Catálogo de publicaciones - revistas

<jats:p>The adaptive immune response to helminth infection and allergens is stimulated by cytokines secreted by innate immune cells.</jats:p>

<jats:p> New radiocarbon evidence suggests that the Southern Ocean released CO <jats:sub>2</jats:sub> into the atmosphere at the end of the last ice age. Two scenarios could explain how and why. </jats:p>

<jats:p>An online course takes a systems approach to teaching Environmental Science.</jats:p>

<jats:p> A monthly roundup of recent news and projects of <jats:italic>Science</jats:italic> 's publisher, the American Association for the Advancement of Science. </jats:p>

<jats:title>Arsenic in Asia</jats:title> <jats:p> Millions of humans in South and Southeast Asia are exposed to potentially dangerous levels of the carcinogen arsenic via their drinking water every day. Although high arsenic levels are a known problem, a growing demand for drinking water drives the continued construction of new groundwater wells in these regions. <jats:bold> Fendorf <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="1123" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1172974">1123</jats:related-article> ) review chemical and hydrological factors controlling the release of arsenic in groundwater in South and Southeast Asia, which include the distribution of arsenic in groundwater aquifers used for drinking water and irrigation. Despite incomplete sampling and characterization of these factors across these regions, several key directions for improvements to water quality are presented. </jats:p>

<jats:p>Genes have transferred from a crop plant to an evolutionarily divergent parasitic weed.</jats:p>

<jats:title>Thymocyte Egress</jats:title> <jats:p> A critical step during the development of the immune system is the egress of developing T lymphocytes, or thymocytes, from the thymus to peripheral organs, where they can defend against infectious microorganisms. Egress requires detection of the lipid mediator, sphingosine-1-phosphate (S1P), by thymocytes, but whether S1P detection is sufficient for egress, the source of S1P and the location where T lymphocytes exit the thymus are unknown. <jats:bold>Zachariah and Cyster</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1129" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1188222">1129</jats:related-article> , published online 22 April) found that selective expression of a transgene for the S1P receptor-1 in mouse thymocytes was sufficient for thymocyte egress. Thymocyte egress occurred at corticomedullary junctions via blood vessels, rather than via lymphatics. Pericytes, neural crest-derived cells, which ensheath blood vessels, provided the S1P for exiting thymocytes. </jats:p>

<jats:title>Optical Nanoengineering</jats:title> <jats:p> Optics and electronics operate at very different length scales. Surface plasmons are light-induced electronic excitations that are being pursued as a route to bridge the length scales and bring the processing speed offered by optical communication down to the size scales of electronic chip circuitry. Now, <jats:bold> Fan <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="1135" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1187949">1135</jats:related-article> ) describe the self-assembly of nanoscale dielectric particles coated with gold. Functionalization of the gold surface with polymer ligands allowed controlled production of clusters of nanoparticles. The optical properties of the self-assembled nanostructures depended on the number of components within the cluster and each structure could be selected for its unique optical properties. Such a bottom-up approach should help in fabricating designed optical circuits on the nanoscale. </jats:p>

<jats:title>Taking the Rough with the Smooth</jats:title> <jats:p> Even with extensive annealing at high temperatures, most polycrystalline materials will not become a perfect single crystal, which would represent the thermodynamically preferred state. The stability of the polycrystalline state has been attributed to the presence of impurities that accumulate at the grain boundaries, but even very pure materials show grain growth stagnation. Using simulations, <jats:bold>Holm and Foiles</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1138" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1187833">1138</jats:related-article> ) show that grain boundaries can be classified as “rough” and “smooth.” Rough boundaries move continuously with well-defined activation energies, while the smooth boundaries have low mobility and move in a jerky, stepwise manner. With heating, a boundary can change from smooth to rough, but the transition temperature can vary by hundreds of degrees from one grain boundary to the next. These smooth, low-mobility boundaries thus pin the polycrystalline structure, even in the absence of impurities. </jats:p>

<jats:title>Catalysis at the Edge</jats:title> <jats:p> Many catalysts in solution, such as metalloenzymes and homogeneous metal complexes, create active sites where the metal ion is available to bind and activate reactants. Such coordinately unsaturated ferrous sites, or CUFs, have been created in a supported heterogeneous catalyst by <jats:bold> Fu <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="1141" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1188267">1141</jats:related-article> ). Ferrous oxide islands grown on platinum single-crystal surfaces were much more reactive for CO oxidation at low temperatures than more oxidized ferric islands. This difference arose from sites at the interface between the islands and the Pt surface that activated oxygen. Silica-supported Pt-Fe catalysts were active for CO removal from hydrogen streams, a reaction critical for maintaining the activity of fuel cells. </jats:p>