Catálogo de publicaciones - revistas

<jats:title>Bend Me, Stretch Me</jats:title> <jats:p> In the push toward flexible electronics, much research has focused on using organic conducting materials, including light-emitting diodes (LEDs), because they are more readily processed using scalable techniques. <jats:bold> Park <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="977" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175690">977</jats:related-article> ) have developed a series of techniques for depositing and assembling inorganic LEDs onto glass, plastic, or rubber. Conventional processing techniques are used to connect the LEDs in order to create flexible, stretchable displays, which, because the active diode material only covers a small part of the substrate, are mostly transparent. </jats:p>

<jats:title>Silver Emission Follows Golden Rule</jats:title> <jats:p> Electrons emitted from the tip of a scanning tunneling microscope (STM) can be used in certain cases to excite optical emission from surface structure. Such methods can be used to characterize the “particle-in-a-box” states created in chains of varying lengths of metal atoms on surfaces. <jats:bold> Chen <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="981" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1174592">981</jats:related-article> ) were able to spatially resolve photon emission for silver chains up to 10 atoms long, assembled on a nickel-aluminum alloy surface. The emission maxima correlated with the nodes seen in the derivative of STM current with voltage. This correlation follows from Fermi's golden rule, which connects the initial and final states of the radiation transition through the momentum operator and leads to a better understanding of the light-emission process. </jats:p>

<jats:title>Solar Chronometer</jats:title> <jats:p> The use of the short-lived radioactive isotope <jats:sup>26</jats:sup> Al as a precise chronometer of early solar system processes relies on the assumption that it was uniformly distributed in the initial solar accretion disk. <jats:bold> Villeneuve <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="985" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173907">985</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="5943" page="951" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176730">Davis</jats:related-article> </jats:bold> ) validate this assumption on the basis of high-precision isotopic analyses of primitive meteoritic materials. Furthermore, chondrules—constituents of the most common type of meteorites and among the first materials to have formed in the solar system—formed episodically over a period of more than one million years. </jats:p>

<jats:title>Crustal Details Revealed</jats:title> <jats:p> In seismic tomography, a large collection of data representing paths through Earth are inverted to provide an analysis of variation of density in which errors are minimized. Typically, the inversion starts with a simple layered model of the tomographic region. <jats:bold> Tape <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="988" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175298">988</jats:related-article> ) show how, starting with a three-dimensional model, based on synthetic seismograms, an improved iterative inversion approach can lead to a much more detailed view of a region. Using the rich data for Southern California, the model reveals details of the geologic history of the crust in this region. </jats:p>

<jats:title>Attacks Wasps</jats:title> <jats:p> The bacterium <jats:italic>Hamiltonella defensa</jats:italic> infects aphids and carries virulence determinants from a bacteriophage virus. <jats:bold> Oliver <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="992" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1174463">992</jats:related-article> ) have now found that the toxin-bearing phage does not harm the aphid host of the bacterium, but targets the larvae of parasitoid wasps that infest the aphids. If an aphid population is not infested by wasps, the allied bacteriophage is shed by the bacterium, presumably because there is a cost to carrying it. If the wasps then resume their predation, the aphids are no longer protected and succumb to the parasitoid. </jats:p>

<jats:title>Going Retro</jats:title> <jats:p> In a year celebrating Darwin, the question of how new functional genes arise during evolution is of particular interest. Through a multibreed genetic analysis of the domestic dog, <jats:bold> Parker <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="995" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173275">995</jats:related-article> , published online 16 July; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5943" page="958" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1178487">Kaessmann</jats:related-article> </jats:bold> ) find that the short-legged phenotype that characterizes at least 19 common dog breeds, including the corgi, dachshund, and basset hound, is specifically associated with the expression in developing bone of a gene encoding fibroblast growth factor 4 ( <jats:italic>fgf4</jats:italic> ), a member of a gene family previously implicated in dwarfism in humans. Interestingly, the culprit <jats:italic>fgf4</jats:italic> gene in dogs has the hallmarks of a “retrogene,” a gene that arises when a parental gene is duplicated through an RNA-based copying mechanism. </jats:p>

