M. D. Driessen

It's not about seat time: Blending, flipping, and efficiency in active learning classrooms

This study examines the effect of reducing the seat time of a large lecture chemistry class by two-thirds and conducting it in an active learning classroom rather than a traditional amphitheater. To account for the reduced lecture, didactic content was recorded and posted online for viewing outside of the classroom. A second experimental section, also in a blended and flipped format, was examined the following semester as a replication. To measure student subject-matter learning, we used a standardized multiple-choice exam, and to measure student perceptions of the classroom, we used a validated survey instrument. Our findings demonstrated that in an active learning classroom, student faculty contact could be reduced by two-thirds and students achieved learning outcomes that were at least as good, and in one comparison significantly better than, those in a traditional classroom. Concurrently, student perceptions of the learning environment were improved. This suggests that pedagogically speaking, active learning classrooms, though they seat fewer students per square foot, are actually a more efficient use of physical space.

On the characterization of environmental nanoparticles

Abstract The presence and release of nanoparticles into the environment has important implications for human health and the environment. This article highlights and describes techniques that are effective in the characterization of anthropogenic and naturally occurring nanoparticles. Particle attributes like size, size distribution, shape, structure, microstructure, composition, and homogeneity are critically important to determining the potential impact of such materials on health and the environment. Many techniques yield data for a collection of nanoparticles; while others yield data for individual nanoparticles; and still others yield data showing the size, distribution of chemical species, and variations in structure and microstructure for a single nanoparticle. All are important in the context of environmental nanoparticles. Many of these techniques are complementary, and depending on the information required, the ideal characterization usually employs multiple techniques.

Photocatalytic oxidation of trichloroethylene on zinc oxide: Characterization of surface-bound and gas-phase products and intermediates with FT-IR spectroscopy

Abstract The gas-phase heterogeneous photooxidation of trichloroethylene (TCE) on ZnO has been investigated. In the presence of ZnO and molecular oxygen, trichloroethylene photooxidizes upon irradiation with wavelengths of light between 300 and 390 nm. Surface-bound and gas-phase products and intermediates formed during the photocatalytic oxidation of TCE were characterized with infrared spectroscopy. The gas-phase product distribution was found to be dependent on TCE pressure. At low TCE pressures, CO 2 and CO were produced as the predominant carbon-containing, gas-phase products. At high TCE pressures, additional carbon-containing products were detected. These products include phosgene, and dichloroacetylchloride. It is postulated that phosgene and dichloroacetylchloride form only after the ZnO surface becomes saturated with adsorbed products. These adsorbed photoproducts have been identified as water, bidentate formate and dichloroacetate. These adsorbed photoproducts block sites so that partial oxidation products cannot undergo further oxidation on the ZnO surface.