Bulk Effects

This Section examines the dielectric and conduction mechanisms in bulk materials, assuming that the medium is linear (at the applied electric field strength) and homogeneous. Effects of interfaces and inhomogeneities are discussed in Section 3.2. Additional discussion can be found in basic texts 21 23). 

---

Criticize or defend the following proposition In dilute solutions, branching affects viscosity only inasmuch as the branched molecule has a more compact shape. At higher concentrations, the effect of branching is closer to a bulk effect. 

For the bulk effect we elect to proceed on the basis of a unit volume (superscript V) and immediately write... 

Bulking sweeteners provide a bulking effect, along with some of the sweetness and functional properties of sugar. They may be used alone to replace sugar in appHcations that can tolerate some reduction in sweetness. Products that fall into this category include mannitol [69-65-8], a sugar alcohol... 

The energy release rate (G) represents adherence and is attributed to a multiplicative combination of interfacial and bulk effects. The interface contributions to the overall adherence are captured by the adhesion energy (Go), which is assumed to be rate-independent and equal to the thermodynamic work of adhesion (IVa)-Additional dissipation occurring within the elastomer is contained in the bulk viscoelastic loss function 0, which is dependent on the crack growth velocity (v) and on temperature (T). The function 0 is therefore substrate surface independent, but test geometry dependent. 

Any real sample of a colloidal suspension has boundaries. These may stem from the walls of the container holding the suspension or from a free interface towards the surroundings. One is faced with surface effects that are small compared to volume effects. But there are also situations where surface effects are comparable to bulk effects because of strong confinement of the suspension. Examples are cylindrical pores (Fig. 8), porous media filled with suspension (Fig. 9), and thin colloidal films squeezed between parallel plates (Fig. 10). Confined systems show physical effects absent in the bulk behavior of the system and absent in the limit of extreme confinement, e.g., a onedimensional system is built up by shrinking the size of a cylindrical pore to the particle diameter. 

Bulk effects of the aqueous solvent have been evaluated by C-PCM solvation model. The specific effect of the solvation on the alkylation pathways has also been... 

The bulk effect of water as a solvent is rather dramatic since it causes a drastic reduction of the nucleophilicity of 9-methyladenine N1 and even more of 9-methylguanine 06. As a result, there is a reversal of the nucleophilicity order of the purine bases passing from gas phase to aqueous solution. In fact, in solution, methyladenine is more nucleophilic than methylguanine. Moreover, oxygen and N7 nucleophilic centers of 9-methylguanine compete almost on the same footing in solution (Table 2.2) and also the reactivity gap between N1 and N7 of 9-methyladenine is highly reduced in comparison to the gas phase. 

Use of the relatively small cyclopropane ring drastically reduces the potential for deleterious steric bulk effects and adds only a relatively small lipophilic increment to the partition coefficient of the drug. One of the clever elements of the rolicyprine synthesis itself is the reaction of d,l tranylcypromine (67) with L-5-pyrrolidone-2-carboxylic acid (derived from glutamic acid) to form a highly crystalline diastereomeric salt, thereby effecting resolution. Addition of dicyclohexylcarbodiimide activates the carboxyl group to nucleophilic attack by the primary amine thus forming the amide rolicyprine (68). 

The use of mesitoate esters in the elucidation of reaction mechanisms has been pioneered by Burrows and Topping (1969,1970). This system has been used to suppress the competitive intermolecular reaction by steric bulk effects and to detect participation by the identification of the products formed. Under identical conditions (pH 11.28 at 30°C in 9.5% ethanol-water), 2-acetylphenyl mesitoate [41]is hydrolysed 130 times more readily than 4-acetylphenyl mesitoate, clearly indicating intramolecular catalysis. However, the products of hydrolysis provided no clue to the mechanism of... 

Next, when a stable base line was achieved in 13 min, a concentration of 200 ig/ml solution of a-HSA in PBS was flowed in channel 1 for 30 min, and the flow was changed back to PBS buffer solution to correct for the bulk effect of a-HSA. Binding of a-HSA resulted in a phase change of 12 x 2k, which corresponds to a mass coverage of 3.1 mg/m2. Next, after the buffer solution was flowed for 10 min until a stable signal was achieved, a solution of 50 pg/ml HSA prepared in PBS was applied. Finally, the flow in channel 1 was changed back to PBS solution and... 

