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1.  A Quantitative Theory of Human Color Choices 
PLoS ONE  2013;8(2):e55986.
The system for colorimetry adopted by the Commission Internationale de l’Eclairage (CIE) in 1931, along with its subsequent improvements, represents a family of light mixture models that has served well for many decades for stimulus specification and reproduction when highly controlled color standards are important. Still, with regard to color appearance many perceptual and cognitive factors are known to contribute to color similarity, and, in general, to all cognitive judgments of color. Using experimentally obtained odd-one-out triad similarity judgments from 52 observers, we demonstrate that CIE-based models can explain a good portion (but not all) of the color similarity data. Color difference quantified by CIELAB ΔE explained behavior at levels of 81% (across all colors), 79% (across red colors), and 66% (across blue colors). We show that the unexplained variation cannot be ascribed to inter- or intra-individual variations among the observers, and points to the presence of additional factors shared by the majority of responders. Based on this, we create a quantitative model of a lexicographic semiorder type, which shows how different perceptual and cognitive influences can trade-off when making color similarity judgments. We show that by incorporating additional influences related to categorical and lightness and saturation factors, the model explains more of the triad similarity behavior, namely, 91% (all colors), 90% (reds), and 87% (blues). We conclude that distance in a CIE model is but the first of several layers in a hierarchy of higher-order cognitive influences that shape color triad choices. We further discuss additional mitigating influences outside the scope of CIE modeling, which can be incorporated in this framework, including well-known influences from language, stimulus set effects, and color preference bias. We also discuss universal and cultural aspects of the model as well as non-uniformity of the color space with respect to different cultural biases.
PMCID: PMC3569434  PMID: 23409103
2.  Color-tunable mixed photoluminescence emission from Alq3 organic layer in metal-Alq3-metal surface plasmon structure 
Nanoscale Research Letters  2014;9(1):569.
This work reports the color-tunable mixed photoluminescence (PL) emission from an Alq3 organic layer in an Au-Alq3-Au plasmonic structure through the combination of organic fluorescence emission and another form of emission that is enabled by the surface plasmons in the plasmonic structure. The emission wavelength of the latter depends on the Alq3 thickness and can be tuned within the Alq3 fluorescent spectra. Therefore, a two-color broadband, color-tunable mixed PL structure was obtained. Obvious changes in the Commission Internationale d’Eclairage (CIE) coordinates and the corresponding emission colors of Au-Alq3-Au samples clearly varied with the Alq3 thickness (90, 130, and 156 nm).
PMCID: PMC4199778  PMID: 25328506
Surface plasmon polariton; White light; Organic light-emitting; Photoluminescence
3.  Behavior, Color Change and Time for Sexual Inversion in the Protogynous Grouper (Epinephelus adscensionis) 
PLoS ONE  2011;6(5):e19576.
Hermaphroditism, associated with territoriality and dominance behavior, is common in the marine environment. While male sex-specific coloration patterns have been documented in groupers, particularly during the spawning season, few data regarding social structure and the context for these color displays are available. In the present study, we define the social structure and male typical behavior of rock hind (Epinephelus adscensionis) in the wild. In addition, we detail the captive conditions and time period necessary to induce the onset of the sex-specific coloration and sexual change. At six oil production platform locations in the Gulf of Mexico, rock hind social group size and typical male rock hind social behavior were documented. We observed a rapid temporary color display in rock hind that could be turned on and off within three seconds and was used for confronting territory intruders and displays of aggression towards females. The male-specific “tuxedo” pattern consists of a bright yellow tail, a body with alternating dark brown and white patches and a dark bar extending from the upper mandible to the operculum. Identification and size ranges of male, female and intersex fish collected from oil platforms were determined in conjunction with gonadal histology. Rock hind social order is haremic with one dominant male defending a territory and a linear dominance hierarchy among individuals. In five captive experiments, the largest remaining female rock hind displayed the male specific color pattern within 32d after dominant male removal from the social group. To our knowledge, this is the first evidence in a grouper species of color patterning used to display territoriality and dominance outside of spawning aggregations. The behavioral paradigm described here is a key advance that will enable mechanistic studies of this complex sex change process.
PMCID: PMC3102057  PMID: 21647429
4.  Color Selectivity of Neurons in the Posterior Inferior Temporal Cortex of the Macaque Monkey 
Cerebral Cortex (New York, NY)  2009;20(7):1630-1646.
We recorded the activities of neurons in the lateral surface of the posterior inferior temporal cortex (PIT) of 3 hemispheres of 3 monkeys performing a visual fixation task. We characterized the color and shape selectivities of each neuron, mapped its receptive field (RF), and studied the distributions of these response properties. Using a set of color stimuli that were systematically distributed in Commission Internationale de l'Eclairage-xy chromaticity diagram, we found numerous color-selective neurons distributed throughout the area examined. Neurons in the ventral region tended to have sharper color tuning than those in the dorsal region. We also found a crude retinotopic organization in the ventral region. Within the ventral region of PIT, neurons in the dorsal part had RFs that overlapped the foveal center; the eccentricity of RFs increased in the more ventral part, and neurons in the anterior and posterior parts had RFs that represented the lower and upper visual fields, respectively. In all 3 hemispheres, the region where sharply tuned color-selective neurons were concentrated was confined within this retinotopic map. These findings suggest that PIT is a heterogeneous area and that there is a circumscribed region within it that has crude retinotopic organization and is involved in the processing of color.
