Catálogo de publicaciones - revistas

<jats:title>Experimental Economics</jats:title> <jats:p> The disciplines of social science, with the notable exception of psychology, have traditionally steered clear of laboratory. The field of economics, and in particular econometrics, has amassed an imposing arsenal of quantitative and statistical methods for analyzing observational data in assessing economic theory and in making causal inferences. More recently, laboratory experiments carried out under controlled conditions and randomized field experiments carried out under natural conditions have gained some currency as complementary approaches. <jats:bold>Falk and Heckman</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="535" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1168244">535</jats:related-article> ) review the strengths and shortfalls of these recent developments. </jats:p>

<jats:p>In the Arctic Ocean, phytoplankton cell sizes have decreased with warming temperatures and fresher surface waters.</jats:p>

<jats:title> <jats:italic>Drosophila</jats:italic> Body Color </jats:title> <jats:p> Fly body color is controlled by a variety of genes and alleles. Now <jats:bold> Wittkopp <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="540" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1176980">540</jats:related-article> ) describe how two genes at the ebony and tan genetic loci control body color among two closely related species, <jats:italic>Drosophila americana</jats:italic> and <jats:italic>D. novamexicana</jats:italic> . Variations at the tan locus and linked to the ebony locus also contribute to intraspecific pigmentation changes with geography in <jats:italic>D. americana</jats:italic> . The sequencing of multiple isolates suggests that some strains of <jats:italic>D. americana</jats:italic> carry alleles of tan and ebony that are more closely related to the <jats:italic>D. novamexicana</jats:italic> alleles than they are to other <jats:italic>D. americana</jats:italic> alleles. Thus, the genetic determinants of both inter- and intraspecies color variation is due to shared alleles. </jats:p>

<jats:title>Yeast Joins RNAi Club</jats:title> <jats:p> RNA interference (RNAi) silences gene expression via small interfering (si) RNAs that bind to target sequences. RNAi has been found in almost all eukaryotes examined, with the notable exception of the budding yeast, <jats:italic>Saccharomyces cerevisiae</jats:italic> , one of the most prominent organisms used in the study of molecular biology. Indeed, RNAi has been thought to be missing from all budding yeast. <jats:bold> Drinnenberg <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="544" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1176945">544</jats:related-article> , published online 10 September; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="533" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1182102">Moazed</jats:related-article> </jats:bold> ) now show that several species of budding yeast do possess RNAi, which seems to act primarily on transposable elements and subtelomeric repeats. A noncanonical Dicer protein generates siRNAs that are loaded onto Ago1 protein in <jats:italic>S. castellii</jats:italic> . Introduction of these two genes into <jats:italic>S. cerevisiae</jats:italic> was sufficient to reconstitute RNAi, where it also acted to dampen the activity of transposons. </jats:p>

<jats:title>Measuring Magnetic Light</jats:title> <jats:p> Compared to its electric component, the coupling between the magnetic field component of light and matter is usually extremely weak. With no effective way to measure it, we are effectively blind to light's magnetic component. <jats:bold> Burresi <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="550" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1177096">550</jats:related-article> , published online 1 October; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="529" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181552">Giessen and Vogelgesang</jats:related-article> </jats:bold> ) coupled a metamaterial split-ring resonator to the tip of a scanning probe to measure the magnetic field vector of light at optical frequencies. The ability to measure the magnetic component of light should prove useful for the nanoscale characterization of optical waveguides and other optical devices. </jats:p>

<jats:title>Methane Loosely Bound</jats:title> <jats:p> For the most part, molecular bonds involve sharing of electrons between two discrete atoms. In certain cases, however, a third atom can also attract a portion of the electron density without fully cleaving the bond. Such loose complexes between C-H bonds and transition metals are often invoked as short-lived intermediates in metal-catalyzed reactions of hydrocarbons, though they are rarely observed directly. <jats:bold> Bernskoetter <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="553" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1177485">553</jats:related-article> ) glimpse this coordination motif for methane (CH <jats:sub>4</jats:sub> ) and rhodium (Rh) using low-temperature nuclear magnetic resonance spectroscopy after protonation of an Rh-CH <jats:sub>3</jats:sub> precursor. Kinetics measurements revealed a half-life of just over 80 minutes at −87°C. </jats:p>

