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991.
Classical and quantum conformal field theory 总被引:8,自引:0,他引:8
We define chiral vertex operators and duality matrices and review the fundamental identities they satisfy. In order to understand the meaning of these equations, and therefore of conformal field theory, we define the classical limit of a conformal field theory as a limit in which the conformal weights of all primary fields vanish. The classical limit of the equations for the duality matrices in rational field theory together with some results of category theory, suggest that (quantum) conformal field theory should be regarded as a generalization of group theory.On leave of absence from the Department of Physics, Weizmann Institute of Science, Rehovot 76100, Israel 相似文献
992.
Energy and momentum of cylindrical gravitational waves 总被引:2,自引:0,他引:2
It was found manyyears ago that in cylindrical polar coordinates the energy and momentum densities of gravitational waves, calculated with the help of a pseudo-tensor, vanish. However, using cartesian coordinates, one finds them to be finite and reasonable. 相似文献
993.
Borman CJ Custelcean R Hay BP Bill NL Sessler JL Moyer BA 《Chemical communications (Cambridge, England)》2011,47(27):7611-7613
meso-Octamethylcalix[4]pyrrole (C4P) enhances sulfate selectivity in solvent extraction by Aliquat? 336N, an effect ascribed to the supramolecular preorganization and thermodynamic stability imparted by insertion of the methyl group of the Aliquat cation into the cup of C4P in its cone conformation. 相似文献
994.
Chemically induced anion radical cycloadditions: intramolecular cyclobutanation of bis(enones) via homogeneous electron transfer 总被引:1,自引:0,他引:1
Yang J Felton GA Bauld NL Krische MJ 《Journal of the American Chemical Society》2004,126(6):1634-1635
The first examples of anion radical cycloaddition induced by homogeneous electron transfer from chemical agents are described. Specifically, upon exposure to chrysene anion radical, bis(enone) substrates are found to engage in stereoselective intramolecular [2 + 2] cycloaddition. These studies, along with the corresponding electrochemically initiated reactions, provide insight into this fundamentally new pattern of reactivity and support the feasibility of expanding this novel reaction type. 相似文献
995.
The absolute enthalpies of formation of 3,4-, 2,3-, and/or 2,4-didehydropyridines (3,4-, 2,3- and 2,4-pyridynes) have been determined by using energy-resolved collision-induced dissociation of deprotonated 2- and 3-chloropyridines. Bracketing experiments find the gas-phase acidities of 2- and 3-chloropyridines to be 383 ± 2 and 378 ± 2 kcal/mol, respectively. Whereas deprotonation of 3-chloropyridine leads to formation of a single ion isomer, deprotonation of the 2-chloro isomer results in a nearly 60:40 mixture of regioisomers. The enthalpy of formation of 3,4-pyridyne is measured to be 121 ± 3 kcal/mol by using the chloride dissociation energy for deprotonated 3-chloropyridine. The structure of the product formed upon dissociation of the ion from 2-chloropyridine cannot be unequivocally assigned because of the isomeric mixture of reactant ions and the fact that the potential neutral products (2,3-pyridyne and 2,4-pyridyne) are predicted by high level spin-flip coupled-cluster calculations to be nearly the same in energy. Consequently, the enthalpies of formation for both neutral products are assigned to be 130 ± 3 kcal/mol. Comparison of the enthalpies of dehydrogenation of benzene and pyridine indicates that the nitrogen in the pyridine ring does not have any effect on the stability of the aryne triple bond in 3,4-pyridyne, destabilizes the aryne triple bond in 2,3-pyridyne, and stabilizes the 1,3-interaction in 2,4-pyridyne compared to that in m-benzyne. Natural bond order calculations show that the effects on the 2,3- and 2,4-pyridynes result from polarization of the electrons caused by interaction with the lone pair. The polarization in 2,4-pyridyne is stabilizing because it creates a 1,2-interaction between the nitrogen and dehydrocarbons that is stronger than the 1,3-interaction between the dehydrocarbons. 相似文献
996.
997.
Two families of statistical measures are used for quantitative characterization of nonequilibrium patterns and their evolution. The first quantifies the disorder in labyrinthine patterns, and captures features like the domain size, defect density, variations in wave number, etc. The second class of characteristics can be used to quantify the disorder in more general nonequilibrium structures, including those observed during domain growth. The presence of distinct stages of relaxation in spatiotemporal dynamics under the Swift-Hohenberg equation is analyzed using both classes of measures. 相似文献
998.
Dunkelman Orr Eichlseder Maria Kales Daniel Keller Nathan Leurent Gatan Schofnegger Markus 《Designs, Codes and Cryptography》2022,90(4):983-1007
Designs, Codes and Cryptography - FlexAEAD is a block cipher candidate submitted to the NIST Lightweight Cryptography standardization project, based on repeated application of an... 相似文献
999.
Nathan Kodjo Mintah Churcher Sayali Upasham Paul Rice Cornelia Felicia Greyling Shalini Prasad 《Electroanalysis》2022,34(2):375-386
Cortisol and Neuropeptide Y(NPY) are chronobiological markers of stress. Non-invasive tracking of these two biomolecules can provide great insight into an individual's physiological and neurological wellbeing. This work presents the development of a platform that tracks the two biomarkers in ultra-low volumes (5 μL) of sweat using electrochemical impedance spectroscopy (EIS). The sensing platform was able to detect both molecules in their relevant physiological ranges (8.16–141.7 ng/mL and 50–200 pg/mL respectively) with good sensitivity and specificity. This platform is envisioned to aid in the monitoring of pathophysiologies of stress-based disorders. 相似文献
1000.
Monica Miranda Clara Carvetta Neel Sisodia Luke Shirley Cristina D. Day Kay L. McGuinness Jay D. Wadhawan Nathan S. Lawrence 《Electroanalysis》2022,34(8):1273-1279
This work summarizes the electrochemical response of flavanone carbon composite electrodes in comparison with Nafion®-coated flavanone carbon composite electrodes, for use as voltammetric pH sensors in both buffered and low-buffered media. Square wave voltammetric measurements suggest the peak potential achieved from the electrochemical polymerization after the electron-proton oxidation responds with accuracy to buffered pH solutions for both coated and non-coated electrodes, with a potential shift of 55.1 mV and 54.6 mV per pH unit respectively. However, a considerable improvement in stability, accuracy and sensitivity is provided by the proton-transfer Nafion® layer in CO2 bubbled sea water. Furthermore, Nafion®-coated flavanone carbon composite electrodes predicted a pH of 8.04 for the commercial seawater, which is in excellent agreement with the measured pH 8.05 value. 相似文献