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111.
This paper is concerned with the construction and analysis ofcompact finite difference approximations to the model linearsource problem (pu')' + qu = f where the functions p,q, and f can have jump discontinuities at a finite number ofpoints. Explicit formulae that give O(h2) O(h3) and O(h4) accuracyare derived, and a procedure for computing three-point schemesof any prescribed order of accuracy is presented. A rigoroustruncation and discretization error analysis is offered. Numericalresults are also given. 相似文献
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Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Costa I Cremaldi LM Darling C Denisenko K Fernandez A Gagnon P Gerzon S Gobel C Gounder K Granite D Halling AM Herrera G Hurvits G James C Kasper PA Kondakis N Kwan S Langs DC Leslie J Lichtenstadt J Lundberg B Manacero A MayTal-Beck S Meadows B de Mello Neto JR Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV 《Physical review letters》1996,76(3):364-367
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A-setS in a symmetric 2-(v, k, ) design is a subset which every block meets in 0, 1 or points such that for any point ofS there is a unique block meetingS at that point only. Ovoids in three-dimensional projective spaces are examples of-secs. It is shown that if has a-set then is a geometroid withv=u
2+u+1 andk=u+1, whereu–1. The cases whenu is–1, and+1 are investigated and some open problems discussed. 相似文献
117.
De La Fuente JR Canete A Zanocco AL Saitz C Jullian C 《The Journal of organic chemistry》2000,65(23):7949-7958
The photophysical and photochemical behavior of 1-methyl-3-phenylquinoxalin-2-one (MeNQ) and 3-phenylquinoxalin-2-one (HNQ) in the presence of amines is reported. While HNQ fluorescence shows an auxochromic effect and a bathochromic shift with added amines, explained by association of HNQ with amine in the ground state and emission from both excited species HNQ and [HNQ-amine], both MeNQ and HNQ are photoreduced efficiently on irradiation in the presence of amines, leading to the semireduced quinoxalin-2-ones, MeNQH(-) and HNQH(-), respectively, via an electron-proton-electron transfer, with unit quantum yields at high amine concentrations. The semireduced quinoxalin-2-ones XNQH(-) (X = H, Me) revert almost quantitatively to the parent XNQ in a dark thermal reaction with an activation free energy for MeNQH(-) of 17.4 and 25.9 kcal/mol in acetonitrile and benzene, respectively. Kinetic and spectroscopic (UV and NMR) evidence supports the proposed reaction mechanism for the reversible photoreduction. 相似文献
118.
Abstract— Absorption and emission spectra of several N-arylbenzamides have been measured. The quantum yields for their fluorescence were found to be dependent on matrix viscosity and temperature. Singlet-triplet splittings for these compounds were determined from their emission spectra and found to be abnormally small for π. π* states (˜ 1500 cm-1 ). Indeed, the phosphorescence maxima of N-arylbenzamides occur slightly to the blue relative to their fluorescence maxima. Intersystem crossing efficiencies were determined for several of these compounds and are consistent with S1 → S 0 radiationless decay. 相似文献
119.
Henrik T. Rasmussen Robert McDonough Robert J. Gargiullo Bruce P. McPherson 《Journal of separation science》1996,19(6):359-361
A validated gas chromatographic method for the determination of triclosan in human dental plaque is described. Based on plaque sample weights of 10 mg, the limit of detection (2 × S/N) is 0.5 μg/g. The method is linear (r = 0.9986) from the limit of detection to 50 μg/g. Recoveries from placebos spiked with 2.0, 25, and 50 μg/g of triclosan were 105.6%±7.5%, 107.2%±3.1%, and 99.1%±1.1%, respectively (n = 3 at each level). Twenty replicate preparations and analyses of a homogenized sample, conducted by two operators over the course of 4 days, showed agreement to within 9% RSD. Analyses of dental plaque collected from patients after brushing with dental cream containing triclosan, shows triclosan to be retained in dental plaque at concentrations above the minimum inhibitory concentration (1 μg/g) after 12 h. 相似文献
120.
H. E. Marsh JR. 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):1397-1418
Abstract The complex and important role of the propellant binder in solid-propellant rockets is described. The severe weight problems of space exploratrion cause high propellant performance to be of major concern in a highly competitive field. Binders contribute to performance, not only in terms of fuel value, but by being compatible with energetic components and by providing good mechanical properties. Both sterilization required for planetary landings and compatibility problems of new energetic oxidizers generate new requirements too stringent for existing binders; only binders composed essentially of saturated aliphatic hydrocarbon are predicted to be suitable. Several saturated-binder developments are in progress. The achievements of one of these programs, based on free-radical synthesis, are evaluated against the goals of the new binder. 相似文献