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排序方式: 共有183条查询结果,搜索用时 984 毫秒
1.
Mathiazhagan C Molzon WR Cousins RD Konigsberg J Kubic J Melese P Rubin P Slater WE Wagner D Hart GW Kinnison WW Lee DM McKee RJ Milner EC Sanders GH Ziock HJ Arisaka K Knibbe P Urheim J Axelrod S Biery KA Irwin GM Lang K Margulies J Ouimette DA Ritchie JL Trang QH Wojcicki SG Auerbach LB Buchholz P Highland VL McFarlane WK Sivertz M Chapman MD Eckhause M Ginkel JF Hancock AD Joyce D Kane JR Kenney CJ Vulcan WF Welsh RE Whyley RJ Winter RG 《Physical review letters》1989,63(20):2181-2184
2.
Mohanad A. Hussein Dr. Uyen P. N. Tran Dr. Vien T. Huynh Dr. Junming Ho Dr. Mohan Bhadbhade Prof. Dr. Herbert Mayr Dr. Thanh V. Nguyen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1471-1475
Tropylium bromide undergoes noncatalyzed, regioselective additions to a large variety of Michael acceptors. In this way, acrylic esters are converted into β-bromo-α-cycloheptatrienylpropionic esters. The reactions are interpreted as nucleophilic attack of bromide ions at the electron-deficient olefins and the approach of the tropylium ion to the incipient carbanion. Quantum chemical calculations were performed to elucidate the analogy to the amine- or phosphine-catalyzed Rauhut–Currier reactions. Subsequent synthetic transformations of the bromo-cycloheptatrienylated adducts are reported. 相似文献
3.
Optical,Electrical, and Magnetic Studies of Organic Solar Cells Based on Low Bandgap Copolymer with Spin ½ Radical Additives
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Tek Basel Uyen Huynh Tianyue Zheng Tao Xu Luping Yu Z. Valy Vardeny 《Advanced functional materials》2015,25(12):1895-1902
The charge photogeneration and recombination processes in organic photovoltaic solar cells based on blend of the low bandgap copolymer, PTB7 (fluorinated poly‐thienothiophene‐benzodithiophene) with C60‐PCBM using optical, electrical, and magnetic measurements in thin films and devices is studied. A variety of steady state optical and magneto‐optical techniques were employed, such as photoinduced absorption (PA), magneto‐PA, doping‐induced absorption, and PA‐detected magnetic resonance (PADMR); as well as picosecond time‐resolved PA. The charge polarons and triplet exciton dynamics in films of pristine PTB7, PTB7/fullerene donor–acceptor (D–A) blend is followed. It is found that a major loss mechanism that limits the power conversion efficiency (PCE) of PTB7‐based solar cell devices is the “back reaction” that leads to triplet exciton formation in the polymer donor from the photogenerated charge‐transfer excitons at the D–A interfaces. A method of suppressing this “back reaction” by adding spin½ radicals Galvinoxyl to the D–A blend is presented; this enhances the cell PCE by ≈30%. The same method is not effective for cells based on PTB7/C70‐PCBM blend, where high PCE is reached even without Galvinoxyl radical additives. 相似文献
4.
Gregory B. Kharas Xue Tian Trang H. Huynh Thomas W. Lyons Lani A. Macartney Dylan Smith 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):469-473
Electrophilic trisubstituted ethylene monomers, halogen ring‐disubstituted 2‐cyano‐N,N‐dimethyl‐3‐phenyl‐2‐propenamides, RC6H3CH?C(CN)CON(CH3)2 (where R is 2,3‐dichloro, 2,4‐dichloro, 2,6‐dichloro, 3,4‐dichloro, 3,5‐dichloro, 2,3‐difluoro, 2,4‐difluoro, 2,6‐difluoro, 3,4‐difluoro, 3,5‐difluoro), were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring‐substituted benzaldehydes and N,N‐dimethyl cyanoacetamide, and characterized by CHN elemental analysis, IR, 1H‐ and 13C‐NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, ABCN at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C NMR, GPC, DSC, and TGA. High Tg of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. The gravimetric analysis indicated that the copolymers decompose in the 300–450°C range. 相似文献
5.
