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1. Measurement and Assessment of Head-to-Helmet Contact Forces

   https://doi.org/10.1007/s10439-025-03677-3  

   Jennings, Turner; Tillman, Aidan; Mukasa, D’mitra; Marchev, Michael; Müftü, Sinan; Amini, Rouzbeh (January 2025, Annals of Biomedical Engineering)

   Abstract PurposeTo evaluate the population variation in head-to-helmet contact forces in helmet users. MethodsFour different size Kevlar composite helmets were instrumented with contact pressure sensors and chinstrap tension meters. A total number of 89 volunteers (25 female and 64 male volunteers) participated in the study. The length, width, and circumference of their heads were measured and each volunteer was assigned a helmet size. Volunteers were asked to wear the helmet in three different configurations and the chinstrap tension and contact force between the head and each of the seven interior pads were recorded. ResultsThe majority of forces measured on any individual pad were between 0 and 5 N. However, some users exhibited pressure points with forces as high as 30 N. The contact force distribution is non-uniform across the interior of the helmet, with the largest force concentrated at the front. Head shape is a major driver of the observed contact force. There was a statistically significant difference between female and male volunteers, and between groups with different experience levels. ConclusionsThe fit of helmet systems is highly subject specific. The current metrics used to assign helmet sizes may not accurately predict correct helmet fit. 

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2. A Survey of Electric-Scooter Riders’ Route Choice, Safety Perception, and Helmet Use

   https://doi.org/10.3390/su15086609  

   Sievert, Kelsey; Roen, Madeleine; Craig, Curtis M.; Morris, Nichole L. (April 2023, Sustainability)

   This study investigated electric-scooter (e-scooter) rider behaviors and preferences to inform ways to increase safety for e-scooter riders. Data was collected from 329 e-scooter riders via two online and one in-person survey. Survey questions considered rider roadway infrastructure preferences, safety perceptions, and helmet-wearing behavior. Protected bike lanes were more commonly indicated as the safest infrastructure (62.4%) but were less likely to be the most preferred infrastructure (49.7%). Sidewalks were better matched between riders, indicating them as their preferred riding infrastructure (22.7%) and the perceived safest riding infrastructure (24.5%). Riders had low feelings of safety and preference for riding on major/neighborhood streets or on unprotected bike lanes. Riders reported significant concern about being hit by a moving vehicle, running into a pothole/rough roadway, and running into a moving vehicle. In line with the Theory of Planned Behavior, a significant relationship was found between the frequency of riding and helmet-wearing behavior, with more frequent riders being more likely to wear helmets. Findings suggest that existing roadway infrastructure may pose safety challenges and encourage rider-selected workarounds. Public policy may consider emphasizing protected bicycle lane development, rather than helmet mandates, to support e-scooter riding safety for all vulnerable road users. 

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3. Improved Carbon Corrosion and Platinum Dissolution Durability in Automotive Fuel Cell Startup and Shutdown Operation

   https://doi.org/10.1149/1945-7111/abe6ea  

   Wang, Chunmei; Ricketts, Mark; Soleymani, Amir Peyman; Jankovic, Jasna; Waldecker, James; Chen, Jixin; Xu, Chunchuan (March 2021, Journal of The Electrochemical Society)

   Three protocols of accelerated startup and shutdown (SU/SD) test were investigated: startup and shutdown with air supply and soak to both anode and cathode (air-SU/SD), hydrogen protected startup and shutdown (H 2 -SU/SD), and hydrogen protected startup and shutdown with a load (H 2 -SU/SD with a load). The performance losses, electrochemical surface area (ECSA) reduction, and catalyst layer degradation were characterized and compared for these SU/SD protocols. Air-SU/SD protocol showed much more severe performance loss and catalyst layer degradation than hydrogen protected ones, which confirmed the benefits of hydrogen protection. The temperature effect on air-SU/SD was significant in a broad range from 20 °C to 70 °C, with low temperature greatly reducing the degradation. The mechanism of H 2 protection and load drawn in alleviating carbon corrosion was explained based on reactions and charge conservation during SU/SD. This paper provides comprehensive test data and failure analysis to quantify the benefits of H 2 protection and load drawn and to facilitate future enhancement of system strategies on SU/SD durability. 

