ALUMINA-FORMING NANOLAMINATED CARBIDES AND BORIDES

Alumina-forming materials, such as FeCrAl-based alloys, Ni, Co or Fe based superalloys, have been long studied because of their excellent oxidation resistance and promising applications at high temperatures. Recently, alumina forming ceramics (carbides, nitrides and borides) with nanolayered structures, gained a lot of attention as a good candidate material for high temperature applications because of their excellent oxidation resistance, good mechanical properties, and thermal stability at much higher temperatures than alumina forming metallic alloys. Some of the most interesting alumina forming ceramics belongs to families of nanolayered ternary carbides and nitrides with a generalized formula Mvn+1AXvn (n=1,2,3) (MAX), and nanolayered ternary borides with a generalized formula (MB)v2zAvx(MBv2)vy (z = 1-2, x=1-2 and y=0-2) (MAB), with A element being Al. In this dissertation work, alumina-forming mechanism of MAX phases, namely Tiv2AlC is studied. The results of this study indicate that Al deficient of approximately 4% in Tiv2AlC leads to the breakaway oxidation, i.e. formation of Alv2Ov3+TiO2 oxide, instead of protective Al2O3 oxide layer. The outcomes of this study expected to be contributing towards the research and development of advanced Tiv2AlC MAX phase with good oxidation resistance behavior. A thin layer of Tiv2AlC was successfully diffusion bonded onto Ti alloy Ti6242 at 800 °C by Pulsed Electric Current Sintering (PECS) to evaluate feasibility of using Ti2AlC as environmental barrier coating (EBC) for high-temperature Ti-alloys. Crv2AlC is another MAX phase with the potential of forming protective alumina oxide layer when exposed to high temperature in oxidizing environment. The results in this study show that formation of Crv7Cv3 sub-layer can be avoided in Cr2AlC samples free of chromium-carbide impurities or in samples with excess Al. In addition, we have shown that small amounts of impurities in starting Cr powders (such as Fe) as well as absence of Cr7C3 sub-layer leads to the wrinkling of alumina scale and its premature spallation. Although MoAlB has been proposed as good candidate material for high temperature applications because it forms stable and protective alumina oxide layer, its mechanical properties at high temperatures have not been studied in the past. In this study a quasi-static and cyclic compression testing at room and high temperatures were conducted on MoAlB. The results show that MoAlB goes through a brittle-to-plastic transition (BPT) at around 800 °C, similar to that observed in MAX phases. While posttesting microstructural observation showed only a few bends and kinks of individual grains, extensive microcracking was observe

Understanding the Closed-end Fund Puzzle from the Chinese Experience

Although many characteristics of Chinese closed-end funds resemble those of the U.S. funds, investors and environment are different. For example, institutions such as insurance companies hold a substantial amount in closed-end funds, there are no capital gains taxes, and there is no private investment by the funds. These differences allow us find that the discounts are negatively related to liquidity, percentage of stock holdings, and past risk-adjusted performance. Discounts are also positively influenced by the R2 from a market model applied to the underlying asset returns, managerial ownership, and the size of the fund. We further show that “investor overconfidence” and liquidity are major factors that affect the dynamics of discounts

Can Government Environmental Auditing Help to Improve Environmental Quality? Evidence from China

Promoting environmental governance to achieve green and low-carbon development is the focus of attention from all walks of life. As a policy tool to control environmental pollution, the effectiveness of environmental audits remains to be verified. Based on China’s provincial data from 2004 to 2019, this paper aims to examine the impact and mechanisms of government environmental auditing on environmental quality. Results show that government environmental auditing helps to improve overall environmental quality, but there is a certain lag effect occurring. The heterogeneity test suggests that the impact of environmental auditing on comprehensive environmental quality is more significant when the government competition is smaller, the financial situation is better, and the institutional environment is weaker. Our analysis provides empirical evidence for understanding the role and function of government environmental auditing in environmental governance

Can Government Environmental Auditing Help to Improve Environmental Quality? Evidence from China

Promoting environmental governance to achieve green and low-carbon development is the focus of attention from all walks of life. As a policy tool to control environmental pollution, the effectiveness of environmental audits remains to be verified. Based on China’s provincial data from 2004 to 2019, this paper aims to examine the impact and mechanisms of government environmental auditing on environmental quality. Results show that government environmental auditing helps to improve overall environmental quality, but there is a certain lag effect occurring. The heterogeneity test suggests that the impact of environmental auditing on comprehensive environmental quality is more significant when the government competition is smaller, the financial situation is better, and the institutional environment is weaker. Our analysis provides empirical evidence for understanding the role and function of government environmental auditing in environmental governance

