Co-photolysis of poly(styrene) and poly(vinylacetophenone)—I. Vacuum photolysis

Films made from blends of poly(styrene) (PS) and poly(vinylacetophenone) (PVAP) (up to 12% mol PVAP) were exposed under high vacuum to long wave u.v. radiation (λ > 300nm). Spectral changes (phosphorescence, NMR and i.r. indicated that PVAP was photolysed: the nature of gaseous products (in order of abundance, methane, carbon monoxide, ethane and acetaldehyde) confirmed that PVAP was undergoing a Norrish Type I decomposition. There was also evidence of photoreduction, OH absorptions appearing in the i.r. The blended films undergo cross-linking but the insoluble material formed after about 10hr contains little carbonyl. The effects of PVPA concentration and molecular weight on the rate of product formation were also investigated. Experiments with poly(α-D-styrene) confirmed that methyl radicals were abstracting H atoms at the α-position in PS. The implications of such reactions in the initiation of photo-oxidation by polymeric ketonic species are discussed.     

Assessment of numeracy in sports and exercise science students at an Australian university

The effect of high school study of mathematics on numeracy performance of sports and exercise science (SES) students is not clear. To investigate this further, we tested the numeracy skills of 401 students enrolled in a Bachelor of Health Sciences degree in SES using a multiple-choice survey consisting of four background questions and 39 numeracy test questions. Background questions (5-point scale) focused on highest level of mathematics studied at high school, self-perception of mathematics proficiency, perceived importance of mathematics to SES and likelihood of seeking help with mathematics. Numeracy questions focused on rational number, ratios and rates, basic algebra and graph interpretation. Numeracy performance was based on answers to these questions (1 mark each) and represented by the total score (maximum = 39). Students from first (n = 212), second (n = 78) and third (n = 111) years of the SES degree completed the test. The distribution of numeracy test scores for the entire cohort was negatively skewed with a median (IQR) score of 27(11). We observed statistically significant associations between test scores and the highest level of mathematics studied (P < 0.05), being lowest in students who studied Year 10 Mathematics (20 (9)), intermediate in students who studied Year 12 General Mathematics (26 (8)) and highest in two groups of students who studied higher-level Year 12 Mathematics (31 (9), 31 (6)). There were statistically significant associations between test scores and level of self-perception of mathematics proficiency and also likelihood of seeking help with mathematics (P < 0.05) but not with perceived importance of mathematics to SES. These findings reveal that the level of mathematics studied in high school is a critical factor determining the level of numeracy performance in SES students.     

Magnetic Resonance Imaging of Hydrodynamic Dispersion in a Saturated Porous Medium

By using nuclear magnetic resonance imaging (NMRI) we have been able to analyse dispersion at the microscopic scale during steady-state flow through water-saturated glass beads. The flow rate through the porous medium was chosen high enough in order to neglect the influence of molecular diffusion on dispersion. Velocity statistics were measured, by NMRI, within slices of increasing thickness perpendicular to the direction of flow. It took more than two bead diameters before a representative elementary volume (REV) for the mean velocity was reached. This was in a region in the middle of the column that was not influenced by the boundary conditions. There the velocity variance decreased exponentially as a function of the slice thickness, due we consider to the formation of an interconnecting streamline network. The exponential decrease in the velocity variance reflects the transition from a local pattern of stochastic–convective flow to a convective–dispersion regime at the scale of the REV. We found that the point-like preferential influx and efflux boundary condition increased velocity variances and thus enhanced longitudinal hydrodynamic dispersion. Using the transverse correlation length of longitudinal velocity variance, we derived a mean transverse dispersivity that agreed well with Saffmans (1959) model. So we have been able to provide for the first time a direct observation verification of a part of Saffmans (1959) conjectures. By NMRI we observed this value to be independent of the observation scale of the slice thickness.