Samples discrete

Swabs (sterile, moistened, alginate wool tips) are used for sampling discrete surfaces areas or difficult-to-reach locations. Subsequent direct inoculation on solid media or membrane filtration of the swab rinsing fluid can be used to cultivate the micro-organisms. 

While chromatographic methods separate chemical compounds, they do not identify them as specific compounds. For this purpose one needs a good knowledge of what is most likely to be in the mixture. Known control substances can be analyzed along side the unknown samples. Discrete bands of the various components can then be identified against the known material that travels the same distance on the paper or glass sheet (Fig. 4.34). 

Vibrational-Rotational Transitions Vibrational energy levels are also quanli/ed. and for mosl molecules the energy differences between quantum stales correspond to the iiiid-IR region. The IR spectrum of a gas usually consists of a series of closely spaced lines, because there arc several rotational energy levels for each vibrational level. Ou the other hand, rotation is highly restricted in liquids and solids in such samples, discrete vibrational-rotational lines disappear, leaving only somewhat broadened vibrational bands. 

The unique measurement challenges in polymerization then may be summarized as follows vague control and measurement objectives, difficult sampling, discrete sensor output, large dead times and sampling intervals, off-line analyses, large measurement errors and high noise levels. 

Containers are necessary to keep each sample discrete and are essential when the sampling site is remote from the laboratory. They should be of sufficient size and volume to ensure that they hold sufficient sample for the analysis and any repeat assays. This may not always be the case but the analyst should discuss with the submitter the minimum requirements for a particular assay. 

Ac signals (controlled potential or current) can be considered "simply as signals varying in time in a known manner. They can be followed (sampled) discretely in the same manner as, for example, a linear potential sweep and this has, in fact, been done. Sine-wave signals, however, are a special category and a great body of mathematical theory is available from the electrical engineering field. 

It was shown in Eqs. 2.12 and 2.13 that to compute the complete spectrum from 0 to oo cm, the inteiferogram would have to be sampled at infinitesimally small increments of retardation. That is, of course, impossible, as an infinite number of data points must be collected and computer storage space would be exhausted. Even if these data could be collected, the Fourier transform would take forever to be computed. Obviously, interferograms must be sampled discretely. Just how often the interferogram should be sampled is a problem that has been solved mathematically. 

The sampling of dynamic spectrum does not always have to occur with a constant increment of t. For unevenly sampled discrete data [10], some modifications are then required for Equations (F30), (F31), and (F33). The modified form of correlation spectra are given by... 

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