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891.
Chi-Yu Chen Charles U. Pittman John N. Helbert 《Journal of polymer science. Part A, Polymer chemistry》1980,18(1):169-178
The radiation degradation behavior of methyl α-chloroacrylate (MCA) and methacrylonitrile (MCN) copolymers has been investigated as part of a program to develop high-sensitivity polymeric resists for integrated circuit manufacture. High-molecular-weight copolymers were prepared by emulsion techniques. Several different copolymer compositions were prepared varying from 19 to 68 mole % MCA. These copolymers were fractionated and then subjected to γ irradiation from a 60Co Source. The Gs - Gs, Gs - 4Gs values were determined from M?;F>nk?1 and Gu?1 versus dose plots, and the Gfs and Gs Values were then calculated. Molecular weights of both unirradiated and irradiated polymers were analyzed by membrane osmometry and gel permeation chromatography. All copolymers exhibited higher degradation susceptibilities than that of poly(methyl methacrylate) (PPMA), which has Gx = 1.3. The individual Gx and Gx values of the copolymers were found to fall between those of the two homopolymers, poly(methyl α-chloroacrylate) (Gx = 6.0) and polymethacrylonitrile (Gx ~ 3.1). The dependence of Gx and Gx values on molecular weight was minor. The crosslinking susceptibility of the poly(methyl α-chloroacrylate) (Gx ~ 0.8), was greatly decreased by copolymerization with MCN. Relatively small amounts of MCN caused a large drop in Gx, i.e., Gx ~ 0.15 at 32% MCN and Gx ~ 0.03 at 51% MCN. The observation could be attributed to the decreasing probability that crosslinking sites, in the MCA monomer units on adjacent chains, would lie in close proximity. 相似文献
892.
Yu. Arestov A. Borovikov E. Kozlovsky A. Minaenko A. Moiseev C. Cochet D. Denegri C. Lewin M. A. Turluer U. Gensch H. J. Grabosch W. Lohmann J. MacNaughton France-USSR Collaboration CERN-USSR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1981,8(4):283-289
New data on the inclusive production of the non-strange resonances ?0(770), ω(783), ?(1020) andf(1270) inK ? p interactions at 32 GeV/c are presented. The inclusive production cross sections are equal to (4.32±0.72) mb, (3.7±1.4) mb, (0.65±0.10) mb and (0.91±0.35) mb respectively. Estimates of the topological cross sections are also obtained. The invariant and non-invariantx-distributions for the vector mesons ?0 and ? indicate the prevalence of forward resonance production in the c.m. system. For the tensorf-meson the rapidity andx-distributions are presented. Thet′-distributions for ?0, ?, andf have exponential slopes of 0.6±0.1 GeV?2, 1.2±0.2 GeV?2, and 0.8±0.5 GeV?2 respectively. The exponential slope ofp T 2 -distribution of thef-meson is equal to (2.3±0.5) GeV?2. 相似文献
893.
Summary A simple method has been developed to determine the concentration of organic chlorine in waste oil. The determination is based on the conversion of organic chlorine to inorganic chloride by reaction with sodium biphenyl followed by extraction with nitric acid and a mixture of nitric acid and water. The concentration of chloride is determined by direct potentiometry with an ion-selective electrode. The limit of determination amounts to 3·10–5 mol·l–1 chloride ions with a standard deviation of 3.5%. Different samples of waste oil have been analyzed and the results have been compared to those obtained by combustion in a H2/O2 flame followed by potentiometric titration with silver nitrate. 相似文献
894.
S. Ravi S. Ravi A. K. Deepa A. K. Deepa S. Susheela S. Susheela P. V. Achuthan P. V. Achuthan S. Anil Kumar U. Jambunathan 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(1):79-82
Summary A method has been developed for the estimation of 90Sr in reprocessed uranium oxide samples obtained from the Purex processing of natural uranium spent fuel discharged from the
research reactor. The method employs a combination of precipitation and solvent extraction procedure to eliminate other beta-impurities
prior to resorting to the estimation of 90Sr by beta-counting. 106Ru was eliminated by volatalizing with perchloric acid, uranium was removed by carrier precipitation with strontium as sulphate.
The sulphate precipitate was converted to carbonate and dissolved in nitric acid. 234Th and 234Pa were eliminated by synergistic solvent extraction using tri-n-butyl phosphate and thenoyl trifluoroacetone extractant mixture
in xylene. An iron scavenging step was included to remove any residual impurities. Finally, strontium is precipitated as SrC2O4. H2O. The separated 90Sr activity was followed to check the equilibrium growth of 90Y. 相似文献
895.
