Differential conductance instantaneous

The ability of a GC column to theoretically separate a multitude of components is normally defined by the capacity of the column. Component boiling point will be an initial property that determines relative component retention. Superimposed on this primary consideration is then the phase selectivity, which allows solutes of similar boiling point or volatility to be differentiated. In GC X GC, capacity is now defined in terms of the separation space available (11). As shown below, this space is an area determined by (a) the time of the modulation period (defined further below), which corresponds to an elution property on the second column, and (b) the elution time on the first column. In the normal experiment, the fast elution on the second column is conducted almost instantaneously, so will be essentially carried out under isothermal conditions, although the oven is temperature programmed. Thus, compounds will have an approximately constant peak width in the first dimension, but their widths in the second dimension will depend on how long they take to elute on the second column (isothermal conditions mean that later-eluting peaks on 2D are broader). In addition, peaks will have a variance (distribution) in each dimension depending on... 

Modified Hodgkin-Huxley Model. In the HH model, the membrane current I, written as a function of V is expressed by the system of coupled equations given in Table I. In these equations V is the displacement of membrane potential from the resting value (depolarization negative). Constants Cm, g, gjga, 8i VK VNa and V] are explained in detail in ( 1). In Table I, l n and g m h are the potassium and sodium conductances, respectively. The dimensionless dynamical quantities m, n, and h are solutions of the given first order differential equations and vary between zero and unity after a change in membrane potential. The a and 3 rate constants are assumed to depend only on the instantaneous value of membrane potential. 

The instantaneous rate of thermal energy transport into the reactive fluid across the wall at radius R is given by dQ/dV in (4-34), with units of energy per volume per time. The differential control volume of interest that contains the reactive fluid is t/V = itR dz, where z is the spatial coordinate that increases in the primary flow direction. Four possibilities allow one to determine this rate of conductive heat transfer across the lateral surface of the reactor ... 

Constant Outer Wall Temperature. If the chemical reaction is exothermic and the outer wall temperature of the reactor is lower than the temperature of the reactive fluid, then conductive heat transfer across the lateral surface will provide the necessary cooling. This condition is required to prevent thermal runaway. The differential rate of thermal energy transport d Q into the reactor across the lateral surface is given by the product of (1) an overall heat transfer coefficient that accounts for resistances in the thermal boundary layer within the reactive fluid, as well as the tube wall itself (2) an instantaneous temperature difference Twaii — T, where T is the bulk temperature of the reactive fluid at axial position z and (3) the differential lateral surface area, 2nR dz. Hence,... 

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