排序方式: 共有70条查询结果,搜索用时 15 毫秒
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Ionic liquids (ILs) are recognized as an environmentally friendly alternative to replacing volatile molecular solvents. Knowledge of vaporization thermodynamics is crucial for practical applications. The vaporization thermodynamics of five ionic liquids containing a pyridinium cation and the [NTf2] anion were studied using a quartz crystal microbalance. Vapor pressure-temperature dependences were used to derive the enthalpies of vaporization of these ionic liquids. Vaporization enthalpies of the pyridinium-based ionic liquids available in the literature were collected and uniformly adjusted to the reference temperature T = 298.15 K. The consistent sets of evaluated vaporization enthalpies were used to develop the “centerpiece”-based group-additivity method for predicting enthalpies of vaporization of ionic compounds. The general transferability of the contributions to the enthalpy of vaporization from the molecular liquids to the ionic liquids was established. A small, but not negligible correction term was supposed to reconcile the estimated results with the experiment. The corrected “centerpiece” approach was recommended to predict the vaporization enthalpies of ILs. 相似文献
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Verevkin SP Zaitsau DH Tong B Welz-Biermann U 《Physical chemistry chemical physics : PCCP》2011,13(28):12708-12711
Activity coefficients at infinite dilution of some common solvents in a protic ionic liquid ethylammonium nitrate have been measured using well established gas-chromatography-method. This method was possible to apply due to extremely low vapour pressure of ethylammonium nitrate at temperatures below 100 °C. Activity coefficients and separation factors were compared with those for aprotic ionic liquids. A new window for intensive accumulation of thermodynamic properties of protic ionic liquids has been opened. 相似文献
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Shcharbin D Pedziwiatr E Nowacka O Kumar M Zaborski M Ortega P de la Mata FJ Gómez R Muñoz-Fernandez MA Bryszewska M 《Colloids and surfaces. B, Biointerfaces》2011,83(2):464-391
A new mechanism of gene expression inhibition has been discovered as RNA interference, in which the ability of double-stranded RNA to stimulate specific degradation of an mRNA target with a complementary sequence to one of the double-stranded RNA strands. Water-soluble carbosilane dendrimers containing ammonium or amine groups at their periphery are biocompatible molecules that may be good candidates as non-viral carriers of small interfering RNA. In studying the formation of complex between anti-HIV siRNA siGAG1 and carbosilane dendrimers NN8 and NN16 by circular dichroism, fluorescence, and zeta-potential, the size of nanoparticles formed has been estimated by dynamic light scattering. At a charge ratio of 1:3-4 (siGAG1:dendrimer), the dendriplexes formed were in the size range of 250-350 nm. 相似文献
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In this paper, we present a concrete counterexample to the conjecture of Kontsevich about the polynomial countability of graph
hypersurfaces. In contrast to this, we show that the “wheel with spokes” graphs WS
n
are polynomially countable. 相似文献
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Dhopeshwarkar R Hlushkou D Nguyen M Tallarek U Crooks RM 《Journal of the American Chemical Society》2008,130(32):10480-10481
Electrokinetic transport within a buffer-filled microchannel incorporating a flat bipolar electrode is investigated. The key finding is that the presence of the electrode disrupts the passage of electrical current through the microchannel and thereby alters the uniformity of the local electric field. Electroosmotic flow further modulates the local field gradient. These dynamics are demonstrated experimentally by utilizing the field gradient for concentration enrichment of negatively charged tracer molecules, and a set of computer simulations is presented to interpret the underlying electrokinetics. 相似文献
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The influence of membrane ion-permselectivity on electrokinetic concentration enrichment in membrane-based preconcentration units 总被引:2,自引:0,他引:2
The performance of nanoporous hydrogel microplugs with varying surface charge density is described in concentrating charged analytes electrokinetically in a microfluidic device. A neutral hydrogel plug with a mean pore size smaller than the size of charged analytes acts as a simple size-exclusion membrane. The presence of fixed charges on the backbone of a nanoporous hydrogel creates ion-permselectivity which results in charge-selective transport through the hydrogel. This leads to the development of concentration polarization (CP) in the adjoining bulk electrolyte solutions under the influence of an applied electrical field. CP strongly affects the distribution of the local electrical field strength, in particular, in the vicinity of the hydrogel plug which can significantly reduce the concentration enrichment factors compared to the neutral hydrogel. A theoretical model and simulations are presented, together with experimental data, to explain the interplay of hydrogel or membrane cation-selectivity, electrical field-induced CP, and the distribution of the local electrical field strength with respect to concentration enrichment of negatively charged analytes at the cathodic membrane-solution interface. 相似文献
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Osipenko Maria A. Kasach Aliaksandr A. Adamiec Janusz Zimowska Małgorzata Kurilo Irina I. Kharytonau Dzmitry S. 《Journal of Solid State Electrochemistry》2023,27(7):1847-1860
In this work, corrosion of the AZ31 magnesium alloy was examined in 0.05 M NaCl solutions containing 0.01–0.150 mol/dm3 of potassium permanganate as a corrosion inhibitor. A set of electrochemical impedance spectroscopy, linear sweep voltammetry, and hydrogen evolution measurements revealed high inhibitor effectiveness at relatively high (0.150 mol/dm3) KMnO4 concentrations. Based on data of energy-dispersive X-ray analysis, scanning electron microscopy, and Raman spectroscopy, a mechanism of the corrosion inhibition of AZ31 alloy by potassium permanganate in chloride-containing media was proposed.
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