was expected for a sustainable farm. In a general sense, the values of the indicators of diversity of the agroecosystem were optimal and demonstrate its functionality, represented by diversif ication and agriculture-livestock integration, although it is recommended to expand the area destined to agricultural crops, to achieve greater self-sufficiency food.

The Mexican cucumber is one of the main vegetables that generate foreign exchange for the country, since more than 90% of national production is exported to the United States of North America (USA) and generates a wide economic spill in the producing region, due to the jobs that demand. The objective was to quantify the prof itability and competitiveness of two greenhouses where Persian cucumbers are grown, one from the State of Mexico and the other from Morelos, which have a contract farming agreement with a commercial integrator. The Policy Analysis Matrix (MAP) was used at private prices. The results show that the cultivation of Persian cucumber in the larger greenhouse had a private prof itability coef f icient of (CRP) of 42% and the smaller one was 27%, while the private cost ratios (RCP) were 0.61 for the f irst and 0.71 for the second, conf irming that this type of cultivation, in the contract farming modality, is prof itable and competitive, with the greatest competitiveness being observed in the greenhouse with a larger surface area.

Infectious pancreatic necrosis virus is one of the most important infectious agents in the salmon and trout industry since it causes high mortality in f irst-fed calves. In Mexico, it is the only viral disease that af fects rainbow trout, therefore, information on the characterization and genetic origin of the viral isolates that circulate in our country have already been described, however, an analysis with the complete genome no, which is why this research work aims to analyze the complete genome of the infectious pancreatic necrosis virus that commonly circulates in the country. Based on the genetic relationships of a prototype of this virus isolated in Mexico in relation to other isolates that circulate worldwide, it was found that the Mexican isolate of infectious pancreatic necrosis virus belongs to genogroup I and originates from the Buhl strain.

Objective: To implement a Postal Quality Control System to verify the Treatment Planning System in Teletherapy using Dosimeters Al2O3 :C, based on optically stimulated luminescence (OSL), commercially known as OSLD nanoDotTM.  Materials and Methods: A mannequin containing OSLD nanoDot TM dosimeters, (Al2O3 :C), previously characterized and calibrated for the energy of a 6.0 MV x-ray beam generated in a linear accelerator, the absorbed dose values were measured with: a Semiflex, ionization chamber, PTW – Freigburg electrometer,  3D radiation geometries, such as: Simple geometry (open field at 0º and 25º), Complex geometry (three open fields at 0º, 90º and 270º) and Combined geometry (field and various variations of Gantry rotation), using square fields (6cm2), circular (diameter 6cm), oblique (6cm x 6cm) and Irregular, equal weights and virtual wedge filters in different regions of the photon beam.  Results: The values of the characterization of the nanodot OSLD were: homogeneity (0.9999), by fading over time (0.9989), by correction of depletion (0.9985), of reproducibility (0.9953), by angular dependence (0.9925) and by linearity (1.0000) for a range of absorbed doses 100cGy to 200cGy.  The evaluations in the different regions of the beam, in homogeneous medium, were the following: Simple geometry (Uncertainty: 3.01%), Complex geometry (Uncertainty: 2.16%) and Combined geometry (Uncertainty: 2.62%) Conclusions: The results obtained are within the tolerance values, thus concluding that the OSLD nanoDot TM is a highly reliable dosimeter, in addition to its convenience in its integration into a postal dosimetric audit program.

An experimental model of a wind solar chimney for electrical supply was developed, firstly, the most suitable geographic space was selected for the implementation of the model. Next, we carried out a study in order to determine the environmental, wind and solar parameters using the viewers of the Ministry of Energy and Mines; Taking renewable energy resources as a starting point, a pre-dimensioning was established in order to guarantee economic and technical viability to be able to build the model.The theory of similarity was applied to define the preliminary geometry of the chimney considering built plants as referents, marking the difference of adding two additional subsystems, one wind and the other photovoltaic in order to give it greater autonomy; the wind subsystem located in the upper part of the chimney and the photovoltaic subsystem along the outer surface of the chimney collector and in the central part. Thermal fluid modeling was carried out in the collector considering the differential control volume applying the Reynolds transport equations, mass, moment, energy using Bousnik approximations in order to be able to determine the evolution of pressure, density and temperature working with a simplified model. of heat input in the collector, taking into account the radiation per square meter instantaneous in the place. Then the simulation was carried out in Matlab and satisfactory results of the model were obtained, with respect to the wind and photovoltaic subsystems, the simulations were developed to guarantee the energy contribution. The chimney components began to be designed considering the ease of transport, assembly handling, drawing the plans considering structural strength parameters, the anchoring component and the first chimney body; the number of bodies was established to achieve the design height. The collector was articulated to the first body of the chimney through 12 sectors which were built with structural T and with the design slope, to later cover it with standard transparent plastic number 12 and glue it to the collector. At the same time, the wind subsystem was designed, consisting of two wind turbines with an aerodynamic fuselage, blades with a NACA 624 profile. The foundation of the anchor was made and later the installation of all the bodies in which speed, temperature and humidity sensors of the chimney were installed considering wind turbines. Then the centralized system of accumulation, regulation and monitoring in the form of a column outside the collector was installed and the tests were carried out. The objective of developing the self-sufficient integral model was met considering 3 supply subsystems, in the collector temperature gradients were obtained significant, but according to the research schedule, the test dates corresponded to the month of August, where there is not a high level of radiation, which was expected from the beginning of the project, this did not generate a sufficient gradient for the operation of the thermal turbine. The photovoltaic and wind subsystems worked as expected in the experimentation area.