Solvent-free electrospinning of liquid polybutadienes and their in-situ photocuring

A single-step approach to rapidly convert low molecular weight polybutadienes into fine rubber crosslinked fibers and nonwoven mats without using any heat or solvent was described. This environmentally friendly method consisted in the electrospinning at room temperature of liquid polybutadiene and polybutadiene-graft-maleic anhydride polymers without any solvent; the flying jet was irradiated to trigger the in-situ curing of the forming fibers at ambient conditions, obtaining a good control over the fibrous morphology and enhancing the performance of the membranes. The kinetics of the photo-crosslinking reaction was studied through FT-IR spectroscopy. Liquid polybutadiene-graft-maleic anhydride polymers demonstrated a faster rate of photocuring, compared to neat polybutadienes. In order to further speed up the reaction, a thiol-based crosslinker and a photoinitiator were introduced into the formulations. The photo-induced crosslinking was more efficient as different reactions concomitantly took place: besides the thiol-ene crosslinking involving the multifunctional thiol crosslinker, the oxidation of the polybutadiene chains and the esterification of the maleic anhydride moieties occurred. Moreover, a polar additive was used to control the electrospinning process by lowering the viscosity and increasing the electrical conductivity. The structural, thermal and surface properties of the fabricated polybutadiene-based electrospun membranes were assessed. The membranes exhibited an excellent morphology stability, high insolubility, good thermal properties and a pronounced hydrophobic character

Assessment of the rapid shallow breathing index as a predictor of weaning of patients with prolonged mechanical ventilation

Background: About 8 of patients experience prolonged mechanical ventilation after cardiac surgery. Development of criteria for successful liberation of a patient from mechanical ventilation and extubation may be highly dependent on the clinical situation. Different criteria were used for ventilator weaning. We designed a clinical trial to determine the usefulness of rapid shallow breathing index (RSBI) as a predictor for successful weaning from mechanical ventilation. Materials and Methods: In a prospective observational study, 52 patients who had prolonged mechanical ventilation (> 72 h) after open cardiac surgery were studied. Patients had 60 - min spontaneous breathing trials and satisfied at least 5 weaning predictors and fulfilled the criteria for discontinuing mechanical ventilation. Traditional weaning criteria and RSBI were determined. According to the outcome assessment of weaning, patients were divided into failure or success groups. Results: The mean RSBI values were significantly different between the failure (103.5±21.9 breath/min/L) and success groups (80.4±15.3 breath/min/L, p=0.0001). There was no significant difference regarding the values of other prediction criteria between the two groups. Using RSBI <105 (breath/min/L) as the threshold value for predicting successful weaning, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy were 92.5, 70, 92.5, 70 and 88 respectively. Conclusion: Although a small number of patients require prolonged ventilatory support after open cardiothoracic surgeries, growing experience in critical care settings and mechanical ventilation cause favorable outcomes. Ventilator weaning is more likely to be successful if RSBI is less than 105 (breath/min/L). This index is a more valuable and accurate predictor of weaning than other weaning predictors. © 2007 NRITLD, National Research Institute of Tuberculosis and Lung Disease, Iran

Formulation, characterisation and stabilisation of buccal films for paediatric drug delivery of omeprazole

This study aimed to develop films for potential delivery of omeprazole (OME) via the buccal mucosa of paediatric patients. Films were prepared using hydroxypropylmethylcellulose (HPMC), methylcellulose (MC), sodium alginate (SA), carrageenan (CA) and metolose (MET) with polyethylene glycol (PEG 400) as plasticiser, OME (model drug) and L-arg (stabiliser). Gels (1% w/w) were prepared at 40°C using water and ethanol with PEG 400 (0–1% w/w) and dried in an oven (40°C). Optimised formulations containing OME and L-arg (1:1, 1:2 and 1:3) were prepared to investigate the stabilisation of the drug. Tensile properties (Texture analysis, TA), physical form (differential scanning calorimetry, DSC; X-ray diffraction, XRD; thermogravimetric analysis, TGA) and surface topography (scanning electron microscopy, SEM) were investigated. Based on the TA results, SA and MET films were chosen for OME loading and stabilisation studies as they showed a good balance between flexibility and toughness. Plasticised MET films were uniform and smooth whilst unplasticised films demonstrated rough lumpy surfaces. SA films prepared from aqueous gels showed some lumps on the surface, whereas SA films prepared from ethanolic gels were smooth and uniform. Drug-loaded gels showed that OME was unstable and therefore required addition of L-arg. The DSC and XRD suggested molecular dispersion of drug within the polymeric matrix. Plasticised (0.5% w/w PEG 400) MET films prepared from ethanolic (20% v/v) gels and containing OME: L-arg 1:2 showed the most ideal characteristics (transparency, ease of peeling and flexibility) and was selected for further investigation

Conceptualizing and measuring strategy implementation – a multi-dimensional view

Through quantitative methodological approaches for studying the strategic management and planning process, analysis of data from 208 senior managers involved in strategy processes within ten UK industrial sectors provides evidence on the measurement properties of a multi-dimensional instrument that assesses ten dimensions of strategy implementation. Using exploratory factor analysis, results indicate the sub-constructs (the ten dimensions) are uni-dimensional factors with acceptable reliability and validity; whilst using three additional measures, and correlation and hierarchical regression analysis, the nomological validity for the multi-dimensional strategy implementation construct was established. Relative importance of ten strategy implementation dimensions (activities) for practicing managers is highlighted, with the mutually and combinative effects drawing conclusion that senior management involvement leads the way among the ten key identified activities vital for successful strategy implementation

Radial consolidation model incorporating the effects of vacuum preloading and non-Darcian flow

A modified 150 mm Rowe cell equipped with pore water pressure measurement was used to capture the flow relationship during vacuum-assisted radial consolidation. Based on the measured data, a radial consolidation model incorporating the effects of vacuum preloading is proposed, based on a non-linear relationship between the flow velocity and hydraulic gradient. The predictions of the proposed consolidation model are then compared with the predictions based on Hansbo’s Darcian and non- Darcian models. The agreement between the proposed model and the measured data is shown, and the advantages of the proposed model compared with the existing models are discussed. An embankment case history taken from the reclamation project at the Port of Brisbane, Australia, was analysed, based on the current solution, and compared with the field measurements