Eg character

We have followed a phenomenological approach and used the cluster model [18]. In this model the eg-type distortion interacts more strongly with the electronic state of an octahedral coordinated Cr3+ ion than the distortions of t2g symmetry. According to Ham [19], we assume that the continuum of vibrational modes with eg character can be approximated by a single mode with an effective frequency o>, mass /r and coupling constant V. The collective coordinates of the eg mode are conventionally known as Qe x2 — y2) and Qs ( 3z2 — r2). The linear Jahn-Teller Hamiltonian in equation (1) for the X state is [18] ... 

The (d/z/ + dz, ) orbital relevant to the threefold hollow species is preferentially filled by electrons due to a strong eg character. Then, the threefold fee and hep hollow site adsorption is suppressed by the s-d hybridization in the alloy. For CO adsorption a similar discussion is made using the dyy orbital instead of the (dyy + dz, ) orbital and the bridge site adsorption is also suppressed. It is emphasized that the characteristic properties of this alloy are represented by the global picture. 

Writing the state wavefunctions in equation (50a) as products of one-electron orbitals, e.g. ij/( Eg) = dn dK- dn dfs, leads to equation (50b). Equation (50b) is written in terms of the actual redox orbitals involved in electron transfer and is, therefore, in the same form as equation (17) for V. The result shown in equation (50b) gives only the contribution to V from mixing Eg character into the Co" ground state. Important contributions to V arising from mixing into the ground states of excited states on Co " and of other excited states on Co" also exist. ... 

Blending to increase the alcohol (or other component) or to impart a special character to other wines or even other products, eg, whiskey... 

Flavors are often used to create the impression of flavor where Httie or none exist, and they impart food products with a recognizable character. Some food products would not exist without the addition of flavorings, eg, soft drinks, water ices, confectionery, milk desserts, etc. Many food products need a specific flavor note to characterize them among other similar products of the same food category, eg, citms soft drinks, mint candies, gingerbread, yogurt, and cottage cheese. 

Several aspects affect the extent and character of taste and smell. People differ considerably in sensitivity and appreciation of smell and taste, and there is lack of a common language to describe smell and taste experiences. A hereditary or genetic factor may cause a variation between individual reactions, eg, phenylthiourea causes a bitter taste sensation which may not be perceptible to certain people whose general abiUty to distinguish other tastes is not noticeably impaired (17). The variation of pH in saUva, which acts as a buffer and the charge carrier for the depolarization of the taste cell, may influence the perception of acidity differently in people (15,18). Enzymes in saUva can cause rapid chemical changes in basic food ingredients, such as proteins and carbohydrates, with variable effects on the individual. 

Several manuals devoted, at least in part, to flavor formulation have been published (52—63), eg, literature from the Fragrance Materials Association of the United States, Washington, D.C. The increasing number of materials available has resulted in the improvement of flavor characteristics and has permitted a closer rendition of natural flavors. Often such materials bear a scant sensory relationship to the tme natural flavor character. When used as a component and judiciously applied, these materials serve a useful purpose in a properly compounded flavor. 

Cha.ra.cter Impa.ct Items. The character impact item is a chemical or blend of chemicals that provide the principal portion of a flavor s sensory identity, ie, when tasted and/or smelled, the item is reminiscent of the named character, eg, vanillin is the character impact item for vanilla flavors (Table 6). A character item for one flavor can contribute to another flavor in a different way, for example, ethyl oenanthate is a character item for the grape flavor of the Vinus vinifera type and is a contributor to the flavor of the concord grape, ie, the labmska-type grape. 

The polymer may be prepared ia high degrees of polymeriza tion (n > 1000) and has good solubiHty characteristics. It is an exceUent model system because many variables, eg, molecular weight, supporting solvent character, concentration, and temperature, may be easily controUed for study over wide ranges. 

This system of nomenclature has withstood the impact of later experimental discoveries and theoretical developments that have since the time of Guyton de Morveau and Lavoisier greatiy altered the character of chemical thought, eg, atomic theory (Dalton, 1802), the hydrogen theory of acids (Davy, 1809), the duahstic theory (Berzehus, 1811), polybasic acids (Liebig, 1834), Periodic Table (Mendeleev and Meyer, 1869), electrolytic dissociation theory (Arrhenius, 1887), and electronic theory and modem knowledge of molecular stmcture. 

Spice Family. This is an easily recognizable fragrance that has a strong, spicy character, eg. Old Spice (Shulton 1937). 

Very unstable modifications, like the reddish, chlorine-free a-copper phthalocyanine, can be stabilized with amides or salts of copper phthalocyanine sulfonic acids (59—63). Mixture with other metal phthalocyanines, eg, tin, vanadium, aluminum, or magnesium, also inhibits crystallization change and poor performance in binders and prints (flocculation) due to the hydrophobic character of unsubstituted phthalocyanines. 

