Catálogo de publicaciones - revistas

<jats:title>Probing the intergalactic magnetic field</jats:title> <jats:p> Fast radio bursts (FRBs) are powerful flashes of astronomical radio waves that last just milliseconds and whose origins are a matter of debate. Ravi <jats:italic>et al.</jats:italic> discovered a FRB that is exceptionally bright (see the Perspective by Kaspi). This allowed them to measure how the polarization of the signal varies with wavelength (Faraday rotation). Combining this with the time delay of the flash at different wavelengths revealed the mean magnetic field along the line of sight. Assuming that the FRB originates from a colocated galaxy, the results constrain the intergalactic magnetic field and will inform models of galaxy formation and cosmology. </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="6317" page="1249" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aaf6807">1249</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1230" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aag1600">1230</jats:related-article> </jats:p>

<jats:title>Aspects of the design</jats:title> <jats:p> In microfluidics systems, the small size of the channels ensures that the flow profiles are laminar, so solute mixing is largely governed by diffusion in the absence of active mixing. Aminian <jats:italic>et al.</jats:italic> revisited the classic phenomenon of Taylor diffusion to investigate the effects that the aspect ratio of the conduit has on the longtime axial distribution of solutes. They show both numerically and experimentally that the aspect ratio controls the skewness of this distribution, and thus pipe design alone is enough to control mixing profiles. </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="6317" page="1252" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aag0532">1252</jats:related-article> </jats:p>

<jats:title>Super sensitive, not so silly, putty</jats:title> <jats:p> Many composites blend stiff materials, such as glass or carbon fibers, into a softer elastic polymer matrix to generate a material with better overall mechanical toughness. Boland <jats:italic>et al.</jats:italic> added graphene to a lightly cross-linked silicone polymer (also known as Silly Putty). The resulting composite has unusual mechanical properties, allowing the manufacture of strain sensors that can detect respiration and the footsteps of spiders. </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="6317" page="1257" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aag2879">1257</jats:related-article> </jats:p>

<jats:title>Catching a break in polyphenol synthesis</jats:title> <jats:p> Chemical synthesis is usually rather different from playing with a modeling kit. If two large fragments of a molecule are not properly oriented, it is not typically possible to break them apart, rotate one, and then paste them back together. Yet that is precisely the trick that Keylor <jats:italic>et al.</jats:italic> used to synthesize two plant-derived polyphenols. Resveratrol forms a variety of dimers, trimers, and tetramers. When one central carbon-carbon bond links the fragments, it is weak enough to break spontaneously and reversibly at room temperature. The authors leveraged this equilibrium to generate an efficient route to two of the tetramers, nepalensinol B and vateriaphenol C. </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="6317" page="1260" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aaj1597">1260</jats:related-article> </jats:p>

<jats:title>Crafting chiral boron building blocks</jats:title> <jats:p> Carbon-boron bonds are easily transformed into a wide variety of C–C, C–N, and C–O bonds. With that flexibility in mind, Schmidt <jats:italic>et al.</jats:italic> show that nickel complexes can catalyze asymmetric alkylation of carbon centers adjacent to boron. This protocol creates chiral alkylboronates that function as stable precursors to numerous complex molecules. The reaction proceeds in stereo-convergent fashion—forming a single product from either mirror image of the α-haloboronate reagent. Successive reactions can also create chains of adjacent chiral alkyl centers with stereochemistry set by the configuration of the ligand bound to nickel. </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="6317" page="1265" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aai8611">1265</jats:related-article> </jats:p>

<jats:title>An edge that is hard to get rid of</jats:title> <jats:p> A distinguishing characteristic of topological insulators (TIs) is that they have conducting states on their boundary—a surface for a three-dimensional (3D) TI or a line edge for a 2D TI. Sessi <jats:italic>et al.</jats:italic> used scanning tunneling spectroscopy to discover unusual 1D states in a 3D crystalline TI. The states appeared on the edge of a particular kind of step in the crystal and survived large magnetic fields and increased temperatures. This robustness bodes well for the potential use of these states in practical 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="6317" page="1269" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6233">1269</jats:related-article> </jats:p>

<jats:title>Time is a subjective experience</jats:title> <jats:p> Time, like space, is one of the fundamental dimensions of all our experiences. However, organisms do not work like clocks, and our judgment about the passage of time is variable, depending on circumstances. Soares <jats:italic>et al.</jats:italic> systematically investigated midbrain dopaminergic neurons during timing behavior in mice (see the Perspective by Simen and Matell). When measuring and manipulating mouse activity, the authors observed that dopaminergic neurons controlled temporal judgments on a time scale of seconds. </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="6317" page="1273" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah5234">1273</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1231" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aal4021">1231</jats:related-article> </jats:p>

<jats:title>Birds of a feather sing together</jats:title> <jats:p> How do birds know that a song that they hear is from a member of their own species, and how do they learn their songs in the first place? Araki <jats:italic>et al.</jats:italic> identified two types of brain cells involved in how finches learn their songs (see the Perspective by Tchernichovski and Lipkind). When zebra finches were raised by Bengalese finch foster parents, they learned a song whose morphology resembled that of their foster father. However, the temporal structure remained zebra finch–specific, suggesting that it is innate. Gadagkar <jats:italic>et al.</jats:italic> recorded activity in specific dopamine neurons in singing zebra finches while controlling perceived song quality with distorted auditory feedback. This distorted feedback represented worse performance than predicted and resulted in negative prediction errors. These findings suggest again that finches have an innate internal goal for their learned songs. </jats:p> <jats:p> <jats:bold>Science</jats:bold> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1282" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6799">1282</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1234" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aal3205">1234</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1278" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6837">1278</jats:related-article> </jats:p>

<jats:title>Birds of a feather sing together</jats:title> <jats:p> How do birds know that a song that they hear is from a member of their own species, and how do they learn their songs in the first place? Araki <jats:italic>et al.</jats:italic> identified two types of brain cells involved in how finches learn their songs (see the Perspective by Tchernichovski and Lipkind). When zebra finches were raised by Bengalese finch foster parents, they learned a song whose morphology resembled that of their foster father. However, the temporal structure remained zebra finch–specific, suggesting that it is innate. Gadagkar <jats:italic>et al.</jats:italic> recorded activity in specific dopamine neurons in singing zebra finches while controlling perceived song quality with distorted auditory feedback. This distorted feedback represented worse performance than predicted and resulted in negative prediction errors. These findings suggest again that finches have an innate internal goal for their learned songs. </jats:p> <jats:p> <jats:bold>Science</jats:bold> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1282" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6799">1282</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1234" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aal3205">1234</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6317" page="1278" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6837">1278</jats:related-article> </jats:p>

<jats:title>Substituting minutes for money</jats:title> <jats:p>In developing countries, bank branches and fixed-line telecommunications are scarce, whereas mobile phones are plentiful. These factors have led to the use of mobile money, whereby money can be deposited to an account linked to a phone, transferred to other users, and converted back into cash. Suri and Jack show that increased access to mobile money has increased long-term consumption in Kenya and reduced the number of households in extreme poverty.</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="6317" page="1288" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah5309">1288</jats:related-article> </jats:p>