Catálogo de publicaciones - revistas

<jats:p> The crystallographic pore sizes of zeolites are substantially smaller than those inferred from catalytic transformation and molecular sieving capabilities, which reflects flexible variation in zeolite opening pores. Using in situ electron microscopy, we imaged the straight channels of ZSM-5 zeolite with benzene as a probe molecule and observed subcell flexibility of the framework. The opening pores stretched along the longest direction of confined benzene molecules with a maximum aspect change of 15%, and the <jats:italic>Pnma</jats:italic> space group symmetry of the MFI framework caused adjacent channels to deform. This compensation maintained the stability and rigidity of the overall unit cell within 0.5% deformation. The subcell flexibility originates mainly from the topologically soft silicon-oxygen-silicon hinges between rigid tetrahedral SiO <jats:sub>4</jats:sub> units, with inner angles varying from 135° to 153°, as confirmed by ab initio molecular dynamics simulations. </jats:p>

<jats:p> Animal genomes are folded into loops and topologically associating domains (TADs) by CTCF and loop-extruding cohesins, but the live dynamics of loop formation and stability remain unknown. Here, we directly visualized chromatin looping at the <jats:italic>Fbn2</jats:italic> TAD in mouse embryonic stem cells using super-resolution live-cell imaging and quantified looping dynamics by Bayesian inference. Unexpectedly, the <jats:italic>Fbn2</jats:italic> loop was both rare and dynamic, with a looped fraction of approximately 3 to 6.5% and a median loop lifetime of approximately 10 to 30 minutes. Our results establish that the <jats:italic>Fbn2</jats:italic> TAD is highly dynamic, and about 92% of the time, cohesin-extruded loops exist within the TAD without bridging both CTCF boundaries. This suggests that single CTCF boundaries, rather than the fully CTCF-CTCF looped state, may be the primary regulators of functional interactions. </jats:p>

<jats:p>The human somatosensory network relies on ionic currents to sense, transmit, and process tactile information. We investigate hydrogels that similarly transduce pressure into ionic currents, forming a piezoionic skin. As in rapid- and slow-adapting mechanoreceptors, piezoionic currents can vary widely in duration, from milliseconds to hundreds of seconds. These currents are shown to elicit direct neuromodulation and muscle excitation, suggesting a path toward bionic sensory interfaces. The signal magnitude and duration depend on cationic and anionic mobility differences. Patterned hydrogel films with gradients of fixed charge provide voltage offsets akin to cell potentials. The combined effects enable the creation of self-powered and ultrasoft piezoionic mechanoreceptors that generate a charge density four to six orders of magnitude higher than those of triboelectric and piezoelectric devices.</jats:p>

<jats:p>The biological bases of wanting have been characterized in mammals, but whether an equivalent wanting system exists in insects remains unknown. In this study, we focused on honey bees, which perform intensive foraging activities to satisfy colony needs, and sought to determine whether foragers leave the hive driven by specific expectations about reward and whether they recollect these expectations during their waggle dances. We monitored foraging and dance behavior and simultaneously quantified and interfered with biogenic amine signaling in the bee brain. We show that a dopamine-dependent wanting system is activated transiently in the bee brain by increased appetite and individual recollection of profitable food sources, both en route to the goal and during waggle dances. Our results show that insects share with mammals common neural mechanisms for encoding wanting of stimuli with positive hedonic value.</jats:p>

<jats:p>How acute pathogens persist and what curtails their epidemic growth in the absence of acquired immunity remains unknown. Canine rabies is a fatal zoonosis that circulates endemically at low prevalence among domestic dogs in low- and middle-income countries. We traced rabies transmission in a population of 50,000 dogs in Tanzania from 2002 to 2016 and applied individual-based models to these spatially resolved data to investigate the mechanisms modulating transmission and the scale over which they operate. Although rabies prevalence never exceeded 0.15%, the best-fitting models demonstrated appreciable depletion of susceptible animals that occurred at local scales because of clusters of deaths and dogs already incubating infection. Individual variation in rabid dog behavior facilitated virus dispersal and cocirculation of virus lineages, enabling metapopulation persistence. These mechanisms have important implications for prediction and control of pathogens that circulate in spatially structured populations.</jats:p>