For a more detailed analysis of measured transport restrictions and reaction kinetics, a more complex reactor simulation tool developed at Haldor Topsoe was used. The model used for sulphuric acid catalyst assumes plug flow and integrates differential mass and heat balances through the reactor length [16], The bulk effectiveness factor for the catalyst pellets is determined by solution of differential equations for catalytic reaction coupled with mass and heat transport through the porous catalyst pellet and with a film model for external transport restrictions. The model was used both for optimization of particle size and development of intrinsic rate expressions. Even more complex models including radial profiles or dynamic terms may also be used when appropriate. 

The most common cause of it is the neglect of 3-dimensional effects as compared with those in two dimensions. Thus, all stresses in a loaded wire or ribbon are disregarded in the shrinkage method, Section III. 1. The work of deformation leading to rupture is a bulk effect which does not receive its due consideration in the calculation of fracture energy, Section III.3. Bulk deformations associated with thermal etching, Section III.4, demand more attention than was alloted to them by many scientists. The method of bubbles, Section III.5, is invalid both because of the above neglect (that is, that of the volume stresses around the bubble) and because of another popular error, namely an erroneous treatment of capillary pressure Pc. 

The first reported study of a reaction of wood with an epoxide appears to be that of McMillan (1963). This involved the use of gaseous ethylene oxide (Figure 4.9, R=H) at a temperature of 93 °C and a pressure of 3 atmospheres (0.3 MPa). In some cases, the wood was diffusion pre-treated with trimethylamine vapour as the catalyst. A 65 % ASE at 20 % WPG was obtained, attributed to a bulking effect due to in situ polymerization of the epoxide. There was no effect on the static bending strength of samples, and the modified wood became distinctly brown at higher levels of treatment. 

Fig. 10.4 Impedance diagrams for a non-blocking interface when (a) bulk effects are neglected (b) bulk effects are taken into account. The impedance diagrams are different if diffusional effects are significant.

ALIS reports only compounds that bind directly to the target of interest, preventing false positives that arise from off-target activity or interactions with substrates or other reagents. Since ALIS directly identifies bound components by MS, the incidence of false positives based on bulk effects and non-specific binding is lower than that of biochemical assays that yield a secondary readout of activity. 

Notwithstanding the natural heterogeneity of the subsurface, we can usefully consider homogeneous (bulk, effective) descriptions for at least some problems, especially for water flow (but less so for contaminant migration see Sect. 10.1). Therefore, two basic approaches to modeling generally are used to describe and quantify flow and transport continuum-based models and pore-network models. We discuss each of these here. 

This type of interaction is not restricted to one dimension, as indicated in the formulation. The bonds between AsCls and SeOa would be much weaker if the amphoteric properties of the molecules were less well developed. This is analogous to bulk effects in solutions and solvate structures involving amphoteric molecules. 

It may be convenient to consider the entire system to be confined within a very large container having inpenetrable walls if realistic equilibrium of vapour and condensed phases is important. In cases of immediate interest, the true vapour phase is not an essential feature and the relatively small volume occupied by the condensed phase is the more important thermodynamical variable. There are still subtleties associated with taking the thermodynamic limit, particularly when isolating surface and bulk effects, but the problems with vanishing density of particles can be controlled. 

Thermal Polymerization of Styrene in Bulk (Effect of Temperature)... 

The dilution buffer solutions and SPR running buffer must be the same. The lot of buffer should not be changed during the single experiment. Slight component difference of the buffers affect SPR signals, it is so-called bulk effect. ... 

The total interaction between the two metal spheres can therefore be classified into two parts (1) the surface, or double-layer, interaction determined by the Gouy-Chapman potential t f0e"Krand (2) the volume, or bulk, interaction —Ar-6 + Br 12. The interaction between double layers ranges from indifference at large distances to increasing repulsion as the particles approach. The bulk interaction leads to an attraction unless the spheres get too close, when there is a sharp repulsion (Fig. 6.131). The total interaction energy depends on the interplay of the surface (double layer) and volume (bulk) effects and may be represented thus... 

Despite limitations, the most common sorption medium is activated charcoal — a form of carbon treated in such a way as to open a large number of pores. The surface energy of the material and the pores combine to produce a material that can first attract and then trap small organic molecules. The attraction is via adsorption rather than absorption. Adsorption applies to attachment to the surface absorption is a bulk effect. Extraction is a bulk phenomenon. Simply put, adsorption is a function of surface area while absorption is a mass effect. 

---