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排序方式: 共有412条查询结果,搜索用时 929 毫秒
101.
Yang JY Koo BS Kang MK Rho HW Sohn HS Jhee EC Park JW 《Experimental & molecular medicine》2002,34(5):353-360
The present study was undertaken to explore whether retinoids, which are known to have immunomodulatory actions, could attenuate tumor necrosis factor-alpha (TNF)-stimulated inducible nitric oxide synthase (iNOS) expression in 3T3-L1 adipocytes. Adipocytes incubated with TNF induced dose- and time-dependent accumulation of nitrite in the culture medium through the iNOS induction as confirmed by Western blotting. Treatment of cells with TNF in the presence of all-trans-retinoic acid (RA) significantly decreased their ability to produce nitrite and iNOS induction. Both 13-cis- and all- trans-RA-induced suppression was dose-dependent, and all-trans-RA was somewhat potent than 13-cis-RA. The inhibitory effect of RA on TNF-induced iNOS induction was reversible, completely recovered after 2 days, and was exerted through the inhibition of NF-kappaB activation. TNF also suppressed the lipoprotein lipase (LPL) activity of 3T3-L1 adipocytes. RA could not reverse the TNF- induced LPL suppression at RA levels causing near complete inhibition of the TNF-induced NO production. These results indicate that RAs attenuate iNOS expression reversibly in TNF-stimulated 3T3-L1 adipocytes, and that the TNF-induced LPL suppression is not the result of NO overproduction. 相似文献
102.
Jong Rack Sohn Young Il Pae Man Young Park Sung Guk Jo 《Reaction Kinetics and Catalysis Letters》1995,55(2):325-332
For V2O5–ZrO2 catalysts, up to 10 mol% the crystalline structure of V2O5 was not observed, indicating a good dispersity the surface of ZrO2. V2O5–ZrO2 catalyst modified with H2SO4 exhibited much on higher catalytic activity for propene partial oxidation than unmodified catalysts due to the increased acidity and acid strength of modified catalyst. 相似文献
103.
Park Y Choi YW Park S Cho CS Fasolka MJ Sohn D 《Journal of colloid and interface science》2005,283(2):322-328
Physicochemical properties of PBLG (poly(gamma-benzyl-l-glutamate))-PEO (poly(ethylene oxide)) diblock copolymers composed of PBLG as the hydrophobic rod component and PEO as the hydrophilic component were investigated at the air-water interface. Surface pressure-area isotherms obtained by the Wilhelmy plate method provide several variables such as molecular size, compressibility of PEO, and the free energy change of the PBLG-PEO block copolymer. GE-1 (M(w) of PBLG:PEO=103,700:12,000), with a relatively longer rod, has negative temperature effects and GE-3 (M(w) of PBLG:PEO=8400:12,000), with a relatively shorter rod, shows a positive temperature effect because of the large entropy loss. These competitions were based on the block size of PBLG and PEO and were affected by various microstructures of the PBLG-PEO diblock copolymer. Monolayer aggregations transferred onto mica from the air-water interface were analyzed with AFM. AFM images of GE-1 monolayers show cylindrical micelles, but the self-assembled structure has many large domains. The monolayer of GE-2 (M(w) of PBLG:PEO=39,800:12,000), which has a medium size rod, forms a spherical structure at the air-water interface. Monolayers of GE-3, with a short rod length, form bilayer structures. These results demonstrate that the microstructures of PBLG-PEO diblock copolymers are related to free energy changes between rod and coil blocks. 相似文献
104.
Numerous types of cells have been shown to undergo apoptosis when exposed to oxidant agent such as hydrogen peroxide. In order to understand the functional relationship between the anti- and pro-apoptotic regulatory proteins in the cells under oxidant stress, we have studied the level of expression of apoptosis regulatory proteins, bcl-2 and bax, in human leukemia HL-60 cells. The exposure of HL-60 cells to different concentrations of H2O2 for 6 h resulted in a typical apoptosis of the cells as characterized by flow cytometry, cell cycle analysis, and DNA fragmantation. There was a block in G1 to S transition and apoptotic cells were mainly derived from S and G2 cells. Kinetic study demonstrated that the levels of both bcl-2-mRNA and -protein expression were decreased with the progression of cellular apoptosis whereas the level of bax-mRNA was unchanged but the expressed bax-protein was not detectable. Cycloheximide, a nonspecific translation inhibitor, did not prevent the hydrogen peroxide-mediated apoptosis in HL-60 cells. These results suggest that the regulation of bcl-2, but not of bax are important factor in the oxidative stress-induced apoptosis in HL-60 cells. 相似文献
105.
