PNAS nexus最新文献

{"title":"The global structure of classroom social networks predicts academic and psychosocial adjustment.","authors":"Claudia Neuendorf, Naoki Masuda, Kou Murayama","doi":"10.1093/pnasnexus/pgag291","DOIUrl":"10.1093/pnasnexus/pgag291","url":null,"abstract":"<p><p>Humans are deeply social, and in early life, classroom friendships shape academic and socio-emotional development. Classroom peer ecologies describe the social structure in which individual relationships are situated and which form the context for student learning and development within these classrooms. Yet, research has only begun to explore how these global social network structures are related to classroom-level outcomes. Using a large-scale dataset of 35,038 students in 1,433 classrooms, we extracted 314 social network metrics from four different network types (i.e. friendship, rejection, help, and break-time contacts) and applied machine learning to predict various classroom-level outcomes, including academic achievement, motivation, and social integration. Classroom networks predicted both academic achievement (up to 2% of variance) and well-being (up to 18% of variance), beyond school tracks, socioeconomic status, and demographic factors. However, they did not significantly improve predictions for other characteristics of the teaching and learning environment-such as instructional methods and motivational characteristics. The predictive power for different outcomes was highly dependent upon the type of network and categories of network metrics. These insights position social networks as a powerful tool for understanding aspects of educational environments and for informing network-based interventions.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 9","pages":"pgag291"},"PeriodicalIF":4.8,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13591403/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149019172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Video-rate label-free molecular mapping in living plant tissue with a deployable optical encoder.","authors":"Alexander Ingold, Richard G Baird, Dasmeet Kaur, Nidhi Dwivedi, Reed Sorenson, Leslie Sieburth, Chang-Jun Liu, Rajesh Menon","doi":"10.1093/pnasnexus/pgag290","DOIUrl":"10.1093/pnasnexus/pgag290","url":null,"abstract":"<p><p>Living tissues contain dynamic biochemical information that is difficult to capture with conventional hyperspectral microscopes because sequential spectral acquisition is poorly matched to in vivo molecular processes that evolve during measurement. Here, we introduce a task-specific optical encoding framework for video-rate molecular inference in living plant tissue. The system integrates a passive spectral encoder, implemented here as a low-angle scattering low-density polyethylene (LDPE) layer, into a 22-mm miniaturized probe and learns a supervised mapping from ultraviolet-excited autofluorescence measurements to biomolecular abundance maps. Unlike conventional pipelines that first reconstruct hyperspectral datacubes and then perform spectral unmixing, the deployed system directly estimates endogenous molecular contrast associated primarily with lignin and chlorophyll in poplar tissue, with additional suberin-associated contrast evaluated in suberin-rich tissue. This reframing makes the measurement task biomolecular inference rather than spectral reconstruction, enabling biochemical mapping under low-photon autofluorescence conditions while reducing data burden and computational latency. In living poplar stems, the platform captures autofluorescence-derived videos of embolism propagation and wound-induced biochemical remodeling, dynamic processes for which sequential spectral acquisition can introduce temporal mixing because the molecular contrast evolves during the scan itself. The system also resolves genotype-dependent reductions in lignin-associated autofluorescence in engineered poplar lines. Direct molecular inference improves biomolecular estimation relative to a reconstruction-based pipeline, while probabilistic decoding provides uncertainty estimates. These results show that compact passive spectral encoding, when optimized for biological inference rather than datacube recovery, enables deployable, label-free molecular videography of living plant tissue dynamics after task-specific calibration.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 9","pages":"pgag290"},"PeriodicalIF":4.8,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13586757/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149009263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Is entropy objective? Rethinking the foundations of irreversibility and the second law.","authors":"Juan M R Parrondo","doi":"10.1093/pnasnexus/pgag288","DOIUrl":"10.1093/pnasnexus/pgag288","url":null,"abstract":"<p><p>The standard formulations of statistical mechanics and the explanations of irreversibility rely on the way we describe physical systems. They use concepts such as coarse-graining or macroscopic states, which depend on the observables used to describe the system and their precision. In this Perspective, we examine the extent to which entropy, irreversibility, and the second law of thermodynamics can be regarded as observer-independent. To this end, we use Einstein's observable-dependent entropy and discuss the objectivity of several concepts and phenomena separately: irreversibility, equilibrium, entropy, temperature, and the second law. We also discuss the role of symmetry-breaking transitions in generating low-entropy states and in the arrow of time, as manifested through traces and footprints. Finally, we discuss the mechanical rationale of the second law based on ergotropy and passive states.