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Open Access Publications from the University of California

Recent Work

UC Research Initiatives supports multicampus research teams, partners UC and national laboratory scientists, and advances innovations that benefit California.

Cover page of Working Paper: Are Voters Polarized Along Party Lines About How to Run Elections During the COVID-19 Crisis?

Working Paper: Are Voters Polarized Along Party Lines About How to Run Elections During the COVID-19 Crisis?


Are voters as polarized as political leaders when it comes to their preferences about how to cast their ballots in November 2020 and their policy positions on how elections should be run in light of the COVID-19 outbreak? Prior research has shown little party divide on voting by mail, with nearly equal percentages of voters in both parties choosing to vote this way where it is an option. Has a divide opened up this year in how voters aligned with the Democratic and Republican parties prefer to cast a ballot? We address these questions by presenting the findings of an online survey of a nationally diverse sample of 5,612 eligible voters, fielded from April 8-10, with an embedded experiment providing treated respondents with scientific projections about the COVID-19 outbreak. We find an eight-percentage point difference between Democrats and Republicans in their preference for voting by mail in the control group, but this party divide doubles in the treatment group. We also find that exposure to scientific projections about the outbreak increases support for vote-by-mail legislation and confidence in vote-by-mail election integrity for both Democrats and Republicans.

Cover page of Foundations for California's Water Security in a Changing Climate

Foundations for California's Water Security in a Changing Climate


California’s water supplies are facing unprecedented stresses, and the state’s water-management systems are struggling to meet both environmental and human needs (agricultural, municipal, industrial). Supplies are highly vulnerable to climate variability and extreme events, limiting options to respond to the combined stresses of a changing climate, population, and land cover. Strategic, coordinated investments in California’s water infrastructure, institutions, and information will provide the foundation for a secure, equitable, and efficient water future. The cornerstone of water security, and priority need for California, is a modern, robust water-information system that enables accurate, timely, and transparent accounting through the water-supply and use cycle. This system must extend from mountain headwaters through valley groundwater. Investments are also needed in capacity building for use of water information among institutions and stakeholders across the state. Priority infrastructure improvements are needed for central elements of the state’s “green” infrastructure: restoration of Sierra Nevada and other forests in source-water areas, and additional groundwater recharge on farmland and expanded floodplains. With better-informed management, California’s existing water supplies could go further to meeting the state’s urban, agricultural, ecological, and industrial needs.

Cover page of Skeletal Editing Approach to Bridge-Functionalized Bicyclo[1.1.1]pentanes from Azabicyclo[2.1.1]hexanes.

Skeletal Editing Approach to Bridge-Functionalized Bicyclo[1.1.1]pentanes from Azabicyclo[2.1.1]hexanes.


Azabicyclo[2.1.1]hexanes (aza-BCHs) and bicyclo[1.1.1]pentanes (BCPs) have emerged as attractive classes of sp3-rich cores for replacing flat, aromatic groups with metabolically resistant, three-dimensional frameworks in drug scaffolds. Strategies to directly convert, or scaffold hop, between these bioisosteric subclasses through single-atom skeletal editing would enable efficient interpolation within this valuable chemical space. Herein, we describe a strategy to scaffold hop between aza-BCH and BCP cores through a nitrogen-deleting skeletal edit. Photochemical [2+2] cycloadditions, used to prepare multifunctionalized aza-BCH frameworks, are coupled with a subsequent deamination step to afford bridge-functionalized BCPs, for which few synthetic solutions currently exist. The modular sequence provides access to various privileged bridged bicycles of pharmaceutical relevance.

Cover page of A latent profile analysis of U.S. undocumented college students’ advocacy communication strategies and its relationship with health

A latent profile analysis of U.S. undocumented college students’ advocacy communication strategies and its relationship with health


Undocumented youth engage in advocacy efforts to improve their social conditions. Deploying an expanded definition of advocacy communication, this study (a) examined the heterogeneity of undocumented collegestudents' advocacy communication by identifying profiles of undocumented college students based on their participation in various advocacy communication strategies and (b) examined how these advocacy profiles are associated with health (i.e. anxiety, depression, and self-rated health). Latent profile analysis of 1277 California undocumented, mostly Latina/o/x, college students identified four profiles.Frequent advocators had lower levels of self-rated health and higher levels of anxiety and depression than infrequent advocators. Media advocators reported higher levels of anxiety and depression than infrequent advocators. Finally, organizational advocators reported lower levels of anxiety than media advocators and frequent advocators. Our study advances research on the relationship between advocacy communication and health. We provide suggestions that university staff and programs can take to support undocumented students' advocacy efforts and health.

