Substance dependence definition

A systematic approach to the relationship between the explosive properties of a molecule and its structure was proposed by van t Hoff in 1909 and Piets in 1953. According to Piets, the explosive properties of any substance depend upon the presence of definite structural groupings. Piets divided explosives into eight classes as shown in Table 2.1. 

According to the Pletz theory the expl props of any given substance depend upon the presence of definite structural groupings called explosophores, while the auxoexploses modify or fortify the expl props brought about by explosophores... 

In general, in industrial processes, the necessity of a separation operation occurs after the mixing/reaction operations. Therefore, the separation operation is an indispensable process for chemical engineering. The purpose of the separation process is different from that of the mixing process, and the purpose of separation is only to separate substances depending on the requirements. However, identical to the mixing phenomenon, the separation phenomenon is definitely a function of space and time. The separation equipment is classified into two groups ... 

The final decision rests with the Commission but is to be taken after Committee procedure (Article 133), commonly known as comitology, in this case with the Regulatory procedure with scrutiny (EC 2006b), which basically means that the Commission has the unique power to draft proposals but that a member state committee, the Council or the European Parliament, given certain conditions, can block the proposals. In summary, these processes mean that there is no guarantee at all that a substance, which definitely meets the criteria in Article 57, will be listed.14 In practice, the listing may depend on resources and viewpoints among member states. At present, the candidate list contains 15 substances, of which 7 have been placed on ECHA s first priority list (ECHA 2009), as compared with the 1,400 substances mentioned for authorisation in the White Paper (European Commission 2001). 

Equation 8.2 shows how the net flux density of substance depends on its diffusion coefficient, Dj, and on the difference in its concentration, Ac] 1, across a distance Sbl of the air. The net flux density Jj is toward regions of lower Cj, which requires the negative sign associated with the concentration gradient and otherwise is incorporated into the definition of Acyin Equation 8.2. We will specifically consider the diffusion of water vapor and C02 toward lower concentrations in this chapter. Also, we will assume that the same boundary layer thickness (Sbl) derived for heat transfer (Eqs. 7.10-7.16) applies for mass transfer, an example of the similarity principle. Outside Sbl is a region of air turbulence, where we will assume that the concentrations of gases are the same as in the bulk atmosphere (an assumption that we will remove in Chapter 9, Section 9.IB). Equation 8.2 indicates that Jj equals Acbl multiplied by a conductance, gbl, or divided by a resistance, rbl. 

A definition of this kind has been offered for addiction. Thus in the Dta ttosttc and Statistical Manual of Mmtal Disorders, 4th edition (American Psychiatric Association 1994, p. 181) substance dependence is identified by the copresence of any three of seven defining features. Although this criterion may be justified by pragmatic diagnostic needs, it cannot serve as a definition for more theoretical purposes. 

In addition to the previous definition, withdrawal can be further described as the development of a substance-specific syndrome after cessation of or reduction in intake of a substance that was used regularly by the individual to induce a state of intoxication. Withdrawal causes significant distress to the individual and is associated with impairment in social, occupational, or other areas of functioning. Withdrawal is usually associated with substance dependence. Withdrawal generally is also associated with a craving to readminister the drug to relieve the symptoms. 

By definition, the virial coefficients B, C,... or B, C,... of the pure substances depend solely on temperature. The values of the coefficients are very different for each of the forms, but they are convertible into each other, for example, the second virial coefficients may be converted as... 

The value of AfH° for a given substance depends only on T. By definition, AfH for the reference state of an element is zero. 

Pure substances have definite, unchanging physical and chemical properties. The properties of a mixture, however, depend on how much of each component is in the mixture. As the composition changes, so do the properties. This is shown in Figure 2.9, Section 2.4. 

We can rewrite this expression in a slightly different but more general way by defining a = P/P° as the activity of an ideal gas. Thus, for an ideal gas, the activity is simply the partial pressure of the gas divided by P° = 1 bar, the standard state pressure. Although we will have more to say about activity in Section 13-8, for now we need only say that ultimately, the activity of a substance depends not only on the amount of substance but also on the form in which it appears in the system. The following rules summarize how the activity of various substances is defined (see also Table 13.5). It is beyond the scope of this discussion to explain the reasons for defining activities in these ways, so we will simply accept these definitions and use them. However, it is important to note that the activity of a substance is defined with respect to a specific reference state. 

The key to experimental gas-phase kinetics arises from the measurement of time, concentration, and temperature. Chemical kinetics is closely linked to time-dependent observation of concentration or amount of substance. Temperature is the most important single statistical parameter influencing the rates of chemical reactions (see chapter A3.4 for definitions and fiindamentals). 

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