Algunos indicadores del desarrollo del esquema de derivada de una función

El objetivo de esta investigación es caracterizar algunos indicadores del desarrollo del esquema de derivada en estudiantes de pos-secundaria. Usamos los niveles intra, inter y trans del desarrollo de un esquema propuestos por Piaget y García para caracterizar el uso flexible que los estudiantes hacen de la equivalencia lógica entre diferentes elementos matemáticos cuando resuelven un problema, como un indicador del desarrollo del esquema de derivada. Este indicador ayuda a explicar la transición entre los niveles inter y trans de desarrollo del esquema derivada.

La Validación Lingüística en los Principales Cuestionarios de Salud y Calidad de Vida

The goals of this article are to summarize the problems and solutions found in translating seven Health-Related Quality of Life (HRQOL) questionnaires from English into Spanish which have used a common international protocol based on back-translation techniques. The methodology used is based on the linguistic validation model including both the linguistic and the sociopragmatic equivalence. Five questionnaires from seven have obtained good results, not so two of them. Considering linguistic questions, there were more problems than good solutions on the lexical-semantic level. With respect to the sociocultural questions, there were more solutions than problems. The Spanish translated questionnaires still present deficiencies to be corrected, so both linguistic and sociocultural questions have to be studied more carefully in order not to allow differences between the translated versions and the source questionnaires.

Semivolatile and Volatile Compound Evolution during Pyrolysis and Combustion of Colombian Coffee Husk

Thermal characterization of coffee husk (Coffea arabica) from Colombian coffee has been studied. Different products, mostly volatile and semivolatile compounds, were analyzed, paying special attention to 16 polycyclic aromatic hydrocarbons (PAHs) classified by the United States Environmental Protection Agency (U.S. EPA) as priority pollutants, frequently used for checking toxicity in environmental samples. A fixed amount of raw material was exposed to different excess air ratios (λ = 0–2.33) and nominal temperature of 1123 K in a horizontal quartz reactor. The results show that coffee husk is a promising biomass for energetic exploitation with reduced formation of PAHs in a low air excess ratio. This implies reduction of carcinogenic potential in the limited presence of oxygen, demonstrated by calculating the carcinogenic potential (KE) for each experimental condition. Most volatile and semivolatile compounds followed different trends, with the oxygen presence prevailing their decomposition with increasing the air excess ratio.