Host medium

Fig. 7. Model calculations for the reflectivity (a) and the optical conductivity (b) for a simple (bulk) Drude metal and an effective medium of small metallic spherical particles in a dielectric host within the MG approach. The (bulk) Drude and the metallic particles are defined by the same parameters set the plasma frequency = 2 eV, the scattering rate hr = 0.2 eV. A filling factor/ = 0.5 and a dielectric host-medium represented by a Lorentz harmonic oscillator with mode strength fttOy, 1 = 10 eV, damping ftF] = I eV and resonance frequency h(H = 15 eV were considered for the calculations.

Benzimidazolone pigments, especially those covering the red range of the spectrum, were originally developed and used mostly for plastics. None of them were found to adversely affect the physical characteristics of their host medium. Benzimidazolone pigments do not bloom in plasticized PVC and other polymers. They are usually bleed resistant under typical application conditions. 

The first barrier is the form of the waste, which will immobilize the radioactive materials. The waste form should not be damaged by heat or radiation nor be attacked by groundwater. The waste is placed in a steel canister, which is resistant to leaching. The canister is surrounded by packing materials that prevent radioactivity from escaping, and the entire repository is backfilled with a material that absorbs or resists chemical intrusion. The final barrier is the host medium that separates the repository from the surrounding area. 

The host medium can be bedded salt, salt domes, granite, basalt, or volcanic tuff. Each medium has advantages and disadvantages with regard to resistance to water intrusion, site availability, and political considerations. Each medium can work and the most important factor is how the local site is designed. An additional factor is the... 

Zeolites provide a novel host for the generation of semiconductor hyperlattices within their pore volume. The control of the connectivity between the clusters of semiconductor is unparalleled in any other host medium and so has allowed a detailed study of the optical consequences of such connectivity6. However, from the practical standpoint, such materials have some severe drawbacks - most notably the lack of single crystals of sufficient size to produce viable optical devices such as optical transistors or spatial light modulators. We have therefore moved on to look at more practical/processable quantum-dot materials such as semiconductor-doped porous glasses. 

Colloid Fine-grained materials (usually 2-10 000 A in diameter) that remain indefinitely suspended in their host medium. For example, solid colloids may occur in water. Double layers often exist on colloids. 

As a result, the site-dependent nonradiative process of individual C molecules is responsible to biexponential fluorescence decay curves of CV observed in the ensemble-averaged measurement. Our single-molecule study presented in this section will open new possibilities in the experimental study of dynamic response of condensed matter, such as polymers and liquid. We further expect that dye molecules with flexible molecular structures like CV are useful to sensitive local probes for microscopic dynamics of various host mediums. 

Accounting for the effect of the host material on the interactions between the dipoles involves the refractive index, the relative orientation of the charges, and the local or internal field. The local or internal field problem is associated with the fact that molecules in a host medium occupy a particular volume or a cavity . This cavity description has been used to formalize the description of interactions between dipoles. The region occupied by the molecule results in an additional correction so the field acting on the molecule will be an effective local field rather than the mean macroscopic field. The field acting on the molecule may be an applied electromagnetic field (such as in absorption), the effect of another dipole or a combination of the two. 

There are two important cases in which the impulsively driven vibrational response travels through the host medium, often leaving the region... 

For v A = 1 this is the ordinary rate coefficient for an interaction of a mono-energetic beam with a Maxwellian host medium (e.g., [20]). Since any... 

As for the linear properties, numerous approaches have been proposed to predict and explain the nonlinear optical response of nanocomposite materials beyond the hypothesis leading to the simple model presented above ( 3.2.2). Especially, Eq. (27) does not hold as soon as metal concentration is large and, a fortiori, reaches the percolation threshold. Several EMT or topological methods have then been developed to account for such regimes and for different types of material morphology, using different calculation methods [38, 81, 83, 88, 96-116]. Let us mention works devoted to ellipsoidal [99, 100, 109] or cylindrical [97] inclusions, effect of a shape distribution [110, 115], core-shell particles [114, 116], layered composites [103], nonlinear inclusions in a nonlinear host medium [88], linear inclusions in a nonlinear host medium [108], percolated media and fractals [101, 104-106, 108]. Attempts to simulate in a nonlinear EMT the influence of temperature have also been reported [107, 113]. 

It appears to us worthwhile to point out the different parameters relevant to the analysis of the tlrird-order nonlinear optical response of nanocomposite materials, because some of them are sometimes omitted in the literature, rendering the comparison difficult. They can be classified into two main sets. First, some parameters are linked wltlr the optical excitation source, which usually consists of a pulsed laser beam Wavelength X, pulse energy E, pulse duration t, repetition rate v. Secondly, otlrer relevant parameters concern the material Itself Particle size and shape (and distributions), metal volume fraction p, particle spatial arrangement in the host medium. 

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