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981.
This study is aimed at attempting to improve both the selectivity and the permeation rates for the separation of 1-methylnaphthalene from dodecane using aqueous surfactant membranes. This enhancement is achieved by adding various water-soluble chemical compounds (“additives”) to the water phase. Seven different additives were tried in this study and their efficacy was determined by carrying out mass transfer permeation experiments to determine both the rates of transfer and the selectivity of separation. In line with our previous work (Sharma et al. [5]; Krishna et al. [6]), we have corrected the mass transfer coefficients for emulsion breakage, and found these coefficients, and the selectivity, to correlate well with the work of transfer of the additive-containing surfactant system. The increase in selectivity in the presence of the additive has been shown to be due to the relative increase in the activity coefficient of 1-methylnaphthalene in the aqueous solution with respect to that of dodecane. The presence of the additive increases the selectivity by about one order of magnitude, and the present study should aid in the development of a viable liquid membrane separation process for the selective removal of aromatics from kerosene, a process which is required for the production of aviation turbine fuel from crudes having a high aromatic content in the lighter distillates. 相似文献
982.
L. Chatterjee G. Das R. Goswami 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,32(1):73-78
Cross sections for radiative Coulomb capture of muons in hydrogen are shown to be enhanced by two orders of magnitude for muon energies in the neighbourhood of 2.8 keV. This effect has not been recognised earlier and has important consequences for negative muon physics as shown. 相似文献
983.
A detailed study has been conducted on the long-term changes in the diurnal, semi-diurnal and tri-diurnal anisotropies of
cosmic rays in terms of the high/low amplitude anisotropic wave train events (HAE/LAE) during the period 1981–94 using the
neutron monitor data from Deep River Neutron Monitoring Station. In all, 38 HAE and 28 LAE cases have been studied. An inter-comparison
of the first three harmonics during these events has been made so as to understand the basic reason for the occurrence of
these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs and
it shifts towards earlier hour as compared to 18-h direction for LAEs. For semi-diurnal anisotropy, phase remains statistically
the same for both HAE and LAE. In the case of tri-diurnal anisotropy, phase is evenly distributed for both types of events.
The interplanetary magnetic field (IMF) and solar wind plasma (SWP) parameters during these events are also investigated.
It has also been observed that HAE/LAEs are weakly dependent on high-speed solar wind velocity. The two types of solar wind
streams (corotating streams and flare-generated streams) produce significant deviations in cosmic ray intensity during HAE/LAE.
相似文献
984.
Shyamaprosad Goswami Subrata Jana Anita Hazra Avijit Kumar Adak 《Journal of heterocyclic chemistry》2007,44(5):1191-1194
985.
986.
Small-angle X-ray scattering (SAXS) study on nonionic fluorinated micelles in aqueous system 总被引:1,自引:0,他引:1
Shrestha LK Sharma SC Sato T Glatter O Aramaki K 《Journal of colloid and interface science》2007,316(2):815-824
We have investigated the self-organization structures of perfluoroalkyl sulfonamide ethoxylate, C(8)F(17)SO(2)N(C(3)H(7))(CH(2)CH(2)O)(10)H, a nonionic fluorinated surfactant in aqueous system by small-angle X-ray scattering (SAXS) technique. Structural modulation of the nonionic fluorinated micelle induced by temperature change, surfactant concentration, and the added fluorinated oils have been systematically studied. The SAXS data were analyzed by the indirect Fourier transformation (IFT), and the generalized indirect Fourier transformation (GIFT) depending on the volume fraction of the surfactant. Various plausible classical model calculations have been performed to confirm the consistency of the GIFT analysis of the SAXS data. Upon successive increase in temperature, the cylindrical micelles formed at lower temperatures undergo a continuous one-dimensional growth and ultimately near the cloud point an indication of flat planar like structural pattern is observed. The evolution in structure of particle near the demixing temperature may be due to onset of attractive interactions. The shape and size of the micelle is apparently unaffected by changing the surfactant concentration from 1 to 5 wt% at 25 degrees C. Nevertheless, addition of small amount of perfluoropolyether (PFPE) oil, of structure F(CF(2)CF(2)CF(2)O)(n)CF(2)CF(2)COOH (n approximately 21) modulate the micellar shape and size. Long cylindrical micelles eventually transform into globular like particles. The onset cylinder-to-sphere transition in the structure of micelles in the surfactant/water/oil system is probably due to amphiphilic nature of the oil, which tends to increase the spontaneous curvature. The lipophilic part of the oil tends to reside in the micellar core, whereas, the hydrophilic part goes close to the polar head group of the surfactant so that effective cross-sectional area per surfactant molecules increases and as a result spherical micelles tend to form. Perfluorodecalin (PFD) also decreases size of the micelles but its effect is poor compared to the PFPE oil. 相似文献
987.
