White cell optics

The reaction cell has a White cell optical system (see Chapter ll.A.lc) with a pulsed xenon lamp light source. Once the radicals are formed, they are detected by their absorptions in the UV using the Xe lamp and a monochromator-photomultiplier or photodiode array detector. Thus the absorption spectra of the free radicals generated in the system can be measured and the absorption at a particular wavelength used to follow their reaction kinetics. 

Table 1 lists many of the short-lived species detected in the gas phase with Fourier transform infrared spectroscopy. Two prominent groups are those headed by Bernath, now at the University of Waterloo, and by Howard at the National Oceanic and Atmospheric Administration (NO AA). The former group has used IR emission to study unstable diatomics produced in discharge sources or furnaces. The molecules studied in this group tend to be of astrophysical interest. The research team at NOAA mainly studies short-lived molecules of atmospheric significance. They employ a long flow tube fitted with White cell optics and coupled to a Bomem DA3.002 spectrometer. They usually make the transient they are interested in by performing a carefully controlled series of chemical reactions. 

The special design of the Latham bowl allows for a specific blood cell separation known as SURGE. This technique makes use of the principle of critical velocity. The Latham bowl is filled until the huffy coat, ie, layer of platelets and white cells, moves in front of the bowl optics. At this point the machine starts to recirculate plasma through the bowl at increasing rates. The smallest particles, ie, platelets, ate the first to leave the bowl. Their high number causes the effluent line to turn foggy. The optical density of the fluid in the effluent line is monitored by the line sensor. A special algorithm then determines when to open and close the appropriate valves, as well as the optimum recirculation rate. 

Sensing Volume. The sensing volume of a sensor is the volume where the air is actually monitored. The sensing volume is the reaction chamber of a flame photometric detector or a chemiluminescence device, the field of view of an open-path sensor, or the White cell of a reduced-pressure optical system. The residence time of the sample within the sensing volume ultimately limits the temporal resolution of most chemical sensors. 

Figure 3.4-2 a Approximate optical conductance of a grating spectrometer, an interferometer (R = 1000 at 1000 cm ) or a laser b cuvette of minimal volume for trace analyses of gases c multiple reflexion cell (White cell) d cell for liquids with minimal volume. 

IWo models of long optical path cells, shown in Figure 17-32, have been investigated. One is an adaptation of the White cell [185] for measuring hydrocarbons [173, 186]. The second, used in solutions for nuclear plants, was made specially with optical fibers for maximum improvement of the optical path/dead volume ratio of the cell [187]. The best performance ob-... 

Figure 17-32. Flow sensing in absorption with long optical path cells, (a) White cell [185] (b) CEA cell I187J.

Infrared spectrophotometry of ozone based on the principal absorption band near 9.5 pm is relatively free from interference by the bands of other atmospheric constituents. However, a long optical path is necessary for detection of atmospheric ozone. A White cell (multiple reflection cell, 10-1000 m path) combined with a Fourier-transform infrared (FTIR) spectrometer (spectral resolution of lcm or better) with a HgCdTe detector is often used in multi-component air-monitoring and smog chamber experiments. 

Anderson, B. L., Rabb, D. J., Wamky, C. M. Abou-Galala, F. (2006). Binary Optical True-Time Delay Based on the White Cell Design and Demonstration. J. Lightwave Technol., Vol. 24, pp. 10... 

Mital, R., Wamky, C. M. Anderson, B. L. (2006a). Design and demonstration of an optical true-time-delay device based on an octic-style white cell. Journal of Lightwave Technology, Vol. 24, No. 2, pp. 982-990, Issn 0733-8724. 

The most common sample compartment in high-resolution FT-IR spectrometers is the White cell, where the beam passes a path of 1-1000 m. In a long-path gas cell, however, a small f/number (focal length of the mirror/diameter of the pupil) and a large size of the circular image may lead to a loss of effectivity. In the Oulu interferometer this problem was solved by an alternative multiple-path gas cell, where the images at the focal planes occur on a circle around the principal axis of the cell. The aberrations remain small in spite of a small f/number, because the successive images are relatively near to the principal axis of the optics. 

A 15-year-old girl developed acute oliguric renal faUure after taking 3 g of glafenine with alcohol after an argument with her father. The blood urea and creatinine rose to a maximum of 120 and 3.0 mg/100 mL The urine contained protein, and increased numbers of red and white blood cells. Optical and electron microscopic appearances of renal biopsy iruterial were described (93. ... 

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