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- 저자 : Wanli Cheng (검색결과 146 건)
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Cheng-gang Ci,Hong-bo Yu,Su-qin Wan,Jing-yao Liu,Chia-Chung Sun 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.4
The hydrogen abstraction reaction of CF_3CH_2CHO + OH has been studied theoretically by dual-level direct dynamics method. Two stable conformers, trans- and cis-CF_3CH_2CHO, have been located, and there are four distinct OH hydrogen-abstraction channels from t-CF_3CH_2CHO and two channels from c-CF_3CH_2CHO. The required potential energy surface information for the kinetic calculation was obtained at the MCG3-MPWB//M06-2X/aug-cc-pVDZ level. The rate constants, which were calculated using improved canonical transitionstate theory with small-curvature tunneling correction (ICVT/SCT) were fitted by a four-parameter Arrhenius equation. It is shown that the reaction proceeds predominantly via the H-abstraction from the -CHO group over the temperature range 200-2000 K. The calculated rate constants were in good agreement with the experimental data between 263 and 358 K.
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Wan-Guo Yu,Yun He,Yun-Fang Chen,Xiao-Yao Gao,Wan-E Ning,Chun-You Liu,Ting-Fan Tang,Quan Liu,Xiao-Cheng Huang 대한약리학회 2019 The Korean Journal of Physiology & Pharmacology Vol.23 No.3
Fumigaclavine C (FC), an active indole alkaloid, is obtained from endophytic Aspergillus terreus (strain No. FC118) by the root of Rhizophora stylosa (Rhizophoraceae). This study is designed to evaluate whether FC has anti-adipogenic effects in 3T3-L1 adipocytes and whether it ameliorates lipid accumulation in highfat diet (HFD)-induced obese mice. FC notably increased the levels of glycerol in the culture supernatants and markedly reduced lipid accumulation in 3T3-L1 adipocytes. FC differentially inhibited the expressions of adipogenesis-related genes, including the peroxisome proliferator-activated receptor proteins, CCAAT/enhancer-binding proteins, and sterol regulatory element-binding proteins. FC markedly reduced the expressions of lipid synthesis-related genes, such as the fatty acid binding protein, lipoprotein lipase, and fatty acid synthase. Furthermore, FC significantly increased the expressions of lipolysis-related genes, such as the hormone-sensitive lipase, Aquaporin- 7, and adipose triglyceride lipase. In HFD-induced obese mice, intraperitoneal injections of FC decreased both the body weight and visceral adipose tissue weight. FC administration significantly reduced lipid accumulation. Moreover, FC could dosedependently and differentially regulate the expressions of lipid metabolism-related transcription factors. All these data indicated that FC exhibited anti-obesity effects through modulating adipogenesis and lipolysis.
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Value of CT in the Discrimination of Fatal from Non-Fatal Stercoral Colitis
Cheng-Hsien Wu,Chen-Chih Huang,Li-Jen Wang,Yon-Cheong Wong,Chao-Jan Wang,Wan-Chak Lo,Being-Chuan Lin,Yung-Liang Wan,Chuen Hsueh 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.3
Objective: Clinical presentation and physical signs may be unreliable in the diagnosis of stercoral colitis (SC). This study evaluates the value of computed tomography (CT) in distinguishing fatal from non-fatal SC. Materials and Methods: Ten patients diagnosed as SC were obtained from inter-specialist conferences. Additional 13 patients with suspected SC were identified via the Radiology Information System (RIS). These patients were divided into two groups; fatal and non-fatal SCs. Their CT images are reviewed by two board-certified radiologists blinded to the clinical data and radiographic reports. Results: SC occurred in older patients and displayed no gender predisposition. There was significant correlation between fatal SC and CT findings of dense mucosa (p = 0.017), perfusion defects (p = 0.026), ascites (p = 0.023), or abnormal gas (p = 0.033). The sensitivity, specificity, and accuracy of dense mucosa were 71%, 86%, and 81%, respectively. These figures were 75%, 79%, and 77% for perfusion defects; 75%, 80%, and 78% for ascites; and 50%, 93%, and 78% for abnormal gas, respectively. Each CT sign of mucosal sloughing and pericolonic abscess displayed high specificity of 100% and 93% for diagnosing fatal SC, respectively. However, this did not reach statistical significance in diagnosing fatal SC. Conclusion: CT appears to be valuable in discriminating fatal from non-fatal SC. Objective: Clinical presentation and physical signs may be unreliable in the diagnosis of stercoral colitis (SC). This study evaluates the value of computed tomography (CT) in distinguishing fatal from non-fatal SC. Materials and Methods: Ten patients diagnosed as SC were obtained from inter-specialist conferences. Additional 13 patients with suspected SC were identified via the Radiology Information System (RIS). These patients were divided into two groups; fatal and non-fatal SCs. Their CT images are reviewed by two board-certified radiologists blinded to the clinical data and radiographic reports. Results: SC occurred in older patients and displayed no gender predisposition. There was significant correlation between fatal SC and CT findings of dense mucosa (p = 0.017), perfusion defects (p = 0.026), ascites (p = 0.023), or abnormal gas (p = 0.033). The sensitivity, specificity, and accuracy of dense mucosa were 71%, 86%, and 81%, respectively. These figures were 75%, 79%, and 77% for perfusion defects; 75%, 80%, and 78% for ascites; and 50%, 93%, and 78% for abnormal gas, respectively. Each CT sign of mucosal sloughing and pericolonic abscess displayed high specificity of 100% and 93% for diagnosing fatal SC, respectively. However, this did not reach statistical significance in diagnosing fatal SC. Conclusion: CT appears to be valuable in discriminating fatal from non-fatal SC.
