Catálogo de publicaciones - revistas

<jats:title>Quantum dipoles go liquid</jats:title> <jats:p> Quantum spin liquids do not achieve an ordered magnetic state, even at the lowest temperatures. Hassan <jats:italic>et al.</jats:italic> studied an organic compound that may be both a spin liquid and a dipole liquid (see the Perspective by Powell). In the layered material κ-(BEDT-TTF) <jats:sub>2</jats:sub> Hg(SCN) <jats:sub>2</jats:sub> Br, molecules form charged dimers whose sites are arranged on a triangular lattice. The extra charge associated with each dimer can “live” on one of the two molecules in the dimer, resulting in a nonzero electric dipole moment for the dimer. Raman spectroscopy and heat capacity measurements revealed that, like spins in a quantum spin liquid, these dimers remained disordered down to the lowest temperatures. </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="6393" page="1101" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aan6286">1101</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6393" page="1073" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat7282">1073</jats:related-article> </jats:p>

<jats:title>Metasurfaces for molecular detection</jats:title> <jats:p> Although mid-infrared (mid-IR) spectroscopy is a mainstay of molecular fingerprinting, its sensitivity is diminished somewhat when looking at small volumes of sample. Nanophotonics provides a platform to enhance the detection capability. Tittl <jats:italic>et al.</jats:italic> built a mid-IR nanophotonic sensor based on reflection from an all-dielectric metasurface array of specially designed scattering elements. The scattering elements could be tuned via geometry across a broad range of wavelengths in the mid-IR. The approach successfully detected and differentiated the absorption fingerprints of various molecules. The technique offers the prospect of on-chip molecular fingerprinting without the need for spectrometry, frequency scanning, or moving mechanical parts. </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="6393" page="1105" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aas9768">1105</jats:related-article> </jats:p>

<jats:title>Antenna switches partners in the shade</jats:title> <jats:p> A cloudy day or an overshadowing tree causes fluctuations in light that can throw off the balance of energy flow in plant photosystems I and II (PSI and PSII). Pan <jats:italic>et al.</jats:italic> solved structures of PSI bound to two light-harvesting complexes (LHCs). One LHC is permanently associated with PSI. The other LHC delivers light energy to PSII under optimal conditions but can switch to a PSI-associated state after phosphorylation by a kinase that senses the redox environment of the chloroplast. The movement of LHCs between the photosystems helps maintain even energy flux. Two chlorophyll-containing subunits are visible in the structure that connect the PSI core to each LHC. </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="6393" page="1109" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat1156">1109</jats:related-article> </jats:p>

<jats:title>Making silicon shine bright</jats:title> <jats:p> Silicon is the workhorse of the semiconductor electronics industry, but its lack of optical functionality is a barrier to developing a truly integrated silicon-based optoelectronics platform. Although there are several ways of exploiting nonlinear light-matter interactions to coax silicon into optical functionality, the effects tend to be weak. Otterstrom <jats:italic>et al.</jats:italic> used a suspended silicon waveguide racetrack structure to stimulate the stronger nonlinear effect of Brillouin scattering and achieve lasing from silicon. The ability to engineer the nonlinearity and tune the optical response through the design of the suspended cavity provides a powerful and flexible route for developing silicon-based optoelectronic circuits and devices. </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="6393" page="1113" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar6113">1113</jats:related-article> </jats:p>

<jats:title>Tipping points in social convention</jats:title> <jats:p> Once a population has converged on a consensus, how can a group with a minority viewpoint overturn it? Theoretical models have emphasized tipping points, whereby a sufficiently large minority can change the societal norm. Centola <jats:italic>et al.</jats:italic> devised a system to study this in controlled experiments. Groups of people who had achieved a consensus about the name of a person shown in a picture were individually exposed to a confederate who promoted a different name. The only incentive was to coordinate. When the number of confederates was roughly 25% of the group, the opinion of the majority could be tipped to that of the minority. </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="6393" page="1116" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aas8827">1116</jats:related-article> </jats:p>

<jats:title>Out of Antarctica</jats:title> <jats:p>When we think of Devonian tetrapods, the ancestors of all modern vertebrates, we tend to picture amphibian-like creatures emerging from the water into a wet tropical forest or swamp. Indeed, all previously described specimens of this group have been recovered from the tropics. Gess and Ahlberg now describe two fossil tetrapods from Devonian Antarctica. Thus, the distribution of tetrapods may have been global, which encourages us to rethink the environments in which this important group was shaped.</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="6393" page="1120" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aaq1645">1120</jats:related-article> </jats:p>

<jats:title>Understanding zero</jats:title> <jats:p> It has been said that the development of an understanding of zero by society initiated a major intellectual advance in humans, and we have been thought to be unique in this understanding. Although recent research has shown that some other vertebrates understand the concept of the “empty set,” Howard <jats:italic>et al.</jats:italic> now show that an understanding of this concept is present in untrained honey bees (see the Perspective by Nieder). This finding suggests that such an understanding has evolved independently in distantly related species that deal with complexity in their environments, and that it may be more widespread than previously appreciated. </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="6393" page="1124" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar4975">1124</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6393" page="1069" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat8958">1069</jats:related-article> </jats:p>

<jats:title>Defense cargo shuttles in vesicles</jats:title> <jats:p> Plants can use small RNAs (sRNAs) to interfere with virulence factor gene expression in pathogens. Cai <jats:italic>et al.</jats:italic> show that the small mustard plant <jats:italic>Arabidopsis</jats:italic> shuttles defensive sRNAs into the necrotrophic fungus <jats:italic>Botrytis cinerea</jats:italic> via extracellular vesicles (see the Perspective by Thomma and Cook). The vesicles are associated with tetraspanin proteins, which can interact and form membrane microdomains. Several dozen different sRNAs targeting the pathogenic process were transported from <jats:italic>Arabidopsis</jats:italic> to <jats:italic>B. cinerea</jats:italic> in a selective manner. </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="6393" page="1126" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar4142">1126</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6393" page="1070" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat9343">1070</jats:related-article> </jats:p>

<jats:title>Sterility in rice via toxin and antidote</jats:title> <jats:p> Crossing wild and domestic rice often results in hybrid sterility. Such genetic barriers can prevent the movement of potentially beneficial genes from wild rice into domestic varieties. To understand the barriers preventing gene flow, Yu <jats:italic>et al.</jats:italic> mapped a quantitative trait locus (QTL) that determines sterility between wild-type and domestic rice. This QTL encodes two open reading frames (ORFs) that are both expressed during gametogenesis. The ORFs encode a toxin, which affects the development of pollen, and an antidote, which is required for pollen viability. Thus, selfish genetic elements can underlie evolutionary strategies that facilitate reproductive isolation. </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="6393" page="1130" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar4279">1130</jats:related-article> </jats:p>

<jats:title>Toward more predictable birthdays</jats:title> <jats:p> Low-cost methods for monitoring fetal development could improve prenatal care, especially in low-resource settings. By measuring the levels of certain placental RNA transcripts in maternal blood, Ngo <jats:italic>et al.</jats:italic> developed two noninvasive blood tests that provide a window into the progression of individual pregnancies. In a small proof-of-concept study, the first blood test predicted fetal age and delivery date with an accuracy comparable to that of ultrasound. The second blood test, also examined in a small pilot study, discriminated women at risk of preterm delivery from those who delivered at full term. The next step will be to assess the reliability of the tests in large, blinded clinical trials. </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="6393" page="1133" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar3819">1133</jats:related-article> </jats:p>