RESUMEN
Vanadium dioxide (VO2) undergoes a fully reversible first-order metal-insulator transition from the M1 monoclinic phase (P21/c) to a high-temperature tetragonal phase (P42/mnm) at around 68 °C. Modulation of the phase transition of VO2 by chemical doping is of fundamental and technological interest. Here, we report the synthesis of highly crystallized Fe-doped VO2 powders by a carbo-thermal reduction process. The impact of Fe doping on the structural and phase transition of VO2 is studied. The as-prepared Fe-doped VO2 samples crystallize in the M2 monoclinic form (C2/m), which is linked to segregation of the doping ions in the V2 zigzag chains. A large increase in the transition temperature to 134 °C is observed, which does correspond to a breakthrough in VO2-type thermochromic materials.
RESUMEN
Objective: To determine the history of dental caries and the need for dental treatment among visually disabled children between 6 and 12 years old attending special Schools in Chile during 2014. Material and method: Descriptive and observational cross-sectional study. The target population was children with visual disabilities from special schools in Chile. A clinical examination was performed to obtain a dmft/DMFT index and know the need for treatment. Two calibrated examiners performed the visual clinical examination, according to the WHO criteria. Additionally, clinically detectable enamel lesions on cavitated and non cavitated surfaces were recorded. The recorded data were analyzed using descriptive statistics. Results: Ninety-four children attending to seven special schools were examined. The average dmft index was 2.05 (SD+/-2.6) and DMFT index was 0.96 (SD+/-1.3). For 6 year olds, the dmft/DMFT index was 3/0, respectively. For 12 year olds, the dmft index was 0.17 and the DMFT index was 1.42. Caries prevalence was 56.3 percent From the total, 95 percent of children needed sealants, 50 percent needed at least one restoration of one face, and 29 percent restoration of 2 or more surfaces. As for enamel lesions, 34 percent of children had at least one non cavitated lesion and 48 percent of them had a cavitated lesion. Conclusion: History of dental caries is similar to that reported in the general population; however, there is a high need for preventive treatment. Therefore, it is necessary to conduct more research to clarify whether these patients have a higher cariogenic risk due to their visual impairment in order to establish effective promotional/ preventive strategies.
Objetivo: Determinar la historia de caries y la necesidad de tratamiento odontológico de niños con discapacidad visual entre 6-12 años, pertenecientes a Escuelas Especiales de Chile, el año 2014. Material y método: Estudio observacional descriptivo de corte transversal. Se examina-ron niños con discapacidad visual de escuelas especiales en Chile, según los criterios de la OMS, para obtener el ceod, COPD y la necesidad de tratamiento. Se registraron las lesiones de esmalte clínicamente detectables en superficies cavitadas y no cavitadas. Los resultados se analizaron mediante estadística descriptiva. Resultados: 94 niños fueron examinados, pertenecientes a 7 escuelas especiales. El ceod promedio fue 2,05 (SD +/- 2,6) y el COPD fue de 0,96 (SD +/- 1,3). A los 6 años el ceod/COPD fue de 3/0 respectivamente. A los 12 años el ceod fue 0,17 y COPD fue 1,42. La prevalencia de caries fue de 56,3 por ciento. El 95 por ciento necesita sellantes, el 50 por ciento necesita a lo menos una restauración de una cara, y el 29 por ciento una restauración de 2 o más superficies. En cuanto a las lesiones de esmalte, el 34 por ciento de los niños presentaban al menos una lesión no cavitada y un 48 por ciento de ellos tenían una lesión cavitada. Conclusión: La historia de caries es similar a lo descrito en la población general, sin embargo, existe una alta necesidad de tratamiento preventivo. Es necesario realizar más investigaciones que permitan esclarecer si poseen un mayor riesgo cariogénico debido a su alteración visual, para así establecer estrategias promocionales/preventivas efectivas.