The stability paradox : why expansion of education for women has not delayed age at first union or childbearing in Latin America

Despite substantial improvements in women's education, the age atwhich Latin American women marry (cohabit) or become mothers for the first time has barely decreased over the past four decades. We refer to this as the "stability paradox." We examine the relationship between years of schooling and transitions to first union or child, analyzing retrospective information from 50 cohorts of women born between 1940 and 1989 in 12 Latin American countries. Absolute and relative measures of schooling are compared. Data is drawn from 38 Demographic Health Surveys (DHS) conducted between 1986 and 2012 in these countries. Results show that expected postponement in family transitions due to educational expansion was offset by a rise in union formation and childbearing within strata of absolute education, but stayed approximately constant within strata of relative education. The relative measure of education retains the stratifying power of education but neutralizes any effect attached to a specific number of years of schooling and the learning skills associated with them. This is consistent with the idea that access to education in Latin America reproduces existing patterns of socioeconomic advantage, rather than creating a more equitable distribution of learning opportunities and outcomes

Molecular diagnostics of banana Fusarium wilt targeting Secreted-in-Xylem genes

Fusarium wilt is currently spreading in banana growing regions around the world leading to substantial losses. The disease is caused by the fungus Fusarium oxysporum f. sp. cubense (Foc), which is further classified into distinct races according to the banana varieties that they infect. Cavendish banana is resistant to Foc race 1, to which the popular Gros Michel variety succumbed last century. Cavendish effectively saved the banana industry, and became the most cultivated commercial variety worldwide. However, Foc tropical race 4 (TR4) subsequently emerged in Southeast Asia, causing significant yield losses due to its high level of aggressiveness to Cavendish and other commonly grown varieties. Preventing further spread is crucially important in the absence of effective control methods or resistant market-acceptable banana varieties. Implementation of quarantine and containment measures depends on early detection of the pathogen through reliable diagnostics. In this study, we tested the hypothesis that secreted in xylem (SIX) genes, which currently comprise the only known family of effectors in F. oxysporum, contain polymorphisms to allow the design of molecular diagnostic assays that distinguish races and relevant VCGs of Foc. We present specific and reproducible diagnostic assays based on conventional PCR targeting SIX genes, using as templates DNA extracted from pure Foc cultures. Sets of primers specifically amplify regions of: SIX6 in Foc race 1, SIX1 gene in TR4, SIX8 in subtropical race 4, SIX9/SIX10 in Foc VCG 0121, and SIX13 in Foc VCG 0122. These assays include simplex and duplex PCRs, with additional restriction digestion steps applied to amplification products of genes SIX1 and SIX13. Assay validations were conducted to a high international standard including the use of 250 Fusarium spp. isolates representing 16 distinct Fusarium species, 59 isolates of F. oxysporum, and 21 different vegetative compatibility groups (VCGs). Tested parameters included inter and intraspecific analytical specificity, sensitivity, robustness, repeatability and reproducibility. The resulting suite of assays is able to reliably and accurately detect R1, STR4, TR4 as well as two VCGs (0121 and 0122) causing Fusarium wilt in bananas

Theoretical design of stable small aluminium-magnesium binary clusters

We explore in detail the potential energy surfaces of the AlxMgy (x, y = 1–4) systems as case studies to test the utility and limitations of simple rules based on electron counts and the phenomenological shell model (PSM) for bimetallic clusters. We find that it is feasible to design stable structures that are members of this set of small Al–Mg binary clusters, using simple electron count rules, including the classical 4n + 2 Hückel model, and the most recently proposed PSM. The thermodynamic stability of the title compounds has been evaluated using several different descriptors, including the fragmentation energies and the electronic structure of the systems. Three stable systems emerge from the analysis: the Al4Mg, Al2Mg2 and Al4Mg4 clusters. The relative stability of Al4Mg is explained by the stability of the Al42- subunit to which the Mg atom donates its electrons. Here the Mg2+ sits above the aromatic 10 π-electron Al42- planar ring. The Al2Mg2 and Al4Mg4 clusters present more complicated 3D structures, and their stabilities are rationalized as a consequence of their closed shell nature in the PSM, with 10 and 20 itinerant electrons, respectively

Uso de residuos de café como biosorbente para la remoción de metales pesados en aguas residuales

