Transit time distributions

The cumulative curve obtained from the transit time distribution in Figure 9 was fitted by Eq. (48) to determine the number of compartments. An additional compartment was added until the reduction in residual (error) sum of squares (SSE) with an additional compartment becomes small. An F test was not used, because the compartmental model with a fixed number of compartments contains no parameters. SSE then became the only criterion to select the best compartmental model. The number of compartments generating the smallest SSE was seven. The seven-compartment model was thereafter referred to as the compartmental transit model. 

LX Yu, GL Amidon. Characterization of small intestinal transit time distribution in humans. Int J Pharm 171 157-163, 1998. 

Lambert, M., C. M. Sadowski, and T. Carrington, Uses of the Transit Time Distribution in Kinetic Flow Systems, Int. J. Chem. Kinet., 7, 685-708 (1985). 

Weiss, M., Moments of physiological transit time distributions and the time course of drug disposition in the body, Journal of Mathematical Biology, Vol. 15, 1982, pp. 305-318. 

The equation developed on the basis of transit time distribution, takes the form ... 

Koplik et al. (1988) considered flow rates in percolation networks from zero (pure diffusion) to extremely high (the convective limit where the average transit time varies linearly with 1/v). The results obtained for many network realizations were averaged. In the case of 2 x 2 and 3x3 network lattices, all possible configurations could be evaluated and hence, the exact averaged transit time moments could be determined. These authors found that anomalous diffusion occurs on networks at the percolation threshold at zero flow. Hence, the CDE does not apply in this case. Koplik et al. (1988) demonstrate that the moments of the transit time distribution for transport near the percolation threshold scale universally. 

As an example. Fig. 1.4 shows the single-electron response measured with a high-speed oscilloscope and the transit-time distribution for a Hamamatsu R3809U MCP PMT measured by TCSPC. 

Fig. 1.4 Single photon response (left) and transit-time distribution (right) of a Hamamatsu R3809U MCP, from [211]...

Like all photon counting techniques, gated photon counting uses a fast, high-gain detector, which is usually a PMT or a single-photon avalanche photodiode. Due to the moderate time resolution of the gating technique, there are no special requirements to the transit time spread of the detector. However, the transit time distribution should be free of bumps, prepulses or afterpulses, and should remain stable up to a count rate of several tens of MHz. 

Fig. 6.12 left Different electron trajectories cause different transit times in a PMT. Right general shape of the transit time distribution... 

Moreover, some of the photoelectrons may be reflected at the first dynode, return a few hundred ps or a few ns later, and release secondary electrons. These electrons cause a tail or secondary peaks in the transit time distribution. Another peak can appear before the main peak. This usually results from photoeleetron emission at the first dynode. Transit time distributions for a number of deteetors are shown under Sect. 6.4, page 242. 

Unfortunately the resulting transit time spread depends on the wavelength. With decreasing wavelength, i.e. increasing photon energy, the start veloeity and the velocity dispersion of the photoelectron increases, whieh eauses ehanges in the transit time distribution. 

The transit-time distribution of most PMTs depends on the illuminated area and on the voltage at the foeusing eleetrodes. TTS shapes for a number of PMTs are shown in ehapter Seet. 6.4, page 242. 

Vlad, M. O. Ross, J. Moran, R Joel, Y. Delayed response in tracer experiments and fragment-carrier approach to transit time distribution in nonlinear chemical kinetics. Int. 

Lifetime and Transit Time Distributions and Response Experiments in Chemical Kinetics... 

Transit Time Distributions in Complex Chemical Systems... 

Transit Time Distributions, Linear Response, and Extracting Kinetic Information from Experimental Data... 

Vlad, M. O. Moran, F. Ross, J. Transit time distributions for biochemical networks far from equilibrium amplification of tfie probability of net transformation due to multiple reflections. J. Phys. Chem. B 1999,103, 3965-3974. 

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