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101.
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103.
Summary Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation
of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples
and exhaustive solvent extraction, a carbodiimide-coupled esterification of the free carboxylic acids with hexafluoroisopropanol
(HFIP) is applied. Identification of the derivatives formed is achieved by low-resolution electron-impact mass spectrometry
(EIMS) using an ion-trap detector. Quantitation was by capillary gas chromatography—high-resolution mass spectrometry using
negative chemical ionization (GC-NCIMS). 2-Phenoxybenzoic acid (2-PBA) served as internal standard. The limits of detection
forcis- andtrans-DCCA,cis-DBCA, FPBA and 3-PBA were 0.03 μg L−1 or below. The applicability of the presented method was tested on urine samples of persons exposed to low levels of pyrethroids. 相似文献
104.
现实中很多复杂网络是由完全子图通过公共的节点连接而成的.本文提出了一个复杂网络中完全子图的搜索算法,并通过实例说明了所提算法的有效性. 相似文献
105.
We study the asymptotics at zero of continuous functions on (0, 1] by means of their asymptotic ideals, i.e., ideals in the ring of continuous functions on (0, 1] satisfying a polynomial growth condition at 0 modulo rapidly decreasing functions at 0. As our main result, we characterize maximal and prime ideals in terms of maximal and prime filters. 相似文献
106.
107.
《代数通讯》2013,41(4):1519-1530
Abstract Let G = GL n (q) be the general linear group over a finite field 𝔽 q with q elements. We call a Gel'fand–Graev module to be the module which affords the Gel'fand–Graev character defined in Definition I.1. It is known that every cuspidal module of G is isomorphic to a (unique) direct summand of a Gel'fand–Graev module. In this article, we investigate a certain endomorphism so that each irreducible cuspidal module is contained in a certain eigenspace corresponding to the cuspidal character. Furthermore, we determine the eigenvalue of that endomorphism by using character theory of finite general linear group. 相似文献
108.
Ana C. Stephens 《The Journal of Mathematical Behavior》2008,27(1):33-47
This study examined conceptions of algebra held by 30 preservice elementary teachers. In addition to exploring participants’ general “definitions” of algebra, this study examined, in particular, their analyses of tasks designed to engage students in relational thinking or a deep understanding of the equal sign as well as student work on these tasks. Findings from this study suggest that preservice elementary teachers’ conceptions of algebra as subject matter are rather narrow. Most preservice teachers equated algebra with the manipulation of symbols. Very few identified other forms of reasoning - in particular, relational thinking - with the algebra label. Several participants made comments implying that student strategies that demonstrate traditional symbol manipulation might be valued more than those that demonstrate relational thinking, suggesting that what is viewed as algebra is what will be valued in the classroom. This possibility, along with implications for mathematics teacher education, will be discussed. 相似文献
109.
《代数通讯》2013,41(9):3537-3541
Abstract Let A be an absolute valued algebra. We prove that if A satisfies the identity (x 2, x 2, x 2) = 0 for all x in A, and contains a central idempotent e, that is ex = xe for all x in A, then A is finite dimensional. This result enables us to prove that if A satisfies (x 2, x 2, x 2) = 0 and admits an involution then A is finite dimensional. To show that our assumptions on A are essential we recall that in El-Mallah [El-Mallah, M. L. (1988). Absolute valued algebras with an involution. Arch. Math. 51:39–49] it was shown that the existence of a central idempotent in A is not a sufficient condition for A to be finite dimensional; and the example given in El-Mallah [El-Mallah, M. L. (2003). Semi-algebraic absolute valued algebras with an involution. Comm. Algebra 31(7):3135–3141] shows that there exist infinite dimensional semi-algebraic absolute valued algebras satisfying the identity (x 2, x 2, x 2) = 0. 相似文献
110.
《代数通讯》2013,41(7):3135-3141
Abstract Let A be an absolute valued algebra. In El-Mallah (El-Mallah,M. L. (1988). Absolute valued algebras with an involution. Arch. Math. 51: 39–49) we proved that,if A is algebraic with an involution,then A is finite dimensional. This result had been generalized in El-Amin et al. (El-Amin,K.,Ramirez,M. I.,Rodriguez,A. (1997). Absolute valued algebraic algebras are finite dimensional. J. Algebra 195:295–307),by showing that the condition “algebraic” is sufficient for A to be finite dimensional. In the present paper we give a generalization of the concept “algebraic”,which will be called “semi-algebraic”,and prove that if A is semi-algebraic with an involution then A is finite dimensional. We give an example of an absolute valued algebra which is semi-algebraic and infinite dimensional. This example shows that the assumption “with an involution” cannot be removed in our result. 相似文献