Simultaneous effects on vowel duration in American English: a covariance structure modeling approach

The powerful techniques of covariance structure modeling (CSM) long have been used to study complex behavioral phenomenon in the social and behavioral sciences. This study employed these same techniques to examine simultaneous effects on vowel duration in American English. Additionally, this study investigated whether a single population model of vowel duration fits observed data better than a dual population model where separate parameters are generated for syllables that carry large information loads and for syllables that specify linguistic relationships. For the single population model, intrinsic duration, phrase final position, lexical stress, post-vocalic consonant voicing, and position in word all were significant predictors of vowel duration. However, the dual population model, in which separate model parameters were generated for (1) monosyllabic content words and lexically stressed syllables and (2) monosyllabic function words and lexically unstressed syllables, fit the data better than the single population model. Intrinsic duration and phrase final position affected duration similarly for both the populations. On the other hand, the effects of post-vocalic consonant voicing and position in word, while significant predictors of vowel duration in content words and stressed syllables, were not significant predictors of vowel duration in function words or unstressed syllables. These results are not unexpected, based on previous research, and suggest that covariance structure analysis can be used as a complementary technique in linguistic and phonetic research.     

Spin relaxation resonances due to the spin-axis interaction in dense rubidium and cesium vapor

Resonances in the magnetic decoupling curves for the spin relaxation of dense alkali-metal vapors prove that much of the relaxation is due to the spin-axis interaction in triplet dimers. Initial estimates of the spin-axis coupling coefficients for the dimers (likely accurate to a factor of 2) are |lambda|/h = 290 MHz for Rb; 2500 MHz for Cs.     

An oligopoly model of dynamic advertising competition

An oligopoly model is presented that allows the determination of feedback Nash equilibrium advertising strategies for an oligopoly. Analyses of symmetric and asymmetric oligopolies with the model show that unit contribution and advertising effectiveness have positive effects on a competitor’s own advertising and steady-state sales, while discount rate and decay rate have negative effects. An asymmetric analysis further shows that unit contribution and advertising effectiveness affect positively, and discount rate and decay rate negatively, a competitor’s rivals’ advertising, but have effects in opposite directions regarding rivals’ steady-state sales. The symmetric and asymmetric analyses also show that steady-state sales per competitor decline with the number of competitors in the oligopoly, while total oligopoly steady-state sales increase. The model is applied empirically to the triopolistic competition involving Anheuser-Busch, SABMiller, and Molson Coors in the beer industry.     

Efficiently Hex-Meshing Things with Topology

A topological quadrilateral mesh \(Q\) of a connected surface in \(\mathbb {R}^3\) can be extended to a topological hexahedral mesh of the interior domain \(\varOmega \) if and only if \(Q\) has an even number of quadrilaterals and no odd cycle in \(Q\) bounds a surface inside \(\varOmega \) . Moreover, if such a mesh exists, the required number of hexahedra is within a constant factor of the minimum number of tetrahedra in a triangulation of \(\varOmega \) that respects \(Q\) . Finally, if \(Q\) is given as a polyhedron in \(\mathbb {R}^3\) with quadrilateral facets, a topological hexahedral mesh of the polyhedron can be constructed in polynomial time if such a mesh exists. All our results extend to domains with disconnected boundaries. Our results naturally generalize results of Thurston, Mitchell, and Eppstein for genus-zero and bipartite meshes, for which the odd-cycle criterion is trivial.     

The stereochemical outcome of electrophilic addition reactions on the 5,6-double bond in the spinosyns.

The electrophilic addition of reagents to the 5,6-double bond in spinosyn A and spinosyn D systems occurred with high pi-diastereofacial selectivity. Addition occurred preferentially from the beta face of the molecule with selectivities ranging from 5:1 to better than 30:1. Various NMR properties were investigated in order to distinguish the beta and alpha isomers with the help of theoretical models of the products. These NMR properties include a (13)C gamma effect to C-11 and vicinal coupling between H-4 and H-5. To help rationalize the selectivity, computational studies on the transition states for epoxidation were calculated using density functional theory. The results indicate that beta epoxidation is favored and that the geometries of the transition structures are consistent with torsional steering being the source of the selectivity.     

Preservice Mathematics and Science Teachers' Case Studies of a Diverse Population of Workers

Sixteen preservice science and mathematics teachers in the last term of a Master of Arts in Teaching (MAT) program completed case studies of workers from a variety of settings including a radio station, department store, manufacturing plant, health care facility, water treatment plant, and engineering firm. These preservice teachers then examined their findings and reflected about the knowledge and skills necessary for high school graduates to be successful in the present day workplace. Finally, the preservice teachers examined how they could personally contribute to these desirable student outcomes within the high school science or mathematics curriculum for which they will eventually be responsible in their future teaching situations.     

Optimization of a permeation-based microfluidic direct formic acid fuel cell (DFAFC)

A design for a passive, air-breathing microfluidic fuel cell utilizing formic acid (FA) as a fuel is described and its performance characterized. The fuel cell integrates high surface area platinum (cathode) and palladium-platinum (anode) alloy electrodes within a PDMS microfluidic network that keeps them fully immersed in a liquid electrolyte. The polymer network that comprises the device also serves as a self-supporting membrane through which FA and oxygen are supplied to the alloy anode and cathode, respectively, by passive permeation from external sources. The cell is based on a planar form-factor and in its operation exploits FA concentration gradients that form across the PDMS membrane. These latter gradients allow the device to operate stably, producing a nearly constant limiting power density of ~0.2 mW/cm2, without driven laminar flow of fluids or the incorporation of an in-channel separator between the anodic and the cathodic compartments. The power output of this elementary device in air is subject to electrolyte mass transport impacts, which can be reduced for a given design rule by decreasing the internal ohmic resistance of the cell. The results suggest that operational stability can be improved by decreasing the kinetic losses imposed on the cathode side of the cell due to FA crossover and modalities for doing so, such as by increasing the efficiency of fuel capture at the anode.