This article shows a review of the different waste from the process and consumption coffee, used as adsorbent material in the biosorption of the heavy metal of aqueous solutions. In the first instance, some peculiarities of biosorption are outlined, such as the capturing pollutants mechanisms, kind of adsorbent materials including those from coffee, as well as the variables that control the process. In a second instance, different investigations are carried out in relation to biosorption, in which chemical kinetics was developed to assessment of heavy metals removal rates, and adsorption isotherms to determine adsorption rates or capacities with thermally or chemically modified coffee waste. It can then be noted that many authors have found competitive advantages over the use of waste such as pulp,  husks, mucilage, spend grain, among others, compared to conventional adsorbents, since their physicochemical properties make them excellent ion exchangers with metals heavy, are of high abundance due to the agricultural vocation of our country and the high  coffee consumption  that is presented nationally and internationally, in addition to its low cost and ease in handling and treatment, concluding then that these materials present a future promising in the treatment of liquid effluents with heavy metals.El presente artículo presenta una revisión de los diferentes residuos  del beneficio y consumo de café, usados como material adsorbente en la biosorción de metales pesados de soluciones acuosas. Se esboza en primera instancia particularidades de la biosorción, como  los mecanismos de captura de los contaminantes, tipos de materiales adsorbentes, entre ellos los provenientes del café, como las variables que controlan el proceso. En una segunda instancia se plasman investigaciones en relación a la biosorción, en las que se desarrollaron cinéticas químicas para evaluar velocidades de remoción de los metales pesados, e isotermas  para determinar tasas o capacidades de adsorción con los residuos de café modificados térmica o químicamente. Se puede señalar  que muchos autores han encontrado ventajas competitivas frente al uso de residuos café como la pulpa, borra, mucílago, entre otros, en comparación con adsorbentes convencionales, debido a su propiedades fisicoquímicas los convierten en unos excelentes intercambiadores iónicos , son de alta abundancia debido a la vocación agrícola del  país y al  alto consumo del café a nivel nacional e internacional, además de su bajo costo y facilidad de manejo y tratamiento, concluyéndose entonces que dichos materiales presentan un futuro promisorio en el tratamiento de efluentes líquidos

Los medios de comunicación: representación de la variedad dialectal y cultural de Colombia e instrumento pedagógico para la enseñanza-aprendizaje del español como lengua extranjera

El documento da razón de los avances del proyecto de investigación Caracterización de las variedades del español de Colombia y su efecto en los estudios del español como lengua extranjera a partir de un corpus que da cuenta de las zonas dialectales del país, que se espera se convierta en material didáctico para la enseñanza del español como lengua extranjera. El interrogante en torno al cual se desarrolla la propuesta es: ¿cuáles son las variedades lingüísticas del español de Colombia que transmiten los medios de comunicación y de qué forma pueden contribuir en el diseño de material didáctico para la enseñanza-aprendizaje del español como lengua extranjera? La identificación de las variedades del español de Colombia, se realizó a partir del método diferencial contrastivo de los niveles léxico-semántico, fonéticofonológico, morfosintáctico y pragmático de la lengua, con los principales medios de comunicación;prensa, radio y televisión. El corpus se seleccionó teniendo en cuenta la propuesta de clasificación dialectal de Colombia, del profesor José Joaquín Montes

Convivencia escolar en relación con la formación ciudadana en el aula, de los estudiantes del grado décimo de la institución educativa Técnico Mariscal Sucre (sede José Norbey Grajales) en el municipio de Miranda, Cauca.

Maestría en Educación desde la Diversidad, Facultad de Ciencias Sociales y Humanas.El presente trabajo expone los hallazgos encontrados en la investigación que tuvo como objetivo comprender la convivencia escolar en relación con la formación ciudadana, en los estudiantes del grado décimo de la Institución Educativa Técnico Mariscal Sucre, ubicada en el municipio de Miranda al norte del departamento del Cauca. Para el desarrollo de la investigación se trazó un diseño metodológico basado en un enfoque mixto, lo que posibilitó la recolección y el análisis de datos cuantitativos por medio de la aplicación del test de Convivencia escolar, y cualitativos obtenidos mediante una entrevista semiestructurada desarrollando las categorías de análisis convivencia escolar y formación ciudadana. Se obtuvo como resultado que los estudiantes relacionan la convivencia con la comunicación y los valores humanos como el respeto por el otro; así mismo, posicionan a la familia como agente fundamental en su formación como ciudadanos

Strain Effects on the Oxidation of CO and HCOOH at Au-Pd Core-Shell Nanoparticles

