Chemical equivalence 348 INDEX

World Patents Index DIALOG, ORBIT, Questel, STN Derwent Information Ltd. international limited bibliographic data patent families comprehensive English language abstracts of basic and some equivalent granted patents polymer and chemical stmcture indexing for subscribers drawings... 

USPATFULL STN Chemical Abstracts Service U.S. full bibhographic data full text Chemical Abstracts indexing from U.S. patent or equivalent... 

The TEF approach normalizes exposures to common mechanism chemicals with different potencies to yield a total equivalent exposure (TEQ) to one of the chemicals, the index compound. TEFs are derived as the ratio of the POD of the index compound to that of each member in the group. The exposure to each chemical is then multiplied by the respective TEF value to express exposure in terms of the index compound. Summation of these values result in the total combined exposure (TEQ) expressed in terms of the index compound. 

TEF Toxicity equivalency factor. Ratio of the toxicity of a chemical to that of another structurally related chemical (or index compound) chosen as a reference. TEFs are toxicity potency factors used to evaluate the toxicities of highly variable mixtures of dioxin-like compounds. The most toxic members, 2,3,7,8-TCDD and 1,2,3,7,8-pentachlorodibenzo-p-dioxin, are... 

In the RPF method (eqn (1)), the user must identify the constraints of the application of a set of RPFs. For example, the health effect, dose range of component doses, route(s) of exposure, and dura-tion(s) of exposure for which the RPFs can be applied must be specified (e.g., a set of RPFs may be constrained to oral exposures and not be used for exposures to the same mixture through the inhalation route). To apply the method, an RPF is estimated for each mixture component the RPF estimates the toxicity of the component relative to that of the IC. RPFs commonly are estimated from a ratio of equally toxic doses of the individual dose-response functions for the component and the IC. For example, the quotient of the effective dose at which ten percent of a test population exhibits an effect (EDio) of the IC and the component could serve as a value for the component s RPF obviously, the RPF for the IC equals 1. The index chemical equivalent dose of an individual component is the product of the component dose and the RPF of the component. These equivalent doses are summed across all components. The risk posed by the mixture is estimated by comparing the summed index chemical equivalent doses of the mixture to the dose-response function of the IC ... 

These topological indexes, based on the molecular connectivity approach, include three types the ""Xr molecular connectivity chi indexes that characterize the structural attributes of molecules, the ""k kappa indexes of molecular shape, and the topological equivalence state T values that individually characterize atoms and groups in the molecular skeleton and are used primarily to determine chemically equivalent atoms within a molecule. A further development of this approach has led to the electrotopological state atom indexes, which will not be discussed here but will be presented elsewhere. Molecular connectivity chi indexes are discussed in the first part of this paper along with illustrative applications. Then kappa shape indexes are discussed. The topological state index is discussed in the final section. 

CAS Number Index con[a ns CAS number entries followed by a listing of their trade name product and chemical equivalents in alphabetical order. 

Many suppliers of polyurethane systems provide them in the form of two components and advise on the actual weight of each component to be combined to form the polymer. This is the weight ratio, sometimes and confusingly called the index. Such a practice is to be decried as causing confusion with the chemical term isocyanate index . In many cases there is little difference in value between weight ratio and chemical equivalent weight ratio of index but it is important to understand the difference. Most suppliers supply an NCO-free system for one component and an NCO component (quoted in terms of the OH number) for the other side. 

Further steps toward universality are taken by the replacement of element and compound names wherever possible by symbols and formulas, and by adding to data in older units their recalculated SI equivalents. The usefulness of the reference sections has been increased by giving journal-title abbreviations according to the Chemical Abstracts Service Source Index, by listing in each reference all of its authors and by accompanying references to patents and journals that may be difficult to access by their Chemical... 

An important feature of the analytical methods for the total petroleum hydrocarbons is the use of an equivalent carbon number index (EC). This index represents equivalent boiling points for hydrocarbons and is the physical characteristic that is the basis for separating petroleum (and other) components in chemical analysis. 

World Patents Index. WPI, produced by Derwent Publications, Ltd., contains records of patent publications from 32 issuing authorities around the world. Since 1970, all chemical technologies are included. Prior to then, content varies as follows polymers from 1966, agricultural chemicals from 1965, and pharmaceuticals from 1963. Records contain bibliographic data and an abstract, which describes the novel features of the patent. The patent tides and abstracts in WPI are created by Derwent and generally give a more definitive description of the patent s content than the title and abstract, which appear on the document itself Records also list equivalent or family member patents that have been identified as covering the same or related invention(s) (92). 

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