Catálogo de publicaciones - revistas

<jats:title>How long does a neutron live?</jats:title> <jats:p> Unlike the proton, whose lifetime is longer than the age of the universe, a free neutron decays with a lifetime of about 15 minutes. Measuring the exact lifetime of neutrons is surprisingly tricky; putting them in a container and monitoring their decay can lead to errors because some neutrons will be lost owing to interactions with the container walls. To overcome this problem, Pattie <jats:italic>et al.</jats:italic> measured the lifetime in a trap where ultracold polarized neutrons were levitated by magnetic fields, precluding interactions with the trap walls (see the Perspective by Mumm). This more precise determination of the neutron lifetime will aid our understanding of how the first nuclei formed after the Big Bang. </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="6389" page="627" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aan8895">627</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6389" page="605" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat7140">605</jats:related-article> </jats:p>

<jats:title>Giving a hand to metamaterials</jats:title> <jats:p> Auxetic materials expand in an unusual way: perpendicular to the direction in which they are stretched. Lipton <jats:italic>et al.</jats:italic> engineered a type of auxetic material that also has handedness. When this material is sheared, it twists either to the right or the left. By tiling the underlying patterns onto spheres and cylinders, rigid or compliant structures can be made. Linear and 4-degree-of-freedom actuators can thus be made from hollow tubes, which could be valuable for a variety of engineering and medical 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="6389" page="632" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar4586">632</jats:related-article> </jats:p>

<jats:title>A vibrating molecular cloud in three dimensions</jats:title> <jats:p>Molecular clouds are relatively dense assemblies of interstellar dust and gas (mostly molecular hydrogen) from which stars form. Determining the three-dimensional (3D) morphology of these clouds is difficult because we only see a 2D projection of them onto the sky. While examining far-infrared observations of the nearby Musca cloud, Tritsis and Tassis discovered that the cloud is vibrating with magnetohydrodynamic waves. The pattern of vibrations reveals the 3D structure and shows that Musca is a sheet seen edge-on, not a filament as previously assumed.</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="6389" page="635" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aao1185">635</jats:related-article> </jats:p>

<jats:title>H-bond to deliver fluoride</jats:title> <jats:p> Simple fluoride salts are theoretically convenient reagents for carbon-fluorine bond formation. In practice, they are often insoluble in the solvents that dissolve their reaction partners. Pupo <jats:italic>et al.</jats:italic> developed urea-based catalysts that make fluoride soluble through hydrogen bonding. Moreover, their chiral substituents bias the reaction toward one of two mirror image products of C–F bond formation. This strategy should be applicable to the asymmetric addition of other salts, too. </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="6389" page="638" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar7941">638</jats:related-article> </jats:p>

<jats:title>Big mamas matter for fish</jats:title> <jats:p> The theoretical relationship between reproduction and body size has assumed that total mass relates directly to fecundity, regardless of the number of individuals involved. This assumption leads to fisheries management practices that suggest that one large female fish can be replaced by several smaller females. However, this assumption is incorrect. Barneche <jats:italic>et al.</jats:italic> show that larger females are far more productive than the same weight's worth of smaller females. Management practices that ignore the value of large females could contribute to unexplained declines seen in some fish stocks. </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="6389" page="642" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aao6868">642</jats:related-article> </jats:p>

<jats:title>Making males and back again</jats:title> <jats:p> Temperature-dependent sex determination occurs in many reptilian species. An epigenetic mechanism is presumed to be at work, but thus far it has not been identified. Ge <jats:italic>et al.</jats:italic> show that in the red-eared slider turtle, an epigenetic modifier, the histone demethylase KDM6B, binds to the promoter of the dominant male gene to activate male development (see the Perspective by Georges and Holleley). Knock down the expression of KDM6B, and embryos destined to be male turn into females. </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="6389" page="645" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aap8328">645</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6389" page="601" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat5993">601</jats:related-article> </jats:p>

<jats:title>A fast-melting snowball</jats:title> <jats:p> The Marinoan “snowball Earth” glaciation covered most of the planet in ice. The surface melted only when enough carbon dioxide had accumulated in the atmosphere to trap the Sun's warmth. Melting must have occurred rapidly, but just how fast has been a topic of conjecture. Myrow <jats:italic>et al.</jats:italic> analyzed the wave ripples preserved in tidally deposited siltstones of the Elatina Formation, South Australia, to determine that sea level must have risen at the astounding rate of nearly 30 centimeters per year during the melting epoch, or roughly 100 times the rate that it is rising today. </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="6389" page="649" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aap8612">649</jats:related-article> </jats:p>

<jats:title>Balancing costs and performance</jats:title> <jats:p>Deciding whether a novel object is another instance of something already known or an example of something different is an easily solved problem. Empirical mapping of human performance across a wide range of domains has established an exponential relationship between the generalization gradient and interstimuli distance. Sims now shows that this relationship can be derived from a consideration of the costs of optimal information coding.</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="6389" page="652" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aaq1118">652</jats:related-article> </jats:p>

<jats:title>Selection, recombination, and hybrid evolution</jats:title> <jats:p> Hybridization is an important force in evolution. The effects of hybridization across the whole genome are not understood. Using a fine-scale genetic map, Schumer <jats:italic>et al.</jats:italic> examined local ancestry in replicate natural hybrid populations of swordtail fish. Each parental species contributes different proportions of genetic material to the genomes of their descendants. Genes from the “minor” (less well-represented) parent occur in regions of the genome that are subject to higher recombination rates and where there are fewer potentially deleterious genes. Neanderthal ancestry in human genomes shows similar patterns. </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="6389" page="656" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar3684">656</jats:related-article> </jats:p>

<jats:title>Anatomically correct tumor genomics</jats:title> <jats:p> Glioblastoma is the most lethal form of human brain cancer. The genomic alterations and gene expression profiles characterizing this tumor type have been widely studied. Puchalski <jats:italic>et al.</jats:italic> created the Ivy Glioblastoma Atlas, a freely available online resource for the research community. The atlas, a collaborative effort between bioinformaticians and pathologists, maps molecular features of glioblastomas, such as transcriptional signatures, to histologically defined anatomical regions of the tumors. The relationships identified in this atlas, in conjunction with associated databases of clinical and genomic information, could provide new insights into the pathogenesis, diagnosis, and treatment of glioblastoma. </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="6389" page="660" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aaf2666">660</jats:related-article> </jats:p>