<jats:title>Blast-Resistant Rice</jats:title> <jats:p> The durability of disease resistance for an agricultural crop reflects the extent to which the defense stands up to evolutionary dodges on the part of the pathogen. <jats:italic>Pi21</jats:italic> , which is a quantitative trait locus (QTL) of rice, contributes to a particularly durable resistance to a fungal rice blast disease: Rice plants carrying the resistant allele have been in cultivation for more than a century, and yet the pathogen has been unable to find a way through the defense. <jats:bold> Fukuoka <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="998" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175550">998</jats:related-article> ; see the news story by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5943" page="925" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.2009.325.5943.325_925">Normile</jats:related-article> </jats:bold> ) have now cloned the responsible <jats:italic>Pi21</jats:italic> QTL allele and were able to separate <jats:italic>Pi21</jats:italic> resistance from tightly linked reductions in grain quality, paving the way for more widespread use of this allele in rice breeding. </jats:p>

<jats:title>T Follicular Helper Cell Differentiation</jats:title> <jats:p> When B cells respond to an infection, they often require help from CD4 <jats:sup>+</jats:sup> T cells to mount a proper response. It is thought that a subset of CD4 <jats:sup>+</jats:sup> effector T cells, called T follicular helper cells (T <jats:sub>FH</jats:sub> ), performs this function. Several subsets of effector CD4 <jats:sup>+</jats:sup> T cells arise, depending on the type of infection, which have distinct transcriptional programs driving their differentiation. Whether this is also the case for T <jats:sub>FH</jats:sub> cells has not been clear (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5943" page="953" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1178752">Awasthi and Kuchroo</jats:related-article> </jats:bold> ). <jats:bold> Nurieva <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1001" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176676">1001</jats:related-article> , published online 23 July) and <jats:bold> Johnston <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1006" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175870">1006</jats:related-article> ; published online 16 July) now demonstrate that the transcription factor Bcl6 is both necessary and sufficient for T <jats:sub>FH</jats:sub> differentiation and subsequent B cell–mediated immunity, suggesting that it is a master regulator of this lineage. Johnston <jats:italic>et al.</jats:italic> also show that expression of Bcl6 and the transcription factor, Blimp-1, are reciprocally regulated in T <jats:sub>FH</jats:sub> cells and that, when ectopically expressed, Blimp-1 inhibits T <jats:sub>FH</jats:sub> development. </jats:p>

<jats:title>T Follicular Helper Cell Differentiation</jats:title> <jats:p> When B cells respond to an infection, they often require help from CD4 <jats:sup>+</jats:sup> T cells to mount a proper response. It is thought that a subset of CD4 <jats:sup>+</jats:sup> effector T cells, called T follicular helper cells (T <jats:sub>FH</jats:sub> ), performs this function. Several subsets of effector CD4 <jats:sup>+</jats:sup> T cells arise, depending on the type of infection, which have distinct transcriptional programs driving their differentiation. Whether this is also the case for T <jats:sub>FH</jats:sub> cells has not been clear (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5943" page="953" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1178752">Awasthi and Kuchroo</jats:related-article> </jats:bold> ). <jats:bold> Nurieva <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1001" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176676">1001</jats:related-article> , published online 23 July) and <jats:bold> Johnston <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1006" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175870">1006</jats:related-article> ; published online 16 July) now demonstrate that the transcription factor Bcl6 is both necessary and sufficient for T <jats:sub>FH</jats:sub> differentiation and subsequent B cell–mediated immunity, suggesting that it is a master regulator of this lineage. Johnston <jats:italic>et al.</jats:italic> also show that expression of Bcl6 and the transcription factor, Blimp-1, are reciprocally regulated in T <jats:sub>FH</jats:sub> cells and that, when ectopically expressed, Blimp-1 inhibits T <jats:sub>FH</jats:sub> development. </jats:p>

<jats:title>APC Transporter Structure</jats:title> <jats:p> Amino acid, polyamine, and organocation (APC) transporters that move a range of organic molecules across the cell membrane are important in many cellular processes. <jats:bold> Shaffer <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1010" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176088">1010</jats:related-article> ; published online 16 July) report the crystal structure of apoApcT, a proton-dependent APC transporter. The structure shows similarity to the sodium-coupled amino acid transporter LeuT and has an amino group from a lysine in an equivalent position to a sodium ion in LeuT. This suggests common principles between proton- and sodium-coupled transporters. </jats:p>