Effect of induced anisometropia on binocular through-focus contrast sensitivity.

PURPOSE: The aim of this study was to characterize binocular through-focus function in white light and to investigate the effect of induced anisometropia on binocular depth of focus. METHODS: The subjects viewed sine-wave gratings generated on a monitor through a modified Badal system that produced gradual changes in target vergence ranging from -4.00 to +2.00 D. Binocular through-focus contrast sensitivity curves were obtained at a spatial frequency of 11 cpd and for different levels of induced anisometropia. Subjective depths of focus were derived from the through-focus curves. RESULTS: An induced anisometropia lower than 1.00 D led to a monomodal through-focus curve involving a single depth of focus, whereas with higher anisometropia, the curves became bimodal indicating a lack of performance at intermediate distance. Binocular thresholds predicted by the quadratic summation model from our monocular measurements were well correlated to our binocular measurements. Predictions allowed us to estimate optimum levels of induced anisometropia.

Electrochemical synthesis of conjugated polymer wires and nanotubules

Two electrochemical methods designed for the synthesis of polypyrrole (PPy) wires and nanotubules are the topic of this paper. The concept that allows the morphology of PPy to be controlled is discussed for each method, and the performances of the two complementary techniques are compared in terms of dimension, shape and conductivity of PPy.

Adsorption of albumin, collagen, and fibronectin on the surface of poly(hydroxybutyrate-hydroxyvalerate) (PHB/HV) and of poly (epsilon-caprolactone) (PCL) films modified by an alkaline hydrolysis and of poly(ethylene terephtalate) (PET) track-etched membranes.

The effect of alkaline hydrolysis on several surface properties of poly(hydroxybutyrate-hydroxyvalerate) (92/8) (PHB/HV) and poly(epsilon-caprolactone) (PCL) films and of poly(ethylene terephtalate) (PET) track-etched membranes have been characterized, as well as the adsorption of three proteins normally encountered by mammalian cells in vivo, namely albumin, collagen, and fibronectin. The water contact angle decreases and the number of -COOH functions accessible to a chemical reaction at the surface of PCL increases with alkaline hydrolysis. Analysis by atomic force microscopy pictures reveals a change in surface morphology. The modifications of surface properties are correlated with a two times increase of the adsorption of three radiolabelled proteins. The hydrolysis results in a slight increase in the water contact angle of one face of the PHB/HV film and a sharp increase in the number of -COOH functions. Important morphology changes are also induced. The adsorption of the radiolabelled proteins is almost 100 times higher on the hydrolyzed polymer than on the native surface. The increase in hydrophilicity of different PET batches correlates to an increase in the number of -COOH functions. Nevertheless, the surface chemical composition and rugosity are constant and no significant difference in the amount of radiolabelled fibronectin adsorbed on the different surfaces is detectable. In conclusion, the effect of hydrolysis on the surface properties of each of the polyesters studied as well as the proteins adsorption on the different surfaces are different. The results strongly support the hypothesis that, in the system studied, parameters other than hydrophilicity influence protein adsorption: the main parameters that might play a role are the total surface area accessible to the proteins, as well as the surface chemical composition.

Physico-mechanical properties of poly (epsilon-caprolactone) for the construction of rumino-reticulum devices for grazing animals.

The solid-state degradation of poly(epsilon-caprolactone) in the rumen of fistulated cattle was investigated. The degradation process was studied by measurement of changes in weight loss, crystallinity, Young's modulus, molecular weight by size exclusion chromatography and by intrinsic viscosity. In vitro degradation studies were conducted at 39 degrees C in aqueous solutions with a pH and ionic strength as near as possible to those encountered in vivo. Such studies demonstrated that the poly (epsilon-caprolactone) degraded more rapidly in vivo than in vitro. In vivo, chain scission is associated with an increase in crystallinity. The faster degradation in vivo was attributed to fatty acids and bacteria that are present in the rumen, the first portion of the stomach of the grazing animals.