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Friction Experiment of Linear Motion Roller Guide THK SRG25
Cheng, De-Jun,Yang, Wan-Suk,Park, Je-Hong,Park, Tae-Jo,Kim, Su-Jin,Kim, Gyung-Ho,Park, Chun-Hong 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.3
Friction is a characteristic that can be found in machine elements in common engineering use, and it has great effect on the machining performance of a machine tool. Linear motion (LM) guides supported by rolling elements are used for accurate positioning of precision machine. For accurate positioning, the frictional behavior of the LM guide must be understood. In this investigation, a new experiment is conducted to measure friction, and the behavior of LM roller guide friction is measured under various external loads, preloads, velocities, and lubricants. The results obtained from experiment are compared with reference data, and the experimental friction equation of LM roller guide THK SRG25 is achieved from experiment, which can be used to calculate LM roller guide friction and control positioning accuracy.
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Cheng-En Ho,Wan-Zhen Hsieh,Tsung-Hsun Yang 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.1
The early stage of soldering reaction between Sn-3Ag-0.5Cu solderand ultrathin-Ni(P)-type Au/Pd(P)/Ni(P)/Cu pad was investigatedby field-emission scanning electron microscopy (FE-SEM) inconjunction with field-emission electron probe microanalysis (FEEPMA)and high-resolution transmission electron microscopy(HRTEM). FE-SEM, FE-EPMA, and HRTEM investigationsshowed that Ni2SnP and Ni3P were the predominant P-containingintermetallic compounds (IMCs) in the soldering reaction and thattheir growth behaviors strongly depended on the depletion of Ni(P). The growth of Ni3P dominated over that of Ni2SnP in the earlystage of soldering, whereas the Ni3P gradually transformed intoNi2SnP after Ni(P) depletion. This Ni(P)-depletion-induced Ni2SnPgrowth behavior is different from the reaction mechanisms reported in the literature. Detailed analyses of the microstructuralevolution of the IMC during Ni(P) depletion were conducted, and a two-stage reaction mechanism was proposed to rationalizethe unique IMC growth behavior.
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Calibration Practices in Clinical Mass Spectrometry: Review and Recommendations
Cheng Wan Ling,Markus Corey,Lim Chun Yee,Tan Rui Zhen,Sethi Sunil Kumar,Loh Tze Ping 대한진단검사의학회 2023 Annals of Laboratory Medicine Vol.43 No.1
Background: Calibration is a critical component for the reliability, accuracy, and precision of mass spectrometry measurements. Optimal practice in the construction, evaluation, and implementation of a new calibration curve is often underappreciated. This systematic review examined how calibration practices are applied to liquid chromatography-tandem mass spectrometry measurement procedures. Methods: The electronic database PubMed was searched from the date of database inception to April 1, 2022. The search terms used were “calibration,” “mass spectrometry,” and “regression.” Twenty-one articles were identified and included in this review, following evaluation of the titles, abstracts, full text, and reference lists of the search results. Results: The use of matrix-matched calibrators and stable isotope-labeled internal standards helps to mitigate the impact of matrix effects. A higher number of calibration standards or replicate measurements improves the mapping of the detector response and hence the accuracy and precision of the regression model. Constructing a calibration curve with each analytical batch recharacterizes the instrument detector but does not reduce the actual variability. The analytical response and measurand concentrations should be considered when constructing a calibration curve, along with subsequent use of quality controls to confirm assay performance. It is important to assess the linearity of the calibration curve by using actual experimental data and appropriate statistics. The heteroscedasticity of the calibration data should be investigated, and appropriate weighting should be applied during regression modeling. Conclusions: This review provides an outline and guidance for optimal calibration practices in clinical mass spectrometry laboratories.
