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

The leaves of the tropical tree Leucaena leucocephala are often used as a livestock feed input. However, they contain mimosine, an antinutritional factor that can negatively affect animal physical parameters. An evaluation was done of testicular characteristics in pubescent ram that had consumed fresh L. leucocephala leaves. Experimental animals were 20, 5-month-old male Creole ram (average weight = 24.4 ± 3.21 kg) housed in individual pens. During the 120 d experimental period 10 males were fed a 0 % Leucaena diet (control) and another 10 were fed a diet including 25 % fresh L. leucocephala (Leucaena). Real leucocephala intake was determined by the difference between the quantity that was offered, and the quantity was rejected. For the determination of testosterone and mimosine in blood, an ELISA kit and HPLC were used respectively. Scrotal circumference measurements were taken, and testicular volume was estimated. A histological study was carried out; to determine the integrity of the testicular parenchyma testicular. The 40 % of male’s intake L. leucocephala presented interstitial edema and tubular atrophy in the testicular parenchyma of pubescent ram. Scrotal circumference and testicular volume were not affected; however, edema and atrophy of the seminiferous tubules were found in animals that intake Leucaena leucocephala

The brewing industry in Mexico is a key sector in the national economy. This is demonstrated by its economic performance: it generates 2.5 million direct and indirect jobs, produces a turnover of 6 billion dollars and incorporates 100 000 national farmers into its supply chain. The objective of this research was to analyze the factors that determine the competitiveness of the barley value chain (VC). Thus, links and strategies that contribute to strengthening competitiveness were characterized. Analytically, we started from Porter's four components that explain the competitive advantages of an economic actor, and the method formulated by ECLAC to identify internal and external variables of the VC, as well as their control or absence. It was found that the VC-cebada is made up of five links and its articulation is the result of the governance exercised by Grupo Modelo-ABInBev and Cuauhtémoc Moctezuma-Heineken México. Four factors explain the chain's competitiveness: level of articulation, innovation, physical infrastructure and organization. The VC is well articulated in the production zone; however, the brewers generate strong links only with large and medium-sized producers and limit the participation of small producers, generating an asymmetrical and exclusively functional vertical VC.

In this paper, we analyze the social representations about disability in a group of high school students, from two Mexican cities: Oaxaca and Estado de México.  The research was based on an associative method. For that purpose, we designed a questionnaire in which students were asked to write the three words that came into mind when they thought about «person with disability», and then to briefly explain the reason for each one. For the analysis of information, we used the natural semantic network technique. The complete network included 107 words, with a semantic weight of 587. Based on this diversity of expressions, we characterized four representations: Social, Medical-rehabilitative, Tragic-charity, and Optimistic. The first two representations had the highest semantic weight in the complete network, 223 and 184 respectively, meanwhile, the last two reached scores of 103 and 73 each. These outcomes may be seen as a contradiction; however, they show that social representations are not monolithic entities, on the contrary, they are the result of scientific knowledge and common sense; nor belong to a certain group, but they are the product of the information disseminated by the different socializing agents.

Recently it has been pointed out that an outstanding application of an IBM quantum computer is to reverse the arrow of time (Lesovik et al., 2019). It is explored such a possibility in a two qubits system coupled to a common structured reservoir at zero temperature. It is shown that population rates of the quantum states become the same both towards the remote past and towards the remote future. A two qubits system in presence of noise can reverse the arrow of time.

Products have tangible and intangible attributes that influence consumption decisions. In a consumer survey they chose the 13 most important human values ​​and the 13 least important, from a list of 40; they rated the importance of six tangible attributes of the calla lily and expressed the frequency of consumption of the flower. Multidimensional scaling analysis was used to identify structure of human values ​​in consumers. Tangible values ​​and attributes were reduced by factor analysis. Three correlation coefficients were obtained: a) tangible attributes and consumption; b) human and residual values ​​of tangible attributes, and consumption, and c) human values ​​and consumption. Consumers were shown an image of a calla lily and asked to mention three words that came to mind. Proportions k test and Marascuilo procedure were applied to related word categories. Influence of human values ​​occurred mainly via the direct route, evidencing the existence of intangible attributes, in addition to the tangible ones, that influence consumption decisions. The calla lily has a greater number of symbolic psychological meanings (81.3 %), than utilitarian (18.7 %). The symbolic psychological function includes sensory, emotional, and affective aspects. Results may vary within other cultural/regional contexts and with other research tools.