Much work has been done on the structure of the metal alkoxides (49). The simple alkaU alkoxides have an ionic lattice and a layer stmcture, but alkaline earth alkoxides show more covalent character. The aluminum alkoxides have been thoroughly studied and there is no doubt as to their covalent nature the lower alkoxides are associated, even in solution and in the vapor phase. The degree of association depends on the bulkiness of the alkoxy group and can range from 2 to 4, eg, the freshly distilled isopropylate is trimeric (4) ... 

A variation of this procedure is used for sulfisomidine because of the different character of the amino group in the 4-position of a pyrimidine ring. Two moles of the sulfonyl chloride are condensed with one mole of 4-amino-2,6-dimethy1pyrimidine in the presence of triethylamine. The resulting bis(acetylsulfanilyl) derivative is readily hydrolyzed to the product. The formation of the bis(acetylsulfanilyl) derivative has also been employed for other heterocycHc amines, eg, for synthesis of sulfathiazole and sulfamoxole (44), but the 1 1 reaction is probably preferable. 

The tautomeric character of the pyrazolones is also illustrated by the mixture of products isolated after certain reactions. Thus alkylation normally takes place at C, but on occasion it is accompanied by alkylation on O and N. Similar problems can arise during acylation and carbamoylation reactions, which also favor C. Pyrazolones react with aldehydes and ketones at to form a carbon—carbon double bond, eg (41). Coupling takes place when pyrazolones react with diazonium salts to produce azo compounds, eg (42). 

The furnace process involves injecting low end fraction of cmde oil, eg. Bunker Euel C, into a heated chamber. The temperature, shape of the injectors of the oil, rate of injection, and other factors are controlled to produce black fillers of different particle si2e and stmcture. The particle si2e and stmcture control the reinforcing character of the carbon black. There are 30 common grades of carbon black used in the mbber industry. There are numerous specialty grades produced, and several hundred are used in plastic, conductive appHcations, and other uses. 

Addition of sodium dithionite to formaldehyde yields the sodium salt of hydroxymethanesulfinic acid [79-25-4] H0CH2S02Na, which retains the useful reducing character of the sodium dithionite although somewhat attenuated in reactivity. The most important organic chemistry of sodium dithionite involves its use in reducing dyes, eg, anthraquinone vat dyes, sulfur dyes, and indigo, to their soluble leuco forms (see Dyes, anthraquinone). Dithionite can reduce various chromophores that are not reduced by sulfite. Dithionite can be used for the reduction of aldehydes and ketones to alcohols (348). Quantitative studies have been made of the reduction potential of dithionite as a function of pH and the concentration of other salts (349,350). 

Because of the time and expense involved, biological assays are used primarily for research purposes. The first chemical method for assaying L-ascorbic acid was the titration with 2,6-dichlorophenolindophenol solution (76). This method is not appHcable in the presence of a variety of interfering substances, eg, reduced metal ions, sulfites, tannins, or colored dyes. This 2,6-dichlorophenolindophenol method and other chemical and physiochemical methods are based on the reducing character of L-ascorbic acid (77). Colorimetric reactions with metal ions as weU as other redox systems, eg, potassium hexacyanoferrate(III), methylene blue, chloramine, etc, have been used for the assay, but they are unspecific because of interferences from a large number of reducing substances contained in foods and natural products (78). These methods have been used extensively in fish research (79). A specific photometric method for the assay of vitamin C in biological samples is based on the oxidation of ascorbic acid to dehydroascorbic acid with 2,4-dinitrophenylhydrazine (80). In the microfluorometric method, ascorbic acid is oxidized to dehydroascorbic acid in the presence of charcoal. The oxidized form is reacted with o-phenylenediamine to produce a fluorescent compound that is detected with an excitation maximum of ca 350 nm and an emission maximum of ca 430 nm (81). 

The compositions of the conversion baths are proprietary and vary greatly. They may contain either hexavalent or trivalent chromium (179,180), but baths containing both Cr(III) and Cr(VI) are rare. The mechanism of film formation for hexavalent baths has been studied (181,182), and it appears that the strength of the acid and its identity, as well as time and temperature, influences the film s thickness and its final properties, eg, color. The newly prepared film is a very soft, easily damaged gel, but when allowed to age, the film slowly hardens, assumes a hydrophobic character and becomes resistant to abrasion. The film s stmcture can be described as a cross-linked Cr(III) polymer, that uses anion species to link chromium centers. These anions may be hydroxide, chromate, fluoride, and/or others, depending on the composition of the bath (183). 

The material was marketed as a fibre in 1968 jointly by the Japanese companies Unitika and Mitsubishi as A-Tell. The polymer is about 41% crystalline, and has a specific gravity of 1.34, a of 223°C and a Eg of 65°C. The fibres are somewhat silk-like in character. 

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