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The blooming cosmopolitan coccolithophore Emiliania huxleyi and its viruses (EhVs) are a model for density-dependent virulent dynamics. EhVs commonly exhibit rapid viral reproduction and drive host death in high-density laboratory cultures and mesocosms that simulate blooms. Here we show that this system exhibits physiology-dependent temperate dynamics at environmentally relevant E. huxleyi host densities rather than virulent dynamics, with viruses switching from a long-term non-lethal temperate phase in healthy hosts to a lethal lytic stage as host cells become physiologically stressed. Using this system as a model for temperate infection dynamics, we present a template to diagnose temperate infection in other virus-host systems by integrating experimental, theoretical, and environmental approaches. Finding temperate dynamics in such an established virulent host-virus model system indicates that temperateness may be more pervasive than previously considered, and that the role of viruses in bloom formation and decline may be governed by host physiology rather than by host-virus densities.

Viral lysis of phytoplankton is one of the most common forms of death on Earth. Building on an assay used extensively to assess rates of phytoplankton loss to predation by grazers, lysis rates are increasingly quantified through dilution-based techniques. In this approach, dilution of viruses and hosts are expected to reduce infection rates and thus increase host net growth rates (i.e., accumulation rates). The difference between diluted and undiluted host growth rates is interpreted as a measurable proxy for the rate of viral lytic death. These assays are usually conducted in volumes ≥ 1 L. To increase throughput, we implemented a miniaturized, high-throughput, high-replication, flow cytometric microplate dilution assay to measure viral lysis in environmental samples sourced from a suburban pond and the North Atlantic Ocean. The most notable outcome we observed was a decline in phytoplankton densities that was exacerbated by dilution, instead of the increased growth rates expected from lowered virus-phytoplankton encounters. We sought to explain this counterintuitive outcome using theoretical, environmental, and experimental analyses. Our study shows that, while die-offs could be partly explained by a 'plate effect' due to small incubation volumes and cells adhering to walls, the declines in phytoplankton densities are not volume-dependent. Rather, they are driven by many density- and physiology-dependent effects of dilution on predation pressure, nutrient limitation, and growth, all of which violate the original assumptions of dilution assays. As these effects are volume-independent, these processes likely occur in all dilution assays that our analyses show to be remarkably sensitive to dilution-altered phytoplankton growth and insensitive to actual predation pressure. Incorporating altered growth as well as predation, we present a logical framework that categorizes locations by the relative dominance of these mechanisms, with general applicability to dilution-based assays. [ABSTRACT FROM AUTHOR]

This article is a brief personal reflection on the state of research into the relation between education and social mobility. Quantitative methods are both essential and advancing in this field. Sociologists seek scientific solutions but achieve ethical neutrality only with difficulty because all are tempted to bias from social and political background. I commend the political arithmetic tradition but summarise possible sources of distortion in my own biography. Finally I go beyond the boundaries of scientific social science to advocate social policies which might result in a fairer and more equal society.

This paper examines the sociology of education from the perspective of its recent history and attempts to assess the current state of the field. The authors argue that cognate disciplines such as economics and social policy have taken over some of the key questions that were once the preserve of sociology of education. This raises the question of what is lost if the sociology of education is no longer making a significant contribution, in key areas, to the major educational, social and economic issues of the day. (Contains 3 notes.)

Has Harry Judge's career reproduced in a lifetime the centuries-old history of Brasenose College and the University of Oxford? His biography and the history of his college in relation to Christian belief and modern university reform are briefly recapitulated. All tell a story of adaptation and modernisation, the man short, the college long, the university in ceaseless change from a clerical foundation through an association of colleges as finishing schools for the Establishment to a collegiate university aspiring to place itself in the "world league" of research centres. (Contains 25 notes.)