Hunter System

The R,G,B values of the Berger formula measured by tristimulus colorimeters are linearly related to the X,Y,Z tristimulus values of the CIE system. The Stensby formula incorporates the L,a,b tristimulus values of the Hunter system. In the CIE 1982 formula, x and yn are the chromaticity coordinates of the D65 (2° or 10° observer) light source. 

Fig. 3.4b), known as CIELAB, has generally replaced the Hunter space for industrial applications although this has been somewhat slower in parts of the food industry where methods established on the Hunter system have economic reasons for its continued use. The improvements in CIELAB are due to the nonlinear cube root transformation of the 1931 tristimulus values, which more approximate the visual spacing of the coloured samples in the Munsell system. The formulae are... 

Porphyrin system typical of those studied by Hunter and Saunders [Hunter and Saunders 1990],... 

The first empirical and qualitative approach to the electronic structure of thiazole appeared in 1931 in a paper entitled Aspects of the chemistry of the thiazole group (115). In this historical review. Hunter showed the technical importance of the group, especially of the benzothiazole derivatives, and correlated the observed reactivity with the mobility of the electronic system. In 1943, Jensen et al. (116) explained the low value observed for the dipole moment of thiazole (1.64D in benzene) by the small contribution of the polar-limiting structures and thus by an essentially dienic character of the v system of thiazole. The first theoretical calculation of the electronic structure of thiazole. benzothiazole, and their methyl derivatives was performed by Pullman and Metzger using the Huckel method (5, 6, 8). 

Measurement of Whiteness. The Ciba-Geigy Plastic White Scale is effective in the visual assessment of white effects (79), but the availabihty of this scale is limited. Most evaluations are carried out (ca 1993) by instmmental measurements, utilising the GIF chromaticity coordinates or the Hunter Uniform Color System (see Color). Spectrophotometers and colorimeters designed to measure fluorescent samples must have reversed optics, ie, the sample is illuminated by a polychromatic source and the reflected light passes through the analy2er to the detector. 

Hunter L,a,b and Other Color Spaces. The CIELAB and CIELUV color spaces were the outgrowth of a large and complex group of interrelated early systems and have replaced essentially all of them except for the 1942 Hunter Y,a,b group of color spaces (3). This was the earliest practical opponent-based system which is still widely used. In this system, for illuminant C and the 2° standard observer ... 

Color Difference Assessment. Color difference scales include those of Judd-Hunter, Macadam, Adams-Nickerson, ANLAB, and ANLAB40. AH of these have limitations in some way or another they are described in most texts (1 4). Each appHes only to the precise conditions used in thek determination and interconversion is not possible. Modifications of CIELAB in the metric form such as the CMC(1 c) system (14) promise improved performance for the future. 

Landolt-Bornstein Physikalische-chemische TabeUen, Eg. I, p. 303, 1927. Phase-equilibrium data for the binary system NH3-H2O are given by Clifford and Hunter,y. Fhys. Chem., 37, 101 (1933). 

Kohl, R, Noble, D., Winslow, R. L. fit Hunter, P. J. 2000 Computational modelling of biological systems tools and visions. Phil. Trans. R. Soc. Land. A 358, 579-610. 

Three attributes characterize color hue, lighmess (or value), and saturation (or chroma) and they are graphically represented in color solids (e.g., Munsell solid. Hunter solid). The Munsell Color Notation is a rapid, portable, widespread, and economical system of color determination. However, as it depends on sensory evaluation by panels, many laboratories prefer when possible to replace human judgment by instrumental techniques that are easier to handle. The CIELAB established by the Commission International d Eclairage (CIE) has become widely used with the availability of reflectance spectrophotometric instrumentation. 

A related study, aimed at demonstrating how a change in the structure of the ligand covalently bound to the porphyrin modified the selfassembling properties of the system, was reported by Hunter (71)1. The... 

Hunter, R. J., The double layer in colloidal systems, CTEy 1, 397 (1980). 

Harvey Rappaport, Tracey Hunter, Joseph Roy, and Kelly Straker Managing Pharmacy Practice Principles, Strategies, and Systems... 

