Mechanical characterisation of hydrophobic and hydrophilic acrylates used in intraocular lenses through depth sensing indentation

In this work, the mechanical behaviour of hydrophilic and hydrophobic acrylates has been characterised by depth sensing indentation. Time-dependent behaviour has been studied using load-relaxation tests. Experiments have been simulated with a finite element software using a visco-hyperelastic material model. The parameters of this model have been determined using deep learning techniques. The developed material models have been used to mechanically simulate a standard compression test of a prototype intraocular lens

Community Risk Factors for Ocular Chlamydia Infection in Niger: Pre-Treatment Results from a Cluster-Randomized Trachoma Trial

Trachoma is one of the most important neglected tropical diseases because it is the leading cause of blindness from an infection in the world. There are about 1.3 million persons blind from the disease and many more at risk of blindness in the future. It is caused by the common bacterium Chlamydia trachomatis and can be treated with mass drug administrations (MDA) of azithromycin. We have begun a clinical trial in Niger, a country with limited resources in Africa, to determine the best treatment strategy. Our study from May to July 2010, which began before MDA's were given, showed that 26% of children aged 0–5 years were infected with the disease. In these children, we found that discharge from the nose, presence of flies on the face, and the number of years of education completed by the head of the household were risk factors for infection in 48 different communities. We hope to use this information about risk factors of infection to help guide future studies for trachoma and also to help with the WHO goal of eliminating the disease worldwide by the year 2020

Active Trachoma among Children in Mali: Clustering and Environmental Risk Factors

Active trachoma is not uniformly distributed in endemic areas, and local environmental factors influencing its prevalence are not yet adequately understood. Determining whether clustering is a consistent phenomenon may help predict likely modes of transmission and help to determine the appropriate level at which to target control interventions. In this work, we estimated the magnitude of clustering at different levels and investigated the influence of socio-economic factors and environmental features on active trachoma prevalence among children in Mali (1996–1997 nationwide survey). Clustering revealed significant results at the child, caretaker, household, and village levels. Moreover, beyond some well-established individual risk factors (age between 3 and 5, dirty face, and flies on the face), we found that temperature, sunshine fraction, and presence of rainy days were negatively associated with active trachoma prevalence. This study clearly indicates the importance of directing control efforts both at children with active trachoma as well as those with close contact, and at communities. These results support facial cleanliness and environmental improvements as population-health initiatives to combat blinding trachoma

Crosslinker concentration effect on the poroviscoelastic relaxation of polyacrylamide hydrogels using depth-sensing indentation

The effect of crosslinker concentration on the mechanical behaviour of polyacrylamide based hydrogels is established by using depth sensing indentation. In this work, hydrogels are considered as poroviscoelastic solids, being viscoelasticity and poroelasticity taken into account at intermediate length scales such as those here explored. A constrained fitting method is derived to implement a multiplicative rule that accommodates the contribution of each deformation mechanism on the global material response. The proposed method is robust enough to properly separate poroelastic and viscoelastic contributions from relaxation curves measured at different indentation depths and strain rates. At the length scales here tested viscoelasticity appears as dominant, but the poroelastic contribution becomes increasingly important as the crosslinker concentration is reduced