Catálogo de publicaciones - revistas

<jats:p> An organic reaction creates an intermediate in which a fluorine atom, the most electronegative of the elements, formally bears a positive charge. <jats:named-content content-type="related-content"> [Also see Report by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="57" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1231247"> Struble <jats:italic>et al.</jats:italic> </jats:related-article> ] </jats:named-content> </jats:p>

<jats:p>Numerical simulations are changing our views on the dynamo process underlying the solar magnetic activity cycle.</jats:p>

<jats:title>A Supernova in 3D</jats:title> <jats:p> When a star explodes, it expels matter at supersonic speeds. <jats:bold> Nikolić <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="45" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1228297">45</jats:related-article> , published online 14 February) used integral-field spectroscopy to obtain high-resolution, spatially resolved spectra of the shock waves associated with supernova 1006. The physical characteristics of the shocks around this supernova exhibit a strong spatial variation that suggests the presence of suprathermal (∼10 to 100 keV) protons, which are the potential seeds for generating cosmic rays. </jats:p>

<jats:title>Bio-Inspired Synthetic Network</jats:title> <jats:p> Collective behavior comes through the ability of neighboring objects to communicate and interact with each other. <jats:bold> Villar <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="48" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1229495">48</jats:related-article> ; see the cover) produced three-dimensionally patterned, interconnected networks of lipid-bounded structures functionalized with transmembrane proteins, which allowed electrical communication along specific pathways. </jats:p>

<jats:title>A Light in the Dark</jats:title> <jats:p> Carotenoids enhance the efficiency of photosynthesis by absorbing light at wavelengths inaccessible to chlorophyll. However, the mechanism underlying transfer of the absorbed energy from these pigments to the site of chemical catalysis is unclear. Studies have debated the involvement of a “dark” state in the carotenoid electronic structure—a state inaccessible by direct absorption populated by partial relaxation of the initial excited state. <jats:bold> Ostroumov <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="52" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1230106">52</jats:related-article> ) used two-dimensional electronic spectroscopy to provide evidence of this state. </jats:p>

<jats:title>Fluorine Learns to Share</jats:title> <jats:p> Though halides typically coordinate to just one carbon center, their transient coordination to a second carbon (forming a positively charged bridge) explains the spatial dynamics of many reactions. However, unlike chlorine, bromine, and iodine—which can all form such halonium ions—fluorine does not appear to engage in carbon-bridging behavior, presumably because of its very high electronegativity. <jats:bold> Struble <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="57" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1231247">57</jats:related-article> , see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="41" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1236150">Hennecke</jats:related-article> </jats:bold> ) synthesized a rigid molecule, particularly well-poised to manifest fluoride bridging, and provide evidence for a fluoronium intermediate in a displacement reaction. </jats:p>

<jats:title>Amorphous and More Active</jats:title> <jats:p> The electrochemical generation of hydrogen from water could help in the storage of energy generated by renewable resources at off-peak times. However, catalysts for the slow step of this reaction, the oxygen evolution reaction (OER), are based on oxides of noble metals (iridium and ruthenium) that have limited abundance. A strategy for improving the performance of earth-abundant elements is to explore mixed-metal oxides and to prepare these as amorphous phases. <jats:bold> Smith <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="60" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1233638">60</jats:related-article> , published online 28 March) developed a general method for preparing amorphous oxides, based on photodecomposition of organometallic precursors. Amorphous mixed-metal oxides of iron, nickel, and cobalt were more active than comparable crystalline materials and provided OER performance comparable to noble metal oxides. </jats:p>

<jats:title>Cycling in Unison</jats:title> <jats:p> Many small mammals, especially voles, display semi-regular cycles of population boom and bust. Given the fundamental importance of small mammals as basal consumers and prey, such cycles can have cascading effects in trophic food webs. <jats:bold> Cornulier <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="63" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1228992">63</jats:related-article> ) collated raw data from vole populations across Europe collected over the past 18 years. Reduction in winter growth rate was common across a wide variety of habitats with very different local climates, suggesting the presence of a continental-scale climatic driver of vole populations. </jats:p>

<jats:title>Flowers and Bees Have “Sparks”</jats:title> <jats:p> Plants and their pollinators have very intimate interactions, as emphasized by the many classic cases of coevolution among species of each. Such close relationships require signaling between plant and pollinator. Coordination between plant signals and pollinator perception has been shown to exist in flower color, shape, and odor. <jats:bold> Clarke <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="66" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1230883">66</jats:related-article> , published online 21 February) report the potential for a distinct mode of plant–pollinator communication, electric fields. Natural floral electric fields, which are impacted by visits from naturally charged bees, were easily discriminated by bees, based on their level, pattern, and structure, and improved the rate at which bees remembered the location of a nectar reward. </jats:p>

<jats:title>Reef Repair</jats:title> <jats:p> Coral reefs suffer mass mortality because of coral bleaching, disease, and tropical storms, but we know much more about when, where, and how rapidly these ecosystems have collapsed than we do about their recovery. <jats:bold> Gilmour <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/content/340/6128/69.full">69</jats:ext-link> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6128" page="34" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1236833"> <jats:bold>Polidoro and Carpenter</jats:bold> </jats:related-article> ) studied a highly isolated coral reef before and after a climate-induced mass mortality event that killed 70 to 90% of the reef corals. The initial recovery of coral cover involved growth and survival of remnant colonies, which was followed by increases in larval recruitment. Thus, in the absence of chronic disturbance, even isolated reefs can recover from catastrophic disturbance. </jats:p>