Search

Reports on a survey of faculty members (n=29) asking them to define active learning, to rate how effectively different teaching techniques contribute to active learning, and to list the three teaching techniques they use most frequently. Concludes that active learning requires establishing an environment rather than employing a specific teaching technique. (MM)

KCl[O.sub.3] thermal decomposition has been studied from 29-76 kilobars using a multianvil high-pressure device and in-situ energy-dispersive X-ray diffraction and off-line quenching experiments. The rhombohedral form of KCl[O.sub.3] was found to decompose to the B2 form of KCl and [O.sub.2] via an orthorhombic KCl[O.sub.4] intermediate over this pressure interval. The decomposition temperature was found to vary only slightly with pressure. The online experiments gave decomposition temperatures between 500 and 580 [degrees] C. Further off-line quenching experiments using sealed gold tubes determined the equilibrium decomposition boundary to be 550 [+ or -] 15 [degrees] C over this pressure range. Unit-cell parameters and volumes were determined for the high-pressure phases of KCl[O.sub.3] and KCl from the diffraction data. The partial molar volume of [O.sub.2] was calculated from the difference in the solid volumes. Oxygen fluid volumes were then calculated along the decomposition boundary and vary from 10.6 [+ or -] 0.2 c[m.sup.3]/mol at 29 kbar to 9.6 [+ or -] 0.1 c[m.sup.3]/mol at 76 kbar. These volumes are 30 to 50% less than previous estimates determined from shock wave data, and imply that oxygen can be more easily stored in Earth's mantle and core than previously believed. The thermal equation of state of the B2 form of KCl was investigated online using NaCl as an internal pressure standard. KCl was then used as an internal pressure calibrant for the online KCl[O.sub.3] decomposition experiments. The mechanical behavior of the multianvil high-pressure device was also studied and load vs. force characteristics are presented here.

Differential thermal analysis and quenching experiments are conducted to determine brucite dehydration equilibrium from 1 to 15 GPa and study H20 compressibility at very high pressures. The results of the analysis are used to calculate the molar volume of H2O along the dehydration curve and indicate a decrease in H2O molar volume from 21 cubic cm at 1 GPa and 845 degrees C to 10 cubic cm at 15 GPa and 1280 degrees C. A comparison of the analysis results with previous studies suggest that the periclase and fluid stability field can be notably overestimated.

The melting point of PbS up to 25 kbar and the shape and slope of the PbS melting curve are compared to those of similarly sized and structured compounds namely AgCl, AgBr, KCl, NaBr and monosulfide FeS is discussed.

A new geobarometer based on the Al content of igneous hornblendes in equilibrium with melt, fluid, biotite, quartz, sanidine, plagioclase, sphene, and magnetite or ilmenite has been calibrated experimentally. The calibration was performed by equilibrating the required phase assemblage over the pressure range 2-8 kbar at 740-780 [degrees]C, and then analyzing euhedral hornblendes in equilibrium with glass (melt). Experiments were performed on natural samples of both volcanic and plutonic rocks. Earlier empirical calibrations of this geobarometer relied on analyzing natural hornblendes from plutons with the required phase assemblage and inferring pressure from nearby metamorphic country rocks. The experimental calibration differs from the empirical calibrations, especially above 5 kbar, and shows that the AI content of hornblendes in equilibrium with the required phase assemblage is greater for a given total pressure than previously thought. The geobarometer's uncertainty is dramatically reduced. The derived equation is P ([+ or -]0.5 kbar) = 3 -3.46 ([+ or -]0.24) + 4.23 ([+ or -]0.13) ([Al.sup.T]). The geobarometer is applied to post-Bishop Tuff volcanic rocks from Long Valley caldera, California, and reveals that most rhyodacites in this complex erupted from depths of about 6 km. These eruptions occurred over 500 000 yr, suggesting that the rhyodacitic magma reservoir Long Valley had reached a steady P (depth)-T state.

Presents a study which investigated the thermal decomposition of KClO[sub 3] using a multianvil high-pressure device and in-situ energy-dispersive X-ray diffraction and off-line quenching experiments. Experimental techniques; Characterization of the multianvil device; Pressure calibration.