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In this work, we report metals concentrations in 80 PM10 samples collected at four sites in the Mexico City Metropolitan Area (MCMA): Tlalnepantla (NE), Xalostoc (NE), Merced (C), and Pedregal (S), during the dry/cold season (October to January) for the 2004–2014 period. Mean PM10 mass concentration (66.1 µg m−3) significantly exceeds the annual mean air quality guidelines recommended by the World Health Organization. The statistical analysis of concentration data and meteorological parameters allows us to recognize the importance of wind intensity speed (Wsp) and wind direction conditions in the enrichment of PM concentrations. The proximity and magnitude of the emitting source is also relevant for PM concentration. Such conditions favored that higher metal concentration was recognized at the north of the studied area. By means principal component analysis (PCA) was difficult to identify the groups of metals associated with specific sources (anthropogenic and geogenic) given the high complexity of the study area and the long period of time evaluated. Metal concentration trend shows an important positive trend for Pt, V and Cr, while PM10, Ni, Cu, Ag and Sb show a trend of moderate increase. In contrast, Pb and Co registered a strong percentage reduction, while Hg, Mn, As and Cd show a slight reduction, probably resulting from the implementation of regulatory measures and influenced by urban changes associated at the north of the studied area. The results of this research provide information that should be considered for evaluating the impact of anthropogenic sources and applying regulatory measures to control emissions.

The application of Sb, Pt and Hg in the development of new strategic technologies has increased significantly in recent years. This study evaluates the impact of vehicular traffic on the rise in emission of Sb, Pt and Hg in the atmospheric environmen of Mexico City and their correlation to Co, Cr, Cu, Ni, Pb, V and Zn. Ficus benjamina leaves were collected as biomonitor of atmospheric metals deposited in areas exposed to heavy vehicular traffic. High enrichment factor values (metal(loid) concentration/background values) were calculated: 146 (Sb), 52.8 (Pb), 29.7 (Pt) and 25.1 (Cr). Enrichment factors of Ni, Zn, Co, V, Cu and Hg decrease in that order and are

Platinum (Pt) concentrations in PM2.5 were evaluated by means of inductively coupled plasma mass spectrometry (ICP-MS) to evaluate the spatial and temporal behavior and to assess trends. Samples we...

In this study, atmospheric mercury concentration in airborne particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM2.5) was analyzed by ICP-MS. Samples were collected in the Mexico City Metropolitan Area (MCMA), during 2013, in five locations, Northwest, Northeast (NE), Central, Southwest and Southeast, along three seasons: dry warm, rainy, and dry cold (DC). It can be observed that NE shows the highest mercury concentration (p

The Mexico City Metropolitan Area (MCMA) was the object of a chemical elemental characterization (Ti, V, Cr, Mn, Co, Ni, Cu, Mo, Ag, Cd, Sb, Pb, La, Sm, Ce, and Eu) of PM2.5 collected during 2013 and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Sampling campaigns were carried out at five locations simultaneously—northwest, northeast, center, southwest, and southeast—during dry-warm season (April), rainy season (August), and dry-cold season (November). By means of enrichment factor (EF) and principal component analysis (PCA), it was possible to attribute the analyzed elements to geogenic and anthropogenic sources, as well as to identify a group of elements with mixed provenance sources. The highest concentrations for most metals were found in northwest and northeast, and during dry-warm (DW), confirming the trend observed in PM2.5 samples collected in 2011. Despite similarities between 2011 and 2013, an increase of 17% in PM2.5 mass concentration was observed, mainly attributable to geogenic sources, whereby the importance of wind intensity to the impact of emission sources is highlighted. The effect of wind intensity was revealed, by means of polar plots, as the controlling mechanism for this increase. This allowed us to conclude that high-speed episodes (5 m s−1) were responsible for raising geogenic metal concentrations rather than wind direction.

During 2003, 2007, 2008 and 2010, bat assemblages were studied at different dry valleys in Guatemala. Ten individuals of Choeronycteris mexicana (7 females and 3 males) were captured almost exclusively during the dry season. Pollen of columnar cacti (Stenocereus pruinosus and Pilosocereus leucocephalus) and Ceiba aesculifolia were found in samples recovered from hair. Remains of insects were recovered from feces samples of one individual. Reproductive females and a juvenile were captured between March and June of the different years. The captures coincided with the blooming of columnar cacti flowers, and with the presence of Leptonycteris yerbabuenae. Our data suggest that C. mexicana is a seasonal visitant at sub-humid biological corridor in Guatemala.

The study of airborne metals in urban areas is relevant due to their toxic effects on human health and organisms. In this study, we analyzed metals including rare earth elements (REE) in particles smaller than 2.5 μm (PM2.5), collected at five sites around the Mexico City Metropolitan Area (MCMA), during three periods in 2011: April (dry-warm season, DW), August (rainy season, R), and November (dry-cold season, DC). Principal component analysis allowed identifying factors related to geogenic sources and factors related to anthropogenic sources. The recognition of the high impact of geogenic sources in PM2.5 is in agreement with the REE distribution patterns, which show similar behavior as those shown by igneous rocks, confirming the influence of the regional geogenic material. Metals associated to geogenic sources showed higher concentration (p 0.05) and no similar seasonal pattern among them. These unexpected results exposed outstanding information regarding the identification of different geogenic sources as the main contributors of metals in the atmospheric environment in the MCMA and highlighted the importance of meteorology in the spatial and seasonal metal patterns.

