Kinetics of the precipitation of palladium dimethylglyoximate from homogeneous solution.
The kinetics of formation of palladium dimethylglyoximate in the post-nucleation and pre-nucleation stages, and the effect of palladium on the reaction of biacetyl and hydroxylamine, have been studied.
The oximation of biacetyl
Abstract Spectrophotometric evidence indicates that the reaction of biacetyl with hydroxylamine proceeds through the formation of two carbinolamine intermediates. The second of these intermediates is also encountered in the reaction of biacetyl monoxime with hydroxylamine. The rate-limiting step in the oximation of biacetyl is the slow dehydration of the initially formed intermediate, as is evidenced from the various rate constants obtained for the two reactions over the range 0–10°. When niekel(II) is present in the biacetyl-hydroxylamine system, the formation of nickel dimethylglyoximate proceeds by two independent mechanisms, whereas only a single mechanism is responsible for precipitate formation in the biacetyl monoxime-hydroxylamine system.
Complications of motility peg placement for porous hydroxyapatite orbital implants
Aim: To evaluate the complications associated with pegging of porous hydroxyapatite orbital implants. Methods: Complications associated with pegging were retrospectively reviewed from the charts of 100 of 133 patients with hydroxyapatite implantation from 1993 to 2000. Results: 48 (48%) of the 100 hydroxyapatite implanted patients who had undergone pegging were found to have problems with their pegs, including discharge (45.8%), peg falling out (20.8%), pyogenic granulomas (16.7%), popping peg (14.6%), hydroxyapatite visible around peg hole (8.3%), part of peg shaft visible (6.2%), peg drilled off centre (6.2%), peg drilled at an angle (4.2%), and excess movement of peg (4.2%). The standard peg fell out statistically more often than the peg and sleeve system (Yates's corrected χ2, p=0.038). There was a trend towards complications of the peg with use of a standard peg (versus sleeved peg) (p=0.226). Conclusions: There are several potential complications of pegging. Most complications are minor and can be managed successfully.