How can we make plants grow faster? A source-sink perspective on growth rate.

Growth is a major component of fitness in all organisms, an important mediator of competitive interactions in plant communities, and a central determinant of yield in crops. Understanding what limits plant growth is therefore of fundamental importance to plant evolution, ecology, and crop science, but each discipline views the process from a different perspective. This review highlights the importance of source-sink interactions as determinants of growth. The evidence for source- and sink-limitation of growth, and the ways in which regulatory molecular feedback systems act to maintain an appropriate source:sink balance, are first discussed. Evidence clearly shows that future increases in crop productivity depend crucially on a quantitative understanding of the extent to which sources or sinks limit growth, and how this changes during development. To identify bottlenecks limiting growth and yield, a holistic view of growth is required at the whole-plant scale, incorporating mechanistic interactions between physiology, resource allocation, and plant development. Such a holistic perspective on source-sink interactions will allow the development of a more integrated, whole-system level understanding of growth, with benefits across multiple disciplines.

Vortices and turbulence in trapped atomic condensates.

After more than a decade of experiments generating and studying the physics of quantized vortices in atomic gas Bose-Einstein condensates, research is beginning to focus on the roles of vortices in quantum turbulence, as well as other measures of quantum turbulence in atomic condensates. Such research directions have the potential to uncover new insights into quantum turbulence, vortices, and superfluidity and also explore the similarities and differences between quantum and classical turbulence in entirely new settings. Here we present a critical assessment of theoretical and experimental studies in this emerging field of quantum turbulence in atomic condensates.

Service priorities and unmet service needs among people living with HIV/AIDS: results from a nationwide interview of HIV/AIDS housing organizations.

Housing for people living with HIV/AIDS (PLWHA) has been linked to a number of positive physical and mental health outcomes, in addition to decreased sexual and drug-related risk behavior. The current study identified service priorities for PLWHA, services provided by HIV/AIDS housing agencies, and unmet service needs for PLWHA through a nationwide telephone survey of HIV/AIDS housing agencies in the USA. Housing, alcohol/drug treatment, and mental health services were identified as the three highest priorities for PLWHA and assistance finding employment, dental care, vocational assistance, and mental health services were the top needs not being met. Differences by geographical region were also examined. Findings indicate that while housing affords PLWHA access to services, there are still areas (e.g., mental health services) where gaps in linkages to care exist.

Us versus Them in Context: Meta-Analysis as a Tool for Geotemporal Trends in Intergroup Relations.

The increasing availability of studies from many nations offers important potential insights into group-based psychology and behavior, conflict, and violence. Nonetheless, to date, few cross-national or cultural comparisons of study findings have been made, representing a gap in our understanding of the historical causes and courses of intergroup conflict in current comparative approaches. Meta-analytic methods offer researchers the ability to combine data from studies with groups as well as across time. Our review of statistical methods available for comparative analyses in intergroup research found strengths and limitations for understanding group differences, conflict, and violence, and meta-analytic methods address these limitations by exploring potential structural-level moderators and by identifying how temporal and geographical variations may relate directly to group-based variables. Such methods can contribute to our understanding of broad structural effects on group-based variables by elucidating the mechanisms underlying them.