Catálogo de publicaciones - revistas

<jats:title>Four varieties of carbonyl sandwich</jats:title> <jats:p> Compounds with adjacent carbons sandwiched between two carbonyl (C=O) centers turn up frequently in organic chemistry. When these central carbons each have a substituent, there are four possible mutual geometries, all with potentially distinct biochemical properties. Kaldre <jats:italic>et al.</jats:italic> present a single method to access each stereoisomer individually. The outcome depends on the straightforwardly tunable configuration of a sulfoxide group in a precursor, which guides a rearrangement. The versatility of the method should facilitate selective access to 1,4-dicarbonyl motifs in pharmaceutical research. </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="6403" page="664" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aat5883">664</jats:related-article> </jats:p>

<jats:title>Radically transforming light hydrocarbons</jats:title> <jats:p> The methane, ethane, and propane in natural gas are mostly inert under ambient conditions. Mainly they are burned to produce heat. Hu <jats:italic>et al.</jats:italic> show that a simple cerium salt paired with an alcohol can catalytically transform these and other simple hydrocarbons into reactive radicals at room temperature (see the Perspective by Kanai). The reactions rely on light to photolytically cleave cerium alkoxide bonds, producing alkoxy radicals that strip H atoms from the hydrocarbons and regenerate the alcohol. The resultant alkyl radicals readily add to azo compounds, olefins, and aromatics. </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="6403" page="668" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aat9750">668</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6403" page="647" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aau5379">647</jats:related-article> </jats:p>

<jats:p>Efficient methods for excavating in narrow channels are studied through the observation of ants, robot analogs, and cellular automata.</jats:p>

<jats:title>Laser-shocking deuterium into metal</jats:title> <jats:p> The conditions in which hydrogen disassociates and becomes an atomic metal occur in high-energy-density environments, such as the interiors of giant planets and nuclear explosions. Celliers <jats:italic>et al.</jats:italic> trained 168 lasers on deuterium samples at the National Ignition Facility to measure the pressure and temperature conditions of the hydrogen transition. Careful optical measurements led to the addition of four new points on the phase diagram, consistent with static estimates and theoretical calculations. </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="6403" page="677" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aat0970">677</jats:related-article> </jats:p>

<jats:title>Spraying makes it smoother</jats:title> <jats:p> Commercial reverse osmosis processes for water desalination use membranes made by the polymerization of polyamide at the oil/water interface. Chowdhury <jats:italic>et al.</jats:italic> show that thinner, smoother membranes can be made with an electrospray technique. Using high voltage, the two precursors are finely sprayed onto a substrate and polymerize on contact. The composition of the resulting membrane can be tuned on the basis of the proportion of the two components. At optimum conditions, the membranes appear to be better at desalination than current commercial reverse osmosis membranes. </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="6403" page="682" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aar2122">682</jats:related-article> </jats:p>

<jats:title>Unmasking the glow of silver clusters</jats:title> <jats:p> Small silver clusters stabilized by organic materials or inorganic surfaces can exhibit bright photoluminescence, but the origin of this effect has been difficult to establish, in part because the materials are heterogeneous and contain many larger but inactive clusters. Grandjean <jats:italic>et al.</jats:italic> studied silver clusters in zeolites, using x-ray excited optical luminescence to monitor only the emissive structures (see the Perspective by Quintanilla and Liz-Marzán). Aided by theoretical calculations, they identified the electronic states of four-atom silver clusters bound with water molecules that produce bright green emission—thus identifying candidate materials for application in lighting, imaging, and therapeutics. </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="6403" page="686" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aaq1308">686</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6403" page="645" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aau5256">645</jats:related-article> </jats:p>

<jats:title>Controlling two-dimensional twist</jats:title> <jats:p> In heterostructures assembled from two-dimensional materials such as graphene, electron tunneling between layers varies strongly with the rotation angle between the crystal lattices. Usually, the twist angle between layers is fixed after assembly. Ribeiro-Palau <jats:italic>et al.</jats:italic> encapsulated graphene with boron nitride, but the top boron nitride flake was shaped so that an atomic force microscope tip could push on it to vary the twist angle by as little as 0.2°. They observed variations with twist angle in properties such as the charge neutrality point, which would be difficult to observe in static rotated structures. </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="6403" page="690" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aat6981">690</jats:related-article> </jats:p>

<jats:p>An insect herbivore thrives on plant-derived iron complexes that its host uses for micronutrient uptake.</jats:p>

<jats:title>A shrinking marine refrigerator</jats:title> <jats:p> Low subtropical marine clouds scatter solar radiation back to space and thereby cool the climate system. Most work on understanding changes in the coverage of these types of clouds has focused on the effects of sea surface temperatures or on aerosols. Yuter <jats:italic>et al.</jats:italic> show that dynamic effects due to atmospheric gravity waves are responsible for the rapid clearing of large areas of these clouds. This phenomenon also has implications for marine ecology and biogeochemistry. </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="6403" page="697" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aar5836">697</jats:related-article> </jats:p>

<jats:title>A tale of not-so-pure tails</jats:title> <jats:p> The poly(A) tail of mRNA has been thought to be a pure stretch of adenosine nucleotides with little informational content except for length. Lim <jats:italic>et al.</jats:italic> identified enzymes that can decorate poly(A) tails with non-A nucleotides. The noncanonical poly(A) polymerases, TENT4A and TENT4B, incorporate intermittent non-A residues (G, U, or C) with a preference for guanosine, which results in a heterogenous poly(A) tail. Deadenylases trim poly(A) tails to initiate mRNA degradation but stall at the non-A residues. In effect, the not-so-pure tail stabilizes mRNAs by slowing down deadenylation. </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="6403" page="701" related-article-type="in-this-issue" vol="361" xlink:href="10.1126/science.aam5794">701</jats:related-article> </jats:p>