Chain-type

In order to represent 3D molecular models it is necessary to supply structure files with 3D information (e.g., pdb, xyz, df, mol, etc.. If structures from a structure editor are used directly, the files do not normally include 3D data. Indusion of such data can be achieved only via 3D structure generators, force-field calculations, etc. 3D structures can then be represented in various display modes, e.g., wire frame, balls and sticks, space-filling (see Section 2.11). Proteins are visualized by various representations of helices, / -strains, or tertiary structures. An additional feature is the ability to color the atoms according to subunits, temperature, or chain types. During all such operations the molecule can be interactively moved, rotated, or zoomed by the user. 

A screw conveyor was used originally to convey the cake, but this has been replaced with a chain-type conveyor. The first prototype used a tapered screw to form a plug before discharge into atmospheric pressure this has been replaced by compaction in a vertical pipe. 

Chemical Factors. Because knock is caused by chemical reactions in the engine, it is reasonable to assume that chemical stmcture plays an important role in determining the resistance of a particular compound to knock. Reactions that produce knock are generally free-radical chain-type reactions which are different from those that occur in the body of the flame the former occur at lower temperatures and are called cool flame reactions. 

Calcium—Silicon. Calcium—silicon and calcium—barium—siUcon are made in the submerged-arc electric furnace by carbon reduction of lime, sihca rock, and barites. Commercial calcium—silicon contains 28—32% calcium, 60—65% siUcon, and 3% iron (max). Barium-bearing alloys contains 16—20% calcium, 9—12% barium, and 53—59% sihcon. Calcium can also be added as an ahoy containing 10—13% calcium, 14—18% barium, 19—21% aluminum, and 38—40% shicon These ahoys are used to deoxidize and degasify steel. They produce complex calcium shicate inclusions that are minimally harm fill to physical properties and prevent the formation of alumina-type inclusions, a principal source of fatigue failure in highly stressed ahoy steels. As a sulfide former, they promote random distribution of sulfides, thereby minimizing chain-type inclusions. In cast iron, they are used as an inoculant. 

Other Chain-Type Conveyors. A number of drivea chaia coaveyors are used for coaveyiag bulk soflds ia horizoatal or inclined paths. 

Chain-type elevators, such as arm and tray units, are commonly used for drums and barrels. Shght gravity runs at feed and discharge allow these units to roll on and off the conveyor easily and without special equipment. 

As an over-all conclusion, it can be stated that the assumption of ring-chain tautomerism in the pseudo bases derived from the heterocyclic quaternary ammonium salts is quite unnecessary as an explanation of the formation of two (cyclic and open-chain) types of deriva-... 

If (P ) is terminated by a chain transfer to a solvent or a monomer, a graft copolymer is formed, or, if the termination is from a combination, a crosslinked network polymer is formed. If the pre-existing polymer (B) contains an end group that itself is photosensitive (or can produce a radical by interacting with photoinitiator) and in the presence of a vinyl monomer (A), block copolymer of type AB can be produced if the photosensitive group is on one end of the polymeric chain. Type ABA block copolymer can be produced if the polymer chain (B) contains a photosensitive group on both ends. 

Some of these are shown in Figure 3-26. Because most modern power transmissions use roller chains, silent chains or the offset link (Ewart) chains, these will be the only chain types discussed since they are quite important in oil field applications. 

There are design considerations for the various chain power transmission applications that are common to nearly all chain types [8]. These are discussed in the following. 

Crystal chemistry of Ta and Nb fluorides - Compounds with chain-type structures... 

Since the coordination number of tantalum or niobium in fluoride and oxyfluoride compounds cannot be lower than 6 due to steric limitations, further decrease of the X Me ratio (lower than 6) leads to linkage between complex ions in order to achieve coordination saturation by sharing of ligands between different central atoms of the complexes. The resulting compounds have X Me ratios between 6 and 4, and form crystals with a chain-type structure. 

Typical chain-type crystal structure is observed for compounds with the general formula MNbOF4. Table 30 presents cell parameters of tantalum and niobium pentafluorides and of other compounds with X Me = 5. 

Sharing of an oxygen atom by two central atoms in compounds with chain-type structures weakens the binary Nb=0 bond compared to the corresponding bond in pure isolated ions such as NbOF52 This phenomenon affects the vibration spectra and increases wave numbers of NbO vibrations in the case of isolated oxyfluoride complex ions. Table 31 displays IR absorption spectra of some chain- type compounds. Raman spectra are discussed in [212],... 

Table 31. Wave numbers (cm1) of IR absorption spectra of chain-type compounds (Me = Nb or Ta).

Crystal chemistry ofTa and Nb fluorides — Compounds with chain-type structures 91... 

NH4NbOF4 Infinite chains of octahedrons -Nb02F43 MNbOF4 (M=K, Rb, Cs) refers also to a chain-type structure. 

The thermal decomposition of alkali metal oxyfluoroniobates is also not a trivial process. MNbOF4 compounds (where M = alkali metal) with a chain-type structure are relatively stable up to temperatures in the range of 500-600°C. Fig. 90 presents mass loss dependences on temperature of several MNbOF4 compounds. As can be seen, among the compounds presented, only CsNbOF4 exhibits significantly different behavior, beginning its thermal decomposition at a lower temperature of about 400°C. 

Fig. 90. Mass loss temperature dependences for compounds with chain-type structure - MNbOF4, where M — Li (curve 1) Na (curve 2) K (curve 3) Rb (curve 4) Cs (curve 5) (after Agulyansky et al. [379]).

Thus, it is possible to make a very important assumption that chain-type compounds decompose forming gaseous niobium-containing components, while island-type compounds release upon thermal decomposition only light atoms and molecules into the gaseous phase [383]. 

It seems that structural irregularities that cause spontaneous polarization are a relatively common property of niobium and tantalum oxyfluoride crystals. Fig. 100 shows the temperature dependence of SHG signals for several compounds that form island-type and chain-type structures. 

The crystal structure of MsM OF compounds, where M = NH4, K, Rb, is made up of infinite chains of oxyfluoroniobate octahedrons that are similar to MNbOF4 chain-type compounds. Infinite chains are separated by isolated complexes NbFy2, whose structure is similar to that found in the island-type compound K2NbF7. The structure of the M5Nb30Fi8 compounds was described and discussed in Chapter 3.2. Due to the separation of the chains, the displacement of the niobium ion is in the same direction in all chains. The above displacement leads to a spontaneous polarization value that is as high as 4-5 pC/cm2. 

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