Initial isolation zone

FIGURE 17.1 Defining initial isolation zone and protective action distances. 

Protective actions should be initialed to the extent furtliest possible, beginning with those closest to the spill site and working away from the site in the downwind direction. Again, the shape of the area in which protective actions should be taken (the Protective Action ne) is illustrated in Figure 1. In this figure, the spill is located at the center of the small circle. The larger circle represents the initial isolation zone around the spill. 

Figure I. Illustrates protective action and initial isolation zones.

Agent Estimated Initial isolation (hot zone) Downwind (day) Dawnwind (night)... 

The pressure difference is created by using a large difference between the supply and exhaust flow rates (in either direction). Higher pressure than the surroundings is used to prevent airborne transport into the room and lower pressure to prevent transport from the room. The airflow is then directed from the room with the (initial) higher pressure to the room with the lower pressure, and the transport of contaminants in the other direction is largely prevented. The pressure difference will disappear, for example, when a door is opened between the t o zones. When the pressure difference has disappeared, which could happen in fractions of a second, the preventive effect diminishes since, as has been pointed out earlier, it is impossible to have total isolation only by using air. 

Initially the free C02 is distributed in radially decreasing concentrations in zones around the injection site (Fig. 2a van der Meer 1996). Nearest the injection site lies a zone of near completely saturated pores, containing isolated beads of trapped brine, some of which evaporate into the C02 (Pruess etal. 2003). The middle zone contains mixed brine and C02 (Saripalli McGrail 2002 Pruess et al. 2003). In the outer zone C02 is present only as aqueous species. Following injection, C02 saturations around the injection site are predicted to decrease over tens of years as the free C02 rises buoyantly, spreads laterally, and dissolves into the brine (Weir et al. 1995). Over time-scales of hundreds of years, dispersion, diffusion, and dissolution can reduce the concentration of both free and aqueous C02 to near zero (McPherson Cole 2000). 

This study (34) implies that a right dispersion of rubber particles may permit optimum stress field overlap that affords lower craze-initiation stresses and therefore can rapidly dissipate the strain energy in the HIPS. A more homogeneous spatial distribution of rubber particles allow for a uniform development of crazes. Prevention of the strain localization phenomenon to avoid the detrimental situation, where crazes prefer to develop in certain areas and quickly lead to a catastrophic crack, could result in a larger total volume of crazed material. Further, Donald and Kramer (22) discovered no crazes nucleating from an isolated rubber particle with diameter smaller than 1 urn because of an insufficient size of stress-enhanced zone. Since Sample-A has a small average particle size it should contain a large number of small rubber particles. Two small rubber... 

Pyrolysis of monosubstituted di-p-xylylenes, such as acetyl-di-p-xylylene (V) results in formation of two reactive p-xylylenes with different Tcs. The two species were separated as their polymers by using the principle of threshold condensation temperature. The pyrolysis vapors containing the two monomers VI and VII were passed initially through a zone maintained at a temperature low enough to permit rapid condensation and polymerization of acetyl-p-xylylene, but substantially above the Tc of p-xylylene which passed through the first zone and polymerized in a final zone maintained at ambient temperature. In a sense, the monomers were fractionated on the basis of volatility, and the monomers were isolated in the form of their polymers. These transformations are illustrated at the top of p. 646. 

Lesions created in both bovine and human enamel, in an acidified methyl cellulose gel system, displayed many of the same qualitative trends [Lynch, unpubl. data]. After an initial period of approximately 3 days when dissolution was negligible, mineral loss was typically found at a series of discrete locations, with no apparent mineral loss between these pockets of demineralisation. Surface zones were typically poorly defined or absent. After 5 or more days, the isolated pockets had coalesced and lesions were uniform in terms of both depth and mineral loss across the bulk of the lesion body, with well-defined surface zones. When observed under polarised light, these initial pockets of demineralisation were very often coincident with Hunter-Schreger banding. This was particularly noticeable in bovine enamel. Shellis [64] reported variations in solubility related to enamel microstructure and suggested that structure/solubility relationships are likely to influence lesion formation. 

---