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      • KCI등재

        Tribological performances of copper perrhenate/graphene nanocomposite as lubricating additive under various temperatures

        Junhai Wang,Weipeng Zhuang,Tingting Yan,Wenfeng Liang,Ting Li,Lixiu Zhang,Xiaoyi Wei 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.100 No.-

        Herein, copper perrhenate (Cu(ReO4)2) was synthesized using a micro-emulsion method and adhered tographene (Gr) using an ultrasonic process. Then, the as-prepared Cu(ReO4)2/Gr composite was added intothe synthetic oil as a lubricant additive with the help of ionic liquid to achieve enhanced dispersionstability within the base oil. The tribological performances of the Cu(ReO4)2/Gr additive wereinvestigated using four-ball tests and the ball-on-disk reciprocating configuration under varioustemperatures. The potential lubrication mechanisms of the Cu(ReO4)2/Gr additive were performed usinga series of characterization methods including XRD, Raman, SEM-EDS, TEM, DSC/TG, and XPS. The resultsof four-ball tests at room temperature indicated that the Cu(ReO4)2/Gr additive could substantiallyimprove the tribological performances of the base oil. The smallest coefficient of friction (COF) and wearscar diameter (WSD) values were 0.068 and 495 mm, respectively, when 0.05 wt% of Cu(ReO4)2/Gr wasadded. Additionally, the graphene accelerated friction-induced heat transfer, which led to decreasedfriction and wear. The results of reciprocating friction experiments at elevated temperatures revealedthat the Cu(ReO4)2/Gr additive had excellent friction-reduction properties when the temperature washigh. This could be attributed to the generation of a protective layer containing tribo-oxides from thealloy, some residual carbides and copper perrhenate induced by friction heat and stress. This protectivelayer was uniformly and stably covered on the worn surface, which could effectively alleviate directcontact between the rubbing pair.

      • KCI등재

        Retrospective Electrocardiography-Gated Real-Time Cardiac Cine MRI at 3T: Comparison with Conventional Segmented Cine MRI

        Chen Cui,Gang Yin,Minjie Lu,Xiuyu Chen,Sainan Cheng,Lu Li,Weipeng Yan,Yanyan Song,Sanjay Prasad,Yan Zhang,Shihua Zhao 대한영상의학회 2019 Korean Journal of Radiology Vol.20 No.1

        Objective: Segmented cardiac cine magnetic resonance imaging (MRI) is the gold standard for cardiac ventricular volumetric assessment. In patients with difficulty in breath-holding or arrhythmia, this technique may generate images with inadequate quality for diagnosis. Real-time cardiac cine MRI has been developed to address this limitation. We aimed to assess the performance of retrospective electrocardiography-gated real-time cine MRI at 3T for left ventricular (LV) volume and mass measurement. Materials and Methods: Fifty-one patients were consecutively enrolled. A series of short-axis cine images covering the entire left ventricle using both segmented and real-time balanced steady-state free precession cardiac cine MRI were obtained. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), and LV mass were measured. The agreement and correlation of the parameters were assessed. Additionally, image quality was evaluated using European CMR Registry (Euro-CMR) score and structure visibility rating. Results: In patients without difficulty in breath-holding or arrhythmia, no significant difference was found in Euro-CMR score between the two techniques (0.3 ± 0.7 vs. 0.3 ± 0.5, p > 0.05). Good agreements and correlations were found between the techniques for measuring EDV, ESV, EF, SV, and LV mass. In patients with difficulty in breath-holding or arrhythmia, segmented cine MRI had a significant higher Euro-CMR score (2.3 ± 1.2 vs. 0.4 ± 0.5, p < 0.001). Conclusion: Real-time cine MRI at 3T allowed the assessment of LV volume with high accuracy and showed a significantly better image quality compared to that of segmented cine MRI in patients with difficulty in breath-holding and arrhythmia.

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        Phosphodiesterase 4D contributes to angiotensin II-induced abdominal aortic aneurysm through smooth muscle cell apoptosis

        Gao Ran,Guo Wenjun,Fan Tianfei,Pang Junling,Hou Yangfeng,Feng Xiaohang,Li Bolun,Ge Weipeng,Fan Tianhui,Zhang Tiantian,Lu Jiakai,Jing He,Jin Mu,Yan Chen,Wang Jing 생화학분자생물학회 2022 Experimental and molecular medicine Vol.54 No.-

        Abdominal aortic aneurysm (AAA) is a permanent expansion of the abdominal aorta that has a high mortality but limited treatment options. Phosphodiesterase (PDE) 4 family members are cAMP-specific hydrolyzing enzymes and have four isoforms (PDE4A-PDE4D). Several pan-PDE4 inhibitors are used clinically. However, the regulation and function of PDE4 in AAA remain largely unknown. Herein, we showed that PDE4D expression is upregulated in human and angiotensin II-induced mouse AAA tissues using RT-PCR, western blotting, and immunohistochemical staining. Furthermore, smooth muscle cell (SMC)-specific Pde4d knockout mice showed significantly reduced vascular destabilization and AAA development in an experimental AAA model. The PDE4 inhibitor rolipram also suppressed vascular pathogenesis and AAA formation in mice. In addition, PDE4D deficiency inhibited caspase 3 cleavage and SMC apoptosis in vivo and in vitro, as shown by bulk RNA-seq, western blotting, flow cytometry and TUNEL staining. Mechanistic studies revealed that PDE4D promotes apoptosis by suppressing the activation of cAMP-activated protein kinase A (PKA) instead of the exchange protein directly activated by cAMP (Epac). Additionally, the phosphorylation of BCL2-antagonist of cell death (Bad) was reversed by PDE4D siRNA in vitro, which indicates that PDE4D regulates SMC apoptosis via the cAMP-PKA-pBad axis. Overall, these findings indicate that PDE4D upregulation in SMCs plays a causative role in AAA development and suggest that pharmacological inhibition of PDE4 may represent a potential therapeutic strategy.

      • KCI등재

        Adsorption Mechanism of Magnetic Induction Free- Abrasive Grain and Its Effect on Cutting Performance of Wire Saws

        Wei Peng,Teng-wei Qiu,Chun-yan Yao,Chen Tang,Wei Zhang 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

        This paper proposes a method of free-abrasive wire sawing in the magnetic field. Magnetic abrasive grains are absorbed on surface of the wire by magnetic force, and therefore more magnetic abrasive grains are carried into cutting area. This mechanism is helpful to improve the cutting performance of wire saws. Theoretical modeling of the movement trajectory of magnetic abrasive grains is done in the magnetic field, and it is also verified by observation experiments of movement trajectory of magnetic abrasive grains. Absorption angle, which is used as the indicator of adsorption capacity about magnetic abrasive grain on surface of the wire, is proposed in this paper. The effect of magnetic field intensity on absorption angle is analyzed through computer simulations and observation experiments. Practical experiments and cutting results show that the change of magnetic field intensity has a significant impact on cutting efficiency, surface roughness, and kerf width.

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