Dissymmetry sources

The helix can be approximated as a rod therefore values of L/X which are consistent with the observed dissymmetries can be read from Fig. 10.13 or equivalent sources. Also, X = Xo/n = 436/1.446 = 302 nm in each of these systems. In view of these considerations, the following results are obtained ... 

Obviously, the analysis of the correlation between the two fields emerging from the telescope and related devices makes necessary to avoid dissymmetry between the interferometric arms. Otherwise, it may result in confusion between a low correlation due to a low spatial coherence of the source and a degradation of the fringe contrast due to defects of the interferometer. The following paragraphs summarize the parameters to be controlled in order to get calibrated data. 

An asymmetric carbon atom has four different atoms or groups of atoms attached to it and may be a source of dissymmetry in the molecule. The asymmetric carbon atom may have two possible arrangements of the groups around it. The two structures may be nonsuperimposable mirror images, and can be expected to differ in the rotation of plane-polarized light to an equal extent but in the opposite direction. 

Small clearly recognized these changes as partial racemizations, but appears to think it possible that a number of asymmetric centres can be inverted in a single step, for he calls the optical antipode of (+)-a (—)-a. It is preferable to term it (—)-S, however, for then (+), (—), a, and 8 can be taken as symbols representing left-hand or right-hand at two sources of dissymmetry and the partial racemization of (+)-a by heat then gives (—)-a [6, 7],... 

Circular dichroism employs standard dispersive or interferometric instrumentation, but uses a thermal source that is rapidly modulated between circular polarization states using a photoelastic or electro-optic modulator. Using phase-sensitive detection, a difference signal proportional to the absorption difference between left- and right-polarized light, A A = AL — AR, is recorded as a function of wavenumber. Relative differential absorptions (dissymmetry factors) AA/A at absorption maxima are typically 0.1—0.01 for uv—vis electronic transitions and 10-4 —10-5 for vibrational modes in the ir. 

There are other sources of electrical dissymmetry in a bond, some... 

Convinced that the functioning of a potentiometric sensor relies on the dissymmetry of the physico-chemical effect which occurs at the two electrodes, we have thought it appropriate to check whether a mere geometric dissyimnetiy could be the source of potentiometric effects. 

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