Catálogo de publicaciones - revistas

<jats:title>Electrifying Prospects</jats:title> <jats:p> Greenhouse gas emissions need to be reduced in order to decrease the risk of dangerous climate change, and a commonly advocated intermediate step to decarbonizing our energy production is to cut emissions by 80% by the year 2050. <jats:bold> Williams <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="53" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1208365">53</jats:related-article> , published online 24 November) analyze the infrastructure and technology requirements required to meet this goal in California and conclude that simply using the most technologically advanced types of energy supply now available will not be enough. Instead, transportation and other sectors will need to be converted largely to electrical systems, which would make decarbonized electricity the dominant form of energy supply. Such a transformation will require technologies that are not yet commercialized and intensive public-private and interindustry coordination at every stage of the process. </jats:p>

<jats:title>Plasmon Probe</jats:title> <jats:p> When light of certain wavelengths strikes a metal surface, it sets the metal's electrons in motion along trajectories termed “plasmon modes.” <jats:bold> Yurtsever <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="59" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1213504">59</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="47" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215588"> <jats:bold>Batson</jats:bold> </jats:related-article> ) constructed a type of electron microscope that can probe the electric fields associated with this process by measuring the energy of a separate pulse of electrons that is bounced off the surface immediately (less than trillionths of a second) after the light strikes. The spatial resolution was sufficient to map intensities in distinct regions of a single silver nanoparticle. </jats:p>

<jats:title>Wiring Up Silicon Surfaces</jats:title> <jats:p> One of the challenges in downsizing electronic circuits is maintaining low resistivity of wires, because shrinking their diameter to near atomic dimensions increases interface effects and can decrease the effectiveness of dopants. <jats:bold> Weber <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="64" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214319">64</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="45" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215900"> <jats:bold>Ferry</jats:bold> </jats:related-article> ) created nanowires on a silicon surface with the deposition of phosphorus atoms through decomposition of PH <jats:sub>3</jats:sub> with a scanning tunneling microscope tip. A brief thermal annealing embedded these nanowires, which varied from 1.5 to 11 nanometers in width, into the silicon surface. Their resistivity was independent of width, and their current-carrying capability was comparable to that of thicker copper interconnects. </jats:p>

<jats:title>In the Stick of It</jats:title> <jats:p> If a coating makes a surface nonstick, how do you stick the coating to the surface in the first place? For many nonstick coatings, this involves procedures to ensure good adhesion to the underlying surface though the use of surface roughening or intermediary layers. <jats:bold> Deng <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="67" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1207115">67</jats:related-article> , published online 1 December; see the cover) found a very simple route using little more than candle soot as a temporary sublayer that is coated with a silica shell and subsequently removed via calcination. Once top-coated with a semifluorinated silane, the resulting material possessed a low surface energy for water and also repelled oils, alchohols, and alkanes. While the coating could be damaged through mechanical wear, the remaining material continued to show superhydrophobic and superoleophobic behavior. </jats:p>

<jats:title>Controlling Zeolite Nucleation</jats:title> <jats:p> Small zeolite crystals are of increasing interest as catalysts and for membrane separations because they allow the high selectivity of their cages to be exploited while minimizing the kinetic limitations caused by diffusion. <jats:bold> Ng <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="70" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214798">70</jats:related-article> , published online 8 December) synthesized ultrasmall crystals (6 to 15 nanometers) of the EMT zeolite, which has a low framework density and good catalytic properties for hydrocarbon “cracking” (conversion of a large hydrocarbon to smaller ones). The synthesis of EMT has normally required expensive organic templates that limit its industrial use. Careful control of the synthesis conditions, such as ratios of reactants and short bursts of microwave heating, allowed small EMT crystals to nucleate and avoid formation of zeolites with closely related structures. </jats:p>

<jats:title>Continental Thermocouple</jats:title> <jats:p> The patchy presence of billions-of-years-old continental crust indicates a complex coupling between the buoyant forces keeping the lithosphere floating on the mantle and the persistent erosional forces gradually wearing the crust away. Measuring long-term rates of exhumation—the creation of new rock surfaces due to erosion—can reveal how the crust is thermally coupled to the underlying mantle, but techniques to do so have often only been able to resolve a limited temperature range across narrow slices of geologic time. <jats:bold> Blackburn <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="73" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1213496">73</jats:related-article> ) used uranium-lead thermochronology, which is sensitive to the much higher temperatures representative of lower crustal depths, to construct a long-term quantitative model of exhumation and erosion for North America. </jats:p>

<jats:title>Stable Flow</jats:title> <jats:p> Whole-ocean deep circulation in the Atlantic, the Atlantic Meridional Overturning Circulation (AMOC), transports great quantities of heat from low latitudes to higher ones, which, for example, helps to warm Europe's climate. <jats:bold> Matei <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="76" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1210299">76</jats:related-article> ) describe a modeling technique that allows AMOC strength to be predicted for up to 4 years in advance and suggests that AMOC should remain stable until at least 2014. </jats:p>

<jats:title>Supersoldier Throwbacks</jats:title> <jats:p> Anomalous traits reflecting those of an ancestor sporadically appear in individuals that normally should not have them. Through their work with the hyperdiverse ant genus <jats:italic>Pheidole</jats:italic> , <jats:bold> Rajakumar <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="79" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1211451">79</jats:related-article> ) suggest that these anomalies represent raw materials for selection to act upon. The ants possess an ancestral developmental potential, to produce “supersoldiers,” that has been retained for over 30 million years for which recurrent induction has facilitated the adaptive and parallel evolution of supersoldiers. </jats:p>

<jats:title>All Worms Are Not Equal</jats:title> <jats:p> Why do specific mutations not affect all individuals who inherit them? <jats:bold> Casanueva <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="82" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1213491">82</jats:related-article> , published online 15 December; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="44" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1216823"> <jats:bold>Deplancke and Verstrepen</jats:bold> </jats:related-article> ) found that prior exposure to mild environmental stimuli and the stimulation of a stress response in the nematode <jats:italic>Caenorhabditis elegans</jats:italic> reduced the detrimental effects of diverse mutations. Moreover, because of interindividual variation in stress signaling, this protective effect was not the same in all individuals. In the absence of mutations, a stronger response increased stress resistance but also delayed reproduction. Such variability among individuals may be beneficial in an unpredictable environment, acting as a “bet-hedging” strategy to diversify risk. </jats:p>

<jats:title>Musical Chairs</jats:title> <jats:p> The plant hormone abscisic acid (ABA) helps plants to respond to changes in the environment, such as drought. Physiological responses are initiated when ABA binds to its receptor. In the absence of ABA, downstream kinases are held inactive by phosphatases. <jats:bold> Soon <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="85" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215106">85</jats:related-article> , published online 24 November; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="46" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1217667"> <jats:bold>Leung</jats:bold> </jats:related-article> ) now show that both the hormone-receptor complex and the downstream kinase bind to the same site on the phosphatase. Thus, in the presence of hormone, the phosphatase is occupied and unable to interfere with downstream kinase activity. </jats:p>