Catálogo de publicaciones - revistas

<jats:p>Recent results show that Earth's core has a large thermal conductivity, raising questions over how the geodynamo evolved.</jats:p>

<jats:p> Mucus is a determinant of gut immune specification and immune tolerance. <jats:named-content content-type="related-content"> [Also see Research Article by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6157" page="447" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1237910"> Shan <jats:italic>et al.</jats:italic> </jats:related-article> ] </jats:named-content> </jats:p>

<jats:p>A positive feedback exists between eutrophication and the global proliferation of toxin-producing cyanobacterial blooms.</jats:p>

<jats:p>Inquiry into Radioactivity, an IBI prize-winning module, enables students to develop meaningful understandings of ionizing radiation through guided experimentation.</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>Bite Me!</jats:title> <jats:p> As unpleasant as it is, pain serves a purpose, to alert the body to potential damage. This protective function may explain why few predators have evolved resistance to the painful venoms used as a defense by their prey. The grasshopper mouse, however, is insensitive to one of the most painful stings in the animal kingdom—that of the bark scorpion. <jats:bold> Rowe <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="6157" page="441" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1236451">441</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="6157" page="428" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1244375">Lewin</jats:related-article> </jats:bold> ) now show that grasshopper mice use the toxins present in the scorpion venom to block voltage-gated pain transmission, temporarily reducing their sensitivity to nonvenom-induced pain. Thus, grasshopper mice use the scorpion's painful defense to their advantage and have evolved a mechanism that allows for reduction of pain sensitivity only when it is needed. </jats:p>

<jats:title>Guardian of the Gut</jats:title> <jats:p> The intestine is able to tolerate continual exposure to large amounts of commensal bacteria and foreign food antigens without triggering an inappropriate inflammatory immune response. In the large intestine, this immunological tolerance is thought to occur via a physical separation between environment and host imposed by a continuous mucous layer built up from the secreted mucin protein, MUC2. However, in the small intestine, this mucous layer is porous, necessitating an additional layer of immune control. <jats:bold> Shan <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="6157" page="447" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1237910">447</jats:related-article> , published online 26 September; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6157" page="432" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1246252"> <jats:bold>Belkaid and Grainger</jats:bold> </jats:related-article> ) now report that in the small intestine, MUC2 plays an active role in immunological tolerance by activating a transcription factor in resident dendritic cells, thereby selectively blocking their ability to launch an inflammatory response. This work identifies MUC2 as a central mediator of immune tolerance to maintain homeostasis in the gut and possibly at other mucosal surfaces in the body. </jats:p>

<jats:title>Topological Replicas</jats:title> <jats:p> When a periodic perturbation couples strongly to electrons in a solid, replicas of the original electronic levels are predicted to develop at certain energies—the so-called Floquet-Bloch states. Such conditions can be achieved by shining light on a solid, but the effect is challenging to observe. <jats:bold> Wang <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="6157" page="453" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1239834">453</jats:related-article> ) used time- and angle-resolved photoemission spectroscopy to photoexcite Bi <jats:sub>2</jats:sub> Se <jats:sub>3</jats:sub> and observe its dispersion at various delay times. The replicas were seen at expected energy shifts, along with the gaps predicted to occur at the new energy-level crossings caused by the appearance of the replicas. Because Bi <jats:sub>2</jats:sub> Se <jats:sub>3</jats:sub> is a topological insulator, the breaking of the time-reversal symmetry caused by circularly polarized light resulted in the appearance of an energy gap at the Dirac point, indicating an interesting route toward manipulating electronic states in such materials. </jats:p>

<jats:title>Not Very Many</jats:title> <jats:p> In physics, the behavior of a system sometimes becomes easier to grasp when the number of particles is large and statistics begin to matter, but knowing how large the system needs to be for that to happen is a challenging computational problem. <jats:bold> Wenz <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="6157" page="457" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1240516">457</jats:related-article> ) used a one-dimensional trapped gas of <jats:sup>6</jats:sup> Li atoms to study this crossover from few to many. To simplify the problem, they worked with one “impurity” atom that was in a state unlike the other—“majority”—atoms. For weak and intermediate interactions, the system approached the many-body limit with as few as four majority atoms. </jats:p>

<jats:title>Dynamic Surfactants</jats:title> <jats:p> Surfactants are used to form a stable interface between two nonmiscible liquids, like oil and water, so that droplets of one fluid can be entrained in the other. <jats:bold> Cui <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="6157" page="460" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242852">460</jats:related-article> ) designed a surfactant based on the association of a hydrophilic nanoparticle with a functionalized oleophilic molecule that self-assembles at a water-oil interface to produce a composite surfactant. Once adsorbed, the nanoparticles tend to remain in place causing them to accumulate and “jam” at the interface. When a drop was deformed, more surfactant could assemble at the surface, allowing droplets of various shapes to be produced. </jats:p>