Waiting periods

As noted, this procedure is adapted from a standard spectrophotometric method. The instructions for the spectrophotometric method indicate that the absorbance should be measured 5-10 min after adding the ascorbic acid. Why is this waiting period necessary in the spectrophotometric method, but not necessary in the FIA method ... 

Note 1. When loading volatile products such as gasoline, whose vapor concentration can be shown to rapidly exceed the upper flammable limit during tank filling, the velocity-diameter product may be increased to 0.50 mVs- This is consistent with API RP2003 [3]. Similarly, shorter wait periods of 1-2 min can be used. 

It is essential, however, to follow a r rous experimental protocol for such applications. To maintain the quantitadve character of NMR spectroscopy, the reped-tion rate of signal averaging experiments has to be at least five times the longest spin-latdce relaxadon dme present in the sample. This waiting period is necessary to ensure that the magnetizadon is probed in a reproducible state, corresponding to thermodynamic equilibrium. 

Yucca Mountain, if it becomes the site for the isolation of SNF, will be laced with tunnels, waste in storage casks and monitoring equipment. A waiting period is planned while better isolation alteniadvcs are sought. IfYucca Mountain is not used, it is to be refilled with the tuff material removed earlier. In the United States the SNF that would be isolated in Yucca Mountain would be waste that has not been reprocessed it would be material that has come out of nuclear reactors and has been cooled at the plant site. 

For example, when cementing a casing string run to shallow depth or when setting a directional drilling kick-off plug, it is necessary to accelerate the cement hydration so that the waiting period will be minimized. The most commonly... 

Fig. 15. 2H FT NMR spectra of the mobile amorphous fraction of LPE for various temperatures. The total magnetization was saturated first by a series of 90° pulses and then the solid echo was created after a waiting period r0 T, (amorphous) ranging from 25 to 200 ms...

There must be a waiting period between application and harvesting, and few of these products can be used in organic farming. 

After the IND has been filed with FDA and the date of receipt noted, a 30-day waiting period is needed... 

As stated in Section 2.1, there is a waiting period between the time of release of one bubble and the time of nucleation of the next at a given nucleation site. This is the period when the thermal boundary layer is reestablished and when the surface temperature of the heater is reheated to that required for nucleation of the next bubble. To predict the waiting period, Hsu and Graham (1961) proposed a model using an active nucleus cavity of radius rc which has just produced a bubble that eventually departs from the surface and has trapped some residual vapor or gas that serves as a nucleus for a new bubble. When heating the liquid, the temperature of the gas in the nucleus also increases. Thus the bubble embryo is not activated until the surrounding liquid is hotter than the bubble interior, which is at... 

Han and Griffith (1965a) developed a modified version of an ebullition cycle and, using a simplification in the temperature profile equation, they obtained an explicit form for the waiting period ... 

Hatton and Hall (1966) further improve the model by taking into consideration the heat capacity of the heating element, since during the waiting period the heat surf ace has to be heated to a sufficiently high temperature to initiate the new bubble. The heat balance used by Hatton and Hall is... 

Figure 2.6 Temperature profiles in liquid and heating solid during waiting period, according to mathematical model of Deane and Rohsenow. (From Deane Rohsenow, 1969. Copyright 1969 by American Society of Mechanical Engineers, New York. Reprinted with permission.)...

Initial conditions (1) The temperature distribution in the solid at the beginning of the waiting period is the same as that at the end of the bubble growth period. (2) The temperature of the liquid at the beginning of the waiting period is assumed to be uniform at Tsat. 

A longer waiting period means a larger growth rate such a trend has been observed experimentally (Hatton and Hall, 1966). There are three limiting conditions for 4>c to satisfy ... 

Repeat step 3 for each sample. During the 10-min waiting period, the next sample(s) may be prepared, but be sure to measure each sample immediately after the 10-min period. 

However, if the temperature were raised from 410 to 420 K, then J lO nuclei/m sec. Now 7 is a very large number and nucleation is prompt, with a waiting period of—10 sec for a cubic meter of superheated ether ... 

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