Sliding conductivity of charge-density waves

A classical model of charge-density wave motion at large velocities is used to describe the nonlinear response of the charge-density wave in fields well above the threshold. The charge-density wave is regarded as a charged, deformable medium and its interaction with pinning centers is treated in perturbation theory. The results fit the available high-field data on NbSe3 well. The observed interference effects between a large dc field and an ac field are also explained

Local community playgroup participation and associations with social capital

Issue addressed The study aim was to investigate the relationships between social capital measures and playgroup participation in a local residential area for parents with children of playgroup age (1-4 years) compared with non-participation and participation in a playgroup outside the local residential area. Research indicates playgroup participation has benefits for families, however, less is known about the potential local community social capital for parents who participate in playgroups. Methods Data were collected through a cross-sectional survey from March 2013 to January 2014 in Perth, Western Australia. The data from a group of parents (n=405) who had at least one child aged between 1 and 4 years were analysed using multivariable regression. Reported playgroup participation (local, outside the area or non-participation) in the previous 12 months was investigated for associations with three measures (Neighbourhood Cohesion Index, Social Capital and Citizenship Survey and local reciprocity) that capture attributes of social capital. Results Participation in playgroup locally was generally associated with higher levels of social capital than both participation in playgroup outside the local area and non-participation. Mothers with two or more children fared better for social capital measures than mothers with one child. Conclusions Participation in a locally placed playgroup may provide an important opportunity for families with children of playgroup age (1-4 years) to build social capital in their local community. So what? Playgroups in a family's local area have the potential to foster locally placed social capital through community interaction, social networks and cohesion, which are important for mental health promotion in communities