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Aiqing Zhang Xiangdan Li Changwoon Nah Keejun Hwang Myong‐Hoon Lee 《Journal of polymer science. Part A, Polymer chemistry》2003,41(1):22-29
A soluble aromatic polyimide was chloromethylated via a reaction with chloromethyl methyl ether in the presence of tin(IV) chloride to produce a new starting material for the modification of aromatic polyimides. The chemical structure of the resulting polymer was confirmed by 1H NMR and Fourier transform infrared spectroscopy. The maximum number of chloromethyl groups per repeat unit was 1.81. The chloromethylated polyimide was stable up to 250 °C and soluble in both chloroform and tetrahydrofuran. So that its utilization for further modification could be demonstrated, cinnamic acid was reacted with the formed polyimide, and it produced a new photosensitive polyimide with a cinnamoyl side chain. The photosensitivity of the resulting polyimide was investigated with ultraviolet spectroscopic methods. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 22–29, 2003 相似文献
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Jin-Young Park Kwang-Soon Ahn Yoon-Chae Nah Hee-Sang Shim Yung-Eun Sung 《Journal of Sol-Gel Science and Technology》2004,31(1-3):323-328
Nickel oxide thin films, which are well known anodic coloration materials that are used in electrochromic devices, were prepared by a sol–gel method, and their electrochemical and electrochromic properties were investigated. The sol was prepared from Ni(OH)2 powder with an average size of 7 nm, in a mixture of ethylene glycol and absolute ethanol. The films were coated on an ITO substrate using the powder, dispersed in the solution. When additive materials, acetyl acetone and glycerol, were added to the sol its hardness and adhesion properties were improved. The optimized thin film formed an amorphous, porous structure, and showed a large current density during continuous potential and pulse potential cycling. The film also was transparent and had a high coloration efficiency (33.5 cm2/C) and a rapid response time (1.0–2.5 s) during the coloring/bleaching process. 相似文献
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Kim SW Oh HM Kim BS Chung HT Han WC Kim EC Kim TH Seo GS Lyou JH Nah YH Jung JC Choi SC Jun CD 《Experimental & molecular medicine》2003,35(1):53-59
Tumor target-derived soluble secretary factor has been known to influence macrophage activation to induce nitric oxide (NO) production. Since heme oxygenase-1 (HO-1) is induced by a variety of conditions associated with oxidative stress, we questioned whether soluble factor from tumor cells induces HO-1 through NO-dependent mechanism in macrophages. We designated this factor as a tumor-derived macrophage-activating factor (TMAF), because of its ability to activate macrophages to induce iNOS. Although TMAF alone showed modest activity, TMAF in combination with IFN-gamma significantly induced iNOS expression and NO synthesis. Simultaneously, TMAF induced HO-1 and this induction was slightly augmented by IFN-gamma. Surprisingly, however, induction of HO-1 by TMAF was not inhibited by the treatment with the highly selective iNOS inhibitor, 1400 W, indicating that TMAF induces the HO-1 enzyme by a NO-independent mechanism. While rIFN-gamma alone induced iNOS, it had no effect on HO-1 induction by itself. Collectively, the current study reveals that soluble factor from tumor target cells induces HO-1 enzyme in macrophages. However, overall biological significance of this phenomenon remains to be determined. 相似文献
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Jae‐Woon Nah Mi‐Kyeong Jang 《Journal of polymer science. Part A, Polymer chemistry》2002,40(21):3796-3803
Low molecular, water‐soluble chitosan (LMWSC) with a free amine group was prepared by the novel salts‐removal method described in this study. A weight‐average molecular weight and degree of deacetylation (DDA) of LMWSC were determined by viscometry and Kina titration, resulting in 18,579 Da and 93% DDA, respectively. In the Fourier transform infrared spectroscopic, 1H NMR, and 13C NMR spectra the absorption band by the carboxyl group derived from lactic acid and the impurities formed in the enzymatic process disappeared or were significantly lower than that of the control chitosan. Also, from the 1H NMR and 13C NMR spectra the empirical value for the area ratio of the proton and carbon corresponds nearly to its theoretical values. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum identified the difference in the two adjacent peaks as 161. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3796–3803, 2002 相似文献
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Targeted Delivery of Vaccine to Dendritic Cells by Chitosan Nanoparticles Conjugated with a Targeting Peptide Ligand Selected by Phage Display Technique
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Jun-Gill Kang Tack-Jin Kim Hee-Jung Kang Younbong Park Min-Koo Nah 《Journal of luminescence》2008,128(12):1867-1872
Two novel complexes of Sm(III) and Dy(III) with mixed oxydiacetate (ODA) and 1,10-phenanthroline (phen) ligands were synthesized and their structure and luminescence properties were characterized. The complexes of [Ln(ODA)(phen)·4H2O]Cl·5H2O [Ln=Sm and Dy] crystallize in the monoclinic space group P21/n with Sm: a=12.3401(14) Å, b=16.821(2), c=12.6847(11) Å, β=107.939(10)°, V=2505.0(5) Å3, Z=4 and ρ=1.841 mg/m3, and with Dy: a=12.289(7) Å, b=16.805(6) Å, c=12.705(4) Å, β=108.144(18)°, V=2493.4(19) Å3, Z=4 and ρ=1.786 mg/m3. The complexes of [Sm(ODA)(phen)·4H2O]+ and [Dy(ODA)(phen)·4H2O]+ excited by UV light produce orange red and lightly white emissions, respectively, via the nonradiative energy transfer from phen to the metals. The quantum yield of the sensitized luminescence of [Dy(ODA)(phen)·4H2O]+ (Q=19%) is much greater than that of [Sm(ODA)(phen)·4H2O]+ (Q=1.4%). The luminescence decay times of the complexes were in a few microsecond range and independent of temperature. 相似文献
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Ha-Yoon Nah Vinayak G. Parale Kyu-Yeon Lee Haryeong Choi Taehee Kim Chang-Hyun Lim Ji-Yeon Seo Yang Seo Ku Jae-Woo Park Hyung-Ho Park 《Journal of Sol-Gel Science and Technology》2018,87(2):319-330
Trimethylethoxysilane (TMES) has been recognized as a good co-precursor to increase the degree of hydrophobicity during the synthesis of a silica aerogel because of its methyl groups. Therefore, some physical properties of silica aerogels, including the contact angle and porosity, were investigated using TMES as a co-precursor at different molar ratios with the main precursor such as tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS). In contrast to TMES, most silylating agents such as hexamethyldisilazane (HMDZ) and trimethylchlorosilane (TMCS) have been used for surface modification because of their ability to enhance the hydrophobicity of the aerogel surface. This work examines the silylation effect, which includes increasing hydrophobicity by TMES to determine the possibility of using it as an alternative silylating agent during ambient pressure drying in the synthesis of sodium silicate-based silica aerogel. In addition, the physical properties of sodium silicate-based silica aerogels with silylation under different TMES/TMCS volume ratio are investigated. The physical properties of sodium silicate-based aerogels can be changed by the TMES/TMCS volume ratio during the surface modification step. Aerogels with a high specific surface area (458?m2/g), pore volume (3.215?cm3/g), porosity (92.7%), and contact angle (131.8°) can be obtained TMES/TMCS volume ratio of 40/60. 相似文献