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

For 2.1 GHz, propagation models used to estimate signal attenuation in LTE (Long Term Evolution) mobile communications systems are mainly the Xia-Bertoni and Walfisch-Bertoni Model [2, 3, 5, 9, 10, 15], which are models applicable up to 3GHz. For these models the equations depend on different variables of the propagation environment (effect of roofs and height of buildings, among others), which makes them precise, however, they are more complex in their calculation [8, 13]. In this paper, an analysis of path loss is made using the simplified empirical propagation method, which depends on fewer variables than the traditionally used models and the data collected in the field presents a better performance for the frequency of 2.130 GHz. The final part of the paper shows the equations of the simplified model for two areas of Mexico City, which are used to generalize the model to other areas with similar characteristics.

Grazing native vegetation does not satisfy the nutritional needs of the dairy goats, especially in early lactation. Therefore, there are strategies of food supplementation to increase milk production; most of the feed supplementation research has focused on meeting the needs of the drought period. However, it is necessary to evaluate whether in the rainy season the availability of forage species may cover the nutritional requirements of the goats, or at least the deficit is lower and therefore avoid unnecessary expenses in extra feeding. Therefore, the objective of this study was to evaluate the effect of pre-partum and post-partum concentrate supplementation and its effect on body weitgth, body condition, milk production and milk quality, in the early lactation and during the rainy season at the Comarca Lagunera in Northern Mexico.Method: There were used 33 adult local goats. a) Control group (control) (n = 11), which were fed exclusively with the forages collected by the animal in the grazing route. b) Pre kidding goat group (N = 11) who aditionaly to the pasture grazed were offered 500 g of commercial concentrate per animal and day, during 30 days before the kidding time and c) Postpartum group (n = 11) free pasture grazed plus 500 g of concentrate Commercial by animal and day during 30 days from the date of kidding time. The variables of body weight (PV) and body condition (CC) were measured weekly, during 14 weeks. Milk production and milk quality (Fat, Protein and Lactose) were measured weekly from the date of parturition during 8 weeks. The statistical analysis for milk production and quality variables were performed using the MIXED procedure. The PV and CC data were analyzed using the GLM procedure and the Tukey test fitted for the comparison of means was used. Concentrate consumption data were analyzed with a t-test to determine differences between supplemented groups.Results: There were no differences (p> 0.05) in the consumption of concentrate in the pre- and postpartum groups. There were found differences (p <0.05) in PV and CC prior to kidding time. Post partum the PV and CC were similar in all groups with losses until the end of the experiment. There were no differences (p> 0.05) in milk production, fat content, protein or lactose, nor effects of treatment * time interaction.Discussion: It is concluded, that supplement used one month before or after birth do not improve milk production, chemical composition of milk or body weigth from local goats in early lactation and rainy season under extensive grazing conditions in the Comarca Lagunera in northern Mexico.

The Lagunera Region stands out as the most important melon area in Mexico with an annual area of around 5,000 hectares and a production of 134,000 tons. Production in this region is threatened by imports, pests, diseases, marketing problems, high production costs, lack of financing and increased quality requirements by the self-service stores. The objective of this work was to propose a series of strategies, alliances and business portfolio to improve the competitiveness of the melon production chain in the Comarca Lagunera, Mexico to avoid being displaced by competing regions of the country and abroad.                       Method: In this work we used the methodology known as "Focus Group". There were 27 participants, of whom 18 were producers of melon, five technicians, two officials from the Ministry of Rural Development of the state government of Coahuila and two representatives of companies supplying agricultural inputs. Two days in several dynamics based on previously elaborated formats. The obtained information was classified having obtained the competitive forces, the strategies, the alliances and the portfolio of businesses.                       Results: Six strategies were identified for the development of competitiveness, their scope, limitations and the estimated time to be carried out. The strategies were: 1) technical training aimed at obtaining certification in food safety, 2) transfer of the technological package, 3) management of resources to finance and ensure production, 4) direct sale of melon to the retail self-service stores, 5) establish alliances with academic and research institutions and 6) establish alliances with state and federal agencies of the Agricultural Sector. As for the alliances are specific to each strategy, highlighting those with federal and state agencies, Universities and research centers of the agricultural sector; institutions of financing and assurance to the field and chains of stores of self-service. Finally, in the business portfolio it is proposed the creation of 1) a melon marketing management office, 2) a credit union, 3) a professional services rendering agency, and 4) a marketing agency for equipment and supplies.                       Conclusion: The results allowed to define the main strategies, pacts to be realized and the portfolio of businesses tending to develop the productivity and competitiveness of the melon in the Comarca Lagunera de Coahuila. These results were presented and validated in a meeting of the melon product system of the Comarca Lagunera; however, its implementation will depend on the producers being able to organize and carry out the actions proposed here.

