Contrast sensitivity functions

The key featme of Daly s visible-difference predictor is a model of the human visual system that concentrates on the lower-order processing of the system such as optics, retina, lateral geniculate nucleus and some higher-order processing in striate cortex. The model contains three main components (i) an amplitude nonlinearity (in image-processing terms, a point process), (ii) the contrast sensitivity functions (implemented as a filter process), and (iii) a detection process which models masking processes within the visual system. 

In contrast, the a-peroxy lactones, also members of the dioxetane family, display a higher reactivity toward nucleophiles, in view of the inherent polarization of the peroxide bond by the carbonyl functionality. Consequently, the nucleophilic attack is expected to take place at the more sterically hindered but more electrophilic alkoxy-type oxygen atom of the peroxide bond. A recent detailed study of the oxidation of various di-, tri-and tetrasubstituted alkenes 6 with dimethyl a-peroxy lactone (7) revealed, however, much complexity, as illustrated in Scheme 7 for R = CH3, since cycloaddition (8), ene-reaction (9 and 10) and epoxidation (11) products were observed. In the presence of methanol, additionally the trapping products 12 and 13 were obtained, at the expense of the polyester 14. The preferred reaction mode is a sensitive function of the steric demand imposed by the attacking alkene nucleophile. 

Another proof against inhomogeneous cure in simple epoxy-amine and other systems has been supplied by gel point measurements. The critical conversion at the gel point (cf. Sect. 4) is a sensitive function of any inhomogeneity. For epoxy-amine systems, the gel point conversion has been found to agree well with the prediction of the theory assuming uniform distribution of reactive groups throughout the volume The deviation does not exceed 1 %. In contrast, for free-radical... 

Besides the most important area of surface coatings, the use of photopolymers as photoresists in the manufacture of printed circuits is well established. Photoimaging with aryldiazonium salt photoinitiators and multifunctional cresol-novolac epoxides was first described by Schlesinger Crivello has mentioned several new photoresists based on the photopolymerization of epoxides with onium initiators Meier and Zweifel have shown that iron arene salts in combination with multifunctional cresol-novolac epoxides yield photoresists with high resolution and contrast. Dual functional epoxides (cf. Sect. 5) containing chalcone groups as light-sensitive units have been described as suitable photoresists especially... 

The effect of tiagabine on visual function has been stndied in 15 patients with chronic partial epilepsy treated for 23-55 months with tiagabine monotherapy after fail-nre with standard antiepileptic drug monotherapy (23). Three patients had localized field losses (two qnadranta-nopic and one hemianopic) from earlier brain lesions. Tiagabine had no effect on visual fields but acquired color vision defects were found in seven of 14 patients contrast sensitivity was unaffected. 

Information on microviscosity is obtained by studying the excimer forming capabilities of suitable fluorescent probes. The excimer, which is a complex of a ground state and excited state monomer, has a characteristic emission frequency. The intramolecular excimer formation for example, of 1,3-dinaphthyl propane (DNP), is a sensitive function of the microviscosity of its neighborhood. This property, expressed as the ratio of the excimer and monomer yield (/e//m) for DNP, has been determined for dodecyl sulfonate solutions and its adsorbed layer for the various regions of the adsorption isotherm (Fig. 4.18) (Somasundaran et al., 1986). Comparing the ratios thus obtained to the /e//m values of DNP in mixtures of ethanol and glycerol of known viscosities, a microviscosity value of 90 to 120 cPs is obtained for the adsorbed layer in contrast to a value of 8 cPs for micelles. The constancy of microviscosity as reported by DNP is indicative of the existence of a condensed surfactant assembly (solloids) that holds the probe. 

Another useful contrast values are related to the resist chemistry in the film, which will subsequently affect the lithographic contrast. Sensitivity (contrast) curves similar to Fig. 3 can be generated by following the degree of reaction (deprotection, for example) with IR or by measuring thinning (in deprotection, for example) as the function of exposure dose. Comparison of a chemical contrast curve with a development contrast curve provides useful information on resist behavior, such as a degree of deprotection at E0. 

Picosecond laser spectroscopy offers direct access to molecular vibrational (T,) and phase (Tj) relaxation as well as orientational dynamics of molecules, t,< . In contrast to experiments on vibrational relaxation in liquids, all those on the reorientational process have been confined to large polyatomic molecules, particularly dye molecules in probe solvents for pragmatic reasons. Since the slip boundary conditions are also a sensitive function of the shape of the molecules and solute-solvent interactions, there is some uncertainty in deciding whether or not it is the local interaction in terms of the solvation volume, or the boundary condition, or both, that varies for a given molecule in a range of liquids such as the... 

---