Marta Cruz-Guzmán

An Analysis of the Questions Proposed by Elementary Pre-Service Teachers When Designing Experimental Activities as Inquiry.

ABSTRACT A qualitative study of an interpretative nature is presented of the topics that elementary pre-service teachers (EPTs) choose and the types of questions they propose when designing an experimental activity (ExA) as inquiry, after receiving explicit instruction about it. The participants in the study were 154 EPTs organised into small groups to design an ExA. The data were processed using a rubric designed and applied through processes of inter- and intra-rater analysis. The results showed the instruction they had received to be, in general, effective for their formulation of quality questions that can generate ExA-based inquiry. Questions dealing with relations between variables were the commonest. In their free selection of the topic, the EPTs were most likely to ask high-order questions (i.e. ones that foster inquiry) on a wide variety of physics content. There were very few questions concerning biology, and none on chemistry, the environment, health sciences, and so on. After a discussion of the results, specific actions are proposed to improve future EPT training in the formulation of questions with which to initiate school science inquiry.

Fragmentation and gas phase aggregation processes in the laser desorption ionization of chlorodiaminotriazines.

Fragmentation and supramolecular aggregation induced during the laser desorption/ionization (LDI) of four chlorodiaminotriazines (simazine, atrazine, terbutylazine and propazine) have been investigated. The laser wavelength employed (266 nm) lies within the first absorption band of the four triazines. The main fragmentation channel observed involves the prompt cleavage of the Cl atom, followed by partial or total fragmentation of the side alkyl chains. Breakage of the triazinic ring becomes efficient at moderate laser powers; however, the deamination of the triazine is not observed to take place. In addition, the formation of both covalent and non-covalent triazinic aggregates in the desorption plume is found to be particularly efficient. Aggregates as large as heptamers are neatly detected, with the observation that those with the most intense signal involve the dechlorinated triazinic fragment. Both aggregation and fragmentation are largely suppressed upon dilution of the triazine under matrix-assisted laser desorption/ionization conditions.