PNAS nexus最新文献

Addressing climate change depends on large-scale system changes, which require public advocacy. Here, we identified and tested 17 expert-crowdsourced theory-informed behavioral interventions designed to promote public, political, and financial advocacy in a large quota-matched sample of US residents (n = 31,324). The most consistently effective intervention emphasized both the collective efficacy and emotional benefits of climate action, increasing advocacy by up to 10 percentage points. This was also the top intervention among participants identifying as Democrats. Appealing to binding moral foundations, such as purity and sanctity, was also among the most effective interventions, showing positive effects even among participants identifying as Republicans. These findings provide critical insights to policymakers and practitioners aiming to galvanize the public behind collective action and advocacy on climate change with affordable and scalable interventions.

Ph.D. training across academic disciplines has faced significant challenges, with news and media outlets regularly highlighting student struggles, including frequent distrust and antagonism in relationships with faculty advisors. Given the centrality of the advisor-advisee relationship in doctoral education-most programs follow an apprenticeship model where students are mentored closely by a primary faculty advisor-the quality of this relationship may be particularly important. Yet almost no empirical research has systematically examined the long-term implications of advisor trust in doctoral education. In a prospective longitudinal study of 558 incoming Ph.D. students-primarily in STEM (Science, Technology, Engineering, and Mathematics) fields-at three US research universities, we examined the role of Ph.D. students' trust in their advisor early in graduate school on 17 outcomes measured repeatedly during students' first year, a sensitive period when a disproportionate number of students have historically exited. Results revealed a surprisingly broad and consistent effect of advisor trust, such that students who had greater trust in their advisor finished their first year more motivated, higher in well-being, and more academically successful than those with lower advisor trust. These effects were independent of student and advisor demographics, students' academic preparation, individual characteristics, and existing differences in outcomes measured at the start of graduate school, highlighting the potential causal implications of advisor trust for shaping a successful and healthy Ph.D. journey.

Every conflict follows its own course, and every peace its own design. Engineering shapes whether societies move toward confrontation or cooperation. That dual nature is evident in the divided legacy of nuclear technology to today's infrastructure-driven struggles. Every technical decision, from power grids to satellites and from semiconductors to supply chains, can fuel either contest or connection. Here, we ask whether peace can be engineered through professional competence, the ability to build systems that work as intended; through capability, the foresight to anticipate how they may be repurposed; and through character, the willingness to bear the moral weight of design choices. "Peace engineering" is not a distinct discipline, but rather a mode of practice guided by civic purpose, measuring success by how design choices reduce conflict and reinforce stability. We argue that durable peace requires addressing technical debt and ethical debt, where expedient fixes and divisive decisions erode trust. Drawing lessons from the institutionalization of safety and quality, we propose embedding conflict awareness into professional standards, procurement, and education. The goal is not to purge engineering's security functions, but rather to balance them with incentives for prevention and resilience. In a world in which every tool serves both harm and healing, peace becomes not the by-product of progress but its measure. Redirecting engineering toward stability may make peace its defining purpose. Can engineering truly foster enduring civic life, or remain bound to conflict?

Whether in search of better trade opportunities or escaping wars, humans have always been on the move. For almost a century, mathematical models of human mobility have been instrumental in the quantification of commuting patterns and migratory fluxes. Equity is a common premise of most of these mathematical models, such that living conditions and job opportunities are assumed to be equivalent across cities. Growing inequalities in modern urban economy and pressing effects of climate change significantly strain this premise. Here, we propose a mobility model that is aware of inequalities across cities in terms of living conditions and job opportunities. Comparing results with real datasets, we show that the proposed model outperforms the state-of-the-art in predicting migration patterns in South Sudan and commuting fluxes in the United States. This model paves the way to critical research on resilience and sustainability of urban systems.

The bacterial flagellum is a complex nanomachine essential for motility, colonization, and invasion in diverse species. Helicobacter pylori has evolved elaborate sheathed flagella that enable migration through the highly viscous gastric mucus layer to reach its colonization niche on the gastric epithelium, yet the molecular basis for these unique adaptations has remained elusive. Here, we use in situ single-particle cryo-electron microscopy to determine near-atomic structures of the flagellar filament within the membranous sheath of H. pylori. The major flagellin FlaA constitutes the bulk of the filament, whereas the minor flagellin FlaB contributes critically to the hook-proximal region. Both FlaA and FlaB form a conserved core surrounded by variable surface-exposed domains. Our structures further reveal that pseudaminic acid glycans decorate these domains, where they mediate inter- and intra-subunit contacts that stabilize the filament and confer a negatively charged surface. Together, these findings support a model in which the filament rotates independently of the membranous sheath to drive H. pylori motility and provide a molecular framework for understanding how the sheathed flagellum enables colonization and persistence within the gastric niche.