Cover page of Water, environment, and socioeconomic justice in California: A multi-benefit cropland repurposing framework

Water, environment, and socioeconomic justice in California: A multi-benefit cropland repurposing framework


Low-income, rural frontline communities of California's Central Valley experience environmental and socioeconomic injustice, water insecurity, extremely poor air quality, and lack of fundamental infrastructure (sewage, green areas, health services), which makes them less resilient. Many communities depend financially on agriculture, while water scarcity and associated policy may trigger farmland retirement further hindering socioeconomic opportunities. Here we propose a multi-benefit framework to repurpose cropland in buffers inside and around (400-m and 1600-m buffers) 154 rural disadvantaged communities of the Central Valley to promote socioeconomic opportunities, environmental benefits, and business diversification. We estimate the potential for (1) reductions in water and pesticide use, nitrogen leaching, and nitrogen gas emissions, (2) managed aquifer recharge, and (3) economic and employment impacts associated with clean industries and solar energy. Retiring cropland within 1600-m buffers can result in reductions in water use of 2.18 km3/year, nitrate leaching into local aquifers of 105,500 t/year, greenhouse gas emissions of 2,232,000 t CO2-equivalent/year, and 5388 t pesticides/year, with accompanying losses in agricultural revenue of US$4213 million/year and employment of 25,682 positions. Buffer repurposing investments of US$27 million/year per community for ten years show potential to generate US$101 million/year per community (total US$15,578 million/year) for 30 years and 407 new jobs/year (total 62,697 jobs/year) paying 67 % more than prior farmworker jobs. In the San Joaquin Valley (southern Central Valley), where groundwater overdraft averages 2.3 km3/year, potential water use reduction is 1.8 km3/year. We have identified 99 communities with surficial soils adequate for aquifer recharge and canals/rivers within 1600 m. This demonstrates the potential of managed aquifer recharge in buffered zones to substantially reduce overdraft. The buffers framework shows that well-planned land repurposing near disadvantaged communities can create multiple benefits for farmers and industry stakeholders, while improving quality of life in disadvantaged communities and producing positive externalities for society.

Barriers and opportunities to incorporating environmental justice in the National Environmental Policy act


Environmental justice, which seeks to achieve equity in the process and outcomes of environmental policy and decision-making, is a broadly recognized policy objective. As a foundational environmental regulation and opportunity for public engagement with federal decision-making, the United States' National Environmental Policy Act (NEPA) is frequently considered a promising venue for addressing environmental justice. While environmental justice has been a recognized consideration within the NEPA process since the 1990s, it is by no means a streamlined process. Understanding the barriers and opportunities to better incorporation of EJ principles in NEPA review processes is critical for understanding how to move from EJ as a concept to actual implementation. Drawing on interviews with federal agencies, project developers, nongovernmental organizations, and other organizations who contributed to NEPA reviews for projects across the US, this paper explores how environmental justice–specifically procedural, distributive, and recognition justice–is currently addressed in the preparation of Environmental Impact Statements and identifies barriers and opportunities for better inclusion. We find that many NEPA practitioners see NEPA as a valuable tool for achieving procedural and distributive justice. However, a number of institutional and organizational barriers exist, most prominently a structure that hinders opportunities for meaningful public engagement, ambiguity in how distributive justice is defined and implemented, and a lack of substantive requirements for potential distributional inequities to be addressed.

Cover page of Genetic polymorphism in <i>Methylenetetrahydrofolate Reductase chloride transport protein 6</i> (<i>MTHFR CLCN6</i>) gene is associated with keratinocyte skin cancer in a cohort of renal transplant recipients.

Genetic polymorphism in Methylenetetrahydrofolate Reductase chloride transport protein 6 (MTHFR CLCN6) gene is associated with keratinocyte skin cancer in a cohort of renal transplant recipients.



