Catálogo de publicaciones - revistas

<jats:p> Identification of genes that regulate the complex life cycles of land plants helps to explain their evolutionary origins. <jats:named-content content-type="related-content"> [Also see Report by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1067" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1230082"> Sakakibara <jats:italic>et al.</jats:italic> </jats:related-article> ] </jats:named-content> </jats:p>

<jats:title>A Hidden Black Hole?</jats:title> <jats:p> Black holes with masses comparable to that of the Sun are often associated with variable x-ray sources. <jats:bold> Corral-Santana <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1048" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1228222">1048</jats:related-article> ) report optical observations of a faint and variable x-ray source detected in our galaxy with the Swift Burst Alert Telescope. The optical data reveal a black hole with a mass greater than three times that of the Sun in a 2.8-hour period around a low-mass donor star. Unusual for this type of system, the black hole binary is seen at a very high inclination. </jats:p>

<jats:title>Controlling Magnetic Noise</jats:title> <jats:p> Ferromagnetic materials contain a number of magnetic domains, with individual domains switching stochastically as the field strength is increased. As magnetic memory elements shrink in size, it is important to understand, and ultimately control, this magnetic noise. Using a magnetic vortex core integrated with a nanomechanical torsion balance, <jats:bold> Burgess <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1051" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1231390">1051</jats:related-article> , published online 17 January) created a two-dimensional map of the magnetic potential within the sample with nanoscale resolution. Moreover, introducing geometric defects (dimples) in the sample allowed the magnetization to be stabilized. </jats:p>

<jats:title>Interfering Single Electrons</jats:title> <jats:p> Quantum information processing requires the generation of indistinguishable and coherent particles. While these have been demonstrated for photons, carrying it over for electrons and the possibility of quantum electronic implementations has been challenging. Using two independent single-electron sources patterned into a two-dimensional electron gas, <jats:bold> Bocquillon <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1054" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1232572">1054</jats:related-article> , published online 24 January; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1041" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1234199">Schönenberger</jats:related-article> </jats:bold> ) performed single-electron interference experiments. The results demonstrate that the generated electrons can possess the desired properties for potential quantum applications. </jats:p>

<jats:title>Improving Nanowire Photovoltaics</jats:title> <jats:p> In principle, solar cells based on arrays of nanowires made from compound inorganic semiconductors, such as indium phosphide (InP), should decrease materials and fabrication costs compared with planar junctions. In practice, device efficiencies tend to be low because of poor light absorption and increased rates of unproductive charge recombination in the surface region. <jats:bold> Wallentin <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1057" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1230969">1057</jats:related-article> , published online 17 January) now report that arrays of p-i-n InP nanowires (that switch from positive to negative doping), grown to millimeter lengths, can be optimized by varying the nanowire diameter and length of the n-doped segment. Efficiencies as high as 13.8% were achieved, which are comparable to the best planar InP photovoltaics. </jats:p>

<jats:title>No Leader to Follow</jats:title> <jats:p> Changes in the concentration of atmospheric CO <jats:sub>2</jats:sub> and surface air temperature are closely related. However, temperature can influence atmospheric CO <jats:sub>2</jats:sub> as well as be influenced by it. Studies of polar ice cores have concluded that temperature increases during periods of rapid warming have preceded increases in CO <jats:sub>2</jats:sub> by hundreds of years. <jats:bold> Parrenin <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1060" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1226368">1060</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1042" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1234239">Brook</jats:related-article> </jats:bold> ) present a revised age scale for the atmospheric component of Antarctic ice cores, based on the isotopic composition of the N <jats:sub>2</jats:sub> that they contain, and suggest that temperature and CO <jats:sub>2</jats:sub> changed synchronously over four intervals of rapid warming during the last deglaciation. </jats:p>

<jats:title>Coo Coo</jats:title> <jats:p> Charles Darwin was fascinated by the domestic rock pigeon and used this dramatic example of diversity within a species to communicate his ideas about natural selection. Many derived traits in domestic pigeons converge on ecologically and evolutionarily relevant traits in wild species. <jats:bold> Shapiro <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1063" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1230422">1063</jats:related-article> , published online 31 January; see the cover) sequenced the genome of the domestic rock pigeon ( <jats:italic>Columba livia</jats:italic> ), along with those of 36 breeds and two feral accessions and its sister species, the hill pigeon ( <jats:italic>C. rupestris</jats:italic> ). The results reveal the underlying genetics of the head crest and suggest that all crested breeds may have originated from a single mutational event. </jats:p>

<jats:title>A Mossy Veil</jats:title> <jats:p> Land plants have two distinct generations: a haploid gametophyte responsible for producing the gametes, and a diploid sporophyte, that in most land plants is the dominant form observed. However, in mosses, a basal land plant, the primary biomass is composed of the haploid gametophyte. <jats:bold> Sakakibara <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1067" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1230082">1067</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1045" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1234992">Friedman</jats:related-article> </jats:bold> ) analyzed loss-of-function mutants of KNOX2 (class 2 KNOTTED1-LIKE HOMEOBOX) genes in the moss <jats:italic>Physcomitrella patens.</jats:italic> Mutant plants exhibit apospory, where fertilization apparently occurs, but the normal sporophyte phase is bypassed and instead a diploid structure resembling a haploid gametophyte is produced. The results suggest that KNOX2 regulates the alternation of generations by suppressing the haploid body plan in the diploid phase. </jats:p>

<jats:title>Mastering Meiosis</jats:title> <jats:p> Two conserved kinases (Ipl1/Aurora B and Mps1) are known to be critical for correct chromosome orientation on the spindle during meiosis, but their roles and relationships in controlling chromosome segregation are unclear. Working in yeast, <jats:bold> Meyer <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1071" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1232518">1071</jats:related-article> , published online 31 January) monitored chromosomes as they go through the steps of properly attaching to the spindle microtubules and dissected the roles of the two kinases in chromosome pairing, orientation, and segregation. </jats:p>

<jats:title>The Regulatory Genome</jats:title> <jats:p> Multicellular organisms contain a variety of cell types that are morphologically and functionally distinct even though they typically contain the same genomic DNA. Differences stem from differential gene expression. Gene regulatory genomic regions (enhancers) are well studied, yet despite major efforts, such as Encode and modEncode, the number of enhancers in animal genomes and their genomic positions, cell-type specificity, and strengths are largely unknown. <jats:bold> Arnold <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6123" page="1074" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1232542">1074</jats:related-article> , published online 17 January) report a method, termed STARR-seq, that measures the strength of enhancers genome-wide, giving insight into the organization of the regulatory genome. </jats:p>