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651.
652.
Alessandro Lupi Maria Patamia Ingeborg Grgurina Rinaldo Marini Bettolo Ornella Di Leo Patrizia Gioia Simonetta Autnaroli 《Helvetica chimica acta》1984,67(8):2261-2263
A biogenetic-type total synthesis of(±)-2-deoxystemodinone ( 1 ), by solvolytic rearrangement of the 1-methyl[2.2.2]oct-2-yl methanesulphonate 4 , is described. 相似文献
653.
Let L be a linear space of real bounded random variables on the probability space $(\varOmega ,\mathcal{A},P_{0})$ . There is a finitely additive probability P on $\mathcal{A}$ such that P~P 0 and E P (X)=0 for all X∈L if and only if cE Q (X)≤ess?sup?(?X), X∈L, for some constant c>0 and (countably additive) probability Q on $\mathcal{A}$ such that Q~P 0. A necessary condition for such a P to exist is $\overline{L-L_{\infty}^{+}}\cap L_{\infty}^{+}=\{0\}$ , where the closure is in the norm-topology. If P 0 is atomic, the condition is sufficient as well. In addition, there is a finitely additive probability P on $\mathcal{A}$ such that P?P 0 and E P (X)=0 for all X∈L if and only if ess?sup?(X)≥0 for all X∈L. 相似文献
654.
In this article we furnish a representation of the solutions of some classes of first-order and second-order evolution problems as limit of iterates of classical sequences of approximating operators. The method is based on Trotter's theorem on the approximation of semigroups which is applied here also for the approximation of groups and cosine functions. We apply this method in spaces of continuous periodic functions and using some classical sequences of trigonometric polynomials. 相似文献
655.
We consider the graph Γ(G), associated with the conjugacy classes of a group G. Its vertices are the nontrivial conjugacy classes of G, and we join two different classes C, D, whenever there exist x ∈ G and y ∈ D such that xy = yx. The aim of this article is twofold. First, we investigate which graphs can occur in various contexts and second, given a graph Γ(G) associated with G, we investigate the possible structure of G. We proved that if G is a periodic solvable group, then Γ(G) has at most two components, each of diameter at most 9. If G is any locally finite group, then Γ(G) has at most 6 components, each of diameter at most 19. Finally, we investigated periodic groups G with Γ(G) satisfying one of the following properties: (i) no edges exist between noncentral conjugacy classes, and (ii) no edges exist between infinite conjugacy classes. In particular, we showed that the only nonabelian groups satisfying (i) are the three finite groups of order 6 and 8. 相似文献
656.
A group G is called a Camina group if G′ ≠ G and each element x ∈ G?G′ satisfies the equation x G = xG′, where x G denotes the conjugacy class of x in G. Finite Camina groups were introduced by Alan Camina in 1978, and they had been studied since then by many authors. In this article, we start the study of infinite Camina groups. In particular, we characterize infinite Camina groups with a finite G′ (see Theorem 3.1) and we show that infinite non-abelian finitely generated Camina groups must be nonsolvable (see Theorem 4.3). We also describe locally finite Camina groups, residually finite Camina groups (see Section 3) and some periodic solvable Camina groups (see Section 5). 相似文献
657.
658.
Density functional calculations have been performed for small nickel clusters, Ni(n), Ni(n) (+), and Ni(n)(-) (n相似文献
659.
Bicchi C Cordero C Liberto E Sgorbini B Rubiolo P 《Journal of chromatography. A》2007,1152(1-2):138-149
This article evaluates the HS-SPME recovery repeatability, intermediate precision and their performance over time when applied to HS-SPME sampling for quality control of medicinal and aromatic plants. Experiments were carried out on two sets of fibres coated with two different coatings and belonging to different lots (i.e 100 microm polydimethylsyloxane (PDMS) and Carboxen/divinylbenzene/PDMS 50/30 microm, l: 1 cm (CAR/DVB/PDMS)) and on chamomile (Matricaria chamomilla L.), sage (Salvia lavandulifolia Vahl.) and a standard solution containing 3-hexanol, isoamyl acetate, 1,8-cineole and menthol in diisobutyl phthalate. The performance of each set of fibres was evaluated by determining a group of complementary statistical parameters including: (i) repeatability of the absolute areas of each marker from each matrix with each fibre; (ii) intra-fibre repeatability of the total absolute areas of the markers of each matrix obtained with each fibre of each set; (iii) inter-fibre intermediate precision of the total absolute areas of the markers of each matrix obtained with all fibres of each set; and (iv) analysis of variance by one-way ANOVA with Fisher and Tukey tests. The influence of the number of analyses on fibre effectiveness (fibre life-time) was studied by linear regression analysis (LRA). The results proved that HS-SPME can successfully be used for routine control analysis of aromatic ad medicinal plants since both types of fibres showed good repeatability and intermediate precision of analytes recovery and consistency over time. Unlike data previously reported by other authors, CAR/DVB/PDMS coated fibres gave better results than those coated with PDMS. The fibre-life seemed mainly to be influenced by the number and conditions of samplings and nature of the matrix investigated. 相似文献
660.
A wide number of supra-molecular association modes are observed in mixtures containing water and bile salts, BS, (with, eventually, other components). Molecular or micellar solutions transform into hydrated solids, fibres, lyotropic liquid crystals and/or gels by raising the concentration, the temperature, adding electrolytes, surfactants, lipids and proteins. Amorphous or ordered phases may be formed accordingly. The forces responsible for this very rich polymorphism presumably arise from the unusual combination of electrostatic, hydrophobic and hydrogen-bond contributions to the system stability, with subsequent control of the supra-molecular organisation modes. The stabilising effect due to hydrogen bonds does not occur in almost all surfactants or lipids and is peculiar to bile acids and salts. Some supra-molecular organisation modes, supposed to be related to malfunctions and dis-metabolic diseases in vivo, are briefly reported and discussed. 相似文献