Catálogo de publicaciones - revistas

<jats:title>A mysteriously misbehaving phase</jats:title> <jats:p> Two electrons in a vacuum repel each other because they carry like charges. But in a metal, with a bunch of other electrons, in some ways they behave as if they didn't interact. This phenomenon, known as the Fermi liquid (FL) behavior, comes with a typical quadratic dependence of the solid's electrical resistance on temperature. Cases where the resistance deviates from the FL dependence are commonly associated with magnetic quantum criticality. Tomita <jats:italic>et al.</jats:italic> measured the resistivity of the heavy-fermion compound β-YbAlB <jats:sub>4</jats:sub> over a range of pressures and temperatures to identify a non-FL phase removed from a magnetic phase by an intervening FL. Explaining the non-FL behavior in the absence of magnetism presents a challenge to theorists. </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="6247" page="506" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.1262054">506</jats:related-article> </jats:p>

<jats:title> Glimpsing resonances as F and H <jats:sub>2</jats:sub> react </jats:title> <jats:p> The reaction of fluorine atoms with hydrogen molecules has long provided a window into the subtle effects of quantum mechanics on chemical dynamics. Kim <jats:italic>et al.</jats:italic> now show that the system still has some secrets left to reveal. The authors applied photodetachment to FH <jats:sub>2</jats:sub> <jats:sup>−</jats:sup> anions and their deuterated analogs. This allowed them to intercept the reaction trajectory in the middle and thereby uncover unanticipated weakly bound resonances. Theoretical calculations explain these observations and predict additional similar features that have yet to be seen. </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="6247" page="510" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac6939">510</jats:related-article> </jats:p>

<jats:title>A metal-free catalyst born of frustration</jats:title> <jats:p> Boron (a Lewis acid) and nitrogen or phosphorus fragments (both Lewis bases) tend to pair up. Keeping them separated on opposite ends of the same molecule creates a “frustrated” Lewis pair. Such molecules can manifest powerful reactivity, such as scission of the hydrogen-hydrogen bond in H <jats:sub>2</jats:sub> . Légaré <jats:italic>et al.</jats:italic> now extend this reactivity to the cleavage of carbon-hydrogen bonds in heteroaromatic compounds such as furans and pyrroles (see the Perspective by Bose and Marder). Their frustrated Lewis pair complex catalyzed borylation of these compounds. The selectivity pattern of the reaction complemented that seen with the metal catalysts conventionally used. </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="6247" page="513" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab3591">513</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6247" page="473" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac9244">473</jats:related-article> </jats:p>

<jats:title>How to walk and jump on water</jats:title> <jats:p> Jumping on land requires the coordinated motion of a number of muscles and joints in order to overcome gravity. Walking on water requires specialized legs that are designed to avoid breaking the surface tension during motion. But how do insects, such as water striders and fishing spiders, manage to jump on water, where extra force is needed to generate lift? Koh <jats:italic>et al.</jats:italic> studied water striders to determine the structure of the legs needed to make jumping possible, as well as the limits on the range of motion that avoids breaking the surface tension (see the Perspective by Vella). They then built water-jumping robots to verify the key parameters of leg design and motion. </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="6247" page="517" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab1637">517</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6247" page="472" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac7882">472</jats:related-article> </jats:p>

<jats:title>Unlocking Earth's ancient magnetic past</jats:title> <jats:p> The magnetic field protects Earth's surface from deadly cosmic radiation and provides clues about the planet's interior. Tarduno <jats:italic>et al.</jats:italic> found that some of the oldest minerals on Earth, Jack Hills zircons, preserved a record of a magnetic field over 4 billion years ago (see the Perspective by Aubert). Earth's magnetic field appears to have been fully operational a mere few hundred million years after the planet formed. This suggests an early start for plate tectonics and an ancient cosmic radiation shield that was important for habitability </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="6247" page="521" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa9114">521</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6247" page="475" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac6224" /> </jats:p>

<jats:title>Electronic junctions on edge</jats:title> <jats:p> Two-dimensional materials such as graphene are attractive materials for making smaller transistors because they are inherently nanoscale and can carry high currents. However, graphene has no band gap and the transistors are “leaky”; that is, they are hard to turn off. Related transition metal dichalcogenides (TMDCs) such as molybdenum sulfide have band gaps. Transistors based on these materials can have high ratios of “on” to “off” currents. However, it is often difficult to make a good voltage-biased (p-n) junction between different TMDC materials. Li <jats:italic>et al.</jats:italic> succeeded in making p-n heterojunctions between two of these materials, molybdenum sulfide and tungsten selenide. They did this not by stacking the layers, which make a weak junction, but by growing molybdenum sulfide on the edge of a triangle of tungsten selenide with an atomically sharp boundary </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="6247" page="524" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab4097">524</jats:related-article> </jats:p>

<jats:title>Drought effects on carbon cycling</jats:title> <jats:p> The response of forest ecosystems to drought is increasingly important in the context of a warming climate. Anderegg <jats:italic>et al.</jats:italic> studied a tree-ring database of 1338 forest sites from around the globe. They found that forests exhibit a drought “legacy effect” with 3 to 4 years' reduced growth following drought. During this postdrought delay, forests will be less able to act as a sink for carbon. Incorporating forest legacy effects into Earth system models will provide more accurate predictions of the effects of drought on the global carbon cycle. </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="6247" page="528" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab1833">528</jats:related-article> </jats:p>

<jats:title>Looking for the missing heat</jats:title> <jats:p> Global warming apparently slowed, or even stopped, during the first decade of the 21st century. This pause is commonly called the “hiatus.” We know, however, that Earth's climate system is accumulating excess solar energy owing to the build-up of greenhouse gases in the atmosphere. Where, then, has this energy gone if not into the air? Nieves <jats:italic>et al.</jats:italic> find that over this period, the surface Pacific Ocean has cooled but the upper Indian and Southern Oceans have warmed. Thus, the decade-long hiatus that began in 2003 would appear to be the result of a redistribution of heat within the ocean, rather than a change in the whole-Earth warming rate. </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="6247" page="532" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa4521">532</jats:related-article> </jats:p>

<jats:title>A little toxin can do a lot</jats:title> <jats:p> The actin cross-linking domain (ACD) is an actin-specific toxin produced by several bacterial pathogens. Heisler <jats:italic>et al.</jats:italic> discovered that ACD's pathogenic mechanism involves a highly unusual toxicity amplification cascade. Rather than directly inactivating the actin cytoskeleton, ACD blocks the activity of formins, actin regulatory proteins that play crucial roles in numerous cellular activities. ACD is exceptionally potent, even though its substrate is the most abundant protein of a eukaryotic cell: actin. </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="6247" page="535" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab4090">535</jats:related-article> </jats:p>

<jats:title>How plant parasites evolved to find hosts</jats:title> <jats:p> The seeds of parasitic plants need to be able to sense their host's presence to germinate at the correct time and in the correct place. This is done through the detection of plant hormones, strigolactones. However, the origin of this sensory system is unknown. Conn <jats:italic>et al.</jats:italic> investigated the diversity of strigolactone receptors in multiple lineages of parasitic plants and their close relatives. They found a greater copy number and accelerated evolution in parasitic plants as compared with nonparasitic relatives. Functional analyses of parasitic plant strigolactone receptors in transgenic <jats:italic>Arabidopsis</jats:italic> suggested that convergent evolution has occurred to allow the parasitic plants to detect their hosts. </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="6247" page="540" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab1140">540</jats:related-article> </jats:p>