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61.
Canonical correlation analysis is used to detect orange juice dilutions masked by addition of citric acid and sugars. The values of 28 analytical characteristics (experimental variables) were determined in 105 pure orange juices, and canonical correlation analysis was applied to two groups of experimental variables (citric acid, sucrose, glucose, and fructose versus the other variables). The first pair of canonical correlation variables (one from each group) showed a correlation coefficient of 0.966. By dividing the whole set of 105 juices into reference sets (to compute predictive equations) and test sets (to check the efficiency of the equations), dilutions of 10, 20, and 30% were detected in, respectively, 28, 62, and 91% of the juices from the test sets. 相似文献
62.
63.
64.
Isidoro Izquierdo María T. Plaza Juan A. Tamayo Miguel Rodríguez Alicia Martos 《Tetrahedron》2006,62(25):6006-6011
(1R,2S,3S,5R,7aR)-1,2-Dihydroxy-3-hydroxymethyl-5-methylpyrrolizidine[(−)-3-epihyacinthacine A5, 1a] and (1S,2R,3R,5S 7aS)-1,2-dihydroxy-3-hydroxymethylpyrrolizidine[(+)-3-epihyacinthacine A5, 1b] have been synthesized either by Wittig's or Horner-Wadsworth-Emmond's (HWE's) methodology using aldehydes 4 and 9, both prepared from (2S,3S,4R,5R)-3,4-dibenzyloxy-2′-O-tert-butyldiphenylsilyl-2,5-bis(hydroxymethyl)pyrrolidine (2, partially protected DADP), and the appropriate ylides, followed by cyclization through an internal reductive amination process of the resulting α,β-unsaturated ketones 5 and 10, respectively, and total deprotection. 相似文献
65.
Flors C Ogilby PR Luis JG Grillo TA Izquierdo LR Gentili PL Bussotti L Nonell S 《Photochemistry and photobiology》2006,82(1):95-103
Experiments were performed to elucidate the excited-state behavior of 9-phenylphenalenones, which are phototoxic plant secondary metabolites involved in mechanisms of light-mediated plant defense. Using a combination of time-resolved and steady-state UV/visible spectroscopies, time-resolved IR absorption spectroscopy, time-resolved singlet oxygen phosphorescence measurements and cyclic voltammetry, we provide evidence of an intramolecular charge-transfer process in the excited singlet and the triplet states of 9-phenylphenalenones that modulates the photosensitized production of singlet oxygen. 相似文献
66.
Predominant physical phenomenon in highly scattering materials is the attenuation due to dispersion. Therefore, received echo has high frequencies more severely attenuated than low frequencies and the structural noise can be modeled as a non-stationary random process. Most of the proposed techniques for enhancing the flaw visibility do not exploit the frequency dependency of the incoming flaw signal, assuming homogeneous behaviour of the insonified material. In this work, a new technique based on exploiting the non-stationary nature of the incoming UT signal is presented. Proposed technique is based on the prediction error obtained with a linear and time-varying parametric model of the noise. By this method, when the analyzed UT echo has only structural noise, the prediction error is low, however, if it contains a flaw, high prediction error occurs because a flaw is a non-predictable alteration of the material structure. Experiments with stainless steel show that this method has an excellent performance on SNR enhancement. 相似文献
67.
We describe the general nonassociative version of Lie theory that relates unital formal multiplications (formal loops), Sabinin
algebras and nonassociative bialgebras. 相似文献
68.
Let X be a Riemann surface of genus g2. A symmetry of of X is an antiholomorphic involution acting of X. A classical theorem of Harnack states that the set Fix () of fixed points of is either emplty or it consists of g+1 disjoint simple closed curves called, following Hilberts terminology, the ovals of . A Riemann surface admitting a symmetry corresponds to a real algebraic curve and nonconjugate symmetries correspond to different real models of the curve. The number of ovals of the symmetry equals the number of connected components of the corresponding real model. It is well known that two symmetries of a Riemann surface of genus g have at most 2g+2 ovals, and the bound is attained for every genus and just for commuting symmetries. Natanzon showed that three and four nonconjugate symmetries of a Riemann surface of genus g have at most 2g+4 and 2g+8 ovals respectively, and these bounds are attained for every odd genus and for commuting symmetries. Natanzon found that a Riemann surface of genus g has at most 2(
+1) nonconjugate symmetries and, again, this bound is attained for infinitely many of g. Recently we have showed that a Riemann surface of even genus g admits at most four symmetries. Our aim here is to show, using NEC groups and combinatorial methods, that three nonconjugate symmetries of a surface of even genus g has at most 2g+3 ovals and, surprisingly, if such a surface admits four nonconjugate symmetries then its total number of ovals does not exceed 2g+2. Furthermore, we show that this last bound is sharp for every even genus g and for surfaces with automorphism group D
n
× Z2, for each n dividing 2g. 相似文献
69.
Botta B Ricciardi P Galeffi C Botta M Tafi A Pogni R Iacovino R Garella I Di Blasio B Delle Monache G 《Organic & biomolecular chemistry》2003,1(17):3131-3137
Three new resorcin[4]arene-capped porphyrins (3, 5 and 7) different in the porphyrin skeleton, in the linking arms and in the cavity dimensions, have been synthesised. Molecular modelling calculations explored the conformations and the cavity size of the three compounds and showed that their hydrophobic pockets can accommodate one molecule of water or methane (3 and 5), or benzene (7) without any distortion. Notably, the capped porphyrin 5 was able to inhibit the oxidation of Co(II) to Co(III), whereas compound 7 did it only partially. 相似文献
70.
Natanzon proved that a Riemann surface of genus has at most conjugacy classes of symmetries, and this bound is attained for infinitely many genera . The aim of this note is to prove that a Riemann surface of even genus has at most four conjugacy classes of symmetries and this bound is attained for an arbitrary even as well. An equivalent formulation in terms of algebraic curves is that a complex curve of an even genus has at most four real forms which are not birationally equivalent.