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排序方式: 共有119条查询结果,搜索用时 125 毫秒
101.
Dr. Gangadhar Rao Mathi Byeongseok Kweon Yonghoon Moon Yujin Jeong Prof. Dr. Sungwoo Hong 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22864-22872
Although N-alkenoxyheteroarenium salts have been widely used as umpoled synthons with nucleophilic (hetero)arenes, the use of electron-poor heteroarenes has remained unexplored. To overcome the inherent electron deficiency of quinolinium salts, a traceless nucleophile-triggered strategy was designed, wherein the quinolinium segment is converted into a dearomatized intermediate, thereby allowing simultaneous C8-functionalization of quinolines at room temperature. Experimental and computational studies support the traceless operation of a nucleophile, which enables the previously inaccessible transformation of N-alkenoxyheteroarenium salts. Remarkably, the generality of this strategy has been further demonstrated by broad applications in the regioselective C−H functionalization of other electron-deficient heteroarenes such as phenanthridine, isoquinoline, and pyridine N-oxides, offering a practical tool for the late-stage functionalization of complex biorelevant molecules. 相似文献
102.
Na Young Kwon Geun Seok Jang Ji Hye Son Minjung Lee Hye‐Jin Cho Hee‐Seok Kweon Taek Seung Lee 《Journal of polymer science. Part A, Polymer chemistry》2011,49(1):138-146
Anionically charged fluorescent conjugated polyelectrolytes of poly{[4,7‐(2,1,3‐benzothiadiazole)‐alt‐1,4‐phenylene]‐co‐[2,5‐bis(4‐sulfonatobutoxy)‐alt‐1,4‐phenylene]} ( P1 ) and poly{[4,7‐(bis(thiophen‐2‐yl)benzo‐2,1,3‐thiadiazole)‐alt‐1,4‐phenylene]‐co‐[2,5‐bis(4‐sulfonatobutoxy)‐alt‐1,4‐phenylene]} ( P2 ) were synthesized by Suzuki crosscoupling polymerization in the presence of a palladium catalyst. The conjugated polyelectrolytes with sulfonate groups, as efficient signal amplifying reporters, were carefully designed to be soluble in water over the entire pH range examined and interact with proteins through intermolecular forces. The polymers exhibited blue emission in aqueous solutions but green or red emission in solid form depending on the conjugation length due to intermolecular exciton migration. The anionic conjugated polymers exhibited blue‐to‐green or blue‐to‐red changes in fluorescence upon exposure to charged proteins, indicating that the polymers have potential applications in fluorescent array systems for protein. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
103.
104.
The aim of this study is to measure the dose area product (DAP) in digital radiography by using a DAP meter to determine the X-ray exposure. Pediatric X-ray examinations can be obtained for any radiographic examinations using the selected radiographic examination parameters (kVp and mAs), the DAP information recorded. The best peak signal-to-noise ratio (PSNR) at a fixed tube voltage of 70 kVp was obtained at tube currents of 20 and 32 mA, whereas the best PSNR at a fixed tube current of 25 mA was obtained at a tube voltage of 73 kVp. The fixed tube voltage of 70 kVp and the fixed tube current of 25 mA could help to obtain the best image quality and depict the spatial resolution of an anthropomorphic torso phantom radiographic examination. The normalized data over the DAP were provided to determine the patient dose from radiography. 相似文献
105.
Jae Hwan Yang Jin Myeong Shin Chang Hwa Lee Chul Min Heo Min Ku Jeon Kweon Ho Kang 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):211-219
The present study a promising method for stabilizing spent filters trapping cesium and technetium by using magnesium phosphate ceramics. Simulated spent filters were fabricated by vaporizing nonradioactive cesium and rhenium (a surrogate of Tc) through the voloxidizer. In order to reveal the characteristics of spent filters, phase structures and thermal stability were analyzed by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and thermogravimetric analysis techniques. Waste forms were fabricated by crushing spent filters and mixing them with magnesium oxide and potassium phosphate. Characterizations of the waste forms were performed by the analyses of compressive strength, apparent porosity, XRD, and scanning electron microscopy. The waste forms showed the excellent mechanical property compared with that of ordinary Portland cement, with the highest compressive strength of 38.1 MPa in the sample with 30 wt% of Cs-filter. Microstructural analysis suggests that waste materials are encapsulated by the binding matrix composed of magnesium potassium phosphate. The results of characterization suggest that fabricating a sound and durable waste form is possible with magnesium phosphate ceramics. 相似文献
106.
Su-Dong Cho Deok-Heon Kweon Young-Jin Kang Sang-Gyeong Lee Woo Song Lee Yong-Jin Yoon 《Journal of heterocyclic chemistry》1999,36(5):1151-1156
Some 6,7-dimethoxy-1-halobenzyl-1,2,3,4-tetrahydroisoquinolines were synthesized from 2-(3,4-dimethoxyphenyl)ethylamine and halophenylacetic acids in three steps in good yield. 相似文献
107.
Deok-Heon Kweon Young-Jin Kang Hyun-A Chung Jung-Won Park Woo Song Lee Yong-Jin Yoon Sung-Kyu Kim Motoo Shiro 《Journal of heterocyclic chemistry》1999,36(5):1301-1306
This paper presents the synthesis of 4,5-dichloro-1-(4,5-dichloropyridazin-3-yl)pyridazin-6-one from 4,5-dichloropyridazin-6-one. 相似文献
108.
109.
A compressible Stokes system is studied in a polygon with one concave vertex. A corner singularity expansion is obtained up
to second order. The expansion contains the usual corner singularity functions for the velocity plus an “associated” velocity
singular function, and a pressure singular function. In particular the singularity of pressure is not local but occurs along
the streamline emanating from the incoming concave vertex. It is observed that certain first derivatives of the pressure become
infinite along the streamline of the ambient flow emanating from the concave vertex. Higher order regularity is shown for
the remainder.
This work was supported by the Com2MaC-SRC/ERC program of MOST/KOSEF (grant R11-1999-054), and by the U.S. National Science
Foundation. 相似文献
110.
Xiufeng Yang Manjil Ray Song-Charng Kong Chol-Bum M. Kweon 《Proceedings of the Combustion Institute》2019,37(3):3279-3286
The interaction of liquid drops and heated surfaces is of great importance in many applications. This paper describes a numerical method, based on smoothed particle hydrodynamics (SPH), for simulating n-heptane drop impact on a heated surface. The SPH method uses numerical Lagrangian particles, which obey the laws of fluid dynamics, to describe the fluid flows. By incorporating the Peng–Robinson equation of state, the present SPH method can directly simulate both the liquid and vapor phases and the phase change process between them. The numerical method was validated by two experiments on drop impact on heated surfaces at low impact velocities. The numerical method was then used to predict drop-wall interactions at various temperatures and velocities. The model was able to predict the different outcomes, such as rebound, spread, splash, breakup, and the Leidenfrost phenomenon, consistent with the physical understanding. 相似文献