Glasses Tech – Prescription Glasses, Prescription Eyeglasses

March 8, 2010

Rose-Colored Glasses

Filed under: Glasses 1999 — admin @ 2:02 am


The social information-processing (SIP) model has generated significant knowledge concerning the social cognitions of rejected and aggressive children. However, the model rarely has been applied to the cognitions and behavior of prosocial children or adolescents. This study examined SIP patterns of prosocial young adolescents (10 through 12 years of age). Hypothetical situation instruments were used to assess the intent attributions, feelings of distress, and response-ecision processes (for relational and instrumental provocation situations) of fourth- through sixth-grade young adoles-cents (N = 675). (more…)

Carbonatite Metasomatism of the Oceanic Upper Mantle: Evidence from Clinopyroxenes and Glasses in Ultramafic Xenoliths of Grande Comore, Indian Ocean

Filed under: Glasses 1999 — admin @ 2:01 am

Petrological and geochemical data are presented for a suite of ultramafic xenoliths (lherzolites and wehrlites) from La Grille volcano, Grande Comore island. These xenoliths have peculiar textural features characterized by reaction rims or glassy patches, where clinopyroxene grows at the expense of orthopyroxene. The glasses vary from very strongly silica-oversaturated to strongly undersaturated varieties. They are generally homogeneous within a single xenolith, are extremely alkali rich, with Na2O contents (up to 14 wt %) higher than any previously encountered, and are highly evolved (mg-number 34–37). The major element (especially Na) and trace element abundances, together with some remarkable Ti and Zr negative anomalies in chondrite-normalized diagrams, suggest that the metasomatizing agent was an ephemeral alkali-rich carbonatite. These metasomatic reactions appear to have involved an increase in oxygen fugacity from lherzolites (–0.56 to 1.29log units) to wehrlites (up to 2.68log units), with a concomitant decrease in temperature (lherzolites: 908–993°C; wehrlites: 816–893°C). (more…)

Empirical calibration of the sulphur valence oxygen barometer from natural and experimental glasses; method and applications

Filed under: Glasses 1999 — admin @ 1:38 am

New data on sulphur valence and magmatic oxidation state for Central Andean volcanic rocks, in combination with published data for experimental and natural samples, allow derivation of a simple relationship between magma oxidation state and sulphur speciation. For a number of highly oxidized Central Andean volcanic rocks f O2 has been calculated using magnetite-ilmenite or olivine-spinel pairs and the sulphur valence in glasses has been measured using the peak shift of S-Kalpha radiation relative to a pyrite standard. (more…)

Al-O-Al oxygen sites in crystalline aluminates and aluminosilicate glasses; high-resolution oxygen-17 NMR results

Filed under: Glasses 1999 — admin @ 1:22 am

We report 17 O magic-angle spinning (MAS) NMR data for crystalline NaAlO 2 and CaAl 2 O 4 at external magnetic fields of 9.4 and 14.1 T, as model compounds for Al-O-Al sites in tetrahedral networks. The former contains one peak with isotropic chemical shift (delta iso ) = 30.9 ppm and quadrupolar coupling constant (C Q ) nearly equal 1.8 MHz. The latter contains several peaks with delta iso ranging from 39 to 87 ppm and C Q nearly equal 1.5 to 2.4 MHz. (more…)

The degree of aluminum avoidance in aluminosilicate glasses

Filed under: Glasses 1999 — admin @ 1:20 am

For two series of aluminosilicate glasses on the SiO 2 -NaAlO 2 and SiO 2 -CaAl 2 O 4 joins, 29 Si magic-angle-spinning (MAS) NMR spectra were measured. Systematic variations in peak positions and widths with composition are closely related to the extent of ordering of Si and Al cations. A statistical thermodynamic model based on the quasi-chemical approximation was formulated to calculate the proportions of SiO 4 groups with varying numbers of Al neighbors and thus to quantify the extent of ordering. (more…)

Structural investigation of platinum solubility in silicate glasses

Filed under: Glasses 1999 — admin @ 1:17 am

The coordination environment of 20-200 ppm Pt in yellowish glasses from the CaO-Al 2 O 3 -SiO 2 (CAS) ternary was studied using X-ray absorption fine structure spectroscopy at the Pt-L III edge. Analysis of the Pt-L III edge region suggests that Pt in these glasses is mainly tetravalent and sixfold-coordinated by O (with a mean Pt-O distance of 2.08+ or -0.02 Aa). No evidence for Pt (super 2+) or Pt (super 6+) was found in any of the glasses studied, suggesting that one can not derive valence information easily from solubility data. (more…)

Hydrothermal conversion of trachytic glass to zeolite; 3, Monocationic model glasses

Filed under: Glasses 1999 — admin @ 1:14 am

Experiments on zeolitization were conducted on four synthetic monocationic glasses (Na, K, Ca, or Mg-rich glass) with Si/Al molar ratios of 2.67, similar in acidity to many volcanic glasses of partially zeolitized Italian tuffs. The products of the hydrothermal treatment at 100, 150, and 200 degrees C of single glasses or glass mixtures with deionized H 2 O or monosaline solutions (NaCl, KCl, CaCl 2 ) were characterized by X-ray diffraction, thermal, microscopic and chemical analyses. (more…)

Glasses Tech – Prescription Glasses, Prescription Eyeglasses