Chemical substances selection

TABLE 5. Chemical substances selected for detection when destructing CW... 

J. H. Eletcher, O. C. Dermer, and R. B. Pox, Nomenclature of Organic Compounds, American Chemical Society Advances in Chemistry Series, Vol. 126, Washington, D.C., 1974 Selection of Index Namesfor Chemical Substances, Chem. Abstracts 82, Index Guide, American Chemical Society, Washington, D.C., 1982. 

W. M. Meylan and P. H. Howard, Chemical Market Input] Ouput Analysis of Selected Chemical Substances to Assess Sources of Environmental Contamination ... 

A.ntibiotic is an organic chemical substance produced by microorganisms that has the capacity in low concentration to selectively destroy or inhibit the growth of other microorganisms without injuring the host cells. It may be adrninistered systemicaHy and be an antimicrobial chemotherapeutic agent. 

The values given in the following table for the heats and free energies of formation of inorganic compounds are derived from a) Bichowsky and Rossini, Thermochemistry of the Chemical Substances, Reinhold, New York, 1936 (h) Latimer, Oxidation States of the Elements and Their Potentials in Aqueous Solution, Prentice-Hall, New York, 1938 (c) the tables of the American Petroleum Institute Research Project 44 at the National Bureau of Standards and (d) the tables of Selected Values of Chemical Thermodynamic Properties of the National Bureau of Standards. The reader is referred to the preceding books and tables for additional details as to methods of calculation, standard states, and so on. 

The material in this section is divided into three parts. The first subsection deals with the general characteristics of chemical substances. The second subsection is concerned with the chemistry of petroleum it contains a brief review of the nature, composition, and chemical constituents of crude oil and natural gases. The final subsection touches upon selected topics in physical chemistry, including ideal gas behavior, the phase rule and its applications, physical properties of pure substances, ideal solution behavior in binary and multicomponent systems, standard heats of reaction, and combustion of fuels. Examples are provided to illustrate fundamental ideas and principles. Nevertheless, the reader is urged to refer to the recommended bibliography [47-52] or other standard textbooks to obtain a clearer understanding of the subject material. Topics not covered here owing to limitations of space may be readily found in appropriate technical literature. 

The European Commission (EC) has sponsored four reports that evaluate a set of 553 substances selected by experts and stakeholders for assessment for endocrine disruption. Each report addresses a subset of the total set based on priorities such as whether the chemicals are persistent, bioaccumulating or High Production Volume chemicals and/or whether or not there is already regulatory control of the chemical. 

MAP makes use of physical phenomena that are fundamentally different compared to those applied in current sample preparation techniques. Previously, application of microwave energy as a heat source, as opposed to a resistive source of heating, was based upon the ability to heat selectively an extractant over a matrix. The fundamental principle behind MAP is just the opposite. It is based upon the fact that different chemical substances absorb microwave energy... 

Flotation. In many cases, contaminants adsorbed on the surface of clay particles, or contaminants occurring in soil as discriminate particles, have different surface properties to clean soil particles. By adding special chemical substances, the formation of a hydrophobic surface on the contaminated particles is possible. Pulp aeration results in the attachment of hydrophobic contaminated particles to the surface of the small bubbles that are formed. In this way, selective flotation of these particles is achieved. Contrary to the gravimetric separation methods, flotation offers the possibility to separate contaminated and noncontaminated particles of the same grain size and density but with different surface properties. 

In natural circumstances, at least one individual in 10,000 carries an unusual mutation, which, if fixed by selection, may turn into a new characteristic. Insensitivity to a chemical substance that has not been seen over millions of years of evolution is a rare characteristic, and the frequency of such mutations is not 104, but closer to 107 or even 109. If there are over one billion individuals in the population of the target species, then less sensitive members will always be present in the first generation. They will survive, and will have progeny. Three to four generations later, the population of the target species will be the same size as, or even larger than, it was before pesticide use however, the majority of individuals will be less sensitive to the pesticide. 

