Catálogo de publicaciones - revistas

<jats:title>Optimizing a catalyst many ways at once</jats:title> <jats:p> Optimization strategies are often likened to hikes in a hilly landscape. If your goal is to get to the top of the highest hill, and you only take steps toward higher ground, you might never find a peak on a route that requires a preliminary descent. So it is in chemistry, where optimizing each structural feature of a catalyst consecutively might gloss over subtle tradeoffs that in combination offer the best performance. Milo <jats:italic>et al.</jats:italic> use multidimensional analysis techniques to generate a predictive model of how selectivity depends on multiple characteristics of the catalyst and substrate in a C-N bond-forming reaction (see the Perspective by Lu). They then apply this model to improve the catalyst globally. </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="6223" page="737" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261043">737</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6223" page="719" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa5624">719</jats:related-article> </jats:p>

<jats:title>Light switch for superconductivity</jats:title> <jats:p> The conducting properties of materials sensitively depend on the available carrier concentration. Physicists can vary this concentration by inducing carriers in the material; for example, by placing it next to an ionic liquid in an electric field. Suda <jats:italic>et al.</jats:italic> instead used a layer of the molecule spiropyran, which changes from a non-ionic to an ionic form when it is irradiated by ultraviolet (UV) light. The authors placed the layer on top of a thin crystal of an organic material. When they shone UV light on the spiropyran, the adjacent material became superconducting, thanks to the carriers induced at the interface. </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="6223" page="743" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1256783">743</jats:related-article> </jats:p>

<jats:title>Key trace minerals greatly strengthen teeth</jats:title> <jats:p> The outer layers of teeth are made up of nanowires of enamel that are prone to decay. Gordon <jats:italic>et al.</jats:italic> analyzed the composition of tooth enamel from a variety of rodents at the nanometer scale (see the Perspective by Politi). In regular and pigmented enamel, which contain different trace elements at varying boundary regions, two intergranular phases—magnesium amorphous calcium phosphate or a mixed-phase iron oxide—control the rates of enamel demineralization. This suggests that there may be alternative options to fluoridation for strengthening teeth against decay. </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="6223" page="746" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1258950">746</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6223" page="712" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa5245">712</jats:related-article> </jats:p>

<jats:title>Double trouble for Criegee intermediates</jats:title> <jats:p> Atmospheric ozone reacts with unsaturated hydrocarbons to form unstable compounds called Criegee intermediates. Only recently did a reliable method emerge to make and study these compounds in the laboratory, and they didn't seem to react with water. Now, Chao <jats:italic>et al.</jats:italic> show that the simplest Criegee intermediate, CH <jats:sub>2</jats:sub> OO, does in fact react very rapidly with pairs of water molecules (see the Perspective by Okumura). Earlier studies may have missed this result because they were conducted at low pressure, where water dimers are scarce, or because they monitored downstream processes. The new rate measurements imply that reactivity with atmospheric water pairs is a major decay channel for Criegees. </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="6223" page="751" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261549">751</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6223" page="718" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa5506">718</jats:related-article> </jats:p>

<jats:title>Taking a snapshot of active brain circuitry</jats:title> <jats:p> Neuroscientists now have a method to mark active populations of neurons in vivo to study circuit activity in the behaving animal. Fosque <jats:italic>et al.</jats:italic> designed and thoroughly validated a fluorescent protein–based reagent that allows permanent marking of active cells over short time scales. This indicator, termed CaMPARI, switches from its native green to a red fluorescent state by simultaneous illumination with violet light and exposure to increased levels of intracellular calcium. CaMPARI successfully marked active nerve cells in <jats:italic>Drosophila</jats:italic> , zebrafish, and mouse brains. </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="6223" page="755" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260922">755</jats:related-article> </jats:p>

<jats:title>Taking advantage of new neighborhoods</jats:title> <jats:p> Mammals are one of the most morphologically diverse organisms, with adaptation to unique ecological conditions creating a wide array of forms, from mice to whales. Two new basal mammals from the mid-Jurassic period suggest that this diversification was well under way millions of years earlier than previously thought. Luo <jats:italic>et al.</jats:italic> describe a burrowing species with limb and digit modifications similar to those of current burrowers and identify the likely genes and developmental pathways involved. Meng <jats:italic>et al.</jats:italic> describe an arboreal species with modifications for climbing and that possessed teeth clearly adapted for a herbivorous diet, including the consumption of sap. </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="6223" page="760" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260880">760</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6223" page="764" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260879">764</jats:related-article> </jats:p>

<jats:title>Taking advantage of new neighborhoods</jats:title> <jats:p> Mammals are one of the most morphologically diverse organisms, with adaptation to unique ecological conditions creating a wide array of forms, from mice to whales. Two new basal mammals from the mid-Jurassic period suggest that this diversification was well under way millions of years earlier than previously thought. Luo <jats:italic>et al.</jats:italic> describe a burrowing species with limb and digit modifications similar to those of current burrowers and identify the likely genes and developmental pathways involved. Meng <jats:italic>et al.</jats:italic> describe an arboreal species with modifications for climbing and that possessed teeth clearly adapted for a herbivorous diet, including the consumption of sap. </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="6223" page="760" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260880">760</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6223" page="764" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260879">764</jats:related-article> </jats:p>

<jats:title>Dumping lots of plastics into our oceans</jats:title> <jats:p> Considerable progress has been made in determining the amount and location of plastic debris in our seas, but how much plastic actually enters them in the first place is more uncertain. Jambeck <jats:italic>et al.</jats:italic> combine available data on solid waste with a model that uses population density and economic status to estimate the amount of land-based plastic waste entering the ocean. Unless waste management practices are improved, the flux of plastics to the oceans could increase by an order of magnitude within the next decade. </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="6223" page="768" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260352">768</jats:related-article> </jats:p>

<jats:title>A view of the HCV polymerase at work</jats:title> <jats:p> More than 3% of the world's population is infected with hepatitis C virus (HCV), a predisposing factor for life-threatening liver diseases such as cirrhosis and cancer. HCV encodes a polymerase called NS5B that catalyzes replication of the viral RNA genome. Drugs inhibiting NS5B have shown impressive antiviral activity in recent clinical trials. Appleby <jats:italic>et al.</jats:italic> (see the Perspective by Bressanelli) reveal the inner workings of HCV RNA replication by analyzing crystal structures of stalled NS5B polymerase ternary complexes during the initiation and elongation of RNA synthesis. They also define the way in which sofosbuvir, a drug with potent clinical efficacy, interacts with the NS5B active site. </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="6223" page="771" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1259210">771</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6223" page="715" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa5980">715</jats:related-article> </jats:p>