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Kelly A. Burke Sona Sivakova Blayne M. McKenzie Patrick T. Mather Stuart J. Rowan 《Journal of polymer science. Part A, Polymer chemistry》2006,44(17):5049-5059
We report herein studies on the liquid crystalline behavior of a series of supramolecular materials that contain different ratios of two complementary symmetrically-substituted alkoxy-bis(phenylethynyl)benzene AA- and BB-type monomers. One monomer has thymine units placed at either end of the rigid mesogenic core, while the other has N6-(4-methoxybenzoyl)-adenine units placed on the ends. Differential scanning calorimetric and polarized optical microscopy studies have been carried out on these systems. These studies show that the material's behavior is strongly dependent on its thermal history. As a result, the materials can exhibit, on heating, either a liquid crystalline phase, a crystalline phase, or the coexistence of crystalline and liquid crystalline regions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5049–5059, 2006 相似文献
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Everette S. GardnerJr. Ed. McKenzie 《The Journal of the Operational Research Society》1988,39(9):863-867
Model identification has traditionally been ignored in forecasting via exponential smoothing. The usual practice is to apply the same model to every time-series in a collection. This paper develops a procedure for model identification in large forecasting applications based on an examination of variances of differences of the time-series. The order of differencing yielding minimum variance suggests an appropriate model for the series. Empirical results show that this procedure selects models that give reasonable ex ante forecast accuracy. 相似文献
4.
Ghandi K Addison-Jones B Brodovitch JC McCollum BM McKenzie I Percival PW 《Journal of the American Chemical Society》2003,125(32):9594-9595
Muoniated free radicals have been detected in muon-irradiated aqueous solutions of acetone at high temperatures and pressures. At temperatures below 250 degrees C, the radical product is consistent with muonium addition to the keto form of acetone. However, at higher temperatures, a different radical was detected, which is attributed to muonium addition to the enol form. Muon hyperfine coupling constants have been determined for both radicals over a wide range of temperatures, significantly extending the range of conditions under which these radicals and the keto-enol equilibrium have been studied. 相似文献
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Ramnial T McKenzie I Gorodetsky B Tsang EM Clyburne JA 《Chemical communications (Cambridge, England)》2004,(9):1054-1055
One-electron oxidation of N-heterocyclic carbenes (NHCs) has been carried out using oxidising agents such as tetracyanoethylene (TCNE) and ferrocenium [Cp(2)Fe](+); the formation of carbene radical cations is postulated. 相似文献
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Powell BJ Baruah T Bernstein N Brake K McKenzie RH Meredith P Pederson MR 《The Journal of chemical physics》2004,120(18):8608-8615
We report first-principles density-functional calculations for hydroquinone (HQ), indolequinone (IQ), and semiquinone (SQ). These molecules are believed to be the basic building blocks of the eumelanins, a class of biomacromolecules with important biological functions (including photoprotection) and with the potential for certain bioengineering applications. We have used the difference of self-consistent fields method to study the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, Delta(HL). We show that Delta(HL) is similar in IQ and SQ, but approximately twice as large in HQ. This may have important implications for our understanding of the observed broadband optical absorption of the eumelanins. The possibility of using this difference in Delta(HL) to molecularly engineer the electronic properties of eumelanins is discussed. We calculate the infrared and Raman spectra of the three redox forms from first principles. Each of the molecules have significantly different infrared and Raman signatures, and so these spectra could be used in situ to nondestructively identify the monomeric content of macromolecules. It is hoped that this may be a helpful analytical tool in determining the structure of eumelanin macromolecules and hence in helping to determine the structure-property-function relationships that control the behavior of the eumelanins. 相似文献
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A mixed-valence dimanganese complex with two water ligands bound to the Mn(II) ion and two methoxide ligands bound to the Mn(III) ion in a H-bonded arrangement has been structurally characterised and models possible resting state water/hydroxide coordination in purple acid phosphatases. 相似文献
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A computational study has been performed to examine the reactions of a model beta-diketiminatoaluminium (I) complex with the hydrogen atom and with the electron. It was found that the hydrogen atom adds to the metal centre exothermically (DeltaH(rxn)=-202 kJ mol(-1)), and the spin density in the resulting radical resides entirely on the beta-diketiminato ligand. The spin density of the corresponding radical anion is very similar to the H-adduct. 相似文献