Carbon substances

Terpenes (and terpenoids) are further classified according to the number of 5-carbon units they contain. Thus, monoterpenes are 10-carbon substances biosynthesized from two isoprene units, sesquiterpenes are 15-carbon molecules from three isoprene units, diterpenes are 20-carbon substances from four isoprene units, and so on. Monoterpenes and sesquiterpenes are found primarily in plants, but the higher terpenoids occur in both plants and animals, and many have important biological roles. The triterpenoid lanosterol, for example, is the precursor from which all steroid hormones are made. 

Finely dispersed carbon substances introduced into the active mass of pseudocapacitive electrodes of hybrid (asymmetric) capacitors play the most important role in operation of an efficient volumetric collector. 

Munster, U. 1993. Concentrations and fluxes of organic carbon substances in the aquatic environment. Antonie van Leeuwenhoek 63 243-274. 

The extent of modification in the cocarbonization process is also influenced by the principal carbonizing substances (28-31). The authors introduced the term "cocarbonization susceptibility" to describe this situation. The presence of oxygen-containing functional groups, which is often observed in coal-derived pitch, is one of the major factors which influence the susceptibility (31). The molecular-size distribution of aromatic and paraffinic components in the feedstock is another factor (28). The combined effect of modifying ability and susceptibility on the resultant optical texture is illustrated schematically in Figure 4. 

Figure 4. Schematic diagram to illustrate three possible effects of cocarbonization on the development of optical anisotropy. A, additive B, principal carbonizing substance.

Experimental results showed that carbonmineral composites are much better than others adsorbents, for example, the mineral one. A good selectivity of carbon materials made us to assume that it is a carbon substance is responsible both for selectivity and synergistic effect of adsorption too. From our point of view one of the reason of such a behavior could be specially organized carbon structures such as intermediate complexes (clusters), which possess peculiar electron properties only to them. Probably similariy toxic substances are adsorbed, such as phenols, cresols, quaiacol, aldehydes, polyatomic alcohols, ethers etc. (Table 1). 

The laser printer is the most sophisticated type of printer. A laser jet printer uses lasers, electric charges, and toner (a black carbon substance similar to the lead in a pencil) to create images on paper. Laser printers have the highest image quality and speed when compared to dot-matrix and ink-jet printers. They can print at a speed of several pages per minute, which is similar to the speed of photocopiers. Laser printers are more expensive than the other types of printers. They take up more space, and their consumables (like toner) are more expensive than those used by other types of printers. However, they are very popular in offices where high capacity and quality are priorities. 

Terpenes are classified according to the number of isoprene units they contain. Thus, monoterpenes are 10-carbon substances biosynthesized from two isoprene units, sesquiterpenes are 15-carbon molecules from three isoprene units, and so on (Table 27.3). 

Terpenes are most familiar, at least by odor, as compounds of the so-called essential oils obtained by steam distillation or ether extraction of various plants. Thousands of different terpenes are known. According to the isoprene rule proposed by L. Ruzicka in 1921, they can be considered to arise from head-to-tail joining of simple five-carbon isoprene (2-methyl-1,3-butadiene) units. Terpenes are subdivided into groups depending on the number of isoprene units [9]. For example, monoterpenes are 10-carbon substances biosynthesized from two isoprene units, which can be divided into aliphatic, monocyclic, or bicyclic species Some typical exponents of each monoterpene subgroup are shown in Fig 1... 

Pimephales promelas (fathead minnow) is 505mgl in a 96h flowthrough bioassay. MIBK can contribute to the formation of photochemical smog when it reacts with other volatile organic carbon substances in air. 

The process of carbon deposit formation in complex carbon-mineral adsorbents may be initiated and terminated in any stage or stages of scheme 1. This is dependent on the chemical nature of the carbonized substance, porous structure and chemical nature of adsorption and catalytic sites of the mineral matrix, etc. For this reason, the complex adsorbents prepared by the third and fourth methods have the carbon deposits consisting of the substances of different chemical and physical structure formed during the defined stages of Scheme 1. 

The ease of formation of carboneous substance in the above reaction results from the stoichometry of this reaction as well as the high energy of HCl formation. Reaction (4) performed on the surface of a solid adsorbent permits to obtain practically any amount of carbon [36]. Owing to that both patch-wise and random topography of carbosil adsorption sites can be easily regulated. 

Certain proteins such as Ras and transducin undergo the addition of iso-prenoid groups attached to cysteine residue of the protein. Isoprenoids such as farnesyl and geranyl are 15- and 20-carbon substances, respectively. 

Some novel procedures have been introduced for the synthesis of diaryl carbonates, substances of interest in polymer chemistry. Unsymmetrical compounds in the series have been obtained by the slow addition over 5 hours at OX of... 

Humins (humus coal) are soluble neither in alkalies nor in acids. This group in humic substances have been very little investigated. They are characterized as an insoluble form of humic acids. Humins are considered as the oldest, and ultimate products of the humification process. They are assumed to be strongly carbonized substances, where the high stability is increased by a strong bond to the mineral fraction. Due to their high chemical stability or even inert character, humins do not participate in the soil formation process and they do not fulfil the function of the true humus. 

Our own results using Py-GC for more than 40 analyzed wax samples produced quite distinctive fingerprints even within the same class (for example, plant waxes). Also, as was demonstrated by the comparison of beeswax from fresh samples to some approximately 40(X) years old, the fingerprints for this material are very stable and could be easily recognized in spite of minor differences in the middle portion of the pyrogram (see Figure 6.1). Only in beeswax, in the last portion of pyrogram, which represents undecomposed hydrocarbons, can one easily spot differences in the amount of even- and odd-carbon substances (in beeswax odd carbon number hydrocarbons will always dominate). 

This biosynthetic path consists of the Claisen-type condensation of two acetyl CoA units to form the four-carbon substance acetoacetyl CoA a third equivalent of acetyl CoA is then added in an aldol-type reaction giving, after hydrolysis of one of the thiol esters, hydroxymethylglutaryl CoA (HMG-CoA). HMG-CoA is then reduced by a net four electrons to mevalonic acid and is subsequently phosphorylated to mevalonic acid 5-pyrophosphate (MVA-5PP). This substrate is finally phosphorylated and decarboxylated with concomitant loss of inorganic phosphate to give the five-carbon isoprenoid isopentenyl pyrophosphate (IPP). IPP is then isomerized to DMAPP by an isomerase. 

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