Regional analysis of climate variability at three time scales and its effect on rainfed maize production in the Upper Lerma River Basin, Mexico

Rainy season use to be from May to September and actually is from June to September. Rainy season use to be from May to September and actually is from June to September. In the region, the most determinant factor for maize crop losses is the water deficit.This study explored climate variability in the Upper Lerma River Basin, State of Mexico, Mexico, at three timescales: annual (1960–2010), monthly (1980–2010) and seasonal (1980–2010). The effects of monthly and seasonal (2003–2010) variability on rainfed maize crops were also evaluated. The variables of rainfall, maximum temperature, minimum temperature and number of hailstorms were interpolated to generate monthly spatial-temporal series. Over a period of 51 years, the climate of the region shows an accumulative annual increase of 131 mm in rainfall and an increase of 0.8 and 0.74 °C in maximum and minimum temperature, respectively. In conclusion, significant changes in the climate variables were found at the three analyzed timescales. Seasonal climate changes were found to coincide with the most vulnerable stage or flowering period of maize; particularly, a shift in the rainfall pattern generates a water deficit that impacts production yield. Hailstorms have increased in frequency, yet their phase shift results in a lesser impact to maize during its most critical stage of development.This study was financed by the Basic Science research project, SEP-CONACYT “Mesoamerican Corn and Scenarios for Local development (El maíz473 mesoamericano y sus escenarios de desarrollo local), No. 130947. The authors also wish to thank the two anonymous reviewers and their comments for improving and restructuring the manuscript in order to highlight the results of this research

Continuous Drip Flow System to Develop Biofilm of E. faecalis

Purpose. To evaluate a structurally mature E. faecalis biofilm developed under anaerobic/dynamic conditions in an in vitro system. Methods. An experimental device was developed using a continuous drip flow system designed to develop biofilm under anaerobic conditions. The inoculum was replaced every 24 hours with a fresh growth medium for up to 10 days to feed the system. Gram staining was done every 24 hours to control the microorganism purity. Biofilms developed under the system were evaluated under the scanning electron microscope (SEM). Results. SEM micrographs demonstrated mushroom-shaped structures, corresponding to a mature E. faecalis biofilm. In the mature biofilm bacterial cells are totally encased in a polymeric extracellular matrix. Conclusions. The proposed in vitro system model provides an additional useful tool to study the biofilm concept in endodontic microbiology, allowing for a better understanding of persistent root canal infections

Dispersion of atmospheric coarse particulate matter in the San Luis Potosí, Mexico, urban area

"La contaminación atmosférica en áreas urbanas de México se ha convertido en un problema grave. Por ello, el estudio de la evolución espacial y temporal de las concentraciones del material particulado es un asunto importante. En el periodo de mayo de 2003 a abril de 2004 se recolectó un total de 188 muestras diarias con un equipo de alto volumen en el área urbana de San Luis Potosí, ubicada en la parte centro-norte de México, usando filtros de fibra de cuarzo. Se realizó una serie de experimentos de modelación numérica en el mismo periodo que las mediciones, para investigar las concentraciones de material particulado (PM) en dicha área urbana. Aunque hay una considerable variabilidad anual en la circulación atmosférica, el análisis de los resultados indica patrones de circulación estacionales preferenciales: vientos del suroeste en invierno y vientos del sureste en verano. Los altos valores de concentración de material particulado estuvieron estrechamente vinculados con características locales de la circulación atmosférica. El transporte neto de la zona industrial es una de las más importantes conclusiones de la investigación.""Atmospheric pollution in urban areas of Mexico has become a serious problem. The study of spatio-temporal evolution of concentrations of particulate matter is an important issue. A total of 188 samples were randomly collected at 24-hour running time within the period from May 2003 to April 2004 for the San Luis Potosí urban area, located in the central-north part of Mexico, using quartz fiber filters. A series of numerical modeling experiments were conducted for the same period of measurements to investigate particulate matter (PM) concentrations in the above-mentioned urban area. Although there is a considerable annual variability in the atmospheric circulation, the analysis of results indicates preferential seasonal circulation patterns: southwesterly winds during winter and southeasterly during summer. High concentration values of particulate matter were closely associated to local characteristics of the atmospheric circulation. A net transport from the industrial zone into the urban area is one of most important outcomes of the investigation.