[reaction: see text] The synthetic utility of chiral N-heterocyclic carbenes, which have been used mainly in transition metal-catalyzed reactions as a ligand, was demonstrated by the enantioselective acylation of secondary alcohols.

No abstract

The mechanism and kinetics of the phase separation of ternary mixtures of PS/PB/Tol and PS/SB/Tol [PS, PB, SB, and Tol represent respectively polystyrene, polybutadiene, polystyrene-polybutadiene diblock polymer, and toluene (a good solvent for each of these polymers)] were studied by the time-resolved light scattering technique. In this method, evolution of the structure with time after the temperature drops from temperatures above the cloud points to those below them was isothermally observed at given polymer concentrations as a function of quench depth, AT, and polymer compositions. It was found that (i) an early stage of spinodal decomposition (up to a few tens of seconds for the particular systems studied) can be described by the linearized theory proposed by Cahn and that (ii) the time-dependent variation of the scattering profiles dramatically depends on the phase-separation mechanism (spinodal decomposition vs. nucleation and growth).It was also found that (iii) the phase-separated structures observed in solvent-cast films are generally those which were frozen in at some concentrations during the solvent evaporation process and very much reflect the spinodal decomposition and its coalescence processes occurring in the solutions.

A retrospective survey of 1,445 snowboarders and 10,152 skiers was undertaken to determine the incidence, pattern and severity of both snowboarding and skiing injuries. The incidence of snowboarding injury (0.33%) was higher than that of skiing injury (0.11%, P < 0. 01). Also, in showboarding there was frequent involvement of the arms (51.3%) when compared with skiing (25.9%, P < 0.001). In the arms, fracture (45.7%) was frequently observed in snowboarding, vs 31.3% in skiing. The wrist was the most affected site (18.7%, P < 0. 01) in snowboarding (skiing 2.3%), and the fracture rate was significantly high (71.6%, P < 0.001). The rate of dislocation of the elbow (27.7%) was also higher in snowboarding than in skiing (13. 5%, P < 0.001). Regarding arm injuries, 57.9% of injured snowboarders were beginners whose experience was shorter than 1 year, and 91.5% was caused by falling down. These results indicate that a snowboarding injury involving the upper limb region is a severe accident, with a frequent risk of fracture in the wrist and dislocation of the elbow. The severity of arm injuries in snowboarding seems to be caused by direct force on the wrist and elbow, which receive the full impact of a fall. These data suggest that beginners should have appropriate lessons of basic skills including safe falling. The development of a safety system also appears sensible to prevent such severe injuries in snowboarding.

The main left coronary artery of rats was ligated near its origin under light ether anaesthesia and the infarction observed for 48 h. The ischaemic area was determined after an intravenous injection of pontamine sky blue dye 1 h before induction of cardiac arrest with potassium chloride. The unstained area (true ischaemic area) decreased with time to 27.1% of the left ventricle at 48 h, whereas the intensely stained area between the normal and the true ischaemic areas increased with time, suggesting that blood was flowing to the border from the normal surrounding tissue. The infarcted area, identified by its lack of triphenyltetrazolium chloride staining, became evident after 3 h and stabilised at 12 h (42% of left ventricle). The polymorphonuclear leucocyte counts in the hearts, differentiated by staining of their chloroacetate esterase, increased gradually up to 5500 cells per section at 24 h. The leukotriene B4 concentration, determined by radioimmunoassay after freezing of the beating heart in liquid nitrogen, increased to eight times that of the sham operated hearts and peaked at 8 h (9.4(0.6) ng per heart, mean(SEM) n = 5) before the leucocyte counts reached their maximum. A single oral dose of a selective 5-lipoxygenase inhibitor (AA-861, 80 mg.kg-1, 1 h before ligation) lowered the leukotriene B4 concentration to that of the sham operated hearts and decreased the leucocyte count by 49.4% and 41.2% at 12 and 24 h respectively. The inhibitor also reduced the infarct size at 48 h by 34.4%. It was concluded that leukotriene B4, generated in ischaemic cardiac tissue, may increase infarct size through migration of polymorphonuclear leucocytes.