A cross-coupling model of vertical vergence adaptation

Vertical disparity vergence aligns the two eyes in response to vertical misalignment (disparity) of the two ocular images. An adaptive response to vertical disparity vergence is demonstrated by the continuation of vertical vergence when one eye is occluded. The adaptive response is quantified by vertical phoria, the eye alignment error during monocular viewing. Vertical phoria can be differentially adapted to vertical disparities of opposite sign located at two positions along the horizontal or vertical head-referenced axes. Vertical phoria aftereffects vary in amplitude as the eyes move from one adapted direction of gaze to another along the adaptation axis. A cross-coupling model was developed to account for the spatial variations of vertical phoria aftereffects. The model is constrained according to both single cell recordings of eye position sensitive neurons, and eye position measurements during and following adaptation. The vertical phoria is computed by scaling the activities of eye position sensitive neurons and converting the scaled activities into a vertical vergence signal. The three components of the model are: neural activities associated with conjugate eye position, cross-coupling weights to scale the activities, and vertical vergence transducers to convert the weighted activities to vertical vergence. The model provides a biologically plausible mechanism for vertical vergence adaptation     

Bivariate median splits and spurious statistical significance.

Despite pleas from methodologists, researchers often continue to dichotomize continuous predictor variables. The primary argument against this practice has been that it underestimates the strength of relationships and reduces statistical power. Although this argument is correct for relationships involving a single predictor, a different problem can arise when multiple predictors are involved. Specifically, dichotomizing 2 continuous independent variables can lead to false statistical significance. As a result, the typical justification for using a median split as long as results continue to be statistically significant is invalid, because such results may in fact be spurious. Thus, researchers who dichotomize multiple continuous predictor variables not only may lose power to detect true predictor–criterion relationships in some situations but also may dramatically increase the probability of Type I errors in other situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Superconductivity and Magnetism in Pure and Substituted RuSr2GdCu2O8

We describe results of several macroscopic and local measurements of magnetic and superconducting properties for pure and Ce and Cu substituted RuSr₂GdCu₂O₈. From various experiments the physical properties phase diagram is derived as a function of the hole doping. We show that the large contribution of polarized Gd³⁺ magnetic moments to magnetization causes apparent absence of the Meissner state and augments the weak Ru ferromagnetism. This weak ferromagnetism in the superconducting state can be significantly enhanced by the external magnetic field. These results indicate that the low-temperature behavior can be qualitatively explained assuming a quasi-two-dimensional character of the superconducting regions.     

Improving command and control speech recognition on mobile devices: using predictive user models for language modeling

Command and control (C&C) speech recognition allows users to interact with a system by speaking commands or asking questions restricted to a fixed grammar containing pre-defined phrases. Whereas C&C interaction has been commonplace in telephony and accessibility systems for many years, only recently have mobile devices had the memory and processing capacity to support client-side speech recognition. Given the personal nature of mobile devices, statistical models that can predict commands based in part on past user behavior hold promise for improving C&C recognition accuracy. For example, if a user calls a spouse at the end of every workday, the language model could be adapted to weight the spouse more than other contacts during that time. In this paper, we describe and assess statistical models learned from a large population of users for predicting the next user command of a commercial C&C application. We explain how these models were used for language modeling, and evaluate their performance in terms of task completion. The best performing model achieved a 26% relative reduction in error rate compared to the base system. Finally, we investigate the effects of personalization on performance at different learning rates via online updating of model parameters based on individual user data. Personalization significantly increased relative reduction in error rate by an additional 5%.     

Power in randomized group comparisons: The value of adding a single intermediate time point to a traditional pretest-posttest design.

Adding a pretest as a covariate to a randomized posttest-only design increases statistical power, as does the addition of intermediate time points to a randomized pretest-posttest design. Although typically 5 waves of data are required in this instance to produce meaningful gains in power, a 3-wave intensive design allows the evaluation of the straight-line growth model and may reduce the effect of missing data. The authors identify the statistically most powerful method of data analysis in the 3-wave intensive design. If straight-line growth is assumed, the pretest-posttest slope must assume fairly extreme values for the intermediate time point to increase power beyond the standard analysis of covariance on the posttest with the pretest as covariate, ignoring the intermediate time point. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The dynamic properties of elastomers above the limit of linear viscoelastic response

A method of measuring the dynamic viscoelastic properties of polymers at large strain magnitudes, well above the limit of linear viscoelastic response, has been developed. A straight line relationship has been found between the dynamic stress and the dynamic strain above the limit of linear viscoelastic response. This straight line relationship can be described by a dynamic in-phase modulus that is a function of the maximum strain applied and the frequency of the applied dynamic strain. This rheological characterization method is demonstrated for a series of synthetic elastomers with various carbon black loadings.     

Quantitative isolation of lipids of partially defatted and whole peanuts by a dry column method

A dry column method of lipid extraction was found to be applicable to peanuts—partially defatted as well as whole. Total lipid was obtained from the peanut/sodium sulfate/Celite 545 columns by isocratic elution with dichloromethane/methanol 9:1. Moreover, neutral lipids were obtained by sequential elution that were completely free from polar lipids. First, dichloromethane eluted the neutral lipids, then the 9:1 solvent eluted the polar lipids—at times containing small quantities of neutral lipids. Total lipid values obtained by the column extraction method were slightly higher than those obtained by the standard Soxhlet extraction procedure. This was due in part to the more complete polar lipid isolation produced by the column method. In partially defatted peanuts produced by mechanical pressing, 99% of the polar lipids remained in the retained oil, and these were shown to be slightly less unsaturated than the neutral lipids.     

The application of melt elasticity to polymer processing

The present state of knowledge of polymer melt elasticity is reviewed together with consideration of the problems that elastic effects cause in polymer processing systems. Two examples of the useful application of melt elasticity are presented, one in melt extrusion the other in polymer melt mixing.     

Dry column method for the quantitative extraction and simultaneous class separation of lipids from muscle tissue

A method for lipid isolation is presented that is alternative to the traditional chloroform/methanol extraction methods. This new method allows lipid isolation by solvent elution of a dry column composed of a tissue sample, anhydrous sodium sulfate, and Celite 545 diatomaceous earth groud together. To isolate total lipids, the dry column is eluted with a mixture of dichloromethane/methanol (90∶10, v/v). Alternatively, the lipids may be isolated and simultaneously separated into neutral and polar fractions by a sequential elution procedure; neutral lipids free of polar lipids are eluted first with dichloromethane, followed by elution of polar lipids with the dichloromethane/methanol (90∶10) mixture. The two dry column methods-isocratic or sequential elution-were compared with the traditional chloroform/methanol methods by gravimetric, thin layer chromatographic and phosphorus analyses. Presented in part at the AOCS 70th Annual Meeting, San Francisco, May 1979. Agricultural Research, Science and Education Administration, U.S. Department of Agriculture.