Spreading factor applications

The present authors have had experience using rotary samplers for field studies involving relatively small droplets for vector control applications and for the measurement of droplet size at far-field distances. When using magnesium oxide slides, the spread factor for droplets varies from 0.75 for crater diameters up to 15 jam, to 0.8 for 15-20 p.m and 0.86 for crater diameters above 20 am. 

Currently, there is a need for high-throughput determination of nucleic acid sequences. At present, detection systems most commonly employ fluorescence-based methods. However, wide spread applications of such methods are limited by low speed, high cost, size, and number of incubations steps, among other factors. Application of electrochemical methods in affinity DNA sensors presents likely a promising alternative, allowing miniaturization and cost reduction, and potentially allowing application in point-of-care assays. 

Another surface chemical factor that can affect the efficacy of the foliar spray application of agrochemicals is the extent to which the liquid wets, spreads and covers the foliage surface. A very convenient parameter describing spreading is the spread factor 5F, which is simply the ratio of the diameter of the area wetted, D, and the diameter of the drop applied, d, as follows ... 

Although specific calculations for i and g are not made until Sect. 3.5 onwards, the mere postulate of nucleation controlled growth predicts certain qualitative features of behaviour, which we now investigate further. First the effect of the concentration of the polymer in solution is addressed - apparently the theory above fails to predict the observed concentration dependence. Several modifications of the model allow agreement to be reached. There should also be some effect of the crystal size on the observed growth rates because of the factor L in Eq. (3.17). This size dependence is not seen and we discuss the validity of the explanations to account for this defect. Next we look at twin crystals and any implications that their behaviour contain for the applicability of nucleation theories. Finally we briefly discuss the role of fluctuations in the spreading process which, as mentioned above, are neglected by the present treatment. 

No doubt, an extensive investigation of the combustion wave structure under different conditions would permit to verify many conceptions of the current flame spread theories, and also to determine the applicability limits of the latter. Even now, since more experimental investigations of the rate of flame spread over polymer material surfaces as a function of various factors are bdng carried out, it is becoming increasingly clear that the mechanism of heat transfer from the flame to the combustible surface can change radically as the size of the combustion zone increases. 

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