Catálogo de publicaciones - revistas

<jats:title>Selecting the most successful strategy</jats:title> <jats:p> The brain's prefrontal cortex helps us to make decisions in an uncertain and constantly changing environment. Donoso <jats:italic>et al.</jats:italic> present a model of human reasoning as an algorithm implemented in the prefrontal cortex (see the Perspective by Hare). Brain-imaging experiments supported this model. Depending on the prevailing circumstances, human reasoning can either adapt ongoing behavioral strategies or switch to previously learned strategies. Only when neither approach is appropriate will the brain create new strategies. </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="6191" page="1481" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1252254">1481</jats:related-article> , see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6191" page="1446" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1256862">1446</jats:related-article> </jats:p>

<jats:title>Measuring tiny forces with atomic clouds</jats:title> <jats:p> For projects such as detecting gravity waves, physicists need to measure tiny forces precisely. Schreppler <jats:italic>et al.</jats:italic> developed an extremely sensitive method for force measurement. They applied a known force on a cloud of ultracold rubidium atoms in an optical cavity. The force caused the atoms to oscillate, and the researchers used optical measurements to monitor the motion. Under optimal conditions, the authors could measure forces with a level of sensitivity only four times worse than the fundamental limit imposed by the Heisenberg uncertainty principle. </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="6191" page="1486" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1249850">1486</jats:related-article> </jats:p>

<jats:title> Using the valleys in monolayer MoS <jats:sub>2</jats:sub> </jats:title> <jats:p> The electronic structure of the two-dimensional material MoS <jats:sub>2</jats:sub> has two distinct “valleys” of energy that may help to carry information in future electronic devices. Mak <jats:italic>et al.</jats:italic> observed the so-called valley Hall effect in a monolayer of MoS <jats:sub>2</jats:sub> . The electrons from different valleys moved in opposite directions across the sample, with one valley being overrepresented with respect to the other. The scientists achieved this by shining circularly polarized light on the material, which created an imbalance in the population of the two valleys. The findings may enable practical applications in the newly formed field of valleytronics. </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="6191" page="1489" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1250140">1489</jats:related-article> </jats:p>

<jats:title>Discerning clusters of data points</jats:title> <jats:p>Cluster analysis is used in many disciplines to group objects according to a defined measure of distance. Numerous algorithms exist, some based on the analysis of the local density of data points, and others on predefined probability distributions. Rodriguez and Laio devised a method in which the cluster centers are recognized as local density maxima that are far away from any points of higher density. The algorithm depends only on the relative densities rather than their absolute values. The authors tested the method on a series of data sets, and its performance compared favorably to that of established techniques.</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="6191" page="1492" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1242072">1492</jats:related-article> </jats:p>

<jats:title>Watching lead flow at the nanoscale</jats:title> <jats:p>Microfluidic devices have recently become useful in commercial chemical synthesis. But what about fluid dynamics at the nanometer scale? Lorenz and Zewail used an electron microscope with nanosecond time resolution to capture images of molten lead flowing through a nanotube. They flash-melted the metal with a laser pulse to begin their flow measurements at a precise time point. The experiments offered insights into viscous friction as well as heat-transfer dynamics in a channel one-thousandth as wide as a strand of hair.</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="6191" page="1496" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1253618">1496</jats:related-article> </jats:p>

<jats:title>Making of methane deep underground</jats:title> <jats:p> Technologies such as hydraulic fracturing, or “fracking,” can now extract natural gas from underground reservoirs. Within the gas, the ratio of certain isotopes holds clues to its origins. Stolper <jats:italic>et al.</jats:italic> analyzed a wide range of natural gas, including samples from some of the most active fracking sites in the United States. Using a “clumped isotope” technique, the authors could estimate the high temperatures at which methane formed deep underground, as well as the lower temperatures at which ancient microbes produced methane. The approach can help to distinguish the degree of mixing of gas from both sources. </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="6191" page="1500" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1254509">1500</jats:related-article> </jats:p>

<jats:title>Building coral reefs in ancient times</jats:title> <jats:p> 540 million years ago, in the dawn before the Cambrian explosion, evolution was setting the stage for the global rise of animals. Before they took over the seas, the earliest animals developed strategies to defend themselves against predators. These strategies, which remain common today, include forming skeletons and building reefs. Penny <jats:italic>et al.</jats:italic> discovered a massive fossil reef deposit in Namibia made up of tiny coneshaped early animals known as <jats:italic>Cloudina.</jats:italic> The reef, which is 20 million years older than other ancient reefs, was probably formed as the <jats:italic>Cloudina</jats:italic> adapted to benefit from reefs, which protect the animals and allow them to feed more efficiently. </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="6191" page="1504" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1253393">1504</jats:related-article> </jats:p>

<jats:title>How Lassa virus breaks and enters</jats:title> <jats:p> Lassa virus, which spreads from rodents to humans, infecting about half a million people every year, can lead to deadly hemorrhagic fever. Like many viruses, Lassa virus binds to cell surface receptors. Jae <jats:italic>et al.</jats:italic> now show that to enter a cell, the virus requires a second receptor, this one inside the infected cell. This requirement sheds light on the “enigmatic resistance” of bird cells to Lassa virus observed three decades ago. Although bird cells have the cell surface receptor, the intracellular receptor cannot bind the virus, stopping it in its tracks. </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="6191" page="1506" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1252480">1506</jats:related-article> </jats:p>