Data from one pair of urban–suburban (Tacubaya and Airport) andone pair of urban–rural (School of Mines and Plan Texcoco) temperature and humidity measuring stations were used to illustrate specific humidity(q) contrasts in Mexico City. Results show a marked seasonal variation of q from around 7·9 g kg−1 during the dry months to 10 g kg−1 in the wet season (May–October) on both urban and suburban sites. The mean monthly contrasts for this pair of stations, albeit small, show that the city air is somewhat drier during the first half of the year. Comparison of urban and rural q on an hourly basis shows that although urban air is more humid at night the reverse is true during the afternoon. Areal distribution of q shows two centres of maximum humidity over the city at night and a corresponding minimum during the afternoon. On average the urban–rural contrasts in q were found to be somewhat smaller than the estimated uncertainty. The above results are in agreement with mid‐latitude experience. © 1997 by the Royal Meteorological Society.

Bioclimatic conditions have been assessed for a large urban area located in the tropical highlands of central Mexico using the indices (in °C) of resultant temperature (RT) and effective temperature (ET). The welldeveloped heat island effect the city generates, reduces the number of nights categorized as cold (ET between 5 and 15° C) to cool (ET from 15 to 18.5° C). Most days fall in the cold to cool range and during the warm season (April to June) the bioclimate of Mexico City is mostly within the neutral (comfort) range. The effect of the nocturnal (to the west) and daytime (to the east of the town) heat island is noticeable in the central and northern sectors. The daytime heat island located in these regions, albeit small (urban air temperature 2-3° C greater than rural), compared with the nocturnal heat island intensity (9-10° C) still adds energy to the already heated afternoon urban air. ET values in the north and central sectors approach the threshold for comfort (ET of 25° C) during the warm months around noon. It is not surprising to find that as the nocturnal heat island has increased over the years as the city grew, so has the ET for the central district and indicating the dominating role of temperature in the ET index. Assessment of the diurnal cycle of bioclimatic conditions in downtown Mexico City by means of two empirical indices (effective temperature and thermopreferendum) throughout the years gave similar results to those obtained from the application of Fanger's predicted mean vote (PMV) model. An attempt has been made to characterize four bioclimatic zones in the capital city.

The present paper reports the behavior of gamma‐irradiated hybrid sol–gel coatings based on the copolymerization of 3‐glycydoxypropyltrimethoxysilane and tetra‐n‐propoxyzirconium applied onto aluminum alloy AA2024‐T3. Doses from 1 to 100 kGy were applied on undoped sol–gel coatings and coatings doped with hydrotalcite at 1% and 5%, w/w. The sol–gel coatings were deposited by using the dip‐coating method on an aluminum substrate with a final grinding of a 240‐grit. Scanning electron microscopy revealed that the hydrotalcite particles were heterogeneously dispersed at several micrometers in length. High irradiation doses on doped hydrotalcite coatings showed no improvement in the corrosion resistance of the films at longer immersion times in saline media obtained by electrochemical impedance spectroscopy. Differential scanning calorimetry showed that the gamma‐irradiated doses and the hydrotalcite content modify the thermal properties of the sol–gel coatings. X‐ray diffraction results revealed modification of the hydrotalcite crystallite size as a function of irradiation dose. Copyright © 2014 John Wiley & Sons, Ltd.

The kinetics of replacement of H 2 O by [Ru(NH 3 )pz] 2+ (pz = pyrazine) in [Fe(CN) 5 H 2 O] 3− have been studied in various concentrated electrolyte solutions and in various water-cosolvent mixtures, at 298 K. Salt and cosolvent effects can be rationalized taking into account specific medium effects on both the encounter complex formation process and the ligand-substitution process, once the encounter complex is formed. These effects in watercosolvent mixtures depend on the solvation of the reactants by the components of the mixture, as well as on the solvent-solvent interactions in these mixtures. Salt effects seem to be related to a primary salt effect as well as to the effect of the cations on the electronic density on the iron complex.

En este trabajo se explora la utilidad climática de las observaciones visuales del estado del cielo a nivel medio mensual, mediante la búsqueda de relaciones estadísticas de alto nivel de ajuste con la heliofanía diaria media mensual medida con el heliógrafo Campbell-Stokes, para 56 puntos de México durante el periodo 1951-1980. Se muestra que el modelo estadístico obtenido para todos los puntos y todos los meses tiene un nivel de ajuste mayor que agrupando los datos por meses, por tipos de climas o por cinturones de latitud. Este modelo es una herramienta útil para estimar las horas promedio mensual de brillo de sol en lugares de México durante sólo se cuente con observaciones de largo periodo del estado del cielo.