The Electrostatic Interaction of a Charged Particle with a Surface: The Effect of Surface Charge Rearrangement

In this paper we investigate the electric interaction between a charged particle and a surface in which the charged ions are capable of moving in response to the electric potential disturbance caused by the approach of the charged particle. Such surfaces include ionic surfactants distributed in air-water interface and charged lipids in bilayer membranes. On the basis of the mean field theory, the free energy of the system, which includes the electrostatic internal energy and the entropy of the mobile ions and surface ions, can be written down. The surface charge-potential relation is then derived by the calculus of variation. When the potential disturbance is small enough, a linear charge regulation model is obtained. The interaction energy associated with a long rod parallel to the interface is studied and an analytical expression is obtained. When a rod approaches an oppositely charged surface, the interaction can change from attraction to repulsion, depending on the ratio of the characteristic regulation length to the Debye length. At low surface charge density, the surface behaves as under the condition of constant charge density and acts as that of constant potential for high enough charge density. Copyright 2001 Academic Press.     

Isolation and purification of acteoside and isoacteoside from Plantago psyllium L. by high-speed counter-current chromatography

Two isomeric phenylethanoid glycosides, acteoside and isoacteoside were isolated and purified from the seeds of Plantago psyllium L. for the first time by high-speed counter-current chromatography (HSCCC) using a solvent system consisting of ethyl acetate-water (1:1, v:v). By injecting 200 mg of the n-butanol extract of P. psyllium for five consecutive times, the two-step HSCCC procedure yielded a total of 165 mg of acteoside and 17.5 mg of isoacteoside from 978 mg extract. The recovery rates for acteoside and isoacteoside were 90 and 84%, respectively, and the purities were 98 and 94%, respectively. The HSCCC fractions were analyzed by HPLC and the structures were identified by UV, LC-APCI-MS in negative ion mode, and confirmed by NMR experiments.     

Synthetic and modified isoflavonoids. X. Synthesis of 2-ethyl and 2-propyl homologues of pseudobaptigenin

Homologues of pseudobaptigenin containing ethyl and propyl groups in position 2 have been synthesized. The structures of the new compounds have been comfirmed by PMR.KIEN, Karakalpak Division, Academy of Sciences of the Republic of Uzbekistam, Nukus. Taras Shevchenko Kiev University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 334–337, May–June, 1994.     

Process engineering of high-ethanol-tolerance yeast for the manufacture of ethanol

Applied Biochemistry and Biotechnology - Inhibitory effects of ethanol and glucose on a high-ethanol-tolerance yeast strain (fusion product ofSaccharomyces diastaticus andSaccharomyces uvarum)...     

The impact of loyalty and promotion effects on retention rate

Researching customer retention rates is made difficult because of the lack of suitable systems with which to measure it. From a first-order Markov brand-switching model, serial equations are derived to estimate the retention rate using market share and loyalty. To explore the impact of loyalty and promotion programme on retention rate, data from five leading brands for three product categories were obtained to fit the developed model. Findings suggest that: (1) when the loyalty effect remains unchanged over a period of time, the greater the effect of a promotion programme, the greater the retention rate; (2) when the promotion effects among brands are similar, the retention rate varies depending on level of loyalty; and (3) when the proportion of loyal customers is high, the proportion of potential switchers affected by promotion programmes is low. In this case, the impact of a promotion programme on the retention rate is not significant. This model successfully demonstrates how the Markov brand-switching model can be employed to estimate a measure of retention rate from consumer panel data as well as to better understand how promotion affects loyalty, switching behaviour, and retention rate.     

Improvement in the thermal conductivity of aluminum substrate for the desktop PC Central Processing Unit (CPU) by the Taguchi method

This paper examines the thermal conductivity of thin films (Cu or Ag) deposited on 1050 aluminum alloy substrates (99.57% purity) by various sputtering. The Taguchi method was used to clarify the influence of various deposition conditions (target, sputtering method, power, deposition time and annealing temperature). This paper employs the signal-to-noise (S/N) ratio and analysis of variance (ANOVA) to study the coating operation performance. The experimental results point out the optimum conditions of highly thermal conduction were the Ag target, sputtering method of RF, power of 300 W, deposition time of 15 min, and no annealing temperature. The sputtering method and power are the most significant factors among the five controllable factors affecting the thermal conductivity of aluminum substrate in the sputtering process.     

Chiral cyclobutane synthesis by exploiting a heteroatom-directed conjugate addition

The syntheses of both enantiomers of cyclobutanes B and ent-B are achieved through heteroatom-directed conjugate addition (HADCA) of nucleophiles to the epoxyvinylsulfone-substituted carbohydrates A and ent-A, which provided carbanions that intramolecularly attacked the epoxide with concomitant formation of the cyclobutane ring.