Critical Quenching Rate for High Hardness and Good Exfoliation Corrosion Resistance of Al-Zn-Mg-Cu Alloy Plate

Dongfeng Li,Bangwen Yin,Yue Lei,Shengdan Liu,Yunlai Deng,Xinming Zhang 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.2

By means of the end-quenching technique, we investigated the relationship between quenching rate and hardness as well as exfoliation corrosion rating for Al-2.21 Zn-3.59 Mg-0.45 Cu-0.038 Zr (at%) alloy plate. In order to achieve an exfoliation corrosion rating of P or EA, the quenching rate must be greater than approximately 460 °C/min and 300 °C/min, respectively, and the drop degree in hardness should simultaneously be lower than approximately 2.0% and 3.5%, respectively. The results of microstructural and microchemical examination using a scanning transmission electron microscope indicate that a lower quenching rate leads to a higher content of Zn, Mg, and Cu in the grain-boundary particles and a greater width of precipitate-free zones near grain boundaries; therefore, grain-boundary particles with Zn and Mg contents less than approximately 13.39% and 10.23% (at%), respectively, and precipitate-free zones near grain boundaries with widths less than about 107 nm can contribute to an exfoliation corrosion rating better than EA. The amount of quench-induced η- phase particles, which lead to lower hardness, increases with decreasing quenching rate, and the area fraction of these particles is approximately 2.9% at a quenching rate of 300 °C/min.

Precipitation Behavior in Al-Zn-Mg-Cu Alloy After Direct Quenching

Shengdan Liu,Chengbo Li,Yunlai Deng,Xinming Zhang,Qiming Zhong 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.2

The precipitation behavior in an Al-6.8Zn-1.9Mg-1.0Cu-0.12Zr alloy after direct quenching from solutionheat treatment temperature of 470 °C to 205-355 °C was investigated by means of hardness tests, electricalconductivity tests, and transmission electron microscopy. At temperatures below 265 °C, the hardnessincreased gradually to a peak value and then decreased rapidly with time. At 265 °C, the hardness wasalmost unchanged within the initial 2000 s and then decreased gradually. At higher temperatures, the hardnessdecreased slowly with time. The electrical conductivity started to increase after a certain period oftime and then tended to maintain a constant value at all temperatures. Microstructure examination indicatedheterogeneous precipitation of the η phase at grain boundaries and inside grains during holding at205 °C and 325 °C. Based on the electrical conductivity data, the precipitation kinetics could be describedquite well by the Johnson-Mehl-Avrami-Komolgorov relationship with a n value varying between 0.78 and1.33. The activation energy was estimated to be about 44.9 kJ/mol, which is close to that expected for a dislocationdiffusion mechanism. Time-temperature-transformation diagrams were constructed and the nosetemperature ranged from 295 °C to 325 °C.

Upregulation of miR-20b Protects Against Cerebral Ischemic Stroke by Targeting Thioredoxin Interacting Protein (TXNIP)

Dejiang Yang,Yu Tan,Huanhuan Li,Xiaowei Zhang,Xinming Li,Feng Zhou 한국뇌신경과학회 2021 Experimental Neurobiology Vol.30 No.2

Dysregulation of microRNAs (miRNAs) is involved in abnormal development and pathophysiology in the brain. Although miR-20b plays essential roles in various human diseases, its function in cerebral ischemic stroke remains unclear. A cell model of oxygen glucose deprivation/reoxygenation (OGD/R) and A rat model of middle cerebral artery occlusion/reperfusion (MCAO/R) were constructed. qRT-PCR and western blot were used to evaluate the expression of miR-20b and TXNIP. Cell viability was detected by MTT assay, and cell apoptosis was evaluated by flow cytometry. Targetscan and Starbase were used to predict the potential targets of miR-20b. Luciferase reporter assay was applied to determine the interaction between miR-20b and TXNIP. Rescue experiments were conducted to confirm the functions of miR-20b/TXNIP axis in cerebral ischemic stroke. MiR-20b was significantly downregulated after I/R both in vitro and in vivo. Upregulation of miR-20b inhibited OGD/R-induced neurons apoptosis and attenuated ischemic brain injury in rat model. Bioinformatic prediction suggested that TXNIP might be a target of miR-20b, and luciferase reporter assay revealed that miR-20b negatively regulated TXNIP expression by directly binding to the 3’-UTR of TXNIP. Downregulation of TXNIP inhibited OGD/R-induced neurons apoptosis in vitro and ischemic brain injury in vivo. Rescue experiments indicated that downregulation of TXNIP effectively reversed the effect of miR-20b inhibitor in neurons apoptosis after OGD/R-treatment and ischemic brain injury in a mouse model after MCAO/R-treatment. Our study demonstrated that upregulation of miR-20b protected the brain from ischemic brain injury by targeting TXNIP, extending our understanding of miRNAs in cerebral ischemic stroke

