Measured digitized value

The most popular method of measuring peak area is by integration. Integration is a method in which the series of digital values acquired by the data system as the peak is being traced are summed. The sum is thus a number generated and presented by the data system and is taken to be the peak area. See Figure 11.20. We will discuss in Chapters 12 and 13 exactly how this area is converted to the quantity of analyte in GC and HPLC and the issues involved. See Workplace Scene 11.7. 

To indicate the uncertainty in a measurement, the value you record should use all the digits you are sure of, plus one additional digit that you estimate. In reading a mercury thermometer that has a mark for each degree, for example, you could be certain about the digits of the nearest mark—say 25°C—but you would have to estimate between two marks—say 25.3°C. 

For competitive, reversible enzyme inhibition, the lowest measurable IC50 value is half of the enzyme concentration used in the assay (Cheng and Prusoff, 1973). From a practical view, kcJKM values of 104 M 1 s 1 and above are desirable for inhibitor profiling assays. With an enzyme-substrate pair characterized by a kcJKM value of 104 M 1 s, an assay can usually be run with a protease concentration in the single-digit nanomolar range in an automated setting. 

The gap between mathematical theories and their applications, which is the theme of all the foregoing quotes, arises from one common source the discrepancy between the precision required by classical set theory (and its associated logic) and the inherent resolution limits of our perceptual capabilities as well as measuring instruments. Consider, for example, measurements of a physical quantity taken by a particular instrument. Due to the finite resolution of the instrument employed, appropriate quantization of the measurement is inevitable. Assume, for example, that the considered range of the quantity is [0,1] and that the measuring instrument allows us to measure with the accuracy of one decimal digit. Then, measurements are values taken from the collection of values 0, 0.1, 0.2,.. ., 0.9, 1, which stand for the intervals [0,0.05), [0.05,0.15),...,[0.85,0.95), [0.95,1]. This example of the usual quantization is illustrated in Fig. 4a. 

To merely characterise the multiplet structure a digital resolution in fi of around 20 Hz/pt should suffice, requiring as little as 20 increments. If one wished to measure the value of Jch from the multiplet structure, a digital resolution of somewhat less than 5 Hz/pt would be more appropriate. Some 200 increments would be required for 2 Hz/pt leading to a significantly longer experiment, particularly if many scans are required p>er increment for reasons... 

Brix Value. Brix is one of the most common quality factors of fruits. Beside water, soluble sugars, determined as Brix, is the major component in most fruits— say 10-20% by fresh weight. Therefore, in a spectmm of typical fruit, there is an adequate amount of information related to the sugar absorption. The reference measurement of Brix is also simple. The value can be precisely determined by duplicate analyses of fruit juice with a temperature-compensated digital refractometer. The critical factor is to measure Brix value as fast as possible after juice extraction. The evaporation of water from the juice will increase the Brix reading. The use of gauze to squeeze the juice from the flesh may seem to be a convenience and is a common way to obtain... 

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