Catálogo de publicaciones - revistas

<jats:title>A light on the origin of cosmic rays</jats:title> <jats:p>There's a new lab for studying the origins of cosmic rays: our neighbor galaxy, the Large Magellanic Cloud. Astronomers are now making progress on this topic by examining the gamma rays that are produced when cosmic rays interact with gas or lower-energy photons. The H.E.S.S. Collaboration has detected three sources of gamma rays in a variety of forms in the galactic satellite to the Milky Way. The sources include the pulsar wind nebula of N 157B, the supernova remnant N 132D, and the superbubble 30 Dor C. Oddly, supernova 1987A was not detected.</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="6220" page="406" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261313">406</jats:related-article> </jats:p>

<jats:title>Of water and methane on Mars</jats:title> <jats:p> The Curiosity rover has been collecting data for the past 2 years, since its delivery to Mars (see the Perspective by Zahnle). Many studies now suggest that many millions of years ago, Mars was warmer and wetter than it is today. But those conditions required an atmosphere that seems to have vanished. Using the Curiosity rover, Mahaffy <jats:italic>et al.</jats:italic> measured the ratio of deuterium to hydrogen in clays that were formed 3.0 to 3.7 billion years ago. Hydrogen escapes more readily than deuterium, so this ratio offers a snapshot measure of the ancient atmosphere that can help constrain when and how it disappeared. Most methane on Earth has a biological origin, so planetary scientists have keenly pursued its detection in the martian atmosphere as well. Now, Webster <jats:italic>et al.</jats:italic> have precisely confirmed the presence of methane in the martian atmosphere with the instruments aboard the Curiosity rover at Gale crater. </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="6220" page="412" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260291">412</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="415" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261713">415</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="370" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa3687">370</jats:related-article> </jats:p>

<jats:title>Of water and methane on Mars</jats:title> <jats:p> The Curiosity rover has been collecting data for the past 2 years, since its delivery to Mars (see the Perspective by Zahnle). Many studies now suggest that many millions of years ago, Mars was warmer and wetter than it is today. But those conditions required an atmosphere that seems to have vanished. Using the Curiosity rover, Mahaffy <jats:italic>et al.</jats:italic> measured the ratio of deuterium to hydrogen in clays that were formed 3.0 to 3.7 billion years ago. Hydrogen escapes more readily than deuterium, so this ratio offers a snapshot measure of the ancient atmosphere that can help constrain when and how it disappeared. Most methane on Earth has a biological origin, so planetary scientists have keenly pursued its detection in the martian atmosphere as well. Now, Webster <jats:italic>et al.</jats:italic> have precisely confirmed the presence of methane in the martian atmosphere with the instruments aboard the Curiosity rover at Gale crater. </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="6220" page="412" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260291">412</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="415" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261713">415</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="370" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa3687">370</jats:related-article> </jats:p>

<jats:title>Melting silica in massive planets</jats:title> <jats:p> To simulate the extreme conditions inside large planets requires extreme experiments. Millot <jats:italic>et al.</jats:italic> used high-pressure shock waves almost twice that of the center of Earth to melt silica, one of the primary components of planetary interiors. This was possible only by shocking a very dense form of silica called stishovite. Determining the melting point of silica is vital for developing better computational models of the interior of planets several times the mass of Earth. The high-pressure liquid was electrically conductive, a property that may contribute to magnetic dynamos in very large terrestrial exoplanets. </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="6220" page="418" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261507">418</jats:related-article> </jats:p>

<jats:title>Tilting toward two properties</jats:title> <jats:p> Opposing electronic and symmetry constraints can make it difficult to combine some pairs of material properties in a single crystalline material. Magnetization and electrical polarization are such a pair, but their combination could be useful for applications such as magnetoelectric information storage. Pitcher <jats:italic>et al.</jats:italic> now show that careful design of chemical substitutions in a layered perovskite are both electrically polar and weakly ferromagnetic at temperatures up to 330 K. </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="6220" page="420" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1262118">420</jats:related-article> </jats:p>

