The Sequence of Events

Finally, it is worth remembering the sequence of events which occur during hydrocarbon accumulation. Initially, the pores in the structure are filled with water. As oil migrates into the structure, it displaces water downwards, and starts with the larger pore throats where lower pressures are required to curve the oil-water interface sufficiently for oil to enter the pore throats. As the process of accumulation continues the pressure difference between the oil and water phases increases above the free water level because of the density difference between the two fluids. As this happens the narrower pore throats begin to fill with oil and the smallest pore throats are the last to be filled. 

The sequence of events in a surface-catalyzed reaction comprises (1) diffusion of reactants to the surface (usually considered to be fast) (2) adsorption of the reactants on the surface (slow if activated) (3) surface diffusion of reactants to active sites (if the adsorption is mobile) (4) reaction of the adsorbed species (often rate-determining) (5) desorption of the reaction products (often slow) and (6) diffusion of the products away from the surface. Processes 1 and 6 may be rate-determining where one is dealing with a porous catalyst [197]. The situation is illustrated in Fig. XVIII-22 (see also Ref. 198 notice in the figure the variety of processes that may be present). 

Mechanism of Antibacterial Action. In spite of the fact that the antibacterial activity of the amiaoglycosides has been known siace the 1940s, the mechanisms iavolved are stiU incompletely understood. Numerous reviews have appeared (eg, 108 —113) and the sequence of events seems to be as outlined below. 

For certain types of stochastic or random-variable problems, the sequence of events may be of particular importance. Statistical information about expected values or moments obtained from plant experimental data alone may not be sufficient to describe the process completely. In these cases, computet simulations with known statistical iaputs may be the only satisfactory way of providing the necessary information. These problems ate more likely to arise with discrete manufactuting systems or solids-handling systems rather than the continuous fluid-flow systems usually encountered ia chemical engineering studies. However, there ate numerous situations for such stochastic events or data ia process iadustries (7—10). 

At this point, the sequence of events eventually leading to the tube wall perforations could be established ... 

One of the products of a nuclear power plant PSA is a list of plant responses to initiating events (accident starters) and the sequences of events that could follow. By evaluating the significance of the identified risk contributors, it is possible to identify the high-risk accident. sequences and take actions to mitigate them. 

Cuvette Small cylinder (test tube) used to hold a sample in a spectrophotometer. Cycle The sequence of events in a heat engine, refrigerating machine, or any prtKess where, during the performance of mechanical work, heat is supplied to and rejected from the working fluid, which is returned to its original condition. 

Risk assessment The sequence of events necessary to ensure that a system is designed to provide the safest possible working arrangement. 

Internal Error Mode The stage in the sequence of events preceding an external error mode at which the failure occurred (e.g., failed to detect the initial signal). 

It seems likely that the sequence of events in the process of smelling is, after the odoriferous substance has reached the nostrils, first for the substance to dissolve in the aqueous outer layer, thence passing to the lipoid fats, wherein an addition reaction takes place, causing a change of energy which produces a sensation perceptible to the nervous centre. 

Example of the sequence of events within the cylinder at 90 degrees BTDC (before top-dead center) and 90 degrees ATDC (after top-dead center). 

Figure 7-44 shows the sequence of events involved in diffraction of a blast vave about a circular cylinder (Bishop and Rowe 1967). In these figures the shock fronts are sho m as thick lines and their direction of movement by arrows normal to the shock front. In Figure 1.13a, the incident shock 1 and reflected shock are joined to the cylinder surface by a Mach stem M. R is now much weaker and is omitted in succeeding figures. 

As von Nimitz points out, only cyclic stresses are directly related to failure probability. These stresses are often produced by pulsations in the fluid system, by mechanical vibrations produced by the mechanical movement of certain equipment components, and as a result of the fluid pulsations. Figure 13-8 lists the sequence of events that leads to most failures of equipment and piping. 

The fundamental requirement of an efffective outage plan is well-defined work orders for each task that must be performed during the available time interval. Too many plants fail to fully plan each of the tasks that are to be performed. Instead, they rely on a master schedule that defines the sequence of events that must occur in order to complete all of the tasks included in the scope of work. 

The permeation of hydrogen through an iron diaphragm is illustrated in Fig. 20.20 for the sequence of events... 

Bacillus thuringiensis produces a variety of organic compounds which are toxic to the larvae of certain susceptible insect hosts. Among the toxic entities are proteinaceous crystals, probably three soluble toxins, and certain enzymes. The protein material is the major toxin active in killing lepidopterous larvae. The protein is formed by the cells apparently in close synchrony with sporulation, and its nature is a constant function of bacterial strain. The mode of action of the protein is under study. The sequence of events in the pathology observed is probably solubilization of the crystal (enzymatic or physical)—>liberation of toxic unit—>alteration of permeability of larval gut wall— change in hemolymph pH—>invasion of hemolymph by spores or vegetative cells of the bacterium. 

The presence of the catalyst can also favor multiple Diels-Alder reactions of cycloalkenones. Two typical examples are reported in Schemes 3.6 and 3.7. When (E)-l-methoxy-1,3-butadiene (14) interacted with 2-cyclohexenone in the presence of Yb(fod)3 catalyst, a multiple Diels-Alder reaction occurred [21] and afforded a 1 1.5 mixture of the two tricyclic ketones 15 and 16 (Scheme 3.6). The sequence of events leading to the products includes the elimination of methanol from the primary cycloadduct to afford a bicyclic dienone that underwent a second cycloaddition. Similarly, 4-acetoxy-2-cyclopenten-l-one (17) (Scheme 3.7) has been shown to behave as a conjunctive reagent for a one-pot multiple Diels-Alder reaction with a variety of dienes under AICI3 catalysis, providing a mild and convenient methodology to synthesize hydrofluorenones [22]. The role of the Lewis acid is crucial to facilitate the elimination of acetic acid from the cycloadducts. The results of the reaction of 17 with diene... 

The sequence of events taking place during a CVD reaction is shown graphically in Fig. 2.3 and can be summarized as follows 1 ... 

The sequence of events described above occurs at any given spot in a CVD flow reactor. As an example, one can consider the deposition of tungsten on the interior wall of a graphite tube by the hydrogen reduction of the fluoride as follows ... 

For instance, doped phosphosilicate glasses used in planarization cannot be heated above their flow temperature of 725°C. Likewise, after a layer of aluminum is deposited, subsequent temperatures cannot exceed 380°C because spiking and the formation of hillocks would occur rapidly (see diffusion barrier in the following chapter). The factor of time at a given temperature is just as important, as it will influence phenomena, such as diffusion and dissolution. In the planning of a CVD process, the sequence of events and the thermal budget are essential considerations. 

Broecker, W. S. and Henderson, G. M. (1998). The sequence of events surrounding Termination II and their implications for the cause of glacial-interglacial CO2 changes. Paleoceanography 13,352-364. 

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