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 9","pages":"pgag288"},"PeriodicalIF":4.8,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13560077/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148945247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Knotted folds induced by homochiral all-parallel (or all-antiparallel) double-helices.","authors":"Stephen T Hyde, Myfanwy E Evans, Callum A R Metzke, Neave Taylor","doi":"10.1093/pnasnexus/pgag278","DOIUrl":"10.1093/pnasnexus/pgag278","url":null,"abstract":"<p><p>Many biomolecules and their synthetic counterparts preferentially assemble into double-helices with a preferred handedness and parallelism, such as all-antiparallel, right-handed double-helical polymorphs of DNA and RNA favored under ambient conditions by Watson-Crick duplexing. We analyze knots formed by double-helices which are exclusively all-parallel (or exclusively all-antiparallel) and all right-handed (or all left-handed) . Most simpler knot enantiomers are unrealizable. Among the nearly 500 distinct knot enantiomers with up to 10 crossings, fewer than 10% can be formed by such double-helices. Simplest designs for the folding of admissible knot enantiomers via duplexing of complementary base pairs in single-stranded RNA (or DNA) are enumerated for those knots.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 8","pages":"pgag278"},"PeriodicalIF":4.8,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13505510/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148820770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"From hyperspectral to multispectral: Robust corrosion detection in iron and steel using minimal bands.","authors":"Emma Hernández-Suárez, Ámbar Pérez-García, Adrián Rodríguez-Molina, R J Hernández De La Iglesia, José Fco López","doi":"10.1093/pnasnexus/pgag259","DOIUrl":"10.1093/pnasnexus/pgag259","url":null,"abstract":"<p><p>Corrosion in iron and steel structures is a major challenge in coastal environments, where exposure to saline conditions accelerates material degradation and demands continuous monitoring. Multispectral cameras are a promising tool for detecting corrosion in a noninvasive, noncontact, accurate, and fast manner. The wavelengths used by the multispectral camera significantly impact detection performance, which is also influenced by the type of coating on the metal. This study presents a hyperspectral analysis to identify the three most informative bands for detecting corrosion across different coating types and to transfer the selected bands to a multispectral system. For this purpose, a dataset is created consisting of five sample sets with uncoated surfaces and various coatings (differing in paint and color). The optimal spectral bands are selected for each sample set using a Sequential Forward Selector (SFS) and a Random Forest (RF) classifier. Band and pretrained transferability are evaluated across datasets. The generalizable model, incorporating all samples, identifies 518, 655, and 838 nm as the most relevant wavelengths. Incorporating texture features from the Gray-Level Co-occurrence Matrix (GLCM) improves accuracy by up to 6%. Robustness is validated using an independent dataset with unknown coatings. These bands are subsequently mapped to a Silios commercial multispectral camera (547, 665, and 826 nm), and the generalizable hyperspectral model is applied to the resulting multispectral images. This model achieves high accuracy, confirming its cross-sensor applicability. This approach enables future deployment on UAV platforms for large-scale, automated corrosion monitoring in coastal environments.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 8","pages":"pgag259"},"PeriodicalIF":4.8,"publicationDate":"2026-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13504711/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148820765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neural integrator and orchestrator communities shape spontaneous signaling in the human brain.","authors":"Lorenzo Pini, Ranieri Dugo, Paolo Pigato, Maurizio Corbetta","doi":"10.1093/pnasnexus/pgag285","DOIUrl":"10.1093/pnasnexus/pgag285","url":null,"abstract":"<p><p>Understanding how intrinsic brain dynamics are organized is critical for explaining cognition and sensory processing. Theoretical frameworks propose a hierarchical architecture in which some neural systems behave as orchestrators, broadcasting information across the brain, whereas others serve as net receivers (integrators), transforming incoming signals. Here, we test whether this orchestration-integration framework is embedded in intrinsic brain activity, that is, in the absence of cognitive/sensorial tasks. We adopt a multivariate fractional modeling framework originally developed in financial mathematics to characterize how volatility propagates across interacting markets, thereby identifying systems that act as orchestrators or integrators. We then test whether this integrator-orchestrator axis is related to human intelligence. To this end, using 7T resting-state functional magnetic resonance imaging data from 173 healthy young adults, we