Catálogo de publicaciones - revistas

<jats:title>Revealing spin-orbit coupling in a cuprate</jats:title> <jats:p> Strong coupling between the spin and orbital degrees of freedom is crucial in generating the exotic band structure of topological insulators. The combination of spin-orbit coupling with electronic correlations could lead to exotic effects; however, these two types of interactions are rarely found to be strong in the same material. Gotlieb <jats:italic>et al.</jats:italic> used spin- and angle-resolved photoemission spectroscopy to map out the spin texture in the cuprate Bi2212. Surprisingly, they found signatures of spin-momentum locking, not unlike that seen in topological insulators. Thus, in addition to strong electronic correlations, this cuprate also has considerable spin-orbit coupling. </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="6420" page="1271" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aao0980">1271</jats:related-article> </jats:p>

<jats:title>Combine and conquer</jats:title> <jats:p> Platinum (Pt)–group metals, which are scarce and expensive, are used for the demanding oxygen reduction reaction (ORR) in hydrogen fuel cells. One competing approach for reducing their use is to create nanoparticles with earth-abundant metals to increase their activity and surface area; another is to replace them with metals such as cobalt (Co) in carbide or nitride sites. Chong <jats:italic>et al.</jats:italic> thermally activated a Co metal-organic framework compound to create ORR-active Co sites and then grew PtCo alloy nanoparticles on this substrate. The resulting catalyst had high activity and durability, despite its relatively low Pt content. </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="6420" page="1276" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau0630">1276</jats:related-article> </jats:p>

<jats:title>Shrinking problems in 3D printing</jats:title> <jats:p> Although a range of materials can now be fabricated using additive manufacturing techniques, these usually involve assembly of a series of stacked layers, which restricts three-dimensional (3D) geometry. Oran <jats:italic>et al.</jats:italic> developed a method to print a range of materials, including metals and semiconductors, inside a gel scaffold (see the Perspective by Long and Williams). When the hydrogels were dehydrated, they shrunk 10-fold, which pushed the feature sizes down to the nanoscale. </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="6420" page="1281" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau5119">1281</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6420" page="1244" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aav5712">1244</jats:related-article> </jats:p>

<jats:title>Evolution trains a from-scratch catalyst</jats:title> <jats:p> Metal-bound peptides can catalyze simple reactions such as ester hydrolysis and may have been the starting point for the evolution of modern enzymes. Studer <jats:italic>et al.</jats:italic> selected progressively more-proficient variants of a small protein derived from a computationally designed zinc-binding peptide. The resulting enzyme could perform the trained reaction at rates typical for naturally evolved enzymes and serendipitously developed a strong preference for a single enantiomer of the substrate. A structure of the final catalyst highlights how small, progressive changes can remodel both catalytic residues and protein architecture in unpredictable ways. </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="6420" page="1285" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau3744">1285</jats:related-article> </jats:p>

<jats:title>Pinpointing the role of geometric phase</jats:title> <jats:p> During chemical reactions, electrons usually rearrange more quickly than nuclei. Thus, theorists often adopt an adiabatic framework that considers vibrational and rotational dynamics within single electronic states. Near the regime where two electronic states intersect, the dynamics get more complicated, and a geometric phase factor is introduced to maintain the simplifying power of the adiabatic treatment. Yuan <jats:italic>et al.</jats:italic> conducted precise experimental measurements that validate this approach. They studied the elementary H + HD reaction at energies just above the intersection of electronic states and observed angular oscillations in the product-state cross sections that are well reproduced by simulations that include the geometric phase. </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="6420" page="1289" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aav1356">1289</jats:related-article> </jats:p>

<jats:title>The whole story</jats:title> <jats:p> An accurate, precise record of the carbon-14 ( <jats:sup>14</jats:sup> C) content of the atmosphere is important for developing chronologies in climate change, archaeology, and many other disciplines. Cheng <jats:italic>et al.</jats:italic> provide a record that covers the full range of the <jats:sup>14</jats:sup> C dating method (∼54,000 years), using paired measurements of <jats:sup>14</jats:sup> C/ <jats:sup>12</jats:sup> C and thorium-230 ( <jats:sup>230</jats:sup> Th) ages from two stalagmites from Hulu Cave, China. The advantage of matching absolute <jats:sup>230</jats:sup> Th ages and <jats:sup>14</jats:sup> C/ <jats:sup>12</jats:sup> C allowed the authors to fashion a seamless record from a single source with low uncertainties, particularly in the older sections. </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="6420" page="1293" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau0747">1293</jats:related-article> </jats:p>

<jats:title>Early humans in northern Africa</jats:title> <jats:p> Evidence for the earliest stone tools produced by human ancestors (from ∼2.6 million years ago) has hitherto come from East Africa. Sahnouni <jats:italic>et al.</jats:italic> report the discovery of Oldowan stone artifacts and associated cutmarks on fossil bones excavated in Algeria, with the earliest dated to 2.4 million years ago. Thus, hominins inhabited the Mediterranean fringe in North Africa earlier than commonly believed. Furthermore, either stone tool manufacture and use dispersed early from East Africa or stone tool manufacture and use originated in both North and East Africa. </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="6420" page="1297" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau0008">1297</jats:related-article> </jats:p>

<jats:title>A step toward control of a noxious weed</jats:title> <jats:p> The parasitic plant <jats:italic>Striga hermonthica</jats:italic> causes extensive crop losses, particularly in Africa. Strigolactone hormones can be used to initiate germination of <jats:italic>Striga</jats:italic> seeds when no host crop is present, which causes the nascent <jats:italic>Striga</jats:italic> plants to die. Unfortunately, strigolactones are also used by crop plants to establish beneficial mutualisms. Uraguchi <jats:italic>et al.</jats:italic> developed a hybrid molecule that can initiate <jats:italic>Striga</jats:italic> germination without interfering with strigolactone-dependent events in the host (see the Perspective by Bouwmeester). The compound has the potential to diversify routes toward protecting fields from <jats:italic>Striga</jats:italic> infestation. </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="6420" page="1301" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau5445">1301</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6420" page="1248" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aav8482">1248</jats:related-article> </jats:p>

<jats:title>IgE B cells unmasked</jats:title> <jats:p> Immunoglobulin E (IgE) antibodies play a central role in immune responses against helminth and protozoan parasites; however, they also contribute to allergies. IgE antibodies (and the B cells generating them) are rare and thus poorly characterized. Croote <jats:italic>et al.</jats:italic> performed single-cell RNA sequencing of peripheral blood B cells from patients with peanut allergies and delineated each cell's gene expression, splice variants, and antibody sequences (see the Perspective by Gould and Ramadani). Unlike other isotypes, circulating IgE B cells were mostly immature plasmablasts. Surprisingly, certain IgE antibodies manifested identical gene rearrangements in unrelated individuals. These IgE antibodies showed high affinity and unexpected cross-reactivity to peanut allergens. </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="6420" page="1306" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau2599">1306</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6420" page="1247" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aav3709">1247</jats:related-article> </jats:p>