Catálogo de publicaciones - revistas

<jats:title>Simulating magnetism out of equilibrium</jats:title> <jats:p> A major goal of quantum simulation is to help us understand problems that are difficult to describe analytically or solve with conventional computers. This goal has been very challenging to reach experimentally, requiring, for example, extremely low temperatures to determine the effects of quantum magnetism in equilibrium. Brown <jats:italic>et al.</jats:italic> studied a nonequilibrium system of ultracold <jats:sup>87</jats:sup> Rb atoms in a two-dimensional optical lattice. They monitored the atoms' dynamics after a sudden change in the lattice parameters and were able to reach a regime where the magnetic interactions dominated the dynamics. </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="6234" page="540" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa1385">540</jats:related-article> </jats:p>

<jats:title>Making a monopole in an atomic gas</jats:title> <jats:p> Some “grand unified theories” of physics predict the existence of the so-called magnetic monopole. No such particles have been seen, but analogs of monopoles may be observable in quantum fluids. Ray <jats:italic>et al.</jats:italic> created such an analog in a gas of ultracold <jats:sup>87</jats:sup> Rb atoms with three spin states at their disposal. The authors used a protocol involving external magnetic fields with particular spatial distributions to create and observe a monopole-like spin texture in the gas. </jats:p> <jats:p> Science, this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6234" page="544" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.1258289">544</jats:related-article> </jats:p>

<jats:title>Getting closure in ferroelectric films</jats:title> <jats:p> Ferroelectric materials have a spontaneous electric polarization that can be manipulated for applications. The polarization is usually not uniform throughout the material, and for nanosized ferroelectrics, polarization can be quite complex. Using scanning transmission electron microscopy, Tang <jats:italic>et al.</jats:italic> found that in thin films of the ferroelectric PbTiO <jats:sub>3</jats:sub> , the polarization vector rotated in space, forming a closed loop, the so-called flux closure. The flux closure structures formed an array, with the period dependent on the width of the thin film, and caused the buildup of considerable strain within the crystal lattice of the material </jats:p> <jats:p> Science, this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6234" page="547" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.1259869">547</jats:related-article> </jats:p>

<jats:title>Helium caught in the act of triangulating</jats:title> <jats:p> Helium is the noblest of noble gases, almost completely unattracted to itself or any other chemical element. Of course, when quantum mechanics comes into play, that “almost” is an inevitable caveat. For several decades, researchers have been intrigued by a theoretically predicted Efimov state composed of three helium atoms held loosely together in a triangle. Kunitski <jats:italic>et al.</jats:italic> now report experimental realization of that state and detection of its acute triangular geometry (see the Perspective by Kornilov). Beyond completing a long quest in helium studies, the results shed light on three-body physics more broadly. </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="6234" page="551" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa5601">551</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6234" page="498" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa9102">498</jats:related-article> </jats:p>

<jats:title>Ions' response to hydrophobic surfaces</jats:title> <jats:p> The strength of interactions between ions depends on their solvation environment. Schellman postulated in the 1950s that when aqueous solvated ions approached a hydrophobic surface (such as a parts of a protein surface), interactions between ions would be enhanced. Chen <jats:italic>et al.</jats:italic> experimentally tested this theory by studying the dissociation of organic ions bonded by salt bridges after the addition of acid. The ion pairs were held by tethers at different distances from hydrophobic surfaces. The salt bridge was stronger when it was closer to the hydrophobic surface. </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="6234" page="555" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa7532">555</jats:related-article> </jats:p>

<jats:title>How the brain sorts and routes messages</jats:title> <jats:p> How do higher brain areas communicate with each other? Do they send out all computations equally to all target areas and leave the recipient to extract the needed and relevant information? Or does the transmitting region package and route computations differentially to distinct target areas, depending on the content? Ciocchi <jats:italic>et al.</jats:italic> found that the ventral hippocampus routes anxiety-related information preferentially to the prefrontal cortex and goal-related information preferentially to the nucleus accumbens. Hippocampal neurons with multiple projections were more involved in a variety of behavioral tasks and in memory consolidation. </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="6234" page="560" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa3245">560</jats:related-article> </jats:p>

<jats:title>A beetle's internal bomb</jats:title> <jats:p> Bombardier beetles shoot a toxic pulse at potential predators and other harassers. The toxic spray is created by a chemical reaction that occurs inside the beetle's body. Although the details of the reaction are known, how the beetle is able to precisely combine the chemicals at appropriate times and release the pulse at regular intervals has remained a mystery. Arndt <jats:italic>et al.</jats:italic> used synchrotron x-ray imagery to observe the process as it occurs within live beetles. Expansion and contraction of an internal expansion membrane facilitate the precise cyclic injection of reactants and the subsequent ejection of toxic sprays that keep the beetle's predators at bay. </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="6234" page="563" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.1261166">563</jats:related-article> </jats:p>