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121.
122.
Two atom insertions into the silacyclopropane and silacyclopropene rings: mechanistic considerations
Dietmar Seyferth Steven C. Vick Mark L. Shannon Thomas F.O. Lim Don P. Duncan 《Journal of organometallic chemistry》1977,135(2):C37-C44
Novel two atom insertion reactions into the SiC2 rings of hexamethylsilirane and 1,1-dimethyl-2,3-bis(trimethylsilyl)-1-silirene involving the C bonds of styrene and α-methylstyrene, 1,3-butadiene and its 2-methyl and 2,3-dimethyl derivatives, and, in the presence of ultraviolet radiation, of aliphatic aldehydes and ketones, are reported. A radical mechanism is suggested tobe operative in these reactions. Also described are novel palladium-catalyzed reactions of the silirene with terminal and internal acetylenes. 相似文献
123.
Jiang W Zhitenev N Bao Z Meng H Abusch-Magder D Tennant D Garfunkel E 《Langmuir : the ACS journal of surfaces and colloids》2005,21(19):8751-8757
Organic thiols have received extensive attention recently because of their relative stability and ease of examination compared to other potential molecular electronic materials. In this work, scanning probe microscopy (SPM) is used to study (i) the structural properties of self-assembled monolayers (SAMs) containing conjugated dithiols and (ii) the formation of the upper molecule-metal interface on dithiol SAMs. The top gold film is deposited either by thermal evaporation or by nano-transfer printing (nTP). Generally, the utility of thermal evaporation is limited because of Au diffusion through the SAMs. However, several dithiol SAMs are identified in this work that bond well to Au overlayers and act as satisfactory diffusion barriers. Coassembly of conjugated dithiols and alkanemonothiols is suggested as a route to obtain dithiols that are denser packed and more vertical (than is obtained from pure dithiol routes). High-yield nTP is demonstrated on coassembled SAMs. Advantages and limitations of different Au deposition and transfer techniques are compared on a variety of length scales. 相似文献
124.
Don?A.?GrundelEmail author Panos?M.?Pardalos 《Computational Optimization and Applications》2005,30(2):133-146
The multidimensional assignment problem (MAPs) is a higher dimensional version of the standard linear assignment problem. Test problems of known solution are useful in exercising solution methods. A method of generating an axial MAP of controllable size with a known unique solution is presented. Certain characteristics of the generated MAPs that determine realism and difficulty are investigated. 相似文献
125.
Dedication
Willem J. Blok 1947–2003 相似文献126.
127.
The relationship between the closed-shell repulsive interactions and overlap of the electron densities is investigated. It is found that the repulsive interactions vary in almost direct proportion to the absolute size of the density overlaps. 相似文献
128.
Froimowitz Mark Wu Kuo-Ming George Clifford VanDerveer Don Shi Qing Deutsch Howard M. 《Structural chemistry》1998,9(4):295-303
The crystal structures of the chloride salts of five analogs of threo-methylphenidate have been obtained. Four of these have different substituents on the phenyl ring while the fifth is the ethyl ester of methylphenidate. All five structures have similar three-dimensional conformations and these are compared with the global minimum obtained by MM2-87 calculations. There is good agreement between the crystal structures and the computed global minimum with the major difference being the presence of a chloride counterion in the crystal structures that prevents the carbonyl oxygen from approaching the equatorial ammonium hydrogen as closely as in the computed global minimum. 相似文献
129.
Jae Hyoung Ryu S. Chandramohan Hee Yun Kim Hyun Kyu Kim Ji Hye Kang Chang-Hee Hong Hyun Kyong Cho Hyun Don Song Ho-Ki Kwon 《Journal of Crystal Growth》2011,314(1):66-70
The effect of selective area growth (SAG) on wafer bowing of GaN-based light-emitting diodes (LEDs) is investigated. The SAG of LED structures was carried out on a silicon dioxide (SiO2) mask pattern with periodic 1000×1000 μm openings, along the sapphire 〈1?1 0 0〉 and 〈?1?1 2 0〉 directions. The morphology of a selectively-grown n-GaN epilayer was examined in relation to various growth parameters such as temperature, pressure, and V/III ratio. Under optimized growth conditions, formation of a ridge-shaped epilayer with a v-pit free smooth surface was realized. Furthermore, the ridge-shaped vertical LED structure, after the removal of the sapphire substrate by laser lift-off (LLO) showed less wafer bowing compared with conventional vertical LED structures. This is attributed to the suppression of lateral strain and dislocations during the site-selective growth process, due to a reduction in the lateral dimensions. 相似文献
130.
Feng-Hsi Huang Ching-Chung Chen Dar-Jong Lin Trong-Ming Don Liao-Ping Cheng 《Journal of nanoparticle research》2010,12(8):2941-2950
A series of photochromic phosphotungstic acid (PWA)/SiO2 composites were synthesized using the sol-gel method. Depending on the feeding schedule of PWA during synthesis, the size of the formed PWA/SiO2 particles varied considerably from as small as 1.2 nm to ca. 10 nm. With decreasing silica particle size, the total contact area/interaction between SiO2 and PWA increases, as revealed by FT-IR and solid-state 29Si-NMR analyses. Particularly, when the size of PWA/SiO2 is ~1 nm, crystallization of PWA is inhibited, and PWA presents as amorphous molecular entities distributing uniformly in the SiO2 host, which is in evidence in the XRD spectroscopy and HR-TEM imaging. In contrast, substantial crystallization of PWA takes place when PWA/SiO2 particles are as large as 10 nm, in which case less amount of surface free Si-OH is available for PWA to make bonds with. Photochromism occurs activated by ultraviolet light irradiation. The rate of coloration/bleaching is found to depend strongly on the particle size of PWA/SiO2; specifically, the rate increases twice when the particle size is reduced from 10 nm to 1.2 nm. 相似文献