A Kinetic Study of Acrylamide/ Acrylic Acid Copolymerization

Homo- and co-polymers of acrylamide (AAm) and acrylic acid (or acrylate salt) (AA) or methacrylic acid (MAA)) are important classes of water-soluble polymers due to their numerous applications in fields such as super absorbents, additives in cosmetics, membrane technology, waste-water treatment and oil field operations. These polymers are generally made by free radical polymerization. For copolymerization reactions it is extremely important to know the details of reaction kinetics in order to ascertain the kinetic effects of different reaction parameters, which ultimately dictate final copolymer composition, microstructure and properties. The reactivity ratios for copolymerization of AAm and AA have been shown to be dependent on pH and they also change with reaction solvent. The present experimental investigation has been performed to study the kinetics of copolymerization of these monomers in aqueous and alcoholic media by considering factors such as type of initiator and solvent, and pH, in order to determine how they affect the reactivity ratios of these monomers. Reactivity ratios were determined by non-linear least squares (NLLS) and the error-in-variables-model (EVM) techniques and full conversion range kinetic investigations were carried out to confirm these values

Simulated effect of pneumococcal vaccination in the Netherlands on existing rules constructed in a non-vaccinated cohort predicting sequelae after bacterial meningitis

BACKGROUND: Previously two prediction rules identifying children at risk of hearing loss and academic or behavioral limitations after bacterial meningitis were developed. Streptococcus pneumoniae as causative pathogen was an important risk factor in both. Since 2006 Dutch children receive seven-valent conjugate vaccination against S. pneumoniae. The presumed effect of vaccination was simulated by excluding all children infected by S. pneumoniae with the serotypes included in the vaccine, from both previous collected cohorts (between 1990-1995). METHODS: Children infected by one of the vaccine serotypes were excluded from both original cohorts (hearing loss: 70 of 628 children; academic or behavioral limitations: 26 of 182 children). All identified risk factors were included in multivariate logistic regression models. The discriminative ability of both new models was calculated. RESULTS: The same risk factors as in the original models were significant. The discriminative ability of the original hearing loss model was 0.84 and of the new model 0.87. In the academic or behavioral limitations model it was 0.83 and 0.84 respectively. CONCLUSION: It can be assumed that the prediction rules will also be applicable on a vaccinated population. However, vaccination does not provide 100% coverage and evidence is available that serotype replacement will occur. The impact of vaccination on serotype replacement needs to be investigated, and the prediction rules must be validated externally