José María Romero Rodríguez

Electrorheology of clay particle suspensions. Effects of shape and surface treatment

AbstractWe investigate the electrorheological (ER) properties of clay (montmorillonite, sepiolite, and laponite®). The selected clays allow to distinguish between planar particles of different sizes (montmorillonite and laponite®), and elongated ones (sepiolite). The effect of coating them with the surfactant CTAB improves dispersibility in the oil medium and favors the ER response, prticularly in the case of laponite®, whereas in the case of montmorillonite, microscopic observations show that the columnar structures are broken in places leading to a reduced yield stress. Both the static yield stress and the storage modulus grow faster with the field in sepiolite suspensions as compared to laponite®. When dealing with mixed systems, it is found that the field-induced montmorillonite structures are reinforced by the addition of either laponite® or sepiolite, whereas when the latter two are combined, it is laponite® that dominates the ER response. Graphical abstractᅟ

Desarrollo profesional y formación continua de profesores: un análisis del contexto de la educación en Angola

The analysis of the actions of continuous training of teachers is a relevant question to know the level of training and professional development of teachers in schools. It also allows us to obtain data on updating professional skills that are fundamental to the exercise of an ever-changing profession.Therefore, this article aims to analyze the continuing education and professional development of teachers in private schools in Luanda, Angola.Thus, the research methodology on which this work is based is both quantitative and qualitative.In this way, the interview and the questionnaire were used as instruments to collect information. The main results are that there is no specific program of continuous training in private institutions, noting the absence of periodic balance sheets to analyze the level of professional development of teachers and other professionals involved. In conclusion, teachers in Angola are motivated to continue training, but there are certain institutional barriers that do not favor continuous training and professional development.