Catálogo de publicaciones - revistas

<jats:title>Tyrannosaurs Revisited</jats:title> <jats:p> Tyrannosaurs represent some of the most successful and largest carnivores in Earth's history. An expanding fossil record has allowed studies of their evolution and behavior that now allow broader comparisons with other groups, not just dinosaurs. <jats:bold> Brusatte <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="1481" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1193304">1481</jats:related-article> ) review the biology and evolutionary history of tyrannosaurs and update their phylogenetic relations to include several new fossils. The analysis suggests that tyrannosaurs remained relatively small (less than about 5 meters long) until the Late Cretaceous (about 80 million years ago). </jats:p>

<jats:p>Separation of the island of Bioko from West Africa about 10,000 years ago dates the origins of simian immunodeficiency virus.</jats:p>

<jats:title>Clean or Dirty</jats:title> <jats:p> Aerosols strongly affect atmospheric properties and processes—including visibility, cloud formation, and radiative behavior. Knowing their effects in both clean and polluted air is necessary in order to understand their influence (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5998" page="1474" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192930">Baltensperger</jats:related-article> </jats:bold> ). <jats:bold>Clarke and Kapustin</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1488" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188838">1488</jats:related-article> ) examine vertical atmospheric profiles collected above the Pacific Ocean, where air quality is affected by the transport of polluted air from the west, and find significant regional enhancements in light scattering, aerosol mass, and aerosol number associated with combustion. Aerosol particle concentrations in this region can exceed values in clean, unperturbed regions by over an order of magnitude. Thus combustion affects hemispheric aerosol optical depth and the distribution of cloud condensation nuclei. <jats:bold> Pöschl <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="1513" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191056">1513</jats:related-article> ) discuss the composition of aerosols above the Amazon Basin, in the pristine conditions of the rainy season. The aerosols in this region are derived mostly from gaseous biogenic precursors, plants, and microorganisms, and particle concentration is orders of magnitude lower than in polluted continental regions. </jats:p>

<jats:title>Glucose Metabolism Revisited</jats:title> <jats:p> Cancer cells are revved up to reproduce rapidly and typically consume glucose rapidly by glycolysis. Why then do cancer cells express an isoform of a rate-limiting enzyme in glycolysis, pyruvate kinase M2, which has decreased activity? <jats:bold> Vander Heiden <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="1492" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188015">1492</jats:related-article> ) propose that consequent accumulation of phosphoenolpyruvate, with the help of an enzymatic activity that remains to be characterized, can lead to phosphate transfer to phosphoglycerate mutase, another glycolytic enzyme, providing the cell with a different way to make pyruvate. This may allow cancer cells to produce pyruvate without generating excess adenosine triphosphate, which can act through feedback to inhibit glycolyis. </jats:p>

<jats:title>A Correlated Quantum Walk</jats:title> <jats:p> Random walks are powerful tools for modeling statistical events. The analogous quantum walk involves particles tunneling between available sites. <jats:bold> Peruzzo <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="1500" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1193515">1500</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="5998" page="1477" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1195446">Hillery</jats:related-article> </jats:bold> ) now report on the quantum walk of a correlated pair of photons propagating through a coupled waveguide array. The output pattern resulting from the injection of two correlated photons possess quantum features, indicating that the photons retain their correlations as they walk randomly through the waveguide array, allowing scale-up and parallel searches over many possible paths. </jats:p>

<jats:title>Lunar Reconnaissance</jats:title> <jats:p> The Lunar Reconnaissance Orbiter reached lunar orbit on 23 June 2009. Global data acquired since then now tell us about the impact history of the Moon and the igneous processes that shaped it. Using the Lunar Orbiter Laser Altimeter, <jats:bold> Head <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="1504" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1195050">1504</jats:related-article> ; see the cover) provide a new catalog of large lunar craters. In the lunar highlands, large-impact craters have obliterated preexisting craters of similar size, implying that crater counts in this region cannot be used effectively to determine the age of the underlying terrain. Crater counts based on the global data set indicate that the nature of the Moon's impactor population has changed over time. <jats:bold> Greenhagen <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="1507" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192196">1507</jats:related-article> ) and <jats:bold> Glotch <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="1510" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192148">1510</jats:related-article> ) analyzed data from the Diviner Lunar Radiometer Experiment, which measures emitted thermal radiation and reflected solar radiation at infrared wavelengths. The silicate mineralogy revealed suggests the existence of more complex igneous processes on the Moon than previously assumed. </jats:p>

