Early Additivity Studies

The recent interest in substituted silane polymers has resulted in a number of theoretical (15-19) and spectroscopic (19-21) studies. Most of the theoretical studies have assumed an all-trans planar zig-zag backbone conformation for computational simplicity. However, early PES studies of a number of short chain silicon catenates strongly suggested that the electronic properties may also depend on the conformation of the silicon backbone (22). This was recently confirmed by spectroscopic studies of poly(di-n-hexylsilane) in the solid state (23-26). Complementary studies in solution have suggested that conformational changes in the polysilane backbone may also be responsible for the unusual thermochromic behavior of many derivatives (27,28). In order to avoid the additional complexities associated with this thermochromism and possible aggregation effects at low temperatures, we have limited this report to polymer solutions at room temperature. 

The above results justify a simple ligand field model for the bis(ligand) metal species which is based on the assumption of pseudoaxial symmetry (40). This model allowed a consistent reinterpretation of an early ESR study of Co(C5H5BPh)2 (13) (42) the reinterpretation was later confirmed by additional and more sophisticated ESR work on 13 (43,44). 

It was recognized very early that diffuse reflectance spectroscopy could be used to study the interactions of various compounds in a formulation, and the technique has been particularly useful in the characterization of solid state reactions [24]. Lach concluded that diffuse reflectance spectroscopy could also be used to verify the potency of a drug in its formulation. In addition, studies conducted under stress conditions would be useful in the study of drug-excipient interactions, drug degradation pathways, and alterations in bioavailability owing to chemisorption of the drug onto other components in the formulation [24]. 

Atomic force microscopy (AFM) can be used to obtain high-resolution imagery of molecular orientation and ordering for materials adsorbed onto substrates. Early AFM studies on gluconamides were hampered by the tendency of the fibers to unravel on substrates forming bilayer sheets.41 These layers showed the head-to-tail packing of a monolayer which is similar to the crystal structure reported for anhydrous gluconamides.38 A procedure to retain the fiber networks on surfaces with the addition of a small fraction of... 

The status quo provided by the early mechanistic studies described above was incomplete in several respects. Although the affinity of the solvate complex for dihydrogen was known to be low, the addition product remained uncharacterized. Likewise, the putative H2 addition intermediate between the enamide complex and the transient, but observable, alkylhydride had not been characterized. 

In addition, NSE measurements have allowed confirmation of the relation between non-Debye behaviour and Q-dispersion of r eif (Eq. 4.11) proposed from the early BS studies of Sseif(Q,t) [148]. Figure 4.14b displays for PIB the characteristic times determined from the NSE experiments. The law pro-... 

Etherton studied the growth and nucleation kinetics of gypsum crystallization from simulated stack gas liquor using a one-liter seeded mininucleator with a Mixed Suspension Mixed Product Removal (MSMPR) configuration for the fines created by the retained parent seed. The effect of pH and chemical additives on crystallization kinetics of gypsum was measured. This early fundamental study has been the basis for later CSD studies. 

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