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Grant JA Haigh JA Pickup BT Nicholls A Sayle RA 《Journal of chemical information and modeling》2006,46(5):1912-1918
We apply a recently published method of text-based molecular similarity searching (LINGO) to standard data sets for the purpose of quantifying the accuracy of the approach. Our implementation is based on a pattern-matching finite state machine (FSM) which results in fast search times. The accuracy of LINGO is demonstrated to be comparable to that of a path-based fingerprint and offers a simple yet effective method for similarity searching. 相似文献
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Haigh J. A. Nguyen C. Alamo R. G. Mandelkern L. 《Journal of Thermal Analysis and Calorimetry》2000,59(1-2):435-450
The crystallization and melting of three model polyethylenes of different chain structures have been studied. The polymers studied were a linear copolymer, hydrogenated poly(butadiene); a hydrogenated poly(butadiene)-atactic poly(propylene) diblock copolymer; and a three-arm star hydrogenated poly(butadiene). An important feature of this work was that the crystallizing portions of the copolymers all have the same molecular lengths.It was found that the overall crystallization rate decreases steadily from a linear to a diblock to the star copolymer. The differences in crystallization rates are related primarily to the activation energy for segmental transport. The non-crystallizable structure affects the segmental mobility to different degrees. An estimation of this effect is presented from the analysis of the overall crystallization rates using classical nucleation theory. In spite of thedifferences in their molecular structure, there are no major differences in the supermolecular structure of samples crystallized rapidly or slowly cooled.The melting process followed by DSC of the isothermally crystallized linear and star copolymers shows two endothermic peaks at intermediate undercoolings. The double melting is associated with a partitioning of crystallizable ethylene sequences during crystallization. The longest sequences are preferentially selected in the early stages of the crystallization. Single melting peaks are obtained for high and very low undercoolings for the linear and the star copolymers as well as for the diblock in the whole range of temperatures. The lack of the second, lower melting endotherm in the diblock could be associated with the influence in the crystallization process of the amorphous block in the microphase segregated melt.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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Theoretical treatments of the distorted square pyramidal co-ordination observed in vanadyl β-keto-enolates predict restricted interligand conjugation and minimal π-interaction in the oxovanadium-ligand bonds. The effects of ligand substitution on the vibrational and electronic spectra of vanadyl β-keto-enolates yield evidence that strong σ-bonding and ionic contributions are chiefly responsible for the strong vanadium-ligand bonding. 相似文献
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A new theory6 for ‘ring current’ effects on the chemical shifts of protons in or out of the plane of a benzene ring is summarized, and pictorially compared with the predictions of the earlier semi-classical theory of Johnson and Bovey.1 In the Appendix are presented extensive numerical tables of the predicted shieldings. 相似文献
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The results of high-resolution studies of the 91Zr(d, p) reaction at Ed = 12 MeV and the 90Zr(t, p) reaction at Et = 11.85 MeV are presented. Absolute cross sections have been measured for both reactions and (d, p) spectroscopic factors determined. A comparison of these results with earlier data has been made, and although many of the previous assignments have been confirmed, many new features concerning the structure of 92Zr have been discovered. Shell-model calculations have been performed for 91Zr and 92Zr using a neutron space which includes the , , , and orbits and a proton space comprising the and orbits. Realistic proton-neutron and neutron-neutron interactions based on the Sussex matrix elements were used in the calculations. Spectroscopic factors have been calculated for the 90Zr(d, p) and 91Zr(d, p) reactions and cross sections calculated for the 90Zr(t, p) reaction. In general, good agreement between the theoretical and the experimental results has been obtained. 相似文献