Engagement and performance in a first year natural resource science course

Quantifying student engagement with online learning resources on virtual learning environments such as BlackBoard is important in understanding how these technologies enhance the student learning. In the present study, it was examined when, and how often, first‐year students accessed lecture recordings, lecture slides, and lecture notes via BlackBoard, in an introductory natural resource course taken by both on campus students and remote students. The findings demonstrated that lecture recordings were not well utilized by students—although only 58% of on campus students attended face‐to‐face lectures, less than 15% of absent students downloaded the missed lecture. Overall, more students downloaded lecture slides (an average of 63% per week) than notes (38%) or recordings (16%). Indeed, the average student downloaded only 1.1 types of the 3 online resources (recordings, slides, and notes) that were available each week, with 5.7% of students downloading all 3 types of resources, 23% downloading 2 types of resources, 42% downloading only 1 type of resource, and 29% downloading none of the 3 types of resources. Finally, remote students were more likely to download lecture notes and recordings than were on campus students. The information presented here is important in understanding student behaviour and engagement.     

High solids content emulsions. IV. Improved strategies for producing concentrated latices

A new means of producing high solids content latices with low viscosity is presented. The replacement of water‐soluble initiators that decompose to give charged free radicals is shown to perturb the stability of highly concentrated latices. Their replacement by an oil‐soluble initiator during particle growth, then by an activated, water‐soluble system to remove residual monomer has been shown to help significantly reduce the number of stable particles generated by homogeneous nucleation. Latices with 73% (v/v) solids have been produced with a bimodal particle size distribution (PSD) consisting of 900 and 110 nm particles. The viscosity of these latices can be as low as 300 mPa s^?1 at 20 s^?1. Despite the presence of water‐soluble monomers, excellent control over the evolution of the PSD allows one to obtain highly reproducible results. In addition, latices produced with the new initiator system have a much lower water uptake and their viscosity is much less sensitive to changes in pH than is the case for latices produced using standard emulsion polymerization techniques. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1935–1948, 2002; DOI 10.1002/app.10514     

Physical aging of nylon 66

The physical aging behavior of nylon 66 as a function of aging temperature, magnitude of applied stress, and aging time has been investigated. Creep tests were performed for samples quenched from a stabilization temperature of 160°C to aging temperatures between 41°C and 65°C, for aging times ranging from 0.5 to 64 h, and at stresses levels from 4 MPa to 24 MPa. Volume recovery was investigated for samples quenched from 160°C to aging temperatures of 41°C and 65°C. The creep compliance curves at different aging times were able to be superimposed. The double logarithmic shift rate was calculated and its dependence on aging temperature and applied stress was determined. Also, it was found that the volume recovery rate depends on the aging temperature. The time-temperature and stress-temperature superpositions were not possible for our data.     

Some volatile constituents of female dog urine

The volatile compounds from female beagle urine, across the state of estrus, were examined by headspace gas chromatography and mass spectrometry. The major constituents identified were methyl propyl sulfide, methyl butyl sulfide, and acetone. Nine minor constituents, including trimethyl amine and five disulfides, were identified. Two of the unidentified minor constituents may possibly be associated with the state of estrus.     

The Solid State Postcondensation of PET, 4

Summary: A new method of polymerising PET in the solid state is proposed in either a gas phase reactor, or in hydrocarbon dispersion. It is shown that the reaction can be carried out efficiently at temperatures on the order of 200–240 °C directly from a prepolymer without the need for a melt phase step. It is shown that the crystal structure of the prepolymer plays a determining role in the kinetics of the SSP reaction.

Schema of the reactor used for gas phase SSP.     

Novel nanobubble inflation method for determining the viscoelastic properties of ultrathin polymer films

We describe a novel experimental technique for measuring the viscoelastic properties of ultrathin polymer films. The method is based on the classic bubble inflation technique for measuring the biaxial creep compliance of films, reduced in size to measure films with thicknesses down to at least 13 nm. The method uses the imaging capabilities of the atomic force microscope to determine the time evolution of the geometry of nanobubbles. Using these data, along with the applied pressure, the absolute creep compliance of the films can be determined.