Occurrence and distribution

the ending on being intended to stress the analogy with carbon and boron. 

Silicon never occurs free it invariably occurs combined with oxygen and, with trivial exceptions, is always 4-coordinate in nature. The Si04 unit may occur as an individual group or be linked into chains, ribbons, rings, sheets or three-dimensional frameworks (pp. 347-59). 

The great affinity of silicon for oxygen delayed its isolation as the free element until 1823 when 

Pauling, The Nature of the Chemical Bond, 3rd edn., pp. 543-62, Cornell University Press, 1960, and references cited therein. 

F) into the structures. Extensive isomorphous substitution among the metals is also possible. Subsequent weathering, transport and deposition leads to sedimentary rocks such as clays, shales and sandstones. Metamorphism at high temperatures and pressures can effect further 

The acids are also constituents of certain oligosaccharides in milk. A dialyzable form of a nonulosaminic acid has been detected in cerebrospinal fluid i this compound may be such an oligosaccharide. 

The distribution of the acids does not appear to be confined solely to the animal kingdom, for Barry and GoebeP have reported the isolation of colominic acid, a polymerized form of iV-acetylneuraminic acid, from culture filtrates of Escherichia coli. It remains to be established whether other bacteria and microorganisms possess the capacity to synthesize and utilize these acids. 

It is perhaps worth noting that D-galactose has been found in all those mucosubstances and oligosaccharides of animal origin which contain nonulosaminic acids. 

Nonulosaminic acids are found as constituents of certain water-soluble, lipid fractions (glycolipids) of animal tissues, being particularly associated with gangliosides as well as with more complex lipopolysaccharides. The detection and characterization of the nonulosaminic acid component in these mucolipids has been based upon one or more of the color reactions (see below) applied to the macromolecular material, followed by isolation therefrom of methoxyneuraminic acid after methanolysis. The question of whether or not one or more acylated forms of neuraminic acid are actually present in the mucolipid has still to be resolved. Svennerholm has reported the isolation of A-acetylneuraminic acid from brain gangliosides. 

Ganglioside containing amino sugar horse erythrocytes 15 35 

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The literature of alkaloids can conveniently be divided into five sections, dealing with (1) the occurrence and distribution of these substances in plants (2) biogenesis, or the methods by which alkaloids are produced in the course of plant metabolism (3) analysis, ranging from the commercial and industrial estimation of particular alkaloids to the separation, purification and description of the individual components of the natural mixture of alkaloids, which normally occurs in plants (4) determination of structure and (5) pharmacological action. 

Krapac IG, Roy WR, Smyth CA, et al. 1995. Occurrence and distribution of pesticides in soil at agrichemical facilities in Illinois. J Soil Contam 4 209-226. 

Schomburg CJ, Glotfelty DW, Seiber JN. 1991. Pesticide occurrence and distribution in fog collected near Monterey, California. Environ Sci Technol 25 155-160. 

Lewis, D.H. (1984). Occurrence and distribution of storage carbohydrates in vascular plants. In Storage Carbohydrates in Vascular Plants, ed. D.H. Lewis, pp. 1-32. Cambridge Cambridge University Press. 

YOUNG A J (1993) Occurrence and distribution of carotenoids in photo synthetic systems , in Young A J and Britton G, Carotenoids in Photosynthesis, London, Chapman and Hall, 16-71. 

Rutherford, T.A., Mamiya, Y. and Webster, J.M. (1990) Nematode-induced pine wilt disease factors influencing its occurrence and distribution. Forest Science 36, 145-155. 

Occurrence and distribution of a wide range of priority and emerging contaminants (pharmaceuticals, drugs of abuse, polar pesticides, etc.)... 

Pereira, W.E., F.D. Hostettler, J.R. Cashman, and R.S. Nishioka. 1994. Occurrence and distribution of organochlorine compounds in sediment and livers of striped bass (Morone saxatilis) from the San Francisco Bay-Delta estuary. Mar. Pollut. Bull. 28 434-441. 

Tucker, E.S. and S.B. Powles. 1988. Occurrence and distribution in south-eastern Australia of barley grass (Hordeum glaucum Steud.) resistant to paraquat. Plant Protection Q. 3 19-21. 

Hladik ML, Kuivila KM (2009) Assessing the occurrence and distribution of pyrethroids in water and suspended sediments. J Agric Food Chem 57 9079-9085... 

Griffin CT, Chaerani R, Fallon D, Reid AP, Downes MJ. (2000) Occurrence and distribution of the entomopathogenic nematodes Steinemema spp. and Heterorhabditis indica in Indonesia. J Helmin 74 143-150. 

Sim WJ, Lee JW, Lee ES, Shin SK, Hwang SR, Oh JE (2011) Occurrence and distribution of pharmaceuticals in wastewater from households, livestock farms, hospitals and pharmaceutical manufactures. Chemosphere 82 179-186... 

Regnery J, Puttmann W, Merz, C, Berthold G (2011) Occurrence and distribution of organo-phosphorus flame retardants and plasticizers in anthropogenically affected groundwater. J Environ Monit 13 347-354... 

Holm JV, RUgge K, Bjerg PL, Christensen TH (1995) Occurrence and distribution of pharmaceutical organic compounds in the groundwater downgradient of a landfill (Grindsted, Denmark). Environ Sci Technol 29 1415-1420... 

Analysis of the mechanically removed water showed some significant variations especially with respect to sodium. It can be seen that for Bowmans, Lochiel and Sedan lignites, the sodium content detected by mechanical removal of water is noticeab less than that for the water soluble sodium. This aspect of the occurrence and distribution of sodium (and chlorine) within these samples was discussed in detail in a paper presented by the authors recently (32). The distribution of sodium was found to be a function of the high negative surface charge of the coal surface resulting in adsorption of sodium at this surface. 

WoUenweber E, Dietz VH, Occurrence and distribution of free flavonoid agly-cones in plants. Phytochemistry 20 869—932, 1981. 

Lewis, D. W. (1973). Vitamin A, occurrence and distribution in fractionated mucus. Lipids 8, 321-323. 

Marine biological material, radioactivity of, 3 315-316 Marine samples arsenic in, 44 148-151 compounds found, 44 151-162 occurrence and distribution, 44 149-151, 162-169... 

Plouvier, V. Occurrence and distribution of syringoside, calycanthoside and similar coumarinic glycosides in several botanical groups. C R Acad Sci Ser II 1985 301(4) 117-120. 

Occurrence and Distribution of Arsenic Compounds in Marine Samples... 

Reinhard, M., Goodman, N.L. Barker, J. F. (1984). Occurrence and distribution of organic chemicals in two landfill leachate plumes. Environmental Science andTethnology, 18(12), 933-61. 

This circular reviews the occurrence of 34 trace elements in coal and the occurrence and distribution of chlorine, phosphorus, titanium, and manganese, which are not considered rare in coal. Separate chapters are devoted to germanium, gallium, and uranium in coal. 

There is, therefore, much interest in determining the concentration of various trace elements in coal. The Illinois State Geological Survey recently concluded a study of the occurrence and distribution of potentially volatile trace elements in coal sponsored by the U. S. Environmental... 

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