model spontaneous brain fluctuations with a multivariate fractional Ornstein-Uhlenbeck process to derive directional influence indices. Consistent with our predictions, we identified a bipartite organization, stable across modeling choices. At the subcortical level, the anterior thalamus, putamen, and caudate emerged as orchestrating transmitters, whereas the posterior thalamus, globus pallidus, hippocampus, amygdala, and nucleus accumbens acted as integrating receivers. At the cortical level, attentional and sensory networks functioned as orchestrating transmitters, while higher-order cognitive networks served as integrating receivers. These findings provide support for a theoretically grounded integration-orchestration framework, showing that directional asymmetries in brain spontaneous fluctuations are organized along this axis, with a moderate association with intelligence scores. The proposed fractional framework offers a principled tool to investigate how disruptions of this balance may contribute to brain disorders.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 9","pages":"pgag285"},"PeriodicalIF":4.8,"publicationDate":"2026-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13552504/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148914506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"11β-HSD2 buffers fetal glucocorticoid exposure inducing <i>Per1</i> expression under maternal stress.","authors":"Kazuya Yabumoto, Yasuhiro Umemura, Hitomi Watanabe, Yasuhiro Endo, Nobuya Koike, Akiyo Kakibuchi, Akira Sugimoto, Taisuke Mori, Gen Kondoh, Kazuhiro Yagita","doi":"10.1093/pnasnexus/pgag286","DOIUrl":"10.1093/pnasnexus/pgag286","url":null,"abstract":"<p><p>Glucocorticoids (GCs) have been proposed as maternal-fetal communication signals. However, fetal circadian rhythms are initially shielded from maternal entrainment, in addition to delayed circadian clock emergence due to CLOCK suppression. Premature CLOCK/BMAL1 activation disrupts <i>Hes7</i>-driven somite-like structure in gastruloids. Given the genomic proximity of <i>Per1</i> to <i>Hes7</i> and their transcriptional ripple effect, the physiological significance of delayed cell-autonomous circadian clock development and the temporal program of maternal-fetal communication during the developmental process has remained unclear. Here, based on a marked decline in <i>Hsd11b2</i>, encoding a GC-inactivating 11β-HSD2 enzyme, during organogenesis, we performed split-litter embryo-transfer experiments in which <i>Hsd11b2</i> knockout (KO) and wild-type embryos shared the same maternal environment. Amniotic fluid GCs remained low and arrhythmic under basal conditions. In contrast, maternal stress caused a pronounced GC surge and <i>Per1</i> induction in KO, suggesting that 11β-HSD2 buffers acute maternal GC surges. Despite the genomic proximity of <i>Per1</i> to <i>Hes7</i> and their transcriptional ripple effect, stress-associated and pharmacological GC exposure recapitulated no overt segmentation defects in vivo. Embryonic stem cell-derived gastruloid assays confirmed that neither GC exposure nor <i>Per1</i> induction arrested <i>Hes7</i> oscillations, whereas premature CLOCK/BMAL1 activation impaired these processes even in <i>Hes7</i> KO gastruloid with ectopic rescue, suggesting that interference with the segmentation clock is mediated by premature CLOCK/BMAL1 activation, not by GC-induced <i>Per1</i> expression. These findings clearly show that maternal GC signals are selectively buffered during early development. In addition, suppression of CLOCK/BMAL1 activity preserves segmentation clock function, indicating delayed circadian clock emergence is actively regulated during embryogenesis.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 9","pages":"pgag286"},"PeriodicalIF":4.8,"publicationDate":"2026-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13546787/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148901769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural identifiability of constitutive relations from indirect field observations.","authors":"Y Sungtaek Ju","doi":"10.1093/pnasnexus/pgag281","DOIUrl":"10.1093/pnasnexus/pgag281","url":null,"abstract":"<p><p>Constitutive relations-functions linking a local state variable to a material or system property such as thermal conductivity, hydraulic permeability, or reaction rate constant-appear across the physical, engineering, and life sciences. They must often be inferred from sparse, indirect observations of the field they govern rather than from direct assays. Unlike the well-studied spatially varying parameter <math><mi>ϕ</mi> <mo>(</mo> <mi>x</mi> <mo>)</mo></math> , the scalar state-dependent function <math><mi>ϕ</mi> <mo>(</mo> <mi>u</mi> <mo>)</mo> <mspace></mspace> <mo>:</mo> <mspace></mspace> <mrow><mrow><mi>R</mi></mrow> </mrow> <mo>→</mo> <msup> <mrow><mrow><mi>R</mi></mrow> </mrow> <mo>+</mo></msup> </math> of a single local state variable has received no systematic Bayesian treatment, and a basic question remains open: how much can sparse indirect observations actually inform <math><mi>ϕ</mi> <mo>(</mo> <mi>u</mi> <mo>)</mo></math> ? We show the answer is governed by a two-factor attenuation: information must pass first through the inverse of the linearized partial differential equation (PDE) Jacobian and then through the sparse observation mask. The product of these factors lies far below unity for practical