Surface Factors

G, = surface factor, noted with the McNelly equation cited earlier... 

We will assiune a spherical shape factor and use the latter of the two equations. Since the first part of Ap.2.4. is the volume factor while the last part is the surface factor, we can do this with some justification. For a spherical nucleus, i.e.- Ap.2.5., we get ... 

Mechanically initiated reactions can be used to create thermally stable polymer films. Such films form on various surface factors. They are very dense, although amorphous (Simonescu et al. 1983). The films are thermally and frictionally more stable than the thermally stable polymers obtained by conventional methods (Krasnov et al. 2002). The discussed case of polymerization can be of interest if amorphous polymers with moderate molecular weights are needed. 

That the adsorbate resides on the adsorbent surface with a structure similar to a plane of molecules within the bulk liquid, as depicted in Fig. 6.1, is a simplified view of the real situation on surfaces. Factors that make this model and therefore equation (6.2) of limited value include the following. 

To overcome this difficulty, Kraus and Janzen 16) suggested a correction by a surface factor. Thus, for a property P of a composite, a would be given by the relation ... 

However, in our experimental set up for rat in situ experiments, we measure the concentration versus time evolution reflecting the disappearance of the drug from the lumen because of the absorption process. From the absorption rate constants values obtained, permeabilities are calculated using the area/volume ratio. For this calculation we actually use the surface area of the geometrical cylinder (A) instead of the actual surface area available due to Kerkring s fold, villi and microvilli (A x Sf, where A is the surface of the geometrical cylinder and Sf is the increase surface factor due to folds and villi). Accordingly, as we use an estimation of the intestinal surface area that is lower than the real value, the experimental permeability value in rat is overestimated (i.e. already includes Sjj. 

Shape Coefficients and Shape Factors There are various types of shape factors, the majority based on statistical considerations. In essence this translates to the use of shape factors that do refer not to the shape of an individual particle but rather to the average shape of all the particles in a mass of powder. However, a method developed by Hausner [38] that uses three factors—elongation factor, bulkiness factor, and surface factor—may be used to characterize the shape of individual particles (Table 5). 

Passive Active soluble factors Active cell-surface factors... 

Biofilm development is affected by both physical and chemical factors. The abundance and condition of bacteria in the water column plays a major role in initial rate of settlement on a surface 181]. Surface factors such as wettability [82] and critical surface tension [83], surface hydrophobicity [84], fluid dynamic forces [85], shear stress [86], electrolyte concentration [87] and metabolic inhibitors [88] can all affect microbial attachment, adhesion or growth. The low surface energy of a gorgonian octocoral has been implicated as a passive fouling resistance mechanism used in conjunction with other antifouling defences [82]. 

Note that the double bonds are considered simple with respect to their contribution to the surface factor. 

Martin et a , have shown that a volume factor, Ov, and a surface factor, a, can be assigned as a correction factor to the chosen statistical diameter, d, of the irregular particle of interest when estimating its volume and surface (36). One can then write the surface area and volume as ... 

The volume and surface factor can also be used in the specific surface (5w) equation, when is of interest. Therefore, for 1 g compound, the volume and surface equation can be written as ... 

Example 6. Calculate the volume, surface factor and specific surface for a perfect sphere with density of l.Og/cm and surface-volume mean diameter of 100pm. 

Since the statistical diameter, d, chosen for a perfect sphere is equal to dy and d the volume and surface factor are ... 

Another semiempirical PCM formulation has been presented by Rauhut et al. (1993). They use a marching-cube algorithm to define tesserae (Lorensen and Cline, 1987). The flat mesh thus obtained is then projected on a van der Waals surface (factor Z =1.15). These authors point out that the full NDDO (Neglect of Diatomic Differential Overlap) expression of the (xm VBf xJ elements is convenient in order to have good results, when combined with the original PCM procedure for the surface charge renormalization. 

Literature presents numerous data on the syntheses by ML method of oxide layers of titanium, aluminum, chromium, phosphorus, tantalum and series of other elements on silica and alumina surfaces, when appropriate chloride and vapour of water are used as initial reagents [13,35,18,42]. The synthesis thus proceeds without the change of oxidation state of elements. But the stability of Si-O-M bonds in the process of gaseous treatment of element-chloride surface structures is of significant importance. Our researches have shown [44,68], that the strength of Si-O-M bonds is influenced by the thermal stability of element-oxide chloride groups, quantity of their bonds with surfaces (factor m) and series other ones. The reason for the destruction is the hydrogen chloride which educes in the process of vapour hydrolysis [68]. 

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