Initial briefings

The manufacturer s instructions for operating a combustible gas indicator should be carefully reviewed before the device is used. In general, all explosimeters require a brief initial warm-up period so that the batteries can heat the filaments. Then battery strength should be checked, and the zero scale adjusted. When zero is established and the indicating needle is stable, the instrument is ready for use. 

At the start the cathode is invariably a metal different from that to be deposited. Frequently, the aim is to coat a base metal with a more noble one, but it may not be possible to do this in one step. When a metal is immersed in a plating bath it will corrode unless its potential is sufficiently low to suppress its ionisation. Fortunately, a low rate of corrosion is tolerable for a brief initial period. There are cases where even when a cathode is being plated at a high cathodic (nett) current density, the substrate continues to corrode rapidly because the potential (determined by the metal deposited) is too high. No satisfactory coating forms if the substrate dissolves at a high rate concurrently with electrodeposition. This problem can be overcome by one or more of the following procedures ... 

Figure 8.3. Initial variations in the number of product C ingredients for the A + B C + D reaction of Example 8.2. Note the brief initial adjustment period before the system settles into...

The only kinetic data that permits direct comparison of the rates of Reactions (36) and (37) is that of Baur, Gibbs and Wadsworth (3). After a very brief initial period of rapid reaction, Reactions (36) and (37) are followed. Extrapolation of the data of Baur, Gibbs and Wadsworth to long times and transformation of variables indicate that after the initial rapid reaction, chalcopyrite and oxygen react in a constant ratio, i.e., the fraction of the total copper dissolved due to O2 is... 

FIGURE 1.30 The bubble-cap of a bubble at the champagne surface has just ruptured (on a time scale of 10-100 gs) during this extremely brief initial phase, the bulk shape of the bubble has been frozen, and a nearly millimetric open cavity remains as a tiny indentation in the liquid surface (bar = 1 mm photograph by Gerard Liger-Belair). 

The problem of attaining sufficiently brief initiation times with fluidic initiators was ex-... 

The shaded portion of the top graph is shown in expanded form in the bottom graph. After a brief initial period (usually less than a few seconds) the concentration of ES remains approximately constant for an extended period. The steady-state approximation is applicable during this second period. Most measurements of enzyme kinetics are made in the steady state. 

The discussion will be confined to pure NiO, since most work has been done with this catalyst. It appears from the 180 extraction results that at low pressures the primary act of chemisorption of N20 determines the number of active sites for each reaction, since x increases roughly as P o between 1 and 4.2 cm. (Table IV). At very low Pn2o, decomposition still takes place, although no appreciable pressure change occurs N2 appears in the gas phase and the 02 is retained by the catalyst. Again, simultaneous measurements (32) of the rate of the reaction and of the change of semiconductivity of a compressed pellet of the catalyst show that immediately on admission of N20 the resistance of the pellet begins to fall there is no trace of a brief initial increase in resistance such as would be expected if... 

The essence of the steady-state assumption is that the concentration of a reactive intermediate (X) is assumed to build up during a brief initial induction period, but then, during most of the rest of the reaction, its formation and decomposition are balanced (i.e. d [ X ] /d f = 0) so that its concentration remains essentially constant. Obviously, during the final stages of the reaction, the concentration of the intermediate decreases to zero. 

A brief initial phase of weak inhibition of Ach release, lasting few minutes, which is absent with some toxins such as notexin and paradaxin, and which has a different relevance in mice and rats NMJ preparations. 

Following a brief initial report by Carlo Unverzagt [57], 5-azido-based sialyl donors were prepared by various groups and their reactivity investigated [58-61],... 

Measurements show that ammonium does not accumulate appreciably on these surfaces after a brief initial exposure. 

ANG II is known to be implicated in many forms of hypertension other than renal. For example, the antihypertensive effect of (3-blockers is now understood also to involve a reduction of renin release. The octapeptide salarasin antagonizes its effect competitively at target cells and, after a brief initial pressor effect (because of residual agonist activity), will lower blood pressure. 

