Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
Calculations of nuclear winter are become mainstream academic work, and thus less contentious than a few years ago. They may, in this new role, point usefully to solutions of other problems.
The frontiers of molecular biology and immunology have been expanded through the use of radioisotopic and fluorescent labels. Several new reagents are described below.