Sistema Nacional de Investigadores

Maass, J., P. Balvanera, A. Castillo, G. C. Daily, H. A. Mooney, P. Ehrlich, M. Quesada, A. Miranda, V. J. Jaramillo, F. García-Oliva, A. Martínez-Yrizar, H. Cotler, J. López-Blanco, A. Pérez-Jiménez, A. Búrquez, C. Tinoco, G. Ceballos, L. Barraza, R. Ayala, and J. Sarukhán. 2005. Ecosystem services of tropical dry forests: insights from long-term ecological and social research on the Pacific Coast of Mexico. Ecology and Society 10(1): 17. https://doi.org/10.5751/ES-01219-100117

Abstract The C ommunity of I nquiry framework, originally proposed by G arrison, A nderson and A rcher, identifies teaching, social and cognitive presences as central to a successful online educational experience. This paper presents the findings of a study conducted in U ruguay between 2007 and 2010. The research aimed to establish the role of cognitive, social and teaching presences in the professional development of 40 E nglish language teachers on continuous professional development programmes delivered in blended learning settings. The findings suggest that teaching presence and cognitive presence have themselves “become social.” The research points to social presence as a major lever for engagement, sense‐making and peer support. Based on the patterns identified in the study, this paper puts forward an adjustment to the C ommunity of I nquiry framework, which shows social presence as more prominent within the teaching and cognitive constructs than the original version of the framework suggests.

On Earth, methane is produced mainly by life, and it has been proposed that, under certain conditions, methane detected in an exoplanetary spectrum may be considered a biosignature. Here, we estimate how much methane may be produced in hydrothermal vent systems by serpentinization, its main geological source, using the kinetic properties of the main reactions involved in methane production by serpentinization. Hydrogen production by serpentinization was calculated as a function of the available FeO in the crust, given the current spreading rates. Carbon dioxide is the limiting reactant for methane formation because it is highly depleted in aqueous form in hydrothermal vent systems. We estimated maximum CH4 surface fluxes of 6.8×10(8) and 1.3×10(9) molecules cm(-2) s(-1) for rocky planets with 1 and 5 M⊕, respectively. Using a 1-D photochemical model, we simulated atmospheres with volume mixing ratios of 0.03 and 0.1 CO2 to calculate atmospheric methane concentrations for the maximum production of this compound by serpentinization. The resulting abundances were 2.5 and 2.1 ppmv for 1 M⊕ planets and 4.1 and 3.7 ppmv for 5 M⊕ planets. Therefore, low atmospheric concentrations of methane may be produced by serpentinization. For habitable planets around Sun-like stars with N2-CO2 atmospheres, methane concentrations larger than 10 ppmv may indicate the presence of life.

The photoluminescence and crystalline structure characterization of undoped and several samarium doped ZrO2 samples are reported. Strong fluorescence emission produced by the transitions G5/24→6H5/2,7/2,9/2 of Sm3+ was obtained by the excitation of the host at 320 nm. The energy transfer process from the host to the samarium ion was confirmed by the analysis of the ZrO2 fluorescence decay curve. It is shown that the content of the active ions stabilizes the tetragonal structure of ZrO2 at 1000 °C, being 73% for 2 mol % Sm2O3 doped and 3% for undoped samples. The dependence between the fluorescence emission and the crystalline structure is discussed.

The solution treatment of an as-cast ASTM F-75 alloy was investigated. Microstructural evolution was followed during thermal processing, in particular with regard to the content and type of carbides formed. To evidence any probable carbide transformations occurring during the heating stage, as well as to clarify their effect on the carbide dissolution kinetics, three heating rates were studied. Image analysis and scanning electron microscopy techniques were used for microstructural characterization. For the identification of precipitates, these were electrolytically extracted from the matrix and then analyzed by X-ray diffraction. It was found that the precipitates in the as-cast alloy were constituted by both a M(23)C(6) carbide and a sigma intermetallic phase. The M(23)C(6) carbide was the only phase identified in solution-treated specimens, regardless of the heating rate employed, which indicated that this carbide dissolved directly into the matrix without being transformed first into an M(6)C carbide, as reported in the literature. It was found that the kinetics of dissolution for the M(23)C(6) carbide decreased progressively during the solution treatment, and that it was sensitive to the heating rate, decreasing whenever the latter was decreased. Because the M(23)C(6) carbide was not observed to suffer a phase transformation prior to its dissolution into the matrix, the effect of the heating rate was associated to the morphological change occurred as the specimens were heated. The occurrence of the observed phases was analyzed with the aid of phase diagrams computed for the system Co-Cr-Mo-C.