In this study, atmospheric mercury concentration in airborne particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM

The study of airborne metals in urban areas is relevant due to their toxic effects on human health and organisms. In this study, we analyzed metals including rare earth elements (REE) in particles smaller than 2.5 μm (PM

The goal of this study was to optimize methyl parathion (O,O-dimethyl-O-4-p-nitrophenyl phosphorothioate) degradation using a strain of Escherichia coli DH5α expressing the opd gene. Our results indicate that this strain had lower enzymatic activity compared to the Flavobacterium sp. ATCC 27551 strain from which the opd gene was derived. Both strains were assessed for their ability to degrade methyl parathion (MP) in a mineral salt medium with or without the addition of glucose either as suspended cells or immobilized on tezontle, a volcanic rock. MP was degraded by both strains with similar efficiencies, but immobilized cells degraded MP more efficiently than cells in suspension. However, the viability of E. coli cells was much higher than that of the Flavobacterium sp. We confirmed the decrease in toxicity from the treated effluents through acetylcholinesterase activity tests, indicating the potential of this method for the treatment of solutions containing MP.

COATLI is a new instrument and telescope that will provide 0.3 arcsec FWHM images from 550 to 920 nm over a large fraction of the sky. It consists of a robotic 50-cm telescope with a diffraction-limited imager. The imager has a steering mirror for fast guiding, a blue channel using an EMCCD from 400 to 550 nm to measure image motion, a red channel using a standard CCD from 550 to 920 nm, and an active optics system based on a deformable mirror to compensate static aberrations in the red channel. Since the telescope is small, fast guiding will provide diffraction-limited image quality in the red channel over a large fraction of the sky, even in relatively poor seeing. The COATLI telescope will be installed at the Observatorio Astronomico Nacional in Sierra San Pedro Martir, Baja California, Mexico, in 2016 and will initially operate with a simple interim imager. The definitive COATLI instrument will be installed in 2017. In this work we present the general optomechanical and control electronics design of COATLI.

Nowadays, hydrogen has a preponderant position among the potentially sustainable energy sources. Due to its power density, its storage is of main concern when considering a broad use in practical applications. Carbon nanotubes constitute promising candidates for the design and construction of hydrogen storage devices. This work explores the use of some procedures involving electrochemistry, aimed to bond atomic Ti on the outer surface of MWNTs. Each titanium atom has the potential of hosting two hydrogen molecules and relinquishing them by heating. Nevertheless, nanotubes are difficult to handle due to electrostatic charge and agglomeration, and in this context, two routes were tested as procedures to spread and stick nanotubes on an electrode: (1) a functionalization capable of attaching gold was tested in two forms, as either using 4 nm particles or a flat gold electrode. The fixation of Au particles was confirmed by HRTEM. (2) A simpler route that consisted on drying a CH2Cl2/nanotubes solution previously spread on a glassy carbon flat electrode. CH2Cl2was selected as the medium and TiCl4as the precursor for attaching atomic Ti to the nanotubes. The results revealed that hydrogen adsorption, estimated from voltamperometry, was five times higher on Ti-MWNTs than on bare nanotubes.

En la actualidad nos encontramos ante un aumento de problemas relacionados con el peso y la alimentación, caracterizados por la realización de conductas de riesgo asociados al desarrollo de Trastornos de la Conducta Alimentaria (TCA). La interiorización del modelo estético corporal trasmitido por los medios de comunicación, el cual es, en general, incompatible con unos parámetros antropométricos y fisiológicos saludables, ha sido asociada al desarrollo de dichas conductas de riesgo. Por lo anterior, uno de los objetivos en materia de prevención de TCA, es la utilización de estrategias que reduzcan los efectos negativos de la interiorización de los mensajes emitidos por los medios de comunicación masivos, como la alfabetización de medios.

This work shows the results of de investigations concerning Pt concentration in the environment of Mexico City, product of the impact of the use of catalytic converters in the urban area. This research was carried out by assessing Pt concentration in dust samples and PM2.5 collected in the metropolitan area of Mexico City. Dust samples were divided in “road dust” and “urban dust” according to vehicle traffic exposure. Pt concentration in road dust samples, exposed to high traffic density, range from 37.7 to 231 µg kg−1 (mean 112 µg kg−1), whereas Pt concentration found in urban dust, collected in areas with low traffic density, varied between 26.4 and 86.6 µg kg−1 (mean 57 µg kg−1). PM2.5 samples were collected in five sites of the urban area during three different seasons (dry-warm, rainy, dry-cold). Results do not show significant spatial or temporal variation. Pt concentration ranges from 1 to 79 pg m−3. The comparison of Pt concentration in dust and PM2.5 samples presented here, with data reported for other urban areas, as well as with data previously reported for PM10 collected in 1991 and 2003 for the metropolitan area of Mexico City, allows to conclude a significant increase of Pt in this urban environment.

COATLI will provide 0.3 arcsec FWHM images from 550 to 900 nm over a large fraction of the sky. It consists of a robotic 50-cm telescope with a diffraction-limited fast-guiding imager. Since the telescope is small, fast guiding will provide diffraction-limited image quality over a field of at least 1 arcmin and with coverage of a large fraction of the sky, even in relatively poor seeing. The COATLI telescope will be installed at the at the Observatorio Astron\'omico Nacional in Sierra San Pedro M\'artir, M\'exico, during 2016 and the diffraction-limited imager will follow in 2017., Comment: To appear in the proceedings of SPIE conference 9908 "Ground-based and Airborne Instrumentation for Astronomy VI". 9 pages