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41.
1,1-Dimethyl-3-phenylpyrazolium-5-oxide (1) was isolated as a minor product (3%) in the reaction of ethyl benzoylacetate with 1,1-dimethylhydrazine and also was obtained as the major product (58%) from the reaction of methyl p-toluenesulfonate with ethyl benzoylacetate dimethylhydrazone. The structural assignment was made on the basis of chemical reactions and spectral data and the formula is represented by a resonance structure for which there are two principal canonical forms. Reaction of 1 with methanol at room temperature afforded methyl benzoylacetate dimethylhydrazone. Ethyl benzoylacetate dimethylhydrazone was shown to exist as a tautomeric mixture containing 65% of the imine form at room temperature. 相似文献
42.
D. J. Williams E. G. Bobalek 《Journal of polymer science. Part A, Polymer chemistry》1966,4(12):3065-3079
It is possible to generate, in specially formulated styrene emulsion polymerizations, latices in which the monomer—polymer particles are uniform through all stages of growth. These latices are kinetically similar to their polydispersed counterparts and can therefore be used as model systems in generalized kinetic studies of emulsion polymerization. The most important feature of these systems is the fact that the particles are uniform throughout the reaction with regard to all intrinsic properties and rate processes, and the particles can be characterized by this complete, continuous uniformity. Certain remarkably simple, but precise, relationships exist between the overall, measurable kinetic parameters and the individual particle kinetic parameters, thereby resulting in a heretofore unrealized analytic accessibility. Molecular weight kinetic analyses are an order of magnitude more accurate than in non-uniform systems. Application of these continuously uniform systems in actual kinetic studies indicates an inconsistency in the current concepts of emulsion polymerization, i.e., the generation of polymer at a constant molecular weight is predicted while an increase of several fold is observed. Before the situation can be clarified, further studies with continuously uniform systems are needed to evaluate molecular weight development, molecular weight distribution, and molecular structure and also to re-evaluate the rate and diffusion processes which control these structural features. 相似文献
43.
While it is well-known that the RSA public-key cryptosystem can be broken if its modulusN can be factored, it is not known whether there are other ways of breaking RSA. This paper presents a public-key scheme which necessarily requires knowledge of the factorization of its modulus in order to be broken. Rabin introduced the first system whose security is equivalent to the difficulty of factoring the modulus. His scheme is based on squaring (cubing) for encryption and extracting square (cube) roots for decryption. This introduces a 14 (19) ambiguity in the decryption. Various schemes which overcome this problem have been introduced for both the quadratic and cubic case. We generalize the ideas of Williams' cubic system to larger prime exponents. The cases of higher prime order introduce a number of problems not encountered in the quadratic and cubic cases, namely the existence of fundamental units in the underlying cyclotomic field, the evaluation of higher power residue symbols, and the increased difficulty of Euclidean division in the field. 相似文献
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Balakin V Alexandrov VA Mikhailichenko A Flöttmann K Peters F Voss G Bharadwaj V Halling M Holt JA Buon J Jeanjean J LeDiberder F Lepeltier V Puzo P Heimlinger G Settles R Stierlin U Hayano H Ishihara N Nakayama H Oide K Shintake T Takeuchi Y Yamamoto N Bulos F Burke D Field R Hartman S Helm R Irwin J Iverson R Rokni S Roy G Spence W Tenenbaum P Wagner SR Walz D Williams S 《Physical review letters》1995,74(13):2479-2482
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