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811.
Bo Ram Park 《Tetrahedron letters》2010,51(50):6568-6571
An efficient synthesis of trans-α-methylene-γ-butyrolactones is disclosed from syn-homoallylic alcohols via the intramolecular mesylate displacement reaction promoted by nearby ester group under the influence of MsCl/Et3N. syn-Homoallylic alcohols were prepared via the In-mediated Barbier reaction of the bromides of Baylis-Hillman adducts. 相似文献
812.
813.
Crystalline TiO2 nanowire-nanoparticle hetero-structures were successfully synthesized from titanium foils by using a simple thermal annealing method with the aid of CuCl2 at the atmospheric pressure. Nanowires were grown from Ti foils by simply annealing Ti foils at 850 °C. Then, TiCl4 was delivered to TiO2 nanowires so as to precipitate TiO2 nanoparticles on nanowire surfaces. At 750 °C reaction temperature, nanoparticles of tens of nanometers in diameter were well distributed on pre-grown nanowire forests. Nanoparticles were likely to be precipitated by TiCl4 decomposition or oxidation and that require high temperatures above ∼650 °C. Electron microscopy, X-ray diffraction, and UV-vis spectroscopy analyses show they have the rutile polycrystalline structure with a slightly enlarged bandgap compared to that of bulk TiO2. The influence of key synthesis parameters including reaction temperature, reaction time, and quantity of supplied materials on the incorporating nanoparticles was also systematically studied. The optimum reaction condition in the present paper was identified to be 750 °C annealing with repetitive 20 min reactions. A higher reaction temperature yielded larger diameter particles, and higher loading of Ti produced dense particles without changing the particle size. Finally, this method could be utilized for synthesizing other metal oxide nanowires-nanoparticle hetero-structures. 相似文献
814.
Joohong Park Gary M. Halliday Devita Surjana Diona L. Damian 《Photochemistry and photobiology》2010,86(4):942-948
UV radiation is carcinogenic by causing mutations in the skin and also by suppressing cutaneous antitumor immunity. We previously found nicotinamide (vitamin B3) to be highly effective at reducing UV-induced immunosuppression in human volunteers, with microarray studies on in vivo irradiated human skin suggesting that nicotinamide normalizes subsets of apoptosis, immune function and energy metabolism-related genes that are downregulated by UV exposure. Using human adult low calcium temperature keratinocytes, we further investigated nicotinamide’s effects on cellular energy metabolism. We found that nicotinamide prevented UV-induced cellular ATP loss and protected against UV-induced glycolytic blockade. To determine whether nicotinamide alters the effects of UV-induced oxidative stress posttranslationally, we also measured UV-induced reactive oxygen species (ROS). Nicotinamide had no effect on ROS formation, and at the low UV doses used in these studies, equivalent to ambient daily sun exposure, there was no evidence of apoptosis. Hence, nicotinamide appears to exert its UV protective effects on the skin via its role in cellular energy pathways. 相似文献
815.
B. J. Park J. K. Yeon W. S. Lim S. K. Kang J. W. Bae G. Y. Yeom M. S. Jhon S. H. Shin K. S. Chang J. I. Song Y. T. Lee J. H. Jang 《Plasma Chemistry and Plasma Processing》2010,30(5):633-640
Highly selective and low damage etching of the GaAs cap layer on AlGaAs is essential in fabricating GaAs/AlGaAs high electron mobility transistors. The GaAs on AlGaAs was etched using a low energy Cl2/O2 neutral beam and the Schottky device characteristics fabricated on the exposed AlGaAs were compared with those fabricated after the etching using wet etching and a Cl2/O2 ion beam. Using a low energy Cl2/O2 ion beam or a Cl2/O2 neutral beam, highly selective etching of the GaAs cap layer to AlGaAs similar to wet etching could be achieved through the formation of Al2O3 on the exposed AlGaAs during the etching. When the electrical characteristics of the Schottky devices were compared, the devices fabricated after the etching using the neutral beam showed the best electrical characteristics such as electrical stability, low leakage current, higher barrier height, etc. by showing low damage to the exposed AlGaAs surface. 相似文献
816.
