Steady-State and dynamic properties of concentrated fiber-filled thermoplastics

Rheometric data for short-fiber-filled thermoplastics are presented using a parallel-plate viscometer. Polypropylene tensile bars contain short and long fibers with glass weight percentages of 0%, 5%, 10%, 20%, and 30%, polycarbonate tensile bars with glass percentages of 0%, 5%, and 10% long fibers, and nylon 6/6 tensile bars with 0%, 15%, 30%, and 45% short fibers. The short fibers were initially 3 mm in length and 12.7 microns in diameter. The long fibers were initially 6 mm in length and 10 microns in diameter. In the steady-state experiments, the fibers increase the viscous stresses and the normal stresses in proportion to the concentration of fibers. At low shear rates, the viscosity is increased by the addition of the fibers, but at high shear rates the viscosity approaches that of the neat resin. In dynamic testing, the fibers increase the viscous and elastic components as measured by the complex viscosity and modulus. The fibers increase the viscous and elastic nature of the fiber-filled composite at low frequencies and to a lesser extent at higher frequencies. The fibers increase the elastic component more than the viscous component at low frequencies and less at higher frequencies as demonstrated by tan δ.     

Numerical analysis of injection molding of glass fiber reinforced thermoplastics. Part 1: Injection pressures and flow

Numerical calculations of flow and injection pressures during injection molding of fiber-filled thermoplastics are compared to experimental measurements. The flow is modeled as a 2–D, nonisothermal, free-surface flow with a new viscosity model dependent upon temperature, pressure, and fiber concentration. The steady-state viscosity model is developed to account for the fiber-concentration and shear-thinning viscosities of the polymer based upon combining the Dinh-Armstrong fiber model with the Carreau viscosity model. The new model has four parameters, three from the Carreau model and one from Dinh-Armstrong for fiber concentrations. The new model calculates reasonably well the steady-state viscosity of fiber-filled polypropylene over the shear rate range of 0.01 s^?1to 20 s^?1. The numerical work successfully describes the flow of fiber-filled polymers during injection molding using finite-difference solutions for the transport equations and marker particles to track the flow front. The comparisons between the calculated and measured pressure drops for an injection molded part were reasonable for the unfilled and fiber-filled polypropylene materials. The pressure drop comparison is very good for slow fill of a base case resin, Himont polypropylene, but not as good for fast fill of the resin. The pressure drop comparison is very good for fast fill of glass-filled resin, DSM polypropylene with 10% and 20% short fibers, but not as good for slow fill of the resin and resin plus fibers.     

Sulfolane biodegradation potential in aquifer sediments at sour natural gas plant sites

Sulfolane is used in the treatment of sour natural gas. It is a highly water soluble compound that has been introduced into soils and groundwaters at a number of sour gas processing plant sites. Aquifer sediments from contaminated locations at three sites in western Canada were assessed for microbial activity and their ability to degrade sulfolane under aerobic and five anaerobic (nitrate-, Mn(IV)-, Fe(III)-, sulfate- and CO₂-reducing) conditions. The microcosms were supplemented with 200 mg/L sulfolane and adequate supplies of N, P, and the appropriate terminal electron acceptor. Microcosms containing contaminated aquifer sediments from each of the three sites were able to degrade sulfolane aerobically at 8°C and 28°C, and the biodegradation followed zero-order kinetics. The lag times before the onset of sulfolane biodegradation were shorter when sulfolane-contaminated sediments were used as inocula than when uncontaminated soils were used. No anaerobic sulfolane biodegradation was observed at 28°C, nor was sulfolane biodegradation observed at 8°C under Fe(III)-, sulfate- and CO₂-reducing conditions. At 8°C, anaerobic degradation of sulfolane coupled to Mn(IV) reduction was observed in microcosms from two sites, and degradation coupled to nitrate reduction was seen in a microcosm from one of the contaminated sites.     

Selection of metal ion irradiation for controlling Ti1−xAlxN alloy growth via hybrid HIPIMS/magnetron co-sputtering

We demonstrate, for the first time, the growth of metastable single-phase NaCl-structure high-AlN-content Ti_1−xAl_xN alloys (x ≤ 0.64) which simultaneously possess high hardness and low residual stress. The films are grown using a hybrid approach combining high-power pulsed magnetron (HPPMS/HIPIMS) and dc magnetron sputtering of opposing metal targets. With HIPIMS applied to the Al target, Alⁿ⁺ ion irradiation (dominated by Alⁿ⁺) of the growing film results in alloys 0.55 ≤ x ≤ 0.60 which exhibit hardness H ∼ 30 GPa and low stress σ = 0.2-0.7 GPa, tensile. In sharp contrast, films with corresponding AlN concentrations grown with HIPIMS applied to the Ti target, giving rise to Tiⁿ⁺ ion irradiation (with a significant Ti²⁺ component), are two-phase - cubic (Ti,Al)N and hexagonal AlN - with low hardness, H = 18-19 GPa, and high compressive stress ranging up to 2.7 GPa. Annealing alloys grown with HIPIMS applied to the Al target results in age hardening due to spinodal decomposition; the hardness of Ti_0.41Al_0.59N increases from 30 to 33 GPa following a 900 °C anneal.     

