Effect of dispersion

The poor dispersibility of CNTs in biological media can affect both the cytotoxicity [38] and the in vivo toxicity [39] of such nanomaterials. 

In vivo, SWNTs individually dispersed by Pluronic F108NF were demonstrated to be nontoxic after intratracheal administration to mice, whereas aggregated SWNTs caused granuloma-like structures with mild fibrosis in the lungs of the treated animals [39]. 

---

Effect of dispersion on a sample s flow profile at different times during a flow injection analysis (a) at injection and when the dispersion is due to (b) convection ... 

The farther into the uv and the narrower the distribution of the resonant electron frequencies, the smaller the effect of dispersion in the visible region. The Pb(II) ion exhibits absorption in the near-uv, and addition of Pb(II) to a glass increases both n and dispersion. However, the use of Ba(II) and La(III) increases n without increasing dispersion. Fluorophosphates, having absorption bands located well into the uv, are examples of glasses with high AbbH numbers and low refractive indexes. 

Fig. 3. Effect of dispersants on settling rate of 700 mg/L dehydrated iron oxide in water. Left, no dispersant. Right, 3 mg/L styrenesulfonate—maleic acid...

The gas rate at which coalescence begins to reduce the effectiveness of dispersion appears to depend not only on the pore size and pore structure of tlie di.spersiiig medium but also on the li( iiid properties, li( iiid depth, agitation, and other features of the pin giiig environment coalescence is strongly dependent on the concentration of... 

In a packed column, however, the situation is quite different and more complicated. Only point contact is made between particles and, consequently, the film of stationary phase is largely discontinuous. It follows that, as solute transfer between particles can only take place at the points of contact, diffusion will be severely impeded. In practice the throttling effect of the limited contact area between particles renders the dispersion due to diffusion in the stationary phase insignificant. This is true even in packed LC columns where the solute diffusivity in both phases are of the same order of magnitude. The negligible effect of dispersion due to diffusion in the stationary phase is also supported by experimental evidence which will be included later in the chapter. 

Sengupta, B. and Dutta, T.K., 1990. Effect of dispersions on CSD in continuous MSMPR crystallizers. Chemical Engineering and Technology, 13(6), 426-431. 

The effects of dispersion and birefringence on stellar interferometry will be discussed in Sections 17.2.3 and 17.2.4. New kind of fibres has been design to manage the dispersion properties using a silica / air structure. These fibres, so called Photonic Crystal Fibres, are very promising for many applications (Peyrilloux et al., 2002). 

The effects of dispersion of the electrocatalyst and of particle size on the kinetics of electrooxidation of methanol have been the subject of numerous studies because of the utilization of carbon support in DMFC anodes. The main objective is to determine the optimum size of the platinum anode particles in order to increase the effectiveness factor of platinum. Such a size effect, which is widely recognized in the case of the reduction of oxygen, is still a subject of discussion for the oxidation of methanol. According to some investigators, an optimum of 2 nm for the platinum particle size exists, but studying particle sizes up to 1.4 nm, other authors observed no size effect. According to a recent study, the rate of oxidation of methanol remains constant for particles greater than 4.5 nm, but decreases with size for smaller particles (up to 2.2 nm). 

As an alternative approach towards the above requirement, Somorjai introduced the method of electron lithography [119] which represents an advanced HIGHTECH sample preparation technique. The method ensures uniform particle size and spacing e.g. Pt particles of 25 nm size could be placed with 50 nm separation. This array showed a uniform activity similar to those measured on single crystal in ethylene hydrogenation. The only difficulty with the method is that the particle size is so far not small enough. Comprehensive reviews have been lined up for the effect of dispersion and its role in heterogeneous catalysis [23,124,125]. 

In the case of river streams, the effect of dispersing the oil creates a strong peak of pollution running along the river flow. The living organisms are submitted to short-term but intense pollution, leading to acute effects. 

