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At least 271 records · Page 15Linked to original sources

PubMed1988

Positive colored afterimages from the figure-ground configurations of colored lights: effects of chromaticity, luminance and a spatial parameter of the adapting stimuli.

Colored afterimages were obtained after the eye was exposed to the adapting field consisting of the figure-ground configuration of colored lights with the same hue and different saturation. When a colored patch was surrounded by a more saturated field, the color of the afterimage was similar to that of the previous patch (positive afterimage). By measuring the threshold chromaticity difference between the patch and the surround for the production of the positive afterimage, the effects of the chromaticity, luminance and a spatial parameter of the adapting field were determined. The obtained threshold chromaticity differences increased with an increase in the saturation of the adapting field, and with a decrease in the surround luminance. When the adapting field consisted of an equiluminous saturation-modulated rectangular grating, the threshold chromaticity difference curves showed similar properties as those of the contrast thresholds for equiluminous chromaticity-modulated gratings. The results suggest the existence of a set of mechanisms at higher-order level in the visual system, tuning the difference in hue and/or saturation across contours.

Adaptation, Ocular↗

PubMed1996

Accuracy of color doppler velocity in the flow field proximal to a regurgitant orifice: implications for color doppler quantitation of valvular incompetence.

Color Doppler is routinely used in estimates of valvular regurgitation. Velocity and subsequently flow measurements are made at about 7-10 cm from the ultrasonic transducer. Error in velocity measurement may occur due to spatial broadening of the color Doppler beam in the axial, azimuthal and lateral directions. Error in velocity may also occur due to wall filters since the filtering process is not uniform throughout the velocity range indicated by the color bar. An attempt to estimate this error was made using an in vitro orifice model, a numerical finite element model (FEM), and information from the manufacturer. We found that the acoustic beam spatial expansion, wall filter sensitivity and Nyquist limit (NYL) have to be considered simultaneously to account for errors. The combined spatial expansion and wall filter effect on velocity was estimated as a weighted average over the sample volume. The error distributions are not universal but depend on orifice size and flow. For a 3-mm orifice and 100 cm s NYL the overall effect was overestimation of low velocities and significant underestimation of high velocities due to the high velocity gradients inside the sample volume. For the 5- and the 10-mm orifice the effect was less accentuated. Based on this overall error distribution, a correction was incorporated on color Doppler obtained data. The incorporated correction yielded better agreement with numerical velocity data. This correction is important in the application of the proximal isovelocity surface area (PISA) technique and the evaluation of regurgitant flowrates.

Blood Flow Velocity↗

PubMed2006

The proximate control of pupal color in swallowtail butterflies: implications for the evolution of environmentally cued pupal color in butterflies (Lepidoptera: Papilionidae).

The environmentally cued production of cryptic green/yellow or brown/melanized pupae is widespread in butterflies, occurring in the Nymphalidae, Pieridae, and the Papilionidae subfamily Papilioninae. The dimorphism is controlled by the hormone pupal melanization reducing factor (PMRF). In the nymphalid Inachis io dibutryl cAMP mimics PMRF, and inhibits pupal melanization. However, in the papilionid Papilio polyxenes PMRF stimulates browning, suggesting that the control of pupal color by PMRF has evolved independently in the swallowtail and nymphalid-pierid lineages. We examined this hypothesis by using ligatures to prevent hormone release in five species representing three Papilioninae tribes. One species, Papilio glaucus, produces only brown pupae. Ligatures resulted in green cuticle posterior to the ligature in all five swallowtail species, including P. glaucus, suggesting that the mode of action of PMRF is the same in the three tribes. We also found that in P. polyxenes injections of dibutryl cAMP into prepupal larvae mimic the effect of PMRF, by causing dose-dependent pupal browning. Our results support the hypothesis that the control of pupal color by PMRF has evolved independently in the two lineages. The observation that green pupal color can be induced in P. glaucus by ligature indicates that environmentally cued pupal color could evolve by facultative inhibition of PMRF release.

Animals↗

PubMed2006

Infant color vision: prediction of infants' spontaneous color preferences.