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( Wan Xing Yong ),( Xu Cheng Fu ),( Lu Chao ),( Yu Wei Lai ),( Zhu Hua Tuo ),( Yu Chao Hui ),( Li You Ming ) 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1
Background: Serum uric acid is strongly associated with nonalcoholic fatty liver disease (NAFLD) and insulin resistance in patients. However, whether this association is causally or coincidentally with NAFLD and insulin resistance remains uncertain, neither the mechanisms behind this association are unclear so far. Methods: We first analyzed the impact of uric acid on development of hepatic steatosis in mice and two cell models (HepG2 and HL7702), and then explored the effect of uric acid on insulin signaling, including phosphorylation of insulin receptor substrate 1 (IRS1) and Akt in HepG2 and HL7702 cells. Further, we studied the role of NLRP3 inflammasome in regulation of hepatic steatosis and insulin signaling. Results: Uric acid directly induced hepatocyte fat accumulation both in vivo and in vitro. Further, uric acid treatment decreased insulin-induced phospho-Akt (ser437) and enhanced the phospho-IRS1(ser307) in HepG2 and HL7702 cells. Then, we found significant increases of NLRP3 inflammasome-related molecules, both mRNA and protein levels, including NLPR3, caspase-1, IL-1ß, and IL-18, in HepG2 and HL7702 cells stimulated with uric acid. We also found that uric acid induced significant elevations of IL-1ß and IL-18 levels in culture supernatants of HepG2 and HL7702 cells. Consistent with in vitro results, mice fed 8 weeks of hyperuricemia-inducing diet resulted in significant up-regulation of hepatic mRNA and protein expressions of NLPR3, caspase-1, IL-1ß and IL-18, and elevation of serum IL-1ß and IL-18 levels. Further experiments indicated that silencing NLRP3 expression significantly alleviated uric acid-induced fat accumulation in vitro. Moreover, inhibition of NLRP3 expression ameliorated uric acid induced insulin signaling impairing, confirmed by increased insulin- induced phospho-Akt (ser437) and reduced the phospho-IRS1(ser307) in vitro. Conclusions: Our results suggest that uric acid contributes to hepatic steatosis and impairs insulin signaling through the NLRP3 inflammasome dependent mechanism.
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Enhanced Corrosion Resistance of PVD-CrN Coatings by ALD Sealing Layers
Wan, Zhixin,Zhang, Teng Fei,Ding, Ji Cheng,Kim, Chang-Min,Park, So-Won,Yang, Yang,Kim, Kwang-Ho,Kwon, Se-Hun SPRINGER SCIENCE + BUSINESS MEDIA 2017 NANOSCALE RESEARCH LETTERS Vol.12 No.1
<P>Multilayered hard coatings with a CrN matrix and an Al<SUB>2</SUB>O<SUB>3</SUB>, TiO<SUB>2</SUB>, or nanolaminate-Al<SUB>2</SUB>O<SUB>3</SUB>/TiO<SUB>2</SUB> sealing layer were designed by a hybrid deposition process combined with physical vapor deposition (PVD) and atomic layer deposition (ALD). The strategy was to utilize ALD thin films as pinhole-free barriers to seal the intrinsic defects to protect the CrN matrix. The influences of the different sealing layers added in the coatings on the microstructure, surface roughness, and corrosion behaviors were investigated. The results indicated that the sealing layer added by ALD significantly decreased the average grain size and improved the corrosion resistance of the CrN coatings. The insertion of the nanolaminate-Al<SUB>2</SUB>O<SUB>3</SUB>/TiO<SUB>2</SUB> sealing layers resulted in a further increase in corrosion resistance, which was attributed to the synergistic effect of Al<SUB>2</SUB>O<SUB>3</SUB> and TiO<SUB>2</SUB>, both acting as excellent passivation barriers to the diffusion of corrosive substances.</P>
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