Dynamic Recrystallization Mechanism and Precipitation Behavior of Mg-6Gd-3Y-3Sm-0.5Zr Alloy During Hot Compression

Hao Pang,Quanan Li,Xiaoya Chen,Peijun Chen,Xiangyu Li,Jinfeng Tan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.2

The effects of temperature and strain on dynamic recrystallization (DRX) and dynamic precipitation of Mg-6Gd-3Y-3Sm-0.5Zr alloy were studied through uniaxial compression. The main conclusions were as follows: the increase of strain ortemperature can promote DRX. The texture strength decreases with the increase of DRX fraction. The pyramidal <a> slipand pyramidal <c + a> slip were activated to coordinate strain when deformed at high-temperature. Under the deformationcondition of T = 400 °C, ̇ = 0.002 s−1 and ε = 0.35, the mechanism of DRX was mainly discontinuous dynamic recrystallization. The rotation continuous dynamic recrystallization gradually becomes the main mechanism with the increase ofstrain and temperature. At the same time, the particle stimulated nucleation (PSN) caused by a single large-sized Mg5(Gd,Y, Sm) or the aggregation of multiple Mg5(Gd, Y, Sm) phases was also found. The dynamic precipitation can stimulate thenucleation of DRX, and the boundary of DRXed grains can become an effective nucleation site for dynamic precipitation. DRX and dynamic precipitation can promote nucleation mutually.

Experiment Study and Finite Element Analysis of Spring Constant of Welded Metal Bellows

Piao, Chang Hao,Cho, Chong Du,Kim, Chang Boo,Pang, Qiang Trans Tech Publications, Ltd. 2006 Key Engineering Materials Vol.326 No.-

<P>This study tries to obtain the spring constant of welded metal bellows through experimental and numerical method respectively. The prediction of spring constant plays a great role in the design and application of the welded metal bellows. To derive the spring constant of the bellows, we employ commercial package to build up 2 axi-symmetric FEM models by using plane 42 and shell 51 elements. In the experiment, we use UTM to measure the spring constant of the bellows. And, the predicted spring constant resulting from the analysis is compared with the experimental one to discuss the rationality of spring constant analysis. The analytical results correspond well with experimental data and hence explaining the validity of FEM model.</P>

Effects of epigallocatechin-3-gallate on bovine oocytes matured in vitro

Huang, Ziqiang,Pang, Yunwei,Hao, Haisheng,Du, Weihua,Zhao, Xueming,Zhu, Huabin Asian Australasian Association of Animal Productio 2018 Animal Bioscience Vol.31 No.9

Objective: Epigallocatechin-3-gallate (EGCG) is a major ingredient of catechin polyphenols and is considered one of the most promising bioactive compounds in green tea because of its strong antioxidant properties. However, the protective role of EGCG in bovine oocyte in vitro maturation (IVM) has not been investigated. Therefore, we aimed to study the effects of EGCG on IVM of bovine oocytes. Methods: Bovine oocytes were treated with different concentrations of EGCG (0, 25, 50, 100, and $200{\mu}M$), and the nuclear and cytoplasmic maturation, cumulus cell expansion, intracellular reactive oxygen species (ROS) levels, total antioxidant capacity, the early apoptosis and the developmental competence of in vitro fertilized embryos were measured. The mRNA abundances of antioxidant genes (nuclear factor erythriod-2 related factor 2 [NRF2], superoxide dismutase 1 [SOD1], catalase [CAT], and glutathione peroxidase 4 [GPX4]) in matured bovine oocytes were also quantified. Results: Nuclear maturation which is characterized by first polar body extrusion, and cytoplasmic maturation characterized by peripheral and cortical distribution of cortical granules and homogeneous mitochondrial distribution were significantly improved in the $50{\mu}M$ EGCG-treated group compared with the control group. Adding $50{\mu}M$ EGCG to the maturation medium significantly increased the cumulus cell expansion index and upregulated the mRNA levels of cumulus cell expansion-related genes (hyaluronan synthase 2, tumor necrosis factor alpha induced protein 6, pentraxin 3, and prostaglandin 2). Both the intracellular ROS level and the early apoptotic rate of matured oocytes were significantly decreased in the $50{\mu}M$ EGCG group, and the total antioxidant ability was markedly enhanced. Additionally, both the cleavage and blastocyst rates were significantly higher in the $50{\mu}M$ EGCG-treated oocytes after in vitro fertilization than in the control oocytes. The mRNA abundance of NRF2, SOD1, CAT, and GPX4 were significantly increased in the $50{\mu}M$ EGCG-treated oocytes. Conclusion: In conclusion, $50{\mu}M$ EGCG can improve the bovine oocyte maturation, and the protective role of EGCG may be correlated with its antioxidative property.

