0000000000335738
AUTHOR
Esther López
Characterization of Chemical Composition along the Molar Mass Distribution in Polyolefin Copolymers by GPC Using a Modern Filter-Based IR Detector
Summary Gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC), is the technique routinely used at high temperature to analyze the molar mass distribution in polyolefins. The distribution of comonomer along the molar mass distribution in a copolymer is a key microstructural feature that determines the macroscopic properties of the material, and thus, its range of possible applications and performance. The direct coupling of a modern filter-based infrared (IR) detector to a high temperature GPC instrument, by means of a heated flow-through cell, is here described. The analyses are carried out by recording the continuous IR absorbance chromatograms at selected …
Application of field portable EDXRF spectrometry to analysis of pigments of Levantine rock art
The results of the analyses of elemental composition of red and black pigments of Levantine rock art from La Saltadora rock shelters (Valltorta gorge, Castellon, Spain) are presented in this paper. Nondestructive analyses were carried out using a portable energy dispersive X-ray fluorescence (EDXRF) spectrometer developed for in situ analysis. The results revealed the strong presence of calcium in all the analyzed locations due to the contribution of the underlying calcareous bedrock and the overlying crust. Iron is the main element detected in red pigments and manganese in black pigments. Iron and calcium ratios have been found indicative of the degree of preservation of the pictorial laye…
Perceptions of Motivational Climate and Teachers' Strategies to Sustain Discipline as Predictors of Intrinsic Motivation in Physical Education
This study examined the relationship among pupils' perceptions of the motivational climate, pupils' perceptions of teachers' strategies to maintain discipline and pupils' intrinsic motivation in physical education. A sample of 2189 Spanish adolescents, ages 13 to 17 years, completed Spanish versions of the EPCM, SSDS, and IMI. Confirmatory factor analyses were carried out to confirm the factorial validity of the scales. Then, the relationship among the variables was explored through Structural Equation Modelling. The most important predictors of pupils' intrinsic motivation were the perceived mastery climate, and perceived teachers' emphasis on intrinsic reasons to maintain discipline. Perc…
Motivación, comportamiento de los alumnos y rendimiento académico
ResumenEn este trabajo se han analizado las relaciones entre el clima motivational, la motivacion intrinseca, el comportamiento de los alumnos y su rendimiento academico en educacion fisica. Para ello, 2189 adolescentes espanoles de 13 a 17 anos cumplimentaron cuestionarios sobre clima motivational de la clase, motivacion intrinseca y disciplina. Sus profesores valoraron el comportamiento de los alumnos y su rendimiento academico. Un Modelo de Ecuaciones Estructurales ha mostrado que el clima de aprendizaje, el interes/diversion y el esfuerzo/importancia predicen la disciplina; el clima de comparacion, la percepcion de competencia y la tension/presion predicen la indisciplina; el interes/di…
Percepción de las estrategias que emplean los profesores para mantener la disciplina, razones de los alumnos para ser disciplinados y comportamiento en educación física. (Perceived teachers’ strategies to sustain discipline, pupils’ reasons for being disciplined, and pupils’ behavior in physical education).
Este trabajo ha relacionado la percepcion de las estrategias de los profesores para la disciplina, las razones de los alumnos para ser disciplinados y su comportamiento en educacion fisica (EF). Participaron 2189 adolescentes de 13 a 17 anos, que respondieron cuestionarios sobre estrategias para mantener la disciplina, razones para la disciplina y disciplina-indisciplina en EF. La edad y el genero de los alumnos son variables diferenciadoras, mientras que la interaccion genero de los alumnos x genero de los profesores no aporta diferencias significativas. Los analisis de regresion han mostrado que las razones intrinsecas de los alumnos y de los profesores y las razones responsables y de pre…