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Bani-Jaber AK Alkawareek MY Al-Gousous JJ Abu Helwa AY 《Chemical & pharmaceutical bulletin》2011,59(2):155-160
The aim of this study was to evaluate the influence of Na-bicarbonate as an effervescent agent on the floating and sustained-release characteristics in 0.1 M HCl of tablets made of Eudragit E PO (EE) and/or Eudragit L-100-55 (EL) as matrix formers at different EE:EL weight ratios: 0:100, 25:75, 50:50, 75:25, and 100:0. The tablets were made by direct compression utilizing metronidazole as a model drug. Effervescent tablets with 50EE/50EL (w/w) showed the best floating and sustained drug release properties in the dissolution medium. The corresponding noneffervescent tablets were nonfloating and showed significantly faster drug release. Effervescent tablets with single polymers showed an immediate drug release pattern. These results were explained by Fourier-transform infrared spectroscopy and elemental analysis, which showed strong evidence of interpolyelectrolyte complexation between EE and EL when they were exposed to 0.1 M HCl as an effervescent hybrid matrix, but not as a noneffervescent hybrid matrix. The role of Na-bicarbonate in allowing EE-EL complexation during dissolution was explained as due to raising the pH around EL particles for sufficient polymer ionization and ionic-interaction with the ionized EE. 相似文献
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We go back and forth between, on the one hand, presentations of arithmetic and Kac-Moody groups and, on the other hand, presentations of profinite groups, deducing along the way new results on both. 相似文献
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Geometric and dynamic properties of embeddings of SL(2; ℤ) into the Cremona group are studied. Infinitely many nonconjugate
embeddings that preserve the type (i.e., that send elliptic, parabolic and hyperbolic elements onto elements of the same type)
are provided. The existence of infinitely many nonconjugate elliptic, parabolic and hyperbolic embeddings is also shown. In
particular, a group G of automorphisms of a smooth surface S obtained by blowing up 10 points of the complex projective plane is given. The group G is isomorphic to SL(2; ℤ), preserves an elliptic curve and all its elements of infinite order are hyperbolic. 相似文献
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