PMCID: PMC2882824  PMID: 19880593
color; inferior temporal cortex; primate; retinotopy; TEO; visual cortex
5.  Comparison of the Commercial Color LCD and the Medical Monochrome LCD Using Randomized Object Test Patterns 
PLoS ONE  2012;7(5):e37769.
Workstations and electronic display devices in a picture archiving and communication system (PACS) provide a convenient and efficient platform for medical diagnosis. The performance of display devices has to be verified to ensure that image quality is not degraded. In this study, we designed a set of randomized object test patterns (ROTPs) consisting of randomly located spheres with various image characteristics to evaluate the performance of a 2.5 mega-pixel (MP) commercial color LCD and a 3 MP diagnostic monochrome LCD in several aspects, including the contrast, resolution, point spread effect, and noise. The ROTPs were then merged into 120 abdominal CT images. Five radiologists were invited to review the CT images, and receiver operating characteristic (ROC) analysis was carried out using a five-point rating scale. In the high background patterns of ROTPs, the sensitivity performance was comparable between both monitors in terms of contrast and resolution, whereas, in the low background patterns, the performance of the commercial color LCD was significantly poorer than that of the diagnostic monochrome LCD in all aspects. The average area under the ROC curve (AUC) for reviewing abdominal CT images was 0.717±0.0200 and 0.740±0.0195 for the color monitor and the diagnostic monitor, respectively. The observation time (OT) was 145±27.6 min and 127±19.3 min, respectively. No significant differences appeared in AUC (p = 0.265) and OT (p = 0.07). The overall results indicate that ROTPs can be implemented as a quality control tool to evaluate the intrinsic characteristics of display devices. Although there is still a gap in technology between different types of LCDs, commercial color LCDs could replace diagnostic monochrome LCDs as a platform for reviewing abdominal CT images after monitor calibration.
PMCID: PMC3365102  PMID: 22701534
6.  Beyond Correlation: Do Color Features Influence Attention in Rainforest? 
Recent research indicates a direct relationship between low-level color features and visual attention under natural conditions. However, the design of these studies allows only correlational observations and no inference about mechanisms. Here we go a step further to examine the nature of the influence of color features on overt attention in an environment in which trichromatic color vision is advantageous. We recorded eye-movements of color-normal and deuteranope human participants freely viewing original and modified rainforest images. Eliminating red–green color information dramatically alters fixation behavior in color-normal participants. Changes in feature correlations and variability over subjects and conditions provide evidence for a causal effect of red–green color-contrast. The effects of blue–yellow contrast are much smaller. However, globally rotating hue in color space in these images reveals a mechanism analyzing color-contrast invariant of a specific axis in color space. Surprisingly, in deuteranope participants we find significantly elevated red–green contrast at fixation points, comparable to color-normal participants. Temporal analysis indicates that this is due to compensatory mechanisms acting on a slower time scale. Taken together, our results suggest that under natural conditions red–green color information contributes to overt attention at a low-level (bottom-up). Nevertheless, the results of the image modifications and deuteranope participants indicate that evaluation of color information is done in a hue-invariant fashion.
PMCID: PMC3079176  PMID: 21519395
attention; eye-movements; color
7.  Color Discrimination in the Tufted Capuchin Monkey, Sapajus spp 
PLoS ONE  2013;8(4):e62255.
The present study evaluated the efficacy of an adapted version of the Mollon-Reffin test for the behavioral investigation of color vision in capuchin monkeys. Ten tufted capuchin monkeys (Sapajus spp., formerly referred to as Cebus apella) had their DNA analyzed and were characterized as the following: one trichromat female, seven deuteranope dichromats (six males and one female), and two protanope males, one of which was identified as an “ML protanope.” For their behavioral characterization, all of the subjects were tested at three regions of the Commission International de l'Eclairage (CIE) 1976 u′v′ diagram, with each test consisting of 20 chromatic variation vectors that were radially distributed around the chromaticity point set as the test background. The phenotypes inferred from the behavioral data were in complete agreement with those predicted from the genetic analysis, with the threshold distribution clearly differentiating between trichromats and dichromats and the estimated confusion lines characteristically converging for deuteranopes and the “classic” protanope. The discrimination pattern of the ML protanope was intermediate between protan and deutan, with confusion lines horizontally oriented and parallel to each other. The observed phenotypic differentiation confirmed the efficacy of the Mollon-Reffin test paradigm as a useful tool for evaluating color discrimination in nonhuman primates. Especially noteworthy was the demonstration of behavioral segregation between the “classic” and “ML” protanopes, suggesting identifiable behavioral consequences of even slight variations in the spectral sensitivity of M/L photopigments in dichromats.
PMCID: PMC3631197  PMID: 23620819
8.  Characterization of color CRT display systems for monochrome applications 
Journal of Digital Imaging  1999;12(3):102-113.
Soft-copy presentation of medical images is becoming more and more important as medical imaging is strongly moving toward digital technology, and health care facilities are converting to filmless hospital and radiological information management. Although most medical images are monochrome, frequently they are displayed on color CRTs, particularly if general-purpose workstations or PCs are used for medical viewing. In the present report, general measurement and modeling procedures for the characterization of color CRT monitors for monochrome presentation are introduced. The contributions from the three color channels (red, green, and blue) are weighted according to the spectral sensitivity of the human eye for photopic viewing. The luminance behavior and the resolution capabilities of color CRT monitors are analyzed with the help of photometer and charge-coupled device (CCD) camera measurements. For the evaluation of spatial resolution, a two-dimensional Fourier analysis of special test images containing white noise (broadband response) is employed. A stage model for a color CRT monitor is developed to discuss the effects of scanning and dot sampling. Furthermore, display intrinsic veiling glare and reflectivity of typical color CRT monitors are measured and compared with those of monochrome CRT monitors. The developed methods and models allow one to describe the image quality aspects of color monitors if they are applied for medical monochrome image presentation. Particularly, because of the reduced luminance and dynamic range of color monitors, the calibration and control of their luminance curves is a very important task. For present color CRT monitors, 1,280×1,024 turns out to be an intrinsic limit for the displayable matrix of medical images.
