Optical and fluorescence spectroscopy of Eu2O3-doped P2O5-K2O-KF-MO-Al2O3 (M = Mg, Sr and Ba) glasses

Fluorophosphate glasses of composition, P₂O₅ + K₂O + KF + MO + Al₂O₃ + xEu₂O₃ (M = Mg, Sr and Ba; x = 0.01, 0.05, 0.1, 1.0, 2.0, 4.0 and 6.0 mol%) were prepared and characterized their optical properties. Crystal-field (CF) analysis revealed a relatively weak CF strength around Eu³⁺ ions in the Ba based fluorophosphate glasses. The Judd-Ofelt parameters have been estimated from the oscillator strengths of ⁷F₀ → ⁵D₂, ⁷F₀ → ⁵D₄ and ⁷F₀ → ⁵L₆ absorption transitions of Eu³⁺ ions and were used to evaluate the radiative properties of the ⁵D₀ → ⁷F_J (J = 0-4) transitions. Considerable variation has been observed in the relative intensity ratio of ⁵D₀ → ⁷F₂ to ⁵D₀ → ⁷F₁ transitions of Eu³⁺ ions due to change in the alkaline earth metal ions. The decay of the ⁵D₀ level shows single exponential and less sensitive to Eu³⁺ ions concentration as well as MgO/SrO/BaO modifiers.     

Dynamics of semi-flexible tethered sheets

The dynamics of a semi-flexible sheet or tethered membrane in a solvent is studied using the method of stochastic rotation dynamics. Hydrodynamic interactions between different parts of the sheet are naturally included in this method. We confirm the scaling law for the radius of gyration versus sheet size predicted for a self-avoiding tethered membrane. The mean-square displacement shows both sub-diffusive and diffusive behavior similar to linear polymers. In the intermediate scattering function the sub-diffusive behavior appears as stretched exponential which we reproduce in our simulations. Thereby, we confirm an early prediction between the roughness and the sub-diffusion exponent derived from Zimm dynamics (E. Frey, D.R. Nelson, J. Phys. I 1, 1715 (1991)). Finally, we show that the diffusion coefficient of the square sheet is inversely proportional to the edge length of the sheet again in good agreement with theoretical predictions.     

Dynamics of semi-flexible tethered sheets : a simulation study using stochastic rotation dynamics

The dynamics of a semi-flexible sheet or tethered membrane in a solvent is studied using the method of stochastic rotation dynamics. Hydrodynamic interactions between different parts of the sheet are naturally included in this method. We confirm the scaling law for the radius of gyration versus sheet size predicted for a self-avoiding tethered membrane. The mean-square displacement shows both sub-diffusive and diffusive behavior similar to linear polymers. In the intermediate scattering function the sub-diffusive behavior appears as stretched exponential which we reproduce in our simulations. Thereby, we confirm an early prediction between the roughness and the sub-diffusion exponent derived from Zimm dynamics (E. Frey, D.R. Nelson, J. Phys. I 1, 1715 (1991)). Finally, we show that the diffusion coefficient of the square sheet is inversely proportional to the edge length of the sheet again in good agreement with theoretical predictions.     

Refractive index, birefringence, third-order non-linearity and piezoelectric resonance studies of L-lysine monohydrochloride dihydrate single crystals

The principal refractive indices of L-lysine monohydrochloride dihydrate (L-LMHCl) single crystal for different wavelengths were measured by minimum deviation method at room temperature. The experimental values of refractive indices fit well with the theoretical Cauchy's equations. The birefringence and the crossing angle between the optical axes were calculated. The parameters of Sellmeier's single term dispersion equation were determined by least square method. A simple interferometric technique was used to observe the interference patterns along the optic plane and to qualitatively analyze the optical homogeneity of the grown crystal. The nonlinear refractive index (n₂) and nonlinear absorption coefficient (β) were also determined using Z-scan technique. The piezoelectric resonance in dielectric dispersions was observed at room temperature.     

Average potential energy criterion: Force fields of some planar XY3 and tetrahedral XY4 molecules

Minimization of the average potential energy contributions from bending deformations due to zero point vibration serves as a good criterion for fixing the harmonic force fields in planar XY₃ and tetrahedral XY₄ nonhydride molecules. An explanation based on the concept of rehybridization of the orbitals of the central atom during a bending vibration is offered.     