The dual-purpose cattle are that used to produce meat and milk, is usually the product of miscegenation Cebu origin x European and / or creole. This genetic group has adapted to the climatic conditions of temperature, humidity, low quality pastures and any kind of parasite prevalent in tropical regions. In this work, a molecular thorough examination was performed to observe the frequency of two polymorphisms gene μ-calpain (CAPN1-316, CAPN1-530) and one gene calpastatin (CAST), associated with the softness of meat cattle dual purpose of the Cuenca Papaloapan. The tests were based on polymerase chain reaction (PCR) and length polymorphisms Restriction Fragment (LPRF) with restriction enzymes Btg I, Ava II and Rsa I for CG, AG and CG alleles, respectively (n = 331). To CAPN1-316 the genotypic frequencies obtained were 0.03 (AA), 0.86 (GG) and 0.11 (GA) and allele frequencies were 0.86 (G) and 0.14 (A). CAPN1-530 marker for the genotype frequencies were 0.02 (CC), 0.85 (GG) and 0.13 (GC) with an allele frequency of 0.85 to 0.15 for G and C. The genotype frequencies for the marker CAST were 0.32 (CC), 0.28 (GG) and 0.4 (GC) with an allele frequency of 0.68 for the G and 0.32 allele for allele C. The study population was found in Hardy Weinberg and values χ2P two degrees of liberty were 0.964, 0.985 and 0.9803 for CAPN1-316, CAPN1-530 and CAST, respectively. According to the percentage of genotyping markers on capn1 and CAST genes it concludes that the analyzed population has low levels of markers for softness or tenderness of the meat, probably by cross undirected carried out regularly, thus it aims to improve the quality of meat based on genetic programs improved using genetically superior animals resulting from this study.

The objective of this study was to describe and assess the relationship between technological practices of herd management of cattle of dual purpose and productivity. In addition to its association with different seasons of the year. For this, the monthly records of the productive variables and technological practices of thirty farms in the States of Chiapas, Tabasco and Sinaloa were analyzed for a year. Using the Canonical Correlations analysis, the relationship between the technological practices was estimated; supplementation, health management, prevention and control of diseases, and pasture management (X) with productive variables; milk production, percentage of milking cows and number of offspring (Y). The correspondence analysis measured the association of the use of technological practices and the seasons of year. The results showed three canonical correlations, the first one was 3.33 and significant, with an observed variability of 89% and the technological practices that best explain the productive variables are the supplementation, health management, prevention and control of diseases. Correspondence analysis showed that farmers in Tabasco and Chiapas vary the technological management practices of the herd according to the seasons of year (rain, dry and transition) while Sinaloa farmers used them throughout the entire year, regardless of the seasons of the year. The use of technological practices in farms influences the productive variables, mainly in the milk production.