PMCID: PMC3452435  PMID: 10461573
monitor characterization; color CRT monitors; soft-copy viewing; image quality
9.  Standardization of In vitro Macrophotography for Assessment of Cutaneous Responses 
Photochemistry and photobiology  2009;85(4):1032-1037.
The increased popularity of commercially available 3-dimensional human skin equivalents in recent years has allowed for assessment of melanogenesis modulated by compounds topically applied to the skin or directly incorporated from the medium. These skin equivalents provide a suitable model for elucidating the mechanisms of action of various factors that modulate skin pigmentation or other properties of the skin. As such, researchers need to objectively quantify cutaneous responses at the macroscopic level. A simple method to standardize macrophotography images is reported that can quantify cutaneous responses in human skin equivalents of Asian, Black or African American, and Caucasian or White racial/ethnic origin. Macrophotographs are analyzed using the Commission Internationale de l’Eclairage L*a*b* color space system in combination with a personal computer and image editing software. Pigmentation changes monitored over a 9 day period showed a high correlation with melanin content evaluated in Fontana-Masson stained sections. These results indicate the feasibility of using a macrophotography setup in a sterile tissue culture environment to objectively assess in vitro cutaneous responses in human skin equivalents. This serves as an adjunct tool to biochemical and morphological methods to effectively quantify changes in pigmentation over time.
PMCID: PMC2705686  PMID: 19320841
10.  Dissociation of Color and Figure-Ground Effects in the Watercolor Illusion 
Spatial vision  2006;19(2-4):323-340.
Two phenomena can be observed in the watercolor illusion: illusory color spreading and figure-ground organization. We performed experiments to determine whether the figure-ground effect is a consequence of the color illusion or due to an independent mechanism. Subjects were tested with displays consisting of six adjacent compartments, three that generated the illusion alternating with three that served for comparison. In a first set of experiments, the illusory color was measured by finding the matching physical color in the alternate compartments. Figureness (probability of ‘figure’ responses, 2AFC) of the watercolor compartments was then determined with and without the matching color in the alternate compartments. The color match reduced figureness, but did not abolish it. There was a range of colors in which the watercolor compartments dominated as figures over the alternate compartments although the latter appeared more saturated in color. In another experiment, the effect of tinting alternate compartments was measured in displays without watercolor illusion. Figureness increased with color contrast, but its value at the equivalent contrast fell short of the figureness value obtained for the watercolor pattern. Thus, in both experiments figureness produced by the watercolor pattern was stronger than expected from the color effect, suggesting independent mechanisms. Considering the neurophysiology, we propose that the color illusion follows from the principles of representation of surface color in the visual cortex, while the figure-ground effect results from two mechanisms of border ownership assignment, one that is sensitive to asymmetric shape of edge profile, the other to consistency of color borders.
PMCID: PMC1551905  PMID: 16862843
Watercolor illusion; figure-ground segregation; border ownership; surface color; neural coding of contour
11.  Identification of QTL controlling meat quality traits in an F2 cross between two chicken lines selected for either low or high growth rate 
BMC Genomics  2007;8:155.
Meat technological traits (i.e. meat pH, water retention and color) are important considerations for improving further processing of chicken meat. These quality traits were originally characterized in experimental lines selected for high (HG) and low (LG) growth. Presently, quantitative trait loci (QTL) for these traits were analyzed in an F2 population issued from the HG × LG cross. A total of 698 animals in 50 full-sib families were genotyped for 108 microsatellite markers covering 21 linkage groups.
The HG and LG birds exhibit large differences in body weight and abdominal fat content. Several meat quality traits [pH at 15 min post-slaughter (pH15) and ultimate pH (pHu), breast color-redness (BCo-R) and breast color-yellowness (BCo-Y)] were lower in HG chickens. In contrast, meat color-lightness (BCo-L) was higher in HG chickens, whereas meat drip loss (DL) was similar in both lines. HG birds were more active on the shackle line. Association analyses were performed using maximum-likelihood interval mapping in QTLMAP. Five genome-wide significant QTLs were revealed: two for pH15 on GGA1 and GGA2, one for DL on GGA1, one for BCo-R and one for BCo-Y both on GGA11. In addition, four suggestive QTLs were identified by QTLMAP for BCo-Y, pHu, pH15 and DL on GGA1, GGA4, GGA12 and GGA14, respectively. The QTL effects, averaged on heterozygous families, ranged from 12 to 31% of the phenotypic variance. Further analyses with QTLExpress confirmed the two genome-wide QTLs for meat color on GGA11, failed to identify the genome-wide QTL for pH15 on GGA2, and revealed only suggestive QTLs for pH15 and DL on GGA1. However, QTLExpress qualified the QTL for pHu on GGA4 as genome-wide.
The present study identified genome-wide significant QTLs for all meat technological traits presently assessed in these chickens, except for meat lightness. This study highlights the effects of divergent selection for growth rate on some behavioral traits, muscle biochemistry and ultimately meat quality traits. Several QTL regions were identified that are worthy of further characterization. Some QTLs may in fact co-localize, suggesting pleiotropic effects for some chromosomal regions.
