Induction intervals

Hydrocarbons exhibit induction intervals that are followed by a very rapid reaction rate. Below 400°C, these rates are of the order of 1 s or a fraction thereof, and below 300°C they are of the order of 60 s. 

Almost all of the tests described above evaluate the response as production of visible dermatitis, using descriptive scales for erythema and edema. Some assays specify use of one sex or one half of each sex. The tests differ significantly in route of exposure, use of adjuvants, induction interval, and number of exposures. The principal features of the most commonly used assays and the assays acceptable to regulatory agencies to predict sensitization are summarized in Table 1. 

Data from an earlier study have been reanalysed to test the hypothesis that MMR vaccine might cause autism but that the induction interval needs to be short (495). Evidence for an increased incidence was sought using the case-series method. The study used data on all... 

Acquisition of free induction decay data during the time interval m which the equi librium distribution of nuclear spins is restored... 

Figure 4-301 shows sample neutron-density Pe log over the same interval. Figure 4-302 shows sample MWD resistivity (left) and wireline dual induction (right) for the same interval. 

The Production Department was not amused, because lower values had been expected. Quality Control was blamed for using an insensitive, unse-lective, and imprecise test, and thereby unnecessarily frightening top management. This outcome had been anticipated, and a better method, namely polarography, was already being set up. The same samples were run, this time in duplicate, with much the same results. A relative confidence interval of 25% was assumed. Because of increased specificity, there were now less doubts as to the amounts of this particular heavy metal that were actually present. To rule out artifacts, the four samples were sent to outside laboratories to do repeat tests with different methods X-ray fluorescence (XRFi °) and inductively coupled plasma spectrometry (ICP). The confidence limits were determined to be 10% resp. 3%. Figure 4.23 summarizes the results. Because each method has its own specificity pattern, and is subject to intrinsic artifacts, a direct statistical comparison cannot be performed without first correcting the apparent concentrations in order to obtain presumably true... 

Watters, R. L., Jr., Carroll, R. J., and Spiegelman, C. H., Error Modeling and Confidence Interval Estimation for Inductively Coupled Plasma Calibration Curves, Anal. Chem. 59, 1987, 1639-1643. 

A very fast testing of polymer stability is based on non-isothermal experiments (DSC, chemiluminescence) where the whole plot of the parameter followed may be visualized over a large temperature interval. The transfer of non-isothermal data to isothermal induction times involves a variety of more or less sophisticated approaches such as published in Ref. [8] or discussed later. 

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