Real-time techniques

The goal of luminescent sensing is perhaps to implement methods and instrumentation capable of performing simple, accurate, and precise measurements in real time. These qualities of sensing systems are especially desirable in the biomedical field in which relevant physiological parameters may change constantly during time expands from a fraction of a second to several hours. 

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Laser desorption methods (such as LD-ITMS) are indicated as cost-saving real-time techniques for the near future. In a single laser shot, the LDI technique coupled with Fourier-transform mass spectrometry (FTMS) can provide detailed chemical information on the polymeric molecular structure, and is a tool for direct determination of additives and contaminants in polymers. This offers new analytical capabilities to solve problems in research, development, engineering, production, technical support, competitor product analysis, and defect analysis. Laser desorption techniques are limited to surface analysis and do not allow quantitation, but exhibit superior analyte selectivity. 

The ability to in situ characterize the growth and properties of organic thin Aims enables us to better understand the associated underlying mechanisms. Many techniques allow such studies. For films a few MLs thick the techniques should be sufficiently surface sensitive. In situ is too often confused with real-time techniques. Real-time clearly means that the physical or chemical phenomena are studied without interruption of the process. Indeed, this has to be done in situ during growth. However, some in situ techniques, because of the experimental geometry. 

Table 1 Performance of real-time techniques for kinetic analysis of high-speed photopolymerization reactions.

An atomic or molecular beam of Ga, As, Al, and/or other elements is created thermally in a ultrahigh-vacuum chamber and directed at a specific, well-defined, atomically flat facet of a single-crystal substrate. A very low deposition rate, associated with a precisely controlled substrate temperature and various real-time techniques for monitoring the state of the surface, permit one to find growth conditions that preserve a coherent crystalline order or minimize the density of structural... 

An advantage that PTR-MS and the other techniques discussed in this chapter have over conventional analytical methods is that they are real-time techniques and can provide an immediate analysis of a sample. In PTR-MS for a reaction between HjO and an analyte M in an air sample, we have... 

From the optical standpoint the outstanding properties of dynamic scattering are that it can be electrically controlled in two dimensions and the active motion of the scattering centers. By utilizing the property that dynamic scattering can be electrically controlled, it is possible to build electrooptic devices with transmission characteristics that can be controlled in two dimensions and as a function of time. Such devices can lead to new real time techniques in ultrasonic and microwave holography and in coherent optics data processing. 

There is a continuing need for better ways to characterize membranes and membrane processes. In particular, noninvasive, real-time techniques are needed for characterizing membrane fouling, cleaning, module hydrodynamics, compaction, formation, morphology, and quality control. There is a particular need for characterization techniques that can be readily adapted to commercial membrane modules and processes. 

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