6.
Mohanad A. Hussein Uyen P. N. Tran Vien T. Huynh Junming Ho Mohan Bhadbhade Herbert Mayr Thanh V. Nguyen 《Angewandte Chemie (International ed. in English)》2020,59(4):1455-1459
Tropylium bromide undergoes noncatalyzed, regioselective additions to a large variety of Michael acceptors. In this way, acrylic esters are converted into β‐bromo‐α‐cycloheptatrienylpropionic esters. The reactions are interpreted as nucleophilic attack of bromide ions at the electron‐deficient olefins and the approach of the tropylium ion to the incipient carbanion. Quantum chemical calculations were performed to elucidate the analogy to the amine‐ or phosphine‐catalyzed Rauhut–Currier reactions. Subsequent synthetic transformations of the bromo‐cycloheptatrienylated adducts are reported. 相似文献
7.
The Internet is a set of interconnected domains in which different QoS technologies can be deployed. The dynamic provision of end-to-end QoS over heterogeneousip networks assumes the negotiation of mutually acceptablesla. This paper presents the concept of intra-, inter- and multiple-domain service level negotiation using thecops-sls protocol. The negotiation process gives different parties in the negotiation the ability to agree upon the service level that a data stream can obtain, along with the permissible pricing of the service. 相似文献
8.
Series of dipeptides, including homodipeptides and alanyl dipeptides, were separated using quadruplex (G-quartet) DNA stationary phases in open-tubular capillary electrochromatography (OTCEC). The stationary phases were constructed by covalently attaching the DNA oligonucleotides to the inner capillary surface. Three different G-quartet forming oligonucleotides were investigated: the two-plane G-quartet forming thrombin-binding aptamer, the four-plane analogue of the thrombin-binding aptamer, and a two-plane oligonucleotide identical to the thrombin-binding aptamer except for the replacement of the guanine by thymine in the central bridging loop of the G-quartet structure. Results were compared with results obtained using capillary electrophoresis on a bare capillary and OTCEC using an oligonucleotide with the same base composition as the thrombin-binding aptamer but in a different sequence that does not allow G-quartet formation as the stationary phase. 相似文献
9.
We report a protocol for on-chip electrophoretic sample loading and sample component separation in which each operation requires simultaneous control of the potential of only two electrodes: during the sample-loading phase, the potentials at the ends of the separation channel are electrically floating; during electrophoresis of the sample mixture down the separation channel, the potentials at the ends of the sample-introduction channel are floating. This method, which we call "floating-stacking," avoids the dispersion/distortion of the sample plug that is commonly associated with simultaneous electrical control of only two electrodes in a crossed-channel or offset-double-tee injection system. Further, when this floating loading/separation is done in the presence of back-transient-isotachophoresis, sample loss from the plug of material being injected is minimal and a significant concentration increase--up to 13x--of the sample components in the separated bands occurs relative to the commonly used "pinch-and-pull-back" technique (which requires simultaneous electrical control of four electrodes). 相似文献
10.
Dr. Nguyet Trang Thanh Chau Maxime Meyer Dr. Shinsuke Komagawa Dr. Floris Chevallier Prof. Yves Fort Prof. Masanobu Uchiyama Prof. Florence Mongin Dr. Philippe C. Gros 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(41):12425-12433
Homoleptic lithium tri‐ and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine–metal exchanges were realized at room temperature with a substoichiometric amount of nBu4ZnLi2?TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine). This reactivity contrasted with that of tBu4ZnLi2?TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N???Li stabilized polypyridyl zincates in the reaction. The one‐pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C? Zn bonds in bromopyridines enabled us to perform efficient Negishi‐type cross‐couplings. 相似文献