Casimir Funk had come from Poland to the Lister Institute in London, England to investigate the chemical nature of the substance in rice-polishings (rice bran) that cured or prevented polyneuritis in birds, a disease closely related to beri-beri in humans. His research in this subject coupled with his awareness of what were becoming known as diet-related diseases, the deficiency diseases, led to his review article of 1912 in which he coined the term, vitamine. Vitamine, to Funk, was actually a variety of chemical substances, organic amines, that acted selective-... 

But if affinity was like gravity, electricity, or, to a lesser extent, magnetism, it could not be identical to them. An important difference was that affinity was selective or "elective." Elementary chemical substances chose friends and foes on the basis of kind, not just the quantity of a thing and its distance. Defining affinity in the nineteenth century, Wurtz called it the "force which... 

A variety of mammalian cell culture systems can be used to detect mutations induced by chemical substances. The L5178Y mouse l)nnphoma line, measuring mutation at the TK locus, is preferred. TK is an important enz)une involved in DNA synthesis. Cells are exposed to the test substance at various concentrations, in the presence and absence of a metabolic activation system, for a suitable period of time, and then subcultured to assess cytotoxicity and to allow phenotypic expression prior to mutant selection. Cells deficient in TK because of a forward mutation are resistant to the cytotoxic effects of pyrimidine analogues (antimetabolites), such as trifluorothymidine (TFT). This is because the antimetabolites cannot be incorporated into cellular nucleotides and kill the cell through inhibition of cellular metabolism. After treatment, cells are grown in a medium containing TFT mutant cells can proliferate in the presence of TFT, whereas normal cells containing TK are killed. This allows the detection of an increase in mutant... 

The simplest way to represent chemical substances is to use formulae, which are assemblages of chemical symbols. Formulae are particularly useful for listing and indexing and also when names become very complex. The precise form of a formula selected depends upon the use to which it is to be put. 

The FDA investigators have the authority to collect samples as described under the comphance program 7348.808. Samples of a test article, the carrier, the control article or test and control article mixtures may be selected and sent to FDA laboratories to determine the identity, strength, potency, purity, composition, or other characteristics that wiU accurately define the coUected sample. In fact, even physical samples such as wet tissues, tissue blocks, and slides may be collected. When the field investigator collects a sample of any chemical substance, he will also coUect a copy of the methodology from the sponsor of the testing facihty. The copy of the methodology will be sent to the FDA laboratory selected to perform the sample analysis. 

Because drug selectivity is based on the fact that different pathways use different transmitters, a primary goal of neuropharmacologists is to identify the transmitters in CNS pathways. Establishing that a chemical substance is a transmitter has been far more difficult for central synapses than for peripheral synapses. The following criteria have been established for transmitter identification. 

Most modern explosives used for practical purposes are not single chemical substances, but composite mixtures, their ingredients being selected to obtain the required properties. 

The assembly of a self-consistent table of values for the heats of formation of all the chemical substances requires (1) that all the original experimental data be recalculated with the use of appropriate auxiliary data, (2) that the value selected for the heat of formation of a given substance be as accurate as it is possible to obtain from the known data, and (3) that the selected best value be as consistent as possible with all the other values in the table and with all the known thermochemical data on reactions involving that substance. 

For input, storage, manipulation, and output within computer-based systems, a representation of the chemical substance must be selected. The selection of a particular representation scheme for an information system is based on the size of the files to which it applies, the functions to be performed, the available hardware and software, and the desired balance between... 

Algorithm I - Registration - Canonicalization of Connection Tables. A connection table for a chemical substance with n atoms can be numbered in as many as n different ways. The problem of generating a canonical form involves selecting a... 

Hormone. A chemical substance made in one cell and secreted so as to influence the metabolic activity of a select group of cells located elsewhere in the organism. 

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