Presentation trimodal

The mode of distribution is simply the value of the most frequent size present. A distribution exhibiting a single maximum is referred to as a unimodal distribution. When two or more maxima are present, the distribution is caUed bimodal, trimodal, and so on. The mode representing a particle population may have different values depending on whether the measurement is carried out on the basis of particle length, surface area, mass, or volume, or whether the data are represented ia terms of the diameter or log (diameter). 

The mode, the most commonly occurring (most popular) value in a distribution, passes through the peak of the relative distribution curve, i.e. it is the value at which the frequency is a maximum (Figure 2.6). More than one high density region may be present in which case the distribution is said to be multi-modal, i.e. bimodal, trimodal and so on. 

The early observations that human serum PONl activity presented a bimodal/trimodal distribution led to the hypothesis that low metabolizers may be more sensitive to the toxicity of OPs. The studies summarized previously have characterized the PON 1 polymorphisms responsible for different catalytic activities and levels of expression, demonstrated the relevance of PONl in modulating OP toxicity in various animal models, and indicated the importance of an individual s PONl status. Direct confirmation in humans of the relevance of PONl. status in determining relative sensitivity to OP toxicity, however, is still elusive. Nevertheless, in recent years, some studies have. started to investigate the role of PON 1 in OP toxicity in humans and have provided some interesting findings. 

While clearly of major importance, further studies of trimodal anisotropy have been plagued by lack of reproducibility. It is thought that the essential conditions for the effect are related to extremely low levels of cations or other impurities, present in the subphase and the LB film material. 

---