Ample research effort has been oriented into developing damage indices with the aim of estimating in a reasonable manner the consequences, in terms of structural damage and deterioration, of severe plastic cycling. Although several studies have been devoted to calibrate damage indices for steel and reinforced concrete members; currently, there is a challenge to study and calibrate the use of such indices for the practical evaluation of complex structures. The aim of this paper is to introduce an energy-based damage index for multi-degree-of-freedom steel buildings that accounts explicitly for the effects of cumulative plastic deformation demands. The model has been developed by complementing the results obtained from experimental testing of steel members with those derived from analytical studies regarding the distribution of plastic demands on several steel frames designed according to the Mexico City Building Code. It is concluded that the approach discussed herein is a promising tool for practical structural evaluation of framed structures subjected to large energy demands.

La pandemia ha cambiado la “domiciliación” de lo escolar, trasladándola hacia el espacio doméstico. Este artículo se pregunta por los efectos de esta domestización de las escuelas, particularmente cuando se la considera en su intersección con las desigualdades preexistentes y con las tecnologías y las pedagogías disponibles. El argumento central es que, de manera contraria a lo que sostienen los argumentos tecnofílicos, estos cambios introducen numerosas tensiones difíciles de resolver, y permiten ver la relevancia de la estructura material y simbólica de la escuela para producir unespacio otroque haga lugar a una autonomía intelectual y afectiva progresiva. También se presenta la idea de que la clase es un entorno socio-técnico particular que habilita formas de trabajo con los saberes, a la par que organiza a los cuerpos y los tiempos en actividades que deberían proponerdesafíos intelectuales; esto está desacomodado en los arreglos educativos improvisados en la emergencia, que muestran un desplazamiento de los énfasis y jerarquías del trabajo escolar. En la parte final, se esbozan claves para debatir algunos de los aprendizajes de estos tiempos dislocados.

Uruguay shows a contradiction. The values found for the attitudinal dimensions of malaise in representation are low and, in this sense, malaise in representation is weak. On the other hand, however, the behavioral dimensions of malaise have high values compared to Chile and Argentina. We argue that this contradiction is only apparent. Between 1985 and 2014, some particularities of the Uruguayan political system and its institutional framework operated virtuously, channeling social demands institutionally. This resulted in a system of representation in which social protests (the behavioral dimensions of malaise) acted as a way of integrating citizens into the political system, rather than being a symptom of problems of representation. As a consequence, the attitudinal dimensions of malaise have been historically low in this country.

Abstract In this paper we consider the inverse scattering problem for the non‐linear Schrödinger equation on the line \def\dr{{\rm d}}$$i{\partial\over\partial t}u(t,x)=‐{\dr^2\over\dr x^2}u(t,x)+V_0(x)u(t,x)+\sum_{j=1}^{\infty}V_j(x)|u|^{2(j_0+j)}u(t,x)$$\nopagenumbers\end We prove, under appropriate conditions, that the small‐amplitude limit of the scattering operator determines uniquely V j , j =0,1,… . Our proof gives also a method for the reconstruction of the V j , j =0,1,… . Copyright © 2001 John Wiley & Sons, Ltd.

This paper aims to make a balance of the magnitude and dimensions of the high school dropout, using some theoretical contributions and a review about the main Mexican policies. Oriented by a qualitative methodology, based on the theoretical review, the recovery of fundamental statistical information and the systematization of experiences of policies and programs oriented to the prevention of abandonment in the high school, an analytical framework was generated to organize and analyze the main government strategies, as well as the guidelines issued by the National Institute for the Evaluation of Education. The analysis finds a policy trend to address risk factors, mainly socioeconomic, but ignores fundamental issues such as the school environment and school integration. Therefore, some recommendations are proposed to strengthen public policy in the educational field, recognizing the heterogeneity of the causes of dropout.