Detrimental effects of lipopolysaccharides on maturation of bovine oocytes

Shanjiang Zhao,Yunwei Pang,Xueming Zhao,Weihua Du,Haisheng Hao,Huabin Zhu 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.8

Objective: Gram-negative bacteria lipopolysaccharide (LPS) has been reported to be associated with uterine impairment, embryonic resorption, ovarian dysfunction, and follicle retardation. Here, we aimed to investigate the toxic effects of LPS on the maturation ability and parthenogenetic developmental competence of bovine oocytes. Methods: First, we developed an in vitro model to study the response of bovine cumulus-oocyte complexes (COCs) to LPS stress. After incubating germinal vesicle COCs in 10 μg/mL of LPS, we analyzed the following three aspects: the expression levels of the LPS receptor toll-like receptor 4 (TLR4) in COCs, activities of intracellular signaling protein p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-kappa B (NF-κB); and the concentrations of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6. Furthermore, we determined the effects of LPS on the maturation ability and parthenogenetic developmental competence of bovine oocytes. Results: The results revealed that LPS treatment significantly elevated TLR4 mRNA and protein expression levels in COCs. Exposure of COCs to LPS also resulted in a marked increase in activity of the intracellular signaling protein p-p38 MAPK and NF-κB. Furthermore, oocytes cultured in maturation medium containing LPS had significantly higher concentrations of the proinflammatory cytokines IL-1β, TNF-α, and IL-6. LPS exposure significantly decreased the first polar body extrusion rate. The cytoplasmic maturation, characterized by polar body extrusion and distribution of peripheral cortical granules, was significantly impaired in LPS-treated oocytes. Moreover, LPS exposure significantly increased intracellular reactive oxygen species levels and the relative mRNA abundance of the antioxidants thioredoxin (Trx), Trx2, and peroxiredoxin 1 in oocytes. Moreover, the early apoptotic rate and the release of cytochrome C were significantly increased in response to LPS. The cleavage, morula, and blastocyst formation rates were significantly lower in parthenogenetically activated oocytes exposed to LPS, while the incidence of apoptotic nuclei in blastocysts was significantly increased. Conclusion: Together, these results provide an underlying mechanism by which LPS impairs maturation potential in bovine oocytes.

Mechanical Properties of (Ce + Yb) Modified in situ TiB2/Al-Si Matrix Composites Enhanced via Thermal Deformation Combined with Heat Treatment

Mingkun Qiu,Wenru Hu,Hao Liu,Yafei Pang,Xiaodong Du 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10

In the current work, the microstructure evolution and mechanical properties of (Ce + Yb) modified in situ TiB2/Al-Si matrix composite were systematically investigated by thermal deformation at strain rates of 0.0005–0.0125 s− 1 and temperatures of 250–450 °C. The enhanced strength and plasticity of the composite have a good correlation with the microstructure evolution under different thermal deformation parameters. The obtained results indicated that under the hot deformation parameters of strain rate of 0.0025 s− 1 and deformation temperature of 250 °C, the defects of micropores can be reduced or even eliminated and improved the density of the composite. The coarse α-Al grains, eutectic Si and Fe-rich phases and undissolved primary (Ce + Yb)-containing intermetallics were significantly refined under high shear stress. At the same time, the distribution of in-situ synthesized submicron TiB2 particles in the Al matrix tends to be more uniform. The substructures such as high density dislocations and low angle grain boundaries were introduced under the thermal deformation of 250 °C/0.0025 s− 1, which provided the necessary conditions for the formation of recrystallized grains that are less likely to overgrow and further promoted the aging precipitation of nano-strengthening precipitates. Finally, the UTS, YS and elongation of the composite reached the maximum values of 385 MPa, 316 MPa and 9.6% respectively, which were 60.4%, 85.9% and 45.5% higher than the as-cast and undeformed composite.

Expression and tissue distribution analysis of vimentin and transthyretin proteins associated with coat colors in sheep (Ovis aries)

Yin Zhihong,Ma Zhisheng,Wang Siting,Hao Shitong,Liu Xinyou,Pang Quanhai,Wang Xinzhuang 아세아·태평양축산학회 2023 Animal Bioscience Vol.36 No.9

Objective: Pigment production and distribution are controlled through multiple proteins, resulting in different coat color phenotypes of sheep. Methods: The expression distribution of vimentin (VIM) and transthyretin (TTR) in white and black sheep skins was detected by liquid chromatography–electrospray ionization tandem MS (LC–ESI–MS/MS), gene ontology (GO) statistics, immunohistochemistry, Western blot, and quantitative real time polymerase chain reaction (qRT-PCR) to evaluate their role in the coat color formation of sheep. Results: LC–ESI–MS/MS results showed VIM and TTR proteins in white and black skin tissues of sheep. Meanwhile, GO functional annotation analysis suggested that VIM and TTR proteins were mainly concentrated in cellular components and biological process, respectively. Further research confirmed that VIM and TTR proteins were expressed at significantly higher levels in black sheep skins than in white sheep skins by Western blot, respectively. Immunohistochemistry notably detected VIM and TTR in hair follicle, dermal papilla, and outer root sheath of white and black sheep skins. qRT-PCR results also revealed that the expression of VIM and TTR mRNAs was higher in black sheep skins than in white sheep skins. Conclusion: The expression of VIM and TTR were higher in black sheep skins than in white sheep skins and the transcription and translation were unanimous in this study. VIM and TTR proteins were expressed in hair follicles of white and black sheep skins. These results suggested that VIM and TTR were involved in the coat color formation of sheep.

