Catálogo de publicaciones - revistas

<jats:p>Reconstructions of past seawater chemistry provide insights into the driving forces behind long-term climate change.</jats:p>

<jats:p>A cytosolic protein controls interactions between key ubiquitin-conjugating enzymes, thereby regulating the expression of proinflammatory genes.</jats:p>

<jats:p>A place is described for faculty to share their teaching expertise and to remain current with advances in geoscience.</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>Critical Mediators</jats:title> <jats:p> Helper T cells are the immune system's ringmasters, having a multiplicity of functions that mediate the body's immune responses to infections. Depending on the type of infection, CD4 <jats:sup>+</jats:sup> helper T cells respond by secreting specific patterns of cytokines, which provide important cues to other subsets of immune cells. CD4 <jats:sup>+</jats:sup> T cells with distinct cytokine profiles have been viewed classically as separate lineages; however, there is mounting evidence that these cells may not be terminally differentiated but are in fact quite plastic. <jats:bold>O'Shea and Paul</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1098" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1178334">1098</jats:related-article> ) review the current understanding of CD4 <jats:sup>+</jats:sup> T cell subset differentiation and the underlying mechanisms that drive cell-lineage commitment. </jats:p>

<jats:title>Supernova Remnant Observations</jats:title> <jats:p> The sources of the cosmic rays that bombard Earth have been mysterious, but more recent explanations invoke high-energy acceleration of protons by the remnants of stellar explosions. Using the Fermi Large Area Telescope, <jats:bold> Abdo <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="1103" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182787">1103</jats:related-article> , published online 5 January) obtained an image of the supernova remnant W44, which shows associated gamma-ray emissions in the order of gigaelectronvolts, conforming with models indicating local proton and nuclei acceleration. </jats:p>

<jats:title>Spin into Control</jats:title> <jats:p> Spintronics—the use of the spin direction of subatomic particles to control on and off states, instead of electric charge—has the potential to create low-power electronics, because less energy is needed to flip spin states than to flip switches to create voltage barriers. Theoretical work hints that spin-polarized electrons from a ferromagnetic electrode can be controlled by a change in polarization created in a ferroelectric thin film. <jats:bold> Garcia <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="1106" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1184028">1106</jats:related-article> , published online 14 January) fabricated an iron-barium titanate junction on a lanthanum strontium manganate substrate that acts as a spin detector. Local control of spin polarization was observed in the ferroelectric layer, which retained its polarization without any applied power. </jats:p>

<jats:title>Lactic Fuels</jats:title> <jats:p> In the quest to find sustainable alternatives to petrochemicals, a small cyclic ester, γ-valerolactone, derived from cellulose offers promising raw material. <jats:bold> Bond <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="1110" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1184362">1110</jats:related-article> ) show that carbon dioxide can be catalytically excised from the lactone efficiently at high pressure, leaving a mixture of butanes. In a second-stage reactor, the butanes can be strung together to form heavier hydrocarbons similar to those found in automotive and jet fuels. The method simultaneously yields fuel and a relatively pure stream of pressurized carbon dioxide amenable to sequestration or further chemical modification. </jats:p>

<jats:title>Cations in the Veins</jats:title> <jats:p> Major events in Earth's history, from climate change to tectonic activity, can be revealed by reconstructing past conditions of the oceans. Clues from ancient ocean chemistry can be found in the cation content of fossilized microorganisms, marine carbonates, or salt deposits from old coastal zones. As these proxies are prone to inconsistencies between samples and methodologies, <jats:bold> Coggon <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="1114" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182252">1114</jats:related-article> , published online 4 February; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5969" page="1092" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1186769">Elderfield</jats:related-article> </jats:bold> ) estimated past seawater composition from the geochemistry of resistant carbonate veins precipitated within fresh basalts on the sea floor. The sudden rise to modern-day levels of ocean magnesium:calcium and strontium:calcium ratios occurred about 24 million years ago, and can be explained by a decrease in seafloor hydrothermal activity combined with a decrease in river discharge. </jats:p>

<jats:title>Slip, Tripped, and Faulted</jats:title> <jats:p> Earthquake risk assessment can be improved if we were able to quantify the recurrence and magnitude of slip events. Until recently though, a lack of sophisticated seismometers has forced us to rely on anecdotal evidence from those who survived major earthquakes or to look for clues in the landscape. <jats:bold> Zielke <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="1119" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182781">1119</jats:related-article> , published online 21 January; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5969" page="1089" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1186770">Scharer</jats:related-article> </jats:bold> ) analyzed high-resolution images of the San Andreas Fault in southern California. The data showed that major surface ruptures, such as the 1857 Fort Tejon earthquake, resulted from slips of only about 5 meters; much less than previously thought. In a study that lends support to this discovery, <jats:bold> Grant Ludwig <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="1117" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182837">1117</jats:related-article> , published online 21 January; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5969" page="1089" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1186770">Scharer</jats:related-article> </jats:bold> ) suggest from analysis of the geomorphic features of this region that several smaller earthquakes have occurred during recent centuries rather than infrequent but larger movements. The Perspective by <jats:bold>Scharer</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5969" page="1089" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1186770">1089</jats:related-article> ) discusses how paleoseismological studies like these may be valuable for feeding data into earthquake prediction. </jats:p>