This work evaluated the performance of a full-scale system with wetlands for slaughterhouse (abattoir) effluent treatment in the State of Hidalgo, México. The treatment system consisted of a primary sedimentation tank, an anaerobic lagoon, and a constructed subsurface-flow wetland, in series. The wetland accounted for almost 30% of the removal of organic matter. In general, the treatment system achieved satisfactory pollutant removals, but the final effluent could not meet the Mexican environmental regulations for fecal coliform counts, five-day biochemical oxygen demand (BOD5), and total suspended solids (TSS). Overall, removal levels were 91%, 89%, and 85% for BOD5, chemical oxygen demand, and TSS, respectively. However, BOD5 in the final effluent (137 mg/L) was higher than the maximum level of 30 mg/L allowed by the regulatory agency. Although organic nitrogen removal levels were approximately 80%, the nitrogen persisted in oxidation state -3 as ammonia-nitrogen, the removal of which was only 9% in the wetland stage. On average, phosphorus removal was null, and, on occasion, the phosphorus concentration in the treated effluent was higher than that of the influent. Coliform reductions in the overall system were high (on the order of 5 logs on average), whereas the coliform removal in the wetland was between 2 to 3.5 logs. The treatment system was also effective at removing pathogens (Vibrio cholerae, Salmonella, and Shigella). Further laboratory tests with the wetland effluent suggest that post treatment in a sand filter stage followed by disinfection with sodium hypochlorite (NaOCl) could help meet the Mexican discharge regulations, particularly the criteria for coliforms and total BOD5.

Platymiscium yucatanum is a tropical wood highly resistant to the fungi Lenzites trabea and Coriolus versicolor. In order to determine the reason for this property, heartwood extracts and isolated compounds were tested in vitro against these fungi. The methylene chloride extract completely inhibited (5 mg/ml) the mycellium growth of both fungi. Chromatographic separation of the extract afforded several flavonoids and isoflavonoids, among them the novel 4,2',5'-trihydroxy-chalcone, isoliquiritigenin (4,2',4'-trihydroxychalcone), (+)-liquiriti-genin, (+)-medicarpin, and homopterocarpin. The coumarin aesculetin dimethyl ether was also isolated. Antifungal activity of five of the isolated compounds were measured at 0.25 mg/ml. (+)-Medicarpin and the two chalcones inhibited the growth of both fungi. Aesculetin dimethyl ether and (+)-liquiritigenin were only active against C. versicolor. (+)-Medicarpin was the most active of the compounds tested and had greater activity than phenol against C. versicolor. The results suggest that the various compounds present all contributions in some degree to the heartwood durability, but not all compounds are equally effective.

Genetic variation in the common bush‐tanager Chlorospingus ophthalmicus complex in Mesoamerica was studied. An 800‐bp mitochondrial DNA fragment, including a portion of COII, full tRNA‐Lys, ATP8, and partial ATP6, was sequenced and analyzed for 96 individuals of the species and related taxa, resulting in a detailed framework of genetic differentiation in the northern half of the distribution of the complex. Phylogenetic analyses based on maximum parsimony, maximum likelihood, and Bayesian optimality criteria found deep divergence between South American and Mesoamerican isolates, and seven differentiated populations corresponding to clear geographic breaks across the highlands of Mesoamerica. These distinct populations coincide with geographic structure found in previous analyses of morphological and molecular data for Chlorospingus ophthalmicus , as well as in previous phylogeographic studies of other taxa in the region. Species status for these populations is discussed under the evolutionary and biological species concepts.

The question that frames the article is the capacity and effectiveness of the process by which a society is steered. After some initial considerations about the features and some limits of New Public Management and New Public Governance, which have been the dominant approaches to solve this question in recent years, the article explains the reasons why New Public Governance is considered the most effective process of leading the contemporary society, and outlines as well its two essential dimensions (the institutional and the technical) and its three levels of performance: the public governance of society, the governance of the public administration, and the governance of the specific organizations of public administration, which is beginning to be named “public corporate governance”, and which has not been studied in a systematic way. The article concludes pointing out some ideas to fill the knowledge gap on such subjects.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPuberulin and isopuberulin, benzonorcaradiene and benzocyclo-heptatriene diterpenoids of clerodanic origin from Salvia puberulaLydia Rodriguez-Hahn, Baldomero Esquivel, Ana Adela Sanchez, Jorge Cardenas, Olga G. Tovar, Manuel Soriano-Garcia, and Alfredo ToscanoCite this: J. Org. Chem. 1988, 53, 17, 3933–3936Publication Date (Print):August 1, 1988Publication History Published online1 May 2002Published inissue 1 August 1988https://pubs.acs.org/doi/10.1021/jo00252a010https://doi.org/10.1021/jo00252a010research-articleACS PublicationsRequest reuse permissionsArticle Views298Altmetric-Citations35LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Los pronósticos son una herramienta que proporciona un estimado cuantitativo de la probabilidad de eventos futuros. La relevancia de incorporar pronósticos en la demanda de almacenamiento en productos perecederos dentro de la cadena de frio deriva de su importancia económica y social. Este caso de estudio presenta una empresa con tendencia de crecimiento dedicada al almacenamiento de productos perecederos e incorpora técnicas de pronósticos de series de tiempo, en el volumen de ingreso y egreso de los productos en una cámara frigorífica, con el fin de estimar el volumen de almacenamiento para prever los requerimientos de instalaciones adicionales, personal y materiales necesarios para la movilidad de los productos.

