Concept Delineation

Aroma substances are volatile compounds which are perceived by the odor receptor sites of the smell organ, i. e. the olfactory tissue of the nasal cavity. They reach the receptors when drawn in through the nose (orthonasal detection) and via the throat after being released by chewing (retronasal detection). The concept of aroma substances, like the concept of taste substances, should be used loosely, since a compound might contribute to the typical odor or taste of one food, while in another food it might cause a faulty odor or taste, or both, resulting in an off-flavor. 

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Chapter 3 by Robert M. Whitnell and Kent R. Wilson extends some of the concepts delineated in Chapter 2. The chapter on computational molecular dynamics of chemical reactions in solution is a definitive, long-awaited bridge between the organic and chemical physics communities. Techniques for simulating reaction dynamics are covered in nonmathematical language. Work on thermally activated reactions, such as isomerization, atom exchange, 5 2, and S l reactions, as well as ion-pair association, and proton transfers, are reviewed. For nonthermally activated reactions, a variety of photodissociations and isomerizations are discussed. The interplay of computer simulations of solution reaction dynamics and models of the reactions is explained. 

As part of extensive studies of carbonyl additions in the presence of Lewis acidic catalysts, Reetz found that both TiCb and SnClj produced stereoselective allylations of aldehyde 94 to afford 95 in dr = 95 5, consistently with chelation control (Equation 5) [6]. The use of BFj OEtj furnished 95 with only slightly diminished preference for the same diastereomer (dr=85 15). The results are surprising, given that BF3-OEt2 possesses only a single free coordination site and is incapable of participating in chelation. This study underscores the concepts delineated earlier namely, that the observed diastereo-... 

Colloidal State. The principal outcome of many of the composition studies has been the delineation of the asphalt system as a colloidal system at ambient or normal service conditions. This particular concept was proposed in 1924 and described the system as an oil medium in which the asphaltene fraction was dispersed. The transition from a coUoid to a Newtonian Hquid is dependent on temperature, hardness, shear rate, chemical nature, etc. At normal service temperatures asphalt is viscoelastic, and viscous at higher temperatures. The disperse phase is a micelle composed of the molecular species that make up the asphaltenes and the higher molecular weight aromatic components of the petrolenes or the maltenes (ie, the nonasphaltene components). Complete peptization of the micelle seems probable if the system contains sufficient aromatic constituents, in relation to the concentration of asphaltenes, to allow the asphaltenes to remain in the dispersed phase. 

The basic blocks with which to build an arrangement for plot plans are often used in the unit area concept. This method of planning is particularly well adapted to large plant layouts. Unit areas are often delineated by means of distinct process phases and operational procedures by the presence or absence of contamination and by safety requirements. Thus, the determination of the shape and extent of a unit area and the interrelationships of each area in a... 

Prior to the delineation of the concept of conservation of orbital symmetry by Woodward and Hoffmann, Bachmann and Deno reported that all Diels-Alder reactions... 

An alternative programme of instraction aimed at reinforcing the use of the triplet relationship when describing and explaining the seven types of chemical reactions was developed by the second anthor and incorporated into the prescribed scheme of work. In order to delineate the content of the alternative instructional prograrmne, the concept map in Fig. 7.1 (Chandrasegaran, 2004) was developed. The concept map encapsulates the characteristics of the seven chemical reactions and indicates... 

In summary, we found that the students received lower scores on items that were at different pressures than on items with the same amount of pressure. Also, we found that although the students learned the concept of diffusion in their seventh grade biology class, they did not generate the conception of diffusion in a submicro-scopic maimer. Instead, they tended to conceptualize the diffusion of the particles in a more intuitive way (the heavier object sinking to the bottom of the container) than in a scientific model that was designed to delineate the random nature of the particle motion. 

Although Modern Pharmaceutics continues to evolve, our basic goals remain those which we developed in the 1970s when we first delineated the concept of this comprehensive and integrated treatment of pharmaceutics, with a focus on drug product quality and performance. We are committed to producing an up-to-date, authoritative, multiauthored treatise on pharmaceutics, which can be used by both students and practitioners. 

This article does not cover the extensive research carried out to delineate the cause and severity of RPTs possible in nuclear reactor accidents. Although there is not universal agreement, the general consensus is that the superheated liquid concept can explain many of these events and, more importantly, can indicate when RPTs are unlikely to occur in hypothetical reactor accidents. 

The volume properties of crystalline mixtures must be related to the crystal chemical properties of the various cations that occupy the nonequivalent lattice sites in variable proportions. This is particularly true for olivines, in which the relatively rigid [Si04] groups are isolated by Ml and M2 sites with distorted octahedral symmetry. To link the various interionic distances to the properties of cations, the concept of ionic radius is insufficient it is preferable to adopt the concept of crystal radius (Tosi, 1964 see section 1.9). This concept, as we have already noted, is associated with the radial extension of the ion in conjunction with its neighboring atoms. Experimental electron density maps for olivines (Fujino et al., 1981) delineate well-defined minima (cf figure 1.7) marking the maximum radial extension (rn, ,x) of the neighboring ions ... 

It should be noted that the above strategy, although first employed In the delineation of protein antigenic sites. Is applicable, with appropriate adaptations, to the precise delineation and chemical synthesis of other types of protein binding sites. The Introduction of the concept of surface-simulation synthesis ( 4, ) has provided a methodology by which In principle any type of protein binding site can be mimicked synthetically after careful chemical characterization. 

The way in which we systematize our notion of symmetry is by introducing the concept of a symmetry operation, which is an action which moves the nuclear framework into a position indistinguishable from the original one. At first sight it would appear that there are very many such operations possible. We will see, however, that each falls into one of five clearly delineated types identity, rotation, reflection, rotation-reflection, and inversion. 

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