Best Practicable Means concept

Kiely (1996) gives a comprehensive summary of EU and US environmental legislation. All the legislation embodies the concept of Best Practicable Means (BPM). This requires the designer to use the most appropriate treatment to comply with the regulation, whilst taking into account local conditions, current technology and cost. The concept of BPM also applies to the installation, maintenance and operation of the plant. 

In this chapter some of the theoretical concepts used in these models will be outlined. In particular, emphasis will be given to the chemical thermodynamic principles that can be used to predict the stable forms of a given element. Such chemical principles provide the theoretical foundation of the commonly used chemical models. These models can be used to predict the final extent of reaction but not the rate. It is probably fair to say that these laws as basic principles are indisputable scientific fact however, problems arise when we try to apply them to ill-defined complex natural media such as soils and soil solutions where some reactions are kinetically slow and practically irreversible. However inadequate our chemical models are in relation to real-world situations they are the best we have and can be used to give valuable insight and meaning into the processes we observe. 

No, none is to be preferred in principle , meaning on grounds of theoretical appropriateness. This is because MM is severely practical, in the sense that the forcefield need only satisfactorily and swiftly reproduce molecular properties, mainly geometries. The method makes no apologies for ad hoc additions which improve results. An example of this is seen in the inclusion of a special term to force the oxygen of cyclobutanone to lie in the ring plane [1], Identifying the terms in a forcefield with distinct theoretical concepts like force constants and van der Waals forces is at best an approximation. 

Specific surface areas and pore size distributions of mesoporous materials are best probed by nitrogen/argon adsorption and capillary condensation which will be outlined in detail below. It should be emphasized that the concept of specific surface area is not applicable when the size of the sorbed molecules approaches the diameter of the pore. Thus, for microporous substances values for specific surface areas have no physical meaning, but are rather characteristic of the volume of gas adsorbed. Nevertheless, these values are frequently used as practical numbers to compare the quality and porosity of microporous materials. The average pore size of microporous materials has to be probed by size exclusion measurements. For this purpose the uptake of a series of sorbates with increasing minimal kinetic diameter on a solid are explored. The drop in the adsorbed amount with increasing size of the sorbate defines the minimum pore diameter of the tested solid. The method will be described in detail below. 

Two of the best developed and most widely used traditional medicinal systems, which are both well documented and rich in concept and practice, are the various Indian and Chinese systems of medicines. Among traditional Indian systems of medicine, the ayurvedic system has been the most popular and best known in the West. Ayurveda literally means knowledge or science of life. The system is based primarily on three classic texts known as samhitas, which were written by Sushruta, Charaka, and Vaghata in the period between 100 B.c. and 100 a.d. Ayurvedic physiology also views bodily functions in terms of three... 

It will be useful to estimate how far from the glass transition temperature an amorphous material can be stored to ensure that the material is kinetically stable over the duration of shelf life. Several rules of thumb have been proposed, of which probably the best known is the Tg - 50 rule for estimating the required storage temperature (Hancock et al. 1995). If this temperature is far below room temperature, storage of the amorphous dmg at that temperature will not be practical, and alternative means of stabilizing the amorphous drug will be needed. (It should be noted that the Tg - 50 rule is a generalization based on concepts such as those detailed above. While many materials do not follow this rule, it is still a useful concept.)... 

Inevitably, even the best mechanistic models require some data fitting, leading to the concept of gray box models. This is the normal practice in industrial modeling of such systems. It means that adequate data must be available to carry out the validation studies. This task is particularly difficult for the validation of dynamic models. 

The model of free volume going back to the classical papers of Frenkel and Firing [48, 80, 144-147] has been widespread in the physics of liquid and solid states of matter. Some concepts allowing improvement in the nature of fluctuation free volume have been offered in the last 15 years [148-150]. Nevertheless, there is one more aspect of the problem, which has not been mentioned earlier. As a rule, the application of free volume theory for the description of the properties of amorphous bodies is based on a notion that the free volume characterises the structure of the indicated bodies. This postulate is due to a considerable extent to the absence of a quantitative model of the structure of the amorphous condensed state, including the structure of amorphous state polymers. Strictly speaking, one should understand that by structure we mean distribution of body elements in space [151]. It is evident that free volume microvoids cannot be structural elements and at best only mirror the structural state of the studied object. Taking the introduction of some structural elements (relaxators, see for example, [148]) into consideration has practically no influence on the structural representation of free volume. 

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