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Ultraviolet light induced free radical alkylation of poly U or of poly A with 2-propanol leads to the specific formation of 6-(2-hydroxy 2-propyl) 5,6-dihydro-UMP or 8-(2-hydroxy 2-propyl)-AMP residues, respectively. The biochemical significance of the alterations in the modified polynucleotides was studied by testing their messenger activities in a cell free system of E. coli. Both photoalkylated poly U and poly A have reduced functional activity, with no change in functional specificity. This was demonstrated by inhibition of polymerization of phenylalanine and lysine directed by photoalkylated poly U and poly A, respectively, and by lack of misincorporation of other amino acids. The modification of poly U also caused the disappearance of misincorporation of serine that was found with the native polynucleotide. 相似文献
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Zvi Ritz 《Mathematical Social Sciences》1983,4(2):155-179
An n-person social choice problem is considered in which the alternatives are n dimensional vectors, with the ith component of such a vector being the part of the alternatives affecting individual i alone. Assuming that individuals are selfish (individual i must be indifferent between any two alternatives with the same components), that they may be indifferent among alternatives and that each individual may choose his preferences out of a different set of permissible preferences, we prove that any set of restricted domains of preferences admits an n person non-dictatorial Arrow-type social welfare function if and only if it admits a two-person Arrow-type social welfare function: we characterize all the sets of restricted domains of preferences which admit two-person Arrow-type social welfare functions (and therefore also admit n-person Arrow-type social welfare functions) and then we prove that we also characterized all the sets of restricted domains of preferences which admit nondictatorial, nonmanipulable, noncorruptible and rational social choice correspondences. 相似文献
98.
Zvi Drezner 《Operations Research Letters》2005,33(5):475-480
We introduce the compounded genetic algorithm. We propose to run a quick genetic algorithm several times as Phase 1, and compile the best solutions in each run to create a starting population for Phase 2. This new approach was tested on the quadratic assignment problem with very good results. 相似文献
99.
Retail facility location under changing market conditions 总被引:2,自引:0,他引:2
In this paper we investigate the location of retail facilitiesunder changing market conditions when market conditions areexpected to change during the planning horizon. Three modelsare presented: (1) the minimax regret model where the objectivefunction is to minimize the maximum possible loss under differentmarket scenarios, (2) the Stackelberg equilibrium model wherebya future competitor enters the market and one wishes to maximizethe market share captured throughout the planning horizon incorporatingthe market share loss to the competitor, and (3) the thresholdmodel in which we consider a minimum threshold level such thatif the market share captured by the new facility fails to reachthat threshold, the facility will not survive. Our objectiveis to minimize the probability of failure. 相似文献
100.
Bernasconi CF Brown SD Eventova I Rappoport Z 《The Journal of organic chemistry》2007,72(9):3302-3310
A spectroscopic and kinetic study of the reaction of methyl beta-methylthio-alpha-nitrocinnamate (4-SMe) with morpholine, piperidine, and hydroxide ion in 50% DMSO/50% water (v/v) at 20 degrees C is reported. The reactions of 4-SMe with piperidine in a pH range from 10.12 to 11.66 and those with morpholine at pH 12.0 are characterized by two kinetic processes when monitored at lambdamax (364 nm) of the substrate, but by only one process when monitored at lambdamax (388) nm of the product. The rate constants obtained at 388 nm were the same as those determined for the slower of the two processes at 364 nm. These rate constants refer to product formation, whereas the faster process observed at 364 nm is associated with the loss of reactant to form an intermediate. In contrast, for the reaction of 4-SMe with morpholine at pH 8.62 the rates of product formation and disappearance of the substrate were the same, i.e., there is no accumulation of an intermediate. Likewise, the reaction of 4-SMe with OH- did not yield a detectable intermediate. The factors that allow the accumulation of intermediates in certain SNV reactions but not in others are discussed in detail, and structure-reactivity comparisons are made with reactions of piperidine and morpholine with other highly activated vinylic substrates. 相似文献