Glass-Transition Dynamics of Mixtures of Linear Poly(Vinyl Methyl Ether) with Single-Chain Polymer Nanoparticles: Evidence of a New Type of Nanocomposite Materials

Single-chain polymer nanoparticles (SCNPs) obtained through chain collapse by intramolecular cross-linking are attracting increasing interest as components of all-polymer nanocomposites, among other applications. We present a dielectric relaxation study on the dynamics of mixtures of poly(vinyl methyl ether) (PVME) and polystyrene (PS)-based SCNPs with various compositions. Analogous dielectric measurements on a miscible blend of PVME with the linear precursor chains of the SCNPs are taken as reference for this study. Both systems present completely different behaviors: While the blend with the linear precursor presents dynamics very similar to that reported for PVME/PS miscible blends, in the PVME/SCNP mixtures there are an appreciable amount of PVME segments that are barely affected by the presence of SCNPs, which nearly vanishes only for mixtures with high SCNP content. Interestingly, in the frame of a simple two-phase system, our findings point towards the existence of a SCNP-rich phase with a constant PVME fraction, regardless of the overall concentration of the mixture. Moreover, the dynamics of the PVME segments in this SCNP-rich phase display an extreme dynamic heterogeneity, a signature of constraint effects.This research was funded by Eusko Jaurlaritza project code: IT-654-13 and the Ministerio de Economia y Competitividad project code: MAT2015-63704-P (MINECO/FEDER, UE)

EL GÉNERO CORCHORUS (TILIACEAE) EN MÉXICO

The genus Corchorus L. belongs to the family Tiliaceae (sensu Cronquist, 1981) and includes an estimated 100 species worldwide.Most are herbaceous and occur mainly inpantropical regions. In America, there are 10species currently recorded (Martínez, 1981)and in Mexico seven, of which C. aestuansL., C. hirtus. L., C. orinocensis Kunth, and C. siliquosus L. are native to America, Ccapsularis L. and C. olitorius L. are nativeto Asia and C. trilocularis L., to Africa. Asynopsis of the genus in Mexico is presented, including a key to species, descriptionsdistribution and ecological information, aswell as common names and uses.El género Corchorus L. es el único integrante de la familia Tiliaceae (sensu Cronquist,1981) con especies de hábito herbáceo, conaproximadamente 100 especies y de distribución mundial, sobre todo en las regionespantropicales. En América, se han registrado alrededor de 10 especies (Martínez,1981); en México existen siete especies, delas cuales C. aestuans L., C. hirtus L., C.orinocensis Kunth y C. siliquosus L., sonnativas de América; C. capsularis L., y C.olitorius L., son originarias de Asia y C.trilocularis L., procede de África. Se presenta una sinopsis del género para México,incluyendo una clave para determinación de especies, descripciones, datos de distribución y ecológicos, así como nombrescomunes y usos

The Current Population of the Plains Tortoise, Gopherus flavomarginatus Legler, 1959 (Reptilia: Testudinidae) in the Mapimi Biosphere Reserve, Durango, Mexico

La tortuga llanera o tortuga del Bolsón es la especie emblema de la Reserva de la Biosfera Mapimí. La IUCN la considera especie en peligro crítico, la CITES como amenazada y la NOM-059-SEMARNAT-2010 la cataloga en peligro de extinción. Este estudio tiene el objetivo de describir las causas antropogénicas y naturales sobre el declive demográfico de esta especie. El enfoque utilizado fue cualitativo con los niveles de profundidad exploratorio y descriptivo a fin de destacar el estatus de especie endémica, amenazada, el hábitat y aspectos generales bióticos; así como los distintos factores antropogénicos y naturales que afectan la población. Los hallazgos muestran que los factores históricos como la cacería, comercio ilegal, fragmentación y pérdida del hábitat, competencia de la ganadería por el forraje, depredadores naturales, baja variabilidad genética, sequía y desbalance hídrico han sido determinantes sobre el decremento poblacional. La condición actual de la tortuga llanera se encuentra confinada en seis regiones de los estados de Coahuila, Durango y Chihuahua. La población total se compone de tan solo 2 000 individuos al interior de la Reserva y 500 fuera de ella. Ante esta crítica situación, distintas organizaciones internacionales e instituciones gubernamentales han llevado a cabo la creación de sitios protegidos, a fin de evitar la pérdida total de la especie y mantener sus funciones en el ecosistema.The plains tortoise or Bolson tortoise is the emblematic species of the Mapimi Biosphere Reserve. The IUCN considers it a critically endangered species, the CITES as a threatened species, and according to NOM-059-SEMARNAT-2010 it is classified as an endangered species. This study aims to describe the anthropogenic and natural causes of the demographic decline of this species. The approach used was qualitative with exploratory and descriptive depth levels in order to highlight the status of endemic and threatened species, the habitat and general biotic aspects; as well as the different anthropogenic and natural factors that affect the population. The findings show that the historical factors such as hunting, illegal trade, habitat fragmentation and loss, livestock competition for forage, natural predators, low genetic variability, drought and water imbalance have been determining factors in the population decline. The current condition of the plains turtle is confined to six home ranges in the states of Coahuila, Durango and Chihuahua. The total population is made up of only 2,000 individuals inside the Reserve and 500 outside it. Faced with this critical situation, different international organizations and government institutions have carried out the creation of protected sites, in order to avoid the total loss of the species and maintain its functions in the ecosystem

