Glasses Tech – Prescription Glasses, Prescription Eyeglasses

We argue that the intrinsic glassy degrees of freedom in amorphous solids giving rise to the thermal conductivity plateau and the “boson peak” in the heat capacity at moderately low temperatures are directly connected to those motions giving rise to the two-level-like excitations seen at still lower temperatures. These degrees of freedom can be thought of as strongly anharmonic transitions between the local minima of the glassy energy landscape that are accompanied by ripplon-like domain wall motions of the glassy mosaic structure predicted to occur at T g by the random first-order transition theory. (more…)

Property and structure data from binary and ternary silicate and aluminosilicate melts and glasses often reveal simple and systematic relationships to composition and temperature. Properties whose dominant structural control is the abundance of fully polymerized Q4-species, exhibit smooth variations with silica content. Such properties include activation energies associated with transport. Properties that depend on the type and abundance of coexisting structural species in depolymerized melts, either show smooth functional relationships to melt polymerization, NBO/T, or exhibit pronounced minimum or maximum values at intermediate NBO/T-values. (more…)

Molar absorptivity of the infrared (IR) fundamental OH-stretching vibration band at 3550 cm–1 was determined for rhyolitic glasses. Five obsidian samples, unheated and heated at 500–700 °C using an internally heated pressure vessel, were used to evaluate the dependence of the molar absorptivity and final quenched H2O speciation on H2O contents and temperature. Water contents of the obsidians were measured by Karl-Fischer titration first, then the amount of unextracted H2O was calibrated by IR (more…)

AbstractThe low Re abundance in arc-type volcanic rocks characterized by high 187Os/188Os ratios is an unsolved puzzle of the 187Re-187Os isotope system, leaving a significant gap in our understanding of the evolution of the upper mantle–continental crust system. Here we report new observations of high Re concentrations in fresh, submarine-erupted—i.e., relatively undegassed—island arc–like volcanic glasses dredged from the eastern Manus Basin, offshore Papua New Guinea. (more…)

A series of titanium silicate glasses along the composition joins TiO2–SiO2, TiO2–Na2SiO3, TiO2–K2SiO3 and TiO2–CaSiO3, has been examined using oxygen K-edge X-ray absorption near edge structure spectroscopy (XANES) confined to the near-surface region. Sharp pre-edge features in the spectra can be used to determine the Ti coordination in the glasses. The presence of [4]Ti is indicated by a pre-edge peak at ~534 eV while [5]Ti is indicated by a peak at ~533 eV. Titanium exists in all these glasses as [4]Ti and [5]Ti with no [6]Ti being present. For alkali-containing glasses the [5]Ti site becomes more prevalent with increasing TiO2. TiO2-K2SiO3 compositions contain a greater proportion of [4]Ti than comparable (more…)

Gifted children are often Big Picture thinkers (Schultz & Delisle, 1997). Even as young children, they may ask profound questions and view life from the perspective of The Most Important Things: meaning, goodness, truth, spirituality, death, and the like. J. D. Salinger’s stories about the gifted and precocious Glass children offer a vivid, provocative, and very useful description of a spiritual Big Picture perspective on life. (more…)

A novel composite material has been developed based on thermoplastic polymers on one hand and thermoplastic chalcogenide glass on the other hand. Extrusion technique and pressing allowed the production of very different structures of the composite, ranging from fibrous to “sandwich” structures. Also obtained were highly homogenous compositions that contain perfectly spherical glass particles of 1-6 mm in diameter dispersed into a polymer matrix. (more…)

Purpose: to examine the effect of correction type on myopia progression in subjects who completed a randomized clinical trial of bifocal glasses.
Methods: Forty nine of 55 subjects, who completed a 42-month clinical trial, returned for a 1-yr post-treatment visit (54 months of follow-up). Original treatment assignments were single-vision glasses (SV) or bifocal glasses (BF) with a +1.50 D add. Once released from treatment, children chose either to wear soft contact lenses (CL), to continue in their assigned glasses, or to switch to the other type of glasses. Progression during that year, i.e. from 42 to 54 mos., was used to estimate the effect of switching correction type. Myopia was measured with automated refraction 30 min after instilling two drops of 1% tropicamide. We used ANOVA with age as co-variate and averaged myopia over both eyes. Means presented here are age-adjusted. (more…)

The effects of source composition and source evolution during progressive partial melting on the chemistry of mantle-derived mid-ocean ridge basalt (MORB) melts were tested using a comprehensive geochemical and Sr–Nd–Pb isotopic dataset for fresh, magnesian basaltic glasses from the Miocene Macquarie Island ophiolite, SW Pacific. These glasses: (1) exhibit clear parent–daughter relationships; (2) allow simple reconstruction of primary melt compositions; (3) show exceptional compositional diversity (e.g. K2O/TiO2 0·09–0·9; La/Yb 1·5–22; 206Pb/204Pb 18·70–19·52); (4) preserve changes in major element and isotope compositions, which are correlated with the degree of trace element enrichment (e.g. La/Sm). (more…)