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51.
The unstirred, ferroin (Fe(phen)(3)2+)-catalyzed Belousov-Zhabotinsky (BZ) reaction1-4 is the prototype oscillatory chemical system. After an induction period of several minutes, one sees "spontaneous" formation of "pacemaker" sites, which oscillate between a blue, oxidized state (high [Fe(phen)3(3+)]) and a red, reduced state (low [Fe(phen)(3)3+]). The reaction medium appears red (reduced) during the induction phase, and the pacemaker sites generate target patterns of concentric, outwardly moving waves of oxidation (blue). Auto-oscillatory behavior is also seen in the Oregonator model of Field, Kor?s, and Noyes (FKN), a robust, reduced model which captures qualitative BZ kinetics in the auto-oscillatory regime. However, the Oregonator model predicts a blue (oxidized) induction phase. Here, we show that including reaction R8 of the FKN mechanism, not incorporated in the original Oregonator, accounts for bromide release during the induction phase, thus producing the observed red oxidation state. 相似文献
52.
Three sharp absorption features in the energy range 2.36–2.55 eV have been detected in the transmission spectrum of Co-diffused ZnSe, and a number of luminescence transitions originating from the lowest of these states at 2.361 eV have been observed. Photoluminescence excitation spectra prove that these are high energy excited states of the Co2+Zn impurity, a conclusion confirmed by comparison of measured and predicted luminescence energies. This represents the first identification of luminescence branching from a higher excited state of a transition metal ion in any semiconductor. The sharp, weakly phonon-coupled transitions involve either intra-impurity excitation or transitions from the impurity to localised states split off from a minimum in the conduction band. The implications of these observations for the mechanism of host-impurity energy transfer and for the nature of the excited state wavefunctions are discussed. 相似文献
53.
54.
A. Sherman D. Sperber M. I. Sobel J. P. Bondorf 《Zeitschrift für Physik A Hadrons and Nuclei》1978,286(1):11-17
A classical dynamical theory for heavy ion collisions is developed which allows for transfer through the window between the strongly interacting target and projectile. The transfer is treated as a random walk process and a feed back effect on the orbital motion from the transfer is obtained by adjusting the ion-ion potentials each time a transfer occurs. The method is used successfully to analyze the reaction Kr + Bi at 600 MeV. It yields very good agreement between theory and experiment for the angular distribution. Furthermore, it accounts very well for the mass distribution at two different angles and for the final energy distributions. The analysis allows the extraction of friction coefficients, diffusion constant and drift rates, which are compared with other models. 相似文献
55.
Christiane Mercier Yves Sobel Jacques-Emile Dubois 《Journal of mathematical chemistry》1992,9(4):351-357
The regular evolution of properties with structural modification is quantitatively formulated. It is defined in a structural space which is exhaustive, ordered, flexible and explicit. It is detected along the ordered pathways of structural filiations by inference tools, which take into account the experimental precision and proceed by a heuristic modulation of the initial representation space. The introduction of nuances in the quantitative formulation of regularity leads to diverse tools for setting up and exploiting the relationships. These latter constitute a prediction law, which is both simple and as precise as the measurements. The detected regularities make for a generalization of certain structural effects and suggest a fruitful interpretation. Zeroth- and first-order regularities, characteristic of strongly linear variation, are used to safely extrapolate the prediction range and to orient experimental planning. 相似文献
56.
Gando Y Fukuda S Fukuda Y Ishitsuka M Itow Y Kajita T Kameda J Kaneyuki K Kobayashi K Koshio Y Miura M Moriyama S Nakahata M Nakayama S Namba T Obayashi Y Okada A Ooyabu T Saji C Sakurai N Shiozawa M Suzuki Y Takeuchi H Takeuchi Y Totsuka Y Yamada S Desai S Earl M Kearns E Messier MD Stone JL Sulak LR Walter CW Goldhaber M Barszczak T Casper D Gajewski W Kropp WR Mine S Liu DW Smy MB Sobel HW Vagins MR Gago A Ganezer KS Hill J Keig WE Ellsworth RW Tasaka S Kibayashi A Learned JG Matsuno S 《Physical review letters》2003,90(17):171302
We present the results of a search for low energy nu(e) from the Sun using 1496 days of data from Super-Kamiokande-I. We observe no significant excess of events and set an upper limit for the conversion probability to nu(e) of the 8B solar neutrino. This conversion limit is 0.8% (90% C.L.) of the standard solar model's neutrino flux for total energy=8-20 MeV. We also set a flux limit for monochromatic nu(e) for E(nu(e))=10-17 MeV. 相似文献
57.
Matthew J Sobel 《Operations Research Letters》1985,4(4):157-159
A stationary policy in an MDP (Markov decision process) induces a stationary probability distribution of the reward from each initial state. The problem analyzed here is maximization of the mean/standard deviation ratio of the stationary distribution. In the unichain case, a solution is obtained via parametric analysis of a linear program having the same number of variables and one more constraint than the formulation for gain-rate optimization. The same linear program suffices in the multichain case if the initial state is an element of choice. The easier problem of maximizing the mean/variance ratio is mentioned at the end of the paper. 相似文献
58.
Hastings HM Sobel SG Lemus A Yuen F Peralta C Cammalleri C Chabrel J Chaterpaul S Frank C Hilaire C Lang D Ravinovitch D Zaharakis A 《The Journal of chemical physics》2005,123(6):64502
The prototype experimental example of "spontaneous" pattern formation in an unstirred chemical medium is the oscillatory Belousov-Zhabotinsky (BZ) reaction: target patterns of outward-moving concentric rings are readily observed when the reaction is run in a thin layer in a Petri dish. In many experimental runs, new target centers appeared to form closer to pre-existing target centers than expected in a randomized model. Here we describe a simple direct test for the presence of temporal order in the spatiotemporal dynamics of target nucleation, and apply this test to detect significant temporal order in target formation in the ferroin-catalyzed BZ reaction. We also describe how mixing heterogeneity can generate temporal order, even in the absence of heterogeneous physical nucleating centers. 相似文献
59.
Blewitt G LoSecco JM Bionta RM Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,55(20):2114-2117
60.