(n.) A mineral having a glassy fracture, occurring in translucent trapezohedral crystals. It is a silicate of alumina and potash. It is found in the volcanic rocks of Italy, especially at Vesuvius.
(n.) A leucoplast.
Example Sentences:
(1) Quantitative x-ray diffraction was performed on the fast- and slow-cooled porcelain specimens with standards containing leucite volume fractions of 0.111, 0.223, 0.334, and 0.445.
(2) Recently introduced with pleasing aesthetic qualities, IPS-Empress (Ivoclar, Schaan, Liechtenstein), a new European leucite-reinforced glass-ceramic, has finally drawn attention in some journals and has been reviewed with promising in vitro test results.
(3) Unpaired, one-tailed t tests were performed on the fast- and slow-cool data, and a significant increase (p less than 0.05) in the amount of leucite (as a function of the slow cooling) was found for each of the porcelains.
(4) A better understanding of compatibility of alloy and ceramic during refiring schedules based upon leucite phase transformations and the ramifications for porcelain failure is emerging.
(5) Besides low leucite and glass, we have found a second crystalline phase in the sintered and slow-cooled porcelains that we propose to be potash feldspar (K2O.Al2O3.6SiO2).
(6) The present study was undertaken to determine whether the increase in porcelain thermal expansion might be attributable to crystallization of additional leucite during slow cooling of the porcelain.
(7) Ceramography confirms the martensitic (displacive) nature of the transformation from high (cubic) to low (tetragonal) leucite upon cooling.
(8) X-ray diffraction analyses verified the leucite content in metal ceramic systems and ceramics of the nonbonded systems.
(9) The chief ingredient of each porcelain was leucite (K2O .
(10) Comparing the metal ceramic systems with the nonbonded systems, an increase in leucite content was observed in the nonbonded systems.
(11) Most commercial dental porcelains designed for ceramo-metallic restorations are partially crystallized feldspathic glasses (glass-ceramics) that consist of low (tetragonal) leucite (K2O.Al2O3.4SiO2) crystals embedded in a glassy matrix.
(12) The purpose of this study was to test the hypothesis that high-leucite content feldspathic porcelain can be strengthened best by thermal tempering followed by ion exchange, compared with either thermal tempering or ion exchange alone.
(13) The increases in the leucite volume fractions resulting from the slow cooling ranged from a low of 8.5% to a high of 55.8%, with an average increase of 26.9%.
(14) The structure analysed in the scanning electron microscope showed leucite in the dendritic and idiomorphic form.
(15) Some other components were metal oxides used as pigment and opaque, for regulating the recrystallization of leucite in the fused porcelain, for controlling the thermal expansion, and for diffusing in the both sides of alloy and porcelain.
(16) The dentine materials of the metal ceramic systems VMK 68 and Biodent as well as the ceramics of all ceramic systems Duceram, Cosmotech, Optec, IPS-Empress and Corum were tested for their leucite content.
Mineral
Definition:
(v. i.) An inorganic species or substance occurring in nature, having a definite chemical composition and usually a distinct crystalline form. Rocks, except certain glassy igneous forms, are either simple minerals or aggregates of minerals.
(v. i.) A mine.
(v. i.) Anything which is neither animal nor vegetable, as in the most general classification of things into three kingdoms (animal, vegetable, and mineral).
(a.) Of or pertaining to minerals; consisting of a mineral or of minerals; as, a mineral substance.
(a.) Impregnated with minerals; as, mineral waters.
Example Sentences:
(1) It is suggested that the Japanese may have lower trabecular bone mineral density than Caucasians but may also have a lower threshold for fracture of the vertebrae.
(2) The absorption of ingested Pb is modified by its chemical and physical form, by interaction with dietary minerals and lipids and by the nutritional status of the individual.
(3) There will be no statutory inquiry or independent review into the notorious clash between police and miners at Orgreave on 18 June 1984 , the home secretary, Amber Rudd, has announced.
(4) There was however no difference in the cross-sectional studies and no significant deleterious effect detected of tobacco use on forearm bone mineral content.
(5) From these results, it was suggested that the inhibitory effect of Cd on in vitro calcification of MC3T3-E1 cells may be due to both a depression of cell-mediated calcification and a decrease in physiochemical mineral deposition.
(6) The effect of dietary fibre digestion in the human gut on its ability to alter bowel habit and impair mineral absorption has been investigated using the technique of metablic balance.
(7) The greatest advantages of spinal QCT for noninvasive bone mineral measurement lie in the high precision of the technique, the high sensitivity of the vertebral trabecular measurement site, and the potential for widespread application.
(8) The model has been used to evaluate mineral changes from the use of fluoride dentifrices and rinses, chewing gum, and food sequencing.
(9) These data indicate improved bone mineralization as compared with previously reported data from very-low-birth-weight neonates.
(10) Gladstone's speech was not made in Parliament, but to a crowd of landless agricultural workers and miners in Scotland's central belt, Gove pointed out.
(11) Artificially produced mineral waters which are identical to natural ones are also applied.
(12) The method of mineral estimation using phalanges is described and its reproducibility was tested on 17 parameters.
(13) Secondary structural features of bovine amelogenin, a hydrophobic protein of developing enamel implicated in ename mineralization, are derived using 2D NMR spectroscopy in solution and molecular mechanics-dynamics studies.
(14) Reduced mineral absorption is fairly well documented and has sound theoretical support from basic chemistry.
(15) Microbiological analyses of sediments located near a point source for petrogenic chemicals resulted in the isolation of a pyrene-mineralizing bacterium.
(16) Years of education completed and poverty status did not significantly affect folate concentrations; however, the prevalence of low folate concentrations among users of vitamin or mineral supplements was significantly lower than it was among nonusers in selected subgroups.
(17) Unsupplemented human breast milk may not provide sufficient calcium and phosphorus for the rapidly growing preterm infant to match the accumulation that should have taken place in utero and to permit normal bone mineralization.
(18) In some areas of the ligament, extracellular plasma membrane-invested matrix vesicles and thick wall-bound matrix giant bodies with or without mineralized deposits were present.
(19) My grandfather was a coal miner and Nana was rather plump and bossy.
(20) These diets were: diet C consisting of commercial Rat Chow: diet CG, the same diet diluted with 70% glucose calories, diet A, a simulated "American" diet made up of 25 widely used foods, diet AS, the same diet supplemented with small amounts of 25 vitamins and minerals.