Shotgun metagenomics of dust microbiome from flight deck and cabin in civil aviation aircraft

Microbial exposure is related to the health of passengers on commercial aircraft, but no studies characterized the microbial composition at the species level and identified their ecological determinants. We collected vacuum dust from floor and seat surfaces in flight decks and cabins of 18 aircraft, and amplification-free shotgun metagenomics was conducted to characterize the microbial composition. In total, 7437 microbial taxa were identified. The relative abundance for bacteria, eukaryote, viruses, and archaea was 96.9%, 1.8%, 0.3%, and 0.03%, respectively. The top bacterial species mainly derived from outdoor air and human skin included Sphingomonas, Corynebacterium, Micrococcus luteus, Variovorax paradoxus, Paracoccus dentrificans, and Propionibacterium acnes. The abundance of NIAID-defined pathogens was low, accounted for only 0.23% of total microbes. The microbial species and functional composition were structured by the indoor surface type (R² = 0.38, Adonis), followed by the manufacturer of the aircraft (R² = 0.12) and flight duration (R² = 0.07). Indoor surfaces affected species derived from different habitats; the abundance of dry skin and desiccated species was higher on textile surfaces, whereas the abundance of moist and oily skin species was higher on leather surfaces. The growth rates for most microbes were stopped and almost stopped.     

Generation of Cochlear Hair Cells from Sox2 Positive Supporting Cells via DNA Demethylation

Regeneration of auditory hair cells in adult mammals is challenging. It is also difficult to track the sources of regenerated hair cells, especially in vivo. Previous paper found newly generated hair cells in deafened mouse by injecting a DNA methyltransferase inhibitor 5-azacytidine into the inner ear. This paper aims to investigate the cell sources of new hair cells. Transgenic mice with enhanced green fluorescent protein (EGFP) expression controlled by the Sox2 gene were used in the study. A combination of kanamycin and furosemide was applied to deafen adult mice, which received 4 mM 5-azacytidine injection into the inner ear three days later. Mice were followed for 3, 5, 7 and 14 days after surgery to track hair cell regeneration. Immunostaining of Myosin VIIa and EGFP signals were used to track the fate of Sox2-expressing supporting cells. The results show that (i) expression of EGFP in the transgenic mice colocalized the supporting cells in the organ of Corti, and (ii) the cell source of regenerated hair cells following 5-azacytidine treatment may be supporting cells during 5–7 days post 5-azacytidine injection. In conclusion, 5-azacytidine may promote the conversion of supporting cells to hair cells in chemically deafened adult mice.     

Temporal Changes of Phospholipids Fatty Acids and Cholesterol in Breast Milk and Relationship with Diet

Phospholipids (PLs) and cholesterol in human milk (HM) are affected by lactation, and differential lipids are closely related to maternal diet. The contents of PLs and cholesterol in Chinese HM are quantified by gas chromatography and high performance liquid chromatography, respectively, and the relationship between differential lipids and the maternal diet is obtained by Pearson. The result shows that SFA, MUFA, and polyunsaturated fatty acid (PUFA) are not affected by lactation and geography for total fatty acids, but almost all sn‐2 fatty acids are influenced by geography and remain unchanged during lactation. Most SFAs show absolute sn‐2 selectivity and the majority of MUFAs and PUFAs are esterified at the sn‐1 position. Cholesterol (13.8–22.6 mg per 100 g milk) and 25‐hydroxycholesterol (0.45–1.01 mg per 100 g milk) increase significantly and remain constant during lactation, respectively, and they are affected by regions. In addition, the differential lipids (22:1n‐9, C9:0, trans‐PUFA, 22:4n‐6, etc.) of PLs are closely related to the maternal diet. PLs and cholesterol content differ from western research and infant formula, which will help to design an infant formula that is more suitable for Chinese babies in the future. Practical Application: Compared with PLs and cholesterol in western countries and infant formula, the specificity of Chinese HM can more accurately target the development of formulas suitable for the growth of Chinese infants. At the same time, according to the influence of the mother?s diet on the composition of HM, it is more reasonable to guide the diet of the mother.     

Formation of a protective layer against corrosion on Mg alloy via alkali pretreatment followed by vanillic acid treatment

Although Mg alloy possesses high specific strength, low density, and good biocompatibility, poor corrosion resistance hinders its further applications. In the present study, an innovative protective layer against corrosion was prepared on the AZ31 Mg alloy via alkali pretreatment followed by vanillic acid treatment. The alkali pretreatment supplied –OH for the AZ31 Mg alloy surface to react with vanillic acid. The vanillic acid treatment played a crucial role in enhancing the corrosion resistance due to the excellent ability to act as a barrier and retard aqueous solution penetration, which effectively isolated the underlying Mg alloy from the corrosive environment. The corrosion current density of alkali and vanillic acid-treated Mg alloy (AZ31V) almost showed two orders of magnitude lower values in comparison with that of the AZ31 Mg alloy, and the corrosion potential of AZ31V Mg alloy increased from −1.41 to −1.25 V. The immersion tests proved that there was no occurrence of severe corrosion. Hence, the alkali pretreatment and vanillic acid treatment may represent a promising method to improve the corrosion resistance of Mg alloy.     

A study of external surface pressure effects on the properties for lithium-ion pouch cells

Lithium-ion pouch cells are widely used in electric vehicles because of their high energy density than other structures. There is an unavoidable external surface pressure between the cells in the process of packing and driving of electric vehicles. The influence of external surface pressure on the main properties of the lithium-ion pouch cell has been studied, which is of great significance to packing batteries and reusing retired cells. In this study, a testing device applied for the measurement of constant external surface pressures of lithium-ion pouch cells was first proposed and the different pressure stress-strain distribution on the external surface of cells under semirigid material pads were analyzed by simulation. The effects of pressure on the capacity, internal resistance, and open circuit voltage of fresh and aged LiNi_xCo_yMn_zO₂ (NCM) lithium-ion pouch cells are analyzed through experiments under 1 Mpa external surface pressure. The results show that the internal resistance of fresh cells tends to decrease. The average percentage of the maximum reduction of internal resistance is 13.28%. The experiments also demonstrate that the capacity of aging cells increased by 2.3%. Irreversibility of capacity improvement indicates applying appropriate external surface pressure can improve the secondary utilization efficiency of aging cells.     

A coke deposition self-removal TBCC thermal management with multi-catalyst coating

How to mitigate coke and improve heat sink is the critical factor for thermal management system of turbine-based combined cycle (TBCC). A novel thermal management method using multi-stage coating structure to mitigate coke and improve heat sink is developed in this study. The multi-stage coating structure includes catalytic steam reforming (CSR) and catalytic steam gasification (CSG) catalyst coatings. Coke is removed by CSG, which provides coke self-removal. In addition, the CSG is a strong endothermic reaction, which enables the increase of the chemical heat sink. The numerical study for the multi-stage coating structure was conducted using a heated channel. Results indicate that the multi-stage coating structure can reduce coke by 50% and increase chemical heat sink by 50%, when the mass ratio of secondary steam injection is 2%. In addition, it is found by a comparative study that the increase of secondary steam addition is helpful to remove coke and increase chemical heat sink. Both coke production and chemical heat sink are significantly affected by the rate distribution of CSG. The optimal performance of multi-stage coating structure can be obtained by properly regulating rate distribution of CSG.