<jats:title>Stretching Carbene Versatility</jats:title> <jats:p> Stable N-heterocyclic carbene (NHC) molecules are versatile catalysts for organic reactions (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="532" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181553">Albrecht</jats:related-article> </jats:bold> ). <jats:bold>Lavallo and Grubbs</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="559" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178919">559</jats:related-article> ) now show that these molecules can also catalyze organometallic transformations. Specifically, the carbenes induce coupling of monomeric iron olefin complexes to form clusters incorporating three or four bonded iron centers. Initial coordination of carbene to iron may facilitate formation of an iron-iron bond with a second complex. In a related development, <jats:bold> Aldeco-Perez <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="556" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178206">556</jats:related-article> ) prepared an NHC isomer in which the divalent carbon is shifted so that it no longer lies between the nitrogens. The compound forms stable complexes with both gold and CO <jats:sub>2</jats:sub> . </jats:p>

<jats:title>Stretching Carbene Versatility</jats:title> <jats:p> Stable N-heterocyclic carbene (NHC) molecules are versatile catalysts for organic reactions (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="532" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181553">Albrecht</jats:related-article> </jats:bold> ). <jats:bold>Lavallo and Grubbs</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="559" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178919">559</jats:related-article> ) now show that these molecules can also catalyze organometallic transformations. Specifically, the carbenes induce coupling of monomeric iron olefin complexes to form clusters incorporating three or four bonded iron centers. Initial coordination of carbene to iron may facilitate formation of an iron-iron bond with a second complex. In a related development, <jats:bold> Aldeco-Perez <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="556" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178206">556</jats:related-article> ) prepared an NHC isomer in which the divalent carbon is shifted so that it no longer lies between the nitrogens. The compound forms stable complexes with both gold and CO <jats:sub>2</jats:sub> . </jats:p>

<jats:title>Lunar Water</jats:title> <jats:p> The Moon has been thought to be primarily anhydrous, although there has been some evidence for accumulated ice in permanently shadowed craters near its poles (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="531" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181471">Lucey</jats:related-article> </jats:bold> , published online 24 September). By analyzing recent infrared mapping by Chandrayaan-1 and Deep Impact, and reexamining Cassini data obtained during its early flyby of the Moon, <jats:bold> Pieters <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="568" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178658">568</jats:related-article> , published online 24 September), <jats:bold> Sunshine <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="565" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1179788">565</jats:related-article> , published online 24 September), and <jats:bold> Clark <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="562" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178105">562</jats:related-article> , published online 24 September) reveal a noticeable absorption signal for H <jats:sub>2</jats:sub> O and OH across much of the surface. Some variability in water abundance is seen over the course of the lunar day. The data imply that solar wind is depositing and/or somehow forming water and OH in minerals near the lunar surface, and that this trapped water is dynamic. </jats:p>

<jats:title>Lunar Water</jats:title> <jats:p> The Moon has been thought to be primarily anhydrous, although there has been some evidence for accumulated ice in permanently shadowed craters near its poles (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5952" page="531" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181471">Lucey</jats:related-article> </jats:bold> , published online 24 September). By analyzing recent infrared mapping by Chandrayaan-1 and Deep Impact, and reexamining Cassini data obtained during its early flyby of the Moon, <jats:bold> Pieters <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="568" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178658">568</jats:related-article> , published online 24 September), <jats:bold> Sunshine <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="565" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1179788">565</jats:related-article> , published online 24 September), and <jats:bold> Clark <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="562" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178105">562</jats:related-article> , published online 24 September) reveal a noticeable absorption signal for H <jats:sub>2</jats:sub> O and OH across much of the surface. Some variability in water abundance is seen over the course of the lunar day. The data imply that solar wind is depositing and/or somehow forming water and OH in minerals near the lunar surface, and that this trapped water is dynamic. </jats:p>