Catálogo de publicaciones - revistas

<jats:p>Why are memories of traumatic events nearly impossible to eliminate?</jats:p>

<jats:p>Insights into how small, isolated fish populations persist in the wild could aid conservation efforts.</jats:p>

<jats:title>Coats, COPS, and GTPases</jats:title> <jats:p> Within cells, vesicles coated with specific proteins, such as clathrin and adaptor complexes, concentrate and package cargo molecules to mediate transport between compartments. <jats:bold>Pucadyil and Schmid</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5945" page="1217" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1171004">1217</jats:related-article> ) review the role of membrane-active GTPases in coated vesicle formation and propose that, although structurally diverse, the Arf-family GTPases and dynamin may play mechanistically similar roles in quality control of cargo packaging and coated-vesicle maturation—and also as components of the machinery that mediates vesicle release into a cellular compartment. </jats:p>

<jats:p>A quantum algorithm to factor numbers is implemented on an optical chip.</jats:p>

<jats:p>X-ray observations show that a white dwarf has a mass near the limit above which these stars become gravitationally unstable.</jats:p>

<jats:title>Stability Through Confinement</jats:title> <jats:p> With the ability to vary experimental parameters—including particle density, geometry, interaction strength, and sign—cold atoms trapped in optical lattices are ideal test systems to probe many-body quantum physics. However, due to dissipation processes most of the scenarios studied to date have necessarily looked at ground state phases. <jats:bold> Haller <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="1224" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175850">1224</jats:related-article> ) describe a technique in which confinement of the atoms to low dimensions, using a confinement-induced resonance, can stabilize excited states with tunable interactions. The ability to create these metastable states will allow a much wider range of quantum systems to be explored. </jats:p>

<jats:title>Hi Fi Quantum Computing</jats:title> <jats:p> In quantum information processing, one goal is to control the entangled states of objects such that they can interact during logical operations but otherwise have minimal interactions with their environment. In one scheme for quantum computing, ions are trapped within and physically moved by electric fields. One drawback is that the entangled states can be sensitive to stray magnetic fields. <jats:bold> Home <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5945" page="1227" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1177077">1227</jats:related-article> , published online 6 August 2009) show that coupling of the ions (in this case, <jats:sup>9</jats:sup> Be <jats:sup>+</jats:sup> ) with a second ion ( <jats:sup>24</jats:sup> Mg <jats:sup>+</jats:sup> ) can create states that are relatively insensitive to magnetic fields and also allows for recooling of the ions during operation. This approach can minimize the loss of fidelity that occurs during ion transport. </jats:p>

<jats:title>Toughing It Out in Membranes</jats:title> <jats:p> The formation of crosslinks in the triple-helical structure of collagen is crucial to its function. In the case of collagen IV, which provides structural integrity to the basement membrane of animal tissues, the chemical nature of the crosslinks has been difficult to pin down. <jats:bold> Vanacore <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5945" page="1230" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176811">1230</jats:related-article> ) report a combination of high-resolution mass spectrometric and nuclear magnetic resonance studies that establish the crosslink between hydroxylysine-211 and methionine-93 is a sulfimine group (-S=N-). This type of bond appears to have evolved to withstand mechanical stress as animals evolved into more structurally complex organisms. </jats:p>

<jats:title>Inside Oort</jats:title> <jats:p> Long-period comets are thought to come from the outermost region of the solar system, the Oort Cloud, where a large number of icy bodies orbit the Sun. Outer Oort Cloud bodies are more likely to penetrate the inner planetary region of the solar system as comets, because they experience stronger external gravitational perturbations. Inner Oort Cloud bodies, by contrast, are thought to be ejected before they reach observable orbits. Using numerical simulations that followed the orbital histories of bodies in the inner Oort Cloud, <jats:bold>Kaib and Quinn</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5945" page="1234" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1172676">1234</jats:related-article> , published online 30 July 2009; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5945" page="1211" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1177312">Duncan</jats:related-article> </jats:bold> ) identified a dynamical pathway that allows comets in the inner Oort Cloud to move to the outer Oort Cloud, where they can be perturbed and enter the visible region in great numbers. According to this mechanism, the amount of mass in this region is consistent with the material needed to form the giant planets. </jats:p>

<jats:title>Climate Reversal</jats:title> <jats:p> The climate and environment of the Arctic have changed drastically over the short course of modern observation. <jats:bold> Kaufman <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5945" page="1236" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173983">1236</jats:related-article> ) synthesized 2000 years of proxy data from lakes above 60° N latitude with complementary ice core and tree ring records, to create a paleoclimate reconstruction for the Arctic with a 10-year resolution. A gradual cooling trend at the start of the record had reversed by the beginning of the 20th century, when temperatures began to increase rapidly. The long-term cooling of the Arctic is consistent with a reduction in summer solar insolation caused by changes in Earth's orbit, while the rapid and large warming of the past century is consistent with the human-caused warming. </jats:p>