The preparation of a variety of novel perfluoroalkyl-substituted compounds in high yields using easily prepared (perfluoroalky1)trimethylsilanes (la-c) is described. (Trifluoromethy1)-, (pentafluoroethy1)-, and (heptafluoropropyl)trimethylsilane, la-c, respectively, react readily with carbonyl compounds, such as aldehydes and ketones, by a fluoride-initiated catalytic process. Fluoride-initiated addition of 1 to a carbonyl group generates an oxyanionic species which then further catalyzes the reaction. Even enolizable carbonyl compounds react cleanly under the reaction conditions. A study of the scope of the reactivity of la toward other carbonyl groups in esters, lactones and an acid chloride was also carried out. Thus la reacts cleanly with five-and six-membered ring lactones.However, unactivated esters do not react under the reaction conditions. The acid chloride reacts with la to give a mixture of products.
Abstract-The Multicast/Broadcast Service (MBS) feature of mobile WiMAX network is a promising technology for providing wireless multimedia, because it allows the delivery of multimedia content to large-scale user communities in a cost-efficient manner. In this paper, we consider WiMAX networks that transmit multiple video streams encoded in scalable manner to mobile receivers using the MBS feature. We focus on two research problems in such networks: 1) maximizing the video quality and 2) minimizing energy consumption for mobile receivers. We formulate and solve the substream selection problem to maximize the video quality, which arises when multiple scalable video streams are broadcast to mobile receivers with limited resources. We show that this problem is NP-Complete, and design a polynomial time approximation algorithm to solve it. We prove that the solutions computed by our algorithm are always within a small constant factor from the optimal solutions. In addition, we extend our algorithm to reduce the energy consumption of mobile receivers. This is done by transmitting the selected substreams in bursts, which allows mobile receivers to turn off their wireless interfaces to save energy. We show how our algorithm constructs burst transmission schedules that reduce energy consumption without sacrificing the video quality. Using extensive simulation and mathematical analysis, we show that the proposed algorithm: 1) is efficient in terms of execution time, 2) achieves high radio resource utilization, 3) maximizes the received video quality, and 4) minimizes the energy consumption for mobile receivers.
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