Rough stability

The mechanism of polystyrene and poly(methyl methacrylate) particle formation in the presence of PEO-MA macromonomer in the presence of conventional stabilizer (PVPo) and the graft copolymers (PSt-gra/f-PEO), respectively, was discussed [77]. At the beginning of dispersion polymerization (in methanol) of MMA (0-250 s) using PVPo, very small particles were formed (12-35 nm in diameter). The population of bigger particles was roughly stabilized at ca. 345 nm in diameter. In the dispersion polymerization of styrene, small particles... 

The first two groups compare a slow, mild stabilization (profile C) with a short, rather rough stabilization (profile A). Whereas the terpolymer AN/MA/VBr clearly... 

A number of refinements and applications are in the literature. Corrections may be made for discreteness of charge [36] or the excluded volume of the hydrated ions [19, 37]. The effects of surface roughness on the electrical double layer have been treated by several groups [38-41] by means of perturbative expansions and numerical analysis. Several geometries have been treated, including two eccentric spheres such as found in encapsulated proteins or drugs [42], and biconcave disks with elastic membranes to model red blood cells [43]. The double-layer repulsion between two spheres has been a topic of much attention due to its importance in colloidal stability. A new numeri-... 

It is helpful to consider qualitatively the numerical magnitude of the surface tensional stabilization of a particle at a liquid-liquid interface. For simplicity, we will assume 6 = 90°, or that 7sa = 7SB- Also, with respect to the interfacial areas, J sA = SB, since the particle will lie so as to be bisected by the plane of the liquid-liquid interface, and. AB = rcr - The free energy to displace the particle from its stable position will then be just trr 7AB- For a particle of l-mm radius, this would amount to about 1 erg, for Tab = 40 ergs/cm. This corresponds roughly to a restoring force of 10 dyn, since this work must be expended in moving the particle out of the interface, and this amounts to a displacement equal to the radius of the particle. 

Migratory aptitude roughly follows the ability of the group to stabilize positive charge ... 

The formation constants of EDTA complexes are gathered in Table 11.34. Based on their stability, the EDTA complexes of the most common metal ions may be roughly divided into three groups ... 

Plywood has essentiahy equal stability in both panel directions and is almost as stable as the parent wood in the direction of the wood grain. Strength properties in bending are roughly proportional in each panel direction to the amount of wood in those layers closest to the surface which are parahel to the wood grain direction. Thus as the number of phes increases, these bending properties become more equalized in both panel directions. 

Pyrotechnics have been used for military purposes for many centuries as propellants, explosive charges, time fuses, and for illumination. There are still many uses of pyrotechnic devices in military appHcations, where they provide portability, storage stability, simplicity of operation, safety, and the reUability required for military scenarios. The devices must be capable of surviving rough handling, weather extremes, and extended storage, yet reUably perform when called on to function. 

Owing to the stability of the uranyl carbonate complex, uranium is universally present in seawater at an average concentration of ca. 3.2/rgL with a daughter/parent activity ratio U) of 1.14. " In particulate matter and bottom sediments that are roughly 1 x 10 " years old, the ratio should approach unity (secular equilibrium). The principal source of dissolved uranium to the ocean is from physicochemical weathering on the continents and subsequent transport by rivers. Potentially significant oceanic U sinks include anoxic basins, organic rich sediments, phosphorites and oceanic basalts, metalliferous sediments, carbonate sediments, and saltwater marshes. " ... 

A study of the lithium-ammonia reduction of 14-en-16-ones would extend our understanding of the configuration favored at C-14 in metal-ammonia reductions. Although several simple 14-en-16-ones are known, their reduction by lithium and ammonia apparently has not been described in the literature. Lithium-ammonia reduction of A-nortestosterone, a compound that structurally is somewhat analogous to a 14-en-16-one, affords roughly equal amounts of the 5a- and 5 -dihydro-A-nortestosterones. " This finding was interpreted as indicating that there is little difference in thermodynamic stability between the two stereoisomeric products. 

Suppose we have a physical system with small rigid particles immersed in an atomic solvent. We assume that the densities of the solvent and the colloid material are roughly equal. Then the particles will not settle to the bottom of their container due to gravity. As theorists, we have to model the interactions present in the system. The obvious interaction is the excluded-volume effect caused by the finite volume of the particles. Experimental realizations are suspensions of sterically stabilized PMMA particles, (Fig. 4). Formally, the interaction potential can be written as... 

This is the general linear equation of motion for an almost planar and rough one-dimensional phase boundary. The fourth-order term in the spatial derivative acts as a stabilizer just like the second-order term, and is not really crucial here. 

The Self-Consistent Reaction Field (SCRF) model considers the solvent as a uniform polarizable medium with a dielectric constant of s, with the solute M placed in a suitable shaped hole in the medium. Creation of a cavity in the medium costs energy, i.e. this is a destabilization, while dispersion interactions between the solvent and solute add a stabilization (this is roughly the van der Waals energy between solvent and solute). The electric charge distribution of M will furthermore polarize the medium (induce charge moments), which in turn acts back on the molecule, thereby producing an electrostatic stabilization. The solvation (free) energy may thus be written as... 

Two independent molecular orbital calculations (HMO method) of delocalization energies for isoindole and isoindolenine tautomers agree that the isoindole form should possess the more resonance stabilization. The actual difference calculated for isoindole-isoindolenine is about 8 kcal/mole, but increases in favor of the isoindole with phenyl substitution at position 1 (Table VI).Since isoindole and isoindolenine tautomers have roughly comparable thermodynamic stabilities, the tautomeric proce.ss is readily obser-... 

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