Effectiveness of Chemical Dispersants Under Real Conditions. It is believed that the effectiveness of dispersants is influenced by a number of factors, including the chemical natures of the dispersant and the nature of the oil, their relative amounts, and the microscopic mixing processes occurring as the dispersant lands on the oil and penetrates it while subject to turbulence originating in the air and water [1143]. In addition, the oil to be treated can also partly evaporate, form mousses, and spread into thick and sheen patches. 

J. L. Belk, D. J. Elliott, and L. M. Flaherty. The comparative effectiveness of dispersants in fresh and low salinity waters. In Proceedings Volume, pages 333-336. API et al Oil Spill (Prev, Behav, Contr, Cleanup) 20th Anniv Conf (San Antonio, TX, 2/13-2/16), 1989. 

M. F. Fingas, D. A. Kyle, J. B. Holmes, and E. J. Tennyson. The effectiveness of dispersants Variation with energy. In Proceedings Volume, pages 567-574. 13th Bien API et al Oil Spill (Prev, Preparedness, Response Coop) Int Conf (Tampa, FL, 3/29-4/1), 1993. 

Neither the capacity factor nor the separation factor take into account the effect of dispersion, which is measured by the plate number or the plate height of the column. These were defined in Section 2.3.2. 

Concerning the effect of dispersion of the particles, straight migration paths as shown in Fig. 9 are effective to show a large ER effect. 

Alpatova, A.L. et al. (2010) Single-walled carbon nanotubes dispersed in aqueous media via noncovalent functionalization effect of dispersant on the stability, cytotoxicity, and epigenetic toxicity of nanotube suspensions. Water Research, 44 (2), 505-520. 

Chin, Y.-R, Weber, Jr., W.J. (1989) Estimating the effects of dispersed organic polymers on the sorption contaminants by natural solid, 1. A predictive thermodynamic humic substance-organic solute interaction model. Environ. Sci. Technol. 23, 978-984. 

The effect of particle size, and hence dispersion, on the coloring properties of aluminum lake dyes has been studied through quantitative measurement of color in compressed formulations [47], It was found that reduction in the particle size for the input lake material resulted in an increase in color strength, and that particles of submicron size contributed greatly to the observed effects. Analysis of the formulations using the parameters of the 1931 CIE system could only lead to a qualitative estimation of the effects, but use of the 1976 CIEL m v system provided a superior evaluation of the trends. With the latter system, the effects of dispersion on hue, chroma, lightness, and total color differences were quantitatively related to human visual perception. 

C0 is the initial concentration of the sample (before the effect of dispersion takes place) while Cmax is the maximum concentration of the sample during the observation time (when the dispersion has taken place),... 

Flush models can also be configured to simulate the effects of dispersive mixing. Dispersion is the physical process by which groundwaters mix in the subsurface (Freeze and Cherry, 1979). With mixing, the groundwaters react with each other... 

The accounting for diffusion in these models, in fact, is in many cases a formality. This is because, as can be seen from Equations 20.19 and 20.21, the contribution of the diffusion coefficient D to the coefficient of hydrodynamic dispersion D is likely to be small, compared to the effect of dispersion. If we assume a dispersivity a of 100 cm, for example, then the product av representing dispersion will be larger than a diffusion coefficient of 10-7-10-6 cm2 s-1 wherever groundwater velocity v exceeds 10 9-10-8 cm s 1, or just 0.03-0.3 cm yr-1. 

For a given wave profile the foregoing solution does not remain singlevalued indefinitely but, due to a concentration of the pulse on the leading side of the wave, develops into a shape that resembles a wave that breaks. Recall that the effect of dispersion is to produce a wave which constantly changes shape, but now in the opposite sense, such that it causes the wave to spread out rather than to steepen. When the two effects are balanced, as shown schematically in figure 1, a wave of permanent form is produced. 

Hori, K., Matsuzaki, Y., Tanji, Y. and Unno, H. (2002). Effect of dispersing oil phase on the biodegradability of a solid alkane dissolved in non-biodegradable oil, Appl. Microbiol. Biotechnol., 59, 574-579. 

---