Search

In the present work, the enhancement in the efficiency of commercial solar cells through the use of Al2O3/ SiNPs multilayer antireflecting coating, is reported. The Al2O3 coatings were deposited by the atomic layer deposition technique, while the silicon nanoparticles were synthesized using a water-dispersible methodology. Based on photoluminescence and absorbance studies of the SiNPs, the underlying mechanism for this improvement can be attributed to the luminescent down-shifting effect. Thermoluminescence studies were achieved to confirm the formation of the Al2O3 layer. The thickness of the Al2O3 thin films were determined by spectroscopic ellipsometry in a range of 25 to 30 nm, while a SiNPs size of approximately 3 nm was obtained using dynamic light scattering method. The coatings of Al2O3 with SiNPs nanoparticles were deposited over solar cells to study their efficiency enhancement. Under a simulated one-sun illumination, coated solar cells achieved an enhancement of 6.74 mA/cm2, in short-circuit current density; while a 54.9% in power conversion efficiency increase was achieved, relative to those obtained for a pristine cell. The results show that the efficiency of solar cells can be significantly increased by combining the downshifting effect of the Si nanoparticles and the antireflective properties of the Al2O3 films. [ABSTRACT FROM AUTHOR]

Badlands are dynamic landforms that cause soil loss over extensive areas. In this study, we analyze recent sediment mobilization in a badland area by using a novel approach that integrates fallout 137Cs and optically stimulated luminescence (OSL). We assess how erosion and sediment storage operate over the Tepezalá volcano, a tephra cone located in central Mexico. We analyzed a set of sediment samples extracted from the surface of an altitudinal sequence with different land uses to explore how landscape management practices relate to erosion and, depth profiles from local sinks, to detect patterns of sediment mobilization and sedimentation. We compared 137Cs and OSL results with reference values to evaluate whether erosion or deposition is predominant and to assess how deep the erosive processes in the landscape are. Results from fallout 137Cs values indicate that in those badlands with implemented actions to mitigate erosion, sediment is retained. The high luminescence values show that the edaphic soil has been flushed away, and subsoil crops out in some of the sampled sites. For the case of depth profiles, maximum values of 137Cs coincide with high luminescence values, suggesting that in such sites, the sediment was mobilized during rapid incision episodes that caused widespread erosion of the landscape. We detected at least three episodes of rapid incision in 10 years of sediment record. We propose that using 137Cs and OSL together can provide valuable information of the sediment transport in settings dominated by fast erosion as do occur for the case of badlands. [ABSTRACT FROM AUTHOR]

Monogenetic structures located at the southern and western ends of the Chichinautzin volcanic field (Trans-Mexican Volcanic Belt, Central Mexico) yield 40Ar/ 39Ar ages ranging from 1.2 Ma in the western portion of the field to 1.0–0.09 Ma in the southern portion, all of which are older than the <0.04 Ma age previously established for the entire volcanic field. These new ages indicate: (1) an eruption rate of 0.47 km 3/kyr, which is much lower than the 11.7 km 3/kyr previously estimated; (2) that the Chichinautzin magmatism coexisted with the Zempoala (0.7 Ma) and La Corona (1.0 Ma) polygenetic volcanoes on the southern edge of Las Cruces Volcanic Range (Trans-Mexican Volcanic Belt); and confirm (3) that the drainage system between the Mexico and Cuernavaca basins was closed during early Pleistocene forming the Texcoco Lake. Whole-rock chemistry and Sr, Nd, and Pb isotopic data indicate heterogeneous magmatism throughout the history of Chichinautzin activity that likely reflects variable degrees of slab and sediment contributions to the mantle wedge, fractional crystallization, and crustal assimilation. Even with the revised duration of volcanism within the Chichinautzin Volcanic Field, its eruption rate is higher than most other volcanic fields of the Trans-Mexican Volcanic Belt and is comparable only to the Tacámbaro-Puruaran area in the Michoacán-Guanajuato Volcanic Field to the west. These variations in eruption rates among different volcanic fields may reflect a combination of variable subduction rates of the Rivera and Cocos plates along the Middle America Trench, as well as different distances from the trench, variations in the depth with respect to the subducted slab, or the upper plate characteristics. [ABSTRACT FROM AUTHOR]

Newborn male with convulsive crisis from the third day of life. Analysis and complementary examination, EEG excepted, were normal. After the 40th day of life, no further crisis were observed. Clinical evolution and psychomotor development were normal. Anamnesic findings: 13 members in five generations presented new born conculsions. No psychomotor alterations in the development were observed in all of them, excepted one. An early knowledge of this clinical picture, already described in six families, may avoid dangerous clinical examinations as well as a prolonged anticonvulsive treatment. The mode of inheritance is dominant autosomial.

Clinical features of a girl with mosaic 9-trisomy (46,XX/47,XX, + 9) are described. Trisomy was identified by means of G bands. Unusual spine, ribs and CNS abnormalities were observed. A comparison with 14 previous by described cases is made.