6-Bromo-, 7-bromo-, 8-bromo- and 6,8-dibromo- 2,2-dimethylchromenes have been synthesised. The 6-bromoand 8-bromo-derivatives were prepared by Claisen rearrangement of aryl propargyl ethers, derived from phenols and 3-chloro-3-methylbut-1-yne. 7-Bromo- and 6,8-dibromo-2,2-dimethylchromenes were obtained by dehydration of the corresponding chroman-4-ols, available from the chroman-4-ones. Addition of bromine to the chromenes gave the corresponding 3,4-dibromochromans which were hydrolysed with aqueous acetone to yield the 3-bromochroman-4-ols. These chromanols were also obtained directly from the chromenes by reaction with N-bromosuccinimide in moist dimethyl sulphoxide. The bromohydrins were oxidised to 3-bromochroman-4-ones and conversion to the chroman-4-ones was achieved by subsequent reaction with benzo±n. The same chroman-4-ones have been synthesised by the condensation of the appropriate brominated 2-hydroxyacetophenories with acetone in the presence of pyrrolidine. Róduction of the chroman-4-ones using sodium borohydride afforded the chroman-4-ols. The bromohydrins have been converted to the corresponding 3,4-epoxychromans and ring opening reactions with lithium aluminium hydride, hydrobromic acid and methanol were studied. Dehydration of the 3-bromochroman- 4-ols yielded the 3-bromochromenes. The isomeric 4-bromochromenes resulted from treatment of the -- - 3,4-dibromochromans with sodium methoxide. Routes to 2,2-dimethylchroman-4-ones based on the Fries rearrangement of phenyl 3-methylbut-2-enoates and the reaction between a phenol and 3-methylbut-2-enoic acid have been examined. In many instances, the isomeric 3,4-dihydro-4,4-dimethylcoumarins were formed either as sole products or admixed with chromanones. Treatment of 4-bromo- 1 6-bromo-, 7-bromo- and 8-bromo-2 ,2-dimethylchromenes with n-butyl-lithium followed by Michler's ketone has given a series of dyes related to Malachite Green, h'.it incorporating an oxygen heterocyclic function. The 6- and 7-bromochromenes gave longitudinally conjugated dyes, whereas transversely conjugated dyes resulted from the 4- and 8-bromochromenes.

No description available.

No description available.

This thesis presents an argument about the basis of our experience of colour. The argument is conducted by means of an interplay between a set of axioms, deductions from a particular theory (including "thought experiments" which explore the logic of those deductions), and concrete empirical evidence. The axioms and the theory are those of James G. Taylor. The title of the thesis refers to the general methodology adopted. The term "experimental transformation" carries specific connotations; and the notions from which it is derived, and to which it gives rise, have to be understood in the context of the total argument. If the argument presented is sound, then certain implications follow which, it is claimed, force us to reconsider many current assumptions about the nature of "colour sensation" and indeed about the very meaning to be ascribed to the term colour. This in turn would have significance for colour science, psychology and epistemology in general.

No / Rendering packages are used by visual psychophysicists to produce complex stimuli for their experiments, tacitly assuming that the simulation results accurately reflect the light-surface interactions of a real scene. RADIANCE is a physically based, freely available, and commonly used rendering software. We validated the calculation accuracy of this package by comparing simulation results with measurements from real scenes. RADIANCE recovers color gradients well but the results are shifted in color space. Currently, there is no better simulation alternative for achieving physical accuracy than by combining a spectral rendering method with RADIANCE.

Yes / Are objects remembered with a more saturated color? Some of the evidence supporting this statement comes from research using “memory colors”—the typical colors of particular objects, for example, the green of grass. The problematic aspect of these findings is that many different exemplars exist, some of which might exhibit a higher saturation than the one measured by the experimenter. Here we avoid this problem by using unique personal items and comparing long- and short-term color memory matches (in hue, value, and chroma) with those obtained with the object present. Our results, on average, confirm that objects are remembered as more saturated than they are.

No description available.

The ability to differentiate between colours varies from individual to individual. This variation is attributed to factors such as the presence of colour blindness. Colour is used to encode information in information visualizations. An example of such an encoding is categorization using colour (e.g., green for land, blue for water).<p> As a result of the variation in colour differentiation ability among individuals, many people experience difficulties when using colour-encoded information visualizations. These difficulties result from the inability to adequately differentiate between two colours, resulting in confusion, errors, frustration, and dissatisfaction.<p> If a user-specific model of colour differentiation was available, these difficulties could be predicted and corrected. Prediction and correction of these difficulties would reduce the amount of confusion, errors, frustration, and dissatisfaction experienced by users. This thesis presents a model of colour differentiation that is tuned to the abilities of a particular user. To construct this model, a series of judgement tasks are performed by the user. The data from these judgement tasks is used to calibrate a general colour differentiation model to the user. This calibrated model is used to construct a predictor. This predictor can then be used to make predictions about the user's ability to differentiate between two colours.<p> Two participant-based studies were used to evaluate this solution. The first study evaluated the basic approach used to model colour differentiation. The second study evaluated the accuracy of the predictor by comparing its performance to the performance of human participants. It was found that the predictor was as accurate as the human participants 86.3% of the time. Using such a predictor, the colour differentiation abilities of particular users can be accurately modeled.

The ability to differentiate between colours varies from individual to individual. This variation is attributed to factors such as the presence of colour blindness. Colour is used to encode information in information visualizations. An example of such an encoding is categorization using colour (e.g., green for land, blue for water).<p> As a result of the variation in colour differentiation ability among individuals, many people experience difficulties when using colour-encoded information visualizations. These difficulties result from the inability to adequately differentiate between two colours, resulting in confusion, errors, frustration, and dissatisfaction.<p> If a user-specific model of colour differentiation was available, these difficulties could be predicted and corrected. Prediction and correction of these difficulties would reduce the amount of confusion, errors, frustration, and dissatisfaction experienced by users. This thesis presents a model of colour differentiation that is tuned to the abilities of a particular user. To construct this model, a series of judgement tasks are performed by the user. The data from these judgement tasks is used to calibrate a general colour differentiation model to the user. This calibrated model is used to construct a predictor. This predictor can then be used to make predictions about the user's ability to differentiate between two colours.<p> Two participant-based studies were used to evaluate this solution. The first study evaluated the basic approach used to model colour differentiation. The second study evaluated the accuracy of the predictor by comparing its performance to the performance of human participants. It was found that the predictor was as accurate as the human participants 86.3% of the time. Using such a predictor, the colour differentiation abilities of particular users can be accurately modeled.

Pontificia Universidad Católica de Valparaíso