Taenia solium cysticercosis is a major parasitic disease that seriously and frequently affects human health and economy in undeveloped countries. Since pigs are an indispensable intermediate host, it is conceivable to curb transmission by reducing pig cysticercosis through their effective vaccination. This article reviews current knowledge on the development vaccines against porcine cysticercosis. It highlights the development of several versions of S3Pvac aimed to increase effectiveness, reduce costs and increase feasibility by novel delivery systems and alternative routes of administration.

The energy change on each Occupied Molecular Orbital as a function of rotation about the C-C bond in ethane was studied using the B3LYP, mPWB95 functional and MP2 methods with different basis sets. Also, the effect of the ZPE on rotational barrier was analyzed. We have found that σ and π energies contribution stabilize a staggered conformation. The σ(s) molecular orbital stabilizes the staggered conformation while the stabilizes the eclipsed conformation and destabilize the staggered conformation. The π(z) and molecular orbitals stabilize both the eclipsed and staggered conformations, which are destabilized by the π(v) and molecular orbitals. The results show that the method of calculation has the effect of changing the behavior of the energy change in each Occupied Molecular Orbital energy as a function of the angle of rotation about the C-C bond in ethane. Finally, we found that if the molecular orbital energy contribution is deleted from the rotational energy, an inversion in conformational preference occurs.

OBJECTIVE: To apply a case-finding strategy in Mexico to identify chronic airway obstruction among individuals with risk factors and/or symptoms compatible with chronic obstructive pulmonary disease (COPD). MATERIAL AND METHODS: Individuals aged ≥ 40 years with known risk factors and/or symptoms compatible with COPD were referred for an interview and spirometry. RESULTS: Of 2293 subjects included, 472 (20.6%) had a post-bronchodilator forced expiratory volume in one second/forced vital capacity ratio of <70% (for Global Initiative for Chronic Obstructive Lung Disease [GOLD] Stages II-IV, prevalence was 17.1%). Those with airflow obstruction had smoked more cigarettes for more years than subjects without (19 vs. 13 cigarettes/day, P < 0.001, and 32 vs. 23 years, P < 0.001); they also had a more frequent history of exposure to biomass smoke (23.3% vs. 18.3%, P = 0.002). Females were exposed to biomass smoke for more years (24 vs. 19 years; P < 0.0001) and more hours per day than males (6.2 vs. 5.1; P < 0.001). In multiple logistic regression analysis, increasing age, male sex, ever smoking, pack-years of smoking and years of exposure to biomass smoke were significantly associated with COPD prevalence. CONCLUSIONS: Airflow obstruction was identified in one in five of Mexican individuals with risk factors and/or COPD symptoms. Exposure to biomass smoke was significantly associated with the presence of airflow obstruction.

Disruption of the quiescent state of blood vessels in the retina leads to aberrant vasopermeability and angiogenesis, the major causes of vision loss in diabetic retinopathy. Prolactin is expressed throughout the retina, where it is proteolytically cleaved to vasoinhibins, a family of peptides (including the 16-kDa fragment of prolactin) with potent antiangiogenic, vasoconstrictive, and antivasopermeability actions. Ocular vasoinhibins act directly on endothelial cells to block blood vessel growth and dilation and to promote apoptosis-mediated vascular regression. Also, vasoinhibins prevent retinal angiogenesis and vasopermeability associated with diabetic retinopathy, and inactivation of endothelial nitric oxide synthase via protein phosphatase 2A is among the various mechanisms mediating their actions. Here, we discuss the potential role of vasoinhibins both in the maintenance of normal retinal vasculature and in the cause and prevention of diabetic retinopathy and other vasoproliferative retinopathies.