the bulk equilibrium value cannot be explained by the heat effects.(c) The surface charge may alter the interfacial equilibrium. In the present study the charge on the droplets ranged from lo4 to lOe elementary charges. For the droplet size range (2 pm 5 a 5 20 pm) encountered in this study the effect of surface charge density on the equilibrium composition is negligible. Moreover, the observed moisture content shows no correlation with the surface charge density. ConclusionsWe have measured the evaporation and growth of single glycerol droplets by suspending them individually inside an electrodynamic balance in a stream air of precisely controlled humidity and temperature. By changing the relative humidity of the air stream, we have obtained the growth and evaporation rates of the same droplets over a wide range of relative humidities. The growth and evaporation rates of the droplets have been obtained from two independent methods: light scattering and balancing voltage data. The data obtained by these two methods are in excellent agreement. We have also demonstrated that the resonant peaks found in an intensity spectrum can be used to obtain droplet size and refractive index simultaneously with high precision. From the experimental data, we draw the following conclusions.(i) The time required by a droplet to reach the maximum size is considerably higher than the time predicted by the diffusion theory for the reported value of the liquid-phase diffusion coefficient of a glycerol-water system. The unusually slow growth rates indicate either the existence of interfacial resistance or the presence of other rate-controlling mechanisms.(ii) During the evaporation period, the square of the droplet radius changes linearly with time. The slope of the a2 versus t plot decreases as the relative humidity increases. At a given relative humidity, the observed slopes are highly reproducible.(iii) From the ratio of the slopes in humid air to that in dry air we have obtained the thermodynamic parameter YAXAPAIWU as a function of relative humidity. The experimentally measured slope ratios are significantly higher than the theoretically predicted values based on the equilibrium composition with respect to water vapor in the bulk gas phase, indicating that the droplet interface contains glycerol in excess of the equilibrium value.(iv) For a given relative humidity, the maximum (Le., steady state) water content found in a droplet is always lower than the value predicted by the glycerol-water bulk equilibrium data. The steady-state water content increases with increasing droplet size. The steady-state water content data also raise the possibility of rate-controlling steps other than diffusion being involved in the growth and evaporation processes. Acknowledgment.Surface characterization by FTIR spectroscopy was carried out on heat-treated and water-exposed colloidal nonstoichiometric calcium hydroxylapatite (HAP), synthesized from orthophosphoric acid and calcium hydroxide in an aqueous phase. Two IR bands were newly found at 3682 a...

No abstract

Synthetic antigens that mimic the terminal hexasaccharide epitope of the O-specific polysaccharide of Vibrio cholerae O1, serotype Ogawa, were conjugated to bovine serum albumin (BSA). Conjugates with carbohydrate-to-carrier molar ratios of 15.5:1, 9.2:1, and 4.6:1 were tested for immunogenicity and efficacy in mice. The role of preimmunity to BSA and the use of adjuvant in the generation of the serologic response to the O-specific polysaccharide and protection against virulent V. cholerae was examined. Preimmunity to BSA did not affect the anti-Ogawa titers but seemed to enhance the protective capacity of antiserum. All 3 conjugates were immunogenic, but adjuvant was effective at inducing higher and earlier antibody responses. In tertiary serum samples, a correlation was found between vibriocidal activity and protection. The protective capacity of antiserum was evident in serum from mice immunized with all conjugates, but it was highest in the groups that received the conjugate with the lowest level of substitution. Further studies are required to increase understanding of the reason for differential protection.

The surface structure of mesoporous silica crystals FSM-16 with a narrowly distributed pore size has been studied by FTIR, measurement of SiOH number and adsorption of N, and H,O. IR spectra of FSM-16 outgassed at temperatures above 170°C showed a sharp band at 3740 cm-' due to free SiOH and a broad shoulder at 3600-3500 cm-' due to hydrogen-bonded SiOH. The SiOH number, determined by a weight-loss method, amounted to 3.3 groups nrn-,, which is less than that of mesoporous silica gels. The amount of H,O adsorbed on FSM-16 decreased with calcination above 800"C, owing to the dehydroxylation of SiOH. On treating with alcohol, the number of free SiOH decreased, leading to a decrease in H,O adsorption. The crystallinity of FSM-16 was lowered by pressing. With increasing pressure the specific surface area decreased and the SiOH number increased, up to 9.5 groups nrn-,.

A complete abrasive‐free process for fabricating copper damascene interconnection has been developed. The process is a combination of newly developed abrasive‐free polishing (AFP) of Cu and dry etching of a barrier metal layer. A new aqueous chemical polishing solution and a polyurethane polishing pad produce complete stop‐on‐barrier characteristics of Cu polishing. The AFP provides a very clean, scratch‐free, anticorrosive polished surface, and the total depth of erosion and dishing is reduced to less than one fifth of that produced by conventional slurries, even after 100% overpolishing. The barrier metal is successfully dry etched by using SF6 gas at a high selectivity ratio (more than 10) of barrier metal to SiO2 . It was found that the developed AFP significantly reduces both Cu line resistance and its deviation. Moreover, AFP can also contribute to cost reduction of chemical mechanical polishing and help solve environmental problems related to waste slurries. © 2000 The Electrochemical Society. All rights reserved.