Olestra formulation and the gastrointestinal tract.

Olestra is a mixture of compounds comprising sucrose esterified with 6-8 long-chain fatty acids. It is not hydrolyzed by pancreatic lipase and as a result is not absorbed from the small intestine. Olestra in general has physical properties similar to those of a triacylglycerol with the same fatty acid composition. Foods made with olestra are virtually identical in taste and texture to those made with typical triacylglycerols. Olestra consumption does not generate hydrolytic products in the small intestine and, therefore, does not generate some of the signals that alter motility in the gastrointestinal tract. A reduction in gastroesophageal reflux with olestra, in contrast to triacylglycerols, is consistent with a lack of effect on stomach emptying. Unlike triacylglycerols that are absorbed in the proximal small intestine, olestra is distributed throughout the small intestine during transit and passes into the colon. In the colon, olestra's effects depend on its physical properties. Liquid nondigestible lipids result in separation of oil from the fecal matrix. Olestra formulations made with specific fatty acid compositions, particularly those containing a solid sucrose polyester component including behenic acid, possess appropriate rheology to hinder separation of oil from the rest of the fecal matrix, thereby reducing gastrointestinal symptoms.

Planar geometry thin-film all-optical programmable switch.

We describe an all-optical programmable switch that can perform logic gate functions. This switch consists of a planar geometry germanium-doped silica waveguide, a Q-switched and mode-locked Nd:YAG laser, and the means of coupling laser light into different waveguiding modes of the thin film at the fundamental and second-harmonic frequencies. By the application of the appropriate optical programming sequence, the film-generated second-harmonic light can be made to perform the functionalities of various gates. In particular, a single waveguide was optically programmed to perform the Or function and was then made to perform the And function with little change to the experimental arrangement.

Second-harmonic generation in planar waveguides of doped silica.

Second-harmonic generation was produced in germanium-doped silica planar waveguides prepared by simulfaneous illumination with 1064- and 532-nm laser light. During preparation using prism coupling to specific waveguiding modes, the film-generated second-harmonic intensity grew as a function of preparation time until it saturated. The growth rate and saturation level for p-polarized second-harmonic intensity was an order of magnitude greater than that observed for the s polarization. The efficiency for a 2-cm waveguide length was at least 0.5%. The comparison of experimental results indicates a mechanism for this planar geometry that is similar to that producing harmonic effects in optical fibers.

Resistance of lipid films to transmission of water vapor and oxygen.

Various lipids, present as thin films on polar filter paper supports, were evaluated for resistance to the transmission of water vapor (rH2O) and oxygen (rO2). Beeswax exhibited the largest r(H2O), followed in order by fully-hydrogenated soy-rapeseed oil, stearyl alcohol, acetylated monoglycerides, hexatriacontane, tristearin, and stearic acid. Most of the lipids exhibited negative activation energies, E, for resistance to transmission of water vapor and positive Es for resistance to transmission of oxygen. The type of lipid support (hydrophobic or hydrophilic) also influenced E for resistance to water vapor transmission. Differences in r(H2O) for the various lipids, comparative r(H2O) and r(O2) values, and the temperature dependence of these values can be explained, in part, by the degree of hydrophilicity of the lipid molecule. Tempering at 48 degrees C of stearyl alcohol caused a substantial decrease in its permeability to oxygen and water vapor. The polymorphic form of a blend of fully-hydrogenated soybean and rapeseed oil had a moderate influence on its permeability to oxygen and water vapor. This information will be useful for formulating lipid-containing films with controlled barrier properties to the passage of water vapor and oxygen.