Glasses Tech – Prescription Glasses, Prescription Eyeglasses

The addition of alkali oxides to silicate glasses results in the disruption of the silicate network and the formation of non-bridging oxygen atoms and Qn species. Lithium-containing silicate glasses behave differently than other alkali-containing silicate glasses. (more…)

We analyzed the glassy-state structural relaxation of polymers near surfaces and interfaces by monitoring fluorescence in multilayer films. Relative to that of bulk, the rate of structural relaxation of poly(methyl methacrylate) is reduced by a factor of 2 at a free surface and by a factor of 15 at a silica substrate interface; the latter exhibits a nearly complete arresting of relaxation. (more…)

The Ontong Java Plateau in the western Pacific is anomalous compared to other oceanic large igneous provinces in that it appears to have never formed a large subaerial plateau. Paleoeruption depths (at 122 Ma) estimated from dissolved H2O and CO2 in submarine basaltic glass pillow rims vary from ∼1100 m below sea level (mbsl) on the central part of the plateau to 2200–3000 mbsl on the northeastern edge. Our results suggest maximum initial uplift for the plateau of 2500–3600 m above the surrounding seafloor and 1500 ± 400 m of postemplacement subsidence since 122 Ma. Our estimates of uplift and subsidence for the plateau are significantly less than predictions from thermal models of oceanic lithosphere, and thus our results are inconsistent with formation of the plateau by a high-temperature mantle plume. (more…)

Video glasses have previously been reported to be an effective instrument for emotion induction or for reducing pain perception. In the present study, we assessed the application of video glasses within the affective picture viewing paradigm. Possible advantages of this new method were tested by a comparison with a commonly used video projector. Twenty-four participants viewed sustained picture series of pleasant, neutral, and unpleasant valence with video glasses and with a projector on different days. Affective report, heart rate (HR), and skin conductance level were measured. (more…)

Evaporative modification of silicates during impacts by large meteorites is the result of high-temperature processing of colliding silicate materials. There are still unresolved questions about the influence of vaporization on the chemical compositions of impact glasses. Here we present the results of experimental modeling of impact-related high-temperature pulse heating of silicates with compositions representative of Earth’s crust. Trends involving differential volatilization of the main rock-forming elements were determined experimentally and compared with those predicted by thermodynamic equilibrium calculations. Our results indicate that impact-induced vaporization is significant for melts at temperatures of 3000–5000 K. As vaporization begins, melts lose Si, Fe, and alkalis and are enriched in Mg, Ca, Al, and Ti. (more…)

Purpose: To compare base-in prism reading glasses with placebo reading glasses for the treatment of symptomatic convergence insufficiency (CI) in children aged 9 to <18 years.

Methods: In a randomised clinical trial, 72 children aged 9 to <18 years with symptomatic CI were assigned to either base-in prism glasses or placebo reading glasses. Symptom level, measured with a quantitative symptom questionnaire (CI Symptom Survey-V15), was the primary outcome measure. Near point of convergence and positive fusional vergence at near were secondary outcomes. (more…)

To better understand the relationship between atomic-scale structures and densities of aluminosilicate glasses and liquids, we used 27Al MAS NMR to determine the speciation of aluminum ions in K3AlSi3O9, Na3AlSi3O9, and Ca3Al2Si6O18 glasses quenched from melts at 3 to 10 GPa. These data are a first approximation of high-pressure melt structure and illustrate the effects of the type of modifier cation. High field strength modifier cations (e.g., Ca) clearly induce more high-coordinated Al than lower field strength cations (e.g., Na and K). (more…)

The structure of multi-component silicate melts and glasses (e.g., Ca-Mg and Ca-Na aluminosilicates) can provide insight into the properties of natural silicate melts and has implications for relevant magmatic processes. In spite of its importance, the atomic and molecular structure of most multi-components (e.g., quaternary) melts and glasses has not been fully described, primarily because of insufficient resolution obtained with conventional spectroscopic and scattering methods; the information obtained by these methods is compromised by severe inhomogeneous peak broadening due to structural complexity. Here we report the first 17O and 27Al 3QMAS NMR spectra for quaternary, (more…)

Typical liquidus temperatures can be over 1000 °C greater than the glass transition temperatures for high-pressure aluminosilicate melts so the effect of temperature must be determined if glass data is to be used to approximate the structural speciation present in geologic melts. This study has investigated the effect of fictive temperature (Tf, taken as the temperature where the melt structure is the same as that of the glass) on the percentage of [5]Al and [6]Al species in two high-pressure (10 GPa) Na-aluminosilicate glasses (Na3AlSi7O17 and NaAlSi3O8) where one glass of each composition was quenched from the high-pressure melt while the other was annealed near the glass transition temperature. (more…)