Mechanics Dependency

Molecular mechanics depends on the concept of atom types and parameters associated with these atom types. Since the number of atom types is very large for the universe of possible molecules, parameters will probably be missing for a random new molecule unless a force field has been developed for molecules similar to the new molecule. Molecular mechanics predicts how the new molecule will behave based upon the behavior of known, similar molecules. 

Flow meters have traditionally been classified as either electrical or mechanical depending on the nature of the output signal, power requirements, or both. However, improvement in electrical transducer technology has blurred the distinction between these categories. Many flow meters previously classified as mechanical are now used with electrical transducers. Some common examples are the electrical shaft encoders on positive displacement meters, the electrical (strain) sensing of differential pressure, and the ultrasonic sensing of weir or flume levels. 

The oxidation of vitreous siUca appears to proceed by one of two mechanisms, depending on the material s hydroxyl content (109,111). In hydroxyl-containing material, the rapid oxidation probably occurs by the diffusion and removal of hydrogen, according to the following reaction ... 

Although most nonionic organic chemicals are subject to low energy bonding mechanisms, sorption of phenyl- and other substituted-urea pesticides such as diuron to sod or sod components has been attributed to a variety of mechanisms, depending on the sorbent. The mechanisms include hydrophobic interactions, cation bridging, van der Waals forces, and charge-transfer complexes. 

Materials may be absorbed by a variety of mechanisms. Depending on the nature of the material and the site of absorption, there may be passive diffusion, filtration processes, faciHtated diffusion, active transport and the formation of microvesicles for the cell membrane (pinocytosis) (61). EoUowing absorption, materials are transported in the circulation either free or bound to constituents such as plasma proteins or blood cells. The degree of binding of the absorbed material may influence the availabiHty of the material to tissue, or limit its elimination from the body (excretion). After passing from plasma to tissues, materials may have a variety of effects and fates, including no effect on the tissue, production of injury, biochemical conversion (metaboli2ed or biotransformed), or excretion (eg, from liver and kidney). 

The efficiency of the vegetable matter (burr and seeds) removal mechanism depends on the carefiil maintenance of settings and speeds and the level of drying of the scouted wool (86). The butt wastes contain wool fiber. Butt, together with fiber which has dropped beneath the card, may be carbonized and used in the woolen system. 

Alkyl-substituted alkynes can react by either the Adg3 or the Adg2 mechanism. The Adg3 mechanism leads to and addition. The preference for one or the other mechanism depends on the individual stmcture and the reaction conditions. Added CP promotes the Adg3 mechanism and increases the overall rate of reaction. 

The relative importance of the potential catalytic mechanisms depends on pH, which also determines the concentration of the other participating species such as water, hydronium ion, and hydroxide ion. At low pH, the general acid catalysis mechanism dominates, and comparison with analogous systems in which the intramolecular proton transfer is not available suggests that the intramolecular catalysis results in a 25- to 100-fold rate enhancement At neutral pH, the intramolecular general base catalysis mechanism begins to operate. It is estimated that the catalytic effect for this mechanism is a factor of about 10. Although the nucleophilic catalysis mechanism was not observed in the parent compound, it occurred in certain substituted derivatives. 

Direct bonding. In many high-volume production applications (i.e., the automotive and appliance industries), elaborate surface preparation of steel ad-herends is undesirable or impossible. Thus, there has been widespread interest in bonding directly to steel coil surfaces that contain various protective oils [55,56,113-116], Debski et al. proposed that epoxy adhesives, particularly those curing at high temperatures, could form suitable bonds to oily steel surfaces by two mechanisms (1) thermodynamic displacement of the oil from the steel surface, and (2) absorption of the oil into the bulk adhesives [55,56]. The relative importance of these two mechanisms depends on the polarity of the oil and the surface area/volume ratio of the adhesive (which can be affected by adherend surface roughness). 

The reaction mechanism depends on the chemistry of the active oxidant and chemical contaminants. Multiple sequential and parallel reaction steps occur frequently. Partial oxidation produces noxious byproducts. 

Decarburization results from hydrogen absorption from gas streams at elevated temperatures. In addition to hydrogen blistering, hydrogen can remove carbon from alloys. The particular mechanism depends to a large extent on the properties of other gases present. Removal of carbon causes the metal to lose strength and fail. 

