Unstable Flow and Non-Monotonic Constitutive Equation of Transient Networks

We have measured the nonlinear rheological response of a model transient network over a large range of steady shear rates. The system is built up from an oil in water droplet microemulsion into which a telechelic polymer is incorporated. The phase behaviour is characterized which comprises a liquid-gas phase separation and a percolation threshold. The rheological measurements are performed in the one phase region above the percolation line. Shear thinning is observed for all samples, leading in most cases to an unstable stress response at intermediate shear rates. We built up a very simple mean field model which involves the reduction of the residence time of the stickers in the droplets due to the chain tensions at high shear. The computed constitutive equation is non-monotonic with a range where the stress is a decreasing function of the rate, a feature that indeed makes homogeneous flows unstable. The computed the flow curves compare well to the experiments.Comment: mai 200

Robust Phase Behavior of Model Transient networks

In order to study the viscoelastic properties of certain complex fluids which are described in terms of a multiconnected transient network we have developed a convenient model system composed of microemulsion droplets linked by telechelic polymers. The phase behavior of such systems has two characteristic features: a large monophasic region which consists of two sub-regions (a fluid sol phase and a viscoelastic gel phase) separated by a percolation line and a two phase region at low volume fraction with separation into a dilute sol phase and a concentrated gel phase. From the plausible origin of these features we expect them to be very similar in different systems. We describe here the phase behavior of four different systems we prepared in order to vary the time scale of the dynamical response of the transient network; they consist of the combination of two oil(decane) in water microemulsions differing by the stabilizing surfactant monolayer (Cetyl pyridinium chloride/octanol or TX100/TX35) and of two telechelic polymers which are end-grafted poly (ethylene oxide) chains, differing by the end-grafted hydrophobic aliphatic chains (C12H25 or C18H37).Comment: April 9 200

Minimizing Variability of Cascade Impaction Measurements in Inhalers and Nebulizers

The purpose of this article is to catalogue in a systematic way the available information about factors that may influence the outcome and variability of cascade impactor (CI) measurements of pharmaceutical aerosols for inhalation, such as those obtained from metered dose inhalers (MDIs), dry powder inhalers (DPIs) or products for nebulization; and to suggest ways to minimize the influence of such factors. To accomplish this task, the authors constructed a cause-and-effect Ishikawa diagram for a CI measurement and considered the influence of each root cause based on industry experience and thorough literature review. The results illustrate the intricate network of underlying causes of CI variability, with the potential for several multi-way statistical interactions. It was also found that significantly more quantitative information exists about impactor-related causes than about operator-derived influences, the contribution of drug assay methodology and product-related causes, suggesting a need for further research in those areas. The understanding and awareness of all these factors should aid in the development of optimized CI methods and appropriate quality control measures for aerodynamic particle size distribution (APSD) of pharmaceutical aerosols, in line with the current regulatory initiatives involving quality-by-design (QbD)

Supplementary Material for: Oesophageal Lichen Planus Successfully Treated with Budesonide Orodispersible Tablets, a Case Report

Introduction Lichen planus is a relatively common inflammatory condition of the nails, skin and mucosal surfaces. Oesophageal involvement of lichen planus is thought to be very rare, mainly described in case reports, but is associated with a high risk of oesophageal stenosis as well as squamous cell carcinoma. No evidence based treatment recommendations exist, with the majority of described treatment regimens involving systemic immunosuppression. Case report In this case report, we describe a novel approach in treating oesophageal lichen planus in a patient with budesonide orodispersible tablets, a treatment normally reserved for oeosinophilic oesophagitis. The patient achieved complete relief of dysphagia, with a follow-up oesophagogastroduodenoscopy 2 months after treatment commencement being macroscopically and microscopically free of inflammatory activity. This case report is to our knowledge the first to report this treatment regimen in oesophageal lichen planus. Conclusion We consider a trial of budesonide orodispersible tablets a reasonable initial management as it’s a local therapy specific to the oesophagus with a more benign side effect profile than systemic immunosuppression, but further studies need to be undertaken to corroborate our findings. Also, based on the severity and malignant potential of oesophageal lichen planus, we suggest that physicians be liberal in ordering oesophagogastroduodenoscopy with biopsy taking as part of the work up of dysphagia in a patient with known lichen planus