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<jats:title>Channeling carbon dioxide</jats:title> <jats:p> The separation of gas molecules with physisorbents can be challenging because there is often a tradeoff between capacity and selectivity. Zhou <jats:italic>et al.</jats:italic> report a template-free hydrothermal synthesis of the one-dimensional channel zeolite mordenite, in which some silicon was replaced by iron. Rather than forming a powder that requires further shaping, this mechanically stable material self-assembled into monoliths. Iron atoms bound in tetrahedral zeolite sites narrowed the channels and enabled the size-exclusion separation of carbon dioxide (CO <jats:sub>2</jats:sub> ) over nitrogen (N <jats:sub>2</jats:sub> ) and methane. High CO <jats:sub>2</jats:sub> uptake and highly efficient CO <jats:sub>2</jats:sub> –N <jats:sub>2</jats:sub> separation was demonstrated for both dry and humid conditions. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , aax5776, this issue p. <jats:related-article issue="6552" page="315" related-article-type="in-this-issue" vol="373">315</jats:related-article> </jats:p>

<jats:title>Autonomous self-healing</jats:title> <jats:p> The ability to autonomously restore shape or self-heal are useful properties that have been incorporated into a range of materials, including metals and polymers. Bhunia <jats:italic>et al.</jats:italic> found that both of these abilities could be achieved in piezoelectric molecular crystals, specifically bipyrazole organic crystals. When the crystals are fractured, they develop charged surfaces that attract each other, drawing the two faces together to enable self-repair as long as they remain within a critical distance of each other. The effect can also be seen in other noncentrosymmetric piezoelectric crystals. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abg3886, this issue p. <jats:related-article issue="6552" page="321" related-article-type="in-this-issue" vol="373">321</jats:related-article> </jats:p>

<jats:title>Fencing in radicals</jats:title> <jats:p> Zeolite catalysis could potentially offer a more direct route from methane to methanol. However, current catalysts tend to deactivate too quickly for practical use. Snyder <jats:italic>et al.</jats:italic> investigated the deactivation mechanism using Mössbauer and Raman spectroscopy and accompanying simulations (see the Perspective by Scott). Their results suggest that in zeolites with large apertures, after iron active sites strip hydrogen from methane, the resulting methyl radicals can leak away and deactivate other iron centers. Zeolites with tighter apertures can keep the radicals nearby longer, favoring the formation of methanol. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abd5803, this issue p. <jats:related-article issue="6552" page="327" related-article-type="in-this-issue" vol="373">327</jats:related-article> ; see also abj4734, p. <jats:related-article issue="6552" page="277" related-article-type="in-this-issue" vol="373">277</jats:related-article> </jats:p>

<jats:title>Shape and nanocrystal transformations</jats:title> <jats:p> Cation exchange reactions that change the composition of a nanocrystal (NC) under mild conditions usually preserve the sublattice of the larger anions. Li <jats:italic>et al.</jats:italic> found that the shape of roxbyite (Cu <jats:sub>1.8</jats:sub> S) nanocrystals, which have a distorted, hexagonal, close-packed sulfide anion sublattice, affected the outcome of exchange reactions with cobalt ions. Flat nanoplates retained the anion lattice and formed cobalt sulfide, but tall nanorods transformed into Co <jats:sub>9</jats:sub> S <jats:sub>8</jats:sub> nanocrystals with a cubic, close-packed structure. Facile crystal plane sliding in the taller nanocrystals appears to have driven the different layer stacking of sulfide anions. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abh2741, this issue p. <jats:related-article issue="6552" page="332" related-article-type="in-this-issue" vol="373">332</jats:related-article> </jats:p>

<jats:title>Piezoelectric bioorganic thin films</jats:title> <jats:p> Piezoelectric materials enable a reversible conversion between mechanical pressure and electric charge and are useful for sensors, actuators, and high-precision motors. Yang <jats:italic>et al.</jats:italic> developed a method for making high-quality crystalline thin films of piezoelectric γ-glycine crystals that are grown and refined between layers of polyvinyl alcohol (PVA) (see the Perspective by Berger). The PVA layers are essential to promoting the crystallization of the preferred crystal phase with the polar axis oriented perpendicular to the film plan because of hydrogen bonding at the PVA-glycine interface. The thin films show a macroscopic piezoelectric response and high stability in aqueous environments. The films are water soluble and, when suitably packaged, could be implanted into a biodegradable energy-harvesting device. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abf2155, this issue p. <jats:related-article issue="6552" page="337" related-article-type="in-this-issue" vol="373">337</jats:related-article> ; see also abj0424, p. <jats:related-article issue="6552" page="278" related-article-type="in-this-issue" vol="373">278</jats:related-article> </jats:p>

<jats:title>Conserved spatial memory mechanisms</jats:title> <jats:p> Food-caching birds are memory specialists that can remember thousands of hidden food items. Using electrophysiological recordings from freely behaving birds, Payne <jats:italic>et al.</jats:italic> analyzed neuronal activity in the likely hippocampus homolog of two bird species, the tufted titmouse and the zebra finch. They chose these two species to compare, respectively, birds that do and do not display food-caching behavior. Place cells and typical hippocampal firing patterns that resembled rodent neuronal activity could be detected in the extreme memory specialists. Compared with titmice, however, spatial activity was noticeably weaker and less abundant in zebra finches. These findings provide evidence that the neural processes underlying spatial memory are remarkably conserved across widely divergent hippocampal circuits separated by millions of years of evolution. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abg2009, this issue p. <jats:related-article issue="6552" page="343" related-article-type="in-this-issue" vol="373">343</jats:related-article> </jats:p>

<jats:title>Mother knows best</jats:title> <jats:p> Inheritance of social status, and its associated costs and benefits, is well demonstrated in humans. Whether such an intergenerational system occurs in other species is harder to demonstrate. Ilany <jats:italic>et al.</jats:italic> looked at nearly 30 years of social interaction data in spotted hyenas, a female-dominated system with a highly structured society, and found that status inheritance is just as prominent (see the Perspective by Firth and Sheldon). Juvenile hyenas had social associations that were similar to their mothers, and the strength of the association was higher for higher-status mothers. Importantly, survival was associated with social inheritance, suggesting that these social roles are essential to hyena life. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abc1966, this issue p. <jats:related-article issue="6552" page="348" related-article-type="in-this-issue" vol="373">348</jats:related-article> ; see also abj5234, p. <jats:related-article issue="6552" page="274" related-article-type="in-this-issue" vol="373">274</jats:related-article> </jats:p>

<jats:title>A transient metal</jats:title> <jats:p> Vanadium dioxide is known to have a coupled structural and electronic transition that can be accessed through light, thermal, or electrical excitation. Ultrafast optical studies of this insulator-to-metal transition indicate that it is mediated by the formation of a transient metallic phase that retains the structure of the original insulating phase. Sood <jats:italic>et al.</jats:italic> show that a similar sequence occurs when the material is electrically excited with a series of voltage pulses. Using ultrafast electron diffraction, the researchers monitored the structure of a vanadium dioxide sample after excitation and found evidence of a metastable metallic phase that appears during the transition. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , abc0652, this issue p. <jats:related-article issue="6552" page="352" related-article-type="in-this-issue" vol="373">352</jats:related-article> </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>