Flashes, spatial distribution

The spatial distribution of flashes can be a significant factor in lightning problems. The fact that consecutive flashes are well separated, often quasi-randomly, is familiar to any careful observer of thunderstorms. Nevertheless, the erroneous concept that the discharges progress in a steady orderly pattern is still prevalent. 

In a diffuse-reflectance laser flash-photolysis experiment, the excited chro-mophores created by the laser excitation may exhibit a nonhomogeneous spatial distribution. Theoretical treatments (Kessler et al. [10b] and Oelkrug et al. [12]) have shown that two extreme types of concentration profiles can be produced. In the first type, the concentration of excited species decreases exponentially as a function of the penetration depth of the excitation radiation whereas, in the second type, the excited species are distributed in a homogeneous manner within a specific width, and then decrease ( plug profile) as in [lOf, lOg]. 

The resulting set of ODEs can be solved by any ODE solver. The drying rate can be calculated between time steps (Equation 3.112) from temporal change of space-averaged moisture content. As a result one obtains simultaneously spatial profiles of moisture content in the solid as well as longitudinal distribution of parameters in the gas phase. Exemplary results are shown for cocurrent flash drying of spherical particles in Figure 3.16. 

In typical DESI imaging experiments, the collected tissue sample is flash frozen in liquid nitrogen and subsequently cut in micron thin sections using a cryostat-microtome the thin tissue slices are thaw mounted onto glass microscope slides for analysis the ions generated by the DESI (Chapter 2) are transported fi om surfaces to the gas phase for mass analysis as the surface is being moved in order to cover the entire sample area a mass spectrum is acquired for each pixel on the surface and finally, tissue images are constructed to display the spatial intensity distribution of individual selected lipid ion. 

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