Doctoral Program in Science/Math Education

Five commercial silicas [Nova-Pak, μPorasil (Waters, Milford, MA), Kromasil (Eka Nobel, Bohus, Sweden) Spherisorb (Sigma, St. Louis, MO) and Select-KP (Biotage, Charlottesville, VA)] were tested for their efficiency in separating vitamin E and γ-oryzanol components from saponified rice bran extracts, with the perspective of future large-scale purification of the various compounds. The effects of mobile phase composition, eluent flow rate, column temperature and the physical properties of the silica on the selectivity and analysis time were studied. All silicas except Select-KP gave baseline separation of the vitamin E components with isooctane/ethyl acetate (97.5∶2.5) at room temperature. However, only the 4-μm Nova-Pak spherical silica gave adequate resolution of the oryzanols into two distinct fractions with an analysis time ofcirca 20 min. Other analytical conditions, i.e., the content of the polar modifier in the mobile phase, temperature and flow rate, can be used to optimize the separation once the silica had been chosen. Speed of separation is enhanced by increasing the polarity of the eluent, temperature and flow rate, while the selectivity is reduced only slightly. The Nova-Pak silica appears resistant to deactivation from both residual water in the mobile phase and polar components left over after sample clean-up and is suitable for preparative separation of the target compounds.

The adsorption isotherms of phenyltridecane, phenylundecane, phenyldecane, and phenyloctane between acetonitrile and graphitized carbon have been measured by frontal analysis. Like the isotherm of phenyldodecane previously reported, all of these isotherms exhibit two inflection points and can be empirically accounted for by the sum of a quadratic and a Langmuir term. The elution profiles of large size samples of these hydrocarbons are calculated from the experimental isotherms, using the equilibrium-dispersive model of chromatography. In spite of the complexity of the profiles, the results of the calculations are in excellent agreement with the experimental band profiles.

Highly divided nonporous iron-based catalysts for the hydroliquefaction of coal have been prepared by a flame method. In order to preserve their original properties, an optimization of process conditions has been conducted, using a specially designed batch reactor whose thermal performances allow a simulation of continuous flow unit conditions.

This paper describes the theoretical basis for a constructivist design which can help students develop a set of mental models that increasingly correspond to scientific models that explain or predict scientific phenomena. These student-constructed models can be linked to form perceptual-to-conceptual bridges via two complementary instructional pathways: (1) interactive multimedia simulations can enhance the student decision-making process in a learning environment by providing guidance through trailand-error experiences that culminate in productive experimental outcomes; and (2) student-generated modeling software can allow visualization of a simple mechanism, which is shown as perceptual icons which can be combined in a meaningful manner that shows conceptual entities and their interactions. The design of both types of software can support scaffolded student understanding of the connection between a scientific phenomenon (studied in the laboratory) and its underlying scientific principle (studied in lecture).

When a strong base anion exchange resin, such as a chlo ride-form strong base anion exchange resin, is conditioned with a low concentration of hydroxyl (for example, an NaOH solution with a concentration between 1 and 10 mM), the conditioned resin separates in, sit, Is from sugars and sugar alcohols, while still allowing ready desorption of the sugars from the resin. The feedstock is first passed over a column containing this conditioned resin, followed by a mobile phase solvent, preferably water. The inositols have a lower affinity for the treated resin than do the sugars and sugar alcohols in the feedstock, and therefore pass through the column more quickly. The process may economically be performed on industrial-scale inositol separations, particu larly when used in a preferred simulated moving bed chro matographic system.

This study aimed to determine the effect of Differentiated Instruction (DI) on learning outcomes of high school science students using a convergent, parallel, mixed method research. The qualitative component of the research was a phenomenological approach which explored individual beliefs, experiences and perceptions of teachers about DI. The quantitative part involved a comparison in the End-of-Course (EOC) performance of biology students exposed to DI versus those not exposed to DI. Personal interviews with six science teachers and survey results from 65 biology students revealed that teachers and students alike have positive perceptions of DI. The teachers perceived DI as an effective instructional method for improving student engagement and academic performance. More students scored Good/Excellent in the DI group (76.9%) compared with the Non-DI group (67.6%). However, analysis of covariance (ANCOVA) suggests that at 5% level, the DI group did not perform significantly higher th...

Le développement des procédés d'hydroliquéfaction dans la perspective d'une valorisation à plus ou moins long terme est lié à la mise au point de catalyseurs performants assurant l'obtention de produits de qualité, à moindre coût d'investissement technologique. Il se pose donc le problème de l'évaluation de leur activité. Notre objectif a donc été la mise au point de méthodes analytiques, permettant de sélectionner un certain nombre de critères d'évaluation de l'activité catalytique en hydroliquéfaction. Cinq critères mettant en jeu un certain nombre de protocoles analytiques ont été considérés. Critère no 1: bilans pondéraux (extrographie-sonication). Ils donnent les bilans de conversion globaux et une distribution en familles des composés en fonction de leur solubilité dans les solvants considérés. Critère no 2: identification structurale et distribution en classes de composés en fonction des zones d'indexe (chromatographie en phase gazeuse sur colo...