Catálogo de publicaciones - revistas

<jats:title>Stacking up the filler material</jats:title> <jats:p> In composite materials, a strong or stiff filler is added to a softer matrix to create a combined material with better mechanical or electrical properties. To minimize the filler content, it needs to be uniformly distributed in the composite, which is particularly challenging for nanoscale materials. Liu <jats:italic>et al.</jats:italic> alternately stacked sheets of graphene and polycarbonate to make a base composite. By further cutting and stacking, up to 320 aligned layers were made with a very uniform filler distribution. Alternatively, the initial stack could be rolled into a rod. In both cases, the properties exceeded what might be expected from a simple combination of the two 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="6297" page="364" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf4362">364</jats:related-article> </jats:p>

<jats:title>Lightweight shapeshifting alloys</jats:title> <jats:p> Shape memory alloys (SMAs) spring back into shape after they are deformed, a useful property for a variety of applications. Transition metal alloys, which are robust but dense, dominate the SMA landscape. Ogawa <jats:italic>et al.</jats:italic> report a new type of lightweight SMA made from magnesium and scandium, which has comparable properties to known SMAs but at significantly lower density. Although this magnesium-scandium alloy is limited to low-temperature applications, development of a new lightweight class of SMAs could be on the horizon. </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="6297" page="368" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf6524">368</jats:related-article> </jats:p>

<jats:title>Steps to ultracold gas expansion</jats:title> <jats:p> Cold atomic gases are often studied while confined in parabolic traps, with the largest atomic density at the center of the trap. When the trap is made shallower, the gas radially expands as the energy cost for atoms that are farther from the trap center decreases. Deng <jats:italic>et al.</jats:italic> observed an interesting effect when they reduced the characteristic frequency of the parabolic trap so that it was at any moment inversely proportional to the elapsed time. Instead of expanding continuously, a strongly interacting Fermi gas held in such a trap stalled at certain time points. These time points formed a geometric progression, a consequence of scale invariance in the strongly interacting limit. </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="6297" page="371" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf0666">371</jats:related-article> </jats:p>

<jats:title>Imaging electromagnetic waveforms</jats:title> <jats:p>Understanding the dynamics of electrons and the spatial and temporal evolution of electromagnetic fields within a material or device is often the key to optimizing performance. Ryabov and Baum show that electron microscopy can be used to measure collective carrier motion and electromagnetic fields with subcycle and subwavelength resolution. As an example, they used a train of compressed electron pulses to produce movies of the electromagnetic excitation in an optical excited metamaterial component.</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="6297" page="374" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf8589">374</jats:related-article> </jats:p>

<jats:title>Groundwater flow drives partitioning</jats:title> <jats:p>Soil evaporation and plant transpiration together contribute a substantial proportion of terrestrial freshwater fluxes. Land surface models are used to understand the partitioning of these fluxes on a continental scale; however, model outputs are often inconsistent with stable isotope observations. Maxwell and Condon incorporated dynamic groundwater flow into an integrated hydrologic model simulation for the entire United States. The model showed that water table depth and lateral flow strongly affect transpiration partitioning, thus explaining the inconsistencies between observations and models.</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="6297" page="377" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf7891">377</jats:related-article> </jats:p>

<jats:title>Human-microbiota coevolution</jats:title> <jats:p> The bacteria that make their home in the intestines of modern apes and humans arose from ancient bacteria that colonized the guts of our common ancestors. Moeller <jats:italic>et al.</jats:italic> have developed a method to compare rapidly evolving <jats:italic>gyrB</jats:italic> gene sequences in fecal samples from humans and wild chimpanzees, bonobos, and gorillas (see the Perspective by Segre and Salafsky). Comparison of the <jats:italic>gyrB</jats:italic> phylogenies of major bacterial lineages reveals that they mostly match the apehominid phylogeny, except for some rare symbiont transfers between primate species. Gut bacteria therefore are not simply acquired from the environment, but have coevolved for millions of years with hominids to help shape our immune systems and development. </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="6297" page="380" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf3951">380</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6297" page="350" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aag2788">350</jats:related-article> </jats:p>

<jats:title>How to link and separate memories</jats:title> <jats:p> Engrams are the changes in brain tissue that store single memories. Neuroscientists can localize and manipulate them, but until now, little was known about how multiple engrams interact to influence memories. Rashid <jats:italic>et al.</jats:italic> examined how neural assemblies in an area called the lateral amygdala interact. If two frightening events occurred within 6 hours, the same set of neurons was used to express fear memories for both events. However, if the events were separated by 24 hours, distinct memory traces were formed. </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="6297" page="383" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf0594">383</jats:related-article> </jats:p>