Microstructure evolution during oxidation of quinary Ti3(AlSiSn)C2 at high temperatures and induced probable performance

Quinary Ti3Al0.6Si0.2Sn0.2C2 and Ti3Al0.5Si0.4Sn0.1C2 solid solution bulks were synthesized via hot-pressing process. High temperature oxidation behaviors were then investigated over a temperature range of 800–1200 °C. The weight gain per surface area and oxidation layer thickness were measured to study the oxidation kinetics. The as-synthesized compounds with varying solid solution ingredients exhibited comparable oxidation kinetics which fitted a parabolic kinetic better with the oxidation duration of 0–20 h, while it appeared to get more complicated after prolonging the oxidation time. The microstructure evolution and phase compositions of the oxide scales during breakaway oxidation were characterized to illuminate the oxidation mechanism. The oxidation layers exhibited a multi-layer structure resulting from the disparities between the diffusion and migration energies of the multi-elements. Anticipated performance induced by high temperature oxidation was further explored through investigation on the crack self-healing and tribological optimization capacities. It was revealed that cracks could be filled by predominant TiO2 and Al2O3 with a high efficiency at 1000 °C during annealing in air. At 800 °C, Ti3Al0.6Si0.2Sn0.2C2 exhibited self-lubricating properties that was attributed to the formation of smoothing tribo-oxide films, as demonstrated by the increasing oxygen content of the friction surface during sliding

Association of Glutathione s-transferase M1 and T1 gene polymorphisms with the susceptibility to acquired sensorineural hearing loss: a systematic review and meta-analysis

Abstract Acquired sensorineural hearing loss (SNHL), including age-related hearing loss (ARHL), noise-induced hearing loss (NIHL), drug-induced hearing loss (DIHL) and sudden sensorineural hearing loss (SSHL), is one of the most common sensory deficits in humans. Several studies have reported that antioxidant gene glutathione s-transferase M1 and T1 (GST M1 and T1) polymorphisms have a close relationship with the susceptibility to acquired SNHL, but other articles have reported opposite results. This meta-analysis aims to identify whether an association exists between GST M1 and T1 polymorphisms and the susceptibility to acquired SNHL. Seventeen independent studies containing 1749 cases and 2018 controls were included. According to the I2 value of the heterogeneity test, random-effects model was selected to calculate the pooled odds ratios (ORs) with their 95% confidence intervals (95% CIs) and p values. The pooled ORs (95% CI, p-value) of GST M1 and T1 were 1.186(0.955–1.473, p = 0.122) and 1.107(0.841–1.458, p = 1.467), respectively. In addition, subgroup analyses according to the type of SNHL and ethnicity showed no relationship between GST M1 and T1 polymorphisms and the susceptibility to acquired SNHL. Our results suggest that no significant relationship was found between GST M1 and T1 polymorphisms and the susceptibility to acquired SNHL

EMP1 as a Potential Biomarker in Liver Fibrosis: A Bioinformatics Analysis

Liver fibrosis is a wound-healing response to chronic injury, which may result in cirrhosis and liver failure. Studies have been carried on the mechanisms and pathogenesis of liver fibrosis. However, the potential cell-specific expressed marker genes involved in fibrotic processes remain unknown. In this study, we combined a publicly accessible single-cell transcriptome of human liver with microarray datasets to evaluate the cell-specific expression patterns of differentially expressed genes in the liver. We noticed that EMP1 (epithelial membrane protein 1) is significantly active not only in CCl4 (carbon tetrachloride)-treated mouse liver fibrosis but also in BDL (bile duct ligation)-induced liver fibrosis and even in human fibrotic liver tissues such as alcoholic hepatitis, NASH (nonalcoholic steatohepatitis), and advanced stage liver fibrosis. Furthermore, we demonstrated that EMP1 is a specific fibrotic gene expressed in HSCs (hepatic stellate cells) and endothelial cells using the Protein Atlas single-cell transcriptome RNA-sequencing clustering. Its expression was significantly elevated in fibrotic HSCs or CCl4 and NASH-induced fibroblasts. Previous research revealed that EMP1 plays a role in proliferation, migration, metastasis, and tumorigeneses in different cancers via a variety of mechanisms. Because HSC activation and proliferation are two important steps following liver injury, it would be interesting to investigate the role of EMP1 in these processes. All of this information suggested that EMP1 could be used as a novel fibrotic liver marker and a possible target in the future

Effect of texturing on thermal, electric and elastic properties of MoAlB, Fe2AlB2, and Mn2AlB2

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