<jats:p> Improving composite battery electrodes requires a delicate control of active materials and electrode formulation. The electrochemically active particles fulfill their role as energy exchange reservoirs through interacting with the surrounding conductive network. We formulate a network evolution model to interpret the regulation and equilibration between electrochemical activity and mechanical damage of these particles. Through statistical analysis of thousands of particles using x-ray phase contrast holotomography in a LiNi <jats:sub>0.8</jats:sub> Mn <jats:sub>0.1</jats:sub> Co <jats:sub>0.1</jats:sub> O <jats:sub>2</jats:sub> -based cathode, we found that the local network heterogeneity results in asynchronous activities in the early cycles, and subsequently the particle assemblies move toward a synchronous behavior. Our study pinpoints the chemomechanical behavior of individual particles and enables better designs of the conductive network to optimize the utility of all the particles during operation. </jats:p>

<jats:p> After large galaxies merge, their central supermassive black holes are expected to form binary systems. Their orbital motion should generate a gravitational wave background (GWB) at nanohertz frequencies. Searches for this background use pulsar timing arrays, which perform long-term monitoring of millisecond pulsars at radio wavelengths. We used 12.5 years of Fermi Large Area Telescope data to form a gamma-ray pulsar timing array. Results from 35 bright gamma-ray pulsars place a 95% credible limit on the GWB characteristic strain of 1.0 × 10 <jats:sup>−14</jats:sup> at a frequency of 1 year <jats:sup>–1</jats:sup> . The sensitivity is expected to scale with <jats:italic>t</jats:italic> <jats:sub>obs</jats:sub> , the observing time span, as <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>t</mml:mi> <mml:mrow> <mml:mtext>obs</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> <mml:mo>/</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> </jats:inline-formula> . This direct measurement provides an independent probe of the GWB while offering a check on radio noise models. </jats:p>

<jats:p>Global warming threatens marine biota with losses of unknown severity. Here, we quantify global and local extinction risks in the ocean across a range of climate futures on the basis of the ecophysiological limits of diverse animal species and calibration against the fossil record. With accelerating greenhouse gas emissions, species losses from warming and oxygen depletion alone become comparable to current direct human impacts within a century and culminate in a mass extinction rivaling those in Earth’s past. Polar species are at highest risk of extinction, but local biological richness declines more in the tropics. Reversing greenhouse gas emissions trends would diminish extinction risks by more than 70%, preserving marine biodiversity accumulated over the past ~50 million years of evolutionary history.</jats:p>

<jats:p> Discovery chemists routinely identify purpose-tailored molecules through an iterative structural optimization approach, but the preparation of each successive candidate in a compound series can rarely be conducted in a manner matching their thought process. This is because many of the necessary chemical transformations required to modify compound cores in a straightforward fashion are not applicable in complex contexts. We report a method that addresses one facet of this problem by allowing chemists to hop directly between chemically distinct heteroaromatic scaffolds. Specifically, we show that selective photolysis of quinoline <jats:italic>N</jats:italic> -oxides with 390-nanometer light followed by acid-promoted rearrangement affords <jats:italic>N</jats:italic> -acylindoles while showing broad compatibility with medicinally relevant functionality. Applications to late-stage skeletal modification of compounds of pharmaceutical interest and more complex transformations involving serial single-atom changes are demonstrated. </jats:p>

<jats:p>Reaction generality is crucial in determining the overall impact and usefulness of synthetic methods. Typical generalization protocols require a priori mechanistic understanding and suffer when applied to complex, less understood systems. We developed an additive mapping approach that rapidly expands the utility of synthetic methods while generating concurrent mechanistic insight. Validation of this approach on the metallaphotoredox decarboxylative arylation resulted in the discovery of a phthalimide ligand additive that overcomes many lingering limitations of this reaction and has important mechanistic implications for nickel-catalyzed cross-couplings.</jats:p>