Olivine intergranular plasticity at mantle pressures and temperatures

The ductile behavior of olivine-rich rocks is critical to constrain thermal convection in the Earth's upper mantle. Classical olivine flow laws for dislocation or diffusion creep fail to explain the fast post-seismic surface displacements observed by GPS, which requires a much weaker lithosphere than predicted by classical laws. Here we compare the plasticity of olivine aggregates deformed experimentally at mantle pressures and temperatures to that of single crystals and demonstrate that, depending on conditions of stress and temperature, strain accommodated through grain-to-grain interactions – here called intergranular strain – can be orders of magnitude larger than intracrystalline strain, which significantly weakens olivine strength. This result, extrapolated along mantle geotherms, suggests that intergranular plasticity could be dominant in most of the upper mantle. Consequently, the strength of olivine-rich aggregates in the upper mantle may be significantly lower than predicted by flow laws based on intracrystalline plasticity models.     

黄海春季海洋病毒的空间分布特征

采用荧光显微技术,报道了春季(2006年4月)海洋病毒丰度在黄海的空间分布,分析了病毒丰度与细菌丰度、叶绿素α浓度、温度和盐度的相关关系.研究结果表明,黄海表层水中病毒丰度的变化范围为1.08x107～9.90x107个/mL,平均值是5.62×107个/mL土2.28x107个/mL,细菌丰度的变化范围为0.01×1...     

The EU as a frontrunner on greenhouse gas emissions trading: how did it happen and will the EU succeed?

The objective of this paper is first to provide empirical evidence of what can be seen as a rather remarkable change in EU’s position on the use of greenhouse gas (GHG) emissions trading (ET) in climate policy, from the role of a sceptic in the run-up to Kyoto towards more of a frontrunner. The paper argues that there is a synergistic and multilevel mix of explanatory factors for this “U-turn”, including developments at the international, EU, Member State, sub-national, and even down to the personal level. Second, the paper explores and discusses the philosophy behind the Commission’s proposal for a directive on GHG ET. Third, the paper examines the prospects for ‘success’ of a scheme for EU-wide ET using a multifaceted set of metrics. In brief, we argue that output success—the chances for having a directive adopted—hinges on the resolution of two key issues. First, whether the preliminary phase is to be mandatory or voluntary, and second, incompatibilities with domestic ET schemes. Outcome success—steering and cost-effectiveness—will in turn depend on factors like the coverage of the scheme and inclusion of project-based credits, while more long-term political implications hinges on the successful adoption and operation of the scheme.

“The Proposal on emissions trading represents a major innovation for environmental policy in Europe. We are de facto creating a big new market, and we are determined to use market forces to achieve our climate objectives in the most cost-conscious way […]. The emissions trading system will be an important cornerstone in our strategy to reduce emissions in the most cost-effective way”.

Environment Commissioner Margot Wallström.