Catálogo de publicaciones - revistas

<jats:p>Reproduction includes two energy investments—the energy in the offspring and the energy expended to make them. The former is well understood, whereas the latter is unquantified but often assumed to be small. Without understanding both investments, the true energy costs of reproduction are unknown. We present a framework for estimating the total energy costs of reproduction by combining data on the energy content of offspring (direct costs) and the metabolic load of bearing them (indirect costs). We find that direct costs typically represent the smaller fraction of the energy expended on reproduction. Mammals pay the highest reproductive costs (excluding lactation), ~90% of which are indirect. Ectotherms expend less on reproduction overall, and live-bearing ectotherms pay higher indirect costs compared with egg-layers. We show that the energy demands of reproduction exceed standard assumptions.</jats:p>

<jats:p>The efficiency and longevity of metal-halide perovskite solar cells are typically dictated by nonradiative defect-mediated charge recombination. In this work, we demonstrate a vapor-based amino-silane passivation that reduces photovoltage deficits to around 100 millivolts (&gt;90% of the thermodynamic limit) in perovskite solar cells of bandgaps between 1.6 and 1.8 electron volts, which is crucial for tandem applications. A primary-, secondary-, or tertiary-amino–silane alone negatively or barely affected perovskite crystallinity and charge transport, but amino-silanes that incorporate primary and secondary amines yield up to a 60-fold increase in photoluminescence quantum yield and preserve long-range conduction. Amino-silane–treated devices retained 95% power conversion efficiency for more than 1500 hours under full-spectrum sunlight at 85°C and open-circuit conditions in ambient air with a relative humidity of 50 to 60%.</jats:p>

<jats:p>Stereoselective construction of γ- and δ-stereocenters in carbonyl compounds is a pivotal objective in asymmetric synthesis. Here, we report chiral bifunctional oxazoline-pyridone ligands that enable enantioselective palladium-catalyzed remote γ-C−H (hetero)arylations of free cycloalkane carboxylic acids, which are essential carbocyclic building blocks in organic synthesis. The reaction establishes γ-tertiary and α-quaternary stereocenters simultaneously in up to &gt;99% enantiomeric excess, providing access to a wide range of cyclic chiral synthons and bioactive molecules. The sequential enantioselective editing of two methylene C–H bonds can be achieved by using chiral ligands with opposite configuration to construct carbocycles containing three chiral centers. Enantioselective remote δ-C−H (hetero)arylation is also realized to establish δ-stereocenters that are particularly challenging to access using classical methodologies.</jats:p>

<jats:p>Power—the asymmetric control of valued resources—affects most human interactions. Although power is challenging to study with real-world data, a distinctive dataset allowed us to do so within the critical context of doctor-patient relationships. Using 1.5 million quasi-random assignments in US military emergency departments, we examined how power differentials between doctor and patient (measured by using differences in military ranks) affect physician behavior. Our findings indicate that power confers nontrivial advantages: “High-power” patients (who outrank their physician) receive more resources and have better outcomes than equivalently ranked “low-power” patients. Patient promotions even increase physician effort. Furthermore, low-power patients suffer if their physician concurrently cares for a high-power patient. Doctor-patient concordance on race and sex also matters. Overall, power-driven variation in behavior can harm the most vulnerable populations in health care settings.</jats:p>

<jats:p>Generally, the acidity of carbon-hydrogen bonds is most sensitive to functionality just one or two bonds away. Here, we present an approach to the formation of carbon-carbon σ bonds by remote proton elimination, a distinct mode of carbon-hydrogen activation enabled by distal acidification through five carbon-carbon bonds. Application of remote proton elimination to cyclodecyl cations unveiled an appealing method for the synthesis of decalins. The transformation is regioconvergent, proceeds without the need for a directing group or precious metal, and demonstrates exquisite site selectivity. An in-depth computational study illuminated the reaction mechanism. Additionally, we describe the complete stereoisomeric enrichment of the decalin products through epimerization mediated by hydrogen atom transfer.</jats:p>

<jats:p>Preparation requires technical research and development, as well as adaptive, proactive governance</jats:p>

<jats:p>In addition to their intrinsic rewarding properties, opioids can also evoke aversive reactions that protect against misuse. Cellular mechanisms that govern the interplay between opioid reward and aversion are poorly understood. We used whole-brain activity mapping in mice to show that neurons in the dorsal peduncular nucleus (DPn) are highly responsive to the opioid oxycodone. Connectomic profiling revealed that DPn neurons innervate the parabrachial nucleus (PBn). Spatial and single-nuclei transcriptomics resolved a population of PBn-projecting pyramidal neurons in the DPn that express μ-opioid receptors (μORs). Disrupting μOR signaling in the DPn switched oxycodone from rewarding to aversive and exacerbated the severity of opioid withdrawal. These findings identify the DPn as a key substrate for the abuse liability of opioids.</jats:p>

<jats:p> How the <jats:italic>KRAS</jats:italic> oncogene drives cancer growth remains poorly understood. Therefore, we established a systemwide portrait of KRAS- and extracellular signal–regulated kinase (ERK)–dependent gene transcription in KRAS-mutant cancer to delineate the molecular mechanisms of growth and of inhibitor resistance. Unexpectedly, our KRAS-dependent gene signature diverges substantially from the frequently cited Hallmark KRAS signaling gene signature, is driven predominantly through the ERK mitogen-activated protein kinase (MAPK) cascade, and accurately reflects KRAS- and ERK-regulated gene transcription in KRAS-mutant cancer patients. Integration with our ERK-regulated phospho- and total proteome highlights ERK deregulation of the anaphase promoting complex/cyclosome (APC/C) and other components of the cell cycle machinery as key processes that drive pancreatic ductal adenocarcinoma (PDAC) growth. Our findings elucidate mechanistically the critical role of ERK in driving KRAS-mutant tumor growth and in resistance to KRAS-ERK MAPK targeted therapies. </jats:p>

<jats:p> As temperatures and evidence of climate impacts mount, so too do pressures to enhance climate policy ambition and implementation. In a previous piece, I have <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.science.org/doi/10.1126/science.adk7428">argued</jats:ext-link> that to respond to these pressures requires rebalancing focus from target setting to implementation through policy formulation and enactment. But following through on policy and its implementation brings its own challenges. One size seldom fits all, and effective climate action requires bespoke policy-making to <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.nature.com/articles/s41560-022-01152-0">tailor policy to national context</jats:ext-link> . This includes, critically, framing policy to win support in diverse national political contexts. </jats:p>

<jats:p> Fundamental limits of cellular deformations, such as hyperextension of a living cell, remain poorly understood. Here, we describe how the single-celled protist <jats:italic>Lacrymaria olor</jats:italic> , a 40-micrometer cell, is capable of reversibly and repeatably extending its necklike protrusion up to 1200 micrometers in 30 seconds. We discovered a layered cortical cytoskeleton and membrane architecture that enables hyperextensions through the folding and unfolding of cellular-scale origami. Physical models of this curved crease origami display topological singularities, including traveling developable cones and cytoskeletal twisted domain walls, which provide geometric control of hyperextension. Our work unravels how cell geometry encodes behavior in single cells and provides inspiration for geometric control in microrobotics and deployable architectures. </jats:p>