Catálogo de publicaciones - revistas

<jats:title>Looking for an exotic decay</jats:title> <jats:p>Neutrinos—elementary fermionic particles with no electrical charge—defy the standard model of particle physics by having a tiny, but nonzero mass. One explanation for their properties is that they are Majorana fermions, which are particles equal to their antiparticles. If neutrinos were Majorana fermions, a process called neutrinoless double-β decay would become possible: an unstable nucleus could decay by turning two of its neutrons into protons with the emission of two electrons but no antineutrinos. The GERDA Collaboration searched for this decay in a particular isotope of germanium. Housed deep underground to reduce the background signal, the experiment did not detect the elusive process but did place improved boundaries on its half-life.</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="6460" page="1445" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aav8613">1445</jats:related-article> </jats:p>

<jats:title>Knot all that it seems</jats:title> <jats:p>Although for some, knots are merely a frustration caused by poorly tied shoelaces, interest in knots in physical systems spans many disciplines, including fluid and optical vortices, Skyrmion states, liquid crystals, excitable media, polymers, proteins, DNA, and even chemical molecules. Tai and Smalyukh describe the creation of localized knotted structures in cholesteric liquid crystals using electric fields (see the Perspective by Alexander). The knots are topologically distinct from the host medium and diffuse and organize like colloidal particles, forming regular crystalline arrangements.</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="6460" page="1449" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aay1638">1449</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6460" page="1377" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aaz0479">1377</jats:related-article> </jats:p>

<jats:title>A hole flatland</jats:title> <jats:p> When two distinct materials are placed on top of each other, the difference in polarization between the two layers can induce charge carriers at the interface. Many such two-dimensional (2D) electron gases have been observed, but engineering a 2D hole gas without the help of doping has been much trickier. Chaudhuri <jats:italic>et al.</jats:italic> used molecular beam epitaxy to grow a layer of gallium nitride on top of aluminum nitride without introducing dopants. This approach resulted in a high-density 2D hole gas at the interface in this technologically relevant system. </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="6460" page="1454" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aau8623">1454</jats:related-article> </jats:p>

<jats:title>Making males in a fruit fly pest</jats:title> <jats:p> The Mediterranean fruit fly or Medfly ( <jats:italic>Ceratitis capitata</jats:italic> ) is a global and highly destructive fruit pest. Meccariello <jats:italic>et al.</jats:italic> identified the master gene for male sex determination on the Y chromosome of Medfly and named it <jats:italic>Maleness-on-the-Y</jats:italic> ( <jats:italic>MoY</jats:italic> ) (see the Perspective by Makki and Meller). Flies of each sex were transformed into the other sex by genetic manipulation, and crosses of transformed files generated male and female progeny. <jats:italic>MoY</jats:italic> is functionally conserved in the olive fruit fly and in the invasive oriental fruit fly. This discovery has potential for insect genetic control based on mass release of sterile males and future strategies based on gene drive. </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="6460" page="1457" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aax1318">1457</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6460" page="1380" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aaz0217">1380</jats:related-article> </jats:p>

<jats:title>Immune landscape of the human kidney</jats:title> <jats:p> Single-cell RNA sequencing has begun to shed light on the full cellular diversity of specific organs. However, these studies rarely examine organ-specific immune cells. Stewart <jats:italic>et al.</jats:italic> sequenced healthy adult and fetal kidney samples at a single-cell level to define the heterogeneity in epithelial, myeloid, and lymphoid cells. From this dataset, they identified zonation of cells, with relevance to disease and the varied perturbations that occur in different tumor settings. This profiling of the human kidney generates a comprehensive census of existing cell populations that will help inform the diagnosis and treatment of kidney-related diseases. </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="6460" page="1461" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aat5031">1461</jats:related-article> </jats:p>

<jats:title>Understanding fertility in young and old</jats:title> <jats:p> Fertility in humans follows a U-curve, with low rates in both teenagers and women of advancing maternal age (mid-30s and above). Gruhn <jats:italic>et al.</jats:italic> found that this distinct shape originates from chromosomal errors in human eggs, which result in genomic imbalance and pregnancy loss. The error types and chromosomes affected in the young and advanced age groups were different, suggesting that two distinct chromosome-based mechanisms balance risk associated with pregnancy and evolutionary fitness as women enter and exit their reproductive life span. The authors show that chromosome structure erodes only with advancing age, acting as a “molecular clock” for reproductive senescence. </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="6460" page="1466" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aav7321">1466</jats:related-article> </jats:p>

<jats:title>Sounding out mammalian cells</jats:title> <jats:p> Live cell imaging allows us to observe cellular processes in real time. Most methods rely on light, and the poor penetration of light into tissues limits their application. Ultrasound penetrates tissues, and cellular reporters that respond to ultrasound have been developed recently. These reporters are air-filled protein structures that provide buoyancy in the bacteria they are derived from, but when surrounded by a fluid medium, they reflect sound waves. Farhadi <jats:italic>et al.</jats:italic> achieved expression from multiple genes to create these complex structures in mammalian cells. In addition to optimizing reporter production and detection, they visualize cells in a proof-of-principle experiment in mouse tumor xenografts. </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="6460" page="1469" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aax4804">1469</jats:related-article> </jats:p>

<jats:title>Probing protein-nanorod aggregates</jats:title> <jats:p> The interaction of proteins with nanoparticles can enhance circular dichroism signals and provide a route for sensitive biodetection. However, ensemble measurements are insufficient for resolving the origin of plasmon-coupled circular dichroism (PCCD). Zhang <jats:italic>et al.</jats:italic> used single-particle circular differential scattering spectroscopy along with correlated tomographic reconstruction and electromagnetic simulations to study individual aggregates of bovine serum albumin and gold nanorods (see the Perspective by Kim and Kotov). Aggregates contribute to PCCD activity through formation of plasmonic hotspots, but single nanoparticles do not contribute. The protein does not function simply as a chiral chromophore but enables assembly of the chiral nanorod-protein complexes. </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="6460" page="1475" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aax5415">1475</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6460" page="1378" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aay7776">1378</jats:related-article> </jats:p>

<jats:title>Habitat connectivity enhances diversity</jats:title> <jats:p> Fragmentation of ecosystems leads to loss of biodiversity in the remaining habitat patches, but retaining connecting corridors can reduce these losses. Using long-term data from a large, replicated experiment, Damschen <jats:italic>et al.</jats:italic> show quantitatively how these losses are reduced. In their pine savanna system, corridors reduced the likelihood of plant extinction in patches by about 2% per year and increased the likelihood of patch colonization by about 5% per year. These benefits continued to accrue over the course of the 18-year experiment. By the end of monitoring, connected patches had 14% more species than unconnected patches. Restoring habitat connectivity may thus be a powerful technique for conserving biodiversity, and investment in connections can be expected to magnify conservation benefit. </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="6460" page="1478" related-article-type="in-this-issue" vol="365" xlink:href="10.1126/science.aax8992">1478</jats:related-article> </jats:p>

<jats:p>Gene editing gets an upgrade with new versions of CRISPR and CRISPR alternatives (zinc-finger nucleases, TALENs, and meganucleases).</jats:p>