Controlled Radical Polymerization

Various methods which lead to the control of molecular weight and polydispersities, and which allow for the preparation of block copolymers by radical polymerization are discussed. Thermal polymerizationof styrenes in the presence of stable radicals, polymerization of vinyl acetate and methyl methacrylate in the presence of chromium complexed by macrocyclic ligands polymerization of vinyl acetate initiated by organoaluminum compounds complexed by dipyridyl and activated by stable radicals, as well as in the presence of phosphites, are described in detail.     

蜂窝电话功率放大器-天线接口的自适应调谐

本文分析了目前无线产品设计面临的挑战，提出了一种只需少量电路，占用较少电路板面积的解决方案，即将功率放大器和前端模块RF装置集成到天线结构的蜂窝无线电天线模块中，针对天线负载条件使天线和RF电路实现最佳匹配。     

Synthesis and structure of a heptanuclear nickel(II) complex uniquely exhibiting four distinct binding modes,two of which are novel,for a hydroxamate ligand

The reaction of 2-(dimethylamino)phenylhydroxamic acid (2-dmAphaH) with NiSO(4).6H2O gives the complex [Ni7(2-dmAphaH-1)2(2-dmApha)8(H2O)2]SO(4).15H2O uniquely exhibiting four distinct hydroxamate binding modes, two of which are novel, and showing both antiferromagnetic and ferromagnetic interactions in contrast to [Cu5(2-dmAphaH-1)4(HSO4)2(MeOH)2].2MeOH, a strongly antiferromagnetic metallacrown formed with CuSO(4).5H2O.     

Probing the dimensions of semi-rigid inner functionalised U-shaped bis-porphyrin cavities

The synthesis of a series of open U-shaped bis-porphyrin cavity molecules is described, with bridged bicyclic backbones to confer rigidity, and a pendant substituted aromatic probe unit suspended on the inside of the cavity. The dimensions and flexibility of the bis-zincporphyrin cavity were probed using several different techniques. Initially the molecular ruler concept was employed, using flexible bidentate ligands as guests with a range of possible linear dimensions. Secondly, NMR methods were employed with rigid bidentate ligand guests of fixed lengths, and thirdly diffusion based NMR methods were utilised. The range of inter-porphyrin distances estimated by these methods suggests that these types of open-cavity systems have a surprising degree of flexibility.     

Simple and effective one‐pot synthesis of (meth)acrylic block copolymers through atom transfer radical polymerization

The synthesis of di‐ and triblock copolymers using atom transfer radical polymerization (ATRP) of n‐butyl acrylate (BA) and methyl methacrylate (MMA) is reported. In particular, synthetic procedures that allow for an easy and convenient synthesis of such block copolymers were developed by using CuBr and CuCl salts complexed with linear amines. Polymerizations were successfully conducted where the monomers were added to the reactor in a sequential manner. Poor cross‐propagation between poly(n‐butyl acrylate) (PBA) macroinitiators and MMA was minimized, and therefore control of molecular weights and distributions was realized, by using halogen exchange—a technique involving the addition of CuCl to the MMA during the chain extension of the PBA macroinitiator. High molecular weight (M_n ∼ 90,000) and low polydispersity (M_w /M_n < 1.35) ABA triblock copolymers were also prepared and their structure and properties in bulk have been preliminary characterized indicating the potential of ATRP for the production of all‐acrylic thermoplastic elastomers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2023–2031, 2000     

Synthesis and characterization of graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates by atom transfer radical polymerization

Graft copolymers of poly(vinyl chloride) with styrene and (meth)acrylates were prepared by atom transfer radical polymerization. Poly(vinyl chloride) containing small amount of pendent chloroacetate units was used as a macroinitiator. The formation of the graft copolymer was confirmed with size exclusion chromatography (SEC), ¹H NMR and IR spectroscopy. The graft copolymers with increasing incorporation of butyl acrylate result in an increase of molecular weight. One glass transition temperature (T_g) was observed for all copolymers. T_g of the copolymer with butyl acrylate decreases with increasing content of butyl acrylate.     

A 10-Gb/s laser/modulator driver IC with a dual-mode activelymatched output buffer

A laser/modulator driver IC for 10-Gb/s-SONET OC-192-fiber optic transmitters is described. Depending on the user application, the IC is capable of driving more than 100 mA of current into a laser diode or over 50 mA into an electro-absorption or Mach-Zehnder modulator. Rise and fall times below 20 pS are achieved. The driver employs a novel dual-mode actively matched output buffer that provides a dc-coupled back termination of either 25 or 50 Ω. Compared to an output buffer with a resistive termination, this buffer dissipates only half as much power. In addition, the buffer has the the ability to reject external bias and will therefore not load bias sources used to set laser threshold currents and modulator offset voltages. The low power consumption makes the IC most suitable for co-packaging with uncooled lasers and electro-absorption modulators. The driver is fabricated in a 0.25-μm gate length production GaAs PHEMT process with substrate thru vias, thin-film resistors, and MIM capacitors     

GC/MSD detection of the metabolic residues of metolachlor in tomato fruit

Summary A gas chromatograph/mass selective detector method is presented for the analysis of the major metabolic residues of metolachlor by acid hydrolysis of tomato fruit. The two major hydrolysis products, CGA-37913 (2-[2-ethyl-6-methylphenyl]amino-1-propanol) and derivatised CGA-49751 (4-[2-ethyl-6-methylphenyl]-2-hydroxy-5-methyl-3-morpholinone) were monitored in the selective ion mode atm/z 162 andm/z 160, respectively. Recoveries from 87 to 96% were obtained for tomato fortified at 50 to 200g kg^–1. The proposed method of analysis will allow for a detection limit of 11 g kg^–1 for CGA-37913 and 12 g kg^–1 for the derivatised CGA-49751.     

The Approach of Operational Research to Planning in India

Journal of the Operational Research Society -