Emerging Biomaterials for Tumor Immunotherapy

Minna Xiao,Qinglai Tang,Shiying Zeng,Qian Yang,Xinming Yang,Xinying Tong,Gangcai Zhu,Lanjie Lei,Shisheng Li 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background The immune system interacts with cancer cells in various intricate ways that can protect the individual from overproliferation of cancer cells; however, these interactions can also lead to malignancy. There has been a dramatic increase in the application of cancer immunotherapy in the last decade. However, low immunogenicity, poor specificity, weak presentation efficiency, and off-target side effects still limit its widespread application. Fortunately, advanced biomaterials effectively contribute immunotherapy and play an important role in cancer treatment, making it a research hotspot in the biomedical field. Main body This review discusses immunotherapies and the development of related biomaterials for application in the field. The review first summarizes the various types of tumor immunotherapy applicable in clinical practice as well as their underlying mechanisms. Further, it focuses on the types of biomaterials applied in immunotherapy and related research on metal nanomaterials, silicon nanoparticles, carbon nanotubes, polymer nanoparticles, and cell membrane nanocarriers. Moreover, we introduce the preparation and processing technologies of these biomaterials (liposomes, microspheres, microneedles, and hydrogels) and summarize their mechanisms when applied to tumor immunotherapy. Finally, we discuss future advancements and shortcomings related to the application of biomaterials in tumor immunotherapy. Conclusion Research on biomaterial-based tumor immunotherapy is booming; however, several challenges remain to be overcome to transition from experimental research to clinical application. Biomaterials have been optimized continuously and nanotechnology has achieved continuous progression, ensuring the development of more efficient biomaterials, thereby providing a platform and opportunity for breakthroughs in tumor immunotherapy.

Analysis of Undrained Shear Characteristics and Structural Damage of Granite Residual Soil

Song Yin,Pengfei Liu,Pan Yan,Xianwei Zhang,Xinming Li 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9

Three-dimensional consolidation testing, scanning electron microscopy, and undrained triaxial testing of granite residual soil (GRS) in Shenzhen, China, were conducted. The effect of the structural strength of GRS was quantitatively analyzed using the method of comprehensive structure potential parameter description. The failure strength ratio of the soil decreases with increasing confining pressure, and it is approximately 1 when the confining pressure is higher than the yield stress (σs). The undrained shear strength (Su) of the undisturbed soil varies in stages with confining pressure σ3. The relationship between Su and σ3 for the reconstituted soil is approximated as a straight line through the origin. The soil’s comprehensive structure potential parameters (the structural contribution rates of the tangential shear modulus, mE, and the deviatoric stress, md) decrease linearly with increasing σ3. The mE and md sample values are similar under the same confining pressure. It is reasonable to use structure potential parameters to quantitatively evaluate the structure contribution rate of GRS. The microstructure is constantly adjusted, and the soil microstructure form for different confining pressures strongly correlates with its shear characteristics.

Efficient Synthesis of Long-wavelength Absorbing Cyanochlorophyll a Derivatives via Stereoselective Horner–Wadsworth–Emmons Reaction

Huiqiang Wu,Xiangmin Wang,Yang Liu,Yu Zhao,Xinyue Wang,Woo-Kyoung Lee,심영기,Il Yoon,Xinming Xu,Jiazhu Li 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.5

In this article, we report the stereoselective Horner?Wadsworth?Emmons reaction of reactive carbonyl-substituted chlorophyll a derivatives with diethyl cyanomethylphosphonate. We found that the formyl or keto group at the chlorin periphery can react stereoselectively with phosphonate carbanions to produce a series of cyanomethylene-substituted chlorins with predominantly E geometry. Considering that no consistent records are available in the literature on the results of the allomerization of methyl pyropheophorbide a, we propose a reliable process for the transformation of this chlorophyll derivative. Our methodology represents a simple and efficient way for the preparation of novel, differently functionalized long-wavelength absorbing chlorins, those can be applied for photodynamic therapy, solar cells, and other relevant purposes.