Microstructure and Performance Study of Al/Cu Laser Welding with Ag Interlayer

Tao Chen,Fei Liu,Lihui Pang,Hao Hu,Ping Gao 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.1

In the past research, there was a gap in the field of Al/Cu dissimilar metal welding with Ag intermediate layer, and attention to the joint resistivity is insufficient. This paper has used laser welding to study this problem. The mechanical and electrical properties of the joints were tested, and the microstructure and fracture surface of the weld were observed, along with the analysis of their phase composition and formation mechanism. The results show that the Ag–Al–Cu ternary system forms on the weld, and Ag inhibits the formation of IMC in the Al/Cu system, with the main IMCs being Al2Cu and Ag3Al. Part of the Ag-rich and Al-rich phases are dispersed in small particle shape, providing a strengthening effect in various areas. After adjusting the welding parameters, excellent joints can be obtained, with a tensile strength of 98.05 MPa, which is 78.5% of the base metal, and a resistivity of 2.47 μΩ cm. The fracture occurs in the softened zone of the Al-side base metal, indicating a ductile fracture. These findings have demonstrated that good mechanical and electrical properties can be obtained by adding Ag as an intermediate layer of the joint.

A recent trend: application of graphene in catalysis

Yuxin Yan,Woo In Shin,Hao Chen,Shar‑Mun Lee,Sivakumar Manickam,Svenja Hanson,Haitao Zhao,Edward Lester,Tao Wu,Cheng Heng Pang 한국탄소학회 2021 Carbon Letters Vol.31 No.2

Abstract Graphene, an allotrope of carbon in 2D structure, has revolutionised research, development and application in various disciplines since its successful isolation 16 years ago. The single layer of sp2-hybridised carbon atoms brings with it a string of unrivalled characteristics at a fraction of the price of its competitors, including platinum, gold and silver. More recently, there has been a growing trend in the application of graphene in catalysis, either as metal-free catalysts, composite catalysts or as catalyst supports. The unique and extraordinary properties of graphene have rendered it useful in increasing the reactivity and selectivity of some reactions. Owing to its large surface area, outstanding adsorptivity and high compatibility with various functional groups, graphene is able to provide a whole new level of possibilities and flexibilities to design and synthesise fit-for-purpose graphene-based catalysts for specific applications. This review is focussed on the progress, mechanisms and challenges of graphene application in four main reactions, i.e., oxygen reduction reaction, water splitting, water treatment and Fischer–Tropsch synthesis. This review also summarises the advantages and drawbacks of graphene over other commonly used catalysts. Given the inherent nature of graphene, coupled with its recent accelerated advancement in the synthesis and modification processes, it is anticipated that the application of graphene in catalysis will grow exponentially from its current stage of infancy.

Serum Zinc Status and Helicobacter Pylori Infection in Gastric Disease Patients

Zhang, Wen-Hua,Wu, Xiao-Jing,Niu, Jing-Xiu,Yan, Hao,Wang, Xin-Zhuo,Yin, Xiao-Dong,Pang, Yan Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.10

The role of Helicobacter pylori status and serum zinc value in gastric disease patients and healthy controls were investigated. Cases used in this work were 45 gastric cancer patients, 44 with peptic ulcers, 52 suffering gastritis and 64 healthy controls, all diagnosed histologically with the controls undergoing medical checkups. Helicobacter pylori status and serum levels of Zn were determined by 13C-urea breath test and flame atomic absorption spectrophotometer, respectively. Our study showed that Helicobacter pylori infection has no change in gastritis, peptic ulcer and gastric cancer group, on the contrast, serum levels of Zn were significantly reduced in gastritis, peptic ulcer and gastric cancer group, compared with healthy controls, and the higher the Zn levels are, the more increased risk of gastric cancer. Helicobacter pylori infection is a cause of gastritis, peptic ulcers and even gastric cancer, while serum zinc level is an indicator of protection of gastric membranes against damage.

Carbon Nanotube Paper as Anode for Flexible Lithium-Ion Battery

Xiaogang Sun,Zhenhong Liu,Neng Li,Xiaoyong Wu,Yanyan Nie,Zhipeng Pang,Lifu Yue,Hao Tang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.11

In this investigation, multiwalled carbon nanotube (MWCNT) paper consists of MWCNTs and cellulose was fabricated by traditional paper-making method. It was applied directly as negative electrode in flexible lithium ion battery to replace ordinary electrode which is combined with anode material and current collector. The electrochemical performances of the as-produced MWCNT paper (AMP) and carbonized MWCNT paper (CMP) were evaluated in this study. The morphology and structure of the MWCNT papers were observed by scanning electron microscopy (SEM). The electrochemical performance of the battery was operated by cell test and electrochemical impedance spectroscopy (EIS) measurement. The charging and discharging results indicated that the CMP behaves with higher capacity than AMP. And the EIS analysis showed that a lower charge transfer resistance can be obtained in the CMP. The excellent electrochemical performance verifies the feasibility of MWCNT papers as a promising candidate for the anode in flexible lithium ion battery.