ABSTRACT Urban dust is a reservoir of potentially toxic elements and particles of various sizes that represent a risk to human health, hence the importance of determining its characteristics. The objectives of this study were the identification of the sites of greatest contamination by potentially toxic elements, magnetic material and particle size in urban dust, as well as evaluating the influence that different types of public transport have on urban dust. Six primary roads were selected, based on constant vehicular traffic during the day, an average travel speed of 30 km/h, and circulation of a single type of public transport. The urban dust sample was taken in an area of 1 m2 on the asphalt strip. Potentially toxic elements, magnetic properties and particle size were analyzed. The urban dust of the roads of Mexico City had variable concentrations of Cr, Cu, Pb, V, Zn, PM10, PM2.5 and magnetic material. The elements with highest concentration in urban dust were Zn and Pb. The content of PM10 and PM2.5 in urban dust was 10 to 30 % of the total weight of the sample. The areas with the greatest accumulation are located at road crossings, roads near the airport and the industrial park.

RESUMEN El polvo urbano es un reservorio de elementos potencialmente tóxicos y de partículas de diversos tamaños que representan un riesgo para la salud humana, por lo cual es importante determinar sus características. Los objetivos de este estudio fueron: identificar los sitios de mayor contaminación por elementos potencialmente tóxicos, material magnético y tamaño de partícula del polvo urbano, así como evaluar la influencia de los diferentes tipos de transporte público en el polvo urbano. Seis vialidades primarias fueron seleccionadas con base en el tránsito vehicular constante durante el día, velocidad de desplazamiento promedio de 30 km/h y circulación de un solo tipo de transporte público. La muestra de polvo urbano se tomó en un área de un 1 m2 sobre la cinta asfáltica. Se determinaron tanto el contenido de elementos potencialmente tóxicos como las propiedades magnéticas y el tamaño de partícula. El polvo urbano de las vialidades de Ciudad de México tuvo concentraciones variables de Cr, Cu, Pb, V, Zn, PM10, PM2.5 y material magnético. Los elementos de mayor concentración en el polvo urbano fueron: Zn y Pb. El contenido de partículas PM10 y PM2.5 en el polvo urbano fue de 10 a 30 % del peso total de la muestra. Las áreas de mayor acumulación se ubican en cruces viales, vialidades cercanas al aeropuerto y el parque industrial.

Resumen Las fallas eléctricas en sistemas fotovoltaicos causan impactos negativos en la economía y la seguridad, reduciendo el desempeño del sistema y generando conexiones eléctricas indeseadas que pueden ser peligrosas para el usuario. Las fallas de línea a línea, conexión a tierra y circuito abierto, son algunas de las principales fallas eléctricas que se pueden presentar en un arreglo fotovoltaico. Este artículo propone una caracterización de los efectos que generan las tres fallas mencionadas en el desempeño del sistema fotovoltaico por medio de un análisis de los circuitos equivalentes y las curvas de voltaje-potencia (VP) que se obtienen frente a diferentes fallas, topologías en el arreglo, condiciones de temperatura y radiación solar. El método propuesto fue validado experimentalmente usando arreglos fotovoltaicos en condiciones reales y puede ser aplicado en trabajos futuros para desarrollar un algoritmo capaz de detectar y clasificar fallas eléctricas en arreglos fotovoltaicos.

Abstract Electric faults in photovoltaic (PV) systems cause negative economic and safety impacts, reducing their performance and making unwanted electric connections that can be dangerous for the user. Line-to-line, ground and open circuit faults, are three of the main faults that happen in a photovoltaic array system. This work proposes a characterization of the equivalent circuits and the voltage-power (VP) curves at the output of multiple PV arrays under different topological configurations and fault conditions to evaluate the effects of these three main faults on the performance of a photovoltaic array system, taking into account the influence of temperature and solar radiation. This work presents a validation of the characterization by measuring the output VP curves of a low-power photovoltaic array system under real outdoor conditions. This method can be useful in future works to develop low cost systems capable of detecting and classifying electric faults in photovoltaic array systems.

Abstract: The first diagnose of heavy metal (Cd, Cr, Cu, Fe, Mn, Ni and Pb) concentrations present in Chetumal, Mexico and its spatial distribution was carried out by analyzing 86 samples of urban dust through atomic absorption spectrophotometry. The assessment of the extent of pollution was undertaken by the use of the Mexican Residential Soil Guideline Values, the calculation of the contamination factor and the pollution load index. The results showed concentrations of heavy metals below the Mexican guidelines in the city, except for chromium and lead in a few samples. However, using the contamination factor the concentrations for chromium, lead and copper are exceeded in some samples. The map of pollution load index shows the areas requiring immediate attention from the decision makers.

Resumen: El primer diagnóstico de concentraciones de metales pesados (Cd, Cr, Cu, Fe, Mn, Ni y Pb) presentes en Chetumal, México y su distribución espacial se realizó analizando 86 muestras de polvo urbano usando espectrofotometría de absorción atómica. La evaluación del alcance de la contaminación se realizó usando los Valores de la Norma Mexicana para Suelo Residencial (NMSR), el cálculo del factor de contaminación y el índice de carga contaminante. Los resultados mostraron concentraciones de metales pesados por debajo de las normas mexicanas, excepto para el cromo y plomo en unas pocas muestras. Sin embargo, usando los índices de contaminación los límites para cromo, plomo y cobre se exceden en varias muestras. El mapa del índice de carga contaminante muestra las áreas que requieren atención inmediata por parte de los tomadores de decisiones.

