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71.
F. Diaz Camacho R. Le Lagadec Alexander D. Ryabov L. Alexandrova 《Journal of polymer science. Part A, Polymer chemistry》2008,46(12):4193-4204
The cyclometalated complex [RuII(o‐C6H4‐py)(MeCN)4]PF6 ( 1 ) with a σ‐Ru? C bond and four substitutionally labile acetonitrile ligands mediates radical polymerization of different vinyl monomers, viz. n‐butyl acrylate, methyl methacrylate, and styrene, initiated by three alkyl bromides: ethyl 2‐bromoisobutyrate, methyl 2‐bromopropionate, and 1‐phenylethyl bromide. The polymerization requires the presence of Al(OiPr)3 and occurs uncontrollably as a conventional radical process. The variation of the molar ratio of the components of the reaction mixture, such as initiator, Al(OiPr)3 and catalyst, affected the polymerization rates and the molecular weights but did not improve the control. A certain level of control has been achieved by adding 0.5 eq of SnCl2 as a reducing agent. Tin(II) chloride decreased the rate of polymerization and simultaneously the molecular weights became conversion‐dependent and the polydispersities were also narrowed. Remarkably, the level of control was radically improved in the presence of excess of the poorly soluble catalyst ( 1 ), when the added amount of ( 1 ) was not soluble any more, i.e., under heterogeneous conditions, the system became adjustable and the living polymerization of all three monomers was finally achieved. Possible mechanisms of the ( 1 )‐catalyzed polymerization are discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4193–4204, 2008 相似文献
72.
The properties of the negative parity states of55Fe and57Fe are investigated in the framework of the intermediate coupling model. In the model, a neutron or a quasineutron is coupled to anharmonic vibrations of the core. Anharmonicities of the vibrations are estimated through the observed properties of the core. Energy levels, spectroscopic factors and electromagnetic properties have been calculated. The results of the present calculations are also compared with available experimental results and other theoretical results. The model reasonably accounts for many of the properties of the low-lying states. 相似文献
73.
Jaume Casabó Andreu Solans Carmen Diaz Joan Ribas Alexandre Seguí Montserrat Corbella 《Transition Metal Chemistry》1985,10(4):128-130
Summary Mixed difluoro(diamine)(diamme)chromium(III) complexes have been synthesized with ethylenediamine (en), 1,3 propanediamine(tn) and 1,2-cyclohexanediamine(chxn):trans-[CrF2(aa)(bb)]Br (aa=en, bb=tn; aa=tn, bb= chxn) andcis-[CrF2(aa)(bb)]Br (aa=en, bb=chxn). The corresponding fluoroaqua(diamine) (diamine)chromium(III) complexes have been prepared by acid hydrolysis as perchlorate or iodide salts. All have been characterized by chemical analysis, electronic and i.r. spectra and conductivity measurements. 相似文献
74.
75.
76.
R. G. Thompson P. S. Dharmapala J. Diaz M. D. González-Lima R. M. Thrall 《Annals of Operations Research》1996,66(2):163-177
The setE of extreme points which are also efficient are of basic importance in defining the efficiency frontier, from which the observations for all other DMUs are evaluated in DEA. A significant question which we address is “What variations in the data can be tolerated before the membership inE is changed?” This topic is explored using (1) a simple illustrative example, and (2) production data for 30 independent oil companies during the period 1983–1985. Data were allowed to vary simultaneously for all observations and in different subsets determined by random drawings of data for points both inE and not inE. The results were found to be robust in this study, thereby lending further support to earlier studies which also found these classifications into efficient and inefficient performers to be robust in DEA. Technical developments for these new methods of sensitivity analysis are supplied. These developments feature an application of analytic center (interior point) algorithms which ensure that the Strong Complementary Slackness Condition (SCSC) is fulfilled. The solutions satisfy a mathematical condition called “centrality”. Generally, the solutions are at interior points calledanalytic centers. At these interior points, continuity of the input-output ratios ensures that DMUs inE remain inE for at least small relative variations in the data, while empirically these properties have been found to extend to much larger variations in the data sets. 相似文献
77.
Thin film coatings were prepared by polymerizing trifluoromethyl-substituted aromatic compounds in a glow discharge with low power levels and medium pressures. Smooth, continuous films which are adherent and insoluble in conventional solvents were produced. A significant amount of the fluorine content from the monomer was retained in the polymer. The trifluoromethyl group was not removed by the plasma conditions and appeared in the film as trifluoromethyl and difluoromethylene groups. The films were slightly less wettable than those of the unfluorinated films. 相似文献
78.
L. H. Tagle J. F. Neira F. R. Diaz R. S. Ramirez 《Journal of polymer science. Part A, Polymer chemistry》1975,13(12):2827-2833
Novel polyamide-imides were prepared from 3′,4′-dicarboxy-4″-chloroformyl terephthaloylphenone anhydride and various aromatic and aliphatic diamines. The polymers were characterized by viscosity, infrared spectra, TGA, DSC, and elemental analysis. The thermal stability of the films was comparable to that of polyamide-imides previously reported. 相似文献
79.
80.
J. B. Diaz 《Annali di Matematica Pura ed Applicata》1960,52(1):163-181
Summary After a preliminary survey of related results, a general uniqueness theorem for the ordinary differential equation dy/dx=f(x,
y) is given in section 4. The general uniqueness theorem for the hyperbolic partial differential equation uxy=f(x, y, u), proved in section 5, is an exact analogue of the general uniqueness theorem for the ordinary differential equation
dy/dx=f(x, y).
This research was supported in part by the United States Air Force through the Air Force Office of Scientific Research and
Development Command under Contract No. AF 49(638)-228.
This is a detailed account of lectures given at the Sixth Conference of Arsenal Mathematicians, held at Duke University Durham,
North Carolina, June 1, 2, 1960, and at the Symposium on the Numerical Treatment of Ordinary Differential Equations, Integral
and Integro-Differential Equations, Rome, 20–24 September 1960. 相似文献