Screening devices

Immunosensors promise to become principal players ia chemical, diagnostic, and environmental analyses by the latter 1990s. Given the practical limits of immunosensors (low ppb or ng/mL to mid-pptr or pg/mL) and their portabiUty, the primary appHcation is expected to be as rapid screening devices ia noncentralized clinical laboratories, ia iatensive care faciUties, and as bedside monitors, ia physicians offices, and ia environmental and iadustrial settings (49—52). Industrial appHcations for immunosensors will also include use as the basis for automated on-line or flow-injection analysis systems to analyze and control pharmaceutical, food, and chemical processing lines (53). Immunosensors are not expected to replace laboratory-based immunoassays, but to open up new appHcations for immunoassay-based technology. 

Screening devices are used to make coarser separations that is, fine products having 95% passing ca 100-mm—50-p.m size. Dry-screening devices have a lower recommended size of ca 500 p.m. Wet-screening devices that produce 95% passing ca 500—50-p.m size are continually being improved. 

To remove the essential oil from the peel of citrus fruits, the oil glands, which are located in the flavedo (the outer coloured portion of the peel), are ruptured by mechanical systems. The oil is washed away with a spray of water to produce an oil-in-water emulsion with small peel particles. To prevent absorption of the essential oil by the spongy albedo (the iimer white portion of the peel), this emulsion is passed through a screening device (finisher) of 0.5 to 0.7 mm in diameter, which removes the coarsest particles of the fruit peels [12]. 

Quantitative immunoassays have also been used as screening devices to determine whether drug residues exceed established maximum residue limits (MRLs) or tolerances in edible tissues. " For these applications, a cut-off value is set at the tolerance or MRL samples detected above this level are positive , and samples below this level are negative. ... 

Claus, P., Honicke, D., Zech, T., Miniaturization of screening devices for the combinatorial development of heterogeneous catalysts, Catal. Today 2001, 67, 319-339. 

But they would stay as screening devices and, more importantly, provide substantial knowledge regarding the various biological mechanisms through which carcinogens act. 

Without being itself a screening device, the reactor of Jensen et al. [6, 42, 43] also has to be mentioned because they opened up a completely new field in catalysis by combining MEMS (micro-electro-mechanical systems) technology with a chip-based catalytic reactor (Fig. 4.10). A mixing-tee was equipped with heaters and temperature and flow sensors, thus giving on-stream information about the reaction conditions. 

Fig. 4.26 Scheme of the screening device in liquid-liquid systems. 

Figure 3.49 Schematic of experimental set-up fora scanning mass spectrometer-assisted catalyst screening device [80] (by courtesy of AlChE).

Multi-port valves belong to the key components in screening. Most equipment for analysis exists only in single-channel versions. Exceptions are, for example, radiation beam measurements of Atkins and Senkan [114] and tools for parallel analysis at Symyx. As long as equipment for parallel analysis does not exist for every type of desired measurement, multi-port valves will always be an essential part of every screening device. 

Another advantage of miniaturisation is that small devices can work with small quantities of biological material, a single cell or a few viruses or macromolecules. This is a highly desirable feature in pharmaceutical screening devices and diagnostic systems. 

Greenwood, P.A., Greenway, G.M., Development of a l.TAS screening device for drug analysis by chemiluminescence. Micro Total Analysis Systems, Proceedings 5th i7A5 Symposium, Monterey, CA, Oct. 21-25, 2001, 343-344. 

Recently, the topic of improvised explosive devices (IEDs) has garnered a lot of attention. IEDs may take the form of roadside bombs, suicide bombers, or vehicle-borne bombs. Roadside bombs share some detection issues with land mines, and in principle, the NQR land mine detectors discussed in the previous section can be used to detect roadside IEDs. However, many IEDs are remotely controlled, and the short standoff distance available with NQR makes IED detection dangerous for the NQR operator. The personnel screening devices already discussed in Section 5.2.3. are applicable to the suicide bomber. 

Our experience has led us to doubt the utility of the Mitre Model for site ranking, beyond its use as a first cut screening device. The model scores for the Louisiana sites do not appear to correlate particularly well with other means of evaluating the relative ranking of problem seriousness, nor do they give any useful insight as to the type or extent of response that may be required. 

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