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991.
992.
The enumeration of permutations with specific forbidden subsequences has applications in areas ranging from algebraic geometry to the study of sorting algorithms. We consider a ranked poset of permutation matrices whose global structure incorporates the solution to the equivalent problem of enumerating permutations which contain a required subsequence. We describe this structure completely for saturated chains of lengths one and two, so settling several new and general instances of the original problem, and conclude with a superficial asymptotic investigation of arbitrary chains whose length is small by comparison with the rank of its constituent permutations. The value of this approach is reflected in the appearance of closed polynomial formulae (related to the Robinson-Schensted correspondence) and of a framework for the systematic analysis of associated combinatorial questions; indeed, we begin by studying a simpler poset of 0-1 sequences as the natural environment in which to introduce our insertion and deletion operators. 相似文献
993.
Manfred J. R. Cantow Julian F. Johnson 《Journal of polymer science. Part A, Polymer chemistry》1967,5(11):2835-2841
The pore-size distributions of various grades of porous glass were determined by gas desorption and mercury porosimeter measurements. This allowed the calculation of elution volumes as a function of pore diameters. The coil sizes of polystyrenes in toluene were obtained for a series of molecular weights from hydrodynamic theory and matched with pore diameters. In this manner, expected calibration curves for gel permeation chromatography could be calculated. Good agreement was found with experimental data. 相似文献
994.
The stereoselective synthesis of piperidine alkaloids deoxymannojirimycin and d-mannolactam from d-serine has been achieved. The key step involves palladium-catalysed decarboxylative carbonylation of a serine-derived 5-vinyloxazolidin-2-one to give 6-(tert-butyldimethylsilyloxymethyl)-3,6-dihydro-1H-pyridin-2-one which was subsequently converted into the title compounds. 相似文献
995.
A wavelet,fourier, and PCA data analysis pipeline: application to distinguishing mixtures of liquids
Köküer M Murtagh F McMillan ND Riedel S O'Rourke B Beverly K Augousti AT Mason J 《Journal of chemical information and computer sciences》2003,43(2):587-594
Using a new optical engineering technique for the "fingerprinting" of beverages and other liquids, we study and evaluate a range of features. The features are based on resolution scale, invariant frequency information, entropy, and energy. They allow mixtures of beverages to be very precisely placed in principal component plots used for the data analysis. To show this we make use of data sets resulting from optical/near-infrared and ultrasound sensors. Our liquid "fingerprinting" is a relatively open analysis framework in order to cater for different practical applications, in particular, on one hand, discrimination and best fit between fingerprints, and, on the other hand, more exploratory and open-ended data mining. 相似文献
996.
Julian Schwinger 《Annals of Physics》1979,119(1):192-237
997.
The alkyl nitrites, C2H5ONO, n-C3H7ONO, n-C4H9ONO, and i-C4H9ONO were photolyzed at 23°C in the presence of 15NO at 366-nm incident radiation. The quantum yields of the corresponding isotopically-enriched alkyl nitrites were measured by mass spectrometry. The results indicated that only part of the absorption leads to photodecomposition. The remainder forms an electronically excited state which isotopically exchanges with 15NO. The indicated reactions of the electronically excited state RONO*, are where k3/k2 = 0.50 ± 0.10, 0.62 ± 0.20, 0.42 ± 0.06, and 0.24 ± 0.03 torr, and that k2a/k2 = 1.0, 1.0, 0.64 ± 0.04, and 0.56 ± 0.03, respectively, for C2H5ONO, n-C3H7ONO, n-C4H9ONO, and i-C4H9ONO. 相似文献
998.
999.
Robert J. Cox Richard C. Gaskill Julian F. Johnson Nicholas J. Clecak 《Thermochimica Acta》1977,21(3):369-373
The transition heats and temperatures of a series of 4-alkyl-4′-cyanostilbenes were measured with the DuPont 990 thermal analyzer. The entropies of both the solid-to-mesophase and the mesophase-to-isotropic liquid was found to be dependent on the number of carbons in the alkyl on the molecule. The entropy change in the nematic-to-smectic transition found in the C7 member of the series was found to be extremely small. 相似文献
1000.
Julian Schwinger 《General Relativity and Gravitation》1976,7(3):251-256
The phenomenological, nonspeculative attitude of source theory is used in parallel developments of electromagnetism and gravitation, based on the analogous properties of the massless particles, photon and graviton, thus providing a methodological unification of these two areas of physics. The power and economy of the approach is illustrated by an application to perihelion precession.This essay received the second award from the Gravity Research Foundation for the year 1975. (Editor) 相似文献