Comet Test

Comet Test for Environmental Genotoxicity Evaluation A Fluorescence Microscopy Application... 

The Comet test is a method that allows measurement of the degree of DNA damage within a nucleic cellular population. The general principle of the comet test method can be described as follows ... 

Figure 16.9 shows the results from a Comet test of normal, apoptotic, and necrotic cells. One should be careful not to confuse apoptotic and damaged cells. 

Nature of damage revealed with the Comet test... 

Figure 16.9 Comet test for lymphocyte cells in three states normal, apoptotic, and necrotic. The reader can refer to the following sites www.cometassayindia.org and www.cometassayindia.org/protocols.htm. Reproduced in Color plate 16.9. 

DNA damage observed via the Comet test is expressed as follows ... 

Koppen, G. (1996) Protocol of the alkaline comet test on plant cells. Comet Newsl., 4, 2-4. Koppen, G. and Verschaeve, L. (1997) The alkaline comet test on plant cells. A new genotoxicity test for DNA strand breaks in Viciafaba. Mutat. Res., 360, 193-200. 

Sample DNA Phytotoxicity Genotoxicity Genotoxicity Comet Test... 

Fig. 10 Pressure trace from gauge in COMET test 1-27 (under water thermite billet with a 1-s delay).

Although we do not know the values of K or a for pressure or impulse for steam explosions, we can make some guesses. For most high explosives, a ranges from about 0.8-1.2. We will assume that a - 1. This will then allow us to develop a similitude relation based on the experimental measurements taken in COMET test 1-27. Such an approximation contains large uncertainties. 

To compare the results from COMET test 1-27, Eqs. (1) and (2) have been tested against an earlier thermite test, RC-2, also conducted at Sandia.2 In that test, the measured peak pressure and impulse were 76 MPa and 110 kPa S. The experimenters reported that a mass of fuel of 9-15 kg was estimated to have participated in the explosion.2 The distance from the assumed center of the explosion to the gauge was about 0.46 m. Using Eqs. (1) and (2) and assuming a mass of 9 kg results in a calculated pressure and impulse of 6.6 MPa and 92 kPa s, respectively. 

Using the upper limit on fuel mass results in a P and I of 7.9 MPa and 129 kPa s, respectively. For the mean mass of 12 kg, calculated P and I are 7.5 MPa and 114 kPa s, respectively. The impulses calculated using Eq. (2) are very close to the measured value of 110 kPa s, even given the experimental uncertainty in participating mass. The calculated pressures, however, are much lower (by an order of magnitude) than the measurement. This provides further evidence that the actual pressure in COMET test 1-27 was probably much higher, and that the pressure measurements in... 

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