Introduction. Tropical cities have climatic conditions for the development of biota. The conservation of natural spaces with abundant mass of vegetation, is vital for the preservation of the biodiversity in the city, as forestation brings improvements to the quality of life. The article presents the results of the project "Forestation and Rescue of Laguna Nuevo Amanecer. Ciudad Madero, México, "funded by the Universidad Autónoma de Tamaulipas, 2015. The objective is to validate the method of study based on indicators in urban forestation projects in the tropical city through the measurement of its impact.                       Method. 1. Indicators of the Urban Sustainability Indicators Plan (Rueda, 2010) were used to assess the current situation of the Laguna Nuevo Amanecer wetland.2. A proposal for urban reforestation was made using the indicators of tree diversity, soil biotic index and tree density.3. The impact of the proposal was evaluated through the Wetland Parks Functionality Index and the Thermal Comfort Indicator for the streets.                       Results. The increase of mass vegetation in the proposal of urban reforestation in the open space presents positive impacts in two complementary situations: the urban natural spaces and the streets, considering the indicators. Stage 1. For the urban natural spaces, the Parks Functionality Index was considered in the reforestation proposal, giving a value close to 10, where it exceeds the desirable value for the case of temperate cities of 7.5, proving the existence of greater ecological wealth in Tropical cities as a value to maintain.Stage 2. For the streets, the thermal comfort indicator was considered in the arborization proposal, between 7 and 9 hours of comfort in 74% of the polygon wh                                                                             Conclusion. Conservation and enhancement of wetland plant communities and tree-lined streets directly improve the quality of life in tropical cities and reduce the impact of climatic change. Mass vegetation continuity between both scenarios reinforces the system of open spaces, diminishing the island of heat. In these contexts, urban forestry projects can be considered as a basic sustainability instrument that contributes to the increase of biodiversity and thermal comfort.

The present work aimed to identify and evaluate degradation capacity of microorganisms isolated from mimosa nodules, which can be used in bioremediation processes of soils contaminated with phenanthrene.Method. Isolation of 122 bacterial strains of mimosa nodules was grown in the Maconkey culture medium to discard enterobacteria; the bacterial strains that resulted negative to this test, were inoculated in the culture medium containing only phenanthrene source carbon. Three isolates had the capacity to grow in this medium. The three strains were identified by sequence of the 16s ribosomal gene, their capacity to grow in the presence of phenanthrene was assessed by microbial growth curves; the ability to degrade phenanthrene of the three strains was quantified by mass-coupled gas chromatography.Results. The sequences obtained from the 16s ribosomal gene are genetically related to the strains of Burkholderia phenoliruptrix, Burkholderia phymatum and Rhizobium paknamense. The microbial growth of the three strains, supplied with phenanthrene, had a similar behavior to the control, which contained succinate as a carbon source. The strain of Burkholderia sp. BB26 degraded 78.5%, Burkholderia sp. BB24 68.5% and Rhizobium sp. BY8 99%.Discussion. The results of phenanthrene degradation by Burkholderia sp. BB26, Burkholderia sp. BB24 and Rhizobium sp. BY8 strains suggest that the three strains have potential to be used in bioremediation processes of soils contaminated with phenanthrene. 

The objective of this study was to test the effectiveness of a procedure to train undergraduate students to write and implement case studies for improving their learning experiences, adapt to the labor environment and be better prepared for career success.Method. Undergraduate students in social service internships at the Higher State Auditing Office in the states of Yucatan, Campeche and Q. Roo, in the Southeast of Mexico, under the guidance of Government Auditors, designed case studies to be implemented with their classmates following the procedure studied in this document, prepared by the author of this research.                      Results. Results showed that after this experience, implementer students were more motivated for learning, more interested in case studies, more confident at working with others and were satisfied with learning. This was compared to the learning through traditional methods, according to their perception.                       Conclusion.This case study procedure is effective for preparing students for improving their technical and socio-emotional competencies in their preparation for career success, but also a professional development opportunity for the Auditors. Learning to write and implement cases help learning and adaptation to work environment. It is learning how to learn and be prepared for career success through experiences such as this in real job contexts.