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31.
Luca Bernazzani Maria Rita Carosi Celia Duce Paolo Gianni Vincenzo Mollica 《Journal of solution chemistry》2006,35(11):1567-1585
Excess molar volumes, V
m
E, over the whole composition range for binary mixtures of 1-butanol, 2-butanol, and 2-methyl-2-propanol + 1-octanol, or 2-octanol, or di-n-butyl ether, or n-hexylacetate were determined at 298.15 K from density measurements carried out with a vibrating-tube densimeter. Small V
m
E values, both positive and negative, are displayed by mixtures containing 1- or 2-octanol, whereas positive and larger values are always found for mixtures containing dibutyl ether and hexylacetate. These results can be justified in terms of H-bonding interactions and/or steric hindrance due to the branched alkyl chains. Partial molar volumes at infinite dilution of the isomeric butanols in the C8 compounds were also calculated from the apparent molar volumes in dilute solution. The solute-solvent interactions and the effects of the local organisation of the solvent around the butanol molecules were discussed using the void and cavity volumes as different estimates of the intrinsic volume of the molecules. The volumetric behavior of butanols seems to be determined by the solute-solvent interactions rather than packaging effects. 相似文献
32.
Alain Valtz 《Thermochimica Acta》2006,443(2):251-255
Densities of the water + ethylenediamine binary system were measured at atmospheric pressure over the whole range of compositions at temperatures from 288.15 to 353.15 K using an Anton Paar digital vibrating glass tube densimeter. Density increases with water content. The experimental excess molar volume data have been correlated with the Redlich-Kister equation, and partial molar volumes calculated at infinite dilution for each component. 相似文献
33.
The solvatochromic behavior of a penta‐tert‐butyl prydinium N‐phenolate betaine dye was studied using UV‐visible spectrophotometry in several binary mixture solvents. The solvent polarity parameter, ET (1) (kcal. mol?1) was calculated from the position of the longest‐wavelength intramolecular charge transfer absorption band of this penta‐tert‐butyl betaine dye. For binary solvent mixtures, all plots of ET (1) versus the mole fraction of a more polar component are nonlinear owing to preferential solvation of the probe by one component of the binary solvent mixture. In the computation of ET (1) it was assumed that the two solvents mixed interact to form a common structure with an ET (1) value not always intermediate between those of the two solvents mixed. The results obtained are explained by the strong synergism observed for some of the binary mixtures with strong hydrogen bond donors (HBD) solvents such as alcohols. 相似文献
34.
Ewa Lada Xiubin Lei Marek K. Kalinowski 《Monatshefte für Chemie / Chemical Monthly》1992,123(5):425-433
Summary The formation constants,K
S, of the 18-crown-6 complex with thallium(I) ion were studied by polarographic measurements in binary mixtures of acetonitrile, acetone, tetrahydrofuran, and dimethylsulfoxide with water, as a function of the solvent mole fraction. In all the cases, the variation of the stability constant can be described by the empirical relation logK
S=a[(–1)/(2+1)]+b where stands for relative permittivity of a given mixture anda andb mark the regression coefficients. The values ofa calculated for four series of binary mixtures showed correlation with the Gutmann donor numbers of the neat organic solvents which form the mixture.On leave from the Department of Chemistry, Jingzhou Teacher's College, Jingzhou, Hubei, China 相似文献
35.
Based on the theory of stochastic resonance, a new method carried on the quantitive analysis to weak chromatographic signal of glyburide in plasma, which was embedded in the noise background and the signal-to-noise ratio (SNR) of HPLC-UV is enhanced remarkably. This method enhances the quantification limit to 1 ng ml−1, which is the same as HPLC-MS, and makes it possible to detect the weak signal accurately by HPLC-UV, which was not suitable before. The results showed good recovery and linear range from 1 to 50 ng ml−1 of glyburide in plasma and the method can be used for quantitative analysis of glyburide. 相似文献
36.
