Catálogo de publicaciones - revistas

<jats:p>Ecological models have limited predictive power, but can provide insights into what makes an ecosystem vulnerable to disturbance.</jats:p>

<jats:p>By using electron spin in a transistor, researchers have developed a new approach for transferring and processing information.</jats:p>

<jats:p>A virologist discovered the eukaryotic mRNA 5′-terminal cap structure and revealed its role in gene expression.</jats:p>

<jats:title>The Primordial Soup</jats:title> <jats:p> Protons and neutrons were originally thought to be indivisible, but we now know that they have constituent parts—quarks. Quarks are bound together tightly through gluons and can only come apart under extreme conditions—conditions believed microseconds after the Big Bang to have formed a hot, dense “soup” of quarks and gluons, called the quark-gluon plasma (QGP). QGP can be made experimentally in heavy ion colliders, where extremely high temperatures are reached. <jats:bold>Jacak and Müller</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="310" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1215901">310</jats:related-article> ) review the progress in this field and its unexpected ties to cold atomic gases and string theory. </jats:p>

<jats:title>Crater Core</jats:title> <jats:p> The high-northern latitudes of the Arctic have an important influence on climate and constitute a region with a unique array of complex feedbacks that make it difficult to understand the workings of its climate. <jats:bold> Melles <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="315" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1222135">315</jats:related-article> , published online 21 June) developed a 2.8-million-year record of Arctic climate, using a sediment core from a lake in northeastern Russia that was formed more than 3.5 million years ago by a meteorite impact. Pronounced glacial episodes began 2.6 million years ago but did not achieve orbital pacing for another 700,000 years. </jats:p>

<jats:title>It's the Oxygens</jats:title> <jats:p> Scanning tunneling microscopy of cuprate high-temperature superconductors has revealed surprising inhomogeneity of the energy scales known as the superconducting gap, pseudogap, and the critical temperature. Some of these effects have been correlated with chemical disorder of the materials caused by doping, but, because of technical limitations, only the dopants in a limited energy range have been imaged. <jats:bold> Zeljkovic <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="320" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1218648">320</jats:related-article> ) extend this range to reveal the positions of the remaining oxygen defects in Bi <jats:sub>2+y</jats:sub> Sr <jats:sub>2-y</jats:sub> CaCu <jats:sub>2</jats:sub> O <jats:sub>8+x</jats:sub> . </jats:p>

<jats:title>A Different Spin Transistor</jats:title> <jats:p> A typical transistor consists of a source and a drain; the current that makes it to the drain is controlled by applying voltage to the third terminal, called the gate. In spin-based electronics, where spin current is used instead of charge, the source and the drain are ferromagnetic materials connected by a narrow semiconducting channel. This design, however, suffers from low efficiency. <jats:bold> Betthausen <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="324" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1221350">324</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6092" page="307" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225219">Žutić and Lee</jats:related-article> </jats:bold> ) combined homogeneous and helical magnetic fields to change the orientation of the spin on its way to the drain, preserving spin information over distances many times the spin mean free path. The transistor is “on” when the transport is adiabatic—i.e., slow enough for the spin to be able to adapt to the local magnetic field—and “off” otherwise. </jats:p>

<jats:title>Magnetically Bound</jats:title> <jats:p> At the macroscopic scale associated with daily life on Earth, magnetic attraction can seem fairly strong—think of the great loads moved by magnetized cranes. Microscopically, however, the field strengths attainable by human construction act as just a small perturbation on the Coulombic forces that bind atoms into molecules. <jats:bold> Lange <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="327" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1219703">327</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6092" page="302" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1224869">Schmelcher</jats:related-article> </jats:bold> ) used theoretical calculations to examine atomic behavior in environments very close to certain stars, where magnetic fields exceed those attainable on Earth by factors of 10,000 or more. The results predict a distinct type of chemical bonding in which spin-parallel hydrogen atoms or ground-state helium atoms are drawn together into pairs. </jats:p>

<jats:title>More than a Dash of Sea Salt</jats:title> <jats:p> The cycling of major elements, such as sulfur, in the oceans depends on a number of processes, from bacterial respiration of organic matter to venting of gases from hydrothermal vents on the seafloor. Over geologic time, sediment deposited on the seafloor preserves chemical records of major changes in sulfur cycling and seawater chemistry (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6092" page="305" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225461">Hurtgen</jats:related-article> </jats:bold> ). <jats:bold> Halevy <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="331" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220224">331</jats:related-article> ) observed swings in sulfur isotopes in a stratigraphic database covering North America and the Caribbean that, when modeled, corresponded to variable evaporite preservation and high turnover of sedimentary pyrite. <jats:bold>Wortmann and Paytan</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="334" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220656">334</jats:related-article> ) modeled the two most recent major swings in sedimentary sulfur isotopes over the last 130 million years and suggest that short periods of rapid fluxes in sulfur cycling were at least in part caused by the growth and dissolution of evaporite deposits. </jats:p>

<jats:title>More than a Dash of Sea Salt</jats:title> <jats:p> The cycling of major elements, such as sulfur, in the oceans depends on a number of processes, from bacterial respiration of organic matter to venting of gases from hydrothermal vents on the seafloor. Over geologic time, sediment deposited on the seafloor preserves chemical records of major changes in sulfur cycling and seawater chemistry (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6092" page="305" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225461">Hurtgen</jats:related-article> </jats:bold> ). <jats:bold> Halevy <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="331" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220224">331</jats:related-article> ) observed swings in sulfur isotopes in a stratigraphic database covering North America and the Caribbean that, when modeled, corresponded to variable evaporite preservation and high turnover of sedimentary pyrite. <jats:bold>Wortmann and Paytan</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="334" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220656">334</jats:related-article> ) modeled the two most recent major swings in sedimentary sulfur isotopes over the last 130 million years and suggest that short periods of rapid fluxes in sulfur cycling were at least in part caused by the growth and dissolution of evaporite deposits. </jats:p>