Jong Hyun Park Kyungkon Kim Young-Rae Hong Jung-Il Jin Byung-Hee Sohn 《Macromolecular Symposia》2004,212(1):51-62
A series of PPV derivatives bearing substituted and unsubstituted carbazole and 2-ethylhexyloxy pendants were prepared and their photo- (PL) and electroluminescence (EL) properties were studied. Substituted carbazole structures were N-phenylcarbazole and 3,6-dimethoxycarbazole. The substituents on the carbazole pendants caused little change in UV-vis absorption, PL, and EL when compared with the polymer bearing the unsubstituted carbazole pendants. The presence of the benzene ring between the main chain and the carbazole pendant increased the threshold electric field in EL. We could obtain maximum brightness of ca. 17,000 - 30,000 cd/m2 for the polymers carrying the unsubstituted and dimethoxy substituted carbazole pendants. 相似文献
106.
107.
Sang‐Wook Park Han‐Soo Yoon Sang‐Bo Park In‐Joe Sohn 《Journal of polymer science. Part A, Polymer chemistry》2000,38(17):3059-3066
The phase‐transfer catalyzed polycondensation of α,α′‐dichloro‐p‐xylene with 4,4′‐isopropylidenediphenol was carried out using benzylethylammonium chloride in a two‐phase system of an aqueous alkaline solution and benzene at 60 °C under nitrogen atmosphere. The rate of polycondensation was expressed as the combined terms of quaternary onium cation and 4,4′‐isopropylidenediphenolate anion rather than the feed concentration of catalyst and 4,4′‐isopropylidenediphenol. The measured concentrations of hydroxide and chloride anion in the aqueous solution and α,α′‐dichloro‐p‐xylene in the organic phase were used to obtain the reaction rate constant with the integral method, and to analyze the polycondensation mechanism with a cyclic phase‐transfer initiation step in the heterogeneous liquid–liquid system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3059–3066, 2000 相似文献
108.
H. Ade C. Wang A. Garcia H. Yan K. E. Sohn A. Hexemer G. C. Bazan T.‐Q. Nguyen E. J. Kramer 《Journal of Polymer Science.Polymer Physics》2009,47(13):1291-1299
Resonant soft X‐ray reflectivity (RSoXR) has been used to quantify the layer thicknesses and the interfacial widths of a single, complex thin film with three polymeric layers supported on an inorganic substrate. By adjusting the photon energy, the sensitivity to particular interfaces within the trilayer can be selectively enhanced. The results significantly improve and broaden the capabilities of RSoXR, which has previously only been demonstrated and used for bilayers on silicon substrates. The capability of RSoXR to characterize polymer trilayers was not readily predictable from prior bilayer results, as the RSoXR characterization of bilayers benefits from a strong X‐ray reflection from the substrate that serves as a reference beam with which the reflections from the other interfaces interfere with. The impact of having the capability to investigate trilayers is exemplified by discussing the utility of RSoXR to characterize organic electronic light emitting multilayers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1291–1299, 2009 相似文献
109.
This study attempts to exploit information from environmental variables together with data envelopment analysis (DEA) efficiency scores for efficiency predictions of groups with more limited information. Based on DEA efficiency scores, decision-making units (DMUs) are sorted into two sets containing efficient and inefficient units, respectively. Then they are reshuffled into homogeneous groups with respect to environmental factors. We assume that the efficiency of DMUs in such a homogeneous group would be correlated. However, efficiency of different groups would vary. A beta binomial logistic model is proposed to fit such phenomena and is applied to predict the performance of a new group of commercialization projects for given environmental characteristics. 相似文献
110.
Technology credit guarantee Fund (TCGF) supports many small and medium companies with high degree of growth potential in technology. Generally, the performance of technology credit guarantee has been evaluated focusing on the probability of default (PD) on the fund recipient companies. But PD itself does not reflect the amount of loss. In this paper, we suggest the way to find the expected loss using the PD, Exposure at Default and Loss Given Default for risk management of the TCGF. Unlike general credit measure, we use the competing risk model in order to estimate the PD for various types of defaults. It is expected that our study can contribute to provide the efficient credit risk management for TCGF and the lending institution. 相似文献