RESUMEN
We use dissipative particle dynamics (DPD) to study micelle formation in alkyl sulfate surfactants, with alkyl chain lengths ranging from 6 to 12 carbon atoms. We extend our recent DPD force field [ J. Chem. Phys. 2017 , 147 , 094503 ] to include a charged sulfate chemical group and aqueous sodium ions. With this model, we achieve good agreement with the experimentally reported critical micelle concentrations (CMCs) and can match the trend in mean aggregation numbers versus alkyl chain length. We determine the CMC by fitting a charged pseudophase model to the dependence of the free surfactant on the total surfactant concentration above the CMC and compare it with a direct operational definition of the CMC as the point at which half of the surfactant is classed as micellar and half as monomers and submicellar aggregates. We find that the latter provides the best agreement with experimental results. Finally, with the same model, we are able to observe the sphere-to-rod morphological transition for sodium dodecyl sulfate (SDS) micelles and determine that it corresponds to SDS concentrations in the region of 300-500 mM.
RESUMEN
INTRODUCTION: Multi-drug resistant TB (MDR-TB) is a complex infectious disease that is a growing threat to global health. It requires lengthy treatment with multiple drugs and specialized laboratory testing. To effectively scale up treatment to thousands of patients requires good information systems to support clinical care, reporting, drug forecasting, supply chain management and monitoring. METHODS: Over the last decade we have developed the PIH-EMR electronic medical record system, and subsequently OpenMRS-TB, to support the treatment of MDR-TB in Peru, Haiti, Pakistan, and other resource-poor environments. RESULTS: We describe here the experience with implementing these systems and evaluating many aspects of their performance, and review other systems for MDR-TB management. CONCLUSIONS: We recommend a new approach to information systems to address the barriers to scale up MDR-TB treatment, particularly access to the appropriate drugs and lab data. We propose moving away from fragmented, vertical systems to focus on common platforms, addressing all stages of TB care, support for open data standards and interoperability, care for a wide range of diseases including HIV, integration with mHealth applications, and ability to function in resource-poor environments.