Creep and stress relaxation in methacrylate polymers: Two mechanisms of relaxation behavior across the glass transition region

This study explores the long‐term behavior of poly(methyl methacrylate), poly(ethyl methacrylate), and poly(2, 2, 2‐trifluoroethyl methacrylate) by creep and stress relaxation (SR) experiments. Dielectric analysis (DEA) and dynamic mechanical analysis (DMA) are used to measure and compare the structural relaxations associated with side group motion and with the glass transition, T_g, region. An analysis of shift factor data for creep and SR experiments reveals two modes of molecular motion in the glass‐rubber relaxation region, but the modes are less discernible than those reported previously for a series of styrene polymers. The high temperature side exhibits WLF behavior while the low temperature side exhibits Arrhenius behavior. The extent of definition of the two modes of deformation is related to the effect of cooperative α dynamics on the β relaxation process. Some discussion is presented concerning the magnitude of the activation energy for both processes and the sharpness of the transition betwen the two modes.     

Efficacy of an iodine backflush for preventing new intramammary infections

Efficacy of an iodine backflush system for reducing new intramammary infection was tested in two 11-wk trials. Forty cows in each trial were paired by breed, age, stage of lactation, and intramammary infection status. Each pair was assigned randomly either to a group milked with clusters that were reverse flushed with water, 25 ppm iodine, water and air or to a group milked with clusters receiving no backflush treatment between cows. Backflushing clusters reduced infections caused by Corynebacterium bovis and coagulase-positive staphylococci in both trials. However, backflushing clusters produced no clear advantage for reducing new infections with coagulase-negative staphylococci, Gram-negative bacilli, or streptococci (species other than Streptococcus agalactiae). No differences in somatic cell counts between experimental groups were observed. Teat cup liners and teat ends were swabbed after 120 and 1200 milkings/liner. Total microbial counts were significantly greater for liners that were not backflushed than from backflushed liners at each swabbing. However, no differences were significant between groups for mean teat end microbial counts in either trial.     

Liquefaction of coal using supercritical fluid mixtures

Powhatan No. 5 and Bruceton coals were liquefied for 15–60 min at 653 K and 30 MPa in supercritical aqueous mixtures containing 10–20 wt% tetrahydroquinoline (THQ), quinoline or tetralin. The THQ-water mixtures produced the highest conversion to tetrahydrofuran (THF) soluble products (up to 74%). Tetralin-water, quinoline-water and pure water solvents gave increasingly lower yields of THF solubles. Addition of hydrogen to the quinoline-water solvent mixture increased yields slightly, but not to the level obtained using the THQ-water mixture.The yields of THF solubles in all instances depended upon the concentration of solvent in the mixture, with the 10 wt% THQ and 10 wt% tetralin (in water) giving higher yields than either 0 or 20 wt% concentrations. The nitrogen-containing solvents were chemically bonded to the THF-soluble product, as observed by g.p.c.     

The impact of a simulation-based learning design project on studentlearning

This study examined the effects of a sophisticated simulation-based task on students' learning of course-related content, ability to deal with complex, open-ended problems, and attitudes toward the Interactive Site Investigation Software (ISIS) and the course. Students were required to conduct a hazardous waste site investigation using the simulation software designed specifically for the course. ISIS simulated physical processes as well as real-world engineering processes. Assessment of student outcomes was based on the use of constructed-response knowledge maps to measure content understanding, and surveys to measure student attitudes and use of cognitive processes. Students reported very positive attitudes toward the ISIS experience, appeared to have gained substantial knowledge over the course of ISIS use, and perceived the ISIS activity as being generally effective in improving their skills in dealing with complex projects, linking theory to real world applications, and improving their problem-solving performance. Our assessment of student outcomes was a successful first attempt, but more work is needed to validate our measures with advanced students, particularly when the task is complex and requires interdisciplinary knowledge     

