Closing rate

Fig. 9. Effect of press closing rate variation of counterpressure and temperature increase as a function of pressing time in the core layer of an OSB panel at a press closing lime of 10 s.

The primary characteristic of a sequential blocker, as observed with the patch clamp technique, is that the reciprocal of the mean duration of the lifetime equals the normal channel closing rate plus the rate constant of channel blockade times the drug concentration. Therefore, increasing the drug concentration shortens the mean channel open time. 

Notice that the problem states that the distribution of open times is a single exponential. This tells you that a mechanism containing a single open state of the receptor can describe the data. Using the above hint, the channel closing rate (call this a) is therefore the reciprocal of the mean open time. Thus, at -60 mV, a = 1/5 msec, or 200 sec-1 at -120 mV, a = 1/10 msec, or 100 sec-1. This indicates that the channel closing conformational change is affected by the electric held across the membrane. 

Experimental plug flow reactors may be small diameter tubes or packed beds with a larger ratio of diameter to length. The argument in favor of their employment is that they may simulate commercial units more closely. Rate data from pilot plant or commercial units also may need to be analyzed. A short packed bed may be operated with a high recycle ratio and will thus achieve substantially isothermal behavior and may have appreciable change in conversion between the net input and output streams. 

Closely rated compounds Dopamine, adrenaline, noradrenaline, terbutaline, DOPA. 

Theory suggests that the most probable loops in proteins contain 10 residues.59 Shorter loops become stiff and longer ones lose more conformational entropy— recall from Chapter 17 that AiSconfig — a — (3/2)/ Inn. Indeed, the kinetics of formation of longer loops does fall off as exp(— 3/2) In n), = n (3/2) where n is the number of residues in the loop.60 A 50-residue loop in cytochrome c closes with ty2 of 40 fJL, implying a maximum closing rate of 106 s-1.7... 

The same applies to Pt-Pt2Si-PtSi-Si specimens. Under conditions of diffusion control the Pt2Si layer grows only at the expense of diffusing platinum atoms, while the PtSi layer grows only at the expense of diffusing silicon atoms, though in those compounds taken alone both components may well happen to diffuse at close rates. 

Therefore, as established by E.K. Ohriner and E.P. George, in the temperature range 1200-1475°C two intermetallic layers Molr and MoIr3 grow between iridium and molybdenum simultaneously at close rates. 

Fig. tt.l Transition rates between the states of a system of three identical channels, in terms of the opening rate a = /ms and the closing rate b = 1 /m0- The small black circles represent states with 0, 1, 2, and 3 channels open, respectively. 

The rate of press closing, particularly under the high pressures that develop in the initial compression of the mat, has an important impact on the development of the density profile through the thickness of the panel. For a batch press the hydraulic pump capacity determines the closing rate. Increasing this rate reduces the quantity of material in which the resin has cured before the required face density has been achieved, and which must be removed in sanding. 

Cukierman S, Krueger BK. 1990. Modulation of sodium channel gating by external divalent cations Differential effects on opening and closing rates. Pflugers Arch(Eur J Physiol) 416 360-367. 

Pressurization rate or ram closing speed depends on the size and shape of the billet and the type of resin. The slower the ram speed, the more completely the air will leave the preform, but productivity suffers at a low closing rate. Very fast ram speeds lead to entrapment of air, resulting in high porosity and low density areas, even billet cracking. Table 5.2 provides ram speeds that offer compromises between productivity and part quality. 

Table 5.2. Press Closing Rates (mm/min) Courtesy DuPont)...

The channels with the (3V266M mutation remain open for longer times. There are several possible explanations for the slower channel closing rate. For example, a tighter binding of acetylcholine (slower release) could keep the channels open longer. Alternatively, acetylcholine could be released at the normal rate, but the mutation could slow the conformational transition from the open state to the closed state. (Other explanations are possible.)... 

An important structural issue concerns the relationship between fech and opening-closing rates. The use of Eq. (3) assumes the relationship in Eq. (4). 

Ginzburg, S.L. Pustovoit, M.A. (2002). Stochastic resonance in two-state model of membrane channel with comparable opening and closing rates, Phys. Reo. E, vol.66, 021107. 

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