The Crystal Structure of OprG from Pseudomonas aeruginosa, a Potential Channel for Transport of Hydrophobic Molecules across the Outer Membrane

Background: The outer membrane (OM) of Gram-negative bacteria provides a barrier to the passage of hydrophobic and hydrophilic compounds into the cell. The OM has embedded proteins that serve important functions in signal transduction and in the transport of molecules into the periplasm. The OmpW family of OM proteins, of which P. aeruginosa OprG is a member, is widespread in Gram-negative bacteria. The biological functions of OprG and other OmpW family members are still unclear. Methodology/Principal Findings: In order to obtain more information about possible functions of OmpW family members we have solved the X-ray crystal structure of P. aeruginosa OprG at 2.4 A ˚ resolution. OprG forms an eightstranded b-barrel with a hydrophobic channel that leads from the extracellular surface to a lateral opening in the barrel wall. The OprG barrel is closed off from the periplasm by interacting polar and charged residues on opposite sides of the barrel wall. Conclusions/Significance: The crystal structure, together with recent biochemical data, suggests that OprG and other OmpW family members form channels that mediate the diffusion of small hydrophobic molecules across the OM by a latera

The child protection system, organizational responses to child sexual abuse and the social construction of social problems

grantor: University of TorontoThe following dissertation is an examination of the relationship between professional policies and practices employed by the Canadian Child Protection system regarding child sexual abuse and the historical social constructions of child sexual abuse as a social problem. The research draws on constructionist and feminist theoretical perspectives and employs a critical interpretive analysis designed to expand our understanding of the relationship between the formal structure, policies, and practices of organization and the process of social problem construction. Two separate conceptual models were developed for the purposes of data organization and analysis. The first, 'The Process of Social Problem Construction Model' was developed and utilized to conceptually frame the analysis of a wide-range of theory, research, and historical data relating to the social construction of child sexual abuse as a social problem. The second model, a 'Three-Part Conceptual Model for Organizational Analysis' was developed specifically to facilitate a critical examination of 'relationship' and a textual analysis of the formal organizational/institutional structures, policies, and practices established by the current official documentation and legislation governing the delivery of child protection services. A system of coding was developed using the relationship dimensions delineated in the 'Three-Part Model for Organizational Analysis' enabling an examination of the connection between specific elements of the official child protection documentation and specific elements of the historical social construction framework and process. The inclusion and analysis of transcripts obtained from personal interviews with eight study key informants served to greatly enrich the analysis of the official organization documentation, legislation, and historical data. Finally, application of the techniques for establishing the trustworthiness of naturalistic inquiry offered by Lincoln and Guba (1985) greatly assisted in establishing the credibility, transferability, dependability, and confirmability of the research methodology. Recommendations are offered regarding the direction of future research in the area of child sexual abuse as well as proposed initiatives for social work educators and professionals.Ph.D

Search for transient gravitational waves in coincidence with short-duration radio transients during 2007-2013

We present an archival search for transient gravitational-wave bursts in coincidence with 27 single pulse triggers from Green Bank Telescope pulsar surveys, using the LIGO, Virgo and GEO interferometer network. We also discuss a check for gravitational-wave signals in coincidence with Parkes Fast Radio Bursts using similar methods. Data analyzed in these searches were collected between 2007 and 2013. Possible sources of emission of both short-duration radio signals and transient gravitational-wave emission include starquakes on neutron stars, binary coalescence of neutron stars, and cosmic string cusps. While no evidence for gravitational-wave emission in coincidence with these radio transients was found, the current analysis serves as a prototype for similar future searches using more sensitive second-generation interferometers