Catálogo de publicaciones - revistas

<jats:title>Designing mechanical complexity</jats:title> <jats:p>The quantum properties of topological insulators translate to mechanical systems governed by Newton's equations of motion. Many-body interactions and the multiple degrees of freedom available to charge carriers give electronic systems a range of exotic behaviors. Süsstrunk and Huber show that this extends to mechanical systems made up of a large lattice of coupled pendula. Mechanical excitations can be eliminated from the inner part of the lattice and confined to the edges, much like topological insulators. In addition to presenting a tractable toy system in which to study complex phenomena, the approach has potential uses in vibration isolation.</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="6243" page="47" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab0239">47</jats:related-article> </jats:p>

<jats:title>Landscape evolution in a sandbox</jats:title> <jats:p> The long-term response of hills and valleys to changes in climate depends on a variety of physical factors. Sweeney <jats:italic>et al.</jats:italic> performed tabletop erosion experiments as a function of rainfall and uplift: variables that are impossible to precisely control in nature (see the Perspective by McCoy). Ridge and valley spacing are set by the balance of sediment moving down hillslopes or being washed out of valleys by rivers. Landscapes therefore evolve as a response to climate change altering erosion rates. </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="6243" page="51" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab0017">51</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6243" page="32" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac5794">32</jats:related-article> </jats:p>

<jats:title>Laser patterning polymer membranes</jats:title> <jats:p> Porous materials are useful for membranes, filters, energy conversion, and catalysis. Their utility often depends on the ability to finely control both the pore sizes and their connectivity. Tan <jats:italic>et al.</jats:italic> prepared porous thin films of block copolymers mixed with phenol-formaldehyde resins (resols) on silicon substrates using a simple laser process. On exposure to ultraviolet light, rapid heating of the substrate causes polymerization of the resols and decomposition of the block copolymer. This method allows direct patterning of the films on a local scale, with tunable pore sizes and size distributions. </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="6243" page="54" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab0492">54</jats:related-article> </jats:p>

<jats:title>An unexpected gaseous sulfur species</jats:title> <jats:p> Sulfuric acid plays a central role in both industrial and atmospheric contexts. As such, the behavior of SO <jats:sub>3</jats:sub> mixtures in gas phases has been studied for over a century. In gas-phase experiments on wet SO <jats:sub>3</jats:sub> and formic acid, Mackenzie <jats:italic>et al.</jats:italic> discovered a previously unrecognized covalent adduct: formic sulfuric anhydride, or HC(O)OSO <jats:sub>3</jats:sub> H. The combination of microwave spectroscopy and theoretical calculations reveals its structural properties. The compound may play a role in the nucleation of atmospheric aerosols by serving as an intermediate to H <jats:sub>2</jats:sub> SO <jats:sub>4</jats:sub> formation. </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="6243" page="58" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa9704">58</jats:related-article> </jats:p>

<jats:title>Elaborate amines from commodity olefins</jats:title> <jats:p> Fine spatial control over the formation of carbon-nitrogen bonds is essential to the synthesis of many pharmaceutical and agrochemical compounds. Yang <jats:italic>et al.</jats:italic> synthesized a copper catalyst that shows exceptional discrimination between similar substituents in the addition of N-H bonds across the C-C double bonds of simple olefins. In particular, the catalyst favors one of two mirror-image products that differ in the relative orientations of methyl and ethyl groups. This selectivity fosters the use of readily available commodity olefins in the preparation of complex chiral amines. </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="6243" page="62" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab3753">62</jats:related-article> </jats:p>

<jats:title>Nickel pincers as enzyme cofactors</jats:title> <jats:p> Organometallic nickel complexes long synthesized in the laboratory exist naturally in enzymes as well. Desguin <jats:italic>et al.</jats:italic> determined the structure and metal-binding residues of the Ni-containing active site in bacterial lactate racemase (see the Perspective by Zamble). A dithiodinicotinic acid mononucleotide derivative cofactor binds Ni through sulfur and carbon bonds, resembling synthetic nickel pincer complexes. Genes encoding accessory proteins involved in the synthesis of this cofactor are widely distributed in other bacteria, suggesting its involvement in other enzymes. </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="6243" page="66" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab2272">66</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6243" page="35" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac5854">35</jats:related-article> </jats:p>

<jats:title>Tracing cells that project to one neuron</jats:title> <jats:p> Feature extraction is a prominent characteristic of cortical neurons involved in the early stages of sensory processing. Wertz <jats:italic>et al.</jats:italic> retrogradely marked an injected neuron and its direct inputs to reveal the network mechanisms that mediate their response. Neurons within each presynaptic network layer of single direction-selective cells showed similar motion direction preferences. In some networks, layer-specific functional modules were identical to the orientation preference of the postsynaptic neuron. Presynaptic neurons, however, displayed a general bias toward the stimulus feature that elicited a response in the postsynaptic neuron. </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="6243" page="70" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aab1687">70</jats:related-article> </jats:p>

<jats:title>The best way to fold a mammalian brain</jats:title> <jats:p>As mammalian brains grew larger through evolution, the organization and folding of brains changed too. In a series of statistical analyses comparing a large number of mammalian species, Mota and Herculano-Houzel found that brain folding is not simply a phylogenetic consequence of brain mass increase (see the Perspective by Striedter and Srinivasan). The exposed surface of the cortex scales across all mammals and across individuals as a single power law of the product of total cortical surface and the square root of cortical thickness.</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="6243" page="74" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa9101">74</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6243" page="31" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aac6531">31</jats:related-article> </jats:p>

<jats:title>Synthesizing more sustainable plastics</jats:title> <jats:p> Zeolites can help synthesize cheaper plastic precursors from biologically sourced feedstocks. Producing sustainable plastics must compete with more cost-effective petrochemical-based synthesis routes. Dusselier <jats:italic>et al.</jats:italic> developed a zeolite-based strategy to catalyze the transformation of microbially produced lactic acid into lactide, a difficult-to-synthesize precursor of biodegradable polylactic acid plastics. The selectivity of nearly 80% is based on active site spatial confinement in the zeolite micropores. This step substantially simplifies current high-cost synthesis routes and generates nearly zero waste using current reactor technologies. </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="6243" page="78" related-article-type="in-this-issue" vol="349" xlink:href="10.1126/science.aaa7169">78</jats:related-article> </jats:p>