Inhaled gaseous compounds are absorbed in all parts of the respiratory system whereas particle size determines how deep into the airways the parti cles will he transported in the airstrearn. Shortness of breath is a typical sign of a chemical exposure that has affected the lungs, and it may be evoked through iminunological mechanisms (e.g., formaldehyde, ethyleneoxide), or through toxic irritation (formaldehyde, isocyanates, sulfur dioxide, nitrogen dioxide, Frequently the mechanism depends on the concentration ol the com... 

The greater the contribution of 4 to the transition state, the more firmly the system is placed in the N category likewise a large contribution from 5 is characteristic of the Lim category. Bentley and Schleyer state that the essential difference between the SnI and Sn2 mechanisms depends upon whether nucleophilic attack... 

The comparison of fractions of these mechanisms is possible only at comparable deformation conditions, for instance for the optimum strain rate (10 - 10 s" ). The share of the gbs mechanism depending on strain rate, grain size and shape has a maximum for the middle... 

Acid-catalyzed ester hydrolysis can occur by more than one mechanism, depending on the structure of the ester. The usual pathway, however, is just the reverse of a Fischer esterification reaction (Section 21.3). The ester is first activated toward nucleophilic attack by protonation of the carboxyl oxygen atom, and nucleophilic addition of water then occurs. Transfer of a proton and elimination of alcohol yields the carboxylic acid (Figure 21.8). Because this hydrolysis reaction is the reverse of a Fischer esterification reaction, Figure 21.8 is the reverse of Figure 21.4. 

Thermal properties and decomposition mechanisms depend on the crystal structure type. Compounds with a crystal structure that includes shared octahedrons decompose forming tantalum- or niobium-containing gaseous components, while island-type compounds release light atoms and molecules into the gaseous phase. 

Problems of short-term and long-term overheating, which leads to fatigue and metal failure, also are associated with deposition on boiler surfaces and restricted BW flow—the particular mechanisms depend on the nature and quantity of the waterside deposits formed. 

The removal of organics by industrial detergent cleaners. These products employ several mechanisms, depending on the formulation, but tend to include dissolution (using nonaqueous solvents such as kerosene, petroleum spirits, and naphtha, saponification, by caustic, or emulsification by nonionic detergents. 

The kinetics of protodeboronation are rather complex, probably due to the occurrence of more than one reaction mechanism depending to some extent on the medium involved. Much of the work has been devoted to showing that a linear log rate versus H0 plot does not mean that the A-l mechanism applies. 

How deeply one wishes to query the mechanism depends on the detail sought. In one sense, the quest is never done a finer and finer resolution of the mechanism may be obtained with further study. For example, the rates and mechanisms of electron transfer reactions have been studied experimentally and theoretically since the 1950s. but the research continues unabated as issues of ever finer detail and broader import are examined. The same can be said of other reactions—nucleophilic substitution, hydrolysis, etc. 

An interesting feature of the ring opening polymerization of siloxanes is their ability to proceed via either anionic or cationic mechanisms depending on the type of the catalyst employed. In the anionic polymerization alkali metal hydroxides, quaternary ammonium (I NOH) and phosphonium (R POH) bases and siloxanolates (Si—Oe M ) are the most widely used catalysts 1,2-4). They are usually employed at a level of 10 2 to KT4 weight percent depending on their activities and the reaction conditions. The activity of alkali metal hydroxides and siloxanolates decrease in the following order 76 79,126). 

Ionic polymerisation is subdivided into cationic and anionic mechanisms depending on the charge developed in the growing polymer molecule. Typical catalysts for the former, the cationic polymerisation process, are Lewis acids such as AICI3 or BFj, which often require a co-catalyst, usually a Lewis base, in order to bring about polymerisation. 

The results presented in this review concern this metal-catalyzed mechanism. Depending on the nature, anionic or neutral, of the different nucleophiles, the result of the arylation can be a neutral substitution product or a cationic one, which most often, in the last case, undergoes an evolution, for example (starting form a phosphite) to a phosphonate or, after deprotonation, to an arylamine or to an arylether (Fig. 2). 

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