Multiple proton ionizable calixarene derivatives with different ring sizes and complexation ability as efficient ionophores for complexation and solvent extraction of trivalent indium

The solvent extraction behavior of multiple proton ionizable p-tert-butylcalix[4]arene and [6]arene carboxylic acid derivatives towards indium has been investigated along with an acyclic monomeric analogue from weakly acidic media into chloroform. The extraction mechanism is ion exchange and carboxylic acid groups are adequate ligating sites for extraction. The cyclic structure of calixarene ligands to accommodate the potential guest species and the cooperativity effect of multifunctional groups significantly affect the complexation behavior and calixarene derivatives are found to be excellent extractants over the monomeric analogue. The composition of the extracted complex depends on the solution pH and attempts to determine the composition of the extracted complex for the extraction of indium have been stymied by complications arising from the formation of polynuclear species of indium and bridged polymeric species of calixarene carboxylic acid derivatives. One mole of calix[4]arene derivative extracts 2.5 moles of indium whereas the calix[6]arene derivative tends to extract 4.0 moles of indium. The loaded indium is back extracted with 1 mol dm(-3) hydrochloric acid solution. Though quantitative back extraction of indium was achieved from the fully loaded calix[6]arene derivative, it was only achieved up to 85% in the case of the calix[4]arene derivative.     

Locking effects in the finite element approximation of elasticity problems

Summary We consider the finite element approximation of the 2D elasticity problem when the Poisson ratiov is close to 0.5. It is well-known that the performance of certain commonly used finite elements deteriorates asv0, a phenomenon calledlocking. We analyze this phenomenon and characterize the strength of the locking androbustness of varioush-version schemes using triangular and rectangular elements. We prove that thep-andh-p versions are free of locking with respect to the error in the energy norm. A generalization of our theory to the 3D problem is also discussed.The work of this author was supported in part by the Office of Naval Research under Naval Research Grant N00014-90-J-1030The work of this author was supported in part by the Air Force Office of Scientific Research, Air Force Systems Command, U.S. Air Force, under grant AFOSR 89-0252     

Synthesis of potential impurities of cloxacillin sodium drug substance

The present work describes the synthesis and characterization of six related compounds of cloxacillin sodium ( 1 ) viz penicilloic acid of cloxacillin (2) , (3-(2-chlorophenyl)-5-methylisoxazole-4-carbonyl) glycine (Glycine analogue of cloxacillin) (3), CMICAA adduct of cloxacillin (4) , (4S)-2-(carboxy(3-(2-chlorophenyl)-5-methylisoxazole-4-carboxamido) methyl)-3-(2-ethylhexanoyl)-5,5-dimethylthiazolidine-4-carboxylic acid (N-2-ethylhexanoyl penicilloic acid of cloxacillin) ( 5 ), N-Acetylated penicilloic acid of cloxacillin ( 6 ), and Cloxacillin Penicillamide (7) . These related compounds are very essential in the process development of cloxacillin sodium and are used as reference standards to determine the quality of the drug substance.     

Radiolysis of resist polymers. IV. Poly(p-substituted-α-methylstyrene)s

The effect of parasubstituents on the radiation chemistry of poly(α-methylstyrene) (PMS) was compared for the fluoro (PFMS), chloro (PCMS), bromo (PBMS), isopropyl (PiPMS), and methoxy (PMeOM) derivatives. Radiolysis yields, ESR spectra, and GC? MS analysis of products were obtained. PMS and PFMS have similar low radiolysis yields, products, and product distributions. Only main-chain radicals which persist to 200° were observed. PCMS has increased values of G_s, G_x, and G_r. The product analysis results suggest that the presence of chlorine contributes to the primary process by dissociative electron capture and enhances the cleavage of α-methyl group. Irradiation of PBMS caused crosslinking and yielded few volatile products. PMeOMS and PiPMS gel readily by γ-irradiation and may be useful as negative radiation resists.     

Synthesis and Characterization of Metabolites and Potential Impurities of the Antiulcerative Drug Tenatoprazole

Tenatoprazole (Ulsacare^®) is a recently developed antiulcerative drug used for the treatment of both erosive and nonerosive gastroesophageal reflux disease. During the bulk synthesis of tenatoprazole, we have observed four impurities (tenatoprazole N‐oxide, tenatoprazole sulfone N‐oxide, N‐methyl tenatoprazole, and desmethoxy tenatoprazole) and two metabolites (tenatoprazole sulfide and tenatoprazole sulfone). The present work describes the synthesis and characterization of these impurities.