Factor similarity

Whatever the physiology of odor perception may be, the sense of smell is keener than that of taste (22). If flavors are classed into odors and tastes as is common practice in science, it can be calculated that there are probably more than 10 possible sensations of odor and only a few, perhaps five, sensations of taste (13,21,35—37). Just as a hereditary or genetic factor may cause taste variations between individuals toward phenylthiourea, a similar factor may be in operation with odor. The odor of the steroid androsterone, found in many foods and human sweat, may eflcit different responses from different individuals. Some are very sensitive to it and find it unpleasant. To others, who are less sensitive to it, it has a musk or sandalwood-like smell. Approximately 50% of the adults tested cannot detect any odor even at extremely high concentrations. It is befleved that this abiUty is genetically determined (38). 

Barrn is caused by uneven tension in knitting, defective yam, improper needle action, or other similar factors that are not recognized until the fabric is dyed. It appears as a repetitive characteristic pattern of varying intensity that is easily recognizable. 

The comparison of the results of a-halogenation with those of a-methylation of six-membered ring sulfoxides345 reveals that similar factors are operative and determine the stereochemical outcomes in both cases. 

The mercuration of ferrocenylimines with Hg(OAc)2 has been studied. - 6 Mercuration occurs selectively at the a-position relative to the imine group to afford compounds 86a-i (Scheme gy107,108 The regioselectivity of these reactions points to the directing role of the Lewis-basic imine functionality. Similar factors probably play a role in the formation of the ferrocenylketone and ferrocenylaldehyde derivatives 87a-f and 87g-j, respectively. These derivatives readily react with amines to afford the corresponding imines (Scheme 9). Presumably, the Lewis-acidic mercury center of the monomercurated ferrocenylketones and ferrocenylaldehydes activates the carbonyl functionality toward nucleophilic attack by the amine. 

For purposes of comparison with stellar abundances, it is useful to have the relative contributions of s- and r-processes to the various elements (as opposed to nuclides) in the Solar System, because in most cases only element abundances without isotopic ratios are available from stellar spectroscopy. At the same time, elements formed in one process may often be expected to vary by similar factors in the course of stellar and Galactic evolution, but to be found in differing ratios to elements formed in another process. Relative contributions are listed for some key elements in Table 6.3. 

The factors that affect the energetics of solid solutions and indirectly solid solubility are to a large extent the same as those that control the enthalpy of formation of compounds. Most often the differences between the atomic radii of the participating elements, in electronegativity and in valence electron density are considered for solutions of elements. For solid solutions of binary compounds, similar factors are used, but some measure of the volume of the compounds is often used instead of atomic radii. 

Orientation, branching and straightness of pores are related to similar factors, namely source of holes and anisotropic effect. Orientation of pores can be explained based on the current difference between (100) and (HI) orientations, Ai = i - i, and the difference between current densities on the pore bottoms of main pores and on side pores, ihoie, mam and ihoie> side, as shown in Figure 27. ihoie> Slde is smaller than... 

Key parameters include temperature, pounds of steam injected (or similar factors for air), and duration and depth of treatment. Steam at a pressure 3.5 to 4.2 kg/cm2 (50 to 60 psi) can heat contaminated soil to 155°C (310°F). The recovery process involves the use of wells to depress the water table and ensure capture of released free-phase NAPLs and vapor-phase hydrocarbons at or near the surface. A conceptual schematic is shown in Figure 10.8. 

Thus in two systems showing very high effective molarities for the formation of five- and six-membered rings there is strong structural evidence for substantial strain in the ground state. The other two most reactive systems (B.1.13 and B.2.16) are intermediate in structural type, and undoubtedly owe their high reactivity to similar factors. 

Gohel MC, Panchal MK. Refinement of lower acceptance value of the similarity Factor F2 in comparison of dissolution profiles. Dissol Technol 2002 9(1). 

At least 12 units should be used for each profile determination. Mean dissolution values can be used to estimate the similarity factor, f2. To use mean data, the percentage coefficient of variation at the earlier point should not be more than 20% and at other time points should not be more than 10%. 

Dissolution Profile Comparison Model Independent Analysis Similarity Factor... 

Shah VP, Tsong Y, Sathe P, Liu JP. In vitro dissolution profile comparison—statistics and analysis of the similarity factor, f2. Pharm Res 1998 15 889-896. 

Vertzoni et al. (30) recently clarified the applicability of the similarity factor, the difference factor, and the Rescigno index in the comparison of cumulative data sets. Although all these indices should be used with caution (because inclusion of too many data points in the plateau region will lead to the outcome that the profiles are more similar and because the cutoff time per percentage dissolved is empirically chosen and not based on theory), all can be useful for comparing two cumulative data sets. When the measurement error is low, i.e., the data have low variability, mean profiles can be used and any one of these indices could be used. Selection depends on the nature of the difference one wishes to estimate and the existence of a reference data set. When data are more variable, index evaluation must be done on a confidence interval basis and selection of the appropriate index, depends on the number of the replications per data set in addition to the type of difference one wishes to estimate. When a large number of replications per data set are available (e.g., 12), construction of nonparametric or bootstrap confidence intervals of the similarity factor appears to be the most reliable of the three methods, provided that the plateau level is 100. With a restricted number of replications per data set (e.g., three), any of the three indices can be used, provided either non-parametric or bootstrap confidence intervals are determined (30). 

The second difference relates to the definition of a cutoff time point for the evaluation of the difference factor and the Rescigno index. When cumulative data are available, evaluation of the difference factor or the Rescigno index usually requires a reference data set in order to define the cutoff time point for index evaluation (30). For the evaluation of fl and the , i.e., when the difference factor and the Rescigno index are evaluated from non-cumulative data, this difficulty does not exist, provided that the release process has been monitored up to the end (i.e., until dissolution of the drug is complete). At this point, it is worth mentioning that a similar conclusion cannot be drawn for the similarity factor (31) because application of this index to non-cumulative data is set apart by the careful scaling procedure required, in addition to the existence of a reference data set. The reason is that this index can continue to change even after dissolution of both products is complete. 

Within the scope of biopharmaceutics and IVIVC, bootstrap techniques have been applied to several specific problems related to the estimation of confidence intervals of, e.g., the similarity factor/ (21), the Chinchilli metric (27), parameters of an open two-compartment system (32), and the SD in general (33). From these few applications, it cannot be judged how much is actually gained from these new techniques. 

Liu JP, Ma MC, Chow SC. Statistical evaluation of the similarity factor as a criterion for assessment of similarity between dissolution profiles. Drug Inf J 1997 31 1255-1271. 

The most common approach for the comparison of dissolution profiles is model-independent approach using the similarity factor f2. The pre-requisites for using the /2-test are the following ... 

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