Infants show spontaneous looking preferences among isoluminant chromatic stimuli [Adams, R. J. (1987). An evaluation of color preferences in early infancy. Infant Behavior and Development, 10, 143-150; Bornstein, M. H. (1975). Qualities of color vision in infancy. Journal of Experimental Social Psychology, 19 (3), 401-419.]. These differences in preference have often been called "hue" or "color" preferences, and attributed to differences in hue, but there are alternative explanations. Spontaneous preference variations remain after stimuli are equated for adult brightness, and thus cannot be attributed to adult-like brightness differences [Teller, D. Y., Civan, A., & Bronson-Castain, K. (2004). Infants' spontaneous color preferences are not due to adult-like brightness variations. Visual Neuroscience, 21 (3), 397-401]. In the present paper, we address three more alternative explanations: colorimetric purity; infant detection thresholds; and adult-like variations in saturation. Three experiments were conducted. In Experiment 1 we measured infants' spontaneous preferences for each of 22 different chromatic stimuli of varying dominant wavelength and colorimetric purity, each paired against the same white standard. In Experiment 2, we measured infants' chromatic detection thresholds. In Experiment 3, adult subjects made saturation matches between a blue-green standard and each of five other chromatic stimuli. Infant detection thresholds accounted for 34% of the variance in infant "hue" preferences, much more than colorimetric purity (2.4%) or adult saturation judgments (3%), but none of the three variables accounted for the majority of the variance. In our view, the most likely remaining option is that infants' spontaneous "hue" preferences indeed arise from preferences for the hues of stimuli that adults see as blue, purple and red.

Adult↗

PubMed2002

Color categories revealed by non-negative matrix factorization of Munsell color spectra.

Non-negative matrix factorization (NMF, Nature 401 (1999) 788-791) is a method to derive non-negative basis functions for sets of data that are inherently non-negative, such as color spectra. We applied NMF to Munsell color spectra and investigated the color names associated with the non-negative basis functions. NMF yields basis functions compatible with established color naming categories.

Color↗

PubMed1986

Conjunction of color and form without attention: evidence from an orientation-contingent color aftereffect.

According to feature-integration theory (Treisman & Gelade, 1980), separable features such as color and shape exist in separate maps in preattentive vision and can be integrated only through the use of spatial attention. Many perceptual aftereffects, however, which are also assumed to reflect the features available in preattentive vision, are sensitive to conjunctions of features. One possible resolution of these views holds that adaptation to conjunctions depends on spatial attention. We tested this proposition by presenting observers with gratings varying in color and orientation. The resulting McCollough aftereffects were independent of whether the adaptation stimuli were presented inside or outside of the focus of spatial attention. Therefore, color and shape appear to be conjoined preattentively, when perceptual aftereffects are used as the measure. These same stimuli, however, appeared to be separable in two additional experiments that required observers to search for gratings of a specified color and orientation. These results show that different experimental procedures may be tapping into different stages of preattentive vision.

Adolescent↗

PubMed1988

Color Doppler flow mapping in patients with coarctation of the aorta: new observations and improved evaluation with color flow diameter and proximal acceleration as predictors of severity.

We performed color Doppler flow mapping in 15 patients, 1 week to 17 years old (mean 42 months), with coarctation of the aorta that was confirmed subsequently by angiography and/or surgery. Twelve patients had native coarctation and three had mild recoarctation after surgical repair. Color Doppler flow maps were analyzed with a digital analysis package and a Sony computer system. The diameter in the region of coarctation from the color Doppler flow map (mean = 2.0 +/- 0.8 mm [SD]) correlated well with the coarctation diameter measured at angiography (mean = 1.8 +/- 0.8 mm; r = .83, SEE 0.43 mm) in the 10 patients with native coarctation undergoing angiography, but the coarctation diameter measured by two-dimensional echocardiography (3.9 +/- 1.5 mm) was poorly predictive of the angiographic severity (r = .23). Additionally, spatial acceleration was seen in all patients proximal to the coarctation site, with an aliased and accelerating stream narrowing progressively as it proceeded toward the coarctation site, a pattern that is not seen in healthy subjects. Computer analysis of the color Doppler images provided pseudo three-dimensional and digital velocity maps for blue, red, and green (turbulent) flow velocities to allow an enhanced appreciation of the accelerating stream, easily separating this from normal descending aortic aliasing patterns. The narrowing of the acceleration area in the proximal descending aorta (distal/proximal acceleration zone ratio) was also predictive of the angiographic severity of coarctation (r = .83). The distribution of low-level turbulence seen proximally paralleled the distribution of the proximal accelerating stream.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗

PubMed1985

Color matching at high illuminances: the color-match-area effect and photopigment bleaching.