Fire Department Attended and Unattended Fires: Estimates from the 2004–2005 National Sample Survey and Comparison with Previous Surveys

Previous national surveys in 1974 and 1984 have shown that although attended and unattended fires differed substantially in severity and fire losses, there were between 10 and 29 unwanted residential fires for every fire reported to, or attended by, U.S. fire departments. The study objective was to obtain new estimates of fires not attended by fire departments. Interest in unattended fires derives from the understanding that most fires begin small, then unless controlled, grow until fire department assistance is needed. To update these analyses, a national telephone survey was conducted during 2004 and 2005. The survey had 916 respondents who reported one or more residential fires during the previous 90-day period. The principal methodological issues in analyzing the survey data included: (1) determining the optimum recall period to balance sampling variance and bias, and (2) imputing incompletely specified fire dates. The resulting estimates were 7.2 million unattended residential fires per year, a 69% decrease from the 1984 survey estimate of 22.9 million fires. During the same time period, fire department attended residential fires decreased by 36%. The greater decrease in unattended fires is at variance with the conjecture in the 1984 survey that increasing availability of smoke alarms would result in more fires detected at an earlier stage when they could be controlled by residents; a conjecture that would predict a greater decrease in attended rather than unattended fires.     

Interlaboratory comparison of real-time PCR protocols for quantification of general fecal indicator bacteria

The application of quantitative real-time PCR (qPCR) technologies for the rapid identification of fecal bacteria in environmental waters is being considered for use as a national water quality metric in the United States. The transition from research tool to a standardized protocol requires information on the reproducibility and sources of variation associated with qPCR methodology across laboratories. This study examines interlaboratory variability in the measurement of enterococci and Bacteroidales concentrations from standardized, spiked, and environmental sources of DNA using the Entero1a and GenBac3 qPCR methods, respectively. Comparisons are based on data generated from eight different research facilities. Special attention was placed on the influence of the DNA isolation step and effect of simplex and multiplex amplification approaches on interlaboratory variability. Results suggest that a crude lysate is sufficient for DNA isolation unless environmental samples contain substances that can inhibit qPCR amplification. No appreciable difference was observed between simplex and multiplex amplification approaches. Overall, interlaboratory variability levels remained low (<10% coefficient of variation) regardless of qPCR protocol.     

Holding parents responsible: Is vicarious responsibility the public's answer to juvenile crime?

Parental responsibility laws hold parents accountable for the delinquent behaviors of their children even when parents' actions are not the direct cause of an offense. Despite the prevalence of these laws, we know little about their perceived fairness. Is it reasonable to make parents vicariously responsible for outcomes they could not have foreseen and if so, under what circumstances? Our series of three studies addressed those questions by systematically examining the impact of various situational and dispositional factors on public opinions regarding parental responsibility. Respondents attributed most of the responsibility for a crime to the child, and attributions of responsibility to the parents varied as a function of the child's age. Case characteristics including the type of crime committed and the described parents' actions versus inactions did not consistently influence responsibility attributions. We conclude that people feel rather lukewarm about the notion of vicarious parental responsibility and this indifference may be related to issues surrounding the laws' enforcement. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Hydrocarbons on Harvester Ant (<Emphasis Type="Italic">Pogonomyrmex barbatus</Emphasis>) Middens Guide Foragers to the Nest

Colony-specific cuticular hydrocarbons are used by social insects in nestmate recognition. Here, we showed that hydrocarbons found on the mound of Pogonomyrmex barbatus nests facilitate the return of foragers to the nest. Colony-specific hydrocarbons, which ants use to distinguish nestmates from non-nestmates, are found on the midden pebbles placed on the nest mound. Midden hydrocarbons occur in a concentration gradient, growing stronger near the nest entrance, which is in the center of a 1–2 m diameter nest mound. Foraging behavior was disrupted when the gradient of hydrocarbons was altered experimentally. When midden material was diluted with artificial pebbles lacking the colony-specific hydrocarbons, the speed of returning foragers decreased significantly. The chemical environment of the nest mound contributes to the regulation of foraging behavior in harvester ants.