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Main-shaft bearings are vital safety components in aeroengines made of bearing steels with outstanding combinational properties. The material is supposed to exhibit high surface hardness，high fracture toughness，high temperature resistance，fatigue resistance and corrosion resistance. However，under harsh operation conditions bearing steels are prone to rolling contact fatigue（RCF）that leads to bearing failure，severely endangering flight. Therefore，accurately predicting the RCF lives of bearing steels is key to the reliability of aeroengine. This manuscript reviews important results and progress in the RCF and life prediction of aeroengine bearing steels and suggests future research directions. Firstly，special stress state as a result of the Hertzian contact between rolling element and raceway is introduced，where shear stress components peak at the subsurface.This explains the origin of complexsubsurface-originated RCF mechanisms in bearing steels and indicates subsurface-originated RCF to be an important failure mode of bearing steels under ideal conditions. Meanwhile，with increasing contact pressure，the response of material evolves from elastic mode to plastic mode. Besides，due to the harsh service environment of aero-engine bearings，surface-originated also takes place and hence the competition between these two mechanisms is present. Next，three methodologies for RCF life prediction are summarized，being probabilistic models，mechanistic models and numerical models，with their advantages and limitations analyzed. Probabilistic models are well developed and widely employed by industry，but they are in nature a kind of statistical models without accounting for RCF mechanisms and are hence lacking scientificity; Deterministic models predict RCF life via describing physical processes，which are rich in science but poor in accuracy due to their simplification; numerical models balancing both engineering practice and scientific characteristic is a powerful tool to tackle the problem of RCF life prediction，although their accuracy requires further improvement. Finally，it is suggested that future research may focus on solving key scientific problems in RCF，modifying life prediction models via inserting RCF mechanisms and applying artificial intelligence in RCF life prediction.

It is still crucial to improve the mechanical characteristics of polyvinyl alcohol (PVA) films without resorting to chemical cross-linking. In this study, boric acid (BA) was used to enhance the mechanical characteristics of PVA films while maintaining their excellent transparency and biodegradability. The hydrogen bond interaction between PVA and BA resulted in a 70% increase in tensile strength (from 48.5 to 82.1 MPa) and a 46% increase in elongation at break (from 150 to 220%). To introduce antibacterial properties, polyhexamethylene guanidine hydrochloride (PHMG) was incorporated into PVA/BA composite films resulting in PVA/BA/PHMG composite films. The PVA/BA/PHMG films exhibited 99.99% bacterial inhibition against Escherichia coli and Staphylococcus aureus with negligible leaching of PHMG. The PVA/BA/PHMG films maintained a tensile strength of 75.3 MPa and an elongation at a break of 208%. These improved mechanical and antimicrobial properties make PVA/BA and PVA/BA/PHMG films promising for applications in food and medicinal packaging. [ABSTRACT FROM AUTHOR]

This study identified a new species ( Cercospora polygonatum ) that causes gray leaf spot (GLS) disease in cultivated Polygonatum cyrtonema . This fungal species was isolated from the affected region of GLS on P. cyrtonema leaves. Pathogenicity bioassays were conducted based on Koch's postulates. Morphology was examined based on the features of conidiomata, conidiogenous loci, conidia/conidiophores, and conidiogenous cells. The rDNA internal transcribed spacer region, calmodulin, translation elongation factor 1-alpha, and histone genes were subjected to phylogenetic analysis using the MrBayes tool in Phylosuite. Bootstrap support analysis for phylogenetic placement confirmed the new species, which was significantly different from the closely related species C. senecionis-walkeri and C. zeae-maydis . The morphological characteristics also supported this finding, with the conidiogenous cells of C. polygonatum being considerably shorter than those of C. senecionis-walkeri or C. zeae-maydis . In addition, C. polygonatum was distinguished by its cultural characteristics. As this fungus was isolated from P. cyrtonema , it was named C. polygonatum F.Q. Yin, M. Liu & W.L. Ma, sp. nov. The type specimen (H8-2) was preserved at the China General Microbiological Culture Collection Center. This is the first report of GLS caused by C. polygonatum on P. cyrtonema leaves in China. The current study enriches the knowledge regarding Cercospora sp., contributes to the identification of a species causing GLS in P. cyrtonema , and provides useful information for the effective management of this disease., Competing Interests: The author(s) declare no conflict of interest.

Sclerotinia rot is a serious disease that occurs on Zephyranthes candida . A thorough understanding of the pathogenic fungal species and understanding the biological characteristics are important for controlling sclerotinia . Fungal strains were isolated from the diseased leaves of Z. candida through tissue isolation. Koch's hypothesis screened pathogenic strains by pathogenicity of healthy leaves, including re-isolation and identification. A multigene phylogenetic tree was constructed by extracting genomic DNA from pathogenic strains and measuring the nucleotide sequences at four sites, including the internal transcribed spacer (ITS), RNA polymerase II second largest subunit (RPB2), glyceraldehyde-3-phosphate dehydrogenase (G3PDH), and heat shock protein 60 (HSP60). Morphological characteristics of the fungal structures were evaluated through microscopic analysis. The growth of pathogens was observed and recorded under different pH, different temperatures, different carbon sources and different nitrogen sources to clarify their biological characteristics. Representative strains D7, D13, X4, and X15 infected Z. candida and caused sclerotinia rot. At the beginning of the culture, white flocculent fungal hyphae appeared on the potato dextrose agar (PDA) medium, and black spherical to irregular-shaped sclerotia appeared at the edge of the colony after 7 days. The diameter of the sclerotia was 2.4-8.6 mm and 0.4-0.9 mm, respectively. One sclerotium was able to germinate from 1 to 5 apothecia. Ascus were cylindrical or spindle-shaped, with a size of 110.0-120.0 × 9.2-11.6 μm. One ascus contained eight colorless, oval ascospores, with a size of 8.4-12.0 × 4.5-5.5 μm. Based on the phylogenetic tree constructed with the gene sequences for ITS, G3PDH, HSP60, and RPB2, D7 and D13 shared 99% homology with sclerotinia sclerotiorum , whereas X4 and X15 shared 99% homology with sclerotinia minor . S. sclerotiorum growth was more suitable when the culture temperature was 15°C-25°C, pH 5.0, carbon source was maltose and nitrogen source was yeast powder. S. minor growth was more suitable when the culture temperature was 15°C, pH 5.0, the carbon source was glucose, and the nitrogen source was yeast powder. The results identified the pathogens as S. sclerotiorum and S. minor . To the best of our knowledge, this is the first report of S. sclerotiorum and S. minor causing sclerotinia rot on Z. candida . We herein aimed to identify the causal agent of sclerotinia rot of Z. candida in China based on morphological characteristics, molecular identification, and pathogenicity tests. Performed the experiments on the biological characteristics, to understand the law of disease occurrence. We also evaluated methods for the effective control of this disease. Our findings provide support for further studies on the pathogenesis mechanism of sclerotinia rot., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yin, Song, Liu, Xu, Jiang, Xiao, Guo, Liu, Zhang, Yuan, Ma and Liu.)