Quantitative approach

Shi et al. [26] noted the following While it is frequently argued that the concentration variation is implicit in qualitative methods, the expression of variation is explicit in quantitative methods due to the specificity of a calibration model for a particular concentration variation.  

In recent years, blend characterization by quantitative means has become particularly popular. Quantitative approaches require a calibration model to capture the concentration variation during the blending process. A quantitative model is able to express blending processes in terms of concentration variation, which is comparable to the standard criteria of current regulatory requirements. 

In most situations, reported results focus on the monitoring of the active ingredient alone, as it is often the only parameter that is being measured by wet chemistry. The predichon of the distribution of lubricant (magnesium stearate) was found to be possible at levels as low as 0.5% w/w [31]. Recognizing the importance of excipient homogeneity for the performance of the delivery form, Shi et al. [26] introduced pooled statistics to consider the distribution of not only the active ingredient, but also the excipients. 

The root mean square error from the nominal value (RMSNV) is a weighted, cumulative, pooled standard deviahon indicator that takes into account the deviation of the predicted concentrahon of the major components of a mixture to their target concentrahon, over a given number of rotations. For an n component system, it is defined as 

The RMSNV allows the evaluation of the trends and distance from target concentrations for not only the achve pharmaceutical ingredient, but also the major excipients of the formulation. In the original paper, the endpoint was determined based on the distribution of RMSNV values. In Zacour et al. [30], the root mean square error of calibration for the components of interests was used as the threshold under which the blend was determined homogeneous. 

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A Quantitative Approach to Biochemical Structure-Activity Relationships. Accounts of nical Research 2 232-239. 

The most notable studies are those of Ingold, on the orienting and activating properties of substituents in the benzene nucleus, and of Dewar on the reactivities of an extensive series of polynuclear aromatic and related compounds ( 5.3.2). The former work was seminal in the foundation of the qualitative electronic theory of the relationship between structure and reactivity, and the latter is the most celebrated example of the more quantitative approaches to the same relationship ( 7.2.3). Both of the series of investigations employed the competitive method, and were not concerned with the kinetics of reaction. 

Another quantitative approach to the reactivity of thiazole (381) in reactions involving a cationic transition state, though not exactly of the electrophilic substitution type, deserves to be mentioned here because of... 

A more quantitative approach to the influence of the thiazole ring on the reactivity of a lateral functional chain was made in a recent study by Noyce and Fike (383), already discussed in Section 10.4. The first-order rates of solvolysis for three isomeric 1-thiazolylethyl chlorides were determined in 80% ethanol. The order of relative reactivity observed. 

Unproven Technology. When a project involves new or unproven technology, the capital estimates tend to understate the development, constmction, and start-up costs. A quantitative approach to account for the capital cost and performance shortfalls associated with unproven technology has been reported (14), but the data are meager. 

As already mentioned molecules cohere because of the presence of one or more of four types of forces, namely dispersion, dipole, induction and hydrogen bonding forces. In the case of aliphatic hydrocarbons the dispersion forces predominate. Many polymers and solvents, however, are said to be polar because they contain dipoles and these can enhance the total intermolecular attraction. It is generally considered that for solubility in such cases both the solubility parameter and the degree of polarity should match. This latter quality is usually expressed in terms of partial polarity which expresses the fraction of total forces due to the dipole bonds. Some figures for partial polarities of solvents are given in Table 5.5 but there is a serious lack of quantitative data on polymer partial polarities. At the present time a comparison of polarities has to be made on a commonsense rather than a quantitative approach. 

Quantitative assessment requires historical data which may be suspect for two reasons. There is the possibility that there are latent accidents not in the database. It is possible that past accidents have been rectified and will not recurr. In the absence of data, judgment based on experience and speculation must be used. Notwithstanding this weakness, the quantitative approach was adopted, d he investigating team identified situations that could cause a number of public casualties. R vents limited to the employees or which might cause single off-site casualties were not included in the assessment. 

Abhitt, J. F., 1969 A Quantitative Approach to the Evaluation of the Safety Function of Operators in Nuclear Reactors, Atomic Health and Safety Board, UK. AHSB(s) R 160. 

T. A. Kletz, Hard Analysis—A Quantitative Approach to Safety, Symposium Series No. 34, Institution of Chemical Engineers, 1971, p. 75. 

How can the hypothesis be tested experimentally There are at least two possibilities, a qualitative and a quantitative approach. 

Some of the uncertainties and ambiguities of qualitative rules such as Kaptein s and Muller s (1972) can be cleared up by computer simulation of polarized spectra. Alternatively, such quantitative approaches can be used to deduce a- and Jgr-values. 

Mechanistic Approaches. Adequate and appropriate river-quality assessment must provide predictive information on the possible consequences of water and land development. This requires an understanding of the relevant cause and effect relationships and suitable data to develop predictive models for basin management. This understanding may be achieved through qualitative, semi-quantitative or quantitative approaches. When quantitative or semi-quantitative methods are not available the qualitative approach must be applied. Qualitative assessments involve knowledge of how basin activities may affect river quality. This requires the use of various descriptive methods. An example of this kind of assessment is laboratory evaluation of the extent to which increases in plant nutrients, temperature or flow may lead to accelerated eutrophication with consequent reduction of water quality. 

A Quantitative Approach Dissolved O i gen Depletion. The classical primary indicator of the health of a river, especially one receiving oxidizable domestic... 

A Semi-quantitative Approach Erosion and Deposition. Over the centuries the primary impact of human activity has been to deforest the surrounding countryside and increase the rate of erosion and deposition into rivers. This results primarily from the destruction of vegetation cover which stabilizes soil systems on gradient. The ecological impact of erosion has at present reached catastrophic proportions. The magnitude of continental erosion into rivers is illustrated in Figure 3. 

The methods described here for a semi-quantitative approach to this... 

In our view, such students difficulties as described above originate, mainly, from a failure to recognise and teach chemical eqniUbrinm as a process. These problems are the outcome of a quantitative approach being taken to the theme to the detriment of understanding chemical eqnilibrinm qnalitatively. As a conseqnence, students have difficulty understanding these and other issnes in terms of Le Chatelier s Principle, which demands knowledge abont how the processes occnr. 

On the theoretical side, study of the dissociation of addition compounds of amines with trimethylborane, boron trifluoride, and borane provide a new quantitative approach to steric strains. These studies quickly removed doubts as to the importance of steric effects in chemical behavior. 

Hansch C. Quantitative approaches to biochemical structure-activity relationships. Acc Chem Res 1969 2 232-9. 

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