UC Merced

A large body of work has advanced our understanding of the neurodevelopment of cognitive control in early childhood. Such work frequently used simplistic visual stimuli, making them well-suited for event-related potentials (ERP) research. However, more naturalistic stimuli may better mirror visually rich environments where cognitive control is engaged. Here, we measured ERPs from 171 kindergartners at public schools with diverse socioeconomic characteristics during a Go/No-Go task using photographs of animals in natural scenes. Instead of the commonly reported N2 in Go/No-Go tasks with simplistic stimuli, the earlier-occurring ERP morphology was dominated by a P2. The later-occurring ERP morphology was consistent with the P3b reported in Go/No-Go tasks with simplistic stimuli. Both the P2 and P3b displayed more positive mean amplitudes for No-Go compared to Go trials. Additionally, P2 amplitudes decreased with age for No-Go stimuli whereas P3b amplitudes decreased for both Go and No-Go stimuli, indicating different developmental changes across earlier- and later-occurring neural processes. Only larger P3b mean amplitudes were associated with better task performance, suggesting that variability in later-occurring neural processes may be more closely related to individual differences in behavioral performance. These findings suggest that earlier-occurring neural indices of cognitive control may not generalize across paradigms varying in stimulus complexity, while later-occurring indices may. Furthermore, results indicate that earlier- and later-occurring ERPs exhibit distinct age-related differences and associations with behavioral performance. Furthermore, our study highlights the feasibility of conducting school-based developmental cognitive neuroscience research, facilitating the inclusion of children from diverse socioeconomic backgrounds.

Molybdenum disulfide (MoS2) dry film lubricants (DFLs) are widely used in aerospace mechanisms when conventional liquid lubricants are impractical. While the effects of environment on MoS2 are well established, the influence of substrate characteristics and operating conditions remains less understood. In this work, three commercial MoS2-based DFLs (Lube-Lok 4396, Everlube 620C, and Everlube 9002) were applied to five aerospace-relevant substrate materials and characterized in terms of surface roughness, flatness, coating thickness, friction, wear life, and load-carrying capacity. Vendor surface preparation and DFL deposition increased roughness, reduced flatness, and shifted the surface toward a more peak-dominated morphology, with the magnitude of these changes depending on both the substrate and coating. Tribological performance was evaluated for a subset of the samples which showed that friction was substantially lower in dry nitrogen than in ambient air, increasing contact pressure reduced friction, and sliding speed had little effect. Lube-Lok 4396 exhibited the longest wear life and highest load-carrying capacity, while Everlube 620C exhibited the lowest friction. Measured friction, wear life, and load-carrying capacity also differed from vendor specifications. These results highlight the effects of substrate material, surface preparation, and operating conditions on the surface characteristics and tribological performance of commercial MoS2 DFLs for aerospace applications.

Short-duration precipitation extremes can threaten public safety and infrastructure by generating flash flooding and geophysical mass wasting events including mudslides and debris flows. Using two surface gauge-based precipitation datasets (1980-2024), we characterize the climatology of annual maximum subdaily precipitation and quantify trends across the western United States (WUS) – a topographically complex region with widely varying precipitation regimes prone to flash flooding. We find that 60.7% of WUS stations, including the vast majority of those located in the continental interior, typically experience 1-hr annual maximum precipitation (AMP) during summer and during the afternoon and evening hours (12:00-23:00 local time). Although most stations do not show statistically significant trends in 1-hr AMP intensity over the full period of record (1980-2024), a significant 10.3% domain-median increase in 1-hr AMP intensity was observed during 2000-2024. These changes largely result from seasonal maximum precipitation (SMP) increases during summer over the continental interior coinciding with a trend toward more favorable summer thermodynamic environments for short-duration precipitation extremes. We also report widespread though statistically insignificant increases in SMP intensity during winter and spring in California since 2000 coinciding with increased column water vapor. These results are suggestive of potential recent intensification of subdaily precipitation extremes in a warming climate in the WUS despite a backdrop of considerable internal variability.

Cutoff lows (COL) are upper-level lows that are displaced from the jet stream and are often associated with a stagnant circulation that facilitates prolonged periods of precipitation and subsequent hydrologic hazards. Here, we quantify the contribution of COL to annual and seasonal precipitation totals, extremes, and hydrologic disasters across the globe, as well as explore how precipitation coincident with COL has changed in observations and is projected to change under future scenarios. Many locations received at least 20% of their annual precipitation coincident to COL across portions of the globe, with notable hotspots along the equatorward flank of the jet stream and in rain shadowed areas of the mid-latitudes. Further, regions—including the Mediterranean, southeastern Australia, the interior western United States (US), South Africa, and Northeast China—had over a third of their three-day annual maximum precipitation events coincident with COL. We also show that an estimated 6.4% of total global economic losses from flood-related disasters outside of the equatorial zone were associated with COL during 2000–2023. Significant increases in precipitation concurrent with COL occurred during 1979–2024 in portions of Europe and the northern US and southern Canada with significant declines in eastern Australia. Projections using output from the Community Earth System Model version 2 Large Ensemble show a robust increase in COL precipitation of ∼20% over the central US and eastern Europe by 2041–2070 tied to a poleward migration of the jet streams. Our results suggest that COL are an important mechanism for generating extreme precipitation and flooding impacts in many global regions, with their contribution to precipitation totals projected to rise in the coming decades in parts of the Northern Hemisphere mid-latitudes.