Variation of the phenolic composition and a-glucosidase inhibition potential of seeds, soaked seeds, and sprouts of four wild forms and four varieties of common bean (Phaseolus vulgaris)

The determination of the changes in the composition of bioactive phenolic compounds of germinating seeds which accumulate high levels of these compounds could contribute to the understanding of the germination mechanism and the development of markers for the selection of plant genotypes. In the current study, the changes in the phenolic composition and a-glucosidase inhibition activity, taking place during the germination of four wild forms and four varieties of common bean (Phaseolus vulgaris L.) from Durango Mexico, were determined. A total of 66 phenolic compounds (19 phenolic acids, 18 isoflavones, 18 flavonol glycosides, 3 flavonol aglycones, 3 flavones, 2 dihydroflavonoids, 2 chalcones and one non-identified type) were found by HPLC-DAD, which were differentially accumulated by the seeds, 24 h-soaked seeds, and 4 day-sprouts of each genotype. The accumulation of the flavonol aglycones, myricetin, quercetin and kaempferol was distinctive of the wild seeds. Soaking not only caused leaching and degradation but also triggered the synthesis of new phenolic compounds whereas germination diversified the composition of isoflavones and flavonol glycosides. The seeds of all genotypes analyzed were important inhibitors of a-glucosidase, improving their potential after soaking and germination. The results suggested that the structure rather than the concentration of the flavonoids and phenolic acids determined the inhibitory potential of a-glucosidase of samples. The principal component analysis and cluster analysis revealed HPLC-DAD phenolic profiles as genotype-specific chemomarkers at any of the states (seeds, soaked seeds, and sprouts). The results have wide implications on agronomy and food quality

LA RUTA DEL MEZCAL EN LA NUEVA VIZCAYA

Los hallazgos recientes de la elaboración del mezcal parecen indicar que ya formaba parte de la cultura precolombina tlaxcalteca, entre esos hallazgos se encuentran restos arqueológicos de la cerámica y vestigios de los hornos donde se hacia el cocimiento de las piñas del agave, y de estructuras para el machacado, fermentación y destilado del mosto. La destilación con alambiques llegó a América, con los conquistadores españoles. El mezcal fue catalogado como bebida prohibida, por órdenes de la Corona Española su producción fue considerada ilegal. La autorización para el libre consumo del aguardiente se da el 9 de diciembre de 1796 por órdenes del entonces virrey de la Nueva España, Revillagigedo. En los albores del siglo XIX, en el periodo de 1800 a 1804, se autoriza la fabricación de mezcal y el establecimiento de sitios con licencia para la venta del mezcal en la ciudad de Durango, a fin de recabar suficientes impuestos para obras destinadas a diversas funciones públicas. La producción de mezcal en el estado de Durango es una actividad eminentemente artesanal, con algunas adecuaciones técnicas, pero conservando en esencia su forma de producción apegada a los sistemas tradicionales

ALGUNAS CONSIDERACIONES DEL MEZCAL EN EL MUNICIPIO DE NOMBRE DE DIOS, DURANGO, MÉXICO.

Artículo de Investigació

The Relationship between Learning Potential in Preschool Children and their Cognitive Abilities

Learning potential can be used to assess and provide direction for action in diverse populations in modern educational settings. This study examined the relationship between the EHPAP dynamic evaluation scale and cognitive abilities (linguistic development, specific cognitive abilities, and executive functioning) in typically developing preschool children. Linear regression models indicated that children’s cognitive abilities formed part of the prediction of their independent performance in tasks before and after mediation. The abilities that formed part of the predictions were related to general linguistic development, specific cognitive functions, and executive functioning. Age as a predictive factor only contributed to verbal planning. This study examined the contribution of these variables in different EHPAP scales

El género Corchorus (Tiliaceae) en México

The genus Corchorus L. belongs to the family Tiliaceae (sensu Cronquist, 1981) and includes an estimated 100 species worldwide. Most are herbaceous and occur mainly in pantropical regions. In America, there are 10 species currently recorded (Martínez, 1981) and in Mexico seven, of which C. aestuans L., C. hirtus. L., C. orinocensis Kunth, and C. siliquosus L. are native to America, C. capsularis L. and C. olitorius L. are native to Asia and C. trilocularis L., to Africa. A synopsis of the genus in Mexico is presented, including a key to species, descriptions, distribution and ecological information, as well as common names and uses.El género Corchorus L. es el único integrante de la familia Tiliaceae (sensu Cronquist, 1981) con especies de hábito herbáceo, con aproximadamente 100 especies y de distribución mundial, sobre todo en las regiones pantropicales. En América, se han registrado alrededor de 10 especies (Martínez, 1981); en México existen siete especies, de las cuales C. aestuans L., C. hirtus L., C. orinocensis Kunth y C. siliquosus L., son nativas de América; C. capsularis L., y C. olitorius L., son originarias de Asia y C. trilocularis L., procede de África. Se presenta una sinopsis del género para México, incluyendo una clave para determinación de especies, descripciones, datos de distribución y ecológicos, así como nombres comunes y usos

NEW RECORDS OF CORCHORUS (TILIACEAE) FOR MEXICO

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