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A model based on an autocatalytic, two-step reaction mechanismincluding two ionic components (of the same charge) and twonon-ionic components, where both reactions are of second orderoverall, is considered when an electric field is applied tothe system. The model is motivated by experimental observationson the iodate-arsenous acid system. The travelling wave equationsare examined first and conditions obtained for the existenceand form of these waves. These conditions are then used to interpretthe results obtained from numerical simulations of the fullsystem. These results display all the main features observedexperimentally, the change in the local stoichiometry and thepossible wave annihilation for sufficiently strong fields. Themodel provides a clear explanation for these features as wellas predicting new features not reported from the experiments.The main one of which is the occurrence of an internal wavepropagating in the reacted part of the system in the directioninduced by the applied field.  相似文献   
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Monocyclic β‐lactams revive the research field on antibiotics, which are threatened by the emergence of resistant bacteria. A six‐step synthetic route was developed, providing easy access to new 3‐amino‐1‐carboxymethyl‐4‐phenyl‐β‐lactams, of which the penicillin‐binding protein (PBP) inhibitory potency was demonstrated biochemically.  相似文献   
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The catalytic efficacy of trans‐[(R3P)2Pd(O2CR′)(LB)][B(C6F5)4] ( 1 ) (LB = Lewis base) and [(R3P)2Pd(κ2O,O‐O2CR′)][B(C6F5)4] ( 2 ) for mass polymerization of 5‐n‐butyl‐2‐norbornene (Butyl‐NB) was investigated. The nature of PR3 and LB in 1 and 2 are the most critical components influencing catalytic activity/latency for the mass polymerization of Butyl‐NB. Further, it was shown that 1 is in general more latent than 2 in mass polymerization of Butyl‐NB. 5‐n‐Decyl‐2‐norbornene (Decyl‐NB) was subjected to solution polymerization in toluene at 63(±3) °C in the presence of several of the aforementioned palladium complexes as catalysts and the polymers obtained were characterized by gel permeation chromatography. Cationic trans‐[(R3P)2PdMe(MeCN)][B(C6F5)4] [R = Cy ( 3a ), and iPr ( 3b )] and trans‐[(R3P)2PdH (MeCN)][B(C6F5)4] [R = Cy ( 4a ), and iPr ( 4b )], possible products from thermolysis of trans‐[(R3P)2Pd(O2CMe)(MeCN)][B(C6F5)4] [R = Cy ( 1a ) and iPr ( 1g )], as well as trans‐[(R3P)2Pd(η3‐C3H5)][B(C6F5)4] [R = Cy ( 5a ), and iPr ( 5b )], were also examined as catalysts for solution polymerization of Decyl‐NB. A maximum activity of 5360 kg/(molPd h) of 2a was achieved at a Decyl‐NB/Pd: 26,700 ratio which is slightly better than that achieved with 5a [activity: 5030 kg/(molPd h)] but far less compared with 4a [activity: 6110 kg/(molPd h)]. Polydispersity values indicate a single highly homogeneous character of the active catalyst species. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 103–110, 2009  相似文献   
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 We prove that, under the assumption of the Generalized Riemann Hypothesis, the exponent of the ideal class group of a CM-field goes to infinity with its absolute discriminant. This gives a positive answer to a question raised by Louboutin and Okazaki [4].  相似文献   
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The effects of an applied electric field on an ionic autocatalyticreaction with a quadratic rate law are considered, where thereacting species, A+ and B+, are present in a system which alsoincludes non-reacting species C- and D+. The conditions areestablished under which the general terms which describe theelectric field effects in the reaction-diffusion equations canbe simplified to those used in previous studies, where theseeffects are modelled by linear advection terms. The resultingequations are then studied in detail by first obtaining conditionsfor the existence of travelling waves of permanent form. Thisdiscussion shows that B, the ratio of the diffusion coefficientsof B+ and A+, is a critical parameter, with different formsof behaviour arising for B < 1 and B > 1. This analysisis augmented by obtaining solutions valid for large times andlarge values of (the dirnensionless applied field). Numericalsolutions of initial-value problems are obtained for a rangeof values of and B, guided by and interpreted through the analysispreviously obtained. These numerical integrations show the formationof reaction fronts, with the possibility of greatly increasedreaction rates caused by the applied electric field, as wellas propagating electrophoretic fronts in B+ being formed incases where a reaction front is also initiated. There is alsothe possibility of separate electrophoretic fronts in A+ andB+ being formed, which become increasingly separated as timeincreases with the reaction being completely inhibited.  相似文献   
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