Catálogo de publicaciones - revistas

<jats:title>Skyrmions emerge in trilayers</jats:title> <jats:p> Skyrmions are tiny whirlpools of magnetic spin with potential to act as carriers of information in future devices. Skyrmions have been observed in multiple materials but usually at impractically low temperatures. Jiang <jats:italic>et al.</jats:italic> used a constriction in a trilayer system to create skyrmions at room temperature (see the Perspective by von Bergmann). The authors pushed elongated magnetic domains through the constriction using an in-plane current, causing individual skyrmion bubbles to form. </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="6245" page="283" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa1442">283</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6245" page="234" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab3689">234</jats:related-article> </jats:p>

<jats:title> Probing the insulating state of SmB <jats:sub>6</jats:sub> </jats:title> <jats:p> When a metal is subjected to a strong magnetic field, its electrons start rearranging into new energy levels, causing its electronic properties to oscillate as a function of the field. Unexpectedly, Tan <jats:italic>et al.</jats:italic> observed this phenomenon, called quantum oscillations, in the Kondo insulator samarium hexaboride (SmB <jats:sub>6</jats:sub> ), which does not conduct electricity. They measured the magnetic torque and detected quantum oscillations originating from the bulk of this heavy fermion compound. These oscillations had an unusual temperature dependence, which presents another puzzle to theorists seeking to understand the nature of the insulating state of SmB <jats:sub>6</jats:sub> . </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="6245" page="287" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa7974">287</jats:related-article> </jats:p>

<jats:title>Looking at teeny tiny platinum particles</jats:title> <jats:p> Electron microscopy is a powerful technique for taking snapshots of particles or images at near-atomic resolution. Park <jats:italic>et al.</jats:italic> studied free-floating platinum nanoparticles using electron microscopy and liquid cells (see the Perspective by Colliex). Using analytical techniques developed to study biological molecules, they reconstructed the threedimensional features of the Pt particles at near-atomic resolution. This approach has the scope to study a mixed population of particles one at a time and to study their synthesis as it occurs in solution. </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="6245" page="290" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab1343">290</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6245" page="232" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac7627">232</jats:related-article> </jats:p>

<jats:title>Not that unusual after all</jats:title> <jats:p> As polar ice recedes, polar bears are facing a changed habitat with reduced summer foraging opportunities. It has been hypothesized that they might be able to resist summer food shortages by reducing their metabolic needs in a sort of “walking hibernation.” Whiteman <jats:italic>et al.</jats:italic> monitored energy expenditure in polar bears both on and off the ice and found energy reductions, but that these were more akin to normal mammalian fasting levels. Thus, it appears that polar bears have no energetic protections against reduced summer food supplies and will face increasing starvation threats if summer foraging habitats continue to decline. </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="6245" page="295" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa8623">295</jats:related-article> </jats:p>

<jats:title>Keeping cool</jats:title> <jats:p> Silver ants inhabit one of the hottest and driest environments on Earth, the Saharan sands, where most insects shrivel and die moments after contact. Shi <jats:italic>et al.</jats:italic> show that the triangular shape of the silver hairs that cover their bodies enables this existence. The hairs both increase the reflection of near-infrared rays and dissipate heat from the ants' bodies, even under full sun conditions. Evolution's simple solution to intense heat management in this species could lead to better designs for passive cooling of human-produced objects. </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="6245" page="298" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab3564">298</jats:related-article> </jats:p>

<jats:title>Grassland diversity and ecosystem productivity</jats:title> <jats:p> The relationship between plant species diversity and ecosystem productivity is controversial. The debate concerns whether diversity peaks at intermediate levels of productivity—the so-called humped-back model—or whether there is no clear predictable relationship. Fraser <jats:italic>et al.</jats:italic> used a large, standardized, and geographically diverse sample of grasslands from six continents to confirm the validity and generality of the humped-back model. Their findings pave the way for a more mechanistic understanding of the factors controlling species diversity. </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="6245" page="302" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab3916">302</jats:related-article> </jats:p>

<jats:title>Movers and shakers</jats:title> <jats:p> When the edge of an ice sheet breaks off and falls into the sea (calves), the remaining section of the ice sheet moves backward and down and can suffer a glacial earthquake. Murray <jats:italic>et al.</jats:italic> studied calving from Greenland's Helheim Glacier. The forces that cause the change in the motion of the ice sheet at its terminus also trigger the accompanying earthquakes. Because these seismic signals can be detected by instruments located all over the globe, it should be possible to use these glacial earthquakes as proxies for glacier calving. </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="6245" page="305" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab0460">305</jats:related-article> </jats:p>

<jats:title>Substrate channeling in morphine biosynthesis</jats:title> <jats:p> Poppies are still the most economically viable source of the excellent painkiller morphine. Winzer <jats:italic>et al.</jats:italic> have now identified a key enzyme in the poppy's biosynthetic pathway for morphine. The enzyme turns out to be an unusual protein that contains both cytochrome P-450 and oxidoreductase modules. Together these modules process two subsequent steps in the biosynthetic pathway. The identification of this enzyme may enable alternate routes for morphine biosynthesis that are less dependent on poppy cultivation. </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="6245" page="309" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab1852">309</jats:related-article> </jats:p>

<jats:title>Biochemical basis of a 24-hour clock</jats:title> <jats:p> Circadian clocks keep organisms in synch with such daily cycles as illumination, activity, and food availability. The circadian clock in cyanobacteria has the necessary 24-hour period despite its three component proteins having biochemical activities that occur on a much faster time scale. Abe <jats:italic>et al.</jats:italic> focused on the cyanobacterial clock component KaiC, an adenosine triphosphatase (ATPase) that can autophosphorylate and autodephosphorylate. The slow ATPase activity of KaiC, which is linked to a peptide isomerisation, provided the slow kinetics that set the speed of the 24-hour clock. Chang <jats:italic>et al.</jats:italic> found that another clock component, KaiB, also has slow changes in its protein conformation that help to set the oscillation period of the clock and its signaling output. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6245" page="312" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.1261040">312</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6245" page="324" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.1260031">324</jats:related-article> </jats:p>

<jats:title>Neutrophil NETs drive atherosclerosis</jats:title> <jats:p> The buildup of fats, cholesterol, and other substances in arteries causes atherosclerosis, which restricts blood flow and can lead to heart attacks and stroke. Inflammation contributes to the pathogenesis of atherosclerosis, but exactly how is not fully understood. Warnatsch <jats:italic>et al.</jats:italic> now show that immune cells called neutrophils release NETs (neutrophil extracellular traps) (see the Perspective by Nahrendorf and Swirski). These NETs are composed of DNA and antimicrobial proteins, and in the setting of atherosclerosis they activate innate immune signaling pathways in macrophages. This causes the macrophages to secrete proinflammatory cytokines, exacerbating the disease. Indirectly, NETS also attract a specialized subset of T cells that further amplify the proinflammatory response. </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="6245" page="316" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa8064">316</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6245" page="237" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac7801">237</jats:related-article> </jats:p>