The reactions and identification of small isomeric species were reviewed by McEwan in 199223 Since that time, additional experimental data have been obtained on more complex systems. In the present review, smaller systems will only be mentioned where there has been an advance since the previous review and emphasis here will be concentrated on the correlation between reactivity, the form of the potential surface, and the isomeric forms. There is also a wealth of kinetic data (rate coefficients and product ion distributions) for ion-molecule reactions in the compilations of Ikezoe et al.24 and Anicich,25,26 some of which refer to isomeric species. Thermochemical data relevant to such systems, and some isomeric information, is contained in the compilations of Rosenstock et al.,27 Lias et al.,28 29 and Hunter and Lias.30... 

Hunter, J., Hirst, B. H., Intestinal secretion of drugs the role of P-glycoprotein and related drug efflux systems in limiting oral drug absorption, A dr. Drug Del. Rev. 1997, 25, 129-157. 

Figure 1A shows that the CCC decreases with increasing sol concentration in the range of 50 to 200 ppm. The variation of the CCC with sol concentration is by no means an unexpected observation in view of previous work with other systems (7). Recently Bensley and Hunter (8) have investigated this aspect of colloidal stability with latices and found that up to a volume fraction of 0.10 the CCC was independent of the volume fraction. These authors also pointed out the difficulties involved in measuring the stability of more... 

Two models may be used to interpret the rheological results of the present flocculating system. Both models have been introduced by Hunter and his coworkers (13,14,29-32). ... 

This model was introduced by Neville and Hunter (13,14) for the case of sterically stabilized dispersions which have undergone reversible flocculation. It is assumed that the major contribution to the excess energy dissipation in such pseudoplastic systems comes from the need to provide energy from the shear field to separate contacting particles. Under these conditions, the extrapolated yield value is given by the expression (13,32,33),... 

Veitch NC. 2004. Horseradish peroxidase a modem view of a classic enzyme. Phytochemistry 65 249—259. Wegrzyn TF, Farr JM, Hunter DC, Au J, Wohlers MW, Skinner MA, Stanley RA and Waterhouse DS. 2008. Stability of antioxidants in an apple polyphenol—milk model system. Food Chem 109 310-318. 

Primary lysosomal hydrolase defects. Two-thirds of the lysosomal storage diseases involve defects in genes that code for acid hydrolases. Table 41-2 lists 29 defects that have been defined so far. They have an autosomal recessive mode of inheritance, except for Hunter s syndrome and Fabry s disease, where the mode is X-linked recessive. The defective genes have been identified and mutations have been defined for nearly all. The nervous system is involved in most. Many of the disorders show a wide range of clinical severity, which may range from death in early childhood to a moderate disability in adulthood. 

The polymerizations of olefins catalysed by metal halides have been interpreted in terms of carbonium ions as the reactive species since the work of Hunter and Yohe (see p.109). Although the discovery of co-catalysis subsequently showed that their theory is not valid for many systems,... 

Tater, Gantmakher and Medvedev [43] revived the Hunter-Yohe mechanism with the addition that they supposed it to operate only in polar solvents, the idea being that the zwitterion would thus be stabilised by solvation. The experiments of Colclough and Dainton [36] with the system styrene-stannic chloride-nitrobenzene, and those of Tongworth, Plesch and Rutherford [44] with isobutene-titanium tetrachloride-various alkyl chloride solvents, then showed that in these systems a co-catalyst is required and that therefore the HY-MG mechanism cannot be operative. It has in fact now been abandoned by its originators, who have conceded that in the styrene-SnCl4-EtCl system a co-catalyst is required [45]. 

Before the publication of Colclough and Dainton s work, Gantmakher and Medvedev [11] had revived Hunter and Yohe s theory of direct initiation, but restricted it to solvents of moderately high dielectric constant. They maintained that in such solvents neither a protonic acid nor an alkyl halide co-catalyst is required. The experiments of Colclough and Dainton make this appear highly unlikely, although they do not disprove it completely. It is important to realise that several types of initiation could co-exist in the same system even if in certain systems co-catalysis by alkyl halides were proved, this does not exclude the existence of a concurrent direct initiation by the Hunter-Yohe, Gantmakher-Medvedev mechanism. 

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