The effect of 4,6-O-benzylidene acetals, 4,6-O-phenylboronate esters, and 4,6-O-polystyrylboronate esters on the stereoselectivity of couplings to galacto-, gluco-, and mannopyranosyl thioglycosides, otherwise protected with benzyl ethers, has been investigated by the benzenesulfinyl piperidine/trifluoromethanesulfonic anhydride (BSP), diphenyl sulfoxide/trifluoromethanesulfonic anhydride (Ph(2)SO), and N-iodosuccinimide/trimethylsilyl trifluoromethanesulfonate (NIS/TMSOTf) methods. The BSP and Ph(2)SO methods give comparable results in all three systems whereas the NIS method affords significantly different stereoselectivities in both the gluco and manno, but not the galacto series. The benzylidene acetal and boronate esters influence the stereochemistry in a similar manner in the beta-selective manno series and the alpha-selective galacto series but show significant differences with the glucose donors. The differences between the glucose, galactose, and mannose series reflect the established differences in reactivity and, especially for mannose, those in the anomeric effect and are best interpreted in terms of changes in the relative energetics between the alpha- and beta-covalent triflate intermediates and the various contact ion pairs with which they are necessarily in equilibrium. 相似文献
896.
Summary Copper, palladium and nickel can be titrated amperometrically with 2,5-dihydroxyacetophenone oxime at –0.15, –0.4 and, –1.2 V vs. S. C. E. respectively, the optimum pH values being 4.6, 4.0, and 9.0. Alkali and alkaline earth metals, Al, Bi, Cd, Co, Cr. Fe(II), Hg, Mn, Ni, Pb, Th, Zn, UO, W, and Zr do not interfere with the estimation of copper and palladium. The interferences due to the presence of silver and iron(III) can be eliminated by adding excess of KCl and KF respectively. Most heavy metals interfere with the estimation of nickel and should be eliminated before titration.
Zusammenfassung Kupfer, Palladium und Nickel können mit 2,5-Dihydroxyaeetophenonoxim bei –0,15, –0,4 bzw. –1,2 V gegen eine gesättigte Kalomelelektrode amperometrisch titriert werden, wobei man das pH am besten auf 4,6, 4,0 bzw. 9,0 hält. Alkalimetalle, Erdalkalien, Al, Bi, Cd, Co, Cr, Fe(II), Hg, Mn, Ni, Pb, Th, Zn, UO2, W und Zr stören die Bestimmung des Kupfers und des Palladiums. Silber und Eisen können mit Kaliumchlorid gefällt bzw. mit Kaliumfluorid maskiert werden. Die meisten Schwermetalle stören die Nickelbestimmung und müssen daher vor der Titration entfernt werden.相似文献
897.
V. N. Odinokov G. Yu. Ishmuratov R. Ya. Kharisov M. P. Yakovleva R. M. Sultanov É. P. Serebryakov U. M. Dzhemilev G. A. Tolstikov 《Chemistry of Natural Compounds》1991,27(4):494-496
The synthesis has been effected of octa-2E,6E-diene-1,8-diol diisovalerate — the sex pheromone of the Crimean click beetleAgriotes tauricus — by the carboxymethylenation of the readily available 6-methylhept-5-en-2-one, the allyl oxidation of a terminal methyl group, reduction of the ester fraction, and interaction of the diol so obtained with isovaleryl chloride. The required pheromone can also be obtained from available cyclic oligomers of isoprene. 相似文献
898.
899.
Primary emphasis is placed on the effects of coating parameters such as coating thickness and tip size, the coating thickness variations due to different draw speeds, and induced maximum shear rate in the applicator. However, in this analysis the flow region is divided into two because of the mixed boundary conditions: non-slip condition (region I) and free shear condition along the meniscus (region II). The surface tension at the edge in region II is balanced with the pressure difference, which becomes a constraint for the flow rate. 相似文献
900.
Energy spectra andB(E2) values of the even-even Kr isotopes74–82Kr have been analyzed in terms of the IBA-2 model of Otsuka, Arima and Iachello [6, 7]. We can reproduce the variation of collectivity along the isotope chain by means of a consistent set of 5 parameters, essentially only one of them has been varied with neutron number. The low lying 0 2 + states have been found to be strongly influenced by shell effects. Predictions are given for the not yet observed gamma bands of74,76Kr. 相似文献