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4. Differences between soil and air temperatures: Implications for geological reconstructions of past climate

   https://doi.org/10.1130/GES02448.1  

   Molnar, Peter (February 2022, Geosphere)

   Abstract Among quantities of interest in paleoclimate, the mean annual air temperature, Ta, directly over the surface looms prominently. Most geologic estimates of past temperatures from continental regions, however, quantify temperatures of the soil or other material below the surface, Ts, and in general Ta < Ts. Both theory and data from the FLUXNET2015 data set of surface energy balance indicate systematic dependences of temperature differences ΔT = Ts − Ta and also of Bowen ratios—ratios of sensible to latent heat fluxes from surface to the atmosphere—on the nature of the land-surface cover. In cold regions, with mean annual temperatures ≲5 °C, latent heat flux tends to be small, and values of ΔT can be large, 3–5 °C or larger. Over wet surfaces, latent heat fluxes dominate sensible heat fluxes, and values of both ΔT and Bowen ratios commonly are small. By contrast, over arid surfaces that provide only limited moisture to the overlying atmosphere, the opposite holds. Both theory and observation suggest the following, albeit approximate, mean annual values of ΔT: for wetlands, 1 °C; forests, 1 ± 1 °C; shrublands, 3–4 °C; savannas, 3.5 °C < ΔT < 5.5 °C; grasslands, 1 °C where wet to 3 °C where arid; and deserts, 4–6 °C. As geological tools for inferring past land-surface conditions improve, these approximate values of ΔT will allow geologic estimates of past mean annual surface temperatures, Ts, to be translated into estimates of past mean annual air temperatures, Ta. 

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5. Quantification and machine learning based N ₂ O–N and CO ₂ –C emissions predictions from a decomposing rye cover crop

   https://doi.org/10.1002/agj2.21185  

   Joshi, Deepak_R; Clay, David_E; Clay, Sharon_A; Moriles‐Miller, Janet; Daigh, Aaron_L_M; Reicks, Graig; Westhoff, Shaina (November 2022, Agronomy Journal)

   Abstract Cover crops improve soil health and reduce the risk of soil erosion. However, their impact on the carbon dioxide equivalence (CO_2e) is unknown. Therefore, the objective of this 2‐yr study was to quantify the effect of cover crop‐induced differences in soil moisture, temperature, organic C, and microorganisms on CO_2e, and to develop machine learning algorithms that predict daily N₂O–N and CO₂–C emissions. The prediction models tested were multiple linear regression, partial least square regression, support vector machine, random forest (RF), and artificial neural network. Models’ performance was accessed using R², RMSE and mean of absolute value of error. Rye (Secale cerealeL.) was dormant seeded in mid‐October, and in the following spring it was terminated at corn's (Zea maysL.) V4 growth stage. Soil temperature, moisture, and N₂O–N and CO₂–C emissions were measured near continuously from soil thaw to harvest in 2019 and 2020. Prior to termination, the cover crop decreased N₂O–N emissions by 34% (p = .05), and over the entire season, N₂O–N emissions from cover crop and no cover crop treatments were similar (p = .71). Based on N₂O–N and CO₂–C emissions over the entire season and the estimated fixed cover crop‐C remaining in the soil, the partial CO_2ewere −1,061 and 496 kg CO_2eha^–1in the cover crop and no cover crop treatments, respectively. The RF algorithm explained more of the daily N₂O–N (73%) and CO₂–C (85%) emissions variability during validation than the other models. Across models, the most important variables were temperature and the amount of cover crop‐C added to the soil. 

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