Catálogo de publicaciones - revistas

<jats:title>How the ionosphere gains influence</jats:title> <jats:p> In Earth's upper atmosphere, the reconnection of magnetic field lines converts latent magnetic energy into the thermal and kinetic energy of plasma flows. But reconnection appears to produce faster flows before midnight compared with after. To find out why, Lotko <jats:italic>et al.</jats:italic> simulated this energy exchange. Challenging common assumptions about our space weather environment, they conclude that the ionosphere plays an active role when coupled to the magnetosphere in driving the behavior of the magnetotail. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="184" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1252907">184</jats:related-article> </jats:p>

<jats:title>Identifying a cuprate look-alike</jats:title> <jats:p> Superconductivity in cuprate compounds remains poorly understood. Recreating its features in an unrelated material may provide insight. Kim <jats:italic>et al.</jats:italic> used a spectroscopic technique to study the electronic states of the material Sr <jats:sub>2</jats:sub> IrO <jats:sub>4</jats:sub> at relatively high temperatures. They observed phenomenology similar to that of cuprates as they varied the surface carrier concentration. The study highlights the essential properties a material needs in order to exhibit cuprate-like features in the normal (nonsuperconducting) state. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="187" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1251151">187</jats:related-article> </jats:p>

<jats:title>Optically probed superconductor</jats:title> <jats:p> The exotic superconductor UPt <jats:sub>3</jats:sub> has two superconducting phases that appear at different temperatures, but their nature remains unclear. Schemm <jats:italic>et al.</jats:italic> shone circularly polarized light on a crystal of UPt <jats:sub>3</jats:sub> and studied its reflection (see the Perspective by van der Marel and Sawatzky). In the low-temperature phase, the pairs of electrons that make the material superconducting have a handedness to them. The finding narrows down the possible descriptions of the electron-pair wave function. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="190" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1248552">190</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="138" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255925">138</jats:related-article> </jats:p>

<jats:title>Peroxidase proton placement</jats:title> <jats:p> Heme enzymes catalyze a variety of biochemical oxidations through the activation of oxygen by iron. Casadei <jats:italic>et al.</jats:italic> used neutron crystallography to elucidate the mechanism of cytochrome c peroxidase (see the perspective by Groves and Boaz). In the highly reactive intermediate state termed compound I, the iron(IV) oxo, or ferryl, fragment was not protonated, whereas a nearby histidine residue was protonated. The sensitivity of neutron scattering to proton locations revealed these protonation states, where more common techniques, such as x-ray diffraction, have yielded more ambiguous results. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="193" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1254398">193</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="142" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1256754">142</jats:related-article> </jats:p>

<jats:title>Assessing calculated DFT properties</jats:title> <jats:p> Density functional theory (DFT) is now widely used to calculate molecular and material properties. DFT's reliability is usually assessed by comparison with experimental values and higher-level theoretical methods. Medford <jats:italic>et al.</jats:italic> used the BEEFvdW, an exchange-correlation density functional tailored for surface chemistry, and looked at uncertainties with ensembles of functionals. For the specific case of ammonia synthesis catalyzed by transition-metal surfaces, relative rates between different catalysts had lower errors than the absolute rates. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="197" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1253486">197</jats:related-article> </jats:p>

<jats:title>Probing interfaces with electrons</jats:title> <jats:p> When molecules move on surfaces, they behave differently from when inside a solid. But surface layers give off limited signals, so to probe these systems, scientists need to act fast. Gulde <jats:italic>et al.</jats:italic> developed an ultrafast low-energy electron diffraction technique and used it to study how a polymer moved and melted on a graphene substrate (see the Perspective by Nibbering). After hitting the sample with a laser pulse, energy transferred across the graphene-polymer interface, the polymer film became less orderly, and an amorphous phase appeared. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="200" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1250658">200</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="137" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1256199">137</jats:related-article> </jats:p>

<jats:title>Supershear rupture down below</jats:title> <jats:p> Deep earthquakes occur in complex fault zones more than 70 kilometers below Earth's surface. Although they do not pose much of a hazard, they can still provide valuable insight into how earthquakes rupture. Zhan <jats:italic>et al.</jats:italic> found that a magnitude 6.7 aftershock of the largest deep earthquake recorded to date—the 2013 magnitude 8.3 Sea of Okhotsk earthquake—ruptured faster than the velocity of its seismic waves. This so-called “supershear” rupture shows that deep earthquakes have diverse rupture mechanisms and have several routes to dissipate energy. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="204" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1252717">204</jats:related-article> </jats:p>

<jats:title>Up and down go the cyanobacteria</jats:title> <jats:p> Plankton move together in strikingly coordinated daily patterns, sinking at night to avoid being eaten and rising to the surface in daylight to photosynthesize. Otteson <jats:italic>et al.</jats:italic> found similar activity patterns in even the smallest of planktonic organisms, such as photosynthetic bacteria (see the Perspective by Armbrust). Because it's hard to take regular samples in the open ocean, the authors built a robotic sampler and set it adrift for several days in the mid-Pacific. The captured bacteria showed immediate responses to changes in light, temperature, and salinity in ways that could affect the ocean's carbon and nitrogen cycles. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="207" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1252476">207</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="134" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1256578">134</jats:related-article> </jats:p>

<jats:title>Balancing your incomings and outgoings</jats:title> <jats:p> Economic theory predicts that when someone receives money should have little effect on their spending patterns. Gelman <jats:italic>et al.</jats:italic> constructed a data set of 60 million transactions made by 75,000 people to test this theory. People do seem to go on a mini–spending spree after they get their paychecks or pensions. However, closer inspection reveals that that's mostly explained by the convenience of linking regular payments, such as rent and utilities, to regular income. Unsurprisingly, cash-strapped people are more likely to increase their spending in response to receiving income. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="212" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1247727">212</jats:related-article> </jats:p>

<jats:title>Staying one step ahead of tumors</jats:title> <jats:p> Cancer treatments require continual adjustment. A drug that works initially will lose its potency as the tumor acquires new mutations that allow it to bypass the drug's lethal effects. To stay ahead of the tumor, oncologists need a noninvasive way to collect tumor cells from patients over the course of their treatment. Analyzing the mutations in these samples may help them choose the right drugs as the tumors change. In a small study of breast cancer patients, Yu <jats:italic>et al.</jats:italic> show that rare tumor cells circulating in the blood can be captured in viable form and used for this purpose. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6193" page="216" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1253533">216</jats:related-article> </jats:p>