排序方式: 共有47条查询结果,搜索用时 31 毫秒
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Giulia Caron Giuseppe Ermondi Donatella Boschi Pierre-Alain Carrupt Roberta Fruttero Bernard Testa Alberto Gasco 《Helvetica chimica acta》1999,82(10):1630-1639
Homologous N,N-dimethyl-phenylalkylamine oxides and N,N-dimethyl-diphenylalkylamine oxides were prepared. Their basicity and lipophilicity (octan-1-ol/H2O) were compared to those of the parent amines. In contrast to the amines, the basicity of all N,N-dimethyl-arylalkylamine oxides showed very limited pKa variations (range 4.65 – 5.01) with increasing chain length and number of Ph groups. The N-oxides in their neutral form had a log PN value lower by 2.77±0.34 (n=9) units than that of the parent amine. The log PC of the cationic N,N-dimethyl-diphenylalkylamines was lower than that of their neutral form, with a decrement diff(log PN−C) that increased from 3.25 to 4.21 in the homologous series. Unexpectedly, the decrement diff(log PN−C) for the N-oxides was much smaller than for the tertiary amines, being 0.23 for the aliphatic N,N-dimethyl-pentylamine oxide, 0.47±0.13 for the phenylalkylamine oxides, and 0.80±0.07 for the diphenylalkylamine oxides. In fact, the protonated N-oxides had log PC values that were quite comparable to those of the protonated parent amines. Because of the differences in basicity, the difference in distribution coefficients at physiological pH (log D7.4) between a tertiary arylalkylamine and its N-oxide was 0.82±0.66 (n=9). The pharmacokinetic implication is that N-oxygenation may have a smaller effect on the urinary excretion of tertiary amines than usually assumed. 相似文献
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A method is described for the fluorimetric determination of zinc, based on formation of a zinc-morin complex in the presence of a non-ionic surfactant. The complex has practically no fluorescence in the absence of surfactant, but the addition of Genapol PF-20 (non-ionic surfactant, ethylene oxide-propylene oxide condensate) makes possible the fluorimetric determination of low concentrations of zinc as it enhances the fluorescence of the complex about 75-fold. Maximum fluorescence is produced at pH 4.7 +/- 0.2 (acetic acid-acetate buffer), with 1.5% surfactant and 0.009% morin. The fluorescence is excited at 433 nm and measured at 503 nm. The calibration graph is linear up to 150 ng/ml zinc concentration and the detection limit is 3 ng/ml. The relative standard deviation (11 replicates) is 2.4% for zinc at 20 ng/ml concentration and 1.7% for 100 ng/ml. Of 29 ions studied, Al(3+), Be(2+), Zr(4+) and Cd(2+) strongly increase the fluorescence of the system, and Fe(3+), Ni(2+), Cu(2+), Ti(IV) and Co(2+) decrease the fluorescence signal. 相似文献
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Jinguo Zhang Jin Young Huh Kiattikhun Manokruang Ponusa Songtipya Maria Mar Jimenez‐Gasco 《Macromolecular rapid communications》2009,30(1):17-23
A novel heat‐sealing performance is achieved by polyethylene (PE) nanocomposites reinforced by ethylene vinyl acetate (EVA) and montmorillonite (MMT). Appropriate nanocomposite design leads to hermetic seals with a general peelable/easy‐open character across the broadest possible sealing temperature range. Observations of the fracture seal surfaces by infrared spectroscopy and electron microscopy reveal that this behavior originates from a synergistic effect of the EVA copolymer and the montmorillonite clay nanofiller. Namely, the combination of EVA‐copolymers and MMT nanofillers provides sufficiently favorable interactions for nanocomposite formation and mechanical robustness, but weak enough interfacial adhesion to promote a general cohesive failure of the sealant at the EVA/MMT interfaces.
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Marco L. Lolli Loretta Lazzarato Antonella Di Stilo Roberta Fruttero Alberto Gasco 《Journal of organometallic chemistry》2002,650(1-2):77-83
Tetraethyl ethenylidenebisphosphonate can undergo facile Michael type addition reaction with simple Grignard reagents to give alkyl, arylalkyl, aryl C-substituted methylene bisphosphonates. This addition easily occurs even if funtionalised Grignard reagents are used. 相似文献
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Vilma Kaškonienė Paulius Kaškonas Audrius Maruška Loreta Kubilienė 《Central European Journal of Chemistry》2014,12(6):736-746
Six samples of propolis were analyzed in the paper: a sample from Brazil, Estonia, China and three samples from different locations of Uruguay. Static headspace technique coupled with gas chromatography-mass spectrometry analysis has been applied for the determination of the characteristic volatile profile with the aim to differentiate the propolis from different regions. Monoterpenes (α- and β-pinenes) were predominant in all samples, except the sample from China. This sample separated itself by the alcohols 3-methyl-3-buten-1-ol and 3-methyl-2-buten-1-ol, (40.33% and 11.57%, respectively) and ester 4-penten-1-yl acetate (9.04%). α-Pinene and β-pinene composed 64.59–77.56% of volatiles in Brazilian and Uruguayan propolis, and 29.43% in Estonian propolis. Brazilian propolis was distinguished by a high amount of β-methyl crotonaldehyde (10.11%), one of Uruguayan samples 3- by limonene (15.58%), and the Estonian sample — by eucalyptol (25.95%). Statistical investigation of the samples was made applying principal component, hierarchical cluster and K-Means cluster analyses. Various data pre-processing techniques were proposed and used to study and obtain the important volatile compounds contributed to the differentiation of the propolis samples from different regions to separate clusters. 相似文献
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Minvydas Ragulskis Loreta Saunoriene Jurate Ragulskiene 《Optics and Lasers in Engineering》2006,44(11):1209-1218
Inverse problem of reconstruction of dynamic displacements from the fringe pattern generated by time average reflection moiré is investigated in this paper. A technique for numerical simulation of time average smoothed reflection moiré fringes is proposed. The smoothing procedure is incorporated into the finite element formulation of the problem. Reconstruction of the field of deflections is illustrated for a centrally clamped disk. Such techniques can be effectively exploited in hybrid numerical–experimental procedures for different objects and grating geometries. 相似文献
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R. Calvino B. Ferrarotti A. Gasco A. Serafino 《Journal of heterocyclic chemistry》1983,20(5):1419-1421
The preparation of some nitrophenyl derivatives of the furazan and furoxan ring systems is reported. The results of an antimicrobial screening on these compounds are also briefly discussed. 相似文献