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171.
Recent advances in catalysis have made the incorporation of fluorine into complex organic molecules easier than ever before, but selective, general and practical fluorination reactions remain sought after. Fluorination of molecules often imparts desirable properties, such as metabolic and thermal stability, and fluorinated molecules are therefore frequently used as pharmaceuticals or materials. But the formation of carbon-fluorine bonds in complex molecules is a significant challenge. Here we discuss reactions to make organofluorides that have emerged within the past few years and which exemplify how to overcome some of the intricate challenges associated with fluorination. 相似文献
172.
Boomsma JJ Beekman M Cornwallis CK Griffin AS Holman L Hughes WO Keller L Oldroyd BP Ratnieks FL 《Nature》2011,471(7339):E4-5; author reply E9-10
Arising from M. A. Nowak, C. E. Tarnita & E. O. Wilson 466, 1057-1062 (2010); Nowak et al. reply. The paper by Nowak et al. has the evolution of eusociality as its title, but it is mostly about something else. It argues against inclusive fitness theory and offers an alternative modelling approach that is claimed to be more fundamental and general, but which, we believe, has no practical biological meaning for the evolution of eusociality. Nowak et al. overlook the robust empirical observation that eusociality has only arisen in clades where mothers are associated with their full-sibling offspring; that is, in families where the average relatedness of offspring to siblings is as high as to their own offspring, independent of population structure or ploidy. We believe that this omission makes the paper largely irrelevant for understanding the evolution of eusociality. 相似文献
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Akimov AV Mukherjee A Yu CL Chang DE Zibrov AS Hemmer PR Park H Lukin MD 《Nature》2007,450(7168):402-406
Control over the interaction between single photons and individual optical emitters is an outstanding problem in quantum science and engineering. It is of interest for ultimate control over light quanta, as well as for potential applications such as efficient photon collection, single-photon switching and transistors, and long-range optical coupling of quantum bits. Recently, substantial advances have been made towards these goals, based on modifying photon fields around an emitter using high-finesse optical cavities. Here we demonstrate a cavity-free, broadband approach for engineering photon-emitter interactions via subwavelength confinement of optical fields near metallic nanostructures. When a single CdSe quantum dot is optically excited in close proximity to a silver nanowire, emission from the quantum dot couples directly to guided surface plasmons in the nanowire, causing the wire's ends to light up. Non-classical photon correlations between the emission from the quantum dot and the ends of the nanowire demonstrate that the latter stems from the generation of single, quantized plasmons. Results from a large number of devices show that efficient coupling is accompanied by more than 2.5-fold enhancement of the quantum dot spontaneous emission, in good agreement with theoretical predictions. 相似文献
175.
Rodrigues AS 《Nature》2007,450(7171):E19; author reply E20
Using data on the global distribution of mammal, bird and amphibian species, Grenyer et al. conclude that planning based on individual taxa does not provide efficient solutions for the conservation of other taxa. They also report that the performance of existing global conservation strategies-endemic bird areas, biodiversity hotspots and global 200 ecoregions-in representing those taxa is often no better (and in some cases worse) than random. I argue here that the methodology used by Grenyer et al. was not appropriate for purported globally comprehensive analyses. Focusing on analyses of rare species as an example, I demonstrate how the data actually reveal substantial cross-taxon surrogacy and good performance of existing global conservation strategies. 相似文献
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Webster AS 《Nature》1972,238(5358):20-24
Published data from X-ray telescopes are not adequate to reveal the fluctuations in the surface brightness of the background radiation caused by clustering or superclustering of the sources giving rise to the background. 相似文献
179.
RNA-mediated gene silencing 总被引:21,自引:0,他引:21
180.
STAT3 signalling is required for leptin regulation of energy balance but not reproduction 总被引:33,自引:0,他引:33
Bates SH Stearns WH Dundon TA Schubert M Tso AW Wang Y Banks AS Lavery HJ Haq AK Maratos-Flier E Neel BG Schwartz MW Myers MG 《Nature》2003,421(6925):856-859