PMCID: PMC1899504  PMID: 17559654
12.  Observer Performance Using Virtual Pathology Slides: Impact of LCD Color Reproduction Accuracy 
Journal of Digital Imaging  2012;25(6):738-743.
The use of color LCDs in medical imaging is growing as more clinical specialties use digital images as a resource in diagnosis and treatment decisions. Telemedicine applications such as telepathology, teledermatology, and teleophthalmology rely heavily on color images. However, standard methods for calibrating, characterizing, and profiling color displays do not exist, resulting in inconsistent presentation. To address this, we developed a calibration, characterization, and profiling protocol for color-critical medical imaging applications. Physical characterization of displays calibrated with and without the protocol revealed high color reproduction accuracy with the protocol. The present study assessed the impact of this protocol on observer performance. A set of 250 breast biopsy virtual slide regions of interest (half malignant, half benign) were shown to six pathologists, once using the calibration protocol and once using the same display in its “native” off-the-shelf uncalibrated state. Diagnostic accuracy and time to render a decision were measured. In terms of ROC performance, Az (area under the curve) calibrated = 0.8570 and Az uncalibrated = 0.8488. No statistically significant difference (p = 0.4112) was observed. In terms of interpretation speed, mean calibrated = 4.895 s; mean uncalibrated = 6.304 s which is statistically significant (p = 0.0460). Early results suggest a slight advantage diagnostically for a properly calibrated and color-managed display and a significant potential advantage in terms of improved workflow. Future work should be conducted using different types of color images that may be more dependent on accurate color rendering and a wider range of LCDs with varying characteristics.
PMCID: PMC3491161  PMID: 22546982
Color displays; Diagnostic accuracy; Color calibration; Color management; Pathology
13.  Color standardization and optimization in Whole Slide Imaging 
Diagnostic Pathology  2011;6(Suppl 1):S15.
Standardization and validation of the color displayed by digital slides is an important aspect of digital pathology implementation. While the most common reason for color variation is the variance in the protocols and practices in the histology lab, the color displayed can also be affected by variation in capture parameters (for example, illumination and filters), image processing and display factors in the digital systems themselves.
We have been developing techniques for color validation and optimization along two paths. The first was based on two standard slides that are scanned and displayed by the imaging system in question. In this approach, one slide is embedded with nine filters with colors selected especially for H&E stained slides (looking like tiny Macbeth color chart); the specific color of the nine filters were determined in our previous study and modified for whole slide imaging (WSI). The other slide is an H&E stained mouse embryo. Both of these slides were scanned and the displayed images were compared to a standard. The second approach was based on our previous multispectral imaging research.
As a first step, the two slide method (above) was used to identify inaccurate display of color and its cause, and to understand the importance of accurate color in digital pathology. We have also improved the multispectral-based algorithm for more consistent results in stain standardization. In near future, the results of the two slide and multispectral techniques can be combined and will be widely available.
We have been conducting a series of researches and developing projects to improve image quality to establish Image Quality Standardization. This paper discusses one of most important aspects of image quality – color.
PMCID: PMC3073208  PMID: 21489185
14.  Color-Shape Associations Revealed with Implicit Association Tests 
PLoS ONE  2015;10(1):e0116954.
Kandinsky proposed a correspondence theory that suggests associations between specific colors and shapes (i.e., circle-blue, square-red, triangle-yellow). Makin and Wuerger tested the theory using the Implicit Association Test (IAT) and did not find clear evidence for Kandinsky’s color-shape associations among British participants. In the present study, we first replicated the previous study among Japanese participants and found similar results to those of Makin and Wuerger, showing little support for Kandinsky’s theory. In the subsequent experiment, we tested another set of color-shape associations that had been revealed by using an explicit matching method (circle-red, square-blue, triangle-yellow) in Japanese participants. The IAT tests showed that response times were significantly faster when circle-red, square-blue, and triangle-yellow combinations were mapped onto the same response key, rather than different key combinations, indicating that these color-shape combinations were encoded. These results provide the first empirical evidence that color-shape associations can be measured by indirect behavioral methods, and in particular, Japanese people’s color-shape associations (circle-red, square-blue, triangle-yellow) can be observed by both direct and indirect experimental methods.
PMCID: PMC4308101  PMID: 25625717
15.  Perceptibility and acceptability of CIELAB color differences in computer-simulated teeth 
Journal of dentistry  2007;35(7):593-599.
To determine the perceptibility and acceptability of tooth color differences using computer-generated pairs of teeth with simulated gingival displayed on a calibrated color monitor using appropriate signal detection theory methodology (SDT).
Twelve dental professionals (four from each of the following groups: dentists, dental auxiliaries, and fixed prosthodontic technicians) and four dental patients served as subjects. Responses to tooth color differences (ΔE) were measured on each of the three principal axes of CIELAB color space (L*, a*, and b*). As a control, responses to ΔE = 0 (the false alarm rate) were also measured in the same experimental session.
No group differences among subjects were found. All gave 50% match or acceptance points that averaged about 1.0 ΔE units in the L* and a* directions, and 2.6 units in the b* direction. False alarm rates across all subjects averaged 27% (4–55%) and 28% (0.4–61%), respectively, for perceptibility and acceptability. A reanalysis of the data based on SDT, which takes subjects’ false alarm rates into account, gave somewhat larger color difference thresholds.
Color difference thresholds for our simulated teeth are generally in line with and extend results obtained with studies using “real” dental materials. No differences between thresholds for acceptability versus perceptibility were found.
Furthermore, subjects often reported color differences when none existed, and this behavior needs to be factored into any determination of quality control standards for the fabrication of dental prostheses.