Studies on accelerated sulphur vulcanization of natural rubber using 1-phenyl-2, 4-dithiobiuret/tertiary butyl benzothiazole sulphenamide 总被引:3,自引:0,他引:3
The use of binary accelerators has gained tremendous importance since it increases the production rate of the article made of that elastomer. The authors have analyzed the performance of a novel binary accelerator system in the sulphur vulcanization of natural rubber (NR). The vulcanizates resulting from the binary accelerated process obtained good mechanical properties, ageing and swelling resistance. Network characterization of the mixes was done using swelling measurements, stress-strain analysis etc. The chain entanglement density was measured using dynamic mechanical analysis. However the performance is found to be dependent on the relative proportion of mono, di and polysulphidic linkages in the material. The result of the study points out that the proposed system can be active in NR regardless of the vulcanization recipe and temperature. The performance of the new binary system in filled vulcanizates is also studied. Based on the processing, mechanical and chemical characterization an optimum concentration is suggested for the new system. 相似文献
37.
《Arabian Journal of Chemistry》2020,13(2):4082-4091
In present study, an investigation was carried out to develop and validate an analytical method for the selective extraction and determination of griseofulvin (GSF) from plasma samples. For this purpose, a rational approach was made to synthesize and characterize the surface molecularly imprinted polymers (SMIPs). The SMIPs were utilized as solid phase extraction (SPE) sorbents. The SMIPs were prepared by using GSF as template molecule on the surface of modified silica particles through a non-covalent technique. The particles demonstrated high adsorption capacity (119.1 µg/mL), fast adsorption equilibrium time (30 min) and good recognition selectivity for the template drug. The scanning electron microscopy and infrared spectroscopy were used to explain the structural and morphological characteristics of the SMIPs and surface non-imprinted polymers. The SPE method was combined with HPLC for plasma analysis. The method validation results demonstrated that the established method possessed good linearity for GSF ranging from 0.1 to 50 µg/mL (R2 = 0.997). The limit of detection for this method was 0.02 µg/mL for rat plasma samples. The recoveries of GSF from spiked plasma samples were (90.7–97.7%) and relative standard deviations were (0.9–4.5%). Moreover, the SMIPs as selective SPE sorbent can be reused more than 8 times which is a clear advantage over commercial SPE sorbents. Finally, the usefulness of the proposed strategy was assessed by extraction and detection of GSF in real rat plasma samples. 相似文献
38.
本文介绍了一种利用学生在电子技术实验课中自己组装的收音机,稍加改造而制作的一种简单适用、并且效果很好的激光通信演示器。 相似文献
39.
A turnout switch machine is key equipment in a railway, and its fault condition has an enormous impact on the safety of train operation. Electrohydraulic switch machines are increasingly used in high-speed railways, and how to extract effective fault features from their working condition monitoring signal is a difficult problem. This paper focuses on the sectionalized feature extraction method of the oil pressure signal of the electrohydraulic switch machine and realizes the fault detection of the switch machine based on this method. First, the oil pressure signal is divided into three stages according to the working principle and action process of the switch machine, and multiple features of each stage are extracted. Then the max-relevance and min-redundancy (mRMR) algorithm is applied to select the effective features. Finally, the mini batch k-means method is used to achieve unsupervised fault diagnosis. Through experimental verification, this method can not only derive the best sectionalization mode and feature types of the oil pressure signal, but also achieve the fault diagnosis and the prediction of the status of the electrohydraulic switch machine. 相似文献
40.
In this paper, the effects of a bistable potential function U(x)=-ax2/2+b|x|2γ/(2γ) on stochastic resonance (SR) is discussed. We investigate the effects of index γ on the performance of the SR system with fixed parameters a and b, and with fixed potential barriers, respectively. To measure the performance of the SR system in the presence of an aperiodic input, the bit error rate is employed, as is commonly used in binary communications. The numerical simulations strongly support the theoretical results. The goal of this investigation is to explore the effects of the shape of potential functions on SR and give a guidance of nonlinear systems in the application of information processing. 相似文献