Herriott cell

An astigmatic variant of the Herriott cell designed for use in ambient air studies is shown in Fig. 11.2a and described by McManus et al. (1995) and Zahniser et al. (1997). In this design, the two mirrors have different radii of curvature, giving the spot patterns shown in Fig. 11.2c. The spots more evenly fill the mirror, so that for a given number of passes, the spots are more widely spaced, or conversely, more passes can be obtained without problems of beam overlap (McManus et al., 1995). 

Nowadays, three basic designs of multipass cells are used in tuneable laser absorption instruments, i.e. plane-plane mirror designs. White cell designs and the Herriott cell designs. 

Tarsitano, C.G., Webster, C.R. (2007) Multilaser Herriott cell for planetary tunable laser spectrometers. Applied Optics, 46(28), 6923-6935. 

Another type of multipass cell, known as the Herriott cell, was described by Herriott and Schulte in 1965 [8]. Although the Herriott cell is most commonly used with lasers, it has also been used for long-path FT-IR measurements. This cell consists of two spherical mirrors with a separation that is about the same as the radius of curvature of the mirrors. If a laser beam is projected in just off the edge of one of the spherical mirrors, so that it hits the center of the other mirror, multiple passing ensues. Because the beam is off-axis and the mirrors are not quite confocal, the beams do not come back on themselves as they do in a White cell, but... 

Nucleic acid synthesis. A striking observation first made by Cohen (52,54) is that in cells infected with T2r+ only DNA, the nucleic acid found in the virus, is synthesized in contrast to normal bacteria which make about 3 times as much RNA as DNA. RNA when measured as pentose by the orcinol reaction remains constant. This phenomenon is clearly of paramount importance. It has been confirmed for T6 bacteriophage by Kozloff (private communication). However, Herriott s data (129) on E. coli infected with T2 give indication of a fall in RNA. Although protein synthesis is apparent from the moment of infection, DNA synthesis begins only after a lag of 7 to 10 minutes (54). This holds for T4 and T6, as well as T2 (62). As shown in Fig. 6, DNA increases linearly with time after a lag of about 10 minutes and finally levels off at about 100 minutes. Doermann and Cohen (unpublished experiments... 

Cleaver, J. E., 1972, Excision repair Our current knowledge based on human (xeroderma pigmentosum) and cattle cells, in Molecular and Cellular Repair Processes (R. F. Beers, Jr., R. M. Herriott, and R. C. Tilghman, eds.), pp. 195-211, The Johns Hopkins University Press, Baltimore. 

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