Development and hot-melt impregnation of a model controlled flow prepreg system

A controlled-flow epoxy-based model prepreg resin system was developed. The formulation of the model controlled-flow resin was designed from performance information obtained from a commercially available controlled-flow resin, presently used in the aircraft industry. Thermoanalytical techniques including rheometry were used to provide the necessary information to develop the model system along with a formulation methodology developed by Seferis and co-workers. The model resin formulation, which was a combination of tetraglycidyl ether of methylenedianiline (TGMDA), diglycidyl ether of bisphenol-A (DGEBA), carboxyl-modified butadiene/acrylonitrile rubber (CMBN), carboxyl-terminated butadiene/acrylonitrile rubber (CTBN), bisphenol-A (BPA), diaminodiphenyl sulfone (DDS), and dicyandiamide (DICY), was hot-melt impregnated into unidirectional carbon fibers on a laboratory scale hot-melt prepreg machine. A two-parameter, three-level design of experiments was performed on the prepreg processing parameters in which impregnation temperature and pressure were varied. Thus, a total of nine different experimental prepregs were produced and characterized by resin content, extent of impregnation, and tack. The results from the characterization of the nine experimental prepregs are compared with the effects of the prepreg processing conditions. These results are also compared with the results generated for the commercial controlled-flow resin. Collectively, this work provides a fundamental basis by which the analysis and rational utilization of controlled-flow matrix prepregs can be effected.     

The perinatal mortality rate as an indicator of quality of care in international comparisons

Priming and recollection are expressions of human memory mediated by different brain events. These brain events were monitored while people discriminated words from nonwords. Mean response latencies were shorter for words that appeared in an earlier study phase than for new words. This priming effect was reduced when the letters of words in study-phase presentations were presented individually in succession as opposed to together as complete words. Based on this outcome, visual word-form priming was linked to a brain potential recorded from the scalp over the occipital lobe about 450 ms after word onset. This potential differed from another potential previously associated with recollection, suggesting that distinct operations associated with these two types of memory can be monitored at the precise time that they occur in the human brain.     

Cognitive interviewing procedures and suggestibility in children's recall

In this study the authors examine the effects of procedures adapted from the cognitive interview of R. E. Geiselman, R.P. Fisher, D.P. MacKinnon, and H.L. Holland (1985) on children's recall following exposure to misleading suggestions. Children aged 5-7 years and 9-11 years saw a videotaped story and were presented with misleading or neutral information concerning story details. All were later given free- and cued-recall tests preceded by standard interview instructions or instructions that reinstated the encoding context and encouraged exhaustive reporting. Increased recall accuracy was found following cognitive interview instructions. Both age groups were susceptible to misleading suggestions, but susceptibility was unaffected by interview type. The authors discuss the implications for interviewing child witnesses.     

Cholesterol interference in analysis of fatty acid methyl esters

In the course of isolating and analyzing the fatty acid methyl esters (FAME) from steelhead trout (Salmo gairdneri) eggs and sac fry, a component was found on gas liquid chromatography to have a retention time longer than any characteristic polyunsaturated fatty acid previously encountered in trout. Subsequent purification and analysis demonstrated this component to be cholesterol. Thus, cholesterol and related compounds can interfere in the analysis of FAME when the methyl esters are prepared by transesterification.     

Effect of β-Lactoglobulin Variant and Environmental Factors on Variation in the Detailed Composition of Bovine Milk Serum Proteins

Between November 1979 and November 1981, 17,086 test-day milk samples were collected from individual Holstein cows in 62 Quebec herds. Samples were analyzed for protein, fat, casein, serum protein, somatic cell count, and the relative percentages of β-lactoglobulin, α-lactalbumin, bovine serum albumin, and the immunoglobulins. Cows included in the study were phenotyped with respect to β-lactoglobulin. Unadjusted means ± standard error for the relative percentages of β-lactoglobulin, α-lactalbumin, bovine serum albumin, and immunoglobulins were 64.80 ± .07%, 21.54 ± .05%, 6.51 ± .02%, and 7.15 ± .04%. Least-square analyses showed that month of test, stage of lactation, age of cow, somatic cell count, and phenotype of the cow for β-lactoglobulin had significant effects on the relative percentages of β-lactoglobulin, α-lactalbumin, bovine serum albumin, and immunoglobulins. Test-day milk yield, fat percent, protein percent, casein percent, casein number, and serum protein percent, when included in a statistical model as covariates, had a significant effect on the relative percentage of Ig. Relative proportion of β-lactoglobulin and α-lactalbuminim were not significantly affected by serum protein and total protein contents. For bovine serum albumin, only the covariates fat percent and serum protein percent were not significant.     