We evaluated whether a self-screening hypothesis can account for changes in red-green color matches with changes in retinal illuminance and changes in the size of the matching field. The dependence of the color match on field size measured at moderate illuminances was not present at high illuminances. For color matches made with normal pupil entry, there was no need to postulate any factors other than self-screening to account for the changes with either illuminance or field size. The self-screening model allowed us to estimate the optical density of the foveal cones and the retinal illuminance that caused half of the photopigment to be bleached at equilibrium. These estimates were in quantitative agreement with previous estimates made using other techniques. We also found that the change in a color match with increasing illuminance was inconsistent with first-order kinetics.

Adult↗

PubMed1975

Color preferences of art students: surface colors: II.

In a previous study (Götz & Götz, 1974b) the preferences of 14 surface colors were analyzed. While this set contained only one red, one blue, one yellow, etc., the color set of the present investigation was extended, and the preferences of 5 different reds, blues, yellow, etc. were analyzed. Between the five variations of red and yellow, respectively, the greatest affective differences were found, while the opposite was true for the 5 oranges, pinks, and grays. The most preferred colors are 2 reds, 2 blues, and 2 yellows; least preferred are a greenish yellow, a penetrating red-violet, and all 5 pinks. Significant sex differences were found for 8 colors.

Adult↗

PubMed1994

On the naming of color words and color patches.

Subjects can name color words faster than they can name color patches. To account for that effect, a generic model of naming is described which assumes that words access the mental lexicon directly, whereas color patches do so only indirectly via an initial imaginal or semantic representation. However, Lund (1927) reported that the naming advantage for words disappeared when all the items to be named on a page were the same (i.e., they were blocked). In the present study, three experiments are reported that were designed to provide a clearer empirical definition of Lund's blocking effect and to ascertain the extent to which it requires a modification of the generic model. The blocked lists had 50 items arranged into 10 blocks, with each block homogeneous with respect to color. The block lengths were either all a predictable length of 5 items or they varied randomly from 1 to 9 items. The data indicated the following: (1) The blocking effect occurred even when the task required a full identification of each item, and (2) the blocking effect was confined to within-block transitions. Blocking seemed to eliminate the word advantage by allowing the subject to re-use the lexical entry used for the immediately prior items, which is consistent with the generic model.

Color Perception↗

PubMed2006

9-color and 10-color flow cytometry in the clinical laboratory.

CONTEXT: The development of commercial flow cytometers capable of detecting more than 10 simultaneous fluorescent signals presents opportunities for improved diagnosis and monitoring of patients with leukemia and lymphoma. OBJECTIVE: To describe instrument and reagent characteristics necessary for successful 9-color and 10-color flow cytometry in a clinical setting. DESIGN: Systematic review of issues related to instrument settings, reagent performance, and general principles of panel construction. RESULTS: Nine-color and 10-color flow cytometry offers the possibility for increased accuracy in population identification, the ability to obtain detailed information from paucicellular specimens, improved laboratory efficiency, and the means to consistently detect abnormal populations at low levels. Careful attention to details of instrument and reagent performance allows for the development of panels suitable for screening of samples for leukemia and lymphoma in a clinical setting. CONCLUSIONS: The characteristics of this technique are particularly well suited to the analysis of leukemia and lymphoma and have the potential to revolutionize and standardize this type of analysis in the clinical laboratory.

Cell Separation↗

PubMed2002

Color image analysis of cervical neoplasia using RGB computer color specification.

OBJECTIVE: To establish quantitative color image analysis for cytology, red, green and blue (RGB) color specification was applied to Papanicolaou-stained cervical smears. STUDY DESIGN: Cell samples used in this study was those from 300 cervical specimens. We analyzed the color tone of nuclei and cytoplasm of the squamous cells in the cervical smear by means of computer image analysis. RESULTS: Papanicolaou stained nuclei displayed basophilic blue to purple. When they were hyperchromatic and deeply stained, B and G values decreased in value. The RGB values of cytoplasm and nuclei decreased significantly (P < .01) as their degree of cellular atypia increased. CONCLUSION: Using RGB color specification to analyze Papanicolaou-stained cervical smears, a significant difference was perceived in the nucleus and cytoplasm between different groups of squamous cells, from normal, dysplastic and squamous cell carcinoma. These findings may help to establish automated cytology.