PMCID: PMC2041906  PMID: 17517460
Tooth color; Perceptibility; Acceptability; Signal detection; Color difference; Computer simulation
16.  Bare-Part Color in Female Budgerigars Changes from Brown to Structural Blue following Testosterone Treatment but Is Not Strongly Masculinized 
PLoS ONE  2014;9(1):e86849.
Whereas several studies have shown that experimentally increased levels of the androgenic steroid testosterone can affect female behavior, fewer studies have focused on the activational effects of exogenous testosterone on female morphology. With respect to colorful displays in birds, almost exclusively the effects of testosterone manipulation on female carotenoid-based colorations have been studied. Other color types such as structural colors (i.e. UV, blue and violet colors that result from differential light reflection in the nanostructures of the tissue) remain largely unstudied. Here, we investigated the short- and long-term effects of exogenous testosterone on the expression of structural bare-part coloration in female budgerigars, Melopsittacus undulatus. In this parrot species, bare-part coloration is expressed in the cere, a structure over the beak which is brown in females and structural blue in males. We experimentally increased plasma testosterone levels in testosterone-treated females (T-females) compared to controls (C-females) and we performed weekly spectrophotometric measurements of the cere for five weeks after implantation and one measurement after ten weeks. We also estimated the extent to which testosterone masculinized female cere color by comparing the experimental females with untreated males. We found significant effects of testosterone on cere color from week four after implantation onwards. T-females expressed significantly bluer ceres than C-females with higher values for brightness and UV reflectance. T-female cere color, however, remained significantly less blue than in males, while values for brightness and UV reflectance were significantly higher in T-females than in males. Our quantitative results show that exogenous testosterone induces the expression of structural blue color in females but does not strongly masculinize female cere coloration. We provide several potential pathways for the action of testosterone on structural color.
PMCID: PMC3901734  PMID: 24475184
17.  ROC Study of Four LCD Displays Under Typical Medical Center Lighting Conditions 
Journal of Digital Imaging  2006;19(1):30-40.
Nine observers reviewed a previously assembled library of 320 chest computed radiography (CR) images. Observers participated in four sessions, reading a different 1/4 of the sample on each of four liquid crystal displays: a 2-megapixel (MP) consumer color display, a 2-MP business color display, a 2-MP medical-grade gray display, and a 3-MP gray display. Each display was calibrated according to the DICOM Part 14 standard. The viewing application required observer login, then randomized the order of the subsample seen on the display, and timed the responses of the observer to render a 1–5 judgment on the absence or presence of ILD on chest CRs. Selections of 1–2 were considered negative, 3 was indeterminate, and 4–5 were positive. The order of viewing sessions was also randomized for each observer. The experiment was conducted under controlled lighting, temperature, and sound conditions to mimic conditions typically found in a patient examination room. Lighting was indirect, and illuminance at the display face was 195 ± 8% lux and was monitored over the course of the experiment. The average observer sensitivity for the 2 MP color consumer, 2 MP business color, 2 MP gray, and 3 MP gray displays were 83.7%, 84.1%, 85.5%, and 86.7%, respectively. The only pairwise significant difference was between the 2-MP consumer color and the 2-MP gray (P = 0.05). Effect of order within a session was not signitfficant (P = 0.21): period 1 (84.3%), period 2 (86.2%), period 3 (85.4%), period 4 (84.1%). Observer specificity for the various displays was not statistically significant (P = 0.21). Finally, a timing analysis showed no significant difference between the displays for the user group (P = 0.13), ranging from 5.3 s (2 MP color business) to 5.9 s (3 MP Gray). There was, however, a reduction in time over the study that was significant (P <<< 0.001) for all users; the group average decreased from 6.5 to 4.7 s per image. Physical measurements of the resolution, contrast, and noise properties of the displays were acquired. Most notably, the noise of the displays varied by 3.5× between the lowest and highest noise displays. Differences in display noise were indicative of observer performance. However, the large difference in the magnitude of the noise was not predictive of the small difference (3%) in the observer sensitivity for various displays. This is likely because detection of interstitial lung disease is limited by “““““anatomical noise””” rather than display or x-ray image noise.
PMCID: PMC3043952  PMID: 16249836
ROC; image quality; displays; interstitial lung disease
18.  All Solution-processed Stable White Quantum Dot Light-emitting Diodes with Hybrid ZnO@TiO2 as Blue Emitters 
Scientific Reports  2014;4:4085.
White quantum dot light-emitting diodes (QD-LEDs) have been a promising candidate for high-efficiency and color-saturated displays. However, it is challenging to integrate various QD emitters into one device and also to obtain efficient blue QDs. Here, we report a simply solution-processed white QD-LED using a hybrid ZnO@TiO2 as electron injection layer and ZnCdSeS QD emitters. The white emission is obtained by integrating the yellow emission from QD emitters and the blue emission generated from hybrid ZnO@TiO2 layer. We show that the performance of white QD-LEDs can be adjusted by controlling the driving force for hole transport and electroluminescence recombination region via varying the thickness of hole transport layer. The device is demonstrated with a maximum luminance of 730 cd/m2 and power efficiency of 1.7 lm/W, exhibiting the Commission Internationale de l'Enclairage (CIE) coordinates of (0.33, 0.33). The unencapsulated white QD-LED has a long lifetime of 96 h at its initial luminance of 730 cd/m2, primarily due to the fact that the device with hybrid ZnO@TiO2 has low leakage current and is insensitive to the oxygen and the moisture. These results indicate that hybrid ZnO@TiO2 provides an alternate and effective approach to achieve high-performance white QD-LEDs and also other optoelectronic devices.
