Catálogo de publicaciones - revistas

<jats:title>X-raying superfluid helium droplets</jats:title> <jats:p> When physicists rotate the superfluid <jats:sup>4</jats:sup> He, it develops a regular array of tiny whirlpools, called vortices. The same phenomenon should occur in helium droplets half a micrometer in size, but studying individual droplets is tricky. Gomez <jats:italic>et al.</jats:italic> used x-ray diffraction to deduce the shape of individual rotating droplets and image the resulting vortex patterns, which confirmed the superfluidity of the droplets. They found that superfluid droplets can host a surprising number of vortices and can rotate faster than normal droplets without disintegrating. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="906" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1252395">906</jats:related-article> </jats:p>

<jats:title>Detailed structure of a gold nanoparticle</jats:title> <jats:p> Adding only a few atoms or changing the capping ligand can dramatically change the structure of individual metal nanoparticles. Azubel <jats:italic>et al.</jats:italic> used aberration-corrected transmission electron microscopy to derive a three-dimensional reconstruction of water-soluble gold nanoparticles. Small-angle x-ray scattering and other techniques have also corroborated this model. They used this to determine the atomic structure, which compared favorably with density functional theory calculations, without assuming any a priori structural knowledge or the use of model fitting. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="909" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1251959">909</jats:related-article> </jats:p>

<jats:title>How huge early stars enriched the universe</jats:title> <jats:p> How big did the first generation of stars get? Knowing their size is critical to understanding how they enriched the chemistry of the universe through supernova explosions. According to numerical simulations, some of the earliest stars were more than 100 times the Sun's mass. However, no traces of these live-fast, die-young stars had been detected in any low-mass stars still extant from that era. Aoki <jats:italic>et al.</jats:italic> now show spectra of one such metal-poor star that may have recorded the activity of a very massive predecessor (see the Perspective by Bromm). This observational evidence will spur further supernova models, as none predicts this specific chemical signature. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="912" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1252633">912</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="868" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255524">868</jats:related-article> </jats:p>

<jats:title>Watching platinum nanocube growth</jats:title> <jats:p> Size and shape drive the properties of metal nanoparticles. Understanding the factors that affect their growth is central to making use of the particles in a range of applications. Liao <jats:italic>et al.</jats:italic> tracked the growth of platinum nanoparticle shapes at high resolution using state-of-the-art liquid cells for in situ monitoring inside an electron microscope. The authors tracked changes in the growth rates at different crystal facets caused by differences in the mobility of the capping ligand. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="916" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1253149">916</jats:related-article> </jats:p>

<jats:title>Putting the heat on Mother Nature</jats:title> <jats:p> Humans are now the biggest cause of glacier melting. Until recently, that was not true. Glaciers take a long time—decades to centuries—to respond to the environmental changes that control their sizes. They have been retreating gradually from the peak levels they reached in the middle of the 19th century, at the end of a 500-year-long cold period called the Little Ice Age. Marzeion <jats:italic>et al.</jats:italic> show that that has recently changed though, as climate warming has continued: Over the past 20 or so years, the anthropogenic contribution to glacial mass loss has increased markedly (see the Perspective by Marshall). </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="919" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1254702">919</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="872" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1258584">872</jats:related-article> </jats:p>

<jats:title>Two vaccines together are better than one alone</jats:title> <jats:p> Polio is proving difficult to eradicate. Making the choice between administering a live attenuated vaccine orally (Sabin) or an inactivated vaccine (Salk) by injection has been highly controversial. Patients prefer the Sabin vaccine, but it requires many doses to offer immunity. Jafari <jats:italic>et al.</jats:italic> tested the two vaccines together in northern India. The injected vaccine significantly reduced virus shedding and boosted intestinal mucosal immunity in children already given the oral vaccine. Thus, using both vaccines could help speed the eventual global demise of polio. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="922" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255006">922</jats:related-article> </jats:p>

<jats:title>Illuminating the pathway to destruction</jats:title> <jats:p> Arctic lakes are an important source of atmospheric CO <jats:sub>2</jats:sub> and therefore play a role in climate change. It is thus vital to know how the rapid Arctic warming will affect them. Cory <jats:italic>et al.</jats:italic> now show that light is the biggest culprit in the breakdown of carbon from thawing permafrost soils (see the Perspective by Tranvik). This carbon then moves out into Arctic lakes and streams. Contrary to previous expectations, these photochemical processes cause much more destruction of the organic molecules in fresh water than bacterial respiration does. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="925" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1253119">925</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="870" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1258235">870</jats:related-article> </jats:p>

<jats:title>The makings of a powerful sweet tooth</jats:title> <jats:p> The main attraction of nectar, a hummingbird favorite, is the sweet taste of sugar. Oddly, though, birds lack the main vertebrate receptor for sweet taste, TIR2. Baldwin <jats:italic>et al.</jats:italic> show that a related receptor, TIR1-T1R3, which generally controls savory taste in vertebrates, adapts in hummingbirds to detect sweet (see the Perspective by Jiang and Beauchamp). This repurposing probably allowed hummingbirds to specialize in nectar feeding and may have assisted the evolution of the many and varied hummingbird species seen today. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="929" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255097">929</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="878" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1259175">878</jats:related-article> </jats:p>

<jats:title>Removing the nucleus in sieve elements</jats:title> <jats:p> Although a cell's nucleus performs critical command and control functions, some cell types, such as enucleated red blood cells, seem to do without. Sieve element cells in plants similarly carry out their function of transporting nutrients and signals from one end of the plant to the other without the guidance of a nucleus. Furuta <jats:italic>et al.</jats:italic> watched how the nucleus self-destructs during the development of sieve element cells (see the Perspective by Geldner). The process is regulated under the control of transcription factors, even as the entire nuclear edifice crumbles into nothingness. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="933" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1253736">933</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="875" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1258711">875</jats:related-article> </jats:p>

<jats:title>A dual-action RNA switch for expression</jats:title> <jats:p> Riboswitches are short segments of RNA that bind small molecules and switch between two different conformations, thereby regulating gene expression (see the Perspective by Chen and Gottesman). DebRoy <jats:italic>et al.</jats:italic> and Mellin <jats:italic>et al.</jats:italic> find a new class of riboswitches—in two different species of bacteria—that are both part of and regulate the production of a noncoding RNA. Each riboswitch ensures that a particular metabolic pathway is only activated in the presence of an essential small-molecule cofactor. In the absence of the cofactor, the full-length non-coding RNA is made and binds a regulator protein, preventing the regulator protein from inappropriately activating the metabolic pathway. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="937" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255091">937</jats:related-article> and p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="940" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255083">940</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6199" page="876" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1258494">876</jats:related-article> </jats:p>