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Impact of Cu2O doping on high dielectric properties of CuO ceramics
Dan-Dan Wang,Feng-Zi Zhou,Jing-Xiao Cao,Li-Ben Li,Guo-Ling Li 한국물리학회 2017 Current Applied Physics Vol.17 No.5
Single-phase CuO ceramic samples were prepared with the starting nano powders of CuO þ xCu2O (x ¼ 0, 1, 3, 7% in mole ratio) via solid state reaction method, and characterized by X-ray diffraction, Raman scattering and scanning electron microscopy. For all the samples, the temperature dependences of dielectric constants and losses were measured at the frequencies of 102, 103, 104, 105 and 106 Hz, respectively. With increasing doping content of Cu2O, a strong correlation is demonstrated at given temperature and frequency between the measured dielectric constants and the unit-cell volumes of CuO. The strong correlation is argued in terms of the change in densities of Cu]O defects (e.g. Cu/O vacancies and/or interstitial Cu impurities) due to Cu2O doping, which is supported by the formation energies of Cu]O defects and the corresponding unit-cell volume from first-principles calculations. The high dielectric constant (~103e105) of CuO ceramic is therefore attributed to the reduction in resistance due to Cu/O defects in the grain by Maxwell-Wagner mechanism.
( Jia Wei ),( Xiao Dan Cao ),( Sheng Min Zhou ),( Chao Chen ),( Hai Jun Yu ),( Yao Zhou ),( Ping Wang ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.8
Vascular endothelial growth factor (VEGF) plays a key role in angiogenesis through binding to its specific receptors, which mainly occurs to VEGF receptor 2 (VEGFR-2), a kinase insert domain-containing receptor. Therefore, the disruption of VEGFR-2 signaling provides a promising therapeutic approach for the treatment of cancer by inhibiting abnormal or tumorinduced angiogenesis. To explore this potential, we expressed the catalytic domain of VEGFR- 2 (VEGFR-2-CD) as a soluble active kinase in Escherichia coli. The recombinant protein was purified and the VEGFR-2-CD activity was investigated. The obtained VEGFR-2-CD showed autophosphorylation activity and phosphate transfer activity comparable to the commercial enzyme. Furthermore, the IC50 value of known VEGFR-2 inhibitor was determined using the purified VEGFR-2-CD. These results indicated a possibility for functional and economical VEGFR-2-CD expression in E. coli to use for inhibitor screening.