Catálogo de publicaciones - revistas

<jats:p> Platelets destroy <jats:italic>P. falciparum</jats:italic> by secreting a factor that enters infected blood cells and destroys the parasite. </jats:p>

<jats:p>The loss of large old trees in many ecosystems around the world poses a threat to ecosystem integrity.</jats:p>

<jats:p>A severe drought in the Horn of Africa delayed the spring arrival in Europe of two migratory species.</jats:p>

<jats:title>Architecture of a CRAC</jats:title> <jats:p> The calcium release–activated calcium (CRAC) channel generates intracellular calcium signals in response to depletion of calcium from the endoplasmic reticulum. <jats:bold> Hou <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="1308" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228757">1308</jats:related-article> , published online 22 November) report a high-resolution crystal structure of Orai, the CRAC channel pore from <jats:italic>Drosophila melanogaster.</jats:italic> Six Orai subunits surround a central pore that extends into the cytosol. The pore is in a closed conformation that is stabilized by anions binding to a basic region near the intracellular side. A ring of glutamates on the extracellular side form a selectivity filter. The channel architecture allows calcium permeation while regulating the flow to prevent overloading the cell with calcium. </jats:p>

<jats:title>Exotic Pulsations</jats:title> <jats:p> The launch of the Fermi Gamma-ray Space Telescope in 2008 enabled the detection of large numbers of pulsars. Millisecond pulsars, neutron stars with millisecond periods, are much more difficult to find in gamma-ray data. In a computational tour de force, <jats:bold> Pletsch <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="1314" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1229054">1314</jats:related-article> , published online 25 October) detected gamma-ray pulsations from a formerly unidentified gamma-ray source in the Fermi Large Area Telescope Second Source Catalog. The pulsating neutron star orbits a companion star more rapidly than any other such neutron star known, and the system may belong to an exotic class of binary systems where the neutron star is systematically destroying its companion. </jats:p>

<jats:title>Mind the Gap</jats:title> <jats:p> Near-field microscopy has benefited from subwavelength near-field plasmonic probes that make use of the field-concentrating properties of gaps. These probes achieve maximum enhancement only in the tip-substrate gap mode, which can yield large near-field signals, but only for a metallic substrate and for very small tip-substrate gap distances. <jats:bold> Bao <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="1317" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1227977">1317</jats:related-article> ) designed a probe that unites broadband field enhancement and confinement with bidirectional coupling between far-field and near-field electromagnetic energy. Their tips primarily rely on the internal gap modes of the tip itself, thereby enabling it to image nonmetallic samples. </jats:p>

<jats:title>Robust Reduction</jats:title> <jats:p> A major challenge in the design of artificial photosynthesis catalysts has been their instability under the reaction conditions—a problem that plants and other autotrophs address by perpetually reproducing their biochemical machinery. <jats:bold> Han <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="1321" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1227775">1321</jats:related-article> , published online 8 November) now demonstrate a system for photoreductive hydrogen generation in water that manifests undiminished activity for weeks at a time. Semiconductor nanoparticles for light absorption were combined with a soluble nickel complex for the catalytic chemistry. The system currently requires a sacrificial electron donor, but its robustness shows promise for future pairing with an integrated oxidation catalyst. </jats:p>

<jats:title> CF <jats:sub>3</jats:sub> from Fluoroform </jats:title> <jats:p> Fluoroform (CF <jats:sub>3</jats:sub> H) is a by-product from the manufacture of fluorocarbon-based materials used, for example, in nonstick coatings and refrigerants. Fluoroform's potency as a greenhouse gas is a growing concern as supplies continue to accumulate. In this context, <jats:bold> Prakash <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="1324" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1227859">1324</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="6112" page="1298" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1231092">Haufe</jats:related-article> </jats:bold> ) show that fluoroform can be used to transfer CF <jats:sub>3</jats:sub> to silicon, sulfur, and carbon centers in the development of CF <jats:sub>3</jats:sub> -bearing pharmaceutical and agrochemical structures. </jats:p>

<jats:title>Atomic Layers from Solution</jats:title> <jats:p> Growth of flat thin films is often plagued by the formation of mounds and pyramids. To avoid this problem, atomic-layer deposition (ALD) can be used whereby alternating self-termination reactions stop the layer growth. Electrochemical approaches to ALD use surface alloys to slow film growth, but often lead to film contamination. <jats:bold> Yihua Liu <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="1327" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228925">1327</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="6112" page="1300" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1231853">Switzer</jats:related-article> </jats:bold> ) show that for platinum films, controlling surface potential can lead to adsorbed hydrogen on the surface, which can terminate film growth at one layer, leaving platinum species in solution available for further reduction. Rapid changes in applied potential can oxidize the hydrogen, which allows efficient contamination-free growth of an additional atomic layer. </jats:p>

<jats:title>Planetary Interiors Under Pressure</jats:title> <jats:p> The interiors of Earth and other rocky planets generally consist of a few common minerals. Depending largely on the size of the planet, the distribution and relative abundance of these minerals varies; for example, MgO is abundant in the mantles of Earth and large Earth-like planets, but is present in Jupiter's core. The properties of MgO also vary with planetary size as a function of temperature and pressure. <jats:bold> McWilliams <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="1330" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1229450">1330</jats:related-article> , published online 22 November) performed laser-shock experiments at pressures over three times higher than Earth's inner core. MgO underwent two phase transformations, first to a solid with a modified crystal structure, and then to a conductive liquid. In terrestrial planets greater than eight Earth masses, MgO in the mantle could generate a magnetic field–generating dynamo such as those that typically found in planetary cores. </jats:p>