PMCID: PMC3923213  PMID: 24522341
19.  Colorimetric Determination of Color of Aerial Mycelium of Streptomycetes1 
Journal of Bacteriology  1965;89(1):159-169.
Lyons, Allister J., Jr. (Northern Regional Research Laboratory, Peoria, Ill.) and Thomas G. Pridham. Colorimetric determination of color of aerial mycelium of streptomycetes. J. Bacteriol. 89:159–169. 1965.—For some time, streptomycete taxonomists have been seeking to describe more accurately the colors of aerial mycelium. Some of the descriptive systems involve many different color names and groups. Others combine many colors into a few groups. All the systems and methods leave much to be desired. To obtain an accurate description, a colorimeter with a reflectance attachment was used to examine streptomycete aerial mycelium of 37 strains, representing all of the major aerial mycelium color groups. Each color was characterized by three values: dominant wavelength in millimicrons, and purity and brightness in percentages. All colors of aerial mycelium were of low purity (< 25%). Most of the dominant wavelengths were in the yellow to yellow-green bands of the spectrum. Most of the color tabs matched visually with the streptomycete strains had purities of a higher value than those of the cultures. The reflectance instrument seems to allow an objective description, and its use may help to clarify the color problem with streptomycetes. It is concluded that present color descriptions are inadequate and that the significance of color in speciation requires critical examination.
PMCID: PMC315564  PMID: 14255657
20.  The dyschromatopsia of optic neuritis: a descriptive analysis of data from the optic neuritis treatment trial. 
PURPOSE: We sought to characterize the dyschromatopsia of optic neuritis, to determine the type and severity of color defect present and its relation to central vision and spatial acuity, to examine changes in this dyschromatopsia over time, and to determine the applicability of Köllner's rule to patients with optic neuritis. METHODS: We analyzed the raw data on color vision performance as assembled within the Optic Neuritis Treatment Trial (ONTT). The ONTT was designed to evaluate corticosteroids as a treatment for acute demyelinating optic neuritis and to allow long-term outcome and natural history analyses. Between July 1, 1988 and June 30, 1991, 488 patients were enrolled in this trial. All patients underwent extensive neurologic and ophthalmologic examinations including standardized testing of visual function that included testing of color vision. The ONTT population thus afforded a unique opportunity to characterize acquired dyschromatopsias in a large, homogenous, well-characterized cohort of patients with optic neuritis. We used quantitative analysis of FM-100 scores from this patient cohort to determine the severity of the dyschromatopsia, the selectivity of the dyschromatopsia (polarity of errors) and the type of dyschromatopsia (axis of confusion) by employing quadrant analysis of FM-100 scores. RESULTS: The results of high-and low-selectivity analyses of the FM-100 data showed that during the acute phase of optic neuritis, blue/yellow, red/ green, and non-selective color defects occurred; among patients with pure defects, blue/yellow defects were more frequent than red/green defects. At 6 months after the acute event, however, analyses showed that red/green defects were more common than blue/yellow defects. Among patients with selective color defects both acutely and at 6 months, the defect was as likely to change over time as remain the same. The likelihood of persistent dyschromatopsia at 6 months was related to the severity of initial central acuity loss, but the type of dyschromatopsia present (red/green versus blue/yellow) was not. CONCLUSIONS: Our results suggest that at the time of the acute attack of optic neuritis, the majority of selective color defects were blue/yellow defects, whereas at 6 months, more of the selective defects were red/green defects, though both types of defects (as well as nonselective defects) were seen acutely and at 6 months. Despite the rigorous inclusion criteria of the ONTT, the large number of patients we studied, correlation of color vision with visual acuity, and longitudinal follow up, this study showed that no single type of color defect was consistently associated with optic neuritis. Demyelinating optic neuritis does not obey Köllner's rule. Moreover, the type of defect present changed in some patients over the course of recovery. Thus, the type of defect may not even be consistent in individual patients as they recover. The type of defect appeared to be related to spatial vision at the time of the test, but the type of defect present at 6 months was not related to the severity of the initial visual loss. Therefore, in evaluating color defects associated with optic neuritis, the level of central visual function must be considered.
PMCID: PMC1312075  PMID: 8719696
21.  The Fall and Rise of US Inequities in Premature Mortality: 1960–2002 
PLoS Medicine  2008;5(2):e46.
Debates exist as to whether, as overall population health improves, the absolute and relative magnitude of income- and race/ethnicity-related health disparities necessarily increase—or derease. We accordingly decided to test the hypothesis that health inequities widen—or shrink—in a context of declining mortality rates, by examining annual US mortality data over a 42 year period.
Methods and Findings
Using US county mortality data from 1960–2002 and county median family income data from the 1960–2000 decennial censuses, we analyzed the rates of premature mortality (deaths among persons under age 65) and infant death (deaths among persons under age 1) by quintiles of county median family income weighted by county population size. Between 1960 and 2002, as US premature mortality and infant death rates declined in all county income quintiles, socioeconomic and racial/ethnic inequities in premature mortality and infant death (both relative and absolute) shrank between 1966 and 1980, especially for US populations of color; thereafter, the relative health inequities widened and the absolute differences barely changed in magnitude. Had all persons experienced the same yearly age-specific premature mortality rates as the white population living in the highest income quintile, between 1960 and 2002, 14% of the white premature deaths and 30% of the premature deaths among populations of color would not have occurred.
