Catálogo de publicaciones - revistas

<jats:title>Electron pulses under control</jats:title> <jats:p> The ability to take snapshots of fast events can often provide insights into the dynamics of the processes involved: chemical reactions, electronic transport, structural transitions, and complex combinations involving of all of these processes. Kealhofer <jats:italic>et al.</jats:italic> describe an ultrafast optics approach for generating bunches of electrons and compressing them by more than an order of magnitude to just femtosecond time scales (see the Perspective by Ropers). The technique opens up the possibility of imaging ultrafast phenomena with atomic-scale spatial resolution. </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="6284" page="429" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aae0003">429</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6284" page="410" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf6393">410</jats:related-article> </jats:p>

<jats:title>Copper adds alkyls asymmetrically</jats:title> <jats:p> Nitrogen-bearing rings are very common features in the molecular structures of modern drugs. Reactions that can modify these N heterocycles selectively are thus especially useful to optimize pharmaceutical properties. Jumde <jats:italic>et al.</jats:italic> developed a method to append alkyl groups in a single mirror-image orientation to substituted C=C double bonds dangling from N heterocycles. The copper-catalyzed reaction, which relies on Grignard reagents to introduce the alkyl groups, manifests high selectivity across a broad range of substrates, with no interference from the nitrogen. </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="6284" page="433" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf1983">433</jats:related-article> </jats:p>

<jats:title>Hydrogen atom makes graphene magnetic</jats:title> <jats:p> Graphene has many extraordinary mechanical and electronic properties, but it's not magnetic. To make it so, the simplest strategy is to modify its electronic structure to create unpaired electrons. Researchers can do that by, for example, removing individual carbon atoms or adsorbing hydrogen onto graphene. This has to be done in a very controlled way because of a peculiarity of the graphene's crystal lattice, which consists of two sublattices. Gonzales-Herrero <jats:italic>et al.</jats:italic> deposited a single hydrogen atom on top of graphene and used scanning tunneling microscopy to detect magnetism on the sublattice lacking the deposited atom (see the Perspective by Hollen and Gupta). </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="6284" page="437" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad8038">437</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6284" page="415" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf4521">415</jats:related-article> </jats:p>

<jats:title>Correlating an atomic condensate</jats:title> <jats:p> Parts of a quantum system can be more “correlated” than what is allowed in the everyday classical world: A measurement on one part of the system can immediately affect a spatially distant component. The strongest of such correlations, Bell correlations, have been detected in small systems containing two to a handful of particles. Schmied <jats:italic>et al.</jats:italic> used collective measurements to detect Bell correlations among the spins of 480 Rb atoms cooled to a condensed state. This many-body correlated state may be useful as a resource in quantum information processing. </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="6284" page="441" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad8665">441</jats:related-article> </jats:p>

<jats:title>Erosion overwhelmed by eruption</jats:title> <jats:p> Volcanism and erosion can feed into long-term climate change, but determining their relative importance is challenging. Erosion is known to be a carbon sink and is thought to play an outsized role in shifting global climate. However, McKenzie <jats:italic>et al.</jats:italic> suggest that long-term oscillations in climate may be tied to the amount of continental arc volcanism (see the Perspective by Kump). A global compilation of arc volcano-produced zircons over the past 700 million years revealed good correlation between warm and cool epochs with the waxing and waning of volcanism. Thus, volcanism may be a more important driver and erosion a less important sink for very long-term climate changes. </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="6284" page="444" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad5787">444</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6284" page="411" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf6612">411</jats:related-article> </jats:p>

<jats:title>Enzymes make fertilizer with sunlight</jats:title> <jats:p> Nitrogenase enzymes catalyze the biological production of fixed nitrogen. Because this is not enough to sustain modern agriculture, industrial fertilizers containing ammonia are produced via the energy-intensive Haber-Bosch process. Brown <jats:italic>et al.</jats:italic> developed a way to use nitrogenase enzymes from nitrogen-fixing bacteria to make ammonia in vitro without other biological steps or high-energy inputs. Light-activated CdS nanorods provided electrons to the FeMo nitrogenase enzyme to reduce nitrogen and produce ammonia at rates up to 64% of biological nitrogen fixation. These nanoparticle-protein complexes show the potential for solar-driven ammonia production. </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="6284" page="448" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf2091">448</jats:related-article> </jats:p>