Microstructure-sensitive modeling of competing failure mode between surface and internal nucleation in high cycle fatigue

Competing fatigue failure between the surface and internal nucleation has been widely observed in metals under the high cycle fatigue regime. To characterize different boundary conditions in surface and internal grain aggregates, a hybrid statistical volume element model was developed by binding two identical periodic stochastic polycrystal microstructure cubes together and superimposing them with a new 2.5 directional periodic boundary condition afterwards. Additional isotropic elastic media was attached on the surface of the hybrid statistical volume element model to represent the oxide layer formed at elevated temperature. Microstructure-sensitive modeling with a crystal plasticity model was implemented by computing multiple hybrid statistical volume elements under two stress levels. The results implied that grains in the surface volume of the hybrid statistical volume element generally tended to deform more easily than their counterparts in the internal one, and the oxide layer had a weak effect in suppressing the surface deformation. It was also demonstrated that the combination of the 2.5 directional periodic boundary condition, additional oxide layer and nonlinear constitutive model jointly brought stochastic effect into the two identical microstructural cubes. Significant competition between the surface and internal nucleation was captured under both stress levels. Since the detrimental influence of oxidation in accelerating crack formation was not considered, the lifetimes from both types of nucleation were overlaid on each other. Given the disruption of the oxide layer under high stress levels, the simulation reproduced the experimental discovery that the probability of surface nucleation increases with the ascending stress level. It is also clarified that the oxide layer cannot prevent surface nucleation under low stress levels, rejecting the hypothesis of the impact of the oxide layer on complete internal nucleation

Rice, wheat, and corn supply response in China

This study analyses the indica rice, winter wheat, and corn production response to prices, rainfall, temperatures, and other parameters for the agriculturally most important provinces in China. System and difference GMM estimators are used as the number of groups is large compared to the time periods and the production response is a dynamic process. We find that all crops strongly respond to prices around planting time and shortly after while prices further away from the time of planting turn out insignificant. Furthermore, rainfall affects the production positively and high temperatures negatively for all crops. The results for other variables differ between the crops. Mixed outcomes are found for irrigation, fertilizer prices, area affected by droughts and interaction terms. Results suggest that irrigation is only partly able to compensate for impacts of weather variability. The presented method for analyzing the price response at different points in time may also be used for general model specification tests

Recent Discovery of Nitrogen Heterocycles from Marine-Derived <i>Aspergillus</i> Species

Nitrogen heterocycles have drawn considerable attention because of their structurally novel and significant biological activities. Marine-derived fungi, especially the Aspergillus species, possess unique metabolic pathways to produce secondary metabolites with novel structures and potent biological activities. This review prioritizes the structural diversity and biological activities of nitrogen heterocycles that are produced by marine-derived Aspergillus species from January 2019 to January 2024, and their relevant biological activities. A total of 306 new nitrogen heterocycles, including seven major categories—indole alkaloids, diketopiperazine alkaloids, quinazoline alkaloids, isoquinoline alkaloids pyrrolidine alkaloids, cyclopeptide alkaloids, and other heterocyclic alkaloids—are presented in this review. Among these nitrogen heterocycles, 52 compounds had novel skeleton structures. Remarkably, 103 compounds showed various biological activities, such as cytotoxic, antimicrobial, anti-inflammatory, antifungal, anti-virus, and enzyme-inhibitory activities, and 21 compounds showed potent activities. This paper will guide further investigations into the structural diversity and biological activities of nitrogen heterocycles derived from the Aspergillus species and their potential contributions to the future development of new natural drug products in the medicinal and agricultural fields

Fused in sarcoma (FUS) inhibits milk production efficiency in mammals

Abstract Efficient milk production in mammals confers evolutionary advantages by facilitating the transmission of energy from mother to offspring. However, the regulatory mechanism responsible for the gradual establishment of milk production efficiency in mammals, from marsupials to eutherians, remains elusive. Here, we find that mammary gland of the marsupial sugar glider contained milk components during adolescence, and that mammary gland development is less dynamically cyclic compared to that in placental mammals. Furthermore, fused in sarcoma (FUS) is found to be partially responsible for this establishment of low efficiency. In mouse model, FUS inhibit mammary epithelial cell differentiation through the cyclin-dependent kinase inhibitor p57Kip2, leading to lactation failure and pup starvation. Clinically, FUS levels are negatively correlated with milk production in lactating women. Overall, our results shed light on FUS as a negative regulator of milk production, providing a potential mechanism for the establishment of milk production from marsupial to eutherian mammals