<jats:title>Soldering semiconductor nanoparticles</jats:title> <jats:p> The optical and electronic properties of semiconductor nanoparticles can be tuned through changes in their size and composition. However, poor contact between interfaces can degrade nanoparticle performance in devices. Dolzhnikov <jats:italic>et al.</jats:italic> report the synthesis of a gel-like “solder” for metal chalcogenide nanoparticles, such as cadmium selenide and lead telluride, by cross-linking molecular wires of these materials. </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="6220" page="425" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260501">425</jats:related-article> </jats:p>

<jats:title>Mechanisms propelling drug resistance</jats:title> <jats:p> If it were to spread, resistance to the drug artemisinin would seriously derail the recent gains of global malaria control programs (see the Perspective by Sibley). Mutations in a region called the K13-propeller are predictive for artemisinin resistance in Southeast Asia. Mok <jats:italic>et al.</jats:italic> looked at the patterns of gene expression in parasites isolated from more than 1000 patients sampled in Africa, Bangladesh, and the Mekong region. A range of mutations that alter protein repair pathways and the timing of the parasite's developmental cycle were only found in parasites from the Mekong region. Straimer <jats:italic>et al.</jats:italic> genetically engineered the K13 region of parasites obtained from recent clinical isolates. Mutations in this region were indeed responsible for the resistance phenotypes. </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="6220" page="431" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260403">431</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="428" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260867">428</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="373" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa4102">373</jats:related-article> </jats:p>

<jats:title>Mechanisms propelling drug resistance</jats:title> <jats:p> If it were to spread, resistance to the drug artemisinin would seriously derail the recent gains of global malaria control programs (see the Perspective by Sibley). Mutations in a region called the K13-propeller are predictive for artemisinin resistance in Southeast Asia. Mok <jats:italic>et al.</jats:italic> looked at the patterns of gene expression in parasites isolated from more than 1000 patients sampled in Africa, Bangladesh, and the Mekong region. A range of mutations that alter protein repair pathways and the timing of the parasite's developmental cycle were only found in parasites from the Mekong region. Straimer <jats:italic>et al.</jats:italic> genetically engineered the K13 region of parasites obtained from recent clinical isolates. Mutations in this region were indeed responsible for the resistance phenotypes. </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="6220" page="431" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260403">431</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="428" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260867">428</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6220" page="373" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa4102">373</jats:related-article> </jats:p>

<jats:title>Chronic malaria shortens telomeres</jats:title> <jats:p> Chronic infections are assumed to cause little damage to the host, but is this true? Migrant birds can pick up various species of malaria parasite while overwintering in the tropics. After initial acute malaria, migrant great reed warblers, which nest in Sweden and overwinter in Africa, are asymptomatically infected for life. Asghar <jats:italic>et al.</jats:italic> discovered that these cryptically infected birds laid fewer eggs and were less successful at rearing healthy offspring than uninfected birds. Furthermore, infected birds had significantly shorter telomeres (the protective caps on the ends of chromosomes) and produced chicks with shortened telomeres. </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="6220" page="436" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261121">436</jats:related-article> </jats:p>

<jats:title>A detailed look at proteasomes in situ</jats:title> <jats:p> The 26 <jats:italic>S</jats:italic> proteasome is a protein machine that degrades intracellular proteins in the cytosol. The proteasome is critical for protein quality control and for the regulation of numerous cellular processes in eukaryotic cells. The structure of isolated proteasomes is well established, but how intact proteasomes look within the cell is less clear. Asano <jats:italic>et al.</jats:italic> used an improved approach to electron cryotomography to look at proteasomes in intact hippocampal neurons. Their analysis suggests that these cells only use about 20% of their proteasomes in an unstressed state, which leaves significant spare capacity to deal with proteotoxic stress. </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="6220" page="439" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261197">439</jats:related-article> </jats:p>