Uses of the Concept

A separate equation is obtained for each component i Consider the important case of steady-state flow of a single fluid through the pipe section of Figure 21b, where the flow is taken to be perpendicular to the cross sections and Making use of the concept of average velocity ... 

Notice that Rahman and Stiliinger make use of the concept of an effective pair potential. The potential energy of any substance may always be resolved systematically into pair, triplet, quadruplet,. .. contributions. If we consider N particles each with position vector R, then formally we can write... 

The Concepts of Faraday and Maxwell. We shall find that the most useful method for estimating the energy of electrostatic charges is to make use of the concepts of Maxwell and Faraday, in which the... 

However, there are numerous examples of polyesterifications where the concept of equal reactivity is not observed some examples have been reported and analyzed by Korshak and Vinogradova2315. None of them is at variance with Flory s postulates but this shows that great caution is needed in the use of the concept of equal reactivity. 

All sciences, medicine, and many fields of commercial activity draw on chemistry. You can be confident that whatever career you choose in a scientific or technical field, it will make use of the concepts discussed in this text. Chemistry is truly central to science. 

In Section F, we saw that one technique used in modern chemical laboratories to determine the empirical formulas of organic compounds is combustion analysis. We are now in a position to understand the basis of the technique, because it makes use of the concept of limiting reactant. 

What Do We Need to Know Already This chapter builds on Chapter 18 and requires the same preparation, as well as the concepts of acid-base and redox reactions (Sections J and K). It also makes use of the concepts of molecular polarity (Section 3.3) and solubility (Section 8.9). 

The convenience and usefulness of the concept of resonance in the discussion of chemical problems are so great as to make the disadvantage of the element of arbitrariness of little significance. Also, it must not be forgotten that the element of arbitrariness occurs in essentially the same way in the simple structure theory of organic chemistry as in the theory of resonance — there is the same use of idealized, hypothetical structural elements. In the resonance discussion of the benzene molecule the two Kekule structures have to be described as hypothetical it is not possible to synthesize molecules with one or the other of the two Kekule structures. In the same way, however, the concept of the carbon-carbon single bond is an idealization. The benzene molecule has its own structure, which cannot be exactly composed of structural elements from other molecules. The propane molecule also has its own structure, which cannot be composed of structural elements from other molecules — it is not possible to isolate a portion of the propane molecule, involving parts of two carbon atoms... 

Thus, the use of the concept of the Power of a Test allows specification of the number of samples (although it may turn out to be very high), and by virtue of that forms the basis for performing experiments as a sequential series. 

Since it is the object of olfactometry to give an indication of the perceived intensity of the odours in the environment, a general warning should be given as to the use of the concept of odour units/m. Even if the number of odour units/m is determined correctly, it does not give a direct indication of the perceived intensity as was already pointed out by Frijters (4). The slope of the curve which relates perceived odour intensity to the odour concentration may vary considerably from odour to odour. A schematic example is given in figure 2 for two substances A and B. 

Although the two scales are identical numerically, their conceptual bases are different. The ideal gas scale is based on the properties of gases in the limit of zero pressure, whereas the thermodynamic scale is based on the properties of heat engines in the limit of reversible operation. That we can relate them so satisfactorily is an illustration of the usefulness of the concepts so far defined. 

Use of the concept of the Excluded Region to limit the orientation of -OH groups and both orientation and translations of water molecules (48). 

The work by Shinnar and Church (S7) on the use of the concept of local isotropy should be pursued and extended. 

Priestley was a thorough-going phlogistean. He seems to have been able to describe the results of his experiments only in the language of the phlogistic theory just as the results of most of the experiments made to-day on the changes of compounds of the element carbon cannot be described by chemists except by making use of the conceptions and the... 

The experimental observation that one has different Debye temperatures for the three distinct surface sites of the AU55 cluster makes the use of a continuum-model picture for discussing the thermal behavior questionable. Indeed, for such small particle sizes, where the surface structure is so manifest, the use of the concept of surface modes becomes dubious, and is certainly inadequate to explain the observed temperature dependence of the f-factors. None the less, it has proven possible to describe the low temperature specific heat of AU55 quite well using such a continuum-model, when the center-of-mass motion is taken into account [99],... 

A good illustration of the usefulness of the concepts local symmetry and chirotopicity is provided by the case of glycerol. The question as to whether the protons of the C,H20 groups are equivalent is problematic for most professional chemists. The answer is that they are not They are chirotopic (property ) and diastereotopic (relationship ). The issue that leads most chemists astray is the symmetry plane, which is the clue to that the molecule is achiral. However, only atoms within the symmetry plane are achirotopic. those outside are chirotopic. 

We now can prepare, in principle, enzyme models by use of the concept of host design, where artificial enzymes are so designed as multiple recognition hosts schematically shown in Fig. 20. Although unsubstituted cyclodextrins are well known to catalyze some organic reactions such as ester hydrolysis, their catalytic activities are relatively small. Recent progress in cyclodextrin chemistry has shown that it is possible to enhance the catalytic... 

The use of the concept of potential production at the country level also means that actual heroin or cocaine production is under-estimated in some countries, and over-estimated in others while the estimate for the global level should be only slightly affected by this. The calculation of potential cocaine production estimates for Peru, for instance, exceeds actual local cocaine production as some of the coca paste or coca base produced in Peru is exported to neighbouring Colombia and other countries for further processing into cocaine. Based on the same reasoning, potential cocaine production estimates for Colombia under-estimate actual cocaine production in the country. Actual cocaine manufacture in Colombia takes place from locally produced coca leaf as well as from coca base imported from Peru. 

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