<jats:title>Lunar Reconnaissance</jats:title> <jats:p> The Lunar Reconnaissance Orbiter reached lunar orbit on 23 June 2009. Global data acquired since then now tell us about the impact history of the Moon and the igneous processes that shaped it. Using the Lunar Orbiter Laser Altimeter, <jats:bold> Head <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="1504" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1195050">1504</jats:related-article> ; see the cover) provide a new catalog of large lunar craters. In the lunar highlands, large-impact craters have obliterated preexisting craters of similar size, implying that crater counts in this region cannot be used effectively to determine the age of the underlying terrain. Crater counts based on the global data set indicate that the nature of the Moon's impactor population has changed over time. <jats:bold> Greenhagen <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="1507" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192196">1507</jats:related-article> ) and <jats:bold> Glotch <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="1510" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192148">1510</jats:related-article> ) analyzed data from the Diviner Lunar Radiometer Experiment, which measures emitted thermal radiation and reflected solar radiation at infrared wavelengths. The silicate mineralogy revealed suggests the existence of more complex igneous processes on the Moon than previously assumed. </jats:p>

<jats:title>Lunar Reconnaissance</jats:title> <jats:p> The Lunar Reconnaissance Orbiter reached lunar orbit on 23 June 2009. Global data acquired since then now tell us about the impact history of the Moon and the igneous processes that shaped it. Using the Lunar Orbiter Laser Altimeter, <jats:bold> Head <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="1504" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1195050">1504</jats:related-article> ; see the cover) provide a new catalog of large lunar craters. In the lunar highlands, large-impact craters have obliterated preexisting craters of similar size, implying that crater counts in this region cannot be used effectively to determine the age of the underlying terrain. Crater counts based on the global data set indicate that the nature of the Moon's impactor population has changed over time. <jats:bold> Greenhagen <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="1507" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192196">1507</jats:related-article> ) and <jats:bold> Glotch <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="1510" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192148">1510</jats:related-article> ) analyzed data from the Diviner Lunar Radiometer Experiment, which measures emitted thermal radiation and reflected solar radiation at infrared wavelengths. The silicate mineralogy revealed suggests the existence of more complex igneous processes on the Moon than previously assumed. </jats:p>

<jats:title>Clean or Dirty</jats:title> <jats:p> Aerosols strongly affect atmospheric properties and processes—including visibility, cloud formation, and radiative behavior. Knowing their effects in both clean and polluted air is necessary in order to understand their influence (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5998" page="1474" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192930">Baltensperger</jats:related-article> </jats:bold> ). <jats:bold>Clarke and Kapustin</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1488" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188838">1488</jats:related-article> ) examine vertical atmospheric profiles collected above the Pacific Ocean, where air quality is affected by the transport of polluted air from the west, and find significant regional enhancements in light scattering, aerosol mass, and aerosol number associated with combustion. Aerosol particle concentrations in this region can exceed values in clean, unperturbed regions by over an order of magnitude. Thus combustion affects hemispheric aerosol optical depth and the distribution of cloud condensation nuclei. <jats:bold> Pöschl <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="1513" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191056">1513</jats:related-article> ) discuss the composition of aerosols above the Amazon Basin, in the pristine conditions of the rainy season. The aerosols in this region are derived mostly from gaseous biogenic precursors, plants, and microorganisms, and particle concentration is orders of magnitude lower than in polluted continental regions. </jats:p>

<jats:title>Under Pressure</jats:title> <jats:p> In order to understand the behavior of materials in the solid deep Earth, it is important to be able to estimate how a material melts at high pressure. To this end, <jats:bold> Fiquet <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="1516" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192448">1516</jats:related-article> ) performed experiments using a laser-heated diamond anvil cell coupled to in situ synchrotron measurements of peridotite rock—a mixture of minerals thought to represent Earth's upper mantle—across a wide pressure range. The results suggest that liquid phases may exist at very high pressure values, such that seismically anomalous zones near the boundary between the core and the mantle may result from isolated pockets of melt. Along similar lines, the base of primitive Earth's mantle may have acquired its trace element signature from partial melting of certain mineral phases higher up in the mantle. </jats:p>