ABSTRACT
The importance of micelles as templates for nanomaterials is growing day by day. This resulted in an increasing interest for micelles in different sizes and shapes. Addition of n-amines to micellar solutions was found to bring change in the shape of the micelles from sphere to rod in aqueous ionic micellar solutions. The change in shape is qualitatively obtained from sudden change in the slope of pH versus amine concentration plots because the degree or protonation of n-alkylamines depends on the shape of micelles. In the present investigation, pH is measured at different temperatures to elucidate the influence of addition of n-amines on sphere-to-rod transition in aqueous micellar solutions. The surfactants employed in the present investigation are cetyltrimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), and sodium dodecyl sulphate (SDS).As the amine concentration is increased, the pH increases linearly at certain amine concentration and the slope of the resulting straight line changes on further addition of amine. It is noticed that increasing temperature requires more amine for structural transition of aqueous ionic micelles. It is also observed that the effectiveness of added amines leading to shape transition from sphere to rod is in the order of C8NH2>C7NH2> C6NH2.
ABSTRACT
Context: Bilateral pediatric cataracts are important cause of visual impairment in children. Aim: To study the outcome of bilateral pediatric cataract surgery in young children. Setting and Design: Retrospective case series in a tertiary center. Materials and Methods: Records of pediatric cataracts operated between January 2001 and December 2003, with a minimum follow-up of 3 months, were reviewed retrospectively. Statistical Methods: Independent sample t-test, Fisher's exact test, and logistic regression using SPSS (Statistical Package for Social Science, Chicago, USA) version 12. Results: 215/257 (83.7%) patients had a minimum follow-up of 3 months. The mean age of presentation to the hospital was 53 months (range: 0-168 months). Congenital cataract was present in 107 patients (58.2%) and developmental cataract in 77 patients (41.8%). The mean age at surgery was 55.2 months (range: 1-168 months). Out of 430 eyes, 269 (62.6%) had an intraocular lens implanted. The mean duration of follow-up was 13.1 months (range: 3-38 months). Pre-operatively, 102 patients (47.3%) had visual acuity <6/60, in the better eye, compared to 37 patients (17.2%) post-operatively (P < 0.001). Eighty-five patients (39.5%) had visual acuity >6/18. The most common early post-operative complication was fibrinous uveitis in 57 eyes (13.3%) and the most common delayed post-operative complication was posterior capsular opacification in 118 eyes (27.4%). The most important prognostic factor for poor outcome was congenital cataract (odds ratio [OR]: 26.3; 95% confidence interval [CI], 4.4-158.5) and total cataract (OR: 4.8; 95% CI, 1.3-17). Conclusion: Nearly half of the eyes had visual acuity>6/18. The outcome was poorer in congenital cataracts, especially those operated after >1 year of age.