Mears factor

K. R. Page and P. Meares, Factors controlling the frequency and amplitude of the Teorell oscillator, Faraday Symp. Chem. Soc., 9 (1974), pp. 166-173. 

J. Lorquin, G. Lortet, M. Ferro, N. Mear, B. Dreyfus, J.-C. Prome, and C. Boivin, Nod factors from Sinorhizobium saheli and 5. teranga bv. sesbaniae are both arabi-nosylated and fucosylated, a structural feature specific to Sesbania rostrata symbionts. Molec. Plant Microbe Interact. I0 il9 (1997). 

For hydrophilic and ionic solutes, diffusion mainly takes place via a pore mechanism in the solvent-filled pores. In a simplistic view, the polymer chains in a highly swollen gel can be viewed as obstacles to solute transport. Applying this obstruction model to the diffusion of small ions in a water-swollen resin, Mackie and Meares [56] considered that the effect of the obstruction is to increase the diffusion path length by a tortuosity factor, 0. The diffusion coefficient in the gel, )3,i2, normalized by the diffusivity in free water, DX1, is related to 0 by... 

Katsuhiko, M., Owens, J.T., Belyaeva, T.A., Meares, C.F., Busby, S.J.W., and Ishihama, A. (1997) Positioning of two alpha subunit carboxy-terminal domains of RNA polymerase at promoters by two transcription factors. PNAS 94, 11274-11278. 

Concentration Gradient Across a Membrane. J. S. Mackie and P. Meares (88) tested the equation (30), derived by them. They measured the diffusion of five different salts through a homogeneous gel membrane of the sulphonated phenolformaldehyde type. The osmotic flow during diffusion was measured too. For the mobilities in the resin the values in free solution were taken, multiplied with the factors Aa [equation (73)] and Q [equation (78)]. 

Axial mixing of the liquid is an important factor inthedesignof trickle bed reactors, and criteria were proposed to establish conditions that limit axial mixing. Mears [Chem. Eng. Sci. 26 1361 (1971)] developed a criterion that when satisfied, ensures that the conversion will be within 5 percent of that predicted by plug flow ... 

A key factor in the apphcation of targeted radiotherapy is the need to maximize the tumour to normal ceU radiation dose ratio. In this study, a new series of peptides — including DOTA-Ahx-Oct (OCT), DOTA-Ahx-Ser-Val-Glu-Phe-Ala-Ahx-Oct (P3) and DOTA-Ahx-Gly-Ser-Val-Glu-Phe-Ahx-Oct (P4), where Ahx is epsilon amino hexyl — developed by Whetstone and Meares of the University of California at Davis, United States of America, were evaluated. These peptides include an additional 5 amino acid sequence, which is cleavable by cathepsin. This modification helps to improve the release and trapping of labelled catabolites within the cell [16.2]. These peptides were directly compared with radioiodinated glycated octreotate (Gluc-TOCA), which was shown to have the best internalization properties of the four peptides studied. A comparison of the binding capacity, internalization, exter-nalization and stability of each peptide was carried out under optimized conditions in order to determine their properties. 

Closure After completing this chapter, the reader should be able to derive differential equations describing diffusion and reaction, discuss the meaning of the effectiveness factor and its relationship to the Thiele modulus, and identify the regions of mass transfer control and reaction rate control. The reader should be able to apply the Weisz-Prater and Mears criteria to identify gradients and diffusion limitations. These principles should be able to be applied to catalyst particles as well as biomaierial tissue engineering. The reader should be able to apply the overall effectiveness factor to a packed bed reactor to calculate the conversion at the exit of the reactor. The reader should be able to describe the reaction and transport steps in slurry reactors, trickle bed reactors, fluidized-besd reactors, and CVD boat reactors and to make calculations for each reactor. 

A very useful method for determining the reasonableness of constants estimated by LH analysis has been advanced by Boudart et al. [M. Boudart, D.E. Mears and M.A. Vannice, Ind. Chim. Beige, 32, 281 (1967)). The method is based on the compensation effect, often noted in the kinetics of catalytic reactions on a aeries of related catalysts, in which there is observed a linear relationship between the logarithm of the pre-exponential factor of the rate equation and the activation energy. Explanations for such behavior abound. Perhaps the most reasonable is... 

Catalyst wetting. As indicated by its name, this model is based on the assumption that the fraction of the outer surface of the catalyst wetted by the liquid phase is the critical factor in determining the overall reaction rate [D.E. Mears,... 

The percentage desulfurization versus liquid flow rate data obtained with this catalyst are shown in Figure 8.24. As one explanation for the results shown in this figure it was proposed that axial dispersion in shorter beds caused their poor performance. Is this a viable explanation Look at it. Based on the criterion of Mears, what is the maximum length required to eliminate axial dispersion as a factor important in reactor performance Assume that the desulfurization reaction is pseudo-first-order, and that the reactor operation was isothermal. The relevant liquid properties are pi = 0.93 g/cm and p. = 0.15cP. 

Table 7.2 Mears (1971) Criteria to Operate under the Conditions That the Ettectiveness Factor, es 1 + 0.05...

Magnesium, density 1.7 g cm , is one of the least dense metals. It has an hexagonal crystal structure with a = 0.320 nm, c = 0.520 nm, and da = 1.624. The basal plane is close-packed and the axial ratio is only slightly greater than the theoretical value for incompressible spheres (Emley, 1966). The atomic diameter is 0.320 nm, so there is a favorable size factor with a diverse range of the solute elements Aluminum (Al), Zinc (Zn), Cerium (Ce), Yttrium (Y), Silver (Ag), Zirconium (Zr), and Thorium (Th) (Pol-mear, 1989). 

The nature of the driving forces behind these factors has been the subject of scientific studies by many scientists in the early part of the twentieth century. In a landmark paper, Mears and Brown have summarized 18 mechanisms, listed in Table 7.1, by which differences... 

In two bonded half planes containing a crack under mode I loading condition, generally mode II stress intensity factor k2 would decrease monotonically as h/a increases. This is, however, not always the case. As shown by Hutchinson, Mear, and Rice [l5], for certain material combinations,k2 may change sign as h/a varies, raising the possibility of crack growth parallel to the interface. 

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