Biofuel blending reduces particle emissions from aircraft engines at cruise conditions.

Aviation-related aerosol emissions contribute to the formation of contrail cirrus clouds that can alter upper tropospheric radiation and water budgets, and therefore climate. The magnitude of air-traffic-related aerosol-cloud interactions and the ways in which these interactions might change in the future remain uncertain. Modelling studies of the present and future effects of aviation on climate require detailed information about the number of aerosol particles emitted per kilogram of fuel burned and the microphysical properties of those aerosols that are relevant for cloud formation. However, previous observational data at cruise altitudes are sparse for engines burning conventional fuels, and no data have previously been reported for biofuel use in-flight. Here we report observations from research aircraft that sampled the exhaust of engines onboard a NASA DC-8 aircraft as they burned conventional Jet A fuel and a 50:50 (by volume) blend of Jet A fuel and a biofuel derived from Camelina oil. We show that, compared to using conventional fuels, biofuel blending reduces particle number and mass emissions immediately behind the aircraft by 50 to 70 per cent. Our observations quantify the impact of biofuel blending on aerosol emissions at cruise conditions and provide key microphysical parameters, which will be useful to assess the potential of biofuel use in aviation as a viable strategy to mitigate climate change.

Racial science now: histories of race and science in the age of personalized medicine.

The revitalization of race-based science and medicine at the very monient in which the history of "race" in science gained such widespread critical attention forces difficult questions regarding the success of the field. This article outlines the current debate over race in contemporary biomedical research and offers a case study of the RaceSci: A History of Race in Science Web project. One of the earliest electronic resources devoted to the history of race in science, RaceSci was relaunched in early 2007 to expand its focus on the present. To date, historians are generally absent from the academic and public dialogue on the "return" of racial science. In response, RaceSci aims to better engage historians with the raced-based organization of current scientific research, particularly in genetics, drug development, and the rise of so-called "personalized" medicine.