Carcinoma in Situ↗

PubMedDate not supplied

Analysis of natural coloring matters in food. III. Application of methylation with diazomethane for the detection of lac color.

A new method has been proposed for detection of lac color in food. Lac color is a natural color additive derived from a secretion of the insect Coccus Laccae (Laccifer lacca Kerr). It is extracted from food with methanolic oxalic acid and eluted from a column of Amberlite XAD-2 with the same solvent. The fraction containing the lac color is treated with diazomethane to produce 2 reddish-orange markers. The marker species in the reaction mixture are detected by both thin-layer chromatography and reverse-phase liquid chromatography.

Animals↗

PubMed1993

[Changes in optic disc rim color with glaucomatous visual field damage--a quantitative study on pattern of color changes].

We developed a new computerized method for measuring the color of the optic disc directly with objective reproductivity. We compared the optic disc color with sensitivity loss in visual fields corresponding to the disc area measured by Humphrey Field Analyzer. 11 normal eyes, 40 glaucomatous eyes, and 27 eyes with ocular hypertension were studied. In the temporal segment of the disc rim, with the exception of the area, a significant correlation between rim color and sensitivity loss was detected. In the nasal rim and macular area, however, the correlation was less significant in early stage glaucoma. Compared with normal discs, glaucomatous discs showed significant decrease in the red color element of the rim area, and some discs with ocular hypertension showed a decrease without any visual field defect.

Aged↗

PubMed1997

[A study of coloring in human lens nucleus--association of four inorganic elements and dielectric behavior with nuclear color].

We classified senile cataractous lenses before surgery into five grades on the basis of their nuclear color and analyzed the extracted nuclei on wet weight, water content (weight %), inorganic element content (sodium, potassium, calcium and magnesium), and dielectric behavior. With increase in the grade, water content (p < 0.01) and potassium content (p < 0.05) significantly decreased, and wet weight (p < 0.01) and sodium (p < 0.05), calcium (p < 0.01) and magnesium (p < 0.001) content significantly increased. In dielectric behavior, limiting conductivity at low frequencies significantly decreased with increase in the grade (p < 0.05), and limiting permittivity at high frequencies showed a trend to decrease, but it was not significant (p = 0.052). These results indicate that changes in water content and in inorganic element content are associated with advancement in color grade, suggesting a close relation between the color grade and the membrane functions of lens fibers. In the nuclei with high color grade, we concluded that part of the active transport systems of the fiber membranes was damaged, although the electrical barrier of the membranes was retained.

Aged↗

PubMed2001

Stereo nonmydriatic digital-video color retinal imaging compared with Early Treatment Diabetic Retinopathy Study seven standard field 35-mm stereo color photos for determining level of diabetic retinopathy.

OBJECTIVE: To evaluate the ability to determine clinical levels of diabetic retinopathy, timing of next appropriate retinal evaluation, and necessity of referral to ophthalmology specialists using stereoscopic nonmydriatic digital-video color retinal images as compared with Early Treatment Diabetic Retinopathy Study (ETDRS) seven standard field 35-mm stereoscopic color fundus photographs. DESIGN: Prospective, clinic-based, comparative instrument validation study. PARTICIPANTS: Fifty-four patients (108 eyes) with type 1 or type 2 diabetes mellitus selected after chart review from a single center to include the full spectrum of diabetic retinopathy. METHODS: Nonsimultaneous 45 degrees -field stereoscopic digital-video color images (JVN images) were obtained from three fields with the Joslin Vision Network (JVN) system before pupil dilation. Following pupil dilation, ETDRS seven standard field 35-mm stereoscopic color 30 degrees fundus photographs (ETDRS photos) were obtained. Joslin Vision Network images and ETDRS photos were graded on a lesion-by-lesion basis by two independent, masked readers to assess ETDRS clinical level of diabetic retinopathy. An independent ophthalmology retina specialist adjudicated interreader disagreements in a masked fashion. MAIN OUTCOME MEASURES: Determination of ETDRS clinical level of diabetic retinopathy, timing of next ophthalmic evaluation of diabetic retinopathy, and need for prompt referral to ophthalmology specialist. RESULTS: There was substantial agreement (kappa = 0.65) between the clinical level of diabetic retinopathy assessed from the undilated JVN images and the dilated ETDRS photos. Agreement was excellent (kappa = 0.87) for suggested referral to ophthalmology specialists for eye examinations. Comparison of individual lesions between the JVN images and the ETDRS photos and for interreader comparisons were comparable to the prior ETDRS study. CONCLUSIONS: Undilated digital-video images using the JVN system were comparable photographs for the determination of diabetic retinopathy level. The results validate the agreement between nonmydriatic JVN images and dilated ETDRS photographs and suggest that this digital technique may be an effective telemedicine tool for remotely determining the level of diabetic retinopathy, suggesting timing of next retinal evaluation and identifying the need for prompt referral to ophthalmology specialists. Thus, the JVN system would be an appropriate tool for facilitating increased access of diabetic patients into recommended eye evaluations, but should not be construed as a paradigm that would replace the need for comprehensive eye examinations.

