Interrupted versus uninterrupted flow: A safety propensity index for driver behavior

The objective of this paper is to develop a quantitative safety propensity index (SPI) that captures the overall propensity of a given surrounding environment to cause unsafe driving. The study is conducted in two different flow conditions: interrupted and uninterrupted. Using structural modeling techniques, the index can be estimated from observed geometric, weather-related, vehicular, driver-related, and traffic-related characteristics. To illustrate the adopted approach, extensive effort was conducted to “sync” data from different sources including the Virginia Department of Transportation and the FARS/GES crash data libraries. The Virginia Department of Transportation provided traffic data for 10 freeway sections with interrupted flow and 9 highway sections with interrupted flow in the Northern Virginia area, USA. Two different structural equations models were found allowing insights to the safety impact of different surrounding elements/dimensions. The SPI provides (a) a basis for quantifying the effects of the aforementioned characteristics on safety, (b) a basis for comparing the differences between the factors affecting safety in different flow scenarios and (c) ranking the corresponding roadway sections/locations for improved safety performance. The framework and methodology used to develop this index have the potential to support safety policy analysis and decision making.     

What can information-asymmetric games tell us about the context of Crick's ‘frozen accident’?

This paper describes a novel application of information-asymmetric (signalling) games to molecular biology in which utility is determined by the message complexity (rate) in addition to the error in information transfer (distortion). We show using a computational model how it is possible for the agents in one such game to evolve a signalling convention (separating equilibrium) that is suboptimal in terms of information transfer, but is nonetheless stable. In the context of an RNA world merging with a nascent amino acid one, such a game''s equilibrium is alluded to by the genetic code, which is nearly optimal in terms of information transfer, but is also near-universal and nearly immutable. Such a framework suggests that cellularity may have emerged to encourage coordination between RNA species and sheds light on other aspects of RNA world biochemistry yet to be fully understood.     

WS2 nanoflakes from nanotubes for electrocatalysis

Next-generation catalysts for water splitting are crucial towards a renewable hydrogen economy. MoS₂ and WS₂ represent earth-abundant, noble metal cathode alternatives with high catalytic activity at edge sites. One challenge in their development is to nanostructure these materials in order to achieve increased performance through the creation of additional edge sites. In this work, we demonstrate a simple route to form nanostructured-WS₂ using sonochemical exfoliation to break interlayer and intralayer bonds in WS₂ nanotubes. The resulting few-layer nanoflakes are ～100 nm wide with a high density of edge sites. WS₂ nanoflakes are utilized as cathodes for the hydrogen evolution reaction (HER) and exhibit superior performance to WS₂ nanotubes and bulk particles, with a lower onset potential, shallower Tafel slope and increased current density. Future work may employ ultra-small nanoflakes, dopant atoms, or graphene hybrids to further improve electrocatalytic activity.      

Aerosol Deposition in a Nasopharyngolaryngeal Replica of a 5-Year-Old Child

Particle deposition in a child's nasal cavity is much different than that in the nasal airway of an adult because of the differences in geometry and breathing patterns. However, most deposition studies have focused on adults, and only a limited number of studies have been reported in a child's nasal cavity. This study was conducted as an in vitro test and computational fluid dynamics (CFD) analysis of particle deposition in the nasal replica of a 5-year-old child; both total and regional depositions were evaluated. The geometry of the nasal replica was based on magnetic resonance images of the head of the child. The replica was made by a rapid-prototyping machine. Monodisperse oleic acid and polystyrene latex aerosols ranging in size between 1 and 20 μm were delivered into the replica at flow rates of 10 and 20 L/min. Results showed that the total deposition from the in vitro experiments and CFD predictions matched to a high degree. Good agreement was also obtained when results were compared to existing in vitro deposition data from children having comparable nasal geometries. For regional depositions, patterns between the replica and CFD data were similar in trend and magnitude for all four regions considered, although some regions deviated slightly. More tests in nasal replicas of different aged children will be carried out.

Copyright 2013 American Association for Aerosol Research     

Supercritical fluid extraction of oil from potato chips: Two scale comparison and mathematical modeling

Oil was extracted from fried chipped potatoes using supercritical carbon dioxide. The goals of the study were to determine the effect of process parameters on the extraction, explore the scalability of the process, and determine useful kinetic parameters. Extraction conditions range 27.6–41.4 MPa (4000–6000 PSI), 35–80 °C and solvent flow rate of 0.5–5.0 g CO₂/min. Up to 100% of the oil was recovered from the potato chips at the highest pressure and temperature conditions. Two process conditions were chosen for comparison of performance with a larger scale (1:5) system, maintaining the same CO₂ flow rate to feed mass ratio. Good agreement between scales was seen at the higher pressure and temperature settings. Kinetic parameters, calculated using a literature model, indicated that, as expected, the extraction is limited by internal diffusion.     

Austempered Materials for Powertrain Applications

Austempered irons and steels offer the design engineer alternatives to conventional material/process combinations. Depending on the material and the application, Austempering may provide the following benefits to producers of powertrain components such as gears and shafts: ease of manufacturing, increased bending and/or contact fatigue strength, better wear resistance and enhanced dampening characteristics resulting in lower noise. Austempered materials have been used to improve the performance of powertrain components in numerous applications for a wide range of industries, from gears and shafts to clutch plates and crankshafts. This paper focuses on Austempered solutions for powertrain applications with an emphasis on gear and shaft solutions.     