[reaction: see text] A highly practical, general method for catalytic formation of substituted pyridines from a variety of unactivated nitriles and alpha,omega-diynes is given. The reactions which were catalyzed by 5 mol % of dppe/CoCl2-6H2O in the presence of Zn powder (10 mol %) could proceed at rt to approximately 50 degrees C with high functional compatibility and regioselectivity. 相似文献
988.
We present a mean-field model of a one-component electrolyte solution where the mobile ions interact not only via Coulomb
interactions but also through a repulsive non-electrostatic Yukawa potential. Our choice of the Yukawa potential represents
a simple model for solvent-mediated interactions between ions. We employ a local formulation of the mean-field free energy
through the use of two auxiliary potentials, an electrostatic and a non-electrostatic potential. Functional minimization of
the mean-field free energy leads to two coupled local differential equations, the Poisson-Boltzmann equation and the Helmholtz-Boltzmann
equation. Their boundary conditions account for the sources of both the electrostatic and non-electrostatic interactions on
the surface of all macroions that reside in the solution. We analyze a specific example, two like-charged planar surfaces
with their mobile counterions forming the electrolyte solution. For this system we calculate the pressure between the two
surfaces, and we analyze its dependence on the strength of the Yukawa potential and on the non-electrostatic interactions
of the mobile ions with the planar macroion surfaces. In addition, we demonstrate that our mean-field model is consistent
with the contact theorem, and we outline its generalization to arbitrary interaction potentials through the use of a Laplace
transformation. 相似文献
989.
Nathalie Renard-Le Galloudec J. Cobble S.L. Nelson A. Merwin Y. Paudel I. Shrestha G.C. Osborne K.M. Williamson V.L. Kantsyrev 《High Energy Density Physics》2011,7(4):247-251
Proton radiography is a very powerful diagnostic but in some high debris environments it may be challenging to get a good signal-to-noise ratio radiograph to gain insights into the electric and magnetic field topology, and thus the basic physics. Such environments are produced for example on z-pinches and also on lasers such as the National Ignition Facility. We demonstrate here the feasibility of clean, very high signal-to-noise ratio proton radiographs in extremely hostile environments. 相似文献
990.
Structure and rheology of reverse micelles in dipentaerythrityl tri-(12-hydroxystearate)/oil systems
Shrestha LK Sato T Shrestha RG Hill J Ariga K Aramaki K 《Physical chemistry chemical physics : PCCP》2011,13(11):4911-4918
We report the formation of reverse rod-like micelles and their rheological properties in novel nonionic surfactant, dipentaerythrityl tri-(12-hydroxystearate) (designated as WO-6)/oil systems without external water addition. Small-angle X-ray scattering (SAXS) was used to investigate the structure of the micelles and their flow properties were studied by rheological measurements. We found that WO-6 spontaneously self-assembles into reverse micelles in a variety of organic solvents at ambient conditions, their structure depending on solvent molecular architecture, surfactant concentration, and temperature. Rod-like micelles with a maximum length of ca. 12 nm and a cross section diameter of ca. 2 nm were observed in cyclohexane. When cyclohexane was replaced with a linear chain octane, the length and the cross section diameter were simultaneously increased. With a further increase of hydrocarbon chain length of solvent oils from octane to hexadecane, the rod-like micelles grew axially, keeping the cross section diameter (ca. 3 nm) virtually constant. Increasing surfactant concentration also favored one-dimensional micellar growth. On the other hand, micelles shrunk with the rise of temperature, which is similar to a rod-to-sphere transition, and is essentially the opposite temperature dependence to that often observed in aqueous micellar systems. A structural picture drawn by SAXS is well supported by rheology; the relative (zero-shear) viscosity of the WO-6/oil systems was found to be markedly greater than that expected for a dispersion of spherical particles due to the elongated micellar structure, despite quantitative inconsistency with semi-empirically predicted values for rigid rod-like particles. 相似文献