Wastewater-based epidemiology (WBE) data are commonly normalized to a human fecal indicator to account for the variability in sample composition and analytical efficiency, which can be introduced by environmental or sewer system differences (e.g., infiltration and inflow, wastewater travel time) as well as sample processing. Normalizing pathogen concentrations by a surrogate can theoretically improve cross-site and longitudinal comparability by providing some measures of how some difficult-to-measure factors affect nucleic acid dilution, decay, and recovery. Members of Crassvirales (‘crAssphage’), bacteriophages with high human specificity and abundance in the human gut, have been used as a human fecal strength indicator with moderate success in improving data credibility. In this study, we leveraged the wastewater crAssphage quantification data accumulated over four years in New York State. We evaluated the spatiotemporal variability of crAssphage load, and whether crAssphage fulfills dual roles as a normalization factor and quality control for COVID-19 wastewater surveillance. The results suggest that crAssphage load has significant spatiotemporal variability, decreasing its potential as a normalizing factor for WBE. Normalizing SARS-CoV-2 wastewater concentrations to crAssphage had very limited effect on the correlation between SARS-CoV-2 concentration and COVID-19 clinical measures. However, we found that the threshold-exceeding values and non-detection of crAssphage may serve as a quality control step for SARS-CoV-2 surveillance. Our findings refine how the co-quantification of crAssphage can assist WBE.
Africa is increasingly being exposed to the negative impacts of climate and environmental change, while having less capacity to respond compared to other continents. The vulnerability partially results from unprecedented demographic growth, urbanization, and industrialization. However, the continent has still largely been underserved by the broader Earth system science (ESS) community, as evidenced by the limited amount of ESS data and research that cover Africa compared to other areas of the world. Here, we present the recent University Corporation for Atmospheric Research (UCAR) Africa Initiative that aims to enhance environmental sustainability in Africa by fostering international collaborative research partnerships coled by African scientists. Specifically, we outline urgent challenges and opportunities identified through an international workshop in six areas of ESS, namely, 1) air quality and health, 2) weather, 3) climate, 4) land and water, 5) social science perspectives, and 6) developing equitable collaboration and sustainable infrastructure. We highlight examples of successful partnerships and conclude with recommendations to advance collaborative, actionable ESS research that addresses Africa's critical environmental challenges.
Proxy records of past climates have yielded powerful insights into regional hydroclimate dynamics. Novel insights may be gained by reconstructing spatiotemporal changes in precipitation isotopologues in past climate states that cannot be gleaned from individual site-level studies. In this paper, we ask whether latitudinal gradients in the stable hydrogen isotopic composition of precipitation, as inferred from sedimentary leaf wax biomarkers, reflect aspects of large-scale climate conditions in western North America (WNA). Modern coretop samples from offshore WNA show that leaf wax hydrogen isotopes broadly track the hydrogen isotopic composition of rainfall between 20 and 40N, but with an offset corresponding to a relatively constant "apparent fractionation" value. Poleward of 40N, the leaf wax signal may be complicated by fluvial transport of leaf waxes from the continental interior. Leaf wax-inferred precipitation hydrogen isotopes show a shift to more negative values between 30 and 40N. We use modern observational data to show that this latitudinal range marks a major transition between the subtropical arid zone and the location of the midlatitude storm tracks over the northeast Pacific. Nudged water isotope-enabled models capture the location of the arid to mesic climate transition with fidelity. This modern data set suggests that reconstructions of the latitudinal gradient of precipitation hydrogen isotopes can constrain the sensitivity of the storm tracks to shifts in climatic boundary conditions in past climate states. This approach can yield novel insights into past, present, and future hydroclimate variability in this arid region.
Children's interactions with artificial intelligence (AI) are growing, yet communication breakdowns-instances where mutual understanding fails-remain a challenge, especially for young children. While generative AI shows promise in engaging children in open-ended conversations, how children navigate and repair these communication breakdowns remains unclear. This study compares how 78 children, aged four to eight years, managed communication breakdowns and repair strategies while co-creating stories with an AI agent (powered by a large language model) versus a human counterpart. Results reveal that the type of conversational partner-human or AI-significantly influenced children's repair behaviors. Children experienced more communication breakdowns when interacting with the AI partner but attempted repairs more frequently with the human counterpart. Misunderstandings and mishearings are the most frequent causes, with clarification requests as the primary repair strategy in both cases. However, when interacting with the AI, children were more likely to go along with the conversation flow to compensate for AI errors, even when the dialogue deviated from their intended meaning-a pattern not observed with human partners. Additionally, children's social perceptions of their partner, especially beliefs about emotional capacity and their psychological closeness to their partner, influenced repair attempts. This study expands research on children's conversational repairs with AI, shedding light on the role of social dynamics in shaping these interactions.
