Ring-Opening polymerization of cycloolefins with catalysts derived from ruthenium and iridium

An investigation was carried out on the polymerization of norbornene, cyclopentene and cyclooctene by the following iridium and ruthenium compounds: chlorobis(cyclooctene)iridium ( 1 ), carbonylchlorobis(cyclooctene)iridium ( 2 ), trifluoroacetatobis(cyclooctene)iridium ( 3 ), chloroiridic(IV) acid ( 4 ), dichloro(2,7-dimethylocta-2,6-diene-1,8-diyl)-ruthenium ( 5a ), and bis(trifluoroacetato)-(2,7-dimethylocta-2,6-diene-1,8-diyl)ruthenium ( 5b ). All the above catalysts were found to be very active for the polymerization of norbornene via ring-opening. Iridium catalysts were practically inactive for the polymerization of cyclopentene and cyclooctene, but gave copolymers of norbornene with cyclopentene and cyclooctene via ring-opening. The ruthenium catalysts displayed no activity for the polymerization of cyclopentene and cyclooctene, but it was found that after treatment with H₂ they became active for the polymerization of cyclopentene. The results obtained from the reaction of norbornene and aliphatic olefins suggest that the above catalysts act by metathesis. The particular features of these catalysts were examined.     

Multicenter evaluation of electrical stimulation systems for walking.

OBJECTIVE: To test the long-term benefits of several noninvasive systems for functional electrical stimulation (FES) during walking. DESIGN: Forty subjects (average years since injury, 5.4) were studied in four centers for an average time of 1 year. Gait parameters were tested for all subjects with and without FES. Thus, subjects served as their own controls, since the specific effect of using FES could be separated from improvements resulting from other factors (e.g., training). SETTING: Subjects used the devices in the community, but were tested in a university or hospital setting. PATIENTS: Subjects with spinal cord injury (n = 31) were compared to subjects with cerebral damage (n = 9). MAIN OUTCOME MEASURES: Gait parameters (speed, cycle time, stride length). Acceptance was studied by means of a questionnaire. RESULTS: Some initial improvement in walking speed (average increase of >20%) occurred, and continuing gains were seen (average total improvement, 45%). The largest relative gains were seen in the slowest walkers (speeds of <0.3 m/sec). Acceptance of the FES systems was good and improved systems have been developed using feedback from the subjects. CONCLUSIONS: Based on the improvements in speed and the acceptance of these FES systems, a greatly increased role for FES in treating gait disorders is suggested.     

Descriptive epidemiology of Hodgkin's disease in the province of Torino, 1965-71.

Age-standardized incidence rates of Hodgkin's disease in the province of Torino in 1965-1971 were 2.81/100,000/year in males and 1.64 in females, i.e., somewhat lower than in urban areas of other industrialized countries. In the whole province, age-distribution for males was similar to previous findings elsewhere, with a young-adult peak at ages 25-34. However, in the city of Torino, males showed a first peak in the age-class 35-44, while in the rest of the province an infantile peak (0-14 years) was found. By dividing the latter area in suburbs and nonmetropolitan area, the infantile peak was confirmed only in the nonmetropolitan area. Females showed a different behavior: in the city of Torino there was a unimodal curve (peak in age-class 55-64), and in the rest of the province there was a bimodal curve with a first peak in age-class 15-24. These patterns have been analyzed in relation to the suggestion of a distribution by age of Hodgkin's disease following 3 types (nonindustrialized countries, urban areas of industrialized countries and rural areas of industrialized countries). No significant differences in the distribution of cases were found among the smallest geographical units considered (ULSs), in contrast with previous findings on cancer of the larynx and bladder, which showed marked geographical differences within the province of Torino.     

Polymerization of propadiene by some η-allylic derivatives of rhodium(III)

An investigation has been carried out on the polymerization of propadiene (allene) by several η-allylic derivatives of rhodium(III). Polymers of a high structural regularity were obtained, along with liquid oligomers, at ca. 70°C. The results are compared with those obtained using complexes of rhodium(I) as catalysts. The catalytic cycle is interpreted on the basis of the formation of a complex of rhodium(III) in the initiation and of a complex of rhodium(I) in the termination.     

Stereospecific polymerization of cis,cis-1,4-dideuterio-1,3-butadiene to trans-1,4 or cis-1,4 polymers

cis,cis-1,4-Dideuterio-1,3-butadiene ( 1 ) was polymerized by various catalyst systems {Al(C₂H₅)₃? VCl₃, Al(C₂H₅)₂ Cl? VO(acac)₂, Al(C₂H₅)₃? TiI₄, Al(C₂H₅)₂ Cl? Co(acac)₂, (π-allyl)NiOCOCl₃, (π-allyl)NiI} to polymers having a trans-1,4 or a cis-1,4 structure. Degradative oxidation of the polymers gave a mixture of racemic and meso 2,3-dideuteriosuccinic acid ( 2 ), in a ratio dependent on the particular catalyst used. The polymers obtained with the catalyst systems Al(C₂H₅)₃? VCl₃ and Al(C₂H₅)₂Cl? Co(acac)₂ gave oxidation products with a high percentage of the racemic form of 2 (85–92%), which is indicative of a threo structure of the polymers. IR examination of the polymers obtained by the cobalt or vanadium system showed them to possess a regular structure (presence of the so-called regularity bands). The results are interpreted on the basis of a cis-addition of the monomer. The factors that determine the stereospecificity in the polymerization of 1 are discussed and possible schemes for the formation of the stereoregular polymers are examined.     

Use of vecuronium bromide and atracurium besylate in continuous intravenous infusion in urologic surgery

The effects of continuous i.v. infusion of atracurium and vecuronium monitored by TOF supplied by an ABM monitor have been compared in 60 patients subdivided into four groups and submitted to anaesthesia with isoflurane for urological surgery interventions. Groups A and V received respectively an initial bolus of 0.5 mg/kg atracurium and of 0.08 mg/kg vecuronium followed immediately by continuous i.v. infusion of 5.5 micrograms/kg/min. Atracurium or 0.9 micrograms/kg/min of vecuronium; recovery of neuromuscular function happened spontaneously. Groups A' and V' differed by virtue of the use of 0.04 mg/kg prostigmin in the recovery phase. Average consumption of atracurium and vecuronium were respectively 5.1 +/- 1.75 micrograms/kg/min (2.6-9.03) and 0.75 +/- 0.20 micrograms/kg/min (0.5-1.2) in groups A-A' and V-V'. In groups A and V Recovery time 25-75" of T1 and TR presented a statistically significant difference (p less than 0.05) in favour of atracurium. In groups A' and V' the same parameters presented a statistically non-significant difference (p greater than 0.05). The ratio TI/TR does not vary to a statistically significant extent in the 4 groups. The number of infusion rate variations needed to maintain stable neuromuscular block was lower in the atracurium groups.