At the start of filtration in a cake filter some solid particles enter the pores of the medium and are immobilized, but soon others begin to collect on the septum surface. After this brief initial period the cake of solids does the filtration, not the septum a visible cake of appreciable thickness builds up on the surface and must be periodically removed. Except as noted under bag filters for gas cleaning, cake filters are used almost entirely for liquid-solid separations. As with other filters they may operate with above-atmospheric pressure upstream from the filter medium or with vacuum applied downstream. Either type can be continuous or discontinuous, but because of the difficulty of discharging the solids against a positive pressure, most pressure filters are discontinuous. 

The key empirical facts surrounding the dissolution of novolac that have been established are outlined below. It was on the basis of these facts that mechanistic models of novolac dissolution were proposed. The dissolution of novolac, with the exception of a brief initial phase, proceeds with a constant rate and follows case II mass transfer kinetics (also called case II Fickian diffusion). In low-molecular-weight novolacs, the width of the gel layer is on the order of 10 nm. Arcus has demonstrated the existence of this gel layer in a high-molecu-lar-weight phenolic novolac resin, as shown in the laser interferogram trace of Fig. 11.34. This interferogram shows three separate sets of reflections, corresponding to the interface between the polymer matrix and the silicon wafer, the interface between the polymer matrix and the swollen gel, and the interface between the gel layer and the developer solution. ... 

The results of brief initial counting—typically for a period of 1-5 min—are reviewed to determine whether they provide sufficient information on radionuclide content. If not, a longer counting period, say 1-2 h, is selected to provide as much reliable data as possible on the presence or absence of specified radionuclides within the necessarily limited period. 

For a coalmine accident causing less than three deaths, the accident investigation is organized by the chief of regional inspectorate. Immediately upon receipt of the accident report, the chief shall select appropriate members to form a capable accident investigation team, and appoint a team. The team shall as soon as practical collect and fill out a brief initial report of the accident, and within 72 hours report to the head of Coalmine Safety and Health Department [PENG Cheng 2001]. 

Respiratory decline, characteristic of vitamin E-deficient liver tissue during the prenecrotic phase of dietary necrotic liver degeneration, consists of the breakdown of respiration in vitro, after brief, initial periods of normal oxygen consumption. The phenomenon is observed with liver slices and also homogenates, but not with isolated mitochondria from the livers of animals during the latent phase of the disease. Respiratory decline is not related to the rate of peroxide formation in the homogenate. Combination experiments disclosed that miorosomes exert a deleterious effect on the... 

Historically, it was the CIMA reaction in which Turing patterns were first found. Under the conditions of these experiments, however, our analysis suggests that, after a relatively brief initial period, it is really the CDIMA reaction that governs the formation of the patterns. Even when the input feeds consist of chlorite and iodide, chlorine dioxide and iodine soon build up within the gel and play the role of reactants whose concentrations vary relatively slowly compared with those of C102 and I . We have therefore found it more practical to work with the CDIMA system, using chlorine dioxide and iodine along with malonic acid as the input species, since in this way the relevant parameters can more easily be measured and controlled. Working with the CDIMA system also leads us naturally toward a simpler version of the model described by eqs. (14.22)-( 14.24). 

Some examples of numerical integrations for the system in Eq. (2.30) are shown in Figure 2.2 for different relative rates in the rapid-equilibrium model. The dashed and solid lines show the calculated time dependence of [B] and [C], respectively, for relative rate constants that satisfy the rapid-equilibrium conditions and the circles represent [C] for the same conditions, calculated from Eq. (2.21). Note that [B] initially increases rapidly to the equilibrium value this type of fast initial change can be a problem for numerical integration. The open and closed squares represent [B] and [C], respectively, for rate-constant values that do not satisfy the rapid-equilibrium conditions. These show a slower increase of [B] to a lower maximum value, and a brief initial induction period for [C]. 

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