Carbon losses from all soils across England and Wales 1978-2003

More than twice as much carbon is held in soils as in vegetation or the atmosphere, and changes in soil carbon content can have a large effect on the global carbon budget. The possibility that climate change is being reinforced by increased carbon dioxide emissions from soils owing to rising temperature is the subject of a continuing debate. But evidence for the suggested feedback mechanism has to date come solely from small-scale laboratory and field experiments and modelling studies. Here we use data from the National Soil Inventory of England and Wales obtained between 1978 and 2003 to show that carbon was lost from soils across England and Wales over the survey period at a mean rate of 0.6% yr(-1) (relative to the existing soil carbon content). We find that the relative rate of carbon loss increased with soil carbon content and was more than 2% yr(-1) in soils with carbon contents greater than 100 g kg(-1). The relationship between rate of carbon loss and carbon content is irrespective of land use, suggesting a link to climate change. Our findings indicate that losses of soil carbon in England and Wales--and by inference in other temperate regions-are likely to have been offsetting absorption of carbon by terrestrial sinks.     

爱因斯坦A-Z

本书是一本传记性著作，记述了20世纪最伟大的科学家之一爱因斯坦的生平。与其他传记体文学不同的是，本书别出心裁的以字母表的顺序，以关键词的方式记录了爱因斯坦的生活、科研、理想等等。从第一个单词大大咧咧的（Absentmindeness），一直到最后一个单词犹太复国主义（Zionism）。每个单词作为一章的标题引出了一段或惊险、或平淡的故事。从本书中读者可以了解爱因斯坦在科学方面的天才想法，可以读到他作为普通人生活的一面——一个可怜的丈夫和父亲，还有他在核武器方面的影响，他创造了相对论却拒绝接受量子力学……     

The identification of chemical intermediates in enzyme catalysis by the rapid quench-flow technique

Traditionally, enzyme transient kinetics have been studied by the stopped-flow and rapid quench-flow (QF) methods. Whereas stopped-flow is the more convenient, it suffers from two weaknesses: optically silent systems cannot be studied, and when there is a signal it cannot always be assigned to a particular step in the reaction pathway. QF is a chemical sampling method; reaction mixtures are aged for a few milliseconds or longer, ‘stopped’ by a quenching agent and the product or the intermediate is measured by a specific analytical method. Here we show that by exploiting the array of current analytical methods and different quenching agents, the QF method is a key technique for identifying, and for characterising kinetically, intermediates in enzyme reaction pathways and for determining the order by which bonds are formed or cleaved by enzymes acting on polymer substrates such as DNA. Received 24 May 2006; received after revision: 3 July 2006; accepted 19 July 2006