Temperature‑Dependent Friction, Wear, and Life of MoS₂ Dry Film Lubricants for Space Mechanisms: A Comprehensive Review

AbstractMolybdenum Disulfide (MoS2) is the most widely used dry film lubricant (DFL) for moving mechanical assemblies that operate in space. For these applications, the MoS2 must provide low friction and wear across a range of temperatures. The temperature dependence of MoS2 tribological behavior has been studied previously. However, the number of temperatures and conditions that can be tested in a single study is necessarily limited, making it difficult to predict or understand the performance of DFLs more broadly. To address this, this review article summarizes and analyzes the results from prior studies of temperature-dependent tribological behavior of MoS2-based dry film lubricants. Friction, wear, and wear life data are compiled into a plot matrix and trends are identified. Then, the mechanisms that have been proposed to explain observed trends are summarized. Finally, gaps in the knowledge and opportunities for future work are discussed such that researchers can build on existing studies to enhance the reliability and performance of MoS2-based dry film lubricants in space environments.Graphical abstractSupplementary informationThe online version contains supplementary material available at 10.1007/s11249-025-02052-6

Plant responses to heterogeneous salinity: agronomic relevance and research priorities

BackgroundSoil salinity, in both natural and managed environments, is highly heterogeneous, and understanding how plants respond to this spatiotemporal heterogeneity is increasingly important for sustainable agriculture in the era of global climate change. While the vast majority of research on crop response to salinity utilizes homogeneous saline conditions, a much smaller, but important, effort has been made in the past decade to understand plant molecular and physiological responses to heterogeneous salinity mainly by using split-root studies. These studies have begun to unravel how plants compensate for water/nutrient deprivation and limit salt stress by optimizing root-foraging in the most favourable parts of the soil.ScopeThis paper provides an overview of the patterns of salinity heterogeneity in rain-fed and irrigated systems. We then discuss results from split-root studies and the recent progress in understanding the physiological and molecular mechanisms regulating plant responses to heterogeneous root-zone salinity and nutrient conditions. We focus on mechanisms by which plants (salt/nutrient sensing, root-shoot signalling and water uptake) could optimize the use of less-saline patches within the root-zone, thereby enhancing growth under heterogeneous soil salinity conditions. Finally, we place these findings in the context of defining future research priorities, possible irrigation management and crop breeding opportunities to improve productivity from salt-affected lands

A Survey of the Effects of Nutrient Spatial Distribution under Heterogeneous Rootzone Salinity in Tomato

This thesis explores the broad physiological responses of tomato (Solanum lycopersicum) in solution culture to various spatial potassium (K) distributions under heterogeneous rootzone salinity (NaCl). Chapter 1 is a collaborative review of heterogeneous soil salinity, introducing how management and environment influence salt distribution patterns, and reviews ensuing physiological responses. The review also summarizes the limited research on interactions between heterogeneous salinity and nutrient distribution, particularly split-root experiments, a line of inquiry which this research seeks to enrich. Chapter 2 outlines an original experiment where tomato plants were grown in solution culture with roots evenly divided between two compartments. Except for a salt-free control group (Treatment 0), the same overall amount of salt (NaCl) was either provided to the plant uniformly across the entire root zone (treatment 1) or provided to only one half of the root system (treatments 2, 3, and 4). Treatments 2, 3, and 4 feature an increase in the share of the K budget which is supplemented in the saline compartment compared to the non-saline compartment. Treatment 2 provides nutrients including K to one side and NaCl to the other. Treatments 3 and 4 increase K in the saline compartment to 40% and 80% of the K budget, respectively. The impacts on biomass accumulation, biomass partitioning, water uptake, sodium uptake, and potassium uptake were measured and analyzed for statistical significance. There was no difference in the total biomass, overall water uptake rate, or root distribution between root halves across uniform treatment groups (0 and 1) despite a major difference in overall solution NaCl concentration (0 mM and 20 mM average, respectively). In all treatments where supplemented sodium (40 mM) was confined to half of the root zone (2, 3, and 4), plant water uptake was restricted almost completely to the non-saline compartment demonstrating a remarkable plasticity of root response to local saline conditions. Whole plant water uptake rates were generally comparable irrespective of saline distribution. Saline compartments of treatments 2, 3, and 4 did not show sodium or potassium uptake, regardless of potassium richness. Across all treatments, there was a strong tendency for water, and potassium uptake, as well as root growth, to occur in the Na-free compartment. The only instance of plants utilizing solution K in the presence of NaCl occurred in treatment 1, where K was supplemented along with all other nutrients uniformly in an overall saline root environment. Interestingly, this treatment was also the only clear instance of sodium uptake to occur among any treatment groups. The results of these experiments suggest a salt-avoidant response, whereby the presence of any salt-free and nutrient-rich root zone will result in preferential water uptake from that zone. Research (summarized in Chapter 1) also demonstrates that the provision of a full nutrient supply exclusively to the saline side of a split root system will result in considerable water uptake from the saline compartment and increase whole plant salt uptake. This research was conducted to determine which of the nutrients in the nutrient-rich zone was responsible for plant activity in the saline zone that may otherwise have been avoided. The research performed here demonstrates that the driving dynamic for this plant response is not K alone. The goals of minimizing the incidence of salinity stress and maximizing nutrient use efficiency are inextricable in the agronomic system. Understanding the relationship between nutrient use and salt localization is important if we are to optimize management systems under the heterogeneous ion distributions that are commonplace in irrigated agriculture

Elementary School Teachers' Perception of Agricultural-Related Literature

Throughout the construction of the United States, agriculture and education have been closely intertwined—until recent years. In 1981, agricultural professionals, educators and policy makers noted the decline in standard agricultural curriculum and a need was established for accurate, realistic and representative materials of American agriculture for the classroom. This issue of agricultural literacy has become an imminent concern in today’s agricultural industry. With these rising concerns of agricultural literacy and the future of agriculture as a whole, this study was aimed at measuring and identifying elementary school educators’ perceptions of the current agricultural literature that is available in their classrooms. In order to assess the knowledge and perceptions of the agricultural-related literature in classrooms, a study of kindergarten through fourth grade teachers was performed. This study utilized a descriptive summated scale instrument. This study focused on elementary school teachers’ perceptions of the available agricultural related literature in their classrooms. This study determined the educators’ perceived accuracy of the literature as well as their perceived perceptions of the elementary school students’ knowledge of modern day agriculture. The accuracies and inaccuracies of the literature, how the literature affects the students’ knowledge of agriculture, and if the teachers perceive a need for agricultural literature in their classrooms were also identified through this descriptive survey. This paper explores these perceptions of agricultural-related literature as well as student knowledge of agriculture and makes recommendations for Agriculture in the Classroom programming

Effect of Temperature and Surface Roughness on the Tribological Behavior of Electric Motor Greases for Hybrid Bearing Materials

Greased bearings in electric motors (EMs) are subject to a wide range of operational requirements and corresponding micro-environments. Consequently, greases must function effectively in these conditions. Here, the tribological performance of four market-available EM greases was characterized by measuring friction and wear of silicon nitride sliding on hardened 52100 steel. The EM greases evaluated had similar viscosity grades but different combinations of polyurea or lithium thickener with mineral or synthetic base oil. Measurements were performed at a range of temperature and surface roughness conditions to capture behavior in multiple lubrication regimes. Results enabled direct comparison of market-available products across different application-relevant metrics, and the analysis methods developed can be used as a baseline for future studies of EM grease performance