Mini tomato production in the greenhouse has reached the last decades, however, the efficient use of fertilizers and the effect on the quality of the fruits are often overlooked. In this work, the ionic concentration ranges were determined, as well as the relationship between the ions (NO3-, K+, Ca2+, and Na+), the pH, electrical conductivity of the nutrient solution, the total soluble solids (TSS) of the cell extract of petiole (PCE) and the fruit cell extract (FCE) in mini tomatoes (Grape, Savantas, and Tov) in the summer-winter cycle. High ranges of ionic concentration were recorded. The Na+ and K+ collected in the emitters showed strong resonance with the same ions recorded in the PCE. The heat map of the correlations showed clusters between the K+ and Ca2+ of the nutrient solution, which were found to be highly correlated with the PCE and FCE content in the winter season. Principal component analysis showed that NO3- and Na+ are far from the K+ and Ca2+ content of PCE and FCE. The concentration ranges found suggest ionic sufficiency for mini tomato genotypes produced in high-tech greenhouse.

Mexico produces 30 790.7 t per year of soursop fruits (FG), Nayarit contributes 75.4 %. The FG are perishable, it is proposed to develop edible coatings (RC). The objective was to evaluate CR based on starch (2 %) of FG (2 % w/v) in FG stored at 15 ± 2 °C and 22 ± 2 °C. Weight loss PP (%), firmness F (N), titratable acidity AT (%), total soluble solids TSS (°Brix) and color (L*C*H) were evaluated. Treatment design: FG without CR at 22 ± 2 °C for 8 d (T1), FG with CR at 22 ± 2 °C for 10 d (T2) and FG without CR (T3) and FG with CR at 15 ± 2 °C for 4 d and subsequently transferred to 22 ± 2 °C for 8 d (T4), RH 90%. The PP was 10.3 (T1) and 6.1(T2), F of 45.9 (T1) and 26.2 (T2), at the end of storage AT of 0.94 (T1) and 0.56 (T2) and SST of 15.8 (T1) and 15.5 (T2). At T3 and T4, PP was 10.5 and 10.4, respectively, F was 9.6 (T3, 8 d) and 19 (T4, 10 d), AT was 0.26 (T3) and 0.27 (T4), SST was 12.2 (T3) and 11.4 (T4) at the end of storage. The fruits of T4 presented a green color with low luminosity (L: 43.9 C: 15.5 H: 105) at the end of storage. The fruits of T2 presented less loss of weight and firmness, high concentration of TSS at 4 d of storage. The coating does not affect the fruits stored in both storage conditions.

The built heritage located in the historic center of the city of Tampico, declared a heritage zone of historic and artistic monuments in 1990, was built between 1890 and 1930 from the Porfiriato period, considered the time of the oil boom. In that sense, the architectural and visual history of the city is compromised in its construction with a landscape built as a consequence of the social needs and consumption of merchandise; companies and industry, which were determinants of that historical moment and gave a representative cultural meaning. This study considers particularly those historical buildings that contain on their facade’s inscriptions, names, numbers or symbols, as a historiographic narrative of the visual and discursive meaning named identification inscriptions. The contribution of a formal study for the defragmented narrativity of the graphic historicity with its own inscribed characteristics of the culture of Tampico, which, due to the affectations caused by diverse factors, put at risk its permanence and veracity in a structural and formal way, becomes important. This is how the contextual historiographic narrative contributes to point out the inscriptional graphic value.

The study of residential segregation by ethnicity in Latin America and Mexico is continuously related to socioeconomic and class variables; however, we have found robustness on data related to religion, birth rate, educational status, occupation, income, migration or feeding in the Population and Housing Censuses from 1990 to 2020. This research aims to broaden and diversify efforts to understand ethnic residential segregation in Mexico and its relation to socioeconomic and sociocultural indicators; therefore, the correlation between ethnicity and religion, educational status, occupation and migration was analyzed. The city of San Cristobal de Las Casas was chosen as a case study due to its characteristics of social and ethnic composition; residential segregation at the AGEB level was measured with data from the 2020 Population and Housing Census based on the calculation of dissimilarity index and Delta index. Finally, the results were correlated through the Pearson coefficient. The results point out that the ethnicity and religion variables have a stronger relation with each other; closely followed by the strength of the relation between variables of ethnicity and educational status. Therefore, the evidence indicates that residential segregation by ethnicity is more closely related to sociocultural residential segregation than to socioeconomic residential segregation.

Humanity has suffered throughout its history from different types of pandemics caused by deadly infectious diseases. Mathematical models are very useful tools to understand the dynamics of the behavior and propagation of these. Among these models are those known as SIS, SIR and SEIR. This paper presents a brief explanation of the structure of these models and its use in some pandemics. In particular, some SIR-type models without and with delays are analyzed with special interest, as well as their applications to the current pandemic caused by the SARS-CoV-2 virus. To determine the correspondence between some of the models analyzed and the data of Infectious and Recovered from Mexico reported by the World Health Organization (WHO), simulations are presented in three different time periods between the years 2020-2021. In addition, an unpublished SIR-type mathematical model with three delays is proposed as a main contribution. Finally, a discussion is given on the application of numerical algorithms to identify some parameters of mathematical models, such as ordinary least squares.