Phase-conjugate processes

The observed dynamics of the self-starting phase conjugation process is governed by the optical nonlinearity and scattered noise amplitude [27], as well as the thermal grating build up time. Both the onset time and build up times are shortened as the input pump power is increased. The total time it takes for the signal to build up to the maximum can be as short as 0.5 ms, at a pump power of about 800 mWatt. These shortenings of the build up and onset times have also been observed as the sample temperature is increased towards T [25]. 

Notice that the generated wave Ai, d) in Equation (11.58) is proportional to the complex conjugate of the wave A2, for this reason, it is sometimes called the forward phase conjugate of 2- the following section we will discuss another phase conjugate process. 

Accordingly, unlike most nonhnear optical materials, liquid crystals enable optical wave mixings to occur with high efficiency in the visible as well as infrared regime. In this section, we discuss two exemplary wave mixing processes in hquid crystals stimulated orientational scatterings and optical phase conjugation processes. 

Figure 12.15. Typical dynamics of self-starting optical phase conjugation process.

Put very simply two sorts of drug-metabolizing enzymatic processes occur in the microsomes of the smooth endoplasmic reticulum or in the cytosol of liver cells. The first, so-called Phase F, reactions may add or subtract a small portion of the drug molecule, commonly by oxidation. This by itself may make a product more water-soluble, but, more commonly, a second step - Phase IF- process is required in which the altered drug is coupled (conjugated - literally married ) to compounds already existing in the liver cells to form salts such as glu-curonides and sulphates (Fig. 3). 

Two types of enzymatic pathways, the so-called phase I and phase II pathways, are generally implicated in drug biotransformation. Phase I pathways correspond to functionalization processes, whereas phase II correspond to biosynthetic or conjugative processes. Phase I functionalization processes include oxidation, reduction, hydrolysis, hydration, and isomerization reactions. 

Repeat question 2 but select five different drugs to demonstrate the following phase II processes acetylation, sulfo-nylation, glucuronidation, conjugation with an amino acid, and conjugation with glutathione. 

Clearly the above scheme of liquid-phase oxidation by oxygen shows H202 and ROOH formed as intermediate products. However, they cannot be related to active sites of another, secondary reaction as is customary in, for example, conjugated processes. The reasons for making such comparisons are as follows firstly, H202 and ROOH are final products of a complex reaction and initial reagents for other thermodynamically probable reactions secondly, their formation and consumption (by the scheme selected) do not correspond to the notion of active site of conjugated reactions. 

X< ) ( —(o CO, CO, — co) Self-focusing, degenerate four-wave mixing, optical Ken-effect Optical bistability, phase conjugation, optical transistors, image processing... 

With an ordinary mirror, the image is reflected rather than redirected. Phase conjugate mirrors can be constructed to provide a number of lensless imaging and image-processing functions. Current values of electronic non-linearities in polymers require laser power densities in the range of kilowatt per square centimeter in order for these effects to be manifested. Photo-refractive materials such as BaTi03 crystals have been used to demonstrate these effects at a power density of approximately 10 mW/cm (12),... 

PAHS are readily absorbed via the gastrointestinal tract and then metabolically transformed to more reactive forms. These toxicants are typically converted into more reactive metabolites through phase I biotransformations, and then converted into more readily excretable conjugates via phase II processes. 

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