Catálogo de publicaciones - revistas

<jats:title>A crowd that flows like water</jats:title> <jats:p>The behavior of large numbers of insects, animals, and other flocks is often based on rules about individual interactions. Bain and Bartolo applied a fluid-like model to the behavior of marathon runners as they walked up to the start line of the Chicago Marathon (see the Perspective by Ouellette). They observed nondamping linear waves with the same speed for different starting corrals of runners and at different races around the world. Their model should apply both to this type of polarized crowd as well as to other groups, which may help guide crowd management.</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="6422" page="46" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aat9891">46</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6422" page="27" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav9869">27</jats:related-article> </jats:p>

<jats:title> C <jats:sub>60</jats:sub> at high resolution </jats:title> <jats:p> It generally takes more energy for molecules to vibrate than to rotate. A vibrational absorption band thus encompasses many distinct concurrent rotational transitions, but these tend to blur together when the molecules have more than a few atoms. Changala <jats:italic>et al.</jats:italic> succeeded in cooling C <jats:sub>60</jats:sub> fullerenes sufficiently to obtain rotational resolution within a C–C stretching band. Success hinged on careful optimization of argon buffer gas flow. Such quantum state–resolved features could aid characterization of fullerene-type compounds in exotic environments such as interstellar space. </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="6422" page="49" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav2616">49</jats:related-article> </jats:p>

<jats:title>A backward current</jats:title> <jats:p> Two-dimensional materials in a magnetic field can exhibit the so-called quantum Hall effect. This regime is characterized by currents running along the edge of the sample in the “downstream” direction determined by the sign of the magnetic field. Lafont <jats:italic>et al.</jats:italic> studied electrical transport in GaAs-AlGaAs heterostructures, focusing on a previously less-studied spin-unpolarized state in the fractional quantum Hall regime. By considering various experimental configurations, they observed a component of the charge current flowing in the opposite, “upstream” direction. </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="6422" page="54" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aar3766">54</jats:related-article> </jats:p>

<jats:title>Nanographenes on oxides</jats:title> <jats:p> The growth of nanographene islands and ribbons on metal surfaces can be accomplished on single-crystal metal surfaces through carbon-carbon coupling reactions, but the surfaces of oxides do not assist these reactions. Kolmer <jats:italic>et al.</jats:italic> show that fluorinated aryl groups can be coupled to form nanographenes on the rutile surface of titanium oxide. The fluorine substitution of the aryl groups was selected so that as the carbon-fluorine bonds were thermally activated, a stepwise process sequentially added aromatic rings around a central aryl group until it was completely substituted. </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="6422" page="57" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav4954">57</jats:related-article> </jats:p>

<jats:title>Making a strongly coupled plasma</jats:title> <jats:p> Plasmas—gases of ionized atoms and electrons—are naturally formed at high temperatures, such as those reached in the interiors of stars. Describing plasmas theoretically is tricky when they are in the strongly coupled regime; reaching that regime in the laboratory would provide a valuable benchmark for theory. To that end, Langin <jats:italic>et al.</jats:italic> worked with a cold plasma created out of atoms of strontium that were ionized by laser light (see the Perspective by Bergeson). They used lasers to cool the ions down to about 50 millikelvin, reaching the desired strongly coupled regime. </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="6422" page="61" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aat3158">61</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6422" page="33" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau7988">33</jats:related-article> </jats:p>

<jats:title>Another primary visual cortex</jats:title> <jats:p>Most functional studies in the visual system have focused on the cortical representation of the geniculo-striate pathway that links the retina to the cortex. The parallel collicular pathway is believed to sparsely project throughout the visual cortex and have a modulatory role on cortical responses to visual stimuli. Beltramo and Scanziani found a visual cortical area that is entirely dedicated to the superior colliculus. This area can discriminate moving visual stimuli that the “classical” primary visual cortex cannot. Thus, the superior colliculus, a phylogenetically ancient structure, has its own projection in neocortex that provides this area with exquisite feature-detection abilities not found in the classical primary visual cortex.</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="6422" page="64" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau7052">64</jats:related-article> </jats:p>

<jats:title>Deep Pacific cooling</jats:title> <jats:p>Earth's climate cooled considerably across the transition from the Medieval Warm Period to the Little Ice Age about 700 years ago. Theoretically, owing to how the ocean circulates, this cooling should be recorded in Pacific deep-ocean temperatures, where water that was on the surface then is found today. Gebbie and Huybers used an ocean circulation model and observations from both the end of the 19th century and the end of the 20th century to detect and quantify this trend. The ongoing deep Pacific is cooling, which revises Earth's overall heat budget since 1750 downward by 35%.</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="6422" page="70" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aar8413">70</jats:related-article> </jats:p>