Adult↗

PubMed2000

Correlation of lycopene measured by HPLC with the L, a, b color readings of a hydroponic tomato and the relationship of maturity with color and lycopene content.

Tomatoes (Lycopersicon esculentum cv. Laura) were separated, according to the ripening stage, by a sensory panel into seven groups, and color was measured on the tomato surface with a Minolta Chroma meter. The L, a, b, hue, chroma, and lycopene content were plotted against the maturity stages of the tomatoes, and several good correlations were found. The a/b ratio and the lycopene content were the parameters that allowed six of seven maturity groups in the tomato to be statistically distinguished. The lycopene content, measured by HPLC, was also correlated with the color measurements, and the a, a/b, and (a/b)(2) color factors produced the best regressions. An estimation of the lycopene content in tomatoes can be achieved by using a portable chroma meter, with a possible field usage application. Equations to calculate the lycopene content of tomatoes based on the color readings are reported.

Carotenoids↗

PubMed2005

Stepwise photocleavage of C-O bonds of bis(substituted-methyl)naphthalenes with stepwise excitation by two-color two-laser and three-color three-laser irradiations.

Stepwise photocleavage of naphthylmethyl-oxygen (C-O) bonds of mono(substituted-methyl)naphthalenes [1- and 2-ROCH2Np, R = 4-benzoylphenyl (BP), phenyl (Ph), and methyl (CH3)] and bis(substituted-methyl)naphthalenes [1,8-(ROCH2)2Np and 1,4-(ROCH2)2Np, R = BP and Ph] was observed to give the naphthylmethyl radicals (NpCH2* or ROCH2NpCH2*) in almost 100% yield with two-step or three-step excitation by the two-color two-laser or three-color three-laser irradiation, respectively, at room temperature. The C-O bond cleavage quantum yields of 1-PhOCH2Np, 2-PhOCH2Np, 1,8-(PhOCH2)2Np, and 1,4-(PhOCH2)2Np were higher than those of 1-BPOCH2Np, 2-BPOCH2Np, 1,8-(BPOCH2)2Np, and 1,4-(BPOCH2)2Np. No C-O bond cleavage occurred from 1,8-(HOCH2)2Np and 2-CH3OCH2Np in the higher triplet excited state (T(n)). The experimental results show that the C-O bond cleavage was determined not only by the position of the substituents on Np but also by the type of the substituents. The C-O bond cleavage of 1-ROCH2Np was more efficient than that of 2-ROCH2Np. In the case of 1,8-(ROCH2)2Np and 1,4-(ROCH2)2Np (R = BP and Ph), the first C-O bond cleavage from the T(n) states occurred to give ROCH2-substituted naphthylmethyl radicals (1,8- and 1,4-ROCH2NpCH2*) when the T1 states, generated with the 308-nm first laser irradiation, were excited using the 430-nm second laser. The second C-O bond cleavage occurred when 1,8- and 1,4-ROCH2NpCH2* in the ground state [1,8- and 1,4-ROCH2NpCH2*(D0)] were excited to the excited states [1,8- and 1,4-ROCH2NpCH2*(D(n))] using the third 355-nm laser during the three-color three-laser flash photolysis at room temperature. It was revealed that acenaphthene was produced as the final product during the stepwise C-O bond cleavages of 1,8-(BPOCH2)2Np and 1,8-(PhOCH2)2Np. This is a successful example of stepwise cleavage of two equivalent C-O bonds in a molecule using the three-color three-laser photolysis method.

Journal Article↗