configurations, leaving the posterior structurally prior-dominated regardless of the number of indirect observations of the same type and configuration. The primary determinant is not the PDE class but the <i>coupling mechanism</i>-whether <math><mi>ϕ</mi> <mo>(</mo> <mi>u</mi> <mo>)</mo></math> enters the residual through a spatial gradient (as for diffusion coefficients) or pointwise (as for source terms). We instantiate the analysis in a sparse variational Gaussian process with an explicit, checkable prior and a closed-form Laplace posterior, and validate it across four PDE classes, four constitutive shapes, and two prior conditions. A small number of direct constitutive measurements at well-placed state values, bypassing the PDE entirely, collapse the posterior where arbitrarily many indirect observations of the same type cannot.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 9","pages":"pgag281"},"PeriodicalIF":4.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13546793/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148901759","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Still very much dead and alive: Incoherence in conspiracism as a departure from Bayesian rationality.","authors":"Alessandro Miani, Nicole Cruz, Stephan Lewandowsky","doi":"10.1093/pnasnexus/pgag250","DOIUrl":"https://doi.org/10.1093/pnasnexus/pgag250","url":null,"abstract":"<p><p>Incoherence has long been considered a hallmark of belief in conspiracy theories, though recent research has cast doubt on this claim. We identify theoretical and methodological shortcomings in previous assessments of incoherence and connect this work to current research on reasoning by modeling conspiracism as a set of probabilistic beliefs and computing incoherence as the departure from Bayesian principles of rational belief. In study 1, reanalyzing data from eight studies involving 8,590 participants, we examined the relationship between conspiracism and belief in mutually incompatible conspiracy theories (e.g. Princess Diana \"was murdered\" and \"faked her own death\"). A robust association with conspiracism emerged, with the strongest conspiracy believers showing a 91% probability of being incoherent. In study 2, a preregistered experiment with 469 participants, we investigated whether incoherence is specific to conspiratorial contents related to a person's worldview, or reflects a more general tendency toward inconsistency. We manipulated the content domain (conspiracy vs. nonconspiracy) and logical relation (contrary vs. contradictory) of incompatible explanations for fictitious vignettes and collected explicit probability ratings. We found evidence for a two-component effect of incoherence: a general component, associated with reduced logical monitoring, that emerges in contradictory pairs, and a content-specific component, associated with worldview-driven endorsement, that emerges in contrary conspiracy pairs. Together, these findings encourage a move from dichotomous judgments of dis/belief to a probabilistic modeling of conspiracy beliefs, grounded in a rigorous definition of logical incompatibility and a Bayesian framework for measuring incoherence.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 8","pages":"pgag250"},"PeriodicalIF":4.8,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13482986/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148802748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Like humans, language models demonstrate face-to-character biases.","authors":"Steven A Lehr, Yash Lothe, Mahzarin R Banaji","doi":"10.1093/pnasnexus/pgag247","DOIUrl":"10.1093/pnasnexus/pgag247","url":null,"abstract":"<p><p>Humans routinely make unjustified character inferences, such as labeling people as <i>trustworthy</i> or <i>untrustworthy</i>, based on facial features. We conducted 13 experiments, using four models and totaling nearly 8,000 trials, to ask: Would large language models (LLMs), trained foundationally on language and not images, mirror human biases by inferring character traits from 2D facial images, or would they be free from this human error? GPT-4o reliably exhibited face-biased judgments of <i>competence</i> and <i>trustworthiness</i> (experiments 1 and 2), generalized these judgments to semantically related traits (experiments 3 and 4), and even to primate faces that were absent from its training data (experiment 5). Strikingly, the LLM's face-to-character inferences escalated to ascriptions of extreme negative behavior such as murder and human trafficking (experiment 6) as well as to positive high-impact decisions like selection for employment or venture capital funding (experiment 7). To ensure these results were not an idiosyncratic feature of a particular LLM (GPT-4o), in experiments 8-13, we showed the same patterns, usually with an even greater degree of bias, in GPT-5, Gemini 3 Flash Preview, and Claude Sonnet 4.5. These robust biases stand in contrast to LLMs' reluctance to explicitly endorse race/gender stereotypes, and suggest that alignment efforts to date have been domain-specific, with current models lacking generalized egalitarian decision-making.</p>","PeriodicalId":74468,"journal":{"name":"PNAS nexus","volume":"5 8","pages":"pgag247"},"PeriodicalIF":4.8,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13482980/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148802784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}