Catálogo de publicaciones - revistas

<jats:title>Making tracks</jats:title> <jats:p> The magnitude of the effect of anthropogenic aerosols on the formation of clouds is an important unknown about how humans are affecting climate. Studies of stratocumulus cloud tracks that are formed by ship exhaust have been used to estimate the radiative impact of this process, but Glassmeier <jats:italic>et al.</jats:italic> now show that this approach overestimates the cooling effect of aerosol addition by up to 200%. These findings underscore the need to quantify stratocumulus cloud responses to anthropogenic aerosols to understand the climate system. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6528" page="485" related-article-type="in-this-issue" vol="371">485</jats:related-article> </jats:p>

<jats:title>How fast is electronic relaxation?</jats:title> <jats:p> Technical advances in extending spectroscopy to the attosecond time scale has caused considerable interest in experimental studies of various ultrafast processes that were previously inaccessible. Using attosecond transient absorption around the carbon K-edge accompanied by ab initio quantum dynamics simulations, Zinchenko <jats:italic>et al.</jats:italic> investigated ultrafast, non-adiabatic dynamics in the ethylene cation. They directly observed the electronic D <jats:sub>1</jats:sub> → D <jats:sub>0</jats:sub> relaxation mediated by the conical intersection taking place within 7 femtoseconds, far shorter than any vibrational period or any previously reported electronic relaxation. The demonstrated technique is directly applicable to liquids and solutions, enabling further studies of charge- and energy-transfer dynamics of organic molecules in chemical and biochemical systems. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6528" page="489" related-article-type="in-this-issue" vol="371">489</jats:related-article> </jats:p>

<jats:title>Pump it up</jats:title> <jats:p> Carbon nanotube yarns can be used as electrochemical actuators because infiltration with ions causes a contraction in length and an expansion in diameter. Either positive or negative ions can cause this effect. Chu <jats:italic>et al.</jats:italic> constructed an all-solid-state muscle that eliminated the need for an electrolyte bath, which may expand the potential for its use in applications. By infiltrating the yarns with charged polymers, the fibers start partially swollen, so the length can increase through the loss of ions. It is thus possible to increase the overall stroke of the muscle. Further, these composite materials show a surprising increase in stroke with scan rate. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6528" page="494" related-article-type="in-this-issue" vol="371">494</jats:related-article> </jats:p>

<jats:title>Watching early stage nucleation</jats:title> <jats:p> In classic nucleation theory, a metastable disordered dense liquid or amorphous solid cluster spontaneously and irreversibly transforms into a crystalline nucleus. Jeon <jats:italic>et al.</jats:italic> observed the formation of gold crystals on a graphene substrate through the reduction of a precursor using an electron beam. Rather than the classic view, they instead observed a nucleation pathway that involves dynamic and reversible fluctuations of developing nuclei between disordered and crystalline states. The lifetime in the disordered state decreases with increasing cluster size, and at sufficiently small sizes, the binding energy per atom is large enough relative to the energy required to induce melting that the heat imparted upon binding is enough to drive partial collapse of an ordered cluster into the disordered state. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6528" page="498" related-article-type="in-this-issue" vol="371">498</jats:related-article> </jats:p>

<jats:p>Naked mole-rats (<jats:italic>Heterocephalus glaber</jats:italic>) form some of the most cooperative groups in the animal kingdom, living in multigenerational colonies under the control of a single breeding queen. Yet how they maintain this highly organized social structure is unknown. Here we show that the most common naked mole-rat vocalization, the soft chirp, is used to transmit information about group membership, creating distinctive colony dialects. Audio playback experiments demonstrate that individuals make preferential vocal responses to home colony dialects. Pups fostered in foreign colonies in early postnatal life learn the vocal dialect of their adoptive colonies, which suggests vertical transmission and flexibility of vocal signatures. Dialect integrity is partly controlled by the queen: Dialect cohesiveness decreases with queen loss and remerges only with the ascendance of a new queen.</jats:p>

<jats:title>Shuttling halide pairs back and forth</jats:title> <jats:p> The transfer of adjacent hydrogens from a saturated to an unsaturated organic compound is a fairly common reaction. However, analogs that shuttle two heavy atoms back and forth are much harder to catalyze. Dong <jats:italic>et al.</jats:italic> report an electrochemical approach that transfers a pair of adjacent chlorines or bromines from an alkyl compound to an olefin. The method could help to remediate halogenated pollutants while concurrently producing fine chemicals. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6528" page="507" related-article-type="in-this-issue" vol="371">507</jats:related-article> </jats:p>

<jats:title>Too close for comfort</jats:title> <jats:p>Tropical cyclones are becoming stronger and occurring at higher latitudes than in the past. Wang and Toumi report that cyclones' points of maximum intensity also have been coming closer to land since 1982, the distance decreasing by about 30 kilometers per decade as their paths drift poleward and westward (see the Perspective by Camargo and Wing). This shift could increase the danger that tropical cyclones pose to coastal populations.</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="6528" page="514" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abb9038">514</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6528" page="458" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abg3651">458</jats:related-article> </jats:p>

<jats:title>Rotation during reaction</jats:title> <jats:p> Determining changes in heterogeneous catalysts under reaction conditions can provide insight into mechanisms. Under reaction conditions, not only can metal nanoparticles change shape but their interaction with the oxide support could also be affected. Yuan <jats:italic>et al.</jats:italic> used aberration-corrected environmental transmission electron microscopy to study gold nanoparticles on titanium surfaces at low electron beam doses. During carbon monoxide (CO) oxidation at total pressures of a few millibars and 500°C, they observed that gold nanoparticles rotated by about 10° but returned to their original position when CO was removed. Density function theory calculations indicated that rotation was induced by changes in the coverage of adsorbed molecular oxygen at the interface. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6528" page="517" related-article-type="in-this-issue" vol="371">517</jats:related-article> </jats:p>

<jats:title>Vaccines get a help-MAIT</jats:title> <jats:p> Mucosal-associated invariant T (MAIT) cells are a T cell subset important for mucosal homeostasis. These cells recognize derivatives of microbiota-derived vitamin B2 precursors but can also be activated by certain cytokines in the context of viral infections. Provine <jats:italic>et al.</jats:italic> report that a leading adenoviral vector vaccine, ChAdOx1, activated MAIT cells in immunized mice (see the Perspective by Juno and O'Connor). This activation required interferon-α produced by plasmacytoid dendritic cells as well as monocyte-derived interleukin-18 and tumor necrosis factor. MAIT cell activation positively correlated with vaccine-mediated T cell responses in human subjects, and mice deficient in MAIT cells showed impaired CD8 <jats:sup>+</jats:sup> T cell immunity to target antigens after vaccination. This work suggests an additional pathway that could be exploited to enhance the efficacy of vaccines. </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="6528" page="521" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.aax8819">521</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6528" page="460" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abf8121">460</jats:related-article> </jats:p>