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.     

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     

Dimensional reduction for Helmholtz's equation on a bounded domain

Summary. The dimensional reduction method for solving boundary value problems of Helmholtz's equation in domain by replacing them with systems of equations in dimensional space are investigated. It is proved that the existence and uniqueness for the exact solution and the dimensionally reduced solution of the boundary value problem if the input data on the faces are in some class of functions. In addition, the difference between and in is estimated as and are fixed. Finally, some numerical experiments in a domain are given in order to compare theretical results. Received April 2, 1996 / Revised version received July 30, 1990     

Glycidyl methacrylate–tert-butyl acrylate copolymers: Synthesis,characterization, and thermal studies

Glycidyl methacrylate was copolymerized with tert-butyl acrylate in bulk at 60°C using benzoyl peroxide as free radical initiator. The copolymer composition was determined by chemical analysis as well as from ¹³C-NMR data. The monomer reactivity ratios were calculated by using the YBR method. The number average sequence length of the copolymers was determined from ¹³C-NMR data and compared with those obtained from reactivity ratios. The intrinsic viscosity of the copolymers was determined in DMF, and thermal stability as well as mechanism of thermal degradation of the copolymers were evaluated.     

Dielectric properties of CaCu3Ti4O12–silicone resin composites

CaCu₃Ti₄O₁₂ (CCTO)–silicone resin composites with various CCTO volume fractions were prepared. Relatively high dielectric constant (ε=119) and low loss (tanδ=0.35) of the composites with CCTO volume fraction of 0.9 were observed. Two theoretical models were employed to predict the dielectric constant of these composites; the dielectric constant obtained via the Maxwell–Garnett model was in close agreement with the experimental data. The dielectric constant of CCTO–silicone resin composites showed a weak frequency dependence at the measuring frequency range and the loss tangent apparently decreases with increase in frequency.     

Fabrication of high performance Gd–Ba–Cu–O single grains in air using a practical melt processing technique

A practical processing route for the fabrication of LRE-Ba–Cu–O single grain superconductors has been developed at the University of Cambridge based on a generic, Mg-doped Nd-123 melt textured seed and suppression of the formation of the solid solution phase in air by enriching the precursors with higher Ba concentration. The processing of high performance Gd–Ba–Cu–O single grains using this processing route is described. The Mg-doped generic seed crystal has been used effectively to promote heterogeneous nucleation via a cold-seeding process. The Gd/Ba solid solution has been suppressed by enriching Gd–Ba–Cu–O precursor powders with two different Ba-rich compositions. This involved adding BaO₂ and GdBa₆Cu₃O_y (Gd-163) (a novel Ba-rich second phase) to the precursor powders, respectively. The Gd-163 phase has been observed not only to suppress formation of the solid solution phase, but also to promote increased heterogeneous grain size. A detailed further study has been carried out with an initial aim of optimizing the BaO₂ and Gd-163 phase content of the precursor composition to produce a single grain almost free of solid solution. Based on the optimized parameters, large single grain Gd–Ba–Cu–O superconductors have been fabricated in an air atmosphere and demonstrated to exhibit record trapped magnetic fields for this material melt processed in air in relatively small single grain samples. The trapped fields of samples produced in air atmosphere are at least comparable to those processed under reduced oxygen partial pressure.     

An Exact Solution for the Optical Absorbance of Thin Films

The electric and magnetic fields within optical thin films are obtained exactly in closed form as solutions of a system of difference equations presented by Berning and utilized by Dill, Neureuther, Tuttle, and Walker in their sample program for modeling optical lithography. The solution allows an explicit closed form expression for the absorbance.     

Aligned magnetic effects through varying permeable bed

The aligned magnetic effects on a steady laminar, viscous, incompressible, conducting fluid down an open inclined channel bounded below by a bed of varying permeability has been studied when the free surface is exposed to atmospheric pressure. Beavers and Joseph slip condition at the interface of the free flow region and the fluid flow in the porous bed and the Darcy’s law in the porous medium have been used. The expressions for velocity, magnetic strength and the mass flow across the cross-section of the channel are obtained.