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On a global scale, African dust is known as one of the major sources of mineral dust particles as they can be efficiently transported to different parts of the planet. Several studies have suggested that the Yucatán Peninsula could be influenced by such particles, especially in July, associated with the strengthening of the Caribbean low level jet. Although these particles have the potential to impact the local air quality significantly, as shown elsewhere (especially particulate matter, PM), the arrival and the impact of African dust into Mexican territory has not been quantitatively reported to date. Two short-term field campaigns were conducted to confirm the arrival of African dust onto the Yucatán Peninsula in July 2017 and July 2018 at the city of Merida atmospheric observatory (20.98N 89.64W). Aerosol particles were monitored at the ground level by different on-line and off-line sensors. Several PM2.5 and PM10 peaks were observed during both sampling periods, with a relative increase in the PM levels ranging between 200% and 500% with respect to the normal background. Given that these peaks were found to highly correlate with super micron particles and chemical elements typically found in mineral dust particles, such as Al, Fe, Si. and K, they are linked with African dust. This conclusion is supported by combining back trajectories with vertical profiles from radiosondes, reanalysis, and satellite images to show that the origin of the air masses arriving at Merida was the Saharan Air Layer (SAL). The good agreement found between the measured PM[sub 10] concentrations and the estimated dust mixing ratio content from MERRA-2 (Version 2 of the Modern-Era Retrospective analysis for Research and Applications) corroborates the conclusion that the degradation of the local (and likely regional) air quality in Merida is a result of the arrival of African dust. [ABSTRACT FROM AUTHOR]

Electrical caracterization was made using mesurements of Hall effect and isoterms curves I-V in layers of cuaternary system GaInAsSb grown by liquid phase epitaxy (LPE) thecnique on single GaSb:Te (100) substrate. The sign and carrier density were determined at room temperature. It was found samples are n-type and the calculated volume densities show strongly doped films. The curves I-V in a range from 75K to 300K, with silver contacs, they present Schottky barrier benhavior, with heights of the barriers around 0.4 eV at room temperature and decrese when the temperature lows. The ideality factors take values heigther than 1 when the temperature decrese. [ABSTRACT FROM AUTHOR]