Recently, Massive Open Online Courses (MOOCs) and problem-based learning (PBL) have been popular in higher education. However, there is little research about the effects of PBL with collaborative ...learning in the flipped classroom on affective processes in English class to influence students’ learning. This study investigates problem-based English learning using flipped MOOCs, combined with ZOOM meetings for group-based discussion in the classroom to examine the relationships among social problem-solving orientations, self-efficacy, motivation, and the willingness to communicate (WTC) of Japanese EFL (English as a Foreign Language) learners. To conduct this investigation, online questionnaires were administered to university EFL students in Japan and in Malaysia. We found that collaborative learning in this PBL setting had a positive effect on self-efficacy, WTC, motivation, and positive problem-solving orientation. We also found that collaborative learning was the strongest predictor of self-efficacy.
•Small particle sizes and slow crystallization exclude aggregates during freezing.•Ice exclusion processes not likely to form mm-scale spherical aggregates on Mars.•Particles become entrapped within ...the ice as aggregate size increases.•Sand and salts affected aggregation, but no mm-sized spherical aggregates formed.
The enigmatic and unexpected occurrence of coarse crystalline (gray) hematite spherules at Terra Meridiani on Mars in association with deposits of jarosite-rich sediments fueled a variety of hypotheses to explain their origin. In this study, we tested the hypothesis that freezing of aqueous hematite nanoparticle suspensions, possibly produced from low-temperature weathering of jarosite-bearing deposits, could produce coarse-grained hematite aggregate spherules. We synthesized four hematite nanoparticle suspensions with a range of sizes and morphologies and performed freezing experiments. All sizes of hematite nanoparticles rapidly aggregate during freezing. Regardless of the size or shape of the initial starting material, they rapidly collect into aggregates that are then too big to push in front of a stable advancing ice front, leading to incohesive masses of particles, rather than solid spherules. We also explored the effects of “seed” silicates, a matrix of sand grains, various concentrations of NaCl and CaCl2, and varying the freezing temperature on hematite nanoparticle aggregation. However, none of these factors resulted in mm-scale spherical aggregates. By comparing our measured freezing rates with empirical and theoretical values from the literature, we conclude that the spherules on Mars could not have been produced through the freezing of aqueous hematite nanoparticle suspensions; ice crystallization front instability disrupts the aggregation process and prevents the formation of mm-scale continuous aggregates.
Display omitted
Several techniques based on laser induced fluorescence (LIF) spectrometry and laser enhanced ionization (LEI) spectrometry have been investigated for ultratrace measurements of arsenic. Studies by ...our group in this area that have been published previously are reviewed here, and are presented along with the results of recent studies that have not yet been published. The techniques presented include LIF detection in the inductively coupled plasma atomizer, the electrothermal atomizer, the tungsten coil atomizer, the flame atomizer and LEI detection in the flame atomizer, and include approaches that utilize hydride generation or laser ablation sample introduction. Recent efforts have been directed towards developing speciation approaches for arsenic that utilize LIF spectrometric detection. The capabilities of each technique are summarized including the sensitivity and limits of detection, which range from sub-pg ml
−1 to ng ml
−1 levels. Selected applications of the techniques are presented to demonstrate their utility for environmental and biological samples, and areas for future investigation and further development are discussed.