This article examines the gender gap in attitudes toward the adoption of AI in the workplace, with a focus on how gender differences in risk orientation and risk exposure drive skepticism toward AI's economic benefits. Using original survey data from $\sim$ 3,000 respondents across Canada and the United States, we find that women consistently perceive AI to be riskier than men. We identify two key drivers behind this gender gap: women's higher general risk aversion and their greater exposure to AI-related risks. To establish a causal relationship between risk and AI attitudes, we show experimentally that as the probability of net positive employment effects decreases, women's support for companies adopting AI falls more sharply than men's. Finally, structural topic modeling of open-ended responses confirms that women express greater uncertainty about AI's benefits and more frequently anticipate little to no benefits. Given AI's potential to exacerbate existing gender inequalities, our study highlights the critical importance of incorporating women's perspectives into AI policy-making. Policies that do not address gender-specific risks may not only reinforce existing inequalities in employment and income but could also generate political backlash against AI adoption.

Live performance is a ubiquitous cultural and social behavior that has not yet benefited from systematic scientific study. We present a computational methodology that visualizes and describes timing structures in live performance, showcasing their engineering. This novel analysis framework, Topology Analysis of Matching Sequences (TAMS), automatically detects matching sequences and maps their timing. Locating material that is repeated across performances reveals the skill behind apparently effortless communication between performer and audience. Applying TAMS to two stand-up comedy tours uncovered structural features at the macro- and microlevels, including consistently placed novel material at the beginning of shows and sections dedicated to tightly timed repeated material. TAMS also provides a new frame of reference for examining audience-performer dynamics through speech microtiming and laughter. TAMS can be applied to other forms of repeated speech, such as political stump speeches, as well as extended to other types of performance, such as dance.

Artificial light at night (ALAN), a growing environmental stressor in urban ecosystems, disrupts natural light-dark cycles and alters plant phenological events such as leaf-out and flowering. However, the extent to which ALAN influences airborne pollen season timing and exacerbates allergy-related health risks remains largely understudied. This study investigates how ALAN influences the timing and duration of the airborne pollen season across the Northeastern United States from 2012 to 2023 and the consequences of allergenic pollen exposure. Using daily pollen concentrations from the National Allergy Bureau, ALAN data from the Visible Infrared Imaging Radiometer Suite product, and gridded Daymet climate data, we derived three key pollen season metrics: start of season, end of season, and season length, and examined their relationship with environmental conditions. We found that higher ALAN exposure was significantly associated with an earlier start of pollen season, a later end of season, and a longer pollen season length, after controlling for temperature and precipitation. ALAN's impact on the end of the season is larger than on the start of the season. ALAN sites experienced more days and higher severity for allergenic pollen exposure, relative to sites with minimal or no ALAN exposure. These results underscore the potential of ALAN to exacerbate allergy-related disease burdens, calling for its integration into urban environmental public health and planning strategies.

We propose a new citation index ν ("nu") and show that it lies between the classical h-index and g-index. This idea is then generalized to a monotone parametric family $\left({\nu }_{\alpha }\right)$ ( $\alpha \ge 0$ ), whereby $h={\nu }_0$ and $\nu ={\nu }_1$ , while the limiting value ${\nu }_{\infty }$ is expressed in terms of the maximum citation.

Repeated interaction is a key mechanism driving the evolution of cooperation, generosity, extortion, and other social behaviors. These behaviors are typically studied using two-player repeated games, where the two players act simultaneously in every round. In this article, we begin with a standard two-action repeated game, but transform it into a leader-follower game. We do this by forcing one player to indicate their impending move, or to openly commit first in each round. We show that this simple transformation provides new and useful analytical insights. In particular, we use this transformation to derive expressions for the main classes of simultaneous-move Nash equilibria of memory-1, when payoffs are discounted. We show that these equilibria also remain stable under the leader-follower structure. We prove that this reassuring property does not always extend to games with more than two actions or to equilibrium strategies with longer memory. Overall, we establish a novel connection between repeated simultaneous-move games and repeated leader-follower games in evolutionary game theory. This approach offers fruitful means of investigating how prediction and anticipation play a role in stable social behavior.