Specific Constituents

Group Contribution Methods. It has been shown that many macroscopic physical properties, ie, those derived from experimental measurements of bulk solutions or substances, can be related to specific constituents of individual molecules. These constituents, or functional groups, are usually composed of commonly found combinations of atoms. One procedure for correlating functional groups to a property is as foUows. (/) A set of... 

Leaching, which is the selective solution of specific constituents of a solid mixture when brought in contact with a liquid solvent. It is particularly useful in separating metals from solid matrices and sludge. 

Some studies have evaluated the quantity of a specific constituent in various herbal products by a thin-layer chromatography spectrophotometric method. Of 44 feverfew products that were evaluated, 14 (32%) did not contain the minimum of 0.2% parthenolide content (active ingredient) and 10 (22%) did not contain any detectable levels of parthenolide [30]. 

Natural gas values were representative only. Exact characteristics require knowledge of specific constituents. 

A second approach is to obtain (extract) water as it naturally occurs in soil pores. Typically, a porous ceramic cup (other materials are available) is placed in an unsaturated soil, either in the field or laboratory. A vacuum is applied (slightly more negative pressure than the water in the soil pores see also Chapter 5) to the ceramic cup via tubing to move water into a receiving container. This water can be analyzed for all its constituents. A reason for obtaining this type of soil water sample is to analyze it for one specific constituent such as a herbicide, insecticide, or pollutant. Water extracted in this way may also better represent the concentration of the analyte of interest to which plant roots are exposed. 

Once formed, the LNAPL is referred to as a pool that is really a continuous accumulation of LNAPL. Subpools are individual accumulations of relatively uniform free-product types based on geochemistry (API gravity, specific constituents, isotope ratios, etc.) that have coalesced, reflecting multiple-source accumulations with time. The LNAPL pool, once formed, also maintains a capillary fringe. The anticipated capillary rise of LNAPL can be calculated as follows ... 

The diffusion coefficient Dx can be expressed as a function of the concentration of the specific constituent in the pore fluid [158]. Figure 8 shows four relationships between the non-dimensional pollutant concentration and Dn (the molecular diffusion coefficient). These show the strong influence from both in characterizing the shape of the relative pollutant concentration profile. Leaching-column test information shows that case (4) in Fig. 8 is the more likely profile (i.e., Dn= ae bc). Using this function in Eq. (90), the final governing equation for (X)+ will be ... 

Condensate release might be equated to the release of volatile constituents but are often named as such because of the specific constituents of the condensate, often with some reference to the gas condensate that is produced by certain petroleum and natural gas wells. However, the condensate is often restricted to the benzene, toluene, ethylbenzene, and xylenes (BTEX) family of compounds. 

Composite interfaces exist in a variety of forms of differing materials. A convenient way to characterize composite interfaces embedded within the bulk material is to analyze the surfaces of the composite constituents before they are combined together, or the surfaces created by fracture. Surface layers represent only a small portion of the total volume of bulk material. The structure and composition of the local surface often differ from the bulk material, yet they can provide critical information in predicting the overall properties and performance. The basic unknown parameters in physico-chemical surface analysis are the chemical composition, depth, purity and the distribution of specific constituents and their atomic/microscopic structures, which constitute the interfaces. Many factors such as process variables, contaminants, surface treatments and exposure to environmental conditions must be considered in the analysis. 

Lightweight, anticorrosive metal that forms few compounds one of its isotopes is useful as a tracer of specific constituents in oil refining. 

In general, the specific constituents of milk are synthesized from small molecules absorbed from the blood. These precursors are absorbed across the basal membrane but very little is known about the mechanism by which they are transported across the membrane. Since the membrane is rich in lipids, and precursors are mostly polar with poor solubility in lipid, it is unlikely that the precursors enter the cell by simple diffusion. It is likely, in common with other tissues, that there are specialized carrier systems to transport small molecules across the membrane such carriers are probably proteins. 

For any individual animal, fat content decreases slightly during successive lactations, by c. 0.2% over a typical productive lifetime (about five lactations). In practice, this factor usually has no overall effect on the fat content of a bulk milk supply because herds normally include cows of various ages. The concentration of fat (and of all other milk-specific constituents) decreases markedly on mastitic infection due to impaired... 

Diet. The constituents and amount of food (deficiency/starvation) may influence disposition and hence toxicity of chemicals. Food constituents may be enzyme inducers or inhibitors. Lack of food or specific constituents (e.g., protein or vitamins) may decrease metabolic capability, for example, a protein-deficient diet decreases cytochrome P-450 activity. Lack of sulfur amino acids decreases glutathione level. The effect on toxicity will depend on the role of metabolism. 

Immunohistochemical stains use antibodies to identify specific constituents in tissue sections. In order to detect the site of reaction, the antibody is labeled with an enzyme that can be reacted with a suitable substrate to give a colored product. The alternative is to use a fluorescent label. The advantage of an enzyme label is that the nuclei can be counter stained thereby revealing the tissue architecture, and that the stain fades slowly, if at all, allowing the slides to be stored. 