Jong Ho Lee Sung Bong Kim Chulhwan Park Bumseok Tae Sung Ok Han Seung Wook Kim 《Applied biochemistry and biotechnology》2010,161(1-8):365-371
In this study, transesterification and esterification were investigated in batch and continuous process using immobilized Candida rugosa and Rhizopus oryzae lipases. In the case of batch process, stepwise reaction method was investigated to prevent the lipase deactivation. Reaction conditions were as follows: temperature, 45 °C; agitation speed, 250 rpm; enzyme concentration, 20%; and water contents 10%. And then, conversion yield was 98.33% at 4 h. In the case of continuous process, circulation and long-term continuous system were investigated for development of efficient mass transfer system. Optimal reaction conditions were as follows: temperature, 45 °C; flow rate, 0.8 mL/min; and water contents, 10%. And then, conversion yield of biodiesel was 97.98% at 3 h. Especially, the maximum conversion yield using a mixture of immobilized lipases exceeded over 90% for 108 h in long-term continuous system under optimal reaction conditions (45 °C; flow rate, 0.8 mL/min; and water contents, 10%). These results should help in determining the best method for the biodiesel production and improving the design and operation of large scale by enzymatic systems. 相似文献
817.
818.
Electrospinning fabrication and characterization of poly(vinyl alcohol)/montmorillonite/silver hybrid nanofibers for antibacterial applications 总被引:1,自引:0,他引:1
Jae Hyeung Park Mohammad Rezaul Karim In Kyo Kim In Woo Cheong Jong Won Kim Do Gyu Bae Jin Won Cho Jeong Hyun Yeum 《Colloid and polymer science》2010,288(1):115-121
Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT)/silver (Ag) nanoparticles have been electrospun for fabricating PVA/MMT/Ag
nanofiber in aqueous solutions. Since PVA is a water-soluble and biocompatible polymer, it is one of the best materials for
preparation of antibacterial nanofiber. MMT has been used as an inorganic filler to enhance properties of homopolymeric nanofiber.
The PVA/MMT/Ag nanofiber diameter increases with increasing contents of MMT clay and Ag nanoparticles. In preservation test,
the PVA/MMT/Ag nanofiber confirms an excellent antibacterial performance, elucidating for practical uses as a new preservative.
Moreover, the PVA/MMT/Ag nanofiber shows improved thermal properties. 相似文献
819.
In order to prevent restenosis after angioplasty or stenting, one of the most popular targets is suppression of the abnormal growth and excess migration of vascular smooth muscle cells (VSMCs) with drugs. However, the drugs also adversely affect vascular endothelial cells (VECs), leading to the induction of late thrombosis. We have investigated the effect of epigallocatechin-3-gallate (EGCG) on the proliferation and migration of VECs and VSMCs. Both cells showed dose-dependent decrease of viability in response to EGCG while they have different IC(50) values of EGCG (VECs, 150 mM and VSMCs, 1050 mM). Incubating both cells with EGCG resulted in significant reduction in cell proliferation irrespective of cell type. The proliferation of VECs were greater affected than that of VSMCs at the same concentrations of EGCG. EGCG exerted differential migration-inhibitory activity in VECs vs. VSMCs. The migration of VECs was not attenuated by 200 mM EGCG, but that of VSMCs was significantly inhibited at the same concentration of EGCG. It is suggested that that EGCG can be effectively used as an efficient drug for vascular diseases or stents due to its selective activity, completely suppressing the proliferation and migration of VSMCs, but not adversely affecting VECs migration in blood vessels. 相似文献
820.
In the present study, we prepared new Li-ion batteries with inorganic membrane-coated electrodes fabricated by the direct
coating of a 400-nm-sized Al2O3 particles onto the anodes and studied their charge–discharge characteristics for the first time. Being made of 94 wt.% Al2O3 powder and 6 wt.% polymeric binder, the membranes on the anodes showed excellent wettability with the liquid electrolytes,
due to their high porosity and capillarity. The Li-ion batteries prepared by the assembly of the inorganic membrane-coated
electrodes showed excellent charge–discharge behavior compared to conventional Li-ion batteries with a polymeric separator.
However, their high-rate performance was affected by the binder contents in the inorganic membranes. The thermal properties
of the Li-ion battery with the inorganic membrane-coated electrodes were compared with those of a conventional one with a
polymeric separator. 相似文献