Absorption scale factor

FIGURE 2 Plot of relative value of 1 IT (absorption scale factor) as a function of at x 90° for native rubredoxin crystal and two derivative crystals. From Harriott etaL1... 

The used S5mbols are K, scale factor n, number of Bragg peaks A, correction factor for absorption P, polarization factor Jk, multiplicity factor Lk, Lorentz factor Ok, preferred orientation correction Fk squared structure factor for the kth reflection, including the Debye-Waller factor profile function describing the profile of the k h reflection. 

Figure 5 Correlation of the fraction of dose absorbed with rat permeability. The rat permeability data were determined using the rat perfusion model. Considering the difference between the human permeability and the rat permeability, a scale factor was used to calculate the absorption number in Eq. (8). (Ref. 34 with kind permission from Plenum Publishing Corporation, New York.)...

In vitro kinetic constants obtained from homogenate or whole-cell experiments under controlled conditions were used, and the constants were scaled to the in vivo scenario using appropriate physiological scale factors. Figure 18.6 shows our simulated results for absorption and metabolism of midazolam when dosed with and without grapefruit juice. Midazolam is metabolized by the gut and liver by cytochrome 3A4. Saquinavir is also metabolized in the gut and liver by 3A4, and it is also a substrate for efflux by P-gp. Figure 18.7 shows our simulated results for absorption and metabolism of saquinavir when dosed with and without grapefruit juice. In both cases, it can be seen that the simulation correctly predicts the... 

In addition to screening molecules for intestinal absorption, Caco-2 cells have also been used to study mechanisms of drug transport. For many compounds, intestinal permeation involves a transporter to either aid or limit transepithelial transport. The value of Caco-2 cells in this type of studies is due to the fact that these cells express various membrane transporters relevant to drug absorption.1719-23,28,30 However, when interpreting results of studies that involve carrier-mediated transport, discretion, and scaling factors may be required because of the difference in expression level of transporters between in vitro and in vivo systems.12 Another important consideration in carrier-mediated transport studies is that some transport systems in Caco-2 cells may achieve maximal expression level at different days in culture.17,21,38,74 Thus, validation of Caco-2 cells for mechanistic studies should include the identification of the time for optimal expression of transporters as well as the qualitative evaluation of the transporters to establish that they are representative of the native intestinal transporters. 

Cohen and Chelikowsky, 1998). (b) An analysis of the absorption edge of Ge. Notice the scale factor in the first plot in relation to the second plot (reproduced with permission from Dash and Newman, 1955). 

Finally, we must say that (noting the scale factor in Figure 4.11) indirect absorption coefficients (from 0.6 to 0.75 eV for Ge) are in general insignificant compared to direct absorption coefficients (energies larger than 0.8 eV for Ge). This is because indirect absorption processes are much weaker than direct absorption processes, due to the second order nature of the former. 

Diffraction patterns may always be multiplied by a constant factor without changing the physics of the system. In MSLS this is a scaling factor which is needed to scale the observed and calculated intensities to the same order of magnitude. This scaling factor is one of the relinable parameters. However, one has to take care with the definition of this factor. It should be defined in such a way that it is not dependent on the change of any other parameter in the refinement procedure, in particularly the crystal thickness and the absorption parameter. Therefore the actual scaling factor, C, was expressed as function of c, the parameter which was used in the refinement process ... 

The mechanical response of polypropylene foam was studied over a wide range of strain rates and the linear and non-linear viscoelastic behaviour was analysed. The material was tested in creep and dynamic mechanical experiments and a correlation between strain rate effects and viscoelastic properties of the foam was obtained using viscoelasticity theory and separating strain and time effects. A scheme for the prediction of the stress-strain curve at any strain rate was developed in which a strain rate-dependent scaling factor was introduced. An energy absorption diagram was constructed. 14 refs. 

Fig. 3.14. Comparison of the absorption profiles of H2-X pairs, with X = H2, He, Ne, Ar, Kr, Xe at room temperature [213]. The spectra are normalized to unit absorption at their peaks, but absolute intensities are indicated in the form of a scaling factor (-6) stands for xlO-6. Reproduced with permission from the National Research Council of Canada from [213].

Table 1 expression parameters are P = station pressure, Po = standard pressure, a = fitting coefficients, m - air mass correction for path length, u = absorber abun dances, A = absorption coefficients, a = absorber/wavelength dependent, Bs = water vapor band, airmass, and pressure scaling factors, on Pi, = Angstrom parameters, / = 1 for X < 500 nm, / 2 for X > 500 nm, Xw Reference wavelength (usually 1000 nm or 1 pm)... 

Optimized geometries, scaled quantum-mechanics (SQM) force fields, and the corresponding vibrational frequencies, IR absorption intensities, and scale factors were calculated for thiazole and the [2(2)-H], [4-H-2], and [2,5-H-2(2)] isotopomers of thiazole using the DFT and B3LYB/6-31G methods <1995JCM354, 1995JCM174>. 

In Fig. 9, Type 1 is the ideal case, a one to one relationship between (Y = bx) in vitro and in vivo data. Type 2 [(y = hx — a), lower line] represents the case where a dissolution exists in vitro without any absorption in vivo. This case is physiologically possible and could possibly be explained by a time lag for example. The FDA suggests in this case a time scaling on condition that the time scaling factor is the same for all formulations. Different time scales for each formulation indicate the absence of an IVIVC. Another possibility would be to modify the dissolution technique. Type 3 (y = bx + a, upper line) represents an impossible case where the drug is dissolved and absorbed in vivo before any in vitro dissolution. This case implies an inappropriate dissolution technique that must be modified. ... 

The correctness of the scale factor is dependent on many parameters. The most critical are the photon flux in the incident beam remains identical during measurements at any Bragg angle the volume of the material producing scattered intensity is constant the number of crystallites approaches infinity and their orientations are completely random the background is accounted precisely the absorption of x-rays (when relevant) is accounted. 

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