Silica hydride intermediate for octadecylsilica and phenyl bonded phase preparation via heterogeneous hydrosilation in supercritical carbon dioxide.

Investigations into the preparation of silica hydride intermediate in supercritical carbon dioxide (sc-CO(2)) that avoids the use of organic solvents such as toluene or dioxane are described. The effects of reaction temperature, pressure and time on the surface coverage of the supercritical fluid generated silica hydride intermediate were studied. Under optimised supercritical conditions of 120°C, 483 bar and 3 h reaction time, silica hydride (Si-H) conversion efficiencies of ca. 40% were achieved for the hydride intermediate prepared from a monofunctional silane reagent (dimethylmethoxysilane). Si-H conversion efficiencies (as determined from (29)Si CP-MAS NMR spectral analysis) for the hydride intermediate prepared from triethoxysilane (TES) in sc-CO(2) were found to be comparable to those obtained using a TES silanisation approach in an organic solvent. (13)C and (29)Si CP-MAS-NMR spectroscopy was employed to provide a complete structural assignment of the silica hydride intermediates. Furthermore, supercritical CO(2) was subsequently employed as a reaction medium for the heterogenous hydrosilation of silica hydride with octadecene and with styrene, in the presence of a free radical initiator. These supercritical fluid generated reversed-phase materials were prepared in a substantially reduced reaction time (3 h) compared to organic solvent based methods (100 h reaction time). Silica functionalisation in sc-CO(2) presents an efficient and clean alternative to organic solvent based methods for the preparation of important silica hydride intermediate and silica bonded stationary phases via a hydrosilation approach.

Hand dominance and performance in a laparoscopic skills curriculum.

BACKGROUND: This study evaluated the influence of hand dominance on skill acquisition during a basic laparoscopic skills curriculum. METHODS: A total of 27 surgical residents (5 postgraduate year 3 [PGY-3] and 22 PGY-2 residents) participated in a 4-week laparoscopic skills curriculum. The residents were pre- and posttested on six laparoscopic tasks during weeks 1 and 4. During weeks 2 and 3, the residents attended a proctored practice session. The results were compared using analysis of variance (ANOVA), (with significance determined by a p value less than 0.05. RESULTS: The posttest scores were significantly higher than the pretest scores. On the pretest, lefthand-dominant (LHD) surgeons (n = 4) performed significantly better than righthand-dominant (RHD) surgeons (n = 23). In the analysis of individual task pretest scores, LHD surgeons performed significantly better on pattern cutting and vessel loop application. Posttest analysis of overall performance did not show significant differences between the RHD and LHD surgeons. CONCLUSIONS: Participation in a laparoscopic skills curriculum improved overall performance. The LHD surgeons demonstrated better initial performance, but posttest comparison showed no difference between the two groups.