The high-temperature gas-cooled reactor (HTGR), as a preferred reactor type for Generation IV nuclear energy systems, widely employs nuclear-grade graphite in its core as the moderator, structural material, and matrix of fuel elements. The friction coefficient between graphite components and the contact stiffness of spherical fuel elements directly affect the structural integrity of the core, the flow characteristics of the pebble bed, and the design of the fuel handling system, serving as critical mechanical parameters for ensuring reactor safety and economic operation. This paper systematically reviews the preparation processes and multi-scale microstructural features of nuclear graphite for HTGRs and summarizes the current research status in two directions: the friction coefficient and the contact stiffness of nuclear graphite. In the field of tribology, the influencing mechanisms of intrinsic factors such as grain size and porosity, as well as extrinsic factors such as ambient atmosphere, temperature, load, and sliding velocity, on the friction behavior of graphite are analyzed with emphasis. The controversies and applicable conditions of the surface energy mechanism and the dangling bond mechanism are discussed. In terms of contact mechanics, the development of asperity models from the Hertz contact and Abbott-Firestone (AF) model to the Kogut-Etsion finite-element based fitting is summarized, along with the evolution from the Greenwood-Williamson (GW) statistical model to the Majumdar-Bhushan (MB) fractal contact model. Experimental methods for measuring stiffness coefficients—namely, the interface displacement method, the impact method, and the acoustic method—are reviewed. On this basis, the severe scarcity of nuclear graphite mechanical data under in-core conditions, such as high temperatures and inert atmospheres, is highlighted. Two systematic experimental works dedicated to graphite materials for HTGRs are integrated: the first measurements of the static and dynamic friction coefficients of isostatically pressed nuclear graphite BG80 in a high-purity helium environment from 25 to 1300 °C, revealing a four-stage variation of the friction coefficient with temperature; and the first acquisition of the temperature dependence and irreversible evolution characteristics of the stiffness coefficient of spherical fuel elements in high temperature helium. These works fill the gaps in fundamental data and can provide quantitative parameter inputs and theoretical support for HTGR core design, pebble-bed flow simulations, and safety analyses.
Genotype × environment (G×E) interactions complicate the identification of stable, high-performing genotypes in plant breeding, particularly under increasing climate variability and water scarcity. To support the development of water-efficient rice cultivars, we evaluated 28 mutant lines derived from the cultivar BRS Pampeira under two irrigation regimes: continuous flooding and alternate wetting and drying (AWD). Agronomic traits were assessed using mixed models (REML/BLUP) to estimate genotypic values, while principal component analysis (PCA) and the multi-trait genotype–ideotype distance index (MGIDI) were used to support genotype selection. Significant G×E interactions were observed for yield-related traits, demonstrating differential responses to irrigation regimes. The MGIDI index identified superior genotypes according to selection scenarios, with m189 showing recurrence under both individual scenarios, m699 selected under AWD and in the multi-environment analysis, and m301 and BRS Pampeira selected under Control and multi-environment conditions. Under AWD, m269 was selected as a promising genotype due to its proximity to the ideotype and balanced multi-trait performance. These findings highlight substantial genetic variability among mutant lines and provide promising candidates for improving rice productivity and adaptation under water-limited production systems.
Preliminary observations show that scab-like symptoms are present in pecan orchards in southern Chihuahua, Mexico. However, its presence has gone unnoticed by growers, who attribute the damage to zinc deficiencies. This disease can cause significant damage to trees and may represent a potential risk for pecan production. Two fungi were frequently isolated from the affected trees, Cladosporium-like fungus and Alternaria-like fungus, making it urgent to identify them using molecular techniques. The role of these fungi in the development of the disease—which commonly is attributed to Cladosporium spp.—should be determined through pathogenicity tests. The incidence and severity of the disease across the various growing regions must be assessed, and crop losses must be calculated. Research into disease epidemiology is also important for developing integrated management strategies that emphasize biological control and predictive systems.
An exploratory study of rural mountain regions in Scotland and North Carolina used a matched-pair multiple case design to consider rural and small-town community planning and local governance, and to understand and compare perceived assets and strengths as well as challenges facing communities in these two regions. Key informants who sat for interviews included planning and related professionals, community leaders, and anonymous residents in 12 towns, revealing some consistent themes and distinctive differences across regions and roles. Notably, housing, employment, access to services, and traffic congestion and parking were universal concerns in these rural and small-town settings, while self-sufficiency, community identity, and attachment to the rural landscape were dominant positive themes. The commonly reported challenges (housing, employment, congestion) are often framed as urban problems—but clearly afflict these rural and small-town settlements.
