Catálogo de publicaciones - revistas

<jats:title>Wing shapes take flight</jats:title> <jats:p> Birds can dynamically alter the shape of their wings during flight, although how this is accomplished is poorly understood. Matloff <jats:italic>et al.</jats:italic> found that two mechanisms control the movement of the individual feathers. Whenever the skeleton moves, the feathers are redistributed passively through compliance of the elastic connective tissue at the feather base. To prevent the feathers from spreading too far apart, hook-shaped microstructures on adjacent feathers form a directional fastener that locks adjacent feathers. These features are found across a range of bird sizes; however, because the detachment of the hooks is noisy, they are notably absent in silent fliers, such as barn owls. </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="6475" page="293" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaz3358">293</jats:related-article> </jats:p>

<jats:title>Water reaches Mars' upper atmosphere</jats:title> <jats:p> Mars once hosted abundant water on its surface but subsequently lost most of it to space. Small amounts of water vapor are still present in the atmosphere, which can escape if they reach sufficiently high altitudes. Fedorova <jats:italic>et al.</jats:italic> used data from the ExoMars Trace Gas Orbiter spacecraft to determine the distribution of water in Mars' atmosphere and investigate how it varies over seasons. Water vapor is sometimes heavily saturated, and its distribution is affected by the planet's large dust storms. Water can efficiently reach the upper atmosphere when Mars is in the warmest part of its orbit, and this behavior may have controlled the overall rate at which Mars lost its water. </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="6475" page="297" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aay9522">297</jats:related-article> </jats:p>

<jats:title>Ion fluxes resolve organellar volume</jats:title> <jats:p> Animal cells continuously sample the surrounding medium, a feature accentuated in immune cells. Sampling is accomplished by trapping external medium into membrane-bound vesicles or vacuoles. These structures are promptly resolved, thus avoiding accumulation of endomembranes and volume expansion. In a variety of cultured cells, Freeman <jats:italic>et al.</jats:italic> found that this resolution entails conversion of spherical vacuoles into thin tubules, a process that involves marked changes in surface-to-volume ratio (see the Perspective by King and Smythe). Shrinkage of membrane-bound structures is driven by ion fluxes and subsequent osmotic transfer of water. Shriveled vacuoles attract curvature-sensing proteins that promote the extension of fine tubules. Ion channels thereby control membrane remodeling, enabling receptor recycling and proper routing of cellular cargo. </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="6475" page="301" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaw9544">301</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6475" page="246" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aba3623">246</jats:related-article> </jats:p>

<jats:title>Making a mammalian ear</jats:title> <jats:p> Mammals have keen hearing owing to their complex inner ear. In our vertebrate ancestors, as in extant reptiles, the three bones that make up the inner ear were instead part of the jaw. Understanding the functional transition of these bones is challenging given their small and delicate nature. Mao <jats:italic>et al.</jats:italic> describe a new genus and species of stem therian mammal represented by six well-preserved specimens, seemingly caught as they slept huddled together (see the Perspective by Schultz). The unprecedented preservation reveals a clear transitional stage between the two very different functions of the bones. </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="6475" page="305" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aay9220">305</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6475" page="244" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aba3808">244</jats:related-article> </jats:p>

<jats:title>Thin graphite gets cool fast</jats:title> <jats:p> In nonmetallic solids, heat is transported primarily through crystal vibrations called phonons. These phonons can have wavelike properties under certain conditions, which increases the thermal conductivity of the material. Machida <jats:italic>et al.</jats:italic> found that making graphite samples thin expands the hydrodynamic regime from cryogenic to room temperatures. The researchers measured an extremely high thermal conductivity in the very thin graphite samples, which may be important for a variety of electronics applications. </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="6475" page="309" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaz8043">309</jats:related-article> </jats:p>

<jats:title>Teaching bismuth to make and break bonds</jats:title> <jats:p> One major reason why transition metals are good catalysts is that they can shuttle between oxidation states. This flexibility lets them slide in and out of chemical bonds; so, for instance, they can snip a bond between carbon and boron and then stitch a carbonfluorine bond in its place. Planas <jats:italic>et al.</jats:italic> now report that bismuth can also orchestrate such bond-swapping events. They implement a fully catalytic cycle for fluorination of aryl boronates, in which bismuth hops between its +3 and +5 oxidation states. </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="6475" page="313" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaz2258">313</jats:related-article> </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>

<jats:p> This issue of <jats:italic>Science</jats:italic> includes the program of the 2020 AAAS Annual Meeting. The theme of the AAAS Annual Meeting in Seattle,Washington, 13 to 16 February 2020, is <jats:italic>Envisioning Tomorrow's Earth</jats:italic> . </jats:p> <jats:p> A <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/cgi/reprint/363/6424/299.pdf">PDF</jats:ext-link> of the program as it appears in this issue is available here; for more information on the meeting (including registration forms and information on accommodations), please visit <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="www.aaas.org/meetings/">www.aaas.org/meetings/</jats:ext-link> . </jats:p>