ABSTRACT Collagen type II (Col‐II) and collagen type I (Col‐I) are major components of articular cartilage present at different ratios at its surface. Understanding how each of these components mediates the assembly of molecular films derived from synovial fluid (SF), the lubricant of synovial joints, is critical to explain the loss of mechanical performance in pathological conditions, guide the design of biomaterial implants meant to be in contact with SF, and develop molecular therapies to restore SF properties. This work demonstrates that Col‐II articular surface model assists in scaffolding SF‐derived films, while Col‐I model lacks SF film scaffolding capabilities. However, when Col‐II and Col‐I are exposed to recombinant equine lubricin (rEqLub), an analog of the major boundary lubricant in SF, both adsorbed and retained similar amounts. These insights, deduced from quartz crystal microbalance with dissipation, diffuse reflectance circular dichroism, and atomic force microscopy, reveal possible mechanisms underlying the loss of mechanical performance of synovial joints in pathology, where Col‐I becomes the major collagenous component of the articular cartilage surface, as well as considerations for designing functional biomaterial implants. Furthermore, this work reinforces the idea of rEqLub as an intra‐articular osteoarthritis therapy with the ability to bind to Col‐II and Col‐I, irrespectively.

Cognitive control fluctuates from moment to moment, even when the sensory and contextual demands of the task remain constant. However, traditional approaches used to measure cognitive control have largely treated such variability as noise and predominantly relied on overall performance metrics, such as accuracy and average response time. Using response time variability as an index of fluctuations in cognitive control, we examined how cognitive control consistency relates to the development of academic skills in children (N = 112) who were followed across kindergarten and first grade, an important period encompassing the transition and acclimation to formal schooling. Cognitive control consistency was assessed via response time variability in a Go/No-Go task, and math and literacy skills were assessed by the Applied Problems and Letter-Word Identification subtests of the Woodcock-Johnson III Tests of Achievement. More consistent cognitive control (indexed by lower response time variability) was associated with stronger math skills both concurrently in kindergarten and prospectively in first grade, above and beyond an accuracy-based metric (d'). In contrast, cognitive control consistency did not relate to literacy skills in kindergarten or first grade, suggesting potential domain-specificity in these relations during the early school years. Together, these findings demonstrate that consistency is an important aspect of cognitive control that uniquely contributes to math performance in early childhood.

Coccidioidomycosis (Valley fever) is a growing public health concern in the western U.S., with California reporting more than an eightfold rise in cases over the past two decades. As climate change, groundwater regulation, and prolonged drought drive major agricultural land-use shifts in the state, including widespread retirement of cultivated lands (i.e., fallowing), understanding their effects on this soil-borne fungal infection is critical. We linked 65,657 confirmed, geolocated cases (2008-2021) to high-resolution maps distinguishing natural vegetation, crop types, and fallowed fields to quantify how land use and land cover were associated with disease rates. Flexible statistical models showed that natural land covers, shrubland, barren ground, and grassland, were associated with higher incidence. Some agricultural uses (grain/hay, field crops, corn, and cotton) were associated with higher incidence, whereas others (orchards, rice, and truck crops/berries) were associated with lower incidence. Recently fallowed land (1 to 4 years) was linked to higher incidence, but the effect depended on prior cultivation. These findings indicate that land use changes may inadvertently impact coccidioidomycosis risk, underscoring the need for dust control and other measures to protect communities.

Effective water and thermal management are crucial for maximizing the performance of proton exchange membrane fuel cells (PEMFCs). This study presents a robust non-isothermal model that integrates two-phase flow, species transport, and heat and mass transfer phenomena to investigate water generation, accumulation, and permeation mechanisms within the gas diffusion layer (GDL) of PEMFCs. Utilizing X-ray computed tomography (XCT) reconstruction, a 2D structure of the Freudenberg GDL is generated. The model incorporates anisotropic thermal conductivity, distinguishes between in-plane and through-plane K IP K TP ratios, and demonstrates its importance to temperature distribution and subsequent condensation rate within the GDL. Additionally, our parametric analysis evaluates the effects of GDL thermal conductivity, current density, operating temperature, and pressure on water condensation and transport processes in PEMFCs. Key findings include the identification of distinct phases of condensation and transport within the porous medium under varying conditions: nucleation, growth, accumulation, and mobilization. Simulation results uncovered condensation regions within the GDL, demonstrating that temperature gradients, strongly influenced by anisotropic thermal conductivity, play a critical role in water generation and transport dynamics. The study further reveals that areas beneath the land in the GDL exhibit lower temperatures, leading to elevated condensation rates and larger droplet formation within those regions. Additionally, the interconnection of condensate droplets via wetting layers emphasizes the impact of temperature distribution on water movement. This study provides deeper insight into water vapor condensation and transport mechanisms within GDLs, informing the design and optimization of GDL structures for enhanced PEMFC performance.