The mechanism of CO and HCOOH electrooxidation in an acidic solution on carbon-supported Au–Pd core–shell nanoparticles was investigated by differential electrochemical mass spectrometry and in situ Fourier transform infrared (FTIR) spectroscopy. Analysis performed in nanostructures with 1.3 ± 0.1 nm (CS1) and 9.9 ± 1.1 nm (CS10) Pd shells provides compelling evidence that the mechanism of adsorbed CO (COads) oxidation is affected by structural and electronic effects introduced by the Au cores. In the case of CS10, a band associated with adsorbed OH species (OHads) is observed in the potential range of CO oxidation. This feature is not detected in the case of CS1, suggesting that the reaction follows an alternative mechanism involving COOHads species. The faradaic charge associated with COads oxidation as well as the Stark slope measured from FTIR indicates that the overall affinity and orbital coupling of CO to Pd are weaker for CS1 shells. FTIR spectroscopy also revealed the presence of HCOOads intermediate species only in the case of CS1. This observation allowed us to conclude that the higher activity of CS10 toward this reaction is due to a fast HCOOads oxidation step, probably involving OHads, to generate CO2. Density functional theory calculations are used to estimate the contributions of the so-called ligand and strain effects on the local density of states of the Pd d-band. The calculations strongly suggest that the key parameter contributing to the change in mechanism is the effective lattice strain

Resistencia a la corrosión de recubrimientos de nitruros metálicos depositados sobre acero AISI M2

In this work the corrosion behavior of zirconium nitride (ZrN), titanium nitride (TiN), chromium nitride (CrN), niobium nitride (NbN) and tantalum nitride (TaN) films deposited on commercial AISI M2 steel using unbalanced magnetron system (UBM) was investigated. The corrosion resistance was evaluated by testing electrochemical impedance spectroscopy (EIS) on a 3% solution of NaCl, changing the test time from 1 h to 7 d. The higher resistance to corrosion was obtained for NbN and ZrN films when these materials were deposited in the lower unbalanced configuration of UBM system. The coatings show degradation with the immersion time due to the microstructure defects, which become diffusion channels so that the corrosive solution can react with the substrate surface. Corrosion mechanisms in the coatings produced are discussed in this research.En este trabajo se estudia el comportamiento frente a la corrosión de películas de nitruro de zirconio (ZrN), nitruro de titanio (TiN), nitruro de cromo (CrN), nitruro de niobio (NbN) y nitruro de tantalio (TaN) depositadas sobre acero para herramientas AISI M2 mediante la técnica de sputtering con magnetrón desbalanceado (UBM). La resistencia a la corrosión fue evaluada con ensayos de espectroscopía de impedancia electroquímica (EIS) en una solución al 3% de NaCl variando el tiempo de ensayo desde 1 h hasta 7 d. En general, los mejores resultados de resistencia a la corrosión se presentaron en las películas de ZrN y NbN cuando son producidas en la configuración de menor bombardeo iónico en un sistema UBM. Los recubrimientos muestran degradación en el tiempo de ensayo debido a los defectos presentes en su microestructura, que se convierten en canales de difusión por los que la solución corrosiva llega a la superficie del sustrato. Los mecanismos de corrosión para los recubrimientos producidos son discutidos en esta investigación

Metabolic syndrome components and their response to lifestyle and metformin interventions are associated with differences in diabetes risk in persons with impaired glucose tolerance

AIMS: To determine the association of metabolic syndrome (MetS) and its components with diabetes risk in participants with impaired glucose tolerance (IGT), and whether intervention-related changes in MetS lead to differences in diabetes incidence. METHODS: We used the National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATP III) revised MetS definition at baseline and intervention-related changes of its components to predict incident diabetes using Cox models in 3234 Diabetes Prevention Program (DPP) participants with IGT over an average follow-up of 3.2 years. RESULTS: In an intention-to-treat analysis, the demographic-adjusted hazard ratios (95% confidence interval) for diabetes in those with MetS (vs. no MetS) at baseline were 1.7 (1.3-2.3), 1.7 (1.2-2.3) and 2.0 (1.3-3.0) for placebo, metformin and lifestyle groups, respectively. Higher levels of fasting plasma glucose and triglycerides at baseline were independently associated with increased risk of diabetes. Greater waist circumference (WC) was associated with higher risk in placebo and lifestyle groups, but not in the metformin group. In a multivariate model, favourable changes in WC (placebo and lifestyle) and high-density lipoprotein cholesterol (placebo and metformin) contributed to reduced diabetes risk. CONCLUSIONS: MetS and some of its components are associated with increased diabetes incidence in persons with IGT in a manner that differed according to DPP intervention. After hyperglycaemia, the most predictive factors for diabetes were baseline hypertriglyceridaemia and both baseline and lifestyle-associated changes in WC. Targeting these cardiometabolic risk factors may help to assess the benefits of interventions that reduce diabetes incidence