Factor analytical modeling of biochemical data

Factor Analysis, a multivariate technique for determining the major trends or factors in a data matrix, is shown in this paper to be appropriate for resolving biochemical reaction networks. As opposed to an algorithmic approach, the methods presented in this article are intended to be a highly interactive set of tools. The researcher can use these tools to investigate a data matrix of concentration-change measurements by proposing different reaction networks. Several tools are adapted from other fields, and a few new techniques are proposed. The new techniques involve the estimation (orextraction ) of reaction stoichiometries and reaction extents when all the reactions are not present at all times. This article presents theoretical elements, simulation results as well as an application of the method to experimental data from the fed-batch production of Baker's yeast grown on glucose. Reaction stoichiometries and reaction extents are estimated for the reactions of glucose fermentation, glucose oxidation and ethanol oxidation.     

Kinetic study of olefin polymerization with a supported metallocene catalyst. IV. Comparison of bridged and unbridged catalyst in gas phase

A kinetic study of ethylene/1‐hexene (E/1‐H) copolymerization is conducted with a supported bridged metallocene catalyst in a gas phase reactor. The investigation into the kinetics of ethylene/1‐hexene copolymerization includes the effects of operational parameters such as the reaction temperature, pressure, and comonomer concentration. On‐line perturbation techniques are implemented to determine key kinetic parameters such as the activation energies for propagation and catalyst deactivation. A comparison of the kinetic parameters and behavior is made between the bridged and a previously studied unbridged catalyst. Finally, a two‐site model is proposed to explain the observed kinetic behavior with changing reaction temperature and comonomer concentration. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1451–1459, 2001     

In vitro fermentation of sugars, grains, and by-product feeds in relation to initiation of ruminal lactate production

In vitro fermentations of various sugars, grains, and by-products were conducted to investigate the relationships between soluble carbohydrates and initiation of ruminal lactate production. Fermentation of hexose sugars, both monosaccharides and disaccharides, resulted in greater accumulation of lactate than did fermentation of pentoses. Results of fermentation of grains and by-products, in order of greatest to least potential to produce lactic acid, were steam-flaked barley = barley = wheat greater than moisture corn = sorghum grain. Water-soluble fractions of the grains and by-products were more rapidly fermented to lactate than the insoluble fractions. Combining 10% soluble fractions from wheat, barley, and steam-flaked barley with 90% insoluble fractions from corn resulted in significant increases in lactate concentration. Analysis of sugar composition of these water soluble materials indicated that monosaccharides and disaccharides constitute 23 to 46% by weight. Data suggest that water-soluble materials play a role in initiation of lactate production from grains, and further production is dependent on starch fermentability.     

Prevalence of minor udder pathogens after intramammary dry treatment

A total of 156 dairy cows was randomly assigned to one of four groups at drying off over an 18-mo period: untreated control or intramammary treatment of each mammary quarter with either 400 mg novobiocin, 300 mg cephapirin, or 1 g dihydrostreptomycin with 1 million units penicillin. Quarter foremilk samples were aseptically collected from each cow within 1 mo of drying off and within 1 mo after parturition for bacteriological analysis. Prior to drying off, 28.7% of quarters were positive of which 46.7% were Corynebacterium bovis and 45.5% were coagulase-negative staphylococci. Reductions in infection prevalence from drying off to postpartum samplings for control, novobiocin, cephapirin, and streptomycin-penicillin groups were 13.6, 60.5, 74.4, and 35.3% of quarters. Recovery rates for C. bovis infections were 47.6, 100, 100, and 94.1%; for coagulase-negative staphylococci infections they were 72.7, 86.4, 80.0, and 100%. The cephapirin group showed the lowest new infection rate (1.3%) with coagulase-negative staphylococci compared with control (6.9%). There were no significant differences in lactation milk production among groups following dry period therapy. Results suggest that dry treatment reduces the prevalence of infections by the minor mastitis pathogens.