在线超临界流体萃取-超高效液相色谱-光电二极管检测器联用分析胡椒粉中的胡椒碱

本文介绍的联用分析系统是将超临界流体萃取(SFE)系统与超高效液相色谱(UHPLC)系统联用。使用在线SFE-UHPLC系统,可以完成对胡椒粉中胡椒碱成分的高速萃取和分析。整个分析过程包括萃取时间在内只需要7min。将此方法的萃取回收率与其他萃取方法进行比较,SFE方法得到的回收率与其他方法相当。这种在线SFE-UHPLC方法操作简单,分析速度快。这一方法对于分析固体样品中的化合物组分非常有用,可以有效避免繁琐的样品预处理过程。     

Growth and inequality: a demographic explanation

This paper investigates the relationship between growth and inequality from a demographic point of view. In an extended model of the accidental bequest with endogenous fertility, we analyze the effects of a decrease in old-age mortality rate on the equilibrium growth rate as well as on the income distribution. We show that the relationship between growth and inequality is at first positive and then may be negative in the process of population aging. The results are consistent with the empirical evidence in some developed countries.

Private versus public financing of education and endogenous growth: A comment on Bräuninger and Vidal

This note shows that the long-run effect in the case of a low skill trap in Br?uninger and Vidal (Journal of Population Economics (2000) 13:387–401) contains a mistake. While not affecting the paper's basic intuition, this implies that the discussion in the short-run analysis also applies in the long-run. Received: 24 April 2001/Accepted: 9 June 2001 I wish to thank Alessandro Cigno and an anonymous referee for useful comments. Responsible editor: Alessandro Cigno.     

An algorithm for finding a representation of a subtree distance

Generalizing the concept of tree metric, Hirai (Ann Combinatorics 10:111–128, 2006) introduced the concept of subtree distance. A nonnegative-valued mapping \(d:X\times X \rightarrow \mathbb {R}_+\) is called a subtree distance if there exist a weighted tree T and a family \(\{T_x\mid x \in X\}\) of subtrees of T indexed by the elements in X such that \(d(x,y)=d_T(T_x,T_y)\), where \(d_T(T_x,T_y)\ge 0\) is the distance between \(T_x\) and \(T_y\) in T. Hirai (2006) provided a characterization of subtree distances that corresponds to Buneman’s (J Comb Theory, Series B 17:48–50, 1974) four-point condition for tree metrics. Using this characterization, we can decide whether or not a given mapping is a subtree distance in O\((n^4)\) time. In this paper, we show an O\((n^3)\) time algorithm that finds a representation of a given subtree distance. This results in an O\((n^3)\) time algorithm for deciding whether a given mapping is a subtree distance.