The study of silicates and refractory materials at high pressures and temperatures

To better understand high pressure behavior of solids, both silicates and oxides have been investigated to clarify the high pressure melting, phase transformations and thermal parameters as well as their size dependences, both theoretically and experimentally. ^ To judge the precision of data determined experimentally, the reliabilities of different high pressure techniques have been discussed. A thermodynamic model has been developed and demonstrated to be able to closely reproduce the melting of solids by comparison between results calculated and data obtained experimentally, including metals (Al, Ni and Pt), Silicates (Mg3Al 2Si3O12 and CaMgSi2O6), Halides (NaCl, CsCl and LiF) and Oxides (MgO, FeO and Al2O3). The melting data obtained have been discussed to address the dynamics of the Earth's interior. ^ Results obtained with Raman spectroscopy and x-ray diffraction show that solids including silicates (andradite and pyrope) and oxides (CeO2 and TiO2) undergo a series of pressure-induced phase transformations. The effects of particle size under high pressures have been investigated. The results obtained indicate that the reduction of particle size leads to the enhancement of the bulk modulus and a significant decrease of transition pressure in TiO2 (rutile) and CeO2. The pressure-induced amorphization in anatase also results from the size effects. ^ Combining the data obtained with global seismic tomography, the physics and chemistry of the Earth's mantle and the dynamics of the core-mantle interaction have been discussed. The high pressure phases of Al3+- and Fe3+-bearing minerals play important roles in the dynamics of the lower mantle. ^

Explaining the effects of class size on faculty and students

This study explored the effects of class size on faculty and students. Specifically, it examined the relationship of class size and students' participation in class, faculty interactive styles, and academic environment and how these behaviors affected student achievement (percentage of students passing). The sample was composed of 629 students in 30 sections of Algebra I at a large, urban community college. A survey was administered to the students to solicit their perceptions on their participation in class, their faculty interaction style, and the academic environment in their classes. Selected classes were observed to triangulate the findings. The relationship of class size to student participation, faculty interactive styles, and academic environment was determined by using hierarchical linear modeling (HLM). A significant difference was found on the participation of students related to class size. Students in smaller classes participated more and were more engaged than students in larger classes. Regression analysis using the same variables in small and large classes showed that faculty interactive styles significantly predicted student achievement. Stepwise regression analyses of student and faculty background variables showed that (a) students' estimate of GPA was significantly related to their achievement (r = .63); (b) older students reported more participation than did younger ones, (c) students in classes taught by female, Hispanic faculty earned higher passing grades, and (d) students' participation was greater with adjunct professors. Class observations corroborated these findings. The analysis and observational data provided sufficient evidence to warrant the conclusion that small classes were not always most effective in promoting achievement. It was found that small classes may be an artifact of ineffectual teaching, actual or by reputation. While students in small classes participate and are more engaged than students in larger classes, the class-size effect is essentially due to what happens in instruction to promote learning. The interaction of the faculty with students significantly predicted students' achievement regardless of class size. Since college students select their own classes, students do not register for classes taught by faculty with poor teaching reputation, thereby leading to small classes. Further studies are suggested to determine reasons why classes differ in size.