Renal transplant recipients (RTRs) are at increased risk of keratinocyte cancer (KC), especially cutaneous squamous cell carcinoma (cSCC). Previous studies identified a genetic variant of the Methylenetetrahydrofolate Reductase (MTHFR) gene, C677T, which conferred a risk for diagnosis of cSCC in Irish RTRs.


We sought to find further genetic variation in MTHFR and overlap genes that may be associated with a diagnosis of KC in RTRs.


Genotyping of a combined RTR population (n = 821) from two centres, Ireland (n = 546) and the USA (n = 275), was performed. This included 290 RTRs with KC and 444 without. Eleven single nucleotide polymorphisms (SNPs) in the MTHFR gene and seven in the overlap gene MTHFR Chloride transport protein 6 (CLCN6) were evaluated and association explored by time to event analysis (from transplant to first KC) using Cox proportional hazards model.


Polymorphism at MTHFR CLCN6 (rs9651118) was significantly associated with KC in RTRs (HR 1.50, 95% CI 1.17-1.91, p < 0.00061) and cSCC (HR 1.63, 95% CI 1.14-2.34, p = 0.007). A separate SNP, MTHFR C677T, was also significantly associated with KC in the Irish population (HR 1.31, 95% CI 1.05-1.63, p = 0.016), but not American RTRs.


We report the association of a SNP in the MTHFR overlap gene, CLCN6 and KC in a combined RTR population. While the exact function of CLCN6 is not known, it is proposed to be involved in folate availability. Future applications could include incorporation in a polygenic risk score for KC in RTRs to help identify those at increased risk beyond traditional risk factor assessment.

Cover page of Highly Mobile Excitons in Single Crystal Methylammonium Lead Tribromide Perovskite Microribbons

Highly Mobile Excitons in Single Crystal Methylammonium Lead Tribromide Perovskite Microribbons


Excitons are often given negative connotation in solar energy harvesting in part due to their presumed short diffusion lengths. We investigate exciton transport in single-crystal methylammonium lead tribromide (MAPbBr3) microribbons via spectrally, spatially, and temporally resolved photocurrent and photoluminescence measurements. Distinct peaks in the photocurrent spectra unambiguously confirm exciton formation and allow for accurate extraction of the low temperature exciton binding energy (39 meV). Photocurrent decays within a few μm at room temperature, while a gate-tunable long-range photocurrent component appears at lower temperatures (about 100 μm below 140 K). Carrier lifetimes of 1.2 μs or shorter exclude the possibility of the long decay length arising from slow trapped-carrier hopping. Free carrier diffusion is also an unlikely source of the highly nonlocal photocurrent, due to their small fraction at low temperatures. We attribute the long-distance transport to high-mobility excitons, which may open up new opportunities for novel exciton-based photovoltaic applications.

Cover page of Artificial Intelligence Approach for Estimating Dairy Methane Emissions

Artificial Intelligence Approach for Estimating Dairy Methane Emissions


California's dairy sector accounts for ∼50% of anthropogenic CH4 emissions in the state's greenhouse gas (GHG) emission inventory. Although California dairy facilities' location and herd size vary over time, atmospheric inverse modeling studies rely on decade-old facility-scale geospatial information. For the first time, we apply artificial intelligence (AI) to aerial imagery to estimate dairy CH4 emissions from California's San Joaquin Valley (SJV), a region with ∼90% of the state's dairy population. Using an AI method, we process 316,882 images to estimate the facility-scale herd size across the SJV. The AI approach predicts herd size that strongly (>95%) correlates with that made by human visual inspection, providing a low-cost alternative to the labor-intensive inventory development process. We estimate SJV's dairy enteric and manure CH4 emissions for 2018 to be 496-763 Gg/yr (mean = 624; 95% confidence) using the predicted herd size. We also apply our AI approach to estimate CH4 emission reduction from anaerobic digester deployment. We identify 162 large (90th percentile) farms and estimate a CH4 reduction potential of 83 Gg CH4/yr for these large facilities from anaerobic digester adoption. The results indicate that our AI approach can be applied to characterize the manure system (e.g., use of an anaerobic lagoon) and estimate GHG emissions for other sectors.