What's the difference between leucite and leucoplast?
Leucite
Definition:
(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.
Leucoplast
Definition:
(n.) Alt. of Leucoplastid
Example Sentences:
(1) Heterologous hybridization studies with Chlamydomonas reinhardtii rRNAs showed an estimated 80% homology between the two cytoplasmic rRNAs, but only a 50% homology between chloroplast and leucoplast rRNAs of the two species.
(2) The minor species was present in about 2% of the total ribosomal population but showed an eight-to-ninefold enrichment in the leucoplast pellet, suggesting that it was of organelle origin.
(3) Saturation hybridization indicated that only one copy of the rRNA cistrons was present per leucoplast genome, with an average buoyant density of rho = 1.700.
(4) Cytoplasmic invaginations into the plastid, often containing mitochondria, were of frequent occurrence, and membranes of mitochondria and the leucoplast appeared to be closely apposed.
(5) The colorless alga Polytoma obtusum has been found to possess leucoplasts, and two kinds of ribosomes with sedimentation values of 73S and 79S.
(6) Since Polytoma leucoplasts contain both DNA and ribosomal particles, it is probable that these organelles still possess semiautonomy and limited ability for protein synthesis.
(7) We have concluded that the leucoplasts of P. obtusum contain the beta-DNA (1.6882) and the mitochondria possess the gamma-component (1.714).
(8) These findings support the concept that the Polytoma leucoplast possesses characteristic genetic and protein-forming systems.
(9) Electron microscope studies have been made on the fine structure of the colorless biflagellate, Polytoma obtusum, with main emphasis on the structural organization of the mitochondria and the leucoplast.
(10) The Polytoma leucoplast was, in certain respects, morphologically similar to the plastids of various photosynthetic mutants of Chlamydomonas, most of which show Menedelian segregation.
(11) Reconstructions from serial showed that (a) the mitochondria were highly convoluted and irregular in shape and size, and (b) the leucoplast was a single cup-shaped entity, with large starch grains, localized at the posterior end, and multiple sites of DNA aggregates.
(12) We conclude that the leucoplasts of Polytoma derive from chloroplasts of a Chlamydomonas-like ancestor, but that the leucoplast rRNA cistrons have diverged in evolution more extensively than the cistrons for cytoplasmic rRNA.