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Letn = (a1.a2 … aN) denote a sequence of integers ai={1.2.…n}. A rise is a part ai.ai+1 with ai <ai+1: a fall is a pair with aiai+1: a level is a pair with ai = ai+1. A maximum is a triple ai-1.aiai+1 with ai-1?ai.ai?ai+1. If ei is the number of aj?n withaj = i, then [e1…en] is called the specification of n. In addition, a conventional rise is counted to the left of a1 and a conventional fall to the right of aN: ifa1?a2, then a1 is counted as a conventional maximum, similarly if aN-1 ? aN thenaN is a conventional maximum. Simon Newcomb's problem is to find the number of sequences n with given specification and r rises; the refined problem of determining the number of sequences of given specification with r rises and s falls has also been solved recently. The present paper is concerned with the problem of finding the number of sequences of given specification with r rises, s falls. λ levels and λ maxima. A generating function for this enumerant is obtained as the quotient of two continuants. In certain special cases this result simplifies considerably. 相似文献
44.
The paper presents details of an experimental investigation carried out to determine deflections and bending moments in continuous flat-plate and lift-slab structures under various loading combinations, using the moiré method. A suitable computational method was adopted to compute accurately deflections and moments from the moiré photographs, which thus replaced the usual graphical procedure. 相似文献
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Attempts to resolve the enantiomers of racemic abscisic acid (ABA) by high-performance liquid chromatography on a chiral stationary-phase column were unsuccessful. However, reduction of RS-methyl ABA (RS-Me-ABA) with sodium borohydride generates a new chiral centre and one of the two isomeric products, the RS-Me-1',4'-cis-diol of ABA, was separated into its enantiomers by high-performance liquid chromatography on an optically active Pirkle column. High-performance liquid chromatography on a mu Bondapak C18 column separated the metabolites and conjugates of [2-14C]ABA fed to tomato shoots. The resolution method was used to measure the relative proportions of R and S enantiomers in the free acid liberated from conjugates of ABA. 相似文献
47.
Methods are described for the determination of beryllium (18-90 ng) and zinc (0.6-6 mug), based on their inhibition of calf-intestinal alkaline phosphatase. 相似文献
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It is shown that, in packing a square of side with unit squares, the wasted space always has area . This answers a question of Erdös and Graham. 相似文献
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A. T. M. Vaughan W. Bateman J. Cowan 《Journal of Radioanalytical and Nuclear Chemistry》1981,64(1-2):33-39
A method of labelling biologically active proteins with the alpha emmitting halogen211At is presented. The labelling procedure is discussed with reference to the chemistry of astatine. Proteins which have been
labelled retain approximately 50% of their original biological activity. Using cell specific labelled proteins, dose response
curves are given indicating that such reagents are extremely cytotoxic, D37 human CML cells=5 atmos211At/cell. The research potential of211At labelled biologically active proteins is briefly discussed. 相似文献