Hardness bonding

As a rule, though, these MC models deal instead with hard bonds between the nearest neighbor monomers in a chain. 

Figure 8. Comparison of Number of Bonds per Bead for a) Original Wyodak Coal (initial crosslinks = 290, initial extract yield = 7.4%, oligomer length = 10 and hard bonds = 200) and c) Modified Wyodak Coal (initial crosslinks = 600, initial extract yield = 21.5%, oligomer length = 4 and hard bonds = 0). b and d Compare the Fluid Fraction and Extract Yield for Original Wyodak Coal and Modified Wyodak Coal, Respectively.

The driving force for this migration was proposed to be the more favorable formation of a covalent O—Li (hard-hard) bond than that of a C—Li (soft-hard) bond389,395. 

Fig. 9.8 Comparison of relative ligand dissociation energies for Mn and Co. Zero points for the scales have been arbitrarily chosen. Note that for the. wfi ligands, MeSH, HCN, EtSH. and Me2S, the data points lie above and to the left of those for the oxygen bases. This indicates relatively stronger hard-hard bonding (0—Mn ) or soft-soft bonding (S—Co ), or both. [Modified from Jones. R. W. Staley. R. H. J. Phys. Chem. 1982. 86, 1387. Reproduced with permission.]...

Impedance to gas flow is the result of heavy fouling on tubes in the convective section. Problems of this type are most likely to occur with coals having high sodium contents, such as those found in low rank coal deposits in Western U.S. seams. Hard, bonded deposits can occur which are resistant to removal by the retractable sootblowers. 

While the alkaline metals hardly bond in proteins and the alkaline earth metals do so in a proportion of 50% or slightly less, the trace elements do so almost completely. Zinc is... 

Damp crystalline materials that cake as a mass when they dry out, products that develop hard bonds with age, and materials that compact to a firm bed under pressure, cause the material in the clearance layer to form a firm, unyielding boundary to the sweep of a feeder screw. In further use fine particles tend to trap in any minor gap formed as the flight rotates, either to build up the layer of the static bed, or to exert a binding force on the flight tip. 

Mixed disulfides are obtained when sulfenate esters are treated with trialkyl-thioboranes (9). This reaction is very efficient because the sulfenates contain an unstable soft-hard bond. 

Scale results from crystalline precipitation on metal surfaces with die formation of a hard bonded crust. 

Rubber/cement (RC) failures indicate that the weakest point in the bonded part is at the interface between the rubber and adhesive. These failures are characterised by a relatively glossy and hard bonded surface with little or no rubber present. Common causes of RC failure are the incorrect choice of adhesive, insufficient dry film thickness of adhesive, failure to properly agitate the adhesive to achieve a uniform dispersion prior to application, pre-cure of adhesive caused by excessive dwell time in the mould cavity before introducing rubber, low mould pressure, undercure of the part, migration of plasticisers and other ingredients from the body of the rubber to the rubber/adhesive interface or contamination of the surface of the adhesive coated part. 

From now on, the molecular systems are recognized as hard and soft acids and bases (HSAB), in the sense that each molecule can be seen as hard-hard, soft-soft, hard-soft or soft-hard bonding combinations between acids and bases. The associate HSAB principle of chemical reactivity was formulated as well, providing that hard acids prefer hard bases and soft acids prefer soft bases (Drago Kabler, 1972 Pearson, 1972 Chattaraj etal., 1991) ... 

From the point of view of the values that Y acquire, two main states of bonding may be revealed. One is quantified by the values Y e[0,l], in which case the equihbrium in h-s reaction is departed to its right side however, as Y closely tends to 1, as the hard-hard bond is more favorable to the soft-hard state of adducts h h s h, ot rjl rj S/rj). 

This form may be easily assimilated to both a conservation principle (of chemical bond from adducts) and a probabilistic equation. In fact, one can interpret the chemical bond formation by the competition between the hard-soft and maximum hardness (hard-hard) bonding probabilities. The probability character is crucial to certify the quantum character of the chemical hardness involved in bonding, not only phenomenological but also analytically. Moreover, since the hard-soft term S rf) basically express the emerging HSAB principle and Y values associates with MH quantum effects, the unified chemical hardness of bonding equation may be formulated as (Putz, 2008c) ... 

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