Decadal trends of silver and lead contamination in San Francisco Bay surface waters

Over the past decade, San Francisco Bay surface waters have remained enriched with dissolved (<0.45 microm) silver and lead concentrations (decadal means of 5.7 ng kg(-1) Ag[filtered] and 31 ng kg(-1) Pb[filtered]) compared with those (0.26 ng kg(-1) Ag[filtered] and 2.7 ng kg(-1) Pb[filtered]) of adjacent oceanic surface waters of the northeast Pacific, despite efforts to reduce pollutant loadings to the Bay during that period. While time series models show that there has been a 40% decline in total lead concentrations in the southern reach of the estuarine system between 1989 and 1999, the filtered lead fraction has not changed significantly during that time. That persistence is attributed to (i) the ongoing input from previous atmospheric depositions and industrial lead to its drainage basin, which are slowly being advected into the estuary and (ii) the internal recycling of lead between the surface sediments and the water column within the Bay. In contrast, both filtered and total silver concentrations in the southern reach have declined by 70% and 40%, respectively, within the past decade. These temporal declines are attributed to a 2-fold decrease in silver loadings from publicly owned treatment works and a comparable decline in the silver concentration of surficial sediments within that region during the past decade. In the northern reach, silver and lead concentrations have remained essentially constant between 1989 and 1999, reflecting invariable anthropogenic input of these elements to this embayment over that decade.     

An NMR shielding model for protons above the plane of a carbonyl group

Covalently bonded hydrogen nuclei located over the plane of a carbonyl group in a strong magnetic field experience magnetic shielding (or deshielding) that results from the combined effect of the magnetic anisotropy of the carbon-oxygen double bond and various other intramolecular shielding effects. GIAO-HF in Gaussian 98 was employed to calculate isotropic shielding values and to predict the net proton NMR shielding increment for a simple model system: the proximate proton of methane held in various positions over formaldehyde. The net shielding increments of the proximate proton of methane, plotted against its Cartesian coordinates relative to the center of the carbon-oxygen double bond, led to the development of a single empirical equation for predicting the NMR shielding experienced by a covalently bonded proton over the plane of a carbonyl group. The predictive capability of this equation has been validated by calculating the shielding increments of protons over the plane of a carbonyl group in known structures, using this as a correction to the chemical shift estimated by subtituent effects and comparing the result to experimentally observed chemical shifts. Shielding is predicted by this equation for protons located in the region from over the center of the carbon-oxygen double bond to beyond the carbon atom; deshielding is predicted for protons located above and beyond the oxygen atom. This prediction differs from those made by the long-held "shielding cone" model found in nearly every textbook on NMR, but is consistent with experimental observations. The algorithm for predicting the shielding increment for a proton over a carbonyl group can be used in a spreadsheet or incorporated into software that estimates chemical shifts using additive substituent constants or a database of structures. Its use can improve the accuracy of the estimated chemical shift of a proton in the vicinity of a carbon-oxygen double bond, and thus assist in spectral assignments and in correct structure determination.     

Supercritical fluid generated stationary phases for liquid chromatography and capillary electrochromatography

Chromatographic silica-bonded stationary phases have been prepared using supercritical CO(2) as the reaction medium. (29)Si solid-state NMR spectra of the generated bonded silica phases show unreacted silica species Q(3) and Q(4), alongside important resonances for surface-bound ligands, T(1), T(2), and T(3). Initially, a fluorinated octyl silica (C(8)) phase was produced, by reacting (1)H,(1)H,(2)H,(2)H-perfluorooctyltriethoxysilane with silica particles (3 microm) in sc-CO(2) at 60 degrees C and 450 atm for 3 h. In-house-packed LC columns of this fluorinated sc-C(8) silica phase yielded typical reversed-phase behavior when a standard test mix of benzamide (k' = 1.03), benzophenone (k' = 8.11), and biphenyl (k' = 14.92) was eluted. When packed into fused-silica capillaries for CEC, this fluorinated sc-C(8) silica phase gave linear plots of log k' versus percentage MeOH for benzophenone and biphenyl and, in contrast to octyl or octadecyl silica phases, displayed selectivity for aromatic thioureas when chromatographed among a series of synthetic organic thiourea test solutes. Similarily, an octadecyl silica phase (sc-C(18) silica) was prepared by reaction of n-octadecyltriethoxysilane in sc-CO(2), packed at 9500 psi and examined by LC. The sc-C(18) silica LC column yielded high column efficiency (up to 141 000 N/m (fluorene)) and excellent asymmetry factors (1.06, fluorene) without resource to end-capping. Following a second silylating or end-capping step using hexamethyldisilazane in sc-CO(2), sc-end-capped sc-C(18) silica phases elute N,N-DMA before toluene and the toluidine isomers as a single peak, indicating lowered silanol activity according to the Engelhardt test. A rapid separation of the important pharmaceutical substances, ketoprofen, naproxen, fentoprofen, and ibuprofen, on an sc-end-capped sc-C(18) silica phase is also shown.     

Donald G. Forgays (1926–1993): Obituary.

Memorializes D. G. Forgays, who earned an international reputation for his pioneering research on early environmental influence on psychological and physiological functioning. Forgays worked in a range of areas that included the psychophysiology of sensory deprivation and personality dimensions of addictive behaviors. Most of his projects involved cross-cultural data collection and collaboration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)