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91.
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T. D. J. Perkins J. E. J. Mills P. M. Dean 《Journal of computer-aided molecular design》1995,9(6):479-490
Summary Steric complementarity is a prerequisite for ligand-receptor recognition; this implies that drugs with a common receptor binding site should possess sterically similar binding surfaces. This principle is used as the basis for an automatic and unbiased method that superposes molecules. One molecule is rotated and translated to maximize the overlap between the two molecular surface volumes. A fast grid-based method is used to determine the extent of this overlap, and this is optimized using simulated annealing. Matches with high steric similarity scores are then sorted on the basis of both hydrogen-bond and electrostatic similarity between the matched molecules. Flexible molecules are treated as a set of rigid representative conformers. The algorithm has correctly predicted superpositions between a number of pairs of molecules, according to crystallographic data from ligands that have been co-crystallized at common enzyme binding sites. 相似文献
94.
95.
W.H Mills David P Robbins Howard Rumsey 《Journal of Combinatorial Theory, Series A》1983,34(3):340-359
An alternating sign matrix is a square matrix such that (i) all entries are 1, ?1, or 0, (ii) every row and column has sum 1, and (iii) in every row and column the nonzero entries alternate in sign. Striking numerical evidence of a connection between these matrices and the descending plane partitions introduced by Andrews (Invent. Math.53 (1979), 193–225) have been discovered, but attempts to prove the existence of such a connection have been unsuccessful. This evidence, however, did suggest a method of proving the Andrews conjecture on descending plane partitions, which in turn suggested a method of proving the Macdonald conjecture on cyclically symmetric plane partitions (Invent. Math.66 (1982), 73–87). In this paper is a discussion of alternating sign matrices and descending plane partitions, and several conjectures and theorems about them are presented. 相似文献
96.
The microwave spectrum of SiD3NCO has been observed and analyzed for 18 different vibrational states in the ν10 manifold. Some accidental resonances have been observed and analyzed. The vibrational dependence of the rotational and l-doubling constant and centrifugal distortion constant DJK has been successfully interpreted in terms of the two-dimensional anharmonic oscillator model. 相似文献
97.
Following collection of diesel particulate samples on high efficiency glass fibre papers, and Soxhlet extraction with cyclohexane, a two-stage clean-up involving DMF/H2O partition and silica gel thin-layer chromatography is required in order to simplify the extract. Individual compound identification can then be achieved by high resolution gas chromatography using WCOT quartz capillary columns with flame ionisation or computer-assisted electron impact mass spectrometry detection systems. The technique provides a relatively quick and simple enrichment step, whilst the high separating power of the capillary column is able to resolve the many chromatographically similar isomers and substituted PAH members that are present. Investigations indicate that presence of a vast range of PAH species, comprising both substituted and unsubstituted two- to seven-membered ring systems, many of which are known carcinogens and mutagens. 相似文献
98.
We report measurements of the electron and positron work functions of submonolayer contaminated single crystal surfaces of Cr(100) in ultra high vacuum. The positron work function ø+ is obtained by measuring the spectrum of slow positrons reemitted by the Cr(100) surface when it is bombarded with keV energy positrons. The electron work function ø- is measured relative to Al(100) by comparing the target biases at which the slowest emitted positrons are recollected by the target. We obtain ø+ = ?1.76(10) eV and ø- = 4.46(6) eV for our Cr(100) surface using the value ø- = 4.41(3) eV for Al(100) reported by Grepstad, Gartland and Slagsvold. The ø+ value is in agreement with the ?2.2 eV calculated by Nieminen and Hodges. The positronium work function for Cr implied by these results is ?4.10(10) eV; the positronium negative ion (Ps-) work function for this surface is calculated to be + 0.37(7) eV. A search for Ps- showed that at a 90% confidence level less than one in 103 thermalized positrons reaching the Cr surface are emitted as Ps-. The slow positron emission spectrum was observed not to change over the 70–300 K range in contrast to recent theoretical predictions. 相似文献
99.
Mills Dean III 《Experimental Mechanics》1977,17(8):303-307
New materials and techniques are described for using vulcanized rubber to protect strain gages installed on the components of a controllable-pitch propeller (CPP) system of a Navy destroyer. Strain gages protected by vulcanized rubber have survived many months of full-scale sea trials of the CPP system. 相似文献
100.
M. J. Radler B. G. Landes S. J. Nolan C. F. Broomall T. C. Chritz P. R. Rudolf M. E. Mills R. A. Bubeck 《Journal of Polymer Science.Polymer Physics》1994,32(16):2567-2573
The results of a series of novel synchrontron-based in situ x-ray scattering experiments of monofilament fiber drawing from lyotropic solutions of poly(cis-benzoxazole) (PBO) and poly(trans-benzothiazole) (PBZT) are reported. The purpose of the study is to determine orientation and microstructure development in the draw zone as a function of shear rate in the capillary die, and spin draw ratio (SDR). The transition of the extrudate from opaque to the transparent is complete at about a SDR = 3 and f of 0.9. The filament orientation parameter (f) was found to depend strongly on spin draw ratio, but not shear rate. The orientation was found to increase down the extrudate toward completion of the draw down as one proceeds further from the die face up to an extrudate length of 3.8 cm. Coherence lengths on the order of 19 nm (axial), and 4.5 nm (lateral) have been observed. These “microdomain” sizes are consistent with the “crystallite” sizes typically observed in coagulated fiber. The occurrence of these microdomains in the draw zone as a precursor to the microfibrillar structure is believed to be the origin of low filament compressive strength. © 1994 John Wiley & Sons, Inc. 相似文献