ABSTRACT The maize production in Chiapas implies the decision to grow local or hybrid maize. The latter present higher yields characteristics, but demand more inputs, particularly those related to soil degradation, water pollution, genetic diversity and knowledge losses over local maize varieties. The objective of this research was to identify the criteria used by small maize farmers in the election of seed for sowing in the Villaflores and Villa Corzo municipalities (Chiapas). The data were gathered through semi-structured interviews with farmers’ participating in the ASERCA program and analyzed by percentages and frequencies. The hybrid maize is the most preferred variety by the small farmers in both municipalities, although some still prefer local maize (native) or bet on the cultivation of both due to use and customs reasons. The selectionof hybrid maizeseeds in both municipalities is based mainly on better yield characteristics, although in Villa Corzo, the selection of local varieties is due to their better resistance against pests and diseases. Additional criteria used to select the local seeds were: better lodging resistance, better moisture resistance, lower plant height, less seed rot and better drought tolerance. In local maize varieties, seed yield was considered an important factor in both municipalities, but a greater resistance against pests and diseases was only considered in Villa Corzo. The highest sale price was not an important consideration in neither of the two municipalities. Other criteria used to select the local seeds were better drought tolerance, seed lower cost, greater ear size, personal interest in conserving the local resource, better flavor and the possibility for the rotation of local varieties. The six wished characteristics of local maize varieties to be improved were: a lower plant height, a better yield, a better resistance to humidity and lodging, a greater grain weight, and a bigger size of ears and grains.

RESUMEN La producción de maíz en Chiapas implica la decisión de cultivar maíces locales o híbridos. Estos últimos, tienen rendimientos más altos, pero requieren mayor cantidad de insumos, asociados con la degradación de suelos, contaminación del agua, pérdida de diversidad genética y del conocimiento sobre las variedades locales. El objetivo de esta investigación fue identificar los criterios que usan los pequeños productores, en la selección del material genético, para la siembra de maíz en los municipios de Villaflores y Villa Corzo, Chiapas. Se realizaron entrevistas semi-estructuradas a productores participantes del programa ASERCA. El maíz híbrido presentó mayor preferencia en ambos municipios, aunque algunos productores prefirieron los maíces locales o cultivaron ambos, por razones de usos y costumbres. La selección de maíces híbridos en los dos municipios se hizo principalmente con base en el rendimiento, seguido de la mayor resistencia a plagas y enfermedades. Otros criterios empleados para elegir semillas híbridas fueron: mayor resistencia al acame, mayor resistencia a la humedad, menor altura a la planta, menor pudrición de semillas y mayor tolerancia a la sequía. En maíces locales, el rendimiento fue un parámetro de importancia en ambos municipios, pero la mayor resistencia a plagas y enfermedades fue solo considerada en Villa Corzo. Y el mejor precio de venta del grano no se consideró en ninguno de los dos municipios. Otros criterios empleados para seleccionar las semillas locales fueron: mayor tolerancia a la sequía, menor costo de la semilla, mayor tamaño de la mazorca, interés por conservar dicho material, mejor sabor y permitir la rotación de variedades locales. Las seis características deseables a mejorar en el maíz local fueron: una menor altura de planta, un mayor rendimiento, una mayor resistencia a la humedad y al acame, un mayor peso del grano, un mayor tamaño de mazorca y de granos.

Since 1984, Anopheles (Kerteszia) lepidotus has been considered a mosquito species that is involved in the transmission of malaria in Colombia, after having been incriminated as such with epidemiological evidence from a malaria outbreak in Cunday-Villarrica, Tolima. Subsequent morphological analyses of females captured in the same place and at the time of the outbreak showed that the species responsible for the transmission was not An. lepidotus, but rather Anopheles pholidotus. However, the associated morphological stages and DNA sequences of An. pholidotus from the foci of Cunday-Villarrica had not been analysed. Using samples that were caught recently from the outbreak region, the purpose of this study was to provide updated and additional information by analysing the morphology of female mosquitoes, the genitalia of male mosquitoes and fourth instar larvae of An. pholidotus, which was confirmed with DNA sequences of cytochrome oxidase I and rDNA internal transcribed spacer. A total of 1,596 adult females were collected in addition to 37 larval collections in bromeliads. Furthermore, 141 adult females, which were captured from the same area in the years 1981-1982, were analysed morphologically. Ninety-five DNA sequences were analysed for this study. Morphological and molecular analyses showed that the species present in this region corresponds to An. pholidotus. Given the absence of An. lepidotus, even in recent years, we consider that the species of mosquitoes that was previously incriminated as the malaria vector during the outbreak was indeed An. pholidotus, thus ending the controversy.

The morphologically similar taxa Anopheles calderoni, Anopheles punctimacula, Anopheles malefactor and Anopheles guarao are commonly misidentified. Isofamilies collected in Valle de Cauca, Colombia, showed morphological characters most similar to An. calderoni, a species which has never previously been reported in Colombia. Although discontinuity of the postsubcostal pale spots on the costa (C) and first radial (R1) wing veins is purportedly diagnostic for An. calderoni, the degree of overlap of the distal postsubcostal spot on C and R1 were variable in Colombian specimens (0.003-0.024). In addition, in 98.2% of larvae, seta 1-X was located off the saddle and seta 3-C had 4-7 branches in 86.7% of specimens examined. Correlation of DNA sequences of the second internal transcribed spacer and mtDNA cytochrome c oxidase subunit I gene (COI) barcodes (658 bp of the COI gene) generated from Colombian progeny material and wild-caught mosquitoes from Ecuador with those from the Peruvian type series of An. calderoni confirmed new country records. DNA barcodes generated for the closely related taxa, An. malefactor and An. punctimacula are also presented for the first time. Examination of museum specimens at the University of the Valle, Colombia, revealed the presence of An. calderoni in inland localities across Colombia and at elevations up to 1113 m.