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41.
A theory is developed for the potential distribution around a charged spherical colloidal particle carrying ionized groups on the particle surface in a medium containing its counterions (i.e., counterions produced from dissociation of the particle surface groups) and a small amount of added salts on the basis of the theory of Imai and Oosawa. Numerical solutions to the Poisson–Boltzmann equation for the potential distribution are obtained for the case of dilute (but not infinitely dilute) particle suspensions of volume fraction 1 for
a1 (where is the Debye–Hückel parameter and a is the particle radius). Here we have taken into account the effects of (i) counterions from the particle surface groups, and (ii) the finite particle volume fraction. These effects, which are usually neglected in the conventional Poisson–Boltzmann equation, are found to be important. It is found that, as in the case of completely salt-free media, there is a certain critical value of the particle charge (which is the same as that for the completely salt-free case). When the particle charge is lower than the critical value, the potential is given by a Coulomb potential. If the particle charge is higher than the critical value, then counterions are accumulated in the vicinity of the particle surface (counterion condensation) and the potential becomes less dependent on the particle charge. The above behaviors can be observed even for the case where the electrolyte concentration is higher than the concentration of counterions from the particle surface groups, if the conditions
1 and a1are both satisfied. 相似文献
42.
Summary New separation procedures for alkaloids of similar polarity and structure or of very different polarity and structure, based upon two-dimensional thin-layer chromatography on unmodified silica gel under mild conditions are described. Separation factors and separation mechanisms based on the structure of the bases and mobile phase composition are discussed for some examples of very efficient procedures.Proportions in solvent mixtures are v/v except where otherwise indicated. 相似文献
43.
Tong ZHAO 《数学年刊B辑(英文版)》2022,43(2):195-208
This paper characterizes the limits of a large system of interacting particles distributed on the real line. The interaction occurring among neighbors involves two kinds of independent actions with different rates. This system is a generalization of the voter process, of which each particle is of type A or a. Under suitable scaling, the local proportion functions of A particles converge to continuous functions which solve a class of stochastic partial differential equations driven by Fisher-Wrig... 相似文献
44.
We present new results for the current as a function of transmission rate in the one-dimensional totally asymmetric simple exclusion process (TASEP) with a blockage that lowers the jump rate at one site from one tor<1. Exact finitevolume results serve to bound the allowed values for the current in the infinite system. This proves the existence of a nonequilibrium phase transition, corresponding to an immiscibility gap in the allowed values of the asymptotic densities which the infinite system can have in a stationary state. A series expansion inr, derived from the finite systems, is proven to be asymptotic for all sufficiently large systems. Padé approximants based on this series, which make specific assumptions about the nature of the singularity atr=1, match numerical data for the infinite system to 1 part in 104. 相似文献
45.
Laurent Serlet 《Journal of Theoretical Probability》1996,9(3):561-578
We study super-Brownian motion inR
d
starting from a nontrivial finite measure and conditioned to nonextinction as defined by Evans. If (Y
t
)
t0
denotes this process, we provide a new approach to the immortal particle representation of (Y
t
)
t0
. We then show that the measureZ onR
d
defined byZ(B)=
o
1
Y
t
(B) dt is almost surely finite on compact sets whend5 and almost surely infinite on every ball whend4. 相似文献
46.
Effect of Hydration–Dehydration Processes on the Structure and Porosity of Detemplated Silica Fibers
Kovalenko V. V. Tel'biz G. M. Bobonich F. M. 《Theoretical and Experimental Chemistry》2004,40(1):64-68
A study was carried out on the conditions of template removal (calcination or extraction by solvents) and hydration–dehydration processes on the hexagonal structure and porosity of detemplated fibers. The hydration–dehydration cycle leads to a decrease in fiber porosity, especially in fiber detemplation by extraction with surfactant solvents such as ethanol and acetic acid. 相似文献
47.
Stationary phase crosslinking conditions for fused silica capillary columns were optimized with the use of a factorial design experiment. This experimental strategy was chosen because it provided for the determination of two-factor interactions. A predictive model was developed for the desired chromatographic performance parameters as a function of the variables of the crosslinking reaction. Confirmatory experiments proved the usefulness of the mathematical model which resulted in the production of capillary columns of superior performance with significant improvements in reproducibility. 相似文献
48.
Summary The effect of silanol groups on three types of octadecylmodified column gels using heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at 180°C, 500°C and 950°C, the silicas treated with octadecyldimethylchlorosilane were used for the measurement of physical and chemical analysis. From elemental carbon analysis data, the reactive silanol group concentrations, OH(s), were determined to be 2.0 in the 180°C treated silica, 2.1 in the 500°C treated silica and 1.6 in the 950°C treated silica, respectively (original silica: mean pore diameter 116 Å, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0 m). The separation factors, , of pyridine versus phenol were measured to be 0.79 on 180°C treated silica, 0.91 on 500°C treated silica and 1.98 on 950°C treated silica, using acetonitrile-water mixtures as the eluent. And then, on the basis of the physico-chemical and chromatographic data, the three types of octadecyl modified column gels using heat-treated silicas by calcination have been compared. 相似文献
49.
Cadmium colloids have been prepared by Chemical Liquid Deposition (CLD). The metal is evaporated to yield atoms which are solvated at liquid nitrogen temperature, and upon warming, stable liquid colloids are formed with particle size ranging between 25–100 Å. Zeta potentials were calculated according to the conversion of Hunter and the Hückel equation, for ethanol and dimethyl sulphoxide. UV/VIS measurement of most of the black colloids showed absorption band around 280 nm. For comparison, we prepared CdS colloid with size 400–625 Å. The colloids are stable to oxidation in air and/or oxygen bubbling. The synthesis of colloids and films from Cd with acetone, 2-butanone, ethanol, 2-propanol, 2-methoxyethanol, DMF and DMSO is reported. Transmission Electron Microscopy (TEM) allows us to determine particle size. 相似文献
50.
Summary Five plant oils (peanut, pumpkin seed, sesame seed, soybean, and wheat germ) have been analyzed by high-performance liquid
chromatography-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS). Gradient elution was performed with
acetone-acetonitrile mobile phases on a short monolithic silica column (SilicaROD, RP-18e, 50 mm×4.6 mm). Identification of
plant oil triacylglycerols (TAG) was based on the pseudomolecular ion [M+H]+ and the diacylglycerol [M−RCO2]+ fragments. Positional isomers of triacylglycerols were identified from the relative intensities of the [M-RCO2]+ fragments. Principal-component analysis, used to find similarities and differences between the different oils, indicated
that the different plant oils could be clearly differentiated according to their triacylglycerol composition.
Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001 相似文献