Dielectric direct sensing

This improvement in evaluating the true dipole moment affects the calculation in the correct sense that is, the disagreemrat between the calculated band and the experimental one decreases. However, for a completely satisfactory model, one really allowing prediction of the observed dielectric spectrum of water, much work is still necessary. In this direction we mention two recent papers by Stillinger and Camie and Patey. In Table II we have listed all the data obtained from our model. 

From (9.32), which shows that is determined by the least effective conductivity mechanism, it is evident that this static conductivity may be quite critically dependent upon the presence of proton-donor or proton-acceptor impurities and, in this sense, the behaviour of ice is quite analogous to that of electronic semiconductors like germanium or silicon. Mole fractions of impurity which are significant are of the order of io . The high-frequency conductivity and relaxation time t are, from (9.30) and (9.35), rather less sensitive to impurity content than is doping levels. The static dielectric constant depends on purity in a rather complex way, as we shall discuss presently. 

When a droplet passes through the sensing region, variations in capacitance can be detected in real time due to the contrast in dielectric properties between the aqueous solution and oil phase. Niu and coworkers employed a capacitance method to test the size and speed of droplets by integrating parallel electrodes across the droplet flow channel [8]. Based on the electric signal feedback, the microfluidic droplets can be counted, sorted out, or directed in an automated manner. However, this droplet content assay is limited to certain dielectric materials [9]. 

In many problems involving remote sensing, the molecules of interest comprise the outer surface of the particle or have been adsorbed onto it. The presence of the particle affects the inelastic scattering to about the same degree as for the uniformly filled particle. Figure 4.14 shows the angular distribution of the components for the same number of dipoles distributed uniformly over the surface of an otherwise uniform dielectric sphere of refractive index 1.5 for different values of a. The minimum at 90° is rapidly filled in. The scattering in the forward and backward directions appear particularly sensitive to particle size. 

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