Carriers numbers/concentration

As seen in equations (32)-(34), the forward adsorptive flux depends upon the concentration of free cell surface carriers. Unfortunately, there is only limited information in the literature on determinations of carrier concentrations for the uptake of trace metals. In principle, graphical and numerical methods can be used to determine carrier numbers and the equilibrium constant, As, corresponding to the formation of M — Rcen following measurement of [M] and (M —Rceii. For example, a (Scatchard) plot of (M — RCeii /[M] versus (M — RCeii should yield a straight line with a slope equal to the reciprocal of the dissociation constant and abscissa-intercept equal to the total carrier numbers (e.g. [186]). 

The reverse rate constant y, governs the rate at which molecules leave a cluster. This quantity is more difficult to evaluate theoretically than the forward rate constant p(. What we do know is that, as long as the number concentration of monomer molecules is much smaller than that of the carrier gas, the rate at which a cluster loses monomers should depend only on the cluster size and temperature and be independent of monomer partial pressure. Thus the evaporation rate constant under nucleation conditions (5 > 1) should be identical to that in the saturated (51 = 1) vapor ... 

We assume that a number of dissociation experiments have been performed at temperature T, pressure p and carrier gas concentration [M]. The rates of disappearance of the decomposing substance A and/ or the rates of appearance of decomposition products or intermediates have been measured at different [A] to [M] ratios. The first problem of interpretation is to understand the decomposition mechanism. At high enough temperature and sufficiently large excess of inert carrier gas M, the rate determining step of the dissociation is the unimolecular dissociation of the molecule A ... 

The release of drug from microspheres is influenced by number of factors such as nature of carrier, drug concentration, dispersant concentration, stirring speed, stirring time, external-phase temperature, and external phase. 

The electrical conductivity in conductors is a function of their charge carrier number per unit volume. The relationship between conductivity and concentration is not necessarily a simple function Nevertheless the molar conductivity of each type of charge carrier can be defined by the following equation ... 

If the two migrating defects are also the majority charge carriers, the concentration terms in Eq. (6.54d) disappear. If their charge numbers are also identical, the result is very simple and clear D is then the harmonic mean of the two defect diffusion coefficients. 

More precise coefficients are available (33). At room temperature, cii 1.12 eV and cii 1.4 x 10 ° /cm. Both hole and electron mobilities decrease as the number of carriers increase, but near room temperature and for concentrations less than about 10 there is Htde change, and the values are ca 1400cm /(V-s) for electrons and ca 475cm /(V-s) for holes. These numbers give a calculated electrical resistivity, the reciprocal of conductivity, for pure sihcon of ca 230, 000 Hem. As can be seen from equation 6, the carrier concentration increases exponentially with temperature, and at 700°C the resistivity has dropped to ca 0.1 Hem. 

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