SynopsisPropylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. Intraparticle heat and mass transfer effects are investigated for a range of catalyst activities. For slurry polymerization, intraparticle mass transfer effects may be significant at both the macroparticle and microparticle level; however, for normal gas phase polymerization, microparticle mass transfer effects appear more likely to be important. Intraparticle temperature gradients would appear to be negligible under most normal operating conditions.

OBJECTIVES: The aims of this prospective study were to document the incidence of colon immediate postpolypectomy bleeding (IPPB) according to grade, and to identify potential risk factors of IPPB in patients who have received complete colonoscopy and polypectomy because of a colorectal polyp. METHODS:This was a prospective, cross-sectional study of 5,152 patients treated at 11 tertiary medical centers between July 2003 and July 2004. Patient-related, polyp-related, and procedure-related variables were evaluated as potential risk factors for IPPB. IPPB was defined as a bleeding occurring during the procedure and was graded as G1-G4. Risk factors associated with IPPB were analyzed by univariate and multivariate logistic regression analysis. RESULTS:A total of 9,336 colonic polyps were removed in 5,152 patients, and 262 (2.8%) colorectal polyps in 215 patients presented with IPPB. Polyp-based multivariate analysis revealed that old age (≥65 yr), comorbid cardiovascular or chronic renal disease, anticoagulant use, polyp size greater than 1 cm, gross morphology of polyps such as pedunculated polyp or laterally spreading tumor, poorer bowel preparation, cutting mode of the electrosurgical current, and the inadvertent cutting of a polyp before current application were significant risk factors for IPPB.CONCLUSION: Nine factors have been found to be associated with IPPB and polypectomy should be undertaken with caution under these conditions.

SynopsisPropylene and ethylene polymerization in liquid and gas media are described by a multigrain particle model. External boundary layer heat and mass transfer effects are investigated for various catalysts and operating conditions. For high-activity catalysts used in slurry, external film mass transfer effects may be significant. For gas-phase polymerization of propylene or ethylene, the model predicts significant particle overheating at short times, which may explain the particle sticking and agglomeration problems sometimes observed in industrial reactors.

The prevalence of GERD, uninvestigated dyspepsia and IBS were 3.5%, 11.7% and 2.2% respectively, in the Korean population. The health-related quality of life was significantly impaired in subjects with GERD, uninvestigated dyspepsia and IBS in this community.

SYNOPSISA multistage melt polycondensation of bisphenol-A and diphenyl carbonate has been studied experimentally using LiOH -H 2 0 catalyst. The reaction process consists of batch and semibatch periods with different temperature and pressure conditions. It was observed that a small amount of diphenyl carbonate lost from the reaction mixture by vaporization had little effect on the molecular weight in the batch reaction period but the efficiency of subsequent low-pressure semibatch polycondensation was affected by the change in the mol ratio of the phenyl carbonate group to the hydroxyl end group. A molecular species model developed for the multistage process was used to analyze the kinetics of the polycondensation process. The composition of the reaction mixture was analyzed by HPLC and compared with model simulations. In particular, the effect of evaporative loss of diphenyl carbonate on the progress of reaction is discussed in detail.