Equivalency concept

Dose equivalent or rem is a special radiation protection quantity that is used, for administrative and radiation safety purposes only, to express the absorbed dose in a manner which considers the difference in biological effectiveness of various kinds of ionizing radiation. The ICRU has defined the dose equivalent, H, as the product of the absorbed dose, D, and the quality factor, Q, at the point of interest in biological tissue. This relationship is expressed as H = D x Q. The dose equivalent concept is applicable only to doses that are not great enough to produce biomedical effects. 

Producer surplus as the equivalent concept for the producer. It is the difference between the price and the cost. 

Protein adsorption influences cell No equivalent concept, although cell... 

It should be evident from the comments made that stereoheterotopism and prochirality (or prostereoisomerism) are not equivalent concepts but serve different objectives in a common field. 

Likewise, a one normal solution contains 1 g equivalent weight of solute in 1L of solution for example, 1 mol HCl, 0.5 mol H2SO4, and 0.33 mol H3PO4, each in IL of solution, are one normal solutions. The use of normality is limited in that a given solution may have more than one normality, depending on the type of reaction for which the solution is used. The molarity of a solution, however, is a fixed number because there is only one molecular mass for any substance. Normality is no longer recommended to express concentrations. Nevertheless, the term is included here because it remains in common usage and is related to the equivalent concept sometimes favored for serum electrolyte concentrations in the United States and some other countries. 

The structure of the chapter should be clear from Fig. 7.1. The design must be based on the proper mass and energy balances for the reactor. When there is only one reaction, conversion and yield are equivalent concepts, but with simultaneous reactions, the primary concern of the design... 

Gao X, Son D-S, Terranova PF, et al. 1999. Toxic equivalency factors of polychlorinated dibenzo-p-dioxins in an ovulation model Validation of the toxic equivalency concept for one aspect of endocrine disruption. Toxicol Appl Pharmacol 157 107-116. 

Gao X, Terranova PF, Rozman KK. 2000. Effects of polychlorinated dibenzofurans, biphenyls, and their mixture with dibenzo-p-dioxins on ovulation in the gonadotropin-primed immature rat Support for the toxic equivalency concept. Toxicol Appl Pharmacol 163 115-124. 

Let us start this section by saying that intermolecular interactions and bonds are not equivalent concepts not all intermolecular interactions are bonds (only attractive interactions can become bonds). Furthermore, as we will detail below, not all attractive intermolecular interactions are bonds. 

The model for predicting the ecotoxicological effects of mixtures of metabolites and their parent compounds assumes concentration addition of the effects of metabolites and their parent compound. If concentration addition holds and additionally all assumptions pertinent to the toxic equivalency concept apply [14], the toxic potential of the mixture of a parent compound and its metabolites, TPmixture. is defined as the sum of the fraction of parent after metabolism, /parent, and the product of the fraction of each metabohte i, fi, scaled by the potency of the given metabolite RPi, in relation to 100% potency of the parent compound (Eq. 1). 

While the Codex Alimentarius has taken steps towards international harmonisation of the organic regulations and markets, a proliferation of new obstacles to trade can be observed. Governmental labels excluding imported produce, bureaucratic obstacles, a narrow view of the equivalence concept and a lack of control of private organisations are seen as the main factors. Further efforts are necessary in order to remove these obstacles and to foster international trade in organic products. 

The equivalent is its half-molar mass. In the case of a redox reaction, the equivalent is related to the number of exchanged electrons, and the equivalent factor is chosen for one electron exchanged. The equivalent concept is also used for titrations by the formation of complexes or by precipitation. Its introduction has been of profound importance in the development of titrimetric analysis. 

In the first Corey prostaglandin synthesis we saw the use of an acyl anion equivalent . Now we will see another application of the equivalency concept , use of a real reactant that, after some functional group manipulations, can be used to accomplish a transformation that could not be accomplished otherwise. Let s look at the tactics that were ultimately used by the Corey group. Sodium cyclopentadienide was alkylated with chloromethyl methyl ether to provide 37. Chloromethyl methyl ether is extremely reactive and thus, this reaction could be accomplished at a low temperature, below the temperature at which 37 isomerizes to cyclopentadienes 38 and 39. Cyclopentadiene 37 was then reacted with an excess of 2-chloroacrylonitrile, an extremely reactive dienophile. Under the influence of Lewis acid promotion (copper tetrafluoroborate) this diene-dienophile pair underwent cycloaddition, to give 40 at temperatures where diene isomerization did not occur. Although 40 was obtained as a mixture of endo and exo diasteromers, it is notable that the dienophile approached 37 from the sterically least... 

This chapter was devoted to introducing the thermodynamic concepts and formalism essential to understand chemical reactions. Thus, we reviewed the first and second laws of thermodynamics, introduced the concept of thermodynamic equilibrium, defined the free energy change, and used it to prove that thermodynamic and chemical equilibrium are equivalent concepts. Interestingly, we were able to obtain the las of mass action Ifom purely thermodynamic considerations, suggesting that the thermodynamic and the chemical kinetics approaches are closely related. This connection is explored in detail in the next chapter. Finally, the last section of the chapter was dedicated to understanding the concept of chemical potential from the perspective of statistical mechanics. In later chapters we tackle this same question from different angles. 

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