The observed trends refute arguments that health inequities inevitably widen—or shrink—as population health improves. Instead, the magnitude of health inequalities can fall or rise; it is our job to understand why.
Nancy Krieger and colleagues found evidence of decreasing, and then increasing or stagnating, socioeconomic and racial inequities in US premature mortality and infant death from 1960 to 2002.
Editors' Summary
One of the biggest aims of public health advocates and governments is to improve the health of the population. Improving health increases people's quality of life and helps the population be more economically productive. But within populations are often persistent differences (usually called “disparities” or “inequities”) in the health of different subgroups—between women and men, different income groups, and people of different races/ethnicities, for example. Researchers study these differences so that policy makers and the broader public can be informed about what to do to intervene. For example, if we know that the health of certain subgroups of the population—such as the poor—is staying the same or even worsening as the overall health of the population is improving, policy makers could design programs and devote resources to specifically target the poor.
To study health disparities, researchers use both relative and absolute measures. Relative inequities refer to ratios, while absolute inequities refer to differences. For example, if one group's average income level increases from $1,000 to $10,000 and another group's from $2,000 to $20,000, the relative inequality between the groups stays the same (i.e., the ratio of incomes between the two groups is still 2) but the absolute difference between the two groups has increased from $1,000 to $10,000.
Examining the US population, Nancy Krieger and colleagues looked at trends over time in both relative and absolute differences in mortality between people in different income groups and between whites and people of color.
Why Was This Study Done?
There has been a lot of debate about whether disparities have been widening or narrowing as overall population health improves. Some research has found that both total health and health disparities are getting better with time. Other research has shown that overall health gains mask worsening disparities—such that the rich get healthier while the poor get sicker.
Having access to more data over a longer time frame meant that Krieger and colleagues could provide a more complete picture of this sometimes contradictory story. It also meant they could test their hypothesis about whether, as population health improves, health inequities necessarily widen or shrink within the time period between the 1960s through the 1990s during which certain events and policies likely would have had an impact on the mortality trends in that country.
What Did the Researchers Do and Find?
In order to investigate health inequities, the authors chose to look at two common measures of population health: rates of premature mortality (dying before the age of 65 years) and rates of infant mortality (death before the age of 1).
To determine mortality rates, the authors used death statistics data from different counties, which are routinely collected by state and national governments. To be able to rank mortality rates for different income groups, they used data on the median family incomes of people living within those counties (meaning half the families had income above, and half had incomes below, the median value). They calculated mortality rates for the total population and for whites versus people of color. They used data from 1960 through 2002. They compared rates for 1966–1980 with two other time periods: 1960–1965 and 1981–2002. They also examined trends in the annual mortality rates and in the annual relative and absolute disparites in these rates by county income level.
Over the whole period 1960–2002, the authors found that premature mortality (death before the age of 65) and infant mortality (death before the age of 1) decreased for all income groups. But they also found that disparities between income groups and between whites and people of color were not the same over this time period. In fact, the economic disparities narrowed then widened. First, they shrank between 1966 and 1980, especially for Americans of color. After 1980, however, the relative health inequities widened and the absolute differences did not change. The authors conclude that if all people in the US population experienced the same health gains as the most advantaged did during these 42 years (i.e., as the whites in the highest income groups), 14% of the premature deaths among whites and 30% of the premature deaths among people of color would have been prevented.
What Do These Findings Mean?
The findings provide an overview of the trends in inequities in premature and infant mortality over a long period of time. Different explanations for these trends can now be tested. The authors discuss several potential reasons for these trends, including generally rising incomes across America and changes related to specific diseases, such as the advent of HIV/AIDS, changes in smoking habits, and better management of cancer and cardiovascular disease. But they find that these do not explain the fall then rise of inequities. Instead, the authors suggest that explanations lie in the social programs of the 1960s and the subsequent roll-back of some of these programmes in the 1980s. The US “War on Poverty,” civil rights legislation, and the establishment of Medicare occurred in the mid 1960s, which were intended to reduce socioeconomic and racial/ethnic inequalities and improve access to health care. In the 1980s there was a general cutting back of welfare state provisions in America, which included cuts to public health and antipoverty programs, tax relief for the wealthy, and worsening inequity in the access to and quality of health care. Together, these wider events could explain the fall then rise trends in mortality disparities.
The authors say their findings are important to inform and help monitor the progress of various policies and programmes, including those such as the Healthy People 2010 initiative in America, which aims to increase the quality and years of healthy life and decrease health disparities by the end of this decade.
Additional Information.
Please access these Web sites via the online version of this summary at 0050046.
Healthy People 2010 was created by the US Department of Health and Human Services along with scientists inside and outside of government and includes a comprehensive set of disease prevention and health promotion objectives for the US to achieve by 2010, with two overarching goals: to increase quality and years of healthy life and to eliminate health disparities
Johan Mackenbach and colleagues provide an overview of mortality inequalities in six Western European countries—Finland, Sweden, Norway, Denmark, England/Wales, and Italy—and conclude that eliminating mortality inequalities requires that more cardiovascular deaths among lower socioeconomic groups be prevented, as well as more attention be paid to rising death rates of lung cancer, breast cancer, respiratory disease, gastrointestinal disease, and injuries among women and men in the lower income groups.