COLORIMETRY. A method of chemical analysis thal deals with the measurement of the light absorption by colored solutions. Since light absorption depends upon the concentraiion of a specific constituent in solution, colorimetry is frequently used by geologists to determine qualitatively the trace quantities of many elements. 

The analysis of data give in Table 12 shows that viscosity of the material at 140 °C (moulding temperature) increases for all batches of granulated material, as compared with viscosity of source powder. This increase is apparently due to the use of different agglomerating liquids and specific constituents. 

Reduction of the subjective values or criteria to a specified compound, group of compounds or physical factor is often a very difficult endeavor, but one by one each of the so-called "qualitative criteria" is being linked to the presence or absence of specific constituents. Sometimes only a single compound is involved, however, often the qualitative character is the result of additive or even synergistic interactions of two or more constituents. Thus, since there are so many different characteristics that can contribute to the total quality of any single food product, it is paramount that precise objective methodology be developed for each parameter. 

High-performance liquid chromatography (HPLC) has found great utility in separating different hydrocarbon group types and identifying specific constituent types (Colin and Vion, 1983 Drushel, 1983 Miller et al., 1983 Chattier et al., 1986). Of particular interest, is the application of the HPLC technique to the identification of the molecular types in the heavier feedstocks, especially the... 

Figure 4 Typical proline specific constituents in wort and beer depending on different boiling conditions...

In micro- and ultrafiltrations, the mode of separation is by sieving through line pores, where microfiltration membranes filter colloidal particles and bacteria from 0.1 to 10 mm, and ultrafiltration membranes filter dissolved macromolecules. Usually, a polymer membrane, for example, cellulose nitrate, polyacrilonytrile, polysulfone, polycarbonate, polyethylene, polypropylene, poly-tretrafhioroethylene, polyamide, and polyvinylchloride, permits the passage of specific constituents of a feed stream as a permeate flow through its pores, while other, usually larger components of the feed stream are rejected by the membrane from the permeate flow and incorporated in the retentate flow [10,148,149],... 

Plant substances are said to enhance some insect hormones, to the advantage of the insect. Bedard et al. (44) have described how the western pine beetle (Dendroctonus brevicomis) uses its host pine trees (Firms ponderosa and P. coulteri) to enhance the drawing power of its sex attractant, exobrevicomin. When ready to mate, both sexes emit the attractant. Bedard found the attractant s power (in terms of numbers of insects attracted) was doubled when mixed with myrcene, a normal constituent of pine wood. Myrcene alone was not attractive. Myrcene, however, is not restricted to pine we have seen earlier (10) that it is consistently found in spruce needles, and in general it is not characteristic of any single group of plants. Since the western pine beetle feeds only on pine, of what real ecological significance is Bedard s report of the enhancement of its hormone by myrcene Why isn t a more specific constituent of pine wood involved Perhaps one is, but research has not yet revealed it. Apart from Brower s work with the monarchs, we have not examined the rich area of herbivore—predator interactions. 

The major constituents of parsley leaves are 1,3,8-p-menthatriene, followed by /)-phellandrene, myristicin and myrcene. Parsley accessions high in the specific constituents (percentage of essential oil)... 

An examination of hydrolysates produced by glycosidase enzyme or pH 3.2 acid treatment of reversed-phase isolates frcm juices of "non-floral " itis vinifera vars. Chardonnay, Sauvignon Blanc and Semilion demonstrated that these grapes contain conjugated forms of monoterpenes, C, norisoprenoids, and shikimic acid-derived metabolites. The volatile conpounds obtained hydrolytically from the conjugates were produced in sufficient concentration to permit ready analysis by GC/MS. The products of pH 3.2 hydrolysis have sensory significance when assessed in a neutral wine. The study further develops the precursor analysis approach as a technique to facilitate research into varietally specific constituents of grapes. 

Previous work on precursor fractions from grapes had indicated that analysis of the conjugated constituents would facilitate research in the varietal specific constituents of fruit (21). This study further develcps that research and proves that conjugated forms of... 

Synonyms Primary synonym is coal tar pitch volatiles such as benzene soluble organics. However, synonyms vary depending on the specific constituents in the emissions RTECS No. GH0346000... 

GABA. Dihydrovaltrate, hydroxyvalerenic acid, a hydroalcoholic extract containing 0.8% valerenic acid a lipid extract an aqueous extract of the hydroalcoholic extract, and another aqueous extract of V. officinalis (L.) were assessed for in vitro binding to rat GABA, benzodiazepine, and barbiturate receptors (18). The results indicated that an interaction of some component of the hydroalcoholic extract, the aqueous extract derived from the hydroalcoholic extract, and the other aqueous extract had affinity for the GABAa receptor. Because hydroxyvalerenic acid (a volatile oil sesquiterpene) and dihydrovaltrate (a valepotriate) did not show any notable activity, the investigators could not identify the specific constituents responsible for this activity. The lipophilic extract derived from the hydroalcoholic extract, as well as dihydrovaltrate, showed affinity for barbiturate receptors, and some affinity for peripheral benzodiazepine receptors. 

A set of instruments was installed for on-line concentration measurements of six specific constituents of the exhaust gas. Concentrations of the seventh constituent, HC1, were determined by laboratory titration of individual samples using the Volhard... 

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