Optimization of the Solvent-Free Lipase-Catalyzed Synthesis of Fructose-Oleic Acid Ester Through Programming of Water Removal

Fructose oleate, an environmentally-friendly biobased surfactant, was prepared using solvent-free suspensions of saccharide in a mixture of acyl donor and monoester (the latter present at ≥5 wt% initially) continuously recirculated through a closed-loop packed bed bioreactor (PBBR)-based system at 53 °C, with the PBBR containing immobilized Rhizomucor miehei lipase (Lipozyme^®IM, Novozymes, Franklinton, NC, USA). To replenish the acyl acceptor consumed during the time course of reaction, the medium was isolated, fructose added, and a suspension formed by rigorous stirring at 80 °C for 6 h followed by centrifugation to remove larger particles, with the placement of the acyl acceptor replenishment treatments during the time course of reaction were optimized. Water removal via free evaporation was augmented during the latter portion of the time course (using a molecular sieve packed column, N₂ bubbling, vacuum pressure, or a combination of the latter two), with an optimal performance achieved when initiating N₂ + vacuum (\( 2. 1 6\,{\text{mg}}_{{{\text{H}}_{ 2} {\text{O}}}} \,{\text{h}}^{{^{ - 1} }} \) removal rate) upon reaching 60% ester, to maintain the liquid-phase water content near 0.40 wt%. When employing the above-mentioned conditions, 92.6 wt% fructose oleate was produced within 132 h, yielding a productivity of \( 0. 2 9 7\,{\text{mmol}}_{\text{Ester}} \,{\text{h}}^{ - 1} \, {\text{g}}_{\text{lipase}}^{ - 1} \).     

Numerical modelling and characterization of nanofiltration membranes for the separation of carbohydrate mixtures

The results of an experimental and computational investigation of the selective separation of carbohydrates on nano‐membranes in cross‐flow filtration are reported. Two commercial membranes (NF270‐400 and TFC‐SR3) were characterised in terms of permeability and rejection of carbohydrate solutions. It is shown that the membranes can be used to recover glucose and galactose from their mixtures with lactose. The permeate flux is shown to depend on sugar concentration, with permeate flux decreasing as the concentration increases. Quantitative evaluation using numerical analysis of the above flow and separation process showed that the performance of nano‐membranes can be captured and reproduced with sufficient accuracy, thereby reducing the number of experiments require to evaluate the suitability of membranes in different applications. A Fickian approach is adopted to model the separation, and is shown to be effective.     

Effect of Temperatures up to 90°C on the Early Hydration of Portland–Blastfurnace Slag Cements

Isothermal conduction calorimetry has been used to monitor the early hydration of Portland–blastfurnace slag (BFS)-blended cements. Portland:BFS composite cements with ordinary Portland cement replacements from 0 to 90 wt% were studied at curing temperatures from 12° to 90°C. Peak II, principally associated with alite (Ca₃SiO₅) hydration, was accelerated with increasing temperature for all blends. Peak S, associated with BFS hydration, was particularly noticeable at 40° and 60°C. At higher curing temperatures, peak S merged with peak II, indicating thermal activation of BFS. Novel plots of total heat output against percentage replacement show that BFS contributes to the heat of hydration, even at temperatures below its thermal activation.     

Evolution of supramolecular healable composites: a minireview

Efforts to further extend the range of applications of polymer based materials have resulted in the recent production of healable polymers that can regain their strength after damage. Within this field of healable materials, supramolecular polymers have been subject to extensive investigation. By virtue of their reversible non‐covalent interactions, cracks and fractures in such polymers can be readily and repeatedly healed in order to regain key physical properties. However, many supramolecular polymers are relatively weak and elastomeric in nature, which renders them unsuitable for high strength structural applications. To overcome these deficiencies, preliminary studies have shown that it is possible to reinforce supramolecular polymers with microscale and nanoscale fillers to afford composites that are not only stronger and stiffer compared with the polymers alone but also retain their healing abilities. In this minireview we discuss the evolution of these supramolecular composites and their advantages over more conventional, covalent polymeric materials. © 2014 Society of Chemical Industry     

Bioactive Carbohydrates and Peptides in Foods: An Overview of Sources,Downstream Processing Steps and Associated Bioactivities

Bioactive peptides and carbohydrates are sourced from a myriad of plant, animal and insects and have huge potential for use as food ingredients and pharmaceuticals. However, downstream processing bottlenecks hinder the potential use of these natural bioactive compounds and add cost to production processes. This review discusses the health benefits and bioactivities associated with peptides and carbohydrates of natural origin and downstream processing methodologies and novel processes which may be used to overcome these.