The WHO Health for All program promotes health equity
A primer on absolute versus relative differences is provided by the American College of Physicians
PMCID: PMC2253609  PMID: 18303941
22.  Effect of Particular Breed on the Chemical Composition, Texture, Color, and Sensorial Characteristics of Dry-cured Ham 
The present study demonstrates the impact of specific breed on the characteristics of dry-cured ham. Eighty thighs from Korean native pig (KNP), crossbreed (Landrace×Yorkshire)♀×Duroc♂ (LYD), Berkshire (Ber), and Duroc (Du) pig breeds (n = 10 for each breed) were used for processing of dry-cured ham. The thighs were salted with 6% NaCl (w/w) and 100 ppm NaNO2, and total processing time was 413 days. The effects of breed on the physicochemical composition, texture, color and sensory characteristics were assessed on the biceps femoris muscle of the hams. The results revealed that the highest weight loss was found in the dry-cured ham of LYD breed and the lowest weight loss was found in Ber dry-cured ham. The KNP dry-cured ham contain higher intramuscular fat level than other breed hams (p<0.05). It was observed that the dry-cured ham made from KNP breed had the lowest water activity value and highest salt content, while the LYD dry-cure ham had higher total volatile basic nitrogen content than the Ber and Du hams (p<0.05). Zinc, iron and total monounsaturated fatty acids levels were higher in KNP ham while polyunsaturated fatty acids levels were higher in Du ham when compared to other breed hams (p<0.05). Additionally, the KNP dry-cured ham possessed higher Commission International de l’Eclairage (CIE) a* value, while the Du dry-cured ham had higher L*, CIE b* and hue angle values (p<0.05). Furthermore, breed significantly affected the sensory attributes of dry-cured hams with higher scores for color, aroma and taste found in KNP dry-cured ham as compared to other breed hams (p<0.05). The overall outcome of the study is that the breed has a potential effect on the specific chemical composition, texture, color and sensorial properties of dry-cured hams. These data could be useful for meat processors to select the suitable breeds for economical manufacturing of high quality dry-cured hams.
PMCID: PMC4109873  PMID: 25083111
Breed; Dry-cured Ham; Texture; Color; Sensory
23.  Seasonal Changes in Colour: A Comparison of Structural, Melanin- and Carotenoid-Based Plumage Colours 
PLoS ONE  2010;5(7):e11582.
Plumage coloration is important for bird communication, most notably in sexual signalling. Colour is often considered a good quality indicator, and the expression of exaggerated colours may depend on individual condition during moult. After moult, plumage coloration has been deemed fixed due to the fact that feathers are dead structures. Still, many plumage colours change after moult, although whether this affects signalling has not been sufficiently assessed.
Methodology/Principal Findings
We studied changes in coloration after moult in four passerine birds (robin, Erithacus rubecula; blackbird, Turdus merula; blue tit, Cyanistes caeruleus; and great tit, Parus major) displaying various coloration types (melanin-, carotenoid-based and structural). Birds were caught regularly during three years to measure plumage reflectance. We used models of avian colour vision to derive two variables, one describing chromatic and the other achromatic variation over the year that can be compared in magnitude among different colour types. All studied plumage patches but one (yellow breast of the blue tit) showed significant chromatic changes over the year, although these were smaller than for a typical dynamic trait (bill colour). Overall, structural colours showed a reduction in relative reflectance at shorter wavelengths, carotenoid-based colours the opposite pattern, while no general pattern was found for melanin-based colours. Achromatic changes were also common, but there were no consistent patterns of change for the different types of colours.
Changes of plumage coloration independent of moult are probably widespread; they should be perceivable by birds and have the potential to affect colour signalling.
PMCID: PMC2904367  PMID: 20644723
24.  Facial Skin Coloration Affects Perceived Health of Human Faces 
Numerous researchers have examined the effects of skin condition, including texture and color, on the perception of health, age, and attractiveness in human faces. They have focused on facial color distribution, homogeneity of pigmentation, or skin quality. We here investigate the role of overall skin color in determining perceptions of health from faces by allowing participants to manipulate the skin portions of color-calibrated Caucasian face photographs along CIELab color axes. To enhance healthy appearance, participants increased skin redness (a*), providing additional support for previous findings that skin blood color enhances the healthy appearance of faces. Participants also increased skin yellowness (b*) and lightness (L*), suggesting a role for high carotenoid and low melanin coloration in the healthy appearance of faces. The color preferences described here resemble the red and yellow color cues to health displayed by many species of nonhuman animals.
PMCID: PMC2780675  PMID: 19946602
beauty; diet; flushing; hemoglobin; UV protection
25.  Color change as a potential behavioral strategy 
Hormones and behavior  2008;54(3):463-470.
Within species, color morphs may enhance camouflage, improve communication and/or confer reproductive advantage. However, in the male cichlid Astatotilapia burtoni, body color may also signal a behavioral strategy. A. burtoni live in a lek-like social system in Lake Tanganyika, Africa where bright blue or yellow territorial (T) males (together ~ 10–30% of the population) are reproductively capable and defend territories containing food with a spawning site. In contrast, nonterritorial (NT) males are smaller, cryptically colored, shoal with females and have regressed gonads. Importantly, males switch between these social states depending on their success in aggressive encounters. Yellow and blue morphs were thought to be adaptations to particular habitats, but they co-exist both in nature and in the laboratory. Importantly, individual males can switch colors so we asked whether color influences behavioral and hormonal profiles. When pairing territorial males with opposite colored fish, yellow males became dominant over blue males significantly more frequently. Moreover, yellow T males had significantly higher levels of 11-ketotosterone than blue T males while only blue NT males had higher levels of the stress hormone cortisol compared to the other groups. Thus color differences alone predict dominance status and hormone profiles in T males. Since T males can and do change color, this suggests that A. burtoni may use color as a flexible behavioral strategy.
PMCID: PMC3019090  PMID: 18586245

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