Real-time optical information

For systems that generate a nerve agent aerosol, there are several ways to characterize the chamber atmosphere. Real-time optical aerosol monitors can be used to monitor the concentration and stability of the chamber atmosphere. Alternatively, glass fiber filters can be used to collect aerosol from the chamber. However, this method only provides information about the average concentration of the chamber atmosphere during the period when the sample was collected and does... 

The objective ia any analytical procedure is to determine the composition of the sample (speciation) and the amounts of different species present (quantification). Spectroscopic techniques can both identify and quantify ia a single measurement. A wide range of compounds can be detected with high specificity, even ia multicomponent mixtures. Many spectroscopic methods are noninvasive, involving no sample collection, pretreatment, or contamination (see Nondestructive evaluation). Because only optical access to the sample is needed, instmments can be remotely situated for environmental and process monitoring (see Analytical METHODS Process control). Spectroscopy provides rapid real-time results, and is easily adaptable to continuous long-term monitoring. Spectra also carry information on sample conditions such as temperature and pressure. 

The changes in a and f> can be determined very rapidly, allowing changes in film thickness and optical properties to be determined in real time, hence the technique can be used to gain kinetic information. The speed of data collection is limited only by the response of the instrument and this may be as low as a few tens of microseconds. 

This effect allows optical information to be recorded, erased and rewritten in real time. 

The purple membrane is harvested semiindustrially from halobacteria mutants which are bred in fermenters. The BR is then embedded into a polymeric matrix of poly(vinyl alcohol) or polyacrylamide. The BR films manufactured in this way are used for different applications, preferably in holography, for example, as a reversible transient data storage system for optical information processing (159). Another example is real-time interferometry by using the property of BR films to integrate over time (160). BR has been proposed also as a two-photon memory material because of its unusually large two-photon cross section. 

Chemical sensors are by definition small, inexpensive and preferably hand-held devices, capable of continuously monitoring chemical constituents in liquids or gases. MIP sensors usually consist of an imprinted sensitive layer and a transducer to convert the chemical information, in real time, into an electrical or optical signal which is further evaluated electronically [12]. Figure 21.1 shows the set-up of chemosensors and two typical mass-sensitive devices. 

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