Catálogo de publicaciones - revistas

<jats:p> Highlights from the <jats:italic>Science</jats:italic> family of journals </jats:p>

<jats:p>Editors’ selections from the current scientific literature</jats:p>

<jats:p>Organisms use energy to grow and reproduce, so the processes of energy metabolism and biological production should be tightly bound. On the basis of this tenet, we developed and tested a new theory that predicts the relationships among three fundamental aspects of life: metabolic rate, growth, and reproduction. We show that the optimization of these processes yields the observed allometries of metazoan life, particularly metabolic scaling. We conclude that metabolism, growth, and reproduction are inextricably linked; that together they determine fitness; and, in contrast to longstanding dogma, that no single component drives another. Our model predicts that anthropogenic change will cause animals to evolve decreased scaling exponents of metabolism, increased growth rates, and reduced lifetime reproductive outputs, with worrying consequences for the replenishment of future populations.</jats:p>

<jats:p>Whereas sensory perception relies on specialized sensory pathways, it is unclear whether these pathways originate as modality-specific circuits. We demonstrated that somatosensory and visual circuits are not by default segregated but require the earliest retinal activity to do so. In the embryo, somatosensory and visual circuits are intermingled in the superior colliculus, leading to cortical multimodal responses to whisker pad stimulation. At birth, these circuits segregate, and responses switch to unimodal. Blocking stage I retinal waves prolongs the multimodal configuration into postnatal life, with the superior colliculus retaining a mixed somato-visual molecular identity and defects arising in the spatial organization of the visual system. Hence, the superior colliculus mediates the timely segregation of sensory modalities in an input-dependent manner, channeling specific sensory cues to their appropriate sensory pathway.</jats:p>

<jats:p> Flexible thermoelectrics provide a different solution for developing portable and sustainable flexible power supplies. The discovery of silver sulfide–based ductile semiconductors has driven a shift in the potential for flexible thermoelectrics, but the lack of good p-type ductile thermoelectric materials has restricted the reality of fabricating conventional cross-plane π-shaped flexible devices. We report a series of high-performance p-type ductile thermoelectric materials based on the composition-performance phase diagram in AgCu(Se,S,Te) pseudoternary solid solutions, with high figure-of-merit values (0.45 at 300 kelvin and 0.68 at 340 kelvin) compared with other flexible thermoelectric materials. We further demonstrate thin and flexible π-shaped devices with a maximum normalized power density that reaches 30 μW cm <jats:sup>−2</jats:sup> K <jats:sup>−2</jats:sup> . This output is promising for the use of flexible thermoelectrics in wearable electronics. </jats:p>

<jats:p>Recent advances in flexible and stretchable electronics have led to a surge of electronic skin (e-skin)–based health monitoring platforms. Conventional wireless e-skins rely on rigid integrated circuit chips that compromise the overall flexibility and consume considerable power. Chip-less wireless e-skins based on inductor-capacitor resonators are limited to mechanical sensors with low sensitivities. We report a chip-less wireless e-skin based on surface acoustic wave sensors made of freestanding ultrathin single-crystalline piezoelectric gallium nitride membranes. Surface acoustic wave–based e-skin offers highly sensitive, low-power, and long-term sensing of strain, ultraviolet light, and ion concentrations in sweat. We demonstrate weeklong monitoring of pulse. These results present routes to inexpensive and versatile low-power, high-sensitivity platforms for wireless health monitoring devices.</jats:p>

<jats:p>The enzyme nitrogenase couples adenosine triphosphate (ATP) hydrolysis to the multielectron reduction of atmospheric dinitrogen into ammonia. Despite extensive research, the mechanistic details of ATP-dependent energy transduction and dinitrogen reduction by nitrogenase are not well understood, requiring new strategies to monitor its structural dynamics during catalytic action. Here, we report cryo–electron microscopy structures of the nitrogenase complex prepared under enzymatic turnover conditions. We observe that asymmetry governs all aspects of the nitrogenase mechanism, including ATP hydrolysis, protein-protein interactions, and catalysis. Conformational changes near the catalytic iron-molybdenum cofactor are correlated with the nucleotide-hydrolysis state of the enzyme.</jats:p>

<jats:p>The B cell receptor (BCR) complex plays a critical role in B cell development and immune responses. The assembly mechanisms underlying the BCR complex remain unknown. We determined the cryo–electron microscopy (cryo-EM) structures of human IgG-BCR and IgM-BCR, which consist of membrane-bound immunoglobulin molecules (mIg) and Igα/β subunits at a 1:1 stoichiometry. Assembly of both BCR complexes involves their extracellular domains, membrane-proximal connection peptides, and transmembrane (TM) helices. The TM helices of mIgG and mIgM share a conserved set of hydrophobic and polar interactions with Igα/β TM helices. By contrast, the IgG-Cγ3 and IgM-Cμ4 domains interact with extracellular Ig-like domains of Igα/β through head-to-tail and side-by-side modes, respectively. This work reveals the structural basis for BCR assembly and provides insights into BCR triggering.</jats:p>

<jats:p>Quantum walks provide a framework for designing quantum algorithms that is both intuitive and universal. To leverage the computational power of these walks, it is important to be able to programmably modify the graph a walker traverses while maintaining coherence. We do this by combining the fast, programmable control provided by optical tweezers with the scalable, homogeneous environment of an optical lattice. With these tools we study continuous-time quantum walks of single atoms on a square lattice and perform proof-of-principle demonstrations of spatial search with these walks. When scaled to more particles, the capabilities demonstrated can be extended to study a variety of problems in quantum information science, including performing more effective versions of spatial search using a larger graph with increased connectivity.</jats:p>