Catálogo de publicaciones - revistas

<jats:title>Inspiration from a vitamin</jats:title> <jats:p> Organic synthesis of molecules with defined stereochemistry requires a chiral center, which in turn may involve a chiral catalyst. Chen <jats:italic>et al.</jats:italic> developed an organic catalyst, modeled on vitamin B6, which contains an electron-withdrawing pyridine ring adjacent to an aldehyde group. This catalyst works like the vitamin by reacting with an amine, a derivative of the amino acid glycine, to create an activated species. An appendage on the catalyst coordinates the subsequent reactions, allowing for stereoselective formation of a product with two adjacent amines. </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="6396" page="1438" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat4210">1438</jats:related-article> </jats:p>

<jats:title>Perovskite layers make the grade</jats:title> <jats:p> Inverted planar perovskite solar cells offer opportunities for a simplified device structure compared with conventional mesoporous titanium oxide interlayers. However, their lower open-circuit voltages result in lower power conversion efficiencies. Using mixed-cation lead mixed-halide perovskite and a solution-processed secondary growth method, Luo <jats:italic>et al.</jats:italic> created a surface region in the perovskite film that inhibited nonradiative charge-carrier recombination. This kind of solar cell had comparable performance to that of conventional cells. </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="6396" page="1442" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aap9282">1442</jats:related-article> </jats:p>

<jats:title>Eye can see neural activity</jats:title> <jats:p> Organisms take up a tremendous amount of information through the visual system, which is then processed by the neural circuitry. Hong <jats:italic>et al.</jats:italic> developed a mesh electronics implant that is delivered by injection into mice retinas. With these devices, it is possible to obtain recordings from retinal ganglion cells over long time periods in awake, active mice. Both orientation- and direction-selective retinal ganglion cells can be monitored, as can the circadian modulation of retinal ganglion cell activity. </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="6396" page="1447" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aas9160">1447</jats:related-article> </jats:p>

<jats:title>Golden ultrafast melting</jats:title> <jats:p> Understanding fast melting of metals is important for applications such as welding and micromachining. However, fast melting leaves simulation as the only option for probing the process. Mo <jats:italic>et al.</jats:italic> performed ultrafast electron diffraction experiments on laser-pulsed gold films. This allowed detailed mapping of the melting process, which proceeds through two distinct regimes while the bonding behavior changes in unexpected ways. The results require adding new physical processes to high-energy melting models. </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="6396" page="1451" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar2058">1451</jats:related-article> </jats:p>

<jats:title>Glass-like and crystal-like</jats:title> <jats:p> Crystals with glass-like ultralow thermal conductivity are appealing as barrier coatings and thermoelectric materials. Mukhopadhyay <jats:italic>et al.</jats:italic> developed a class of thallium selenides with glass-like thermal conductivity. These materials may be promising for applications, but they also require the combination of glass-like and crystal-like thermal transport to explain their thermal properties. This two-channel model can be used to identify potential ultralow-thermal-conductivity compounds. </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="6396" page="1455" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar8072">1455</jats:related-article> </jats:p>

<jats:title>Mortality rates level off at extreme age</jats:title> <jats:p> The demography of human longevity is a contentious topic. On the basis of high-quality data from Italians aged 105 and older, Barbi <jats:italic>et al.</jats:italic> show that mortality is constant at extreme ages but at levels that decline somewhat across cohorts. Human death rates increase exponentially up to about age 80, then decelerate, and plateau after age 105. </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="6396" page="1459" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat3119">1459</jats:related-article> </jats:p>

<jats:title>End-of-life health care spending</jats:title> <jats:p> In the United States, one-quarter of Medicare spending occurs in the last 12 months of life, which is commonly seen as evidence of waste. Einav <jats:italic>et al.</jats:italic> used predictive modeling to reassess this interpretation. From detailed Medicare claims data, the extent to which spending is concentrated not just on those who die, but on those who are expected to die, can be estimated. Most deaths are unpredictable; hence, focusing on end-of-life spending does not necessarily identify “wasteful” spending. </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="6396" page="1462" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar5045">1462</jats:related-article> </jats:p>

<jats:title>Perceptual and judgment creep</jats:title> <jats:p> Do we think that a problem persists even when it has become less frequent? Levari <jats:italic>et al.</jats:italic> show experimentally that when the “signal” a person is searching for becomes rare, the person naturally responds by broadening his or her definition of the signal—and therefore continues to find it even when it is not there. From low-level perception of color to higher-level judgments of ethics, there is a robust tendency for perceptual and judgmental standards to “creep” when they ought not to. For example, when blue dots become rare, participants start calling purple dots blue, and when threatening faces become rare, participants start calling neutral faces threatening. This phenomenon has broad implications that may help explain why people whose job is to find and eliminate problems in the world often cannot tell when their work is done. </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="6396" page="1465" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aap8731">1465</jats:related-article> </jats:p>

<jats:title>Warming after the big one</jats:title> <jats:p> The Chicxulub impact 65 million years ago, which caused the mass extinction at the Cretaceous-Paleogene boundary, also initiated a long period of strong global warming. Using data from phosphatic microfossils, including fish teeth, scales, and bone, MacLeod <jats:italic>et al.</jats:italic> estimated global average temperature. Immediately after the asteroid strike, temperatures increased by ∼5°C and remained high for about 100,000 years (see the Perspective by Lécuyer). These results are relevant to current climate projections, because the Chicxulub impact perturbed Earth systems on time scales even shorter than the current rate of change. </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="6396" page="1467" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aap8525">1467</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6396" page="1400" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aau1690">1400</jats:related-article> </jats:p>

<jats:title> <jats:italic>Sox9</jats:italic> regulation during sex determination </jats:title> <jats:p> Sex determination is regulated by the <jats:italic>Sox9</jats:italic> gene. During testis differentiation, this gene is directly targeted by the product of the Y chromosome–encoded gene <jats:italic>Sry</jats:italic> . The regulatory region of <jats:italic>Sox9</jats:italic> is complex, which is typical of genes with multiple roles in development. Gonen <jats:italic>et al.</jats:italic> find that a single far-upstream 557–base pair element is critical for up-regulating <jats:italic>Sox9</jats:italic> . Without it, XY mice develop as females instead of males. The 557–base pair enhancer is conserved, likely to be relevant to human disorders of sex differentiation, and probably essential because it acts early in a time-critical process, and any failure allows ovary-specific factors to dominate. </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="6396" page="1469" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aas9408">1469</jats:related-article> </jats:p>